Sensors

Editorial

Jump to: Research, Review, Other

5 pages, 173 KiB

Open AccessEditorial

Molecular Imprinting and Functional Polymers for All Transducers and Applications

by Franz L. Dickert

Department of Analytical Chemistry, University of Vienna, Währinger Str. 38, A 1090 Vienna, Austria

Sensors 2018, 18(2), 327; https://doi.org/10.3390/s18020327 - 24 Jan 2018

Cited by 14 | Viewed by 3590

Abstract

The main challenge in developing a chemical sensor is the synthesis of recognition coatings, which are very sensitive and selective to analytes of interest. Molecular imprinting has proven to be the most innovative strategy for this purpose in functional polymer design in the [...] Read more.

The main challenge in developing a chemical sensor is the synthesis of recognition coatings, which are very sensitive and selective to analytes of interest. Molecular imprinting has proven to be the most innovative strategy for this purpose in functional polymer design in the last few decades. Moreover, the introduction of functional groups brings about new applications for all available transducers. Sensitivity and selectivity features of sensor coatings can be tuned by this approach. The strategy produces molecular cavities and interaction sites in sensor coatings. The synthesis of these tailored recognition materials is performed in an outstanding manner, saving time and the high costs of chemicals. Furthermore, intermolecular interactions between the analyte and chemical layers will generate sites that are complementary to the analyte. This procedure can easily be done, directly on a transducer surface, which entails engulfing the analyte by a prepolymer and crosslinking the polymeric material. These imprinted polymers form a robust recognition layer on the transducer surface, which cannot be peeled off and can withstand very harsh conditions, both in gaseous and liquid media. These recognition materials are very suitable, for small molecules and even large bioparticles. Full article

(This article belongs to the Special Issue Molecular Imprinting and Functional Polymers for all Transducers and Applications)

Research

Jump to: Editorial, Review, Other

16 pages, 5716 KiB

Open AccessArticle

Impact Analysis of Temperature and Humidity Conditions on Electrochemical Sensor Response in Ambient Air Quality Monitoring

by Peng Wei¹, Zhi Ning^1,*, Sheng Ye¹, Li Sun¹, Fenhuan Yang¹, Ka Chun Wong¹, Dane Westerdahl¹ and Peter K. K. Louie²

¹ School of Energy and Environment, City University of Hong Kong, Tat Avenue, Kowloon, Hong Kong, China

² Environmental Protection Department, the Government of the Hong Kong Special Administration Region, 33/F Revenue Tower, 5 Gloucester Road, Wan Chai, Hong Kong, China

Sensors 2018, 18(2), 59; https://doi.org/10.3390/s18020059 - 23 Jan 2018

Cited by 142 | Viewed by 15217

Abstract

The increasing applications of low-cost air sensors promises more convenient and cost-effective systems for air monitoring in many places and under many conditions. However, the data quality from such systems has not been fully characterized and may not meet user expectations in research [...] Read more.

The increasing applications of low-cost air sensors promises more convenient and cost-effective systems for air monitoring in many places and under many conditions. However, the data quality from such systems has not been fully characterized and may not meet user expectations in research and regulatory uses, or for use in citizen science. In our study, electrochemical sensors (Alphasense B4 series) for carbon monoxide (CO), nitric oxide (NO), nitrogen dioxide (NO₂), and oxidants (O_x) were evaluated under controlled laboratory conditions to identify the influencing factors and quantify their relation with sensor outputs. Based on the laboratory tests, we developed different correction methods to compensate for the impact of ambient conditions. Further, the sensors were assembled into a monitoring system and tested in ambient conditions in Hong Kong side-by-side with regulatory reference monitors, and data from these tests were used to evaluate the performance of the models, to refine them, and validate their applicability in variable ambient conditions in the field. The more comprehensive correction models demonstrated enhanced performance when compared with uncorrected data. One over-arching observation of this study is that the low-cost sensors may promise excellent sensitivity and performance, but it is essential for users to understand and account for several key factors that may strongly affect the nature of sensor data. In this paper, we also evaluated factors of multi-month stability, temperature, and humidity, and considered the interaction of oxidant gases NO₂ and ozone on a newly introduced oxidant sensor. Full article

(This article belongs to the Special Issue Signal and Information Processing in Chemical Sensing)

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18 pages, 6982 KiB

Open AccessArticle

Spatial Vertical Directionality and Correlation of Low-Frequency Ambient Noise in Deep Ocean Direct-Arrival Zones

by Qiulong Yang^1,2, Kunde Yang^1,2,*, Ran Cao^1,2 and Shunli Duan^1,2

¹ School of Marine Science and Technology, Northwestern Polytechnical University, Xi’an 710072, China

² Key Laboratory of Ocean Acoustics and Sensing, Northwestern Polytechnical University, Ministry of Industry and Information Technology, Xi’an 710072, China

Sensors 2018, 18(2), 319; https://doi.org/10.3390/s18020319 - 23 Jan 2018

Cited by 13 | Viewed by 5259

Abstract

Wind-driven and distant shipping noise sources contribute to the total noise field in the deep ocean direct-arrival zones. Wind-driven and distant shipping noise sources may significantly and simultaneously affect the spatial characteristics of the total noise field to some extent. In this work, [...] Read more.

Wind-driven and distant shipping noise sources contribute to the total noise field in the deep ocean direct-arrival zones. Wind-driven and distant shipping noise sources may significantly and simultaneously affect the spatial characteristics of the total noise field to some extent. In this work, a ray approach and parabolic equation solution method were jointly utilized to model the low-frequency ambient noise field in a range-dependent deep ocean environment by considering their calculation accuracy and efficiency in near-field wind-driven and far-field distant shipping noise fields. The reanalysis databases of National Center of Environment Prediction (NCEP) and Volunteer Observation System (VOS) were used to model the ambient noise source intensity and distribution. Spatial vertical directionality and correlation were analyzed in three scenarios that correspond to three wind speed conditions. The noise field was dominated by distant shipping noise sources when the wind speed was less than 3 m/s, and then the spatial vertical directionality and vertical correlation of the total noise field were nearly consistent with those of distant shipping noise field. The total noise field was completely dominated by near field wind generated noise sources when the wind speed was greater than 12 m/s at 150 Hz, and then the spatial vertical correlation coefficient and directionality pattern of the total noise field was approximately consistent with that of the wind-driven noise field. The spatial characteristics of the total noise field for wind speeds between 3 m/s and 12 m/s were the weighted results of wind-driven and distant shipping noise fields. Furthermore, the spatial characteristics of low-frequency ambient noise field were compared with the classical Cron/Sherman deep water noise field coherence function. Simulation results with the described modeling method showed good agreement with the experimental measurement results based on the vertical line array deployed near the bottom in deep ocean direct-arrival zones. Full article

(This article belongs to the Special Issue Advances and Challenges in Underwater Sensor Networks)

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26 pages, 532 KiB

Open AccessArticle

Data-Driven Packet Loss Estimation for Node Healthy Sensing in Decentralized Cluster

by Hangyu Fan, Huandong Wang and Yong Li^*

Department of Electronic Engineering, Tsinghua University, Beijing 100084, China

Sensors 2018, 18(2), 320; https://doi.org/10.3390/s18020320 - 23 Jan 2018

Cited by 1 | Viewed by 3919

Abstract

Decentralized clustering of modern information technology is widely adopted in various fields these years. One of the main reason is the features of high availability and the failure-tolerance which can prevent the entire system form broking down by a failure of a single [...] Read more.

Decentralized clustering of modern information technology is widely adopted in various fields these years. One of the main reason is the features of high availability and the failure-tolerance which can prevent the entire system form broking down by a failure of a single point. Recently, toolkits such as Akka are used by the public commonly to easily build such kind of cluster. However, clusters of such kind that use Gossip as their membership managing protocol and use link failure detecting mechanism to detect link failures cannot deal with the scenario that a node stochastically drops packets and corrupts the member status of the cluster. In this paper, we formulate the problem to be evaluating the link quality and finding a max clique (NP-Complete) in the connectivity graph. We then proposed an algorithm that consists of two models driven by data from application layer to respectively solving these two problems. Through simulations with statistical data and a real-world product, we demonstrate that our algorithm has a good performance. Full article

(This article belongs to the Special Issue Sensor Intelligence Assisted by Data Analytics and Cognitive Computing)

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25 pages, 4121 KiB

Open AccessArticle

Simultaneous Event-Triggered Fault Detection and Estimation for Stochastic Systems Subject to Deception Attacks

by Yunji Li¹, QingE Wu^2,* and Li Peng¹

¹ Key Laboratory of Advanced Process Control for Light Industry (Ministry of Education), Jiangnan University, Wuxi 214122, China

² School of Electrical and Information Engineering, Zhengzhou University of Light Industry, Zhengzhou 450002, China

Sensors 2018, 18(2), 321; https://doi.org/10.3390/s18020321 - 23 Jan 2018

Cited by 23 | Viewed by 4540

Abstract

In this paper, a synthesized design of fault-detection filter and fault estimator is considered for a class of discrete-time stochastic systems in the framework of event-triggered transmission scheme subject to unknown disturbances and deception attacks. A random variable obeying the Bernoulli distribution is [...] Read more.

In this paper, a synthesized design of fault-detection filter and fault estimator is considered for a class of discrete-time stochastic systems in the framework of event-triggered transmission scheme subject to unknown disturbances and deception attacks. A random variable obeying the Bernoulli distribution is employed to characterize the phenomena of the randomly occurring deception attacks. To achieve a fault-detection residual is only sensitive to faults while robust to disturbances, a coordinate transformation approach is exploited. This approach can transform the considered system into two subsystems and the unknown disturbances are removed from one of the subsystems. The gain of fault-detection filter is derived by minimizing an upper bound of filter error covariance. Meanwhile, system faults can be reconstructed by the remote fault estimator. An recursive approach is developed to obtain fault estimator gains as well as guarantee the fault estimator performance. Furthermore, the corresponding event-triggered sensor data transmission scheme is also presented for improving working-life of the wireless sensor node when measurement information are aperiodically transmitted. Finally, a scaled version of an industrial system consisting of local PC, remote estimator and wireless sensor node is used to experimentally evaluate the proposed theoretical results. In particular, a novel fault-alarming strategy is proposed so that the real-time capacity of fault-detection is guaranteed when the event condition is triggered. Full article

(This article belongs to the Special Issue Sensors for Fault Detection)

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11 pages, 808 KiB

Open AccessArticle

A Compact and Low Power RO PUF with High Resilience to the EM Side-Channel Attack and the SVM Modelling Attack of Wireless Sensor Networks

by Yuan Cao¹, Xiaojin Zhao^2,*

, Wenbin Ye², Qingbang Han¹ and Xiaofang Pan³

¹ College of Internet of Things Engineering, Hohai University, Changzhou 213022, China

² College of Electronic Science and Technology, Shenzhen University, Shenzhen 518060, China

³ College of Information Engineering, Shenzhen University, Shenzhen 518060, China

Sensors 2018, 18(2), 322; https://doi.org/10.3390/s18020322 - 23 Jan 2018

Cited by 22 | Viewed by 5950

Abstract

Authentication is a crucial security service for the wireless sensor networks (WSNs) in versatile domains. The deployment of WSN devices in the untrusted open environment and the resource-constrained nature make the on-chip authentication an open challenge. The strong physical unclonable function (PUF) came [...] Read more.

Authentication is a crucial security service for the wireless sensor networks (WSNs) in versatile domains. The deployment of WSN devices in the untrusted open environment and the resource-constrained nature make the on-chip authentication an open challenge. The strong physical unclonable function (PUF) came in handy as light-weight authentication security primitive. In this paper, we present the first ring oscillator (RO) based strong physical unclonable function (PUF) with high resilience to both the electromagnetic (EM) side-channel attack and the support vector machine (SVM) modelling attack. By employing an RO based PUF architecture with the current starved inverter as the delay cell, the oscillation power is significantly reduced to minimize the emitted EM signal, leading to greatly enhanced immunity to the EM side-channel analysis attack. In addition, featuring superior reconfigurability due to the conspicuously simplified circuitries, the proposed implementation is capable of withstanding the SVM modelling attack by generating and comparing a large number of RO frequency pairs. The reported experimental results validate the prototype of a 9-stage RO PUF fabricated using standard 65 nm complementary-metal-oxide-semiconductor (CMOS) process. Operating at the supply voltage of 1.2 V and the frequency of 100 KHz, the fabricated RO PUF occupies a compact silicon area of 250

μ

m

^{2}

and consumes a power as low as 5.16

μ

W per challenge-response pair (CRP). Furthermore, the uniqueness and the worst-case reliability are measured to be 50.17% and 98.30% for the working temperature range of −40∼120

^{\circ}

C and the supply voltage variation of ±2%, respectively. Thus, the proposed PUF is applicable for the low power, low cost and secure WSN communications. Full article

(This article belongs to the Special Issue Security, Trust and Privacy for Sensor Networks)

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14 pages, 3878 KiB

Open AccessArticle

Single-Photon Tracking for High-Speed Vision

by Istvan Gyongy^1,*

, Neale A.W. Dutton²

and Robert K. Henderson¹

¹ School of Engineering, Institute for Integrated Micro and Nano Systems, The University of Edinburgh, Edinburgh EH9 3FF, UK

² STMicroelectronics, Imaging Division, Tanfield, Edinburgh EH3 5DA, UK

Sensors 2018, 18(2), 323; https://doi.org/10.3390/s18020323 - 23 Jan 2018

Cited by 35 | Viewed by 7778

Abstract

Quanta Imager Sensors provide photon detections at high frame rates, with negligible read-out noise, making them ideal for high-speed optical tracking. At the basic level of bit-planes or binary maps of photon detections, objects may present limited detail. However, through motion estimation and [...] Read more.

Quanta Imager Sensors provide photon detections at high frame rates, with negligible read-out noise, making them ideal for high-speed optical tracking. At the basic level of bit-planes or binary maps of photon detections, objects may present limited detail. However, through motion estimation and spatial reassignment of photon detections, the objects can be reconstructed with minimal motion artefacts. We here present the first demonstration of high-speed two-dimensional (2D) tracking and reconstruction of rigid, planar objects with a Quanta Image Sensor, including a demonstration of depth-resolved tracking. Full article

(This article belongs to the Special Issue Special Issue on the 2017 International Image Sensor Workshop (IISW))

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23 pages, 1803 KiB

Open AccessArticle

An Efficient Direct Position Determination Method for Multiple Strictly Noncircular Sources

by Jiexin Yin^1,2

, Ding Wang^1,2,*

and Ying Wu^1,2

¹ National Digital Switching System Engineering and Technology Research Center, Zhengzhou 450002, China

² Zhengzhou Information Science and Technology Institute, Zhengzhou 450002, China

Sensors 2018, 18(2), 324; https://doi.org/10.3390/s18020324 - 23 Jan 2018

Cited by 22 | Viewed by 4304

Abstract

This paper focuses on the localization methods for multiple sources received by widely separated arrays. The conventional two-step methods extract measurement parameters and then estimate the positions from them. In the contrast to the conventional two-step methods, direct position determination (DPD) localizes transmitters [...] Read more.

This paper focuses on the localization methods for multiple sources received by widely separated arrays. The conventional two-step methods extract measurement parameters and then estimate the positions from them. In the contrast to the conventional two-step methods, direct position determination (DPD) localizes transmitters directly from original sensor outputs without estimating intermediate parameters, resulting in higher location accuracy and avoiding the data association. Existing subspace data fusion (SDF)-based DPD developed in the frequency domain is computationally attractive in the presence of multiple transmitters, whereas it does not use special properties of signals. This paper proposes an improved SDF-based DPD algorithm for strictly noncircular sources. We first derive the property of strictly noncircular signals in the frequency domain. On this basis, the observed frequency-domain vectors at all arrays are concatenated and extended by exploiting the noncircular property, producing extended noise subspaces. Fusing the extended noise subspaces of all frequency components and then performing a unitary transformation, we obtain a cost function for each source location, which is formulated as the smallest eigenvalue of a real-valued matrix. To avoid the exhaustive grid search and solve this nonlinear function efficiently, we devise a Newton-type iterative method using matrix Eigen-perturbation theory. Simulation results demonstrate that the proposed DPD using Newton-type iteration substantially reduces the running time, and its performance is superior to other localization methods for both near-field and far-field noncircular sources. Full article

(This article belongs to the Section Physical Sensors)

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28 pages, 1342 KiB

Open AccessArticle

Performance Evaluation of IEEE 802.11ah Networks With High-Throughput Bidirectional Traffic

by Amina Šljivo^1,*

, Dwight Kerkhove¹, Le Tian², Jeroen Famaey²

, Adrian Munteanu³, Ingrid Moerman¹

, Jeroen Hoebeke¹

and Eli De Poorter¹

¹ Department of Information Technology, Ghent University-imec, IDLab, Technologiepark-Zwijnaarde 15, B-9052 Ghent, Belgium

² Department of Mathematics and Computer Science, University of Antwerp-imec, IDLab, Middelheimlaan 1, 2020 Antwerpen, Belgium

³ Department of Electronics and Informatics (ETRO), Vrije Universiteit Brussel, Pleinlaan 2, B-1050 Brussels, Belgium

Sensors 2018, 18(2), 325; https://doi.org/10.3390/s18020325 - 23 Jan 2018

Cited by 61 | Viewed by 7750

Abstract

So far, existing sub-GHz wireless communication technologies focused on low-bandwidth, long-range communication with large numbers of constrained devices. Although these characteristics are fine for many Internet of Things (IoT) applications, more demanding application requirements could not be met and legacy Internet technologies such [...] Read more.

So far, existing sub-GHz wireless communication technologies focused on low-bandwidth, long-range communication with large numbers of constrained devices. Although these characteristics are fine for many Internet of Things (IoT) applications, more demanding application requirements could not be met and legacy Internet technologies such as Transmission Control Protocol/Internet Protocol (TCP/IP) could not be used. This has changed with the advent of the new IEEE 802.11ah Wi-Fi standard, which is much more suitable for reliable bidirectional communication and high-throughput applications over a wide area (up to 1 km). The standard offers great possibilities for network performance optimization through a number of physical- and link-layer configurable features. However, given that the optimal configuration parameters depend on traffic patterns, the standard does not dictate how to determine them. Such a large number of configuration options can lead to sub-optimal or even incorrect configurations. Therefore, we investigated how two key mechanisms, Restricted Access Window (RAW) grouping and Traffic Indication Map (TIM) segmentation, influence scalability, throughput, latency and energy efficiency in the presence of bidirectional TCP/IP traffic. We considered both high-throughput video streaming traffic and large-scale reliable sensing traffic and investigated TCP behavior in both scenarios when the link layer introduces long delays. This article presents the relations between attainable throughput per station and attainable number of stations, as well as the influence of RAW, TIM and TCP parameters on both. We found that up to 20 continuously streaming IP-cameras can be reliably connected via IEEE 802.11ah with a maximum average data rate of 160 kbps, whereas 10 IP-cameras can achieve average data rates of up to 255 kbps over 200 m. Up to 6960 stations transmitting every 60 s can be connected over 1 km with no lost packets. The presented results enable the fine tuning of RAW and TIM parameters for throughput-demanding reliable applications (i.e., video streaming, firmware updates) on one hand, and very dense low-throughput reliable networks with bidirectional traffic on the other hand. Full article

(This article belongs to the Section Sensor Networks)

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17 pages, 5519 KiB

Open AccessArticle

Grasping Force Control for a Robotic Hand by Slip Detection Using Developed Micro Laser Doppler Velocimeter

by Nobutomo Morita^1,*

, Hirofumi Nogami², Eiji Higurashi^3,4 and Renshi Sawada²

¹ Advanced Manufacturing Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), 807-1 Shuku-machi, Tosu, Saga 841-0052, Japan

² Department of Mechanical Engineering, Faculty of Engineering, Kyushu University, 744 Motooka, Nishi-ku, Fukuoka 819-0395, Japan

³ Department of Precision Engineering, School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan

⁴ Research Center for Ubiquitous MEMS and Micro Engineering (UMEMSME), National Institute of Advanced Industrial Science and Technology (AIST), 1-2-1 Namiki, Tsukuba, Ibaraki 305-8564, Japan

Sensors 2018, 18(2), 326; https://doi.org/10.3390/s18020326 - 23 Jan 2018

Cited by 30 | Viewed by 8562

Abstract

The purpose of this paper is to show the feasibility of grasping force control by feeding back signals of the developed micro-laser Doppler velocimeter (μ-LDV) and by discriminating whether a grasped object is slipping or not. LDV is well known as a high [...] Read more.

The purpose of this paper is to show the feasibility of grasping force control by feeding back signals of the developed micro-laser Doppler velocimeter (μ-LDV) and by discriminating whether a grasped object is slipping or not. LDV is well known as a high response surface velocity sensor which can measure various surfaces—such as metal, paper, film, and so on—thus suggesting the potential application of LDV as a slip sensor for grasping various objects. However, the use of LDV as a slip sensor has not yet been reported because the size of LDVs is too large to be installed on a robotic fingertip. We have solved the size problem and enabled the performance of a feasibility test with a few-millimeter-scale LDV referred to as micro-LDV (μ-LDV) by modifying the design which was adopted from MEMS (microelectromechanical systems) fabrication process. In this paper, by applying our developed μ-LDV as a slip sensor, we have successfully demonstrated grasping force control with three target objects—aluminum block, wood block, and white acrylic block—considering that various objects made of these materials can be found in homes and factories, without grasping force feedback. We provide proofs that LDV is a new promising candidate slip sensor for grasping force control to execute target grasping. Full article

(This article belongs to the Special Issue Tactile Sensors and Sensing)

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9 pages, 8396 KiB

Open AccessArticle

Paper-Based Electrochemical Detection of Chlorate

by Lisa C. Shriver-Lake, Dan Zabetakis, Walter J. Dressick

, David A. Stenger and Scott A. Trammell^*

U.S. Naval Research Laboratory, Center for Bio/Molecular Science & Engineering (Code 6900), 4555 Overlook Avenue SW, Washington, DC 20375, USA

Sensors 2018, 18(2), 328; https://doi.org/10.3390/s18020328 - 24 Jan 2018

Cited by 25 | Viewed by 6050

Abstract

We describe the use of a paper-based probe impregnated with a vanadium-containing polyoxometalate anion, [PMo₁₁VO₄₀]⁵⁻, on screen-printed carbon electrodes for the electrochemical determination of chlorate. Cyclic voltammetry (CV) and chronocoulometry were used to characterize the ClO₃ [...] Read more.

We describe the use of a paper-based probe impregnated with a vanadium-containing polyoxometalate anion, [PMo₁₁VO₄₀]⁵⁻, on screen-printed carbon electrodes for the electrochemical determination of chlorate. Cyclic voltammetry (CV) and chronocoulometry were used to characterize the ClO₃⁻ response in a pH = 2.5 solution of 100 mM sodium acetate. A linear CV current response was observed between 0.156 and 1.25 mg/mL with a detection limit of 0.083 mg/mL (S/N > 3). This performance was reproducible using [PMo₁₁VO₄₀]⁵⁻-impregnated filter paper stored under ambient conditions for as long as 8 months prior to use. At high concentration of chlorate, an additional catalytic cathodic peak was seen in the reverse scan of the CVs, which was digitally simulated using a simple model. For chronocoulometry, the charge measured after 5 min gave a linear response from 0.625 to 2.5 mg/mL with a detection limit of 0.31 mg/mL (S/N > 3). In addition, the slope of charge vs. time also gave a linear response. In this case the linear range was from 0.312 to 2.5 mg/mL with a detection limit of 0.15 mg/mL (S/N > 3). Simple assays were conducted using three types of soil, and recovery measurements reported. Full article

(This article belongs to the Special Issue Paper-Based Sensors)

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17 pages, 738 KiB

Open AccessArticle

Service Migration from Cloud to Multi-tier Fog Nodes for Multimedia Dissemination with QoE Support

by Denis Rosário^1,*,†,‡

, Matias Schimuneck^2,‡

, João Camargo^2,‡, Jéferson Nobre^3,‡

, Cristiano Both^4,‡

, Juergen Rochol^2,‡ and Mario Gerla^5,‡

¹ Computer Science Faculty, Federal University of Pará, Belém 66075-110, Brazil

² Institute of Informatics, Federal University of Rio Grande do Sul, Porto Alegre 91501-970, Brazil

³ Polytechnic School, University of Vale do Rio dos Sinos, São Leopoldo 93022-750, Brazil

⁴ Federal University of Health Sciences of Porto Alegre, Porto Alegre 90050-170, Brazil

⁵ Computer Science Department, University of California Los Angeles, Los Angeles, CA 90095-1596, USA

^† Current address: Rua Augusto Corrêa 01, Belém 66075-110, Brazil.

^‡ These authors contributed equally to this work.

Sensors 2018, 18(2), 329; https://doi.org/10.3390/s18020329 - 24 Jan 2018

Cited by 57 | Viewed by 6689

Abstract

A wide range of multimedia services is expected to be offered for mobile users via various wireless access networks. Even the integration of Cloud Computing in such networks does not support an adequate Quality of Experience (QoE) in areas with high demands for [...] Read more.

A wide range of multimedia services is expected to be offered for mobile users via various wireless access networks. Even the integration of Cloud Computing in such networks does not support an adequate Quality of Experience (QoE) in areas with high demands for multimedia contents. Fog computing has been conceptualized to facilitate the deployment of new services that cloud computing cannot provide, particularly those demanding QoE guarantees. These services are provided using fog nodes located at the network edge, which is capable of virtualizing their functions/applications. Service migration from the cloud to fog nodes can be actuated by request patterns and the timing issues. To the best of our knowledge, existing works on fog computing focus on architecture and fog node deployment issues. In this article, we describe the operational impacts and benefits associated with service migration from the cloud to multi-tier fog computing for video distribution with QoE support. Besides that, we perform the evaluation of such service migration of video services. Finally, we present potential research challenges and trends. Full article

(This article belongs to the Special Issue New Paradigms in Data Sensing and Processing for Edge Computing)

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12 pages, 1008 KiB

Open AccessArticle

Secure Transmission of Cooperative Zero-Forcing Jamming for Two-User SWIPT Sensor Networks

by Xuanxuan Tang

, Yueming Cai^*, Wendong Yang, Weiwei Yang, Dechuan Chen and Junquan Hu

College of Communications Engineering, Army Engineering University of PLA, No. 88 Houbiaoying, Qinhuai District, Nanjing 210007, China

Sensors 2018, 18(2), 331; https://doi.org/10.3390/s18020331 - 24 Jan 2018

Cited by 16 | Viewed by 4384

Abstract

In this paper, the secrecy performance of the two-user simultaneous wireless information and power transfer (SWIPT) sensor networks is studied and a novel secure transmission scheme of cooperative zero-forcing (ZF) jamming is proposed. The two sensors opportunistically conduct the SWIPT and cooperative ZF [...] Read more.

In this paper, the secrecy performance of the two-user simultaneous wireless information and power transfer (SWIPT) sensor networks is studied and a novel secure transmission scheme of cooperative zero-forcing (ZF) jamming is proposed. The two sensors opportunistically conduct the SWIPT and cooperative ZF jamming, respectively, where the energy required for jamming the eavesdropper is provided by the SWIPT operation so as to keep the energy balance at the sensors in the long run. By deriving the exact closed-form expressions of the secrecy outage probability and the secrecy throughout, we provide an effective approach to precisely assess the impacts of key parameters on the secrecy performance of the system. It has been shown that the secrecy outage probability is a monotonically increasing function of the growth of secrecy rate (

R_{s}

), and a monotonically decreasing function of the increase of the transmit signal-to-noise ratio (

γ_{S}

), and energy conversion efficiency (

η

). Furthermore, the secrecy throughput could be enhanced when

η

increases, which becomes especially obvious when a large

γ_{S}

is provided. Moreover, the existence of an optimum

R_{s}

maximizing the secrecy throughput is depicted, which also grows with the increase of

γ_{S}

. Simulations are provided for the validation of the analysis. Full article

(This article belongs to the Special Issue Sensor Networks for Collaborative and Secure Internet of Things)

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12 pages, 5809 KiB

Open AccessArticle

Passive Infrared (PIR)-Based Indoor Position Tracking for Smart Homes Using Accessibility Maps and A-Star Algorithm

by Dan Yang¹, Bin Xu^1,*, Kaiyou Rao² and Weihua Sheng³

¹ School of Information Science and Engineering, Northeastern University, Shenyang 110819, China

² School of Physics, Northeast Normal University, Changchun 130000, China

³ School of Electrical and Computer Engineering, Oklahoma State University, Stillwater, OK 74074, USA

Sensors 2018, 18(2), 332; https://doi.org/10.3390/s18020332 - 24 Jan 2018

Cited by 78 | Viewed by 9841

Abstract

Indoor occupants’ positions are significant for smart home service systems, which usually consist of robot service(s), appliance control and other intelligent applications. In this paper, an innovative localization method is proposed for tracking humans’ position in indoor environments based on passive infrared (PIR) [...] Read more.

Indoor occupants’ positions are significant for smart home service systems, which usually consist of robot service(s), appliance control and other intelligent applications. In this paper, an innovative localization method is proposed for tracking humans’ position in indoor environments based on passive infrared (PIR) sensors using an accessibility map and an A-star algorithm, aiming at providing intelligent services. First the accessibility map reflecting the visiting habits of the occupants is established through the integral training with indoor environments and other prior knowledge. Then the PIR sensors, which placement depends on the training results in the accessibility map, get the rough location information. For more precise positioning, the A-start algorithm is used to refine the localization, fused with the accessibility map and the PIR sensor data. Experiments were conducted in a mock apartment testbed. The ground truth data was obtained from an Opti-track system. The results demonstrate that the proposed method is able to track persons in a smart home environment and provide a solution for home robot localization. Full article

(This article belongs to the Special Issue Smart Homes)

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17 pages, 6249 KiB

Open AccessArticle

A Novel Event-Based Incipient Slip Detection Using Dynamic Active-Pixel Vision Sensor (DAVIS)

by Amin Rigi¹

, Fariborz Baghaei Naeini¹

, Dimitrios Makris¹

and Yahya Zweiri^1,2,*

¹ Faculty of Science, Engineering and Computing, Kingston University London, London SW15 3DW, UK

² Robotics Institute, Khalifa University of Science and Technology, P.O. Box 127788, Abu Dhabi 999041, UAE

Sensors 2018, 18(2), 333; https://doi.org/10.3390/s18020333 - 24 Jan 2018

Cited by 49 | Viewed by 8152

Abstract

In this paper, a novel approach to detect incipient slip based on the contact area between a transparent silicone medium and different objects using a neuromorphic event-based vision sensor (DAVIS) is proposed. Event-based algorithms are developed to detect incipient slip, slip, stress distribution [...] Read more.

In this paper, a novel approach to detect incipient slip based on the contact area between a transparent silicone medium and different objects using a neuromorphic event-based vision sensor (DAVIS) is proposed. Event-based algorithms are developed to detect incipient slip, slip, stress distribution and object vibration. Thirty-seven experiments were performed on five objects with different sizes, shapes, materials and weights to compare precision and response time of the proposed approach. The proposed approach is validated by using a high speed constitutional camera (1000 FPS). The results indicate that the sensor can detect incipient slippage with an average of 44.1 ms latency in unstructured environment for various objects. It is worth mentioning that the experiments were conducted in an uncontrolled experimental environment, therefore adding high noise levels that affected results significantly. However, eleven of the experiments had a detection latency below 10 ms which shows the capability of this method. The results are very promising and show a high potential of the sensor being used for manipulation applications especially in dynamic environments. Full article

(This article belongs to the Special Issue Smart Sensors for Mechatronic and Robotic Systems)

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21 pages, 4925 KiB

Open AccessArticle

Ship Detection in Gaofen-3 SAR Images Based on Sea Clutter Distribution Analysis and Deep Convolutional Neural Network

by Quanzhi An^1,2,3

, Zongxu Pan^2,3,*

and Hongjian You^1,2,3

¹ School of Electronic, Electrical and Communication Engineering, University of Chinese Academy of Sciences, Huairou District, Beijing 101408, China

² Institute of Electronics, Chinese Academy of Sciences, Beijing 100190, China

³ Key Laboratory of Technology in Geo-spatial Information Processing and Application System, Beijing 100190, China

Sensors 2018, 18(2), 334; https://doi.org/10.3390/s18020334 - 24 Jan 2018

Cited by 111 | Viewed by 7880

Abstract

Target detection is one of the important applications in the field of remote sensing. The Gaofen-3 (GF-3) Synthetic Aperture Radar (SAR) satellite launched by China is a powerful tool for maritime monitoring. This work aims at detecting ships in GF-3 SAR images using [...] Read more.

Target detection is one of the important applications in the field of remote sensing. The Gaofen-3 (GF-3) Synthetic Aperture Radar (SAR) satellite launched by China is a powerful tool for maritime monitoring. This work aims at detecting ships in GF-3 SAR images using a new land masking strategy, the appropriate model for sea clutter and a neural network as the discrimination scheme. Firstly, the fully convolutional network (FCN) is applied to separate the sea from the land. Then, by analyzing the sea clutter distribution in GF-3 SAR images, we choose the probability distribution model of Constant False Alarm Rate (CFAR) detector from K-distribution, Gamma distribution and Rayleigh distribution based on a tradeoff between the sea clutter modeling accuracy and the computational complexity. Furthermore, in order to better implement CFAR detection, we also use truncated statistic (TS) as a preprocessing scheme and iterative censoring scheme (ICS) for boosting the performance of detector. Finally, we employ a neural network to re-examine the results as the discrimination stage. Experiment results on three GF-3 SAR images verify the effectiveness and efficiency of this approach. Full article

(This article belongs to the Special Issue First Experiences with Chinese Gaofen-3 SAR Sensor)

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18 pages, 4636 KiB

Open AccessArticle

An EEG-Based Person Authentication System with Open-Set Capability Combining Eye Blinking Signals

by Qunjian Wu¹, Ying Zeng^1,2, Chi Zhang¹, Li Tong¹ and Bin Yan^1,*

¹ China National Digital Switching System Engineering and Technological Research Center, Zhengzhou 450001, China

² Key Laboratory for NeuroInformation of Ministry of Education, School of Life Science and Technology, University of Electronic Science and Technology of China, Chengdu 610000, China

Sensors 2018, 18(2), 335; https://doi.org/10.3390/s18020335 - 24 Jan 2018

Cited by 67 | Viewed by 7222

Abstract

The electroencephalogram (EEG) signal represents a subject’s specific brain activity patterns and is considered as an ideal biometric given its superior forgery prevention. However, the accuracy and stability of the current EEG-based person authentication systems are still unsatisfactory in practical application. In this [...] Read more.

The electroencephalogram (EEG) signal represents a subject’s specific brain activity patterns and is considered as an ideal biometric given its superior forgery prevention. However, the accuracy and stability of the current EEG-based person authentication systems are still unsatisfactory in practical application. In this paper, a multi-task EEG-based person authentication system combining eye blinking is proposed, which can achieve high precision and robustness. Firstly, we design a novel EEG-based biometric evoked paradigm using self- or non-self-face rapid serial visual presentation (RSVP). The designed paradigm could obtain a distinct and stable biometric trait from EEG with a lower time cost. Secondly, the event-related potential (ERP) features and morphological features are extracted from EEG signals and eye blinking signals, respectively. Thirdly, convolutional neural network and back propagation neural network are severally designed to gain the score estimation of EEG features and eye blinking features. Finally, a score fusion technology based on least square method is proposed to get the final estimation score. The performance of multi-task authentication system is improved significantly compared to the system using EEG only, with an increasing average accuracy from 92.4% to 97.6%. Moreover, open-set authentication tests for additional imposters and permanence tests for users are conducted to simulate the practical scenarios, which have never been employed in previous EEG-based person authentication systems. A mean false accepted rate (FAR) of 3.90% and a mean false rejected rate (FRR) of 3.87% are accomplished in open-set authentication tests and permanence tests, respectively, which illustrate the open-set authentication and permanence capability of our systems. Full article

(This article belongs to the Special Issue Sensor Signal and Information Processing)

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16 pages, 7160 KiB

Open AccessArticle

Sensing Performance Analysis on Quartz Tuning Fork-Probe at the High Order Vibration Mode for Multi-Frequency Scanning Probe Microscopy

by Xiaofei Zhang^1,2

, Fengli Gao³ and Xide Li^1,2,*

¹ Department of Engineering Mechanics, AML, Tsinghua University, Beijing 100084, China

² Center for Nano and Micro Mechanics, Tsinghua University, Beijing 100084, China

³ Institute of Microelectronics of Chinese Academy of Sciences, Beijing 100029, China

Sensors 2018, 18(2), 336; https://doi.org/10.3390/s18020336 - 24 Jan 2018

Cited by 10 | Viewed by 5553

Abstract

Multi-frequency scanning near-field optical microscopy, based on a quartz tuning fork-probe (QTF-p) sensor using the first two orders of in-plane bending symmetrical vibration modes, has recently been developed. This method can simultaneously achieve positional feedback (based on the 1st in-plane mode called the [...] Read more.

Multi-frequency scanning near-field optical microscopy, based on a quartz tuning fork-probe (QTF-p) sensor using the first two orders of in-plane bending symmetrical vibration modes, has recently been developed. This method can simultaneously achieve positional feedback (based on the 1st in-plane mode called the low mode) and detect near-field optically induced forces (based on the 2nd in-plane mode called the high mode). Particularly, the high mode sensing performance of the QTF-p is an important issue for characterizing the tip-sample interactions and achieving higher resolution microscopic imaging but the related researches are insufficient. Here, we investigate the vibration performance of QTF-p at high mode based on the experiment and finite element method. The frequency spectrum characteristics are obtained by our homemade laser Doppler vibrometer system. The effects of the properties of the connecting glue layer and the probe features on the dynamic response of the QTF-p sensor at the high mode are investigated for optimization design. Finally, compared with the low mode, an obvious improvement of quality factor, of almost 50%, is obtained at the high mode. Meanwhile, the QTF-p sensor has a high force sensing sensitivity and a large sensing range at the high mode, indicating a broad application prospect for force sensing. Full article

(This article belongs to the Special Issue Piezoelectric Micro- and Nano-Devices)

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13 pages, 2103 KiB

Open AccessArticle

New Fault Recognition Method for Rotary Machinery Based on Information Entropy and a Probabilistic Neural Network

by Quansheng Jiang^1,2,*

, Yehu Shen^1,2, Hua Li^1,2 and Fengyu Xu³

¹ School of Mechanical Engineering, Suzhou University of Science and Technology, Suzhou 215009, China

² Suzhou Key Laboratory of Precision and Efficient Machining Technology, Suzhou 215009, China

³ College of Automation, Nanjing University of Posts and Telecommunications, Nanjing 210003, China

Sensors 2018, 18(2), 337; https://doi.org/10.3390/s18020337 - 24 Jan 2018

Cited by 50 | Viewed by 4765

Abstract

Feature recognition and fault diagnosis plays an important role in equipment safety and stable operation of rotating machinery. In order to cope with the complexity problem of the vibration signal of rotating machinery, a feature fusion model based on information entropy and probabilistic [...] Read more.

Feature recognition and fault diagnosis plays an important role in equipment safety and stable operation of rotating machinery. In order to cope with the complexity problem of the vibration signal of rotating machinery, a feature fusion model based on information entropy and probabilistic neural network is proposed in this paper. The new method first uses information entropy theory to extract three kinds of characteristics entropy in vibration signals, namely, singular spectrum entropy, power spectrum entropy, and approximate entropy. Then the feature fusion model is constructed to classify and diagnose the fault signals. The proposed approach can combine comprehensive information from different aspects and is more sensitive to the fault features. The experimental results on simulated fault signals verified better performances of our proposed approach. In real two-span rotor data, the fault detection accuracy of the new method is more than 10% higher compared with the methods using three kinds of information entropy separately. The new approach is proved to be an effective fault recognition method for rotating machinery. Full article

(This article belongs to the Special Issue Sensors for Fault Detection)

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16 pages, 6098 KiB

Open AccessArticle

Monitoring of Bridges by a Laser Pointer: Dynamic Measurement of Support Rotations and Elastic Line Displacements: Methodology and First Test

by Serena Artese^1,*, Vladimiro Achilli² and Raffaele Zinno³

¹ Department of Civil Engineering, University of Calabria, Via Bucci cubo 45B, 87036 Rende, Italy

² Department of Civil, Environmental and Architectural Engineering, Via Marzolo, 9, 35131 Padova, Italy

³ Department of Informatics, Modeling, Electronic and System Engineering, University of Calabria, Via P. Bucci cubo 42C, 87036 Rende, Italy

Sensors 2018, 18(2), 338; https://doi.org/10.3390/s18020338 - 25 Jan 2018

Cited by 29 | Viewed by 5261

Abstract

Deck inclination and vertical displacements are among the most important technical parameters to evaluate the health status of a bridge and to verify its bearing capacity. Several methods, both conventional and innovative, are used for structural rotations and displacement monitoring; however, none of [...] Read more.

Deck inclination and vertical displacements are among the most important technical parameters to evaluate the health status of a bridge and to verify its bearing capacity. Several methods, both conventional and innovative, are used for structural rotations and displacement monitoring; however, none of these allow, at the same time, precision, automation, static and dynamic monitoring without using high cost instrumentation. The proposed system uses a common laser pointer and image processing. The elastic line inclination is measured by analyzing the single frames of an HD video of the laser beam imprint projected on a flat target. For the image processing, a code was developed in Matlab^® that provides instantaneous rotation and displacement of a bridge, charged by a mobile load. An important feature is the synchronization of the load positioning, obtained by a GNSS receiver or by a video. After the calibration procedures, a test was carried out during the movements of a heavy truck maneuvering on a bridge. Data acquisition synchronization allowed us to relate the position of the truck on the deck to inclination and displacements. The inclination of the elastic line at the support was obtained with a precision of 0.01 mrad. The results demonstrate the suitability of the method for dynamic load tests, and the control and monitoring of bridges. Full article

(This article belongs to the Section Remote Sensors)

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15 pages, 2152 KiB

Open AccessArticle

Low Power Operation of Temperature-Modulated Metal Oxide Semiconductor Gas Sensors

by Javier Burgués^1,2,*

and Santiago Marco^1,2

¹ Department of Electronic and Biomedical Engineering, Universitat de Barcelona, Marti i Franqués 1, 08028 Barcelona, Spain

² Signal and Information Processing for Sensing Systems, Institute for Bioengineering of Catalonia (IBEC), The Barcelona Institute of Science and Technology, Baldiri Reixac 10-12, 08028 Barcelona, Spain

Sensors 2018, 18(2), 339; https://doi.org/10.3390/s18020339 - 25 Jan 2018

Cited by 94 | Viewed by 15196

Abstract

Mobile applications based on gas sensing present new opportunities for low-cost air quality monitoring, safety, and healthcare. Metal oxide semiconductor (MOX) gas sensors represent the most prominent technology for integration into portable devices, such as smartphones and wearables. Traditionally, MOX sensors have been [...] Read more.

Mobile applications based on gas sensing present new opportunities for low-cost air quality monitoring, safety, and healthcare. Metal oxide semiconductor (MOX) gas sensors represent the most prominent technology for integration into portable devices, such as smartphones and wearables. Traditionally, MOX sensors have been continuously powered to increase the stability of the sensing layer. However, continuous power is not feasible in many battery-operated applications due to power consumption limitations or the intended intermittent device operation. This work benchmarks two low-power, duty-cycling, and on-demand modes against the continuous power one. The duty-cycling mode periodically turns the sensors on and off and represents a trade-off between power consumption and stability. On-demand operation achieves the lowest power consumption by powering the sensors only while taking a measurement. Twelve thermally modulated SB-500-12 (FIS Inc. Jacksonville, FL, USA) sensors were exposed to low concentrations of carbon monoxide (0–9 ppm) with environmental conditions, such as ambient humidity (15–75% relative humidity) and temperature (21–27 °C), varying within the indicated ranges. Partial Least Squares (PLS) models were built using calibration data, and the prediction error in external validation samples was evaluated during the two weeks following calibration. We found that on-demand operation produced a deformation of the sensor conductance patterns, which led to an increase in the prediction error by almost a factor of 5 as compared to continuous operation (2.2 versus 0.45 ppm). Applying a 10% duty-cycling operation of 10-min periods reduced this prediction error to a factor of 2 (0.9 versus 0.45 ppm). The proposed duty-cycling powering scheme saved up to 90% energy as compared to the continuous operating mode. This low-power mode may be advantageous for applications that do not require continuous and periodic measurements, and which can tolerate slightly higher prediction errors. Full article

(This article belongs to the Special Issue Signal and Information Processing in Chemical Sensing)

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11 pages, 6126 KiB

Open AccessArticle

Fabrications and Performance of Wireless LC Pressure Sensors through LTCC Technology

by Lin Lin^1,2, Mingsheng Ma^1,*

, Faqiang Zhang¹, Feng Liu¹, Zhifu Liu^1,* and Yongxiang Li^1,3

¹ CAS Key Laboratory of Inorganic Functional Materials and Devices, Shanghai Institute of Ceramics, 1295 Dingxi Road, Shanghai 200050, China

² University of Chinese Academy of Sciences, 19 Yuquan Road, Beijing 100049, China

³ School of Engineering, RMIT University, Melbourne, VIC 3001, Australia

Sensors 2018, 18(2), 340; https://doi.org/10.3390/s18020340 - 25 Jan 2018

Cited by 18 | Viewed by 6454

Abstract

This paper presents a kind of passive wireless pressure sensor comprised of a planar spiral inductor and a cavity parallel plate capacitor fabricated through low-temperature co-fired ceramic (LTCC) technology. The LTCC material with a low Young’s modulus of ~65 GPa prepared by our [...] Read more.

This paper presents a kind of passive wireless pressure sensor comprised of a planar spiral inductor and a cavity parallel plate capacitor fabricated through low-temperature co-fired ceramic (LTCC) technology. The LTCC material with a low Young’s modulus of ~65 GPa prepared by our laboratory was used to obtain high sensitivity. A three-step lamination process was applied to construct a high quality cavity structure without using any sacrificial materials. The effects of the thickness of the sensing membranes on the sensitivity and detection range of the pressure sensors were investigated. The sensor with a 148 μm sensing membrane showed the highest sensitivity of 3.76 kHz/kPa, and the sensor with a 432 μm sensing membrane presented a high detection limit of 2660 kPa. The tunable sensitivity and detection limit of the wireless pressure sensors can meet the requirements of different scenes. Full article

(This article belongs to the Section Physical Sensors)

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24 pages, 1237 KiB

Open AccessArticle

A Novel Loss Recovery and Tracking Scheme for Maneuvering Target in Hybrid WSNs

by Hanwang Qian^1,2

, Pengcheng Fu^1,2

, Baoqing Li¹

, Jianpo Liu¹ and Xiaobing Yuan^1,*

¹ Science and Technology on Microsystem Laboratory, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 201800, China

² University of Chinese Academy of Sciences, Beijing 100049, China

Sensors 2018, 18(2), 341; https://doi.org/10.3390/s18020341 - 25 Jan 2018

Cited by 15 | Viewed by 3928

Abstract

Tracking a mobile target, which aims to timely monitor the invasion of specific target, is one of the most prominent applications in wireless sensor networks (WSNs). Traditional tracking methods in WSNs only based on static sensor nodes (SNs) have several critical problems. For [...] Read more.

Tracking a mobile target, which aims to timely monitor the invasion of specific target, is one of the most prominent applications in wireless sensor networks (WSNs). Traditional tracking methods in WSNs only based on static sensor nodes (SNs) have several critical problems. For example, to void the loss of mobile target, many SNs must be active to track the target in all possible directions, resulting in excessive energy consumption. Additionally, when entering coverage holes in the monitoring area, the mobile target may be missing and then its state is unknown during this period. To tackle these problems, in this paper, a few mobile sensor nodes (MNs) are introduced to cooperate with SNs to form a hybrid WSN due to their stronger abilities and less constrained energy. Then, we propose a valid target tracking scheme for hybrid WSNs to dynamically schedule the MNs and SNs. Moreover, a novel loss recovery mechanism is proposed to find the lost target and recover the tracking with fewer SNs awakened. Furthermore, to improve the robustness and accuracy of the recovery mechanism, an adaptive unscented Kalman filter (AUKF) algorithm is raised to dynamically adjust the process noise covariance. Simulation results demonstrate that our tracking scheme for maneuvering target in hybrid WSNs can not only track the target effectively even if the target is lost but also maintain an excellent accuracy and robustness with fewer activated nodes. Full article

(This article belongs to the Section Sensor Networks)

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26 pages, 7839 KiB

Open AccessArticle

Preliminary Results of a New Auxiliary Mechatronic Near-Field Radar System to 3D Mammography for Early Detection of Breast Cancer

by Ashkan Ghanbarzadeh Dagheyan¹

, Ali Molaei², Richard Obermeier², Andrew Westwood³, Aida Martinez⁴ and Jose Angel Martinez Lorenzo^1,2,*

¹ Mechanical Engineering Department, Northeastern University, Boston, MA 02115, USA

² Electrical Engineering Department, Northeastern University, Boston, MA 02115, USA

³ Research Applications Specialist and Quantum Engineering Architect, Keysight Technologies, 65 Alsun Drive, Hollis, NH 03049, USA

⁴ Harvard Vanguard, Wellesley, MA 02481, USA

Sensors 2018, 18(2), 342; https://doi.org/10.3390/s18020342 - 25 Jan 2018

Cited by 2 | Viewed by 6272

Abstract

Accurate and early detection of breast cancer is of high importance, as it is directly associated with the patients’ overall well-being during treatment and their chances of survival. Uncertainties in current breast imaging methods can potentially cause two main problems: (1) missing newly [...] Read more.

Accurate and early detection of breast cancer is of high importance, as it is directly associated with the patients’ overall well-being during treatment and their chances of survival. Uncertainties in current breast imaging methods can potentially cause two main problems: (1) missing newly formed or small tumors; and (2) false alarms, which could be a source of stress for patients. A recent study at the Massachusetts General Hospital (MGH) indicates that using Digital Breast Tomosynthesis (DBT) can reduce the number of false alarms, when compared to conventional mammography. Despite the image quality enhancement DBT provides, the accurate detection of cancerous masses is still limited by low radiological contrast (about 1%) between the fibro-glandular tissue and affected tissue at X-ray frequencies. In a lower frequency region, at microwave frequencies, the contrast is comparatively higher (about 10%) between the aforementioned tissues; yet, microwave imaging suffers from low spatial resolution. This work reviews conventional X-ray breast imaging and describes the preliminary results of a novel near-field radar imaging mechatronic system (NRIMS) that can be fused with the DBT, in a co-registered fashion, to combine the advantages of both modalities. The NRIMS consists of two antipodal Vivaldi antennas, an XY positioner, and an ethanol container, all of which are particularly designed based on the DBT physical specifications. In this paper, the independent performance of the NRIMS is assessed by (1) imaging a bearing ball immersed in sunflower oil and (2) computing the heat Specific Absorption Rate (SAR) due to the electromagnetic power transmitted into the breast. The preliminary results demonstrate that the system is capable of generating images of the ball. Furthermore, the SAR results show that the system complies with the standards set for human trials. As a result, a configuration based on this design might be suitable for use in realistic clinical applications. Full article

(This article belongs to the Section State-of-the-Art Sensors Technologies)

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12 pages, 3180 KiB

Open AccessArticle

Dual-Mode Gas Sensor Composed of a Silicon Nanoribbon Field Effect Transistor and a Bulk Acoustic Wave Resonator: A Case Study in Freons

by Ye Chang¹, Zhipeng Hui², Xiayu Wang¹, Hemi Qu^1,*, Wei Pang¹ and Xuexin Duan^1,*

¹ State Key Laboratory of Precision Measuring Technology & Instruments, Tianjin University, Tianjin 300072, China

² China Marine Development and Research Center (CMDRC), Beijing 100049, China

Sensors 2018, 18(2), 343; https://doi.org/10.3390/s18020343 - 25 Jan 2018

Cited by 13 | Viewed by 5869

Abstract

In this paper, we develop a novel dual-mode gas sensor system which comprises a silicon nanoribbon field effect transistor (Si-NR FET) and a film bulk acoustic resonator (FBAR). We investigate their sensing characteristics using polar and nonpolar organic compounds, and demonstrate that polarity [...] Read more.

In this paper, we develop a novel dual-mode gas sensor system which comprises a silicon nanoribbon field effect transistor (Si-NR FET) and a film bulk acoustic resonator (FBAR). We investigate their sensing characteristics using polar and nonpolar organic compounds, and demonstrate that polarity has a significant effect on the response of the Si-NR FET sensor, and only a minor effect on the FBAR sensor. In this dual-mode system, qualitative discrimination can be achieved by analyzing polarity with the Si-NR FET and quantitative concentration information can be obtained using a polymer-coated FBAR with a detection limit at the ppm level. The complementary performance of the sensing elements provides higher analytical efficiency. Additionally, a dual mixture of two types of freons (CFC-113 and HCFC-141b) is further analyzed with the dual-mode gas sensor. Owing to the small size and complementary metal-oxide semiconductor (CMOS)-compatibility of the system, the dual-mode gas sensor shows potential as a portable integrated sensing system for the analysis of gas mixtures in the future. Full article

(This article belongs to the Section Chemical Sensors)

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17 pages, 1849 KiB

Open AccessArticle

A Novel Noncircular MUSIC Algorithm Based on the Concept of the Difference and Sum Coarray

by Zhenhong Chen, Yingtao Ding, Shiwei Ren

and Zhiming Chen^*

School of Information and Electronics, Beijing Institute of Technology, 5 South Zhongguancun Street, Haidian District, Beijing 100081, China

Sensors 2018, 18(2), 344; https://doi.org/10.3390/s18020344 - 25 Jan 2018

Cited by 39 | Viewed by 3589

Abstract

In this paper, we propose a vectorized noncircular MUSIC (VNCM) algorithm based on the concept of the coarray, which can construct the difference and sum (diff–sum) coarray, for direction finding of the noncircular (NC) quasi-stationary sources. Utilizing both the NC property and the [...] Read more.

In this paper, we propose a vectorized noncircular MUSIC (VNCM) algorithm based on the concept of the coarray, which can construct the difference and sum (diff–sum) coarray, for direction finding of the noncircular (NC) quasi-stationary sources. Utilizing both the NC property and the concept of the Khatri–Rao product, the proposed method can be applied to not only the ULA but also sparse arrays. In addition, we utilize the quasi-stationary characteristic instead of the spatial smoothing method to solve the coherent issue generated by the Khatri–Rao product operation so that the available degree of freedom (DOF) of the constructed virtual array will not be reduced by half. Compared with the traditional NC virtual array obtained in the NC MUSIC method, the diff–sum coarray achieves a higher number of DOFs as it comprises both the difference set and the sum set. Due to the complementarity between the difference set and the sum set for the coprime array, we choose the coprime array with multiperiod subarrays (CAMpS) as the array model and summarize the properties of the corresponding diff–sum coarray. Furthermore, we develop a diff–sum coprime array with multiperiod subarrays (DsCAMpS) whose diff–sum coarray has a higher DOF. Simulation results validate the effectiveness of the proposed method and the high DOF of the diff–sum coarray. Full article

(This article belongs to the Section Physical Sensors)

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12 pages, 4386 KiB

Open AccessArticle

Three-Dimensional Blood Vessel Model with Temperature-Indicating Function for Evaluation of Thermal Damage during Surgery

by Takeshi Hayakawa^*

, Hisataka Maruyama

, Takafumi Watanabe and Fumihito Arai

Room 310, Aerospace Mechanical Engineering Research Building 3F, Department of Micro-Nano Mechanical Science & Engineering, Nagoya University, Furo-cho, Chikusa-ku, Aichi-Pref., Nagoya-shi 464-8603, Japan

Sensors 2018, 18(2), 345; https://doi.org/10.3390/s18020345 - 25 Jan 2018

Cited by 3 | Viewed by 5112

Abstract

Surgical simulators have recently attracted attention because they enable the evaluation of the surgical skills of medical doctors and the performance of medical devices. However, thermal damage to the human body during surgery is difficult to evaluate using conventional surgical simulators. In this [...] Read more.

Surgical simulators have recently attracted attention because they enable the evaluation of the surgical skills of medical doctors and the performance of medical devices. However, thermal damage to the human body during surgery is difficult to evaluate using conventional surgical simulators. In this study, we propose a functional surgical model with a temperature-indicating function for the evaluation of thermal damage during surgery. The simulator is made of a composite material of polydimethylsiloxane and a thermochromic dye, which produces an irreversible color change as the temperature increases. Using this material, we fabricated a three-dimensional blood vessel model using the lost-wax process. We succeeded in fabricating a renal vessel model for simulation of catheter ablation. Increases in the temperature of the materials can be measured by image analysis of their color change. The maximum measurement error of the temperature was approximately −1.6 °C/+2.4 °C within the range of 60 °C to 100 °C. Full article

(This article belongs to the Special Issue Non-Invasive Biomedical Sensors)

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13 pages, 10675 KiB

Open AccessArticle

A Novel Single-Axis MEMS Tilt Sensor with a High Sensitivity in the Measurement Range from 0^∘ to 360^∘

by Shudong Wang, Xueyong Wei^*

, Yinsheng Weng, Yulong Zhao and Zhuangde Jiang

State Key Laboratory for Manufacturing Systems Engineering, Xi’an Jiaotong University, Xi’an 710054, China

Sensors 2018, 18(2), 346; https://doi.org/10.3390/s18020346 - 25 Jan 2018

Cited by 16 | Viewed by 6517

Abstract

In this paper, a novel single-axis MEMS tilt sensor is presented. It contains a hexagonal proof mass, six micro-lever force amplifiers and three double-ended-tuning fork (DETF) resonant strain gauges. The proof mass is placed in the center with the micro-levers and the DETFs [...] Read more.

In this paper, a novel single-axis MEMS tilt sensor is presented. It contains a hexagonal proof mass, six micro-lever force amplifiers and three double-ended-tuning fork (DETF) resonant strain gauges. The proof mass is placed in the center with the micro-levers and the DETFs radially arrayed around. The variation of gravity acceleration applied on the proof mass will result in frequency shifts of the DETFs. Angular tilt can be got by analyzing the frequency outputs. The structural design of the tilt sensor is optimized by finite element simulation and the device is microfabricated using a silicon-on-insulator process, followed by open-loop and closed-loop characterizations. Results show that the scale factor of such sensor is at least 11.53 Hz/degree. Minimum Allan deviation of the DETF oscillator is 220 ppb (parts per billion) of the resonant frequency for an 5 s integration time. Resolution of the tilt sensor is

0.002^{\circ}

in the whole measurement range from

0^{\circ}

to

360^{\circ}

. Full article

(This article belongs to the Special Issue Smart Sensors for Mechatronic and Robotic Systems)

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18 pages, 1590 KiB

Open AccessArticle

VLSI Design of Trusted Virtual Sensors

by Macarena C. Martínez-Rodríguez^*

, Miguel A. Prada-Delgado

, Piedad Brox

and Iluminada Baturone

Instituto de Microelectrónica de Sevilla IMSE-CNM, CSIC, Universidad de Sevilla, Américo Vespucio, 41092 Sevilla, Spain

Sensors 2018, 18(2), 347; https://doi.org/10.3390/s18020347 - 25 Jan 2018

Cited by 7 | Viewed by 6808

Abstract

This work presents a Very Large Scale Integration (VLSI) design of trusted virtual sensors providing a minimum unitary cost and very good figures of size, speed and power consumption. The sensed variable is estimated by a virtual sensor based on a configurable and [...] Read more.

This work presents a Very Large Scale Integration (VLSI) design of trusted virtual sensors providing a minimum unitary cost and very good figures of size, speed and power consumption. The sensed variable is estimated by a virtual sensor based on a configurable and programmable PieceWise-Affine hyper-Rectangular (PWAR) model. An algorithm is presented to find the best values of the programmable parameters given a set of (empirical or simulated) input-output data. The VLSI design of the trusted virtual sensor uses the fast authenticated encryption algorithm, AEGIS, to ensure the integrity of the provided virtual measurement and to encrypt it, and a Physical Unclonable Function (PUF) based on a Static Random Access Memory (SRAM) to ensure the integrity of the sensor itself. Implementation results of a prototype designed in a 90-nm Complementary Metal Oxide Semiconductor (CMOS) technology show that the active silicon area of the trusted virtual sensor is 0.86 mm

^{2}

and its power consumption when trusted sensing at 50 MHz is 7.12 mW. The maximum operation frequency is 85 MHz, which allows response times lower than 0.25

μ

s. As application example, the designed prototype was programmed to estimate the yaw rate in a vehicle, obtaining root mean square errors lower than 1.1%. Experimental results of the employed PUF show the robustness of the trusted sensing against aging and variations of the operation conditions, namely, temperature and power supply voltage (final value as well as ramp-up time). Full article

(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Spain 2017)

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15 pages, 3595 KiB

Open AccessArticle

High Frequency Data Acquisition System for Modelling the Impact of Visitors on the Thermo-Hygrometric Conditions of Archaeological Sites: A Casa di Diana (Ostia Antica, Italy) Case Study

by Paloma Merello¹, Fernando-Juan García-Diego^2,*

, Pedro Beltrán² and Claudia Scatigno³

¹ Department of Accounting, University of Valencia, Av. de los Naranjos s/n, 46071 Valencia, Spain

² Department of Applied Physics, Universitat Politècnica de València, Av. de los Naranjos s/n, 46022 Valencia, Spain

³ Nanoscience & Nanotechnology & Innovative Instrumentation (NAST Centre), University of Rome “Tor Vergata”, Via della Ricerca Scientifica 1, 00133 Rome, Italy

Sensors 2018, 18(2), 348; https://doi.org/10.3390/s18020348 - 25 Jan 2018

Cited by 13 | Viewed by 4625

Abstract

The characterization of the microclimatic conditions is fundamental for the preventive conservation of archaeological sites. In this context, the identification of the factors that influence the thermo-hygrometric equilibrium is key to determine the causes of cultural heritage deterioration. In this work, a characterization [...] Read more.

The characterization of the microclimatic conditions is fundamental for the preventive conservation of archaeological sites. In this context, the identification of the factors that influence the thermo-hygrometric equilibrium is key to determine the causes of cultural heritage deterioration. In this work, a characterization of the thermo-hygrometric conditions of Casa di Diana (Ostia Antica, Italy) is carried out analyzing the data of temperature and relative humidity recorded by a system of sensors with high monitoring frequency. Sensors are installed in parallel, calibrated and synchronized with a microcontroller. A data set of 793,620 data, arranged in a matrix with 66,135 rows and 12 columns, was used. Furthermore, the influence of human impact (visitors) is evaluated through a multiple linear regression model and a logistic regression model. The visitors do not affect the environmental humidity as it is very high and constant all the year. The results show a significant influence of the visitors in the upset of the thermal balance. When a tourist guide takes place, the probability that the hourly temperature variation reaches values higher than its monthly average is 10.64 times higher than it remains equal or less to its monthly average. The analysis of the regression residuals shows the influence of outdoor climatic variables in the thermal balance, such as solar radiation or ventilation. Full article

(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Spain 2017)

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12 pages, 7218 KiB

Open AccessArticle

Development of Low Parasitic Light Sensitivity and Low Dark Current 2.8 μm Global Shutter Pixel

by Toshifumi Yokoyama^1,*, Masafumi Tsutsui¹, Masakatsu Suzuki¹, Yoshiaki Nishi¹, Ikuo Mizuno¹ and Assaf Lahav²

¹ TowerJazz Panasonic Semiconductor Co., Ltd., 800 Higashiyama, Uozu City, Toyama 937-8585, Japan

² Tower Semiconductors, Migdal Haemeq 23105, Israel

Sensors 2018, 18(2), 349; https://doi.org/10.3390/s18020349 - 25 Jan 2018

Cited by 12 | Viewed by 9623

Abstract

We developed a low parasitic light sensitivity (PLS) and low dark current 2.8 μm global shutter pixel. We propose a new inner lens design concept to realize both low PLS and high quantum efficiency (QE). 1/PLS is 7700 and QE is 62% at [...] Read more.

We developed a low parasitic light sensitivity (PLS) and low dark current 2.8 μm global shutter pixel. We propose a new inner lens design concept to realize both low PLS and high quantum efficiency (QE). 1/PLS is 7700 and QE is 62% at a wavelength of 530 nm. We also propose a new storage-gate based memory node for low dark current. P-type implants and negative gate biasing are introduced to suppress dark current at the surface of the memory node. This memory node structure shows the world smallest dark current of 9.5 e⁻/s at 60 °C. Full article

(This article belongs to the Special Issue Special Issue on the 2017 International Image Sensor Workshop (IISW))

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11 pages, 1922 KiB

Open AccessArticle

Control of the Singular Points Location for Miniature Switches with Magnetically Driven Contacts

by Xin Wang^1,*, Marcin Habrych²

, Bogdan Miedzinski³ and Julian Wosik³

¹ Beijing Key Laboratory of Optimized Design for Modern Agricultural Equipment, College of Engineering, China Agricultural University (East Campus), 100083 Beijing, China

² Department of Electrical Power Engineering, Wroclaw University of Science and Technology, Wybrzeze Wyspianskiego 27, 50-370 Wroclaw, Poland

³ Institute of Innovative Technologies EMAG, Leopolda 31, 40-189 Katowice, Poland

Sensors 2018, 18(2), 350; https://doi.org/10.3390/s18020350 - 26 Jan 2018

Cited by 2 | Viewed by 3750

Abstract

This paper presents and discusses usefulness and possibility of control of the singular points location of a driving magnetic field under as structure considerations as well as selection of energizing magnet systems for miniature electromagnetic switches. The sample results of theoretical analysis and [...] Read more.

This paper presents and discusses usefulness and possibility of control of the singular points location of a driving magnetic field under as structure considerations as well as selection of energizing magnet systems for miniature electromagnetic switches. The sample results of theoretical analysis and experimental testing concern selected reed switches with normally open contacts as well as a developed miniature switch with a metallic ball contact. It must be noted that the switch with the contact performed by means of the metallic tiny ball can be effectively used both as a change-over switch as well as a detector of the energizing magnetic field distribution under designing and assembling of any electromagnetic contact device preferably with an increased degree of integration and miniaturization. Full article

(This article belongs to the Special Issue Small Devices and the High-Tech Society)

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14 pages, 2893 KiB

Open AccessArticle

A Novel Inverse Solution of Contact Force Based on a Sparse Tactile Sensor Array

by Weiting Liu, Chunxin Gu^*, Ruimin Zeng, Ping Yu and Xin Fu

The State Key Laboratory of Fluid Power & Mechatronic Systems, Department of Mechanical Engineering, Zhejiang University, Hangzhou 310027, Zhejiang, China

Sensors 2018, 18(2), 351; https://doi.org/10.3390/s18020351 - 26 Jan 2018

Cited by 14 | Viewed by 4722

Abstract

High-density tactile sensing has been pursued for humanoid robotic hands to obtain contact force information while the elastomer skin cover is traditionally considered to impair the force discrimination. In this work, we try to utilize the diffusion effect of the elastomer cover to [...] Read more.

High-density tactile sensing has been pursued for humanoid robotic hands to obtain contact force information while the elastomer skin cover is traditionally considered to impair the force discrimination. In this work, we try to utilize the diffusion effect of the elastomer cover to identify an arbitrary contact force load just based on a sparse tactile sensor array. By numerical analysis, we proved the monotonous relation between the Pearson’s correlation coefficient and the relative distance of two single-force loads. Then, we meshed the elastomer surface and conducted the calibration load process to establish the calibration database of the sensing outputs. Afterwards, we applied the correlation method to the database and the sensing output of the unknown load to determine its location and intensity. For validation tests of the proposed method, we designed and fabricated a 3 × 3 sparse tactile sensor array with flat elastomer cover and established an automatic three-axis loading system. The validation tests were implemented including 100 random points with force intensity ranging from 0.1 to 1 N. The test results show that the method has good accuracy of detecting force load with the mean location error of 0.46 mm and the mean intensity error of 0.043 N, which meets the basic requirements of tactile sensing. Therefore, it is feasible for the sparse tactile sensor array to realize high-density load detection. Full article

(This article belongs to the Section Physical Sensors)

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21 pages, 5031 KiB

Open AccessArticle

Microservices in Web Objects Enabled IoT Environment for Enhancing Reusability

by Muhammad Aslam Jarwar

, Muhammad Golam Kibria

, Sajjad Ali

and Ilyoung Chong^*

Department of Information and Communications Engineering, Hankuk University of Foreign Studies, Seoul 02450, Korea

Sensors 2018, 18(2), 352; https://doi.org/10.3390/s18020352 - 26 Jan 2018

Cited by 31 | Viewed by 6990

Abstract

In the ubiquitous Internet of Things (IoT) environment, reusing objects instead of creating new one has become important in academics and industries. The situation becomes complex due to the availability of a huge number of connected IoT objects, and each individual service creates [...] Read more.

In the ubiquitous Internet of Things (IoT) environment, reusing objects instead of creating new one has become important in academics and industries. The situation becomes complex due to the availability of a huge number of connected IoT objects, and each individual service creates a new object instead of reusing the existing one to fulfill a requirement. A well-standard mechanism not only improves the reusability of objects but also improves service modularity and extensibility, and reduces cost. Web Objects enabled IoT environment applies the principle of reusability of objects in multiple IoT application domains through central objects repository and microservices. To reuse objects with microservices and to maintain a relationship with them, this study presents an architecture of Web of Objects platform. In the case of a similar request for an object, the already instantiated object that exists in the same or from other domain can be reused. Reuse of objects through microservices avoids duplications, and reduces time to search and instantiate them from their registries. Further, this article presents an algorithm for microservices and related objects discovery that considers the reusability of objects through the central objects repository. To support the reusability of objects, the necessary algorithm for objects matching is also presented. To realize the reusability of objects in Web Objects enabled IoT environment, a prototype has been designed and implemented based on a use case scenario. Finally, the results of the prototype have been analyzed and discussed to validate the proposed approach. Full article

(This article belongs to the Section Sensor Networks)

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16 pages, 2339 KiB

Open AccessCommunication

A Proposal for IoT Dynamic Routes Selection Based on Contextual Information

by Harilton Da Silva Araújo^1,2,3

, Raimir Holanda Filho¹, Joel J. P. C. Rodrigues^1,2,4,5,*

, Ricardo De A. L. Rabelo⁶

, Natanael De C. Sousa⁶

, José C. C. L. S. Filho⁶ and José V. V. Sobral^2,7,8

¹ Programa de Pós-Graduação em Informática Aplicada (PPGIA), University of Fortaleza (UNIFOR), Av. Washington Soares, 1321, Edson Queiroz, 60.811-905 Fortaleza-CE, Brazil

² Instituto de Telecomunicações, Av. Rovisco Pais, 1, 1049-001 Lisboa, Portugal

³ Department of Computer Science, University Estacio of Sá, Av. Expedicionários, 790, São João, 64.046-700 Teresina-PI, Brazil

⁴ National Institute of Telecommunications (Inatel), Av. João de Camargo, 510-Centro, 37540-000 Santa Rita do Sapucaí-MG, Brazil

⁵ International Laboratory “Technosphere Safety”, ITMO University, 49 Kronverksky Pr., St. Petersburg 197101, Russia

⁶ Department of Computing, Federal University of Piauí (UFPI), Department of Computing, 64.049-550 Teresina-PI, Brazil

⁷ Departamento de Informática, Universidade da Beira Interior, Rua Marquês D’Ávila e Bolama, 6201-001 Covilhã, Portugal

⁸ Department of Education, Federal Institute of Maranhão (IFMA), Av. Getúlio Vargas, 4, Monte Castelo, 65030-005 São Luiz-MA, Brazil

Sensors 2018, 18(2), 353; https://doi.org/10.3390/s18020353 - 26 Jan 2018

Cited by 48 | Viewed by 5419

Abstract

The Internet of Things (IoT) is based on interconnection of intelligent and addressable devices, allowing their autonomy and proactive behavior with Internet connectivity. Data dissemination in IoT usually depends on the application and requires context-aware routing protocols that must include auto-configuration features (which [...] Read more.

The Internet of Things (IoT) is based on interconnection of intelligent and addressable devices, allowing their autonomy and proactive behavior with Internet connectivity. Data dissemination in IoT usually depends on the application and requires context-aware routing protocols that must include auto-configuration features (which adapt the behavior of the network at runtime, based on context information). This paper proposes an approach for IoT route selection using fuzzy logic in order to attain the requirements of specific applications. In this case, fuzzy logic is used to translate in math terms the imprecise information expressed by a set of linguistic rules. For this purpose, four Objective Functions (OFs) are proposed for the Routing Protocol for Low Power and Loss Networks (RPL); such OFs are dynamically selected based on context information. The aforementioned OFs are generated from the fusion of the following metrics: Expected Transmission Count (ETX), Number of Hops (NH) and Energy Consumed (EC). The experiments performed through simulation, associated with the statistical data analysis, conclude that this proposal provides high reliability by successfully delivering nearly 100% of data packets, low delay for data delivery and increase in QoS. In addition, an 30% improvement is attained in the network life time when using one of proposed objective function, keeping the devices alive for longer duration. Full article

(This article belongs to the Special Issue Sensor Networks for Collaborative and Secure Internet of Things)

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11 pages, 2169 KiB

Open AccessArticle

Label-Free Aptasensor for Lysozyme Detection Using Electrochemical Impedance Spectroscopy

by Dionisia Ortiz-Aguayo

and Manel Del Valle^*

Sensors and Biosensors Group, Department of Chemistry, Universitat Autònoma de Barcelona, Bellaterra 08193, Spain

Sensors 2018, 18(2), 354; https://doi.org/10.3390/s18020354 - 26 Jan 2018

Cited by 43 | Viewed by 6266

Abstract

This research develops a label-free aptamer biosensor (aptasensor) based on graphite-epoxy composite electrodes (GECs) for the detection of lysozyme protein using Electrochemical Impedance Spectroscopy (EIS) technique. The chosen immobilization technique was based on covalent bonding using carbodiimide chemistry; for this purpose, carboxylic moieties [...] Read more.

This research develops a label-free aptamer biosensor (aptasensor) based on graphite-epoxy composite electrodes (GECs) for the detection of lysozyme protein using Electrochemical Impedance Spectroscopy (EIS) technique. The chosen immobilization technique was based on covalent bonding using carbodiimide chemistry; for this purpose, carboxylic moieties were first generated on the graphite by electrochemical grafting. The detection was performed using [Fe(CN)₆]³⁻/[Fe(CN)₆]⁴⁻ as redox probe. After recording the frequency response, values were fitted to its electric model using the principle of equivalent circuits. The aptasensor showed a linear response up to 5 µM for lysozyme and a limit of detection of 1.67 µM. The sensitivity of the established method was 0.090 µM⁻¹ in relative charge transfer resistance values. The interference response by main proteins, such as bovine serum albumin and cytochrome c, has been also characterized. To finally verify the performance of the developed aptasensor, it was applied to wine analysis. Full article

(This article belongs to the Special Issue I3S 2017 Selected Papers)

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15 pages, 4233 KiB

Open AccessArticle

The Response of HeLa Cells to Fluorescent NanoDiamond Uptake

by Simon R. Hemelaar, Babujhi Saspaanithy, Severin R. M. L’Hommelet, Felipe P. Perona Martinez, Kiran J. Van der Laan and Romana Schirhagl^*

Department of Biomedical Engineering, University of Groningen, 9713 AV Groningen, The Netherlands

Sensors 2018, 18(2), 355; https://doi.org/10.3390/s18020355 - 26 Jan 2018

Cited by 43 | Viewed by 7681

Abstract

Fluorescent nanodiamonds are promising probes for nanoscale magnetic resonance measurements. Their physical properties predict them to have particularly useful applications in intracellular analysis. Before using them in intracellular experiments however, it should be clear whether diamond particles influence cell biology. While cytotoxicity has [...] Read more.

Fluorescent nanodiamonds are promising probes for nanoscale magnetic resonance measurements. Their physical properties predict them to have particularly useful applications in intracellular analysis. Before using them in intracellular experiments however, it should be clear whether diamond particles influence cell biology. While cytotoxicity has already been ruled out in previous studies, we consider the non-fatal influence of fluorescent nanodiamonds on the formation of reactive oxygen species (an important stress indicator and potential target for intracellular sensing) for the first time. We investigated the influence of different sizes, shapes and concentrations of nanodiamonds on the genetic and protein level involved in oxidative stress-related pathways of the HeLa cell, an important model cell line in research. The changes in viability of the cells and the difference in intracellular levels of free radicals, after diamond uptake, are surprisingly small. At lower diamond concentrations, the cellular metabolism cannot be distinguished from that of untreated cells. This research supports the claims of non-toxicity and includes less obvious non-fatal responses. Finally, we give a handhold concerning the diamond concentration and size to use for non-toxic, intracellular measurements in favour of (cancer) research in HeLa cells. Full article

(This article belongs to the Special Issue Sensors Based on Quantum Phenomena)

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16 pages, 823 KiB

Open AccessArticle

Impact of MAC Delay on AUV Localization: Underwater Localization Based on Hyperbolic Frequency Modulation Signal

by Sungryul Kim

and Younghwan Yoo^*

Department of Electrical and Computer Engineering, Pusan National University, Busandaehak-ro 63 beon-gil, Geumjeong-gu, Busan 46241, Korea

Sensors 2018, 18(2), 356; https://doi.org/10.3390/s18020356 - 26 Jan 2018

Cited by 7 | Viewed by 3830

Abstract

Medium Access Control (MAC) delay which occurs between the anchor node’s transmissions is one of the error sources in underwater localization. In particular, in AUV localization, the MAC delay significantly degrades the ranging accuracy. The Cramer-Rao Low Bound (CRLB) definition theoretically proves that [...] Read more.

Medium Access Control (MAC) delay which occurs between the anchor node’s transmissions is one of the error sources in underwater localization. In particular, in AUV localization, the MAC delay significantly degrades the ranging accuracy. The Cramer-Rao Low Bound (CRLB) definition theoretically proves that the MAC delay significantly degrades the localization performance. This paper proposes underwater localization combined with multiple access technology to decouple the localization performance from the MAC delay. Towards this goal, we adopt hyperbolic frequency modulation (HFM) signal that provides multiplexing based on its good property, high-temporal correlation. Owing to the multiplexing ability of the HFM signal, the anchor nodes can transmit packets without MAC delay, i.e., simultaneous transmission is possible. In addition, the simulation results show that the simultaneous transmission is not an optional communication scheme, but essential for the localization of mobile object in underwater. Full article

(This article belongs to the Special Issue Advances and Challenges in Underwater Sensor Networks)

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12 pages, 3949 KiB

Open AccessArticle

Detection of Abrin by Electrochemiluminescence Biosensor Based on Screen Printed Electrode

by Shuai Liu, Zhaoyang Tong^*, Xihui Mu, Bing Liu, Bin Du, Zhiwei Liu and Chuan Gao

State Key Laboratory of NBC Protection for Civilian, Beijing 102205, China

Sensors 2018, 18(2), 357; https://doi.org/10.3390/s18020357 - 26 Jan 2018

Cited by 13 | Viewed by 5331

Abstract

For the convenience of fast measurement in the outdoor environment, a portable electrochemiluminescence biosensor with the screen-printed electrode as the reaction center was developed, which possesses the characteristics of high sensitivity, small scale, simplified operation and so on, and has been used for [...] Read more.

For the convenience of fast measurement in the outdoor environment, a portable electrochemiluminescence biosensor with the screen-printed electrode as the reaction center was developed, which possesses the characteristics of high sensitivity, small scale, simplified operation and so on, and has been used for in situ detection of abrin. First, combining with magnetic separation technique, the “biotin-avidin” method was used to immobilize the polyclonal antibody (pcAb) on the magnetic microspheres surface as the capture probe. Secondly, the Ru(bpy)₃²⁺-labeled monoclonal antibody (mcAb) was used as the specific electrochemiluminescence signal probe. Then, the “mcAb-toxin-pcAb” sandwich model was built to actualize the quantitative detection of abrin on the surface of the screen-printed electrode. The linear detection range was 0.5–1000 ng/mL; the regression equation was Y = 89.251lgX + 104.978 (R = 0.9989, n = 7, p < 0.0001); and the limit of detection (LOD) was 0.1 ng/mL. The sensing system showed high sensitivity, excellent specificity and good anti-interference ability, and could be used for the analysis of trace abrin in various environmental samples with good recovery and reproducibility. Compared with the traditional electrochemiluminescence sensing device, its miniaturization and portability gives it potential to satisfy the requirement of in situ detection. Full article

(This article belongs to the Special Issue Environmental Monitoring Biosensors)

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10 pages, 2285 KiB

Open AccessArticle

Photo-Induced Room-Temperature Gas Sensing with a-IGZO Based Thin-Film Transistors Fabricated on Flexible Plastic Foil

by Stefan Knobelspies^1,*

, Benedikt Bierer², Alwin Daus¹

, Alain Takabayashi¹, Giovanni Antonio Salvatore¹, Giuseppe Cantarella¹

, Alvaro Ortiz Perez², Jürgen Wöllenstein^2,3, Stefan Palzer⁴

and Gerhard Tröster¹

¹ Electronics Laboratory, Swiss Federal Institute of Technology (ETH) Zürich, Gloriastrasse 35, 8092 Zürich, Switzerland

² Laboratory for Gas Sensors, Department of Microsystems Engineering (IMTEK), University of Freiburg, Freiburg, Germany

³ Fraunhofer Institute for Physical Measurement Techniques, Freiburg, Germany

⁴ Department of Computer Science, Universidad Autónoma de Madrid, Francisco Tomás y Valiente 11, 28049 Madrid, Spain

Sensors 2018, 18(2), 358; https://doi.org/10.3390/s18020358 - 26 Jan 2018

Cited by 67 | Viewed by 10950

Abstract

We present a gas sensitive thin-film transistor (TFT) based on an amorphous Indium–Gallium–Zinc–Oxide (a-IGZO) semiconductor as the sensing layer, which is fabricated on a free-standing flexible polyimide foil. The photo-induced sensor response to NO₂ gas at room temperature and the cross-sensitivity to [...] Read more.

We present a gas sensitive thin-film transistor (TFT) based on an amorphous Indium–Gallium–Zinc–Oxide (a-IGZO) semiconductor as the sensing layer, which is fabricated on a free-standing flexible polyimide foil. The photo-induced sensor response to NO₂ gas at room temperature and the cross-sensitivity to humidity are investigated. We combine the advantages of a transistor based sensor with flexible electronics technology to demonstrate the first flexible a-IGZO based gas sensitive TFT. Since flexible plastic substrates prohibit the use of high operating temperatures, the charge generation is promoted with the help of UV-light absorption, which ultimately triggers the reversible chemical reaction with the trace gas. Furthermore, the device fabrication process flow can be directly implemented in standard TFT technology, allowing for the parallel integration of the sensor and analog or logical circuits. Full article

(This article belongs to the Special Issue Thin-Film Transistors for Biomedical and Chemical Sensing)

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9 pages, 3060 KiB

Open AccessArticle

A IR-Femtosecond Laser Hybrid Sensor to Measure the Thermal Expansion and Thermo-Optical Coefficient of Silica-Based FBG at High Temperatures

by Litong Li^1,*, Dajuan Lv^1,2, Minghong Yang^2,*, Liangming Xiong¹ and Jie Luo¹

¹ State Key Laboratory of Optical Fiber and Cable Manufacture Technology, Yangtze Optical Fibre and Cable Joint Stock Limited Company, Wuhan 430073, China

² National Engineering Laboratory for Fiber Optic Sensing Technology, Wuhan University of Technology, Wuhan 430070, China

Sensors 2018, 18(2), 359; https://doi.org/10.3390/s18020359 - 26 Jan 2018

Cited by 13 | Viewed by 4729

Abstract

In this paper, a hybrid sensor was fabricated using a IR-femtosecond laser to measure the thermal expansion and thermo-optical coefficient of silica-based fiber Bragg gratings (FBGs). The hybrid sensor was composed of an inline fiber Fabry-Perot interferometer (FFPI) cavity and a type-II FBG. [...] Read more.

In this paper, a hybrid sensor was fabricated using a IR-femtosecond laser to measure the thermal expansion and thermo-optical coefficient of silica-based fiber Bragg gratings (FBGs). The hybrid sensor was composed of an inline fiber Fabry-Perot interferometer (FFPI) cavity and a type-II FBG. Experiment results showed that the type-II FBG had three high reflectivity resonances in the wavelength ranging from 1100 to 1600 nm, showing the peaks in 1.1, 1.3 and 1.5 μm, respectively. The thermal expansion and thermo-optical coefficient (1.3 μm, 1.5 μm) of silica-based FBG, under temperatures ranging from 30 to 1100 °C, had been simultaneously calculated by measuring the wavelength of the type-II FBG and FFPI cavity length. Full article

(This article belongs to the Section Physical Sensors)

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17 pages, 3594 KiB

Open AccessArticle

Strapdown Airborne Gravimetry Quality Assessment Method Based on Single Survey Line Data: A Study by SGA-WZ02 Gravimeter

by Minghao Wang

, Meiping Wu^*, Juliang Cao, Kaidong Zhang, Shaokun Cai and Ruihang Yu

College of Mechatronics and Automation, National University of Defense Technology, Changsha 410073, China

Sensors 2018, 18(2), 360; https://doi.org/10.3390/s18020360 - 26 Jan 2018

Cited by 7 | Viewed by 3540

Abstract

Quality assessment is an important part in the strapdown airborne gravimetry. Root mean square error (RMSE) evaluation method is a classical way to evaluate the gravimetry quality, but classical evaluation methods are preconditioned by extra flight or reference data. Thus, a method, which [...] Read more.

Quality assessment is an important part in the strapdown airborne gravimetry. Root mean square error (RMSE) evaluation method is a classical way to evaluate the gravimetry quality, but classical evaluation methods are preconditioned by extra flight or reference data. Thus, a method, which is able to largely conquer the premises of classical quality assessment methods and can be used in single survey line, has been developed in this paper. According to theoretical analysis, the method chooses the stability of two horizontal attitude angles, horizontal specific force and vertical specific force as the determinants of quality assessment method. The actual data, collected by SGA-WZ02 from 13 flights 21 lines in certain survey, was used to build the model and elaborate the method. To substantiate the performance of the quality assessment model, the model is applied in extra repeat line flights from two surveys. Compared with internal RMSE, standard deviation of assessment residuals are 0.23 mGal and 0.16 mGal in two surveys, which shows that the quality assessment method is reliable and stricter. The extra flights are not necessary by specially arranging the route of flights. The method, summarized from SGA-WZ02, is a feasible approach to assess gravimetry quality using single line data and is also suitable for other strapdown gravimeters. Full article

(This article belongs to the Section Physical Sensors)

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17 pages, 4268 KiB

Open AccessArticle

Artificial Vector Calibration Method for Differencing Magnetic Gradient Tensor Systems

by Qingzhu Li¹

, Zhining Li^1,*, Yingtang Zhang¹ and Gang Yin^1,2

¹ Department of Vehicle and Electrical Engineering, The Army Engineering University of PLA, Shijiazhuang 050003, China

² High Speed Institute, China Aerodynamics Research and Development Center, Mianyang 621000, China

Sensors 2018, 18(2), 361; https://doi.org/10.3390/s18020361 - 26 Jan 2018

Cited by 26 | Viewed by 4527

Abstract

The measurement error of the differencing (i.e., using two homogenous field sensors at a known baseline distance) magnetic gradient tensor system includes the biases, scale factors, nonorthogonality of the single magnetic sensor, and the misalignment error between the sensor arrays, all of which [...] Read more.

The measurement error of the differencing (i.e., using two homogenous field sensors at a known baseline distance) magnetic gradient tensor system includes the biases, scale factors, nonorthogonality of the single magnetic sensor, and the misalignment error between the sensor arrays, all of which can severely affect the measurement accuracy. In this paper, we propose a low-cost artificial vector calibration method for the tensor system. Firstly, the error parameter linear equations are constructed based on the single-sensor’s system error model to obtain the artificial ideal vector output of the platform, with the total magnetic intensity (TMI) scalar as a reference by two nonlinear conversions, without any mathematical simplification. Secondly, the Levenberg–Marquardt algorithm is used to compute the integrated model of the 12 error parameters by nonlinear least-squares fitting method with the artificial vector output as a reference, and a total of 48 parameters of the system is estimated simultaneously. The calibrated system outputs along the reference platform-orthogonal coordinate system. The analysis results show that the artificial vector calibrated output can track the orientation fluctuations of TMI accurately, effectively avoiding the “overcalibration” problem. The accuracy of the error parameters’ estimation in the simulation is close to 100%. The experimental root-mean-square error (RMSE) of the TMI and tensor components is less than 3 nT and 20 nT/m, respectively, and the estimation of the parameters is highly robust. Full article

(This article belongs to the Special Issue Magnetic Sensors and Their Applications)

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9 pages, 2378 KiB

Open AccessArticle

A Micro-Resonant Gas Sensor with Nanometer Clearance between the Pole Plates

by Xiaorui Fu

and Lizhong Xu^*

Mechanical Engineering Institute, Yanshan University, Qinhuangdao 066004, China

Sensors 2018, 18(2), 362; https://doi.org/10.3390/s18020362 - 26 Jan 2018

Cited by 4 | Viewed by 4307

Abstract

In micro-resonant gas sensors, the capacitive detection is widely used because of its simple structure. However, its shortcoming is a weak signal output caused by a small capacitance change. Here, we reduced the initial clearance between the pole plates to the nanometer level, [...] Read more.

In micro-resonant gas sensors, the capacitive detection is widely used because of its simple structure. However, its shortcoming is a weak signal output caused by a small capacitance change. Here, we reduced the initial clearance between the pole plates to the nanometer level, and increased the capacitance between the pole plates and its change during resonator vibration. We propose a fabricating process of the micro-resonant gas sensor by which the initial clearance between the pole plates is reduced to the nanometer level and a micro-resonant gas sensor with 200 nm initial clearance is fabricated. With this sensor, the resonant frequency shifts were measured when they were exposed to several different vapors, and high detection accuracies were obtained. The detection accuracy with respect to ethanol vapor was 0.4 ppm per Hz shift, and the detection accuracy with respect to hydrogen and ammonias vapors was 3 ppm and 0.5 ppm per Hz shift, respectively. Full article

(This article belongs to the Collection Gas Sensors)

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22 pages, 4678 KiB

Open AccessArticle

Hyperspectral Image Classification for Land Cover Based on an Improved Interval Type-II Fuzzy C-Means Approach

by Hongyuan Huo¹

, Jifa Guo^2,*

and Zhao-Liang Li^1,3,*

¹ Key Laboratory of Agricultural Remote Sensing, Ministry of Agriculture/Institute of Agricultural Resources and Regional Planning, Chinese Academy of Agricultural Sciences, Beijing 100081, China

² College of Geography and Environment, Tianjin Normal University, Tianjin 300387, China

³ ICube, CNRS, Université de Strasbourg, 300 Boulevard Sébastien Brant, CS10413, 67412 Illkirch, France

Sensors 2018, 18(2), 363; https://doi.org/10.3390/s18020363 - 26 Jan 2018

Cited by 25 | Viewed by 5411

Abstract

Few studies have examined hyperspectral remote-sensing image classification with type-II fuzzy sets. This paper addresses image classification based on a hyperspectral remote-sensing technique using an improved interval type-II fuzzy c-means (IT2FCM*) approach. In this study, in contrast to other traditional fuzzy c-means-based approaches, [...] Read more.

Few studies have examined hyperspectral remote-sensing image classification with type-II fuzzy sets. This paper addresses image classification based on a hyperspectral remote-sensing technique using an improved interval type-II fuzzy c-means (IT2FCM*) approach. In this study, in contrast to other traditional fuzzy c-means-based approaches, the IT2FCM* algorithm considers the ranking of interval numbers and the spectral uncertainty. The classification results based on a hyperspectral dataset using the FCM, IT2FCM, and the proposed improved IT2FCM* algorithms show that the IT2FCM* method plays the best performance according to the clustering accuracy. In this paper, in order to validate and demonstrate the separability of the IT2FCM*, four type-I fuzzy validity indexes are employed, and a comparative analysis of these fuzzy validity indexes also applied in FCM and IT2FCM methods are made. These four indexes are also applied into different spatial and spectral resolution datasets to analyze the effects of spectral and spatial scaling factors on the separability of FCM, IT2FCM, and IT2FCM* methods. The results of these validity indexes from the hyperspectral datasets show that the improved IT2FCM* algorithm have the best values among these three algorithms in general. The results demonstrate that the IT2FCM* exhibits good performance in hyperspectral remote-sensing image classification because of its ability to handle hyperspectral uncertainty. Full article

(This article belongs to the Special Issue Analysis of Multispectral and Hyperspectral Data)

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27 pages, 5485 KiB

Open AccessArticle

A Novel Grid SINS/DVL Integrated Navigation Algorithm for Marine Application

by Yingyao Kang, Lin Zhao^*, Jianhua Cheng^*, Mouyan Wu

and Xiaoliang Fan

College of Automation, Harbin Engineering University, Harbin 150001, China

Sensors 2018, 18(2), 364; https://doi.org/10.3390/s18020364 - 26 Jan 2018

Cited by 39 | Viewed by 5645

Abstract

Integrated navigation algorithms under the grid frame have been proposed based on the Kalman filter (KF) to solve the problem of navigation in some special regions. However, in the existing study of grid strapdown inertial navigation system (SINS)/Doppler velocity log (DVL) integrated navigation [...] Read more.

Integrated navigation algorithms under the grid frame have been proposed based on the Kalman filter (KF) to solve the problem of navigation in some special regions. However, in the existing study of grid strapdown inertial navigation system (SINS)/Doppler velocity log (DVL) integrated navigation algorithms, the Earth models of the filter dynamic model and the SINS mechanization are not unified. Besides, traditional integrated systems with the KF based correction scheme are susceptible to measurement errors, which would decrease the accuracy and robustness of the system. In this paper, an adaptive robust Kalman filter (ARKF) based hybrid-correction grid SINS/DVL integrated navigation algorithm is designed with the unified reference ellipsoid Earth model to improve the navigation accuracy in middle-high latitude regions for marine application. Firstly, to unify the Earth models, the mechanization of grid SINS is introduced and the error equations are derived based on the same reference ellipsoid Earth model. Then, a more accurate grid SINS/DVL filter model is designed according to the new error equations. Finally, a hybrid-correction scheme based on the ARKF is proposed to resist the effect of measurement errors. Simulation and experiment results show that, compared with the traditional algorithms, the proposed navigation algorithm can effectively improve the navigation performance in middle-high latitude regions by the unified Earth models and the ARKF based hybrid-correction scheme. Full article

(This article belongs to the Special Issue Inertial Sensors for Positioning and Navigation)

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13 pages, 5953 KiB

Open AccessArticle

A Fiber Bragg Grating-Based Dynamic Tension Detection System for Overhead Transmission Line Galloping

by Guo-ming Ma^1,*, Ya-bo Li¹, Nai-qiang Mao¹, Cheng Shi¹, Cheng-rong Li¹ and Bo Zhang²

¹ State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources, North China Electric Power University, Beijing 102206, China

² Henan Electric Power Research Institute, State Grid, Zhengzhou 450000, China

Sensors 2018, 18(2), 365; https://doi.org/10.3390/s18020365 - 26 Jan 2018

Cited by 51 | Viewed by 8246

Abstract

Galloping of overhead transmission lines (OHTLs) may induce conductor breakage and tower collapse, and there is no effective method for long distance distribution on-line galloping monitoring. To overcome the drawbacks of the conventional galloping monitoring systems, such as sensitivity to electromagnetic interference, the [...] Read more.

Galloping of overhead transmission lines (OHTLs) may induce conductor breakage and tower collapse, and there is no effective method for long distance distribution on-line galloping monitoring. To overcome the drawbacks of the conventional galloping monitoring systems, such as sensitivity to electromagnetic interference, the need for onsite power, and short lifetimes, a novel optical remote passive measuring system is proposed in the paper. Firstly, to solve the hysteresis and eccentric load problem in tension sensing, and to extent the dynamic response range, an ‘S’ type elastic element structure with flanges was proposed. Then, a tension experiment was carried out to demonstrate the dynamic response characteristics. Moreover, the designed tension sensor was stretched continuously for 30 min to observe its long time stability. Last but not the least, the sensor was mounted on a 70 m conductor model, and the conductor was oscillated at different frequencies to investigate the dynamic performance of the sensor. The experimental results demonstrate the sensor is suitable for the OHTL galloping detection. Compared with the conventional sensors for OHTL monitoring, the system has many advantages, such as easy installation, no flashover risk, distribution monitoring, better bandwidth, improved accuracy and higher reliability. Full article

(This article belongs to the Special Issue Sensors for Deformation Monitoring of Large Civil Infrastructures)

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20 pages, 5055 KiB

Open AccessArticle

A Low-Cost Data Acquisition System for Automobile Dynamics Applications

by Alejandro González

, José Luis Olazagoitia^*

and Jordi Vinolas

Industrial Engineering Department, Universidad Antonio de Nebrija, 55 Pirineos Street, 28040 Madrid, Spain

Sensors 2018, 18(2), 366; https://doi.org/10.3390/s18020366 - 27 Jan 2018

Cited by 54 | Viewed by 10291

Abstract

This project addresses the need for the implementation of low-cost acquisition technology in the field of vehicle engineering: the design, development, manufacture, and verification of a low-cost Arduino-based data acquisition platform to be used in <80 Hz data acquisition in vehicle dynamics, using [...] Read more.

This project addresses the need for the implementation of low-cost acquisition technology in the field of vehicle engineering: the design, development, manufacture, and verification of a low-cost Arduino-based data acquisition platform to be used in <80 Hz data acquisition in vehicle dynamics, using low-cost accelerometers. In addition to this, a comparative study is carried out of professional vibration acquisition technologies and low-cost systems, obtaining optimum results for low- and medium-frequency operations with an error of 2.19% on road tests. It is therefore concluded that these technologies are applicable to the automobile industry, thereby allowing the project costs to be reduced and thus facilitating access to this kind of research that requires limited resources. Full article

(This article belongs to the Section Physical Sensors)

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16 pages, 2226 KiB

Open AccessArticle

Fuzzy Traffic Control with Vehicle-to-Everything Communication

by Muntaser A. Salman^1,2,*

, Suat Ozdemir³ and Fatih V. Celebi²

¹ Department of Information Systems, College of Computer Sciences and Information Technology, University of Anbar, 55431 Baghdad, 55 Ramadi, Anbar, Iraq

² Computer Engineering Department, Ankara Yildirim Beyazit University, 06010 Ankara, Turkey

³ Computer Engineering Department, Gazi University, 06570 Ankara, Turkey

Sensors 2018, 18(2), 368; https://doi.org/10.3390/s18020368 - 27 Jan 2018

Cited by 20 | Viewed by 5520

Abstract

Traffic signal control (TSC) with vehicle-to everything (V2X) communication can be a very efficient solution to traffic congestion problem. Ratio of vehicles equipped with V2X communication capability in the traffic to the total number of vehicles (called penetration rate PR) is still low, [...] Read more.

Traffic signal control (TSC) with vehicle-to everything (V2X) communication can be a very efficient solution to traffic congestion problem. Ratio of vehicles equipped with V2X communication capability in the traffic to the total number of vehicles (called penetration rate PR) is still low, thus V2X based TSC systems need to be supported by some other mechanisms. PR is the major factor that affects the quality of TSC process along with the evaluation interval. Quality of the TSC in each direction is a function of overall TSC quality of an intersection. Hence, quality evaluation of each direction should follow the evaluation of the overall intersection. Computational intelligence, more specifically swarm algorithm, has been recently used in this field in a European Framework Program FP7 supported project called COLOMBO. In this paper, using COLOMBO framework, further investigations have been done and two new methodologies using simple and fuzzy logic have been proposed. To evaluate the performance of our proposed methods, a comparison with COLOMBOs approach has been realized. The results reveal that TSC problem can be solved as a logical problem rather than an optimization problem. Performance of the proposed approaches is good enough to be suggested for future work under realistic scenarios even under low PR. Full article

(This article belongs to the Special Issue Sensor Networks for Smart Roads)

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18 pages, 3583 KiB

Open AccessArticle

Comparing Two Independent Satellite-Based Algorithms for Detecting and Tracking Ash Clouds by Using SEVIRI Sensor

by Alfredo Falconieri^1,*

, Michael C. Cooke², Carolina Filizzola¹

, Francesco Marchese¹

, Nicola Pergola¹

and Valerio Tramutoli³

¹ Institute of Methodologies for Environmental Analysis (IMAA), Italian Research Council (CNR), 85050 Tito Scalo, Potenza, Italy

² Met Office, FitzRoy Road, Exeter, Devon EX1-3PB, UK

³ School of Engineering, University of Basilicata, Via dell’Ateneo Lucano 10, 85100 Potenza, Italy

Sensors 2018, 18(2), 369; https://doi.org/10.3390/s18020369 - 27 Jan 2018

Cited by 8 | Viewed by 4873

Abstract

The Eyjafjallajökull (Iceland) volcanic eruption of April–May 2010 caused unprecedented air-traffic disruption in Northern Europe, revealing some important weaknesses of current operational ash-monitoring and forecasting systems and encouraging the improvement of methods and procedures for supporting the activities of Volcanic Ash Advisory Centers [...] Read more.

The Eyjafjallajökull (Iceland) volcanic eruption of April–May 2010 caused unprecedented air-traffic disruption in Northern Europe, revealing some important weaknesses of current operational ash-monitoring and forecasting systems and encouraging the improvement of methods and procedures for supporting the activities of Volcanic Ash Advisory Centers (VAACs) better. In this work, we compare two established satellite-based algorithms for ash detection, namely RST_ASH and the operational London VAAC method, both exploiting sensor data of the spinning enhanced visible and infrared imager (SEVIRI). We analyze similarities and differences in the identification of ash clouds during the different phases of the Eyjafjallajökull eruption. The work reveals, in some cases, a certain complementary behavior of the two techniques, whose combination might improve the identification of ash-affected areas in specific conditions. This is indicated by the quantitative comparison of the merged SEVIRI ash product, achieved integrating outputs of the RST_ASH and London VAAC methods, with independent atmospheric infrared sounder (AIRS) DDA (dust-detection algorithm) observations. Full article

(This article belongs to the Section Remote Sensors)

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14 pages, 357 KiB

Open AccessArticle

Securing Cooperative Spectrum Sensing Against Collusive SSDF Attack using XOR Distance Analysis in Cognitive Radio Networks

by Jingyu Feng^1,†, Man Zhang^1,†, Yun Xiao^2,*,† and Hongzhou Yue^3,†

¹ Shaanxi Key Laboratory of Information Communication Network and Security, Xi’an University of Posts & Telecommunications, Xi’an 710121, China

² School of Information Science and Technology, Northwest University, Xi’an 710127, China

³ Information Security Research Center of State Key Laboratory of Integrated Services Networks, Xidian University, Xi’an 710071, China

^† These authors contributed equally to this work.

Sensors 2018, 18(2), 370; https://doi.org/10.3390/s18020370 - 27 Jan 2018

Cited by 22 | Viewed by 3869

Abstract

Cooperative spectrum sensing (CSS) is considered as a powerful approach to improve the utilization of scarce spectrum resources. However, if CSS assumes that all secondary users (SU) are honest, it may offer opportunities for attackers to conduct a spectrum sensing data falsification (SSDF) [...] Read more.

Cooperative spectrum sensing (CSS) is considered as a powerful approach to improve the utilization of scarce spectrum resources. However, if CSS assumes that all secondary users (SU) are honest, it may offer opportunities for attackers to conduct a spectrum sensing data falsification (SSDF) attack. To suppress such a threat, recent efforts have been made to develop trust mechanisms. Currently, some attackers can collude with each other to form a collusive clique, and thus not only increase the power of SSDF attack but also avoid the detection of a trust mechanism. Noting the duality of sensing data, we propose a defense scheme called XDA from the perspective of XOR distance analysis to suppress a collusive SSDF attack. In the XDA scheme, the XOR distance calculation in line with the type of “0” and “1” historical sensing data is used to measure the similarity between any two SUs. Noting that collusive SSDF attackers hold high trust value and the minimum XOR distance, the algorithm to detect collusive SSDF attackers is designed. Meanwhile, the XDA scheme can perfect the trust mechanism to correct collusive SSDF attackers’ trust value. Simulation results show that the XDA scheme can enhance the accuracy of trust evaluation, and thus successfully reduce the power of collusive SSDF attack against CSS. Full article

(This article belongs to the Special Issue Cognitive Radio Sensing and Sensor Networks)

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10 pages, 4165 KiB

Open AccessArticle

An Interdigital Electrode Probe for Detection, Localization and Evaluation of Surface Notch-Type Damage in Metals

by Lanshuo Li¹

, Xiaoqing Yang^1,*, Yang Yin¹, Jianping Yuan², Xu Li³, Lixin Li³ and Kama Huang¹

¹ School of Electronics and Information Engineering, Sichuan University, Chengdu 610065, China

² National Key Laboratory of Aerospace Flight Dynamics, Northwestern Polytechnical University, Xi’an 710129, China

³ School of Electronics and Information, Northwestern Polytechnical University, Xi’an 710129, China

Sensors 2018, 18(2), 371; https://doi.org/10.3390/s18020371 - 27 Jan 2018

Cited by 11 | Viewed by 4719

Abstract

Available microwave notch-type damage detection sensors are typically based on monitoring frequency shift or magnitude changes. However, frequency shift testing needs sweep-frequency data that make scanning detection becomes difficult and time-consuming. This work presents a microwave near-field nondestructive testing sensor for detecting sub-millimeter [...] Read more.

Available microwave notch-type damage detection sensors are typically based on monitoring frequency shift or magnitude changes. However, frequency shift testing needs sweep-frequency data that make scanning detection becomes difficult and time-consuming. This work presents a microwave near-field nondestructive testing sensor for detecting sub-millimeter notch-type damage detection in metallic surfaces. The sensor is loaded with an interdigital electrode element in an open-ended coaxial. It is simple to fabricate and inexpensive, as it is etched on the RC4003 patch by using printed circuit board technology. The detection is achieved by monitoring changes in reflection amplitude, which is caused by perturbing the electromagnetic field around the interdigital structure. The proposed sensor was tested on a metallic plate with different defects, and the experimental results indicated that the interdigital electrode probe can determine the orientation, localization and dimension of surface notch-type damage. Full article

(This article belongs to the Special Issue Intelligent Sensing Technologies for Nondestructive Evaluation)

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20 pages, 3494 KiB

Open AccessArticle

Human Identification by Cross-Correlation and Pattern Matching of Personalized Heartbeat: Influence of ECG Leads and Reference Database Size

by Irena Jekova^1,*, Vessela Krasteva¹

and Ramun Schmid²

¹ Institute of Biophysics and Biomedical Engineering, Bulgarian Academy of Sciences, Acad. G. Bonchev Str. Bl 105, 1113 Sofia, Bulgaria

² Schiller AG, Signal Processing, 6341 Baar, Switzerland

Sensors 2018, 18(2), 372; https://doi.org/10.3390/s18020372 - 27 Jan 2018

Cited by 17 | Viewed by 6325

Abstract

Human identification (ID) is a biometric task, comparing single input sample to many stored templates to identify an individual in a reference database. This paper aims to present the perspectives of personalized heartbeat pattern for reliable ECG-based identification. The investigations are using a [...] Read more.

Human identification (ID) is a biometric task, comparing single input sample to many stored templates to identify an individual in a reference database. This paper aims to present the perspectives of personalized heartbeat pattern for reliable ECG-based identification. The investigations are using a database with 460 pairs of 12-lead resting electrocardiograms (ECG) with 10-s durations recorded at time-instants T1 and T2 > T1 + 1 year. Intra-subject long-term ECG stability and inter-subject variability of personalized PQRST (500 ms) and QRS (100 ms) patterns is quantified via cross-correlation, amplitude ratio and pattern matching between T1 and T2 using 7 features × 12-leads. Single and multi-lead ID models are trained on the first 230 ECG pairs. Their validation on 10, 20, ... 230 reference subjects (RS) from the remaining 230 ECG pairs shows: (i) two best single-lead ID models using lead II for a small population RS = (10–140) with identification accuracy AccID = (89.4–67.2)% and aVF for a large population RS = (140–230) with AccID = (67.2–63.9)%; (ii) better performance of the 6-lead limb vs. the 6-lead chest ID model—(91.4–76.1)% vs. (90.9–70)% for RS = (10–230); (iii) best performance of the 12-lead ID model—(98.4–87.4)% for RS = (10–230). The tolerable reference database size, keeping AccID > 80%, is RS = 30 in the single-lead ID scenario (II); RS = 50 (6 chest leads); RS = 100 (6 limb leads), RS > 230—maximal population in this study (12-lead ECG). Full article

(This article belongs to the Special Issue Wearable and Ambient Sensors for Healthcare and Wellness Applications 2018)

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20 pages, 3315 KiB

Open AccessArticle

Multi-Feature Classification of Multi-Sensor Satellite Imagery Based on Dual-Polarimetric Sentinel-1A, Landsat-8 OLI, and Hyperion Images for Urban Land-Cover Classification

by Tao Zhou

, Zhaofu Li

and Jianjun Pan^*

College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing 210095, Jiangsu, China

Sensors 2018, 18(2), 373; https://doi.org/10.3390/s18020373 - 27 Jan 2018

Cited by 32 | Viewed by 6008

Abstract

This paper focuses on evaluating the ability and contribution of using backscatter intensity, texture, coherence, and color features extracted from Sentinel-1A data for urban land cover classification and comparing different multi-sensor land cover mapping methods to improve classification accuracy. Both Landsat-8 OLI and [...] Read more.

This paper focuses on evaluating the ability and contribution of using backscatter intensity, texture, coherence, and color features extracted from Sentinel-1A data for urban land cover classification and comparing different multi-sensor land cover mapping methods to improve classification accuracy. Both Landsat-8 OLI and Hyperion images were also acquired, in combination with Sentinel-1A data, to explore the potential of different multi-sensor urban land cover mapping methods to improve classification accuracy. The classification was performed using a random forest (RF) method. The results showed that the optimal window size of the combination of all texture features was 9 × 9, and the optimal window size was different for each individual texture feature. For the four different feature types, the texture features contributed the most to the classification, followed by the coherence and backscatter intensity features; and the color features had the least impact on the urban land cover classification. Satisfactory classification results can be obtained using only the combination of texture and coherence features, with an overall accuracy up to 91.55% and a kappa coefficient up to 0.8935, respectively. Among all combinations of Sentinel-1A-derived features, the combination of the four features had the best classification result. Multi-sensor urban land cover mapping obtained higher classification accuracy. The combination of Sentinel-1A and Hyperion data achieved higher classification accuracy compared to the combination of Sentinel-1A and Landsat-8 OLI images, with an overall accuracy of up to 99.12% and a kappa coefficient up to 0.9889. When Sentinel-1A data was added to Hyperion images, the overall accuracy and kappa coefficient were increased by 4.01% and 0.0519, respectively. Full article

(This article belongs to the Special Issue Spatial Analysis and Remote Sensing)

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23 pages, 4411 KiB

Open AccessArticle

Vehicle Detection with Occlusion Handling, Tracking, and OC-SVM Classification: A High Performance Vision-Based System

by Roxana Velazquez-Pupo¹, Alberto Sierra-Romero¹

, Deni Torres-Roman¹, Yuriy V. Shkvarko^1,†, Jayro Santiago-Paz^1,*

, David Gómez-Gutiérrez²

, Daniel Robles-Valdez¹

, Fernando Hermosillo-Reynoso¹

and Misael Romero-Delgado¹

¹ Center for Advanced Research and Education of the National Polytechnic Institute of Mexico, CINVESTAV Guadalajara, Zapopan C.P. 45019, Mexico

² Intel Labs, Intel Tecnología de Mexico, Zapopan C.P. 45019, Mexico

^† Died at August 2016.

Sensors 2018, 18(2), 374; https://doi.org/10.3390/s18020374 - 27 Jan 2018

Cited by 69 | Viewed by 10993

Abstract

This paper presents a high performance vision-based system with a single static camera for traffic surveillance, for moving vehicle detection with occlusion handling, tracking, counting, and One Class Support Vector Machine (OC-SVM) classification. In this approach, moving objects are first segmented from the [...] Read more.

This paper presents a high performance vision-based system with a single static camera for traffic surveillance, for moving vehicle detection with occlusion handling, tracking, counting, and One Class Support Vector Machine (OC-SVM) classification. In this approach, moving objects are first segmented from the background using the adaptive Gaussian Mixture Model (GMM). After that, several geometric features are extracted, such as vehicle area, height, width, centroid, and bounding box. As occlusion is present, an algorithm was implemented to reduce it. The tracking is performed with adaptive Kalman filter. Finally, the selected geometric features: estimated area, height, and width are used by different classifiers in order to sort vehicles into three classes: small, midsize, and large. Extensive experimental results in eight real traffic videos with more than 4000 ground truth vehicles have shown that the improved system can run in real time under an occlusion index of 0.312 and classify vehicles with a global detection rate or recall, precision, and F-measure of up to 98.190%, and an F-measure of up to 99.051% for midsize vehicles. Full article

(This article belongs to the Special Issue Sensors for Transportation)

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29 pages, 750 KiB

Open AccessArticle

Self-Learning Power Control in Wireless Sensor Networks

by Michele Chincoli^1,*

and Antonio Liotta²

¹ Electrical Engineering Department, Eindhoven University of Technology, De Zaale (internal address: Groene Loper 19), 5612 AJ Eindhoven, The Netherlands

² Data Science Centre, University of Derby, Lonsdale House, Quaker Way, Derby DE1 3HD, UK

Sensors 2018, 18(2), 375; https://doi.org/10.3390/s18020375 - 27 Jan 2018

Cited by 64 | Viewed by 7499

Abstract

Current trends in interconnecting myriad smart objects to monetize on Internet of Things applications have led to high-density communications in wireless sensor networks. This aggravates the already over-congested unlicensed radio bands, calling for new mechanisms to improve spectrum management and energy efficiency, such [...] Read more.

Current trends in interconnecting myriad smart objects to monetize on Internet of Things applications have led to high-density communications in wireless sensor networks. This aggravates the already over-congested unlicensed radio bands, calling for new mechanisms to improve spectrum management and energy efficiency, such as transmission power control. Existing protocols are based on simplistic heuristics that often approach interference problems (i.e., packet loss, delay and energy waste) by increasing power, leading to detrimental results. The scope of this work is to investigate how machine learning may be used to bring wireless nodes to the lowest possible transmission power level and, in turn, to respect the quality requirements of the overall network. Lowering transmission power has benefits in terms of both energy consumption and interference. We propose a protocol of transmission power control through a reinforcement learning process that we have set in a multi-agent system. The agents are independent learners using the same exploration strategy and reward structure, leading to an overall cooperative network. The simulation results show that the system converges to an equilibrium where each node transmits at the minimum power while respecting high packet reception ratio constraints. Consequently, the system benefits from low energy consumption and packet delay. Full article

(This article belongs to the Collection Smart Communication Protocols and Algorithms for Sensor Networks)

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19 pages, 6355 KiB

Open AccessArticle

Estimation of the Land Surface Temperature over the Tibetan Plateau by Using Chinese FY-2C Geostationary Satellite Data

by Yuanyuan Hu^1,†, Lei Zhong^1,*,†, Yaoming Ma^2,3,4, Mijun Zou¹, Kepiao Xu¹, Ziyu Huang¹ and Lu Feng⁵

¹ Laboratory for Atmospheric Observation and Climate Environment Research, School of Earth and Space Sciences, University of Science and Technology of China, Hefei 230026, China

² Key Laboratory of Tibetan Environment Changes and Land Surface Processes, Institute of Tibetan Plateau Research, the Chinese Academy of Sciences, Beijing 100101, China

³ CAS Center for Excellence in Tibetan Plateau Earth Sciences, Beijing 100101, China

⁴ University of Chinese Academy of Sciences, Beijing 100049, China

⁵ Institute of Tropical and Marine Meteorology, China Meteorological Administration, Guangzhou 510080, China

^† These authors contributed equally to this study and shared first authorship.

Sensors 2018, 18(2), 376; https://doi.org/10.3390/s18020376 - 28 Jan 2018

Cited by 20 | Viewed by 5534

Abstract

During the process of land–atmosphere interaction, one of the essential parameters is the land surface temperature (LST). The LST has high temporal variability, especially in its diurnal cycle, which cannot be acquired by polar-orbiting satellites. Therefore, it is of great practical significance to [...] Read more.

During the process of land–atmosphere interaction, one of the essential parameters is the land surface temperature (LST). The LST has high temporal variability, especially in its diurnal cycle, which cannot be acquired by polar-orbiting satellites. Therefore, it is of great practical significance to retrieve LST data using geostationary satellites. According to the data of FengYun 2C (FY-2C) satellite and the measurements from the Enhanced Observing Period (CEOP) of the Asia–Australia Monsoon Project (CAMP) on the Tibetan Plateau (CAMP/Tibet), a regression approach was utilized in this research to optimize the split window algorithm (SWA). The thermal infrared data obtained by the Chinese geostationary satellite FY-2C over the Tibetan Plateau (TP) was used to estimate the hourly LST time series. To decrease the effects of cloud, the 10-day composite hourly LST data were obtained through the approach of maximal value composite (MVC). The derived LST was used to compare with the product of MODIS LST and was also validated by the field observation. The results show that the LST retrieved through the optimized SWA and in situ data has a better consistency (with correlation coefficient (R), mean absolute error (MAE), mean bias (MB), and root mean square error (RMSE) values of 0.987, 1.91 K, 0.83 K and 2.26 K, respectively) than that derived from Becker and Li’s SWA and MODIS LST product, which means that the modified SWA can be applied to achieve plateau-scale LST. The diurnal variation of the LST and the hourly time series of the LST over the Tibetan Plateau were also obtained. The diurnal range of LST was found to be clearly affected by the influence of the thawing and freezing process of soil and the summer monsoon evolution. The comparison between the seasonal and diurnal variations of LST at four typical underlying surfaces over the TP indicate that the variation of LST is closely connected with the underlying surface types as well. The diurnal variation of LST is the smallest at the water (5.12 K), second at the snow and ice (5.45 K), third at the grasslands (19.82 K) and largest at the barren or sparsely vegetated (22.83 K). Full article

(This article belongs to the Section Remote Sensors)

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28 pages, 4201 KiB

Open AccessArticle

On the Design of an Efficient Cardiac Health Monitoring System Through Combined Analysis of ECG and SCG Signals

by Prasan Kumar Sahoo^1,4

, Hiren Kumar Thakkar¹

, Wen-Yen Lin^2,4, Po-Cheng Chang⁴ and Ming-Yih Lee^3,4,*

¹ Department of Computer Science and Information Engineering, Chang Gung University, Guishan 33302, Taiwan

² Department of Electrical Engineering and Center for Biomedical Engineering/College of Engineering, Chang Gung University, Guishan 33302, Taiwan

³ Graduate Institute of Medical Mechatronics, Center for Biomedical Engineering, Chang Gung University, Guishan 33302, Taiwan

⁴ Division of Cardiology, Department of Internal Medicine, Chang Gung Memorial Hospital, Linkou 33305, Taiwan

Sensors 2018, 18(2), 379; https://doi.org/10.3390/s18020379 - 28 Jan 2018

Cited by 68 | Viewed by 9032

Abstract

Cardiovascular disease (CVD) is a major public concern and socioeconomic problem across the globe. The popular high-end cardiac health monitoring systems such as magnetic resonance imaging (MRI), computerized tomography scan (CT scan), and echocardiography (Echo) are highly expensive and do not support long-term [...] Read more.

Cardiovascular disease (CVD) is a major public concern and socioeconomic problem across the globe. The popular high-end cardiac health monitoring systems such as magnetic resonance imaging (MRI), computerized tomography scan (CT scan), and echocardiography (Echo) are highly expensive and do not support long-term continuous monitoring of patients without disrupting their activities of daily living (ADL). In this paper, the continuous and non-invasive cardiac health monitoring using unobtrusive sensors is explored aiming to provide a feasible and low-cost alternative to foresee possible cardiac anomalies in an early stage. It is learned that cardiac health monitoring based on sole usage of electrocardiogram (ECG) signals may not provide powerful insights as ECG provides shallow information on various cardiac activities in the form of electrical impulses only. Hence, a novel low-cost, non-invasive seismocardiogram (SCG) signal along with ECG signals are jointly investigated for the robust cardiac health monitoring. For this purpose, the in-laboratory data collection model is designed for simultaneous acquisition of ECG and SCG signals followed by mechanisms for the automatic delineation of relevant feature points in acquired ECG and SCG signals. In addition, separate feature points based novel approach is adopted to distinguish between normal and abnormal morphology in each ECG and SCG cardiac cycle. Finally, a combined analysis of ECG and SCG is carried out by designing a Naïve Bayes conditional probability model. Experiments on Institutional Review Board (IRB) approved licensed ECG/SCG signals acquired from real subjects containing 12,000 cardiac cycles show that the proposed feature point delineation mechanisms and abnormal morphology detection methods consistently perform well and give promising results. In addition, experimental results show that the combined analysis of ECG and SCG signals provide more reliable cardiac health monitoring compared to the standalone use of ECG and SCG. Full article

(This article belongs to the Special Issue Sensors for Health Monitoring and Disease Diagnosis)

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22 pages, 1159 KiB

Open AccessArticle

Joint Interference Alignment and Power Allocation for K-User Multicell MIMO Channel through Staggered Antenna Switching

by Poongundran Selvaprabhu

, Sunil Chinnadurai

, Md.Abdul Latif Sarker and Moon Ho Lee^*

Department of Electronics and Information Engineering, Chonbuk National University, Jeonju 561-756, Korea

Sensors 2018, 18(2), 380; https://doi.org/10.3390/s18020380 - 28 Jan 2018

Cited by 6 | Viewed by 3883

Abstract

In this paper, we characterise the joint interference alignment (IA) and power allocation strategies for a K-user multicell multiple-input multiple-output (MIMO) Gaussian interference channel. We consider a MIMO interference channel with blind-IA through staggered antenna switching on the receiver. We explore the [...] Read more.

In this paper, we characterise the joint interference alignment (IA) and power allocation strategies for a K-user multicell multiple-input multiple-output (MIMO) Gaussian interference channel. We consider a MIMO interference channel with blind-IA through staggered antenna switching on the receiver. We explore the power allocation and feasibility condition for cooperative cell-edge (CE) mobile users (MUs) by assuming that the channel state information is unknown. The new insight behind the transmission strategy of the proposed scheme is premeditated (randomly generated transmission strategy) and partial cooperative CE MUs, where the transmitter is equipped with a conventional antenna, the receiver is equipped with a reconfigurable multimode antenna (staggered antenna switching pattern), and the receiver switches between preset T modes. Our proposed scheme assists and aligns the desired signals and interference signals to cancel the common interference signals because the received signal must have a corresponding independent signal subspace. The capacity for a K-user multicell MIMO Gaussian interference channel with reconfigurable multimode antennas is completely characterised. Furthermore, we show that the proposed K-user multicell MIMO scheduling and K-user L-cell CEUs partial cooperation algorithms elaborate the generalisation of K-user IA and power allocation strategies. The numerical results demonstrate that the proposed intercell interference scheme with partial-cooperative CE MUs achieves better capacity and signal-to-interference plus noise ratio (SINR) performance compared to noncooperative CE MUs and without intercell interference schemes. Full article

(This article belongs to the Section Sensor Networks)

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15 pages, 6399 KiB

Open AccessArticle

An Improved Method for Magnetic Nanocarrier Drug Delivery across the Cell Membrane

by Behzad Mehrafrooz^1,†, Maysam Z. Pedram^2,3,*,† and Ebrahim Ghafar-Zadeh^3,*,†

¹ Department of Mechanical Engineering, K.N. Toosi University of Technology, Tehran 16315-1355, Iran

² Faculty of Electrical and Computer Engineering, K.N. Toosi University of Technology, Tehran 16315-1355, Iran

³ Departement of Electrical Engineering and Computer Science, York University, Toronto, ON M3J1P3, Canada

^† These authors contributed equally to this work.

Sensors 2018, 18(2), 381; https://doi.org/10.3390/s18020381 - 29 Jan 2018

Cited by 16 | Viewed by 5681

Abstract

One of the crucial issues in the pharmacological field is developing new drug delivery systems. The main concern is to develop new methods for improving the drug delivery efficiencies such as low disruptions, precise control of the target of delivery and drug sustainability. [...] Read more.

One of the crucial issues in the pharmacological field is developing new drug delivery systems. The main concern is to develop new methods for improving the drug delivery efficiencies such as low disruptions, precise control of the target of delivery and drug sustainability. Nowadays, there are many various methods for drug delivery systems. Carbon-based nanocarriers are a new efficient tool for translocating drug into the defined area or cells inside the body. These nanocarriers can be functionalized with proteins, peptides and used to transport their freight to cells or defined areas. Since functionalized carbon-based nanocarriers show low toxicity and high biocompatibility, they are used in many nanobiotechnology fields. In this study, different shapes of nanocarrier are investigated, and the suitable magnetic field, which is applied using MRI for the delivery of the nanocarrier, is proposed. In this research, based on the force required to cross the membrane and MD simulations, the optimal magnetic field profile is designed. This optimal magnetic force field is derived from the mathematical model of the system and magnetic particle dynamics inside the nanocarrier. The results of this paper illustrate the effects of the nanocarrier’s shapes on the percentage of success in crossing the membrane and the optimal required magnetic field. Full article

(This article belongs to the Special Issue Bio-MEMS for Precision Medicine)

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16 pages, 10116 KiB

Open AccessArticle

Cutting Pattern Identification for Coal Mining Shearer through a Swarm Intelligence–Based Variable Translation Wavelet Neural Network

by Jing Xu¹, Zhongbin Wang^1,*, Chao Tan¹, Lei Si¹

and Xinhua Liu^1,2

¹ School of Mechatronic Engineering, China University of Mining and Technology, No.1 Daxue Road, Xuzhou 221116, China

² Institute of Sound and Vibration Research, University of Southampton, Highfield, Southampton SO17 1BJ, UK

Sensors 2018, 18(2), 382; https://doi.org/10.3390/s18020382 - 29 Jan 2018

Cited by 22 | Viewed by 4606

Abstract

As a sound signal has the advantages of non-contacted measurement, compact structure, and low power consumption, it has resulted in much attention in many fields. In this paper, the sound signal of the coal mining shearer is analyzed to realize the accurate online [...] Read more.

As a sound signal has the advantages of non-contacted measurement, compact structure, and low power consumption, it has resulted in much attention in many fields. In this paper, the sound signal of the coal mining shearer is analyzed to realize the accurate online cutting pattern identification and guarantee the safety quality of the working face. The original acoustic signal is first collected through an industrial microphone and decomposed by adaptive ensemble empirical mode decomposition (EEMD). A 13-dimensional set composed by the normalized energy of each level is extracted as the feature vector in the next step. Then, a swarm intelligence optimization algorithm inspired by bat foraging behavior is applied to determine key parameters of the traditional variable translation wavelet neural network (VTWNN). Moreover, a disturbance coefficient is introduced into the basic bat algorithm (BA) to overcome the disadvantage of easily falling into local extremum and limited exploration ability. The VTWNN optimized by the modified BA (VTWNN-MBA) is used as the cutting pattern recognizer. Finally, a simulation example, with an accuracy of 95.25%, and a series of comparisons are conducted to prove the effectiveness and superiority of the proposed method. Full article

(This article belongs to the Special Issue Sensor Signal and Information Processing)

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15 pages, 1590 KiB

Open AccessArticle

A Triaxial Applicator for the Measurement of the Electromagnetic Properties of Materials

by Saranraj Karuppuswami¹

, Edward Rothwell^1,*

, Premjeet Chahal¹ and Michael Havrilla²

¹ Department of Electrical and Computer Engineering, Michigan State University, East Lansing, MI 48824, USA

² Department of Electrical and Computer Engineering, Air Force Institute of Technology, Wright-Patterson Air Force Base, OH 45433-7765, USA

Sensors 2018, 18(2), 383; https://doi.org/10.3390/s18020383 - 29 Jan 2018

Cited by 1 | Viewed by 3671

Abstract

The design, analysis, and fabrication of a prototype triaxial applicator is described. The applicator provides both reflected and transmitted signals that can be used to characterize the electromagnetic properties of materials in situ. A method for calibrating the probe is outlined and validated [...] Read more.

The design, analysis, and fabrication of a prototype triaxial applicator is described. The applicator provides both reflected and transmitted signals that can be used to characterize the electromagnetic properties of materials in situ. A method for calibrating the probe is outlined and validated using simulated data. Fabrication of the probe is discussed, and measured data for typical absorbing materials and for the probe situated in air are presented. The simulations and measurements suggest that the probe should be useful for measuring the properties of common radar absorbing materials under usual in situ conditions. Full article

(This article belongs to the Section Physical Sensors)

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12 pages, 4971 KiB

Open AccessArticle

A New Strategy Involving the Use of Peptides and Graphene Oxide for Fluorescence Turn-on Detection of Proteins

by Huan Shi^1,2,†, Bibo Zhang^1,2,†, Shuwen Liu^1,2, Chunyan Tan^1,2, Ying Tan^1,2,*

and Yuyang Jiang^2,3

¹ Department of Chemistry, Tsinghua University, Beijing 100084, China

² The State Key Laboratory Breeding Base-Shenzhen Key Laboratory of Chemical Biology, the Graduate School at Shenzhen, Tsinghua University, Shenzhen 518055, China

³ School of Pharmaceutical Sciences, Tsinghua University, Beijing 100084, China

^† These authors contributed equally to this work.

Sensors 2018, 18(2), 385; https://doi.org/10.3390/s18020385 - 29 Jan 2018

Cited by 8 | Viewed by 4214

Abstract

The detection of proteins is of great biological significance as disease biomarkers in early diagnosis, prognosis tracking and therapeutic evaluation. Thus, we developed a simple, sensitive and universal protein-sensing platform based on peptide and graphene oxide (GO). The design consists of a fluorophore [...] Read more.

The detection of proteins is of great biological significance as disease biomarkers in early diagnosis, prognosis tracking and therapeutic evaluation. Thus, we developed a simple, sensitive and universal protein-sensing platform based on peptide and graphene oxide (GO). The design consists of a fluorophore (TAMRA, TAM), a peptide containing eight arginines and peptide ligand that could recognize the target protein, and GO used as a quencher. To demonstrate the feasible use of the sensor for target detection, Bcl-xL was evaluated as the model target. The sensor was proved to be sensitive and applied for the detection of the target proteins in buffer, 2% serum and living cells. Full article

(This article belongs to the Special Issue Carbon Materials Based Sensors and the Application)

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15 pages, 6868 KiB

Open AccessArticle

Use of Acoustic Emission and Pattern Recognition for Crack Detection of a Large Carbide Anvil

by Bin Chen^1,*, Yanan Wang¹ and Zhaoli Yan²

¹ School of Automation, Beijing University of Posts and Telecommunications, Beijing 100876, China

² Key Laboratory of Noise and Vibration Research, Institute of Acoustics, Chinese Academy of Sciences, Beijing 100190, China

Sensors 2018, 18(2), 386; https://doi.org/10.3390/s18020386 - 29 Jan 2018

Cited by 13 | Viewed by 4695

Abstract

Large-volume cubic high-pressure apparatus is commonly used to produce synthetic diamond. Due to the high pressure, high temperature and alternative stresses in practical production, cracks often occur in the carbide anvil, thereby resulting in significant economic losses or even casualties. Conventional methods are [...] Read more.

Large-volume cubic high-pressure apparatus is commonly used to produce synthetic diamond. Due to the high pressure, high temperature and alternative stresses in practical production, cracks often occur in the carbide anvil, thereby resulting in significant economic losses or even casualties. Conventional methods are unsuitable for crack detection of the carbide anvil. This paper is concerned with acoustic emission-based crack detection of carbide anvils, regarded as a pattern recognition problem; this is achieved using a microphone, with methods including sound pulse detection, feature extraction, feature optimization and classifier design. Through analyzing the characteristics of background noise, the cracked sound pulses are separated accurately from the originally continuous signal. Subsequently, three different kinds of features including a zero-crossing rate, sound pressure levels, and linear prediction cepstrum coefficients are presented for characterizing the cracked sound pulses. The original high-dimensional features are adaptively optimized using principal component analysis. A hybrid framework of a support vector machine with k nearest neighbors is designed to recognize the cracked sound pulses. Finally, experiments are conducted in a practical diamond workshop to validate the feasibility and efficiency of the proposed method. Full article

(This article belongs to the Section Sensor Networks)

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20 pages, 17167 KiB

Open AccessArticle

Compressive Multispectral Spectrum Sensing for Spectrum Cartography

by Jeison Marín Alfonso¹, Jose Ignacio Martínez Torre^2,*, Henry Arguello Fuentes³ and Leonardo Betancur Agudelo¹

¹ GIDATI Research Group, Universidad Pontificia Bolivariana, 050031 Medellín, Colombia

² GHDwSw Research Group, ETSII, Campus Energía Inteligente, Universidad Rey Juan Carlos, 28933 Madrid, España

³ HDSP Research Group, Universidad Industrial de Santander, 680002 Bucaramanga, Colombia

Sensors 2018, 18(2), 387; https://doi.org/10.3390/s18020387 - 29 Jan 2018

Cited by 3 | Viewed by 3890

Abstract

In the process of spectrum sensing applied to wireless communications, it is possible to build interference maps based on acquired power spectral values. This allows the characterization of spectral occupation, which is crucial to take management spectrum decisions. However, the amount of information [...] Read more.

In the process of spectrum sensing applied to wireless communications, it is possible to build interference maps based on acquired power spectral values. This allows the characterization of spectral occupation, which is crucial to take management spectrum decisions. However, the amount of information both in the space and frequency domains that needs to be processed generates an enormous amount of data with high transmission delays and high memory requirements. Meanwhile, compressive sensing is a technique that allows the reconstruction of sparse or compressible signals using fewer samples than those required by the Nyquist criterion. This paper presents a new model that uses compressed multispectral sampling for spectrum sensing. The aim is to reduce the number of data required for the storage and the subsequent construction of power spectral maps with geo-referenced information in different frequency bands. This model is based on architectures that use compressive sensing to analyze multispectral images. The operation of a centralized manager is presented in order to select the power data of different sensors by binary patterns. These sensors are located in different geographical positions. The centralized manager reconstructs a data cube with the transmitted power and frequency of operation of all the sensors based on the samples taken and applying multispectral sensing techniques. The results show that this multispectral data cube can be built with 50% of the samples generated by the devices, and the spectrum cartography information can be stored using only 6.25% of the original data. Full article

(This article belongs to the Section Physical Sensors)

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14 pages, 1385 KiB

Open AccessArticle

Feature Extraction of Electronic Nose Signals Using QPSO-Based Multiple KFDA Signal Processing

by Tailai Wen¹, Jia Yan^1,2,*, Daoyu Huang¹, Kun Lu³, Changjian Deng¹, Tanyue Zeng¹, Song Yu¹ and Zhiyi He¹

¹ College of Electronic and Information Engineering, Southwest University, Chongqing 400715, China

² Chongqing Key Laboratory of Nonlinear Circuits and Intelligent Information Processing, Chongqing 400715, China

³ High Tech Department, China International Engineering Consulting Corporation, Beijing 100048, China

Sensors 2018, 18(2), 388; https://doi.org/10.3390/s18020388 - 29 Jan 2018

Cited by 17 | Viewed by 4752

Abstract

The aim of this research was to enhance the classification accuracy of an electronic nose (E-nose) in different detecting applications. During the learning process of the E-nose to predict the types of different odors, the prediction accuracy was not quite satisfying because the [...] Read more.

The aim of this research was to enhance the classification accuracy of an electronic nose (E-nose) in different detecting applications. During the learning process of the E-nose to predict the types of different odors, the prediction accuracy was not quite satisfying because the raw features extracted from sensors’ responses were regarded as the input of a classifier without any feature extraction processing. Therefore, in order to obtain more useful information and improve the E-nose’s classification accuracy, in this paper, a Weighted Kernels Fisher Discriminant Analysis (WKFDA) combined with Quantum-behaved Particle Swarm Optimization (QPSO), i.e., QWKFDA, was presented to reprocess the original feature matrix. In addition, we have also compared the proposed method with quite a few previously existing ones including Principal Component Analysis (PCA), Locality Preserving Projections (LPP), Fisher Discriminant Analysis (FDA) and Kernels Fisher Discriminant Analysis (KFDA). Experimental results proved that QWKFDA is an effective feature extraction method for E-nose in predicting the types of wound infection and inflammable gases, which shared much higher classification accuracy than those of the contrast methods. Full article

(This article belongs to the Special Issue Artificial Olfaction and Taste)

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22 pages, 20161 KiB

Open AccessArticle

Implementation and Operational Analysis of an Interactive Intensive Care Unit within a Smart Health Context

by Peio Lopez-Iturri¹

, Erik Aguirre¹

, Jesús Daniel Trigo^1,2

, José Javier Astrain^2,3

, Leyre Azpilicueta⁴

, Luis Serrano^1,2

, Jesús Villadangos^2,3

and Francisco Falcone^1,2,*

¹ Department of Electrical and Electronic Engineering, Public University of Navarre, 31006 Pamplona, Navarra, Spain

² Institute of Smart Cities, Public University of Navarre, 31006 Pamplona, Navarra, Spain

³ Department of Mathematical Engineering and Computer Science, Public University of Navarre, 31006 Pamplona, Navarra, Spain

⁴ School of Engineering and Sciences, Tecnologico de Monterrey, 64849 Monterrey, Mexico

Sensors 2018, 18(2), 389; https://doi.org/10.3390/s18020389 - 29 Jan 2018

Cited by 16 | Viewed by 5786

Abstract

In the context of hospital management and operation, Intensive Care Units (ICU) are one of the most challenging in terms of time responsiveness and criticality, in which adequate resource management and signal processing play a key role in overall system performance. In this [...] Read more.

In the context of hospital management and operation, Intensive Care Units (ICU) are one of the most challenging in terms of time responsiveness and criticality, in which adequate resource management and signal processing play a key role in overall system performance. In this work, a context aware Intensive Care Unit is implemented and analyzed to provide scalable signal acquisition capabilities, as well as to provide tracking and access control. Wireless channel analysis is performed by means of hybrid optimized 3D Ray Launching deterministic simulation to assess potential interference impact as well as to provide required coverage/capacity thresholds for employed transceivers. Wireless system operation within the ICU scenario, considering conventional transceiver operation, is feasible in terms of quality of service for the complete scenario. Extensive measurements of overall interference levels have also been carried out, enabling subsequent adequate coverage/capacity estimations, for a set of Zigbee based nodes. Real system operation has been tested, with ad-hoc designed Zigbee wireless motes, employing lightweight communication protocols to minimize energy and bandwidth usage. An ICU information gathering application and software architecture for Visitor Access Control has been implemented, providing monitoring of the Boxes external doors and the identification of visitors via a RFID system. The results enable a solution to provide ICU access control and tracking capabilities previously not exploited, providing a step forward in the implementation of a Smart Health framework. Full article

(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Spain 2017)

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14 pages, 4345 KiB

Open AccessArticle

The Effect of Zeolite Composition and Grain Size on Gas Sensing Properties of SnO₂/Zeolite Sensor

by Yanhui Sun^1,2

, Jing Wang^1,*, Xiaogan Li^1,*, Haiying Du^1,3, Qingpan Huang¹ and Xiaofeng Wang⁴

¹ Faculty of Electronic Information and Electrical Engineering, Dalian University of Technology, Dalian 116024, China

² College of Information & Communication Engineering, Dalian Minzu University, Dalian 116600, China

³ College of Mechanical and Electronic Engineering, Dalian Minzu University, Dalian 116600, China

⁴ School of Mathematical and Physical Sciences, Dalian University of Technology, Panjin Campus, Panjin 124000, China

Sensors 2018, 18(2), 390; https://doi.org/10.3390/s18020390 - 29 Jan 2018

Cited by 29 | Viewed by 6303

Abstract

In order to improve the sensing properties of tin dioxide gas sensor, four kinds of different SiO₂/Al₂O₃ ratio, different particle size of MFI type zeolites (ZSM-5) were coated on the SnO₂ to prepared zeolite modified gas sensors, [...] Read more.

In order to improve the sensing properties of tin dioxide gas sensor, four kinds of different SiO₂/Al₂O₃ ratio, different particle size of MFI type zeolites (ZSM-5) were coated on the SnO₂ to prepared zeolite modified gas sensors, and the gas sensing properties were tested. The measurement results showed that the response values of ZSM-5 zeolite (SiO₂/Al₂O₃ = 70, grain size 300 nm) coated SnO₂ gas sensors to formaldehyde vapor were increased, and the response to acetone decreased compared with that of SnO₂ gas sensor, indicating an improved selectivity property. The other three ZSM-5 zeolites with SiO₂/Al₂O₃ 70, 150 and 470, respectively, and grain sizes all around 1 μm coated SnO₂ sensors did not show much difference with SnO₂ sensor for the response properties to both formaldehyde and acetone. The sensing mechanism of ZSM-5 modified sensors was briefly analyzed. Full article

(This article belongs to the Special Issue Novel Sensors Based on Metal Oxide Films and Structures)

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22 pages, 5822 KiB

Open AccessArticle

Research on the Effects of Drying Temperature on Nitrogen Detection of Different Soil Types by Near Infrared Sensors

by Pengcheng Nie^1,2,3, Tao Dong^1,2

, Yong He^1,2,*

and Shupei Xiao^1,2

¹ College of Biosystems Engineering and Food Science, Zhejiang University, Hangzhou 310058, China

² Key Laboratory of Sensors Sensing, Ministry of Agriculture, Zhejiang University, Hangzhou 310058, China

³ State Key Laboratory of Modern Optical Instrumentation, Zhejiang University, Hangzhou 310058, China

Sensors 2018, 18(2), 391; https://doi.org/10.3390/s18020391 - 29 Jan 2018

Cited by 17 | Viewed by 5278

Abstract

Soil is a complicated system whose components and mechanisms are complex and difficult to be fully excavated and comprehended. Nitrogen is the key parameter supporting plant growth and development, and is the material basis of plant growth as well. An accurate grasp of [...] Read more.

Soil is a complicated system whose components and mechanisms are complex and difficult to be fully excavated and comprehended. Nitrogen is the key parameter supporting plant growth and development, and is the material basis of plant growth as well. An accurate grasp of soil nitrogen information is the premise of scientific fertilization in precision agriculture, where near infrared sensors are widely used for rapid detection of nutrients in soil. However, soil texture, soil moisture content and drying temperature all affect soil nitrogen detection using near infrared sensors. In order to investigate the effects of drying temperature on the nitrogen detection in black soil, loess and calcium soil, three kinds of soils were detected by near infrared sensors after 25 °C placement (ambient temperature), 50 °C drying (medium temperature), 80 °C drying (medium-high temperature) and 95 °C drying (high temperature). The successive projections algorithm based on multiple linear regression (SPA-MLR), partial least squares (PLS) and competitive adaptive reweighted squares (CARS) were used to model and analyze the spectral information of different soil types. The predictive abilities were assessed using the prediction correlation coefficients (R_P), the root mean squared error of prediction (RMSEP), and the residual predictive deviation (RPD). The results showed that the loess (R_P = 0.9721, RMSEP = 0.067 g/kg, RPD = 4.34) and calcium soil (R_P = 0.9588, RMSEP = 0.094 g/kg, RPD = 3.89) obtained the best prediction accuracy after 95 °C drying. The detection results of black soil (R_P = 0.9486, RMSEP = 0.22 g/kg, RPD = 2.82) after 80 °C drying were the optimum. In conclusion, drying temperature does have an obvious influence on the detection of soil nitrogen by near infrared sensors, and the suitable drying temperature for different soil types was of great significance in enhancing the detection accuracy. Full article

(This article belongs to the Special Issue Sensors in Agriculture)

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18 pages, 3874 KiB

Open AccessArticle

A Total Bounded Variation Approach to Low Visibility Estimation on Expressways

by Xiaogang Cheng^1,2,3,*, Bin Yang^2,4, Guoqing Liu⁵, Thomas Olofsson² and Haibo Li^1,3

¹ College of Telecommunications and Information Engineering, Nanjing University of Posts and Telecommunications, Nanjing 210003, China

² Department of Applied Physics and Electronics, Umeå University, 90187 Umeå, Sweden

³ School of Electrical Engineering and Computer Science, Royal Institute of Technology, 10044 Stockholm, Sweden

⁴ School of Environmental and Municipal Engineering, Xi’an University of Architecture and Technology, Xi’an 710055, China

⁵ School of Physical and Mathematical Sciences, Nanjing Tech University, Nanjing 211800, China

Sensors 2018, 18(2), 392; https://doi.org/10.3390/s18020392 - 29 Jan 2018

Cited by 10 | Viewed by 4696

Abstract

Low visibility on expressways caused by heavy fog and haze is a main reason for traffic accidents. Real-time estimation of atmospheric visibility is an effective way to reduce traffic accident rates. With the development of computer technology, estimating atmospheric visibility via computer vision [...] Read more.

Low visibility on expressways caused by heavy fog and haze is a main reason for traffic accidents. Real-time estimation of atmospheric visibility is an effective way to reduce traffic accident rates. With the development of computer technology, estimating atmospheric visibility via computer vision becomes a research focus. However, the estimation accuracy should be enhanced since fog and haze are complex and time-varying. In this paper, a total bounded variation (TBV) approach to estimate low visibility (less than 300 m) is introduced. Surveillance images of fog and haze are processed as blurred images (pseudo-blurred images), while the surveillance images at selected road points on sunny days are handled as clear images, when considering fog and haze as noise superimposed on the clear images. By combining image spectrum and TBV, the features of foggy and hazy images can be extracted. The extraction results are compared with features of images on sunny days. Firstly, the low visibility surveillance images can be filtered out according to spectrum features of foggy and hazy images. For foggy and hazy images with visibility less than 300 m, the high-frequency coefficient ratio of Fourier (discrete cosine) transform is less than 20%, while the low-frequency coefficient ratio is between 100% and 120%. Secondly, the relationship between TBV and real visibility is established based on machine learning and piecewise stationary time series analysis. The established piecewise function can be used for visibility estimation. Finally, the visibility estimation approach proposed is validated based on real surveillance video data. The validation results are compared with the results of image contrast model. Besides, the big video data are collected from the Tongqi expressway, Jiangsu, China. A total of 1,782,000 frames were used and the relative errors of the approach proposed are less than 10%. Full article

(This article belongs to the Special Issue The Architectures, Systems, and Applications of Internet of Things for Smart Cities)

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22 pages, 4199 KiB

Open AccessArticle

A Compact Operational Amplifier with Load-Insensitive Stability Compensation for High-Precision Transducer Interface

by Zhanghao Yu^1,*

, Xi Yang² and SungWon Chung¹

¹ Department of Electrical Engineering, University of Southern California, Los Angeles, CA 90089, USA

² Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, MA 02139, USA

Sensors 2018, 18(2), 393; https://doi.org/10.3390/s18020393 - 29 Jan 2018

Cited by 3 | Viewed by 6970

Abstract

High-resolution electronic interface circuits for transducers with nonlinear capacitive impedance need an operational amplifier, which is stable for a wide range of load capacitance. Such operational amplifier in a conventional design requires a large area for compensation capacitors, increasing costs and limiting applications. [...] Read more.

High-resolution electronic interface circuits for transducers with nonlinear capacitive impedance need an operational amplifier, which is stable for a wide range of load capacitance. Such operational amplifier in a conventional design requires a large area for compensation capacitors, increasing costs and limiting applications. In order to address this problem, we present a gain-boosted two-stage operational amplifier, whose frequency response compensation capacitor size is insensitive to the load capacitance and also orders of magnitude smaller compared to the conventional Miller-compensation capacitor that often dominates chip area. By exploiting pole-zero cancellation between a gain-boosting stage and the main amplifier stage, the compensation capacitor of the proposed operational amplifier becomes less dependent of load capacitance, so that it can also operate with a wide range of load capacitance. A prototype operational amplifier designed in 0.13-

μ

m complementary metal–oxide–semiconductor (CMOS) with a 400-fF compensation capacitor occupies 900-

μ

m

^{2}

chip area and achieves 0.022–2.78-MHz unity gain bandwidth and over 65

^{\circ}

phase margin with a load capacitance of 0.1–15 nF. The prototype amplifier consumes 7.6

μ

W from a single 1.0-V supply. For a given compensation capacitor size and a chip area, the prototype design demonstrates the best reported performance trade-off on unity gain bandwidth, maximum stable load capacitance, and power consumption. Full article

(This article belongs to the Section Physical Sensors)

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17 pages, 3824 KiB

Open AccessArticle

What is the Best Configuration of Wearable Sensors to Measure Spatiotemporal Gait Parameters in Children with Cerebral Palsy?

by Lena Carcreff^1,2,*

, Corinna N. Gerber³

, Anisoara Paraschiv-Ionescu²

, Geraldo De Coulon⁴, Christopher J. Newman³

, Stéphane Armand¹ and Kamiar Aminian²

¹ Laboratory of Kinesiology Willy Taillard, Geneva University Hospitals and University of Geneva, 1205 Geneva, Switzerland

² Laboratory of Movement Analysis and Measurement, Ecole Polytechnique Fédérale de Lausanne, 1015 Lausanne, Switzerland

³ Pediatric Neurology and Neurorehabilitation Unit, Department of Pediatrics, Lausanne University Hospital, 1011 Lausanne, Switzerland

⁴ Pediatric orthopedics, Geneva University Hospitals, 1205 Geneva, Switzerland

Sensors 2018, 18(2), 394; https://doi.org/10.3390/s18020394 - 30 Jan 2018

Cited by 46 | Viewed by 8235

Abstract

Wearable inertial devices have recently been used to evaluate spatiotemporal parameters of gait in daily life situations. Given the heterogeneity of gait patterns in children with cerebral palsy (CP), the sensor placement and analysis algorithm may influence the validity of the results. This [...] Read more.

Wearable inertial devices have recently been used to evaluate spatiotemporal parameters of gait in daily life situations. Given the heterogeneity of gait patterns in children with cerebral palsy (CP), the sensor placement and analysis algorithm may influence the validity of the results. This study aimed at comparing the spatiotemporal measurement performances of three wearable configurations defined by different sensor positioning on the lower limbs: (1) shanks and thighs, (2) shanks, and (3) feet. The three configurations were selected based on their potential to be used in daily life for children with CP and typically developing (TD) controls. For each configuration, dedicated gait analysis algorithms were used to detect gait events and compute spatiotemporal parameters. Fifteen children with CP and 11 TD controls were included. Accuracy, precision, and agreement of the three configurations were determined in comparison with an optoelectronic system as a reference. The three configurations were comparable for the evaluation of TD children and children with a low level of disability (CP-GMFCS I) whereas the shank-and-thigh-based configuration was more robust regarding children with a higher level of disability (CP-GMFCS II–III). Full article

(This article belongs to the Special Issue Sensors for Gait, Posture, and Health Monitoring)

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22 pages, 18224 KiB

Open AccessArticle

Analysis of 3D Scan Measurement Distribution with Application to a Multi-Beam Lidar on a Rotating Platform

by Jesús Morales

, Victoria Plaza-Leiva, Anthony Mandow

, Jose Antonio Gomez-Ruiz^*

, Javier Serón and Alfonso García-Cerezo

Robotics and Mechatronics Lab, Andalucía Tech, Universidad de Málaga, 29071 Málaga, Spain

Sensors 2018, 18(2), 395; https://doi.org/10.3390/s18020395 - 30 Jan 2018

Cited by 27 | Viewed by 10426

Abstract

Multi-beam lidar (MBL) rangefinders are becoming increasingly compact, light, and accessible 3D sensors, but they offer limited vertical resolution and field of view. The addition of a degree-of-freedom to build a rotating multi-beam lidar (RMBL) has the potential to become a common solution [...] Read more.

Multi-beam lidar (MBL) rangefinders are becoming increasingly compact, light, and accessible 3D sensors, but they offer limited vertical resolution and field of view. The addition of a degree-of-freedom to build a rotating multi-beam lidar (RMBL) has the potential to become a common solution for affordable rapid full-3D high resolution scans. However, the overlapping of multiple-beams caused by rotation yields scanning patterns that are more complex than in rotating single beam lidar (RSBL). In this paper, we propose a simulation-based methodology to analyze 3D scanning patterns which is applied to investigate the scan measurement distribution produced by the RMBL configuration. With this purpose, novel contributions include: (i) the adaption of a recent spherical reformulation of Ripley’s K function to assess 3D sensor data distribution on a hollow sphere simulation; (ii) a comparison, both qualitative and quantitative, between scan patterns produced by an ideal RMBL based on a Velodyne VLP-16 (Puck) and those of other 3D scan alternatives (i.e., rotating 2D lidar and MBL); and (iii) a new RMBL implementation consisting of a portable tilting platform for VLP-16 scanners, which is presented as a case study for measurement distribution analysis as well as for the discussion of actual scans from representative environments. Results indicate that despite the particular sampling patterns given by a RMBL, its homogeneity even improves that of an equivalent RSBL. Full article

(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Spain 2017)

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17 pages, 3109 KiB

Open AccessArticle

A Flexible Multiring Concentric Electrode for Non-Invasive Identification of Intestinal Slow Waves

by Victor Zena-Giménez¹

, Javier Garcia-Casado^1,*

, Yiyao Ye-Lin¹, Eduardo Garcia-Breijo²

and Gema Prats-Boluda¹

¹ Centro de Investigación e Innovación en Bioingeniería, Universitat Politècnica de València, Valencia 46022, Spain

² Instituto Interuniversitario de Investigación de Reconocimiento Molecular y Desarrollo Tecnológico, Universitat Politècnica de València, Valencia 46022, Spain

Sensors 2018, 18(2), 396; https://doi.org/10.3390/s18020396 - 30 Jan 2018

Cited by 15 | Viewed by 5368

Abstract

Developing new types of optimized electrodes for specific biomedical applications can substantially improve the quality of the sensed signals. Concentric ring electrodes have been shown to provide enhanced spatial resolution to that of conventional disc electrodes. A sensor with different electrode sizes and [...] Read more.

Developing new types of optimized electrodes for specific biomedical applications can substantially improve the quality of the sensed signals. Concentric ring electrodes have been shown to provide enhanced spatial resolution to that of conventional disc electrodes. A sensor with different electrode sizes and configurations (monopolar, bipolar, etc.) that provides simultaneous records would be very helpful for studying the best signal-sensing arrangement. A 5-pole electrode with an inner disc and four concentric rings of different sizes was developed and tested on surface intestinal myoelectrical recordings from healthy humans. For good adaptation to a curved body surface, the electrode was screen-printed onto a flexible polyester substrate. To facilitate clinical use, it is self-adhesive, incorporates a single connector and can perform dry or wet (with gel) recordings. The results show it to be a versatile electrode that can evaluate the optimal configuration for the identification of the intestinal slow wave and reject undesired interference. A bipolar concentric record with an outer ring diameter of 30 mm, a foam-free adhesive material, and electrolytic gel gave the best results. Full article

(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Spain 2017)

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17 pages, 17821 KiB

Open AccessArticle

Automatic Coregistration Algorithm to Remove Canopy Shaded Pixels in UAV-Borne Thermal Images to Improve the Estimation of Crop Water Stress Index of a Drip-Irrigated Cabernet Sauvignon Vineyard

by Tomas Poblete¹

, Samuel Ortega-Farías^1,2,*

and Dongryeol Ryu³

¹ Centro de Investigación y Transferencia en Riego y Agroclimatología (CITRA), Universidad de Talca, Casilla 747, Talca 3460000, Chile

² Research Program on Adaptation of Agriculture to Climate Change (A2C2), Universidad de Talca, Casilla 747, Talca 3460000, Chile

³ Department of Infrastructure Engineering, The University of Melbourne, Parkville 3010, Australia

Sensors 2018, 18(2), 397; https://doi.org/10.3390/s18020397 - 30 Jan 2018

Cited by 66 | Viewed by 7453

Abstract

Water stress caused by water scarcity has a negative impact on the wine industry. Several strategies have been implemented for optimizing water application in vineyards. In this regard, midday stem water potential (SWP) and thermal infrared (TIR) imaging for crop water stress index [...] Read more.

Water stress caused by water scarcity has a negative impact on the wine industry. Several strategies have been implemented for optimizing water application in vineyards. In this regard, midday stem water potential (SWP) and thermal infrared (TIR) imaging for crop water stress index (CWSI) have been used to assess plant water stress on a vine-by-vine basis without considering the spatial variability. Unmanned Aerial Vehicle (UAV)-borne TIR images are used to assess the canopy temperature variability within vineyards that can be related to the vine water status. Nevertheless, when aerial TIR images are captured over canopy, internal shadow canopy pixels cannot be detected, leading to mixed information that negatively impacts the relationship between CWSI and SWP. This study proposes a methodology for automatic coregistration of thermal and multispectral images (ranging between 490 and 900 nm) obtained from a UAV to remove shadow canopy pixels using a modified scale invariant feature transformation (SIFT) computer vision algorithm and Kmeans++ clustering. Our results indicate that our proposed methodology improves the relationship between CWSI and SWP when shadow canopy pixels are removed from a drip-irrigated Cabernet Sauvignon vineyard. In particular, the coefficient of determination (R²) increased from 0.64 to 0.77. In addition, values of the root mean square error (RMSE) and standard error (SE) decreased from 0.2 to 0.1 MPa and 0.24 to 0.16 MPa, respectively. Finally, this study shows that the negative effect of shadow canopy pixels was higher in those vines with water stress compared with well-watered vines. Full article

(This article belongs to the Special Issue UAV or Drones for Remote Sensing Applications)

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22 pages, 6583 KiB

Open AccessArticle

A Liquid-Surface-Based Three-Axis Inclination Sensor for Measurement of Stage Tilt Motions

by Yuki Shimizu^*, Satoshi Kataoka, Tatsuya Ishikawa, Yuan-Liu Chen

, Xiuguo Chen

, Hiraku Matsukuma

and Wei Gao

Department of Finemechanics, Tohoku University, Sendai 980-8579, Japan

Sensors 2018, 18(2), 398; https://doi.org/10.3390/s18020398 - 30 Jan 2018

Cited by 17 | Viewed by 7913

Abstract

In this paper a new concept of a liquid-surface-based three-axis inclination sensor for evaluation of angular error motion of a precision linear slide, which is often used in the field of precision engineering such as ultra-precision machine tools, coordinate measuring machines (CMMs) and [...] Read more.

In this paper a new concept of a liquid-surface-based three-axis inclination sensor for evaluation of angular error motion of a precision linear slide, which is often used in the field of precision engineering such as ultra-precision machine tools, coordinate measuring machines (CMMs) and so on, is proposed. In the liquid-surface-based three-axis inclination sensor, a reference float mounting a line scale grating having periodic line grating structures is made to float over a liquid surface, while its three-axis angular motion is measured by using an optical sensor head based on the three-axis laser autocollimation capable of measuring three-axis angular motion of the scale grating. As the first step of research, in this paper, theoretical analysis on the angular motion of the reference float about each axis has been carried out based on simplified kinematic models to evaluate the possibility of realizing the proposed concept of a three-axis inclination sensor. In addition, based on the theoretical analyses results, a prototype three-axis inclination sensor has been designed and developed. Through some basic experiments with the prototype, the possibility of simultaneous three-axis inclination measurement by the proposed concept has been verified. Full article

(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Japan 2017)

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7 pages, 2442 KiB

Open AccessArticle

Compact Surface Plasmon Resonance System with Au/Si Schottky Barrier

by Takuya Tsukagoshi¹, Yuta Kuroda², Kentaro Noda², Nguyen Binh-Khiem², Tetsuo Kan³

and Isao Shimoyama^1,2,*

¹ Information and Robot Technology Research Initiative, The University of Tokyo, Tokyo 113-8656, Japan

² Department of Mechano-Informatics, Graduate School of Information Science and Technology, The University of Tokyo, Tokyo 113-8656, Japan

³ Graduate School of Informatics and Engineering, The University of Electro-Communications, Tokyo 182-8585, Japan

Sensors 2018, 18(2), 399; https://doi.org/10.3390/s18020399 - 30 Jan 2018

Cited by 18 | Viewed by 5607

Abstract

Ethanol concentration was quantified by the use of a compact surface plasmon resonance (SPR) system, which electrically detects hot electrons via a Schottky barrier. Although it is well known that SPR can be used as bio/chemical sensors, implementation is not necessarily practical, due [...] Read more.

Ethanol concentration was quantified by the use of a compact surface plasmon resonance (SPR) system, which electrically detects hot electrons via a Schottky barrier. Although it is well known that SPR can be used as bio/chemical sensors, implementation is not necessarily practical, due to the size and cost impediments associated with a system with variable wavelength or angle of incidence. However, scanning capability is not a prerequisite if the objective is to use SPR in a sensor. It is possible to build a small, inexpensive SPR sensor if the optics have no moving parts and a Schottky barrier is used for electrical current detection in place of a photodetector. This article reports on the design and performance of such a novel SPR sensor, and its application for quantifying ethanol concentration. As the concentration of ethanol is increased, the change in the angle dependence of the SPR current is observed. This change can be understood as a superposition of contributions of SPR coupled with the +3rd- and −3rd-order diffraction. Moreover, real-time monitoring of ethanol concentration was demonstrated using the proposed SPR system. Full article

(This article belongs to the Section Biosensors)

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25 pages, 14667 KiB

Open AccessArticle

Prototyping a Web-of-Energy Architecture for Smart Integration of Sensor Networks in Smart Grids Domain

by Víctor Caballero^*

, David Vernet

, Agustín Zaballos

and Guiomar Corral

Engineering Department, Universitat Ramon Llull (URL), La Salle, 08022 Barcelona, Spain

Sensors 2018, 18(2), 400; https://doi.org/10.3390/s18020400 - 30 Jan 2018

Cited by 20 | Viewed by 6080

Abstract

Sensor networks and the Internet of Things have driven the evolution of traditional electric power distribution networks towards a new paradigm referred to as Smart Grid. However, the different elements that compose the Information and Communication Technologies (ICTs) layer of a Smart Grid [...] Read more.

Sensor networks and the Internet of Things have driven the evolution of traditional electric power distribution networks towards a new paradigm referred to as Smart Grid. However, the different elements that compose the Information and Communication Technologies (ICTs) layer of a Smart Grid are usually conceived as isolated systems that typically result in rigid hardware architectures which are hard to interoperate, manage, and to adapt to new situations. If the Smart Grid paradigm has to be presented as a solution to the demand for distributed and intelligent energy management system, it is necessary to deploy innovative IT infrastructures to support these smart functions. One of the main issues of Smart Grids is the heterogeneity of communication protocols used by the smart sensor devices that integrate them. The use of the concept of the Web of Things is proposed in this work to tackle this problem. More specifically, the implementation of a Smart Grid’s Web of Things, coined as the Web of Energy is introduced. The purpose of this paper is to propose the usage of Web of Energy by means of the Actor Model paradigm to address the latent deployment and management limitations of Smart Grids. Smart Grid designers can use the Actor Model as a design model for an infrastructure that supports the intelligent functions demanded and is capable of grouping and converting the heterogeneity of traditional infrastructures into the homogeneity feature of the Web of Things. Conducted experimentations endorse the feasibility of this solution and encourage practitioners to point their efforts in this direction. Full article

(This article belongs to the Collection Smart Communication Protocols and Algorithms for Sensor Networks)

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20 pages, 2198 KiB

Open AccessArticle

A Brief Review of Facial Emotion Recognition Based on Visual Information

by Byoung Chul Ko

Department of Computer Engineering, Keimyung University, Daegu 42601, Korea

Sensors 2018, 18(2), 401; https://doi.org/10.3390/s18020401 - 30 Jan 2018

Cited by 572 | Viewed by 44974

Abstract

Facial emotion recognition (FER) is an important topic in the fields of computer vision and artificial intelligence owing to its significant academic and commercial potential. Although FER can be conducted using multiple sensors, this review focuses on studies that exclusively use facial images, [...] Read more.

Facial emotion recognition (FER) is an important topic in the fields of computer vision and artificial intelligence owing to its significant academic and commercial potential. Although FER can be conducted using multiple sensors, this review focuses on studies that exclusively use facial images, because visual expressions are one of the main information channels in interpersonal communication. This paper provides a brief review of researches in the field of FER conducted over the past decades. First, conventional FER approaches are described along with a summary of the representative categories of FER systems and their main algorithms. Deep-learning-based FER approaches using deep networks enabling “end-to-end” learning are then presented. This review also focuses on an up-to-date hybrid deep-learning approach combining a convolutional neural network (CNN) for the spatial features of an individual frame and long short-term memory (LSTM) for temporal features of consecutive frames. In the later part of this paper, a brief review of publicly available evaluation metrics is given, and a comparison with benchmark results, which are a standard for a quantitative comparison of FER researches, is described. This review can serve as a brief guidebook to newcomers in the field of FER, providing basic knowledge and a general understanding of the latest state-of-the-art studies, as well as to experienced researchers looking for productive directions for future work. Full article

(This article belongs to the Section Intelligent Sensors)

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27 pages, 3300 KiB

Open AccessArticle

Design and Evaluation of a Pervasive Coaching and Gamification Platform for Young Diabetes Patients

by Randy Klaassen^1,*, Kim C. M. Bul², Rieks Op den Akker¹, Gert Jan Van der Burg³, Pamela M. Kato⁴

and Pierpaolo Di Bitonto⁵

¹ Human Media Interaction, Faculty of Electrical Engineering, Mathematics and Computer Science, University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands

² Centre for Innovative Research across the Life Course, Faculty of Health and Life Sciences, Coventry University, CV1 5FB Coventry, UK

³ Gelderse Vallei Hospital, P.O. Box 9025, 6710 HN Ede, The Netherlands

⁴ School of Computing, Electronics and Mathematics, Faculty of Engineering, Environment and Computing, Coventry University, CV1 5FB Coventry, UK

⁵ Grifo multimedia Srl, Via Bruno Zaccaro, 19-70126 Bari, Italy

Sensors 2018, 18(2), 402; https://doi.org/10.3390/s18020402 - 30 Jan 2018

Cited by 63 | Viewed by 10531

Abstract

Self monitoring, personal goal-setting and coaching, education and social support are strategies to help patients with chronic conditions in their daily care. Various tools have been developed, e.g., mobile digital coaching systems connected with wearable sensors, serious games and patient web portals to [...] Read more.

Self monitoring, personal goal-setting and coaching, education and social support are strategies to help patients with chronic conditions in their daily care. Various tools have been developed, e.g., mobile digital coaching systems connected with wearable sensors, serious games and patient web portals to personal health records, that aim to support patients with chronic conditions and their caregivers in realizing the ideal of self-management. We describe a platform that integrates these tools to support young patients in diabetes self-management through educational game playing, monitoring and motivational feedback. We describe the design of the platform referring to principles from healthcare, persuasive system design and serious game design. The virtual coach is a game guide that can also provide personalized feedback about the user’s daily care related activities which have value for making progress in the game world. User evaluations with patients under pediatric supervision revealed that the use of mobile technology in combination with web-based elements is feasible but some assumptions made about how users would connect to the platform were not satisfied in reality, resulting in less than optimal user experiences. We discuss challenges with suggestions for further development of integrated pervasive coaching and gamification platforms in medical practice. Full article

(This article belongs to the Special Issue Smart Sensing Technologies for Personalised Coaching)

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12 pages, 1335 KiB

Open AccessArticle

Polarimetric Calibration and Quality Assessment of the GF-3 Satellite Images

by Yonglei Chang¹, Pingxiang Li^1,*, Jie Yang¹, Jinqi Zhao¹

, Lingli Zhao² and Lei Shi¹

¹ State Key Laboratory of Information Engineering in Surveying, Mapping and Remote Sensing, Wuhan University, Wuhan 430079, China

² School of Remote Sensing and Engineering, Wuhan University, Wuhan 430079, China

Sensors 2018, 18(2), 403; https://doi.org/10.3390/s18020403 - 30 Jan 2018

Cited by 34 | Viewed by 5002

Abstract

The GaoFen-3 (GF-3) satellite is the first fully polarimetric synthetic aperture radar (SAR) satellite designed for civil use in China. The satellite operates in the C-band and has 12 imaging modes for various applications. Three fully polarimetric SAR (PolSAR) imaging modes are provided [...] Read more.

The GaoFen-3 (GF-3) satellite is the first fully polarimetric synthetic aperture radar (SAR) satellite designed for civil use in China. The satellite operates in the C-band and has 12 imaging modes for various applications. Three fully polarimetric SAR (PolSAR) imaging modes are provided with a resolution of up to 8 m. Although polarimetric calibration (PolCAL) of the SAR system is periodically undertaken, there is still some residual distortion in the images. In order to assess the polarimetric accuracy of this satellite and improve the image quality, we analyzed the polarimetric distortion errors and performed a PolCAL experiment based on scattering properties and corner reflectors. The experiment indicates that the GF-3 images can meet the satellite’s polarimetric accuracy requirements, i.e., a channel imbalance of 0.5 dB in amplitude and ±10 degrees in phase and a crosstalk accuracy of −35 dB. However, some images still contain residual polarimetric distortion. The experiment also shows that the residual errors of the GF-3 standard images can be diminished after further PolCAL, with a channel imbalance of 0.26 dB in amplitude and ±0.2 degrees in phase and a crosstalk accuracy of −42 dB. Full article

(This article belongs to the Special Issue First Experiences with Chinese Gaofen-3 SAR Sensor)

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19 pages, 696 KiB

Open AccessArticle

Wireless Networks under a Backoff Attack: A Game Theoretical Perspective

by Juan Parras^*

and Santiago Zazo

Information Processing and Telecommunications Center, Universidad Politécnica de Madrid, ETSI Telecomunicación, Av. Complutense 30, 28040 Madrid, Spain

Sensors 2018, 18(2), 404; https://doi.org/10.3390/s18020404 - 30 Jan 2018

Cited by 8 | Viewed by 3236

Abstract

We study a wireless sensor network using CSMA/CA in the MAC layer under a backoff attack: some of the sensors of the network are malicious and deviate from the defined contention mechanism. We use Bianchi’s network model to study the impact of the [...] Read more.

We study a wireless sensor network using CSMA/CA in the MAC layer under a backoff attack: some of the sensors of the network are malicious and deviate from the defined contention mechanism. We use Bianchi’s network model to study the impact of the malicious sensors on the total network throughput, showing that it causes the throughput to be unfairly distributed among sensors. We model this conflict using game theory tools, where each sensor is a player. We obtain analytical solutions and propose an algorithm, based on Regret Matching, to learn the equilibrium of the game with an arbitrary number of players. Our approach is validated via simulations, showing that our theoretical predictions adjust to reality. Full article

(This article belongs to the Section Sensor Networks)

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22 pages, 8667 KiB

Open AccessArticle

An Advanced Bio-Inspired PhotoPlethysmoGraphy (PPG) and ECG Pattern Recognition System for Medical Assessment

by Francesco Rundo^1,*

, Sabrina Conoci¹

, Alessandro Ortis²

and Sebastiano Battiato²

¹ STMicroelectronics—ADG Central R&D, 95121 Catania, Italy

² Department of Mathematics and Computer Science, University of Catania, 95125 Catania, Italy

Sensors 2018, 18(2), 405; https://doi.org/10.3390/s18020405 - 30 Jan 2018

Cited by 127 | Viewed by 14129

Abstract

Physiological signals are widely used to perform medical assessment for monitoring an extensive range of pathologies, usually related to cardio-vascular diseases. Among these, both PhotoPlethysmoGraphy (PPG) and Electrocardiography (ECG) signals are those more employed. PPG signals are an emerging non-invasive measurement technique used [...] Read more.

Physiological signals are widely used to perform medical assessment for monitoring an extensive range of pathologies, usually related to cardio-vascular diseases. Among these, both PhotoPlethysmoGraphy (PPG) and Electrocardiography (ECG) signals are those more employed. PPG signals are an emerging non-invasive measurement technique used to study blood volume pulsations through the detection and analysis of the back-scattered optical radiation coming from the skin. ECG is the process of recording the electrical activity of the heart over a period of time using electrodes placed on the skin. In the present paper we propose a physiological ECG/PPG “combo” pipeline using an innovative bio-inspired nonlinear system based on a reaction-diffusion mathematical model, implemented by means of the Cellular Neural Network (CNN) methodology, to filter PPG signal by assigning a recognition score to the waveforms in the time series. The resulting “clean” PPG signal exempts from distortion and artifacts is used to validate for diagnostic purpose an EGC signal simultaneously detected for a same patient. The multisite combo PPG-ECG system proposed in this work overpasses the limitations of the state of the art in this field providing a reliable system for assessing the above-mentioned physiological parameters and their monitoring over time for robust medical assessment. The proposed system has been validated and the results confirmed the robustness of the proposed approach. Full article

(This article belongs to the Special Issue Biomedical Sensors and Systems 2017)

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14 pages, 1654 KiB

Open AccessArticle

Classification of Partial Discharge Signals by Combining Adaptive Local Iterative Filtering and Entropy Features

by Imene Mitiche¹

, Gordon Morison^1,*, Alan Nesbitt¹

, Michael Hughes-Narborough¹

, Brian G. Stewart²

and Philip Boreham³

¹ Department of Engineering, Glasgow Caledonian University, 70 Cowcaddens Road, Glasgow G4 0BA, UK

² Institute of Energy and Environment, University of Strathclyde, 204 George Street, Glasgow G1 1XW, UK

³ Innovation Centre for Online Systems, 7 Townsend Business Park, Bere Regis BH20 7LA, UK

Sensors 2018, 18(2), 406; https://doi.org/10.3390/s18020406 - 31 Jan 2018

Cited by 33 | Viewed by 6146

Abstract

Electromagnetic Interference (EMI) is a technique for capturing Partial Discharge (PD) signals in High-Voltage (HV) power plant apparatus. EMI signals can be non-stationary which makes their analysis difficult, particularly for pattern recognition applications. This paper elaborates upon a previously developed software condition-monitoring model [...] Read more.

Electromagnetic Interference (EMI) is a technique for capturing Partial Discharge (PD) signals in High-Voltage (HV) power plant apparatus. EMI signals can be non-stationary which makes their analysis difficult, particularly for pattern recognition applications. This paper elaborates upon a previously developed software condition-monitoring model for improved EMI events classification based on time-frequency signal decomposition and entropy features. The idea of the proposed method is to map multiple discharge source signals captured by EMI and labelled by experts, including PD, from the time domain to a feature space, which aids in the interpretation of subsequent fault information. Here, instead of using only one permutation entropy measure, a more robust measure, called Dispersion Entropy (DE), is added to the feature vector. Multi-Class Support Vector Machine (MCSVM) methods are utilized for classification of the different discharge sources. Results show an improved classification accuracy compared to previously proposed methods. This yields to a successful development of an expert’s knowledge-based intelligent system. Since this method is demonstrated to be successful with real field data, it brings the benefit of possible real-world application for EMI condition monitoring. Full article

(This article belongs to the Special Issue UHF and RF Sensor Technology for Partial Discharge Detection)

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21 pages, 4181 KiB

Open AccessArticle

Collaborative Indoor Access Point Localization Using Autonomous Mobile Robot Swarm

by Fahed Awad^*, Muhammad Naserllah, Ammar Omar, Alaa Abu-Hantash and Abrar Al-Taj

Department of Network Engineering and Security, Jordan University of Science and Technology, P.O. Box 3030, Irbid 22110, Jordan

Sensors 2018, 18(2), 407; https://doi.org/10.3390/s18020407 - 31 Jan 2018

Cited by 16 | Viewed by 7159

Abstract

Localization of access points has become an important research problem due to the wide range of applications it addresses such as dismantling critical security threats caused by rogue access points or optimizing wireless coverage of access points within a service area. Existing proposed [...] Read more.

Localization of access points has become an important research problem due to the wide range of applications it addresses such as dismantling critical security threats caused by rogue access points or optimizing wireless coverage of access points within a service area. Existing proposed solutions have mostly relied on theoretical hypotheses or computer simulation to demonstrate the efficiency of their methods. The techniques that rely on estimating the distance using samples of the received signal strength usually assume prior knowledge of the signal propagation characteristics of the indoor environment in hand and tend to take a relatively large number of uniformly distributed random samples. This paper presents an efficient and practical collaborative approach to detect the location of an access point in an indoor environment without any prior knowledge of the environment. The proposed approach comprises a swarm of wirelessly connected mobile robots that collaboratively and autonomously collect a relatively small number of non-uniformly distributed random samples of the access point’s received signal strength. These samples are used to efficiently and accurately estimate the location of the access point. The experimental testing verified that the proposed approach can identify the location of the access point in an accurate and efficient manner. Full article

(This article belongs to the Special Issue Sensors and Sensing in Indoor Localization, Tracking, Navigation and Activity Monitoring)

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15 pages, 2207 KiB

Open AccessArticle

An Omnidirectional Vision Sensor Based on a Spherical Mirror Catadioptric System

by Sandro Barone¹, Marina Carulli², Paolo Neri^1,*

, Alessandro Paoli¹

and Armando Viviano Razionale¹

¹ Department of Civil and Industrial Engineering, University of Pisa, Largo Lucio Lazzarino 1, 56122 Pisa, Italy

² Dipartimento di Meccanica, Politecnico di Milano, Via Giuseppe La Masa, 1, 20156 Milano, Italy

Sensors 2018, 18(2), 408; https://doi.org/10.3390/s18020408 - 31 Jan 2018

Cited by 12 | Viewed by 4534

Abstract

The combination of mirrors and lenses, which defines a catadioptric sensor, is widely used in the computer vision field. The definition of a catadioptric sensors is based on three main features: hardware setup, projection modelling and calibration process. In this paper, a complete [...] Read more.

The combination of mirrors and lenses, which defines a catadioptric sensor, is widely used in the computer vision field. The definition of a catadioptric sensors is based on three main features: hardware setup, projection modelling and calibration process. In this paper, a complete description of these aspects is given for an omnidirectional sensor based on a spherical mirror. The projection model of a catadioptric system can be described by the forward projection task (FP, from 3D scene point to 2D pixel coordinates) and backward projection task (BP, from 2D coordinates to 3D direction of the incident light). The forward projection of non-central catadioptric vision systems, typically obtained by using curved mirrors, is usually modelled by using a central approximation and/or by adopting iterative approaches. In this paper, an analytical closed-form solution to compute both forward and backward projection for a non-central catadioptric system with a spherical mirror is presented. In particular, the forward projection is reduced to a 4th order polynomial by determining the reflection point on the mirror surface through the intersection between a sphere and an ellipse. A matrix format of the implemented models, suitable for fast point clouds handling, is also described. A robust calibration procedure is also proposed and applied to calibrate a catadioptric sensor by determining the mirror radius and center with respect to the camera. Full article

(This article belongs to the Section Physical Sensors)

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12 pages, 2799 KiB

Open AccessArticle

Brillouin Frequency Shift of Fiber Distributed Sensors Extracted from Noisy Signals by Quadratic Fitting

by Hanrong Zheng^1,2

, Zujie Fang¹, Zhaoyong Wang^1,*, Bin Lu^1,2, Yulong Cao³, Qing Ye¹, Ronghui Qu¹ and Haiwen Cai^1,*

¹ Shanghai Key Laboratory of All Solid-State Laser and Applied Techniques, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai 201800, China

² University of Chinese Academy of Sciences, Beijing 100049, China

³ Nanjing Pioneer Lasersensing, Nanjing 210019, China

Sensors 2018, 18(2), 409; https://doi.org/10.3390/s18020409 - 31 Jan 2018

Cited by 27 | Viewed by 4058

Abstract

It is a basic task in Brillouin distributed fiber sensors to extract the peak frequency of the scattering spectrum, since the peak frequency shift gives information on the fiber temperature and strain changes. Because of high-level noise, quadratic fitting is often used in [...] Read more.

It is a basic task in Brillouin distributed fiber sensors to extract the peak frequency of the scattering spectrum, since the peak frequency shift gives information on the fiber temperature and strain changes. Because of high-level noise, quadratic fitting is often used in the data processing. Formulas of the dependence of the minimum detectable Brillouin frequency shift (BFS) on the signal-to-noise ratio (SNR) and frequency step have been presented in publications, but in different expressions. A detailed deduction of new formulas of BFS variance and its average is given in this paper, showing especially their dependences on the data range used in fitting, including its length and its center respective to the real spectral peak. The theoretical analyses are experimentally verified. It is shown that the center of the data range has a direct impact on the accuracy of the extracted BFS. We propose and demonstrate an iterative fitting method to mitigate such effects and improve the accuracy of BFS measurement. The different expressions of BFS variances presented in previous papers are explained and discussed. Full article

(This article belongs to the Section Physical Sensors)

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15 pages, 731 KiB

Open AccessArticle

Node Location Privacy Protection Based on Differentially Private Grids in Industrial Wireless Sensor Networks

by Jun Wang¹

, Rongbo Zhu^1,*, Shubo Liu² and Zhaohui Cai²

¹ College of Computer Science, South-Central University for Nationalities, Wuhan 430074, China

² School of Computer, Wuhan University, Wuhan 430074, China

Sensors 2018, 18(2), 410; https://doi.org/10.3390/s18020410 - 31 Jan 2018

Cited by 44 | Viewed by 5583

Abstract

Wireless sensor networks (WSNs) are widely applied in industrial application with the rapid development of Industry 4.0. Combining with centralized cloud platform, the enormous computational power is provided for data analysis, such as strategy control and policy making. However, the data analysis and [...] Read more.

Wireless sensor networks (WSNs) are widely applied in industrial application with the rapid development of Industry 4.0. Combining with centralized cloud platform, the enormous computational power is provided for data analysis, such as strategy control and policy making. However, the data analysis and mining will bring the issue of privacy leakage since sensors will collect varieties of data including sensitive location information of monitored objects. Differential privacy is a novel technique that can prevent compromising single record benefits. Geospatial data can be indexed by a tree structure; however, existing differentially private release methods pay no attention to the concrete analysis about the partition granularity of data domains. Based on the overall analysis of noise error and non-uniformity error, this paper proposes a data domain partitioning model, which is more accurate to choose the grid size. A uniform grid release method is put forward based on this model. In order to further reduce the errors, similar cells are merged, and then noise is added into the merged cells. Results show that our method significantly improves the query accuracy compared with other existing methods. Full article

(This article belongs to the Collection Smart Industrial Wireless Sensor Networks)

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19 pages, 4766 KiB

Open AccessArticle

Multichannel High Resolution Wide Swath SAR Imaging for Hypersonic Air Vehicle with Curved Trajectory

by Rui Zhou¹, Jinping Sun^1,*

, Yuxin Hu² and Yaolong Qi¹

¹ Electronics & Information Engineering, Beihang University, Beijing 100191, China

² Key Laboratory of Technology in Geospatial Information Processing and Application System, Institute of Electronics, Chinese Academy of Sciences, Beijing 100191, China

Sensors 2018, 18(2), 411; https://doi.org/10.3390/s18020411 - 31 Jan 2018

Cited by 10 | Viewed by 4869

Abstract

Synthetic aperture radar (SAR) equipped on the hypersonic air vehicle in near space has many advantages over the conventional airborne SAR. However, its high-speed maneuvering characteristics with curved trajectory result in serious range migration, and exacerbate the contradiction between the high resolution and [...] Read more.

Synthetic aperture radar (SAR) equipped on the hypersonic air vehicle in near space has many advantages over the conventional airborne SAR. However, its high-speed maneuvering characteristics with curved trajectory result in serious range migration, and exacerbate the contradiction between the high resolution and wide swath. To solve this problem, this paper establishes the imaging geometrical model matched with the flight trajectory of the hypersonic platform and the multichannel azimuth sampling model based on the displaced phase center antenna (DPCA) technology. Furthermore, based on the multichannel signal reconstruction theory, a more efficient spectrum reconstruction model using discrete Fourier transform is proposed to obtain the azimuth uniform sampling data. Due to the high complexity of the slant range model, it is difficult to deduce the processing algorithm for SAR imaging. Thus, an approximate range model is derived based on the minimax criterion, and the optimal second-order approximate coefficients of cosine function are obtained using the two-population coevolutionary algorithm. On this basis, aiming at the problem that the traditional Omega-K algorithm cannot compensate the residual phase with the difficulty of Stolt mapping along the range frequency axis, this paper proposes an Exact Transfer Function (ETF) algorithm for SAR imaging, and presents a method of range division to achieve wide swath imaging. Simulation results verify the effectiveness of the ETF imaging algorithm. Full article

(This article belongs to the Special Issue Synthetic Aperture Radar (SAR) Technology: New Perspectives Offered by New-Generation and Forthcoming SAR Sensors)

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15 pages, 15581 KiB

Open AccessArticle

Development of Wind Speed Retrieval from Cross-Polarization Chinese Gaofen-3 Synthetic Aperture Radar in Typhoons

by Weizeng Shao¹

, Xinzhe Yuan^2,*, Yexin Sheng¹

, Jian Sun³

, Wei Zhou⁴ and Qingjun Zhang⁵

¹ Marine Science and Technology College, Zhejiang Ocean University, Zhoushan 316022, China

² National Satellite Ocean Application Service, State Oceanic Administration, Beijing 100081, China

³ Physical Oceanography Laboratory/CIMST, Ocean University of China and Qingdao National Laboratory for Marine Science and Technology, Qingdao 266100, China

⁴ South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou 510301, China

⁵ Beijing Institute of Spacecraft System Engineering, Beijing 100076, China

Sensors 2018, 18(2), 412; https://doi.org/10.3390/s18020412 - 31 Jan 2018

Cited by 38 | Viewed by 5518

Abstract

The purpose of our work is to determine the feasibility and effectiveness of retrieving sea surface wind speeds from C-band cross-polarization (herein vertical-horizontal, VH) Chinese Gaofen-3 (GF-3) SAR images in typhoons. In this study, we have collected three GF-3 SAR images acquired in [...] Read more.

The purpose of our work is to determine the feasibility and effectiveness of retrieving sea surface wind speeds from C-band cross-polarization (herein vertical-horizontal, VH) Chinese Gaofen-3 (GF-3) SAR images in typhoons. In this study, we have collected three GF-3 SAR images acquired in Global Observation (GLO) and Wide ScanSAR (WSC) mode during the summer of 2017 from the China Sea, which includes the typhoons Noru, Doksuri and Talim. These images were collocated with wind simulations at 0.12° grids from a numeric model, called the Regional Assimilation and Prediction System-Typhoon model (GRAPES-TYM). Recent research shows that GRAPES-TYM has a good performance for typhoon simulation in the China Sea. Based on the dataset, the dependence of wind speed and of radar incidence angle on normalized radar cross (NRCS) of VH-polarization GF-3 SAR have been investigated, after which an empirical algorithm for wind speed retrieval from VH-polarization GF-3 SAR was tuned. An additional four VH-polarization GF-3 SAR images in three typhoons, Noru, Hato and Talim, were investigated in order to validate the proposed algorithm. SAR-derived winds were compared with measurements from Windsat winds at 0.25° grids with wind speeds up to 40 m/s, showing a 5.5 m/s root mean square error (RMSE) of wind speed and an improved RMSE of 5.1 m/s wind speed was achieved compared with the retrieval results validated against GRAPES-TYM winds. It is concluded that the proposed algorithm is a promising potential technique for strong wind retrieval from cross-polarization GF-3 SAR images without encountering a signal saturation problem. Full article

(This article belongs to the Special Issue First Experiences with Chinese Gaofen-3 SAR Sensor)

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16 pages, 14722 KiB

Open AccessArticle

Structural Health Monitoring of Railway Transition Zones Using Satellite Radar Data

by Haoyu Wang^*

, Ling Chang and Valeri Markine

Railway Section, Delft University of Technology, 2628CN Delft, The Netherlands

Sensors 2018, 18(2), 413; https://doi.org/10.3390/s18020413 - 31 Jan 2018

Cited by 55 | Viewed by 9320

Abstract

Transition zones in railway tracks are locations with considerable changes in the rail-supporting structure. Typically, they are located near engineering structures, such as bridges, culverts and tunnels. In such locations, severe differential settlements often occur due to the different material properties and structure [...] Read more.

Transition zones in railway tracks are locations with considerable changes in the rail-supporting structure. Typically, they are located near engineering structures, such as bridges, culverts and tunnels. In such locations, severe differential settlements often occur due to the different material properties and structure behavior. Without timely maintenance, the differential settlement may lead to the damage of track components and loss of passenger’s comfort. To ensure the safety of railway operations and reduce the maintenance costs, it is necessary to consecutively monitor the structural health condition of the transition zones in an economical manner and detect the changes at an early stage. However, using the current in situ monitoring of transition zones is hard to achieve this goal, because most in situ techniques (e.g., track-measuring coaches) are labor-consuming and usually not frequently performed (approximately twice a year in the Netherlands). To tackle the limitations of the in situ techniques, a Satellite Synthetic Aperture Radar (InSAR) system is presented in this paper, which provides a potential solution for a consecutive structural health monitoring of transition zones with bi-/tri-weekly data update and mm-level precision. To demonstrate the feasibility of the InSAR system for monitoring transition zones, a transition zone is tested. The results show that the differential settlement in the transition zone and the settlement rate can be observed and detected by the InSAR measurements. Moreover, the InSAR results are cross-validated against measurements obtained using a measuring coach and a Digital Image Correlation (DIC) device. The results of the three measuring techniques show a good correlation, which proves the applicability of InSAR for the structural health monitoring of transition zones in railway track. Full article

(This article belongs to the Section Remote Sensors)

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21 pages, 4595 KiB

Open AccessArticle

Development of a Kalman Filter in the Gauss-Helmert Model for Reliability Analysis in Orientation Determination with Smartphone Sensors

by Andreas Ettlinger^1,*, Hans Neuner¹ and Thomas Burgess²

¹ Department of Geodesy and Geoinformation, TU Wien, 1040 Wien, Austria

² indoo.rs GmbH, 1150 Wien, Austria

Sensors 2018, 18(2), 414; https://doi.org/10.3390/s18020414 - 31 Jan 2018

Cited by 12 | Viewed by 4920

Abstract

The topic of indoor positioning and indoor navigation by using observations from smartphone sensors is very challenging as the determined trajectories can be subject to significant deviations compared to the route travelled in reality. Especially the calculation of the direction of movement is [...] Read more.

The topic of indoor positioning and indoor navigation by using observations from smartphone sensors is very challenging as the determined trajectories can be subject to significant deviations compared to the route travelled in reality. Especially the calculation of the direction of movement is the critical part of pedestrian positioning approaches such as Pedestrian Dead Reckoning (“PDR”). Due to distinct systematic effects in filtered trajectories, it can be assumed that there are systematic deviations present in the observations from smartphone sensors. This article has two aims: one is to enable the estimation of partial redundancies for each observation as well as for observation groups. Partial redundancies are a measure for the reliability indicating how well systematic deviations can be detected in single observations used in PDR. The second aim is to analyze the behavior of partial redundancy by modifying the stochastic and functional model of the Kalman filter. The equations relating the observations to the orientation are condition equations, which do not exhibit the typical structure of the Gauss-Markov model (“GMM”), wherein the observations are linear and can be formulated as functions of the states. To calculate and analyze the partial redundancy of the observations from smartphone-sensors used in PDR, the system equation and the measurement equation of a Kalman filter as well as the redundancy matrix need to be derived in the Gauss-Helmert model (“GHM”). These derivations are introduced in this article and lead to a novel Kalman filter structure based on condition equations, enabling reliability assessment of each observation. Full article

(This article belongs to the Special Issue Smartphone-based Pedestrian Localization and Navigation)

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14 pages, 4596 KiB

Open AccessArticle

A Rotational Gyroscope with a Water-Film Bearing Based on Magnetic Self-Restoring Effect

by Dianzhong Chen¹, Xiaowei Liu¹, Haifeng Zhang^1,*

, Hai Li², Rui Weng³

, Ling Li¹, Wanting Rong¹ and Zhongzhao Zhang⁴

¹ MEMS Center, Harbin Institute of Technology, Harbin 150001, China

² Center for Integrated Spintronic Devices, Hangzhou Dianzi University, Hangzhou 310018, China

³ School of Software and Microelectronics, Harbin University of Science and Technology, Harbin 150001, China

⁴ Communication Research Center, Harbin Institute of Technology, Harbin 150001, China

Sensors 2018, 18(2), 415; https://doi.org/10.3390/s18020415 - 31 Jan 2018

Cited by 6 | Viewed by 5081

Abstract

Stable rotor levitation is a challenge for rotational gyroscopes (magnetically suspended gyroscopes (MSG) and electrostatically suspended gyroscopes (ESG)) with a ring- or disk-shaped rotor, which restricts further improvement of gyroscope performance. In addition, complicated pick-up circuits and feedback control electronics propose high requirement [...] Read more.

Stable rotor levitation is a challenge for rotational gyroscopes (magnetically suspended gyroscopes (MSG) and electrostatically suspended gyroscopes (ESG)) with a ring- or disk-shaped rotor, which restricts further improvement of gyroscope performance. In addition, complicated pick-up circuits and feedback control electronics propose high requirement on fabrication technology. In the proposed gyroscope, a ball-disk shaped rotor is supported by a water-film bearing, formed by centrifugal force to deionized water at the cavity of the lower supporting pillar. Water-film bearing provides stable mechanical support, without the need for complicated electronics and control system for rotor suspension. To decrease sliding friction between the rotor ball and the water-film bearing, a supherhydrophobic surface (SHS) with nano-structures is fabricated on the rotor ball, resulting in a rated spinning speed increase of 12.4% (under the same driving current). Rotor is actuated by the driving scheme of brushless direct current motor (BLDCM). Interaction between the magnetized rotor and the magnetic-conducted stator produces a sinusoidal rotor restoring torque, amplitude of which is proportional to the rotor deflection angle inherently. Utilization of this magnetic restoring effect avoids adding of a high amplitude voltage for electrostatic feedback, which may cause air breakdown. Two differential capacitance pairs are utilized to measure input angular speeds at perpendicular directions of the rotor plane. The bias stability of the fabricated gyroscope is as low as 0.5°/h. Full article

(This article belongs to the Section Physical Sensors)

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24 pages, 15954 KiB

Open AccessArticle

Facial Emotion Recognition: A Survey and Real-World User Experiences in Mixed Reality

by Dhwani Mehta, Mohammad Faridul Haque Siddiqui and Ahmad Y. Javaid^*

EECS Department, The University of Toledo, Toledo, OH 43606, USA

Sensors 2018, 18(2), 416; https://doi.org/10.3390/s18020416 - 1 Feb 2018

Cited by 128 | Viewed by 21416

Abstract

Extensive possibilities of applications have made emotion recognition ineluctable and challenging in the field of computer science. The use of non-verbal cues such as gestures, body movement, and facial expressions convey the feeling and the feedback to the user. This discipline of Human–Computer [...] Read more.

Extensive possibilities of applications have made emotion recognition ineluctable and challenging in the field of computer science. The use of non-verbal cues such as gestures, body movement, and facial expressions convey the feeling and the feedback to the user. This discipline of Human–Computer Interaction places reliance on the algorithmic robustness and the sensitivity of the sensor to ameliorate the recognition. Sensors play a significant role in accurate detection by providing a very high-quality input, hence increasing the efficiency and the reliability of the system. Automatic recognition of human emotions would help in teaching social intelligence in the machines. This paper presents a brief study of the various approaches and the techniques of emotion recognition. The survey covers a succinct review of the databases that are considered as data sets for algorithms detecting the emotions by facial expressions. Later, mixed reality device Microsoft HoloLens (MHL) is introduced for observing emotion recognition in Augmented Reality (AR). A brief introduction of its sensors, their application in emotion recognition and some preliminary results of emotion recognition using MHL are presented. The paper then concludes by comparing results of emotion recognition by the MHL and a regular webcam. Full article

(This article belongs to the Special Issue Wearable Smart Devices)

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20 pages, 1488 KiB

Open AccessArticle

A Decentralized Framework for Multi-Agent Robotic Systems

by Andrés C. Jiménez^1,*

, Vicente García-Díaz²

and Sandro Bolaños³

¹ Department of Electronic Engineering, Los Libertadores Foundation University, Cr.16#63A-68 Bogotá, Colombia

² Department of Computer Sciences, University of Oviedo, Street San Francisco 1, 33003 Oviedo, Asturias, Spain

³ Department of Engineering, Distrital University Francisco José de Caldas, Cr.7#40B-53 Bogotá, Colombia

Sensors 2018, 18(2), 417; https://doi.org/10.3390/s18020417 - 1 Feb 2018

Cited by 41 | Viewed by 6546

Abstract

Over the past few years, decentralization of multi-agent robotic systems has become an important research area. These systems do not depend on a central control unit, which enables the control and assignment of distributed, asynchronous and robust tasks. However, in some cases, the [...] Read more.

Over the past few years, decentralization of multi-agent robotic systems has become an important research area. These systems do not depend on a central control unit, which enables the control and assignment of distributed, asynchronous and robust tasks. However, in some cases, the network communication process between robotic agents is overlooked, and this creates a dependency for each agent to maintain a permanent link with nearby units to be able to fulfill its goals. This article describes a communication framework, where each agent in the system can leave the network or accept new connections, sending its information based on the transfer history of all nodes in the network. To this end, each agent needs to comply with four processes to participate in the system, plus a fifth process for data transfer to the nearest nodes that is based on Received Signal Strength Indicator (RSSI) and data history. To validate this framework, we use differential robotic agents and a monitoring agent to generate a topological map of an environment with the presence of obstacles. Full article

(This article belongs to the Section Sensor Networks)

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10 pages, 3715 KiB

Open AccessArticle

Sensitive and Flexible Polymeric Strain Sensor for Accurate Human Motion Monitoring

by Hassan Khan¹, Amir Razmjou²

, Majid Ebrahimi Warkiani³

, Ajay Kottapalli⁴

and Mohsen Asadnia^1,*

¹ School of Engineering, Macquarie University, Sydney 2109, Australia

² Department of Biotechnology, Faculty of Advanced Sciences and Technologies, University of Isfahan, Isfahan 81746-73441, Iran

³ School of Biomedical Engineering, University of Technology Sydney, Sydney 2007, Australia

⁴ Center for Environmental Sensing and Modeling (CENSAM) IRG, Singapore-MIT Alliance for Research and Technology (SMART) Centre, 1 Create Way, Singapore 117543, Singapore

Sensors 2018, 18(2), 418; https://doi.org/10.3390/s18020418 - 1 Feb 2018

Cited by 74 | Viewed by 11414

Abstract

Flexible electronic devices offer the capability to integrate and adapt with human body. These devices are mountable on surfaces with various shapes, which allow us to attach them to clothes or directly onto the body. This paper suggests a facile fabrication strategy via [...] Read more.

Flexible electronic devices offer the capability to integrate and adapt with human body. These devices are mountable on surfaces with various shapes, which allow us to attach them to clothes or directly onto the body. This paper suggests a facile fabrication strategy via electrospinning to develop a stretchable, and sensitive poly (vinylidene fluoride) nanofibrous strain sensor for human motion monitoring. A complete characterization on the single PVDF nano fiber has been performed. The charge generated by PVDF electrospun strain sensor changes was employed as a parameter to control the finger motion of the robotic arm. As a proof of concept, we developed a smart glove with five sensors integrated into it to detect the fingers motion and transfer it to a robotic hand. Our results shows that the proposed strain sensors are able to detect tiny motion of fingers and successfully run the robotic hand. Full article

(This article belongs to the Special Issue Printed Sensors 2018)

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13 pages, 1835 KiB

Open AccessArticle

Stress Prediction for Distributed Structural Health Monitoring Using Existing Measurements and Pattern Recognition

by Wei Lu^*, Jun Teng^*, Qiushi Zhou and Qiexin Peng

Harbin Institute of Technology (Shenzhen), Shenzhen 518055, China

Sensors 2018, 18(2), 419; https://doi.org/10.3390/s18020419 - 1 Feb 2018

Cited by 14 | Viewed by 4463

Abstract

The stress in structural steel members is the most useful and directly measurable physical quantity to evaluate the structural safety in structural health monitoring, which is also an important index to evaluate the stress distribution and force condition of structures during structural construction [...] Read more.

The stress in structural steel members is the most useful and directly measurable physical quantity to evaluate the structural safety in structural health monitoring, which is also an important index to evaluate the stress distribution and force condition of structures during structural construction and service phases. Thus, it is common to set stress as a measure in steel structural monitoring. Considering the economy and the importance of the structural members, there are only a limited number of sensors that can be placed, which means that it is impossible to obtain the stresses of all members directly using sensors. This study aims to develop a stress response prediction method for locations where there are insufficent sensors, using measurements from a limited number of sensors and pattern recognition. The detailed improved aspects are: (1) a distributed computing process is proposed, where the same pattern is recognized by several subsets of measurements; and (2) the pattern recognition using the subset of measurements is carried out by considering the optimal number of sensors and number of fusion patterns. The validity and feasibility of the proposed method are verified using two examples: the finite-element simulation of a single-layer shell-like steel structure, and the structural health monitoring of the space steel roof of Shenzhen Bay Stadium; for the latter, the anti-noise performance of this method is verified by the stress measurements from a real-world project. Full article

(This article belongs to the Special Issue Sensor Technologies for Health Monitoring of Composite Structures)

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16 pages, 3933 KiB

Open AccessArticle

Study of the Integration of the CNU-TS-1 Mobile Tunnel Monitoring System

by Liming Du^1,2

, Ruofei Zhong^1,2,*, Haili Sun^1,2,*, Qiang Zhu^1,2 and Zhen Zhang^1,2

¹ Beijing Advanced Innovation Center for Imaging Technology, Capital Normal University, Beijing 100048, China

² College of Resource Environment and Tourism, Capital Normal University, Beijing 100048, China

Sensors 2018, 18(2), 420; https://doi.org/10.3390/s18020420 - 1 Feb 2018

Cited by 30 | Viewed by 5015

Abstract

A rapid, precise and automated means for the regular inspection and maintenance of a large number of tunnels is needed. Based on the depth study of the tunnel monitoring method, the CNU-TS-1 mobile tunnel monitoring system (TS1) is developed and presented. It can [...] Read more.

A rapid, precise and automated means for the regular inspection and maintenance of a large number of tunnels is needed. Based on the depth study of the tunnel monitoring method, the CNU-TS-1 mobile tunnel monitoring system (TS1) is developed and presented. It can efficiently obtain the cross-sections that are orthogonal to the tunnel in a dynamic way, and the control measurements that depend on design data are eliminated. By using odometers to locate the cross-sections and correcting the data based on longitudinal joints of tunnel segment lining, the cost of the system has been significantly reduced, and the interval between adjacent cross-sections can reach 1–2 cm when pushed to collect data at a normal walking speed. Meanwhile, the relative deformation of tunnel can be analyzed by selecting cross-sections from original data. Through the measurement of the actual tunnel, the applicability of the system for tunnel deformation detection is verified, and the system is shown to be 15 times more efficient than that of the total station. The simulation experiment of the tunnel deformation indicates that the measurement accuracy of TS1 for cross-sections is 1.1 mm. Compared with the traditional method, TS1 improves the efficiency as well as increases the density of the obtained points. Full article

(This article belongs to the Special Issue Indoor LiDAR/Vision Systems)

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16 pages, 4302 KiB

Open AccessArticle

Estimation of Foot Plantar Center of Pressure Trajectories with Low-Cost Instrumented Insoles Using an Individual-Specific Nonlinear Model

by Xinyao Hu¹, Jun Zhao¹, Dongsheng Peng¹, Zhenglong Sun²

and Xingda Qu^1,*

¹ Institute of Human Factors and Ergonomics, Shenzhen University, Shenzhen 518060, China

² Institute of Robotics and Intelligent Manufacturing, the Chinese University of Hong Kong, Shenzhen 518172, China

Sensors 2018, 18(2), 421; https://doi.org/10.3390/s18020421 - 1 Feb 2018

Cited by 38 | Viewed by 7469

Abstract

Postural control is a complex skill based on the interaction of dynamic sensorimotor processes, and can be challenging for people with deficits in sensory functions. The foot plantar center of pressure (COP) has often been used for quantitative assessment of postural control. Previously, [...] Read more.

Postural control is a complex skill based on the interaction of dynamic sensorimotor processes, and can be challenging for people with deficits in sensory functions. The foot plantar center of pressure (COP) has often been used for quantitative assessment of postural control. Previously, the foot plantar COP was mainly measured by force plates or complicated and expensive insole-based measurement systems. Although some low-cost instrumented insoles have been developed, their ability to accurately estimate the foot plantar COP trajectory was not robust. In this study, a novel individual-specific nonlinear model was proposed to estimate the foot plantar COP trajectories with an instrumented insole based on low-cost force sensitive resistors (FSRs). The model coefficients were determined by a least square error approximation algorithm. Model validation was carried out by comparing the estimated COP data with the reference data in a variety of postural control assessment tasks. We also compared our data with the COP trajectories estimated by the previously well accepted weighted mean approach. Comparing with the reference measurements, the average root mean square errors of the COP trajectories of both feet were 2.23 mm (±0.64) (left foot) and 2.72 mm (±0.83) (right foot) along the medial–lateral direction, and 9.17 mm (±1.98) (left foot) and 11.19 mm (±2.98) (right foot) along the anterior–posterior direction. The results are superior to those reported in previous relevant studies, and demonstrate that our proposed approach can be used for accurate foot plantar COP trajectory estimation. This study could provide an inexpensive solution to fall risk assessment in home settings or community healthcare center for the elderly. It has the potential to help prevent future falls in the elderly. Full article

(This article belongs to the Special Issue Sensors for Gait, Posture, and Health Monitoring)

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13 pages, 2290 KiB

Open AccessArticle

The Effects of Graphene Stacking on the Performance of Methane Sensor: A First-Principles Study on the Adsorption, Band Gap and Doping of Graphene

by Ning Yang¹

, Daoguo Yang^1,*, Guoqi Zhang^1,2, Liangbiao Chen³, Dongjing Liu¹, Miao Cai¹ and Xuejun Fan³

¹ The Faculty of Mechanical and Electrical Engineering, Guilin University of Electronic Technology, Guilin 541004, China

² EEMCS Faculty, Delft University of Technology, 2628 Delft, The Netherlands

³ The Department of Mechanical Engineering, Lamar University, Beaumont, TX 77706, USA

Sensors 2018, 18(2), 422; https://doi.org/10.3390/s18020422 - 1 Feb 2018

Cited by 12 | Viewed by 5586

Abstract

The effects of graphene stacking are investigated by comparing the results of methane adsorption energy, electronic performance, and the doping feasibility of five dopants (i.e., B, N, Al, Si, and P) via first-principles theory. Both zigzag and armchair graphenes are considered. It is [...] Read more.

The effects of graphene stacking are investigated by comparing the results of methane adsorption energy, electronic performance, and the doping feasibility of five dopants (i.e., B, N, Al, Si, and P) via first-principles theory. Both zigzag and armchair graphenes are considered. It is found that the zigzag graphene with Bernal stacking has the largest adsorption energy on methane, while the armchair graphene with Order stacking is opposite. In addition, both the Order and Bernal stacked graphenes possess a positive linear relationship between adsorption energy and layer number. Furthermore, they always have larger adsorption energy in zigzag graphene. For electronic properties, the results show that the stacking effects on band gap are significant, but it does not cause big changes to band structure and density of states. In the comparison of distance, the average interlamellar spacing of the Order stacked graphene is the largest. Moreover, the adsorption effect is the result of the interactions between graphene and methane combined with the change of graphene’s structure. Lastly, the armchair graphene with Order stacking possesses the lowest formation energy in these five dopants. It could be the best choice for doping to improve the methane adsorption. Full article

(This article belongs to the Special Issue Carbon Materials Based Sensors and the Application)

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16 pages, 5457 KiB

Open AccessArticle

Energy Level-Based Abnormal Crowd Behavior Detection

by Xuguang Zhang^1,2, Qian Zhang^1,3, Shuo Hu¹, Chunsheng Guo² and Hui Yu^4,*

¹ The Institute of Electrical Engineering, YanShan University, Qinhuangdao 066004, China

² School of Communication Engineering, Hangzhou Dianzi University, Hangzhou 310018, China

³ LargeV Instrument Corporation Limited, Beijing 100084, China

⁴ School of Creative Technologies, University of Portsmouth, Portsmouth PO1 2DJ, UK

Sensors 2018, 18(2), 423; https://doi.org/10.3390/s18020423 - 1 Feb 2018

Cited by 32 | Viewed by 5890

Abstract

The change of crowd energy is a fundamental measurement for describing a crowd behavior. In this paper, we present a crowd abnormal detection method based on the change of energy-level distribution. The method can not only reduce the camera perspective effect, but also [...] Read more.

The change of crowd energy is a fundamental measurement for describing a crowd behavior. In this paper, we present a crowd abnormal detection method based on the change of energy-level distribution. The method can not only reduce the camera perspective effect, but also detect crowd abnormal behavior in time. Pixels in the image are treated as particles, and the optical flow method is adopted to extract the velocities of particles. The qualities of different particles are distributed as different value according to the distance between the particle and the camera to reduce the camera perspective effect. Then a crowd motion segmentation method based on flow field texture representation is utilized to extract the motion foreground, and a linear interpolation calculation is applied to pedestrian’s foreground area to determine their distance to the camera. This contributes to the calculation of the particle qualities in different locations. Finally, the crowd behavior is analyzed according to the change of the consistency, entropy and contrast of the three descriptors for co-occurrence matrix. By calculating a threshold, the timestamp when the crowd abnormal happens is determined. In this paper, multiple sets of videos from three different scenes in UMN dataset are employed in the experiment. The results show that the proposed method is effective in characterizing anomalies in videos. Full article

(This article belongs to the Section Intelligent Sensors)

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13 pages, 2801 KiB

Open AccessArticle

A Simple Surface-Enhanced Raman Spectroscopic Method for on-Site Screening of Tetracycline Residue in Whole Milk

by Sagar Dhakal¹, Kuanglin Chao^1,*, Qing Huang², Moon Kim¹, Walter Schmidt¹, Jianwei Qin¹ and C. Leigh Broadhurst¹

¹ Environmental Microbial and Food Safety Laboratory, Agricultural Research Service, United States Department of Agriculture, 10300 Baltimore Avenue, Bldg. 303 BARC-East, Beltsville, MD 20705, USA

² Hefei Institute of Physical Science, CAS 350 Shushanhu Road, Hefei 230031, China

Sensors 2018, 18(2), 424; https://doi.org/10.3390/s18020424 - 1 Feb 2018

Cited by 70 | Viewed by 7202

Abstract

Therapeutic and subtherapeutic use of veterinary drugs has increased the risk of residue contamination in animal food products. Antibiotics such as tetracycline are used for mastitis treatment of lactating cows. Milk expressed from treated cows before the withdrawal period has elapsed may contain [...] Read more.

Therapeutic and subtherapeutic use of veterinary drugs has increased the risk of residue contamination in animal food products. Antibiotics such as tetracycline are used for mastitis treatment of lactating cows. Milk expressed from treated cows before the withdrawal period has elapsed may contain tetracycline residue. This study developed a simple surface-enhanced Raman spectroscopic (SERS) method for on-site screening of tetracycline residue in milk and water. Six batches of silver colloid nanoparticles were prepared for surface enhancement measurement. Milk-tetracycline and water-tetracycline solutions were prepared at seven concentration levels (1000, 500, 100, 10, 1, 0.1, and 0.01 ppm) and spiked with silver colloid nanoparticles. A 785 nm Raman spectroscopic system was used for spectral measurement. Tetracycline vibrational modes were observed at 1285, 1317 and 1632 cm⁻¹ in water-tetracycline solutions and 1322 and 1621 cm⁻¹ (shifted from 1317 and 1632 cm⁻¹, respectively) in milk-tetracycline solutions. Tetracycline residue concentration as low as 0.01 ppm was detected in both the solutions. The peak intensities at 1285 and 1322 cm⁻¹ were used to estimate the tetracycline concentrations in water and milk with correlation coefficients of 0.92 for water and 0.88 for milk. Results indicate that this SERS method is a potential tool that can be used on-site at field production for qualitative and quantitative detection of tetracycline residues. Full article

(This article belongs to the Section Biosensors)

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11 pages, 4002 KiB

Open AccessArticle

Amyloid Beta Detection by Faradaic Electrochemical Impedance Spectroscopy Using Interdigitated Microelectrodes

by Jin Soo Park^1,3,†, Hye Jin Kim^2,3,†, Ji-Hoon Lee¹

, Jung Ho Park³, Jinsik Kim⁴, Kyo Seon Hwang^2,* and Byung Chul Lee^1,*

¹ Center for BioMicrosystems, Korea Institute of Science and Technology (KIST), Seoul 02792, Korea

² Department of Clinical Pharmacology and Therapeutics, College of Medicine, Kyung Hee University, Seoul 02447, Korea

³ Department of Electrical Engineering, Korea University, Seoul 02841, Korea

⁴ Department of Medical Biotechnology, College of Life Science and Biotechnology, Dongguk University, Seoul 10326, Korea

^† These authors contributed equally to this work.

Sensors 2018, 18(2), 426; https://doi.org/10.3390/s18020426 - 1 Feb 2018

Cited by 38 | Viewed by 9666

Abstract

Faradaic electrochemical impedance spectroscopy (f-EIS) in the presence of redox reagent, e.g., [Fe(CN)₆]^3−/4−, is widely used in biosensors owing to its high sensitivity. However, in sensors detecting amyloid beta (Aβ), the redox reagent can cause the aggregation of Aβ, [...] Read more.

Faradaic electrochemical impedance spectroscopy (f-EIS) in the presence of redox reagent, e.g., [Fe(CN)₆]^3−/4−, is widely used in biosensors owing to its high sensitivity. However, in sensors detecting amyloid beta (Aβ), the redox reagent can cause the aggregation of Aβ, which is a disturbance factor in accurate detection. Here, we propose an interdigitated microelectrode (IME) based f-EIS technique that can alleviate the aggregation of Aβ and achieve high sensitivity by buffer control. The proposed method was verified by analyzing three different EIS-based sensors: non-faradaic EIS (nf-EIS), f-EIS, and the proposed f-EIS with buffer control. We analyzed the equivalent circuits of nf-EIS and f-EIS sensors. The dominant factors of sensitivity were analyzed, and the impedance change rates via Aβ reaction was compared. We measured the sensitivity of the IME sensors based on nf-EIS, f-EIS, and the proposed f-EIS. The results demonstrate that the proposed EIS-based IME sensor can detect Aβ with a sensitivity of 7.40-fold and 10.93-fold higher than the nf-EIS and the f-EIS sensors, respectively. Full article

(This article belongs to the Special Issue Sensors for Health Monitoring and Disease Diagnosis)

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21 pages, 9553 KiB

Open AccessArticle

A New Real-Time Cycle Slip Detection and Repair Method under High Ionospheric Activity for a Triple-Frequency GPS/BDS Receiver

by Wanke Liu^1,2,3, Xueyuan Jin¹

, Mingkui Wu^4,*, Jie Hu¹ and Yun Wu¹

¹ School of Geodesy and Geomatics, Wuhan University, Wuhan 430079, China

² Collaborative Innovation Center for Geospatial Technology, Wuhan 430079, China

³ Key Laboratory of Geophysical Geodesy, National Administration of Surveying, Mapping and Geoinformation, Wuhan 430079, China

⁴ Faculty of Information Engineering, China University of Geosciences, Wuhan 430074, China

Sensors 2018, 18(2), 427; https://doi.org/10.3390/s18020427 - 1 Feb 2018

Cited by 34 | Viewed by 5002

Abstract

Cycle slip detection and repair is a prerequisite for high-precision global navigation satellite system (GNSS)-based positioning. With the modernization and development of GNSS systems, more satellites are available to transmit triple-frequency signals, which allows the introduction of additional linear combinations and provides new [...] Read more.

Cycle slip detection and repair is a prerequisite for high-precision global navigation satellite system (GNSS)-based positioning. With the modernization and development of GNSS systems, more satellites are available to transmit triple-frequency signals, which allows the introduction of additional linear combinations and provides new opportunities for cycle slip detection and repair. In this paper, we present a new real-time cycle slip detection and repair method under high ionospheric activity for undifferenced Global Positioning System (GPS)/BeiDou Navigation Satellite System (BDS) triple-frequency observations collected with a single receiver. First, three optimal linearly independent geometry-free pseudorange minus phase combinations are selected to correctly and uniquely determine the cycle slips on the original triple-frequency carrier phase observations. Then, a second-order time-difference algorithm is employed for the pseudorange minus phase combinations to mitigate the impact of between-epoch ionospheric residuals on cycle slip detection, which is especially beneficial under high ionospheric activity. The performance of the approach is verified with static GPS/BDS triple-frequency observations that are collected with a 30 s sampling interval under active ionospheric conditions, and observations are manually inserted with simulated cycle slips. The results show that the method can correctly detect and repair cycle slips at a resolution as small as 1 cycle. Moreover, kinematic data collected from car-driven and airborne experiments are also processed to verify the performance of the method. The experimental results also demonstrate that the method is effective in processing kinematic data. Full article

(This article belongs to the Section Remote Sensors)

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16 pages, 8491 KiB

Open AccessArticle

Experimental Study of Multispectral Characteristics of an Unmanned Aerial Vehicle at Different Observation Angles

by Haijing Zheng¹, Tingzhu Bai^1,*, Quanxi Wang², Fengmei Cao¹, Long Shao¹ and Zhaotian Sun¹

¹ School of Optics and Photonics, Beijing Institute of Technology, Beijing 100081, China

² System Division, Navy Equipment Research Institute, Beijing 100161, China

Sensors 2018, 18(2), 428; https://doi.org/10.3390/s18020428 - 1 Feb 2018

Cited by 5 | Viewed by 4643

Abstract

This study investigates multispectral characteristics of an unmanned aerial vehicle (UAV) at different observation angles by experiment. The UAV and its engine are tested on the ground in the cruise state. Spectral radiation intensities at different observation angles are obtained in the infrared [...] Read more.

This study investigates multispectral characteristics of an unmanned aerial vehicle (UAV) at different observation angles by experiment. The UAV and its engine are tested on the ground in the cruise state. Spectral radiation intensities at different observation angles are obtained in the infrared band of 0.9–15 μm by a spectral radiometer. Meanwhile, infrared images are captured separately by long-wavelength infrared (LWIR), mid-wavelength infrared (MWIR), and short-wavelength infrared (SWIR) cameras. Additionally, orientation maps of the radiation area and radiance are obtained. The results suggest that the spectral radiation intensity of the UAV is determined by its exhaust plume and that the main infrared emission bands occur at 2.7 μm and 4.3 μm. At observation angles in the range of 0°–90°, the radiation area of the UAV in MWIR band is greatest; however, at angles greater than 90°, the radiation area in the SWIR band is greatest. In addition, the radiance of the UAV at an angle of 0° is strongest. These conclusions can guide IR stealth technique development for UAVs. Full article

(This article belongs to the Special Issue UAV or Drones for Remote Sensing Applications)

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19 pages, 10871 KiB

Open AccessArticle

The Impact of Curviness on Four Different Image Sensor Forms and Structures

by Wei Wen^*

and Siamak Khatibi

Department of Technology and Aesthetics, Blekinge Tekniska Högskola, 37141 Karlskrona, Sweden

Sensors 2018, 18(2), 429; https://doi.org/10.3390/s18020429 - 1 Feb 2018

Cited by 4 | Viewed by 3916

Abstract

The arrangement and form of the image sensor have a fundamental effect on any further image processing operation and image visualization. In this paper, we present a software-based method to change the arrangement and form of pixel sensors that generate hexagonal pixel forms [...] Read more.

The arrangement and form of the image sensor have a fundamental effect on any further image processing operation and image visualization. In this paper, we present a software-based method to change the arrangement and form of pixel sensors that generate hexagonal pixel forms on a hexagonal grid. We evaluate four different image sensor forms and structures, including the proposed method. A set of 23 pairs of images; randomly chosen, from a database of 280 pairs of images are used in the evaluation. Each pair of images have the same semantic meaning and general appearance, the major difference between them being the sharp transitions in their contours. The curviness variation is estimated by effect of the first and second order gradient operations, Hessian matrix and critical points detection on the generated images; having different grid structures, different pixel forms and virtual increased of fill factor as three major properties of sensor characteristics. The results show that the grid structure and pixel form are the first and second most important properties. Several dissimilarity parameters are presented for curviness quantification in which using extremum point showed to achieve distinctive results. The results also show that the hexagonal image is the best image type for distinguishing the contours in the images. Full article

(This article belongs to the Section Physical Sensors)

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21 pages, 6150 KiB

Open AccessArticle

An Intraoperative Visualization System Using Hyperspectral Imaging to Aid in Brain Tumor Delineation

by Himar Fabelo^1,*

, Samuel Ortega¹

, Raquel Lazcano²

, Daniel Madroñal²

, Gustavo M. Callicó¹

, Eduardo Juárez², Rubén Salvador²

, Diederik Bulters³, Harry Bulstrode⁴

, Adam Szolna⁵, Juan F. Piñeiro⁵, Coralia Sosa⁵, Aruma J. O’Shanahan⁵, Sara Bisshopp⁵, María Hernández⁵, Jesús Morera⁵, Daniele Ravi⁶, B. Ravi Kiran⁷, Aurelio Vega¹, Abelardo Báez-Quevedo¹, Guang-Zhong Yang⁶, Bogdan Stanciulescu⁸ and Roberto Sarmiento¹ Show full author list Hide full author list

¹ Institute for Applied Microelectronics (IUMA), University of Las Palmas de Gran Canaria (ULPGC), Las Palmas de Gran Canaria 35017, Spain

² Centre of Software Technologies and Multimedia Systems (CITSEM), Technical University of Madrid (UPM), Madrid 28031, Spain

³ Wessex Neurological Centre, University Hospital Southampton, Tremona Road, Southampton SO16 6YD, UK

⁴ Department of Neurosurgery, Addenbrookes Hospital and University of Cambridge, Cambridge CB2 0QQ, UK

⁵ Department of Neurosurgery, University Hospital Doctor Negrin, Las Palmas de Gran Canaria 35010, Spain

⁶ The Hamlyn Centre, Imperial College London (ICL), London SW7 2AZ, UK

⁷ Laboratoire CRISTAL, Université Lille 3, Villeneuve-d’Ascq 59653, France

⁸ Ecole Nationale Supérieure des Mines de Paris (ENSMP), MINES ParisTech, Paris 75006, France

Sensors 2018, 18(2), 430; https://doi.org/10.3390/s18020430 - 1 Feb 2018

Cited by 126 | Viewed by 11942

Abstract

Hyperspectral imaging (HSI) allows for the acquisition of large numbers of spectral bands throughout the electromagnetic spectrum (within and beyond the visual range) with respect to the surface of scenes captured by sensors. Using this information and a set of complex classification algorithms, [...] Read more.

Hyperspectral imaging (HSI) allows for the acquisition of large numbers of spectral bands throughout the electromagnetic spectrum (within and beyond the visual range) with respect to the surface of scenes captured by sensors. Using this information and a set of complex classification algorithms, it is possible to determine which material or substance is located in each pixel. The work presented in this paper aims to exploit the characteristics of HSI to develop a demonstrator capable of delineating tumor tissue from brain tissue during neurosurgical operations. Improved delineation of tumor boundaries is expected to improve the results of surgery. The developed demonstrator is composed of two hyperspectral cameras covering a spectral range of 400–1700 nm. Furthermore, a hardware accelerator connected to a control unit is used to speed up the hyperspectral brain cancer detection algorithm to achieve processing during the time of surgery. A labeled dataset comprised of more than 300,000 spectral signatures is used as the training dataset for the supervised stage of the classification algorithm. In this preliminary study, thematic maps obtained from a validation database of seven hyperspectral images of in vivo brain tissue captured and processed during neurosurgical operations demonstrate that the system is able to discriminate between normal and tumor tissue in the brain. The results can be provided during the surgical procedure (~1 min), making it a practical system for neurosurgeons to use in the near future to improve excision and potentially improve patient outcomes. Full article

(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Spain 2017)

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24 pages, 14636 KiB

Open AccessArticle

A Review of Depth and Normal Fusion Algorithms

by Doris Antensteiner^1,*

, Svorad Štolc¹ and Thomas Pock^1,2

¹ Center for Vision, Automation and Control, Austrian Institute of Technology, Vienna 1210, Austria

² Institute of Computer Graphics and Vision, Graz University of Technology, Graz 8010, Austria

Sensors 2018, 18(2), 431; https://doi.org/10.3390/s18020431 - 1 Feb 2018

Cited by 21 | Viewed by 6283

Abstract

Geometric surface information such as depth maps and surface normals can be acquired by various methods such as stereo light fields, shape from shading and photometric stereo techniques. We compare several algorithms which deal with the combination of depth with surface normal information [...] Read more.

Geometric surface information such as depth maps and surface normals can be acquired by various methods such as stereo light fields, shape from shading and photometric stereo techniques. We compare several algorithms which deal with the combination of depth with surface normal information in order to reconstruct a refined depth map. The reasons for performance differences are examined from the perspective of alternative formulations of surface normals for depth reconstruction. We review and analyze methods in a systematic way. Based on our findings, we introduce a new generalized fusion method, which is formulated as a least squares problem and outperforms previous methods in the depth error domain by introducing a novel normal weighting that performs closer to the geodesic distance measure. Furthermore, a novel method is introduced based on Total Generalized Variation (TGV) which further outperforms previous approaches in terms of the geodesic normal distance error and maintains comparable quality in the depth error domain. Full article

(This article belongs to the Section Physical Sensors)

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22 pages, 4712 KiB

Open AccessArticle

Random Access for Underwater Acoustic Cellular Systems

by Rothna Pec, Mohammed Saquib Khan, Muhammad Asim and Yong Soo Cho^*

School of Electrical and Electronics Engineering, Chung-Ang University, Seoul 156-756, Korea

Sensors 2018, 18(2), 432; https://doi.org/10.3390/s18020432 - 1 Feb 2018

Cited by 7 | Viewed by 6299

Abstract

In this paper, a random access preamble (RAP) design technique for underwater acoustic cellular systems is proposed. After showing that the conventional RAP used in long term evolution (LTE) systems is not appropriate for underwater acoustic cellular systems, two different types of RAPs [...] Read more.

In this paper, a random access preamble (RAP) design technique for underwater acoustic cellular systems is proposed. After showing that the conventional RAP used in long term evolution (LTE) systems is not appropriate for underwater acoustic cellular systems, two different types of RAPs (RAP 1 and RAP 2) are proposed to detect the identity of underwater equipment/nodes (UEs) and estimate the time delay between a UE and an underwater base station (UBS) at the physical layer. RAP 1 is generated using a Zadoff-Chu (ZC) sequence where the identity of the UE is mapped to its root index, whereas RAP 2 is generated using a linear frequency modulation (LFM) waveform where the identity of the UE is mapped to its frequency sweeping parameter and frequency shifting parameter. Ambiguity functions (AFs) and cross-ambiguity functions (CAFs) of RAP 1 and RAP 2 are derived to investigate their correlation properties under the effect of time delay and Doppler shift. The performance of RAP detection is investigated by analyzing the detection probabilities and false alarm probabilities of RAP 1 and RAP 2 in a Doppler environment. By evaluating the performances of RAP 1 and RAP 2 in various situations, it is concluded that RAP 2 is more suitable for underwater acoustic cellular systems. The AF and CAF analytically obtained in this paper are shown to be similar to those obtained using experimental data. Full article

(This article belongs to the Special Issue Advances and Challenges in Underwater Sensor Networks)

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20 pages, 2535 KiB

Open AccessArticle

On-Line Temperature Estimation for Noisy Thermal Sensors Using a Smoothing Filter-Based Kalman Predictor

by Xin Li^*

, Xingtao Ou

, Zhi Li, Henglu Wei, Wei Zhou and Zhemin Duan

School of Electronics and Information, Northwestern Polytechnical University, Xi’an 710072, China

Sensors 2018, 18(2), 433; https://doi.org/10.3390/s18020433 - 2 Feb 2018

Cited by 7 | Viewed by 4931

Abstract

Dynamic thermal management (DTM) mechanisms utilize embedded thermal sensors to collect fine-grained temperature information for monitoring the real-time thermal behavior of multi-core processors. However, embedded thermal sensors are very susceptible to a variety of sources of noise, including environmental uncertainty and process variation. [...] Read more.

Dynamic thermal management (DTM) mechanisms utilize embedded thermal sensors to collect fine-grained temperature information for monitoring the real-time thermal behavior of multi-core processors. However, embedded thermal sensors are very susceptible to a variety of sources of noise, including environmental uncertainty and process variation. This causes the discrepancies between actual temperatures and those observed by on-chip thermal sensors, which seriously affect the efficiency of DTM. In this paper, a smoothing filter-based Kalman prediction technique is proposed to accurately estimate the temperatures from noisy sensor readings. For the multi-sensor estimation scenario, the spatial correlations among different sensor locations are exploited. On this basis, a multi-sensor synergistic calibration algorithm (known as MSSCA) is proposed to improve the simultaneous prediction accuracy of multiple sensors. Moreover, an infrared imaging-based temperature measurement technique is also proposed to capture the thermal traces of an advanced micro devices (AMD) quad-core processor in real time. The acquired real temperature data are used to evaluate our prediction performance. Simulation shows that the proposed synergistic calibration scheme can reduce the root-mean-square error (RMSE) by 1.2

^{\circ}

C and increase the signal-to-noise ratio (SNR) by 15.8 dB (with a very small average runtime overhead) compared with assuming the thermal sensor readings to be ideal. Additionally, the average false alarm rate (FAR) of the corrected sensor temperature readings can be reduced by 28.6%. These results clearly demonstrate that if our approach is used to perform temperature estimation, the response mechanisms of DTM can be triggered to adjust the voltages, frequencies, and cooling fan speeds at more appropriate times. Full article

(This article belongs to the Special Issue Advances in Infrared Imaging: Sensing, Exploitation and Applications)

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20 pages, 1629 KiB

Open AccessArticle

La-CTP: Loop-Aware Routing for Energy-Harvesting Wireless Sensor Networks

by Guodong Sun^1,2,*, Xinna Shang^1,3 and Yan Zuo⁴

¹ School of Information Science and Technology, Beijing Forestry University, Beijing 100083, China

² Embedded Networked Systems Lab, Beijing Forestry University, Beijing 100083, China

³ College of Robotics, Beijing Union University, Beijing 100101, China

⁴ Department of Computer Science and Technology, Dalian Neusoft University of Information, Dalian 116023, China

Sensors 2018, 18(2), 434; https://doi.org/10.3390/s18020434 - 2 Feb 2018

Cited by 9 | Viewed by 4252

Abstract

In emerging energy-harvesting wireless sensor networks (EH-WSN), the sensor nodes can harvest environmental energy to drive their operation, releasing the user’s burden in terms of frequent battery replacement, and even enabling perpetual sensing systems. In EH-WSN applications, usually, the node in energy-harvesting or [...] Read more.

In emerging energy-harvesting wireless sensor networks (EH-WSN), the sensor nodes can harvest environmental energy to drive their operation, releasing the user’s burden in terms of frequent battery replacement, and even enabling perpetual sensing systems. In EH-WSN applications, usually, the node in energy-harvesting or recharging state has to stop working until it completes the energy replenishment. However, such temporary departures of recharging nodes severely impact the packet routing, and one immediate result is the routing loop problem. Controlling loops in connectivity-intermittent EH-WSN in an efficient way is a big challenge in practice, and so far, users still lack of effective and practicable routing protocols with loop handling. Based on the Collection Tree Protocol (CTP) widely used in traditional wireless sensor networks, this paper proposes a loop-aware routing protocol for real-world EH-WSNs, called La-CTP, which involves a new parent updating metric and a proactive, adaptive beaconing scheme to effectively suppress the occurrence of loops and unlock unavoidable loops, respectively. We constructed a 100-node testbed to evaluate La-CTP, and the experimental results showed its efficacy and efficiency. Full article

(This article belongs to the Section Sensor Networks)

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22 pages, 598 KiB

Open AccessArticle

Optimized Sensor Network and Multi-Agent Decision Support for Smart Traffic Light Management

by Luis Cruz-Piris^*

, Diego Rivera

, Susel Fernandez

and Ivan Marsa-Maestre

Departamento de Automática, Escuela Politécnica Superior, Universidad de Alcalá, 28805 Alcalá de Henares, Madrid, Spain

Sensors 2018, 18(2), 435; https://doi.org/10.3390/s18020435 - 2 Feb 2018

Cited by 41 | Viewed by 7676

Abstract

One of the biggest challenges in modern societies is to solve vehicular traffic problems. Sensor networks in traffic environments have contributed to improving the decision-making process of Intelligent Transportation Systems. However, one of the limiting factors for the effectiveness of these systems is [...] Read more.

One of the biggest challenges in modern societies is to solve vehicular traffic problems. Sensor networks in traffic environments have contributed to improving the decision-making process of Intelligent Transportation Systems. However, one of the limiting factors for the effectiveness of these systems is in the deployment of sensors to provide accurate information about the traffic. Our proposal is using the centrality measurement of a graph as a base to locate the best locations for sensor installation in a traffic network. After integrating these sensors in a simulation scenario, we define a Multi-Agent Systems composed of three types of agents: traffic light management agents, traffic jam detection agents, and agents that control the traffic lights at an intersection. The ultimate goal of these Multi-Agent Systems is to improve the trip duration for vehicles in the network. To validate our solution, we have developed the needed elements for modelling the sensors and agents in the simulation environment. We have carried out experiments using the Simulation of Urban MObility (SUMO) traffic simulator and the Travel and Activity PAtterns Simulation (TAPAS) Cologne traffic scenario. The obtained results show that our proposal allows to reduce the sensor network while still obtaining relevant information to have a global view of the environment. Finally, regarding the Multi-Agent Systems, we have carried out experiments that show that our proposal is able to improve other existing solutions such as conventional traffic light management systems (static or dynamic) in terms of reduction of vehicle trip duration and reduction of the message exchange overhead in the sensor network. Full article

(This article belongs to the Collection Smart Communication Protocols and Algorithms for Sensor Networks)

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24 pages, 13256 KiB

Open AccessArticle

A Real-Time Construction Safety Monitoring System for Hazardous Gas Integrating Wireless Sensor Network and Building Information Modeling Technologies

by Weng-Fong Cheung¹, Tzu-Hsuan Lin² and Yu-Cheng Lin^1,*

¹ Department of Civil Engineering, National Taipei University of Technology, Taipei 10608, Taiwan

² Department of Civil Engineering, National Central University, Taoyuan 32001, Taiwan

Sensors 2018, 18(2), 436; https://doi.org/10.3390/s18020436 - 2 Feb 2018

Cited by 163 | Viewed by 18311

Abstract

In recent years, many studies have focused on the application of advanced technology as a way to improve management of construction safety management. A Wireless Sensor Network (WSN), one of the key technologies in Internet of Things (IoT) development, enables objects and devices [...] Read more.

In recent years, many studies have focused on the application of advanced technology as a way to improve management of construction safety management. A Wireless Sensor Network (WSN), one of the key technologies in Internet of Things (IoT) development, enables objects and devices to sense and communicate environmental conditions; Building Information Modeling (BIM), a revolutionary technology in construction, integrates database and geometry into a digital model which provides a visualized way in all construction lifecycle management. This paper integrates BIM and WSN into a unique system which enables the construction site to visually monitor the safety status via a spatial, colored interface and remove any hazardous gas automatically. Many wireless sensor nodes were placed on an underground construction site and to collect hazardous gas level and environmental condition (temperature and humidity) data, and in any region where an abnormal status is detected, the BIM model will alert the region and an alarm and ventilator on site will start automatically for warning and removing the hazard. The proposed system can greatly enhance the efficiency in construction safety management and provide an important reference information in rescue tasks. Finally, a case study demonstrates the applicability of the proposed system and the practical benefits, limitations, conclusions, and suggestions are summarized for further applications. Full article

(This article belongs to the Special Issue Sensors for Deformation Monitoring of Large Civil Infrastructures)

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26 pages, 2670 KiB

Open AccessArticle

Accurate Energy Consumption Modeling of IEEE 802.15.4e TSCH Using Dual-Band OpenMote Hardware

by Glenn Daneels^*

, Esteban Municio, Bruno Van de Velde, Glenn Ergeerts

, Maarten Weyn

, Steven Latré and Jeroen Famaey

IDLab Research Group, University of Antwerp—imec, 2000 Antwerp, Belgium

Sensors 2018, 18(2), 437; https://doi.org/10.3390/s18020437 - 2 Feb 2018

Cited by 22 | Viewed by 5706

Abstract

The Time-Slotted Channel Hopping (TSCH) mode of the IEEE 802.15.4e amendment aims to improve reliability and energy efficiency in industrial and other challenging Internet-of-Things (IoT) environments. This paper presents an accurate and up-to-date energy consumption model for devices using this IEEE 802.15.4e TSCH [...] Read more.

The Time-Slotted Channel Hopping (TSCH) mode of the IEEE 802.15.4e amendment aims to improve reliability and energy efficiency in industrial and other challenging Internet-of-Things (IoT) environments. This paper presents an accurate and up-to-date energy consumption model for devices using this IEEE 802.15.4e TSCH mode. The model identifies all network-related CPU and radio state changes, thus providing a precise representation of the device behavior and an accurate prediction of its energy consumption. Moreover, energy measurements were performed with a dual-band OpenMote device, running the OpenWSN firmware. This allows the model to be used for devices using 2.4 GHz, as well as 868 MHz. Using these measurements, several network simulations were conducted to observe the TSCH energy consumption effects in end-to-end communication for both frequency bands. Experimental verification of the model shows that it accurately models the consumption for all possible packet sizes and that the calculated consumption on average differs less than 3% from the measured consumption. This deviation includes measurement inaccuracies and the variations of the guard time. As such, the proposed model is very suitable for accurate energy consumption modeling of TSCH networks. Full article

(This article belongs to the Special Issue Energy Harvesting Sensors for Long Term Applications in the IoT Era)

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19 pages, 3917 KiB

Open AccessArticle

A Real-Time Reaction Obstacle Avoidance Algorithm for Autonomous Underwater Vehicles in Unknown Environments

by Zheping Yan, Jiyun Li^*, Gengshi Zhang and Yi Wu

Marine Assembly and Automatic Technology Institute, College of Automation, Harbin Engineering University, Harbin 150001, China

Sensors 2018, 18(2), 438; https://doi.org/10.3390/s18020438 - 2 Feb 2018

Cited by 31 | Viewed by 6605

Abstract

A novel real-time reaction obstacle avoidance algorithm (RRA) is proposed for autonomous underwater vehicles (AUVs) that must adapt to unknown complex terrains, based on forward looking sonar (FLS). To accomplish this algorithm, obstacle avoidance rules are planned, and the RRA processes are split [...] Read more.

A novel real-time reaction obstacle avoidance algorithm (RRA) is proposed for autonomous underwater vehicles (AUVs) that must adapt to unknown complex terrains, based on forward looking sonar (FLS). To accomplish this algorithm, obstacle avoidance rules are planned, and the RRA processes are split into five steps Introduction only lists 4 so AUVs can rapidly respond to various environment obstacles. The largest polar angle algorithm (LPAA) is designed to change detected obstacle’s irregular outline into a convex polygon, which simplifies the obstacle avoidance process. A solution is designed to solve the trapping problem existing in U-shape obstacle avoidance by an outline memory algorithm. Finally, simulations in three unknown obstacle scenes are carried out to demonstrate the performance of this algorithm, where the obtained obstacle avoidance trajectories are safety, smooth and near-optimal. Full article

(This article belongs to the Special Issue Smart Sensors for Mechatronic and Robotic Systems)

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16 pages, 5192 KiB

Open AccessArticle

Design Optimization and Fabrication of a Novel Structural SOI Piezoresistive Pressure Sensor with High Accuracy

by Chuang Li^*, Francisco Cordovilla, R. Jagdheesh and José L. Ocaña

E.T.S. Ingenieros Industriales, Polytechnical University of Madrid, C/José Gutiérrez Abascal, 2. 28006 Madrid, Spain

Sensors 2018, 18(2), 439; https://doi.org/10.3390/s18020439 - 2 Feb 2018

Cited by 69 | Viewed by 9102

Abstract

This paper presents a novel structural piezoresistive pressure sensor with four-grooved membrane combined with rood beam to measure low pressure. In this investigation, the design, optimization, fabrication, and measurements of the sensor are involved. By analyzing the stress distribution and deflection of sensitive [...] Read more.

This paper presents a novel structural piezoresistive pressure sensor with four-grooved membrane combined with rood beam to measure low pressure. In this investigation, the design, optimization, fabrication, and measurements of the sensor are involved. By analyzing the stress distribution and deflection of sensitive elements using finite element method, a novel structure featuring high concentrated stress profile (HCSP) and locally stiffened membrane (LSM) is built. Curve fittings of the mechanical stress and deflection based on FEM simulation results are performed to establish the relationship between mechanical performance and structure dimension. A combination of FEM and curve fitting method is carried out to determine the structural dimensions. The optimized sensor chip is fabricated on a SOI wafer by traditional MEMS bulk-micromachining and anodic bonding technology. When the applied pressure is 1 psi, the sensor achieves a sensitivity of 30.9 mV/V/psi, a pressure nonlinearity of 0.21% FSS and an accuracy of 0.30%, and thereby the contradiction between sensitivity and linearity is alleviated. In terms of size, accuracy and high temperature characteristic, the proposed sensor is a proper choice for measuring pressure of less than 1 psi. Full article

(This article belongs to the Special Issue Sensors for MEMS and Microsystems)

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10 pages, 1360 KiB

Open AccessArticle

Improvement in Limit of Detection of Enzymatic Biogas Sensor Utilizing Chromatography Paper for Breath Analysis

by Masanobu Motooka and Shigeyasu Uno^*

Department of Electrical and Electronic Engineering, Ritsumeikan University, Kusatsu, Shiga 525-8577, Japan

Sensors 2018, 18(2), 440; https://doi.org/10.3390/s18020440 - 2 Feb 2018

Cited by 16 | Viewed by 5602

Abstract

Breath analysis is considered to be an effective method for point-of-care diagnosis due to its noninvasiveness, quickness and simplicity. Gas sensors for breath analysis require detection of low-concentration substances. In this paper, we propose that reduction of the background current improves the limit [...] Read more.

Breath analysis is considered to be an effective method for point-of-care diagnosis due to its noninvasiveness, quickness and simplicity. Gas sensors for breath analysis require detection of low-concentration substances. In this paper, we propose that reduction of the background current improves the limit of detection of enzymatic biogas sensors utilizing chromatography paper. After clarifying the cause of the background current, we reduced the background current by improving the fabrication process of the sensors utilizing paper. Finally, we evaluated the limit of detection of the sensor with the sample vapor of ethanol gas. The experiment showed about a 50% reduction of the limit of detection compared to previously-reported sensor. This result presents the possibility of the sensor being applied in diagnosis, such as for diabetes, by further lowering the limit of detection. Full article

(This article belongs to the Special Issue I3S 2017 Selected Papers)

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20 pages, 10383 KiB

Open AccessArticle

Specim IQ: Evaluation of a New, Miniaturized Handheld Hyperspectral Camera and Its Application for Plant Phenotyping and Disease Detection

by Jan Behmann^1,*, Kelvin Acebron²

, Dzhaner Emin², Simon Bennertz², Shizue Matsubara²

, Stefan Thomas¹, David Bohnenkamp¹, Matheus T. Kuska¹, Jouni Jussila⁴, Harri Salo⁴, Anne-Katrin Mahlein^1,3 and Uwe Rascher²

¹ INRES-Plant Diseases and Plant Protection, University of Bonn, 53115 Bonn, Germany

² IBG-2, Forschungszentrum Jülich (FZJ), Jülich, 52428 Germany

³ Institute of Sugar Beet Research (IFZ), 37079 Göttingen, Germany

⁴ Specim Ltd., FI-90571 Oulu, Finland

Sensors 2018, 18(2), 441; https://doi.org/10.3390/s18020441 - 2 Feb 2018

Cited by 178 | Viewed by 22624

Abstract

Hyperspectral imaging sensors are promising tools for monitoring crop plants or vegetation in different environments. Information on physiology, architecture or biochemistry of plants can be assessed non-invasively and on different scales. For instance, hyperspectral sensors are implemented for stress detection in plant phenotyping [...] Read more.

Hyperspectral imaging sensors are promising tools for monitoring crop plants or vegetation in different environments. Information on physiology, architecture or biochemistry of plants can be assessed non-invasively and on different scales. For instance, hyperspectral sensors are implemented for stress detection in plant phenotyping processes or in precision agriculture. Up to date, a variety of non-imaging and imaging hyperspectral sensors is available. The measuring process and the handling of most of these sensors is rather complex. Thus, during the last years the demand for sensors with easy user operability arose. The present study introduces the novel hyperspectral camera Specim IQ from Specim (Oulu, Finland). The Specim IQ is a handheld push broom system with integrated operating system and controls. Basic data handling and data analysis processes, such as pre-processing and classification routines are implemented within the camera software. This study provides an introduction into the measurement pipeline of the Specim IQ as well as a radiometric performance comparison with a well-established hyperspectral imager. Case studies for the detection of powdery mildew on barley at the canopy scale and the spectral characterization of Arabidopsis thaliana mutants grown under stressed and non-stressed conditions are presented. Full article

(This article belongs to the Special Issue Sensors in Agriculture)

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14 pages, 12202 KiB

Open AccessArticle

Analysis of Flow Cytometric Fluorescence Lifetime with Time-Delay Estimation of Pulse Signals

by Lianqing Zhu^1,†, Wenchang Zhang^2,†

, Mingli Dong^1,* and Xiaoping Lou¹

¹ Beijing Key Laboratory for Optoelectronics Measurement Technology, Beijing Information Science and Technology University, Beijing 100192, China

² Key Lab of Microelectronic Devices & Integrated Technology, Institute of Microelectronics, Chinese Academy of Sciences, Beijing 100029, China

^† These authors contributed equally to this work.

Sensors 2018, 18(2), 442; https://doi.org/10.3390/s18020442 - 3 Feb 2018

Cited by 2 | Viewed by 6111

Abstract

The measurement of fluorescence lifetimes emerged in flow cytometry because it is not impacted by the non-linearity, which occurs in fluorescence intensity measurements. However, this significantly increases the cost and complexity of a traditional flow cytometer. This work reports a simple method of [...] Read more.

The measurement of fluorescence lifetimes emerged in flow cytometry because it is not impacted by the non-linearity, which occurs in fluorescence intensity measurements. However, this significantly increases the cost and complexity of a traditional flow cytometer. This work reports a simple method of fluorescence lifetime measurement of a flow cytometer based on the cytometric fluorescence pulse time-delay estimation and hardware time-delay calibration. The modified chirp Z-transform (MCZT) algorithm, combined with the algorithm of fine interpolation of correlation peak (FICP), is applied to improve the temporal resolution of the cross-correlation function of the scattering and fluorescence signals, which in turn improves the time-delay estimation accuracy. The estimation accuracy is verified by Gauss fitting. Cells that were labeled simultaneously with three-color reagents are measured; the statistical results of 5000 cells are compared with reference values and are verified with the pulse width variation. The results show the potential of fluorescence lifetime measurements in the traditional flow cytometer. Full article

(This article belongs to the Special Issue Optical Biochemical Sensor Systems and Applications)

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13 pages, 918 KiB

Open AccessArticle

Speed Bump Detection Using Accelerometric Features: A Genetic Algorithm Approach

by Jose M. Celaya-Padilla^1,*

, Carlos E. Galván-Tejada²

, F. E. López-Monteagudo², O. Alonso-González³, Arturo Moreno-Báez², Antonio Martínez-Torteya⁴, Jorge I. Galván-Tejada², Jose G. Arceo-Olague², Huizilopoztli Luna-García²

and Hamurabi Gamboa-Rosales²

¹ Unidad Académica de Ingeniería Eléctrica, CONACyT—Universidad Autónoma de Zacatecas, Jardín Juárez 147, Centro Histórico, 98000 Zacatecas, Mexico

² Unidad Académica de Ingeniería Eléctrica, Universidad Autónoma de Zacatecas, Jardín Juárez 147, Centro Histórico, 98000 Zacatecas, Mexico

³ Unidad Académica de Ingeniería I, Universidad Autónoma de Zacatecas, Jardín Juárez 147, Centro Histórico, 98000 Zacatecas, Mexico

⁴ Departamento de ingeniería, Universidad de Monterrey, Avenida Ignacio Morones Prieto 4500 Pte., Jesús M. Garza, 66238, San Pedro Garza García, Nuevo León, Mexico

Sensors 2018, 18(2), 443; https://doi.org/10.3390/s18020443 - 3 Feb 2018

Cited by 77 | Viewed by 12744

Abstract

Among the current challenges of the Smart City, traffic management and maintenance are of utmost importance. Road surface monitoring is currently performed by humans, but the road surface condition is one of the main indicators of road quality, and it may drastically affect [...] Read more.

Among the current challenges of the Smart City, traffic management and maintenance are of utmost importance. Road surface monitoring is currently performed by humans, but the road surface condition is one of the main indicators of road quality, and it may drastically affect fuel consumption and the safety of both drivers and pedestrians. Abnormalities in the road, such as manholes and potholes, can cause accidents when not identified by the drivers. Furthermore, human-induced abnormalities, such as speed bumps, could also cause accidents. In addition, while said obstacles ought to be signalized according to specific road regulation, they are not always correctly labeled. Therefore, we developed a novel method for the detection of road abnormalities (i.e., speed bumps). This method makes use of a gyro, an accelerometer, and a GPS sensor mounted in a car. After having the vehicle cruise through several streets, data is retrieved from the sensors. Then, using a cross-validation strategy, a genetic algorithm is used to find a logistic model that accurately detects road abnormalities. The proposed model had an accuracy of 0.9714 in a blind evaluation, with a false positive rate smaller than 0.018, and an area under the receiver operating characteristic curve of 0.9784. This methodology has the potential to detect speed bumps in quasi real-time conditions, and can be used to construct a real-time surface monitoring system. Full article

(This article belongs to the Special Issue Smart Vehicular Mobile Sensing)

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11 pages, 3352 KiB

Open AccessArticle

Electrochemical Immunoassay Using Open Circuit Potential Detection Labeled by Platinum Nanoparticles

by Kanokwan Charoenkitamorn^1,2, Phan Trong Tue¹, Keiko Kawai¹, Orawon Chailapakul^2,3,* and Yuzuru Takamura^1,*

¹ School of Materials Science, Japan Advanced Institute of Science and Technology, 1-1 Asahidai, Nomi City, Ishikawa 923-1292, Japan

² Department of Chemistry, Faculty of Science, Chulalongkorn University, 254 Phayathai Road, Patumwan, Bangkok 10330, Thailand

³ National Center of Excellent of Petroleum, Petrochemicals and Advanced Materials, Chulalongkorn University, Patumwan, Bangkok 10330, Thailand

Sensors 2018, 18(2), 444; https://doi.org/10.3390/s18020444 - 3 Feb 2018

Cited by 21 | Viewed by 7528

Abstract

In this work, a simple electrochemical immunoassay based on platinum nanoparticles (PtNPs) using open circuit potential (OCP) detection was developed. The detection of human chorionic gonadotropin hormone (hCG) as a model analyte, was demonstrated by direct electrical detection of PtNPs in hydrazine solution [...] Read more.

In this work, a simple electrochemical immunoassay based on platinum nanoparticles (PtNPs) using open circuit potential (OCP) detection was developed. The detection of human chorionic gonadotropin hormone (hCG) as a model analyte, was demonstrated by direct electrical detection of PtNPs in hydrazine solution using OCP measurement without any application of either potential or current to the system. Disposable screen-printed carbon electrodes (SPCEs) were utilized for the development of our immunosensor, which required a sample volume as small as 2 μL. After preparation of a sandwich-type immunosystem, hydrazine solution was dropped on the electrode’s surface, which was followed immediately by electrical detection using OCP. The change of the OCP signal originated from electrocatalytic oxidation of the hydrazine on PtNPs. Under the optimal conditions of a pH of 6.0 and a hydrazine concentration of 1 mM, a detection limit of 0.28 ng mL⁻¹ and a linearity of 0–10 ng mL⁻¹ were obtained. The PtNP-based OCP method is a simpler electrochemical detection procedure than those obtained from other electrochemical methods and has an acceptable sensitivity and reproducibility. The simplicity of the detection procedure and the cost-effectiveness of the disposable SPCE illustrate the attractive benefits of this sensor. Moreover, it could be applied to a simplified and miniaturized diagnostic system with minimal user manipulation. Full article

(This article belongs to the Special Issue Dedication to Professor Eiichi Tamiya: Over 30 Years of Outstanding Contributions to the Field of Sensors and Biosensors)

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16 pages, 3751 KiB

Open AccessArticle

SNDR Limits of Oscillator-Based Sensor Readout Circuits

by Fernando Cardes^1,*

, Andres Quintero¹

, Eric Gutierrez¹

, Cesare Buffa², Andreas Wiesbauer² and Luis Hernandez¹

¹ Department of Electronics Technology, Carlos III University of Madrid, 28911 Leganes, Spain

² Infineon Technologies Austria AG, Villach 9500, Austria

Sensors 2018, 18(2), 445; https://doi.org/10.3390/s18020445 - 3 Feb 2018

Cited by 28 | Viewed by 8054

Abstract

This paper analyzes the influence of phase noise and distortion on the performance of oscillator-based sensor data acquisition systems. Circuit noise inherent to the oscillator circuit manifests as phase noise and limits the SNR. Moreover, oscillator nonlinearity generates distortion for large input signals. [...] Read more.

This paper analyzes the influence of phase noise and distortion on the performance of oscillator-based sensor data acquisition systems. Circuit noise inherent to the oscillator circuit manifests as phase noise and limits the SNR. Moreover, oscillator nonlinearity generates distortion for large input signals. Phase noise analysis of oscillators is well known in the literature, but the relationship between phase noise and the SNR of an oscillator-based sensor is not straightforward. This paper proposes a model to estimate the influence of phase noise in the performance of an oscillator-based system by reflecting the phase noise to the oscillator input. The proposed model is based on periodic steady-state analysis tools to predict the SNR of the oscillator. The accuracy of this model has been validated by both simulation and experiment in a 130 nm CMOS prototype. We also propose a method to estimate the SNDR and the dynamic range of an oscillator-based readout circuit that improves by more than one order of magnitude the simulation time compared to standard time domain simulations. This speed up enables the optimization and verification of this kind of systems with iterative algorithms. Full article

(This article belongs to the Special Issue Integrated Microfluidic CMOS (imCMOS) Sensors and Actuators for Life Science Applications)

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20 pages, 578 KiB

Open AccessArticle

Distributed Algorithm for Voronoi Partition of Wireless Sensor Networks with a Limited Sensing Range

by Chenlong He^1,*

, Zuren Feng¹ and Zhigang Ren²

¹ State Key Laboratory for Manufacturing System Engineering, Systems Engineering Institute, Xi’an Jiaotong University, Xi’an 710049, China

² Autocontrol Research Institute, Xi’an Jiaotong University, Xi’an 710049, China

Sensors 2018, 18(2), 446; https://doi.org/10.3390/s18020446 - 3 Feb 2018

Cited by 12 | Viewed by 5023

Abstract

For Wireless Sensor Networks (WSNs), the Voronoi partition of a region is a challenging problem owing to the limited sensing ability of each sensor and the distributed organization of the network. In this paper, an algorithm is proposed for each sensor having a [...] Read more.

For Wireless Sensor Networks (WSNs), the Voronoi partition of a region is a challenging problem owing to the limited sensing ability of each sensor and the distributed organization of the network. In this paper, an algorithm is proposed for each sensor having a limited sensing range to compute its limited Voronoi cell autonomously, so that the limited Voronoi partition of the entire WSN is generated in a distributed manner. Inspired by Graham’s Scan (GS) algorithm used to compute the convex hull of a point set, the limited Voronoi cell of each sensor is obtained by sequentially scanning two consecutive bisectors between the sensor and its neighbors. The proposed algorithm called the Boundary Scan (BS) algorithm has a lower computational complexity than the existing Range-Constrained Voronoi Cell (RCVC) algorithm and reaches the lower bound of the computational complexity of the algorithms used to solve the problem of this kind. Moreover, it also improves the time efficiency of a key step in the Adjust-Sensing-Radius (ASR) algorithm used to compute the exact Voronoi cell. Extensive numerical simulations are performed to demonstrate the correctness and effectiveness of the BS algorithm. The distributed realization of the BS combined with a localization algorithm in WSNs is used to justify the WSN nature of the proposed algorithm. Full article

(This article belongs to the Special Issue Mobile Sensing Applications)

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12 pages, 2138 KiB

Open AccessArticle

Visual Estimation of Bacterial Growth Level in Microfluidic Culture Systems

by Kyukwang Kim¹, Seunggyu Kim²

and Jessie S. Jeon^2,3,*

¹ Robotics Program, Korea Advanced Institute of Science and Technology, 291 Daehak-ro, Daejeon 34141, Korea

² Department of Mechanical Engineering, Korea Advanced Institute of Science and Technology, 291 Daehak-ro, Daejeon 34141, Korea

³ KAIST Institute for Health Science and Technology, 291 Daehak-ro, Daejeon 34141, Korea

Sensors 2018, 18(2), 447; https://doi.org/10.3390/s18020447 - 3 Feb 2018

Cited by 25 | Viewed by 9417

Abstract

Microfluidic devices are an emerging platform for a variety of experiments involving bacterial cell culture, and has advantages including cost and convenience. One inevitable step during bacterial cell culture is the measurement of cell concentration in the channel. The optical density measurement technique [...] Read more.

Microfluidic devices are an emerging platform for a variety of experiments involving bacterial cell culture, and has advantages including cost and convenience. One inevitable step during bacterial cell culture is the measurement of cell concentration in the channel. The optical density measurement technique is generally used for bacterial growth estimation, but it is not applicable to microfluidic devices due to the small sample volumes in microfluidics. Alternately, cell counting or colony-forming unit methods may be applied, but these do not work in situ; nor do these methods show measurement results immediately. To this end, we present a new vision-based method to estimate the growth level of the bacteria in microfluidic channels. We use Fast Fourier transform (FFT) to detect the frequency level change of the microscopic image, focusing on the fact that the microscopic image becomes rough as the number of cells in the field of view increases, adding high frequencies to the spectrum of the image. Two types of microfluidic devices are used to culture bacteria in liquid and agar gel medium, and time-lapsed images are captured. The images obtained are analyzed using FFT, resulting in an increase in high-frequency noise proportional to the time passed. Furthermore, we apply the developed method in the microfluidic antibiotics susceptibility test by recognizing the regional concentration change of the bacteria that are cultured in the antibiotics gradient. Finally, a deep learning-based data regression is performed on the data obtained by the proposed vision-based method for robust reporting of data. Full article

(This article belongs to the Special Issue Lab-on-a-Chip–From Point of Care to Precision Medicine)

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21 pages, 6536 KiB

Open AccessArticle

Integrated Change Detection and Classification in Urban Areas Based on Airborne Laser Scanning Point Clouds

by Thi Huong Giang Tran^1,2,*, Camillo Ressl¹

and Norbert Pfeifer¹

¹ Department of Geodesy and Geoinformation, Technische Universität Wien, Gußhausstraße 27-29, 1040 Vienna, Austria

² Faculty of Geomatics and Land Administration, Hanoi University of Mining and Geology, Hanoi 10000, Vietnam

Sensors 2018, 18(2), 448; https://doi.org/10.3390/s18020448 - 3 Feb 2018

Cited by 71 | Viewed by 8543

Abstract

This paper suggests a new approach for change detection (CD) in 3D point clouds. It combines classification and CD in one step using machine learning. The point cloud data of both epochs are merged for computing features of four types: features describing the [...] Read more.

This paper suggests a new approach for change detection (CD) in 3D point clouds. It combines classification and CD in one step using machine learning. The point cloud data of both epochs are merged for computing features of four types: features describing the point distribution, a feature relating to relative terrain elevation, features specific for the multi-target capability of laser scanning, and features combining the point clouds of both epochs to identify the change. All these features are merged in the points and then training samples are acquired to create the model for supervised classification, which is then applied to the whole study area. The final results reach an overall accuracy of over 90% for both epochs of eight classes: lost tree, new tree, lost building, new building, changed ground, unchanged building, unchanged tree, and unchanged ground. Full article

(This article belongs to the Section Remote Sensors)

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16 pages, 21222 KiB

Open AccessArticle

A Hybrid Readout Solution for GaN-Based Detectors Using CMOS Technology

by Preethi Padmanabhan^1,*

, Bruce Hancock², Shouleh Nikzad², L. Douglas Bell², Kees Kroep³ and Edoardo Charbon^1,3

¹ AQUA Laboratory, École Polytechnique Fédérale de Lausanne (EPFL), 2000 Neuchâtel, Switzerland

² Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA

³ AQUA Laboratory, Delft University of Technology, 2628 CD Delft, The Netherlands

Sensors 2018, 18(2), 449; https://doi.org/10.3390/s18020449 - 3 Feb 2018

Cited by 7 | Viewed by 6836

Abstract

Gallium nitride (GaN) and its alloys are becoming preferred materials for ultraviolet (UV) detectors due to their wide bandgap and tailorable out-of-band cutoff from 3.4 eV to 6.2 eV. GaN based avalanche photodiodes (APDs) are particularly suitable for their high photon sensitivity and [...] Read more.

Gallium nitride (GaN) and its alloys are becoming preferred materials for ultraviolet (UV) detectors due to their wide bandgap and tailorable out-of-band cutoff from 3.4 eV to 6.2 eV. GaN based avalanche photodiodes (APDs) are particularly suitable for their high photon sensitivity and quantum efficiency in the UV region and for their inherent insensitivity to visible wavelengths. Challenges exist however for practical utilization. With growing interests in such photodetectors, hybrid readout solutions are becoming prevalent with CMOS technology being adopted for its maturity, scalability, and reliability. In this paper, we describe our approach to combine GaN APDs with a CMOS readout circuit, comprising of a linear array of 1 × 8 capacitive transimpedance amplifiers (CTIAs), implemented in a 0.35 µm high voltage CMOS technology. Further, we present a simple, yet sustainable circuit technique to allow operation of APDs under high reverse biases, up to ≈80 V with verified measurement results. The readout offers a conversion gain of 0.43 µV/e⁻, obtaining avalanche gains up to 10³. Several parameters of the CTIA are discussed followed by a perspective on possible hybridization, exploiting the advantages of a 3D-stacked technology. Full article

(This article belongs to the Special Issue Special Issue on the 2017 International Image Sensor Workshop (IISW))

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28 pages, 8173 KiB

Open AccessArticle

The Application of Social Characteristic and L1 Optimization in the Error Correction for Network Coding in Wireless Sensor Networks

by Guangzhi Zhang^1,2,*, Shaobin Cai^1,3 and Naixue Xiong⁴

¹ Computer Science Department, Harbin Engineering University, Harbin 150001, China

² Department of Information Engineering, Suihua University, Suihua 152000, China

³ Computer Science Department, Huaqiao University, Xiamen 361021, China

⁴ Department of Computer Science, Georgia State University, Atlanta, GA 30302, USA

Sensors 2018, 18(2), 450; https://doi.org/10.3390/s18020450 - 3 Feb 2018

Cited by 6 | Viewed by 4130

Abstract

One of the remarkable challenges about Wireless Sensor Networks (WSN) is how to transfer the collected data efficiently due to energy limitation of sensor nodes. Network coding will increase network throughput of WSN dramatically due to the broadcast nature of WSN. However, the [...] Read more.

One of the remarkable challenges about Wireless Sensor Networks (WSN) is how to transfer the collected data efficiently due to energy limitation of sensor nodes. Network coding will increase network throughput of WSN dramatically due to the broadcast nature of WSN. However, the network coding usually propagates a single original error over the whole network. Due to the special property of error propagation in network coding, most of error correction methods cannot correct more than C/2 corrupted errors where C is the max flow min cut of the network. To maximize the effectiveness of network coding applied in WSN, a new error-correcting mechanism to confront the propagated error is urgently needed. Based on the social network characteristic inherent in WSN and L1 optimization, we propose a novel scheme which successfully corrects more than C/2 corrupted errors. What is more, even if the error occurs on all the links of the network, our scheme also can correct errors successfully. With introducing a secret channel and a specially designed matrix which can trap some errors, we improve John and Yi’s model so that it can correct the propagated errors in network coding which usually pollute exactly 100% of the received messages. Taking advantage of the social characteristic inherent in WSN, we propose a new distributed approach that establishes reputation-based trust among sensor nodes in order to identify the informative upstream sensor nodes. With referred theory of social networks, the informative relay nodes are selected and marked with high trust value. The two methods of L1 optimization and utilizing social characteristic coordinate with each other, and can correct the propagated error whose fraction is even exactly 100% in WSN where network coding is performed. The effectiveness of the error correction scheme is validated through simulation experiments. Full article

(This article belongs to the Special Issue Sensor Intelligent Data Analysis for Social Networks: Theory and Applications)

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10 pages, 3280 KiB

Open AccessArticle

Polymeric Flexible Immunosensor Based on Piezoresistive Micro-Cantilever with PEDOT/PSS Conductive Layer

by Rui Zhao^*,†

and Ying Sun^†

¹ School of Instrument and Electronics, North University of China, Taiyuan 030051, China

^† These authors contributed equally to this work.

Sensors 2018, 18(2), 451; https://doi.org/10.3390/s18020451 - 3 Feb 2018

Cited by 12 | Viewed by 7111

Abstract

In this paper, a fully polymeric micro-cantilever with the surface passivation layer of parylene-C and the strain resistor of poly(3,4-ethylenedioxythiophene)/poly (styrene sulfonate) (PEDOT/PSS) was proposed and demonstrated for immunoassays. By optimizing the design and fabrication of the polymeric micro-cantilever, a square resistance of [...] Read more.

In this paper, a fully polymeric micro-cantilever with the surface passivation layer of parylene-C and the strain resistor of poly(3,4-ethylenedioxythiophene)/poly (styrene sulfonate) (PEDOT/PSS) was proposed and demonstrated for immunoassays. By optimizing the design and fabrication of the polymeric micro-cantilever, a square resistance of 220 Ω/□ for PEDOT/PSS conductive layer have been obtained. The experimental spring constant and the deflection sensitivity were measured to be 0.017 N/m and 8.59 × 10⁻⁷ nm⁻¹, respectively. The biological sensing performances of polymeric micro-cantilever were investigated by the immunoassay for human immunoglobulin G (IgG). The immunosensor was experimentally demonstrated to have a linear behavior for the detection of IgG within the concentrations of 10~100 ng/mL with a limit of detection (LOD) of 10 ng/mL. The experimental results indicate that the proposed polymeric flexible conductive layer-based sensors are capable of detecting trace biological substances. Full article

(This article belongs to the Special Issue Polymer-Based Sensors for Bioanalytes)

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11 pages, 3506 KiB

Open AccessArticle

Two Solutions of Soil Moisture Sensing with RFID for Landslide Monitoring

by Sérgio Francisco Pichorim^1,*

, Nathan J. Gomes² and John C. Batchelor²

¹ Graduate School of Electrical Engineering and Computer Science (CPGEI-DAELN), Federal University of Technology, Paraná (UTFPR), 80230-901 Curitiba, Brazil

² School of Engineering and Digital Arts, University of Kent, CT2 7NT Canterbury, UK

Sensors 2018, 18(2), 452; https://doi.org/10.3390/s18020452 - 3 Feb 2018

Cited by 53 | Viewed by 10553

Abstract

Two solutions for UHF RFID tags for soil moisture sensing were designed and are described in this paper. In the first, two conventional tags (standard transponders) are employed: one, placed close to the soil surface, is the sensor tag, while the other, separated [...] Read more.

Two solutions for UHF RFID tags for soil moisture sensing were designed and are described in this paper. In the first, two conventional tags (standard transponders) are employed: one, placed close to the soil surface, is the sensor tag, while the other, separated from the soil, is the reference for system calibration. By transmission power ramps, the tag’s turn-on power levels are measured and correlated with soil condition (dry or wet). In the second solution, the SL900A chip, which supports up to two external sensors and an internal temperature sensor, is used. An interdigital capacitive sensor was connected to the transponder chip and used for soil moisture measurement. In a novel design for an UHF RFID tag the sensor is placed below the soil surface, while the transponder and antenna are above the soil to improve communication. Both solutions are evaluated practically and results show the presence of water in soil can be remotely detected allowing for their application in landslide monitoring. Full article

(This article belongs to the Special Issue Sensors in Agriculture)

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16 pages, 4922 KiB

Open AccessArticle

Self-Test Procedures for Gas Sensors Embedded in Microreactor Systems

by Andreas Helwig¹, Angelika Hackner¹, Gerhard Müller^2,*

, Dario Zappa³ and Giorgio Sberveglieri³

¹ Airbus Central R&T, D-81663 Munich, Germany

² Department of Applied Sciences and Mechatronics, Munich University of Applied Sciences, D-80335 Munich, Germany

³ SENSOR, Dipartimento di Ingegneria dell’Informazione, Università degli Studi di Brescia, via Valotti 9, 25123 Brescia, Italy

Sensors 2018, 18(2), 453; https://doi.org/10.3390/s18020453 - 3 Feb 2018

Cited by 6 | Viewed by 7945

Abstract

Metal oxide (MOX) gas sensors sensitively respond to a wide variety of combustible, explosive and poisonous gases. However, due to the lack of a built-in self-test capability, MOX gas sensors have not yet been able to penetrate safety-critical applications. In the present work [...] Read more.

Metal oxide (MOX) gas sensors sensitively respond to a wide variety of combustible, explosive and poisonous gases. However, due to the lack of a built-in self-test capability, MOX gas sensors have not yet been able to penetrate safety-critical applications. In the present work we report on gas sensing experiments performed on MOX gas sensors embedded in ceramic micro-reaction chambers. With the help of an external micro-pump, such systems can be operated in a periodic manner alternating between flow and no-flow conditions, thus allowing repetitive measurements of the sensor resistances under clean air,

R_{0}

, and under gas exposure,

R_{g a s}

, to be obtained, even under field conditions. With these pairs of resistance values, eventual drifts in the sensor baseline resistance can be detected and drift-corrected values of the relative resistance response

R e s p = (R_{0} - R_{g a s}) / R_{0}

can be determined. Residual poisoning-induced changes in the relative resistance response can be detected by reference to humidity measurements taken with room-temperature-operated capacitive humidity sensors which are insensitive to the poisoning processes operative on heated MOX gas sensors. Full article

(This article belongs to the Special Issue Gas Sensors based on Semiconducting Metal Oxides)

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10 pages, 1486 KiB

Open AccessArticle

The Taste of Commercially Available Clarithromycin Oral Pharmaceutical Suspensions in the Palestinian Market: Electronic Tongue and In Vivo Evaluation

by Nawaf Abu-Khalaf¹, Abdel Naser Zaid^2,*, Nidal Jaradat²

, Alaaldin AlKilany^2,3, Basima Abu Rumaila¹, Rowa Al Ramahi², Shrouq Shweiki², Safaa Nidal² and Nibal Surakhi²

¹ College of Agricultural Sciences and Technology, Palestine Technical University-Kadoorie (PTUK), Tulkarm B.O.Box 7, Palestine

² Department of Pharmacy, Faculty of Medicine and Health Sciences, An-Najah National University, Nablus B.O.Box 7, Palestine

³ School of Pharmacy, Jordan University, Amman 11942, Jordan

Sensors 2018, 18(2), 454; https://doi.org/10.3390/s18020454 - 3 Feb 2018

Cited by 19 | Viewed by 5419

Abstract

Background: The taste of oral liquid dosage forms is a crucial factor that impacts paediatric patient compliance. The electronic tongue (ET) is an emerging tool that could be useful in taste assessment in order to minimize the involvement of humans in such [...] Read more.

Background: The taste of oral liquid dosage forms is a crucial factor that impacts paediatric patient compliance. The electronic tongue (ET) is an emerging tool that could be useful in taste assessment in order to minimize the involvement of humans in such evaluations. Purpose: The aim of this study is to evaluate the taste of commercially available clarithromycin (CM) oral pharmaceutical suspensions in the Palestinian market. Method: Commercially available CM suspensions (the brand Klacid^® and two generic K1 and K2) were assayed using the high performance liquid chromatography (HPLC) method. Then, the taste of these products was assessed using alpha-astree ET. In addition, an in vivo taste assessment was conducted on paediatric patients by a hedonic panel test. Moreover, volunteering community pharmacists were asked to rank the taste of these three products according to their experience from the best to the worst. Results: All suspension products had a CM concentration not less than 98% of the label amount. The ET results coupled with the principal component analysis (PCA) showed a very clear discrimination of the samples with different distances between groups (p-values < 0.001). Suspensions were in the following order in terms of taste: Klacid^® > K1 > K2. Moreover, The pattern discrimination index between (K1 and Klacid^®), (K1 and K2) and (Klacid^® and K2) were 8.81%, 65.75%, and71.94%, respectively which suggests that K1 and Klacid^® are the most similar preparations in terms of taste. Interestingly, these results were in excellent agreement with the pharmacist ranking and patient acceptance test. Conclusions: The evaluated preparations showed significantly different taste within the order of Klacid^® > K1 > K2, as suggested by both the ET and in vivo results. Moreover, our results confirm the capability of alpha-astree ET in the taste assessment of oral suspensions and in predicting volunteer responses, which highlights its beneficial use as an in vitro taste assessment tool and as an alternative to human-based taste evaluations. Full article

(This article belongs to the Section Biosensors)

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19 pages, 8073 KiB

Open AccessArticle

Research on Synthetic Aperture Radar Processing for the Spaceborne Sliding Spotlight Mode

by Shijian Shen^1,2

, Xin Nie² and Xinggan Zhang^1,*

¹ School of Electronic Science and Engineering, Nanjing University, Nanjing 210023, China

² Nanjing Research Institute of Electronics Technology, Nanjing 210039, China

Sensors 2018, 18(2), 455; https://doi.org/10.3390/s18020455 - 3 Feb 2018

Cited by 4 | Viewed by 5522

Abstract

Gaofen-3 (GF-3) is China’ first C-band multi-polarization synthetic aperture radar (SAR) satellite, which also provides the sliding spotlight mode for the first time. Sliding-spotlight mode is a novel mode to realize imaging with not only high resolution, but also wide swath. Several key [...] Read more.

Gaofen-3 (GF-3) is China’ first C-band multi-polarization synthetic aperture radar (SAR) satellite, which also provides the sliding spotlight mode for the first time. Sliding-spotlight mode is a novel mode to realize imaging with not only high resolution, but also wide swath. Several key technologies for sliding spotlight mode in spaceborne SAR with high resolution are investigated in this paper, mainly including the imaging parameters, the methods of velocity estimation and ambiguity elimination, and the imaging algorithms. Based on the chosen Convolution BackProjection (CBP) and PFA (Polar Format Algorithm) imaging algorithms, a fast implementation method of CBP and a modified PFA method suitable for sliding spotlight mode are proposed, and the processing flows are derived in detail. Finally, the algorithms are validated by simulations and measured data. Full article

(This article belongs to the Special Issue First Experiences with Chinese Gaofen-3 SAR Sensor)

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34 pages, 7966 KiB

Open AccessArticle

Deep Learning-Based Gaze Detection System for Automobile Drivers Using a NIR Camera Sensor

by Rizwan Ali Naqvi, Muhammad Arsalan, Ganbayar Batchuluun, Hyo Sik Yoon and Kang Ryoung Park^*

Division of Electronics and Electrical Engineering, Dongguk University, 30 Pildong-ro, 1-gil, Jung-gu, Seoul 100-715, Korea

Sensors 2018, 18(2), 456; https://doi.org/10.3390/s18020456 - 3 Feb 2018

Cited by 134 | Viewed by 16112

Abstract

A paradigm shift is required to prevent the increasing automobile accident deaths that are mostly due to the inattentive behavior of drivers. Knowledge of gaze region can provide valuable information regarding a driver’s point of attention. Accurate and inexpensive gaze classification systems in [...] Read more.

A paradigm shift is required to prevent the increasing automobile accident deaths that are mostly due to the inattentive behavior of drivers. Knowledge of gaze region can provide valuable information regarding a driver’s point of attention. Accurate and inexpensive gaze classification systems in cars can improve safe driving. However, monitoring real-time driving behaviors and conditions presents some challenges: dizziness due to long drives, extreme lighting variations, glasses reflections, and occlusions. Past studies on gaze detection in cars have been chiefly based on head movements. The margin of error in gaze detection increases when drivers gaze at objects by moving their eyes without moving their heads. To solve this problem, a pupil center corneal reflection (PCCR)-based method has been considered. However, the error of accurately detecting the pupil center and corneal reflection center is increased in a car environment due to various environment light changes, reflections on glasses surface, and motion and optical blurring of captured eye image. In addition, existing PCCR-based methods require initial user calibration, which is difficult to perform in a car environment. To address this issue, we propose a deep learning-based gaze detection method using a near-infrared (NIR) camera sensor considering driver head and eye movement that does not require any initial user calibration. The proposed system is evaluated on our self-constructed database as well as on open Columbia gaze dataset (CAVE-DB). The proposed method demonstrated greater accuracy than the previous gaze classification methods. Full article

(This article belongs to the Special Issue Sensors Signal Processing and Visual Computing)

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12 pages, 1903 KiB

Open AccessArticle

Effective Peroxidase-Like Activity of Co-Aminoclay [CoAC] and Its Application for Glucose Detection

by Han Pill Song¹, Yongil Lee^2,3, Vu Khac Hoang Bui¹, You-Kwon Oh⁴, Hyun Gyu Park⁵, Moon Il Kim^1,*

and Young-Chul Lee^1,*

¹ Department of BioNano Technology, Gachon University, 1342 Seongnamdae-ro, Sujeong-gu, Seongnam-Si, Gyeonggi-do 13120, Korea

² Korea Railroad Research Institute (KRRI), 176 Cheoldobakmulkwan-ro, Uiwang-si, Gyeonggi-do 16105, Korea

³ Department of Mechanical Engineering, Sungkyunkwan University, Suwon, Gyeonggi-do 16419, Korea

⁴ School of Chemical and Biomolecular Engineering, Pusan National University, Busan 46241, Korea

⁵ Department of Chemical and Biomolecular Engineering (BK21+ Program), Korea Advanced Institute of Science and Technology (KAIST), 291 Daehak-ro, Yuseong-gu, Daejeon 34141, Korea

Sensors 2018, 18(2), 457; https://doi.org/10.3390/s18020457 - 3 Feb 2018

Cited by 15 | Viewed by 5495

Abstract

In this study, we describe a novel peroxidase-like activity of Co-aminoclay [CoAC] present at pH ~5.0 and its application to fluorescent biosensor for the determination of H₂O₂ and glucose. It is synthesized with aminoclays (ACs) entrapping cationic metals such as [...] Read more.

In this study, we describe a novel peroxidase-like activity of Co-aminoclay [CoAC] present at pH ~5.0 and its application to fluorescent biosensor for the determination of H₂O₂ and glucose. It is synthesized with aminoclays (ACs) entrapping cationic metals such as Fe, Cu, Al, Co., Ce, Ni, Mn, and Zn to find enzyme mimicking ACs by sol–gel ambient conditions. Through the screening of catalytic activities by the typical colorimetric reaction employing 2,2′-azino-bis(3-ethylbenzo-thiazoline-6-sulfonic acid)diammonium salt (ABTS) as a substrate with or without H₂O₂, Fe, Cu, and CoACs are found to exhibit peroxidase-like activity, as well as oxidase-like activity was observed from Ce and MnACs. Among them, CoAC shows exceptionally high peroxidase-like activity, presumably due to its ability to induce electron transfer between substrates and H₂O₂. CoAC is then used to catalyze the oxidation of Amplex^® UltraRed (AUR) into a fluorescent end product, which enables a sensitive fluorescent detection of H₂O₂. Moreover, a highly sensitive and selective glucose biosensing strategy is developed, based on enzyme cascade reaction between glucose oxidase (GOx) and CoAC. Using this strategy, a highly linear fluorescence enhancement is verified when the concentration of glucose is increased in a wide range from 10 μM to 1 mM with a lower detection limit of 5 μM. The practical diagnostic capability of the assay system is also verified by its use to detect glucose in human blood serum. Based on these results, it is anticipated that CoAC can serve as potent peroxidase mimetics for the detection of clinically important target molecules. Full article

(This article belongs to the Section Chemical Sensors)

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26 pages, 2939 KiB

Open AccessArticle

Using Psychophysiological Sensors to Assess Mental Workload During Web Browsing

by Angel Jimenez-Molina^1,*, Cristian Retamal² and Hernan Lira¹

¹ Department of Industrial Engineering, Faculty of Physical and Mathematical Sciences, University of Chile, Santiago 8370456, Chile

² Department of Electrical Engineering, Faculty of Physical and Mathematical Sciences, University of Chile, Santiago 8370448, Chile

Sensors 2018, 18(2), 458; https://doi.org/10.3390/s18020458 - 3 Feb 2018

Cited by 77 | Viewed by 9791

Abstract

Knowledge of the mental workload induced by a Web page is essential for improving users’ browsing experience. However, continuously assessing the mental workload during a browsing task is challenging. To address this issue, this paper leverages the correlation between stimuli and physiological responses, [...] Read more.

Knowledge of the mental workload induced by a Web page is essential for improving users’ browsing experience. However, continuously assessing the mental workload during a browsing task is challenging. To address this issue, this paper leverages the correlation between stimuli and physiological responses, which are measured with high-frequency, non-invasive psychophysiological sensors during very short span windows. An experiment was conducted to identify levels of mental workload through the analysis of pupil dilation measured by an eye-tracking sensor. In addition, a method was developed to classify mental workload by appropriately combining different signals (electrodermal activity (EDA), electrocardiogram, photoplethysmo-graphy (PPG), electroencephalogram (EEG), temperature and pupil dilation) obtained with non-invasive psychophysiological sensors. The results show that the Web browsing task involves four levels of mental workload. Also, by combining all the sensors, the efficiency of the classification reaches 93.7%. Full article

(This article belongs to the Special Issue Advanced Physiological Sensing)

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19 pages, 6085 KiB

Open AccessArticle

Modeling Electronic Skin Response to Normal Distributed Force

by Lucia Seminara

Department of Electrical, Electronics and Telecommunication Engineering and Naval Architecture, via Opera Pia 11A, University of Genoa, Genoa 16145, Italy

Sensors 2018, 18(2), 459; https://doi.org/10.3390/s18020459 - 3 Feb 2018

Cited by 7 | Viewed by 5127

Abstract

The reference electronic skin is a sensor array based on PVDF (Polyvinylidene fluoride) piezoelectric polymers, coupled to a rigid substrate and covered by an elastomer layer. It is first evaluated how a distributed normal force (Hertzian distribution) is transmitted to an extended PVDF [...] Read more.

The reference electronic skin is a sensor array based on PVDF (Polyvinylidene fluoride) piezoelectric polymers, coupled to a rigid substrate and covered by an elastomer layer. It is first evaluated how a distributed normal force (Hertzian distribution) is transmitted to an extended PVDF sensor through the elastomer layer. A simplified approach based on Boussinesq’s half-space assumption is used to get a qualitative picture and extensive FEM simulations allow determination of the quantitative response for the actual finite elastomer layer. The ultimate use of the present model is to estimate the electrical sensor output from a measure of a basic mechanical action at the skin surface. However this requires that the PVDF piezoelectric coefficient be known a-priori. This was not the case in the present investigation. However, the numerical model has been used to fit experimental data from a real skin prototype and to estimate the sensor piezoelectric coefficient. It turned out that this value depends on the preload and decreases as a result of PVDF aging and fatigue. This framework contains all the fundamental ingredients of a fully predictive model, suggesting a number of future developments potentially useful for skin design and validation of the fabrication technology. Full article

(This article belongs to the Special Issue Tactile Sensors and Sensing)

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17 pages, 1043 KiB

Open AccessArticle

Naive Bayes Bearing Fault Diagnosis Based on Enhanced Independence of Data

by Nannan Zhang^1,2,3,4, Lifeng Wu^1,2,3,4,*, Jing Yang^1,2,3,4 and Yong Guan^1,2,3,4

¹ College of Information Engineering, Capital Normal University, Beijing 100048, China

² Beijing Key Laboratory of Electronic System Reliability Technology, Capital Normal University, Beijing 100048, China

³ Beijing Key Laboratory of Light Industrial Robot and Safety Verification, Capital Normal University, Beijing 100048, China

⁴ Beijing Advanced Innovation Center for Imaging Technology, Capital Normal University, Beijing 100048, China

Sensors 2018, 18(2), 463; https://doi.org/10.3390/s18020463 - 5 Feb 2018

Cited by 98 | Viewed by 7324

Abstract

The bearing is the key component of rotating machinery, and its performance directly determines the reliability and safety of the system. Data-based bearing fault diagnosis has become a research hotspot. Naive Bayes (NB), which is based on independent presumption, is widely used in [...] Read more.

The bearing is the key component of rotating machinery, and its performance directly determines the reliability and safety of the system. Data-based bearing fault diagnosis has become a research hotspot. Naive Bayes (NB), which is based on independent presumption, is widely used in fault diagnosis. However, the bearing data are not completely independent, which reduces the performance of NB algorithms. In order to solve this problem, we propose a NB bearing fault diagnosis method based on enhanced independence of data. The method deals with data vector from two aspects: the attribute feature and the sample dimension. After processing, the classification limitation of NB is reduced by the independence hypothesis. First, we extract the statistical characteristics of the original signal of the bearings effectively. Then, the Decision Tree algorithm is used to select the important features of the time domain signal, and the low correlation features is selected. Next, the Selective Support Vector Machine (SSVM) is used to prune the dimension data and remove redundant vectors. Finally, we use NB to diagnose the fault with the low correlation data. The experimental results show that the independent enhancement of data is effective for bearing fault diagnosis. Full article

(This article belongs to the Special Issue Sensors for Fault Detection)

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15 pages, 4949 KiB

Open AccessArticle

Foil Strain Gauges Using Piezoresistive Carbon Nanotube Yarn: Fabrication and Calibration

by Jandro L. Abot^1,*

, Mário R. Góngora-Rubio², Jude C. Anike¹

, César Y. Kiyono³, Luis A. M. Mello², Valtemar F. Cardoso⁴, Reinaldo L. S. Rosa⁴, Derek A. Kuebler¹, Grace E. Brodeur¹, Amani H. Alotaibi¹, Marisa P. Coene¹, Lauren M. Coene¹, Elizabeth Jean¹, Rafael C. Santiago³, Francisco H. A. Oliveira³, Ricardo Rangel⁴, Gilles P. Thomas³, Kalayu Belay⁵, Luciana W. Da Silva², Rafael T. Moura³, Antonio C. Seabra⁴ and Emílio C. N. Silva³ Show full author list Hide full author list

¹ Department of Mechanical Engineering, The Catholic University of America, 620 Michigan Ave. NE, Washington, DC 20064, USA

² Institute of Technological Research, Bionanomanufacturing Group, Av. Prof. Almeida Prado, 532, São Paulo SP-05508-901, Brazil

³ Department of Mechatronics Engineering and Mechanical Systems, School of Engineering, University of São Paulo, Av. Prof. Mello Moraes, 2231, São Paulo SP-05508-900, Brazil

⁴ Department of Electrical Engineering, School of Engineering, University of São Paulo, Av. Prof. Luciano Gualberto, 158, São Paulo SP-05508-010, Brazil

⁵ Department of Physics, Florida Agricultural and Mechanical University, 2077 East Paul Dirac Dr., Tallahassee, FL 32310, USA

Sensors 2018, 18(2), 464; https://doi.org/10.3390/s18020464 - 5 Feb 2018

Cited by 28 | Viewed by 9483

Abstract

Carbon nanotube yarns are micron-scale fibers comprised by tens of thousands of carbon nanotubes in their cross section and exhibiting piezoresistive characteristics that can be tapped to sense strain. This paper presents the details of novel foil strain gauge sensor configurations comprising carbon [...] Read more.

Carbon nanotube yarns are micron-scale fibers comprised by tens of thousands of carbon nanotubes in their cross section and exhibiting piezoresistive characteristics that can be tapped to sense strain. This paper presents the details of novel foil strain gauge sensor configurations comprising carbon nanotube yarn as the piezoresistive sensing element. The foil strain gauge sensors are designed using the results of parametric studies that maximize the sensitivity of the sensors to mechanical loading. The fabrication details of the strain gauge sensors that exhibit the highest sensitivity, based on the modeling results, are described including the materials and procedures used in the first prototypes. Details of the calibration of the foil strain gauge sensors are also provided and discussed in the context of their electromechanical characterization when bonded to metallic specimens. This characterization included studying their response under monotonic and cyclic mechanical loading. It was shown that these foil strain gauge sensors comprising carbon nanotube yarn are sensitive enough to capture strain and can replicate the loading and unloading cycles. It was also observed that the loading rate affects their piezoresistive response and that the gauge factors were all above one order of magnitude higher than those of typical metallic foil strain gauges. Based on these calibration results on the initial sensor configurations, new foil strain gauge configurations will be designed and fabricated, to increase the strain gauge factors even more. Full article

(This article belongs to the Special Issue Structural Health Monitoring Using Carbon Nanotube Yarn-Based Sensors)

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15 pages, 4196 KiB

Open AccessArticle

Calibration of Elasto-Magnetic Sensors on In-Service Cable-Stayed Bridges for Stress Monitoring

by Carlo Cappello^1,*

, Daniele Zonta²

, Hassan Ait Laasri³, Branko Glisic⁴ and Ming Wang⁵

¹ Department of Civil, Environmental and Mechanical Engineering, University of Trento, 38122 Trento, Italy

² Department of Civil and Environmental Engineering, University of Strathclyde, Glasgow G1 1XQ, UK

³ Faculty of Sciences, Ibn Zohr University, 80000 Agadir, Morocco

⁴ Department of Civil and Environmental Engineering, Princeton University, Princeton, NJ 08544, USA

⁵ Department of Civil and Environmental Engineering, Northeastern University, Boston, MA 02115, USA

Sensors 2018, 18(2), 466; https://doi.org/10.3390/s18020466 - 5 Feb 2018

Cited by 58 | Viewed by 9217

Abstract

The recent developments in measurement technology have led to the installation of efficient monitoring systems on many bridges and other structures all over the world. Nowadays, more and more structures have been built and instrumented with sensors. However, calibration and installation of sensors [...] Read more.

The recent developments in measurement technology have led to the installation of efficient monitoring systems on many bridges and other structures all over the world. Nowadays, more and more structures have been built and instrumented with sensors. However, calibration and installation of sensors remain challenging tasks. In this paper, we use a case study, Adige Bridge, in order to present a low-cost method for the calibration and installation of elasto-magnetic sensors on cable-stayed bridges. Elasto-magnetic sensors enable monitoring of cable stress. The sensor installation took place two years after the bridge construction. The calibration was conducted in two phases: one in the laboratory and the other one on site. In the laboratory, a sensor was built around a segment of cable that was identical to those of the cable-stayed bridge. Then, the sample was subjected to a defined tension force. The sensor response was compared with the applied load. Experimental results showed that the relationship between load and magnetic permeability does not depend on the sensor fabrication process except for an offset. The determination of this offset required in situ calibration after installation. In order to perform the in situ calibration without removing the cables from the bridge, vibration tests were carried out for the estimation of the cables’ tensions. At the end of the paper, we show and discuss one year of data from the elasto-magnetic sensors. Calibration results demonstrate the simplicity of the installation of these sensors on existing bridges and new structures. Full article

(This article belongs to the Special Issue Sensors and Sensor Networks for Structural Health Monitoring)

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20 pages, 3183 KiB

Open AccessArticle

Implementation of a Surface Electromyography-Based Upper Extremity Exoskeleton Controller Using Learning from Demonstration

by Ho Chit Siu^1,*

, Ana M. Arenas², Tingxiao Sun¹ and Leia A. Stirling^1,3

¹ Department of Aeronautics and Astronautics, Massachusetts Institute of Technology, 77 Massachusetts Ave, Cambridge, MA 02139, USA

² Department of Mechanical Engineering, Massachusetts Institute of Technology, 77 Massachusetts Ave, Cambridge, MA 02139, USA

³ Institute for Medical Engineering and Science, Massachusetts Institute of Technology, 77 Massachusetts Ave, Cambridge, MA 02139, USA

Sensors 2018, 18(2), 467; https://doi.org/10.3390/s18020467 - 5 Feb 2018

Cited by 32 | Viewed by 6835

Abstract

Upper-extremity exoskeletons have demonstrated potential as augmentative, assistive, and rehabilitative devices. Typical control of upper-extremity exoskeletons have relied on switches, force/torque sensors, and surface electromyography (sEMG), but these systems are usually reactionary, and/or rely on entirely hand-tuned parameters. sEMG-based systems may be able [...] Read more.

Upper-extremity exoskeletons have demonstrated potential as augmentative, assistive, and rehabilitative devices. Typical control of upper-extremity exoskeletons have relied on switches, force/torque sensors, and surface electromyography (sEMG), but these systems are usually reactionary, and/or rely on entirely hand-tuned parameters. sEMG-based systems may be able to provide anticipatory control, since they interface directly with muscle signals, but typically require expert placement of sensors on muscle bodies. We present an implementation of an adaptive sEMG-based exoskeleton controller that learns a mapping between muscle activation and the desired system state during interaction with a user, generating a personalized sEMG feature classifier to allow for anticipatory control. This system is robust to novice placement of sEMG sensors, as well as subdermal muscle shifts. We validate this method with 18 subjects using a thumb exoskeleton to complete a book-placement task. This learning-from-demonstration system for exoskeleton control allows for very short training times, as well as the potential for improvement in intent recognition over time, and adaptation to physiological changes in the user, such as those due to fatigue. Full article

(This article belongs to the Special Issue Sensor Applications in Medical Monitoring and Assistive Devices)

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10 pages, 1375 KiB

Open AccessArticle

Flexible Piezoelectric Sensor-Based Gait Recognition

by Youngsu Cha^1,*

, Hojoon Kim^1,2 and Doik Kim¹

¹ Center for Robotics Research, Korea Institute of Science and Technology, Seoul 02792, Korea

² School of Electrical Engineering, Korea University, Seoul 02841, Korea

Sensors 2018, 18(2), 468; https://doi.org/10.3390/s18020468 - 5 Feb 2018

Cited by 50 | Viewed by 7103

Abstract

Most motion recognition research has required tight-fitting suits for precise sensing. However, tight-suit systems have difficulty adapting to real applications, because people normally wear loose clothes. In this paper, we propose a gait recognition system with flexible piezoelectric sensors in loose clothing. The [...] Read more.

Most motion recognition research has required tight-fitting suits for precise sensing. However, tight-suit systems have difficulty adapting to real applications, because people normally wear loose clothes. In this paper, we propose a gait recognition system with flexible piezoelectric sensors in loose clothing. The gait recognition system does not directly sense lower-body angles. It does, however, detect the transition between standing and walking. Specifically, we use the signals from the flexible sensors attached to the knee and hip parts on loose pants. We detect the periodic motion component using the discrete time Fourier series from the signal during walking. We adapt the gait detection method to a real-time patient motion and posture monitoring system. In the monitoring system, the gait recognition operates well. Finally, we test the gait recognition system with 10 subjects, for which the proposed system successfully detects walking with a success rate over

93 %

. Full article

(This article belongs to the Special Issue Sensors for Gait, Posture, and Health Monitoring)

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23 pages, 3680 KiB

Open AccessArticle

Secure Indoor Localization Based on Extracting Trusted Fingerprint

by Juan Luo^*

, Xixi Yin, Yanliu Zheng and Chun Wang

School of Information Science and Engineering, Hunan University, Changsha 410012, China

Sensors 2018, 18(2), 469; https://doi.org/10.3390/s18020469 - 5 Feb 2018

Cited by 24 | Viewed by 5122

Abstract

Indoor localization based on WiFi has attracted a lot of research effort because of the widespread application of WiFi. Fingerprinting techniques have received much attention due to their simplicity and compatibility with existing hardware. However, existing fingerprinting localization algorithms may not resist abnormal [...] Read more.

Indoor localization based on WiFi has attracted a lot of research effort because of the widespread application of WiFi. Fingerprinting techniques have received much attention due to their simplicity and compatibility with existing hardware. However, existing fingerprinting localization algorithms may not resist abnormal received signal strength indication (RSSI), such as unexpected environmental changes, impaired access points (APs) or the introduction of new APs. Traditional fingerprinting algorithms do not consider the problem of new APs and impaired APs in the environment when using RSSI. In this paper, we propose a secure fingerprinting localization (SFL) method that is robust to variable environments, impaired APs and the introduction of new APs. In the offline phase, a voting mechanism and a fingerprint database update method are proposed. We use the mutual cooperation between reference anchor nodes to update the fingerprint database, which can reduce the interference caused by the user measurement data. We analyze the standard deviation of RSSI, mobilize the reference points in the database to vote on APs and then calculate the trust factors of APs based on the voting results. In the online phase, we first make a judgment about the new APs and the broken APs, then extract the secure fingerprints according to the trusted factors of APs and obtain the localization results by using the trusted fingerprints. In the experiment section, we demonstrate the proposed method and find that the proposed strategy can resist abnormal RSSI and can improve the localization accuracy effectively compared with the existing fingerprinting localization algorithms. Full article

(This article belongs to the Special Issue Security, Trust and Privacy for Sensor Networks)

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18 pages, 5294 KiB

Open AccessArticle

Fabrication and Optimization of Bilayered Nanoporous Anodic Alumina Structures as Multi-Point Interferometric Sensing Platform

by Mahdieh Nemati¹, Abel Santos^1,2,3

and Dusan Losic^1,*

¹ School of Chemical Engineering, The University of Adelaide, Engineering North Building, Adelaide 5005, Australia

² Institute for Photonics and Advanced Sensing (IPAS), The University of Adelaide, Adelaide 5005, Australia

³ ARC Centre of Excellence for Nanoscale BioPhotonics (CNBP), The University of Adelaide, Adelaide 5005, Australia

Sensors 2018, 18(2), 470; https://doi.org/10.3390/s18020470 - 6 Feb 2018

Cited by 14 | Viewed by 4734

Abstract

Herein, we present an innovative strategy for optimizing hierarchical structures of nanoporous anodic alumina (NAA) to advance their optical sensing performance toward multi-analyte biosensing. This approach is based on the fabrication of multilayered NAA and the formation of differential effective medium of their [...] Read more.

Herein, we present an innovative strategy for optimizing hierarchical structures of nanoporous anodic alumina (NAA) to advance their optical sensing performance toward multi-analyte biosensing. This approach is based on the fabrication of multilayered NAA and the formation of differential effective medium of their structure by controlling three fabrication parameters (i.e., anodization steps, anodization time, and pore widening time). The rationale of the proposed concept is that interferometric bilayered NAA (BL-NAA), which features two layers of different pore diameters, can provide distinct reflectometric interference spectroscopy (RIfS) signatures for each layer within the NAA structure and can therefore potentially be used for multi-point biosensing. This paper presents the structural fabrication of layered NAA structures, and the optimization and evaluation of their RIfS optical sensing performance through changes in the effective optical thickness (EOT) using quercetin as a model molecule. The bilayered or funnel-like NAA structures were designed with the aim of characterizing the sensitivity of both layers of quercetin molecules using RIfS and exploring the potential of these photonic structures, featuring different pore diameters, for simultaneous size-exclusion and multi-analyte optical biosensing. The sensing performance of the prepared NAA platforms was examined by real-time screening of binding reactions between human serum albumin (HSA)-modified NAA (i.e., sensing element) and quercetin (i.e., analyte). BL-NAAs display a complex optical interference spectrum, which can be resolved by fast Fourier transform (FFT) to monitor the EOT changes, where three distinctive peaks were revealed corresponding to the top, bottom, and total layer within the BL-NAA structures. The spectral shifts of these three characteristic peaks were used as sensing signals to monitor the binding events in each NAA pore in real-time upon exposure to different concentrations of quercetin. The multi-point sensing performance of BL-NAAs was determined for each pore layer, with an average sensitivity and low limit of detection of 600 nm (mg mL⁻¹)⁻¹ and 0.14 mg mL⁻¹, respectively. BL-NAAs photonic structures have the capability to be used as platforms for multi-point RIfS sensing of biomolecules that can be further extended for simultaneous size-exclusion separation and multi-analyte sensing using these bilayered nanostructures. Full article

(This article belongs to the Special Issue Nanostructured Hybrid Materials Based Opto-Electronics Sensors)

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10 pages, 1971 KiB

Open AccessArticle

Knowledge Reasoning with Semantic Data for Real-Time Data Processing in Smart Factory

by Shiyong Wang¹, Jiafu Wan^1,*

, Di Li¹ and Chengliang Liu²

¹ School of Mechanical & Automotive Engineering, South China University of Technology, Guangzhou 510640, China

² School of Mechanical Engineering, Shanghai Jiao Tong University, Shanghai 200240, China

Sensors 2018, 18(2), 471; https://doi.org/10.3390/s18020471 - 6 Feb 2018

Cited by 56 | Viewed by 7426

Abstract

The application of high-bandwidth networks and cloud computing in manufacturing systems will be followed by mass data. Industrial data analysis plays important roles in condition monitoring, performance optimization, flexibility, and transparency of the manufacturing system. However, the currently existing architectures are mainly for [...] Read more.

The application of high-bandwidth networks and cloud computing in manufacturing systems will be followed by mass data. Industrial data analysis plays important roles in condition monitoring, performance optimization, flexibility, and transparency of the manufacturing system. However, the currently existing architectures are mainly for offline data analysis, not suitable for real-time data processing. In this paper, we first define the smart factory as a cloud-assisted and self-organized manufacturing system in which physical entities such as machines, conveyors, and products organize production through intelligent negotiation and the cloud supervises this self-organized process for fault detection and troubleshooting based on data analysis. Then, we propose a scheme to integrate knowledge reasoning and semantic data where the reasoning engine processes the ontology model with real time semantic data coming from the production process. Based on these ideas, we build a benchmarking system for smart candy packing application that supports direct consumer customization and flexible hybrid production, and the data are collected and processed in real time for fault diagnosis and statistical analysis. Full article

(This article belongs to the Special Issue Sensor Intelligence Assisted by Data Analytics and Cognitive Computing)

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19 pages, 15882 KiB

Open AccessArticle

Deep Learning-Based Banknote Fitness Classification Using the Reflection Images by a Visible-Light One-Dimensional Line Image Sensor

by Tuyen Danh Pham, Dat Tien Nguyen, Wan Kim, Sung Ho Park and Kang Ryoung Park^*

Division of Electronics and Electrical Engineering, Dongguk University, 30 Pildong-ro 1-gil, Jung-gu, Seoul 100-715, Korea

Sensors 2018, 18(2), 472; https://doi.org/10.3390/s18020472 - 6 Feb 2018

Cited by 8 | Viewed by 5404

Abstract

In automatic paper currency sorting, fitness classification is a technique that assesses the quality of banknotes to determine whether a banknote is suitable for recirculation or should be replaced. Studies on using visible-light reflection images of banknotes for evaluating their usability have been [...] Read more.

In automatic paper currency sorting, fitness classification is a technique that assesses the quality of banknotes to determine whether a banknote is suitable for recirculation or should be replaced. Studies on using visible-light reflection images of banknotes for evaluating their usability have been reported. However, most of them were conducted under the assumption that the denomination and input direction of the banknote are predetermined. In other words, a pre-classification of the type of input banknote is required. To address this problem, we proposed a deep learning-based fitness-classification method that recognizes the fitness level of a banknote regardless of the denomination and input direction of the banknote to the system, using the reflection images of banknotes by visible-light one-dimensional line image sensor and a convolutional neural network (CNN). Experimental results on the banknote image databases of the Korean won (KRW) and the Indian rupee (INR) with three fitness levels, and the Unites States dollar (USD) with two fitness levels, showed that our method gives better classification accuracy than other methods. Full article

(This article belongs to the Special Issue Sensor Signal and Information Processing)

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14 pages, 3906 KiB

Open AccessArticle

A Quantization-Based Multibit Data Fusion Scheme for Cooperative Spectrum Sensing in Cognitive Radio Networks

by Yuanhua Fu^1,*, Fan Yang¹

and Zhiming He^1,2

¹ School of Information and Communication Engineering, University of Electronic Science and Technology of China, Chengdu 611731, China

² Institute of Electronic and Information Engineering of University of Electronic Science and Technology of China in Guangdong, Dongguan 523808, China

Sensors 2018, 18(2), 473; https://doi.org/10.3390/s18020473 - 6 Feb 2018

Cited by 42 | Viewed by 5204

Abstract

Spectrum sensing remains a challenge in the context of cognitive radio networks (CRNs). Compared with traditional single-user sensing, cooperative spectrum sensing (CSS) exploits multiuser diversity to overcome channel fading, shadowing, and hidden terminal problems, which can effectively enhance the sensing performance and protect [...] Read more.

Spectrum sensing remains a challenge in the context of cognitive radio networks (CRNs). Compared with traditional single-user sensing, cooperative spectrum sensing (CSS) exploits multiuser diversity to overcome channel fading, shadowing, and hidden terminal problems, which can effectively enhance the sensing performance and protect licensed users from harmful interference. However, for a large number of sensing nodes that need high bandwidth of the control channel for data transmitting, CSS increases cooperative overhead. To address this problem, we investigated the soft decision fusion strategy under a limited bandwidth of the control channel and proposed a simple quantization-based multibit data soft fusion rule for CSS for its simple structure and easily implementation. Under the quantization-based sensing strategy, each cooperative secondary user (SU) adopts an energy detector for local spectrum sensing. Each SU transmits quantized multibit data that sends local sensing information, instead of forwarding local one-bit hard decision results or original observation statistics, to the fusion center (FC). Furthermore, the closed-form expressions of the quantization levels and the quantization thresholds are analytically derived. Simulation results indicate that the detection performance of the proposed method approaches that of the conventional soft fusion rule with less cooperative overhead and outperforms the hard decision rules. Extensive simulations also show that multibit quantization fusion achieves a desirable tradeoff between the sensing performance and the control channel overhead for CSS. Full article

(This article belongs to the Section Sensor Networks)

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21 pages, 3450 KiB

Open AccessArticle

Design and Implementation of Cloud-Centric Configuration Repository for DIY IoT Applications

by Shabir Ahmad

, Lei Hang

and Do Hyeun Kim^*

Department of Computer Engineering, Jeju National University, Jeju 63243, Korea

Sensors 2018, 18(2), 474; https://doi.org/10.3390/s18020474 - 6 Feb 2018

Cited by 46 | Viewed by 7578

Abstract

The Do-It-Yourself (DIY) vision for the design of a smart and customizable IoT application demands the involvement of the general public in its development process. The general public lacks the technical knowledge for programming state-of-the-art prototyping and development kits. The latest IoT kits, [...] Read more.

The Do-It-Yourself (DIY) vision for the design of a smart and customizable IoT application demands the involvement of the general public in its development process. The general public lacks the technical knowledge for programming state-of-the-art prototyping and development kits. The latest IoT kits, for example, Raspberry Pi, are revolutionizing the DIY paradigm for IoT, and more than ever, a DIY intuitive programming interface is required to enable the masses to interact with and customize the behavior of remote IoT devices on the Internet. However, in most cases, these DIY toolkits store the resultant configuration data in local storage and, thus, cannot be accessed remotely. This paper presents the novel implementation of such a system, which not only enables the general public to customize the behavior of remote IoT devices through a visual interface, but also makes the configuration available everywhere and anytime by leveraging the power of cloud-based platforms. The interface enables the visualization of the resources exposed by remote embedded resources in the form of graphical virtual objects (VOs). These VOs are used to create the service design through simple operations like drag-and-drop and the setting of properties. The configuration created as a result is maintained as an XML document, which is ingested by the cloud platform, thus making it available to be used anywhere. We use the HTTP approach for the communication between the cloud and IoT toolbox and the cloud and real devices, but for communication between the toolbox and actual resources, CoAP is used. Finally, a smart home case study has been implemented and presented in order to assess the effectiveness of the proposed work. Full article

(This article belongs to the Special Issue The Architectures, Systems, and Applications of Internet of Things for Smart Cities)

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19 pages, 986 KiB

Open AccessArticle

Hard Fusion Based Spectrum Sensing over Mobile Fading Channels in Cognitive Vehicular Networks

by Xiaomin Qian¹

, Li Hao^1,*, Dadong Ni¹ and Quang Thanh Tran^1,2

¹ Key Lab of Information Coding and Transmission, Southwest Jiaotong University, Chengdu 610031, China

² Faculty of Electrical and Electronic Engineering, University of Transport and Communications, Hanoi 117262, Vietnam

Sensors 2018, 18(2), 475; https://doi.org/10.3390/s18020475 - 6 Feb 2018

Cited by 8 | Viewed by 4142

Abstract

An explosive growth in vehicular wireless applications gives rise to spectrum resource starvation. Cognitive radio has been used in vehicular networks to mitigate the impending spectrum starvation problem by allowing vehicles to fully exploit spectrum opportunities unoccupied by licensed users. Efficient and effective [...] Read more.

An explosive growth in vehicular wireless applications gives rise to spectrum resource starvation. Cognitive radio has been used in vehicular networks to mitigate the impending spectrum starvation problem by allowing vehicles to fully exploit spectrum opportunities unoccupied by licensed users. Efficient and effective detection of licensed user is a critical issue to realize cognitive radio applications. However, spectrum sensing in vehicular environments is a very challenging task due to vehicle mobility. For instance, vehicle mobility has a large effect on the wireless channel, thereby impacting the detection performance of spectrum sensing. Thus, gargantuan efforts have been made in order to analyze the fading properties of mobile radio channel in vehicular environments. Indeed, numerous studies have demonstrated that the wireless channel in vehicular environments can be characterized by a temporally correlated Rayleigh fading. In this paper, we focus on energy detection for spectrum sensing and a counting rule for cooperative sensing based on Neyman-Pearson criteria. Further, we go into the effect of the sensing and reporting channel conditions on the sensing performance under the temporally correlated Rayleigh channel. For local and cooperative sensing, we derive some alternative expressions for the average probability of misdetection. The pertinent numerical and simulating results are provided to further validate our theoretical analyses under a variety of scenarios. Full article

(This article belongs to the Special Issue Smart Vehicular Mobile Sensing)

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18 pages, 18471 KiB

Open AccessArticle

The Use of Tactile Sensors and PIV Analysis for Understanding the Bearing Mechanism of Pile Groups

by Zhijia You^1,† and Yulong Chen^2,*,†

¹ College of Civil Engineering and Architecture, Shandong University of Science and Technology, Qingdao 266590, China

² Department of Hydraulic Engineering, Tsinghua University, Beijing 100084, China

^† These authors contributed equally to this work.

Sensors 2018, 18(2), 476; https://doi.org/10.3390/s18020476 - 6 Feb 2018

Cited by 7 | Viewed by 4007

Abstract

Model tests were carried out in dry silica sand under pile loading and visualizing observation to investigate the behavior of a pile group. The pile group consisted of nine cylindrical model piles of 40 mm in diameter in most tests or three rectangular [...] Read more.

Model tests were carried out in dry silica sand under pile loading and visualizing observation to investigate the behavior of a pile group. The pile group consisted of nine cylindrical model piles of 40 mm in diameter in most tests or three rectangular parallelepiped model piles in the visualizing observation. Pile spacings of 200 mm and 100 mm between pile centers were used in the models. Tactile sensors were installed to measure the pressure distribution in the ground and colored sand layer with particle image velocimetry (PIV) analysis to reveal the ground deformation in addition to strain gauges inside the model piles to investigate the interaction among group piles. The tests results showed that a narrower spacing between piles resulted in a wider affected area of the ground and the interaction was more significant below the tips. Full article

(This article belongs to the Section Physical Sensors)

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13 pages, 4734 KiB

Open AccessArticle

Comparison of Ultra-Rapid Orbit Prediction Strategies for GPS, GLONASS, Galileo and BeiDou

by Tao Geng^1,2

, Peng Zhang^1,*, Wei Wang^3,* and Xin Xie¹

¹ GNSS Research Center, Wuhan University, No.129 Luoyu Road, Wuhan 430079, China

² Collaborative Innovation Center of Geospatial Technology, No.129 Luoyu Road, Wuhan 430079, China

³ Beijing Institute of Tracking and Telecommunication Technology, No. 26 Beiqing Road, Beijing 100094, China

Sensors 2018, 18(2), 477; https://doi.org/10.3390/s18020477 - 6 Feb 2018

Cited by 12 | Viewed by 5069

Abstract

Currently, ultra-rapid orbits play an important role in the high-speed development of global navigation satellite system (GNSS) real-time applications. This contribution focuses on the impact of the fitting arc length of observed orbits and solar radiation pressure (SRP) on the orbit prediction performance [...] Read more.

Currently, ultra-rapid orbits play an important role in the high-speed development of global navigation satellite system (GNSS) real-time applications. This contribution focuses on the impact of the fitting arc length of observed orbits and solar radiation pressure (SRP) on the orbit prediction performance for GPS, GLONASS, Galileo and BeiDou. One full year’s precise ephemerides during 2015 were used as fitted observed orbits and then as references to be compared with predicted orbits, together with known earth rotation parameters. The full nine-parameter Empirical Center for Orbit Determination in Europe (CODE) Orbit Model (ECOM) and its reduced version were chosen in our study. The arc lengths of observed fitted orbits that showed the smallest weighted root mean squares (WRMSs) and medians of the orbit differences after a Helmert transformation fell between 40 and 45 h for GPS and GLONASS and between 42 and 48 h for Galileo, while the WRMS values and medians become flat after a 42 h arc length for BeiDou. The stability of the Helmert transformation and SRP parameters also confirmed the similar optimal arc lengths. The range around 42–45 h is suggested to be the optimal arc length interval of the fitted observed orbits for the multi-GNSS joint solution of ultra-rapid orbits. Full article

(This article belongs to the Section Remote Sensors)

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12 pages, 6665 KiB

Open AccessArticle

UV Absorption Spectroscopy in Water-Filled Antiresonant Hollow Core Fibers for Pharmaceutical Detection

by Mona Nissen¹, Brenda Doherty¹, Jonas Hamperl¹, Jens Kobelke¹, Karina Weber¹, Thomas Henkel¹ and Markus A. Schmidt^1,2,*

¹ Leibniz Institute of Photonic Technology, Albert-Einstein-Str. 9, 07745 Jena, Germany

² Otto Schott Institute of Materials Research (OSIM), Friedrich Schiller University of Jena, Fraunhoferstr. 6, 07743 Jena, Germany

Sensors 2018, 18(2), 478; https://doi.org/10.3390/s18020478 - 6 Feb 2018

Cited by 62 | Viewed by 7879

Abstract

Due to a worldwide increased use of pharmaceuticals and, in particular, antibiotics, a growing number of these substance residues now contaminate natural water resources and drinking supplies. This triggers a considerable demand for low-cost, high-sensitivity methods for monitoring water quality. Since many biological [...] Read more.

Due to a worldwide increased use of pharmaceuticals and, in particular, antibiotics, a growing number of these substance residues now contaminate natural water resources and drinking supplies. This triggers a considerable demand for low-cost, high-sensitivity methods for monitoring water quality. Since many biological substances exhibit strong and characteristic absorption features at wavelengths shorter than 300 nm, UV spectroscopy presents a suitable approach for the quantitative identification of such water-contaminating species. However, current UV spectroscopic devices often show limited light-matter interaction lengths, demand sophisticated and bulky experimental infrastructure which is not compatible with microfluidics, and leave large fractions of the sample analyte unused. Here, we introduce the concept of UV spectroscopy in liquid-filled anti-resonant hollow core fibers, with large core diameters and lengths of approximately 1 m, as a means to overcome such limitations. This extended light-matter interaction length principally improves the concentration detection limit by two orders of magnitude while using almost the entire sample volume—that is three orders of magnitude smaller compared to cuvette based approaches. By integrating the fibers into an optofluidic chip environment and operating within the lowest experimentally feasible transmission band, concentrations of the application-relevant pharmaceutical substances, sulfamethoxazole (SMX) and sodium salicylate (SS), were detectable down to 0.1 µM (26 ppb) and 0.4 µM (64 ppb), respectively, with the potential to reach significantly lower detection limits for further device integration. Full article

(This article belongs to the Special Issue Lab on Fiber Optrodes for Chemical and Biological Sensing: Recent Trends and Advances)

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11 pages, 1119 KiB

Open AccessArticle

Analysis of Dark Current in BRITE Nanostellite CCD Sensors

by Adam Popowicz

Institute of Automatic Control, Silesian University of Technology, Akademicka 16, 44-100 Gliwice, Poland

Sensors 2018, 18(2), 479; https://doi.org/10.3390/s18020479 - 6 Feb 2018

Cited by 15 | Viewed by 5652

Abstract

The BRightest Target Explorer (BRITE) is the pioneering nanosatellite mission dedicated for photometric observations of the brightest stars in the sky. The BRITE charge coupled device (CCD) sensors are poorly shielded against extensive flux of energetic particles which constantly induce defects in the [...] Read more.

The BRightest Target Explorer (BRITE) is the pioneering nanosatellite mission dedicated for photometric observations of the brightest stars in the sky. The BRITE charge coupled device (CCD) sensors are poorly shielded against extensive flux of energetic particles which constantly induce defects in the silicon lattice. In this paper we investigate the temporal evolution of the generation of the dark current in the BRITE CCDs over almost four years after launch. Utilizing several steps of image processing and employing normalization of the results, it was possible to obtain useful information about the progress of thermal activity in the sensors. The outcomes show a clear and consistent linear increase of induced damage despite the fact that only about 0.14% of CCD pixels were probed. By performing the analysis of temperature dependencies of the dark current, we identified the observed defects as phosphorus-vacancy (PV) pairs, which are common in proton irradiated CCD matrices. Moreover, the Meyer-Neldel empirical rule was confirmed in our dark current data, yielding

E_{M N} = 24.8

meV for proton-induced PV defects. Full article

(This article belongs to the Special Issue Charge-Coupled Device (CCD) Sensors)

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25 pages, 6051 KiB

Open AccessArticle

Dynamic Vertical Mapping with Crowdsourced Smartphone Sensor Data

by Georgios Pipelidis^1,*

, Omid Reza Moslehi Rad², Dorota Iwaszczuk²

, Christian Prehofer¹ and Urs Hugentobler³

¹ Software and Systems Engineering Research Group, Technical University of Munich, Boltzmannstr. 3, 85748 Garching bei München, Germany

² Astronomical and Physical Geodesy, Technical University of Munich, Arcisstr. 21, 80333 Munich, Germany

³ Satellite Geodesy, Technical University of Munich, Arcisstr. 21, 80333 Munich, Germany

Sensors 2018, 18(2), 480; https://doi.org/10.3390/s18020480 - 6 Feb 2018

Cited by 6 | Viewed by 5124

Abstract

In this paper, we present our novel approach for the crowdsourced dynamic vertical mapping of buildings. For achieving this, we use the barometric sensor of smartphones to estimate altitude differences and the moment of the outdoor to indoor transition to extract reference pressure. [...] Read more.

In this paper, we present our novel approach for the crowdsourced dynamic vertical mapping of buildings. For achieving this, we use the barometric sensor of smartphones to estimate altitude differences and the moment of the outdoor to indoor transition to extract reference pressure. We have identified the outdoor–indoor transition (OITransition) via the fusion of four different sensors. Our approach has been evaluated extensively over a period of 6 months in different humidity, temperature, and cloud-coverage situations, as well as over different hours of the day, and it is found that it can always predict the correct number of floors, while it can approximate the altitude with an average error of 0.5 m. Full article

(This article belongs to the Special Issue Sensors and Sensing in Indoor Localization, Tracking, Navigation and Activity Monitoring)

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15 pages, 2045 KiB

Open AccessArticle

Self-Tuning Threshold Method for Real-Time Gait Phase Detection Based on Ground Contact Forces Using FSRs

by Jing Tang^1,2, Jianbin Zheng^1,2, Yang Wang^1,2,*, Lie Yu³, Enqi Zhan^1,2 and Qiuzhi Song⁴

¹ School of Information Engineering, Wuhan University of Technology, Wuhan 430070, China

² Key Laboratory of Fiber Optic Sensing Technology and Information Processing, Ministry of Education, Wuhan University of Technology, Wuhan 430070, China

³ School of Electronic and Electrical Engineering, Wuhan Textile University, Hongshan District, Wuhan 430070, China

⁴ School of Electromechanical, Beijing Institute of Technology, Beijing 100081, China

Sensors 2018, 18(2), 481; https://doi.org/10.3390/s18020481 - 6 Feb 2018

Cited by 16 | Viewed by 5124

Abstract

This paper presents a novel methodology for detecting the gait phase of human walking on level ground. The previous threshold method (TM) sets a threshold to divide the ground contact forces (GCFs) into on-ground and off-ground states. However, the previous methods for gait [...] Read more.

This paper presents a novel methodology for detecting the gait phase of human walking on level ground. The previous threshold method (TM) sets a threshold to divide the ground contact forces (GCFs) into on-ground and off-ground states. However, the previous methods for gait phase detection demonstrate no adaptability to different people and different walking speeds. Therefore, this paper presents a self-tuning triple threshold algorithm (STTTA) that calculates adjustable thresholds to adapt to human walking. Two force sensitive resistors (FSRs) were placed on the ball and heel to measure GCFs. Three thresholds (i.e., high-threshold, middle-threshold andlow-threshold) were used to search out the maximum and minimum GCFs for the self-adjustments of thresholds. The high-threshold was the main threshold used to divide the GCFs into on-ground and off-ground statuses. Then, the gait phases were obtained through the gait phase detection algorithm (GPDA), which provides the rules that determine calculations for STTTA. Finally, the STTTA reliability is determined by comparing the results between STTTA and Mariani method referenced as the timing analysis module (TAM) and Lopez–Meyer methods. Experimental results show that the proposed method can be used to detect gait phases in real time and obtain high reliability when compared with the previous methods in the literature. In addition, the proposed method exhibits strong adaptability to different wearers walking at different walking speeds. Full article

(This article belongs to the Special Issue Sensors for Gait, Posture, and Health Monitoring)

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14 pages, 9578 KiB

Open AccessArticle

Low-Pass Filter for HV Partial Discharge Testing

by Vladimir Kindl^*

, Bohumil Skala, Roman Pechanek

, Vaclav Kus

and Jaroslav Hornak

University of West Bohemia, Faculty of Electrical Engineering, Regional Innovation Centre for Electrical Engineering (RICE), Univerzitni 8, 301 00 Pilsen, Czech Republic

Sensors 2018, 18(2), 482; https://doi.org/10.3390/s18020482 - 6 Feb 2018

Cited by 9 | Viewed by 6404

Abstract

The most common cause of high voltage electric machine malfunction is an electrical failure of the insulation system due to extreme partial discharges activity. The paper discusses the methodology for the construction of a low-pass high voltage filter for partial discharge measurement. It [...] Read more.

The most common cause of high voltage electric machine malfunction is an electrical failure of the insulation system due to extreme partial discharges activity. The paper discusses the methodology for the construction of a low-pass high voltage filter for partial discharge measurement. It focuses mainly on the shape optimization, using an analytical approach with subsequent verification using the finite element method. The experimental verification is given together with important conclusions. Full article

(This article belongs to the Section Physical Sensors)

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10 pages, 1770 KiB

Open AccessArticle

Fiber-Optic Pyrometer with Optically Powered Switch for Temperature Measurements

by Carmen Vázquez^*

, Sandra Pérez-Prieto, Juan D. López-Cardona, Alberto Tapetado

, Enrique Blanco, Jorge Moreno-López, David S. Montero

and Pedro C. Lallana

Electronics Technology Department, University Carlos III of Madrid, 28911 Leganés, Spain

Sensors 2018, 18(2), 483; https://doi.org/10.3390/s18020483 - 6 Feb 2018

Cited by 19 | Viewed by 8601

Abstract

We report the experimental results on a new infrared fiber-optic pyrometer for very localized and high-speed temperature measurements ranging from 170 to 530 °C using low-noise photodetectors and high-gain transimpedance amplifiers with a single gain mode in the whole temperature range. We also [...] Read more.

We report the experimental results on a new infrared fiber-optic pyrometer for very localized and high-speed temperature measurements ranging from 170 to 530 °C using low-noise photodetectors and high-gain transimpedance amplifiers with a single gain mode in the whole temperature range. We also report a shutter based on an optical fiber switch which is optically powered to provide a reference signal in an optical fiber pyrometer measuring from 200 to 550 °C. The tests show the potential of remotely powering via optical means a 300 mW power-hungry optical switch at a distance of 100 m, avoiding any electromagnetic interference close to the measuring point. Full article

(This article belongs to the Special Issue Optical Fiber Sensors 2017)

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15 pages, 2897 KiB

Open AccessArticle

Analytic and Unambiguous Phase-Based Algorithm for 3-D Localization of a Single Source with Uniform Circular Array

by Le Zuo^1,2,*

, Jin Pan¹ and Boyuan Ma¹

¹ Department of Microwave Engineering, University of Electronic Science and Technology of China, Chengdu 611731, China

² School of Electrical and Electronic Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore

Sensors 2018, 18(2), 484; https://doi.org/10.3390/s18020484 - 6 Feb 2018

Cited by 4 | Viewed by 3698

Abstract

This paper presents an analytic algorithm for estimating three-dimensional (3-D) localization of a single source with uniform circular array (UCA) interferometers. Fourier transforms are exploited to expand the phase distribution of a single source and the localization problem is reformulated as an equivalent [...] Read more.

This paper presents an analytic algorithm for estimating three-dimensional (3-D) localization of a single source with uniform circular array (UCA) interferometers. Fourier transforms are exploited to expand the phase distribution of a single source and the localization problem is reformulated as an equivalent spectrum manipulation problem. The 3-D parameters are decoupled to different spectrums in the Fourier domain. Algebraic relations are established between the 3-D localization parameters and the Fourier spectrums. Fourier sampling theorem ensures that the minimum element number for 3-D localization of a single source with a UCA is five. Accuracy analysis provides mathematical insights into the 3-D localization algorithm that larger number of elements gives higher estimation accuracy. In addition, the phase-based high-order difference invariance (HODI) property of a UCA is found and exploited to realize phase range compression. Following phase range compression, ambiguity resolution is addressed by the HODI of a UCA. A major advantage of the algorithm is that the ambiguity resolution and 3-D localization estimation are both analytic and are processed simultaneously, hence computationally efficient. Numerical simulations and experimental results are provided to verify the effectiveness of the proposed 3-D localization algorithm. Full article

(This article belongs to the Section Sensor Networks)

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22 pages, 12206 KiB

Open AccessArticle

VEHIOT: Design and Evaluation of an IoT Architecture Based on Low-Cost Devices to Be Embedded in Production Vehicles

by Jonatan Pajares Redondo^1,*,†

, Lisardo Prieto González^2,†

, Javier García Guzman^2,†

, Beatriz L. Boada^1,†

and Vicente Díaz^1,†

¹ Mechanical Engineering Department, Institute for Automotive Vehicle Safety (ISVA), Universidad Carlos III de Madrid, Avda. de la Universidad 30, 28911 Leganés, Madrid, Spain

² Computer Science Department, Institute for Automotive Vehicle Safety (ISVA), Universidad Carlos III de Madrid, Avda. de la Universidad 30, 28911 Leganés, Madrid, Spain

^† These authors contributed equally to this work.

Sensors 2018, 18(2), 486; https://doi.org/10.3390/s18020486 - 6 Feb 2018

Cited by 14 | Viewed by 7414

Abstract

Nowadays, the current vehicles are incorporating control systems in order to improve their stability and handling. These control systems need to know the vehicle dynamics through the variables (lateral acceleration, roll rate, roll angle, sideslip angle, etc.) that are obtained or estimated from [...] Read more.

Nowadays, the current vehicles are incorporating control systems in order to improve their stability and handling. These control systems need to know the vehicle dynamics through the variables (lateral acceleration, roll rate, roll angle, sideslip angle, etc.) that are obtained or estimated from sensors. For this goal, it is necessary to mount on vehicles not only low-cost sensors, but also low-cost embedded systems, which allow acquiring data from sensors and executing the developed algorithms to estimate and to control with novel higher speed computing. All these devices have to be integrated in an adequate architecture with enough performance in terms of accuracy, reliability and processing time. In this article, an architecture to carry out the estimation and control of vehicle dynamics has been developed. This architecture was designed considering the basic principles of IoT and integrates low-cost sensors and embedded hardware for orchestrating the experiments. A comparison of two different low-cost systems in terms of accuracy, acquisition time and reliability has been done. Both devices have been compared with the VBOX device from Racelogic, which has been used as the ground truth. The comparison has been made from tests carried out in a real vehicle. The lateral acceleration and roll rate have been analyzed in order to quantify the error of these devices. Full article

(This article belongs to the Special Issue Sensors, Wireless Connectivity and Systems for Autonomous Vehicles and Smart Mobility)

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27 pages, 436 KiB

Open AccessArticle

Off-Line Evaluation of Mobile-Centric Indoor Positioning Systems: The Experiences from the 2017 IPIN Competition

by Joaquín Torres-Sospedra^1,*,†

, Antonio R. Jiménez^2,*,†

, Adriano Moreira^3,*,†, Tomás Lungenstrass^4,*,†, Wei-Chung Lu^5,†, Stefan Knauth^6,*,†

, Germán Martín Mendoza-Silva¹

, Fernando Seco², Antoni Pérez-Navarro^7,8

, Maria João Nicolau³, António Costa³

, Filipe Meneses⁹

, Joaquín Farina⁴, Juan Pablo Morales⁴, Wen-Chen Lu⁵, Ho-Ti Cheng⁵, Shi-Shen Yang¹⁰, Shih-Hau Fang^5,*

, Ying-Ren Chien^10,*

and Yu Tsao¹¹

¹ Institute of New Imaging Technologies, Universitat Jaume I, 12071 Castelló, Spain

² Centre for Automation and Robotics (CAR), CSIC-UPM, 28500 Arganda del Rey, Spain

³ Algoritmi Research Centre, University of Minho, 4800-058 Guimarães, Portugal

⁴ AraraDS, Monseñor Sótero Sanz 161, 8340457 Santiago, Chile

⁵ Department of Electrical Engineering, Yuan Ze University, Zhongli 32003, Taiwan

⁶ Faculty for Geomatics, Computer Science and Mathematics, HFT Stuttgart—University of Applied Sciences, 70174 Stuttgart, Germany

⁷ Estudis d’Informàtica, Multimèdia i Telecomunicació, Universitat Oberta de Catalunya, Rambla del Poblenou 156, 08018 Barcelona, Spain

⁸ Internet Interdisciplinary Institute IN3, Av. Carl Friedrich Gauss 5, 08860 Castelldefels, Barcelona, Spain

⁹ Centro de Computação Gráfica (CCG), 4800-058 Guimarães, Portugal

¹⁰ Department of Electrical Engineering, National Ilan University, Yilan 26047, Taiwan

¹¹ Research Center for Information Technology Innovation, Academia Sinica, Taipei 11529, Taiwan

^† These authors contributed equally to this work.

Show full affiliation list Hide full affiliation list

Sensors 2018, 18(2), 487; https://doi.org/10.3390/s18020487 - 6 Feb 2018

Cited by 66 | Viewed by 9039

Abstract

The development of indoor positioning solutions using smartphones is a growing activity with an enormous potential for everyday life and professional applications. The research activities on this topic concentrate on the development of new positioning solutions that are tested in specific environments under [...] Read more.

The development of indoor positioning solutions using smartphones is a growing activity with an enormous potential for everyday life and professional applications. The research activities on this topic concentrate on the development of new positioning solutions that are tested in specific environments under their own evaluation metrics. To explore the real positioning quality of smartphone-based solutions and their capabilities for seamlessly adapting to different scenarios, it is needed to find fair evaluation frameworks. The design of competitions using extensive pre-recorded datasets is a valid way to generate open data for comparing the different solutions created by research teams. In this paper, we discuss the details of the 2017 IPIN indoor localization competition, the different datasets created, the teams participating in the event, and the results they obtained. We compare these results with other competition-based approaches (Microsoft and Perf-loc) and on-line evaluation web sites. The lessons learned by organising these competitions and the benefits for the community are addressed along the paper. Our analysis paves the way for future developments on the standardization of evaluations and for creating a widely-adopted benchmark strategy for researchers and companies in the field. Full article

(This article belongs to the Special Issue Smartphone-based Pedestrian Localization and Navigation)

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22 pages, 2185 KiB

Open AccessArticle

Multi-Sensor Optimal Data Fusion Based on the Adaptive Fading Unscented Kalman Filter

by Bingbing Gao^1,*, Gaoge Hu¹, Shesheng Gao¹, Yongmin Zhong²

and Chengfan Gu²

¹ School of Automatics, Northwestern Polytechnical University, Xi’an 710072, China

² School of Engineering, RMIT University, Bundoora, VIC 3083, Australia

Sensors 2018, 18(2), 488; https://doi.org/10.3390/s18020488 - 6 Feb 2018

Cited by 85 | Viewed by 7524

Abstract

This paper presents a new optimal data fusion methodology based on the adaptive fading unscented Kalman filter for multi-sensor nonlinear stochastic systems. This methodology has a two-level fusion structure: at the bottom level, an adaptive fading unscented Kalman filter based on the Mahalanobis [...] Read more.

This paper presents a new optimal data fusion methodology based on the adaptive fading unscented Kalman filter for multi-sensor nonlinear stochastic systems. This methodology has a two-level fusion structure: at the bottom level, an adaptive fading unscented Kalman filter based on the Mahalanobis distance is developed and serves as local filters to improve the adaptability and robustness of local state estimations against process-modeling error; at the top level, an unscented transformation-based multi-sensor optimal data fusion for the case of N local filters is established according to the principle of linear minimum variance to calculate globally optimal state estimation by fusion of local estimations. The proposed methodology effectively refrains from the influence of process-modeling error on the fusion solution, leading to improved adaptability and robustness of data fusion for multi-sensor nonlinear stochastic systems. It also achieves globally optimal fusion results based on the principle of linear minimum variance. Simulation and experimental results demonstrate the efficacy of the proposed methodology for INS/GNSS/CNS (inertial navigation system/global navigation satellite system/celestial navigation system) integrated navigation. Full article

(This article belongs to the Special Issue Integrated Sensors)

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26 pages, 6214 KiB

Open AccessFeature PaperArticle

A Mobility Management Using Follow-Me Cloud-Cloudlet in Fog-Computing-Based RANs for Smart Cities

by Yuh-Shyan Chen^*

and Yi-Ting Tsai

Department of Computer Science and Information Engineering, National Taipei University, No. 151, University Rd., San Shia District, New Taipei City 23741, Taiwan

Sensors 2018, 18(2), 489; https://doi.org/10.3390/s18020489 - 6 Feb 2018

Cited by 26 | Viewed by 6498

Abstract

Mobility management for supporting the location tracking and location-based service (LBS) is an important issue of smart city by providing the means for the smooth transportation of people and goods. The mobility is useful to contribute the innovation in both public and private [...] Read more.

Mobility management for supporting the location tracking and location-based service (LBS) is an important issue of smart city by providing the means for the smooth transportation of people and goods. The mobility is useful to contribute the innovation in both public and private transportation infrastructures for smart cities. With the assistance of edge/fog computing, this paper presents a fully new mobility management using the proposed follow-me cloud-cloudlet (FMCL) approach in fog-computing-based radio access networks (Fog-RANs) for smart cities. The proposed follow-me cloud-cloudlet approach is an integration strategy of follow-me cloud (FMC) and follow-me edge (FME) (or called cloudlet). A user equipment (UE) receives the data, transmitted from original cloud, into the original edge cloud before the handover operation. After the handover operation, an UE searches for a new cloud, called as a migrated cloud, and a new edge cloud, called as a migrated edge cloud near to UE, where the remaining data is migrated from the original cloud to the migrated cloud and all the remaining data are received in the new edge cloud. Existing FMC results do not have the property of the VM migration between cloudlets for the purpose of reducing the transmission latency, and existing FME results do not keep the property of the service migration between data centers for reducing the transmission latency. Our proposed FMCL approach can simultaneously keep the VM migration between cloudlets and service migration between data centers to significantly reduce the transmission latency. The new proposed mobility management using FMCL approach aims to reduce the total transmission time if some data packets are pre-scheduled and pre-stored into the cache of cloudlet if UE is switching from the previous Fog-RAN to the serving Fog-RAN. To illustrate the performance achievement, the mathematical analysis and simulation results are examined in terms of the total transmission time, the throughput, the probability of packet loss, and the number of control messages. Full article

(This article belongs to the Special Issue The Architectures, Systems, and Applications of Internet of Things for Smart Cities)

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19 pages, 5042 KiB

Open AccessArticle

A Strain-Based Method to Detect Tires’ Loss of Grip and Estimate Lateral Friction Coefficient from Experimental Data by Fuzzy Logic for Intelligent Tire Development

by Jorge Yunta^1,*

, Daniel Garcia-Pozuelo¹, Vicente Diaz¹ and Oluremi Olatunbosun²

¹ Department of Mechanical Engineering, Research Institute of Vehicle Safety (ISVA), Universidad Carlos III de Madrid, Avd. De la Universidad, 28911 Leganés (Madrid), Spain

² School of Mechanical Engineering, University of Birmingham, B15 2TT Edgbaston, UK

Sensors 2018, 18(2), 490; https://doi.org/10.3390/s18020490 - 6 Feb 2018

Cited by 30 | Viewed by 10206

Abstract

Tires are a key sub-system of vehicles that have a big responsibility for comfort, fuel consumption and traffic safety. However, current tires are just passive rubber elements which do not contribute actively to improve the driving experience or vehicle safety. The lack of [...] Read more.

Tires are a key sub-system of vehicles that have a big responsibility for comfort, fuel consumption and traffic safety. However, current tires are just passive rubber elements which do not contribute actively to improve the driving experience or vehicle safety. The lack of information from the tire during driving gives cause for developing an intelligent tire. Therefore, the aim of the intelligent tire is to monitor tire working conditions in real-time, providing useful information to other systems and becoming an active system. In this paper, tire tread deformation is measured to provide a strong experimental base with different experiments and test results by means of a tire fitted with sensors. Tests under different working conditions such as vertical load or slip angle have been carried out with an indoor tire test rig. The experimental data analysis shows the strong relation that exists between lateral force and the maximum tensile and compressive strain peaks when the tire is not working at the limit of grip. In the last section, an estimation system from experimental data has been developed and implemented in Simulink to show the potential of strain sensors for developing intelligent tire systems, obtaining as major results a signal to detect tire’s loss of grip and estimations of the lateral friction coefficient. Full article

(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Spain 2017)

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14 pages, 3895 KiB

Open AccessArticle

Statistical Analysis of Stress Signals from Bridge Monitoring by FBG System

by Xiao-Wei Ye^*, You-Hua Su

and Pei-Sen Xi

Department of Civil Engineering, Zhejiang University, Hangzhou 310058, China

Sensors 2018, 18(2), 491; https://doi.org/10.3390/s18020491 - 7 Feb 2018

Cited by 54 | Viewed by 7390

Abstract

In this paper, a fiber Bragg grating (FBG)-based stress monitoring system instrumented on an orthotropic steel deck arch bridge is demonstrated. The FBG sensors are installed at two types of critical fatigue-prone welded joints to measure the strain and temperature signals. A total [...] Read more.

In this paper, a fiber Bragg grating (FBG)-based stress monitoring system instrumented on an orthotropic steel deck arch bridge is demonstrated. The FBG sensors are installed at two types of critical fatigue-prone welded joints to measure the strain and temperature signals. A total of 64 FBG sensors are deployed around the rib-to-deck and rib-to-diagram areas at the mid-span and quarter-span of the investigated orthotropic steel bridge. The local stress behaviors caused by the highway loading and temperature effect during the construction and operation periods are presented with the aid of a wavelet multi-resolution analysis approach. In addition, the multi-modal characteristic of the rainflow counted stress spectrum is modeled by the method of finite mixture distribution together with a genetic algorithm (GA)-based parameter estimation approach. The optimal probability distribution of the stress spectrum is determined by use of Bayesian information criterion (BIC). Furthermore, the hot spot stress of the welded joint is calculated by an extrapolation method recommended in the specification of International Institute of Welding (IIW). The stochastic characteristic of stress concentration factor (SCF) of the concerned welded joint is addressed. The proposed FBG-based stress monitoring system and probabilistic stress evaluation methods can provide an effective tool for structural monitoring and condition assessment of orthotropic steel bridges. Full article

(This article belongs to the Special Issue Sensors and Sensor Networks for Structural Health Monitoring)

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17 pages, 14818 KiB

Open AccessArticle

IoT-Forensics Meets Privacy: Towards Cooperative Digital Investigations

by Ana Nieto^*

, Ruben Rios^*

and Javier Lopez^*

Network, Information and Computer Security (NICS) Lab, University of Malaga, 29071 Malaga, Spain

Sensors 2018, 18(2), 492; https://doi.org/10.3390/s18020492 - 7 Feb 2018

Cited by 73 | Viewed by 10591

Abstract

IoT-Forensics is a novel paradigm for the acquisition of electronic evidence whose operation is conditioned by the peculiarities of the Internet of Things (IoT) context. As a branch of computer forensics, this discipline respects the most basic forensic principles of preservation, traceability, documentation, [...] Read more.

IoT-Forensics is a novel paradigm for the acquisition of electronic evidence whose operation is conditioned by the peculiarities of the Internet of Things (IoT) context. As a branch of computer forensics, this discipline respects the most basic forensic principles of preservation, traceability, documentation, and authorization. The digital witness approach also promotes such principles in the context of the IoT while allowing personal devices to cooperate in digital investigations by voluntarily providing electronic evidence to the authorities. However, this solution is highly dependent on the willingness of citizens to collaborate and they may be reluctant to do so if the sensitive information within their personal devices is not sufficiently protected when shared with the investigators. In this paper, we provide the digital witness approach with a methodology that enables citizens to share their data with some privacy guarantees. We apply the PRoFIT methodology, originally defined for IoT-Forensics environments, to the digital witness approach in order to unleash its full potential. Finally, we show the feasibility of a PRoFIT-compliant digital witness with two use cases. Full article

(This article belongs to the Special Issue Security, Trust and Privacy for Sensor Networks)

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27 pages, 9911 KiB

Open AccessArticle

Customizable Optical Force Sensor for Fast Prototyping and Cost-Effective Applications

by Jorge A. Díez^1,*, José M. Catalán¹

, Andrea Blanco¹

, José V. García-Perez¹, Francisco J. Badesa²

and Nicolás Gacía-Aracil¹

¹ Departamento de Ingeniería de Sistemas y Automática, Universidad Miguel Hernández de Elche, 03202 Elche, Spain

² Departamento de Ingeniería en Automática Electrónica, Arquitectura y Redes de Computadores, Universidad de Cádiz, 11510 Puerto Real, Spain

Sensors 2018, 18(2), 493; https://doi.org/10.3390/s18020493 - 7 Feb 2018

Cited by 11 | Viewed by 7224

Abstract

This paper presents the development of an optical force sensor architecture directed to prototyping and cost-effective applications, where the actual force requirements are still not well defined or the most suitable commercial technologies would highly increase the cost of the device. The working [...] Read more.

This paper presents the development of an optical force sensor architecture directed to prototyping and cost-effective applications, where the actual force requirements are still not well defined or the most suitable commercial technologies would highly increase the cost of the device. The working principle of this sensor consists of determining the displacement of a lens by measuring the distortion of a refracted light beam. This lens is attached to an elastic interface whose elastic constant is known, allowing the estimation of the force that disturbs the optical system. In order to satisfy the requirements of the design process in an inexpensive way, this sensor can be built by fast prototyping technologies and using non-optical grade elements. To deal with the imperfections of this kind of manufacturing procedures and materials, four fitting models are proposed to calibrate the implemented sensor. In order to validate the system, two different sensor implementations with measurement ranges of ±45 N and ±10 N are tested with the proposed models, comparing the resulting force estimation with respect to an industrial-grade load cell. Results show that all models can estimate the loads with an error of about 6% of the measurement range. Full article

(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Spain 2017)

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14 pages, 3911 KiB

Open AccessArticle

Frequency Response of Graphene Electrolyte-Gated Field-Effect Transistors

by Charles Mackin

, Elaine McVay and Tomás Palacios^*

Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 77 Massachusetts Avenue, Cambridge, MA 02139, USA

Sensors 2018, 18(2), 494; https://doi.org/10.3390/s18020494 - 7 Feb 2018

Cited by 22 | Viewed by 8503

Abstract

This work develops the first frequency-dependent small-signal model for graphene electrolyte-gated field-effect transistors (EGFETs). Graphene EGFETs are microfabricated to measure intrinsic voltage gain, frequency response, and to develop a frequency-dependent small-signal model. The transfer function of the graphene EGFET small-signal model is found [...] Read more.

This work develops the first frequency-dependent small-signal model for graphene electrolyte-gated field-effect transistors (EGFETs). Graphene EGFETs are microfabricated to measure intrinsic voltage gain, frequency response, and to develop a frequency-dependent small-signal model. The transfer function of the graphene EGFET small-signal model is found to contain a unique pole due to a resistive element, which stems from electrolyte gating. Intrinsic voltage gain, cutoff frequency, and transition frequency for the microfabricated graphene EGFETs are approximately 3.1 V/V, 1.9 kHz, and 6.9 kHz, respectively. This work marks a critical step in the development of high-speed chemical and biological sensors using graphene EGFETs. Full article

(This article belongs to the Special Issue Thin-Film Transistors for Biomedical and Chemical Sensing)

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14 pages, 2890 KiB

Open AccessArticle

Measurement of Axial Rigidity and Postural Instability Using Wearable Sensors

by Dung Phan¹, Malcolm Horne², Pubudu N. Pathirana^1,* and Parisa Farzanehfar²

¹ School of Engineering, Deakin University, Waurn Ponds, VIC 3216, Australia

² Florey Institute of Neuroscience and Mental Health, Parkville, VIC 3052, Australia

Sensors 2018, 18(2), 495; https://doi.org/10.3390/s18020495 - 7 Feb 2018

Cited by 18 | Viewed by 6598

Abstract

Axial Bradykinesia is an important feature of advanced Parkinson’s disease (PD). The purpose of this study is to quantify axial bradykinesia using wearable sensors with the long-term aim of quantifying these movements, while the subject performs routine domestic activities. We measured back movements [...] Read more.

Axial Bradykinesia is an important feature of advanced Parkinson’s disease (PD). The purpose of this study is to quantify axial bradykinesia using wearable sensors with the long-term aim of quantifying these movements, while the subject performs routine domestic activities. We measured back movements during common daily activities such as pouring, pointing, walking straight and walking around a chair with a test system engaging a minimal number of Inertial Measurement (IM) based wearable sensors. Participants included controls and PD patients whose rotation and flexion of the back was captured by the time delay between motion signals from sensors attached to the upper and lower back. PD subjects could be distinguished from controls using only two sensors. These findings suggest that a small number of sensors and similar analyses could distinguish between variations in bradykinesia in subjects with measurements performed outside of the laboratory. The subjects could engage in routine activities leading to progressive assessments of therapeutic outcomes. Full article

(This article belongs to the Special Issue Smart Decision-Making)

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10 pages, 3370 KiB

Open AccessArticle

Determining Biogenic Content of Biogas by Measuring Stable Isotopologues ¹²CH₄, ¹³CH₄, and CH₃D with a Mid-Infrared Direct Absorption Laser Spectrometer

by Teemu Kääriäinen^*, Craig A. Richmond and Albert Manninen

VTT Technical Research Centre of Finland Ltd., Vuorimiehentie 3, 02150 Espoo, Finland

Sensors 2018, 18(2), 496; https://doi.org/10.3390/s18020496 - 7 Feb 2018

Cited by 8 | Viewed by 4958

Abstract

A tunable laser absorption spectrometer (TLAS) was developed for the simultaneous measurement of δ¹³C and δD values of methane (CH₄). A mid-infrared interband cascade laser (ICL) emitting around 3.27 µm was used to measure the absorption of the [...] Read more.

A tunable laser absorption spectrometer (TLAS) was developed for the simultaneous measurement of δ¹³C and δD values of methane (CH₄). A mid-infrared interband cascade laser (ICL) emitting around 3.27 µm was used to measure the absorption of the three most abundant isotopologues in CH₄ with a single, mode-hop free current sweep. The instrument was validated against methane samples of fossil and biogenic origin with known isotopic composition. Three blended mixtures with varied biogenic content were prepared volumetrically, and their δ¹³C and δD values were determined. Analysis demonstrated that, provided the isotopic composition of the source materials was known, the δ¹³C and δD values alone were sufficient to determine the biogenic content of the blended samples to within 1.5%. Full article

(This article belongs to the Special Issue Spectroscopy Based Sensors)

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12 pages, 4291 KiB

Open AccessArticle

An Improved Calibration Method for a Rotating 2D LIDAR System

by Yadan Zeng¹, Heng Yu^1,2, Houde Dai^1,*

, Shuang Song^3,*, Mingqiang Lin¹, Bo Sun⁴, Wei Jiang^1,2 and Max Q.-H. Meng^3,5

¹ Quanzhou Institute of Equipment Manufacturing, Haixi Institutes, Chinese Academy of Sciences, Jinjiang 362200, China

² College of Electrical and Control Engineering, North University of China, Taiyuan 030051, China

³ Harbin Institute of Technology Shenzhen Graduate School, Shenzhen 518000, China

⁴ Suzhou Sino-Germany Robooster Intelligent Technology Co., Ltd., Suzhou 215000, China

⁵ Department of Electric Engineering, Chinese University of Hong Kong, Hong Kong, China

Sensors 2018, 18(2), 497; https://doi.org/10.3390/s18020497 - 7 Feb 2018

Cited by 37 | Viewed by 8800

Abstract

This paper presents an improved calibration method of a rotating two-dimensional light detection and ranging (R2D-LIDAR) system, which can obtain the 3D scanning map of the surroundings. The proposed R2D-LIDAR system, composed of a 2D LIDAR and a rotating unit, is pervasively used [...] Read more.

This paper presents an improved calibration method of a rotating two-dimensional light detection and ranging (R2D-LIDAR) system, which can obtain the 3D scanning map of the surroundings. The proposed R2D-LIDAR system, composed of a 2D LIDAR and a rotating unit, is pervasively used in the field of robotics owing to its low cost and dense scanning data. Nevertheless, the R2D-LIDAR system must be calibrated before building the geometric model because there are assembled deviation and abrasion between the 2D LIDAR and the rotating unit. Hence, the calibration procedures should contain both the adjustment between the two devices and the bias of 2D LIDAR itself. The main purpose of this work is to resolve the 2D LIDAR bias issue with a flat plane based on the Levenberg–Marquardt (LM) algorithm. Experimental results for the calibration of the R2D-LIDAR system prove the reliability of this strategy to accurately estimate sensor offsets with the error range from −15 mm to 15 mm for the performance of capturing scans. Full article

(This article belongs to the Special Issue Sensors for Transportation)

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20 pages, 22628 KiB

Open AccessArticle

Spatio-Temporal Super-Resolution Reconstruction of Remote-Sensing Images Based on Adaptive Multi-Scale Detail Enhancement

by Hong Zhu^1,2, Xinming Tang^1,3,4, Junfeng Xie^1,3,5,*, Weidong Song⁵, Fan Mo¹ and Xiaoming Gao^1,3,5

¹ Satellite Surveying and Mapping Application Center, NASG, Beijing 100048, China

² College of Resource Environment and Tourism, Capital Normal University, Beijing 100048, China

³ Key Laboratory of Satellite Surveying and Mapping Technology and Application, NASG, Beijing 10048, China

⁴ School of Earth Science and Engineering, Hohai University, Nanjing 211100, China

⁵ School of Surveying and Geographical Science, Liaoning Technical University, Fuxin 123000, China

Sensors 2018, 18(2), 498; https://doi.org/10.3390/s18020498 - 7 Feb 2018

Cited by 26 | Viewed by 5425

Abstract

There are many problems in existing reconstruction-based super-resolution algorithms, such as the lack of texture-feature representation and of high-frequency details. Multi-scale detail enhancement can produce more texture information and high-frequency information. Therefore, super-resolution reconstruction of remote-sensing images based on adaptive multi-scale detail enhancement [...] Read more.

There are many problems in existing reconstruction-based super-resolution algorithms, such as the lack of texture-feature representation and of high-frequency details. Multi-scale detail enhancement can produce more texture information and high-frequency information. Therefore, super-resolution reconstruction of remote-sensing images based on adaptive multi-scale detail enhancement (AMDE-SR) is proposed in this paper. First, the information entropy of each remote-sensing image is calculated, and the image with the maximum entropy value is regarded as the reference image. Subsequently, spatio-temporal remote-sensing images are processed using phase normalization, which is to reduce the time phase difference of image data and enhance the complementarity of information. The multi-scale image information is then decomposed using the L₀ gradient minimization model, and the non-redundant information is processed by difference calculation and expanding non-redundant layers and the redundant layer by the iterative back-projection (IBP) technique. The different-scale non-redundant information is adaptive-weighted and fused using cross-entropy. Finally, a nonlinear texture-detail-enhancement function is built to improve the scope of small details, and the peak signal-to-noise ratio (PSNR) is used as an iterative constraint. Ultimately, high-resolution remote-sensing images with abundant texture information are obtained by iterative optimization. Real results show an average gain in entropy of up to 0.42 dB for an up-scaling of 2 and a significant promotion gain in enhancement measure evaluation for an up-scaling of 2. The experimental results show that the performance of the AMED-SR method is better than existing super-resolution reconstruction methods in terms of visual and accuracy improvements. Full article

(This article belongs to the Section Remote Sensors)

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13 pages, 5235 KiB

Open AccessArticle

Real-Time and Meter-Scale Absolute Distance Measurement by Frequency-Comb-Referenced Multi-Wavelength Interferometry

by Guochao Wang^1,2,*

, Lilong Tan¹ and Shuhua Yan²

¹ High-tech Institution of Xi’an, Xi’an 710025, China

² College of Mechatronic Engineering and Automation, National University of Defense Technology, Changsha 410073, China

Sensors 2018, 18(2), 500; https://doi.org/10.3390/s18020500 - 7 Feb 2018

Cited by 8 | Viewed by 5279

Abstract

We report on a frequency-comb-referenced absolute interferometer which instantly measures long distance by integrating multi-wavelength interferometry with direct synthetic wavelength interferometry. The reported interferometer utilizes four different wavelengths, simultaneously calibrated to the frequency comb of a femtosecond laser, to implement subwavelength distance measurement, [...] Read more.

We report on a frequency-comb-referenced absolute interferometer which instantly measures long distance by integrating multi-wavelength interferometry with direct synthetic wavelength interferometry. The reported interferometer utilizes four different wavelengths, simultaneously calibrated to the frequency comb of a femtosecond laser, to implement subwavelength distance measurement, while direct synthetic wavelength interferometry is elaborately introduced by launching a fifth wavelength to extend a non-ambiguous range for meter-scale measurement. A linearity test performed comparatively with a He–Ne laser interferometer shows a residual error of less than 70.8 nm in peak-to-valley over a 3 m distance, and a 10 h distance comparison is demonstrated to gain fractional deviations of ~3 × 10⁻⁸ versus 3 m distance. Test results reveal that the presented absolute interferometer enables precise, stable, and long-term distance measurements and facilitates absolute positioning applications such as large-scale manufacturing and space missions. Full article

(This article belongs to the Section Physical Sensors)

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17 pages, 2697 KiB

Open AccessArticle

A Glider-Assisted Link Disruption Restoration Mechanism in Underwater Acoustic Sensor Networks

by Zhigang Jin^1,*

, Ning Wang¹, Yishan Su^1,* and Qiuling Yang²

¹ School of Electrical and Information Engineering, Tianjin University, Tianjin 300072, China

² College of Information Science and Technology, Hainan University, Haikou 570228, China

Sensors 2018, 18(2), 501; https://doi.org/10.3390/s18020501 - 7 Feb 2018

Cited by 5 | Viewed by 4027

Abstract

Underwater acoustic sensor networks (UASNs) have become a hot research topic. In UASNs, nodes can be affected by ocean currents and external forces, which could result in sudden link disruption. Therefore, designing a flexible and efficient link disruption restoration mechanism to ensure the [...] Read more.

Underwater acoustic sensor networks (UASNs) have become a hot research topic. In UASNs, nodes can be affected by ocean currents and external forces, which could result in sudden link disruption. Therefore, designing a flexible and efficient link disruption restoration mechanism to ensure the network connectivity is a challenge. In the paper, we propose a glider-assisted restoration mechanism which includes link disruption recognition and related link restoring mechanism. In the link disruption recognition mechanism, the cluster heads collect the link disruption information and then schedule gliders acting as relay nodes to restore the disrupted link. Considering the glider’s sawtooth motion, we design a relay location optimization algorithm with a consideration of both the glider’s trajectory and acoustic channel attenuation model. The utility function is established by minimizing the channel attenuation and the optimal location of glider is solved by a multiplier method. The glider-assisted restoration mechanism can greatly improve the packet delivery rate and reduce the communication energy consumption and it is more general for the restoration of different link disruption scenarios. The simulation results show that glider-assisted restoration mechanism can improve the delivery rate of data packets by 15–33% compared with cooperative opportunistic routing (OVAR), the hop-by-hop vector-based forwarding (HH-VBF) and the vector based forward (VBF) methods, and reduce communication energy consumption by 20–58% for a typical network’s setting. Full article

(This article belongs to the Special Issue Advances and Challenges in Underwater Sensor Networks)

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23 pages, 992 KiB

Open AccessArticle

Predicting Long-Term Stability of Precise Oscillators under Influence of Frequency Drift

by Weiwei Cheng¹ and Guigen Nie^1,2,*

¹ GNSS (Global Navigation Satellite System) Research Center, Wuhan University, 129 Luoyu Road, 430079 Wuhan, China

² Collaborative Innovation Center for Geospatial Information Technology, Wuhan University, 129 Luoyu Road, 430079 Wuhan, China

Sensors 2018, 18(2), 502; https://doi.org/10.3390/s18020502 - 7 Feb 2018

Cited by 2 | Viewed by 4275

Abstract

High-performance oscillators, atomic clocks for instance, are important in modern industries, finance and scientific research. In this paper, the authors study the estimation and prediction of long-term stability based on convex optimization techniques and compressive sensing. To take frequency drift into account, its [...] Read more.

High-performance oscillators, atomic clocks for instance, are important in modern industries, finance and scientific research. In this paper, the authors study the estimation and prediction of long-term stability based on convex optimization techniques and compressive sensing. To take frequency drift into account, its influence on Allan and modified Allan variances is formulated. Meanwhile, expressions for the expectation and variance of discrete-time Hadamard variance are derived. Methods that reduce the computational complexity of these expressions are also introduced. Tests against GPS precise clock data show that the method can correctly predict one-week frequency stability from 14-day measured data. Full article

(This article belongs to the Collection Modeling, Testing and Reliability Issues in MEMS Engineering)

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16 pages, 2053 KiB

Open AccessArticle

Wearable Driver Distraction Identification On-The-Road via Continuous Decomposition of Galvanic Skin Responses

by Omid Dehzangi^*,†,‡, Vikas Rajendra^‡

and Mojtaba Taherisadr^‡

¹ Computer and Information Science Department, University of Michigan-Dearborn, Dearborn, MI 48128, USA

^† Current address: University of Michigan-Dearborn, 4901 Evergreen Road, Dearborn, MI 48128, USA.

^‡ These authors contributed equally to this work.

Sensors 2018, 18(2), 503; https://doi.org/10.3390/s18020503 - 7 Feb 2018

Cited by 37 | Viewed by 7326

Abstract

One of the main reasons for fatal accidents on the road is distracted driving. The continuous attention of an individual driver is a necessity for the task of driving. While driving, certain levels of distraction can cause drivers to lose their attention, which [...] Read more.

One of the main reasons for fatal accidents on the road is distracted driving. The continuous attention of an individual driver is a necessity for the task of driving. While driving, certain levels of distraction can cause drivers to lose their attention, which might lead to an accident. Thus, the number of accidents can be reduced by early detection of distraction. Many studies have been conducted to automatically detect driver distraction. Although camera-based techniques have been successfully employed to characterize driver distraction, the risk of privacy violation is high. On the other hand, physiological signals have shown to be a privacy preserving and reliable indicator of driver state, while the acquisition technology might be intrusive to drivers in practical implementation. In this study, we investigate a continuous measure of phasic Galvanic Skin Responses (GSR) using a wristband wearable to identify distraction of drivers during a driving experiment on-the-road. We first decompose the raw GSR signal into its phasic and tonic components using Continuous Decomposition Analysis (CDA), and then the continuous phasic component containing relevant characteristics of the skin conductance signals is investigated for further analysis. We generated a high resolution spectro-temporal transformation of the GSR signals for non-distracted and distracted (calling and texting) scenarios to visualize the associated behavior of the decomposed phasic GSR signal in correlation with distracted scenarios. According to the spectrogram observations, we extract relevant spectral and temporal features to capture the patterns associated with the distracted scenarios at the physiological level. We then performed feature selection using support vector machine recursive feature elimination (SVM-RFE) in order to: (1) generate a rank of the distinguishing features among the subject population, and (2) create a reduced feature subset toward more efficient distraction identification on the edge at the generalization phase. We employed support vector machine (SVM) to generate the 10-fold cross validation (10-CV) identification performance measures. Our experimental results demonstrated cross-validation accuracy of 94.81% using all the features and the accuracy of 93.01% using reduced feature space. The SVM-RFE selected set of features generated a marginal decrease in accuracy while reducing the redundancy in the input feature space toward shorter response time necessary for early notification of distracted state of the driver. Full article

(This article belongs to the Special Issue Sensing, Data Analysis and Platforms for Ubiquitous Intelligence)

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12 pages, 3405 KiB

Open AccessArticle

A Scheme for Enhancing Precision in 3-Dimensional Positioning for Non-Contact Measurement Systems Based on Laser Triangulation

by Yassine Selami, Wei Tao^*, Qiang Gao, Hongwei Yang and Hui Zhao

Department of Instrument and Engineering, Shanghai Jiao Tong University, Shanghai 200240, China

Sensors 2018, 18(2), 504; https://doi.org/10.3390/s18020504 - 7 Feb 2018

Cited by 23 | Viewed by 5528

Abstract

Laser triangulation allows non-contact measurement in the third dimension. Due to the nonlinearities presented in camera and laser sensor, large range distances are quite difficult to measure with high precision. In order to enhance the precision and accuracy of large range measurement based [...] Read more.

Laser triangulation allows non-contact measurement in the third dimension. Due to the nonlinearities presented in camera and laser sensor, large range distances are quite difficult to measure with high precision. In order to enhance the precision and accuracy of large range measurement based on laser triangulation, we propose a novel scheme composed of four laser emitters, curve fitting subpixel location algorithm for laser center detection, and the linear regression approach based on the Gaussian model for calibration. When an object performs a 100 mm displacement from a closer to a farther point, our system achieved a repeatability up to ±7 µm, an estimated standard deviation of fitting error within 0.0027 mm, an expanded uncertainty of repeatability within 0.13 mm, an average error variation of rotational plane within 0.15 degree and a nonlinearity error within ±0.04% in full scale. Compared to published results, our proposed method shows an enhancement in accuracy. The error is significantly reduced and maintains at the low level for large ranges, which makes this system applicable and suitable for industrial and indoor applications. Full article

(This article belongs to the Section Physical Sensors)

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16 pages, 6821 KiB

Open AccessArticle

Accurate Initial State Estimation in a Monocular Visual–Inertial SLAM System

by Xufu Mu

, Jing Chen^*, Zixiang Zhou, Zhen Leng and Lei Fan

School of Optics and Photonics, Beijing Institute of Technology, Beijing 100081, China

Sensors 2018, 18(2), 506; https://doi.org/10.3390/s18020506 - 8 Feb 2018

Cited by 20 | Viewed by 6012

Abstract

The fusion of monocular visual and inertial cues has become popular in robotics, unmanned vehicles and augmented reality fields. Recent results have shown that optimization-based fusion strategies outperform filtering strategies. Robust state estimation is the core capability for optimization-based visual–inertial Simultaneous Localization and [...] Read more.

The fusion of monocular visual and inertial cues has become popular in robotics, unmanned vehicles and augmented reality fields. Recent results have shown that optimization-based fusion strategies outperform filtering strategies. Robust state estimation is the core capability for optimization-based visual–inertial Simultaneous Localization and Mapping (SLAM) systems. As a result of the nonlinearity of visual–inertial systems, the performance heavily relies on the accuracy of initial values (visual scale, gravity, velocity and Inertial Measurement Unit (IMU) biases). Therefore, this paper aims to propose a more accurate initial state estimation method. On the basis of the known gravity magnitude, we propose an approach to refine the estimated gravity vector by optimizing the two-dimensional (2D) error state on its tangent space, then estimate the accelerometer bias separately, which is difficult to be distinguished under small rotation. Additionally, we propose an automatic termination criterion to determine when the initialization is successful. Once the initial state estimation converges, the initial estimated values are used to launch the nonlinear tightly coupled visual–inertial SLAM system. We have tested our approaches with the public EuRoC dataset. Experimental results show that the proposed methods can achieve good initial state estimation, the gravity refinement approach is able to efficiently speed up the convergence process of the estimated gravity vector, and the termination criterion performs well. Full article

(This article belongs to the Special Issue Indoor LiDAR/Vision Systems)

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13 pages, 2736 KiB

Open AccessArticle

A Novel Method for Remote Depth Estimation of Buried Radioactive Contamination

by Ikechukwu Kevin Ukaegbu^1,*

and Kelum A. A. Gamage²

¹ Engineering Department, Lancaster University, Lancaster LA1 4YW, UK

² School of Engineering, University of Glasgow, Glasgow G12 8QQ, UK

Sensors 2018, 18(2), 507; https://doi.org/10.3390/s18020507 - 8 Feb 2018

Cited by 8 | Viewed by 3655

Abstract

Existing remote radioactive contamination depth estimation methods for buried radioactive wastes are either limited to less than 2 cm or are based on empirical models that require foreknowledge of the maximum penetrable depth of the contamination. These severely limits their usefulness in some [...] Read more.

Existing remote radioactive contamination depth estimation methods for buried radioactive wastes are either limited to less than 2 cm or are based on empirical models that require foreknowledge of the maximum penetrable depth of the contamination. These severely limits their usefulness in some real life subsurface contamination scenarios. Therefore, this work presents a novel remote depth estimation method that is based on an approximate three-dimensional linear attenuation model that exploits the benefits of using multiple measurements obtained from the surface of the material in which the contamination is buried using a radiation detector. Simulation results showed that the proposed method is able to detect the depth of caesium-137 and cobalt-60 contamination buried up to 40 cm in both sand and concrete. Furthermore, results from experiments show that the method is able to detect the depth of caesium-137 contamination buried up to 12 cm in sand. The lower maximum depth recorded in the experiment is due to limitations in the detector and the low activity of the caesium-137 source used. Nevertheless, both results demonstrate the superior capability of the proposed method compared to existing methods. Full article

(This article belongs to the Section Remote Sensors)

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22 pages, 13672 KiB

Open AccessArticle

H∞ Robust Control of a Large-Piston MEMS Micromirror for Compact Fourier Transform Spectrometer Systems

by Huipeng Chen¹

, Mengyuan Li^2,4, Yi Zhang³, Huikai Xie²

, Chang Chen¹, Zhangming Peng¹ and Shaohui Su^1,*

¹ School of Mechanical Engineering, HangZhou DianZi University, Hangzhou 310018, China

² Department of Electrical and Computer Engineering, University of Florida, Gainesville, FL 32611, USA

³ College of Mechanical and Electronic Engineering, Shangdong University of Science and Technology, Qingdao 266590, China

⁴ School of Information and Electronics, Beijing Institute of Technology, Beijing 100081, China

Sensors 2018, 18(2), 508; https://doi.org/10.3390/s18020508 - 8 Feb 2018

Cited by 22 | Viewed by 6844

Abstract

Incorporating linear-scanning micro-electro-mechanical systems (MEMS) micromirrors into Fourier transform spectral acquisition systems can greatly reduce the size of the spectrometer equipment, making portable Fourier transform spectrometers (FTS) possible. How to minimize the tilting of the MEMS mirror plate during its large linear scan [...] Read more.

Incorporating linear-scanning micro-electro-mechanical systems (MEMS) micromirrors into Fourier transform spectral acquisition systems can greatly reduce the size of the spectrometer equipment, making portable Fourier transform spectrometers (FTS) possible. How to minimize the tilting of the MEMS mirror plate during its large linear scan is a major problem in this application. In this work, an FTS system has been constructed based on a biaxial MEMS micromirror with a large-piston displacement of 180 μm, and a biaxial H∞ robust controller is designed. Compared with open-loop control and proportional-integral-derivative (PID) closed-loop control, H∞ robust control has good stability and robustness. The experimental results show that the stable scanning displacement reaches 110.9 μm under the H∞ robust control, and the tilting angle of the MEMS mirror plate in that full scanning range falls within ±0.0014°. Without control, the FTS system cannot generate meaningful spectra. In contrast, the FTS yields a clean spectrum with a full width at half maximum (FWHM) spectral linewidth of 96 cm⁻¹ under the H∞ robust control. Moreover, the FTS system can maintain good stability and robustness under various driving conditions. Full article

(This article belongs to the Special Issue Smart Sensors for Mechatronic and Robotic Systems)

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16 pages, 5757 KiB

Open AccessArticle

Enrichment of OpenStreetMap Data Completeness with Sidewalk Geometries Using Data Mining Techniques

by Amin Mobasheri^1,*

, Haosheng Huang²

, Lívia Castro Degrossi³

and Alexander Zipf¹

¹ GIScience Research Group, Institute of Geography, Heidelberg University, 69120 Heidelberg, Germany

² GIScience Center of the Department of Geography, University of Zurich (UZH), 8057 Zurich, Switzerland

³ Department of Computer Systems, University of São Paulo, São Carlos 13566-590, Brazil

Sensors 2018, 18(2), 509; https://doi.org/10.3390/s18020509 - 8 Feb 2018

Cited by 37 | Viewed by 8612

Abstract

Tailored routing and navigation services utilized by wheelchair users require certain information about sidewalk geometries and their attributes to execute efficiently. Except some minor regions/cities, such detailed information is not present in current versions of crowdsourced mapping databases including OpenStreetMap. CAP4Access European project [...] Read more.

Tailored routing and navigation services utilized by wheelchair users require certain information about sidewalk geometries and their attributes to execute efficiently. Except some minor regions/cities, such detailed information is not present in current versions of crowdsourced mapping databases including OpenStreetMap. CAP4Access European project aimed to use (and enrich) OpenStreetMap for making it fit to the purpose of wheelchair routing. In this respect, this study presents a modified methodology based on data mining techniques for constructing sidewalk geometries using multiple GPS traces collected by wheelchair users during an urban travel experiment. The derived sidewalk geometries can be used to enrich OpenStreetMap to support wheelchair routing. The proposed method was applied to a case study in Heidelberg, Germany. The constructed sidewalk geometries were compared to an official reference dataset (“ground truth dataset”). The case study shows that the constructed sidewalk network overlays with 96% of the official reference dataset. Furthermore, in terms of positional accuracy, a low Root Mean Square Error (RMSE) value (0.93 m) is achieved. The article presents our discussion on the results as well as the conclusion and future research directions. Full article

(This article belongs to the Special Issue Crowd-Sensing and Remote Sensing Technologies for Smart Cities)

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32 pages, 14640 KiB

Open AccessArticle

Ionizing Radiation Measurement Solution in a Hospital Environment

by Antonio-Javier Garcia-Sanchez^1,*, Enrique Angel Garcia Angosto², Pedro Antonio Moreno Riquelme¹, Alfredo Serna Berna³ and David Ramos-Amores³

¹ Department of Information and Communication Technologies, Universidad Politécnica de Cartagena (UPCT), Campus Muralla del Mar, E-30202 Cartagena, Spain

² Services, General Electric Healthcare España S.L.U., 28023 Madrid, Spain

³ Department of Radiophysics, Hospital General Universitario Santa Lucía, C/Mezquita, s/n, Paraje Los Arcos, E-30202 Cartagena, Spain

Sensors 2018, 18(2), 510; https://doi.org/10.3390/s18020510 - 8 Feb 2018

Cited by 16 | Viewed by 8495

Abstract

Ionizing radiation is one of the main risks affecting healthcare workers and patients worldwide. Special attention has to be paid to medical staff in the vicinity of radiological equipment or patients undergoing radioisotope procedures. To measure radiation values, traditional area meters are strategically [...] Read more.

Ionizing radiation is one of the main risks affecting healthcare workers and patients worldwide. Special attention has to be paid to medical staff in the vicinity of radiological equipment or patients undergoing radioisotope procedures. To measure radiation values, traditional area meters are strategically placed in hospitals and personal dosimeters are worn by workers. However, important drawbacks inherent to these systems in terms of cost, detection precision, real time data processing, flexibility, and so on, have been detected and carefully detailed. To overcome these inconveniences, a low cost, open-source, portable radiation measurement system is proposed. The goal is to deploy devices integrating a commercial Geiger-Muller (GM) detector to capture radiation doses in real time and to wirelessly dispatch them to a remote database where the radiation values are stored. Medical staff will be able to check the accumulated doses first hand, as well as other statistics related to radiation by means of a smartphone application. Finally, the device is certified by an accredited calibration center, to later validate the entire system in a hospital environment. Full article

(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Spain 2017)

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17 pages, 948 KiB

Open AccessArticle

Energy Efficient Data Transmission for Sensors with Wireless Charging

by Xiaolin Fang^1,*

, Junzhou Luo¹, Weiwei Wu¹ and Hong Gao²

¹ School of Computer Science and Engineering, Southeast University, Nanjing 211189, China

² School of Computer Science and Technology, Harbin Institute of Technology, Harbin 150001, China

Sensors 2018, 18(2), 511; https://doi.org/10.3390/s18020511 - 8 Feb 2018

Cited by 4 | Viewed by 3670

Abstract

This paper studies the problem of maximizing the energy utilization for data transmission in sensors with periodical wireless charging process while taking into account the thermal effect. Two classes of problems are analyzed: one is the case that wireless charging can process for [...] Read more.

This paper studies the problem of maximizing the energy utilization for data transmission in sensors with periodical wireless charging process while taking into account the thermal effect. Two classes of problems are analyzed: one is the case that wireless charging can process for only a limited period of time, and the other is the case that wireless charging can process for a long enough time. Algorithms are proposed to solve the problems and analysis of these algorithms are also provided. For the first problem, three subproblems are studied, and, for the general problem, we give an algorithm that can derive a performance bound of

(1 - \frac{1}{2 m}) (O P T - E)

compared to an optimal solution. In addition, for the second problem, we provide an algorithm with

\frac{2 m}{2 m - 1} O P T + 1

performance bound for the general problem. Simulations confirm the analysis of the algorithms. Full article

(This article belongs to the Collection Smart Communication Protocols and Algorithms for Sensor Networks)

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22 pages, 2367 KiB

Open AccessArticle

A Dynamic Approach to Rebalancing Bike-Sharing Systems

by Federico Chiariotti¹

, Chiara Pielli¹

, Andrea Zanella^1,2,*

and Michele Zorzi^1,2

¹ Department of Information Engineering, University of Padova, 35131 Padova PD, Italy

² Human Inspired Technologies (HIT) Research Center, University of Padova, 35131 Padova PD, Italy

Sensors 2018, 18(2), 512; https://doi.org/10.3390/s18020512 - 8 Feb 2018

Cited by 114 | Viewed by 10512

Abstract

Bike-sharing services are flourishing in Smart Cities worldwide. They provide a low-cost and environment-friendly transportation alternative and help reduce traffic congestion. However, these new services are still under development, and several challenges need to be solved. A major problem is the management of [...] Read more.

Bike-sharing services are flourishing in Smart Cities worldwide. They provide a low-cost and environment-friendly transportation alternative and help reduce traffic congestion. However, these new services are still under development, and several challenges need to be solved. A major problem is the management of rebalancing trucks in order to ensure that bikes and stalls in the docking stations are always available when needed, despite the fluctuations in the service demand. In this work, we propose a dynamic rebalancing strategy that exploits historical data to predict the network conditions and promptly act in case of necessity. We use Birth-Death Processes to model the stations’ occupancy and decide when to redistribute bikes, and graph theory to select the rebalancing path and the stations involved. We validate the proposed framework on the data provided by New York City’s bike-sharing system. The numerical simulations show that a dynamic strategy able to adapt to the fluctuating nature of the network outperforms rebalancing schemes based on a static schedule. Full article

(This article belongs to the Special Issue The Architectures, Systems, and Applications of Internet of Things for Smart Cities)

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9 pages, 2745 KiB

Open AccessArticle

Nuclear Radiation Degradation Study on HD Camera Based on CMOS Image Sensor at Different Dose Rates

by Congzheng Wang^1,2,3,*, Song Hu¹, Chunming Gao² and Chang Feng¹

¹ Institute of Optics and Electronics, Chinese Academy of Sciences, No. 1 Guangdian Avenue Xihang Port, Shuangliu, Chengdu 610209, China

² School of Optoelectronic Information, University of Electronic Science and Technology of China, No. 4, Block 2, North Jianshe Road, Chengdu 610054, China

³ University of Chinese Academy of Sciences, No. 19, Yuquan Road, Shijingshan District, Beijing 100049, China

Sensors 2018, 18(2), 514; https://doi.org/10.3390/s18020514 - 8 Feb 2018

Cited by 23 | Viewed by 7288

Abstract

In this work, we irradiated a high-definition (HD) industrial camera based on a commercial-off-the-shelf (COTS) CMOS image sensor (CIS) with Cobalt-60 gamma-rays. All components of the camera under test were fabricated without radiation hardening, except for the lens. The irradiation experiments of the [...] Read more.

In this work, we irradiated a high-definition (HD) industrial camera based on a commercial-off-the-shelf (COTS) CMOS image sensor (CIS) with Cobalt-60 gamma-rays. All components of the camera under test were fabricated without radiation hardening, except for the lens. The irradiation experiments of the HD camera under biased conditions were carried out at 1.0, 10.0, 20.0, 50.0 and 100.0 Gy/h. During the experiment, we found that the tested camera showed a remarkable degradation after irradiation and differed in the dose rates. With the increase of dose rate, the same target images become brighter. Under the same dose rate, the radiation effect in bright area is lower than that in dark area. Under different dose rates, the higher the dose rate is, the worse the radiation effect will be in both bright and dark areas. And the standard deviations of bright and dark areas become greater. Furthermore, through the progressive degradation analysis of the captured image, experimental results demonstrate that the attenuation of signal to noise ratio (SNR) versus radiation time is not obvious at the same dose rate, and the degradation is more and more serious with increasing dose rate. Additionally, the decrease rate of SNR at 20.0, 50.0 and 100.0 Gy/h is far greater than that at 1.0 and 10.0 Gy/h. Even so, we confirm that the HD industrial camera is still working at 10.0 Gy/h during the 8 h of measurements, with a moderate decrease of the SNR (5 dB). The work is valuable and can provide suggestion for camera users in the radiation field. Full article

(This article belongs to the Special Issue Image Sensors)

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16 pages, 2862 KiB

Open AccessArticle

Mutual-Information-Based Incremental Relaying Communications for Wireless Biomedical Implant Systems

by Yangzhe Liao^1,2, Mark S. Leeson³

, Qing Cai^1,*, Qingsong Ai^1,2

and Quan Liu^1,2

¹ School of Information Engineering, Wuhan University of Technology, Wuhan 430070, China

² Key Laboratory of Fiber Optic Sensing Technology and Information Processing, Wuhan University of Technology, Ministry of Education, Wuhan 430070, China

³ School of Engineering, University of Warwick, Coventry CV4 7AL, UK

Sensors 2018, 18(2), 515; https://doi.org/10.3390/s18020515 - 8 Feb 2018

Cited by 21 | Viewed by 5590

Abstract

Network lifetime maximization of wireless biomedical implant systems is one of the major research challenges of wireless body area networks (WBANs). In this paper, a mutual information (MI)-based incremental relaying communication protocol is presented where several on-body relay nodes and one coordinator are [...] Read more.

Network lifetime maximization of wireless biomedical implant systems is one of the major research challenges of wireless body area networks (WBANs). In this paper, a mutual information (MI)-based incremental relaying communication protocol is presented where several on-body relay nodes and one coordinator are attached to the clothes of a patient. Firstly, a comprehensive analysis of a system model is investigated in terms of channel path loss, energy consumption, and the outage probability from the network perspective. Secondly, only when the MI value becomes smaller than the predetermined threshold is data transmission allowed. The communication path selection can be either from the implanted sensor to the on-body relay then forwards to the coordinator or from the implanted sensor to the coordinator directly, depending on the communication distance. Moreover, mathematical models of quality of service (QoS) metrics are derived along with the related subjective functions. The results show that the MI-based incremental relaying technique achieves better performance in comparison to our previous proposed protocol techniques regarding several selected performance metrics. The outcome of this paper can be applied to intra-body continuous physiological signal monitoring, artificial biofeedback-oriented WBANs, and telemedicine system design. Full article

(This article belongs to the Special Issue Dependable Monitoring in Wireless Sensor Networks)

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16 pages, 2447 KiB

Open AccessArticle

Non-Orthogonal Multiple Access for Ubiquitous Wireless Sensor Networks

by Asim Anwar¹, Boon-Chong Seet^1,*

and Zhiguo Ding²

¹ Department of Electrical and Electronic Engineering, Auckland University of Technology, Auckland 1010, New Zealand

² School of Computing and Communications, Lancaster University, Lancaster LA1 4YW, UK

Sensors 2018, 18(2), 516; https://doi.org/10.3390/s18020516 - 8 Feb 2018

Cited by 19 | Viewed by 4625

Abstract

Ubiquitous wireless sensor networks (UWSNs) have become a critical technology for enabling smart cities and other ubiquitous monitoring applications. Their deployment, however, can be seriously hampered by the spectrum available to the sheer number of sensors for communication. To support the communication needs [...] Read more.

Ubiquitous wireless sensor networks (UWSNs) have become a critical technology for enabling smart cities and other ubiquitous monitoring applications. Their deployment, however, can be seriously hampered by the spectrum available to the sheer number of sensors for communication. To support the communication needs of UWSNs without requiring more spectrum resources, the power-domain non-orthogonal multiple access (NOMA) technique originally proposed for 5th Generation (5G) cellular networks is investigated for UWSNs for the first time in this paper. However, unlike 5G networks that operate in the licensed spectrum, UWSNs mostly operate in unlicensed spectrum where sensors also experience cross-technology interferences from other devices sharing the same spectrum. In this paper, we model the interferences from various sources at the sensors using stochastic geometry framework. To evaluate the performance, we derive a theorem and present new closed form expression for the outage probability of the sensors in a downlink scenario under interference limited environment. In addition, diversity analysis for the ordered NOMA users is performed. Based on the derived outage probability, we evaluate the average link throughput and energy consumption efficiency of NOMA against conventional orthogonal multiple access (OMA) technique in UWSNs. Further, the required computational complexity for the NOMA users is presented. Full article

(This article belongs to the Special Issue Non-Orthogonal Multi-User Transmissions for 5G Networks)

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12 pages, 1719 KiB

Open AccessArticle

Tuning the Stiffness Balance Using Characteristic Frequencies as a Criterion for a Superconducting Gravity Gradiometer

by Xikai Liu, Dong Ma, Liang Chen and Xiangdong Liu^*

MOE Key Laboratory of Fundamental Physical Quantities Measurement & Hubei Key Laboratory of Gravitation and Quantum Physics, School of Physics, Huazhong University of Science and Technology, Wuhan 430074, China

Sensors 2018, 18(2), 517; https://doi.org/10.3390/s18020517 - 8 Feb 2018

Cited by 8 | Viewed by 3748

Abstract

Tuning the stiffness balance is crucial to full-band common-mode rejection for a superconducting gravity gradiometer (SGG). A reliable method to do so has been proposed and experimentally tested. In the tuning scheme, the frequency response functions of the displacement of individual test mass [...] Read more.

Tuning the stiffness balance is crucial to full-band common-mode rejection for a superconducting gravity gradiometer (SGG). A reliable method to do so has been proposed and experimentally tested. In the tuning scheme, the frequency response functions of the displacement of individual test mass upon common-mode accelerations were measured and thus determined a characteristic frequency for each test mass. A reduced difference in characteristic frequencies between the two test masses was utilized as the criterion for an effective tuning. Since the measurement of the characteristic frequencies does not depend on the scale factors of displacement detection, stiffness tuning can be done independently. We have tested this new method on a single-component SGG and obtained a reduction of two orders of magnitude in stiffness mismatch. Full article

(This article belongs to the Section Physical Sensors)

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10 pages, 1610 KiB

Open AccessArticle

Infrared Thermography as a Non-Invasive Tool to Explore Differences in the Musculoskeletal System of Children with Hemophilia Compared to an Age-Matched Healthy Group

by Axel Seuser^1,†, Karin Kurnik² and Anne-Katrin Mahlein^3,*,†

¹ Practice for Rehabilitation, Prevention and Orthopedics, 53225 Bonn, Germany

² Dr. von Hauner Children’s Hospital, University of Munich, 80337 Munich, Germany

³ Institute of Sugar Beet Research, 37079 Göttingen, Germany

^† These authors contributed equally to this work.

Sensors 2018, 18(2), 518; https://doi.org/10.3390/s18020518 - 8 Feb 2018

Cited by 23 | Viewed by 7821

Abstract

Recurrent joint bleeds and silent bleeds are the most common clinical feature in patients with hemophilia. Every bleed causes an immediate inflammatory response and is the leading cause of chronic crippling arthropathy. With the help of infrared thermography we wanted to detect early [...] Read more.

Recurrent joint bleeds and silent bleeds are the most common clinical feature in patients with hemophilia. Every bleed causes an immediate inflammatory response and is the leading cause of chronic crippling arthropathy. With the help of infrared thermography we wanted to detect early differences between a group of clinical non-symptomatic children with hemophilia (CWH) with no history of clinically detected joint bleeds and a healthy age-matched group of children. This could help to discover early inflammation and help implement early treatment and preventative strategies. It could be demonstrated that infrared thermography is sensitive enough to detect more signs of early inflammatory response in the CWH than in healthy children. It seems to detect more side differences in temperature than clinical examination of silent symptoms detects tender points. Silent symptoms/tender points seem to be combined with early local inflammation. Using such a non-invasive and sensor-based early detection, prevention of overloading and bleeding might be achieved. Full article

(This article belongs to the Special Issue Sensors for Health Monitoring and Disease Diagnosis)

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17 pages, 4528 KiB

Open AccessArticle

Determination of Odour Interactions in Gaseous Mixtures Using Electronic Nose Methods with Artificial Neural Networks

by Bartosz Szulczyński^1,*, Krzysztof Armiński²

, Jacek Namieśnik³

and Jacek Gębicki^1,*

¹ Department of Chemical and Process Engineering, Faculty of Chemistry, Gdańsk University of Technology, 11/12 G. Narutowicza Str., 80-233 Gdańsk, Poland

² Department of Control Engineering, Faculty of Electrical and Control Engineering, Gdańsk University of Technology, 11/12 G. Narutowicza Str., 80-233 Gdańsk, Poland

³ Department of Analytical Chemistry, Faculty of Chemistry, Gdańsk University of Technology, 11/12 G. Narutowicza Str., 80-233 Gdańsk, Poland

Sensors 2018, 18(2), 519; https://doi.org/10.3390/s18020519 - 8 Feb 2018

Cited by 54 | Viewed by 5923

Abstract

This paper presents application of an electronic nose prototype comprised of eight sensors, five TGS-type sensors, two electrochemical sensors and one PID-type sensor, to identify odour interaction phenomenon in two-, three-, four- and five-component odorous mixtures. Typical chemical compounds, such as toluene, acetone, [...] Read more.

This paper presents application of an electronic nose prototype comprised of eight sensors, five TGS-type sensors, two electrochemical sensors and one PID-type sensor, to identify odour interaction phenomenon in two-, three-, four- and five-component odorous mixtures. Typical chemical compounds, such as toluene, acetone, triethylamine, α-pinene and n-butanol, present near municipal landfills and sewage treatment plants were subjected to investigation. Evaluation of predicted odour intensity and hedonic tone was performed with selected artificial neural network structures with the activation functions tanh and Leaky rectified linear units (Leaky ReLUs) with the parameter

a = 0.03

. Correctness of identification of odour interactions in the odorous mixtures was determined based on the results obtained with the electronic nose instrument and non-linear data analysis. This value (average) was at the level of 88% in the case of odour intensity, whereas the average was at the level of 74% in the case of hedonic tone. In both cases, correctness of identification depended on the number of components present in the odorous mixture. Full article

(This article belongs to the Special Issue Signal and Information Processing in Chemical Sensing)

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12 pages, 1740 KiB

Open AccessArticle

An Improved Adaptive Received Beamforming for Nested Frequency Offset and Nested Array FDA-MIMO Radar

by Sibei Cheng¹, Qingjun Zhang^2,*

, Mingming Bian² and Xinhong Hao¹

¹ National Key Laboratory of Mechatronic Engineering and Control, Beijing Institute of Technology, Beijing 100081, China

² Beijing Institute of Spacecraft System Engineering, Beijing 100086, China

Sensors 2018, 18(2), 520; https://doi.org/10.3390/s18020520 - 8 Feb 2018

Cited by 10 | Viewed by 4515

Abstract

For the conventional FDA-MIMO (frequency diversity array multiple-input-multiple-output) Radar with uniform frequency offset and uniform linear array, the DOFs (degrees of freedom) of the adaptive beamformer are limited by the number of elements. A better performance—for example, a better suppression for strong interferences [...] Read more.

For the conventional FDA-MIMO (frequency diversity array multiple-input-multiple-output) Radar with uniform frequency offset and uniform linear array, the DOFs (degrees of freedom) of the adaptive beamformer are limited by the number of elements. A better performance—for example, a better suppression for strong interferences and a more desirable trade-off between the main lobe and side lobe—can be achieved with a greater number of DOFs. In order to obtain larger DOFs, this paper researches the signal model of the FDA-MIMO Radar with nested frequency offset and nested array, then proposes an improved adaptive beamforming method that uses the augmented matrix instead of the covariance matrix to calculate the optimum weight vectors and can be used to improve the output performances of FDA-MIMO Radar with the same element number or reduce the element number while maintain the approximate output performances such as the received beampattern, the main lobe width, side lobe depths and the output SINR (signal-to-interference-noise ratio). The effectiveness of the proposed scheme is verified by simulations. Full article

(This article belongs to the Special Issue First Experiences with Chinese Gaofen-3 SAR Sensor)

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11 pages, 10378 KiB

Open AccessArticle

Silver Eco-Solvent Ink for Reactive Printing of Polychromatic SERS and SPR Substrates

by Mavlavi Dustov¹, Diana I. Golovina¹

, Alexander Yu. Polyakov¹

, Anastasia E. Goldt^1,2, Andrei A. Eliseev¹

, Efim A. Kolesnikov¹

, Irina V. Sukhorukova³

, Dmitry V. Shtansky³

, Wolfgang Grünert⁴ and Anastasia V. Grigorieva^1,*

¹ Department of Materials Science and Department of Chemistry, Lomonosov Moscow State University, Leninskie gory 1, bld. 73, 119991 Moscow, Russia

² Skolkovo Institute of Science and Technology, Skolkovo Innovation Center, bld. 3, 143026 Moscow, Russia

³ National University of Science and Technology MISiS, Leninsky prospect 4, 119049 Moscow, Russia

⁴ Department of Chemistry and Biochemistry, Ruhr-Universität Bochum, Universitätsstraße 150, Bochum 44801, Germany

Sensors 2018, 18(2), 521; https://doi.org/10.3390/s18020521 - 9 Feb 2018

Cited by 10 | Viewed by 5371

Abstract

A new reactive ink based on a silver citrate complex is proposed for a photochemical route to surface-enhanced Raman spectroscopy active substrates with controllable extinction spectra. The drop-cast test of the ink reveals homogeneous nucleation of silver and colloid particle growth originating directly [...] Read more.

A new reactive ink based on a silver citrate complex is proposed for a photochemical route to surface-enhanced Raman spectroscopy active substrates with controllable extinction spectra. The drop-cast test of the ink reveals homogeneous nucleation of silver and colloid particle growth originating directly from photochemical in situ reduction in droplets, while the following evaporation of the deposited ink produces small nano- and micron-size particles. The prepared nanostructures and substrates were accurately characterized by electron microscopy methods and optical extinction spectroscopy. Varying the duration of UV irradiation allows tuning the morphology of individual silver nanoparticles forming hierarchical ring structures with numerous “hot spots” for most efficient Raman enhancement. Raman measurements of probe molecules of rhodamine 6G and methylene blue reached the largest signal enhancement of 10⁶ by the resonance effects. Full article

(This article belongs to the Special Issue Spectroscopy Based Sensors)

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16 pages, 4318 KiB

Open AccessArticle

OSCANN: Technical Characterization of a Novel Gaze Tracking Analyzer

by Erik Hernández^1,†, Santiago Hernández^1,†, David Molina^1,†, Rafael Acebrón^1,† and Cecilia E. García Cena^2,*,†

¹ Aura Innovative Robotics, 28045 Madrid, Spain

² Centre for Robotics and Automation, UPM-CSIC, José Gutiérrez Abascal Street, 28006 Madrid, Spain

^† These authors contributed equally to this work.

Sensors 2018, 18(2), 522; https://doi.org/10.3390/s18020522 - 9 Feb 2018

Cited by 15 | Viewed by 5964

Abstract

Eye-movement analysis has grown exponentially in recent decades. The reason is that abnormalities in oculomotor movements are usually symptoms of injuries in the nervous system. This paper presents a novel regulated solution named OSCANN. OSCANN aims at providing an innovative tool for the [...] Read more.

Eye-movement analysis has grown exponentially in recent decades. The reason is that abnormalities in oculomotor movements are usually symptoms of injuries in the nervous system. This paper presents a novel regulated solution named OSCANN. OSCANN aims at providing an innovative tool for the control, management and visualization of oculomotor neurological examinations. This solution utilizes an eye-tracker sensor based on video electro-oculography (VOG) technology to capture eye movements and store them in video files. Such a sensor can store images at a rate of 100 frames per second. A characterization study was performed using twenty-two volunteers (13 male, 9 female, ages 22–45 years, mean 29.3 years, SD = 6.7) to assess the accuracy and precision specifications of OSCANN during oculomotor movement analysis. The accuracy was evaluated based on the offset, whereas precision was estimated with Root Means Square (RMS). Such a study reported values lower than 0.4

^{\circ}

and 0.03

^{\circ}

of accuracy and precision, respectively. These results suggest that OSCANN can be considered as a powerful tool to measure oculomotor movement alterations involved in some neurological disease progression. Full article

(This article belongs to the Section Physical Sensors)

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16 pages, 2304 KiB

Open AccessArticle

Spectral Analysis and Sensitive Waveband Determination Based on Nitrogen Detection of Different Soil Types Using Near Infrared Sensors

by Shupei Xiao^1,2, Yong He^1,2,*

, Tao Dong^1,2 and Pengcheng Nie^1,2,3

¹ College of Biosystems Engineering and Food Science, Zhejiang University, Hangzhou 310058, China

² Key Laboratory of Spectroscopy Sensing, Ministry of Agriculture, Zhejiang University, Hangzhou 310058, China

³ State Key Laboratory of Modern Optical Instrumentation, Zhejiang University, Hangzhou 310058, China

Sensors 2018, 18(2), 523; https://doi.org/10.3390/s18020523 - 9 Feb 2018

Cited by 31 | Viewed by 5172

Abstract

Compared with the chemical analytical technique, the soil nitrogen acquisition method based on near infrared (NIR) sensors shows significant advantages, being rapid, nondestructive, and convenient. Providing an accurate grasp of different soil types, sensitive wavebands could enhance the nitrogen estimation efficiency to a [...] Read more.

Compared with the chemical analytical technique, the soil nitrogen acquisition method based on near infrared (NIR) sensors shows significant advantages, being rapid, nondestructive, and convenient. Providing an accurate grasp of different soil types, sensitive wavebands could enhance the nitrogen estimation efficiency to a large extent. In this paper, loess, calcium soil, black soil, and red soil were used as experimental samples. The prediction models between soil nitrogen and NIR spectral reflectance were established based on three chemometric methods, that is, partial least squares (PLS), backward interval partial least squares (BIPLS), and back propagation neural network (BPNN). In addition, the sensitive wavebands of four kinds of soils were selected by competitive adaptive reweighted sampling (CARS) and BIPLS. The predictive ability was assessed by the coefficient of determination R² and the root mean square error (RMSE). As a result, loess (

0.93 < R_{p}^{2} < 0.95, 0.066 g / kg < {RMSE}_{p} < 0.075 g / kg

) and calcium soil (

0.95 < R_{p}^{2} < 0.96, 0.080 g / kg < {RMSE}_{p} < 0.102 g / kg

) achieved a high prediction accuracy regardless of which algorithm was used, while black soil (

0.79 < R_{p}^{2} < 0.86, 0.232 g / kg < {RMSE}_{p} < 0.325 g / kg

) obtained a relatively lower prediction accuracy caused by the interference of high humus content and strong absorption. The prediction accuracy of red soil (

0.86 < R_{p}^{2} < 0.87, 0.231 g / kg < {RMSE}_{p} < 0.236 g / kg

) was similar to black soil, partly due to the high content of iron–aluminum oxide. Compared with PLS and BPNN, BIPLS performed well in removing noise and enhancing the prediction effect. In addition, the determined sensitive wavebands were 1152 nm–1162 nm and 1296 nm–1309 nm (loess), 1036 nm–1055 nm and 1129 nm–1156 nm (calcium soil), 1055 nm, 1281 nm, 1414 nm–1428 nm and 1472 nm–1493 nm (black soil), 1250 nm, 1480 nm and 1680 nm (red soil). It is of great value to investigate the differences among the NIR spectral characteristics of different soil types and determine sensitive wavebands for the more efficient and portable NIR sensors in practical application. Full article

(This article belongs to the Section Physical Sensors)

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10 pages, 3661 KiB

Open AccessArticle

Fast Focal Point Correction in Prism-Coupled Total Internal Reflection Scanning Imager Using an Electronically Tunable Lens

by Chenggang Zhu¹, Bilin Ge¹, Ru Chen¹, Xiangdong Zhu², Lan Mi¹

, Jiong Ma¹

, Xu Wang³, Fengyun Zheng⁴ and Yiyan Fei^1,*

¹ Department of Optical Science and Engineering, Shanghai Engineering Research Center of Ultra-Precision Optical Manufacturing, Key Laboratory of Micro and Nano Photonic Structures (Ministry of Education), Fudan University, Shanghai 200433, China

² Department of Physics, University of California, Davis, CA 95616, USA

³ Department of Fundamental Courses, Wuxi Institute of Technology, Wuxi 214121, China

⁴ Institutes of Biomedical Science, Fudan University, Shanghai 200032, China

Sensors 2018, 18(2), 524; https://doi.org/10.3390/s18020524 - 9 Feb 2018

Cited by 9 | Viewed by 4836

Abstract

Total internal reflection (TIR) is useful for interrogating physical and chemical processes that occur at the interface between two transparent media. Yet prism-coupled TIR imaging microscopes suffer from limited sensing areas due to the fact that the interface (the object plane) is not [...] Read more.

Total internal reflection (TIR) is useful for interrogating physical and chemical processes that occur at the interface between two transparent media. Yet prism-coupled TIR imaging microscopes suffer from limited sensing areas due to the fact that the interface (the object plane) is not perpendicular to the optical axis of the microscope. In this paper, we show that an electrically tunable lens can be used to rapidly and reproducibly correct the focal length of an oblique-incidence scanning microscope (OI-RD) in a prism-coupled TIR geometry. We demonstrate the performance of such a correction by acquiring an image of a protein microarray over a scan area of 4 cm² with an effective resolution of less than 20 microns. The electronic focal length tuning eliminates the mechanical movement of the illumination lens in the scanning microscope and in turn the noise and background drift associated with the motion. Full article

(This article belongs to the Special Issue Biosensing for Interfacial Science)

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14 pages, 4833 KiB

Open AccessCommunication

Parametric Evaluation of Errors Using Isolated Dots for Movement Measurement by Image Cross-Correlation

by Belen Ferrer^1,*

and David Mas²

¹ Civil Engineering department, University of Alicante, Carretera San Vicente del Raspeig, s/n, 03690 Sant Vicent del Raspeig, Spain

² Institute of Physics Applied to Sciences and Technologies, University of Alicante, Carretera San Vicente del Raspeig, s/n, 03690 San Vicente del Raspeig, Spain

Sensors 2018, 18(2), 525; https://doi.org/10.3390/s18020525 - 9 Feb 2018

Cited by 7 | Viewed by 3506

Abstract

Digital Image Correlation (DIC) is a common tool for assessing the movement of objects in a scene. Among others, one of the most popular techniques consists of tracking a dotted texture imitating speckle patterns. In this work, we analyzed the individual dots that [...] Read more.

Digital Image Correlation (DIC) is a common tool for assessing the movement of objects in a scene. Among others, one of the most popular techniques consists of tracking a dotted texture imitating speckle patterns. In this work, we analyzed the individual dots that form this pattern in order to propose an optimum size, shape, and dynamic range that allows minimizing the tracking error. Tracking was accomplished by using normalized cross-correlation with peak interpolation in order to obtain subpixel accuracy. For the models here used, we show that dot radii of 30–40 px with 150 gray levels are enough to obtain an accurate subpixel tracking resolution. Also, we show that 0.002 px is the performance limit of this technique, being this limit in accordance with the experimentally achievable subpixel limit. Full article

(This article belongs to the Special Issue Sensor Signal and Information Processing)

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19 pages, 10796 KiB

Open AccessArticle

Monitoring of Soft Deposition Layers in Liquid-Filled Tubes with Guided Acoustic Waves Excited by Clamp-on Transducers

by Sabrina Tietze^*

, Ferdinand Singer, Sandra Lasota, Sandra Ebert, Johannes Landskron, Katrin Schwuchow, Klaus Stefan Drese

and Gerhard Lindner

Institute of Sensor and Actuator Technology, Coburg University of Applied Sciences and Arts, Am Hofbräuhaus 1b, 96450 Coburg, Germany

Sensors 2018, 18(2), 526; https://doi.org/10.3390/s18020526 - 9 Feb 2018

Cited by 8 | Viewed by 5169

Abstract

The monitoring of liquid-filled tubes with respect to the formation of soft deposition layers such as biofilms on the inner walls calls for non-invasive and long-term stable sensors, which can be attached to existing pipe structures. For this task a method is developed, [...] Read more.

The monitoring of liquid-filled tubes with respect to the formation of soft deposition layers such as biofilms on the inner walls calls for non-invasive and long-term stable sensors, which can be attached to existing pipe structures. For this task a method is developed, which uses an ultrasonic clamp-on device. This method is based on the impact of such deposition layers on the propagation of circumferential guided waves on the pipe wall. Such waves are partly converted into longitudinal compressional waves in the liquid, which are back-converted to guided waves in a circular cross section of the pipe. Validating this approach, laboratory experiments with gelatin deposition layers on steel tubes exhibited a distinguishable sensitivity of both wave branches with respect to the thickness of such layers. This allows the monitoring of the layer growth. Full article

(This article belongs to the Section Physical Sensors)

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25 pages, 5786 KiB

Open AccessArticle

Multi-Complementary Model for Long-Term Tracking

by Deng Zhang^*, Junchang Zhang and Chenyang Xia

School of Electronics and Information, Northwestern Polytechnical University, Xi’an 710072, China

Sensors 2018, 18(2), 527; https://doi.org/10.3390/s18020527 - 9 Feb 2018

Cited by 5 | Viewed by 3887

Abstract

In recent years, video target tracking algorithms have been widely used. However, many tracking algorithms do not achieve satisfactory performance, especially when dealing with problems such as object occlusions, background clutters, motion blur, low illumination color images, and sudden illumination changes in real [...] Read more.

In recent years, video target tracking algorithms have been widely used. However, many tracking algorithms do not achieve satisfactory performance, especially when dealing with problems such as object occlusions, background clutters, motion blur, low illumination color images, and sudden illumination changes in real scenes. In this paper, we incorporate an object model based on contour information into a Staple tracker that combines the correlation filter model and color model to greatly improve the tracking robustness. Since each model is responsible for tracking specific features, the three complementary models combine for more robust tracking. In addition, we propose an efficient object detection model with contour and color histogram features, which has good detection performance and better detection efficiency compared to the traditional target detection algorithm. Finally, we optimize the traditional scale calculation, which greatly improves the tracking execution speed. We evaluate our tracker on the Object Tracking Benchmarks 2013 (OTB-13) and Object Tracking Benchmarks 2015 (OTB-15) benchmark datasets. With the OTB-13 benchmark datasets, our algorithm is improved by 4.8%, 9.6%, and 10.9% on the success plots of OPE, TRE and SRE, respectively, in contrast to another classic LCT (Long-term Correlation Tracking) algorithm. On the OTB-15 benchmark datasets, when compared with the LCT algorithm, our algorithm achieves 10.4%, 12.5%, and 16.1% improvement on the success plots of OPE, TRE, and SRE, respectively. At the same time, it needs to be emphasized that, due to the high computational efficiency of the color model and the object detection model using efficient data structures, and the speed advantage of the correlation filters, our tracking algorithm could still achieve good tracking speed. Full article

(This article belongs to the Special Issue Sensor Signal and Information Processing)

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19 pages, 2990 KiB

Open AccessArticle

Hybrid Beamforming for Reduction of Inter-Beam Interference in Millimeter-Wave Cellular Systems

by Sung Joon Maeng, Su Ho Park and Yong Soo Cho^*

School of Electrical and Electronics Engineering, Chung-Ang University, Seoul 06974, Korea

Sensors 2018, 18(2), 528; https://doi.org/10.3390/s18020528 - 9 Feb 2018

Cited by 7 | Viewed by 4919

Abstract

In millimeter-wave (mm-wave) cellular systems, beamforming antennas are necessary at both the base station (BS) and mobile station (MS) to compensate for high attenuation in mm-wave frequency bands and to extend the transmission range. The beamforming antennas also allow [...] Read more.

In millimeter-wave (mm-wave) cellular systems, beamforming antennas are necessary at both the base station (BS) and mobile station (MS) to compensate for high attenuation in mm-wave frequency bands and to extend the transmission range. The beamforming antennas also allow each BS to serve a number of MSs simultaneously, providing a substantial gain in system capacity. In space-division multiple access (SDMA) systems, the challenge is the inter-beam interference (IBI) caused by adjacent beams that are formed by the BS in the same cell and BSs in neighboring cells. The beams that are formed toward MSs in each cell may generate significant interference to MSs in neighboring cells, especially for MSs at the cell boundary. In this paper, we propose four different digital precoding techniques (Type-1, Type-2, Type-3, and Type-4) to reduce IBI in mm-wave cellular systems with a hybrid beamformer. Simulation results show that the proposed techniques can reduce the IBI in mm-wave cellular systems effectively, compared with a single-cell multiuser case. Full article

(This article belongs to the Section Sensor Networks)

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12 pages, 3796 KiB

Open AccessArticle

Laser-Based Monitoring of CH₄, CO₂, NH₃, and H₂S in Animal Farming—System Characterization and Initial Demonstration

by Dorota Stachowiak¹

, Piotr Jaworski¹, Paweł Krzaczek²

, Grzegorz Maj² and Michał Nikodem^1,3,*

¹ Laser Sensing Laboratory, Wroclaw Research Centre EIT+, Stabłowicka 147, 54-066 Wrocław, Poland

² Department of Power Engineering and Transportation, Faculty of Production Engineering, University of Life Sciences in Lublin, Głęboka 28, 20-612 Lublin, Poland

³ Department of Optics and Photonics, Faculty of Fundamental Problems of Technology, Wrocław University of Science and Technology, Wybrzeże Wyspianskiego 27, 50-370 Wrocław, Poland

Sensors 2018, 18(2), 529; https://doi.org/10.3390/s18020529 - 9 Feb 2018

Cited by 25 | Viewed by 9099

Abstract

In this paper, we present a system for sequential detection of multiple gases using laser-based wavelength modulation spectroscopy (WMS) method combined with a Herriot-type multi-pass cell. Concentration of hydrogen sulfide (H₂S), methane (CH₄), carbon dioxide (CO₂), and [...] Read more.

In this paper, we present a system for sequential detection of multiple gases using laser-based wavelength modulation spectroscopy (WMS) method combined with a Herriot-type multi-pass cell. Concentration of hydrogen sulfide (H₂S), methane (CH₄), carbon dioxide (CO₂), and ammonia (NH₃) are retrieved using three distributed feedback laser diodes operating at 1574.5 nm (H₂S and CO₂), 1651 nm (CH₄), and 1531 nm (NH₃). Careful adjustment of system parameters allows for H₂S sensing at single parts-per-million by volume (ppmv) level with strongly reduced interference from adjacent CO₂ transitions even at atmospheric pressure. System characterization in laboratory conditions is presented and the results from initial tests in real-world application are demonstrated. Full article

(This article belongs to the Special Issue Spectroscopy Based Sensors)

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26 pages, 12556 KiB

Open AccessArticle

Cave Pearl Data Logger: A Flexible Arduino-Based Logging Platform for Long-Term Monitoring in Harsh Environments

by Patricia A. Beddows^1,* and Edward K. Mallon²

¹ Department of Earth & Planetary Sciences, Northwestern University, 2145 Sheridan Rd–Tech F374, Evanston, IL 60208-3130, USA

² Triple Point Design, LLC, Evanston, IL 60202-1125, USA

Sensors 2018, 18(2), 530; https://doi.org/10.3390/s18020530 - 9 Feb 2018

Cited by 92 | Viewed by 56446

Abstract

A low-cost data logging platform is presented that provides long-term operation in remote or submerged environments. Three premade “breakout boards” from the open-source Arduino ecosystem are assembled into the core of the data logger. Power optimization techniques are presented which extend the operational [...] Read more.

A low-cost data logging platform is presented that provides long-term operation in remote or submerged environments. Three premade “breakout boards” from the open-source Arduino ecosystem are assembled into the core of the data logger. Power optimization techniques are presented which extend the operational life of this module-based design to >1 year on three alkaline AA batteries. Robust underwater housings are constructed for these loggers using PVC fittings. Both the logging platform and the enclosures, are easy to build and modify without specialized tools or a significant background in electronics. This combination turns the Cave Pearl data logger into a generalized prototyping system and this design flexibility is demonstrated with two field studies recording drip rates in a cave and water flow in a flooded cave system. This paper describes a complete DIY solution, suitable for a wide range of challenging deployment conditions. Full article

(This article belongs to the Section Physical Sensors)

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11 pages, 2507 KiB

Open AccessArticle

Towards Phosphate Detection in Hydroponics Using Molecularly Imprinted Polymer Sensors

by Christopher S. Storer¹, Zachary Coldrick¹, Daniel J. Tate²

, Jack Marsden Donoghue³ and Bruce Grieve^1,*

¹ School of Electrical & Electronic Engineering, University of Manchester, Oxford Road, Manchester M13 9PL, UK

² Organic Materials Innovation Centre, School of Chemistry, University of Manchester, Manchester, M13 9PL, UK

³ School of Materials, University of Manchester, Oxford Road, Manchester M13 9PL, UK

Sensors 2018, 18(2), 531; https://doi.org/10.3390/s18020531 - 10 Feb 2018

Cited by 27 | Viewed by 6408

Abstract

An interdigitated electrode sensor was designed and microfabricated for measuring the changes in the capacitance of three phosphate selective molecularly imprinted polymer (MIP) formulations, in order to provide hydroponics users with a portable nutrient sensing tool. The MIPs investigated were synthesised using different [...] Read more.

An interdigitated electrode sensor was designed and microfabricated for measuring the changes in the capacitance of three phosphate selective molecularly imprinted polymer (MIP) formulations, in order to provide hydroponics users with a portable nutrient sensing tool. The MIPs investigated were synthesised using different combinations of the functional monomers methacrylic acid (MAA) and N-allylthiourea, against the template molecules diphenyl phosphate, triethyl phosphate, and trimethyl phosphate. A cross-interference study between phosphate, nitrate, and sulfate was carried out for the MIP materials using an inductance, capacitance, and resistance (LCR) meter. Capacitance measurements were taken by applying an alternating current (AC) with a potential difference of 1 V root mean square (RMS) at a frequency of 1 kHz. The cross-interference study demonstrated a strong binding preference to phosphate over the other nutrient salts tested for each formulation. The size of template molecule and length of the functional monomer side groups also determined that a short chain functional monomer in combination with a template containing large R-groups produced the optimal binding site conditions when synthesising a phosphate selective MIP. Full article

(This article belongs to the Special Issue Polymer-Based Sensors for Bioanalytes)

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14 pages, 6065 KiB

Open AccessArticle

Low-Cost Wireless Temperature Measurement: Design, Manufacture, and Testing of a PCB-Based Wireless Passive Temperature Sensor

by Dan Yan^1,2, Yong Yang³, Yingping Hong^1,2, Ting Liang^1,2, Zong Yao⁴, Xiaoyong Chen^1,5,* and Jijun Xiong^1,2,*

¹ Key Laboratory of Instrumentation Science & Dynamic Measurement, Ministry of Education, North University of China, Taiyuan 030051, China

² Science and Technology on Electronic Test & Measurement Laboratory, North University of China, Taiyuan 030051, China

³ Taiyuan Research Institute Co., Ltd., China Coal Technology and Engineering Group Corporation, Taiyuan 030006, China

⁴ North Automatic Control Technology Research Institute, Taiyuan 030051, China

⁵ National Demonstration Center for Experimental Chemical Engineering Comprehensive Education, North University of China, Taiyuan 030051, China

Sensors 2018, 18(2), 532; https://doi.org/10.3390/s18020532 - 10 Feb 2018

Cited by 36 | Viewed by 9546

Abstract

Low-cost wireless temperature measurement has significant value in the food industry, logistics, agriculture, portable medical equipment, intelligent wireless health monitoring, and many areas in everyday life. A wireless passive temperature sensor based on PCB (Printed Circuit Board) materials is reported in this paper. [...] Read more.

Low-cost wireless temperature measurement has significant value in the food industry, logistics, agriculture, portable medical equipment, intelligent wireless health monitoring, and many areas in everyday life. A wireless passive temperature sensor based on PCB (Printed Circuit Board) materials is reported in this paper. The advantages of the sensor include simple mechanical structure, convenient processing, low-cost, and easiness in integration. The temperature-sensitive structure of the sensor is a dielectric-loaded resonant cavity, consisting of the PCB substrate. The sensitive structure also integrates a patch antenna for the transmission of temperature signals. The temperature sensing mechanism of the sensor is the dielectric constant of the PCB substrate changes with temperature, which causes the resonant frequency variation of the resonator. Then the temperature can be measured by detecting the changes in the sensor’s working frequency. The PCB-based wireless passive temperature sensor prototype is prepared through theoretical design, parameter analysis, software simulation, and experimental testing. The high- and low-temperature sensing performance of the sensor is tested, respectively. The resonant frequency decreases from 2.434 GHz to 2.379 GHz as the temperature increases from −40 °C to 125 °C. The fitting curve proves that the experimental data have good linearity. Three repetitive tests proved that the sensor possess well repeatability. The average sensitivity is

347.45 KHz / ℃

from repetitive measurements conducted three times. This study demonstrates the feasibility of the PCB-based wireless passive sensor, which provides a low-cost temperature sensing solution for everyday life, modern agriculture, thriving intelligent health devices, and so on, and also enriches PCB product lines and applications. Full article

(This article belongs to the Special Issue Sensors and Materials for Harsh Environments)

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12 pages, 4605 KiB

Open AccessArticle

A Real-Time Wireless Sweat Rate Measurement System for Physical Activity Monitoring

by Andrew Brueck¹, Tashfin Iftekhar¹, Alicja B. Stannard², Kumar Yelamarthi¹

and Tolga Kaya^3,*

¹ School of Engineering and Technology, Central Michigan University, Mt Pleasant, MI 48859, USA

² Department of Physical Therapy and Human Movement Science, Sacred Heart University, Fairfield, CT 06825, USA

³ School of Computing, Sacred Heart University, Fairfield, CT 06825, USA

Sensors 2018, 18(2), 533; https://doi.org/10.3390/s18020533 - 10 Feb 2018

Cited by 48 | Viewed by 10417

Abstract

There has been significant research on the physiology of sweat in the past decade, with one of the main interests being the development of a real-time hydration monitor that utilizes sweat. The contents of sweat have been known for decades; sweat provides significant [...] Read more.

There has been significant research on the physiology of sweat in the past decade, with one of the main interests being the development of a real-time hydration monitor that utilizes sweat. The contents of sweat have been known for decades; sweat provides significant information on the physiological condition of the human body. However, it is important to know the sweat rate as well, as sweat rate alters the concentration of the sweat constituents, and ultimately affects the accuracy of hydration detection. Towards this goal, a calorimetric based flow-rate detection system was built and tested to determine sweat rate in real time. The proposed sweat rate monitoring system has been validated through both controlled lab experiments (syringe pump) and human trials. An Internet of Things (IoT) platform was embedded, with the sensor using a Simblee board and Raspberry Pi. The overall prototype is capable of sending sweat rate information in real time to either a smartphone or directly to the cloud. Based on a proven theoretical concept, our overall system implementation features a pioneer device that can truly measure the rate of sweat in real time, which was tested and validated on human subjects. Our realization of the real-time sweat rate watch is capable of detecting sweat rates as low as 0.15 µL/min/cm², with an average error in accuracy of 18% compared to manual sweat rate readings. Full article

(This article belongs to the Special Issue Sensors for Gait, Posture, and Health Monitoring)

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17 pages, 5982 KiB

Open AccessArticle

Achieving Crossed Strong Barrier Coverage in Wireless Sensor Network

by Ruisong Han¹

, Wei Yang^1,* and Li Zhang²

¹ School of Electronic and Information Engineering, Beijing Jiaotong University, Beijing 100044, China

² School of Electronic and Electrical Engineering, University of Leeds, Leeds LS2 9DX, UK

Sensors 2018, 18(2), 534; https://doi.org/10.3390/s18020534 - 10 Feb 2018

Cited by 19 | Viewed by 3839

Abstract

Barrier coverage has been widely used to detect intrusions in wireless sensor networks (WSNs). It can fulfill the monitoring task while extending the lifetime of the network. Though barrier coverage in WSNs has been intensively studied in recent years, previous research failed to [...] Read more.

Barrier coverage has been widely used to detect intrusions in wireless sensor networks (WSNs). It can fulfill the monitoring task while extending the lifetime of the network. Though barrier coverage in WSNs has been intensively studied in recent years, previous research failed to consider the problem of intrusion in transversal directions. If an intruder knows the deployment configuration of sensor nodes, then there is a high probability that it may traverse the whole target region from particular directions, without being detected. In this paper, we introduce the concept of crossed barrier coverage that can overcome this defect. We prove that the problem of finding the maximum number of crossed barriers is NP-hard and integer linear programming (ILP) is used to formulate the optimization problem. The branch-and-bound algorithm is adopted to determine the maximum number of crossed barriers. In addition, we also propose a multi-round shortest path algorithm (MSPA) to solve the optimization problem, which works heuristically to guarantee efficiency while maintaining near-optimal solutions. Several conventional algorithms for finding the maximum number of disjoint strong barriers are also modified to solve the crossed barrier problem and for the purpose of comparison. Extensive simulation studies demonstrate the effectiveness of MSPA. Full article

(This article belongs to the Section Sensor Networks)

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15 pages, 4764 KiB

Open AccessArticle

Flow Control in Wells Turbines for Harnessing Maximum Wave Power

by Jon Lekube^1,2,*

, Aitor J. Garrido¹, Izaskun Garrido¹, Erlantz Otaola^1,3 and Javier Maseda¹

¹ Automatic Control Group (ACG), Institute of Research and Development of Processes, Faculty of Engineering, University of the Basque Country (UPV/EHU), 48013 Bilbao, Spain

² Promotion and Subsidies Area, Basque Energy Agency (EVE), Urkixo Zumarkalea, 36, 48011 Bilbao, Spain

³ Advanced Design and Analysis (ADA), IDOM Consulting, Engineering and Architecture, 48015 Bilbao, Spain

Sensors 2018, 18(2), 535; https://doi.org/10.3390/s18020535 - 10 Feb 2018

Cited by 47 | Viewed by 5644

Abstract

Oceans, and particularly waves, offer a huge potential for energy harnessing all over the world. Nevertheless, the performance of current energy converters does not yet allow us to use the wave energy efficiently. However, new control techniques can improve the efficiency of energy [...] Read more.

Oceans, and particularly waves, offer a huge potential for energy harnessing all over the world. Nevertheless, the performance of current energy converters does not yet allow us to use the wave energy efficiently. However, new control techniques can improve the efficiency of energy converters. In this sense, the plant sensors play a key role within the control scheme, as necessary tools for parameter measuring and monitoring that are then used as control input variables to the feedback loop. Therefore, the aim of this work is to manage the rotational speed control loop in order to optimize the output power. With the help of outward looking sensors, a Maximum Power Point Tracking (MPPT) technique is employed to maximize the system efficiency. Then, the control decisions are based on the pressure drop measured by pressure sensors located along the turbine. A complete wave-to-wire model is developed so as to validate the performance of the proposed control method. For this purpose, a novel sensor-based flow controller is implemented based on the different measured signals. Thus, the performance of the proposed controller has been analyzed and compared with a case of uncontrolled plant. The simulations demonstrate that the flow control-based MPPT strategy is able to increase the output power, and they confirm both the viability and goodness. Full article

(This article belongs to the Special Issue Low Power Embedded Sensing: Hardware-Software Design and Applications)

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12 pages, 1149 KiB

Open AccessArticle

Performance Analysis of Diversity-Controlled Multi-User Superposition Transmission for 5G Wireless Networks

by Jeong Seon Yeom¹, Eunmi Chu¹

, Bang Chul Jung^1,* and Hu Jin^2,*

¹ Department of Electronics Engineering, Chungnam National University, Daejeon 34134, Korea

² Division of Electrical Engineering, Hanyang University, Ansan 15588, Korea

Sensors 2018, 18(2), 536; https://doi.org/10.3390/s18020536 - 10 Feb 2018

Cited by 9 | Viewed by 4633

Abstract

In this paper, we propose a novel low-complexity multi-user superposition transmission (MUST) technique for 5G downlink networks, which allows multiple cell-edge users to be multiplexed with a single cell-center user. We call the proposed technique diversity-controlled MUST technique since the cell-center user enjoys [...] Read more.

In this paper, we propose a novel low-complexity multi-user superposition transmission (MUST) technique for 5G downlink networks, which allows multiple cell-edge users to be multiplexed with a single cell-center user. We call the proposed technique diversity-controlled MUST technique since the cell-center user enjoys the frequency diversity effect via signal repetition over multiple orthogonal frequency division multiplexing (OFDM) sub-carriers. We assume that a base station is equipped with a single antenna but users are equipped with multiple antennas. In addition, we assume that the quadrature phase shift keying (QPSK) modulation is used for users. We mathematically analyze the bit error rate (BER) of both cell-edge users and cell-center users, which is the first theoretical result in the literature to the best of our knowledge. The mathematical analysis is validated through extensive link-level simulations. Full article

(This article belongs to the Special Issue Non-Orthogonal Multi-User Transmissions for 5G Networks)

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24 pages, 8658 KiB

Open AccessArticle

An IoT-Based Gamified Approach for Reducing Occupants’ Energy Wastage in Public Buildings

by Thanasis G. Papaioannou^1,*

, Nikos Dimitriou², Kostas Vasilakis², Anthony Schoofs³, Manolis Nikiforakis⁴, Fabian Pursche⁵, Nikolay Deliyski⁵, Amr Taha³, Dimosthenis Kotsopoulos⁶

, Cleopatra Bardaki⁶, Sarantis Kotsilitis⁴ and Anastasia Garbi²

¹ Department of Informatics, Athens University of Economics and Business (AUEB), 10434 Athens, Greece

² European Dynamics S.A., 1060 Brussels, Belgium

³ Wattics Ltd., Dublin 8, Ireland

⁴ Plegma Labs S.A., 15125 Marousi, Greece

⁵ Bosch Software Innovations GmbH, 88090 Immenstaad am Bodensee, Germany

⁶ Department of Management Science & Technology, Athens University of Economics and Business (AUEB), 10434 Athens, Greece

Sensors 2018, 18(2), 537; https://doi.org/10.3390/s18020537 - 10 Feb 2018

Cited by 39 | Viewed by 7552

Abstract

Conserving energy amenable to the activities of occupants in public buildings is a particularly challenging objective that includes associating energy consumption to particular individuals and providing them with incentives to alter their behavior. This paper describes a gamification framework that aims to facilitate [...] Read more.

Conserving energy amenable to the activities of occupants in public buildings is a particularly challenging objective that includes associating energy consumption to particular individuals and providing them with incentives to alter their behavior. This paper describes a gamification framework that aims to facilitate achieving greater energy conservation in public buildings. The framework leverages IoT-enabled low-cost devices, to improve energy disaggregation mechanisms that provide energy use and—consequently—wastage information at the device, area and end-user level. The identified wastages are concurrently targeted by a gamified application that motivates respective behavioral changes combining team competition, virtual rewards and life simulation. Our solution is being developed iteratively with the end-users’ engagement during the analysis, design, development and validation phases in public buildings located in three different countries: Luxembourg (Musée National d’Histoire et d’Art), Spain (EcoUrbanBuilding, Institut Català d’Energia headquarters, Barcelona) and Greece (General Secretariat of the Municipality of Athens). Full article

(This article belongs to the Special Issue Advances in Sensors for Sustainable Smart Cities and Smart Buildings)

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26 pages, 9024 KiB

Open AccessArticle

A Railway Track Geometry Measuring Trolley System Based on Aided INS

by Qijin Chen¹, Xiaoji Niu^1,2, Lili Zuo³, Tisheng Zhang^1,*, Fuqin Xiao³, Yi Liu⁴ and Jingnan Liu^1,2

¹ GNSS Research Center, Wuhan University, No. 129 Luoyu Road, Wuhan 430079, China

² Collaborative Innovation Center of Geospatial Technology, Wuhan University, No. 129 Luoyu Road, Wuhan 430079, China

³ Wuhan Municipal Construction Group Co., Ltd., Wuhan 430023, China

⁴ Shenzhen Datie Detecting and Surveying Inc., Shenzhen 518109, China

Sensors 2018, 18(2), 538; https://doi.org/10.3390/s18020538 - 10 Feb 2018

Cited by 83 | Viewed by 13380

Abstract

Accurate measurement of the railway track geometry is a task of fundamental importance to ensure the track quality in both the construction phase and the regular maintenance stage. Conventional track geometry measuring trolleys (TGMTs) in combination with classical geodetic surveying apparatus such as [...] Read more.

Accurate measurement of the railway track geometry is a task of fundamental importance to ensure the track quality in both the construction phase and the regular maintenance stage. Conventional track geometry measuring trolleys (TGMTs) in combination with classical geodetic surveying apparatus such as total stations alone cannot meet the requirements of measurement accuracy and surveying efficiency at the same time. Accurate and fast track geometry surveying applications call for an innovative surveying method that can measure all or most of the track geometric parameters in short time without interrupting the railway traffic. We provide a novel solution to this problem by integrating an inertial navigation system (INS) with a geodetic surveying apparatus, and design a modular TGMT system based on aided INS, which can be configured according to different surveying tasks including precise adjustment of slab track, providing tamping measurements, measuring track deformation and irregularities, and determination of the track axis. TGMT based on aided INS can operate in mobile surveying mode to significantly improve the surveying efficiency. Key points in the design of the TGMT’s architecture and the data processing concept and workflow are introduced in details, which should benefit subsequent research and provide a reference for the implementation of this kind of TGMT. The surveying performance of proposed TGMT with different configurations is assessed in the track geometry surveying experiments and actual projects. Full article

(This article belongs to the Special Issue Sensors for Deformation Monitoring of Large Civil Infrastructures)

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15 pages, 3274 KiB

Open AccessArticle

A COTS-Based Portable System to Conduct Accurate Substance Concentration Measurements

by Juan Aznar-Poveda¹

, Jose Antonio Lopez-Pastor¹, Antonio-Javier Garcia-Sanchez^1,*, Joan Garcia-Haro¹ and Toribio Fernández Otero²

¹ Department of Information and Communication Technologies (TIC), Technical University of Cartagena, ETSIT, Campus Muralla del Mar, E-30202 Cartagena, Spain

² Center for Electrochemistry and Intelligent Materials (CEMI), Technical University of Cartagena, ETSII, Campus Alfonso XIII, E-30203 Cartagena, Spain

Sensors 2018, 18(2), 539; https://doi.org/10.3390/s18020539 - 10 Feb 2018

Cited by 14 | Viewed by 5896

Abstract

Traditionally, electrochemical procedures aimed at determining substance concentrations have required a costly and cumbersome laboratory environment. Specialized equipment and personnel obtain precise results under complex and time-consuming settings. Innovative electrochemical-based sensors are emerging to alleviate this difficulty. However, they are generally scarce, proprietary [...] Read more.

Traditionally, electrochemical procedures aimed at determining substance concentrations have required a costly and cumbersome laboratory environment. Specialized equipment and personnel obtain precise results under complex and time-consuming settings. Innovative electrochemical-based sensors are emerging to alleviate this difficulty. However, they are generally scarce, proprietary hardware and/or software, and focused only on measuring a restricted range of substances. In this paper, we propose a portable, flexible, low-cost system, built from commercial off-the-shelf components and easily controlled, using open-source software. The system is completed with a wireless module, which enables the transmission of measurements to a remote database for their later processing. A well-known PGSTAT100 Autolab device is employed to validate the effectiveness of our proposal. To this end, we select ascorbic acid as the substance under consideration, evaluating the reliability figure and obtaining the calibration curves for both platforms. The final outcomes are shown to be feasible, accurate, and repeatable. Full article

(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Spain 2017)

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16 pages, 4817 KiB

Open AccessArticle

Monitoring Walker Assistive Devices: A Novel Approach Based on Load Cells and Optical Distance Measurements

by Vítor Viegas^1,2,*

, J. M. Dias Pereira^1,2

, Octavian Postolache^1,3

and Pedro Silva Girão^1,4

¹ Instituto de Telecomunicações, 1049-001 Lisboa, Portugal

² ESTSetúbal, Instituto Politécnico de Setúbal, 2910-761 Setúbal, Portugal

³ ISCTE—Instituto Universitário de Lisboa, 1600-077 Lisboa, Portugal

⁴ Instituto Superior Técnico, Universidade de Lisboa, 1049-001 Lisboa, Portugal

Sensors 2018, 18(2), 540; https://doi.org/10.3390/s18020540 - 10 Feb 2018

Cited by 8 | Viewed by 5105

Abstract

This paper presents a measurement system intended to monitor the usage of walker assistive devices. The goal is to guide the user in the correct use of the device in order to prevent risky situations and maximize comfort. Two risk indicators are defined: [...] Read more.

This paper presents a measurement system intended to monitor the usage of walker assistive devices. The goal is to guide the user in the correct use of the device in order to prevent risky situations and maximize comfort. Two risk indicators are defined: one related to force unbalance and the other related to motor incoordination. Force unbalance is measured by load cells attached to the walker legs, while motor incoordination is estimated by synchronizing force measurements with distance data provided by an optical sensor. The measurement system is equipped with a Bluetooth link that enables local supervision on a computer or tablet. Calibration and experimental results are included in the paper. Full article

(This article belongs to the Special Issue Force and Pressure Based Sensing Medical Application)

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19 pages, 3938 KiB

Open AccessArticle

Potential and Limitations of an Improved Method to Produce Dynamometric Wheels

by José Luis Bueno-López^1,*

, Jesús Cardenal^2,†

, Álvaro Deibe^3,†

and Javier García de Jalón^4,†

¹ INSIA, Universidad Politécnica de Madrid, Carretera de Valencia km. 7, 28031 Madrid, Spain

² Vehicle Dynamics Group, University of A Coruña, 15403 Ferrol, Spain

³ Integrated Group for Engineering Research, University of A Coruña, 15403 Ferrol, Spain

⁴ ETSII and INSIA, Universidad Politécnica de Madrid, José Gutiérrez Abascal 2, 28006 Madrid, Spain

^† These authors contributed equally to this work.

Sensors 2018, 18(2), 541; https://doi.org/10.3390/s18020541 - 10 Feb 2018

Cited by 1 | Viewed by 3514

Abstract

A new methodology for the estimation of tyre-contact forces is presented. The new procedure is an evolution of a previous method based on harmonic elimination techniques developed with the aim of producing low cost dynamometric wheels. While the original method required stress measurement [...] Read more.

A new methodology for the estimation of tyre-contact forces is presented. The new procedure is an evolution of a previous method based on harmonic elimination techniques developed with the aim of producing low cost dynamometric wheels. While the original method required stress measurement in many rim radial lines and the fulfillment of some rigid conditions of symmetry, the new methodology described in this article significantly reduces the number of required measurement points and greatly relaxes symmetry constraints. This can be done without compromising the estimation error level. The reduction of the number of measuring radial lines increases the ripple of demodulated signals due to non-eliminated higher order harmonics. Therefore, it is necessary to adapt the calibration procedure to this new scenario. A new calibration procedure that takes into account angular position of the wheel is completely described. This new methodology is tested on a standard commercial five-spoke car wheel. Obtained results are qualitatively compared to those derived from the application of former methodology leading to the conclusion that the new method is both simpler and more robust due to the reduction in the number of measuring points, while contact forces’ estimation error remains at an acceptable level. Full article

(This article belongs to the Special Issue Mechatronic Systems for Automatic Vehicles)

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14 pages, 3223 KiB

Open AccessArticle

Plane Wave SH₀ Piezoceramic Transduction Optimized Using Geometrical Parameters

by Guillaume Boivin^*

, Martin Viens

and Pierre Belanger

Département de génie mécanique, École de technologie supérieure, 1100 rue Notre-Dame Ouest, Montréal, QC H3C 1K3, Canada

Sensors 2018, 18(2), 542; https://doi.org/10.3390/s18020542 - 10 Feb 2018

Cited by 9 | Viewed by 3924

Abstract

Structural health monitoring is a prominent alternative to the scheduled maintenance of safety-critical components. The nondispersive nature as well as the through-thickness mode shape of the fundamental shear horizontal guided wave mode (SH

_{0}

) make it a particularly attractive candidate for ultrasonic [...] Read more.

Structural health monitoring is a prominent alternative to the scheduled maintenance of safety-critical components. The nondispersive nature as well as the through-thickness mode shape of the fundamental shear horizontal guided wave mode (SH

_{0}

) make it a particularly attractive candidate for ultrasonic guided wave structural health monitoring. However, plane wave excitation of SH

_{0}

at a high level of purity remains challenging because of the existence of the fundamental Lamb modes (A

_{0}

and S

_{0}

) below the cutoff frequency thickness product of high-order modes. This paper presents a piezoelectric transducer concept optimized for plane SH

_{0}

wave transduction based on the transducer geometry. The transducer parameter exploration was initially performed using a simple analytical model. A 3D multiphysics finite element model was then used to refine the transducer design. Finally, an experimental validation was conducted with a 3D laser Doppler vibrometer system. The analytical model, the finite element model, and the experimental measurement showed excellent agreement. The modal selectivity of SH

_{0}

within a 20

^{\circ}

beam opening angle at the design frequency of 425 kHz in a 1.59 mm aluminum plate was 23 dB, and the angle of the 6 dB wavefront was 86

^{\circ}

. Full article

(This article belongs to the Special Issue Sensor Technologies for Health Monitoring of Composite Structures)

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15 pages, 8657 KiB

Open AccessArticle

Sub-THz Imaging Using Non-Resonant HEMT Detectors

by Juan A. Delgado-Notario¹, Jesus E. Velazquez-Perez^1,*

, Yahya M. Meziani^1,* and Kristel Fobelets²

¹ Nano Lab, Salamanca University, Salamanca 37008, Spain

² Department of Electrical and Electronic Engineering, Imperial College, South Kensington Campus, London SW7 2AZ, UK

Sensors 2018, 18(2), 543; https://doi.org/10.3390/s18020543 - 10 Feb 2018

Cited by 11 | Viewed by 5509

Abstract

Plasma waves in gated 2-D systems can be used to efficiently detect THz electromagnetic radiation. Solid-state plasma wave-based sensors can be used as detectors in THz imaging systems. An experimental study of the sub-THz response of II-gate strained-Si Schottky-gated MODFETs (Modulation-doped Field-Effect Transistor) [...] Read more.

Plasma waves in gated 2-D systems can be used to efficiently detect THz electromagnetic radiation. Solid-state plasma wave-based sensors can be used as detectors in THz imaging systems. An experimental study of the sub-THz response of II-gate strained-Si Schottky-gated MODFETs (Modulation-doped Field-Effect Transistor) was performed. The response of the strained-Si MODFET has been characterized at two frequencies: 150 and 300 GHz: The DC drain-to-source voltage transducing the THz radiation (photovoltaic mode) of 250-nm gate length transistors exhibited a non-resonant response that agrees with theoretical models and physics-based simulations of the electrical response of the transistor. When imposing a weak source-to-drain current of 5 μA, a substantial increase of the photoresponse was found. This increase is translated into an enhancement of the responsivity by one order of magnitude as compared to the photovoltaic mode, while the NEP (Noise Equivalent Power) is reduced in the subthreshold region. Strained-Si MODFETs demonstrated an excellent performance as detectors in THz imaging. Full article

(This article belongs to the Special Issue Image Sensors)

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19 pages, 8652 KiB

Open AccessArticle

A Maximum Feasible Subsystem for Globally Optimal 3D Point Cloud Registration

by Chanki Yu¹ and Da Young Ju^2,*

¹ Department of Media Technology, Sogang University, Seoul 04107, Korea

² Yonsei Institute of Convergence Technology, Yonsei University, Incheon 21993, Korea

Sensors 2018, 18(2), 544; https://doi.org/10.3390/s18020544 - 10 Feb 2018

Cited by 20 | Viewed by 4664

Abstract

In this paper, a globally optimal algorithm based on a maximum feasible subsystem framework is proposed for robust pairwise registration of point cloud data. Registration is formulated as a branch-and-bound problem with mixed-integer linear programming. Among the putative matches of three-dimensional (3D) features [...] Read more.

In this paper, a globally optimal algorithm based on a maximum feasible subsystem framework is proposed for robust pairwise registration of point cloud data. Registration is formulated as a branch-and-bound problem with mixed-integer linear programming. Among the putative matches of three-dimensional (3D) features between two sets of range data, the proposed algorithm finds the maximum number of geometrically correct correspondences in the presence of incorrect matches, and it estimates the transformation parameters in a globally optimal manner. The optimization requires no initialization of transformation parameters. Experimental results demonstrated that the presented algorithm was more accurate and reliable than state-of-the-art registration methods and showed robustness against severe outliers/mismatches. This global optimization technique was highly effective, even when the geometric overlap between the datasets was very small. Full article

(This article belongs to the Section Remote Sensors)

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16 pages, 2424 KiB

Open AccessArticle

Efficient Deployment of Key Nodes for Optimal Coverage of Industrial Mobile Wireless Networks

by Xiaomin Li¹, Di Li¹, Zhijie Dong^1,*, Yage Hu² and Chengliang Liu³

¹ School of Mechanical and Automotive Engineering, South China University of Technology, Guangzhou 510640, China

² Super Micro Computer, Inc., San Jose 95131, CA, USA

³ School of Mechanical Engineering, Shanghai Jiao Tong University, Shanghai 200240, China

Sensors 2018, 18(2), 545; https://doi.org/10.3390/s18020545 - 10 Feb 2018

Cited by 10 | Viewed by 3261

Abstract

In recent years, industrial wireless networks (IWNs) have been transformed by the introduction of mobile nodes, and they now offer increased extensibility, mobility, and flexibility. Nevertheless, mobile nodes pose efficiency and reliability challenges. Efficient node deployment and management of channel interference directly affect [...] Read more.

In recent years, industrial wireless networks (IWNs) have been transformed by the introduction of mobile nodes, and they now offer increased extensibility, mobility, and flexibility. Nevertheless, mobile nodes pose efficiency and reliability challenges. Efficient node deployment and management of channel interference directly affect network system performance, particularly for key node placement in clustered wireless networks. This study analyzes this system model, considering both industrial properties of wireless networks and their mobility. Then, static and mobile node coverage problems are unified and simplified to target coverage problems. We propose a novel strategy for the deployment of clustered heads in grouped industrial mobile wireless networks (IMWNs) based on the improved maximal clique model and the iterative computation of new candidate cluster head positions. The maximal cliques are obtained via a double-layer Tabu search. Each cluster head updates its new position via an improved virtual force while moving with full coverage to find the minimal inter-cluster interference. Finally, we develop a simulation environment. The simulation results, based on a performance comparison, show the efficacy of the proposed strategies and their superiority over current approaches. Full article

(This article belongs to the Section Sensor Networks)

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14 pages, 3409 KiB

Open AccessArticle

A Survey on Data Storage and Information Discovery in the WSANs-Based Edge Computing Systems

by Xingpo Ma^1,*

, Junbin Liang², Renping Liu³, Wei Ni⁴, Yin Li¹, Ran Li¹, Wenpeng Ma¹ and Chuanda Qi¹

¹ School of Computer and Information Technology, Xinyang Normal University, Xinyang 464000, Henan, China

² School of Computer and Electronic Information, Guangxi University, Nanning 530004, China

³ Global Big Data Technologies Centre, University of Technology Sydney, Ultimo 2007, Australia

⁴ Data61, CSIRO, Sydney NSW 1466, Australia

Sensors 2018, 18(2), 546; https://doi.org/10.3390/s18020546 - 10 Feb 2018

Cited by 19 | Viewed by 4611

Abstract

In the post-Cloud era, the proliferation of Internet of Things (IoT) has pushed the horizon of Edge computing, which is a new computing paradigm with data processed at the edge of the network. As the important systems of Edge computing, wireless sensor and [...] Read more.

In the post-Cloud era, the proliferation of Internet of Things (IoT) has pushed the horizon of Edge computing, which is a new computing paradigm with data processed at the edge of the network. As the important systems of Edge computing, wireless sensor and actuator networks (WSANs) play an important role in collecting and processing the sensing data from the surrounding environment as well as taking actions on the events happening in the environment. In WSANs, in-network data storage and information discovery schemes with high energy efficiency, high load balance and low latency are needed because of the limited resources of the sensor nodes and the real-time requirement of some specific applications, such as putting out a big fire in a forest. In this article, the existing schemes of WSANs on data storage and information discovery are surveyed with detailed analysis on their advancements and shortcomings, and possible solutions are proposed on how to achieve high efficiency, good load balance, and perfect real-time performances at the same time, hoping that it can provide a good reference for the future research of the WSANs-based Edge computing systems. Full article

(This article belongs to the Section Sensor Networks)

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30 pages, 3205 KiB

Open AccessArticle

EDDA: An Efficient Distributed Data Replication Algorithm in VANETs

by Junyu Zhu^1,2, Chuanhe Huang^1,2,*, Xiying Fan^1,2, Sipei Guo³ and Bin Fu⁴

¹ School of computer, Wuhan University, Wuhan 430072, China

² Collaborative Innovation Center of Geospatial Technology, Wuhan University, Wuhan 430072, China

³ School of Mathematics and Statistics, Central China Normal University, Wuhan 430079, China

⁴ Department of Computer Science, The University of Texas Rio Grande Valley, Edinburg, TX 78541, USA

Sensors 2018, 18(2), 547; https://doi.org/10.3390/s18020547 - 10 Feb 2018

Cited by 11 | Viewed by 4090

Abstract

Efficient data dissemination in vehicular ad hoc networks (VANETs) is a challenging issue due to the dynamic nature of the network. To improve the performance of data dissemination, we study distributed data replication algorithms in VANETs for exchanging information and computing in an [...] Read more.

Efficient data dissemination in vehicular ad hoc networks (VANETs) is a challenging issue due to the dynamic nature of the network. To improve the performance of data dissemination, we study distributed data replication algorithms in VANETs for exchanging information and computing in an arbitrarily-connected network of vehicle nodes. To achieve low dissemination delay and improve the network performance, we control the number of message copies that can be disseminated in the network and then propose an efficient distributed data replication algorithm (EDDA). The key idea is to let the data carrier distribute the data dissemination tasks to multiple nodes to speed up the dissemination process. We calculate the number of communication stages for the network to enter into a balanced status and show that the proposed distributed algorithm can converge to a consensus in a small number of communication stages. Most of the theoretical results described in this paper are to study the complexity of network convergence. The lower bound and upper bound are also provided in the analysis of the algorithm. Simulation results show that the proposed EDDA can efficiently disseminate messages to vehicles in a specific area with low dissemination delay and system overhead. Full article

(This article belongs to the Section Internet of Things)

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34 pages, 6352 KiB

Open AccessArticle

Sensor-Oriented Path Planning for Multiregion Surveillance with a Single Lightweight UAV SAR

by Jincheng Li¹, Jie Chen^1,2, Pengbo Wang^1,2,* and Chunsheng Li^1,2

¹ School of Electronic and Information Engineering, Beihang University, Beijing 100191, China

² Collaborative Innovation Center of Geospatial Technology, Wuhan 430079, China

Sensors 2018, 18(2), 548; https://doi.org/10.3390/s18020548 - 11 Feb 2018

Cited by 37 | Viewed by 5950

Abstract

In the surveillance of interested regions by unmanned aerial vehicle (UAV), system performance relies greatly on the motion control strategy of the UAV and the operation characteristics of the onboard sensors. This paper investigates the 2D path planning problem for the lightweight UAV [...] Read more.

In the surveillance of interested regions by unmanned aerial vehicle (UAV), system performance relies greatly on the motion control strategy of the UAV and the operation characteristics of the onboard sensors. This paper investigates the 2D path planning problem for the lightweight UAV synthetic aperture radar (SAR) system in an environment of multiple regions of interest (ROIs), the sizes of which are comparable to the radar swath width. Taking into account the special requirements of the SAR system on the motion of the platform, we model path planning for UAV SAR as a constrained multiobjective optimization problem (MOP). Based on the fact that the UAV route can be designed in the map image, an image-based path planner is proposed in this paper. First, the neighboring ROIs are merged by the morphological operation. Then, the parts of routes for data collection of the ROIs can be located according to the geometric features of the ROIs and the observation geometry of UAV SAR. Lastly, the route segments for ROIs surveillance are connected by a path planning algorithm named the sampling-based sparse A* search (SSAS) algorithm. Simulation experiments in real scenarios demonstrate that the proposed sensor-oriented path planner can improve the reconnaissance performance of lightweight UAV SAR greatly compared with the conventional zigzag path planner. Full article

(This article belongs to the Section Remote Sensors)

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8 pages, 754 KiB

Open AccessArticle

Interaction Multipath in Through-the-Wall Radar Imaging Based on Compressive Sensing

by Yigeng Ma, Hong Hong^* and Xiaohua Zhu

School of Electronic and Optical Engineering, Nanjing University of Science and Technology, Nanjing 210094, China

Sensors 2018, 18(2), 549; https://doi.org/10.3390/s18020549 - 11 Feb 2018

Cited by 9 | Viewed by 3180

Abstract

Clutters caused by multipath have been widely researched in through-the-wall radar imaging (TWRI). The existing research work of multipath only consider reflections from the wall, while in the condition of a small scene, with the increasing number of targets, multipath from targets to [...] Read more.

Clutters caused by multipath have been widely researched in through-the-wall radar imaging (TWRI). The existing research work of multipath only consider reflections from the wall, while in the condition of a small scene, with the increasing number of targets, multipath from targets to targets, named interaction multipath, usually generates ghosts, which degrades the performance of TWRI. In order to mitigate the effect of interaction multipath, considering fast data acquisition and measurement reduction, we made use of the propagation characteristic of interaction multipath to build the sparse model of the target scene and developed a compressive sensing (CS)-based method, which is referred to as ‘interaction CS’. For the number of point targets increasing from 5–8, intensive evaluation and direct comparison of the imaging results with existing methods are conducted to show that the proposed interaction CS performs better at ghost suppression in the same condition of the signal-to-noise ratio (SNR). Full article

(This article belongs to the Section Remote Sensors)

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22 pages, 11745 KiB

Open AccessArticle

On the Temporal Stability of Analyte Recognition with an E-Nose Based on a Metal Oxide Sensor Array in Practical Applications

by Ilia Kiselev^1,*

, Victor Sysoev^2,3,*

, Igor Kaikov⁴, Ilona Koronczi⁵, Ruslan Adil Akai Tegin⁶, Jamila Smanalieva⁶

, Martin Sommer⁴, Coskan Ilicali⁶ and Michael Hauptmannl¹

¹ Breitmeier Messtechnik GmbH, Englerstr. 27, 76275 Ettlingen, Germany

² Laboratory of Sensors and Microsystems, Yuri Gagarin State Technical University of Saratov, 77 Polytechnicheskaya str., 410054 Saratov, Russia

³ National University of Science and Technology MISiS, 4 Leninskiy pr., 119991 Moscow, Russia

⁴ Institute of Microstructure Technology, Karlsruhe Institute of Technology, Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany

⁵ Science and Technology of Nanosystems, Karlsruhe Institute of Technology, Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany

⁶ Faculty of Engineering, Kyrgyz-Turkish Manas University, Mira Avenue 56, 720044 Bishkek, Kyrgyz Republic

Sensors 2018, 18(2), 550; https://doi.org/10.3390/s18020550 - 11 Feb 2018

Cited by 42 | Viewed by 6975

Abstract

The paper deals with a functional instability of electronic nose (e-nose) units which significantly limits their real-life applications. Here we demonstrate how to approach this issue with example of an e-nose based on a metal oxide sensor array developed at the Karlsruhe Institute [...] Read more.

The paper deals with a functional instability of electronic nose (e-nose) units which significantly limits their real-life applications. Here we demonstrate how to approach this issue with example of an e-nose based on a metal oxide sensor array developed at the Karlsruhe Institute of Technology (Germany). We consider the instability of e-nose operation at different time scales ranging from minutes to many years. To test the e-nose we employ open-air and headspace sampling of analyte odors. The multivariate recognition algorithm to process the multisensor array signals is based on the linear discriminant analysis method. Accounting for the received results, we argue that the stability of device operation is mostly affected by accidental changes in the ambient air composition. To overcome instabilities, we introduce the add-training procedure which is found to successfully manage both the temporal changes of ambient and the drift of multisensor array properties, even long-term. The method can be easily implemented in practical applications of e-noses and improve prospects for device marketing. Full article

(This article belongs to the Special Issue Artificial Olfaction and Taste)

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18 pages, 18978 KiB

Open AccessArticle

Partial Discharge Monitoring on Metal-Enclosed Switchgear with Distributed Non-Contact Sensors

by Chongxing Zhang¹

, Ming Dong¹, Ming Ren^1,*, Wenguang Huang¹, Jierui Zhou¹

, Xuze Gao¹ and Ricardo Albarracín^2,*

¹ State Key Laboratory of Electrical Insulation for Power Equipment, Xi’an Jiaotong University, Xi’an 710049, China

² Electrical and Electronic Engineering, Automatic Control, and Applied Physics, Escuela Técnica Superior de Ingeniería y Diseño Industrial, Universidad Politécnica de Madrid, Ronda de Valencia 3, 28012 Madrid, Spain

Sensors 2018, 18(2), 551; https://doi.org/10.3390/s18020551 - 11 Feb 2018

Cited by 32 | Viewed by 12610

Abstract

Metal-enclosed switchgear, which are widely used in the distribution of electrical energy, play an important role in power distribution networks. Their safe operation is directly related to the reliability of power system as well as the power quality on the consumer side. Partial [...] Read more.

Metal-enclosed switchgear, which are widely used in the distribution of electrical energy, play an important role in power distribution networks. Their safe operation is directly related to the reliability of power system as well as the power quality on the consumer side. Partial discharge detection is an effective way to identify potential faults and can be utilized for insulation diagnosis of metal-enclosed switchgear. The transient earth voltage method, an effective non-intrusive method, has substantial engineering application value for estimating the insulation condition of switchgear. However, the practical application effectiveness of TEV detection is not satisfactory because of the lack of a TEV detection application method, i.e., a method with sufficient technical cognition and analysis. This paper proposes an innovative online PD detection system and a corresponding application strategy based on an intelligent feedback distributed TEV wireless sensor network, consisting of sensing, communication, and diagnosis layers. In the proposed system, the TEV signal or status data are wirelessly transmitted to the terminal following low-energy signal preprocessing and acquisition by TEV sensors. Then, a central server analyzes the correlation of the uploaded data and gives a fault warning level according to the quantity, trend, parallel analysis, and phase resolved partial discharge pattern recognition. In this way, a TEV detection system and strategy with distributed acquisition, unitized fault warning, and centralized diagnosis is realized. The proposed system has positive significance for reducing the fault rate of medium voltage switchgear and improving its operation and maintenance level. Full article

(This article belongs to the Special Issue UHF and RF Sensor Technology for Partial Discharge Detection)

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21 pages, 7828 KiB

Open AccessArticle

An Improved Quadrilateral Fitting Algorithm for the Water Column Contribution in Airborne Bathymetric Lidar Waveforms

by Kai Ding^1,2,†

, Qingquan Li^1,2,*, Jiasong Zhu^1,2,†, Chisheng Wang^1,2,*, Minglei Guan^1,2, Zhipeng Chen^1,2, Chao Yang^1,2

, Yang Cui^1,2 and Jianghai Liao^1,2

¹ Key Laboratory for Geo-Environment Monitoring of Coastal Zone of the National Administration of Surveying, Mapping and GeoInformation, Shenzhen University, Shenzhen 518060, China

² Shenzhen Key Laboratory of Spatial Smart Sensing and Services, Shenzhen University, Shenzhen 518060, China

^† These authors contributed equally to this work.

Sensors 2018, 18(2), 552; https://doi.org/10.3390/s18020552 - 11 Feb 2018

Cited by 21 | Viewed by 4268

Abstract

In this paper, an improved method based on a mixture of Gaussian and quadrilateral functions is presented to process airborne bathymetric LiDAR waveforms. In the presented method, the LiDAR waveform is fitted to a combination of three functions: one Gaussian function for the [...] Read more.

In this paper, an improved method based on a mixture of Gaussian and quadrilateral functions is presented to process airborne bathymetric LiDAR waveforms. In the presented method, the LiDAR waveform is fitted to a combination of three functions: one Gaussian function for the water surface contribution, another Gaussian function for the water bottom contribution, and a new quadrilateral function to fit the water column contribution. The proposed method was tested on a simulated dataset and a real dataset, with the focus being mainly on the performance of retrieving bottom response and water depths. We also investigated the influence of the parameter settings on the accuracy of the bathymetry estimates. The results demonstrate that the improved quadrilateral fitting algorithm shows a superior performance in terms of low RMSE and a high detection rate in the water depth and magnitude retrieval. What’s more, compared with the use of a triangular function or the existing quadrilateral function to fit the water column contribution, the presented method retrieved the least noise and the least number of unidentified waveforms, showed the best performance in fitting the return waveforms, and had consistent fitting goodness for all different water depths. Full article

(This article belongs to the Section Remote Sensors)

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24 pages, 2813 KiB

Open AccessArticle

Active Electro-Location of Objects in the Underwater Environment Based on the Mixed Polarization Multiple Signal Classification Algorithm

by Yidong Xu¹

, Wenjing Shang¹

, Lili Guo¹, Junwei Qi^1,*

, Yingsong Li^1,2,3,*

and Wei Xue¹

¹ College of Information and Communication Engineering, Harbin Engineering University, Harbin 150001, China

² National Space Science Center, Chinese Academy of Sciences, Beijing 100190, China

³ Acoustic Science and Technology Laboratory, Harbin Engineering University, Harbin 150001, China

Sensors 2018, 18(2), 554; https://doi.org/10.3390/s18020554 - 11 Feb 2018

Cited by 11 | Viewed by 3871

Abstract

This article proposes a novel active localization method based on the mixed polarization multiple signal classification (MP-MUSIC) algorithm for positioning a metal target or an insulator target in the underwater environment by using a uniform circular antenna (UCA). The boundary element method (BEM) [...] Read more.

This article proposes a novel active localization method based on the mixed polarization multiple signal classification (MP-MUSIC) algorithm for positioning a metal target or an insulator target in the underwater environment by using a uniform circular antenna (UCA). The boundary element method (BEM) is introduced to analyze the boundary of the target by use of a matrix equation. In this method, an electric dipole source as a part of the locating system is set perpendicularly to the plane of the UCA. As a result, the UCA can only receive the induction field of the target. The potential of each electrode of the UCA is used as spatial-temporal localization data, and it does not need to obtain the field component in each direction compared with the conventional fields-based localization method, which can be easily implemented in practical engineering applications. A simulation model and a physical experiment are constructed. The simulation and the experiment results provide accurate positioning performance, with the help of verifying the effectiveness of the proposed localization method in underwater target locating. Full article

(This article belongs to the Section Sensor Networks)

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24 pages, 5983 KiB

Open AccessArticle

UAV-Assisted Dynamic Clustering of Wireless Sensor Networks for Crop Health Monitoring

by Mohammad Ammad Uddin^1,2,*, Ali Mansour¹, Denis Le Jeune¹, Mohammad Ayaz² and El-Hadi M. Aggoune²

¹ Lab STICC, ENSTA Bretagne, Brest 29200, France

² Sensor Networks and Cellular Systems Research Center, University of Tabuk, Tabuk 71491, Saudi Arabia

Sensors 2018, 18(2), 555; https://doi.org/10.3390/s18020555 - 11 Feb 2018

Cited by 79 | Viewed by 8556

Abstract

In this study, a crop health monitoring system is developed by using state of the art technologies including wireless sensors and Unmanned Aerial Vehicles (UAVs). Conventionally data is collected from sensor nodes either by fixed base stations or mobile sinks. Mobile sinks are [...] Read more.

In this study, a crop health monitoring system is developed by using state of the art technologies including wireless sensors and Unmanned Aerial Vehicles (UAVs). Conventionally data is collected from sensor nodes either by fixed base stations or mobile sinks. Mobile sinks are considered a better choice nowadays due to their improved network coverage and energy utilization. Usually, the mobile sink is used in two ways: either it goes for random walk to find the scattered nodes and collect data, or follows a pre-defined path established by the ground network/clusters. Neither of these options is suitable in our scenario due to the factors like dynamic data collection, the strict targeted area required to be scanned, unavailability of a large number of nodes, dynamic path of the UAV, and most importantly, none of these are known in advance. The contribution of this paper is the formation of dynamic runtime clusters of field sensors by considering the above mentioned factors. Furthermore a mechanism (Bayesian classifier) is defined to select best node as cluster head. The proposed system is validated through simulation results, lab and infield experiments using concept devices. The obtained results are encouraging, especially in terms of deployment time, energy, efficiency, throughput and ease of use. Full article

(This article belongs to the Special Issue UAV or Drones for Remote Sensing Applications)

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16 pages, 5405 KiB

Open AccessArticle

Skin Lesion Analysis towards Melanoma Detection Using Deep Learning Network

by Yuexiang Li^1,2 and Linlin Shen^1,2,*

¹ Computer Vision Institute, College of Computer Science and Software Engineering, Shenzhen University, Shenzhen 518060, China

² Guangdong Key Laboratory of Intelligent Information Processing, Shenzhen University, Shenzhen 518060, China

Sensors 2018, 18(2), 556; https://doi.org/10.3390/s18020556 - 11 Feb 2018

Cited by 512 | Viewed by 23709

Abstract

Skin lesions are a severe disease globally. Early detection of melanoma in dermoscopy images significantly increases the survival rate. However, the accurate recognition of melanoma is extremely challenging due to the following reasons: low contrast between lesions and skin, visual similarity between melanoma [...] Read more.

Skin lesions are a severe disease globally. Early detection of melanoma in dermoscopy images significantly increases the survival rate. However, the accurate recognition of melanoma is extremely challenging due to the following reasons: low contrast between lesions and skin, visual similarity between melanoma and non-melanoma lesions, etc. Hence, reliable automatic detection of skin tumors is very useful to increase the accuracy and efficiency of pathologists. In this paper, we proposed two deep learning methods to address three main tasks emerging in the area of skin lesion image processing, i.e., lesion segmentation (task 1), lesion dermoscopic feature extraction (task 2) and lesion classification (task 3). A deep learning framework consisting of two fully convolutional residual networks (FCRN) is proposed to simultaneously produce the segmentation result and the coarse classification result. A lesion index calculation unit (LICU) is developed to refine the coarse classification results by calculating the distance heat-map. A straight-forward CNN is proposed for the dermoscopic feature extraction task. The proposed deep learning frameworks were evaluated on the ISIC 2017 dataset. Experimental results show the promising accuracies of our frameworks, i.e., 0.753 for task 1, 0.848 for task 2 and 0.912 for task 3 were achieved. Full article

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16 pages, 14752 KiB

Open AccessArticle

An Improved Pansharpening Method for Misaligned Panchromatic and Multispectral Data

by Hui Li^*, Linhai Jing^*, Yunwei Tang

and Haifeng Ding

Key Laborary of Digital Earth Sciences, Institute of Remote Sensing and Digital Earth, Chinese Academy of Sciences, Beijing 100094, China

Sensors 2018, 18(2), 557; https://doi.org/10.3390/s18020557 - 11 Feb 2018

Cited by 16 | Viewed by 4229

Abstract

Numerous pansharpening methods were proposed in recent decades for fusing low-spatial-resolution multispectral (MS) images with high-spatial-resolution (HSR) panchromatic (PAN) bands to produce fused HSR MS images, which are widely used in various remote sensing tasks. The effect of misregistration between MS and PAN [...] Read more.

Numerous pansharpening methods were proposed in recent decades for fusing low-spatial-resolution multispectral (MS) images with high-spatial-resolution (HSR) panchromatic (PAN) bands to produce fused HSR MS images, which are widely used in various remote sensing tasks. The effect of misregistration between MS and PAN bands on quality of fused products has gained much attention in recent years. An improved method for misaligned MS and PAN imagery is proposed, through two improvements made on a previously published method named RMI (reduce misalignment impact). The performance of the proposed method was assessed by comparing with some outstanding fusion methods, such as adaptive Gram-Schmidt and generalized Laplacian pyramid. Experimental results show that the improved version can reduce spectral distortions of fused dark pixels and sharpen boundaries between different image objects, as well as obtain similar quality indexes with the original RMI method. In addition, the proposed method was evaluated with respect to its sensitivity to misalignments between MS and PAN bands. It is certified that the proposed method is more robust to misalignments between MS and PAN bands than the other methods. Full article

(This article belongs to the Section Remote Sensors)

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20 pages, 3181 KiB

Open AccessArticle

Comparing the Potential of Multispectral and Hyperspectral Data for Monitoring Oil Spill Impact

by Shruti Khanna^1,*

, Maria J. Santos^2,3, Susan L. Ustin¹

, Kristen Shapiro¹

, Paul J. Haverkamp^1,4 and Mui Lay¹

¹ Center for Spatial Technologies and Remote Sensing, Department of Land Air and Water Resources, University of California, One Shields Avenue, Davis, CA 95616, USA

² Department of Innovation, Environmental and Energy Sciences, Utrecht University, 3584 CS Utrecht, The Netherlands

³ Department of Geography, University of Zürich, 8057 Zürich, Switzerland

⁴ Department of Evolutionary Biology and Environmental Studies, University of Zürich, 8057 Zürich, Switzerland

Sensors 2018, 18(2), 558; https://doi.org/10.3390/s18020558 - 12 Feb 2018

Cited by 36 | Viewed by 6485

Abstract

Oil spills from offshore drilling and coastal refineries often cause significant degradation of coastal environments. Early oil detection may prevent losses and speed up recovery if monitoring of the initial oil extent, oil impact, and recovery are in place. Satellite imagery data can [...] Read more.

Oil spills from offshore drilling and coastal refineries often cause significant degradation of coastal environments. Early oil detection may prevent losses and speed up recovery if monitoring of the initial oil extent, oil impact, and recovery are in place. Satellite imagery data can provide a cost-effective alternative to expensive airborne imagery or labor intensive field campaigns for monitoring effects of oil spills on wetlands. However, these satellite data may be restricted in their ability to detect and map ecosystem recovery post-spill given their spectral measurement properties and temporal frequency. In this study, we assessed whether spatial and spectral resolution, and other sensor characteristics influence the ability to detect and map vegetation stress and mortality due to oil. We compared how well three satellite multispectral sensors: WorldView2, RapidEye and Landsat EMT+, match the ability of the airborne hyperspectral AVIRIS sensor to map oil-induced vegetation stress, recovery, and mortality after the DeepWater Horizon oil spill in the Gulf of Mexico in 2010. We found that finer spatial resolution (3.5 m) provided better delineation of the oil-impacted wetlands and better detection of vegetation stress along oiled shorelines in saltmarsh wetland ecosystems. As spatial resolution become coarser (3.5 m to 30 m) the ability to accurately detect and map stressed vegetation decreased. Spectral resolution did improve the detection and mapping of oil-impacted wetlands but less strongly than spatial resolution, suggesting that broad-band data may be sufficient to detect and map oil-impacted wetlands. AVIRIS narrow-band data performs better detecting vegetation stress, followed by WorldView2, RapidEye and then Landsat 15 m (pan sharpened) data. Higher quality sensor optics and higher signal-to-noise ratio (SNR) may also improve detection and mapping of oil-impacted wetlands; we found that resampled coarser resolution AVIRIS data with higher SNR performed better than either of the three satellite sensors. The ability to acquire imagery during certain times (midday, low tide, etc.) or a certain date (cloud-free, etc.) is also important in these tidal wetlands; WorldView2 imagery captured at high-tide detected a narrower band of shoreline affected by oil likely because some of the impacted wetland was below the tideline. These results suggest that while multispectral data may be sufficient for detecting the extent of oil-impacted wetlands, high spectral and spatial resolution, high-quality sensor characteristics, and the ability to control time of image acquisition may improve assessment and monitoring of vegetation stress and recovery post oil spills. Full article

(This article belongs to the Special Issue Sensors for Oil Applications)

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19 pages, 6303 KiB

Open AccessArticle

An Unsupervised Change Detection Method Using Time-Series of PolSAR Images from Radarsat-2 and GaoFen-3

by Wensong Liu, Jie Yang^*, Jinqi Zhao

, Hongtao Shi and Le Yang

State Key Laboratory of Information Engineering in Surveying, Mapping and Remote Sensing, Wuhan University, Wuhan 430079, China

Sensors 2018, 18(2), 559; https://doi.org/10.3390/s18020559 - 12 Feb 2018

Cited by 18 | Viewed by 5745

Abstract

The traditional unsupervised change detection methods based on the pixel level can only detect the changes between two different times with same sensor, and the results are easily affected by speckle noise. In this paper, a novel method is proposed to detect change [...] Read more.

The traditional unsupervised change detection methods based on the pixel level can only detect the changes between two different times with same sensor, and the results are easily affected by speckle noise. In this paper, a novel method is proposed to detect change based on time-series data from different sensors. Firstly, the overall difference image of the time-series PolSAR is calculated by omnibus test statistics, and difference images between any two images in different times are acquired by R_j test statistics. Secondly, the difference images are segmented with a Generalized Statistical Region Merging (GSRM) algorithm which can suppress the effect of speckle noise. Generalized Gaussian Mixture Model (GGMM) is then used to obtain the time-series change detection maps in the final step of the proposed method. To verify the effectiveness of the proposed method, we carried out the experiment of change detection using time-series PolSAR images acquired by Radarsat-2 and Gaofen-3 over the city of Wuhan, in China. Results show that the proposed method can not only detect the time-series change from different sensors, but it can also better suppress the influence of speckle noise and improve the overall accuracy and Kappa coefficient. Full article

(This article belongs to the Special Issue First Experiences with Chinese Gaofen-3 SAR Sensor)

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15 pages, 2701 KiB

Open AccessArticle

Analysis of the High-Frequency Content in Human QRS Complexes by the Continuous Wavelet Transform: An Automatized Analysis for the Prediction of Sudden Cardiac Death

by Daniel García Iglesias^1,2

, Nieves Roqueñi Gutiérrez³, Francisco Javier De Cos³ and David Calvo^1,2,3,*

¹ Arrhythmia Unit, Hospital Universitario Central de Asturias, 33011 Oviedo, Spain

² Instituto de Investigación Sanitaria del Principado de Asturias, 33011 Oviedo, Spain

³ Grupo para la Modelización Matemática Avanzada (MOMA), Universidad de Oviedo, 33004 Oviedo, Spain

Sensors 2018, 18(2), 560; https://doi.org/10.3390/s18020560 - 12 Feb 2018

Cited by 22 | Viewed by 5212

Abstract

Background: Fragmentation and delayed potentials in the QRS signal of patients have been postulated as risk markers for Sudden Cardiac Death (SCD). The analysis of the high-frequency spectral content may be useful for quantification. Methods: Forty-two consecutive patients with prior history of SCD [...] Read more.

Background: Fragmentation and delayed potentials in the QRS signal of patients have been postulated as risk markers for Sudden Cardiac Death (SCD). The analysis of the high-frequency spectral content may be useful for quantification. Methods: Forty-two consecutive patients with prior history of SCD or malignant arrhythmias (patients) where compared with 120 healthy individuals (controls). The QRS complexes were extracted with a modified Pan-Tompkins algorithm and processed with the Continuous Wavelet Transform to analyze the high-frequency content (85–130 Hz). Results: Overall, the power of the high-frequency content was higher in patients compared with controls (170.9 vs. 47.3 10³nV²Hz⁻¹; p = 0.007), with a prolonged time to reach the maximal power (68.9 vs. 64.8 ms; p = 0.002). An analysis of the signal intensity (instantaneous average of cumulative power), revealed a distinct function between patients and controls. The total intensity was higher in patients compared with controls (137.1 vs. 39 10³nV²Hz⁻¹s⁻¹; p = 0.001) and the time to reach the maximal intensity was also prolonged (88.7 vs. 82.1 ms; p < 0.001). Discussion: The high-frequency content of the QRS complexes was distinct between patients at risk of SCD and healthy controls. The wavelet transform is an efficient tool for spectral analysis of the QRS complexes that may contribute to stratification of risk. Full article

(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Spain 2017)

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25 pages, 8208 KiB

Open AccessArticle

An Architecture Framework for Orchestrating Context-Aware IT Ecosystems: A Case Study for Quantitative Evaluation

by Soojin Park^1,*

, Sungyong Park²

and Young B. Park³

¹ Graduate School of Management of Technology, Sogang University, 35 Baekbeom-ro, Mapo-gu, Seoul 04107, Korea

² Department of Computer Science and Engineering, Sogang University, 35 Baekbeom-ro, Mapo-gu, Seoul 04107, Korea

³ Department of Software Engineering, Dankook University, 152 Jukjeon-ro, Suji-gu, Yongin-si, Gyeonggi-do 16890, Korea

Sensors 2018, 18(2), 562; https://doi.org/10.3390/s18020562 - 12 Feb 2018

Cited by 14 | Viewed by 5485

Abstract

With the emergence of various forms of smart devices and new paradigms such as the Internet of Things (IoT) concept, the IT (Information Technology) service areas are expanding explosively compared to the provision of services by single systems. A new system operation concept [...] Read more.

With the emergence of various forms of smart devices and new paradigms such as the Internet of Things (IoT) concept, the IT (Information Technology) service areas are expanding explosively compared to the provision of services by single systems. A new system operation concept that has emerged in accordance with such technical trends is the IT ecosystem. The IT ecosystem can be considered a special type of system of systems in which multiple systems with various degrees of autonomy achieve common goals while adapting to the given environment. The single systems that participate in the IT ecosystem adapt autonomously to the current situation based on collected data from sensors. Furthermore, to maintain the services supported by the whole IT ecosystem sustainably, the configuration of single systems that participate in the IT ecosystem also changes appropriately in accordance with the changed situation. In order to support the IT ecosystem, this paper proposes an architecture framework that supports dynamic configuration changes to achieve the goal of the whole IT ecosystem, while ensuring the autonomy of single systems through the collection of data from sensors so as to recognize the situational context of individual participating systems. For the feasibility evaluation of the proposed framework, a simulated example of an IT ecosystem for unmanned forest management was constructed, and the quantitative evaluation results are discussed in terms of the extent to which the proposed architecture framework can continuously provide sustainable services in response to diverse environmental context changes. Full article

(This article belongs to the Special Issue Advances in Sensors for Sustainable Smart Cities and Smart Buildings)

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24 pages, 13196 KiB

Open AccessArticle

A Novel Ship Detection Method Based on Gradient and Integral Feature for Single-Polarization Synthetic Aperture Radar Imagery

by Hao Shi¹

, Qingjun Zhang^2,*

, Mingming Bian², Hangyu Wang³, Zhiru Wang³, Liang Chen^3,* and Jian Yang¹

¹ Department of Electronics, Tsinghua University, Beijing 100084, China

² Beijing Institute of Spacecraft System Engineering, Beijing 100094, China

³ Department of Information and Electronic, Beijing Institute of Technology, Beijing 100081, China

Sensors 2018, 18(2), 563; https://doi.org/10.3390/s18020563 - 12 Feb 2018

Cited by 24 | Viewed by 5571

Abstract

With the rapid development of remote sensing technologies, SAR satellites like China’s Gaofen-3 satellite have more imaging modes and higher resolution. With the availability of high-resolution SAR images, automatic ship target detection has become an important topic in maritime research. In this paper, [...] Read more.

With the rapid development of remote sensing technologies, SAR satellites like China’s Gaofen-3 satellite have more imaging modes and higher resolution. With the availability of high-resolution SAR images, automatic ship target detection has become an important topic in maritime research. In this paper, a novel ship detection method based on gradient and integral features is proposed. This method is mainly composed of three steps. First, in the preprocessing step, a filter is employed to smooth the clutters and the smoothing effect can be adaptive adjusted according to the statistics information of the sub-window. Thus, it can retain details while achieving noise suppression. Second, in the candidate area extraction, a sea-land segmentation method based on gradient enhancement is presented. The integral image method is employed to accelerate computation. Finally, in the ship target identification step, a feature extraction strategy based on Haar-like gradient information and a Radon transform is proposed. This strategy decreases the number of templates found in traditional Haar-like methods. Experiments were performed using Gaofen-3 single-polarization SAR images, and the results showed that the proposed method has high detection accuracy and rapid computational efficiency. In addition, this method has the potential for on-board processing. Full article

(This article belongs to the Special Issue First Experiences with Chinese Gaofen-3 SAR Sensor)

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13 pages, 3385 KiB

Open AccessArticle

Hydrogel-Based Fluorescent Dual pH and Oxygen Sensors Loaded in 96-Well Plates for High-Throughput Cell Metabolism Studies

by Shanshan Wu^1,2,†, Siying Wu^1,†, Zheyuan Yi¹, Fei Zeng¹, Weizhen Wu¹, Yuan Qiao¹, Xingzhong Zhao², Xing Cheng^1,*

and Yanqing Tian^1,*

¹ Department of Materials Science and Engineering, Southern University of Science and Technology, No 1088 Xueyuan Road, Xili, Nanshan District, Shenzhen 518055, China

² Department of Physics, Wuhan University, Wuhan 430072, China

^† These authors contribute equally to this work.

Sensors 2018, 18(2), 564; https://doi.org/10.3390/s18020564 - 13 Feb 2018

Cited by 36 | Viewed by 8864

Abstract

In this study, we developed fluorescent dual pH and oxygen sensors loaded in multi-well plates for in-situ and high-throughput monitoring of oxygen respiration and extracellular acidification during microbial cell growth for understanding metabolism. Biocompatible PHEMA-co-PAM materials were used as the hydrogel matrix. A [...] Read more.

In this study, we developed fluorescent dual pH and oxygen sensors loaded in multi-well plates for in-situ and high-throughput monitoring of oxygen respiration and extracellular acidification during microbial cell growth for understanding metabolism. Biocompatible PHEMA-co-PAM materials were used as the hydrogel matrix. A polymerizable oxygen probe (OS2) derived from PtTFPP and a polymerizable pH probe (S2) derived from fluorescein were chemically conjugated into the matrix to solve the problem of the probe leaching from the matrix. Gels were allowed to cure directly on the bottom of 96-well plates at room-temperature via redox polymerization. The influence of matrix’s composition on the sensing behaviors was investigated to optimize hydrogels with enough robustness for repeatable use with good sensitivity. Responses of the dual sensing hydrogels to dissolved oxygen (DO) and pH were studied. These dual oxygen-pH sensing plates were successfully used for microbial cell-based screening assays, which are based on the measurement of fluorescence intensity changes induced by cellular oxygen consumption and pH changes during microbial growth. This method may provide a real-time monitoring of cellular respiration, acidification, and a rapid kinetic assessment of multiple samples for cell viability as well as high-throughput drug screening. All of these assays can be carried out by a conventional plate reader. Full article

(This article belongs to the Special Issue Biosensing for Interfacial Science)

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23 pages, 1808 KiB

Open AccessArticle

Towards Efficient Wireless Body Area Network Using Two-Way Relay Cooperation

by Maham Waheed^1,*

, Rizwan Ahmad¹

, Waqas Ahmed², Micheal Drieberg³

and Muhammad Mahtab Alam⁴

¹ School of Electrical Engineering and Computer Science, National University of Sciences and Technology (NUST), Islamabad 44000, Pakistan

² Pakistan Institute of Engineering and Applied Sciences (PIEAS), Islamabad 45650, Pakistan

³ Department of Electrical and Electronics Engineering, Universiti Teknologi PETRONAS, Seri Iskandar 32610, Malaysia

⁴ Thomas Johann Seebeck Department of Electronics, Tallinn University of Technology, Tallinn 19086, Estonia

Sensors 2018, 18(2), 565; https://doi.org/10.3390/s18020565 - 13 Feb 2018

Cited by 40 | Viewed by 5351

Abstract

The fabrication of lightweight, ultra-thin, low power and intelligent body-borne sensors leads to novel advances in wireless body area networks (WBANs). Depending on the placement of the nodes, it is characterized as in/on body WBAN; thus, the channel is largely affected by body [...] Read more.

The fabrication of lightweight, ultra-thin, low power and intelligent body-borne sensors leads to novel advances in wireless body area networks (WBANs). Depending on the placement of the nodes, it is characterized as in/on body WBAN; thus, the channel is largely affected by body posture, clothing, muscle movement, body temperature and climatic conditions. The energy resources are limited and it is not feasible to replace the sensor’s battery frequently. In order to keep the sensor in working condition, the channel resources should be reserved. The lifetime of the sensor is very crucial and it highly depends on transmission among sensor nodes and energy consumption. The reliability and energy efficiency in WBAN applications play a vital role. In this paper, the analytical expressions for energy efficiency (EE) and packet error rate (PER) are formulated for two-way relay cooperative communication. The results depict better reliability and efficiency compared to direct and one-way relay communication. The effective performance range of direct vs. cooperative communication is separated by a threshold distance. Based on EE calculations, an optimal packet size is observed that provides maximum efficiency over a certain link length. A smart and energy efficient system is articulated that utilizes all three communication modes, namely direct, one-way relay and two-way relay, as the direct link performs better for a certain range, but the cooperative communication gives better results for increased distance in terms of EE. The efficacy of the proposed hybrid scheme is also demonstrated over a practical quasi-static channel. Furthermore, link length extension and diversity is achieved by joint network-channel (JNC) coding the cooperative link. Full article

(This article belongs to the Collection Smart Communication Protocols and Algorithms for Sensor Networks)

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13 pages, 2946 KiB

Open AccessArticle

Compact Hip-Force Sensor for a Gait-Assistance Exoskeleton System

by Hyundo Choi¹, Keehong Seo¹, Seungyong Hyung¹, Youngbo Shim¹ and Soo-Chul Lim^2,*

¹ Device & System Research Center, Samsung Advanced Institute of Technology, 130 Samsung-ro, Yeongtong-gu, Suwon-si, Gyeonggi-do 443-803, Korea

² Department of Mechanical, Robotics and Energy Engineering, Dongguk University, 30, Pildong-ro 1gil, Jung-gu, Seoul 04620, Korea

Sensors 2018, 18(2), 566; https://doi.org/10.3390/s18020566 - 13 Feb 2018

Cited by 36 | Viewed by 11625

Abstract

In this paper, we propose a compact force sensor system for a hip-mounted exoskeleton for seniors with difficulties in walking due to muscle weakness. It senses and monitors the delivered force and power of the exoskeleton for motion control and taking urgent safety [...] Read more.

In this paper, we propose a compact force sensor system for a hip-mounted exoskeleton for seniors with difficulties in walking due to muscle weakness. It senses and monitors the delivered force and power of the exoskeleton for motion control and taking urgent safety action. Two FSR (force-sensitive resistors) sensors are used to measure the assistance force when the user is walking. The sensor system directly measures the interaction force between the exoskeleton and the lower limb of the user instead of a previously reported force-sensing method, which estimated the hip assistance force from the current of the motor and lookup tables. Furthermore, the sensor system has the advantage of generating torque in the walking-assistant actuator based on directly measuring the hip-assistance force. Thus, the gait-assistance exoskeleton system can control the delivered power and torque to the user. The force sensing structure is designed to decouple the force caused by hip motion from other directional forces to the sensor so as to only measure that force. We confirmed that the hip-assistance force could be measured with the proposed prototype compact force sensor attached to a thigh frame through an experiment with a real system. Full article

(This article belongs to the Special Issue Force and Pressure Based Sensing Medical Application)

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10 pages, 3245 KiB

Open AccessArticle

Thermally Optimized Polarization-Maintaining Photonic Crystal Fiber and Its FOG Application

by Chunxi Zhang, Zhihao Zhang^*, Xiaobin Xu and Wei Cai

School of Instrument Science and Opto-electronics Engineering, Beihang University, Beijing 100191, China

Sensors 2018, 18(2), 567; https://doi.org/10.3390/s18020567 - 13 Feb 2018

Cited by 8 | Viewed by 4005

Abstract

In this paper, we propose a small-diameter polarization-maintaining solid-core photonic crystal fiber. The coating diameter, cladding diameter and other key parameters relating to the thermal properties were studied. Based on the optimized parameters, a fiber with a Shupe constant 15% lower than commercial [...] Read more.

In this paper, we propose a small-diameter polarization-maintaining solid-core photonic crystal fiber. The coating diameter, cladding diameter and other key parameters relating to the thermal properties were studied. Based on the optimized parameters, a fiber with a Shupe constant 15% lower than commercial photonic crystal fibers (PCFs) was fabricated, and the transmission loss was lower than 2 dB/km. The superior thermal stability of our fiber design was proven through both simulation and measurement. Using the small-diameter fiber, a split high precision fiber optic gyro (FOG) prototype was fabricated. The bias stability of the FOG was 0.0023 °/h, the random walk was 0.0003 °/

\sqrt{h}

, and the scale factor error was less than 1 ppm. Throughout a temperature variation ranging from −40 to 60 °C, the bias stability was less than 0.02 °/h without temperature compensation which is notably better than FOG with panda fiber. As a result, the PCF FOG is a promising choice for high precision FOG applications. Full article

(This article belongs to the Section State-of-the-Art Sensors Technologies)

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13 pages, 846 KiB

Open AccessArticle

Polynomial Phase Estimation Based on Adaptive Short-Time Fourier Transform

by Fulong Jing, Chunjie Zhang^*, Weijian Si, Yu Wang and Shuhong Jiao

College of Information and Communication Engineering, Harbin Engineering University, Harbin 150001, China

Sensors 2018, 18(2), 568; https://doi.org/10.3390/s18020568 - 13 Feb 2018

Cited by 13 | Viewed by 4153

Abstract

Polynomial phase signals (PPSs) have numerous applications in many fields including radar, sonar, geophysics, and radio communication systems. Therefore, estimation of PPS coefficients is very important. In this paper, a novel approach for PPS parameters estimation based on adaptive short-time Fourier transform (ASTFT), [...] Read more.

Polynomial phase signals (PPSs) have numerous applications in many fields including radar, sonar, geophysics, and radio communication systems. Therefore, estimation of PPS coefficients is very important. In this paper, a novel approach for PPS parameters estimation based on adaptive short-time Fourier transform (ASTFT), called the PPS-ASTFT estimator, is proposed. Using the PPS-ASTFT estimator, both one-dimensional and multi-dimensional searches and error propagation problems, which widely exist in PPSs field, are avoided. In the proposed algorithm, the instantaneous frequency (IF) is estimated by S-transform (ST), which can preserve information on signal phase and provide a variable resolution similar to the wavelet transform (WT). The width of the ASTFT analysis window is equal to the local stationary length, which is measured by the instantaneous frequency gradient (IFG). The IFG is calculated by the principal component analysis (PCA), which is robust to the noise. Moreover, to improve estimation accuracy, a refinement strategy is presented to estimate signal parameters. Since the PPS-ASTFT avoids parameter search, the proposed algorithm can be computed in a reasonable amount of time. The estimation performance, computational cost, and implementation of the PPS-ASTFT are also analyzed. The conducted numerical simulations support our theoretical results and demonstrate an excellent statistical performance of the proposed algorithm. Full article

(This article belongs to the Special Issue Sensor Signal and Information Processing)

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13 pages, 8900 KiB

Open AccessArticle

Touch Locating and Stretch Sensing Studies of Conductive Hydrogels with Applications to Soft Robots

by Yanmin Zhou¹

, Bin He^1,*, Zhe Yan¹, Yinghui Shang², Qigang Wang² and Zhipeng Wang¹

¹ School of Electronics and Information Engineering, Tongji University, Shanghai 201804, China

² School of Chemical Science and Engineering, Tongji University, Shanghai 200092, China

Sensors 2018, 18(2), 569; https://doi.org/10.3390/s18020569 - 13 Feb 2018

Cited by 23 | Viewed by 4888

Abstract

Soft robots possess great potential in environmental adaptations, while their environmental sensing abilities are critical. Conductive hydrogels have been suggested to possess sensing abilities. However, their application in soft robots is lacking. In this work, we fabricated a soft and stretchable gel material, [...] Read more.

Soft robots possess great potential in environmental adaptations, while their environmental sensing abilities are critical. Conductive hydrogels have been suggested to possess sensing abilities. However, their application in soft robots is lacking. In this work, we fabricated a soft and stretchable gel material, introduced its sensing mechanisms, and developed a measurement setup. Both experimental and simulation studies indicate strong nonlinearity of touch locating on a square touch panel with Cartesian coordinates. To simplify the touch locating, we proposed a touch locating system based on round touch panels with polar coordinates. Mathematical calculations and finite element method (FEM) simulations showed that in this system the locating of a touch point was only determined by its polar radius. This was verified by experimental studies. As a resistor, a gel strip’s resistance increases with stretching. To demonstrate their applications on soft robots, a 3D printed three-fingered soft gripper was employed with gel strips attached. During finger bending for rod grasping, the resistances of the gel strips increased, indicating stretching of the soft material. Furthermore, the strain and stress of a gel strip increased with a decrease of the rod diameter. These studies advance the application of conductive hydrogels on soft robots. Full article

(This article belongs to the Section Physical Sensors)

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24 pages, 37076 KiB

Open AccessArticle

A Holistic Approach to the Evaluation of the Montado Ecosystem Using Proximal Sensors

by João Serrano^1,*

, Shakib Shahidian¹, José Marques da Silva^1,2 and Mário De Carvalho¹

¹ Rural Engineering Department, University of Évora, Instituto de Ciências Agrárias e Ambientais Mediterrânicas (ICAAM), Apartado 94, 7002-554 Évora, Portugal

² Agroinsider Lda. (University of Évora, spin-off), PITE, R. Circular Norte, NERE, Sala 18, 7005-841 Évora, Portugal

Sensors 2018, 18(2), 570; https://doi.org/10.3390/s18020570 - 13 Feb 2018

Cited by 9 | Viewed by 5302

Abstract

The Montado is a silvo-pastoral system characterized by open canopy woodlands with natural or cultivated grassland in the undercover and grazing animals. The aims of this study were to present several proximal sensors with potential to monitor relevant variables in the complex montado [...] Read more.

The Montado is a silvo-pastoral system characterized by open canopy woodlands with natural or cultivated grassland in the undercover and grazing animals. The aims of this study were to present several proximal sensors with potential to monitor relevant variables in the complex montado ecosystem and demonstrate their application in a case study designed to evaluate the effect of trees on the pasture. This work uses data collected between March and June 2016, at peak of dryland pasture production under typical Mediterranean conditions, in twenty four sampling points, half under tree canopy (UTC) and half outside tree canopy (OTC). Correlations were established between pasture biomass and capacitance measured by a commercial probe and between pasture quality and normalized difference vegetation index (NDVI) measured by a commercial active optical sensor. The interest of altimetric and apparent soil electrical conductivity maps as the first step in the implementation of precision agriculture projects was demonstrated. The use of proximal sensors to monitor soil moisture content, pasture photosynthetically active radiation and temperature helped to explain the influence of trees on pasture productivity and quality. The significant and strong correlations obtained between capacitance and pasture biomass and between NDVI and pasture nutritive value (in terms of crude protein, CP and neutral detergent fibre, NDF) can make an important contribution to determination of key components of pasture productivity and quality and implementation of site-specific pasture management. Animal tracking demonstrated its potential to be an important tool for understanding the interaction between various factors and components that interrelate in the montado ecosystem and to support grazing management decisions. Full article

(This article belongs to the Special Issue Application of Satellite and Proximal Sensors in Precision Agriculture)

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15 pages, 7883 KiB

Open AccessArticle

A Method on Dynamic Path Planning for Robotic Manipulator Autonomous Obstacle Avoidance Based on an Improved RRT Algorithm

by Kun Wei and Bingyin Ren^*

School of Mechatronics Engineering, Harbin Institute of Technology, Harbin 150001, China

Sensors 2018, 18(2), 571; https://doi.org/10.3390/s18020571 - 13 Feb 2018

Cited by 223 | Viewed by 17472

Abstract

In a future intelligent factory, a robotic manipulator must work efficiently and safely in a Human–Robot collaborative and dynamic unstructured environment. Autonomous path planning is the most important issue which must be resolved first in the process of improving robotic manipulator intelligence. Among [...] Read more.

In a future intelligent factory, a robotic manipulator must work efficiently and safely in a Human–Robot collaborative and dynamic unstructured environment. Autonomous path planning is the most important issue which must be resolved first in the process of improving robotic manipulator intelligence. Among the path-planning methods, the Rapidly Exploring Random Tree (RRT) algorithm based on random sampling has been widely applied in dynamic path planning for a high-dimensional robotic manipulator, especially in a complex environment because of its probability completeness, perfect expansion, and fast exploring speed over other planning methods. However, the existing RRT algorithm has a limitation in path planning for a robotic manipulator in a dynamic unstructured environment. Therefore, an autonomous obstacle avoidance dynamic path-planning method for a robotic manipulator based on an improved RRT algorithm, called Smoothly RRT (S-RRT), is proposed. This method that targets a directional node extends and can increase the sampling speed and efficiency of RRT dramatically. A path optimization strategy based on the maximum curvature constraint is presented to generate a smooth and curved continuous executable path for a robotic manipulator. Finally, the correctness, effectiveness, and practicability of the proposed method are demonstrated and validated via a MATLAB static simulation and a Robot Operating System (ROS) dynamic simulation environment as well as a real autonomous obstacle avoidance experiment in a dynamic unstructured environment for a robotic manipulator. The proposed method not only provides great practical engineering significance for a robotic manipulator’s obstacle avoidance in an intelligent factory, but also theoretical reference value for other type of robots’ path planning. Full article

(This article belongs to the Special Issue Smart Sensors for Mechatronic and Robotic Systems)

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27 pages, 11384 KiB

Open AccessArticle

Robust Object Tracking Based on Motion Consistency

by Lijun He, Xiaoya Qiao, Shuai Wen and Fan Li^*

Department of Information and Communication Engineering, School of Electronic and Information Engineering, Xi’an Jiaotong University, Xi’an 710049, China

Sensors 2018, 18(2), 572; https://doi.org/10.3390/s18020572 - 13 Feb 2018

Cited by 6 | Viewed by 4301

Abstract

Object tracking is an important research direction in computer vision and is widely used in video surveillance, security monitoring, video analysis and other fields. Conventional tracking algorithms perform poorly in specific scenes, such as a target with fast motion and occlusion. The candidate [...] Read more.

Object tracking is an important research direction in computer vision and is widely used in video surveillance, security monitoring, video analysis and other fields. Conventional tracking algorithms perform poorly in specific scenes, such as a target with fast motion and occlusion. The candidate samples may lose the true target due to its fast motion. Moreover, the appearance of the target may change with movement. In this paper, we propose an object tracking algorithm based on motion consistency. In the state transition model, candidate samples are obtained by the target state, which is predicted according to the temporal correlation. In the appearance model, we define the position factor to represent the different importance of candidate samples in different positions using the double Gaussian probability model. The candidate sample with highest likelihood is selected as the tracking result by combining the holistic and local responses with the position factor. Moreover, an adaptive template updating scheme is proposed to adapt to the target’s appearance changes, especially those caused by fast motion. The experimental results on a 2013 benchmark dataset demonstrate that the proposed algorithm performs better in scenes with fast motion and partial or full occlusion compared to the state-of-the-art algorithms. Full article

(This article belongs to the Special Issue Sensor Signal and Information Processing)

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17 pages, 35518 KiB

Open AccessArticle

Measurement of a 3D Ultrasonic Wavefield Using Pulsed Laser Holographic Microscopy for Ultrasonic Nondestructive Evaluation

by Xing Wang¹, Guang-Ming Zhang^2,*, Hongwei Ma¹, Yishu Zhang¹ and Doudou Wang³

¹ School of Mechanical Engineering, Xi’an University of Science and Technology, Xi’an 710054, China

² General Engineering Research Institute, Liverpool John Moores University, Liverpool L3 3AF, UK

³ School of Science, Xi’an University of Science and Technology, Xi’an 710054, China

Sensors 2018, 18(2), 573; https://doi.org/10.3390/s18020573 - 13 Feb 2018

Cited by 7 | Viewed by 5875

Abstract

In ultrasonic array imaging, 3D ultrasonic wavefields are normally recorded by an ultrasonic piezo array transducer. Its performance is limited by the configuration and size of the array transducer. In this paper, a method based on digital holographic interferometry is proposed to record [...] Read more.

In ultrasonic array imaging, 3D ultrasonic wavefields are normally recorded by an ultrasonic piezo array transducer. Its performance is limited by the configuration and size of the array transducer. In this paper, a method based on digital holographic interferometry is proposed to record the 3D ultrasonic wavefields instead of the array transducer, and the measurement system consisting of a pulsed laser, ultrasonic excitation, and synchronization and control circuit is designed. A consecutive sequence of holograms of ultrasonic wavefields are recorded by the system. The interferograms are calculated from the recorded holograms at different time sequence. The amplitudes and phases of the transient ultrasonic wavefields are recovered from the interferograms by phase unwrapping. The consecutive sequence of transient ultrasonic wavefields are stacked together to generate 3D ultrasonic wavefields. Simulation and experiments are carried out to verify the proposed technique, and preliminary results are presented. Full article

(This article belongs to the Special Issue Optical Waveguide Based Sensors)

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35 pages, 663 KiB

Open AccessArticle

Patch Transporter: Incentivized, Decentralized Software Patch System for WSN and IoT Environments

by JongHyup Lee

Department of Mathematical Finance, Gachon University, Seongnam-si 13120, Korea

Sensors 2018, 18(2), 574; https://doi.org/10.3390/s18020574 - 13 Feb 2018

Cited by 28 | Viewed by 4872

Abstract

In the complicated settings of WSN (Wireless Sensor Networks) and IoT (Internet of Things) environments, keeping a number of heterogeneous devices updated is a challenging job, especially with respect to effectively discovering target devices and rapidly delivering the software updates. In this paper, [...] Read more.

In the complicated settings of WSN (Wireless Sensor Networks) and IoT (Internet of Things) environments, keeping a number of heterogeneous devices updated is a challenging job, especially with respect to effectively discovering target devices and rapidly delivering the software updates. In this paper, we convert the traditional software update process to a distributed service. We set an incentive system for faithfully transporting the patches to the recipient devices. The incentive system motivates independent, self-interested transporters for helping the devices to be updated. To ensure the system correctly operates, we employ the blockchain system that enforces the commitment in a decentralized manner. We also present a detailed specification for the proposed protocol and validate it by model checking and simulations for correctness. Full article

(This article belongs to the Section Sensor Networks)

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32 pages, 4807 KiB

Open AccessArticle

Feasibility Assessment of a Fine-Grained Access Control Model on Resource Constrained Sensors

by Mikel Uriarte Itzazelaia^1,*

, Jasone Astorga²

, Eduardo Jacob²

, Maider Huarte² and Pedro Romaña¹

¹ Nextel S. A., Technological Park of Bizkaia 207B, 1B, 48170 Zamudio, Spain

² Department of Communications Engineering, Faculty of Engineering in Bilbao, University of the Basque Country UPV/EHU, Plaza Ingeniero Torres Quevedo, 1, 48013 Bilbao, Spain

Sensors 2018, 18(2), 575; https://doi.org/10.3390/s18020575 - 13 Feb 2018

Viewed by 3513

Abstract

Upcoming smart scenarios enabled by the Internet of Things (IoT) envision smart objects that provide services that can adapt to user behavior or be managed to achieve greater productivity. In such environments, smart things are inexpensive and, therefore, constrained devices. However, they are [...] Read more.

Upcoming smart scenarios enabled by the Internet of Things (IoT) envision smart objects that provide services that can adapt to user behavior or be managed to achieve greater productivity. In such environments, smart things are inexpensive and, therefore, constrained devices. However, they are also critical components because of the importance of the information that they provide. Given this, strong security is a requirement, but not all security mechanisms in general and access control models in particular are feasible. In this paper, we present the feasibility assessment of an access control model that utilizes a hybrid architecture and a policy language that provides dynamic fine-grained policy enforcement in the sensors, which requires an efficient message exchange protocol called Hidra. This experimental performance assessment includes a prototype implementation, a performance evaluation model, the measurements and related discussions, which demonstrate the feasibility and adequacy of the analyzed access control model. Full article

(This article belongs to the Section Sensor Networks)

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13 pages, 5689 KiB

Open AccessArticle

Measuring Device for Air Speed in Macroporous Media and Its Application Inside Apple Storage Bins

by Martin Geyer^1,*, Ulrike Praeger¹, Ingo Truppel¹

, Holger Scaar², Daniel A. Neuwald³, Reiner Jedermann⁴

and Klaus Gottschalk²

¹ Department Horticultural Engineering, Leibniz Institute for Agricultural Engineering and Bioeconomy (ATB), Max-Eyth-Allee 100, 14469 Potsdam, Germany

² Department Postharvest Technology, Leibniz Institute for Agricultural Engineering and Bioeconomy (ATB), Max-Eyth-Allee 100, 14469 Potsdam, Germany

³ Competence Centre for Fruit Growing—Lake Constance, Ravensburg, Germany; University of Hohenheim, Institute of Crop Sciences, Section Crop Physiology of Specialty Crops, 70593 Stuttgart, Germany

⁴ Institute for Microsensors, -Actuators and -Systems (IMSAS), University Bremen, Otto-Hahn-Allee NW1, 28359 Bremen, Germany

Sensors 2018, 18(2), 576; https://doi.org/10.3390/s18020576 - 13 Feb 2018

Cited by 18 | Viewed by 7206

Abstract

In cold storage facilities of fruit and vegetables, airflow is necessary for heat removal. The design of storage facilities influences the air speed in the surrounding of the product. Therefore, knowledge about airflow next to the product is important to plan the layout [...] Read more.

In cold storage facilities of fruit and vegetables, airflow is necessary for heat removal. The design of storage facilities influences the air speed in the surrounding of the product. Therefore, knowledge about airflow next to the product is important to plan the layout of cold stores adapted to the requirements of the products. A new sensing device (ASL, Air speed logger) is developed for omnidirectional measurement of air speed between fruit or vegetables inside storage bins or in bulk. It consists of four interconnected plastic spheres with 80 mm diameter each, adapted to the size of apple fruit. In the free space between the spheres, silicon diodes are fixed for the airflow measurement based on a calorimetric principle. Battery and data logger are mounted inside the spheres. The device is calibrated in a wind tunnel in a measuring range of 0–1.3 m/s. Air speed measurements in fruit bulks on laboratory scale and in an industrial fruit store show air speeds in gaps between fruit with high stability at different airflow levels. Several devices can be placed between stored products for determination of the air speed distribution inside bulks or bin stacks in a storage room. Full article

(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Germany)

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20 pages, 3535 KiB

Open AccessArticle

Evaluation of a Multichannel Non-Contact ECG System and Signal Quality Algorithms for Sleep Apnea Detection and Monitoring

by Ivan D. Castro^1,2,*

, Carolina Varon^1,2

, Tom Torfs²

, Sabine Van Huffel^1,2

, Robert Puers^1,2

and Chris Van Hoof^1,2

¹ KU Leuven, Deptartment of Electrical Engineering—ESAT, 3001 Leuven, Belgium

² IMEC Belgium, 3001 Leuven, Belgium

Sensors 2018, 18(2), 577; https://doi.org/10.3390/s18020577 - 13 Feb 2018

Cited by 49 | Viewed by 6826

Abstract

Sleep-related conditions require high-cost and low-comfort diagnosis at the hospital during one night or longer. To overcome this situation, this work aims to evaluate an unobtrusive monitoring technique for sleep apnea. This paper presents, for the first time, the evaluation of contactless capacitively-coupled [...] Read more.

Sleep-related conditions require high-cost and low-comfort diagnosis at the hospital during one night or longer. To overcome this situation, this work aims to evaluate an unobtrusive monitoring technique for sleep apnea. This paper presents, for the first time, the evaluation of contactless capacitively-coupled electrocardiography (ccECG) signals for the extraction of sleep apnea features, together with a comparison of different signal quality indicators. A multichannel ccECG system is used to collect signals from 15 subjects in a sleep environment from different positions. Reference quality labels were assigned for every 30-s segment. Quality indicators were calculated, and their signal classification performance was evaluated. Features for the detection of sleep apnea were extracted from capacitive and reference signals. Sleep apnea features related to heart rate and heart rate variability achieved high similarity to the reference values, with p-values of 0.94 and 0.98, which is in line with the more than 95% beat-matching obtained. Features related to signal morphology presented lower similarity with the reference, although signal similarity metrics of correlation and coherence were relatively high. Quality-based automatic classification of the signals had a maximum accuracy of 91%. Best-performing quality indicators were based on template correlation and beat-detection. Results suggest that using unobtrusive cardiac signals for the automatic detection of sleep apnea can achieve similar performance as contact signals, and indicates clinical value of ccECG. Moreover, signal segments can automatically be classified by the proposed quality metrics as a pre-processing step. Including contactless respiration signals is likely to improve the performance and provide a complete unobtrusive cardiorespiratory monitoring solution; this is a promising alternative that will allow the screening of more patients with higher comfort, for a longer time, and at a reduced cost. Full article

(This article belongs to the Section Physical Sensors)

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12 pages, 2353 KiB

Open AccessArticle

Circular Array of Magnetic Sensors for Current Measurement: Analysis for Error Caused by Position of Conductor

by Hao Yu

, Zheng Qian^*, Huayi Liu and Jiaqi Qu

School of Instrumentation Science and Opto-Electronics Engineering, Beihang University, Beijing 100191, China

Sensors 2018, 18(2), 578; https://doi.org/10.3390/s18020578 - 14 Feb 2018

Cited by 29 | Viewed by 6230

Abstract

This paper analyzes the measurement error, caused by the position of the current-carrying conductor, of a circular array of magnetic sensors for current measurement. The circular array of magnetic sensors is an effective approach for AC or DC non-contact measurement, as it is [...] Read more.

This paper analyzes the measurement error, caused by the position of the current-carrying conductor, of a circular array of magnetic sensors for current measurement. The circular array of magnetic sensors is an effective approach for AC or DC non-contact measurement, as it is low-cost, light-weight, has a large linear range, wide bandwidth, and low noise. Especially, it has been claimed that such structure has excellent reduction ability for errors caused by the position of the current-carrying conductor, crosstalk current interference, shape of the conduction cross-section, and the Earth’s magnetic field. However, the positions of the current-carrying conductor—including un-centeredness and un-perpendicularity—have not been analyzed in detail until now. In this paper, for the purpose of having minimum measurement error, a theoretical analysis has been proposed based on vector inner and exterior product. In the presented mathematical model of relative error, the un-center offset distance, the un-perpendicular angle, the radius of the circle, and the number of magnetic sensors are expressed in one equation. The comparison of the relative error caused by the position of the current-carrying conductor between four and eight sensors is conducted. Tunnel magnetoresistance (TMR) sensors are used in the experimental prototype to verify the mathematical model. The analysis results can be the reference to design the details of the circular array of magnetic sensors for current measurement in practical situations. Full article

(This article belongs to the Special Issue Magnetic Sensors)

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20 pages, 4433 KiB

Open AccessArticle

The Development and Test of a Sensor for Measurement of the Working Level of Gas–Liquid Two-Phase Flow in a Coalbed Methane Wellbore Annulus

by Chuan Wu, Huafeng Ding^* and Lei Han

Faculty of Mechanical and Electronic Information, China University of Geosciences (Wuhan), Wuhan 430074, China

Sensors 2018, 18(2), 579; https://doi.org/10.3390/s18020579 - 14 Feb 2018

Cited by 6 | Viewed by 4690

Abstract

Coalbed methane (CBM) is one kind of clean-burning gas and has been valued as a new form of energy that will be used widely in the near future. When producing CBM, the working level within a CBM wellbore annulus needs to be monitored [...] Read more.

Coalbed methane (CBM) is one kind of clean-burning gas and has been valued as a new form of energy that will be used widely in the near future. When producing CBM, the working level within a CBM wellbore annulus needs to be monitored to dynamically adjust the gas drainage and extraction processes. However, the existing method of measuring the working level does not meet the needs of accurate adjustment, so we designed a new sensor for this purpose. The principle of our sensor is a liquid pressure formula, i.e., the sensor monitors the two-phase flow patterns and obtains the mean density of the two-phase flow according to the pattern recognition result in the first step, and then combines the pressure data of the working level to calculate the working level using the liquid pressure formula. The sensor was tested in both the lab and on site, and the tests showed that the sensor’s error was ±8% and that the sensor could function well in practical conditions and remain stable in the long term. Full article

(This article belongs to the Special Issue Sensors for MEMS and Microsystems)

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16 pages, 1467 KiB

Open AccessArticle

Analysing the Zenith Tropospheric Delay Estimates in On-line Precise Point Positioning (PPP) Services and PPP Software Packages

by Jorge Mendez Astudillo¹, Lawrence Lau^2,*

, Yu-Ting Tang³ and Terry Moore⁴

¹ International Doctoral Innovation Centre, University of Nottingham Ningbo China, Ningbo 315100, China

² Department of Civil Engineering, University of Nottingham Ningbo China, Ningbo 315100, China

³ School of Geographical Sciences, University of Nottingham Ningbo China, Ningbo 315100, China

⁴ The Nottingham Geospatial Institute, University of Nottingham, Nottingham NG7 2RD, UK

Sensors 2018, 18(2), 580; https://doi.org/10.3390/s18020580 - 14 Feb 2018

Cited by 46 | Viewed by 7564

Abstract

As Global Navigation Satellite System (GNSS) signals travel through the troposphere, a tropospheric delay occurs due to a change in the refractive index of the medium. The Precise Point Positioning (PPP) technique can achieve centimeter/millimeter positioning accuracy with only one GNSS receiver. The [...] Read more.

As Global Navigation Satellite System (GNSS) signals travel through the troposphere, a tropospheric delay occurs due to a change in the refractive index of the medium. The Precise Point Positioning (PPP) technique can achieve centimeter/millimeter positioning accuracy with only one GNSS receiver. The Zenith Tropospheric Delay (ZTD) is estimated alongside with the position unknowns in PPP. Estimated ZTD can be very useful for meteorological applications, an example is the estimation of water vapor content in the atmosphere from the estimated ZTD. PPP is implemented with different algorithms and models in online services and software packages. In this study, a performance assessment with analysis of ZTD estimates from three PPP online services and three software packages is presented. The main contribution of this paper is to show the accuracy of ZTD estimation achievable in PPP. The analysis also provides the GNSS users and researchers the insight of the processing algorithm dependence and impact on PPP ZTD estimation. Observation data of eight whole days from a total of nine International GNSS Service (IGS) tracking stations spread in the northern hemisphere, the equatorial region and the southern hemisphere is used in this analysis. The PPP ZTD estimates are compared with the ZTD obtained from the IGS tropospheric product of the same days. The estimates of two of the three online PPP services show good agreement (<1 cm) with the IGS ZTD values at the northern and southern hemisphere stations. The results also show that the online PPP services perform better than the selected PPP software packages at all stations. Full article

(This article belongs to the Section Remote Sensors)

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18 pages, 6120 KiB

Open AccessArticle

A Modular IoT Platform for Real-Time Indoor Air Quality Monitoring

by Mohieddine Benammar^1,*

, Abderrazak Abdaoui¹, Sabbir H.M. Ahmad¹, Farid Touati¹

and Abdullah Kadri²

¹ Department of Electrical Engineering, College of Engineering, Qatar University, Doha 2713, Qatar

² Qatar Mobility and Innovation Center, QSTP, Doha 210531, Qatar

Sensors 2018, 18(2), 581; https://doi.org/10.3390/s18020581 - 14 Feb 2018

Cited by 191 | Viewed by 15475

Abstract

The impact of air quality on health and on life comfort is well established. In many societies, vulnerable elderly and young populations spend most of their time indoors. Therefore, indoor air quality monitoring (IAQM) is of great importance to human health. Engineers and [...] Read more.

The impact of air quality on health and on life comfort is well established. In many societies, vulnerable elderly and young populations spend most of their time indoors. Therefore, indoor air quality monitoring (IAQM) is of great importance to human health. Engineers and researchers are increasingly focusing their efforts on the design of real-time IAQM systems using wireless sensor networks. This paper presents an end-to-end IAQM system enabling measurement of CO₂, CO, SO₂, NO₂, O₃, Cl₂, ambient temperature, and relative humidity. In IAQM systems, remote users usually use a local gateway to connect wireless sensor nodes in a given monitoring site to the external world for ubiquitous access of data. In this work, the role of the gateway in processing collected air quality data and its reliable dissemination to end-users through a web-server is emphasized. A mechanism for the backup and the restoration of the collected data in the case of Internet outage is presented. The system is adapted to an open-source Internet-of-Things (IoT) web-server platform, called Emoncms, for live monitoring and long-term storage of the collected IAQM data. A modular IAQM architecture is adopted, which results in a smart scalable system that allows seamless integration of various sensing technologies, wireless sensor networks (WSNs) and smart mobile standards. The paper gives full hardware and software details of the proposed solution. Sample IAQM results collected in various locations are also presented to demonstrate the abilities of the system. Full article

(This article belongs to the Section Sensor Networks)

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19 pages, 11988 KiB

Open AccessArticle

Structured Kernel Subspace Learning for Autonomous Robot Navigation

by Eunwoo Kim

, Sungjoon Choi and Songhwai Oh^*

Department of Electrical and Computer Engineering and ASRI, Seoul National University, Seoul 08826, Korea

Sensors 2018, 18(2), 582; https://doi.org/10.3390/s18020582 - 14 Feb 2018

Cited by 4 | Viewed by 5206

Abstract

This paper considers two important problems for autonomous robot navigation in a dynamic environment, where the goal is to predict pedestrian motion and control a robot with the prediction for safe navigation. While there are several methods for predicting the motion of a [...] Read more.

This paper considers two important problems for autonomous robot navigation in a dynamic environment, where the goal is to predict pedestrian motion and control a robot with the prediction for safe navigation. While there are several methods for predicting the motion of a pedestrian and controlling a robot to avoid incoming pedestrians, it is still difficult to safely navigate in a dynamic environment due to challenges, such as the varying quality and complexity of training data with unwanted noises. This paper addresses these challenges simultaneously by proposing a robust kernel subspace learning algorithm based on the recent advances in nuclear-norm and

l_{1}

-norm minimization. We model the motion of a pedestrian and the robot controller using Gaussian processes. The proposed method efficiently approximates a kernel matrix used in Gaussian process regression by learning low-rank structured matrix (with symmetric positive semi-definiteness) to find an orthogonal basis, which eliminates the effects of erroneous and inconsistent data. Based on structured kernel subspace learning, we propose a robust motion model and motion controller for safe navigation in dynamic environments. We evaluate the proposed robust kernel learning in various tasks, including regression, motion prediction, and motion control problems, and demonstrate that the proposed learning-based systems are robust against outliers and outperform existing regression and navigation methods. Full article

(This article belongs to the Special Issue Smart Sensors for Mechatronic and Robotic Systems)

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17 pages, 5644 KiB

Open AccessArticle

Multisensor Analysis of Spectral Dimensionality and Soil Diversity in the Great Central Valley of California

by Daniel Sousa^*

and Christopher Small

Lamont-Doherty Earth Observatory, Columbia University, Palisades, NY 10964, USA

Sensors 2018, 18(2), 583; https://doi.org/10.3390/s18020583 - 14 Feb 2018

Cited by 25 | Viewed by 5388

Abstract

Planned hyperspectral satellite missions and the decreased revisit time of multispectral imaging offer the potential for data fusion to leverage both the spectral resolution of hyperspectral sensors and the temporal resolution of multispectral constellations. Hyperspectral imagery can also be used to better understand [...] Read more.

Planned hyperspectral satellite missions and the decreased revisit time of multispectral imaging offer the potential for data fusion to leverage both the spectral resolution of hyperspectral sensors and the temporal resolution of multispectral constellations. Hyperspectral imagery can also be used to better understand fundamental properties of multispectral data. In this analysis, we use five flight lines from the Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) archive with coincident Landsat 8 acquisitions over a spectrally diverse region of California to address the following questions: (1) How much of the spectral dimensionality of hyperspectral data is captured in multispectral data?; (2) Is the characteristic pyramidal structure of the multispectral feature space also present in the low order dimensions of the hyperspectral feature space at comparable spatial scales?; (3) How much variability in rock and soil substrate endmembers (EMs) present in hyperspectral data is captured by multispectral sensors? We find nearly identical partitions of variance, low-order feature space topologies, and EM spectra for hyperspectral and multispectral image composites. The resulting feature spaces and EMs are also very similar to those from previous global multispectral analyses, implying that the fundamental structure of the global feature space is present in our relatively small spatial subset of California. Finally, we find that the multispectral dataset well represents the substrate EM variability present in the study area – despite its inability to resolve narrow band absorptions. We observe a tentative but consistent physical relationship between the gradation of substrate reflectance in the feature space and the gradation of sand versus clay content in the soil classification system. Full article

(This article belongs to the Special Issue Analysis of Multispectral and Hyperspectral Data)

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12 pages, 2664 KiB

Open AccessArticle

QLog Solar-Cell Mode Photodiode Logarithmic CMOS Pixel Using Charge Compression and Readout

by Yang Ni

New Imaging Technologies, Impasse de la Noisette, 91370 Verrières le Buisson CEDEX, France

Sensors 2018, 18(2), 584; https://doi.org/10.3390/s18020584 - 14 Feb 2018

Cited by 5 | Viewed by 6152

Abstract

In this paper, we present a new logarithmic pixel design currently under development at New Imaging Technologies SA (NIT). This new logarithmic pixel design uses charge domain logarithmic signal compression and charge-transfer-based signal readout. This structure gives a linear response in low light [...] Read more.

In this paper, we present a new logarithmic pixel design currently under development at New Imaging Technologies SA (NIT). This new logarithmic pixel design uses charge domain logarithmic signal compression and charge-transfer-based signal readout. This structure gives a linear response in low light conditions and logarithmic response in high light conditions. The charge transfer readout efficiently suppresses the reset (KTC) noise by using true correlated double sampling (CDS) in low light conditions. In high light conditions, thanks to charge domain logarithmic compression, it has been demonstrated that 3000 electrons should be enough to cover a 120 dB dynamic range with a mobile phone camera-like signal-to-noise ratio (SNR) over the whole dynamic range. This low electron count permits the use of ultra-small floating diffusion capacitance (sub-fF) without charge overflow. The resulting large conversion gain permits a single photon detection capability with a wide dynamic range without a complex sensor/system design. A first prototype sensor with 320 × 240 pixels has been implemented to validate this charge domain logarithmic pixel concept and modeling. The first experimental results validate the logarithmic charge compression theory and the low readout noise due to the charge-transfer-based readout. Full article

(This article belongs to the Special Issue Special Issue on the 2017 International Image Sensor Workshop (IISW))

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22 pages, 6535 KiB

Open AccessArticle

A Single RF Emitter-Based Indoor Navigation Method for Autonomous Service Robots

by Tyrone Sherwin¹

, Mikala Easte¹, Andrew Tzer-Yeu Chen¹

, Kevin I-Kai Wang^1,* and Wenbin Dai^2,*

¹ Department of Electrical and Computer Engineering, The University of Auckland, Auckland 1023, New Zealand

² Department of Automation, Shanghai Jiao Tong University, Shanghai 200000, China

Sensors 2018, 18(2), 585; https://doi.org/10.3390/s18020585 - 14 Feb 2018

Cited by 6 | Viewed by 6824

Abstract

Location-aware services are one of the key elements of modern intelligent applications. Numerous real-world applications such as factory automation, indoor delivery, and even search and rescue scenarios require autonomous robots to have the ability to navigate in an unknown environment and reach mobile [...] Read more.

Location-aware services are one of the key elements of modern intelligent applications. Numerous real-world applications such as factory automation, indoor delivery, and even search and rescue scenarios require autonomous robots to have the ability to navigate in an unknown environment and reach mobile targets with minimal or no prior infrastructure deployment. This research investigates and proposes a novel approach of dynamic target localisation using a single RF emitter, which will be used as the basis of allowing autonomous robots to navigate towards and reach a target. Through the use of multiple directional antennae, Received Signal Strength (RSS) is compared to determine the most probable direction of the targeted emitter, which is combined with the distance estimates to improve the localisation performance. The accuracy of the position estimate is further improved using a particle filter to mitigate the fluctuating nature of real-time RSS data. Based on the direction information, a motion control algorithm is proposed, using Simultaneous Localisation and Mapping (SLAM) and A* path planning to enable navigation through unknown complex environments. A number of navigation scenarios were developed in the context of factory automation applications to demonstrate and evaluate the functionality and performance of the proposed system. Full article

(This article belongs to the Special Issue Sensing, Data Analysis and Platforms for Ubiquitous Intelligence)

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17 pages, 5177 KiB

Open AccessArticle

Using Unmanned Aerial Vehicles in Postfire Vegetation Survey Campaigns through Large and Heterogeneous Areas: Opportunities and Challenges

by José Manuel Fernández-Guisuraga^1,*

, Enoc Sanz-Ablanedo²

, Susana Suárez-Seoane¹

and Leonor Calvo¹

¹ Biodiversity and Environmental Management Department, Faculty of Biological and Environmental Sciences, University of León, 24071 León, Spain

² Mining Technology, Topography and Structures Department, University of León, 22400 Ponferrada, Spain

Sensors 2018, 18(2), 586; https://doi.org/10.3390/s18020586 - 14 Feb 2018

Cited by 95 | Viewed by 8367

Abstract

This study evaluated the opportunities and challenges of using drones to obtain multispectral orthomosaics at ultra-high resolution that could be useful for monitoring large and heterogeneous burned areas. We conducted a survey using an octocopter equipped with a Parrot SEQUOIA multispectral camera in [...] Read more.

This study evaluated the opportunities and challenges of using drones to obtain multispectral orthomosaics at ultra-high resolution that could be useful for monitoring large and heterogeneous burned areas. We conducted a survey using an octocopter equipped with a Parrot SEQUOIA multispectral camera in a 3000 ha framework located within the perimeter of a megafire in Spain. We assessed the quality of both the camera raw imagery and the multispectral orthomosaic obtained, as well as the required processing capability. Additionally, we compared the spatial information provided by the drone orthomosaic at ultra-high spatial resolution with another image provided by the WorldView-2 satellite at high spatial resolution. The drone raw imagery presented some anomalies, such as horizontal banding noise and non-homogeneous radiometry. Camera locations showed a lack of synchrony of the single frequency GPS receiver. The georeferencing process based on ground control points achieved an error lower than 30 cm in X-Y and lower than 55 cm in Z. The drone orthomosaic provided more information in terms of spatial variability in heterogeneous burned areas in comparison with the WorldView-2 satellite imagery. The drone orthomosaic could constitute a viable alternative for the evaluation of post-fire vegetation regeneration in large and heterogeneous burned areas. Full article

(This article belongs to the Special Issue UAV or Drones for Remote Sensing Applications)

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16 pages, 5837 KiB

Open AccessArticle

Mexican-Hat-Like Response in a Flexible Tactile Sensor Using a Magnetorheological Elastomer

by Takumi Kawasetsu^1,*

, Takato Horii², Hisashi Ishihara¹ and Minoru Asada¹

¹ Department of Adaptive Machine Systems, Graduate School of Engineering, Osaka University, Suita 5650871, Japan

² Department of Mechanical Engineering and Intelligent Systems, Graduate School of Informatics and Engineering, The University of Electro-Communications, Chofu 1828585, Japan

Sensors 2018, 18(2), 587; https://doi.org/10.3390/s18020587 - 14 Feb 2018

Cited by 52 | Viewed by 7681

Abstract

A significant challenge in robotics is providing a sense of touch to robots. Even though several types of flexible tactile sensors have been proposed, they still have various technical issues such as a large amount of deformation that fractures the sensing elements, a [...] Read more.

A significant challenge in robotics is providing a sense of touch to robots. Even though several types of flexible tactile sensors have been proposed, they still have various technical issues such as a large amount of deformation that fractures the sensing elements, a poor maintainability and a deterioration in the sensitivity caused by the presence of a thick and soft covering. As one solution for these issues, we proposed a flexible tactile sensor composed of a magnet, magnetic transducer and dual-layer elastomer, which consists of a magnetorheological and nonmagnetic elastomer sheet. In this study, we first investigated the sensitivity of the sensor, which was found to be high (approximately 161 mV/N with a signal-to-noise ratio of 42.2 dB); however, the sensor has a speed-dependent hysteresis in its sensor response curve. Then, we investigated the spatial response and observed the following results: (1) the sensor response was a distorted Mexican-hat-like bipolar shape, namely a negative response area was observed around the positive response area; (2) the negative response area disappeared when we used a compressible sponge sheet instead of the incompressible nonmagnetic elastomer. We concluded that the characteristic negative response in the Mexican-hat-like response is derived from the incompressibility of the nonmagnetic elastomer. Full article

(This article belongs to the Section Physical Sensors)

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16 pages, 14754 KiB

Open AccessArticle

Gradient-Type Magnetoelectric Current Sensor with Strong Multisource Noise Suppression

by Mingji Zhang^1,2

and Siu Wing Or^1,2,*

¹ Department of Electrical Engineering, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong, China

² Hong Kong Branch of National Rail Transit Electrification and Automation Engineering Technology Research Center, Hong Kong, China

Sensors 2018, 18(2), 588; https://doi.org/10.3390/s18020588 - 14 Feb 2018

Cited by 14 | Viewed by 5906

Abstract

A novel gradient-type magnetoelectric (ME) current sensor operating in magnetic field gradient (MFG) detection and conversion mode is developed based on a pair of ME composites that have a back-to-back capacitor configuration under a baseline separation and a magnetic biasing in an electrically-shielded [...] Read more.

A novel gradient-type magnetoelectric (ME) current sensor operating in magnetic field gradient (MFG) detection and conversion mode is developed based on a pair of ME composites that have a back-to-back capacitor configuration under a baseline separation and a magnetic biasing in an electrically-shielded and mechanically-enclosed housing. The physics behind the current sensing process is the product effect of the current-induced MFG effect associated with vortex magnetic fields of current-carrying cables (i.e., MFG detection) and the MFG-induced ME effect in the ME composite pair (i.e., MFG conversion). The sensor output voltage is directly obtained from the gradient ME voltage of the ME composite pair and is calibrated against cable current to give the current sensitivity. The current sensing performance of the sensor is evaluated, both theoretically and experimentally, under multisource noises of electric fields, magnetic fields, vibrations, and thermals. The sensor combines the merits of small nonlinearity in the current-induced MFG effect with those of high sensitivity and high common-mode noise rejection rate in the MFG-induced ME effect to achieve a high current sensitivity of 0.65–12.55 mV/A in the frequency range of 10 Hz–170 kHz, a small input-output nonlinearity of <500 ppm, a small thermal drift of <0.2%/℃ in the current range of 0–20 A, and a high common-mode noise rejection rate of 17–28 dB from multisource noises. Full article

(This article belongs to the Special Issue Magnetic Sensors and Their Applications)

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11 pages, 3168 KiB

Open AccessArticle

Detection of Thrombin Based on Fluorescence Energy Transfer between Semiconducting Polymer Dots and BHQ-Labelled Aptamers

by Yizhang Liu^1,2,*, Xuekai Jiang², Wenfeng Cao², Junyong Sun² and Feng Gao^2,*

¹ Department of Food and Environmental Engineering, Chuzhou Vocational and Technical College, Chuzhou 239001, China

² Laboratory of Functionalized Molecular Solids, Ministry of Education, Anhui Key Laboratory of Chemo/Biosensing, Laboratory of Optical Probes and Bioelectrocatalysis (LOPAB), College of Chemistry and Materials Science, Anhui Normal University, Wuhu 241000, China

Sensors 2018, 18(2), 589; https://doi.org/10.3390/s18020589 - 14 Feb 2018

Cited by 17 | Viewed by 5957

Abstract

Carboxyl-functionalized semiconducting polymer dots (Pdots) were synthesized as an energy donor by the nanoprecipitation method. A black hole quenching dye (BHQ-labelled thrombin aptamers) was used as the energy acceptor, and fluorescence resonance energy transfer between the aptamers and Pdots was used for fluorescence [...] Read more.

Carboxyl-functionalized semiconducting polymer dots (Pdots) were synthesized as an energy donor by the nanoprecipitation method. A black hole quenching dye (BHQ-labelled thrombin aptamers) was used as the energy acceptor, and fluorescence resonance energy transfer between the aptamers and Pdots was used for fluorescence quenching of the Pdots. The addition of thrombin restored the fluorescence intensity. Under the optimized experimental conditions, the fluorescence of the system was restored to the maximum when the concentration of thrombin reached 130 nM, with a linear range of 0–50 nM (R² = 0.990) and a detection limit of 0.33 nM. This sensor was less disturbed by impurities, showing good specificity and signal response to thrombin, with good application in actual samples. The detection of human serum showed good linearity in the range of 0–30 nM (R² = 0.997), with a detection limit of 0.56 nM and a recovery rate of 96.2–104.1%, indicating that this fluorescence sensor can be used for the detection of thrombin content in human serum. Full article

(This article belongs to the Special Issue Semiconductor Materials on Biosensors Application)

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17 pages, 6172 KiB

Open AccessArticle

Error Modelling for Multi-Sensor Measurements in Infrastructure-Free Indoor Navigation

by Laura Ruotsalainen^*, Martti Kirkko-Jaakkola, Jesperi Rantanen and Maija Mäkelä

Finnish Geospatial Research Institute (FGI), Geodeetinrinne 2, 02430 Masala, Finland

Sensors 2018, 18(2), 590; https://doi.org/10.3390/s18020590 - 14 Feb 2018

Cited by 31 | Viewed by 7944

Abstract

The long-term objective of our research is to develop a method for infrastructure-free simultaneous localization and mapping (SLAM) and context recognition for tactical situational awareness. Localization will be realized by propagating motion measurements obtained using a monocular camera, a foot-mounted Inertial Measurement Unit [...] Read more.

The long-term objective of our research is to develop a method for infrastructure-free simultaneous localization and mapping (SLAM) and context recognition for tactical situational awareness. Localization will be realized by propagating motion measurements obtained using a monocular camera, a foot-mounted Inertial Measurement Unit (IMU), sonar, and a barometer. Due to the size and weight requirements set by tactical applications, Micro-Electro-Mechanical (MEMS) sensors will be used. However, MEMS sensors suffer from biases and drift errors that may substantially decrease the position accuracy. Therefore, sophisticated error modelling and implementation of integration algorithms are key for providing a viable result. Algorithms used for multi-sensor fusion have traditionally been different versions of Kalman filters. However, Kalman filters are based on the assumptions that the state propagation and measurement models are linear with additive Gaussian noise. Neither of the assumptions is correct for tactical applications, especially for dismounted soldiers, or rescue personnel. Therefore, error modelling and implementation of advanced fusion algorithms are essential for providing a viable result. Our approach is to use particle filtering (PF), which is a sophisticated option for integrating measurements emerging from pedestrian motion having non-Gaussian error characteristics. This paper discusses the statistical modelling of the measurement errors from inertial sensors and vision based heading and translation measurements to include the correct error probability density functions (pdf) in the particle filter implementation. Then, model fitting is used to verify the pdfs of the measurement errors. Based on the deduced error models of the measurements, particle filtering method is developed to fuse all this information, where the weights of each particle are computed based on the specific models derived. The performance of the developed method is tested via two experiments, one at a university’s premises and another in realistic tactical conditions. The results show significant improvement on the horizontal localization when the measurement errors are carefully modelled and their inclusion into the particle filtering implementation correctly realized. Full article

(This article belongs to the Section Physical Sensors)

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22 pages, 26879 KiB

Open AccessFeature PaperArticle

A Novel Strategy for Very-Large-Scale Cash-Crop Mapping in the Context of Weather-Related Risk Assessment, Combining Global Satellite Multispectral Datasets, Environmental Constraints, and In Situ Acquisition of Geospatial Data

by Fabio Dell’Acqua^1,*

, Gianni Cristian Iannelli², Marco A. Torres³ and Mario L.V. Martina⁴

¹ Department of Electrical, Computer, Biomedical Engineering, University of Pavia, Via Adolfo Ferrata, 5, I-27100 Pavia, Italy

² Ticinum Aerospace S.r.l., I-27100 Pavia, Italy

³ Instituto de Ingeniería, UNAM, C.P. 04510 Ciudad de México, Mexico

⁴ Scuola Universitaria Superiore IUSS Pavia, Piazza della Vittoria, 15, I-27100 Pavia, Italy

Sensors 2018, 18(2), 591; https://doi.org/10.3390/s18020591 - 14 Feb 2018

Cited by 21 | Viewed by 5243

Abstract

Cash crops are agricultural crops intended to be sold for profit as opposed to subsistence crops, meant to support the producer, or to support livestock. Since cash crops are intended for future sale, they translate into large financial value when considered on a [...] Read more.

Cash crops are agricultural crops intended to be sold for profit as opposed to subsistence crops, meant to support the producer, or to support livestock. Since cash crops are intended for future sale, they translate into large financial value when considered on a wide geographical scale, so their production directly involves financial risk. At a national level, extreme weather events including destructive rain or hail, as well as drought, can have a significant impact on the overall economic balance. It is thus important to map such crops in order to set up insurance and mitigation strategies. Using locally generated data—such as municipality-level records of crop seeding—for mapping purposes implies facing a series of issues like data availability, quality, homogeneity, etc. We thus opted for a different approach relying on global datasets. Global datasets ensure homogeneity and availability of data, although sometimes at the expense of precision and accuracy. A typical global approach makes use of spaceborne remote sensing, for which different land cover classification strategies are available in literature at different levels of cost and accuracy. We selected the optimal strategy in the perspective of a global processing chain. Thanks to a specifically developed strategy for fusing unsupervised classification results with environmental constraints and other geospatial inputs including ground-based data, we managed to obtain good classification results despite the constraints placed. The overall production process was composed using “good-enough" algorithms at each step, ensuring that the precision, accuracy, and data-hunger of each algorithm was commensurate to the precision, accuracy, and amount of data available. This paper describes the tailored strategy developed on the occasion as a cooperation among different groups with diverse backgrounds, a strategy which is believed to be profitably reusable in other, similar contexts. The paper presents the problem, the constraints and the adopted solutions; it then summarizes the main findings including that efforts and costs can be saved on the side of Earth Observation data processing when additional ground-based data are available to support the mapping task. Full article

(This article belongs to the Special Issue Earth Observation and In-Situ Sensing for Risk Assessment from Natural Threats)

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17 pages, 1402 KiB

Open AccessFeature PaperArticle

On the Comparison of Wearable Sensor Data Fusion to a Single Sensor Machine Learning Technique in Fall Detection

by Panagiotis Tsinganos^* and Athanassios Skodras

Department of Electrical and Computer Engineering, University of Patras, 265 04 Patras, Greece

Sensors 2018, 18(2), 592; https://doi.org/10.3390/s18020592 - 14 Feb 2018

Cited by 68 | Viewed by 8060

Abstract

In the context of the ageing global population, researchers and scientists have tried to find solutions to many challenges faced by older people. Falls, the leading cause of injury among elderly, are usually severe enough to require immediate medical attention; thus, their detection [...] Read more.

In the context of the ageing global population, researchers and scientists have tried to find solutions to many challenges faced by older people. Falls, the leading cause of injury among elderly, are usually severe enough to require immediate medical attention; thus, their detection is of primary importance. To this effect, many fall detection systems that utilize wearable and ambient sensors have been proposed. In this study, we compare three newly proposed data fusion schemes that have been applied in human activity recognition and fall detection. Furthermore, these algorithms are compared to our recent work regarding fall detection in which only one type of sensor is used. The results show that fusion algorithms differ in their performance, whereas a machine learning strategy should be preferred. In conclusion, the methods presented and the comparison of their performance provide useful insights into the problem of fall detection. Full article

(This article belongs to the Special Issue Soft Sensors and Intelligent Algorithms for Data Fusion)

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19 pages, 4379 KiB

Open AccessArticle

Robust Automatic Target Recognition via HRRP Sequence Based on Scatterer Matching

by Yuan Jiang¹

, Yang Li^1,2, Jinjian Cai¹, Yanhua Wang^1,*

and Jia Xu¹

¹ Radar Research Lab, School of Information and Electronics, Beijing Institute of Technology, Beijing 100081, China

² Beijing Key Laboratory of Embedded Real-time Information Processing Technology, Beijing Institute of Technology, Beijing 100081, China

Sensors 2018, 18(2), 593; https://doi.org/10.3390/s18020593 - 14 Feb 2018

Cited by 20 | Viewed by 4123

Abstract

High resolution range profile (HRRP) plays an important role in wideband radar automatic target recognition (ATR). In order to alleviate the sensitivity to clutter and target aspect, employing a sequence of HRRP is a promising approach to enhance the ATR performance. In this [...] Read more.

High resolution range profile (HRRP) plays an important role in wideband radar automatic target recognition (ATR). In order to alleviate the sensitivity to clutter and target aspect, employing a sequence of HRRP is a promising approach to enhance the ATR performance. In this paper, a novel HRRP sequence-matching method based on singular value decomposition (SVD) is proposed. First, the HRRP sequence is decoupled into the angle space and the range space via SVD, which correspond to the span of the left and the right singular vectors, respectively. Second, atomic norm minimization (ANM) is utilized to estimate dominant scatterers in the range space and the Hausdorff distance is employed to measure the scatter similarity between the test and training data. Next, the angle space similarity between the test and training data is evaluated based on the left singular vector correlations. Finally, the range space matching result and the angle space correlation are fused with the singular values as weights. Simulation and outfield experimental results demonstrate that the proposed matching metric is a robust similarity measure for HRRP sequence recognition. Full article

(This article belongs to the Section Remote Sensors)

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14 pages, 6380 KiB

Open AccessArticle

Enhanced Automated Guidance System for Horizontal Auger Boring Based on Image Processing

by Lingling Wu¹, Guojun Wen^1,*, Yudan Wang¹, Lei Huang² and Jiang Zhou¹

¹ School of Mechanical & Electronic Information, China University of Geosciences, Wuhan 430074, China

² Shandong Institute of Space Electronic Technology, Yantai 264670, China

Sensors 2018, 18(2), 595; https://doi.org/10.3390/s18020595 - 15 Feb 2018

Cited by 2 | Viewed by 5395

Abstract

Horizontal auger boring (HAB) is a widely used trenchless technology for the high-accuracy installation of gravity or pressure pipelines on line and grade. Differing from other pipeline installations, HAB requires a more precise and automated guidance system for use in a practical project. [...] Read more.

Horizontal auger boring (HAB) is a widely used trenchless technology for the high-accuracy installation of gravity or pressure pipelines on line and grade. Differing from other pipeline installations, HAB requires a more precise and automated guidance system for use in a practical project. This paper proposes an economic and enhanced automated optical guidance system, based on optimization research of light-emitting diode (LED) light target and five automated image processing bore-path deviation algorithms. An LED light target was optimized for many qualities, including light color, filter plate color, luminous intensity, and LED layout. The image preprocessing algorithm, direction location algorithm, angle measurement algorithm, deflection detection algorithm, and auto-focus algorithm, compiled in MATLAB, are used to automate image processing for deflection computing and judging. After multiple indoor experiments, this guidance system is applied in a project of hot water pipeline installation, with accuracy controlled within 2 mm in 48-m distance, providing accurate line and grade controls and verifying the feasibility and reliability of the guidance system. Full article

(This article belongs to the Section Physical Sensors)

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22 pages, 14187 KiB

Open AccessArticle

A Novel Method of Autonomous Inspection for Transmission Line based on Cable Inspection Robot LiDAR Data

by Xinyan Qin¹, Gongping Wu^1,*

, Jin Lei^1,2,*

, Fei Fan¹, Xuhui Ye¹ and Quanjie Mei¹

¹ Department of Power and Mechanical Engineering, Wuhan University, Wuhan 430072, China

² Key Laboratory of Hydraulic Machinery Transients, Ministry of Education, Wuhan University, Wuhan 430072, China

Sensors 2018, 18(2), 596; https://doi.org/10.3390/s18020596 - 15 Feb 2018

Cited by 63 | Viewed by 8213

Abstract

With the growth of the national economy, there is increasing demand for electricity, which forces transmission line corridors to become structurally complicated and extend to complex environments (e.g., mountains, forests). It is a great challenge to inspect transmission line in these regions. To [...] Read more.

With the growth of the national economy, there is increasing demand for electricity, which forces transmission line corridors to become structurally complicated and extend to complex environments (e.g., mountains, forests). It is a great challenge to inspect transmission line in these regions. To address these difficulties, a novel method of autonomous inspection for transmission line is proposed based on cable inspection robot (CIR) LiDAR data, which mainly includes two steps: preliminary inspection and autonomous inspection. In preliminary inspection, the position and orientation system (POS) data is used for original point cloud dividing, ground point filtering, and structured partition. A hierarchical classification strategy is established to identify the classes and positions of the abnormal points. In autonomous inspection, CIR can autonomously reach the specified points through inspection planning. These inspection targets are imaged with PTZ (pan, tilt, zoom) cameras by coordinate transformation. The feasibility and effectiveness of the proposed method are verified by test site experiments and actual line experiments, respectively. The proposed method greatly reduces manpower and improves inspection accuracy, providing a theoretical basis for intelligent inspection of transmission lines in the future. Full article

(This article belongs to the Section Remote Sensors)

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21 pages, 5659 KiB

Open AccessArticle

An Efficient Framework Model for Optimizing Routing Performance in VANETs

by Nori M. Al-Kharasani^*

, Zuriati Ahmad Zulkarnain^*, Shamala Subramaniam and Zurina Mohd Hanapi

Department of Wireless and Communication Technology, Faculty of Computer Science and Information Technolog, University Putra Malaysia, Serdang 43400, Malaysia

Sensors 2018, 18(2), 597; https://doi.org/10.3390/s18020597 - 15 Feb 2018

Cited by 29 | Viewed by 4349

Abstract

Routing in Vehicular Ad hoc Networks (VANET) is a bit complicated because of the nature of the high dynamic mobility. The efficiency of routing protocol is influenced by a number of factors such as network density, bandwidth constraints, traffic load, and mobility patterns [...] Read more.

Routing in Vehicular Ad hoc Networks (VANET) is a bit complicated because of the nature of the high dynamic mobility. The efficiency of routing protocol is influenced by a number of factors such as network density, bandwidth constraints, traffic load, and mobility patterns resulting in frequency changes in network topology. Therefore, Quality of Service (QoS) is strongly needed to enhance the capability of the routing protocol and improve the overall network performance. In this paper, we introduce a statistical framework model to address the problem of optimizing routing configuration parameters in Vehicle-to-Vehicle (V2V) communication. Our framework solution is based on the utilization of the network resources to further reflect the current state of the network and to balance the trade-off between frequent changes in network topology and the QoS requirements. It consists of three stages: simulation network stage used to execute different urban scenarios, the function stage used as a competitive approach to aggregate the weighted cost of the factors in a single value, and optimization stage used to evaluate the communication cost and to obtain the optimal configuration based on the competitive cost. The simulation results show significant performance improvement in terms of the Packet Delivery Ratio (PDR), Normalized Routing Load (NRL), Packet loss (PL), and End-to-End Delay (E2ED). Full article

(This article belongs to the Section Sensor Networks)

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8 pages, 3733 KiB

Open AccessArticle

On-Site Detection of Aflatoxin B1 in Grains by a Palm-Sized Surface Plasmon Resonance Sensor

by Jeong Moon¹, Jihyun Byun¹, Hongki Kim¹, Eun-Kyung Lim^1,2, Jinyoung Jeong^1,2

, Juyuen Jung^1,2 and Taejoon Kang^1,2,3,*

¹ Hazards Monitoring Bionano Researh Center, Korea Research Institute of Bioscience and Biotechnology (KRIBB), Daejeon 34141, Korea

² Department of Nanobiotechnology, KRIBB School of Biotechnology, University of Science and Technology (UST), Daejeon 34113, Korea

³ BioNano Health Guard Research Center, Korea Research Institute of Bioscience and Biotechnology (KRIBB), Daejeon 34141, Korea

Sensors 2018, 18(2), 598; https://doi.org/10.3390/s18020598 - 15 Feb 2018

Cited by 43 | Viewed by 7317

Abstract

Aflatoxins (AFs) are highly toxic compounds that can cause both acute and chronic toxicity in humans. Aflatoxin B1 (AFB1) is considered the most toxic of AFs. Therefore, the rapid and on-site detection of AFB1 is critical for food safety management. Here, we report [...] Read more.

Aflatoxins (AFs) are highly toxic compounds that can cause both acute and chronic toxicity in humans. Aflatoxin B1 (AFB1) is considered the most toxic of AFs. Therefore, the rapid and on-site detection of AFB1 is critical for food safety management. Here, we report the on-site detection of AFB1 in grains by a portable surface plasmon resonance (SPR) sensor. For the detection of AFB1, the surface of an SPR Au chip was sequentially modified by cysteine-protein G, AFB1 antibody, and bovine serum albumin (BSA). Then, the sample solution and AFB1-BSA conjugate were flowed onto the Au chip in serial order. In the absence of AFB1, the SPR response greatly increased due to the binding of AFB1-BSA on the Au chip. In the presence of AFB1, the SPR response showed little change because the small AFB1 molecule binds on the Au chip instead of the large AFB1-BSA molecule. By using this portable SPR-based competitive immunoassay, the sensor showed low limits of detection (2.51 ppb) and quantification (16.32 ppb). Furthermore, we successfully detected AFB1 in rice, peanut, and almond samples, which suggests that the proposed sensing method can potentially be applied to the on-site monitoring of mycotoxins in food. Full article

(This article belongs to the Special Issue Nanobiosensors in Food Industry)

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15 pages, 2844 KiB

Open AccessArticle

Hyperpolarized Amino Acid Derivatives as Multivalent Magnetic Resonance pH Sensor Molecules

by Christian Hundshammer^1,2,3

, Stephan Düwel^1,2,3

, David Ruseckas², Geoffrey Topping¹, Piotr Dzien¹, Christoph Müller^4,5,6, Benedikt Feuerecker^1,5, Jan B. Hövener⁷, Axel Haase³, Markus Schwaiger¹, Steffen J. Glaser² and Franz Schilling^1,*

¹ Department of Nuclear Medicine, Klinikum Rechts der Isar, Technical University of Munich, 81675 München, Germany

² Department of Chemistry, Technical University of Munich, 85748 Garching, Germany

³ Munich School of Bioengineering, Technical University of Munich, 85748 Garching, Germany

⁴ Department of Radiology, Medical Physics, University Medical Center Freiburg, Faculty of Medicine, University of Freiburg, 79106 Freiburg, Germany

⁵ German Consortium for Cancer Research (DKTK), 69120 Heidelberg, Germany

⁶ German Cancer Research Center (DKFZ), 69120 Heidelberg, Germany

⁷ Section for Biomedical Imaging, Molecular Imaging North Competence Center (MOINCC), Department for Radiology and Neuroradiology, University Medical Center Kiel, University Kiel, 24118 Kiel, Germany

Sensors 2018, 18(2), 600; https://doi.org/10.3390/s18020600 - 15 Feb 2018

Cited by 29 | Viewed by 6417

Abstract

pH is a tightly regulated physiological parameter that is often altered in diseased states like cancer. The development of biosensors that can be used to non-invasively image pH with hyperpolarized (HP) magnetic resonance spectroscopic imaging has therefore recently gained tremendous interest. However, most [...] Read more.

pH is a tightly regulated physiological parameter that is often altered in diseased states like cancer. The development of biosensors that can be used to non-invasively image pH with hyperpolarized (HP) magnetic resonance spectroscopic imaging has therefore recently gained tremendous interest. However, most of the known HP-sensors have only individually and not comprehensively been analyzed for their biocompatibility, their pH sensitivity under physiological conditions, and the effects of chemical derivatization on their logarithmic acid dissociation constant (pK_a). Proteinogenic amino acids are biocompatible, can be hyperpolarized and have at least two pH sensitive moieties. However, they do not exhibit a pH sensitivity in the physiologically relevant pH range. Here, we developed a systematic approach to tailor the pK_a of molecules using modifications of carbon chain length and derivatization rendering these molecules interesting for pH biosensing. Notably, we identified several derivatives such as [1-¹³C]serine amide and [1-¹³C]-2,3-diaminopropionic acid as novel pH sensors. They bear several spin-1/2 nuclei (¹³C, ¹⁵N, ³¹P) with high sensitivity up to 4.8 ppm/pH and we show that ¹³C spins can be hyperpolarized with dissolution dynamic polarization (DNP). Our findings elucidate the molecular mechanisms of chemical shift pH sensors that might help to design tailored probes for specific pH in vivo imaging applications. Full article

(This article belongs to the Special Issue Biosensors for Theranostics)

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13 pages, 3219 KiB

Open AccessArticle

Ring Laser Gyro G-Sensitive Misalignment Calibration in Linear Vibration Environments

by Lin Wang, Wenqi Wu^*, Geng Li, Xianfei Pan and Ruihang Yu

National University of Defense Technology, Changsha 410073, China

Sensors 2018, 18(2), 601; https://doi.org/10.3390/s18020601 - 16 Feb 2018

Cited by 12 | Viewed by 7249

Abstract

The ring laser gyro (RLG) dither axis will bend and exhibit errors due to the specific forces acting on the instrument, which are known as g-sensitive misalignments of the gyros. The g-sensitive misalignments of the RLG triad will cause severe attitude error in [...] Read more.

The ring laser gyro (RLG) dither axis will bend and exhibit errors due to the specific forces acting on the instrument, which are known as g-sensitive misalignments of the gyros. The g-sensitive misalignments of the RLG triad will cause severe attitude error in vibration or maneuver environments where large-amplitude specific forces and angular rates coexist. However, g-sensitive misalignments are usually ignored when calibrating the strapdown inertial navigation system (SINS). This paper proposes a novel method to calibrate the g-sensitive misalignments of an RLG triad in linear vibration environments. With the SINS is attached to a linear vibration bench through outer rubber dampers, rocking of the SINS can occur when the linear vibration is performed on the SINS. Therefore, linear vibration environments can be created to simulate the harsh environment during aircraft flight. By analyzing the mathematical model of g-sensitive misalignments, the relationship between attitude errors and specific forces as well as angular rates is established, whereby a calibration scheme with approximately optimal observations is designed. Vibration experiments are conducted to calibrate g-sensitive misalignments of the RLG triad. Vibration tests also show that SINS velocity error decreases significantly after g-sensitive misalignments compensation. Full article

(This article belongs to the Section Physical Sensors)

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17 pages, 2429 KiB

Open AccessArticle

Calcium Imaging of GPCR Activation Using Arrays of Reverse Transfected HEK293 Cells in a Microfluidic System

by Margriet Roelse^1,2,*, Maurice G.L. Henquet¹, Harrie A. Verhoeven¹, Norbert C.A. De Ruijter³

, Ron Wehrens^1,4, Marco S. Van Lenthe⁴

, Renger F. Witkamp⁵

, Robert D. Hall^1,2

and Maarten A. Jongsma¹

¹ BU Bioscience, Wageningen University and Research, Droevendaalsesteeg 1, 6708 PB Wageningen, The Netherlands

² Laboratory of Plant Physiology, Wageningen University and Research, 6708 PB Wageningen, The Netherlands

³ Laboratory of Cell Biology, Wageningen University and Research, 6708 PB Wageningen, The Netherlands

⁴ BU Biometris, Wageningen University and Research, 6708 PB Wageningen, The Netherlands

⁵ Human Nutrition and Health, Wageningen University and Research, Stippeneng 4, 6708 WE Wageningen, The Netherlands

Sensors 2018, 18(2), 602; https://doi.org/10.3390/s18020602 - 16 Feb 2018

Cited by 3 | Viewed by 8308

Abstract

Reverse-transfected cell arrays in microfluidic systems have great potential to perform large-scale parallel screening of G protein-coupled receptor (GPCR) activation. Here, we report the preparation of a novel platform using reverse transfection of HEK293 cells, imaging by stereo-fluorescence microscopy in a flowcell format, [...] Read more.

Reverse-transfected cell arrays in microfluidic systems have great potential to perform large-scale parallel screening of G protein-coupled receptor (GPCR) activation. Here, we report the preparation of a novel platform using reverse transfection of HEK293 cells, imaging by stereo-fluorescence microscopy in a flowcell format, real-time monitoring of cytosolic calcium ion fluctuations using the fluorescent protein Cameleon and analysis of GPCR responses to sequential sample exposures. To determine the relationship between DNA concentration and gene expression, we analyzed cell arrays made with variable concentrations of plasmid DNA encoding fluorescent proteins and the Neurokinin 1 (NK1) receptor. We observed pronounced effects on gene expression of both the specific and total DNA concentration. Reverse transfected spots with NK1 plasmid DNA at 1% of total DNA still resulted in detectable NK1 activation when exposed to its ligand. By varying the GPCR DNA concentration in reverse transfection, the sensitivity and robustness of the receptor response for sequential sample exposures was optimized. An injection series is shown for an array containing the NK1 receptor, bitter receptor TAS2R8 and controls. Both receptors were exposed 14 times to alternating samples of two ligands. Specific responses remained reproducible. This platform introduces new opportunities for high throughput screening of GPCR libraries. Full article

(This article belongs to the Special Issue Microfluidic Sensors)

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13 pages, 3902 KiB

Open AccessArticle

Spectral Optical Readout of Rectangular–Miniature Hollow Glass Tubing for Refractive Index Sensing

by Giulia Rigamonti, Valentina Bello

and Sabina Merlo^*

Dipartimento di Ingegneria Industriale e dell’Informazione, Università di Pavia, 27100 Pavia, Italy

Sensors 2018, 18(2), 603; https://doi.org/10.3390/s18020603 - 16 Feb 2018

Cited by 9 | Viewed by 4741

Abstract

For answering the growing demand of innovative micro-fluidic devices able to measure the refractive index of samples in extremely low volumes, this paper presents an overview of the performances of a micro-opto-fluidic sensing platform that employs rectangular, miniature hollow glass tubings. The operating [...] Read more.

For answering the growing demand of innovative micro-fluidic devices able to measure the refractive index of samples in extremely low volumes, this paper presents an overview of the performances of a micro-opto-fluidic sensing platform that employs rectangular, miniature hollow glass tubings. The operating principle is described by showing the analytical model of the tubing, obtained as superposition of different optical cavities, and the optical readout method based on spectral reflectivity detection. We have analyzed, in particular, the theoretical and experimental optical features of rectangular tubings with asymmetrical geometry, thus with channel depth larger than the thickness of the glass walls, though all of them in the range of a few tens of micrometers. The origins of the complex line-shape of the spectral response in reflection, due to the different cavities formed by the tubing flat walls and channel, have been investigated using a Fourier transform analysis. The implemented instrumental configuration, based on standard telecom fiberoptic components and a semiconductor broadband optical source emitting in the near infrared wavelength region centered at 1.55 µm, has allowed acquisition of reflectivity spectra for experimental verification of the expected theoretical behavior. We have achieved detection of refractive index variations related to the change of concentration of glucose-water solutions flowing through the tubing by monitoring the spectral shift of the optical resonances. Full article

(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Italy 2017)

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22 pages, 3517 KiB

Open AccessArticle

Research on the Multiple Factors Influencing Human Identification Based on Pyroelectric Infrared Sensors

by Junwei Yan¹, Ping Lou¹, Ruiya Li², Jianmin Hu¹ and Ji Xiong^1,*

¹ School of Information Engineering, Wuhan University of Technology, Wuhan 430070, China

² School of Mechanical and Electronic Engineering, Wuhan University of Technology, Wuhan 430070, China

Sensors 2018, 18(2), 604; https://doi.org/10.3390/s18020604 - 16 Feb 2018

Cited by 33 | Viewed by 5781

Abstract

Analysis of the multiple factors affecting human identification ability based on pyroelectric infrared technology is a complex problem. First, we examine various sensed pyroelectric waveforms of the human body thermal infrared signal and reveal a mechanism for affecting human identification. Then, we find [...] Read more.

Analysis of the multiple factors affecting human identification ability based on pyroelectric infrared technology is a complex problem. First, we examine various sensed pyroelectric waveforms of the human body thermal infrared signal and reveal a mechanism for affecting human identification. Then, we find that the mechanism is decided by the distance, human target, pyroelectric infrared (PIR) sensor, the body type, human moving velocity, signal modulation mask, and Fresnel lens. The mapping relationship between the sensed waveform and multiple influencing factors is established, and a group of mathematical models are deduced which fuse the macro factors and micro factors. Finally, the experimental results show the macro-factors indirectly affect the recognition ability of human based on the pyroelectric technology. At the same time, the correctness and effectiveness of the mathematical models is also verified, which make it easier to obtain more pyroelectric infrared information about the human body for discriminating human targets. Full article

(This article belongs to the Section Physical Sensors)

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13 pages, 6114 KiB

Open AccessArticle

UAVs and Machine Learning Revolutionising Invasive Grass and Vegetation Surveys in Remote Arid Lands

by Juan Sandino^1,*

, Felipe Gonzalez¹, Kerrie Mengersen² and Kevin J. Gaston³

¹ Institute for Future Environments; Robotics and Autonomous Systems, Queensland University ofTechnology (QUT), 2 George St, Brisbane City QLD 4000, Australia

² School of Mathematical Sciences; ARC Centre of Excellence for Mathematical & Statistical Frontiers(ACEMS), Queensland University of Technology (QUT), 2 George St, Brisbane City QLD 4000, Australia

³ Environment and Sustainability Institute, University of Exeter, Penryn, Cornwall TR10 9FE, UK

Sensors 2018, 18(2), 605; https://doi.org/10.3390/s18020605 - 16 Feb 2018

Cited by 53 | Viewed by 9244

Abstract

The monitoring of invasive grasses and vegetation in remote areas is challenging, costly, and on the ground sometimes dangerous. Satellite and manned aircraft surveys can assist but their use may be limited due to the ground sampling resolution or cloud cover. Straightforward and [...] Read more.

The monitoring of invasive grasses and vegetation in remote areas is challenging, costly, and on the ground sometimes dangerous. Satellite and manned aircraft surveys can assist but their use may be limited due to the ground sampling resolution or cloud cover. Straightforward and accurate surveillance methods are needed to quantify rates of grass invasion, offer appropriate vegetation tracking reports, and apply optimal control methods. This paper presents a pipeline process to detect and generate a pixel-wise segmentation of invasive grasses, using buffel grass (Cenchrus ciliaris) and spinifex (Triodia sp.) as examples. The process integrates unmanned aerial vehicles (UAVs) also commonly known as drones, high-resolution red, green, blue colour model (RGB) cameras, and a data processing approach based on machine learning algorithms. The methods are illustrated with data acquired in Cape Range National Park, Western Australia (WA), Australia, orthorectified in Agisoft Photoscan Pro, and processed in Python programming language, scikit-learn, and eXtreme Gradient Boosting (XGBoost) libraries. In total, 342,626 samples were extracted from the obtained data set and labelled into six classes. Segmentation results provided an individual detection rate of 97% for buffel grass and 96% for spinifex, with a global multiclass pixel-wise detection rate of 97%. Obtained results were robust against illumination changes, object rotation, occlusion, background cluttering, and floral density variation. Full article

(This article belongs to the Special Issue UAV or Drones for Remote Sensing Applications)

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19 pages, 4430 KiB

Open AccessArticle

Distributed Water Pollution Source Localization with Mobile UV-Visible Spectrometer Probes in Wireless Sensor Networks

by Junjie Ma¹

, Fansheng Meng¹

, Yuexi Zhou¹, Yeyao Wang^2,* and Ping Shi³

¹ Chinese Research Academy of Environmental Sciences, Beijing 100012, China

² China National Environmental Monitoring Centre, Beijing 100012, China

³ Yiwen Environmental Science Technology Co., Ltd., Guangzhou 510663, China

Sensors 2018, 18(2), 606; https://doi.org/10.3390/s18020606 - 16 Feb 2018

Cited by 31 | Viewed by 6078

Abstract

Pollution accidents that occur in surface waters, especially in drinking water source areas, greatly threaten the urban water supply system. During water pollution source localization, there are complicated pollutant spreading conditions and pollutant concentrations vary in a wide range. This paper provides a [...] Read more.

Pollution accidents that occur in surface waters, especially in drinking water source areas, greatly threaten the urban water supply system. During water pollution source localization, there are complicated pollutant spreading conditions and pollutant concentrations vary in a wide range. This paper provides a scalable total solution, investigating a distributed localization method in wireless sensor networks equipped with mobile ultraviolet-visible (UV-visible) spectrometer probes. A wireless sensor network is defined for water quality monitoring, where unmanned surface vehicles and buoys serve as mobile and stationary nodes, respectively. Both types of nodes carry UV-visible spectrometer probes to acquire in-situ multiple water quality parameter measurements, in which a self-adaptive optical path mechanism is designed to flexibly adjust the measurement range. A novel distributed algorithm, called Dual-PSO, is proposed to search for the water pollution source, where one particle swarm optimization (PSO) procedure computes the water quality multi-parameter measurements on each node, utilizing UV-visible absorption spectra, and another one finds the global solution of the pollution source position, regarding mobile nodes as particles. Besides, this algorithm uses entropy to dynamically recognize the most sensitive parameter during searching. Experimental results demonstrate that online multi-parameter monitoring of a drinking water source area with a wide dynamic range is achieved by this wireless sensor network and water pollution sources are localized efficiently with low-cost mobile node paths. Full article

(This article belongs to the Special Issue I3S 2017 Selected Papers)

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6 pages, 1557 KiB

Open AccessShort Note

Flame-Oxidized Stainless-Steel Anode as a Probe in Bioelectrochemical System-Based Biosensors to Monitor the Biochemical Oxygen Demand of Wastewater

by Qiaochu Liang¹, Takahiro Yamashita², Ryoko Yamamoto-Ikemoto¹ and Hiroshi Yokoyama^2,*

¹ Graduate School of Nature Science & Technology, Kanazawa University, Kakumamachi Kanazawa, Ishikawa 920-1192, Japan

² Division of Animal Environment and Waste Management Research, Institute of Livestock and Grassland Science, National Agriculture and Food Research Organization (NARO), 2 Ikenodai, Tsukuba 305-0901, Japan

Sensors 2018, 18(2), 607; https://doi.org/10.3390/s18020607 - 16 Feb 2018

Cited by 10 | Viewed by 4562

Abstract

Biochemical oxygen demand (BOD) is a widely used index of water quality in wastewater treatment; however, conventional measurement methods are time-consuming. In this study, we analyzed a novel flame-oxidized stainless steel anode (FO-SSA) for use as the probe of bioelectrochemical system (BES)-based biosensors [...] Read more.

Biochemical oxygen demand (BOD) is a widely used index of water quality in wastewater treatment; however, conventional measurement methods are time-consuming. In this study, we analyzed a novel flame-oxidized stainless steel anode (FO-SSA) for use as the probe of bioelectrochemical system (BES)-based biosensors to monitor the BOD of treated swine wastewater. A thinner biofilm formed on the FO-SSA compared with that on a common carbon-cloth anode (CCA). The FO-SSA was superior to the CCA in terms of rapid sensing; the response time of the FO-SSA to obtain the value of R² > 0.8 was 1 h, whereas the CCA required 4 h. These results indicate that the FO-SSA offers better performance than traditional CCAs in BES biosensors and can be used to improve biomonitoring of wastewater. Full article

(This article belongs to the Special Issue Environmental Monitoring Biosensors)

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27 pages, 6951 KiB

Open AccessArticle

Defect-Repairable Latent Feature Extraction of Driving Behavior via a Deep Sparse Autoencoder

by HaiLong Liu^1,2,*

, Tadahiro Taniguchi³, Kazuhito Takenaka⁴ and Takashi Bando⁵

¹ The Graduate School of Information Science and Engineering, Ritsumeikan University, Kusatsu, Shiga 525-8577, Japan

² Research Fellow (DC) with the Japan Society for the Promotion of Science, Tokyo 102-0083, Japan

³ The College of Information Science and Engineering, Ritsumeikan University, Kusatsu, Shiga 525-8577, Japan

⁴ The Corporate R&D Div.1, Sensing System R&D Dept., DENSO CORPORATION, Aichi 448-8661, Japan

⁵ The DENSO International America, Inc., San Jose, CA 95110, USA

Sensors 2018, 18(2), 608; https://doi.org/10.3390/s18020608 - 16 Feb 2018

Cited by 8 | Viewed by 4844

Abstract

Data representing driving behavior, as measured by various sensors installed in a vehicle, are collected as multi-dimensional sensor time-series data. These data often include redundant information, e.g., both the speed of wheels and the engine speed represent the velocity of the vehicle. Redundant [...] Read more.

Data representing driving behavior, as measured by various sensors installed in a vehicle, are collected as multi-dimensional sensor time-series data. These data often include redundant information, e.g., both the speed of wheels and the engine speed represent the velocity of the vehicle. Redundant information can be expected to complicate the data analysis, e.g., more factors need to be analyzed; even varying the levels of redundancy can influence the results of the analysis. We assume that the measured multi-dimensional sensor time-series data of driving behavior are generated from low-dimensional data shared by the many types of one-dimensional data of which multi-dimensional time-series data are composed. Meanwhile, sensor time-series data may be defective because of sensor failure. Therefore, another important function is to reduce the negative effect of defective data when extracting low-dimensional time-series data. This study proposes a defect-repairable feature extraction method based on a deep sparse autoencoder (DSAE) to extract low-dimensional time-series data. In the experiments, we show that DSAE provides high-performance latent feature extraction for driving behavior, even for defective sensor time-series data. In addition, we show that the negative effect of defects on the driving behavior segmentation task could be reduced using the latent features extracted by DSAE. Full article

(This article belongs to the Section Intelligent Sensors)

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16 pages, 1822 KiB

Open AccessArticle

An Advanced IoT-based System for Intelligent Energy Management in Buildings

by Vangelis Marinakis^*

and Haris Doukas

Decision Support Systems Laboratory, School of Electrical & Computer Engineering, National Technical University of Athens, 9, Iroon Polytechniou str., 157 80 Athens, Greece

Sensors 2018, 18(2), 610; https://doi.org/10.3390/s18020610 - 16 Feb 2018

Cited by 183 | Viewed by 17730

Abstract

The energy sector is closely interconnected with the building sector and integrated Information and Communication Technologies (ICT) solutions for effective energy management supporting decision-making at building, district and city level are key fundamental elements for making a city Smart. The available systems are [...] Read more.

The energy sector is closely interconnected with the building sector and integrated Information and Communication Technologies (ICT) solutions for effective energy management supporting decision-making at building, district and city level are key fundamental elements for making a city Smart. The available systems are designed and intended exclusively for a predefined number of cases and systems without allowing for expansion and interoperability with other applications that is partially due to the lack of semantics. This paper presents an advanced Internet of Things (IoT) based system for intelligent energy management in buildings. A semantic framework is introduced aiming at the unified and standardised modelling of the entities that constitute the building environment. Suitable rules are formed, aiming at the intelligent energy management and the general modus operandi of Smart Building. In this context, an IoT-based system was implemented, which enhances the interactivity of the buildings’ energy management systems. The results from its pilot application are presented and discussed. The proposed system extends existing approaches and integrates cross-domain data, such as the building’s data (e.g., energy management systems), energy production, energy prices, weather data and end-users’ behaviour, in order to produce daily and weekly action plans for the energy end-users with actionable personalised information. Full article

(This article belongs to the Special Issue Advances in Sensors for Sustainable Smart Cities and Smart Buildings)

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20 pages, 12908 KiB

Open AccessArticle

Gaofen-3 PolSAR Image Classification via XGBoost and Polarimetric Spatial Information

by Hao Dong¹

, Xin Xu^1,*, Lei Wang¹

and Fangling Pu^1,2

¹ School of Electronic Information, Wuhan University, Wuhan 430072, China

² Collaborative Innovation Center of Geospatial Technology, Wuhan University, Wuhan 430079, China

Sensors 2018, 18(2), 611; https://doi.org/10.3390/s18020611 - 17 Feb 2018

Cited by 65 | Viewed by 6764

Abstract

The launch of the Chinese Gaofen-3 (GF-3) satellite will provide enough synthetic aperture radar (SAR) images with different imaging modes for land cover classification and other potential usages in the next few years. This paper aims to propose an efficient and practical classification [...] Read more.

The launch of the Chinese Gaofen-3 (GF-3) satellite will provide enough synthetic aperture radar (SAR) images with different imaging modes for land cover classification and other potential usages in the next few years. This paper aims to propose an efficient and practical classification framework for a GF-3 polarimetric SAR (PolSAR) image. The proposed classification framework consists of four simple parts including polarimetric feature extraction and stacking, the initial classification via XGBoost, superpixels generation by statistical region merging (SRM) based on Pauli RGB image, and a post-processing step to determine the label of a superpixel by modified majority voting. Fast initial classification via XGBoost and the incorporation of spatial information via a post-processing step through superpixel-based modified majority voting would potentially make the method efficient in practical use. Preliminary experimental results on real GF-3 PolSAR images and the AIRSAR Flevoland data set validate the efficacy and efficiency of the proposed classification framework. The results demonstrate that the quality of GF-3 PolSAR data is adequate enough for classification purpose. The results also show that the incorporation of spatial information is important for overall performance improvement. Full article

(This article belongs to the Special Issue First Experiences with Chinese Gaofen-3 SAR Sensor)

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18 pages, 6488 KiB

Open AccessArticle

Optimal Scheduling and Fair Service Policy for STDMA in Underwater Networks with Acoustic Communications

by Miguel-Ángel Luque-Nieto^*

, José-Miguel Moreno-Roldán

, Pablo Otero

and Javier Poncela

Department of Ingeniería de Comunicaciones, University of Málaga, Málaga 29010, Spain

Sensors 2018, 18(2), 612; https://doi.org/10.3390/s18020612 - 17 Feb 2018

Cited by 7 | Viewed by 3894

Abstract

In this work, a multi-hop string network with a single sink node is analyzed. A periodic optimal scheduling for TDMA operation that considers the characteristic long propagation delay of the underwater acoustic channel is presented. This planning of transmissions is obtained with the [...] Read more.

In this work, a multi-hop string network with a single sink node is analyzed. A periodic optimal scheduling for TDMA operation that considers the characteristic long propagation delay of the underwater acoustic channel is presented. This planning of transmissions is obtained with the help of a new geometrical method based on a 2D lattice in the space-time domain. In order to evaluate the performance of this optimal scheduling, two service policies have been compared: FIFO and Round-Robin. Simulation results, including achievable throughput, packet delay, and queue length, are shown. The network fairness has also been quantified with the Gini index. Full article

(This article belongs to the Collection Smart Communication Protocols and Algorithms for Sensor Networks)

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13 pages, 348 KiB

Open AccessArticle

An Activity Recognition Framework Deploying the Random Forest Classifier and A Single Optical Heart Rate Monitoring and Triaxial Accelerometer Wrist-Band

by Saeed Mehrang^1,2,*, Julia Pietilä¹ and Ilkka Korhonen¹

¹ BioMediTech Institute and Faculty of Biomedical Sciences and Engineering, Tampere University of Technology, 33720 Tampere, Finland

² Department of Future Technologies, University of Turku, 20500 Turku, Finland

Sensors 2018, 18(2), 613; https://doi.org/10.3390/s18020613 - 22 Feb 2018

Cited by 60 | Viewed by 6248

Abstract

Wrist-worn sensors have better compliance for activity monitoring compared to hip, waist, ankle or chest positions. However, wrist-worn activity monitoring is challenging due to the wide degree of freedom for the hand movements, as well as similarity of hand movements in different activities [...] Read more.

Wrist-worn sensors have better compliance for activity monitoring compared to hip, waist, ankle or chest positions. However, wrist-worn activity monitoring is challenging due to the wide degree of freedom for the hand movements, as well as similarity of hand movements in different activities such as varying intensities of cycling. To strengthen the ability of wrist-worn sensors in detecting human activities more accurately, motion signals can be complemented by physiological signals such as optical heart rate (HR) based on photoplethysmography. In this paper, an activity monitoring framework using an optical HR sensor and a triaxial wrist-worn accelerometer is presented. We investigated a range of daily life activities including sitting, standing, household activities and stationary cycling with two intensities. A random forest (RF) classifier was exploited to detect these activities based on the wrist motions and optical HR. The highest overall accuracy of 89.6 ± 3.9% was achieved with a forest of a size of 64 trees and 13-s signal segments with 90% overlap. Removing the HR-derived features decreased the classification accuracy of high-intensity cycling by almost 7%, but did not affect the classification accuracies of other activities. A feature reduction utilizing the feature importance scores of RF was also carried out and resulted in a shrunken feature set of only 21 features. The overall accuracy of the classification utilizing the shrunken feature set was 89.4 ± 4.2%, which is almost equivalent to the above-mentioned peak overall accuracy. Full article

(This article belongs to the Section Physical Sensors)

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14 pages, 2866 KiB

Open AccessArticle

Feature-Level Fusion of Surface Electromyography for Activity Monitoring

by Xugang Xi

, Minyan Tang

and Zhizeng Luo^*

School of Automation, Hangzhou Dianzi University, Hangzhou 310018, China

Sensors 2018, 18(2), 614; https://doi.org/10.3390/s18020614 - 17 Feb 2018

Cited by 31 | Viewed by 4950

Abstract

Surface electromyography (sEMG) signals are commonly used in activity monitoring and rehabilitation applications as they reflect effectively the motor intentions of users. However, real-time sEMG signals are non-stationary and vary to a large extent within the time frame of signals. Although previous studies [...] Read more.

Surface electromyography (sEMG) signals are commonly used in activity monitoring and rehabilitation applications as they reflect effectively the motor intentions of users. However, real-time sEMG signals are non-stationary and vary to a large extent within the time frame of signals. Although previous studies have focused on the issues, their results have not been satisfactory. Therefore, we present a new method of conducting feature-level fusion to obtain a new feature space for sEMG signals. Eight activities of daily life (ADLs), including falls, were performed to obtain raw data from EMG signals from the lower limb. A feature set combining the time domain, time–frequency domain, and entropy domain was applied to the raw data to establish an initial feature space. A new projection method, the weighting genetic algorithm for GCCA (WGA-GCCA), was introduced to obtain the final feature space. Different tests were carried out to evaluate the performance of the new feature space. The new feature space created with the WGA-GCCA effectively reduced the dimensions and selected the best feature vectors dynamically while improving monotonicity. The Davies–Bouldin index (DBI) based on fuzzy c-means algorithms of the space obtained the lowest value compared with several fusion methods. It also achieved the highest accuracy when applied to support vector machine classifier. Full article

(This article belongs to the Special Issue Sensors for Health Monitoring and Disease Diagnosis)

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12 pages, 730 KiB

Open AccessArticle

Evaluating the Influence of Chromatic and Luminance Stimuli on SSVEPs from Behind-the-Ears and Occipital Areas

by Alan Floriano^1,*

, Pablo F. Diez^2,3,* and Teodiano Freire Bastos-Filho^1,*

¹ Postgraduate Program in Electrical Engineering, Federal University of Espirito Santo, Vitoria 29075-910, Brazil

² Gabinete de Tecnologia Medica (GATEME), Facultad de Ingenieria, Universidad Nacional de San Juan,San Juan J5400ARL, Argentina

³ Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), San Juan C1425FBQ, Argentina

Sensors 2018, 18(2), 615; https://doi.org/10.3390/s18020615 - 17 Feb 2018

Cited by 47 | Viewed by 6128

Abstract

This work presents a study of chromatic and luminance stimuli in low-, medium-, and high-frequency stimulation to evoke steady-state visual evoked potential (SSVEP) in the behind-the-ears area. Twelve healthy subjects participated in this study. The electroencephalogram (EEG) was measured on occipital (Oz) and [...] Read more.

This work presents a study of chromatic and luminance stimuli in low-, medium-, and high-frequency stimulation to evoke steady-state visual evoked potential (SSVEP) in the behind-the-ears area. Twelve healthy subjects participated in this study. The electroencephalogram (EEG) was measured on occipital (Oz) and left and right temporal (TP9 and TP10) areas. The SSVEP was evaluated in terms of amplitude, signal-to-noise ratio (SNR), and detection accuracy using power spectral density analysis (PSDA), canonical correlation analysis (CCA), and temporally local multivariate synchronization index (TMSI) methods. It was found that stimuli based on suitable color and luminance elicited stronger SSVEP in the behind-the-ears area, and that the response of the SSVEP was related to the flickering frequency and the color of the stimuli. Thus, green-red stimulus elicited the highest SSVEP in medium-frequency range, and green-blue stimulus elicited the highest SSVEP in high-frequency range, reaching detection accuracy rates higher than 80%. These findings will aid in the development of more comfortable, accurate and stable BCIs with electrodes positioned on the behind-the-ears (hairless) areas. Full article

(This article belongs to the Special Issue Assistance Robotics and Biosensors)

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18 pages, 3796 KiB

Open AccessArticle

Sensor-Based Assessment of Soil Salinity during the First Years of Transition from Flood to Sprinkler Irrigation

by Mª Auxiliadora Casterad¹

, Juan Herrero^2,*

, Jesús A. Betrán³ and Glen Ritchie⁴

¹ Unidad de Suelos y Riegos (Associated to CSIC), Av. Montañana 930, 50059 Zaragoza, Spain

² Estación Experimental de Aula Dei, CSIC, Av. Montañana 1005, 50059 Zaragoza, Spain

³ Laboratorio Agroambiental, Gobierno de Aragón, Av. Montañana 1005, 50059 Zaragoza, Spain

⁴ Department of Plant and Soil Science, Texas Tech University, Lubbock, TX 79409-2122, USA

Sensors 2018, 18(2), 616; https://doi.org/10.3390/s18020616 - 17 Feb 2018

Cited by 18 | Viewed by 4922

Abstract

A key issue for agriculture in irrigated arid lands is the control of soil salinity, and this is one of the goals for irrigated districts when changing from flood to sprinkling irrigation. We combined soil sampling, proximal electromagnetic induction, and satellite data to [...] Read more.

A key issue for agriculture in irrigated arid lands is the control of soil salinity, and this is one of the goals for irrigated districts when changing from flood to sprinkling irrigation. We combined soil sampling, proximal electromagnetic induction, and satellite data to appraise how soil salinity and its distribution along a previously flood-irrigated field evolved after its transformation to sprinkling. We also show that the relationship between NDVI (normalized difference vegetation index) and ECe (electrical conductivity of the soil saturation extracts) mimics the production function between yield and soil salinity. Under sprinkling, the field had a double crop of barley and then sunflower in 2009 and 2011. In both years, about 50% of the soil of the entire studied field—45 ha—had ECe < 8 dS m⁻¹, i.e., allowing barley cultivation, while the percent of surface having ECe ≥ 16 dS m⁻¹ increased from 8.4% in 2009 to 13.7% in 2011. Our methodology may help monitor the soil salinity oscillations associated with irrigation management. After quantifying and mapping the soil salinity in 2009 and 2011, we show that barley was stunted in places of the field where salinity was higher. Additionally, the areas of salinity persisted after the subsequent alfalfa cropping in 2013. Application of differential doses of water to the saline patches is a viable method to optimize irrigation water distribution and lessen soil salinity in sprinkler-irrigated agriculture. Full article

(This article belongs to the Section Remote Sensors)

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19 pages, 12765 KiB

Open AccessArticle

Research on the Additional Secondary Phase Factor for Automatic Identification System Signals Transmitted over a Rough Sea Surface

by Xiaoye Wang^*

, Shufang Zhang and Xiaowen Sun

Information Science and Technology College, Dalian Maritime University, Dalian 116026, China

Sensors 2018, 18(2), 617; https://doi.org/10.3390/s18020617 - 17 Feb 2018

Cited by 2 | Viewed by 2971

Abstract

This paper investigates the Additional Secondary Phase Factor (ASF) characteristics of Automatic Identification System (AIS) signals spreading over a rough sea surface. According to the change of the ASFs for AIS signals in different signal form, the influences of the different propagation conditions [...] Read more.

This paper investigates the Additional Secondary Phase Factor (ASF) characteristics of Automatic Identification System (AIS) signals spreading over a rough sea surface. According to the change of the ASFs for AIS signals in different signal form, the influences of the different propagation conditions on the ASFs are analyzed. The expression, numerical calculation, and simulation analysis of the ASFs of AIS signal are performed in the rough sea surface. The results contribute to the high-accuracy propagation delay measurement of AIS signals spreading over the rough sea surface as, well as providing a reference for reliable communication link design in marine engineering for Very High Frequency (VHF) signals. Full article

(This article belongs to the Section Remote Sensors)

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11 pages, 4672 KiB

Open AccessArticle

Using Micro-Molding and Stamping to Fabricate Conductive Polydimethylsiloxane-Based Flexible High-Sensitivity Strain Gauges

by Chi-Jui Han, Hsuan-Ping Chiang and Yun-Chien Cheng^*

Department of Mechanical Engineering, National Chiao Tung University, Hsinchu 300, Taiwan

Sensors 2018, 18(2), 618; https://doi.org/10.3390/s18020618 - 18 Feb 2018

Cited by 26 | Viewed by 6019

Abstract

In this study, polydimethylsiloxane (PDMS) and conductive carbon nanoparticles were combined to fabricate a conductive elastomer PDMS (CPDMS). A high sensitive and flexible CPDMS strain sensor is fabricated by using stamping-process based micro patterning. Compared with conventional sensors, flexible strain sensors are more [...] Read more.

In this study, polydimethylsiloxane (PDMS) and conductive carbon nanoparticles were combined to fabricate a conductive elastomer PDMS (CPDMS). A high sensitive and flexible CPDMS strain sensor is fabricated by using stamping-process based micro patterning. Compared with conventional sensors, flexible strain sensors are more suitable for medical applications but are usually fabricated by photolithography, which suffers from a large number of steps and difficult mass production. Hence, we fabricated flexible strain sensors using a stamping-process with fewer processes than photolithography. The piezoresistive coefficient and sensitivity of the flexible strain sensor were improved by sensor pattern design and thickness change. Micro-patterning is used to fabricate various CPDMS microstructure patterns. The effect of gauge pattern was evaluated with ANSYS simulations. The piezoresistance of the strain gauges was measured and the gauge factor determined. Experimental results show that the piezoresistive coefficient of CPDMS is approximately linear. Gauge factor measurement results show that the gauge factor of a 140.0 μm thick strain gauge with five grids is the highest. Full article

(This article belongs to the Section Biosensors)

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11 pages, 5401 KiB

Open AccessArticle

HPT: A High Spatial Resolution Multispectral Sensor for Microsatellite Remote Sensing

by Junichi Kurihara^1,*

, Yukihiro Takahashi¹, Yuji Sakamoto², Toshinori Kuwahara² and Kazuya Yoshida²

¹ Faculty of Science, Hokkaido University, Kita 10 Nishi 8, Kita-ku, Sapporo 060-0810, Japan

² Department of Aerospace Engineering, Tohoku University, Aramaki Aza Aoba 6-6-11, Sendai 980-8579, Japan

Sensors 2018, 18(2), 619; https://doi.org/10.3390/s18020619 - 18 Feb 2018

Cited by 23 | Viewed by 8619

Abstract

Although nano/microsatellites have great potential as remote sensing platforms, the spatial and spectral resolutions of an optical payload instrument are limited. In this study, a high spatial resolution multispectral sensor, the High-Precision Telescope (HPT), was developed for the RISING-2 microsatellite. The HPT has [...] Read more.

Although nano/microsatellites have great potential as remote sensing platforms, the spatial and spectral resolutions of an optical payload instrument are limited. In this study, a high spatial resolution multispectral sensor, the High-Precision Telescope (HPT), was developed for the RISING-2 microsatellite. The HPT has four image sensors: three in the visible region of the spectrum used for the composition of true color images, and a fourth in the near-infrared region, which employs liquid crystal tunable filter (LCTF) technology for wavelength scanning. Band-to-band image registration methods have also been developed for the HPT and implemented in the image processing procedure. The processed images were compared with other satellite images, and proven to be useful in various remote sensing applications. Thus, LCTF technology can be considered an innovative tool that is suitable for future multi/hyperspectral remote sensing by nano/microsatellites. Full article

(This article belongs to the Special Issue Multispectral and Hyperspectral Instrumentation)

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14 pages, 7939 KiB

Open AccessArticle

Characterization of the Body-to-Body Propagation Channel for Subjects during Sports Activities

by Marshed Mohamed^*

, Michael Cheffena and Arild Moldsvor

Norwegian University of Science and Technology (NTNU), N-2815 Gjøvik, Norway

Sensors 2018, 18(2), 620; https://doi.org/10.3390/s18020620 - 18 Feb 2018

Cited by 7 | Viewed by 3341

Abstract

Body-to-body wireless networks (BBWNs) have great potential to find applications in team sports activities among others. However, successful design of such systems requires great understanding of the communication channel as the movement of the body components causes time-varying shadowing and fading effects. In [...] Read more.

Body-to-body wireless networks (BBWNs) have great potential to find applications in team sports activities among others. However, successful design of such systems requires great understanding of the communication channel as the movement of the body components causes time-varying shadowing and fading effects. In this study, we present results of the measurement campaign of BBWN during running and cycling activities. Among others, the results indicated the presence of good and bad states with each state following a specific distribution for the considered propagation scenarios. This motivated the development of two-state semi-Markov model, for simulation of the communication channels. The simulation model was validated using the available measurement data in terms of first and second order statistics and have shown good agreement. The first order statistics obtained from the simulation model as well as the measured results were then used to analyze the performance of the BBWNs channels under running and cycling activities in terms of capacity and outage probability. Cycling channels showed better performance than running, having higher channel capacity and lower outage probability, regardless of the speed of the subjects involved in the measurement campaign. Full article

(This article belongs to the Section Sensor Networks)

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18 pages, 4540 KiB

Open AccessArticle

Comparative Study of the Detection of Chromium Content in Rice Leaves by 532 nm and 1064 nm Laser-Induced Breakdown Spectroscopy

by Jiyu Peng^1,2,†

, Fei Liu^1,2,†

, Tingting Shen¹, Lanhan Ye¹, Wenwen Kong³, Wei Wang¹, Xiaodan Liu¹

and Yong He^1,2,*

¹ College of Biosystems Engineering and Food science, Zhejiang University, Hangzhou 310058, China

² Key Laboratory of Spectroscopy Sensing, Ministry of Agriculture, Hangzhou 310058, China

³ School of Information Engineering, Zhejiang A & F University, Linan 311300, China

^† These authors contribute equally to this work.

Sensors 2018, 18(2), 621; https://doi.org/10.3390/s18020621 - 18 Feb 2018

Cited by 30 | Viewed by 5124

Abstract

Fast detection of toxic metals in crops is important for monitoring pollution and ensuring food safety. In this study, laser-induced breakdown spectroscopy (LIBS) was used to detect the chromium content in rice leaves. We investigated the influence of laser wavelength (532 nm and [...] Read more.

Fast detection of toxic metals in crops is important for monitoring pollution and ensuring food safety. In this study, laser-induced breakdown spectroscopy (LIBS) was used to detect the chromium content in rice leaves. We investigated the influence of laser wavelength (532 nm and 1064 nm excitation), along with the variations of delay time, pulse energy, and lens-to-sample distance (LTSD), on the signal (sensitivity and stability) and plasma features (temperature and electron density). With the optimized experimental parameters, univariate analysis was used for quantifying the chromium content, and several preprocessing methods (including background normalization, area normalization, multiplicative scatter correction (MSC) transformation and standardized normal variate (SNV) transformation were used to further improve the analytical performance. The results indicated that 532 nm excitation showed better sensitivity than 1064 nm excitation, with a detection limit around two times lower. However, the prediction accuracy for both excitation wavelengths was similar. The best result, with a correlation coefficient of 0.9849, root-mean-square error of 3.89 mg/kg and detection limit of 2.72 mg/kg, was obtained using the SNV transformed signal (Cr I 425.43 nm) induced by 532 nm excitation. The results indicate the inspiring capability of LIBS for toxic metals detection in plant materials. Full article

(This article belongs to the Special Issue Sensors in Agriculture)

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14 pages, 803 KiB

Open AccessArticle

A Novel Hard Decision Based Simultaneous Target Tracking and Classification Approach

by Wen Cao^*

, Meng Hui and Qisheng Wu

School of Electronics and Control Engineering, Chang’an University, Xi’an 710064, China

Sensors 2018, 18(2), 622; https://doi.org/10.3390/s18020622 - 19 Feb 2018

Cited by 4 | Viewed by 2893

Abstract

Methods dealing with the problem of Joint Tracking and Classification (JTC) are abundant, among which Simultaneous Tracking and Classification (STC) provides a modularized scheme solving tracking and classification subproblems simultaneously. However, there is no explicit hard decision on the class label but only [...] Read more.

Methods dealing with the problem of Joint Tracking and Classification (JTC) are abundant, among which Simultaneous Tracking and Classification (STC) provides a modularized scheme solving tracking and classification subproblems simultaneously. However, there is no explicit hard decision on the class label but only soft decision (class probability) is provided. This does not fit many practical cases, in which a hard decision is urgently needed. To solve this problem, this paper proposes a Hard decision-based STC (HSTC) method. HSTC takes all the decision error rate, timeliness, and estimation error into account. Specifically, for decision, the sequential probability ratio test is adopted due to its nice properties and also the adaptability to our situation. For estimation, by utilizing the two-way information exchange between the tracker and the classifier, we propose flexible three tracking schemes related to decision. The HSTC tracking result is divided into three parts according to the time of making the hard decision. In general, the proposed HSTC method takes advantage of both SPRT and STC. Finally, two illustrative JTC examples with hard decision verify the effectiveness of the the proposed HSTC method. They show that HSTC can meet the demand of the problem, and also has the performance superiority in both decision and estimation. Full article

(This article belongs to the Section Physical Sensors)

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15 pages, 2306 KiB

Open AccessArticle

Personalized Physical Activity Coaching: A Machine Learning Approach

by Talko B. Dijkhuis^1,2,*, Frank J. Blaauw^1,3

, Miriam W. Van Ittersum⁴, Hugo Velthuijsen² and Marco Aiello¹

¹ Johann Bernoulli Institute for Mathematics and Computer Science, Faculty of Science and Engineering (FSE), University of Groningen, Nijenborgh 9, 9747 AG Groningen, The Netherlands

² Institute of Communication, Hanze University of Applied Sciences, Media and ICT, Zernikeplein 11, 9746 AS Groningen, The Netherlands

³ Developmental Psychology, University of Groningen, Grote Kruisstraat 2/1, 9712 TS Groningen, The Netherlands

⁴ School for Health Care Studies, Hanze University of Applied Sciences, Petrus Driessenstraat 3, 9714 CA Groningen, The Netherlands

Sensors 2018, 18(2), 623; https://doi.org/10.3390/s18020623 - 19 Feb 2018

Cited by 61 | Viewed by 11239

Abstract

Living a sedentary lifestyle is one of the major causes of numerous health problems. To encourage employees to lead a less sedentary life, the Hanze University started a health promotion program. One of the interventions in the program was the use of an [...] Read more.

Living a sedentary lifestyle is one of the major causes of numerous health problems. To encourage employees to lead a less sedentary life, the Hanze University started a health promotion program. One of the interventions in the program was the use of an activity tracker to record participants' daily step count. The daily step count served as input for a fortnightly coaching session. In this paper, we investigate the possibility of automating part of the coaching procedure on physical activity by providing personalized feedback throughout the day on a participant's progress in achieving a personal step goal. The gathered step count data was used to train eight different machine learning algorithms to make hourly estimations of the probability of achieving a personalized, daily steps threshold. In 80% of the individual cases, the Random Forest algorithm was the best performing algorithm (mean accuracy = 0.93, range = 0.88–0.99, and mean F1-score = 0.90, range = 0.87–0.94). To demonstrate the practical usefulness of these models, we developed a proof-of-concept Web application that provides personalized feedback about whether a participant is expected to reach his or her daily threshold. We argue that the use of machine learning could become an invaluable asset in the process of automated personalized coaching. The individualized algorithms allow for predicting physical activity during the day and provides the possibility to intervene in time. Full article

(This article belongs to the Special Issue Smart Sensing Technologies for Personalised Coaching)

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23 pages, 5528 KiB

Open AccessArticle

Devising Mobile Sensing and Actuation Infrastructure with Drones

by Mungyu Bae

, Seungho Yoo

, Jongtack Jung, Seongjoon Park, Kangho Kim, Joon Yeop Lee and Hwangnam Kim^*

School of Electrical Engineering, Korea University, Seoul 02841, Korea

Sensors 2018, 18(2), 624; https://doi.org/10.3390/s18020624 - 19 Feb 2018

Cited by 18 | Viewed by 5993

Abstract

Vast applications and services have been enabled as the number of mobile or sensing devices with communication capabilities has grown. However, managing the devices, integrating networks or combining services across different networks has become a new problem since each network is not directly [...] Read more.

Vast applications and services have been enabled as the number of mobile or sensing devices with communication capabilities has grown. However, managing the devices, integrating networks or combining services across different networks has become a new problem since each network is not directly connected via back-end core networks or servers. The issue is and has been discussed especially in wireless sensor and actuator networks (WSAN). In such systems, sensors and actuators are tightly coupled, so when an independent WSAN needs to collaborate with other networks, it is difficult to adequately combine them into an integrated infrastructure. In this paper, we propose drone-as-a-gateway (DaaG), which uses drones as mobile gateways to interconnect isolated networks or combine independent services. Our system contains features that focus on the service being provided in the order of importance, different from an adaptive simple mobile sink system or delay-tolerant system. Our simulation results have shown that the proposed system is able to activate actuators in the order of importance of the service, which uses separate sensors’ data, and it consumes almost the same time in comparison with other path-planning algorithms. Moreover, we have implemented DaaG and presented results in a field test to show that it can enable large-scale on-demand deployment of sensing and actuation infrastructure or the Internet of Things (IoT). Full article

(This article belongs to the Special Issue UAV or Drones for Remote Sensing Applications)

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20 pages, 10735 KiB

Open AccessArticle

The Prediction of the Gas Utilization Ratio based on TS Fuzzy Neural Network and Particle Swarm Optimization

by Sen Zhang^1,2,*

, Haihe Jiang^1,2, Yixin Yin^1,2, Wendong Xiao^1,2 and Baoyong Zhao^1,2

¹ School of Automation and Electrical Engineering, University of Science and Technology Beijing, Beijing 100083, China

² Key Laboratory of Knowledge Automation for Industrial Processes of Ministry of Education, School of Automation and Electrical Engineering, University of Science and Technology Beijing, Beijing 100083, China

Sensors 2018, 18(2), 625; https://doi.org/10.3390/s18020625 - 20 Feb 2018

Cited by 47 | Viewed by 5091

Abstract

Gas utilization ratio (GUR) is an important indicator that is used to evaluate the energy consumption of blast furnaces (BFs). Currently, the existing methods cannot predict the GUR accurately. In this paper, we present a novel data-driven model for predicting the GUR. The [...] Read more.

Gas utilization ratio (GUR) is an important indicator that is used to evaluate the energy consumption of blast furnaces (BFs). Currently, the existing methods cannot predict the GUR accurately. In this paper, we present a novel data-driven model for predicting the GUR. The proposed approach utilized both the TS fuzzy neural network (TS-FNN) and the particle swarm algorithm (PSO) to predict the GUR. The particle swarm algorithm (PSO) is applied to optimize the parameters of the TS-FNN in order to decrease the error caused by the inaccurate initial parameter. This paper also applied the box graph (Box-plot) method to eliminate the abnormal value of the raw data during the data preprocessing. This method can deal with the data which does not obey the normal distribution which is caused by the complex industrial environments. The prediction results demonstrate that the optimization model based on PSO and the TS-FNN approach achieves higher prediction accuracy compared with the TS-FNN model and SVM model and the proposed approach can accurately predict the GUR of the blast furnace, providing an effective way for the on-line blast furnace distribution control. Full article

(This article belongs to the Special Issue Sensors and Materials for Harsh Environments)

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11 pages, 4645 KiB

Open AccessArticle

Three-Level De-Multiplexed Dual-Branch Complex Delta-Sigma Transmitter

by Anis Ben Arfi^1,*

, Fahmi Elsayed¹, Pouya M. Aflaki¹, Brad Morris² and Fadhel M. Ghannouchi¹

¹ iRadio Lab, University of Calgary, Calgary, AB T2N 1N4, Canada

² Ericsson Canada Inc., Mississauga, ON K2K 2V6, Canada

Sensors 2018, 18(2), 626; https://doi.org/10.3390/s18020626 - 20 Feb 2018

Viewed by 4254

Abstract

In this paper, a dual-branch topology driven by a Delta-Sigma Modulator (DSM) with a complex quantizer, also known as the Complex Delta Sigma Modulator (CxDSM), with a 3-level quantized output signal is proposed. By de-multiplexing the 3-level Delta-Sigma-quantized signal into two bi-level streams, [...] Read more.

In this paper, a dual-branch topology driven by a Delta-Sigma Modulator (DSM) with a complex quantizer, also known as the Complex Delta Sigma Modulator (CxDSM), with a 3-level quantized output signal is proposed. By de-multiplexing the 3-level Delta-Sigma-quantized signal into two bi-level streams, an efficiency enhancement over the operational frequency range is achieved. The de-multiplexed signals drive a dual-branch amplification block composed of two switch-mode back-to-back power amplifiers working at peak power. A signal processing technique known as quantization noise reduction with In-band Filtering (QNRIF) is applied to each of the de-multiplexed streams to boost the overall performances; particularly the Adjacent Channel Leakage Ratio (ACLR). After amplification, the two branches are combined using a non-isolated combiner, preserving the efficiency of the transmitter. A comprehensive study on the operation of this topology and signal characteristics used to drive the dual-branch Switch-Mode Power Amplifiers (SMPAs) was established. Moreover, this work proposes a highly efficient design of the amplification block based on a back-to-back power topology performing a dynamic load modulation exploiting the non-overlapping properties of the de-multiplexed Complex DSM signal. For experimental validation, the proposed de-multiplexed 3-level Delta-Sigma topology was implemented on the BEEcube™ platform followed by the back-to-back Class-E switch-mode power amplification block. The full transceiver is assessed using a 4th-Generation mobile communications standard LTE (Long Term Evolution) standard 1.4 MHz signal with a peak to average power ratio (PAPR) of 8 dB. The dual-branch topology exhibited a good linearity and a coding efficiency of the transmitter chain higher than 72% across the band of frequency from 1.8 GHz to 2.7 GHz. Full article

(This article belongs to the Special Issue Recent Advances in Front-End Designs for Sensors and Wireless Networks)

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14 pages, 1485 KiB

Open AccessArticle

Temporal and Fine-Grained Pedestrian Action Recognition on Driving Recorder Database

by Hirokatsu Kataoka^1,*

, Yutaka Satoh¹, Yoshimitsu Aoki², Shoko Oikawa³ and Yasuhiro Matsui⁴

¹ National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba 305-8560, Japan

² Department of Electronics and Electrical Engineering, Keio University, Yokohama 223-8522, Japan

³ Tokyo Metropolitan University, Tokyo 192-0364, Japan

⁴ National Traffic Safety and Environment Laboratory, Tokyo 182-0012, Japan

Sensors 2018, 18(2), 627; https://doi.org/10.3390/s18020627 - 20 Feb 2018

Cited by 29 | Viewed by 7023

Abstract

The paper presents an emerging issue of fine-grained pedestrian action recognition that induces an advanced pre-crush safety to estimate a pedestrian intention in advance. The fine-grained pedestrian actions include visually slight differences (e.g., walking straight and crossing), which are difficult to distinguish from [...] Read more.

The paper presents an emerging issue of fine-grained pedestrian action recognition that induces an advanced pre-crush safety to estimate a pedestrian intention in advance. The fine-grained pedestrian actions include visually slight differences (e.g., walking straight and crossing), which are difficult to distinguish from each other. It is believed that the fine-grained action recognition induces a pedestrian intention estimation for a helpful advanced driver-assistance systems (ADAS). The following difficulties have been studied to achieve a fine-grained and accurate pedestrian action recognition: (i) In order to analyze the fine-grained motion of a pedestrian appearance in the vehicle-mounted drive recorder, a method to describe subtle change of motion characteristics occurring in a short time is necessary; (ii) even when the background moves greatly due to the driving of the vehicle, it is necessary to detect changes in subtle motion of the pedestrian; (iii) the collection of large-scale fine-grained actions is very difficult, and therefore a relatively small database should be focused. We find out how to learn an effective recognition model with only a small-scale database. Here, we have thoroughly evaluated several types of configurations to explore an effective approach in fine-grained pedestrian action recognition without a large-scale database. Moreover, two different datasets have been collected in order to raise the issue. Finally, our proposal attained 91.01% on National Traffic Science and Environment Laboratory database (NTSEL) and 53.23% on the near-miss driving recorder database (NDRDB). The paper has improved +8.28% and +6.53% from baseline two-stream fusion convnets. Full article

(This article belongs to the Special Issue Sensors for Transportation)

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26 pages, 2365 KiB

Open AccessArticle

A Model-Driven Co-Design Framework for Fusing Control and Scheduling Viewpoints

by Sakthivel Manikandan Sundharam^1,*

, Nicolas Navet¹, Sebastian Altmeyer²

and Lionel Havet³

¹ Laboratory of Advanced Software Systems (LASSY), CSC Research Unit, University of Luxembourg, Maison du Nombre, L-4364 Esch-sur-Alzette, Luxembourg

² CSA Group, University of Amsterdam, 1098XH Amsterdam, The Netherlands

³ RealTime-at-Work (RTaW), 4 Rue Piroux, 54000 Nancy, France

Sensors 2018, 18(2), 628; https://doi.org/10.3390/s18020628 - 20 Feb 2018

Cited by 7 | Viewed by 5532

Abstract

Model-Driven Engineering (MDE) is widely applied in the industry to develop new software functions and integrate them into the existing run-time environment of a Cyber-Physical System (CPS). The design of a software component involves designers from various viewpoints such as control theory, software [...] Read more.

Model-Driven Engineering (MDE) is widely applied in the industry to develop new software functions and integrate them into the existing run-time environment of a Cyber-Physical System (CPS). The design of a software component involves designers from various viewpoints such as control theory, software engineering, safety, etc. In practice, while a designer from one discipline focuses on the core aspects of his field (for instance, a control engineer concentrates on designing a stable controller), he neglects or considers less importantly the other engineering aspects (for instance, real-time software engineering or energy efficiency). This may cause some of the functional and non-functional requirements not to be met satisfactorily. In this work, we present a co-design framework based on timing tolerance contract to address such design gaps between control and real-time software engineering. The framework consists of three steps: controller design, verified by jitter margin analysis along with co-simulation, software design verified by a novel schedulability analysis, and the run-time verification by monitoring the execution of the models on target. This framework builds on CPAL (Cyber-Physical Action Language), an MDE design environment based on model-interpretation, which enforces a timing-realistic behavior in simulation through timing and scheduling annotations. The application of our framework is exemplified in the design of an automotive cruise control system. Full article

(This article belongs to the Special Issue Design and Implementation of Future CPS)

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19 pages, 3981 KiB

Open AccessArticle

Design and Implementation of e-Health System Based on Semantic Sensor Network Using IETF YANG

by Wenquan Jin

and Do Hyeun Kim^*

Department of Computer Engineering, Jeju National University, Jeju 63243, Korea

Sensors 2018, 18(2), 629; https://doi.org/10.3390/s18020629 - 20 Feb 2018

Cited by 46 | Viewed by 7997

Abstract

Recently, healthcare services can be delivered effectively to patients anytime and anywhere using e-Health systems. e-Health systems are developed through Information and Communication Technologies (ICT) that involve sensors, mobiles, and web-based applications for the delivery of healthcare services and information. Remote healthcare is [...] Read more.

Recently, healthcare services can be delivered effectively to patients anytime and anywhere using e-Health systems. e-Health systems are developed through Information and Communication Technologies (ICT) that involve sensors, mobiles, and web-based applications for the delivery of healthcare services and information. Remote healthcare is an important purpose of the e-Health system. Usually, the eHealth system includes heterogeneous sensors from diverse manufacturers producing data in different formats. Device interoperability and data normalization is a challenging task that needs research attention. Several solutions are proposed in the literature based on manual interpretation through explicit programming. However, programmatically implementing the interpretation of the data sender and data receiver in the e-Health system for the data transmission is counterproductive as modification will be required for each new device added into the system. In this paper, an e-Health system with the Semantic Sensor Network (SSN) is proposed to address the device interoperability issue. In the proposed system, we have used IETF YANG for modeling the semantic e-Health data to represent the information of e-Health sensors. This modeling scheme helps in provisioning semantic interoperability between devices and expressing the sensing data in a user-friendly manner. For this purpose, we have developed an ontology for e-Health data that supports different styles of data formats. The ontology is defined in YANG for provisioning semantic interpretation of sensing data in the system by constructing meta-models of e-Health sensors. The proposed approach assists in the auto-configuration of eHealth sensors and querying the sensor network with semantic interoperability support for the e-Health system. Full article

(This article belongs to the Section Sensor Networks)

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22 pages, 26393 KiB

Open AccessArticle

Online Aerial Terrain Mapping for Ground Robot Navigation

by John Peterson^*, Haseeb Chaudhry, Karim Abdelatty, John Bird and Kevin Kochersberger

Virginia Tech Unmanned Systems Laboratory, Blacksburg, VA 24060, USA

Sensors 2018, 18(2), 630; https://doi.org/10.3390/s18020630 - 20 Feb 2018

Cited by 38 | Viewed by 9549

Abstract

This work presents a collaborative unmanned aerial and ground vehicle system which utilizes the aerial vehicle’s overhead view to inform the ground vehicle’s path planning in real time. The aerial vehicle acquires imagery which is assembled into a orthomosaic and then classified. These [...] Read more.

This work presents a collaborative unmanned aerial and ground vehicle system which utilizes the aerial vehicle’s overhead view to inform the ground vehicle’s path planning in real time. The aerial vehicle acquires imagery which is assembled into a orthomosaic and then classified. These terrain classes are used to estimate relative navigation costs for the ground vehicle so energy-efficient paths may be generated and then executed. The two vehicles are registered in a common coordinate frame using a real-time kinematic global positioning system (RTK GPS) and all image processing is performed onboard the unmanned aerial vehicle, which minimizes the data exchanged between the vehicles. This paper describes the architecture of the system and quantifies the registration errors between the vehicles. Full article

(This article belongs to the Special Issue UAV or Drones for Remote Sensing Applications)

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20 pages, 10850 KiB

Open AccessArticle

An Optimal Image-Based Method for Identification of Acoustic Emission (AE) Sources in Plate-Like Structures Using a Lead Zirconium Titanate (PZT) Sensor Array

by Gang Yan^*

and Li Zhou

State Key Laboratory of Mechanics and Control of Mechanical Structures, College of Aerospace Engineering, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China

Sensors 2018, 18(2), 631; https://doi.org/10.3390/s18020631 - 21 Feb 2018

Cited by 3 | Viewed by 3723

Abstract

This paper proposes an innovative method for identifying the locations of multiple simultaneous acoustic emission (AE) events in plate-like structures from the view of image processing. By using a linear lead zirconium titanate (PZT) sensor array to record the AE wave signals, a [...] Read more.

This paper proposes an innovative method for identifying the locations of multiple simultaneous acoustic emission (AE) events in plate-like structures from the view of image processing. By using a linear lead zirconium titanate (PZT) sensor array to record the AE wave signals, a reverse-time frequency-wavenumber (f-k) migration is employed to produce images displaying the locations of AE sources by back-propagating the AE waves. Lamb wave theory is included in the f-k migration to consider the dispersive property of the AE waves. Since the exact occurrence time of the AE events is usually unknown when recording the AE wave signals, a heuristic artificial bee colony (ABC) algorithm combined with an optimal criterion using minimum Shannon entropy is used to find the image with the identified AE source locations and occurrence time that mostly approximate the actual ones. Experimental studies on an aluminum plate with AE events simulated by PZT actuators are performed to validate the applicability and effectiveness of the proposed optimal image-based AE source identification method. Full article

(This article belongs to the Section Physical Sensors)

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12 pages, 1742 KiB

Open AccessArticle

Investigation of Sensitivities and Drift Effects of the Arrayed Flexible Chloride Sensor Based on RuO₂/GO at Different Temperatures

by Shi-Chang Tseng¹, Tong-Yu Wu¹, Jung-Chuan Chou^2,3,*

, Yi-Hung Liao⁴, Chih-Hsien Lai^2,3, Siao-Jie Yan³ and Ting-Wei Tseng²

¹ Graduate School of Mechanical Engineering, National Yunlin University of Science and Technology, Douliu 64002, Taiwan

² Department of Electronic Engineering, National Yunlin University of Science and Technology, Douliu 64002, Taiwan

³ Graduate School of Electronic Engineering, National Yunlin University of Science and Technology, Douliu 64002, Taiwan

⁴ Department of Information and Electronic Commerce Management, TransWorld University, Douliu 64002, Taiwan

Sensors 2018, 18(2), 632; https://doi.org/10.3390/s18020632 - 20 Feb 2018

Cited by 17 | Viewed by 4057

Abstract

We investigate the temperature effect on sensing characteristics and drift effect of an arrayed flexible ruthenium dioxide (RuO₂)/graphene oxide (GO) chloride sensor at different solution temperatures between 10 °C and 50 °C. The average sensor sensitivities according to our experimental results [...] Read more.

We investigate the temperature effect on sensing characteristics and drift effect of an arrayed flexible ruthenium dioxide (RuO₂)/graphene oxide (GO) chloride sensor at different solution temperatures between 10 °C and 50 °C. The average sensor sensitivities according to our experimental results were 28.2 ± 1.4 mV/pCl (10 °C), 42.5 ± 2.0 mV/pCl (20 °C), 47.1 ± 1.8 mV/pCl (30 °C), 54.1 ± 2.01 mV/pCl (40 °C) and 46.6 ± 2.1 mV/pCl (50 °C). We found the drift effects of an arrayed flexible RuO₂/GO chloride sensor in a 1 M NaCl solution to be between 8.2 mV/h and 2.5 mV/h with solution temperatures from 10 °C to 50 °C. Full article

(This article belongs to the Special Issue Potentiometric Chemical Sensors)

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24 pages, 4384 KiB

Open AccessArticle

Exploring 3D Human Action Recognition: from Offline to Online

by Rui Li, Zhenyu Liu^* and Jianrong Tan

State Key Lab of CAD&CG, Zhejiang University, Hangzhou 310027, China

Sensors 2018, 18(2), 633; https://doi.org/10.3390/s18020633 - 20 Feb 2018

Cited by 9 | Viewed by 5780

Abstract

With the introduction of cost-effective depth sensors, a tremendous amount of research has been devoted to studying human action recognition using 3D motion data. However, most existing methods work in an offline fashion, i.e., they operate on a segmented sequence. There are a [...] Read more.

With the introduction of cost-effective depth sensors, a tremendous amount of research has been devoted to studying human action recognition using 3D motion data. However, most existing methods work in an offline fashion, i.e., they operate on a segmented sequence. There are a few methods specifically designed for online action recognition, which continually predicts action labels as a stream sequence proceeds. In view of this fact, we propose a question: can we draw inspirations and borrow techniques or descriptors from existing offline methods, and then apply these to online action recognition? Note that extending offline techniques or descriptors to online applications is not straightforward, since at least two problems—including real-time performance and sequence segmentation—are usually not considered in offline action recognition. In this paper, we give a positive answer to the question. To develop applicable online action recognition methods, we carefully explore feature extraction, sequence segmentation, computational costs, and classifier selection. The effectiveness of the developed methods is validated on the MSR 3D Online Action dataset and the MSR Daily Activity 3D dataset. Full article

(This article belongs to the Section Physical Sensors)

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19 pages, 2407 KiB

Open AccessArticle

Active Prior Tactile Knowledge Transfer for Learning Tactual Properties of New Objects

by Di Feng^†, Mohsen Kaboli^*,†

and Gordon Cheng

¹ Institute for Cognitive Systems (ICS), Technische Universität München, Arcisstrasse 21, 80333 München, Germany

^† Mohsen Kaboli and Di Feng contributed equally to this work.

Sensors 2018, 18(2), 634; https://doi.org/10.3390/s18020634 - 21 Feb 2018

Cited by 23 | Viewed by 5882

Abstract

Reusing the tactile knowledge of some previously-explored objects (prior objects) helps us to easily recognize the tactual properties of new objects. In this paper, we enable a robotic arm equipped with multi-modal artificial skin, like humans, to actively transfer the prior tactile exploratory [...] Read more.

Reusing the tactile knowledge of some previously-explored objects (prior objects) helps us to easily recognize the tactual properties of new objects. In this paper, we enable a robotic arm equipped with multi-modal artificial skin, like humans, to actively transfer the prior tactile exploratory action experiences when it learns the detailed physical properties of new objects. These experiences, or prior tactile knowledge, are built by the feature observations that the robot perceives from multiple sensory modalities, when it applies the pressing, sliding, and static contact movements on objects with different action parameters. We call our method Active Prior Tactile Knowledge Transfer (APTKT), and systematically evaluated its performance by several experiments. Results show that the robot improved the discrimination accuracy by around

10 %

when it used only one training sample with the feature observations of prior objects. By further incorporating the predictions from the observation models of prior objects as auxiliary features, our method improved the discrimination accuracy by over

20 %

. The results also show that the proposed method is robust against transferring irrelevant prior tactile knowledge (negative knowledge transfer). Full article

(This article belongs to the Special Issue Tactile Sensors and Sensing)

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17 pages, 3131 KiB

Open AccessArticle

mIoT Slice for 5G Systems: Design and Performance Evaluation

by Riccardo Trivisonno¹

, Massimo Condoluci², Xueli An¹ and Toktam Mahmoodi^2,*

¹ Huawei Technologies, 80992 Munich, Germany

² Department of Informatics, King’s College London, London WC2R 2LS, UK

Sensors 2018, 18(2), 635; https://doi.org/10.3390/s18020635 - 21 Feb 2018

Cited by 22 | Viewed by 5916

Abstract

Network slicing is a key feature of the upcoming 5G networks allowing the design and deployment of customized communication systems to integrate services provided by vertical industries. In this context, massive Internet of Things (mIoT) is regarded as a compelling use case, both [...] Read more.

Network slicing is a key feature of the upcoming 5G networks allowing the design and deployment of customized communication systems to integrate services provided by vertical industries. In this context, massive Internet of Things (mIoT) is regarded as a compelling use case, both for its relevance from business perspective, and for the technical challenges it poses to network design. With their envisaged massive deployment of devices requiring sporadic connectivity and small data transmission, yet Quality of Service (QoS) constrained, mIoT services will need an ad-hoc end-to-end (E2E) slice, i.e., both access and core network with enhanced Control and User planes (CP/UP). After revising the key requirements of mIoT and identifying major shortcomings of previous generation networks, this paper presents and evaluates an E2E mIoT network slicing solution, featuring a new connectivity model overcoming the load limitations of legacy systems. Unique in its kind, this paper addresses mIoT requirements from an end-to-end perspective highlighting and solving, unlike most prior related work, the connectivity challenges posed to the core network. Results demonstrate that the proposed solution, reducing CP signaling and optimizing UP resource utilization, is a suitable candidate for next generation network standards to efficiently handle massive device deployment. Full article

(This article belongs to the Special Issue Green Wireless Networks in 5G-inspired Applications)

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11 pages, 3437 KiB

Open AccessArticle

Split-Ring Resonator Sensor Penetration Depth Assessment Using In Vivo Microwave Reflectivity and Ultrasound Measurements for Lower Extremity Trauma Rehabilitation

by Syaiful Redzwan Mohd Shah^1,*

, Jacob Velander¹, Parul Mathur², Mauricio D. Perez¹, Noor Badariah Asan¹

, Dhanesh G. Kurup², Taco J. Blokhuis³

and Robin Augustine^1,*

¹ Microwaves in Medical Engineering Group, Solid State Electronics, Department of Engineering Sciences, Angstrom Laboratory, Uppsala University, Box 534, SE 75121 Uppsala, Sweden

² Department of Electronics and Communication, Amrita School of Engineering, Amrita Vishwa Vidyapeetham, Bengaluru , 560035, India

³ Department of surgery, Maastricht University Medical Center, PO Box 5800 6202 AZ Maastricht, The Netherlands

Sensors 2018, 18(2), 636; https://doi.org/10.3390/s18020636 - 21 Feb 2018

Cited by 16 | Viewed by 7559

Abstract

In recent research, microwave sensors have been used to follow up the recovery of lower extremity trauma patients. This is done mainly by monitoring the changes of dielectric properties of lower limb tissues such as skin, fat, muscle, and bone. As part of [...] Read more.

In recent research, microwave sensors have been used to follow up the recovery of lower extremity trauma patients. This is done mainly by monitoring the changes of dielectric properties of lower limb tissues such as skin, fat, muscle, and bone. As part of the characterization of the microwave sensor, it is crucial to assess the signal penetration in in vivo tissues. This work presents a new approach for investigating the penetration depth of planar microwave sensors based on the Split-Ring Resonator in the in vivo context of the femoral area. This approach is based on the optimization of a 3D simulation model using the platform of CST Microwave Studio and consisting of a sensor of the considered type and a multilayered material representing the femoral area. The geometry of the layered material is built based on information from ultrasound images and includes mainly the thicknesses of skin, fat, and muscle tissues. The optimization target is the measured S₁₁ parameters at the sensor connector and the fitting parameters are the permittivity of each layer of the material. Four positions in the femoral area (two at distal and two at thigh) in four volunteers are considered for the in vivo study. The penetration depths are finally calculated with the help of the electric field distribution in simulations of the optimized model for each one of the 16 considered positions. The numerical results show that positions at the thigh contribute the highest penetration values of up to 17.5 mm. This finding has a high significance in planning in vitro penetration depth measurements and other tests that are going to be performed in the future. Full article

(This article belongs to the Special Issue Non-Invasive Biomedical Sensors)

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14 pages, 4262 KiB

Open AccessArticle

Uncertainly Analysis of Two Types of Humidity Sensors by a Humidity Generator with a Divided-Flow System

by Ling-Hsi Chen¹ and Chiachung Chen^2,*

¹ Taichung District Agriculture Research and Extension Station, Changhua County 51541, Taiwan

² Department of Bio-industrial Mechatronics Engineering, National ChungHsing University, Taichung 40227, Taiwan

Sensors 2018, 18(2), 637; https://doi.org/10.3390/s18020637 - 21 Feb 2018

Cited by 6 | Viewed by 5533

Abstract

Humidity measurement is an important technique for the agricultural, foods, pharmaceuticals, and chemical industries. For the sake of convenience, electrical relative humidity (RH) sensors have been widely used. These sensors need to be calibrated to ensure their accuracy and the uncertainty measurement of [...] Read more.

Humidity measurement is an important technique for the agricultural, foods, pharmaceuticals, and chemical industries. For the sake of convenience, electrical relative humidity (RH) sensors have been widely used. These sensors need to be calibrated to ensure their accuracy and the uncertainty measurement of these sensors has become a major concern. In this study, a self-made divided-flow generator was established to calibrate two types of electrical humidity sensors. The standard reference humidity was calculated from dew-point temperature and air dry-bulb temperature measured by a chilled mirror monitor. This divided-flow generator could produce consistent result of RH measurement results. The uncertainty of the reference standard increased with the increase of RH values. The combined uncertainty with the adequate calibration equations were ranged from 0.82% to 1.45% RH for resistive humidity sensors and 0.63% to 1.4% for capacitive humidity sensors, respectively. This self-made, divided-flow generator, and calibration method are cheap, time-saving, and easy to be used. Thus, the proposed approach can easily be applied in research laboratories. Full article

(This article belongs to the Section Physical Sensors)

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19 pages, 1049 KiB

Open AccessArticle

Sensor Compromise Detection in Multiple-Target Tracking Systems

by Juan-Pablo Ramirez-Paredes^1,*

, Emily A. Doucette², Jess W. Curtis² and Victor Ayala-Ramirez¹

¹ Department of Electronics Engineering, University of Guanajuato, Salamanca, Gto. 36885, Mexico

² Munitions Directorate, Air Force Research Laboratory, Eglin AFB, FL 32542, USA

Sensors 2018, 18(2), 638; https://doi.org/10.3390/s18020638 - 21 Feb 2018

Cited by 2 | Viewed by 4018

Abstract

Tracking multiple targets using a single estimator is a problem that is commonly approached within a trusted framework. There are many weaknesses that an adversary can exploit if it gains control over the sensors. Because the number of targets that the estimator has [...] Read more.

Tracking multiple targets using a single estimator is a problem that is commonly approached within a trusted framework. There are many weaknesses that an adversary can exploit if it gains control over the sensors. Because the number of targets that the estimator has to track is not known with anticipation, an adversary could cause a loss of information or a degradation in the tracking precision. Other concerns include the introduction of false targets, which would result in a waste of computational and material resources, depending on the application. In this work, we study the problem of detecting compromised or faulty sensors in a multiple-target tracker, starting with the single-sensor case and then considering the multiple-sensor scenario. We propose an algorithm to detect a variety of attacks in the multiple-sensor case, via the application of finite set statistics (FISST), one-class classifiers and hypothesis testing using nonparametric techniques. Full article

(This article belongs to the Special Issue Security, Trust and Privacy for Sensor Networks)

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20 pages, 932 KiB

Open AccessArticle

Robust Rate Maximization for Heterogeneous Wireless Networks under Channel Uncertainties

by Yongjun Xu^1,2, Yuan Hu¹ and Guoquan Li^1,*

¹ School of Communication and Information Engineering, Chongqing University of Posts and Telecommunications, Chongqing 400065, China

² State Key Laboratory of Integrated Services Networks, Xidian University, Xi’an 710071, China

Sensors 2018, 18(2), 639; https://doi.org/10.3390/s18020639 - 21 Feb 2018

Cited by 15 | Viewed by 4902

Abstract

Heterogeneous wireless networks are a promising technology in next generation wireless communication networks, which has been shown to efficiently reduce the blind area of mobile communication and improve network coverage compared with the traditional wireless communication networks. In this paper, a robust power [...] Read more.

Heterogeneous wireless networks are a promising technology in next generation wireless communication networks, which has been shown to efficiently reduce the blind area of mobile communication and improve network coverage compared with the traditional wireless communication networks. In this paper, a robust power allocation problem for a two-tier heterogeneous wireless networks is formulated based on orthogonal frequency-division multiplexing technology. Under the consideration of imperfect channel state information (CSI), the robust sum-rate maximization problem is built while avoiding sever cross-tier interference to macrocell user and maintaining the minimum rate requirement of each femtocell user. To be practical, both of channel estimation errors from the femtocells to the macrocell and link uncertainties of each femtocell user are simultaneously considered in terms of outage probabilities of users. The optimization problem is analyzed under no CSI feedback with some cumulative distribution function and partial CSI with Gaussian distribution of channel estimation error. The robust optimization problem is converted into the convex optimization problem which is solved by using Lagrange dual theory and subgradient algorithm. Simulation results demonstrate the effectiveness of the proposed algorithm by the impact of channel uncertainties on the system performance. Full article

(This article belongs to the Special Issue Advances on Resources Management for Multi-Platform Infrastructures)

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22 pages, 966 KiB

Open AccessArticle

Approach for the Development of a Framework for the Identification of Activities of Daily Living Using Sensors in Mobile Devices

by Ivan Miguel Pires^1,2,3,*

, Nuno M. Garcia^1,3,4

, Nuno Pombo^1,3,4, Francisco Flórez-Revuelta⁵

and Susanna Spinsante⁶

¹ Instituto de Telecomunicações, Universidade da Beira Interior, 6201-001 Covilhã, Portugal

² Altranportugal, 1990-096 Lisbon, Portugal

³ ALLab—Assisted Living Computing and Telecommunications Laboratory, Computing Science Department, Universidade da Beira Interior, 6201-001 Covilhã, Portugal

⁴ ECATI, Universidade Lusófona de Humanidades e Tecnologias, 1749-024 Lisbon, Portugal

⁵ Department of Computer Technology, Universidad de Alicante, 03690 Sant Vicent del Raspeig, Alicante, Spain

⁶ Department of Information Engineering, Marche Polytechnic University, 60121 Ancona, Italy

Sensors 2018, 18(2), 640; https://doi.org/10.3390/s18020640 - 21 Feb 2018

Cited by 28 | Viewed by 6486

Abstract

Sensors available on mobile devices allow the automatic identification of Activities of Daily Living (ADL). This paper describes an approach for the creation of a framework for the identification of ADL, taking into account several concepts, including data acquisition, data processing, data fusion, [...] Read more.

Sensors available on mobile devices allow the automatic identification of Activities of Daily Living (ADL). This paper describes an approach for the creation of a framework for the identification of ADL, taking into account several concepts, including data acquisition, data processing, data fusion, and pattern recognition. These concepts can be mapped onto different modules of the framework. The proposed framework should perform the identification of ADL without Internet connection, performing these tasks locally on the mobile device, taking in account the hardware and software limitations of these devices. The main purpose of this paper is to present a new approach for the creation of a framework for the recognition of ADL, analyzing the allowed sensors available in the mobile devices, and the existing methods available in the literature. Full article

(This article belongs to the Special Issue Smart Sensors for Mechatronic and Robotic Systems)

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13 pages, 29258 KiB

Open AccessArticle

Experimental L-Band Airborne SAR for Oil Spill Response at Sea and in Coastal Waters

by Cathleen E. Jones^* and Benjamin Holt

Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Dr., Pasadena, CA 91109, USA

Sensors 2018, 18(2), 641; https://doi.org/10.3390/s18020641 - 22 Feb 2018

Cited by 40 | Viewed by 6235

Abstract

Satellite synthetic aperture radar (SAR) is frequently used during oil spill response efforts to identify oil slick extent, but suffers from the major disadvantages of potential long latency between when a spill occurs and when a satellite can image the site and an [...] Read more.

Satellite synthetic aperture radar (SAR) is frequently used during oil spill response efforts to identify oil slick extent, but suffers from the major disadvantages of potential long latency between when a spill occurs and when a satellite can image the site and an inability to continuously track the spill as it develops. We show using data acquired with the Uninhabited Aerial Vehicle SAR (UAVSAR) instrument how a low noise, high resolution, L-band SAR could be used for oil spill response, with specific examples of tracking slick extent, position and weathering; determining zones of relatively thicker or more emulsified oil within a slick; and identifying oil slicks in coastal areas where look-alikes such as calm waters or biogenic slicks can confound the identification of mineral oil spills. From these key points, the essential features of an airborne SAR system for operational oil spill response are described, and further research needed to determine SAR’s capabilities and limitations in quantifying slick thickness is discussed. Full article

(This article belongs to the Special Issue Sensors for Oil Applications)

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15 pages, 3528 KiB

Open AccessArticle

A Novel Early Warning System Based on a Sediment Microbial Fuel Cell for In Situ and Real Time Hexavalent Chromium Detection in Industrial Wastewater

by Shuai Zhao^1,2,†, Pu Liu^2,3,†, Yongyan Niu¹, Zhengjun Chen¹, Aman Khan^1,2, Pengyun Zhang⁴ and Xiangkai Li^1,2,*

¹ MOE Key Laboratory of Cell Activities and Stress Adaptations, School of Life Sciences, Lanzhou University, Tianshuinanlu #222, Lanzhou 730000, Gansu, China

² Gansu Key Laboratory of Biomonitoring and Bioremediation for Environmental Pollution, School of Life Sciences, Lanzhou University, Tianshuinanlu #222, Lanzhou 730000, Gansu, China

³ Department of Developmental Biology, School of Life Sciences, Lanzhou University, Tianshuinanlu #222, Lanzhou 730000, Gansu, China

⁴ Gansu Academy of Membrane Science and Technology, Duanjiatanlu #1272, Lanzhou 730020, Gansu, China

^† These authors contributed equally to this work.

Sensors 2018, 18(2), 642; https://doi.org/10.3390/s18020642 - 22 Feb 2018

Cited by 63 | Viewed by 6461

Abstract

Hexavalent chromium (Cr(VI)) is a well-known toxic heavy metal in industrial wastewater, but in situ and real time monitoring cannot be achieved by current methods used during industrial wastewater treatment processes. In this study, a Sediment Microbial Fuel Cell (SMFC) was used as [...] Read more.

Hexavalent chromium (Cr(VI)) is a well-known toxic heavy metal in industrial wastewater, but in situ and real time monitoring cannot be achieved by current methods used during industrial wastewater treatment processes. In this study, a Sediment Microbial Fuel Cell (SMFC) was used as a biosensor for in situ real-time monitoring of Cr(VI), which was the organic substrate is oxidized in the anode and Cr(VI) is reduced at the cathode simultaneously. The pH 6.4 and temperature 25 °C were optimal conditions for the operation. Under the optimal conditions, linearity (R² = 0.9935) of the generated voltage was observed in the Cr(VI) concentration range from 0.2 to 0.7 mg/L. The system showed high specificity for Cr(VI), as other co-existing ions such as Cu²⁺, Zn²⁺, and Pb²⁺ did not interfere with Cr(VI) detection. In addition, when the sediment MFC-based biosensor was applied for measuring Cr(VI) in actual wastewater samples, a low deviation (<8%) was obtained, which indicated its potential as a reliable biosensor device. MiSeq sequencing results showed that electrochemically active bacteria (Geobacter and Pseudomonas) were enriched at least two-fold on the biofilm of the anode in the biosensor as compared to the SMFC without Cr(VI). Cyclic voltammetry curves indicated that a pair of oxidation/reduction peaks appeared at −111 mV and 581 mV, respectively. These results demonstrated that the proposed sediment microbial fuel cell-based biosensor can be applied as an early warning device for real time in situ detection of Cr(VI) in industrial wastewaters. Full article

(This article belongs to the Special Issue Environmental Monitoring Biosensors)

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13 pages, 4039 KiB

Open AccessArticle

Structural Designing of a MEMS Capacitive Accelerometer for Low Temperature Coefficient and High Linearity

by Jiangbo He^1,*

, Wu Zhou^2,*

, Huijun Yu², Xiaoping He³ and Peng Peng²

¹ School of Mechanical Engineering, Xihua University, Chengdu 610039, China

² School of Mechanical and Electrical Engineering, University of Electronic Science and Technology of China, Chengdu 611731, China

³ Institute of Electronic Engineering, China Academy of Engineering Physics, Mianyang 621900, China

Sensors 2018, 18(2), 643; https://doi.org/10.3390/s18020643 - 22 Feb 2018

Cited by 35 | Viewed by 9381

Abstract

The low temperature coefficient and high linearity of the input-output characteristics are both required for high-performance microelectromechanical systems (MEMS) capacitive accelerometers. In this work, a structural designing of a bulk MEMS capacitive accelerometer is developed for both low temperature coefficient and high linearity. [...] Read more.

The low temperature coefficient and high linearity of the input-output characteristics are both required for high-performance microelectromechanical systems (MEMS) capacitive accelerometers. In this work, a structural designing of a bulk MEMS capacitive accelerometer is developed for both low temperature coefficient and high linearity. Firstly, the contrary effect of the wide-narrow gaps ratio (WNGR) on the temperature coefficient of the scale factor (TCSF) and linearity error is discussed. Secondly, the ability of an improved structure that can avoid the contrary effect is illustrated. The improved structure is proposed in our previous work for reducing the temperature coefficient of bias (TCB) and TCSF. Within the improved structure, both the TCSF and linearity error decrease with increasing WNGR. Then, the precise designing of the improved structure is developed for achieving lower TCB, TCSF, and linearity error. Finally, the precise structural designing is experimentally verified. Full article

(This article belongs to the Special Issue Sensors for MEMS and Microsystems)

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16 pages, 4427 KiB

Open AccessArticle

A Spectral Reconstruction Algorithm of Miniature Spectrometer Based on Sparse Optimization and Dictionary Learning

by Shang Zhang¹, Yuhan Dong¹

, Hongyan Fu²

, Shao-Lun Huang² and Lin Zhang^2,*

¹ Department of Electronic Engineering, Tsinghua University, Beijing 100084, China

² Tsinghua-Berkeley Shenzhen Institute, Tsinghua University, Shenzhen 518055, China

Sensors 2018, 18(2), 644; https://doi.org/10.3390/s18020644 - 22 Feb 2018

Cited by 74 | Viewed by 8258

Abstract

The miniaturization of spectrometer can broaden the application area of spectrometry, which has huge academic and industrial value. Among various miniaturization approaches, filter-based miniaturization is a promising implementation by utilizing broadband filters with distinct transmission functions. Mathematically, filter-based spectral reconstruction can be modeled [...] Read more.

The miniaturization of spectrometer can broaden the application area of spectrometry, which has huge academic and industrial value. Among various miniaturization approaches, filter-based miniaturization is a promising implementation by utilizing broadband filters with distinct transmission functions. Mathematically, filter-based spectral reconstruction can be modeled as solving a system of linear equations. In this paper, we propose an algorithm of spectral reconstruction based on sparse optimization and dictionary learning. To verify the feasibility of the reconstruction algorithm, we design and implement a simple prototype of a filter-based miniature spectrometer. The experimental results demonstrate that sparse optimization is well applicable to spectral reconstruction whether the spectra are directly sparse or not. As for the non-directly sparse spectra, their sparsity can be enhanced by dictionary learning. In conclusion, the proposed approach has a bright application prospect in fabricating a practical miniature spectrometer. Full article

(This article belongs to the Special Issue Spectroscopy Based Sensors)

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13 pages, 820 KiB

Open AccessArticle

Social Image Captioning: Exploring Visual Attention and User Attention

by Leiquan Wang¹

, Xiaoliang Chu¹, Weishan Zhang¹, Yiwei Wei¹, Weichen Sun^2,3 and Chunlei Wu^1,*

¹ College of Computer & Communication Engineering, China University of Petroleum (East China), Qingdao 266555, China

² First Research Institute of the Ministry of Public Security of PRC, Beijing 100048, China

³ School of Information and Communication Engineering, Beijing University of Posts and Telecommunications, Beijing 100876, China

Sensors 2018, 18(2), 646; https://doi.org/10.3390/s18020646 - 22 Feb 2018

Cited by 14 | Viewed by 5197

Abstract

Image captioning with a natural language has been an emerging trend. However, the social image, associated with a set of user-contributed tags, has been rarely investigated for a similar task. The user-contributed tags, which could reflect the user attention, have been neglected in [...] Read more.

Image captioning with a natural language has been an emerging trend. However, the social image, associated with a set of user-contributed tags, has been rarely investigated for a similar task. The user-contributed tags, which could reflect the user attention, have been neglected in conventional image captioning. Most existing image captioning models cannot be applied directly to social image captioning. In this work, a dual attention model is proposed for social image captioning by combining the visual attention and user attention simultaneously.Visual attention is used to compress a large mount of salient visual information, while user attention is applied to adjust the description of the social images with user-contributed tags. Experiments conducted on the Microsoft (MS) COCO dataset demonstrate the superiority of the proposed method of dual attention. Full article

(This article belongs to the Special Issue Sensing, Data Analysis and Platforms for Ubiquitous Intelligence)

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11 pages, 1861 KiB

Open AccessArticle

Determining Forest Duff Water Content Using a Low-Cost Standing Wave Ratio Sensor

by Xiaofei Yan¹, Yajie Zhao¹, Qiang Cheng², Xiaoliang Zheng¹ and Yandong Zhao^1,*

¹ School of Technology, Beijing Forestry University, Beijing 100083, China

² College of Information and Electrical Engineering, China Agricultural University, Beijing 100083, China

Sensors 2018, 18(2), 647; https://doi.org/10.3390/s18020647 - 22 Feb 2018

Cited by 10 | Viewed by 4693

Abstract

Forest duff (fermentation and humus) water content is an important parameter for fire risk prediction and water resource management. However, accurate determination of forest duff water content is difficult due to its loose structure. This study evaluates the feasibility of a standing wave [...] Read more.

Forest duff (fermentation and humus) water content is an important parameter for fire risk prediction and water resource management. However, accurate determination of forest duff water content is difficult due to its loose structure. This study evaluates the feasibility of a standing wave ratio (SWR) sensor to accurately determine the forest duff water content. The performance of this sensor was tested on fermentation and humus with eight different compaction levels. Meanwhile, a commercialized time domain reflectometry (TDR) was employed for comparison. Calibration results showed that there were strong linear relationships between the volumetric water content (θ_V) and the SWR sensor readings (V_SWR) at different compaction classes for both fermentation and humus samples. The sensor readings of both SWR and TDR underestimated the forest duff water content at low compacted levels, proving that the compaction of forest duff could significantly affect the measurement accuracy of both sensors. Experimental data also showed that the accuracy of the SWR sensor was higher than that of TDR according to the root mean square error (RMSE). Furthermore, low cost is another important advantage of the SWR sensor in comparison with TDR. This low-cost SWR sensor performs well in loose materials and is feasible for evaluating the water content of forest duff. In addition, the results indicate that decomposition of the forest duff should be taken into account for continuous and long-term water content measurement. Full article

(This article belongs to the Section Physical Sensors)

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16 pages, 4999 KiB

Open AccessArticle

Surface Plasmon Resonance and Bending Loss-Based U-Shaped Plastic Optical Fiber Biosensors

by Ariadny Da S. Arcas¹, Fábio Da S. Dutra^1,2

, Regina C. S. B. Allil³ and Marcelo M. Werneck^1,3,*

¹ Nanotechnology Engineering Program, Universidade Federal do Rio de Janeiro, Rio de Janeiro 21941-901, Brazil

² Petrobras’ Research and Development Center, CENPES, Rio de Janeiro 21941-915, Brazil

³ Electrical Engineering Program, COPPE, Universidade Federal do Rio de Janeiro, Rio de Janeiro 21941-901, Brazil

Sensors 2018, 18(2), 648; https://doi.org/10.3390/s18020648 - 22 Feb 2018

Cited by 100 | Viewed by 8973

Abstract

Escherichia coli (E. coli) is a large and diverse bacteria group that inhabits the intestinal tract of many mammals. Most E. coli strains are harmless, however some of them are pathogenic, meaning they can make one sick if ingested. By being [...] Read more.

Escherichia coli (E. coli) is a large and diverse bacteria group that inhabits the intestinal tract of many mammals. Most E. coli strains are harmless, however some of them are pathogenic, meaning they can make one sick if ingested. By being in the feces of animals and humans, its presence in water and food is used as indicator of fecal contamination. The main method for this microorganism detection is the bacterial culture medium that is time-consuming and requires a laboratory with specialized personnel. Other sophisticated methods are still not fast enough because they require sending samples to a laboratory and with a high cost of analysis. In this paper, a gold-coated U-shaped plastic optical fiber (POF) biosensor for E. coli bacteria detection is presented. The biosensor works by intensity modulation principle excited by monochromatic light where the power absorption is imposed by predominant effect of either bending loss or surface plasmon resonance (SPR), depending on the gold thickness. Bacterial selectivity is obtained by antibody immobilization on the fiber surface. The biosensor showed a detection limit of 1.5 × 10³ colony-forming units (CFU)/mL, demonstrating that the technology can be a portable, fast response and low-cost alternative to conventional methodologies for quality analysis of water and food. Full article

(This article belongs to the Special Issue Optical Biochemical Sensor Systems and Applications)

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13 pages, 4534 KiB

Open AccessArticle

Application of Ground-Penetrating Radar for Detecting Internal Anomalies in Tree Trunks with Irregular Contours

by Weilin Li, Jian Wen^*, Zhongliang Xiao and Shengxia Xu

School of Technology, Beijing Forestry University, Beijing 100083, China

Sensors 2018, 18(2), 649; https://doi.org/10.3390/s18020649 - 22 Feb 2018

Cited by 26 | Viewed by 7328

Abstract

To assess the health conditions of tree trunks, it is necessary to estimate the layers and anomalies of their internal structure. The main objective of this paper is to investigate the internal part of tree trunks considering their irregular contour. In this respect, [...] Read more.

To assess the health conditions of tree trunks, it is necessary to estimate the layers and anomalies of their internal structure. The main objective of this paper is to investigate the internal part of tree trunks considering their irregular contour. In this respect, we used ground penetrating radar (GPR) for non-invasive detection of defects and deteriorations in living trees trunks. The Hilbert transform algorithm and the reflection amplitudes were used to estimate the relative dielectric constant. The point cloud data technique was applied as well to extract the irregular contours of trunks. The feasibility and accuracy of the methods were examined through numerical simulations, laboratory and field measurements. The results demonstrated that the applied methodology allowed for accurate characterizations of the internal inhomogeneity. Furthermore, the point cloud technique resolved the trunk well by providing high-precision coordinate information. This study also demonstrated that cross-section tomography provided images with high resolution and accuracy. These integrated techniques thus proved to be promising for observing tree trunks and other cylindrical objects. The applied approaches offer a great promise for future 3D reconstruction of tomographic images with radar wave. Full article

(This article belongs to the Special Issue Sensors Signal Processing and Visual Computing)

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12 pages, 3633 KiB

Open AccessArticle

Optical Method for Estimating the Chlorophyll Contents in Plant Leaves

by Madaín Pérez-Patricio¹, Jorge Luis Camas-Anzueto^1,*, Avisaí Sanchez-Alegría¹, Abiel Aguilar-González³, Federico Gutiérrez-Miceli¹

, Elías Escobar-Gómez¹, Yvon Voisin², Carlos Rios-Rojas¹ and Ruben Grajales-Coutiño¹

¹ Tecnológico Nacional de México, 29000 Tuxtla Gutiérrez, Chiapas, Mexico

² Le2i FRE2005, CNRS, Arts et Métiers, Univ. Bourgogne Franche-Comté, av. des Plaines de l’Yonne, BP16, 89010 Auxerre CEDEX, France

³ Institut Pascal, Université Clermont Auvergne, 63178 Clermont Ferrand, France

Sensors 2018, 18(2), 650; https://doi.org/10.3390/s18020650 - 22 Feb 2018

Cited by 107 | Viewed by 12488

Abstract

This work introduces a new vision-based approach for estimating chlorophyll contents in a plant leaf using reflectance and transmittance as base parameters. Images of the top and underside of the leaf are captured. To estimate the base parameters (reflectance/transmittance), a novel optical arrangement [...] Read more.

This work introduces a new vision-based approach for estimating chlorophyll contents in a plant leaf using reflectance and transmittance as base parameters. Images of the top and underside of the leaf are captured. To estimate the base parameters (reflectance/transmittance), a novel optical arrangement is proposed. The chlorophyll content is then estimated by using linear regression where the inputs are the reflectance and transmittance of the leaf. Performance of the proposed method for chlorophyll content estimation was compared with a spectrophotometer and a Soil Plant Analysis Development (SPAD) meter. Chlorophyll content estimation was realized for Lactuca sativa L., Azadirachta indica, Canavalia ensiforme, and Lycopersicon esculentum. Experimental results showed that—in terms of accuracy and processing speed—the proposed algorithm outperformed many of the previous vision-based approach methods that have used SPAD as a reference device. On the other hand, the accuracy reached is 91% for crops such as Azadirachta indica, where the chlorophyll value was obtained using the spectrophotometer. Additionally, it was possible to achieve an estimation of the chlorophyll content in the leaf every 200 ms with a low-cost camera and a simple optical arrangement. This non-destructive method increased accuracy in the chlorophyll content estimation by using an optical arrangement that yielded both the reflectance and transmittance information, while the required hardware is cheap. Full article

(This article belongs to the Special Issue Optical Biochemical Sensor Systems and Applications)

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17 pages, 1905 KiB

Open AccessArticle

A Cross-Layer, Anomaly-Based IDS for WSN and MANET

by Amar Amouri¹, Salvatore D. Morgera^1,*

, Mohamed A. Bencherif²

and Raju Manthena³

¹ Department of Electrical Engineering, University of South Florida, Tampa, FL 33620, USA

² College of Computer & Information Sciences, King Saud University, P.O. Box 51178, Riyadh 11543, Saudi Arabia

³ Jet Propulsion Laboratory, Pasadena, CA 91109, USA

Sensors 2018, 18(2), 651; https://doi.org/10.3390/s18020651 - 22 Feb 2018

Cited by 31 | Viewed by 4611

Abstract

Intrusion detection system (IDS) design for mobile adhoc networks (MANET) is a crucial component for maintaining the integrity of the network. The need for rapid deployment of IDS capability with minimal data availability for training and testing is an important requirement of such [...] Read more.

Intrusion detection system (IDS) design for mobile adhoc networks (MANET) is a crucial component for maintaining the integrity of the network. The need for rapid deployment of IDS capability with minimal data availability for training and testing is an important requirement of such systems, especially for MANETs deployed in highly dynamic scenarios, such as battlefields. This work proposes a two-level detection scheme for detecting malicious nodes in MANETs. The first level deploys dedicated sniffers working in promiscuous mode. Each sniffer utilizes a decision-tree-based classifier that generates quantities which we refer to as correctly classified instances (CCIs) every reporting time. In the second level, the CCIs are sent to an algorithmically run supernode that calculates quantities, which we refer to as the accumulated measure of fluctuation (AMoF) of the received CCIs for each node under test (NUT). A key concept that is used in this work is that the variability of the smaller size population which represents the number of malicious nodes in the network is greater than the variance of the larger size population which represents the number of normal nodes in the network. A linear regression process is then performed in parallel with the calculation of the AMoF for fitting purposes and to set a proper threshold based on the slope of the fitted lines. As a result, the malicious nodes are efficiently and effectively separated from the normal nodes. The proposed scheme is tested for various node velocities and power levels and shows promising detection performance even at low-power levels. The results presented also apply to wireless sensor networks (WSN) and represent a novel IDS scheme for such networks. Full article

(This article belongs to the Section Sensor Networks)

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31 pages, 14153 KiB

Open AccessArticle

The Spectrum Analysis Solution (SAS) System: Theoretical Analysis, Hardware Design and Implementation

by Ram M. Narayanan^1,*

, Richard K. Pooler², Anthony F. Martone³, Kyle A. Gallagher³ and Kelly D. Sherbondy³

¹ Department of Electrical Engineering, The Pennsylvania State University, University Park, PA 16802, USA

² RF and Millimeter-Wave Engineering Group, Johns Hopkins University Applied Physics Laboratory, Laurel, MD 20723, USA

³ Sensors and Electronics Directorate, U.S. Army Research Laboratory, Adelphi, MD 20783, USA

Sensors 2018, 18(2), 652; https://doi.org/10.3390/s18020652 - 22 Feb 2018

Cited by 3 | Viewed by 4872

Abstract

This paper describes a multichannel super-heterodyne signal analyzer, called the Spectrum Analysis Solution (SAS), which performs multi-purpose spectrum sensing to support spectrally adaptive and cognitive radar applications. The SAS operates from ultrahigh frequency (UHF) to the S-band and features a wideband channel with [...] Read more.

This paper describes a multichannel super-heterodyne signal analyzer, called the Spectrum Analysis Solution (SAS), which performs multi-purpose spectrum sensing to support spectrally adaptive and cognitive radar applications. The SAS operates from ultrahigh frequency (UHF) to the S-band and features a wideband channel with eight narrowband channels. The wideband channel acts as a monitoring channel that can be used to tune the instantaneous band of the narrowband channels to areas of interest in the spectrum. The data collected from the SAS has been utilized to develop spectrum sensing algorithms for the budding field of spectrum sharing (SS) radar. Bandwidth (BW), average total power, percent occupancy (PO), signal-to-interference-plus-noise ratio (SINR), and power spectral entropy (PSE) have been examined as metrics for the characterization of the spectrum. These metrics are utilized to determine a contiguous optimal sub-band (OSB) for a SS radar transmission in a given spectrum for different modalities. Three OSB algorithms are presented and evaluated: the spectrum sensing multi objective (SS-MO), the spectrum sensing with brute force PSE (SS-BFE), and the spectrum sensing multi-objective with brute force PSE (SS-MO-BFE). Full article

(This article belongs to the Section Remote Sensors)

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15 pages, 4633 KiB

Open AccessArticle

Adaptive Correlation Model for Visual Tracking Using Keypoints Matching and Deep Convolutional Feature

by Yuankun Li¹, Tingfa Xu^1,2,*, Honggao Deng^1,3, Guokai Shi¹ and Jie Guo¹

¹ School of Optics and Photonics, Image Engineering & Video Technology Lab, Beijing Institute of Technology, Beijing 100081, China

² Key Laboratory of Photoelectronic Imaging Technology and System, Ministry of Education of China, Beijing 100081, China

³ School of Information and Communication, Guangxi Key Laboratory of Wireless Wideband Communication and Signal Processing, Guilin University of Electronic Technology, Guilin 541004, China

Sensors 2018, 18(2), 653; https://doi.org/10.3390/s18020653 - 23 Feb 2018

Cited by 2 | Viewed by 4840

Abstract

Although correlation filter (CF)-based visual tracking algorithms have achieved appealing results, there are still some problems to be solved. When the target object goes through long-term occlusions or scale variation, the correlation model used in existing CF-based algorithms will inevitably learn some non-target [...] Read more.

Although correlation filter (CF)-based visual tracking algorithms have achieved appealing results, there are still some problems to be solved. When the target object goes through long-term occlusions or scale variation, the correlation model used in existing CF-based algorithms will inevitably learn some non-target information or partial-target information. In order to avoid model contamination and enhance the adaptability of model updating, we introduce the keypoints matching strategy and adjust the model learning rate dynamically according to the matching score. Moreover, the proposed approach extracts convolutional features from a deep convolutional neural network (DCNN) to accurately estimate the position and scale of the target. Experimental results demonstrate that the proposed tracker has achieved satisfactory performance in a wide range of challenging tracking scenarios. Full article

(This article belongs to the Section Physical Sensors)

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13 pages, 2670 KiB

Open AccessArticle

Using a Second Order Sigma-Delta Control to Improve the Performance of Metal-Oxide Gas Sensors

by Lukasz Kowalski¹, Joan Pons-Nin¹

, Eric Navarrete²

, Eduard Llobet²

and Manuel Domínguez-Pumar^1,*

¹ Micro and Nano Technologies Group, Electronic Engineering Department, Universitat Politècnica de Catalunya—BarcelonaTech, 08034 Barcelona, Spain

² MINOS-EMaS Group, Electronic Engineering Department, Universitat Rovira i Virgili, 43003 Tarragona, Spain

Sensors 2018, 18(2), 654; https://doi.org/10.3390/s18020654 - 23 Feb 2018

Cited by 8 | Viewed by 6215

Abstract

Controls of surface potential have been proposed to accelerate the time response of MOX gas sensors. These controls use temperature modulations and a feedback loop based on first-order sigma-delta modulators to keep constant the surface potential. Changes in the surrounding gases, therefore, must [...] Read more.

Controls of surface potential have been proposed to accelerate the time response of MOX gas sensors. These controls use temperature modulations and a feedback loop based on first-order sigma-delta modulators to keep constant the surface potential. Changes in the surrounding gases, therefore, must be compensated by average temperature produced by the control loop, which is the new output signal. The purpose of this paper is to present a second order sigma-delta control of the surface potential for gas sensors. With this new control strategy, it is possible to obtain a second order zero of the quantization noise in the output signal. This provides a less noisy control of the surface potential, while at the same time some undesired effects of first order modulators, such as the presence of plateaus, are avoided. Experiments proving these performance improvements are presented using a gas sensor made of tungsten oxide nanowires. Plateau avoidance and second order noise shaping is shown with ethanol measurements. Full article

(This article belongs to the Special Issue Gas Sensors based on Semiconducting Metal Oxides)

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20 pages, 9960 KiB

Open AccessArticle

Parameter Estimation of the Thermal Network Model of a Machine Tool Spindle by Self-made Bluetooth Temperature Sensor Module

by Yuan-Chieh Lo¹, Yuh-Chung Hu^2,* and Pei-Zen Chang¹

¹ Institute of Applied Mechanics, National Taiwan University, No. 1, Sec. 4, Roosevelt Rd., Taipei 10617, Taiwan

² Department of Mechanical and Electromechanical Engineering, National ILan University, No.1, Sec. 1, Shennong Rd., Yilan City, Yilan County 260, Taiwan

Sensors 2018, 18(2), 656; https://doi.org/10.3390/s18020656 - 23 Feb 2018

Cited by 13 | Viewed by 6406

Abstract

Thermal characteristic analysis is essential for machine tool spindles because sudden failures may occur due to unexpected thermal issue. This article presents a lumped-parameter Thermal Network Model (TNM) and its parameter estimation scheme, including hardware and software, in order to characterize both the [...] Read more.

Thermal characteristic analysis is essential for machine tool spindles because sudden failures may occur due to unexpected thermal issue. This article presents a lumped-parameter Thermal Network Model (TNM) and its parameter estimation scheme, including hardware and software, in order to characterize both the steady-state and transient thermal behavior of machine tool spindles. For the hardware, the authors develop a Bluetooth Temperature Sensor Module (BTSM) which accompanying with three types of temperature-sensing probes (magnetic, screw, and probe). Its specification, through experimental test, achieves to the precision ±(0.1 + 0.0029|t|) °C, resolution 0.00489 °C, power consumption 7 mW, and size Ø40 mm × 27 mm. For the software, the heat transfer characteristics of the machine tool spindle correlative to rotating speed are derived based on the theory of heat transfer and empirical formula. The predictive TNM of spindles was developed by grey-box estimation and experimental results. Even under such complicated operating conditions as various speeds and different initial conditions, the experiments validate that the present modeling methodology provides a robust and reliable tool for the temperature prediction with normalized mean square error of 99.5% agreement, and the present approach is transferable to the other spindles with a similar structure. For realizing the edge computing in smart manufacturing, a reduced-order TNM is constructed by Model Order Reduction (MOR) technique and implemented into the real-time embedded system. Full article

(This article belongs to the Special Issue Selected Sensor Related Papers from ICI2017)

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34 pages, 6618 KiB

Open AccessArticle

A Method for Dynamically Selecting the Best Frequency Hopping Technique in Industrial Wireless Sensor Network Applications

by Erlantz Fernández de Gorostiza^1,*, Jorge Berzosa¹

, Jon Mabe¹ and Roberto Cortiñas²

¹ Electronics and Communications Unit, IK4-Tekniker, Calle Iñaki Goenaga 5, 20600 Eibar, Spain

² Computer Science Faculty, University of the Basque Country UPV/EHU, Paseo M. Lardizábal 1, 20018 Donostia-San Sebastián, Spain

Sensors 2018, 18(2), 657; https://doi.org/10.3390/s18020657 - 23 Feb 2018

Cited by 21 | Viewed by 6967

Abstract

Industrial wireless applications often share the communication channel with other wireless technologies and communication protocols. This coexistence produces interferences and transmission errors which require appropriate mechanisms to manage retransmissions. Nevertheless, these mechanisms increase the network latency and overhead due to the retransmissions. Thus, [...] Read more.

Industrial wireless applications often share the communication channel with other wireless technologies and communication protocols. This coexistence produces interferences and transmission errors which require appropriate mechanisms to manage retransmissions. Nevertheless, these mechanisms increase the network latency and overhead due to the retransmissions. Thus, the loss of data packets and the measures to handle them produce an undesirable drop in the QoS and hinder the overall robustness and energy efficiency of the network. Interference avoidance mechanisms, such as frequency hopping techniques, reduce the need for retransmissions due to interferences but they are often tailored to specific scenarios and are not easily adapted to other use cases. On the other hand, the total absence of interference avoidance mechanisms introduces a security risk because the communication channel may be intentionally attacked and interfered with to hinder or totally block it. In this paper we propose a method for supporting the design of communication solutions under dynamic channel interference conditions and we implement dynamic management policies for frequency hopping technique and channel selection at runtime. The method considers several standard frequency hopping techniques and quality metrics, and the quality and status of the available frequency channels to propose the best combined solution to minimize the side effects of interferences. A simulation tool has been developed and used in this work to validate the method. Full article

(This article belongs to the Collection Smart Industrial Wireless Sensor Networks)

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11 pages, 9407 KiB

Open AccessArticle

Methionine-Capped Gold Nanoclusters as a Fluorescence-Enhanced Probe for Cadmium(II) Sensing

by Yan Peng^1,2, Maomao Wang¹, Xiaoxia Wu¹, Fu Wang^1,* and Lang Liu^2,*

¹ Laboratory of Environmental Sciences and Technology, Xinjiang Technical Institute of Physics & Chemistry, Chinese Academy of Sciences, Urumqi 830011, Xinjiang, China

² College of Chemistry and Chemical Engineering, Xinjiang University, Urumqi 830046, Xinjiang, China

Sensors 2018, 18(2), 658; https://doi.org/10.3390/s18020658 - 23 Feb 2018

Cited by 26 | Viewed by 6633

Abstract

Gold nanoclusters (Au NCs) have been considered as novel heavy metal ions sensors due to their ultrafine size, photo-stability and excellent fluorescent properties. In this study, a green and facile method was developed for the preparation of fluorescent water-soluble gold nanoclusters with methionine [...] Read more.

Gold nanoclusters (Au NCs) have been considered as novel heavy metal ions sensors due to their ultrafine size, photo-stability and excellent fluorescent properties. In this study, a green and facile method was developed for the preparation of fluorescent water-soluble gold nanoclusters with methionine as a stabilizer. The nanoclusters emit orange fluorescence with excitation/emission peaks at 420/565 nm and a quantum yield of about 1.46%. The fluorescence of the Au NCs is selectively and sensitively enhanced by addition of Cd(II) ions attributed to the Cd(II) ion-induced aggregation of nanoclusters. This finding was further used to design a fluorometric method for the determination of Cd(II) ions, which had a linear response in the concentration range from 50 nM to 35 μM and a detection limit of 12.25 nM. The practicality of the nanoprobe was validated in various environmental water samples and milk powder samples, with a fairly satisfactory recovery percent. Full article

(This article belongs to the Special Issue Fluorescent Probes and Sensors)

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17 pages, 2676 KiB

Open AccessArticle

Application of Improved 5th-Cubature Kalman Filter in Initial Strapdown Inertial Navigation System Alignment for Large Misalignment Angles

by Wei Wang and Xiyuan Chen^*

Key Laboratory of Micro-Inertial Instrument and Advanced Navigation Technology, Ministry of Education, School of Instrument Science and Engineering, Southeast University, Nanjing 210096, China

Sensors 2018, 18(2), 659; https://doi.org/10.3390/s18020659 - 23 Feb 2018

Cited by 33 | Viewed by 4242

Abstract

In view of the fact the accuracy of the third-degree Cubature Kalman Filter (CKF) used for initial alignment under large misalignment angle conditions is insufficient, an improved fifth-degree CKF algorithm is proposed in this paper. In order to make full use of the [...] Read more.

In view of the fact the accuracy of the third-degree Cubature Kalman Filter (CKF) used for initial alignment under large misalignment angle conditions is insufficient, an improved fifth-degree CKF algorithm is proposed in this paper. In order to make full use of the innovation on filtering, the innovation covariance matrix is calculated recursively by an innovative sequence with an exponent fading factor. Then a new adaptive error covariance matrix scaling algorithm is proposed. The Singular Value Decomposition (SVD) method is used for improving the numerical stability of the fifth-degree CKF in this paper. In order to avoid the overshoot caused by excessive scaling of error covariance matrix during the convergence stage, the scaling scheme is terminated when the gradient of azimuth reaches the maximum. The experimental results show that the improved algorithm has better alignment accuracy with large misalignment angles than the traditional algorithm. Full article

(This article belongs to the Section Physical Sensors)

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10 pages, 4465 KiB

Open AccessArticle

Enhanced Humidity Sensitivity with Silicon Nanopillar Array by UV Light

by Wei Li^1,2,*, Chao Ding¹, Yun Cai¹, Juyan Liu¹, Linlin Wang¹, Qingying Ren¹ and Jie Xu¹

¹ State-Province Joint Engineering Laboratory for RF Integration and Micropackaging, College of Electronic and Optical Engineering & College of Microelectronics, Nanjing University of Posts and Telecommunications, Nanjing 210023, China

² State Key Laboratory of Millimeter Waves, Southeast University, Nanjing 210096, China

Sensors 2018, 18(2), 660; https://doi.org/10.3390/s18020660 - 23 Feb 2018

Cited by 8 | Viewed by 4204

Abstract

The sensitivity of silicon nanopillar array for relative humidity (RH) with UV illumination was investigated in this work. The silicon nanopillar array was prepared by nanosphere lithography. Electrical measurements were performed on its sensing performance with and without UV irradiation. It was found [...] Read more.

The sensitivity of silicon nanopillar array for relative humidity (RH) with UV illumination was investigated in this work. The silicon nanopillar array was prepared by nanosphere lithography. Electrical measurements were performed on its sensing performance with and without UV irradiation. It was found that UV light improved the humidity sensitivity with different UV light wavelengths and power. The sensor response and recovery time were reduced. Furthermore, the turn-on threshold voltage and the operating voltage both decreased. These sensing characteristics can mainly be attributed to the electron-hole pairs generated by UV light. These electron-hole pairs promote the adsorption and desorption processes. The results indicate that silicon nanopillar array materials with UV irradiation might be competitive as novel sensing materials for fabricating humidity sensors with high performances. Full article

(This article belongs to the Section Biosensors)

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12 pages, 5171 KiB

Open AccessArticle

Metal Nanoparticles/Porous Silicon Microcavity Enhanced Surface Plasmon Resonance Fluorescence for the Detection of DNA

by Jiajia Wang¹

and Zhenhong Jia^2,*

¹ School of Chemistry and Chemical Engineering, Xinjiang University, Urumqi 830046, China

² School of Information Science and Engineering, Xinjiang University, Urumqi 830046, China

Sensors 2018, 18(2), 661; https://doi.org/10.3390/s18020661 - 23 Feb 2018

Cited by 26 | Viewed by 5913

Abstract

A porous silicon microcavity (PSiMC) with resonant peak wavelength of 635 nm was fabricated by electrochemical etching. Metal nanoparticles (NPs)/PSiMC enhanced fluorescence substrates were prepared by the electrostatic adherence of Au NPs that were distributed in PSiMC. The Au NPs/PSiMC device was used [...] Read more.

A porous silicon microcavity (PSiMC) with resonant peak wavelength of 635 nm was fabricated by electrochemical etching. Metal nanoparticles (NPs)/PSiMC enhanced fluorescence substrates were prepared by the electrostatic adherence of Au NPs that were distributed in PSiMC. The Au NPs/PSiMC device was used to characterize the target DNA immobilization and hybridization with its complementary DNA sequences marked with Rhodamine red (RRA). Fluorescence enhancement was observed on the Au NPs/PSiMC device substrate; and the minimum detection concentration of DNA ran up to 10 pM. The surface plasmon resonance (SPR) of the MC substrate; which is so well-positioned to improve fluorescence enhancement rather the fluorescence enhancement of the high reflection band of the Bragg reflector; would welcome such a highly sensitive in biosensor. Full article

(This article belongs to the Special Issue Recent Advances in Nucleic Acid Sensors)

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24 pages, 5120 KiB

Open AccessArticle

Leader-Follower Formation Control of UUVs with Model Uncertainties, Current Disturbances, and Unstable Communication

by Zheping Yan, Da Xu, Tao Chen^*, Wei Zhang and Yibo Liu

College of Automation, Harbin Engineering University, Harbin 150001, China

Sensors 2018, 18(2), 662; https://doi.org/10.3390/s18020662 - 23 Feb 2018

Cited by 50 | Viewed by 6528

Abstract

Unmanned underwater vehicles (UUVs) have rapidly developed as mobile sensor networks recently in the investigation, survey, and exploration of the underwater environment. The goal of this paper is to develop a practical and efficient formation control method to improve work efficiency of multi-UUV [...] Read more.

Unmanned underwater vehicles (UUVs) have rapidly developed as mobile sensor networks recently in the investigation, survey, and exploration of the underwater environment. The goal of this paper is to develop a practical and efficient formation control method to improve work efficiency of multi-UUV sensor networks. Distributed leader-follower formation controllers are designed based on a state feedback and consensus algorithm. Considering that each vehicle is subject to model uncertainties and current disturbances, a second-order integral UUV model with a nonlinear function is established using the state feedback linearized method under current disturbances. For unstable communication among UUVs, communication failure and acoustic link noise interference are considered. Two-layer random switching communication topologies are proposed to solve the problem of communication failure. For acoustic link noise interference, accurate representation of valid communication information and noise stripping when designing controllers is necessary. Effective communication topology weights are designed to represent the validity of communication information interfered by noise. Utilizing state feedback and noise stripping, sufficient conditions for design formation controllers are proposed to ensure UUV formation achieves consensus under model uncertainties, current disturbances, and unstable communication. The stability of formation controllers is proven by the Lyapunov-Razumikhin theorem, and the validity is verified by simulation results. Full article

(This article belongs to the Special Issue Sensors, Wireless Connectivity and Systems for Autonomous Vehicles and Smart Mobility)

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15 pages, 5821 KiB

Open AccessArticle

Estimation of Handgrip Force from SEMG Based on Wavelet Scale Selection

by Kai Wang¹, Xianmin Zhang¹, Jun Ota² and Yanjiang Huang^1,2,*

¹ Guangdong Provincial Key Laboratory of Precision Equipment and Manufacturing Technology, South China University of Technology, Guangzhou 510640, China

² Research into Artifacts, Center for Engineering, University of Tokyo, Chiba 113-8654, Japan

Sensors 2018, 18(2), 663; https://doi.org/10.3390/s18020663 - 24 Feb 2018

Cited by 24 | Viewed by 5776

Abstract

This paper proposes a nonlinear correlation-based wavelet scale selection technology to select the effective wavelet scales for the estimation of handgrip force from surface electromyograms (SEMG). The SEMG signal corresponding to gripping force was collected from extensor and flexor forearm muscles during the [...] Read more.

This paper proposes a nonlinear correlation-based wavelet scale selection technology to select the effective wavelet scales for the estimation of handgrip force from surface electromyograms (SEMG). The SEMG signal corresponding to gripping force was collected from extensor and flexor forearm muscles during the force-varying analysis task. We performed a computational sensitivity analysis on the initial nonlinear SEMG-handgrip force model. To explore the nonlinear correlation between ten wavelet scales and handgrip force, a large-scale iteration based on the Monte Carlo simulation was conducted. To choose a suitable combination of scales, we proposed a rule to combine wavelet scales based on the sensitivity of each scale and selected the appropriate combination of wavelet scales based on sequence combination analysis (SCA). The results of SCA indicated that the scale combination VI is suitable for estimating force from the extensors and the combination V is suitable for the flexors. The proposed method was compared to two former methods through prolonged static and force-varying contraction tasks. The experiment results showed that the root mean square errors derived by the proposed method for both static and force-varying contraction tasks were less than 20%. The accuracy and robustness of the handgrip force derived by the proposed method is better than that obtained by the former methods. Full article

(This article belongs to the Special Issue Sensors for Gait, Posture, and Health Monitoring)

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14 pages, 2392 KiB

Open AccessArticle

User Access Management Based on Network Pricing for Social Network Applications

by Fuhong Lin^1,*

, Zhibo Pang²

, Xingmin Ma¹ and Qing Gu³

¹ School of Computer and Communication Engineering, University of Science and Technology Beijing (USTB), Beijing 100083, China

² ABB Corporate Research, Forskargränd 7, SE-721 78 Västerås, Sweden

³ School of Mechanical Engineering, University of Science and Technology Beijing(USTB), Beijing 100083, China

Sensors 2018, 18(2), 664; https://doi.org/10.3390/s18020664 - 24 Feb 2018

Cited by 3 | Viewed by 4326

Abstract

Social applications play a very important role in people’s lives, as users communicate with each other through social networks on a daily basis. This presents a challenge: How does one receive high-quality service from social networks at a low cost? Users can access [...] Read more.

Social applications play a very important role in people’s lives, as users communicate with each other through social networks on a daily basis. This presents a challenge: How does one receive high-quality service from social networks at a low cost? Users can access different kinds of wireless networks from various locations. This paper proposes a user access management strategy based on network pricing such that networks can increase its income and improve service quality. Firstly, network price is treated as an optimizing access parameter, and an unascertained membership algorithm is used to make pricing decisions. Secondly, network price is adjusted dynamically in real time according to network load. Finally, selecting a network is managed and controlled in terms of the market economy. Simulation results show that the proposed scheme can effectively balance network load, reduce network congestion, improve the user's quality of service (QoS) requirements, and increase the network’s income. Full article

(This article belongs to the Special Issue Sensor Intelligent Data Analysis for Social Networks: Theory and Applications)

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9 pages, 2998 KiB

Open AccessArticle

High-Speed Interrogation for Large-Scale Fiber Bragg Grating Sensing

by Chenyuan Hu¹ and Wei Bai^2,*

¹ MOE Key Laboratory of Fundamental Physical Quantities Measurement & Hubei Key Laboratory of Gravitation and Quantum Physics, School of Physics, Huazhong University of Science and Technology, Wuhan 430074, China

² School of Information Engineering, Hubei University of Chinese Medicine, Wuhan 430065, China

Sensors 2018, 18(2), 665; https://doi.org/10.3390/s18020665 - 24 Feb 2018

Cited by 14 | Viewed by 5292

Abstract

A high-speed interrogation scheme for large-scale fiber Bragg grating (FBG) sensing arrays is presented. This technique employs parallel computing and pipeline control to modulate incident light and demodulate the reflected sensing signal. One Electro-optic modulator (EOM) and one semiconductor optical amplifier (SOA) were [...] Read more.

A high-speed interrogation scheme for large-scale fiber Bragg grating (FBG) sensing arrays is presented. This technique employs parallel computing and pipeline control to modulate incident light and demodulate the reflected sensing signal. One Electro-optic modulator (EOM) and one semiconductor optical amplifier (SOA) were used to generate a phase delay to filter reflected spectrum form multiple candidate FBGs with the same optical path difference (OPD). Experimental results showed that the fastest interrogation delay time for the proposed method was only about 27.2 us for a single FBG interrogation, and the system scanning period was only limited by the optical transmission delay in the sensing fiber owing to the multiple simultaneous central wavelength calculations. Furthermore, the proposed FPGA-based technique had a verified FBG wavelength demodulation stability of ±1 pm without average processing. Full article

(This article belongs to the Section Physical Sensors)

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16 pages, 1399 KiB

Open AccessArticle

SmartVeh: Secure and Efficient Message Access Control and Authentication for Vehicular Cloud Computing

by Qinlong Huang^1,*

, Yixian Yang¹ and Yuxiang Shi²

¹ School of Cyberspace Security, Beijing University of Posts and Telecommunications, Beijing 100876, China

² School of Science, Beijing University of Posts and Telecommunications, Beijing 100876, China

Sensors 2018, 18(2), 666; https://doi.org/10.3390/s18020666 - 24 Feb 2018

Cited by 22 | Viewed by 5861

Abstract

With the growing number of vehicles and popularity of various services in vehicular cloud computing (VCC), message exchanging among vehicles under traffic conditions and in emergency situations is one of the most pressing demands, and has attracted significant attention. However, it is an [...] Read more.

With the growing number of vehicles and popularity of various services in vehicular cloud computing (VCC), message exchanging among vehicles under traffic conditions and in emergency situations is one of the most pressing demands, and has attracted significant attention. However, it is an important challenge to authenticate the legitimate sources of broadcast messages and achieve fine-grained message access control. In this work, we propose SmartVeh, a secure and efficient message access control and authentication scheme in VCC. A hierarchical, attribute-based encryption technique is utilized to achieve fine-grained and flexible message sharing, which ensures that vehicles whose persistent or dynamic attributes satisfy the access policies can access the broadcast message with equipped on-board units (OBUs). Message authentication is enforced by integrating an attribute-based signature, which achieves message authentication and maintains the anonymity of the vehicles. In order to reduce the computations of the OBUs in the vehicles, we outsource the heavy computations of encryption, decryption and signing to a cloud server and road-side units. The theoretical analysis and simulation results reveal that our secure and efficient scheme is suitable for VCC. Full article

(This article belongs to the Special Issue Security, Trust and Privacy for Sensor Networks)

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8 pages, 4338 KiB

Open AccessArticle

Second Generation Small Pixel Technology Using Hybrid Bond Stacking

by Vincent C. Venezia^*, Alan Chih-Wei Hsiung, Wu-Zang Yang, Yuying Zhang, Cheng Zhao, Zhiqiang Lin and Lindsay A. Grant

OmniVision Technologies, Inc., Santa Clara, CA 95054, USA

Sensors 2018, 18(2), 667; https://doi.org/10.3390/s18020667 - 24 Feb 2018

Cited by 21 | Viewed by 10500

Abstract

In this work, OmniVision’s second generation (Gen2) of small-pixel BSI stacking technologies is reviewed. The key features of this technology are hybrid-bond stacking, deeper back-side, deep-trench isolation, new back-side composite metal-oxide grid, and improved gate oxide quality. This Gen2 technology achieves state-of-the-art low-light [...] Read more.

In this work, OmniVision’s second generation (Gen2) of small-pixel BSI stacking technologies is reviewed. The key features of this technology are hybrid-bond stacking, deeper back-side, deep-trench isolation, new back-side composite metal-oxide grid, and improved gate oxide quality. This Gen2 technology achieves state-of-the-art low-light image-sensor performance for 1.1, 1.0, and 0.9 µm pixel products. Additional improvements on this technology include less than 100 ppm white-pixel process and a high near-infrared (NIR) QE technology. Full article

(This article belongs to the Special Issue Special Issue on the 2017 International Image Sensor Workshop (IISW))

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13 pages, 1160 KiB

Open AccessArticle

Mn⁴⁺-Doped Magnesium Titanate—A Promising Phosphor for Self-Referenced Optical Temperature Sensing

by Francesca Venturini^1,*

, Michael Baumgartner¹ and Sergey M. Borisov^2,*

¹ Institute of Applied Mathematics and Physics, Zurich University of Applied Sciences, Winterthur 8401, Switzerland

² Institute of Analytical Chemistry and Food Chemistry, Graz University of Technology, Stremayrgasse 9, 8010 Graz, Austria

Sensors 2018, 18(2), 668; https://doi.org/10.3390/s18020668 - 24 Feb 2018

Cited by 19 | Viewed by 6313

Abstract

Phosphors based on magnesium titanate activated with Mn

^{4 +}

ions are of great interest because, when excited with blue light, they display a strong red-emitting luminescence. They are characterized by a luminescence decay which is strongly temperature dependent in the range from [...] Read more.

Phosphors based on magnesium titanate activated with Mn

^{4 +}

ions are of great interest because, when excited with blue light, they display a strong red-emitting luminescence. They are characterized by a luminescence decay which is strongly temperature dependent in the range from −50

^{\circ}

C to 150

^{\circ}

C, making these materials very promising for temperature sensing in the biochemical field. In this work, the optical and thermal properties of the luminescence of Mg

_{2}

TiO

_{4}

are investigated for different Mn

^{4 +}

doping concentrations. The potential of this material for temperature sensing is demonstrated by fabricating a fiber optic temperature microsensor and by comparing its performance against a standard resistance thermometer. The response of the fiber optic sensor is exceptionally fast, with a response time below 1 s in the liquid phase and below 1.1 s in the gas phase. Full article

(This article belongs to the Special Issue Lab on Fiber Optrodes for Chemical and Biological Sensing: Recent Trends and Advances)

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10 pages, 5972 KiB

Open AccessArticle

The Design of a Single-Bit CMOS Image Sensor for Iris Recognition Applications

by Keunyeol Park, Minkyu Song and Soo Youn Kim^*

Department of Semiconductor Science, Dongguk University-Seoul, Seoul 04620, Korea

Sensors 2018, 18(2), 669; https://doi.org/10.3390/s18020669 - 24 Feb 2018

Cited by 12 | Viewed by 6228

Abstract

This paper presents a single-bit CMOS image sensor (CIS) that uses a data processing technique with an edge detection block for simple iris segmentation. In order to recognize the iris image, the image sensor conventionally captures high-resolution image data in digital code, extracts [...] Read more.

This paper presents a single-bit CMOS image sensor (CIS) that uses a data processing technique with an edge detection block for simple iris segmentation. In order to recognize the iris image, the image sensor conventionally captures high-resolution image data in digital code, extracts the iris data, and then compares it with a reference image through a recognition algorithm. However, in this case, the frame rate decreases by the time required for digital signal conversion of multi-bit digital data through the analog-to-digital converter (ADC) in the CIS. In order to reduce the overall processing time as well as the power consumption, we propose a data processing technique with an exclusive OR (XOR) logic gate to obtain single-bit and edge detection image data instead of multi-bit image data through the ADC. In addition, we propose a logarithmic counter to efficiently measure single-bit image data that can be applied to the iris recognition algorithm. The effective area of the proposed single-bit image sensor (174 × 144 pixel) is 2.84 mm² with a 0.18 μm 1-poly 4-metal CMOS image sensor process. The power consumption of the proposed single-bit CIS is 2.8 mW with a 3.3 V of supply voltage and 520 frame/s of the maximum frame rates. The error rate of the ADC is 0.24 least significant bit (LSB) on an 8-bit ADC basis at a 50 MHz sampling frequency. Full article

(This article belongs to the Special Issue Image Sensors)

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12 pages, 2428 KiB

Open AccessArticle

Error Analysis of the K-Rb-²¹Ne Comagnetometer Space-Stable Inertial Navigation System

by Qingzhong Cai^1,*

, Gongliu Yang¹, Wei Quan¹, Ningfang Song¹, Yongqiang Tu¹

and Yiliang Liu²

¹ School of Instrument Science and Opto-electronics Engineering, Beihang University, Beijing 100191, China

² National Remote Sensing Center of China, Beijing 100036, China

Sensors 2018, 18(2), 670; https://doi.org/10.3390/s18020670 - 24 Feb 2018

Cited by 12 | Viewed by 6157

Abstract

According to the application characteristics of the K-Rb-²¹Ne comagnetometer, a space-stable navigation mechanization is designed and the requirements of the comagnetometer prototype are presented. By analysing the error propagation rule of the space-stable Inertial Navigation System (INS), the three biases, the [...] Read more.

According to the application characteristics of the K-Rb-²¹Ne comagnetometer, a space-stable navigation mechanization is designed and the requirements of the comagnetometer prototype are presented. By analysing the error propagation rule of the space-stable Inertial Navigation System (INS), the three biases, the scale factor of the z-axis, and the misalignment of the x- and y-axis non-orthogonal with the z-axis, are confirmed to be the main error source. A numerical simulation of the mathematical model for each single error verified the theoretical analysis result of the system’s error propagation rule. Thus, numerical simulation based on the semi-physical data result proves the feasibility of the navigation scheme proposed in this paper. Full article

(This article belongs to the Special Issue Inertial Sensors for Positioning and Navigation)

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17 pages, 10768 KiB

Open AccessArticle

Study of Impact Damage in PVA-ECC Beam under Low-Velocity Impact Loading Using Piezoceramic Transducers and PVDF Thin-Film Transducers

by Baoxin Qi^1,2,†

, Qingzhao Kong^2,*,†

, Hui Qian³, Devendra Patil²

, Ing Lim⁴

, Mo Li⁵, Dong Liu² and Gangbing Song^2,4

¹ College of Civil Engineering, Shenyang Jianzhu University, Shenyang 110168, China

² Department of Mechanical Engineering, University of Houston, Houston, TX 77204, USA

³ College of Civil Engineering, Zhengzhou University, Zhengzhou 450001, China

⁴ Department of Civil and Environmental Engineering, University of Houston, Houston, TX 77204, USA

⁵ Department of Civil and Environmental Engineering, University of California, E4145 Engineering Gateway, Irvine, CA 92617, USA

^† These authors contributed equally to this paper.

Sensors 2018, 18(2), 671; https://doi.org/10.3390/s18020671 - 24 Feb 2018

Cited by 46 | Viewed by 5829

Abstract

Compared to conventional concrete, polyvinyl alcohol fiber reinforced engineering cementitious composite (PVA-ECC) offers high-strength, ductility, formability, and excellent fatigue resistance. However, impact-induced structural damage is a major concern and has not been previously characterized in PVA-ECC structures. We investigate the damage of PVA-ECC [...] Read more.

Compared to conventional concrete, polyvinyl alcohol fiber reinforced engineering cementitious composite (PVA-ECC) offers high-strength, ductility, formability, and excellent fatigue resistance. However, impact-induced structural damage is a major concern and has not been previously characterized in PVA-ECC structures. We investigate the damage of PVA-ECC beams under low-velocity impact loading. A series of ball-drop impact tests were performed at different drop weights and heights to simulate various impact energies. The impact results of PVA-ECC beams were compared with mortar beams. A combination of polyvinylidene fluoride (PVDF) thin-film sensors and piezoceramic-based smart aggregate were used for impact monitoring, which included impact initiation and crack evolution. Short-time Fourier transform (STFT) of the signal received by PVDF thin-film sensors was performed to identify impact events, while active-sensing approach was utilized to detect impact-induced crack evolution by the attenuation of a propagated guided wave. Wavelet packet-based energy analysis was performed to quantify failure development under repeated impact tests. Full article

(This article belongs to the Section Physical Sensors)

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22 pages, 28018 KiB

Open AccessArticle

An Automatic and Novel SAR Image Registration Algorithm: A Case Study of the Chinese GF-3 Satellite

by Yuming Xiang^1,2,*, Feng Wang¹

and Hongjian You^1,2

¹ Key Laboratory of Technology in Geo-spatial Information Processing and Application System, Institute of Electronics, Chinese Academy of Sciences, Beijing 100190, China

² University of Chinese Academy of Sciences, Beijing 100049, China

Sensors 2018, 18(2), 672; https://doi.org/10.3390/s18020672 - 24 Feb 2018

Cited by 28 | Viewed by 6336

Abstract

The Chinese GF-3 satellite launched in August 2016 is a Synthetic Aperture Radar (SAR) satellite that has the largest number of imaging modes in the world. It achieves a free switch in the spotlight, stripmap, scanSAR, wave, global observation and other imaging modes. [...] Read more.

The Chinese GF-3 satellite launched in August 2016 is a Synthetic Aperture Radar (SAR) satellite that has the largest number of imaging modes in the world. It achieves a free switch in the spotlight, stripmap, scanSAR, wave, global observation and other imaging modes. In order to further utilize GF-3 SAR images, an automatic and fast image registration procedure needs to be done. In this paper, we propose a novel image registration technique for GF-3 images of different imaging modes. The proposed algorithm consists of two stages: coarse registration and fine registration. In the first stage, we combine an adaptive sampling method with the SAR-SIFT algorithm to efficiently eliminate obvious translation, rotation and scale differences between the reference and sensed images. In the second stage, uniformly-distributed control points are extracted, then the fast normalized cross-correlation of an improved phase congruency model is utilized as a new similarity metric to match the reference image and the coarse-registered image in a local search region. Moreover, a selection strategy is used to remove outliers. Experimental results on several GF-3 SAR images of different imaging modes show that the proposed algorithm gives a robust, efficient and precise registration performance, compared with other state-of-the-art algorithms for SAR image registration. Full article

(This article belongs to the Special Issue First Experiences with Chinese Gaofen-3 SAR Sensor)

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15 pages, 2196 KiB

Open AccessArticle

A Feasibility Study on the Use of a Structured Light Depth-Camera for Three-Dimensional Body Measurements of Dairy Cows in Free-Stall Barns

by Andrea Pezzuolo¹

, Marcella Guarino²

, Luigi Sartori¹

and Francesco Marinello^1,*

¹ Department of Agroforesty and Landscape, University of Padua, 35020 Legnaro, Italy

² Department of Environmental Science and Policy, University of Milan, 20123 Milan, Italy

Sensors 2018, 18(2), 673; https://doi.org/10.3390/s18020673 - 24 Feb 2018

Cited by 73 | Viewed by 9458

Abstract

Frequent checks on livestock’s body growth can help reducing problems related to cow infertility or other welfare implications, and recognizing health’s anomalies. In the last ten years, optical methods have been proposed to extract information on various parameters while avoiding direct contact with [...] Read more.

Frequent checks on livestock’s body growth can help reducing problems related to cow infertility or other welfare implications, and recognizing health’s anomalies. In the last ten years, optical methods have been proposed to extract information on various parameters while avoiding direct contact with animals’ body, generally causes stress. This research aims to evaluate a new monitoring system, which is suitable to frequently check calves and cow’s growth through a three-dimensional analysis of their bodies’ portions. The innovative system is based on multiple acquisitions from a low cost Structured Light Depth-Camera (Microsoft Kinect™ v1). The metrological performance of the instrument is proved through an uncertainty analysis and a proper calibration procedure. The paper reports application of the depth camera for extraction of different body parameters. Expanded uncertainty ranging between 3 and 15 mm is reported in the case of ten repeated measurements. Coefficients of determination R² > 0.84 and deviations lower than 6% from manual measurements where in general detected in the case of head size, hips distance, withers to tail length, chest girth, hips, and withers height. Conversely, lower performances where recognized in the case of animal depth (R² = 0.74) and back slope (R² = 0.12). Full article

(This article belongs to the Section Physical Sensors)

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28 pages, 1132 KiB

Open AccessArticle

Towards an Iterated Game Model with Multiple Adversaries in Smart-World Systems

by Xiaofei He^1,‡

, Xinyu Yang^1,*, Wei Yu^2,*,‡, Jie Lin^1,‡ and Qingyu Yang^3,‡

¹ Department of Computer Science and Technology, Xi’an Jiaotong University, Xi’an 710049, China

² Department of Computer and Information Sciences, Towson University, Towson, MD 21252, USA

³ SKLMSE Lab, School of Electronic and Information Engineering, Xi’an Jiaotong University, Xi’an 710049, China

^‡ These authors contributed equally to this work.

Sensors 2018, 18(2), 674; https://doi.org/10.3390/s18020674 - 24 Feb 2018

Cited by 4 | Viewed by 4704

Abstract

Diverse and varied cyber-attacks challenge the operation of the smart-world system that is supported by Internet-of-Things (IoT) (smart cities, smart grid, smart transportation, etc.) and must be carefully and thoughtfully addressed before widespread adoption of the smart-world system can be fully realized. Although [...] Read more.

Diverse and varied cyber-attacks challenge the operation of the smart-world system that is supported by Internet-of-Things (IoT) (smart cities, smart grid, smart transportation, etc.) and must be carefully and thoughtfully addressed before widespread adoption of the smart-world system can be fully realized. Although a number of research efforts have been devoted to defending against these threats, a majority of existing schemes focus on the development of a specific defensive strategy to deal with specific, often singular threats. In this paper, we address the issue of coalitional attacks, which can be launched by multiple adversaries cooperatively against the smart-world system such as smart cities. Particularly, we propose a game-theory based model to capture the interaction among multiple adversaries, and quantify the capacity of the defender based on the extended Iterated Public Goods Game (IPGG) model. In the formalized game model, in each round of the attack, a participant can either cooperate by participating in the coalitional attack, or defect by standing aside. In our work, we consider the generic defensive strategy that has a probability to detect the coalitional attack. When the coalitional attack is detected, all participating adversaries are penalized. The expected payoff of each participant is derived through the equalizer strategy that provides participants with competitive benefits. The multiple adversaries with the collusive strategy are also considered. Via a combination of theoretical analysis and experimentation, our results show that no matter which strategies the adversaries choose (random strategy, win-stay-lose-shift strategy, or even the adaptive equalizer strategy), our formalized game model is capable of enabling the defender to greatly reduce the maximum value of the expected average payoff to the adversaries via provisioning sufficient defensive resources, which is reflected by setting a proper penalty factor against the adversaries. In addition, we extend our game model and analyze the extortion strategy, which can enable one participant to obtain more payoff by extorting his/her opponents. The evaluation results show that the defender can combat this strategy by encouraging competition among the adversaries, and significantly suppress the total payoff of the adversaries via setting the proper penalty factor. Full article

(This article belongs to the Special Issue The Architectures, Systems, and Applications of Internet of Things for Smart Cities)

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28 pages, 6824 KiB

Open AccessArticle

An Automatic Gait Feature Extraction Method for Identifying Gait Asymmetry Using Wearable Sensors

by Arif Reza Anwary¹

, Hongnian Yu^1,*

and Michael Vassallo²

¹ Faculty of Science and Technology, Bournemouth University, Fern Barrow, Poole BH12 5BB, UK

² Royal Bournemouth Hospital, UK, CoPMRE Bournemouth University, Fern Barrow, Poole BH12 5BB, UK

Sensors 2018, 18(2), 676; https://doi.org/10.3390/s18020676 - 24 Feb 2018

Cited by 83 | Viewed by 14250

Abstract

This paper aims to assess the use of Inertial Measurement Unit (IMU) sensors to identify gait asymmetry by extracting automatic gait features. We design and develop an android app to collect real time synchronous IMU data from legs. The results from our method [...] Read more.

This paper aims to assess the use of Inertial Measurement Unit (IMU) sensors to identify gait asymmetry by extracting automatic gait features. We design and develop an android app to collect real time synchronous IMU data from legs. The results from our method are validated using a Qualisys Motion Capture System. The data are collected from 10 young and 10 older subjects. Each performed a trial in a straight corridor comprising 15 strides of normal walking, a turn around and another 15 strides. We analyse the data for total distance, total time, total velocity, stride, step, cadence, step ratio, stance, and swing. The accuracy of detecting the stride number using the proposed method is 100% for young and 92.67% for older subjects. The accuracy of estimating travelled distance using the proposed method for young subjects is 97.73% and 98.82% for right and left legs; and for the older, is 88.71% and 89.88% for right and left legs. The average travelled distance is 37.77 (95% CI ± 3.57) meters for young subjects and is 22.50 (95% CI ± 2.34) meters for older subjects. The average travelled time for young subjects is 51.85 (95% CI ± 3.08) seconds and for older subjects is 84.02 (95% CI ± 9.98) seconds. The results show that wearable sensors can be used for identifying gait asymmetry without the requirement and expense of an elaborate laboratory setup. This can serve as a tool in diagnosing gait abnormalities in individuals and opens the possibilities for home based self-gait asymmetry assessment. Full article

(This article belongs to the Special Issue Sensors for Gait, Posture, and Health Monitoring)

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16 pages, 4167 KiB

Open AccessArticle

Quadrature Errors and DC Offsets Calibration of Analog Complex Cross-Correlator for Interferometric Passive Millimeter-Wave Imaging Applications

by Chao Wang, Xin Xin, Bingyuan Liang, Zhiping Li^* and Jungang Miao

School of Electronics and Information Engineering, Beihang University, Beijing 100191, China

Sensors 2018, 18(2), 677; https://doi.org/10.3390/s18020677 - 24 Feb 2018

Cited by 14 | Viewed by 5741

Abstract

The design and calibration of the cross-correlator are crucial issues for interferometric imaging systems. In this paper, an analog complex cross-correlator with output DC offsets and amplitudes calibration capability is proposed for interferometric passive millimeter-wave security sensing applications. By employing digital potentiometers in [...] Read more.

The design and calibration of the cross-correlator are crucial issues for interferometric imaging systems. In this paper, an analog complex cross-correlator with output DC offsets and amplitudes calibration capability is proposed for interferometric passive millimeter-wave security sensing applications. By employing digital potentiometers in the low frequency amplification circuits of the correlator, the outputs characteristics of the correlator could be digitally controlled. A measurement system and a corresponding calibration scheme were developed in order to eliminate the output DC offsets and the quadrature amplitude error between the in-phase and the quadrature correlating subunits of the complex correlator. By using vector modulators to provide phase controllable correlated noise signals, the measurement system was capable of obtaining the output correlation circle of the correlator. When injected with −18 dBm correlated noise signals, the calibrated quadrature amplitude error was 0.041 dB and the calibrated DC offsets were under 26 mV, which was only 7.1% of the uncalibrated value. Furthermore, we also described a quadrature errors calibration algorithm in order to estimate the quadrature phase error and in order to improve the output phase accuracy of the correlator. After applying this calibration, we were able to reduce the output phase error of the correlator to 0.3°. Full article

(This article belongs to the Special Issue Sensors for Microwave Imaging and Detection)

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21 pages, 8022 KiB

Open AccessArticle

Low Computational Signal Acquisition for GNSS Receivers Using a Resampling Strategy and Variable Circular Correlation Time

by Yeqing Zhang^*, Meiling Wang and Yafeng Li

School of Automation, Beijing Institute of Technology, Beijing 100081, China

Sensors 2018, 18(2), 678; https://doi.org/10.3390/s18020678 - 24 Feb 2018

Cited by 13 | Viewed by 6585

Abstract

For the objective of essentially decreasing computational complexity and time consumption of signal acquisition, this paper explores a resampling strategy and variable circular correlation time strategy specific to broadband multi-frequency GNSS receivers. In broadband GNSS receivers, the resampling strategy is established to work [...] Read more.

For the objective of essentially decreasing computational complexity and time consumption of signal acquisition, this paper explores a resampling strategy and variable circular correlation time strategy specific to broadband multi-frequency GNSS receivers. In broadband GNSS receivers, the resampling strategy is established to work on conventional acquisition algorithms by resampling the main lobe of received broadband signals with a much lower frequency. Variable circular correlation time is designed to adapt to different signal strength conditions and thereby increase the operation flexibility of GNSS signal acquisition. The acquisition threshold is defined as the ratio of the highest and second highest correlation results in the search space of carrier frequency and code phase. Moreover, computational complexity of signal acquisition is formulated by amounts of multiplication and summation operations in the acquisition process. Comparative experiments and performance analysis are conducted on four sets of real GPS L2C signals with different sampling frequencies. The results indicate that the resampling strategy can effectively decrease computation and time cost by nearly 90–94% with just slight loss of acquisition sensitivity. With circular correlation time varying from 10 ms to 20 ms, the time cost of signal acquisition has increased by about 2.7–5.6% per millisecond, with most satellites acquired successfully. Full article

(This article belongs to the Special Issue Sensor Signal and Information Processing)

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22 pages, 2627 KiB

Open AccessArticle

Comparison of Feature Learning Methods for Human Activity Recognition Using Wearable Sensors

by Frédéric Li^1,*, Kimiaki Shirahama¹

, Muhammad Adeel Nisar¹

, Lukas Köping¹ and Marcin Grzegorzek^1,2

¹ Research Group for Pattern Recognition, University of Siegen, Hölderlinstr 3, 57076 Siegen, Germany

² Department of Knowledge Engineering, University of Economics in Katowice, Bogucicka 3, 40-226 Katowice, Poland

Sensors 2018, 18(2), 679; https://doi.org/10.3390/s18020679 - 24 Feb 2018

Cited by 266 | Viewed by 16153

Abstract

Getting a good feature representation of data is paramount for Human Activity Recognition (HAR) using wearable sensors. An increasing number of feature learning approaches—in particular deep-learning based—have been proposed to extract an effective feature representation by analyzing large amounts of data. However, getting [...] Read more.

Getting a good feature representation of data is paramount for Human Activity Recognition (HAR) using wearable sensors. An increasing number of feature learning approaches—in particular deep-learning based—have been proposed to extract an effective feature representation by analyzing large amounts of data. However, getting an objective interpretation of their performances faces two problems: the lack of a baseline evaluation setup, which makes a strict comparison between them impossible, and the insufficiency of implementation details, which can hinder their use. In this paper, we attempt to address both issues: we firstly propose an evaluation framework allowing a rigorous comparison of features extracted by different methods, and use it to carry out extensive experiments with state-of-the-art feature learning approaches. We then provide all the codes and implementation details to make both the reproduction of the results reported in this paper and the re-use of our framework easier for other researchers. Our studies carried out on the OPPORTUNITY and UniMiB-SHAR datasets highlight the effectiveness of hybrid deep-learning architectures involving convolutional and Long-Short-Term-Memory (LSTM) to obtain features characterising both short- and long-term time dependencies in the data. Full article

(This article belongs to the Section Intelligent Sensors)

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Review

Jump to: Editorial, Research, Other

16 pages, 3481 KiB

Open AccessReview

Tactile-Sensing Based on Flexible PVDF Nanofibers via Electrospinning: A Review

by Xiaomei Wang¹, Fazhe Sun², Guangchao Yin¹, Yuting Wang³, Bo Liu^1,*

and Mingdong Dong^3,*

¹ Laboratory of Functional Molecules and Materials, School of Physics and Optoelectronic Engineering, Shandong University of Technology, Zibo 255049, China

² Analysis Testing Center, Shandong University of Technology, Zibo 255100, China

³ Interdisciplinary Nanoscience Center (iNANO), Aarhus University, DK-8000 Aarhus C, Denmark

Sensors 2018, 18(2), 330; https://doi.org/10.3390/s18020330 - 24 Jan 2018

Cited by 228 | Viewed by 19842

Abstract

The flexible tactile sensor has attracted widespread attention because of its great flexibility, high sensitivity, and large workable range. It can be integrated into clothing, electronic skin, or mounted on to human skin. Various nanostructured materials and nanocomposites with high flexibility and electrical [...] Read more.

The flexible tactile sensor has attracted widespread attention because of its great flexibility, high sensitivity, and large workable range. It can be integrated into clothing, electronic skin, or mounted on to human skin. Various nanostructured materials and nanocomposites with high flexibility and electrical performance have been widely utilized as functional materials in flexible tactile sensors. Polymer nanomaterials, representing the most promising materials, especially polyvinylidene fluoride (PVDF), PVDF co-polymer and their nanocomposites with ultra-sensitivity, high deformability, outstanding chemical resistance, high thermal stability and low permittivity, can meet the flexibility requirements for dynamic tactile sensing in wearable electronics. Electrospinning has been recognized as an excellent straightforward and versatile technique for preparing nanofiber materials. This review will present a brief overview of the recent advances in PVDF nanofibers by electrospinning for flexible tactile sensor applications. PVDF, PVDF co-polymers and their nanocomposites have been successfully formed as ultrafine nanofibers, even as randomly oriented PVDF nanofibers by electrospinning. These nanofibers used as the functional layers in flexible tactile sensors have been reviewed briefly in this paper. The β-phase content, which is the strongest polar moment contributing to piezoelectric properties among all the crystalline phases of PVDF, can be improved by adjusting the technical parameters in electrospun PVDF process. The piezoelectric properties and the sensibility for the pressure sensor are improved greatly when the PVDF fibers become more oriented. The tactile performance of PVDF composite nanofibers can be further promoted by doping with nanofillers and nanoclay. Electrospun P(VDF-TrFE) nanofiber mats used for the 3D pressure sensor achieved excellent sensitivity, even at 0.1 Pa. The most significant enhancement is that the aligned electrospun core-shell P(VDF-TrFE) nanofibers exhibited almost 40 times higher sensitivity than that of pressure sensor based on thin-film PVDF. Full article

(This article belongs to the Special Issue Tactile Sensors and Sensing)

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16 pages, 3855 KiB

Open AccessReview

Wearable Intrinsically Soft, Stretchable, Flexible Devices for Memories and Computing

by Krishna Rajan^1,2, Erik Garofalo¹ and Alessandro Chiolerio^1,*

¹ Istituto Italiano di Tecnologia, Center for Sustainable Future Technologies, Corso Trento 21, 10129 Torino, Italy

² Department of Applied Science and Technology, Politecnico di Torino, Corso Duca degli Abruzzi 24, 10129 Torino, Italy

Sensors 2018, 18(2), 367; https://doi.org/10.3390/s18020367 - 27 Jan 2018

Cited by 58 | Viewed by 9073

Abstract

A recent trend in the development of high mass consumption electron devices is towards electronic textiles (e-textiles), smart wearable devices, smart clothes, and flexible or printable electronics. Intrinsically soft, stretchable, flexible, Wearable Memories and Computing devices (WMCs) bring us closer to sci-fi scenarios, [...] Read more.

A recent trend in the development of high mass consumption electron devices is towards electronic textiles (e-textiles), smart wearable devices, smart clothes, and flexible or printable electronics. Intrinsically soft, stretchable, flexible, Wearable Memories and Computing devices (WMCs) bring us closer to sci-fi scenarios, where future electronic systems are totally integrated in our everyday outfits and help us in achieving a higher comfort level, interacting for us with other digital devices such as smartphones and domotics, or with analog devices, such as our brain/peripheral nervous system. WMC will enable each of us to contribute to open and big data systems as individual nodes, providing real-time information about physical and environmental parameters (including air pollution monitoring, sound and light pollution, chemical or radioactive fallout alert, network availability, and so on). Furthermore, WMC could be directly connected to human brain and enable extremely fast operation and unprecedented interface complexity, directly mapping the continuous states available to biological systems. This review focuses on recent advances in nanotechnology and materials science and pays particular attention to any result and promising technology to enable intrinsically soft, stretchable, flexible WMC. Full article

(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Italy 2017)

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23 pages, 1326 KiB

Open AccessReview

Non-Destructive Spectroscopic Techniques and Multivariate Analysis for Assessment of Fat Quality in Pork and Pork Products: A Review

by Christopher T. Kucha, Li Liu and Michael O. Ngadi^*

Department of Bioresource Engineering, McGill University, Macdonald Campus 21,111 Lakeshore Road, Ste-Anne-de-Bellevue, Quebec, QC H9X 3V9, Canada

Sensors 2018, 18(2), 377; https://doi.org/10.3390/s18020377 - 28 Jan 2018

Cited by 57 | Viewed by 8097

Abstract

Fat is one of the most important traits determining the quality of pork. The composition of the fat greatly influences the quality of pork and its processed products, and contribute to defining the overall carcass value. However, establishing an efficient method for assessing [...] Read more.

Fat is one of the most important traits determining the quality of pork. The composition of the fat greatly influences the quality of pork and its processed products, and contribute to defining the overall carcass value. However, establishing an efficient method for assessing fat quality parameters such as fatty acid composition, solid fat content, oxidative stability, iodine value, and fat color, remains a challenge that must be addressed. Conventional methods such as visual inspection, mechanical methods, and chemical methods are used off the production line, which often results in an inaccurate representation of the process because the dynamics are lost due to the time required to perform the analysis. Consequently, rapid, and non-destructive alternative methods are needed. In this paper, the traditional fat quality assessment techniques are discussed with emphasis on spectroscopic techniques as an alternative. Potential spectroscopic techniques include infrared spectroscopy, nuclear magnetic resonance and Raman spectroscopy. Hyperspectral imaging as an emerging advanced spectroscopy-based technology is introduced and discussed for the recent development of assessment for fat quality attributes. All techniques are described in terms of their operating principles and the research advances involving their application for pork fat quality parameters. Future trends for the non-destructive spectroscopic techniques are also discussed. Full article

(This article belongs to the Special Issue Analysis of Multispectral and Hyperspectral Data)

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18 pages, 1560 KiB

Open AccessReview

Plant Pest Detection Using an Artificial Nose System: A Review

by Shaoqing Cui¹, Peter Ling^1,*, Heping Zhu² and Harold M. Keener¹

¹ Department of Food, Agricultural and Biological Engineering, The Ohio State University/Ohio Agricultural Research and Development Center, 1680 Madison Ave, Wooster, OH 44691-4096, USA

² United States Department of Agriculture-Agricultural Research Service (USDA-ARS) Application Technology Research Unit, 1680 Madison Ave, Wooster, OH 44691-4096, USA

Sensors 2018, 18(2), 378; https://doi.org/10.3390/s18020378 - 28 Jan 2018

Cited by 163 | Viewed by 19758

Abstract

This paper reviews artificial intelligent noses (or electronic noses) as a fast and noninvasive approach for the diagnosis of insects and diseases that attack vegetables and fruit trees. The particular focus is on bacterial, fungal, and viral infections, and insect damage. Volatile organic [...] Read more.

This paper reviews artificial intelligent noses (or electronic noses) as a fast and noninvasive approach for the diagnosis of insects and diseases that attack vegetables and fruit trees. The particular focus is on bacterial, fungal, and viral infections, and insect damage. Volatile organic compounds (VOCs) emitted from plants, which provide functional information about the plant’s growth, defense, and health status, allow for the possibility of using noninvasive detection to monitor plants status. Electronic noses are comprised of a sensor array, signal conditioning circuit, and pattern recognition algorithms. Compared with traditional gas chromatography–mass spectrometry (GC-MS) techniques, electronic noses are noninvasive and can be a rapid, cost-effective option for several applications. However, using electronic noses for plant pest diagnosis is still in its early stages, and there are challenges regarding sensor performance, sampling and detection in open areas, and scaling up measurements. This review paper introduces each element of electronic nose systems, especially commonly used sensors and pattern recognition methods, along with their advantages and limitations. It includes a comprehensive comparison and summary of applications, possible challenges, and potential improvements of electronic nose systems for different plant pest diagnoses. Full article

(This article belongs to the Special Issue Sensors in Agriculture)

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29 pages, 3796 KiB

Open AccessReview

Game Theory-Based Cooperation for Underwater Acoustic Sensor Networks: Taxonomy, Review, Research Challenges and Directions

by Dalhatu Muhammed¹, Mohammad Hossein Anisi^2,*, Mahdi Zareei³

, Cesar Vargas-Rosales³ and Anwar Khan⁴

¹ Department of Computer System and Technology, Faculty of Computer Science and Information Technology, University of Malaya, Kuala Lumpur 50603, Malaysia

² School of Computer Science and Electronic Engineering, University of Essex, Colchester CO4 3SQ, UK

³ Tecnologico de Monterrey, Escuela de Ingenieria y Ciencias, Monterrey 64849, Mexico

⁴ Department of Electronics, University of Peshawar, Peshawar 25000, Pakistan

Sensors 2018, 18(2), 425; https://doi.org/10.3390/s18020425 - 1 Feb 2018

Cited by 40 | Viewed by 6621

Abstract

Exploring and monitoring the underwater world using underwater sensors is drawing a lot of attention these days. In this field cooperation between acoustic sensor nodes has been a critical problem due to the challenging features such as acoustic channel failure (sound signal), long [...] Read more.

Exploring and monitoring the underwater world using underwater sensors is drawing a lot of attention these days. In this field cooperation between acoustic sensor nodes has been a critical problem due to the challenging features such as acoustic channel failure (sound signal), long propagation delay of acoustic signal, limited bandwidth and loss of connectivity. There are several proposed methods to improve cooperation between the nodes by incorporating information/game theory in the node’s cooperation. However, there is a need to classify the existing works and demonstrate their performance in addressing the cooperation issue. In this paper, we have conducted a review to investigate various factors affecting cooperation in underwater acoustic sensor networks. We study various cooperation techniques used for underwater acoustic sensor networks from different perspectives, with a concentration on communication reliability, energy consumption, and security and present a taxonomy for underwater cooperation. Moreover, we further review how the game theory can be applied to make the nodes cooperate with each other. We further analyze different cooperative game methods, where their performance on different metrics is compared. Finally, open issues and future research direction in underwater acoustic sensor networks are highlighted. Full article

(This article belongs to the Special Issue Advances and Challenges in Underwater Sensor Networks)

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28 pages, 10324 KiB

Open AccessReview

Crowdsensing in Smart Cities: Overview, Platforms, and Environment Sensing Issues

by Oscar Alvear^1,2,*

, Carlos T. Calafate¹

, Juan-Carlos Cano¹

and Pietro Manzoni¹

¹ Department of Computer Engineering, Universitat Politecnica de Valencia, 46022 Valencia, Spain

² Department of Electrical Engineering, Electronics and Telecommunications, Universidad de Cuenca, Cuenca 010150, Ecuador

Sensors 2018, 18(2), 460; https://doi.org/10.3390/s18020460 - 4 Feb 2018

Cited by 104 | Viewed by 11860

Abstract

Evidence shows that Smart Cities are starting to materialise in our lives through the gradual introduction of the Internet of Things (IoT) paradigm. In this scope, crowdsensing emerges as a powerful solution to address environmental monitoring, allowing to control air pollution levels in [...] Read more.

Evidence shows that Smart Cities are starting to materialise in our lives through the gradual introduction of the Internet of Things (IoT) paradigm. In this scope, crowdsensing emerges as a powerful solution to address environmental monitoring, allowing to control air pollution levels in crowded urban areas in a distributed, collaborative, inexpensive and accurate manner. However, even though technology is already available, such environmental sensing devices have not yet reached consumers. In this paper, we present an analysis of candidate technologies for crowdsensing architectures, along with the requirements for empowering users with air monitoring capabilities. Specifically, we start by providing an overview of the most relevant IoT architectures and protocols. Then, we present the general design of an off-the-shelf mobile environmental sensor able to cope with air quality monitoring requirements; we explore different hardware options to develop the desired sensing unit using readily available devices, discussing the main technical issues associated with each option, thereby opening new opportunities in terms of environmental monitoring programs. Full article

(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Spain 2017)

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26 pages, 8896 KiB

Open AccessFeature PaperReview

A Review of Microfiber-Based Temperature Sensors

by Wanvisa Talataisong^*

, Rand Ismaeel

and Gilberto Brambilla

Optoelectronics Research Centre, University of Southampton, Southampton SO17 1BJ, UK

Sensors 2018, 18(2), 461; https://doi.org/10.3390/s18020461 - 4 Feb 2018

Cited by 64 | Viewed by 9363

Abstract

Optical microfiber-based temperature sensors have been proposed for many applications in a variety of industrial uses, including biomedical, geological, automotive, and defense applications. This increasing demand for these micrometric devices is attributed to their large dynamic range, high sensitivity, fast-response, compactness and robustness. [...] Read more.

Optical microfiber-based temperature sensors have been proposed for many applications in a variety of industrial uses, including biomedical, geological, automotive, and defense applications. This increasing demand for these micrometric devices is attributed to their large dynamic range, high sensitivity, fast-response, compactness and robustness. Additionally, they can perform in-situ measurements remotely and in harsh environments. This paper presents an overview of optical microfibers, with a focus on their applications in temperature sensing. This review broadly divides microfiber-based temperature sensors into two categories: resonant and non-resonant microfiber sensors. While the former includes microfiber loop, knot and coil resonators, the latter comprises sensors based on functionally coated/doped microfibers, microfiber couplers, optical gratings and interferometers. In the conclusions, a summary of reported performances is presented. Full article

(This article belongs to the Special Issue Optical Fiber Sensors 2017)

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32 pages, 1578 KiB

Open AccessFeature PaperReview

Nanomaterial-Based Sensing and Biosensing of Phenolic Compounds and Related Antioxidant Capacity in Food

by Flavio Della Pelle

and Dario Compagnone^*

Faculty of Bioscience and Technology for Food, Agriculture and Environment, University of Teramo, 64023 Teramo, Italy

Sensors 2018, 18(2), 462; https://doi.org/10.3390/s18020462 - 4 Feb 2018

Cited by 143 | Viewed by 10239

Abstract

Polyphenolic compounds (PCs) have received exceptional attention at the end of the past millennium and as much at the beginning of the new one. Undoubtedly, these compounds in foodstuffs provide added value for their well-known health benefits, for their technological role and also [...] Read more.

Polyphenolic compounds (PCs) have received exceptional attention at the end of the past millennium and as much at the beginning of the new one. Undoubtedly, these compounds in foodstuffs provide added value for their well-known health benefits, for their technological role and also marketing. Many efforts have been made to provide simple, effective and user friendly analytical methods for the determination and antioxidant capacity (AOC) evaluation of food polyphenols. In a parallel track, over the last twenty years, nanomaterials (NMs) have made their entry in the analytical chemistry domain; NMs have, in fact, opened new paths for the development of analytical methods with the common aim to improve analytical performance and sustainability, becoming new tools in quality assurance of food and beverages. The aim of this review is to provide information on the most recent developments of new NMs-based tools and strategies for total polyphenols (TP) determination and AOC evaluation in food. In this review optical, electrochemical and bioelectrochemical approaches have been reviewed. The use of nanoparticles, quantum dots, carbon nanomaterials and hybrid materials for the detection of polyphenols is the main subject of the works reported. However, particular attention has been paid to the success of the application in real samples, in addition to the NMs. In particular, the discussion has been focused on methods/devices presenting, in the opinion of the authors, clear advancement in the fields, in terms of simplicity, rapidity and usability. This review aims to demonstrate how the NM-based approaches represent valid alternatives to classical methods for polyphenols analysis, and are mature to be integrated for the rapid quality assessment of food quality in lab or directly in the field. Full article

(This article belongs to the Special Issue Novel Approaches to Biosensing with Nanoparticles)

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15 pages, 2008 KiB

Open AccessReview

Intracranial Pressure Monitoring—Review and Avenues for Development

by Maya Harary¹

, Rianne G. F. Dolmans^1,2 and William B. Gormley^1,*

¹ Computational Neuroscience Outcomes Center, Department of Neurosurgery, Brigham and Women’s Hospital, Harvard Medical School, Boston, MA 02115, USA

² Department of Neurosurgery, University Medical Center, 3584 CS Utrecht, The Netherlands

Sensors 2018, 18(2), 465; https://doi.org/10.3390/s18020465 - 5 Feb 2018

Cited by 128 | Viewed by 25000

Abstract

Intracranial pressure (ICP) monitoring is a staple of neurocritical care. The most commonly used current methods of monitoring in the acute setting include fluid-based systems, implantable transducers and Doppler ultrasonography. It is well established that management of elevated ICP is critical for clinical [...] Read more.

Intracranial pressure (ICP) monitoring is a staple of neurocritical care. The most commonly used current methods of monitoring in the acute setting include fluid-based systems, implantable transducers and Doppler ultrasonography. It is well established that management of elevated ICP is critical for clinical outcomes. However, numerous studies show that current methods of ICP monitoring cannot reliably define the limit of the brain’s intrinsic compensatory capacity to manage increases in pressure, which would allow for proactive ICP management. Current work in the field hopes to address this gap by harnessing live-streaming ICP pressure-wave data and a multimodal integration with other physiologic measures. Additionally, there is continued development of non-invasive ICP monitoring methods for use in specific clinical scenarios. Full article

(This article belongs to the Special Issue Force and Pressure Based Sensing Medical Application)

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13 pages, 1638 KiB

Open AccessReview

VHH Antibodies: Reagents for Mycotoxin Detection in Food Products

by Jia Wang, Hina Mukhtar, Lan Ma, Qian Pang and Xiaohong Wang^*

College of Food Science and Technology, Huazhong Agricultural University, Wuhan 430070, China

Sensors 2018, 18(2), 485; https://doi.org/10.3390/s18020485 - 6 Feb 2018

Cited by 48 | Viewed by 12163

Abstract

Mycotoxins are the toxic secondary metabolites produced by fungi and they are a worldwide public health concern. A VHH antibody (or nanobody) is the smallest antigen binding entity and is produced by heavy chain only antibodies. Compared with conventional antibodies, VHH antibodies overcome [...] Read more.

Mycotoxins are the toxic secondary metabolites produced by fungi and they are a worldwide public health concern. A VHH antibody (or nanobody) is the smallest antigen binding entity and is produced by heavy chain only antibodies. Compared with conventional antibodies, VHH antibodies overcome many pitfalls typically encountered in clinical therapeutics and immunodiagnostics. Likewise, VHH antibodies are particularly useful for monitoring mycotoxins in food and feedstuffs, as they are easily genetic engineered and have superior stability. In this review, we summarize the efforts to produce anti-mycotoxins VHH antibodies and associated assays, presenting VHH as a potential tool in mycotoxin analysis. Full article

(This article belongs to the Section Biosensors)

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25 pages, 4962 KiB

Open AccessReview

Acoustic Sensors for Air and Surface Navigation Applications

by Rohan Kapoor¹

, Subramanian Ramasamy¹, Alessandro Gardi¹

, Ron Van Schyndel² and Roberto Sabatini^1,*

¹ School of Engineering, RMIT University, Aerospace Engineering and Aviation Discipline, Bundoora VIC 3083, Australia

² School of Science, RMIT University, Computer Science and Information Technology Discipline, Melbourne 3000, Australia

Sensors 2018, 18(2), 499; https://doi.org/10.3390/s18020499 - 7 Feb 2018

Cited by 39 | Viewed by 8744

Abstract

This paper presents the state-of-the-art and reviews the state-of-research of acoustic sensors used for a variety of navigation and guidance applications on air and surface vehicles. In particular, this paper focuses on echolocation, which is widely utilized in nature by certain mammals (e.g., [...] Read more.

This paper presents the state-of-the-art and reviews the state-of-research of acoustic sensors used for a variety of navigation and guidance applications on air and surface vehicles. In particular, this paper focuses on echolocation, which is widely utilized in nature by certain mammals (e.g., cetaceans and bats). Although acoustic sensors have been extensively adopted in various engineering applications, their use in navigation and guidance systems is yet to be fully exploited. This technology has clear potential for applications in air and surface navigation/guidance for intelligent transport systems (ITS), especially considering air and surface operations indoors and in other environments where satellite positioning is not available. Propagation of sound in the atmosphere is discussed in detail, with all potential attenuation sources taken into account. The errors introduced in echolocation measurements due to Doppler, multipath and atmospheric effects are discussed, and an uncertainty analysis method is presented for ranging error budget prediction in acoustic navigation applications. Considering the design challenges associated with monostatic and multi-static sensor implementations and looking at the performance predictions for different possible configurations, acoustic sensors show clear promises in navigation, proximity sensing, as well as obstacle detection and tracking. The integration of acoustic sensors in multi-sensor navigation systems is also considered towards the end of the paper and a low Size, Weight and Power, and Cost (SWaP-C) sensor integration architecture is presented for possible introduction in air and surface navigation systems. Full article

(This article belongs to the Special Issue Ultrasonic Sensors 2018)

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25 pages, 3246 KiB

Open AccessReview

Optical Fiber Sensors Based on Fiber Ring Laser Demodulation Technology

by Wen-Ge Xie¹, Ya-Nan Zhang^1,2,*

, Peng-Zhao Wang¹ and Jian-Zhang Wang¹

¹ College of Information Science and Engineering, Northeastern University, Shenyang 110819, China

² State Key Laboratory of Synthetical Automation for Process Industries, Shenyang 110819, China

Sensors 2018, 18(2), 505; https://doi.org/10.3390/s18020505 - 8 Feb 2018

Cited by 37 | Viewed by 7954

Abstract

A review for optical fiber sensors based on fiber ring laser (FRL) demodulation technology is presented. The review focuses on the principles, main structures, and the sensing performances of different kinds of optical fiber sensors based on FRLs. First of all, the theory [...] Read more.

A review for optical fiber sensors based on fiber ring laser (FRL) demodulation technology is presented. The review focuses on the principles, main structures, and the sensing performances of different kinds of optical fiber sensors based on FRLs. First of all, the theory background of the sensors has been discussed. Secondly, four different types of sensors are described and compared, which includes Mach–Zehnder interferometer (MZI) typed sensors, Fabry–Perot interferometer (FPI) typed sensors, Sagnac typed sensors, and fiber Bragg grating (FBG) typed sensors. Typical studies and main properties of each type of sensors are presented. Thirdly, a comparison of different types of sensors are made. Finally, the existing problems and future research directions are pointed out and analyzed. Full article

(This article belongs to the Special Issue Optical Fiber Sensors 2017)

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21 pages, 8044 KiB

Open AccessReview

Recent Advances of Malaria Parasites Detection Systems Based on Mathematical Morphology

by Andrea Loddo^1,*

, Cecilia Di Ruberto^1,† and Michel Kocher^2,†

¹ Department of Mathematics and Computer Science, University of Cagliari, 09124 Cagliari, Italy

² Biomedical Imaging Group, École Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland

^† These authors contributed equally to this work.

Sensors 2018, 18(2), 513; https://doi.org/10.3390/s18020513 - 8 Feb 2018

Cited by 61 | Viewed by 10830

Abstract

Malaria is an epidemic health disease and a rapid, accurate diagnosis is necessary for proper intervention. Generally, pathologists visually examine blood stained slides for malaria diagnosis. Nevertheless, this kind of visual inspection is subjective, error-prone and time-consuming. In order to overcome the issues, [...] Read more.

Malaria is an epidemic health disease and a rapid, accurate diagnosis is necessary for proper intervention. Generally, pathologists visually examine blood stained slides for malaria diagnosis. Nevertheless, this kind of visual inspection is subjective, error-prone and time-consuming. In order to overcome the issues, numerous methods of automatic malaria diagnosis have been proposed so far. In particular, many researchers have used mathematical morphology as a powerful tool for computer aided malaria detection and classification. Mathematical morphology is not only a theory for the analysis of spatial structures, but also a very powerful technique widely used for image processing purposes and employed successfully in biomedical image analysis, especially in preprocessing and segmentation tasks. Microscopic image analysis and particularly malaria detection and classification can greatly benefit from the use of morphological operators. The aim of this paper is to present a review of recent mathematical morphology based methods for malaria parasite detection and identification in stained blood smears images. Full article

(This article belongs to the Special Issue Novel Sensors for Bioimaging)

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39 pages, 3856 KiB

Open AccessReview

Chemical Sensor Systems and Associated Algorithms for Fire Detection: A Review

by Jordi Fonollosa^1,2,3,*

, Ana Solórzano^1,2 and Santiago Marco^1,2

¹ Department of Electronic and Biomedical Engineering, Universitat de Barcelona, 08028 Barcelona, Spain

² Signal and Information Processing for Sensing Systems, Institute for Bioengineering of Catalonia (IBEC), The Barcelona Institute of Science and Technology, 08028 Barcelona, Spain

³ Department of ESAII, Center for Biomedical Engineering Research, Universitat Politècnica de Catalunya, 08028 Barcelona, Spain

Sensors 2018, 18(2), 553; https://doi.org/10.3390/s18020553 - 11 Feb 2018

Cited by 138 | Viewed by 18332

Abstract

Indoor fire detection using gas chemical sensing has been a subject of investigation since the early nineties. This approach leverages the fact that, for certain types of fire, chemical volatiles appear before smoke particles do. Hence, systems based on chemical sensing can provide [...] Read more.

Indoor fire detection using gas chemical sensing has been a subject of investigation since the early nineties. This approach leverages the fact that, for certain types of fire, chemical volatiles appear before smoke particles do. Hence, systems based on chemical sensing can provide faster fire alarm responses than conventional smoke-based fire detectors. Moreover, since it is known that most casualties in fires are produced from toxic emissions rather than actual burns, gas-based fire detection could provide an additional level of safety to building occupants. In this line, since the 2000s, electrochemical cells for carbon monoxide sensing have been incorporated into fire detectors. Even systems relying exclusively on gas sensors have been explored as fire detectors. However, gas sensors respond to a large variety of volatiles beyond combustion products. As a result, chemical-based fire detectors require multivariate data processing techniques to ensure high sensitivity to fires and false alarm immunity. In this paper, we the survey toxic emissions produced in fires and defined standards for fire detection systems. We also review the state of the art of chemical sensor systems for fire detection and the associated signal and data processing algorithms. We also examine the experimental protocols used for the validation of the different approaches, as the complexity of the test measurements also impacts on reported sensitivity and specificity measures. All in all, further research and extensive test under different fire and nuisance scenarios are still required before gas-based fire detectors penetrate largely into the market. Nevertheless, the use of dynamic features and multivariate models that exploit sensor correlations seems imperative. Full article

(This article belongs to the Section Chemical Sensors)

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38 pages, 5115 KiB

Open AccessReview

Force Modeling, Identification, and Feedback Control of Robot-Assisted Needle Insertion: A Survey of the Literature

by Chongjun Yang¹

, Yu Xie^1,2, Shuang Liu^3,* and Dong Sun⁴

¹ Department of Instrumental and Electrical Engineering, Xiamen University, Xiamen 361005, China

² Shenzhen Research Institute of Xiamen University, Shenzhen 518000, China

³ School of Mechanical and Power Engineer, East China University of Science and Technology, Shanghai 200237, China

⁴ Department of Mechanical and Biomedical Engineering, City University of Hong Kong, Hong Kong 999077, China

Sensors 2018, 18(2), 561; https://doi.org/10.3390/s18020561 - 12 Feb 2018

Cited by 81 | Viewed by 19998

Abstract

Robot-assisted surgery is of growing interest in the surgical and engineering communities. The use of robots allows surgery to be performed with precision using smaller instruments and incisions, resulting in shorter healing times. However, using current technology, an operator cannot directly feel the [...] Read more.

Robot-assisted surgery is of growing interest in the surgical and engineering communities. The use of robots allows surgery to be performed with precision using smaller instruments and incisions, resulting in shorter healing times. However, using current technology, an operator cannot directly feel the operation because the surgeon-instrument and instrument-tissue interaction force feedbacks are lost during needle insertion. Advancements in force feedback and control not only help reduce tissue deformation and needle deflection but also provide the surgeon with better control over the surgical instruments. The goal of this review is to summarize the key components surrounding the force feedback and control during robot-assisted needle insertion. The literature search was conducted during the middle months of 2017 using mainstream academic search engines with a combination of keywords relevant to the field. In total, 166 articles with valuable contents were analyzed and grouped into five related topics. This survey systemically summarizes the state-of-the-art force control technologies for robot-assisted needle insertion, such as force modeling, measurement, the factors that influence the interaction force, parameter identification, and force control algorithms. All studies show force control is still at its initial stage. The influence factors, needle deflection or planning remain open for investigation in future. Full article

(This article belongs to the Special Issue Force and Pressure Based Sensing Medical Application)

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17 pages, 2405 KiB

Open AccessReview

Detection-Response Task—Uses and Limitations

by Kristina Stojmenova and Jaka Sodnik^*

Faculty of Electrical engineering, University of Ljubljana, Tržaška cesta 25, 1000 Ljubljana, Slovenia

Sensors 2018, 18(2), 594; https://doi.org/10.3390/s18020594 - 14 Feb 2018

Cited by 51 | Viewed by 6704

Abstract

The Detection-Response Task is a method for assessing the attentional effects of cognitive load in a driving environment. Drivers are presented with a sensory stimulus every 3–5 s, and are asked to respond to it by pressing a button attached to their finger. [...] Read more.

The Detection-Response Task is a method for assessing the attentional effects of cognitive load in a driving environment. Drivers are presented with a sensory stimulus every 3–5 s, and are asked to respond to it by pressing a button attached to their finger. Response times and hit rates are interpreted as indicators of the attentional effect of cognitive load. The stimuli can be visual, tactile and auditory, and are chosen based on the type of in-vehicle system or device that is being evaluated. Its biggest disadvantage is that the method itself also affects the driver’s performance and secondary task completion times. Nevertheless, this is an easy to use and implement method, which allows relevant assessment and evaluation of in-vehicle systems. By following the recommendations and taking into account its limitations, researchers can obtain reliable and valuable results on the attentional effects of cognitive load on drivers. Full article

(This article belongs to the Special Issue Advanced Physiological Sensing)

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16 pages, 3242 KiB

Open AccessReview

Responsive Polydiacetylene Vesicles for Biosensing Microorganisms

by Estelle Lebègue^2,*, Carole Farre¹, Catherine Jose¹, Joelle Saulnier¹

, Florence Lagarde¹

, Yves Chevalier³

, Carole Chaix¹

and Nicole Jaffrezic-Renault^1,*

¹ Institute of Analytical Sciences, University of Lyon, 69100 Villeurbanne, France

² Institute of Chemical Sciences, University of Rennes 1, 35000 Rennes, France

³ University of Lyon, LAGEP, 69622 Villeurbanne, France

Sensors 2018, 18(2), 599; https://doi.org/10.3390/s18020599 - 15 Feb 2018

Cited by 52 | Viewed by 7898

Abstract

Polydiacetylene (PDA) inserted in films or in vesicles has received increasing attention due to its property to undergo a blue-to-red colorimetric transition along with a change from non-fluorescent to fluorescent upon application of various stimuli. In this review paper, the principle for the [...] Read more.

Polydiacetylene (PDA) inserted in films or in vesicles has received increasing attention due to its property to undergo a blue-to-red colorimetric transition along with a change from non-fluorescent to fluorescent upon application of various stimuli. In this review paper, the principle for the detection of various microorganisms (bacteria, directly detected or detected through the emitted toxins or through their DNA, and viruses) and of antibacterial and antiviral peptides based on these responsive PDA vesicles are detailed. The analytical performances obtained, when vesicles are in suspension or immobilized, are given and compared to those of the responsive vesicles mainly based on the vesicle encapsulation method. Many future challenges are then discussed. Full article

(This article belongs to the Special Issue Polymer-Based Sensors for Bioanalytes)

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37 pages, 10483 KiB

Open AccessReview

Recent Advances in Active Infrared Thermography for Non-Destructive Testing of Aerospace Components

by Francesco Ciampa^*

, Pooya Mahmoodi, Fulvio Pinto and Michele Meo

Materials and Structures Centre (MAST), Department of Mechanical Engineering, University of Bath, Bath BA2 7AY, UK

Sensors 2018, 18(2), 609; https://doi.org/10.3390/s18020609 - 16 Feb 2018

Cited by 402 | Viewed by 30892

Abstract

Active infrared thermography is a fast and accurate non-destructive evaluation technique that is of particular relevance to the aerospace industry for the inspection of aircraft and helicopters’ primary and secondary structures, aero-engine parts, spacecraft components and its subsystems. This review provides an exhaustive [...] Read more.

Active infrared thermography is a fast and accurate non-destructive evaluation technique that is of particular relevance to the aerospace industry for the inspection of aircraft and helicopters’ primary and secondary structures, aero-engine parts, spacecraft components and its subsystems. This review provides an exhaustive summary of most recent active thermographic methods used for aerospace applications according to their physical principle and thermal excitation sources. Besides traditional optically stimulated thermography, which uses external optical radiation such as flashes, heaters and laser systems, novel hybrid thermographic techniques are also investigated. These include ultrasonic stimulated thermography, which uses ultrasonic waves and the local damage resonance effect to enhance the reliability and sensitivity to micro-cracks, eddy current stimulated thermography, which uses cost-effective eddy current excitation to generate induction heating, and microwave thermography, which uses electromagnetic radiation at the microwave frequency bands to provide rapid detection of cracks and delamination. All these techniques are here analysed and numerous examples are provided for different damage scenarios and aerospace components in order to identify the strength and limitations of each thermographic technique. Moreover, alternative strategies to current external thermal excitation sources, here named as material-based thermography methods, are examined in this paper. These novel thermographic techniques rely on thermoresistive internal heating and offer a fast, low power, accurate and reliable assessment of damage in aerospace composites. Full article

(This article belongs to the Special Issue Non Destructive Testing and Evaluation of Aerospace Composite Structures)

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35 pages, 6121 KiB

Open AccessReview

Flexible, Stretchable Sensors for Wearable Health Monitoring: Sensing Mechanisms, Materials, Fabrication Strategies and Features

by Yan Liu¹, Hai Wang², Wei Zhao^1,*, Min Zhang²

, Hongbo Qin¹ and Yongqiang Xie¹

¹ Key Laboratory of Electronic Equipment Structure Design, Ministry of Education, Xidian University, Xi’an 710071, China

² School of Aerospace Science and Technology, Xidian University, Xi’an 710071, China

Sensors 2018, 18(2), 645; https://doi.org/10.3390/s18020645 - 22 Feb 2018

Cited by 327 | Viewed by 30511

Abstract

Wearable health monitoring systems have gained considerable interest in recent years owing to their tremendous promise for personal portable health watching and remote medical practices. The sensors with excellent flexibility and stretchability are crucial components that can provide health monitoring systems with the [...] Read more.

Wearable health monitoring systems have gained considerable interest in recent years owing to their tremendous promise for personal portable health watching and remote medical practices. The sensors with excellent flexibility and stretchability are crucial components that can provide health monitoring systems with the capability of continuously tracking physiological signals of human body without conspicuous uncomfortableness and invasiveness. The signals acquired by these sensors, such as body motion, heart rate, breath, skin temperature and metabolism parameter, are closely associated with personal health conditions. This review attempts to summarize the recent progress in flexible and stretchable sensors, concerning the detected health indicators, sensing mechanisms, functional materials, fabrication strategies, basic and desired features. The potential challenges and future perspectives of wearable health monitoring system are also briefly discussed. Full article

(This article belongs to the Special Issue Sensors for Health Monitoring and Disease Diagnosis)

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17 pages, 891 KiB

Open AccessReview

Microwave Sensors for Breast Cancer Detection

by Lulu Wang^1,2

¹ Department of Biomedical Engineering, School of Instrument Science and Opto-Electronics Engineering, Hefei University of Technology, Hefei 230009, China

² Institute of Biomedical Technologies, Auckland University of Technology, Auckland 1142, New Zealand

Sensors 2018, 18(2), 655; https://doi.org/10.3390/s18020655 - 23 Feb 2018

Cited by 134 | Viewed by 14024

Abstract

Breast cancer is the leading cause of death among females, early diagnostic methods with suitable treatments improve the 5-year survival rates significantly. Microwave breast imaging has been reported as the most potential to become the alternative or additional tool to the current gold [...] Read more.

Breast cancer is the leading cause of death among females, early diagnostic methods with suitable treatments improve the 5-year survival rates significantly. Microwave breast imaging has been reported as the most potential to become the alternative or additional tool to the current gold standard X-ray mammography for detecting breast cancer. The microwave breast image quality is affected by the microwave sensor, sensor array, the number of sensors in the array and the size of the sensor. In fact, microwave sensor array and sensor play an important role in the microwave breast imaging system. Numerous microwave biosensors have been developed for biomedical applications, with particular focus on breast tumor detection. Compared to the conventional medical imaging and biosensor techniques, these microwave sensors not only enable better cancer detection and improve the image resolution, but also provide attractive features such as label-free detection. This paper aims to provide an overview of recent important achievements in microwave sensors for biomedical imaging applications, with particular focus on breast cancer detection. The electric properties of biological tissues at microwave spectrum, microwave imaging approaches, microwave biosensors, current challenges and future works are also discussed in the manuscript. Full article

(This article belongs to the Special Issue Label-Free Biosensors)

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21 pages, 3774 KiB

Open AccessFeature PaperReview

Integrated Affinity Biosensing Platforms on Screen-Printed Electrodes Electrografted with Diazonium Salts

by Paloma Yáñez-Sedeño^*, Susana Campuzano

and José M. Pingarrón

Departamento de Química Analítica, Facultad de CC. Químicas, Universidad Complutense de Madrid, E-28040 Madrid, Spain

Sensors 2018, 18(2), 675; https://doi.org/10.3390/s18020675 - 24 Feb 2018

Cited by 55 | Viewed by 12996

Abstract

Adequate selection of the electrode surface and the strategies for its modification to enable subsequent immobilization of biomolecules and/or nanomaterials integration play a major role in the performance of electrochemical affinity biosensors. Because of the simplicity, rapidity and versatility, electrografting using diazonium salt [...] Read more.

Adequate selection of the electrode surface and the strategies for its modification to enable subsequent immobilization of biomolecules and/or nanomaterials integration play a major role in the performance of electrochemical affinity biosensors. Because of the simplicity, rapidity and versatility, electrografting using diazonium salt reduction is among the most currently used functionalization methods to provide the attachment of an organic layer to a conductive substrate. This particular chemistry has demonstrated to be a powerful tool to covalently immobilize in a stable and reproducible way a wide range of biomolecules or nanomaterials onto different electrode surfaces. Considering the great progress and interesting features arisen in the last years, this paper outlines the potential of diazonium chemistry to prepare single or multianalyte electrochemical affinity biosensors on screen-printed electrodes (SPEs) and points out the existing challenges and future directions in this field. Full article

(This article belongs to the Special Issue Screen-Printed Electrodes)

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2 pages, 714 KiB

Open AccessErratum

Erratum: Mei, Y., et al. Mechanics Based Tomography: A Preliminary Feasibility Study. Sensors 2017, 17, 1075

by Yue Mei¹, Sicheng Wang², Xin Shen¹, Stephen Rabke¹ and Sevan Goenezen^1,*

¹ Department of Mechanical Engineering, Texas A&M University, College Station, TX 77843, USA

² Department of Mathematics, Texas A&M University, College Station, TX 77843, USA

Sensors 2018, 18(2), 384; https://doi.org/10.3390/s18020384 - 29 Jan 2018

Cited by 2 | Viewed by 3654

Abstract

The authors wish to correct Figures 12 and 14 in their paper published in Sensors [1], doi:10.3390/s17051075, https://www.mdpi.com/1424-8220/17/5/1075[...] Full article

(This article belongs to the Special Issue Force and Pressure Based Sensing Medical Application)

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