Sensors

39 pages, 2357 KiB

Open AccessArticle

Human Pose Estimation from Monocular Images: A Comprehensive Survey

by Wenjuan Gong, Xuena Zhang, Jordi Gonzàlez, Andrews Sobral, Thierry Bouwmans, Changhe Tu and El-hadi Zahzah

Sensors 2016, 16(12), 1966; https://doi.org/10.3390/s16121966 - 25 Nov 2016

Cited by 115 | Viewed by 19731

Abstract

Human pose estimation refers to the estimation of the location of body parts and how they are connected in an image. Human pose estimation from monocular images has wide applications (e.g., image indexing). Several surveys on human pose estimation can be found in [...] Read more.

Human pose estimation refers to the estimation of the location of body parts and how they are connected in an image. Human pose estimation from monocular images has wide applications (e.g., image indexing). Several surveys on human pose estimation can be found in the literature, but they focus on a certain category; for example, model-based approaches or human motion analysis, etc. As far as we know, an overall review of this problem domain has yet to be provided. Furthermore, recent advancements based on deep learning have brought novel algorithms for this problem. In this paper, a comprehensive survey of human pose estimation from monocular images is carried out including milestone works and recent advancements. Based on one standard pipeline for the solution of computer vision problems, this survey splits the problem into several modules: feature extraction and description, human body models, and modeling methods. Problem modeling methods are approached based on two means of categorization in this survey. One way to categorize includes top-down and bottom-up methods, and another way includes generative and discriminative methods. Considering the fact that one direct application of human pose estimation is to provide initialization for automatic video surveillance, there are additional sections for motion-related methods in all modules: motion features, motion models, and motion-based methods. Finally, the paper also collects 26 publicly available data sets for validation and provides error measurement methods that are frequently used. Full article

(This article belongs to the Section Physical Sensors)

► Show Figures

Figure 1

15 pages, 3969 KiB

Open AccessArticle

Emotion-Bracelet: A Web Service for Expressing Emotions through an Electronic Interface

by Alicia Martinez, Hugo Estrada, Alejandra Molina, Manuel Mejia and Joaquin Perez

Sensors 2016, 16(12), 1980; https://doi.org/10.3390/s16121980 - 24 Nov 2016

Cited by 2 | Viewed by 6766

Abstract

The mechanisms to communicate emotions have dramatically changed in the last 10 years with social networks, where users massively communicate their emotional states by using the Internet. However, people with socialization problems have difficulty expressing their emotions verbally or interpreting the environment and [...] Read more.

The mechanisms to communicate emotions have dramatically changed in the last 10 years with social networks, where users massively communicate their emotional states by using the Internet. However, people with socialization problems have difficulty expressing their emotions verbally or interpreting the environment and providing an appropriate emotional response. In this paper, a novel solution called the Emotion-Bracelet is presented that combines a hardware device and a software system. The proposed approach identifies the polarity and emotional intensity of texts published on a social network site by performing real-time processing using a web service. It also shows emotions with a LED matrix using five emoticons that represent positive, very positive, negative, very negative, and neutral states. The Emotion-Bracelet is designed to help people express their emotions in a non-intrusive way, thereby expanding the social aspect of human emotions. Full article

(This article belongs to the Special Issue Advances in Artificial Intelligence: Selected Papers from MICAI 2013, 2014 and 2015—12th, 13th and 14th Mexican International Conferences on Artificial Intelligence)

► Show Figures

Figure 1

17 pages, 3522 KiB

Open AccessArticle

Remote Blood Glucose Monitoring in mHealth Scenarios: A Review

by Giordano Lanzola, Eleonora Losiouk, Simone Del Favero, Andrea Facchinetti, Alfonso Galderisi, Silvana Quaglini, Lalo Magni and Claudio Cobelli

Sensors 2016, 16(12), 1983; https://doi.org/10.3390/s16121983 - 24 Nov 2016

Cited by 31 | Viewed by 10279

Abstract

Glucose concentration in the blood stream is a critical vital parameter and an effective monitoring of this quantity is crucial for diabetes treatment and intensive care management. Effective bio-sensing technology and advanced signal processing are therefore of unquestioned importance for blood glucose monitoring. [...] Read more.

Glucose concentration in the blood stream is a critical vital parameter and an effective monitoring of this quantity is crucial for diabetes treatment and intensive care management. Effective bio-sensing technology and advanced signal processing are therefore of unquestioned importance for blood glucose monitoring. Nevertheless, collecting measurements only represents part of the process as another critical task involves delivering the collected measures to the treating specialists and caregivers. These include the clinical staff, the patient’s significant other, his/her family members, and many other actors helping with the patient treatment that may be located far away from him/her. In all of these cases, a remote monitoring system, in charge of delivering the relevant information to the right player, becomes an important part of the sensing architecture. In this paper, we review how the remote monitoring architectures have evolved over time, paralleling the progress in the Information and Communication Technologies, and describe our experiences with the design of telemedicine systems for blood glucose monitoring in three medical applications. The paper ends summarizing the lessons learned through the experiences of the authors and discussing the challenges arising from a large-scale integration of sensors and actuators. Full article

(This article belongs to the Special Issue Glucose Sensors: Revolution in Diabetes Management 2016)

► Show Figures

Figure 1

23 pages, 5180 KiB

Open AccessReview

Thermal-Performance Instability in Piezoresistive Sensors: Inducement and Improvement

by Yan Liu, Hai Wang, Wei Zhao, Hongbo Qin and Xuan Fang

Sensors 2016, 16(12), 1984; https://doi.org/10.3390/s16121984 - 24 Nov 2016

Cited by 37 | Viewed by 11364

Abstract

The field of piezoresistive sensors has been undergoing a significant revolution in terms of design methodology, material technology and micromachining process. However, the temperature dependence of sensor characteristics remains a hurdle to cross. This review focuses on the issues in thermal-performance instability of [...] Read more.

The field of piezoresistive sensors has been undergoing a significant revolution in terms of design methodology, material technology and micromachining process. However, the temperature dependence of sensor characteristics remains a hurdle to cross. This review focuses on the issues in thermal-performance instability of piezoresistive sensors. Based on the operation fundamental, inducements to the instability are investigated in detail and correspondingly available ameliorative methods are presented. Pros and cons of each improvement approach are also summarized. Though several schemes have been proposed and put into reality with favorable achievements, the schemes featuring simple implementation and excellent compatibility with existing techniques are still emergently demanded to construct a piezoresistive sensor with excellent comprehensive performance. Full article

(This article belongs to the Collection Modeling, Testing and Reliability Issues in MEMS Engineering)

► Show Figures

Figure 1

9 pages, 3076 KiB

Open AccessArticle

One-Pot Click Access to a Cyclodextrin Dimer-Based Novel Aggregation Induced Emission Sensor and Monomer-Based Chiral Stationary Phase

by Xiaoli Li, Rui Zhao, Xiaoying Tang, Yanyan Shi, Chunyi Li and Yong Wang

Sensors 2016, 16(12), 1985; https://doi.org/10.3390/s16121985 - 24 Nov 2016

Cited by 8 | Viewed by 8278

Abstract

A ‘two birds, one stone’ strategy was developed via a one-pot click reaction to simultaneously prepare a novel cyclodextrin (CD) dimer based aggregation induced emission (AIE) sensor (AIE-DCD) and a monomer based chiral stationary phase (CSP-MCD) for chiral high performance liquid chromatography (CHPLC). [...] Read more.

A ‘two birds, one stone’ strategy was developed via a one-pot click reaction to simultaneously prepare a novel cyclodextrin (CD) dimer based aggregation induced emission (AIE) sensor (AIE-DCD) and a monomer based chiral stationary phase (CSP-MCD) for chiral high performance liquid chromatography (CHPLC). AIE-DCD was found to afford satisfactory AIE response for specific detection of Zn²⁺ with a detection limit of 50 nM. CSP-MCD exhibits excellent enantioseparation ability toward dansyl amino acids, where the resolution of dansyl amino leucine reaches 5.43. Full article

(This article belongs to the Special Issue Colorimetric and Fluorescent Sensor)

► Show Figures

Graphical abstract

17 pages, 10468 KiB

Open AccessArticle

Toward Optimal Computation of Ultrasound Image Reconstruction Using CPU and GPU

by Udomchai Techavipoo, Denchai Worasawate, Wittawat Boonleelakul, Rachaporn Keinprasit, Treepop Sunpetchniyom, Nobuhiko Sugino and Pairash Thajchayapong

Sensors 2016, 16(12), 1986; https://doi.org/10.3390/s16121986 - 24 Nov 2016

Cited by 6 | Viewed by 5606

Abstract

An ultrasound image is reconstructed from echo signals received by array elements of a transducer. The time of flight of the echo depends on the distance between the focus to the array elements. The received echo signals have to be delayed to make [...] Read more.

An ultrasound image is reconstructed from echo signals received by array elements of a transducer. The time of flight of the echo depends on the distance between the focus to the array elements. The received echo signals have to be delayed to make their wave fronts and phase coherent before summing the signals. In digital beamforming, the delays are not always located at the sampled points. Generally, the values of the delayed signals are estimated by the values of the nearest samples. This method is fast and easy, however inaccurate. There are other methods available for increasing the accuracy of the delayed signals and, consequently, the quality of the beamformed signals; for example, the in-phase (I)/quadrature (Q) interpolation, which is more time consuming but provides more accurate values than the nearest samples. This paper compares the signals after dynamic receive beamforming, in which the echo signals are delayed using two methods, the nearest sample method and the I/Q interpolation method. The comparisons of the visual qualities of the reconstructed images and the qualities of the beamformed signals are reported. Moreover, the computational speeds of these methods are also optimized by reorganizing the data processing flow and by applying the graphics processing unit (GPU). The use of single and double precision floating-point formats of the intermediate data is also considered. The speeds with and without these optimizations are also compared. Full article

(This article belongs to the Section Physical Sensors)

► Show Figures

Figure 1

19 pages, 571 KiB

Open AccessArticle

On Performance Analysis of Protective Jamming Schemes in Wireless Sensor Networks

by Xuran Li, Hong-Ning Dai, Hao Wang and Hong Xiao

Sensors 2016, 16(12), 1987; https://doi.org/10.3390/s16121987 - 24 Nov 2016

Cited by 7 | Viewed by 4474

Abstract

Wireless sensor networks (WSNs) play an important role in Cyber Physical Social Sensing (CPSS) systems. An eavesdropping attack is one of the most serious threats to WSNs since it is a prerequisite for other malicious attacks. In this paper, we propose a novel [...] Read more.

Wireless sensor networks (WSNs) play an important role in Cyber Physical Social Sensing (CPSS) systems. An eavesdropping attack is one of the most serious threats to WSNs since it is a prerequisite for other malicious attacks. In this paper, we propose a novel anti-eavesdropping mechanism by introducing friendly jammers to wireless sensor networks (WSNs). In particular, we establish a theoretical framework to evaluate the eavesdropping risk of WSNs with friendly jammers and that of WSNs without jammers. Our theoretical model takes into account various channel conditions such as the path loss and Rayleigh fading, the placement schemes of jammers and the power controlling schemes of jammers. Extensive results show that using jammers in WSNs can effectively reduce the eavesdropping risk. Besides, our results also show that the appropriate placement of jammers and the proper assignment of emitting power of jammers can not only mitigate the eavesdropping risk but also may have no significant impairment to the legitimate communications. Full article

(This article belongs to the Special Issue New Paradigms in Cyber-Physical Social Sensing)

► Show Figures

Figure 1

21 pages, 6850 KiB

Open AccessArticle

A Dual Frequency Carrier Phase Error Difference Checking Algorithm for the GNSS Compass

by Shuo Liu, Lei Zhang and Jian Li

Sensors 2016, 16(12), 1988; https://doi.org/10.3390/s16121988 - 24 Nov 2016

Cited by 9 | Viewed by 5586

Abstract

The performance of the Global Navigation Satellite System (GNSS) compass is related to the quality of carrier phase measurement. How to process the carrier phase error properly is important to improve the GNSS compass accuracy. In this work, we propose a dual frequency [...] Read more.

The performance of the Global Navigation Satellite System (GNSS) compass is related to the quality of carrier phase measurement. How to process the carrier phase error properly is important to improve the GNSS compass accuracy. In this work, we propose a dual frequency carrier phase error difference checking algorithm for the GNSS compass. The algorithm aims at eliminating large carrier phase error in dual frequency double differenced carrier phase measurement according to the error difference between two frequencies. The advantage of the proposed algorithm is that it does not need additional environment information and has a good performance on multiple large errors compared with previous research. The core of the proposed algorithm is removing the geographical distance from the dual frequency carrier phase measurement, then the carrier phase error is separated and detectable. We generate the Double Differenced Geometry-Free (DDGF) measurement according to the characteristic that the different frequency carrier phase measurements contain the same geometrical distance. Then, we propose the DDGF detection to detect the large carrier phase error difference between two frequencies. The theoretical performance of the proposed DDGF detection is analyzed. An open sky test, a manmade multipath test and an urban vehicle test were carried out to evaluate the performance of the proposed algorithm. The result shows that the proposed DDGF detection is able to detect large error in dual frequency carrier phase measurement by checking the error difference between two frequencies. After the DDGF detection, the accuracy of the baseline vector is improved in the GNSS compass. Full article

(This article belongs to the Section Remote Sensors)

► Show Figures

Figure 1

17 pages, 2871 KiB

Open AccessArticle

Utilizing a Wristband Sensor to Measure the Stress Level for People with Dementia

by Basel Kikhia, Thanos G. Stavropoulos, Stelios Andreadis, Niklas Karvonen, Ioannis Kompatsiaris, Stefan Sävenstedt, Marten Pijl and Catharina Melander

Sensors 2016, 16(12), 1989; https://doi.org/10.3390/s16121989 - 24 Nov 2016

Cited by 71 | Viewed by 12471

Abstract

Stress is a common problem that affects most people with dementia and their caregivers. Stress symptoms for people with dementia are often measured by answering a checklist of questions by the clinical staff who work closely with the person with the dementia. This [...] Read more.

Stress is a common problem that affects most people with dementia and their caregivers. Stress symptoms for people with dementia are often measured by answering a checklist of questions by the clinical staff who work closely with the person with the dementia. This process requires a lot of effort with continuous observation of the person with dementia over the long term. This article investigates the effectiveness of using a straightforward method, based on a single wristband sensor to classify events of “Stressed” and “Not stressed” for people with dementia. The presented system calculates the stress level as an integer value from zero to five, providing clinical information of behavioral patterns to the clinical staff. Thirty staff members participated in this experiment, together with six residents suffering from dementia, from two nursing homes. The residents were equipped with the wristband sensor during the day, and the staff were writing observation notes during the experiment to serve as ground truth. Experimental evaluation showed relationships between staff observations and sensor analysis, while stress level thresholds adjusted to each individual can serve different scenarios. Full article

(This article belongs to the Special Issue Sensing Technology for Healthcare System)

► Show Figures

Figure 1

10 pages, 2193 KiB

Open AccessArticle

Micro-Doppler Based Classification of Human Aquatic Activities via Transfer Learning of Convolutional Neural Networks

by Jinhee Park, Rios Jesus Javier, Taesup Moon and Youngwook Kim

Sensors 2016, 16(12), 1990; https://doi.org/10.3390/s16121990 - 24 Nov 2016

Cited by 120 | Viewed by 9085

Abstract

Accurate classification of human aquatic activities using radar has a variety of potential applications such as rescue operations and border patrols. Nevertheless, the classification of activities on water using radar has not been extensively studied, unlike the case on dry ground, due to [...] Read more.

Accurate classification of human aquatic activities using radar has a variety of potential applications such as rescue operations and border patrols. Nevertheless, the classification of activities on water using radar has not been extensively studied, unlike the case on dry ground, due to its unique challenge. Namely, not only is the radar cross section of a human on water small, but the micro-Doppler signatures are much noisier due to water drops and waves. In this paper, we first investigate whether discriminative signatures could be obtained for activities on water through a simulation study. Then, we show how we can effectively achieve high classification accuracy by applying deep convolutional neural networks (DCNN) directly to the spectrogram of real measurement data. From the five-fold cross-validation on our dataset, which consists of five aquatic activities, we report that the conventional feature-based scheme only achieves an accuracy of 45.1%. In contrast, the DCNN trained using only the collected data attains 66.7%, and the transfer learned DCNN, which takes a DCNN pre-trained on a RGB image dataset and fine-tunes the parameters using the collected data, achieves a much higher 80.3%, which is a significant performance boost. Full article

(This article belongs to the Special Issue Non-Contact Sensing)

► Show Figures

Figure 1

11 pages, 6477 KiB

Open AccessArticle

Design and Fabrication of Micro Hemispheric Shell Resonator with Annular Electrodes

by Renxin Wang, Bing Bai, Hengzhen Feng, Ziming Ren, Huiliang Cao, Chenyang Xue, Binzhen Zhang and Jun Liu

Sensors 2016, 16(12), 1991; https://doi.org/10.3390/s16121991 - 25 Nov 2016

Cited by 14 | Viewed by 7227

Abstract

Electrostatic driving and capacitive detection is widely used in micro hemispheric shell resonators (HSR). The capacitor gap distance is a dominant factor for the initial capacitance, and affects the driving voltage and sensitivity. In order to decrease the equivalent gap distance, a micro [...] Read more.

Electrostatic driving and capacitive detection is widely used in micro hemispheric shell resonators (HSR). The capacitor gap distance is a dominant factor for the initial capacitance, and affects the driving voltage and sensitivity. In order to decrease the equivalent gap distance, a micro HSR with annular electrodes fabricated by a glassblowing method was developed. Central and annular cavities are defined, and then the inside gas drives glass softening and deformation at 770 °C. While the same force is applied, the deformation of the hemispherical shell is about 200 times that of the annular electrodes, illustrating that the deformation of the electrodes will not affect the measurement accuracy. S-shaped patterns on the annular electrodes and internal-gear-like patterns on the hemispherical shell can improve metal malleability and avoid metal cracking during glass expansion. An arched annular electrode and a hemispheric shell are demonstrated. Compared with HSR with a spherical electrode, the applied voltage could be reduced by 29%, and the capacitance could be increased by 39%, according to theoretical and numerical calculation. The surface roughness of glass after glassblowing was favorable (Rq = 0.296 nm, Ra = 0.217 nm). In brief, micro HSR with an annular electrode was fabricated, and its superiority was preliminarily confirmed. Full article

(This article belongs to the Special Issue Resonator Sensors)

► Show Figures

Figure 1

19 pages, 38442 KiB

Open AccessArticle

Optical Microbubble Resonators with High Refractive Index Inner Coating for Bio-Sensing Applications: An Analytical Approach

by Andrea Barucci, Simone Berneschi, Ambra Giannetti, Francesco Baldini, Alessandro Cosci, Stefano Pelli, Daniele Farnesi, Giancarlo C. Righini, Silvia Soria and Gualtiero Nunzi Conti

Sensors 2016, 16(12), 1992; https://doi.org/10.3390/s16121992 - 25 Nov 2016

Cited by 14 | Viewed by 5466

Abstract

The design of Whispering Gallery Mode Resonators (WGMRs) used as an optical transducer for biosensing represents the first and crucial step towards the optimization of the final device performance in terms of sensitivity and Limit of Detection (LoD). Here, we propose an analytical [...] Read more.

The design of Whispering Gallery Mode Resonators (WGMRs) used as an optical transducer for biosensing represents the first and crucial step towards the optimization of the final device performance in terms of sensitivity and Limit of Detection (LoD). Here, we propose an analytical method for the design of an optical microbubble resonator (OMBR)-based biosensor. In order to enhance the OMBR sensing performance, we consider a polymeric layer of high refractive index as an inner coating for the OMBR. The effect of this layer and other optical/geometrical parameters on the mode field distribution, sensitivity and LoD of the OMBR is assessed and discussed, both for transverse electric (TE) and transverse magnetic (TM) polarization. The obtained results do provide physical insights for the development of OMBR-based biosensor. Full article

(This article belongs to the Special Issue Label-Free Optical Biosensors)

► Show Figures

Figure 1

18 pages, 556 KiB

Open AccessArticle

Privacy-Preserving Location-Based Service Scheme for Mobile Sensing Data

by Qingqing Xie and Liangmin Wang

Sensors 2016, 16(12), 1993; https://doi.org/10.3390/s16121993 - 25 Nov 2016

Cited by 11 | Viewed by 5353

Abstract

With the wide use of mobile sensing application, more and more location-embedded data are collected and stored in mobile clouds, such as iCloud, Samsung cloud, etc. Using these data, the cloud service provider (CSP) can provide location-based service (LBS) for users. However, the [...] Read more.

With the wide use of mobile sensing application, more and more location-embedded data are collected and stored in mobile clouds, such as iCloud, Samsung cloud, etc. Using these data, the cloud service provider (CSP) can provide location-based service (LBS) for users. However, the mobile cloud is untrustworthy. The privacy concerns force the sensitive locations to be stored on the mobile cloud in an encrypted form. However, this brings a great challenge to utilize these data to provide efficient LBS. To solve this problem, we propose a privacy-preserving LBS scheme for mobile sensing data, based on the RSA (for Rivest, Shamir and Adleman) algorithm and ciphertext policy attribute-based encryption (CP-ABE) scheme. The mobile cloud can perform location distance computing and comparison efficiently for authorized users, without location privacy leakage. In the end, theoretical security analysis and experimental evaluation demonstrate that our scheme is secure against the chosen plaintext attack (CPA) and efficient enough for practical applications in terms of user side computation overhead. Full article

(This article belongs to the Special Issue Big Data and Cloud Computing for Sensor Networks)

► Show Figures

Figure 1

16 pages, 5099 KiB

Open AccessArticle

Test of the Practicality and Feasibility of EDoF-Empowered Image Sensors for Long-Range Biometrics

by Sheng-Hsun Hsieh, Yung-Hui Li and Chung-Hao Tien

Sensors 2016, 16(12), 1994; https://doi.org/10.3390/s16121994 - 25 Nov 2016

Cited by 5 | Viewed by 5471

Abstract

For many practical applications of image sensors, how to extend the depth-of-field (DoF) is an important research topic; if successfully implemented, it could be beneficial in various applications, from photography to biometrics. In this work, we want to examine the feasibility and practicability [...] Read more.

For many practical applications of image sensors, how to extend the depth-of-field (DoF) is an important research topic; if successfully implemented, it could be beneficial in various applications, from photography to biometrics. In this work, we want to examine the feasibility and practicability of a well-known “extended DoF” (EDoF) technique, or “wavefront coding,” by building real-time long-range iris recognition and performing large-scale iris recognition. The key to the success of long-range iris recognition includes long DoF and image quality invariance toward various object distance, which is strict and harsh enough to test the practicality and feasibility of EDoF-empowered image sensors. Besides image sensor modification, we also explored the possibility of varying enrollment/testing pairs. With 512 iris images from 32 Asian people as the database, 400-mm focal length and F/6.3 optics over 3 m working distance, our results prove that a sophisticated coding design scheme plus homogeneous enrollment/testing setups can effectively overcome the blurring caused by phase modulation and omit Wiener-based restoration. In our experiments, which are based on 3328 iris images in total, the EDoF factor can achieve a result 3.71 times better than the original system without a loss of recognition accuracy. Full article

(This article belongs to the Special Issue Imaging: Sensors and Technologies)

► Show Figures

Figure 1

11 pages, 6097 KiB

Open AccessArticle

Design of a Solar Tracking System Using the Brightest Region in the Sky Image Sensor

by Ching-Chuan Wei, Yu-Chang Song, Chia-Chi Chang and Chuan-Bi Lin

Sensors 2016, 16(12), 1995; https://doi.org/10.3390/s16121995 - 25 Nov 2016

Cited by 29 | Viewed by 14613

Abstract

Solar energy is certainly an energy source worth exploring and utilizing because of the environmental protection it offers. However, the conversion efficiency of solar energy is still low. If the photovoltaic panel perpendicularly tracks the sun, the solar energy conversion efficiency will be [...] Read more.

Solar energy is certainly an energy source worth exploring and utilizing because of the environmental protection it offers. However, the conversion efficiency of solar energy is still low. If the photovoltaic panel perpendicularly tracks the sun, the solar energy conversion efficiency will be improved. In this article, we propose an innovative method to track the sun using an image sensor. In our method, it is logical to assume the points of the brightest region in the sky image representing the location of the sun. Then, the center of the brightest region is assumed to be the solar-center, and is mathematically calculated using an embedded processor (Raspberry Pi). Finally, the location information on the sun center is sent to the embedded processor to control two servo motors that are capable of moving both horizontally and vertically to track the sun. In comparison with the existing sun tracking methods using image sensors, such as the Hough transform method, our method based on the brightest region in the sky image remains accurate under conditions such as a sunny day and building shelter. The practical sun tracking system using our method was implemented and tested. The results reveal that the system successfully captured the real sun center in most weather conditions, and the servo motor system was able to direct the photovoltaic panel perpendicularly to the sun center. In addition, our system can be easily and practically integrated, and can operate in real-time. Full article

(This article belongs to the Section Physical Sensors)

► Show Figures

Figure 1

14 pages, 7261 KiB

Open AccessArticle

Visualization of Venous Compliance of Superficial Veins Using Non-Contact Plethysmography Based on Digital Red-Green-Blue Images

by Kazuya Nakano, Yuta Aoki, Ryota Satoh, Hiroyuki Suzuki and Izumi Nishidate

Sensors 2016, 16(12), 1996; https://doi.org/10.3390/s16121996 - 25 Nov 2016

Cited by 4 | Viewed by 9052

Abstract

We propose the visualization of venous compliance (VC) using a digital red-green-blue (RGB) camera. The new imaging method, which transforms RGB values into VC, combines VC evaluation with blood concentration estimation from the RGB values of each pixel. We evaluate a non-contact plethysmography [...] Read more.

We propose the visualization of venous compliance (VC) using a digital red-green-blue (RGB) camera. The new imaging method, which transforms RGB values into VC, combines VC evaluation with blood concentration estimation from the RGB values of each pixel. We evaluate a non-contact plethysmography (NCPG) system for VC based on comparisons with conventional strain gauge plethysmography (SPG). We conduct in vivo measurements using both systems and investigate their differences by evaluating the VC. The results show that the two methods measure different blood vessels and that errors caused by interstitial fluid accumulation are negligible for the NCPG system, whereas SPG is influenced by such errors. Additionally, we investigate the relationship between VC and physical activity using NCPG. Full article

(This article belongs to the Special Issue Non-Contact Sensing)

► Show Figures

Figure 1

17 pages, 8308 KiB

Open AccessArticle

Atmospheric Correction of Satellite GF-1/WFV Imagery and Quantitative Estimation of Suspended Particulate Matter in the Yangtze Estuary

by Pei Shang and Fang Shen

Sensors 2016, 16(12), 1997; https://doi.org/10.3390/s16121997 - 25 Nov 2016

Cited by 25 | Viewed by 5936

Abstract

The Multispectral Wide Field of View (WFV) camera on the Chinese GF-1 satellite, launched in 2013, has advantages of high spatial resolution (16 m), short revisit period (4 days) and wide scene swath (800 km) compared to the Landsat-8/OLI, which make it an [...] Read more.

The Multispectral Wide Field of View (WFV) camera on the Chinese GF-1 satellite, launched in 2013, has advantages of high spatial resolution (16 m), short revisit period (4 days) and wide scene swath (800 km) compared to the Landsat-8/OLI, which make it an ideal means of monitoring spatial-temporal changes of Suspended Particulate Matter (SPM) in large estuaries like the Yangtze Estuary. However, a lack of proper atmospheric correction methods has limited its application in water quality assessment. We propose an atmospheric correction method based on a look up table coupled by the atmosphere radiative transfer model (6S) and the water semi-empirical radiative transfer (SERT) model for inversion of water-leaving reflectance from GF-1 top-of-atmosphere radiance, and then retrieving SPM concentration from water-leaving radiance reflectance of the Yangtze Estuary and its adjacent sea. Results are validated by the Landsat-8/OLI imagery together with autonomous fixed station data, and influences of human activities (e.g., waterway construction and shipping) on SPM distribution are analyzed. Full article

(This article belongs to the Special Issue Sensors and Sensing in Water Quality Assessment and Monitoring)

► Show Figures

Figure 1

21 pages, 626 KiB

Open AccessArticle

Reciprocally-Benefited Secure Transmission for Spectrum Sensing-Based Cognitive Radio Sensor Networks

by Dawei Wang, Pinyi Ren, Qinghe Du, Li Sun and Yichen Wang

Sensors 2016, 16(12), 1998; https://doi.org/10.3390/s16121998 - 25 Nov 2016

Cited by 5 | Viewed by 4457

Abstract

The rapid proliferation of independently-designed and -deployed wireless sensor networks extremely crowds the wireless spectrum and promotes the emergence of cognitive radio sensor networks (CRSN). In CRSN, the sensor node (SN) can make full use of the unutilized licensed spectrum, and the spectrum [...] Read more.

The rapid proliferation of independently-designed and -deployed wireless sensor networks extremely crowds the wireless spectrum and promotes the emergence of cognitive radio sensor networks (CRSN). In CRSN, the sensor node (SN) can make full use of the unutilized licensed spectrum, and the spectrum efficiency is greatly improved. However, inevitable spectrum sensing errors will adversely interfere with the primary transmission, which may result in primary transmission outage. To compensate the adverse effect of spectrum sensing errors, we propose a reciprocally-benefited secure transmission strategy, in which SN’s interference to the eavesdropper is employed to protect the primary confidential messages while the CRSN is also rewarded with a loose spectrum sensing error probability constraint. Specifically, according to the spectrum sensing results and primary users’ activities, there are four system states in this strategy. For each state, we analyze the primary secrecy rate and the SN’s transmission rate by taking into account the spectrum sensing errors. Then, the SN’s transmit power is optimally allocated for each state so that the average transmission rate of CRSN is maximized under the constraint of the primary maximum permitted secrecy outage probability. In addition, the performance tradeoff between the transmission rate of CRSN and the primary secrecy outage probability is investigated. Moreover, we analyze the primary secrecy rate for the asymptotic scenarios and derive the closed-form expression of the SN’s transmission outage probability. Simulation results show that: (1) the performance of the SN’s average throughput in the proposed strategy outperforms the conventional overlay strategy; (2) both the primary network and CRSN benefit from the proposed strategy. Full article

(This article belongs to the Special Issue Trusted and Secure Wireless Sensor Network Designs and Deployments)

► Show Figures

Figure 1

21 pages, 3566 KiB

Open AccessArticle

Mitigating RF Front-End Nonlinearity of Sensor Nodes to Enhance Spectrum Sensing

by Lin Hu, Hong Ma, Hua Zhang and Wen Zhao

Sensors 2016, 16(12), 1999; https://doi.org/10.3390/s16121999 - 25 Nov 2016

Cited by 1 | Viewed by 6403

Abstract

The cognitive radio wireless sensor network (CR-WSN) has gained worldwide attention in recent years for its potential applications. Reliable spectrum sensing is the premise for opportunistic access to sensor nodes. However, as a result of the radio frequency (RF) front-end nonlinearity of sensor [...] Read more.

The cognitive radio wireless sensor network (CR-WSN) has gained worldwide attention in recent years for its potential applications. Reliable spectrum sensing is the premise for opportunistic access to sensor nodes. However, as a result of the radio frequency (RF) front-end nonlinearity of sensor nodes, distortion products can easily degrade the spectrum sensing performance by causing false alarms and degrading the detection probability. Given the limitations of the widely-used adaptive interference cancellation (AIC) algorithm, this paper develops several details to avoid these limitations and form a new mitigation architecture to alleviate nonlinear distortions. To demonstrate the efficiency of the proposed algorithm, verification tests for both simulations and actual RF front-end measurements are presented and discussed. The obtained results show that distortions can be suppressed significantly, thus improving the reliability of spectrum sensing. Moreover, compared to AIC, the proposed algorithm clearly shows better performance, especially at the band edges of the interferer signal. Full article

(This article belongs to the Special Issue Advanced Technologies and Techniques for Microwave and Wireless Sensors)

► Show Figures

Figure 1

18 pages, 9502 KiB

Open AccessArticle

Validation and Parameter Sensitivity Tests for Reconstructing Swell Field Based on an Ensemble Kalman Filter

by Xuan Wang, Pierre Tandeo, Ronan Fablet, Romain Husson, Lei Guan and Ge Chen

Sensors 2016, 16(12), 2000; https://doi.org/10.3390/s16122000 - 25 Nov 2016

Viewed by 5884

Abstract

The swell propagation model built on geometric optics is known to work well when simulating radiated swells from a far located storm. Based on this simple approximation, satellites have acquired plenty of large samples on basin-traversing swells induced by fierce storms situated in [...] Read more.

The swell propagation model built on geometric optics is known to work well when simulating radiated swells from a far located storm. Based on this simple approximation, satellites have acquired plenty of large samples on basin-traversing swells induced by fierce storms situated in mid-latitudes. How to routinely reconstruct swell fields with these irregularly sampled observations from space via known swell propagation principle requires more examination. In this study, we apply 3-h interval pseudo SAR observations in the ensemble Kalman filter (EnKF) to reconstruct a swell field in ocean basin, and compare it with buoy swell partitions and polynomial regression results. As validated against in situ measurements, EnKF works well in terms of spatial–temporal consistency in far-field swell propagation scenarios. Using this framework, we further address the influence of EnKF parameters, and perform a sensitivity analysis to evaluate estimations made under different sets of parameters. Such analysis is of key interest with respect to future multiple-source routinely recorded swell field data. Satellite-derived swell data can serve as a valuable complementary dataset to in situ or wave re-analysis datasets. Full article

(This article belongs to the Special Issue Synthetic Aperture Radars: Models, Algorithms, Techniques and Tools for Data Exploitation)

► Show Figures

Figure 1

11 pages, 4352 KiB

Open AccessArticle

The Design and Characterization of a Flexible Tactile Sensing Array for Robot Skin

by Zhangping Ji, Hui Zhu, Huicong Liu, Nan Liu, Tao Chen, Zhan Yang and Lining Sun

Sensors 2016, 16(12), 2001; https://doi.org/10.3390/s16122001 - 25 Nov 2016

Cited by 64 | Viewed by 11846

Abstract

In this study, a flexible tactile sensing array based on a capacitive mechanism was designed, fabricated, and characterized for sensitive robot skin. A device with 8 × 8 sensing units was composed of top and bottom flexible polyethyleneterephthalate (PET) substrates with copper (Cu) [...] Read more.

In this study, a flexible tactile sensing array based on a capacitive mechanism was designed, fabricated, and characterized for sensitive robot skin. A device with 8 × 8 sensing units was composed of top and bottom flexible polyethyleneterephthalate (PET) substrates with copper (Cu) electrodes, a polydimethylsiloxane (PDMS) dielectric layer, and a bump contact layer. Four types of microstructures (i.e., pyramids and V-shape grooves) atop a PDMS dielectric layer were well-designed and fabricated to enhance tactile sensitivity. The optimal sensing unit achieved a high sensitivity of 35.9%/N in a force range of 0–1 N. By incorporating a tactile feedback control system, the flexible sensing array as the sensitive skin of a robotic manipulator demonstrated a potential capability of robotic obstacle avoidance. Full article

(This article belongs to the Special Issue Flexible Electronics and Sensors)

► Show Figures

Figure 1

13 pages, 6457 KiB

Open AccessArticle

Reconfigurable Multiparameter Biosignal Acquisition SoC for Low Power Wearable Platform

by Jongpal Kim and Hyoungho Ko

Sensors 2016, 16(12), 2002; https://doi.org/10.3390/s16122002 - 25 Nov 2016

Cited by 15 | Viewed by 6997

Abstract

A low power and low noise reconfigurable analog front-end (AFE) system on a chip (SoC) for biosignal acquisition is presented. The presented AFE can be reconfigured for use in electropotential, bioimpedance, electrochemical, and photoelectrical modes. The advanced healthcare services based on multiparameter physiological [...] Read more.

A low power and low noise reconfigurable analog front-end (AFE) system on a chip (SoC) for biosignal acquisition is presented. The presented AFE can be reconfigured for use in electropotential, bioimpedance, electrochemical, and photoelectrical modes. The advanced healthcare services based on multiparameter physiological biosignals can be easily implemented with these multimodal and highly reconfigurable features of the proposed system. The reconfigurable gain and input referred noise of the core instrumentation amplifier block are 25 dB to 52 dB, and 1 μV_RMS, respectively. The power consumption of the analog blocks in one readout channel is less than 52 μW. The reconfigurable capability among various modes of applications including electrocardiogram, blood glucose concentration, respiration, and photoplethysmography are shown experimentally. Full article

(This article belongs to the Section Biosensors)

► Show Figures

Figure 1

27 pages, 2526 KiB

Open AccessArticle

Data-Driven Multiresolution Camera Using the Foveal Adaptive Pyramid

by Martin González, Antonio Sánchez-Pedraza, Rebeca Marfil, Juan A. Rodríguez and Antonio Bandera

Sensors 2016, 16(12), 2003; https://doi.org/10.3390/s16122003 - 26 Nov 2016

Cited by 5 | Viewed by 5739

Abstract

There exist image processing applications, such as tracking or pattern recognition, that are not necessarily precise enough to maintain the same resolution across the whole image sensor. In fact, they must only keep it as high as possible in a relatively small region, [...] Read more.

There exist image processing applications, such as tracking or pattern recognition, that are not necessarily precise enough to maintain the same resolution across the whole image sensor. In fact, they must only keep it as high as possible in a relatively small region, but covering a wide field of view. This is the aim of foveal vision systems. Briefly, they propose to sense a large field of view at a spatially-variant resolution: one relatively small region, the fovea, is mapped at a high resolution, while the rest of the image is captured at a lower resolution. In these systems, this fovea must be moved, from one region of interest to another one, to scan a visual scene. It is interesting that the part of the scene that is covered by the fovea should not be merely spatial, but closely related to perceptual objects. Segmentation and attention are then intimately tied together: while the segmentation process is responsible for extracting perceptively-coherent entities from the scene (proto-objects), attention can guide segmentation. From this loop, the concept of foveal attention arises. This work proposes a hardware system for mapping a uniformly-sampled sensor to a space-variant one. Furthermore, this mapping is tied with a software-based, foveal attention mechanism that takes as input the stream of generated foveal images. The whole hardware/software architecture has been designed to be embedded within an all programmable system on chip (AP SoC). Our results show the flexibility of the data port for exchanging information between the mapping and attention parts of the architecture and the good performance rates of the mapping procedure. Experimental evaluation also demonstrates that the segmentation method and the attention model provide results comparable to other more computationally-expensive algorithms. Full article

(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Spain 2016)

► Show Figures

Figure 1

12 pages, 1265 KiB

Open AccessArticle

Estimating Leaf Area Index (LAI) in Vineyards Using the PocketLAI Smart-App

by Francesca Orlando, Ermes Movedi, Davide Coduto, Simone Parisi, Lucio Brancadoro, Valentina Pagani, Tommaso Guarneri and Roberto Confalonieri

Sensors 2016, 16(12), 2004; https://doi.org/10.3390/s16122004 - 26 Nov 2016

Cited by 34 | Viewed by 10058

Abstract

Estimating leaf area index (LAI) of Vitis vinifera using indirect methods involves some critical issues, related to its discontinuous and non-homogeneous canopy. This study evaluates the smart app PocketLAI and hemispherical photography in vineyards against destructive LAI measurements. Data were collected during six [...] Read more.

Estimating leaf area index (LAI) of Vitis vinifera using indirect methods involves some critical issues, related to its discontinuous and non-homogeneous canopy. This study evaluates the smart app PocketLAI and hemispherical photography in vineyards against destructive LAI measurements. Data were collected during six surveys in an experimental site characterized by a high level of heterogeneity among plants, allowing us to explore a wide range of LAI values. During the last survey, the possibility to combine remote sensing data and in-situ PocketLAI estimates (smart scouting) was evaluated. Results showed a good agreement between PocketLAI data and direct measurements, especially for LAI ranging from 0.13 to 1.41 (R² = 0.94, RRMSE = 17.27%), whereas the accuracy decreased when an outlying value (vineyard LAI = 2.84) was included (R² = 0.77, RRMSE = 43.00%), due to the saturation effect in case of very dense canopies arising from lack of green pruning. The hemispherical photography showed very high values of R², even in presence of the outlying value (R² = 0.94), although it showed a marked and quite constant overestimation error (RRMSE = 99.46%), suggesting the need to introduce a correction factor specific for vineyards. During the smart scouting, PocketLAI showed its reliability to monitor the spatial-temporal variability of vine vigor in cordon-trained systems, and showed a potential for a wide range of applications, also in combination with remote sensing. Full article

(This article belongs to the Special Issue Precision Agriculture and Remote Sensing Data Fusion)

► Show Figures

Figure 1

17 pages, 8114 KiB

Open AccessArticle

Identification of Object Dynamics Using Hand Worn Motion and Force Sensors

by Henk G. Kortier, H. Martin Schepers and Peter H. Veltink

Sensors 2016, 16(12), 2005; https://doi.org/10.3390/s16122005 - 26 Nov 2016

Cited by 16 | Viewed by 7247

Abstract

Emerging microelectromechanical system (MEMS)-based sensors become much more applicable for on-body measurement purposes lately. Especially, the development of a finger tip-sized tri-axial force sensor gives the opportunity to measure interaction forces between the human hand and environmental objects. We have developed a new [...] Read more.

Emerging microelectromechanical system (MEMS)-based sensors become much more applicable for on-body measurement purposes lately. Especially, the development of a finger tip-sized tri-axial force sensor gives the opportunity to measure interaction forces between the human hand and environmental objects. We have developed a new prototype device that allows simultaneous 3D force and movement measurements at the finger and thumb tips. The combination of interaction forces and movements makes it possible to identify the dynamical characteristics of the object being handled by the hand. With this device attached to the hand, a subject manipulated mass and spring objects under varying conditions. We were able to identify and estimate the weight of two physical mass objects (0.44 kg:

29.3 % \pm 18.9 %

and 0.28 kg:

19.7 % \pm 10.6 %

) and the spring constant of a physical spring object (

16.3 % \pm 12.6 %

). The system is a first attempt to quantify the interactions of the hand with the environment and has many potential applications in rehabilitation, ergonomics and sports. Full article

(This article belongs to the Section Physical Sensors)

► Show Figures

Figure 1

12 pages, 593 KiB

Open AccessArticle

Gap Measurement of Point Machine Using Adaptive Wavelet Threshold and Mathematical Morphology

by Tianhua Xu, Guang Wang, Haifeng Wang, Tangming Yuan and Zhiwang Zhong

Sensors 2016, 16(12), 2006; https://doi.org/10.3390/s16122006 - 26 Nov 2016

Cited by 23 | Viewed by 5504

Abstract

A point machine’s gap is an important indication of its healthy status. An edge detection algorithm is proposed to measure and calculate a point machine’s gap from the gap image captured by CCD plane arrays. This algorithm integrates adaptive wavelet-based image denoising, locally [...] Read more.

A point machine’s gap is an important indication of its healthy status. An edge detection algorithm is proposed to measure and calculate a point machine’s gap from the gap image captured by CCD plane arrays. This algorithm integrates adaptive wavelet-based image denoising, locally adaptive image binarization, and mathematical morphology technologies. The adaptive wavelet-based image denoising obtains not only an optimal denoising threshold, but also unblurred edges. Locally adaptive image binarization has the advantage of overcoming the local intensity variation in gap images. Mathematical morphology may suppress speckle spots caused by reflective metal surfaces in point machines. The subjective and objective evaluations of the proposed method are presented by using point machine gap images from a railway corporation in China. The performance between the proposed method and conventional edge detection methods has also been compared, and the result shows that the former outperforms the latter. Full article

(This article belongs to the Section Physical Sensors)

► Show Figures

Figure 1

11 pages, 3831 KiB

Open AccessArticle

Fast Interrogation of Fiber Bragg Gratings with Electro-Optical Dual Optical Frequency Combs

by Julio E. Posada-Roman, Jose A. Garcia-Souto, Dragos A. Poiana and Pablo Acedo

Sensors 2016, 16(12), 2007; https://doi.org/10.3390/s16122007 - 26 Nov 2016

Cited by 31 | Viewed by 8127

Abstract

Optical frequency combs (OFC) generated by electro-optic modulation of continuous-wave lasers provide broadband coherent sources with high power per line and independent control of line spacing and the number of lines. In addition to their application in spectroscopy, they offer flexible and optimized [...] Read more.

Optical frequency combs (OFC) generated by electro-optic modulation of continuous-wave lasers provide broadband coherent sources with high power per line and independent control of line spacing and the number of lines. In addition to their application in spectroscopy, they offer flexible and optimized sources for the interrogation of other sensors based on wavelength change or wavelength filtering, such as fiber Bragg grating (FBG) sensors. In this paper, a dual-OFC FBG interrogation system based on a single laser and two optical-phase modulators is presented. This architecture allows for the configuration of multimode optical source parameters such as the number of modes and their position within the reflected spectrum of the FBG. A direct read-out is obtained by mapping the optical spectrum onto the radio-frequency spectrum output of the dual-comb. This interrogation scheme is proposed for measuring fast phenomena such as vibrations and ultrasounds. Results are presented for dual-comb operation under optimized control. The optical modes are mapped onto detectable tones that are multiples of 0.5 MHz around a center radiofrequency tone (40 MHz). Measurements of ultrasounds (40 kHz and 120 kHz) are demonstrated with this sensing system. Ultrasounds induce dynamic strain onto the fiber, which generates changes in the reflected Bragg wavelength and, hence, modulates the amplitude of the OFC modes within the reflected spectrum. The amplitude modulation of two counterphase tones is detected to obtain a differential measurement proportional to the ultrasound signal. Full article

(This article belongs to the Special Issue Optical Fiber Sensors 2016)

► Show Figures

Figure 1

17 pages, 9042 KiB

Open AccessArticle

An Alternative Approach for Registration of
High-Resolution Satellite Optical Imagery and ICESat Laser Altimetry Data

by Shijie Liu, Yi Lv, Xiaohua Tong, Huan Xie, Jun Liu and Lei Chen

Sensors 2016, 16(12), 2008; https://doi.org/10.3390/s16122008 - 27 Nov 2016

Cited by 8 | Viewed by 5844

Abstract

Satellite optical images and altimetry data are two major data sources used in Antarctic research. The integration use of these two datasets is expected to provide more accurate and higher quality products, during which data registration is the first issue that needs to [...] Read more.

Satellite optical images and altimetry data are two major data sources used in Antarctic research. The integration use of these two datasets is expected to provide more accurate and higher quality products, during which data registration is the first issue that needs to be solved. This paper presents an alternative approach for the registration of high-resolution satellite optical images and ICESat (Ice, Cloud, and land Elevation Satellite) laser altimetry data. Due to the sparse distribution characteristic of the ICESat laser point data, it is difficult and even impossible to find same-type conjugate features between ICESat data and satellite optical images. The method is implemented in a direct way to correct the point-to-line inconsistency in image space through 2D transformation between the projected terrain feature points and the corresponding 2D image lines, which is simpler than discrepancy correction in object space that requires stereo images for 3D model construction, and easier than the indirect way of image orientation correction via photogrammetric bundle adjustment. The correction parameters are further incorporated into imaging model through RPCs (Rational Polynomial Coefficients) generation/regeneration for the convenience of photogrammetric applications. The experimental results by using the ASTER (Advanced Spaceborne Thermal Emission and Reflection Radiometer) images and ZY-3 (Ziyuan-3 satellite) images for registration with ICESat data showed that sub-pixel level registration accuracies were achieved after registration, which have validated the feasibility and effectiveness of the presented approach. Full article

(This article belongs to the Section Remote Sensors)

► Show Figures

Figure 1

21 pages, 4433 KiB

Open AccessArticle

MECS-VINE^®: A New Proximal Sensor for Segmented Mapping of Vigor and Yield Parameters on Vineyard Rows

by Matteo Gatti, Paolo Dosso, Marco Maurino, Maria Clara Merli, Fabio Bernizzoni, Facundo José Pirez, Bonfiglio Platè, Gian Carlo Bertuzzi and Stefano Poni

Sensors 2016, 16(12), 2009; https://doi.org/10.3390/s16122009 - 27 Nov 2016

Cited by 29 | Viewed by 9484

Abstract

Ground-based proximal sensing of vineyard features is gaining interest due to its ability to serve in even quite small plots with the advantage of being conducted concurrently with normal vineyard practices (i.e., spraying, pruning or soil tilling) with no dependence upon weather conditions, [...] Read more.

Ground-based proximal sensing of vineyard features is gaining interest due to its ability to serve in even quite small plots with the advantage of being conducted concurrently with normal vineyard practices (i.e., spraying, pruning or soil tilling) with no dependence upon weather conditions, external services or law-imposed limitations. The purpose of the present work was to test performance of the new terrestrial multi-sensor MECS-VINE^® in terms of reliability and degree of correlation with several canopy growth and yield parameters in the grapevine. MECS-VINE^®, once conveniently positioned in front of the tractor, can provide simultaneous assessment of growth features and microclimate of specific canopy sections of the two adjacent row sides. MECS-VINE^® integrates a series of microclimate sensors (air relative humidity, air and surface temperature) with two (left and right) matrix-based optical RGB imaging sensors and a related algorithm, termed Canoyct). MECS-VINE^® was run five times along the season in a mature cv. Barbera vineyard and a Canopy Index (CI, pure number varying from 0 to 1000), calculated through its built-in algorithm, validated vs. canopy structure parameters (i.e., leaf layer number, fractions of canopy gaps and interior leaves) derived from point quadrat analysis. Results showed that CI was highly correlated vs. any canopy parameter at any date, although the closest relationships were found for CI vs. fraction of canopy gaps (R² = 0.97) and leaf layer number (R² = 0.97) for data pooled over 24 test vines. While correlations against canopy light interception and total lateral leaf area were still unsatisfactory, a good correlation was found vs. cluster and berry weight (R² = 0.76 and 0.71, respectively) suggesting a good potential also for yield estimates. Besides the quite satisfactory calibration provided, main improvements of MECS-VINE^® usage versus other current equipment are: (i) MECS-VINE^® delivers a segmented evaluation of the canopy up to 15 different sectors, therefore allowing to differentiate canopy structure and density at specific and crucial canopy segments (i.e., basal part where clusters are located) and (ii) the sensor is optimized to work at any time of the day with any weather condition without the need of any supplemental lighting system. Full article

(This article belongs to the Section Remote Sensors)

► Show Figures

Figure 1

17 pages, 8874 KiB

Open AccessArticle

Is the Geographic Range of Mangrove Forests in the Conterminous United States Really Expanding?

by Chandra Giri and Jordan Long

Sensors 2016, 16(12), 2010; https://doi.org/10.3390/s16122010 - 28 Nov 2016

Cited by 60 | Viewed by 9603

Abstract

Changes in the distribution and abundance of mangrove species within and outside of their historic geographic range can have profound consequences in the provision of ecosystem goods and services they provide. Mangroves in the conterminous United States (CONUS) are believed to be expanding [...] Read more.

Changes in the distribution and abundance of mangrove species within and outside of their historic geographic range can have profound consequences in the provision of ecosystem goods and services they provide. Mangroves in the conterminous United States (CONUS) are believed to be expanding poleward (north) due to decreases in the frequency and severity of extreme cold events, while sea level rise is a factor often implicated in the landward expansion of mangroves locally. We used ~35 years of satellite imagery and in situ observations for CONUS and report that: (i) poleward expansion of mangrove forest is inconclusive, and may have stalled for now, and (ii) landward expansion is actively occurring within the historical northernmost limit. We revealed that the northernmost latitudinal limit of mangrove forests along the east and west coasts of Florida, in addition to Louisiana and Texas has not systematically expanded toward the pole. Mangrove area, however, expanded by 4.3% from 1980 to 2015 within the historic northernmost boundary, with the highest percentage of change in Texas and southern Florida. Several confounding factors such as sea level rise, absence or presence of sub-freezing temperatures, land use change, impoundment/dredging, changing hydrology, fire, storm, sedimentation and erosion, and mangrove planting are responsible for the change. Besides, sea level rise, relatively milder winters and the absence of sub-freezing temperatures in recent decades may be enabling the expansion locally. The results highlight the complex set of forcings acting on the northerly extent of mangroves and emphasize the need for long-term monitoring as this system increases in importance as a means to adapt to rising oceans and mitigate the effects of increased atmospheric CO₂. Full article

(This article belongs to the Section Remote Sensors)

► Show Figures

Figure 1

21 pages, 6536 KiB

Open AccessArticle

Anatomical Calibration through Post-Processing of Standard Motion Tests Data

by Weisheng Kong, Salvatore Sessa, Massimiliano Zecca and Atsuo Takanishi

Sensors 2016, 16(12), 2011; https://doi.org/10.3390/s16122011 - 28 Nov 2016

Cited by 16 | Viewed by 8148

Abstract

The inertial measurement unit is popularly used as a wearable and flexible tool for human motion tracking. Sensor-to-body alignment, or anatomical calibration (AC), is fundamental to improve accuracy and reliability. Current AC methods either require extra movements or are limited to specific joints. [...] Read more.

The inertial measurement unit is popularly used as a wearable and flexible tool for human motion tracking. Sensor-to-body alignment, or anatomical calibration (AC), is fundamental to improve accuracy and reliability. Current AC methods either require extra movements or are limited to specific joints. In this research, the authors propose a novel method to achieve AC from standard motion tests (such as walking, or sit-to-stand), and compare the results with the AC obtained from specially designed movements. The proposed method uses the limited acceleration range on medial-lateral direction, and applies principal component analysis to estimate the sagittal plane, while the vertical direction is estimated from acceleration during quiet stance. The results show a good correlation between the two sets of IMUs placed on frontal/back and lateral sides of head, trunk and lower limbs. Moreover, repeatability and convergence were verified. The AC obtained from sit-to-stand and walking achieved similar results as the movements specifically designed for upper and lower body AC, respectively, except for the feet. Therefore, the experiments without AC performed can be recovered through post-processing on the walking and sit-to-stand data. Moreover, extra movements for AC can be avoided during the experiment and instead achieved through the proposed method. Full article

(This article belongs to the Special Issue Inertial Sensors and Systems 2016)

► Show Figures

Figure 1

31 pages, 673 KiB

Open AccessArticle

Potential of Wake-Up Radio-Based MAC Protocols for Implantable Body Sensor Networks (IBSN)—A Survey

by Vignesh Raja Karuppiah Ramachandran, Eyuel D. Ayele, Nirvana Meratnia and Paul J. M. Havinga

Sensors 2016, 16(12), 2012; https://doi.org/10.3390/s16122012 - 29 Nov 2016

Cited by 6 | Viewed by 5907

Abstract

With the advent of nano-technology, medical sensors and devices are becoming highly miniaturized. Consequently, the number of sensors and medical devices being implanted to accurately monitor and diagnose a disease is increasing. By measuring the symptoms and controlling a medical device as close [...] Read more.

With the advent of nano-technology, medical sensors and devices are becoming highly miniaturized. Consequently, the number of sensors and medical devices being implanted to accurately monitor and diagnose a disease is increasing. By measuring the symptoms and controlling a medical device as close as possible to the source, these implantable devices are able to save lives. A wireless link between medical sensors and implantable medical devices is essential in the case of closed-loop medical devices, in which symptoms of the diseases are monitored by sensors that are not placed in close proximity of the therapeutic device. Medium Access Control (MAC) is crucial to make it possible for several medical devices to communicate using a shared wireless medium in such a way that minimum delay, maximum throughput, and increased network life-time are guaranteed. To guarantee this Quality of Service (QoS), the MAC protocols control the main sources of limited resource wastage, namely the idle-listening, packet collisions, over-hearing, and packet loss. Traditional MAC protocols designed for body sensor networks are not directly applicable to Implantable Body Sensor Networks (IBSN) because of the dynamic nature of the radio channel within the human body and the strict QoS requirements of IBSN applications. Although numerous MAC protocols are available in the literature, the majority of them are designed for Body Sensor Network (BSN) and Wireless Sensor Network (WSN). To the best of our knowledge, there is so far no research paper that explores the impact of these MAC protocols specifically for IBSN. MAC protocols designed for implantable devices are still in their infancy and one of their most challenging objectives is to be ultra-low-power. One of the technological solutions to achieve this objective so is to integrate the concept of Wake-up radio (WuR) into the MAC design. In this survey, we present a taxonomy of MAC protocols based on their use of WuR technology and identify their bottlenecks to be used in IBSN applications. Furthermore, we present a number of open research challenges and requirements for designing an energy-efficient and reliable wireless communication protocol for IBSN. Full article

(This article belongs to the Special Issue Advances in Body Sensor Networks: Sensors, Systems, and Applications)

► Show Figures

Figure 1

20 pages, 1323 KiB

Open AccessArticle

Task and Participant Scheduling of Trading Platforms in Vehicular Participatory Sensing Networks

by Heyuan Shi, Xiaoyu Song, Ming Gu and Jiaguang Sun

Sensors 2016, 16(12), 2013; https://doi.org/10.3390/s16122013 - 28 Nov 2016

Cited by 2 | Viewed by 4887

Abstract

The vehicular participatory sensing network (VPSN) is now becoming more and more prevalent, and additionally has shown its great potential in various applications. A general VPSN consists of many tasks from task, publishers, trading platforms and a crowd of participants. Some literature treats [...] Read more.

The vehicular participatory sensing network (VPSN) is now becoming more and more prevalent, and additionally has shown its great potential in various applications. A general VPSN consists of many tasks from task, publishers, trading platforms and a crowd of participants. Some literature treats publishers and the trading platform as a whole, which is impractical since they are two independent economic entities with respective purposes. For a trading platform in markets, its purpose is to maximize the profit by selecting tasks and recruiting participants who satisfy the requirements of accepted tasks, rather than to improve the quality of each task. This scheduling problem for a trading platform consists of two parts: which tasks should be selected and which participants to be recruited? In this paper, we investigate the scheduling problem in vehicular participatory sensing with the predictable mobility of each vehicle. A genetic-based trading scheduling algorithm (GTSA) is proposed to solve the scheduling problem. Experiments with a realistic dataset of taxi trajectories demonstrate that GTSA algorithm is efficient for trading platforms to gain considerable profit in VPSN. Full article

(This article belongs to the Special Issue New Paradigms in Cyber-Physical Social Sensing)

► Show Figures

Figure 1

14 pages, 4706 KiB

Open AccessArticle

Measurement of M²-Curve for Asymmetric Beams by Self-Referencing Interferometer Wavefront Sensor

by Yongzhao Du

Sensors 2016, 16(12), 2014; https://doi.org/10.3390/s16122014 - 29 Nov 2016

Cited by 5 | Viewed by 6103

Abstract

For asymmetric laser beams, the values of beam quality factor

M_{x}^{2}

and

M_{y}^{2}

are inconsistent if one selects a different coordinate system or measures beam quality with different experimental conditionals, even when analyzing the same beam. To overcome this [...] Read more.

For asymmetric laser beams, the values of beam quality factor

M_{x}^{2}

and

M_{y}^{2}

are inconsistent if one selects a different coordinate system or measures beam quality with different experimental conditionals, even when analyzing the same beam. To overcome this non-uniqueness, a new beam quality characterization method named as M²-curve is developed. The M²-curve not only contains the beam quality factor

M_{x}^{2}

and

M_{y}^{2}

in the x-direction and y-direction, respectively; but also introduces a curve of

M_{x α}^{2}

versus rotation angle α of coordinate axis. Moreover, we also present a real-time measurement method to demonstrate beam propagation factor M²-curve with a modified self-referencing Mach-Zehnder interferometer based-wavefront sensor (henceforth SRI-WFS). The feasibility of the proposed method is demonstrated with the theoretical analysis and experiment in multimode beams. The experimental results showed that the proposed measurement method is simple, fast, and a single-shot measurement procedure without movable parts. Full article

(This article belongs to the Section Physical Sensors)

► Show Figures

Figure 1

16 pages, 5989 KiB

Open AccessArticle

Localization Based on Magnetic Markers for an All-Wheel Steering Vehicle

by Yeun Sub Byun and Young Chol Kim

Sensors 2016, 16(12), 2015; https://doi.org/10.3390/s16122015 - 29 Nov 2016

Cited by 12 | Viewed by 7581

Abstract

Real-time continuous localization is a key technology in the development of intelligent transportation systems. In these systems, it is very important to have accurate information about the position and heading angle of the vehicle at all times. The most widely implemented methods for [...] Read more.

Real-time continuous localization is a key technology in the development of intelligent transportation systems. In these systems, it is very important to have accurate information about the position and heading angle of the vehicle at all times. The most widely implemented methods for positioning are the global positioning system (GPS), vision-based system, and magnetic marker system. Among these methods, the magnetic marker system is less vulnerable to indoor and outdoor environment conditions; moreover, it requires minimal maintenance expenses. In this paper, we present a position estimation scheme based on magnetic markers and odometry sensors for an all-wheel-steering vehicle. The heading angle of the vehicle is determined by using the position coordinates of the last two detected magnetic markers and odometer data. The instant position and heading angle of the vehicle are integrated with an extended Kalman filter to estimate the continuous position. GPS data with the real-time kinematics mode was obtained to evaluate the performance of the proposed position estimation system. The test results show that the performance of the proposed localization algorithm is accurate (mean error: 3 cm; max error: 9 cm) and reliable under unexpected missing markers or incorrect markers. Full article

(This article belongs to the Special Issue Sensors for Autonomous Road Vehicles)

► Show Figures

Figure 1

14 pages, 386 KiB

Open AccessArticle

Optimal Resource Allocation Policies for Multi-User Backscatter Communication Systems

by Bin Lyu, Zhen Yang, Guan Gui and Youhong Feng

Sensors 2016, 16(12), 2016; https://doi.org/10.3390/s16122016 - 29 Nov 2016

Cited by 15 | Viewed by 5007

Abstract

This paper considers a backscatter communication (BackCom) system including a reader and N tags, where each tag receives excitation signals transmitted by the reader and concurrently backscatters information to the reader in time-division-multiple-access (TDMA) mode. In this system, we aim to maximize the [...] Read more.

This paper considers a backscatter communication (BackCom) system including a reader and N tags, where each tag receives excitation signals transmitted by the reader and concurrently backscatters information to the reader in time-division-multiple-access (TDMA) mode. In this system, we aim to maximize the total system goodput by jointly optimizing reader transmission power, time allocation, and reflection ratio for the cases of passive and semi-passive tags. For each case, an optimization problem is formulated, which is non-convex and can be solved by being decomposed into at most N feasible sub-problems based on the priority of allocated reader transmission power. First, for the passive tags case, by solving the convex sub-problems sequentially and comparing their maximum total goodput, we derive the optimal resource allocation policy. Then, for the semi-passive tags case, we find a close-to-optimal solution, since each sub-problem can be reformulated as a biconvex problem, which is solved by a proposed block coordinate descent (BCD)-based optimization algorithm. Finally, simulation results demonstrate the superiority of the proposed resource allocation policies. Full article

(This article belongs to the Special Issue New Paradigms in Cyber-Physical Social Sensing)

► Show Figures

Figure 1

20 pages, 2249 KiB

Open AccessArticle

MEMS IMU Error Mitigation Using Rotation Modulation Technique

by Shuang Du, Wei Sun and Yang Gao

Sensors 2016, 16(12), 2017; https://doi.org/10.3390/s16122017 - 29 Nov 2016

Cited by 46 | Viewed by 10349

Abstract

Micro-electro-mechanical-systems (MEMS) inertial measurement unit (IMU) outputs are corrupted by significant sensor errors. The navigation errors of a MEMS-based inertial navigation system will therefore accumulate very quickly over time. This requires aiding from other sensors such as Global Navigation Satellite Systems (GNSS). However, [...] Read more.

Micro-electro-mechanical-systems (MEMS) inertial measurement unit (IMU) outputs are corrupted by significant sensor errors. The navigation errors of a MEMS-based inertial navigation system will therefore accumulate very quickly over time. This requires aiding from other sensors such as Global Navigation Satellite Systems (GNSS). However, it will still remain a significant challenge in the presence of GNSS outages, which are typically in urban canopies. This paper proposed a rotary inertial navigation system (INS) to mitigate navigation errors caused by MEMS inertial sensor errors when external aiding information is not available. A rotary INS is an inertial navigator in which the IMU is installed on a rotation platform. Application of proper rotation schemes can effectively cancel and reduce sensor errors. A rotary INS has the potential to significantly increase the time period that INS can bridge GNSS outages and make MEMS IMU possible to maintain longer autonomous navigation performance when there is no external aiding. In this research, several IMU rotation schemes (rotation about X-, Y- and Z-axes) are analyzed to mitigate the navigation errors caused by MEMS IMU sensor errors. As the IMU rotation induces additional sensor errors, a calibration process is proposed to remove the induced errors. Tests are further conducted with two MEMS IMUs installed on a tri-axial rotation table to verify the error mitigation by IMU rotations. Full article

(This article belongs to the Special Issue Inertial Sensors and Systems 2016)

► Show Figures

Figure 1

15 pages, 2146 KiB

Open AccessArticle

A Pilot Study of Individual Muscle Force Prediction during Elbow Flexion and Extension in the Neurorehabilitation Field

by Jiateng Hou, Yingfei Sun, Lixin Sun, Bingyu Pan, Zhipei Huang, Jiankang Wu and Zhiqiang Zhang

Sensors 2016, 16(12), 2018; https://doi.org/10.3390/s16122018 - 29 Nov 2016

Cited by 18 | Viewed by 7833

Abstract

This paper proposes a neuromusculoskeletal (NMS) model to predict individual muscle force during elbow flexion and extension. Four male subjects were asked to do voluntary elbow flexion and extension. An inertial sensor and surface electromyography (sEMG) sensors were attached to subject's forearm. Joint [...] Read more.

This paper proposes a neuromusculoskeletal (NMS) model to predict individual muscle force during elbow flexion and extension. Four male subjects were asked to do voluntary elbow flexion and extension. An inertial sensor and surface electromyography (sEMG) sensors were attached to subject's forearm. Joint angle calculated by fusion of acceleration and angular rate using an extended Kalman filter (EKF) and muscle activations obtained from the sEMG signals were taken as the inputs of the proposed NMS model to determine individual muscle force. The result shows that our NMS model can predict individual muscle force accurately, with the ability to reflect subject-specific joint dynamics and neural control solutions. Our method incorporates sEMG and motion data, making it possible to get a deeper understanding of neurological, physiological, and anatomical characteristics of human dynamic movement. We demonstrate the potential of the proposed NMS model for evaluating the function of upper limb movements in the field of neurorehabilitation. Full article

(This article belongs to the Special Issue Sensors and Analytics for Precision Medicine)

► Show Figures

Figure 1

14 pages, 6665 KiB

Open AccessArticle

A Novel Gravity Compensation Method for High Precision Free-INS Based on “Extreme Learning Machine”

by Xiao Zhou, Gongliu Yang, Qingzhong Cai and Jing Wang

Sensors 2016, 16(12), 2019; https://doi.org/10.3390/s16122019 - 29 Nov 2016

Cited by 13 | Viewed by 5181

Abstract

In recent years, with the emergency of high precision inertial sensors (accelerometers and gyros), gravity compensation has become a major source influencing the navigation accuracy in inertial navigation systems (INS), especially for high-precision INS. This paper presents preliminary results concerning the effect of [...] Read more.

In recent years, with the emergency of high precision inertial sensors (accelerometers and gyros), gravity compensation has become a major source influencing the navigation accuracy in inertial navigation systems (INS), especially for high-precision INS. This paper presents preliminary results concerning the effect of gravity disturbance on INS. Meanwhile, this paper proposes a novel gravity compensation method for high-precision INS, which estimates the gravity disturbance on the track using the extreme learning machine (ELM) method based on measured gravity data on the geoid and processes the gravity disturbance to the height where INS has an upward continuation, then compensates the obtained gravity disturbance into the error equations of INS to restrain the INS error propagation. The estimation accuracy of the gravity disturbance data is verified by numerical tests. The root mean square error (RMSE) of the ELM estimation method can be improved by 23% and 44% compared with the bilinear interpolation method in plain and mountain areas, respectively. To further validate the proposed gravity compensation method, field experiments with an experimental vehicle were carried out in two regions. Test 1 was carried out in a plain area and Test 2 in a mountain area. The field experiment results also prove that the proposed gravity compensation method can significantly improve the positioning accuracy. During the 2-h field experiments, the positioning accuracy can be improved by 13% and 29% respectively, in Tests 1 and 2, when the navigation scheme is compensated by the proposed gravity compensation method. Full article

(This article belongs to the Special Issue Inertial Sensors and Systems 2016)

► Show Figures

Figure 1

13 pages, 8487 KiB

Open AccessArticle

Three-Dimensional Continuous Displacement Measurement with Temporal Speckle Pattern Interferometry

by Jie Qin, Zhan Gao, Xu Wang and Shanwei Yang

Sensors 2016, 16(12), 2020; https://doi.org/10.3390/s16122020 - 29 Nov 2016

Cited by 28 | Viewed by 5945

Abstract

A speckle interferometer which can measure whole field three-dimensional displacements continuously and dynamically has been built. Three different wavelength lasers are used to produce the speckle interferograms of the two in-plane displacements (displacements in the x- and y-direction) and one out-of-plane [...] Read more.

A speckle interferometer which can measure whole field three-dimensional displacements continuously and dynamically has been built. Three different wavelength lasers are used to produce the speckle interferograms of the two in-plane displacements (displacements in the x- and y-direction) and one out-of-plane displacement (displacement in the z-direction), respectively. One color CCD camera is employed to collect these mixed speckle interferograms simultaneously. The mixed interferograms are separated by the Red, Green and Blue channels of the color CCD camera, and then are processed by the wavelet transform technique to extract the phase information of the measured object. The preliminary experiment is carried out to demonstrate the performance of this new device. Full article

(This article belongs to the Section Physical Sensors)

► Show Figures

Figure 1

16 pages, 917 KiB

Open AccessArticle

Market Model for Resource Allocation in Emerging Sensor Networks with Reinforcement Learning

by Yue Zhang, Bin Song, Ying Zhang, Xiaojiang Du and Mohsen Guizani

Sensors 2016, 16(12), 2021; https://doi.org/10.3390/s16122021 - 29 Nov 2016

Cited by 3 | Viewed by 5909

Abstract

Emerging sensor networks (ESNs) are an inevitable trend with the development of the Internet of Things (IoT), and intend to connect almost every intelligent device. Therefore, it is critical to study resource allocation in such an environment, due to the concern of efficiency, [...] Read more.

Emerging sensor networks (ESNs) are an inevitable trend with the development of the Internet of Things (IoT), and intend to connect almost every intelligent device. Therefore, it is critical to study resource allocation in such an environment, due to the concern of efficiency, especially when resources are limited. By viewing ESNs as multi-agent environments, we model them with an agent-based modelling (ABM) method and deal with resource allocation problems with market models, after describing users’ patterns. Reinforcement learning methods are introduced to estimate users’ patterns and verify the outcomes in our market models. Experimental results show the efficiency of our methods, which are also capable of guiding topology management. Full article

(This article belongs to the Special Issue Topology Control in Emerging Sensor Networks)

► Show Figures

Figure 1

14 pages, 2704 KiB

Open AccessArticle

Error Analysis and Experimental Study of a Bi-Planar Parallel Mechanism in a Pedicle Screw Robot System

by Qingjuan Duan, Zhijiang Du, Hongjian Yu, Yongfeng Wang and Wei Dong

Sensors 2016, 16(12), 2022; https://doi.org/10.3390/s16122022 - 30 Nov 2016

Cited by 4 | Viewed by 6502

Abstract

Due to the urgent need for high precision surgical equipment for minimally invasive spinal surgery, a novel robot-assistant system was developed for the accurate placement of pedicle screws in lumbar spinal surgeries. The structure of the robot was based on a macro-micro mechanism, [...] Read more.

Due to the urgent need for high precision surgical equipment for minimally invasive spinal surgery, a novel robot-assistant system was developed for the accurate placement of pedicle screws in lumbar spinal surgeries. The structure of the robot was based on a macro-micro mechanism, which includes a serial mechanism (macro part) and a bi-planar 5R parallel mechanism (micro part). The macro part was used to achieve a large workspace, while the micro part was used to obtain high stiffness and accuracy. Based on the transfer function of dimension errors, the factors affecting the accuracy of the end effectors were analyzed. Then the manufacturing errors and joint angle error on the position-stance of the end effectors were investigated. Eventually, the mechanism of the strain energy produced by the deformation of linkage via forced assembly and displacements of the output point were calculated. The amount of the transfer errors was quantitatively analyzed by the simulation. Experimental tests show that the error of the bi-planar 5R mechanism can be controlled no more than 1 mm for translation and 1° for rotation, which satisfies the required absolute position accuracy of the robot. Full article

(This article belongs to the Special Issue Advanced Robotics and Mechatronics Devices)

► Show Figures

Figure 1

11 pages, 3471 KiB

Open AccessArticle

One-Step Fabrication of Microchannels with Integrated Three Dimensional Features by Hot Intrusion Embossing

by Mike Debono, Dan Voicu, Mohammad Pousti, Muhammad Safdar, Robert Young, Eugenia Kumacheva and Jesse Greener

Sensors 2016, 16(12), 2023; https://doi.org/10.3390/s16122023 - 29 Nov 2016

Cited by 14 | Viewed by 6104

Abstract

We build on the concept of hot intrusion embossing to develop a one-step fabrication method for thermoplastic microfluidic channels containing integrated three-dimensional features. This was accomplished with simple, rapid-to-fabricate imprint templates containing microcavities that locally control the intrusion of heated thermoplastic based on [...] Read more.

We build on the concept of hot intrusion embossing to develop a one-step fabrication method for thermoplastic microfluidic channels containing integrated three-dimensional features. This was accomplished with simple, rapid-to-fabricate imprint templates containing microcavities that locally control the intrusion of heated thermoplastic based on their cross-sectional geometries. The use of circular, rectangular and triangular cavity geometries was demonstrated for the purposes of forming posts, multi-focal length microlense arrays, walls, steps, tapered features and three-dimensional serpentine microchannels. Process variables, such as temperature and pressure, controlled feature dimensions without affecting the overall microchannel geometry. The approach was demonstrated for polycarbonate, cycloolefin copolymer and polystyrene, but in principle is applicable to any thermoplastic. The approach is a step forward towards rapid fabrication of complex, robust, microfluidic platforms with integrated multi-functional elements. Full article

(This article belongs to the Special Issue Microfluidics-Based Microsystem Integration Research)

► Show Figures

Figure 1

8 pages, 3845 KiB

Open AccessArticle

SAW Humidity Sensor Sensitivity Enhancement via Electrospraying of Silver Nanowires

by Farid Sayar Irani and Bahadir Tunaboylu

Sensors 2016, 16(12), 2024; https://doi.org/10.3390/s16122024 - 30 Nov 2016

Cited by 17 | Viewed by 6588

Abstract

In this research, we investigated the influence of the surface coatings of silver nanowires on the sensitivity of surface acoustic wave (SAW) humidity sensors. Silver nanowires, with poly(vinylpyrrolidone) (PVP), which is a hydrophilic capping agent, were chemically synthesized, with an average length of [...] Read more.

In this research, we investigated the influence of the surface coatings of silver nanowires on the sensitivity of surface acoustic wave (SAW) humidity sensors. Silver nanowires, with poly(vinylpyrrolidone) (PVP), which is a hydrophilic capping agent, were chemically synthesized, with an average length of 15 µm and an average diameter of 60 nm. Humidity sensors, with 433 MHz frequency dual-port resonator Rayleigh-SAW devices, were coated by silver nanowires (AgNWs) using the electrospray coating method. It was demonstrated that increasing thickness of coated AgNW on the surfaces of SAW devices results in increased sensitivity. The highest frequency shift (262 kHz) in these SAW devices was obtained with an injection of 0.5 mL of the AgNW solution with a concentration of 0.5 mg/mL at an injection rate of 1 mL/h. It also showed the highest humidity sensitivity among the other prepared SAW devices. Full article

(This article belongs to the Special Issue Gas Nanosensors)

► Show Figures

Figure 1

18 pages, 6081 KiB

Open AccessArticle

Short-Range Vital Signs Sensing Based on EEMD and CWT Using IR-UWB Radar

by Xikun Hu and Tian Jin

Sensors 2016, 16(12), 2025; https://doi.org/10.3390/s16122025 - 30 Nov 2016

Cited by 103 | Viewed by 14034

Abstract

The radar sensor described realizes healthcare monitoring capable of detecting subject chest-wall movement caused by cardiopulmonary activities and wirelessly estimating the respiration and heartbeat rates of the subject without attaching any devices to the body. Conventional single-tone Doppler radar can only capture Doppler [...] Read more.

The radar sensor described realizes healthcare monitoring capable of detecting subject chest-wall movement caused by cardiopulmonary activities and wirelessly estimating the respiration and heartbeat rates of the subject without attaching any devices to the body. Conventional single-tone Doppler radar can only capture Doppler signatures because of a lack of bandwidth information with noncontact sensors. In contrast, we take full advantage of impulse radio ultra-wideband (IR-UWB) radar to achieve low power consumption and convenient portability, with a flexible detection range and desirable accuracy. A noise reduction method based on improved ensemble empirical mode decomposition (EEMD) and a vital sign separation method based on the continuous-wavelet transform (CWT) are proposed jointly to improve the signal-to-noise ratio (SNR) in order to acquire accurate respiration and heartbeat rates. Experimental results illustrate that respiration and heartbeat signals can be extracted accurately under different conditions. This noncontact healthcare sensor system proves the commercial feasibility and considerable accessibility of using compact IR-UWB radar for emerging biomedical applications. Full article

(This article belongs to the Special Issue Sensing Technology for Healthcare System)

► Show Figures

Figure 1

11 pages, 5335 KiB

Open AccessArticle

A Fiber-Optic Sensor for Acoustic Emission Detection in a High Voltage Cable System

by Tongzhi Zhang, Fufei Pang, Huanhuan Liu, Jiajing Cheng, Longbao Lv, Xiaobei Zhang, Na Chen and Tingyun Wang

Sensors 2016, 16(12), 2026; https://doi.org/10.3390/s16122026 - 30 Nov 2016

Cited by 83 | Viewed by 10991

Abstract

We have proposed and demonstrated a Michelson interferometer-based fiber sensor for detecting acoustic emission generated from the partial discharge (PD) of the accessories of a high-voltage cable system. The developed sensor head is integrated with a compact and relatively high sensitivity cylindrical elastomer. [...] Read more.

We have proposed and demonstrated a Michelson interferometer-based fiber sensor for detecting acoustic emission generated from the partial discharge (PD) of the accessories of a high-voltage cable system. The developed sensor head is integrated with a compact and relatively high sensitivity cylindrical elastomer. Such a sensor has a broadband frequency response and a relatively high sensitivity in a harsh environment under a high-voltage electric field. The design and fabrication of the sensor head integrated with the cylindrical elastomer is described, and a series of experiments was conducted to evaluate the sensing performance. The experimental results demonstrate that the sensitivity of our developed sensor for acoustic detection of partial discharges is 1.7

rad / (m \cdot Pa)

. A high frequency response up to 150 kHz is achieved. Moreover, the relatively high sensitivity for the detection of PD is verified in both the laboratory environment and gas insulated switchgear. The obtained results show the great potential application of a Michelson interferometer-based fiber sensor integrated with a cylindrical elastomer for in-situ monitoring high-voltage cable accessories for safety work. Full article

(This article belongs to the Section Physical Sensors)

► Show Figures

Figure 1

15 pages, 3567 KiB

Open AccessArticle

A Multi-Pumping Flow System for In Situ Measurements of Dissolved Manganese in Aquatic Systems

by David Meyer, Ralf D. Prien, Olaf Dellwig, Joanna J. Waniek, Ingo Schuffenhauer, Jan Donath, Siegfried Krüger, Malte Pallentin and Detlef E. Schulz-Bull

Sensors 2016, 16(12), 2027; https://doi.org/10.3390/s16122027 - 30 Nov 2016

Cited by 11 | Viewed by 6086

Abstract

A METals In Situ analyzer (METIS) has been used to determine dissolved manganese (II) concentrations in the subhalocline waters of the Gotland Deep (central Baltic Sea). High-resolution in situ measurements of total dissolved Mn were obtained in near real-time by spectrophotometry using 1-(2-pyridylazo)-2-naphthol [...] Read more.

A METals In Situ analyzer (METIS) has been used to determine dissolved manganese (II) concentrations in the subhalocline waters of the Gotland Deep (central Baltic Sea). High-resolution in situ measurements of total dissolved Mn were obtained in near real-time by spectrophotometry using 1-(2-pyridylazo)-2-naphthol (PAN). PAN is a complexing agent of dissolved Mn and forms a wine-red complex with a maximum absorbance at a wavelength of 562 nm. Results are presented together with ancillary temperature, salinity, and dissolved O

_{2}

data. Lab calibration of the analyzer was performed in a pressure testing tank. A detection limit of 77 nM was obtained. For validation purposes, discrete water samples were taken by using a pump-CTD system. Dissolved Mn in these samples was determined by an independent laboratory based method (inductively coupled plasma–optical emission spectrometry, ICP-OES). Mn measurements from both METIS and ICP-OES analysis were in good agreement. The results showed that the in situ analysis of dissolved Mn is a powerful technique reducing dependencies on heavy and expensive equipment (pump-CTD system, ICP-OES) and is also cost and time effective. Full article

(This article belongs to the Special Issue Colorimetric and Fluorescent Sensor)

► Show Figures

Figure 1

24 pages, 1541 KiB

Open AccessReview

Enabling Smart Air Conditioning by Sensor Development: A Review

by Chin-Chi Cheng and Dasheng Lee

Sensors 2016, 16(12), 2028; https://doi.org/10.3390/s16122028 - 30 Nov 2016

Cited by 33 | Viewed by 11398

Abstract

The study investigates the development of sensors, in particular the use of thermo-fluidic sensors and occupancy detectors, to achieve smart operation of air conditioning systems. Smart operation refers to the operation of air conditioners by the reinforcement of interaction to achieve both thermal [...] Read more.

The study investigates the development of sensors, in particular the use of thermo-fluidic sensors and occupancy detectors, to achieve smart operation of air conditioning systems. Smart operation refers to the operation of air conditioners by the reinforcement of interaction to achieve both thermal comfort and energy efficiency. Sensors related to thermal comfort include those of temperature, humidity, and pressure and wind velocity anemometers. Improvements in their performance in the past years have been studied by a literature survey. Traditional occupancy detection using passive infra-red (PIR) sensors and novel methodologies using smartphones and wearable sensors are both discussed. Referring to the case studies summarized in this study, air conditioning energy savings are evaluated quantitatively. Results show that energy savings of air conditioners before 2000 was 11%, and 30% after 2000 by the integration of thermo-fluidic sensors and occupancy detectors. By utilizing wearable sensing to detect the human motions, metabolic rates and related information, the energy savings can reach up to 46.3% and keep the minimum change of predicted mean vote (∆PMV→0), which means there is no compromise in thermal comfort. This enables smart air conditioning to compensate for the large variations from person to person in terms of physiological and psychological satisfaction, and find an optimal temperature for everyone in a given space. However, this tendency should be evidenced by more experimental results in the future. Full article

(This article belongs to the Section Physical Sensors)

► Show Figures

Figure 1

18 pages, 4857 KiB

Open AccessArticle

Uniformly Porous Nanocrystalline CaMgFe_1.33Ti₃O₁₂ Ceramic Derived Electro-Ceramic Nanocomposite for Impedance Type Humidity Sensor

by Ashis Tripathy, Sumit Pramanik, Ayan Manna, Hanie Nadia Shasmin, Zamri Radzi and Noor Azuan Abu Osman

Sensors 2016, 16(12), 2029; https://doi.org/10.3390/s16122029 - 30 Nov 2016

Cited by 20 | Viewed by 6296

Abstract

Since humidity sensors have been widely used in many sectors, a suitable humidity sensing material with improved sensitivity, faster response and recovery times, better stability and low hysteresis is necessary to be developed. Here, we fabricate a uniformly porous humidity sensor using Ca, [...] Read more.

Since humidity sensors have been widely used in many sectors, a suitable humidity sensing material with improved sensitivity, faster response and recovery times, better stability and low hysteresis is necessary to be developed. Here, we fabricate a uniformly porous humidity sensor using Ca, Ti substituted Mg ferrites with chemical formula of CaMgFe_1.33Ti₃O₁₂ as humidity sensing materials by solid-sate step-sintering technique. This synthesis technique is useful to control the grain size with increased porosity to enhance the hydrophilic characteristics of the CaMgFe_1.33Ti₃O₁₂ nanoceramic based sintered electro-ceramic nanocomposites. The highest porosity, lowest density and excellent surface-hydrophilicity properties were obtained at 1050 °C sintered ceramic. The performance of this impedance type humidity sensor was evaluated by electrical characterizations using alternating current (AC) in the 33%–95% relative humidity (RH) range at 25 °C. Compared with existing conventional resistive humidity sensors, the present sintered electro-ceramic nanocomposite based humidity sensor showed faster response time (20 s) and recovery time (40 s). This newly developed sensor showed extremely high sensitivity (%S) and small hysteresis of <3.4%. Long-term stability of the sensor had been determined by testing for 30 consecutive days. Therefore, the high performance sensing behavior of the present electro-ceramic nanocomposites would be suitable for a potential use in advanced humidity sensors. Full article

(This article belongs to the Section Physical Sensors)

► Show Figures

Figure 1

19 pages, 7325 KiB

Open AccessArticle

A Context-Recognition-Aided PDR Localization Method Based on the Hidden Markov Model

by Yi Lu, Dongyan Wei, Qifeng Lai, Wen Li and Hong Yuan

Sensors 2016, 16(12), 2030; https://doi.org/10.3390/s16122030 - 30 Nov 2016

Cited by 19 | Viewed by 6471

Abstract

Indoor positioning has recently become an important field of interest because global navigation satellite systems (GNSS) are usually unavailable in indoor environments. Pedestrian dead reckoning (PDR) is a promising localization technique for indoor environments since it can be implemented on widely used smartphones [...] Read more.

Indoor positioning has recently become an important field of interest because global navigation satellite systems (GNSS) are usually unavailable in indoor environments. Pedestrian dead reckoning (PDR) is a promising localization technique for indoor environments since it can be implemented on widely used smartphones equipped with low cost inertial sensors. However, the PDR localization severely suffers from the accumulation of positioning errors, and other external calibration sources should be used. In this paper, a context-recognition-aided PDR localization model is proposed to calibrate PDR. The context is detected by employing particular human actions or characteristic objects and it is matched to the context pre-stored offline in the database to get the pedestrian’s location. The Hidden Markov Model (HMM) and Recursive Viterbi Algorithm are used to do the matching, which reduces the time complexity and saves the storage. In addition, the authors design the turn detection algorithm and take the context of corner as an example to illustrate and verify the proposed model. The experimental results show that the proposed localization method can fix the pedestrian’s starting point quickly and improves the positioning accuracy of PDR by 40.56% at most with perfect stability and robustness at the same time. Full article

(This article belongs to the Special Issue Scalable Localization in Wireless Sensor Networks)

► Show Figures

Figure 1

15 pages, 1202 KiB

Open AccessArticle

Evaluation of a Tracking System for Patients and Mixed Intravenous Medication Based on RFID Technology

by María Martínez Pérez, Guillermo Vázquez González and Carlos Dafonte

Sensors 2016, 16(12), 2031; https://doi.org/10.3390/s16122031 - 30 Nov 2016

Cited by 22 | Viewed by 6672

Abstract

At present, one of the primary concerns of healthcare professionals is how to increase the safety and quality of the care that patients receive during their stay in hospital. This is particularly important in the administration of expensive and high-risk medicines with which [...] Read more.

At present, one of the primary concerns of healthcare professionals is how to increase the safety and quality of the care that patients receive during their stay in hospital. This is particularly important in the administration of expensive and high-risk medicines with which it is fundamental to minimize the possibility of adverse events in the process of prescription-validation-preparation/dosage-dispensation-administration of intravenous mixes. This work is a detailed analysis of the evaluation, carried out by the health personnel involved in the Radiofrequency Identification (RFID) system developed in the Day Hospital and Pharmacy services of the Complejo Hospitalario Universitario A Coruña (CHUAC). The RFID system is evaluated by analyzing surveys completed by said health personnel, since their questions represent the key indicators of the patient care process (safety, cost, adequacy with the clinical practice). This work allows us to conclude, among other things, that the system tracks the patients satisfactorily and that its cost, though high, is justified in the context of the project context (use of dangerous and costly medication). Full article

(This article belongs to the Special Issue Selected Papers from UCAmI, IWAAL and AmIHEALTH 2015)

► Show Figures

Figure 1

21 pages, 3048 KiB

Open AccessArticle

A Routing Protocol for Multisink Wireless Sensor Networks in Underground Coalmine Tunnels

by Xu Xia, Zhigang Chen, Hui Liu, Huihui Wang and Feng Zeng

Sensors 2016, 16(12), 2032; https://doi.org/10.3390/s16122032 - 30 Nov 2016

Cited by 19 | Viewed by 5788

Abstract

Traditional underground coalmine monitoring systems are mainly based on the use of wired transmission. However, when cables are damaged during an accident, it is difficult to obtain relevant data on environmental parameters and the emergency situation underground. To address this problem, the use [...] Read more.

Traditional underground coalmine monitoring systems are mainly based on the use of wired transmission. However, when cables are damaged during an accident, it is difficult to obtain relevant data on environmental parameters and the emergency situation underground. To address this problem, the use of wireless sensor networks (WSNs) has been proposed. However, the shape of coalmine tunnels is not conducive to the deployment of WSNs as they are long and narrow. Therefore, issues with the network arise, such as extremely large energy consumption, very weak connectivity, long time delays, and a short lifetime. To solve these problems, in this study, a new routing protocol algorithm for multisink WSNs based on transmission power control is proposed. First, a transmission power control algorithm is used to negotiate the optimal communication radius and transmission power of each sink. Second, the non-uniform clustering idea is adopted to optimize the cluster head selection. Simulation results are subsequently compared to the Centroid of the Nodes in a Partition (CNP) strategy and show that the new algorithm delivers a good performance: power efficiency is increased by approximately 70%, connectivity is increased by approximately 15%, the cluster interference is diminished by approximately 50%, the network lifetime is increased by approximately 6%, and the delay is reduced with an increase in the number of sinks. Full article

(This article belongs to the Special Issue Enabling the Move from Wireless Sensor Networks to Internet of Things and Cyber-Physical Systems)

► Show Figures

Figure 1

7 pages, 1481 KiB

Open AccessCommunication

Label-Free Detection of Human Glycoprotein (CgA) Using an Extended-Gated Organic Transistor-Based Immunosensor

by Tsukuru Minamiki, Tsuyoshi Minami, Yui Sasaki, Shin-ichi Wakida, Ryoji Kurita, Osamu Niwa and Shizuo Tokito

Sensors 2016, 16(12), 2033; https://doi.org/10.3390/s16122033 - 30 Nov 2016

Cited by 35 | Viewed by 8270

Abstract

Herein, we report on the fabrication of an extended-gated organic field-effect transistor (OFET)-based immunosensor and its application in the detection of human chromogranin A (hCgA). The fabricated OFET device possesses an extended-gate electrode immobilized with an anti-CgA antibody. The titration results of hCgA [...] Read more.

Herein, we report on the fabrication of an extended-gated organic field-effect transistor (OFET)-based immunosensor and its application in the detection of human chromogranin A (hCgA). The fabricated OFET device possesses an extended-gate electrode immobilized with an anti-CgA antibody. The titration results of hCgA showed that the electrical changes in the OFET characteristics corresponded to the glycoprotein recognition ability of the monoclonal antibody (anti-CgA). The observed sensitivity (detection limit: 0.11 µg/mL) and selectivity indicate that the OFET-based immunosensor can be potentially applied to the rapid detection of the glycoprotein concentration without any labeling. Full article

(This article belongs to the Special Issue Sensors for Glycoproteins and Glycated Proteins)

► Show Figures

Graphical abstract

15 pages, 12026 KiB

Open AccessArticle

A Multipurpose CMOS Platform for Nanosensing

by Alberto Bonanno, Alessandro Sanginario, Simone L. Marasso, Beatrice Miccoli, Katarzyna Bejtka, Simone Benetto and Danilo Demarchi

Sensors 2016, 16(12), 2034; https://doi.org/10.3390/s16122034 - 30 Nov 2016

Cited by 8 | Viewed by 6223

Abstract

This paper presents a customizable sensing system based on functionalized nanowires (NWs) assembled onto complementary metal oxide semiconductor (CMOS) technology. The Micro-for-Nano (M4N) chip integrates on top of the electronics an array of aluminum microelectrodes covered with gold by means of a customized [...] Read more.

This paper presents a customizable sensing system based on functionalized nanowires (NWs) assembled onto complementary metal oxide semiconductor (CMOS) technology. The Micro-for-Nano (M4N) chip integrates on top of the electronics an array of aluminum microelectrodes covered with gold by means of a customized electroless plating process. The NW assembly process is driven by an array of on-chip dielectrophoresis (DEP) generators, enabling a custom layout of different nanosensors on the same microelectrode array. The electrical properties of each assembled NW are singularly sensed through an in situ CMOS read-out circuit (ROC) that guarantees a low noise and reliable measurement. The M4N chip is directly connected to an external microcontroller for configuration and data processing. The processed data are then redirected to a workstation for real-time data visualization and storage during sensing experiments. As proof of concept, ZnO nanowires have been integrated onto the M4N chip to validate the approach that enables different kind of sensing experiments. The device has been then irradiated by an external UV source with adjustable power to measure the ZnO sensitivity to UV-light exposure. A maximum variation of about 80% of the ZnO-NW resistance has been detected by the M4N system when the assembled 5

μ

m × 500 nm single ZnO-NW is exposed to an estimated incident radiant UV-light flux in the range of 1 nW–229 nW. The performed experiments prove the efficiency of the platform conceived for exploiting any kind of material that can change its capacitance and/or resistance due to an external stimulus. Full article

(This article belongs to the Special Issue System-Integrated Intelligence and Intelligent Systems)

► Show Figures

Figure 1

15 pages, 9434 KiB

Open AccessArticle

Neuron Stimulation Device Integrated with Silicon Nanowire-Based Photodetection Circuit on a Flexible Substrate

by Suk Won Jung, Jong Yoon Shin, Kilwha Pi, Yong Sook Goo and Dong-il “Dan” Cho

Sensors 2016, 16(12), 2035; https://doi.org/10.3390/s16122035 - 1 Dec 2016

Cited by 12 | Viewed by 7783

Abstract

This paper proposes a neural stimulation device integrated with a silicon nanowire (SiNW)-based photodetection circuit for the activation of neurons with light. The proposed device is comprised of a voltage divider and a current driver in which SiNWs are used as photodetector and [...] Read more.

This paper proposes a neural stimulation device integrated with a silicon nanowire (SiNW)-based photodetection circuit for the activation of neurons with light. The proposed device is comprised of a voltage divider and a current driver in which SiNWs are used as photodetector and field-effect transistors; it has the functions of detecting light, generating a stimulation signal in proportion to the light intensity, and transmitting the signal to a micro electrode. To show the applicability of the proposed neural stimulation device as a high-resolution retinal prosthesis system, a high-density neural stimulation device with a unit cell size of

110 \times 110 μ m

and a resolution of

32 \times 32

was fabricated on a flexible film with a thickness of approximately 50 μm. Its effectiveness as a retinal stimulation device was then evaluated using a unit cell in an in vitro animal experiment involving the retinal tissue of retinal Degeneration 1 (rd1) mice. Experiments wherein stimulation pulses were applied to the retinal tissues successfully demonstrate that the number of spikes in neural response signals increases in proportion to light intensity. Full article

(This article belongs to the Special Issue Optical Methods in Sensing and Imaging for Medical and Biological Applications)

► Show Figures

Figure 1

16 pages, 5286 KiB

Open AccessArticle

Trend-Residual Dual Modeling for Detection of Outliers in Low-Cost GPS Trajectories

by Xiaojian Chen, Tingting Cui, Jianhong Fu, Jianwei Peng and Jie Shan

Sensors 2016, 16(12), 2036; https://doi.org/10.3390/s16122036 - 1 Dec 2016

Cited by 11 | Viewed by 6366

Abstract

Low-cost GPS (receiver) has become a ubiquitous and integral part of our daily life. Despite noticeable advantages such as being cheap, small, light, and easy to use, its limited positioning accuracy devalues and hampers its wide applications for reliable mapping and analysis. Two [...] Read more.

Low-cost GPS (receiver) has become a ubiquitous and integral part of our daily life. Despite noticeable advantages such as being cheap, small, light, and easy to use, its limited positioning accuracy devalues and hampers its wide applications for reliable mapping and analysis. Two conventional techniques to remove outliers in a GPS trajectory are thresholding and Kalman-based methods, which are difficult in selecting appropriate thresholds and modeling the trajectories. Moreover, they are insensitive to medium and small outliers, especially for low-sample-rate trajectories. This paper proposes a model-based GPS trajectory cleaner. Rather than examining speed and acceleration or assuming a pre-determined trajectory model, we first use cubic smooth spline to adaptively model the trend of the trajectory. The residuals, i.e., the differences between the trend and GPS measurements, are then further modeled by time series method. Outliers are detected by scoring the residuals at every GPS trajectory point. Comparing to the conventional procedures, the trend-residual dual modeling approach has the following features: (a) it is able to model trajectories and detect outliers adaptively; (b) only one critical value for outlier scores needs to be set; (c) it is able to robustly detect unapparent outliers; and (d) it is effective in cleaning outliers for GPS trajectories with low sample rates. Tests are carried out on three real-world GPS trajectories datasets. The evaluation demonstrates an average of 9.27 times better performance in outlier detection for GPS trajectories than thresholding and Kalman-based techniques. Full article

(This article belongs to the Section Remote Sensors)

► Show Figures

Figure 1

9 pages, 4337 KiB

Open AccessArticle

Dielectrically-Loaded Cylindrical Resonator-Based Wireless Passive High-Temperature Sensor

by Jijun Xiong, Guozhu Wu, Qiulin Tan, Tanyong Wei, Dezhi Wu, Sanmin Shen, Helei Dong and Wendong Zhang

Sensors 2016, 16(12), 2037; https://doi.org/10.3390/s16122037 - 1 Dec 2016

Cited by 31 | Viewed by 6577

Abstract

The temperature sensor presented in this paper is based on a microwave dielectric resonator, which uses alumina ceramic as a substrate to survive in harsh environments. The resonant frequency of the resonator is determined by the relative permittivity of the alumina ceramic, which [...] Read more.

The temperature sensor presented in this paper is based on a microwave dielectric resonator, which uses alumina ceramic as a substrate to survive in harsh environments. The resonant frequency of the resonator is determined by the relative permittivity of the alumina ceramic, which monotonically changes with temperature. A rectangular aperture etched on the surface of the resonator works as both an incentive and a coupling device. A broadband slot antenna fed by a coplanar waveguide is utilized as an interrogation antenna to wirelessly detect the sensor signal using a radio-frequency backscattering technique. Theoretical analysis, software simulation, and experiments verified the feasibility of this temperature-sensing system. The sensor was tested in a metal-enclosed environment, which severely interferes with the extraction of the sensor signal. Therefore, frequency-domain compensation was introduced to filter the background noise and improve the signal-to-noise ratio of the sensor signal. The extracted peak frequency was found to monotonically shift from 2.441 to 2.291 GHz when the temperature was varied from 27 to 800 °C, leading to an average absolute sensitivity of 0.19 MHz/°C. Full article

(This article belongs to the Special Issue Resonator Sensors)

► Show Figures

Figure 1

32 pages, 9091 KiB

Open AccessArticle

A Framework to Implement IoT Network Performance Modelling Techniques for Network Solution Selection

by Declan T. Delaney and Gregory M. P. O’Hare

Sensors 2016, 16(12), 2038; https://doi.org/10.3390/s16122038 - 1 Dec 2016

Cited by 10 | Viewed by 6532

Abstract

No single network solution for Internet of Things (IoT) networks can provide the required level of Quality of Service (QoS) for all applications in all environments. This leads to an increasing number of solutions created to fit particular scenarios. Given the increasing number [...] Read more.

No single network solution for Internet of Things (IoT) networks can provide the required level of Quality of Service (QoS) for all applications in all environments. This leads to an increasing number of solutions created to fit particular scenarios. Given the increasing number and complexity of solutions available, it becomes difficult for an application developer to choose the solution which is best suited for an application. This article introduces a framework which autonomously chooses the best solution for the application given the current deployed environment. The framework utilises a performance model to predict the expected performance of a particular solution in a given environment. The framework can then choose an apt solution for the application from a set of available solutions. This article presents the framework with a set of models built using data collected from simulation. The modelling technique can determine with up to 85% accuracy the solution which performs the best for a particular performance metric given a set of solutions. The article highlights the fractured and disjointed practice currently in place for examining and comparing communication solutions and aims to open a discussion on harmonising testing procedures so that different solutions can be directly compared and offers a framework to achieve this within IoT networks. Full article

(This article belongs to the Special Issue Recent Advances in Sensor Technologies and Applications in the Web of Things (WoT))

► Show Figures

Figure 1

7 pages, 2501 KiB

Open AccessArticle

Tunable Multiple-Step Plasmonic Bragg Reflectors with Graphene-Based Modulated Grating

by Qinglu Qian, Youjian Liang, Yue Liang, Hongyan Shao, Menglai Zhang, Ting Xiao and Jicheng Wang

Sensors 2016, 16(12), 2039; https://doi.org/10.3390/s16122039 - 1 Dec 2016

Cited by 7 | Viewed by 5294

Abstract

We propose a novel plasmonic Bragg reflector (PBR) based on graphene with multiple-step silicon structure. The monolayer graphene bears locally variable optical properties by modulation of electric fields, and the periodical change of effective refractive index on graphene can be obtained by external [...] Read more.

We propose a novel plasmonic Bragg reflector (PBR) based on graphene with multiple-step silicon structure. The monolayer graphene bears locally variable optical properties by modulation of electric fields, and the periodical change of effective refractive index on graphene can be obtained by external bias voltage in the mid-infrared region. Through patterning the PBR units into multiple-step structures, we can decrease the insertion loss and suppress the rippling in transmission spectra. By introducing the defect into the multiple-step PBRs, the multiple resonance modes are formed inside the stopband by increasing the step number. This work may pave the ways for the further development of ultra-compact low-cost hyperspectral sensors in the mid-infrared region. Full article

(This article belongs to the Section Physical Sensors)

► Show Figures

Figure 1

9 pages, 2487 KiB

Open AccessArticle

Femtosecond Laser Ablated FBG with Composite Microstructure for Hydrogen Sensor Application

by Meng Zou, Yutang Dai, Xian Zhou, Ke Dong and Minghong Yang

Sensors 2016, 16(12), 2040; https://doi.org/10.3390/s16122040 - 1 Dec 2016

Cited by 13 | Viewed by 5371

Abstract

A composite microstructure in fiber Bragg grating (FBG) with film deposition for hydrogen detection is presented. Through ablated to FBG cladding by a femtosecond laser, straight-trenches and spiral micro-pits are formed. A Pd–Ag film is sputtered on the surface of the laser processed [...] Read more.

A composite microstructure in fiber Bragg grating (FBG) with film deposition for hydrogen detection is presented. Through ablated to FBG cladding by a femtosecond laser, straight-trenches and spiral micro-pits are formed. A Pd–Ag film is sputtered on the surface of the laser processed FBG single mode fiber, and acts as hydrogen sensing transducer. The demonstrated experimental outcomes show that a composite structure produced the highest sensitivity of 26.3 pm/%H, nearly sevenfold more sensitive compared with original standard FBG. It offers great potential in engineering applications for its good structure stability and sensitivity. Full article

(This article belongs to the Section Chemical Sensors)

► Show Figures

Figure 1

10 pages, 6031 KiB

Open AccessArticle

Manipulation and Immobilization of a Single Fluorescence Nanosensor for Selective Injection into Cells

by Hairulazwan Hashim, Hisataka Maruyama, Taisuke Masuda and Fumihito Arai

Sensors 2016, 16(12), 2041; https://doi.org/10.3390/s16122041 - 1 Dec 2016

Cited by 7 | Viewed by 6586

Abstract

Manipulation and injection of single nanosensors with high cell viability is an emerging field in cell analysis. We propose a new method using fluorescence nanosensors with a glass nanoprobe and optical control of the zeta potential. The nanosensor is fabricated by encapsulating a [...] Read more.

Manipulation and injection of single nanosensors with high cell viability is an emerging field in cell analysis. We propose a new method using fluorescence nanosensors with a glass nanoprobe and optical control of the zeta potential. The nanosensor is fabricated by encapsulating a fluorescence polystyrene nanobead into a lipid layer with 1,3,3-trimethylindolino-6′-nitrobenzopyrylospiran (SP), which is a photochromic material. The nanobead contains iron oxide nanoparticles and a temperature-sensitive fluorescent dye, Rhodamine B. The zeta potential of the nanosensor switches between negative and positive by photo-isomerization of SP with ultraviolet irradiation. The positively-charged nanosensor easily adheres to a negatively-charged glass nanoprobe, is transported to a target cell, and then adheres to the negatively-charged cell membrane. The nanosensor is then injected into the cytoplasm by heating with a near-infrared (NIR) laser. As a demonstration, a single 750 nm nanosensor was picked-up using a glass nanoprobe with optical control of the zeta potential. Then, the nanosensor was transported and immobilized onto a target cell membrane. Finally, it was injected into the cytoplasm using a NIR laser. The success rates of pick-up and cell immobilization of the nanosensor were 75% and 64%, respectively. Cell injection and cell survival rates were 80% and 100%, respectively. Full article

(This article belongs to the Section Chemical Sensors)

► Show Figures

Figure 1

16 pages, 3497 KiB

Open AccessArticle

Comparing ∆T_max Determination Approaches for Granier-Based Sapflow Estimations

by Inken Rabbel, Bernd Diekkrüger, Holm Voigt and Burkhard Neuwirth

Sensors 2016, 16(12), 2042; https://doi.org/10.3390/s16122042 - 1 Dec 2016

Cited by 32 | Viewed by 6670

Abstract

Granier-type thermal dissipation probes are common instruments for quantifying tree water use in forest hydrological studies. Estimating sapflow using Granier-type sapflow sensors requires determining the maximum temperature gradient (∆T_max) between the heated probe and the reference probe below. ∆T_max represents [...] Read more.

Granier-type thermal dissipation probes are common instruments for quantifying tree water use in forest hydrological studies. Estimating sapflow using Granier-type sapflow sensors requires determining the maximum temperature gradient (∆T_max) between the heated probe and the reference probe below. ∆T_max represents a state of zero sap flux, which was originally assumed to occur each night leading to a ∆T_max determination on a daily basis. However, researchers have proven that, under certain conditions, sapflow may continue throughout the night. Therefore alternative approaches to determining ∆T_max have been developed. Multiple ∆T_max approaches are now in use; however, sapflow estimates remain imprecise because the empirical equation that transfers the raw temperature signal (∆T) to sap flux density (F_d) is strongly sensitive to ∆T_max. In this study, we analyze the effects of different ∆T_max determination approaches on sub-daily, daily and (intra-)seasonal F_d estimations. On this basis, we quantify the uncertainty of sapflow calculations, which is related to the raw signal processing. We show that the ∆T_max determination procedure has a major influence on absolute ∆T_max values and the respective sap flux density computations. Consequently, the choice of the ∆T_max determination approach may be a significant source of uncertainty in sapflow estimations. Full article

(This article belongs to the Special Issue Sensors for Environmental Monitoring 2016)

► Show Figures

Figure 1

12 pages, 1714 KiB

Open AccessArticle

A Robust and Device-Free System for the Recognition and Classification of Elderly Activities

by Fangmin Li, Mohammed Abdulaziz Aide Al-qaness, Yong Zhang, Bihai Zhao and Xidao Luan

Sensors 2016, 16(12), 2043; https://doi.org/10.3390/s16122043 - 1 Dec 2016

Cited by 32 | Viewed by 6608

Abstract

Human activity recognition, tracking and classification is an essential trend in assisted living systems that can help support elderly people with their daily activities. Traditional activity recognition approaches depend on vision-based or sensor-based techniques. Nowadays, a novel promising technique has obtained more attention, [...] Read more.

Human activity recognition, tracking and classification is an essential trend in assisted living systems that can help support elderly people with their daily activities. Traditional activity recognition approaches depend on vision-based or sensor-based techniques. Nowadays, a novel promising technique has obtained more attention, namely device-free human activity recognition that neither requires the target object to wear or carry a device nor install cameras in a perceived area. The device-free technique for activity recognition uses only the signals of common wireless local area network (WLAN) devices available everywhere. In this paper, we present a novel elderly activities recognition system by leveraging the fluctuation of the wireless signals caused by human motion. We present an efficient method to select the correct data from the Channel State Information (CSI) streams that were neglected in previous approaches. We apply a Principle Component Analysis method that exposes the useful information from raw CSI. Thereafter, Forest Decision (FD) is adopted to classify the proposed activities and has gained a high accuracy rate. Extensive experiments have been conducted in an indoor environment to test the feasibility of the proposed system with a total of five volunteer users. The evaluation shows that the proposed system is applicable and robust to electromagnetic noise. Full article

(This article belongs to the Special Issue New Paradigms in Cyber-Physical Social Sensing)

► Show Figures

Figure 1

14 pages, 1548 KiB

Open AccessArticle

Lightweight Sensor Authentication Scheme for Energy Efficiency in Ubiquitous Computing Environments

by Jaeseung Lee, Yunsick Sung and Jong Hyuk Park

Sensors 2016, 16(12), 2044; https://doi.org/10.3390/s16122044 - 1 Dec 2016

Cited by 20 | Viewed by 6423

Abstract

The Internet of Things (IoT) is the intelligent technologies and services that mutually communicate information between humans and devices or between Internet-based devices. In IoT environments, various device information is collected from the user for intelligent technologies and services that control the devices. [...] Read more.

The Internet of Things (IoT) is the intelligent technologies and services that mutually communicate information between humans and devices or between Internet-based devices. In IoT environments, various device information is collected from the user for intelligent technologies and services that control the devices. Recently, wireless sensor networks based on IoT environments are being used in sectors as diverse as medicine, the military, and commerce. Specifically, sensor techniques that collect relevant area data via mini-sensors after distributing smart dust in inaccessible areas like forests or military zones have been embraced as the future of information technology. IoT environments that utilize smart dust are composed of the sensor nodes that detect data using wireless sensors and transmit the detected data to middle nodes. Currently, since the sensors used in these environments are composed of mini-hardware, they have limited memory, processing power, and energy, and a variety of research that aims to make the best use of these limited resources is progressing. This paper proposes a method to utilize these resources while considering energy efficiency, and suggests lightweight mutual verification and key exchange methods based on a hash function that has no restrictions on operation quantity, velocity, and storage space. This study verifies the security and energy efficiency of this method through security analysis and function evaluation, comparing with existing approaches. The proposed method has great value in its applicability as a lightweight security technology for IoT environments. Full article

(This article belongs to the Special Issue Topology Control in Emerging Sensor Networks)

► Show Figures

Figure 1

18 pages, 3051 KiB

Open AccessReview

Recent Progress in Electrochemical Biosensors for Glycoproteins

by Uichi Akiba and Jun-ichi Anzai

Sensors 2016, 16(12), 2045; https://doi.org/10.3390/s16122045 - 1 Dec 2016

Cited by 29 | Viewed by 8561

Abstract

This review provides an overview of recent progress in the development of electrochemical biosensors for glycoproteins. Electrochemical glycoprotein sensors are constructed by combining metal and carbon electrodes with glycoprotein-selective binding elements including antibodies, lectin, phenylboronic acid and molecularly imprinted polymers. A recent trend [...] Read more.

This review provides an overview of recent progress in the development of electrochemical biosensors for glycoproteins. Electrochemical glycoprotein sensors are constructed by combining metal and carbon electrodes with glycoprotein-selective binding elements including antibodies, lectin, phenylboronic acid and molecularly imprinted polymers. A recent trend in the preparation of glycoprotein sensors is the successful use of nanomaterials such as graphene, carbon nanotube, and metal nanoparticles. These nanomaterials are extremely useful for improving the sensitivity of glycoprotein sensors. This review focuses mainly on the protocols for the preparation of glycoprotein sensors and the materials used. Recent improvements in glycoprotein sensors are discussed by grouping the sensors into several categories based on the materials used as recognition elements. Full article

(This article belongs to the Special Issue Sensors for Glycoproteins and Glycated Proteins)

► Show Figures

Figure 1

22 pages, 1250 KiB

Open AccessArticle

Optimized Energy Harvesting, Cluster-Head Selection and Channel Allocation for IoTs in Smart Cities

by Saleem Aslam, Najam Ul Hasan, Ju Wook Jang and Kyung-Geun Lee

Sensors 2016, 16(12), 2046; https://doi.org/10.3390/s16122046 - 2 Dec 2016

Cited by 19 | Viewed by 5818

Abstract

This paper highlights three critical aspects of the internet of things (IoTs), namely (1) energy efficiency, (2) energy balancing and (3) quality of service (QoS) and presents three novel schemes for addressing these aspects. For energy efficiency, a novel radio frequency (RF) energy-harvesting [...] Read more.

This paper highlights three critical aspects of the internet of things (IoTs), namely (1) energy efficiency, (2) energy balancing and (3) quality of service (QoS) and presents three novel schemes for addressing these aspects. For energy efficiency, a novel radio frequency (RF) energy-harvesting scheme is presented in which each IoT device is associated with the best possible RF source in order to maximize the overall energy that the IoT devices harvest. For energy balancing, the IoT devices in close proximity are clustered together and then an IoT device with the highest residual energy is selected as a cluster head (CH) on a rotational basis. Once the CH is selected, it assigns channels to the IoT devices to report their data using a novel integer linear program (ILP)-based channel allocation scheme by satisfying their desired QoS. To evaluate the presented schemes, exhaustive simulations are carried out by varying different parameters, including the number of IoT devices, the number of harvesting sources, the distance between RF sources and IoT devices and the primary user (PU) activity of different channels. The simulation results demonstrate that our proposed schemes perform better than the existing ones. Full article

(This article belongs to the Special Issue Smart City: Vision and Reality)

► Show Figures

Figure 1

18 pages, 1601 KiB

Open AccessArticle

A Hyperspectral Survey of New York City Lighting Technology

by Gregory Dobler, Masoud Ghandehari, Steven E. Koonin and Mohit S. Sharma

Sensors 2016, 16(12), 2047; https://doi.org/10.3390/s16122047 - 5 Dec 2016

Cited by 25 | Viewed by 7685

Abstract

Using side-facing observations of the New York City (NYC) skyline, we identify lighting technologies via spectral signatures measured with Visible and Near Infrared (VNIR) hyperspectral imaging. The instrument is a scanning, single slit spectrograph with 872 spectral channels from 0.4–1.0

μ

m. With [...] Read more.

Using side-facing observations of the New York City (NYC) skyline, we identify lighting technologies via spectral signatures measured with Visible and Near Infrared (VNIR) hyperspectral imaging. The instrument is a scanning, single slit spectrograph with 872 spectral channels from 0.4–1.0

μ

m. With a single scan, we are able to clearly match the detected spectral signatures of 13 templates of known lighting types. However, many of the observed lighting spectra do not match those that have been measured in the laboratory. We identify unknown spectra by segmenting our observations and using Template-Activated Partition (TAP) clustering with a variety of underlying unsupervised clustering methods to generate the first empirically-determined spectral catalog of roughly 40 urban lighting types. We show that, given our vantage point, we are able to determine lighting technology use for both interior and exterior lighting. Finally, we find that the total brightness of our scene shows strong peaks at the 570 nm

Na

-

II

, 595 nm

Na

-

II

and 818 nm

Na

-

I

lines that are common in high pressure sodium lamps, which dominate our observations. Full article

(This article belongs to the Section Remote Sensors)

► Show Figures

Figure 1

26 pages, 3131 KiB

Open AccessArticle

Wearable Sensor-Based Human Activity Recognition Method with Multi-Features Extracted from Hilbert-Huang Transform

by Huile Xu, Jinyi Liu, Haibo Hu and Yi Zhang

Sensors 2016, 16(12), 2048; https://doi.org/10.3390/s16122048 - 2 Dec 2016

Cited by 49 | Viewed by 9973

Abstract

Wearable sensors-based human activity recognition introduces many useful applications and services in health care, rehabilitation training, elderly monitoring and many other areas of human interaction. Existing works in this field mainly focus on recognizing activities by using traditional features extracted from Fourier transform [...] Read more.

Wearable sensors-based human activity recognition introduces many useful applications and services in health care, rehabilitation training, elderly monitoring and many other areas of human interaction. Existing works in this field mainly focus on recognizing activities by using traditional features extracted from Fourier transform (FT) or wavelet transform (WT). However, these signal processing approaches are suitable for a linear signal but not for a nonlinear signal. In this paper, we investigate the characteristics of the Hilbert-Huang transform (HHT) for dealing with activity data with properties such as nonlinearity and non-stationarity. A multi-features extraction method based on HHT is then proposed to improve the effect of activity recognition. The extracted multi-features include instantaneous amplitude (IA) and instantaneous frequency (IF) by means of empirical mode decomposition (EMD), as well as instantaneous energy density (IE) and marginal spectrum (MS) derived from Hilbert spectral analysis. Experimental studies are performed to verify the proposed approach by using the PAMAP2 dataset from the University of California, Irvine for wearable sensors-based activity recognition. Moreover, the effect of combining multi-features vs. a single-feature are investigated and discussed in the scenario of a dependent subject. The experimental results show that multi-features combination can further improve the performance measures. Finally, we test the effect of multi-features combination in the scenario of an independent subject. Our experimental results show that we achieve four performance indexes: recall, precision, F-measure, and accuracy to 0.9337, 0.9417, 0.9353, and 0.9377 respectively, which are all better than the achievements of related works. Full article

(This article belongs to the Special Issue Body Worn Behavior Sensing)

► Show Figures

Figure 1

10 pages, 2255 KiB

Open AccessCommunication

A Touch Sensing Technique Using the Effects of Extremely Low Frequency Fields on the Human Body

by Hatem Elfekey, Hany Ayad Bastawrous and Shogo Okamoto

Sensors 2016, 16(12), 2049; https://doi.org/10.3390/s16122049 - 2 Dec 2016

Cited by 12 | Viewed by 7188

Abstract

Touch sensing is a fundamental approach in human-to-machine interfaces, and is currently under widespread use. Many current applications use active touch sensing technologies. Passive touch sensing technologies are, however, more adequate to implement low power or energy harvesting touch sensing interfaces. This paper [...] Read more.

Touch sensing is a fundamental approach in human-to-machine interfaces, and is currently under widespread use. Many current applications use active touch sensing technologies. Passive touch sensing technologies are, however, more adequate to implement low power or energy harvesting touch sensing interfaces. This paper presents a passive touch sensing technique based on the fact that the human body is affected by the surrounding extremely low frequency (ELF) electromagnetic fields, such as those of AC power lines. These external ELF fields induce electric potentials on the human body—because human tissues exhibit some conductivity at these frequencies—resulting in what is called AC hum. We therefore propose a passive touch sensing system that detects this hum noise when a human touch occurs, thus distinguishing between touch and non-touch events. The effectiveness of the proposed technique is validated by designing and implementing a flexible touch sensing keyboard. Full article

(This article belongs to the Section Physical Sensors)

► Show Figures

Figure 1

14 pages, 7230 KiB

Open AccessArticle

A Brain-Machine Interface Based on ERD/ERS for an Upper-Limb Exoskeleton Control

by Zhichuan Tang, Shouqian Sun, Sanyuan Zhang, Yumiao Chen, Chao Li and Shi Chen

Sensors 2016, 16(12), 2050; https://doi.org/10.3390/s16122050 - 2 Dec 2016

Cited by 92 | Viewed by 9889

Abstract

To recognize the user’s motion intention, brain-machine interfaces (BMI) usually decode movements from cortical activity to control exoskeletons and neuroprostheses for daily activities. The aim of this paper is to investigate whether self-induced variations of the electroencephalogram (EEG) can be useful as control [...] Read more.

To recognize the user’s motion intention, brain-machine interfaces (BMI) usually decode movements from cortical activity to control exoskeletons and neuroprostheses for daily activities. The aim of this paper is to investigate whether self-induced variations of the electroencephalogram (EEG) can be useful as control signals for an upper-limb exoskeleton developed by us. A BMI based on event-related desynchronization/synchronization (ERD/ERS) is proposed. In the decoder-training phase, we investigate the offline classification performance of left versus right hand and left hand versus both feet by using motor execution (ME) or motor imagery (MI). The results indicate that the accuracies of ME sessions are higher than those of MI sessions, and left hand versus both feet paradigm achieves a better classification performance, which would be used in the online-control phase. In the online-control phase, the trained decoder is tested in two scenarios (wearing or without wearing the exoskeleton). The MI and ME sessions wearing the exoskeleton achieve mean classification accuracy of 84.29% ± 2.11% and 87.37% ± 3.06%, respectively. The present study demonstrates that the proposed BMI is effective to control the upper-limb exoskeleton, and provides a practical method by non-invasive EEG signal associated with human natural behavior for clinical applications. Full article

(This article belongs to the Special Issue Wearable Biomedical Sensors)

► Show Figures

Figure 1

22 pages, 2168 KiB

Open AccessArticle

On the Use of a Feedback Tracking Architecture for Satellite Navigation Spoofing Detection

by Esteban Garbin Manfredini and Fabio Dovis

Sensors 2016, 16(12), 2051; https://doi.org/10.3390/s16122051 - 2 Dec 2016

Cited by 7 | Viewed by 5001

Abstract

In this paper, the Extended Coupled Amplitude Delay Lock Loop (ECADLL) architecture, previously introduced as a solution able to deal with a multipath environment, is revisited and improved to tailor it to spoofing detection purposes. Exploiting a properly-defined decision algorithm, the architecture is [...] Read more.

In this paper, the Extended Coupled Amplitude Delay Lock Loop (ECADLL) architecture, previously introduced as a solution able to deal with a multipath environment, is revisited and improved to tailor it to spoofing detection purposes. Exploiting a properly-defined decision algorithm, the architecture is able to effectively detect a spoofer attack, as well as distinguish it from other kinds of interference events. The new algorithm is used to classify them according to their characteristics. We also introduce the use of a ratio metric detector in order to reduce the detection latency and the computational load of the architecture. Full article

(This article belongs to the Section Remote Sensors)

► Show Figures

Figure 1

9 pages, 2987 KiB

Open AccessArticle

Potentiometric Aptasensing of Vibrio alginolyticus Based on DNA Nanostructure-Modified Magnetic Beads

by Guangtao Zhao, Jiawang Ding, Han Yu, Tanji Yin and Wei Qin

Sensors 2016, 16(12), 2052; https://doi.org/10.3390/s16122052 - 2 Dec 2016

Cited by 25 | Viewed by 6251

Abstract

A potentiometric aptasensing assay that couples the DNA nanostructure-modified magnetic beads with a solid-contact polycation-sensitive membrane electrode for the detection of Vibrio alginolyticus is herein described. The DNA nanostructure-modified magnetic beads are used for amplification of the potential response and elimination of the [...] Read more.

A potentiometric aptasensing assay that couples the DNA nanostructure-modified magnetic beads with a solid-contact polycation-sensitive membrane electrode for the detection of Vibrio alginolyticus is herein described. The DNA nanostructure-modified magnetic beads are used for amplification of the potential response and elimination of the interfering effect from a complex sample matrix. The solid-contact polycation-sensitive membrane electrode using protamine as an indicator is employed to chronopotentiometrically detect the change in the charge or DNA concentration on the magnetic beads, which is induced by the interaction between Vibrio alginolyticus and the aptamer on the DNA nanostructures. The present potentiometric aptasensing method shows a linear range of 10–100 CFU mL⁻¹ with a detection limit of 10 CFU mL⁻¹, and a good specificity for the detection of Vibrio alginolyticus. This proposed strategy can be used for the detection of other microorganisms by changing the aptamers in the DNA nanostructures. Full article

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

► Show Figures

Figure 1

22 pages, 4253 KiB

Open AccessArticle

Fuzzy Computing Model of Activity Recognition on WSN Movement Data for Ubiquitous Healthcare Measurement

by Shu-Yin Chiang, Yao-Chiang Kan, Yun-Shan Chen, Ying-Ching Tu and Hsueh-Chun Lin

Sensors 2016, 16(12), 2053; https://doi.org/10.3390/s16122053 - 3 Dec 2016

Cited by 17 | Viewed by 6887

Abstract

Ubiquitous health care (UHC) is beneficial for patients to ensure they complete therapeutic exercises by self-management at home. We designed a fuzzy computing model that enables recognizing assigned movements in UHC with privacy. The movements are measured by the self-developed body motion sensor, [...] Read more.

Ubiquitous health care (UHC) is beneficial for patients to ensure they complete therapeutic exercises by self-management at home. We designed a fuzzy computing model that enables recognizing assigned movements in UHC with privacy. The movements are measured by the self-developed body motion sensor, which combines both accelerometer and gyroscope chips to make an inertial sensing node compliant with a wireless sensor network (WSN). The fuzzy logic process was studied to calculate the sensor signals that would entail necessary features of static postures and dynamic motions. Combinations of the features were studied and the proper feature sets were chosen with compatible fuzzy rules. Then, a fuzzy inference system (FIS) can be generated to recognize the assigned movements based on the rules. We thus implemented both fuzzy and adaptive neuro-fuzzy inference systems in the model to distinguish static and dynamic movements. The proposed model can effectively reach the recognition scope of the assigned activity. Furthermore, two exercises of upper-limb flexion in physical therapy were applied for the model in which the recognition rate can stand for the passing rate of the assigned motions. Finally, a web-based interface was developed to help remotely measure movement in physical therapy for UHC. Full article

(This article belongs to the Special Issue Advances in Body Sensor Networks: Sensors, Systems, and Applications)

► Show Figures

Figure 1

21 pages, 6293 KiB

Open AccessArticle

A Novel Method for Vertical Acceleration Noise Suppression of a Thrust-Vectored VTOL UAV

by Huanyu Li, Linfeng Wu, Yingjie Li, Chunwen Li and Hangyu Li

Sensors 2016, 16(12), 2054; https://doi.org/10.3390/s16122054 - 2 Dec 2016

Cited by 2 | Viewed by 8581

Abstract

Acceleration is of great importance in motion control for unmanned aerial vehicles (UAVs), especially during the takeoff and landing stages. However, the measured acceleration is inevitably polluted by severe noise. Therefore, a proper noise suppression procedure is required. This paper presents a novel [...] Read more.

Acceleration is of great importance in motion control for unmanned aerial vehicles (UAVs), especially during the takeoff and landing stages. However, the measured acceleration is inevitably polluted by severe noise. Therefore, a proper noise suppression procedure is required. This paper presents a novel method to reduce the noise in the measured vertical acceleration for a thrust-vectored tail-sitter vertical takeoff and landing (VTOL) UAV. In the new procedure, a Kalman filter is first applied to estimate the UAV mass by using the information in the vertical thrust and measured acceleration. The UAV mass is then used to compute an estimate of UAV vertical acceleration. The estimated acceleration is finally fused with the measured acceleration to obtain the minimum variance estimate of vertical acceleration. By doing this, the new approach incorporates the thrust information into the acceleration estimate. The method is applied to the data measured in a VTOL UAV takeoff experiment. Two other denoising approaches developed by former researchers are also tested for comparison. The results demonstrate that the new method is able to suppress the acceleration noise substantially. It also maintains the real-time performance in the final estimated acceleration, which is not seen in the former denoising approaches. The acceleration treated with the new method can be readily used in the motion control applications for UAVs to achieve improved accuracy. Full article

(This article belongs to the Special Issue UAV-Based Remote Sensing)

► Show Figures

Figure 1

26 pages, 5392 KiB

Open AccessArticle

Coordinate-Based Clustering Method for Indoor Fingerprinting Localization in Dense Cluttered Environments

by Wen Liu, Xiao Fu and Zhongliang Deng

Sensors 2016, 16(12), 2055; https://doi.org/10.3390/s16122055 - 2 Dec 2016

Cited by 15 | Viewed by 5951

Abstract

Indoor positioning technologies has boomed recently because of the growing commercial interest in indoor location-based service (ILBS). Due to the absence of satellite signal in Global Navigation Satellite System (GNSS), various technologies have been proposed for indoor applications. Among them, Wi-Fi fingerprinting has [...] Read more.

Indoor positioning technologies has boomed recently because of the growing commercial interest in indoor location-based service (ILBS). Due to the absence of satellite signal in Global Navigation Satellite System (GNSS), various technologies have been proposed for indoor applications. Among them, Wi-Fi fingerprinting has been attracting much interest from researchers because of its pervasive deployment, flexibility and robustness to dense cluttered indoor environments. One challenge, however, is the deployment of Access Points (AP), which would bring a significant influence on the system positioning accuracy. This paper concentrates on WLAN based fingerprinting indoor location by analyzing the AP deployment influence, and studying the advantages of coordinate-based clustering compared to traditional RSS-based clustering. A coordinate-based clustering method for indoor fingerprinting location, named Smallest-Enclosing-Circle-based (SEC), is then proposed aiming at reducing the positioning error lying in the AP deployment and improving robustness to dense cluttered environments. All measurements are conducted in indoor public areas, such as the National Center For the Performing Arts (as Test-bed 1) and the XiDan Joy City (Floors 1 and 2, as Test-bed 2), and results show that SEC clustering algorithm can improve system positioning accuracy by about 32.7% for Test-bed 1, 71.7% for Test-bed 2 Floor 1 and 73.7% for Test-bed 2 Floor 2 compared with traditional RSS-based clustering algorithms such as K-means. Full article

(This article belongs to the Special Issue Scalable Localization in Wireless Sensor Networks)

► Show Figures

Figure 1

14 pages, 1358 KiB

Open AccessArticle

Minimum Interference Channel Assignment Algorithm for Multicast in a Wireless Mesh Network

by Sangil Choi and Jong Hyuk Park

Sensors 2016, 16(12), 2056; https://doi.org/10.3390/s16122056 - 2 Dec 2016

Cited by 5 | Viewed by 5331

Abstract

Wireless mesh networks (WMNs) have been considered as one of the key technologies for the configuration of wireless machines since they emerged. In a WMN, wireless routers provide multi-hop wireless connectivity between hosts in the network and also allow them to access the [...] Read more.

Wireless mesh networks (WMNs) have been considered as one of the key technologies for the configuration of wireless machines since they emerged. In a WMN, wireless routers provide multi-hop wireless connectivity between hosts in the network and also allow them to access the Internet via gateway devices. Wireless routers are typically equipped with multiple radios operating on different channels to increase network throughput. Multicast is a form of communication that delivers data from a source to a set of destinations simultaneously. It is used in a number of applications, such as distributed games, distance education, and video conferencing. In this study, we address a channel assignment problem for multicast in multi-radio multi-channel WMNs. In a multi-radio multi-channel WMN, two nearby nodes will interfere with each other and cause a throughput decrease when they transmit on the same channel. Thus, an important goal for multicast channel assignment is to reduce the interference among networked devices. We have developed a minimum interference channel assignment (MICA) algorithm for multicast that accurately models the interference relationship between pairs of multicast tree nodes using the concept of the interference factor and assigns channels to tree nodes to minimize interference within the multicast tree. Simulation results show that MICA achieves higher throughput and lower end-to-end packet delay compared with an existing channel assignment algorithm named multi-channel multicast (MCM). In addition, MICA achieves much lower throughput variation among the destination nodes than MCM. Full article

(This article belongs to the Special Issue Advances on Resources Management for Multi-Platform Infrastructures)

► Show Figures

Figure 1

21 pages, 3832 KiB

Open AccessArticle

Managing the Quality of Experience in the Multimedia Internet of Things: A Layered-Based Approach

by Alessandro Floris and Luigi Atzori

Sensors 2016, 16(12), 2057; https://doi.org/10.3390/s16122057 - 2 Dec 2016

Cited by 50 | Viewed by 6943

Abstract

This paper addresses the issue of evaluating the Quality of Experience (QoE) for Internet of Things (IoT) applications, with particular attention to the case where multimedia content is involved. A layered IoT architecture is firstly analyzed to understand which QoE influence factors have [...] Read more.

This paper addresses the issue of evaluating the Quality of Experience (QoE) for Internet of Things (IoT) applications, with particular attention to the case where multimedia content is involved. A layered IoT architecture is firstly analyzed to understand which QoE influence factors have to be considered in relevant application scenarios. We then introduce the concept of Multimedia IoT (MIoT) and define a layered QoE model aimed at evaluating and combining the contributions of each influence factor to estimate the overall QoE in MIoT applications. Finally, we present a use case related to the remote monitoring of vehicles during driving practices, which is used to validate the proposed layered model, and we discuss a second use case for smart surveillance, to emphasize the generality of the proposed framework. The effectiveness in evaluating classes of influence factors separately is demonstrated. Full article

(This article belongs to the Special Issue New Advances in Identification, Information & Knowledge in the Internet of Things)

► Show Figures

Figure 1

10 pages, 9061 KiB

Open AccessArticle

Real-Time Analysis of Isoprene in Breath by Using Ultraviolet-Absorption Spectroscopy with a Hollow Optical Fiber Gas Cell

by Takuro Iwata, Takashi Katagiri and Yuji Matsuura

Sensors 2016, 16(12), 2058; https://doi.org/10.3390/s16122058 - 5 Dec 2016

Cited by 20 | Viewed by 9354

Abstract

A breath analysis system based on ultraviolet-absorption spectroscopy was developed by using a hollow optical fiber as a gas cell for real-time monitoring of isoprene in breath. The hollow optical fiber functions as an ultra-small-volume gas cell with a long path. The measurement [...] Read more.

A breath analysis system based on ultraviolet-absorption spectroscopy was developed by using a hollow optical fiber as a gas cell for real-time monitoring of isoprene in breath. The hollow optical fiber functions as an ultra-small-volume gas cell with a long path. The measurement sensitivity of the system was evaluated by using nitric-oxide gas as a gas sample. The evaluation result showed that the developed system, using a laser-driven, high-intensity light source and a 3-m-long, aluminum-coated hollow optical fiber, could successfully measure nitric-oxide gas with a 50 ppb concentration. An absorption spectrum of a breath sample in the wavelength region of around 200–300 nm was measured, and the measured spectrum revealed the main absorbing components in breath as water vapor, isoprene, and ozone converted from oxygen by radiation of ultraviolet light. The concentration of isoprene in breath was estimated by multiple linear regression. The regression analysis results showed that the proposed analysis system enables real-time monitoring of isoprene during the exhaling of breath. Accordingly, it is suitable for measuring the circadian variation of isoprene. Full article

(This article belongs to the Section Physical Sensors)

► Show Figures

Figure 1

28 pages, 6452 KiB

Open AccessArticle

A Fault Tolerance Mechanism for On-Road Sensor Networks

by Lei Feng, Shaoyong Guo, Jialu Sun, Peng Yu and Wenjing Li

Sensors 2016, 16(12), 2059; https://doi.org/10.3390/s16122059 - 3 Dec 2016

Cited by 9 | Viewed by 6630

Abstract

On-Road Sensor Networks (ORSNs) play an important role in capturing traffic flow data for predicting short-term traffic patterns, driving assistance and self-driving vehicles. However, this kind of network is prone to large-scale communication failure if a few sensors physically fail. In this paper, [...] Read more.

On-Road Sensor Networks (ORSNs) play an important role in capturing traffic flow data for predicting short-term traffic patterns, driving assistance and self-driving vehicles. However, this kind of network is prone to large-scale communication failure if a few sensors physically fail. In this paper, to ensure that the network works normally, an effective fault-tolerance mechanism for ORSNs which mainly consists of backup on-road sensor deployment, redundant cluster head deployment and an adaptive failure detection and recovery method is proposed. Firstly, based on the N − x principle and the sensors’ failure rate, this paper formulates the backup sensor deployment problem in the form of a two-objective optimization, which explains the trade-off between the cost and fault resumption. In consideration of improving the network resilience further, this paper introduces a redundant cluster head deployment model according to the coverage constraint. Then a common solving method combining integer-continuing and sequential quadratic programming is explored to determine the optimal location of these two deployment problems. Moreover, an Adaptive Detection and Resume (ADR) protocol is deigned to recover the system communication through route and cluster adjustment if there is a backup on-road sensor mismatch. The final experiments show that our proposed mechanism can achieve an average 90% recovery rate and reduce the average number of failed sensors at most by 35.7%. Full article

(This article belongs to the Section Sensor Networks)

► Show Figures

Figure 1

13 pages, 3224 KiB

Open AccessArticle

A Novel Wireless Wearable Volatile Organic Compound (VOC) Monitoring Device with Disposable Sensors

by Yue Deng, Cheng Chen, Xiaojun Xian, Francis Tsow, Gaurav Verma, Rob McConnell, Scott Fruin, Nongjian Tao and Erica S. Forzani

Sensors 2016, 16(12), 2060; https://doi.org/10.3390/s16122060 - 3 Dec 2016

Cited by 20 | Viewed by 10099

Abstract

A novel portable wireless volatile organic compound (VOC) monitoring device with disposable sensors is presented. The device is miniaturized, light, easy-to-use, and cost-effective. Different field tests have been carried out to identify the operational, analytical, and functional performance of the device and its [...] Read more.

A novel portable wireless volatile organic compound (VOC) monitoring device with disposable sensors is presented. The device is miniaturized, light, easy-to-use, and cost-effective. Different field tests have been carried out to identify the operational, analytical, and functional performance of the device and its sensors. The device was compared to a commercial photo-ionization detector, gas chromatography-mass spectrometry, and carbon monoxide detector. In addition, environmental operational conditions, such as barometric change, temperature change and wind conditions were also tested to evaluate the device performance. The multiple comparisons and tests indicate that the proposed VOC device is adequate to characterize personal exposure in many real-world scenarios and is applicable for personal daily use. Full article

(This article belongs to the Special Issue Gas Sensors for Health Care and Medical Applications)

► Show Figures

Figure 1

23 pages, 6993 KiB

Open AccessReview

Integrating Deoxyribozymes into Colorimetric Sensing Platforms

by Dingran Chang, Sandy Zakaria, Mimi Deng, Nicholas Allen, Kha Tram and Yingfu Li

Sensors 2016, 16(12), 2061; https://doi.org/10.3390/s16122061 - 3 Dec 2016

Cited by 41 | Viewed by 10031

Abstract

Biosensors are analytical devices that have found a variety of applications in medical diagnostics, food quality control, environmental monitoring and biodefense. In recent years, functional nucleic acids, such as aptamers and nucleic acid enzymes, have shown great potential in biosensor development due to [...] Read more.

Biosensors are analytical devices that have found a variety of applications in medical diagnostics, food quality control, environmental monitoring and biodefense. In recent years, functional nucleic acids, such as aptamers and nucleic acid enzymes, have shown great potential in biosensor development due to their excellent ability in target recognition and catalysis. Deoxyribozymes (or DNAzymes) are single-stranded DNA molecules with catalytic activity and can be isolated to recognize a wide range of analytes through the process of in vitro selection. By using various signal transduction mechanisms, DNAzymes can be engineered into fluorescent, colorimetric, electrochemical and chemiluminescent biosensors. Among them, colorimetric sensors represent an attractive option as the signal can be easily detected by the naked eye. This reduces reliance on complex and expensive equipment. In this review, we will discuss the recent progress in the development of colorimetric biosensors that make use of DNAzymes and the prospect of employing these sensors in a range of chemical and biological applications. Full article

(This article belongs to the Special Issue Colorimetric and Fluorescent Sensor)

► Show Figures

Figure 1

17 pages, 6307 KiB

Open AccessArticle

Boundary-Layer Detection at Cryogenic Conditions Using Temperature Sensitive Paint Coupled with a Carbon Nanotube Heating Layer

by Kyle Z. Goodman, William E. Lipford and Anthony Neal Watkins

Sensors 2016, 16(12), 2062; https://doi.org/10.3390/s16122062 - 3 Dec 2016

Cited by 20 | Viewed by 5602

Abstract

Detection of flow transition on aircraft surfaces and models can be vital to the development of future vehicles and computational methods for evaluating vehicle concepts. In testing at ambient conditions, IR thermography is ideal for this measurement. However, for higher Reynolds number testing, [...] Read more.

Detection of flow transition on aircraft surfaces and models can be vital to the development of future vehicles and computational methods for evaluating vehicle concepts. In testing at ambient conditions, IR thermography is ideal for this measurement. However, for higher Reynolds number testing, cryogenic facilities are often used, in which IR thermography is difficult to employ. In these facilities, temperature sensitive paint is an alternative with a temperature step introduced to enhance the natural temperature change from transition. Traditional methods for inducing the temperature step by changing the liquid nitrogen injection rate often change the tunnel conditions. Recent work has shown that adding a layer consisting of carbon nanotubes to the surface can be used to impart a temperature step on the model surface with little change in the operating conditions. Unfortunately, this system physically degraded at 130 K and lost heating capability. This paper describes a modification of this technique enabling operation down to at least 77 K, well below the temperature reached in cryogenic facilities. This is possible because the CNT layer is in a polyurethane binder. This was tested on a Natural Laminar Flow model in a cryogenic facility and transition detection was successfully visualized at conditions from 200 K to 110 K. Results were also compared with the traditional temperature step method. Full article

(This article belongs to the Section Physical Sensors)

► Show Figures

Graphical abstract

29 pages, 630 KiB

Open AccessArticle

Derivation of the Cramér-Rao Bound in the GNSS-Reflectometry Context for Static, Ground-Based Receivers in Scenarios with Coherent Reflection

by Miguel Angel Ribot, Cyril Botteron and Pierre-André Farine

Sensors 2016, 16(12), 2063; https://doi.org/10.3390/s16122063 - 5 Dec 2016

Cited by 6 | Viewed by 5150

Abstract

The use of the reflected Global Navigation Satellite Systems’ (GNSS) signals in Earth observation applications, referred to as GNSS reflectometry (GNSS-R), has been already studied for more than two decades. However, the estimation precision that can be achieved by GNSS-R sensors in some [...] Read more.

The use of the reflected Global Navigation Satellite Systems’ (GNSS) signals in Earth observation applications, referred to as GNSS reflectometry (GNSS-R), has been already studied for more than two decades. However, the estimation precision that can be achieved by GNSS-R sensors in some particular scenarios is still not fully understood yet. In an effort to partially fill this gap, in this paper, we compute the Cramér–Rao bound (CRB) for the specific case of static ground-based GNSS-R receivers and scenarios where the coherent component of the reflected signal is dominant. We compute the CRB for GNSS signals with different modulations, GPS L1 C/A and GPS L5 I/Q, which use binary phase-shift keying, and Galileo E1 B/C and E5, using the binary offset carrier. The CRB for these signals is evaluated as a function of the receiver bandwidth and different scenario parameters, such as the height of the receiver or the properties of the reflection surface. The CRB computation presented considers observation times of up to several tens of seconds, in which the satellite elevation angle observed changes significantly. Finally, the results obtained show the theoretical benefit of using modern GNSS signals with GNSS-R techniques using long observation times, such as the interference pattern technique. Full article

(This article belongs to the Section Remote Sensors)

► Show Figures

Figure 1

15 pages, 5865 KiB

Open AccessArticle

A Geometry-Based Cycle Slip Detection and Repair Method with Time-Differenced Carrier Phase (TDCP) for a Single Frequency Global Position System (GPS) + BeiDou Navigation Satellite System (BDS) Receiver

by Chuang Qian, Hui Liu, Ming Zhang, Bao Shu, Longwei Xu and Rufei Zhang

Sensors 2016, 16(12), 2064; https://doi.org/10.3390/s16122064 - 5 Dec 2016

Cited by 23 | Viewed by 5768

Abstract

As the field of high-precision applications based on carriers continues to expand, the development of low-cost, small, modular receivers and their application in diverse scenarios and situations with complex data quality has increased the requirements of carrier-phase data preprocessing. A new geometry-based cycle [...] Read more.

As the field of high-precision applications based on carriers continues to expand, the development of low-cost, small, modular receivers and their application in diverse scenarios and situations with complex data quality has increased the requirements of carrier-phase data preprocessing. A new geometry-based cycle slip detection and repair method based on Global Position System (GPS) + BeiDou Navigation Satellite System (BDS) is proposed. The method uses a Time-differenced Carrier Phase (TDCP) model, which eliminates the Inner-System Bias (ISB) between GPS and BDS, and it is conducive to the effective combination of GPS and BDS. It avoids the interference of the noise of the pseudo-range with cycle slip detection, while the cycle slips are preserved as integers. This method does not limit the receiver frequency number, and it is applicable to single-frequency data. The process is divided into two steps to detect and repair cycle slip. The first step is cycle slip detection, using the Improved Local Analysis Method (ILAM) to find satellites that have cycle slips; The second step is to repair the cycle slips, including estimating the float solution of changes in ambiguities at the satellites that have cycle slips with the least squares method and the integer solution of the cycle slips by rounding. In the process of rounding, in addition to the success probability, a decimal test is carried out to validate the result. Finally, experiments with filed test data are carried out to prove the effectiveness of this method. The results show that the detectable cycle slips number with GPS + BDS is much greater than that with GPS. The method can also detect the non-integer outliers while fixing the cycle slip. The maximum decimal bias in repair is less than that with GPS. It implies that this method takes full advantages of multi-system. Full article

(This article belongs to the Section Remote Sensors)

► Show Figures

Figure 1

10 pages, 1364 KiB

Open AccessArticle

Detection of Ciprofloxacin in Urine through Sensitized Lanthanide Luminescence

by Subhankar Singha and Kyo Han Ahn

Sensors 2016, 16(12), 2065; https://doi.org/10.3390/s16122065 - 5 Dec 2016

Cited by 42 | Viewed by 8685

Abstract

Ciprofloxacin, a fluoroquinolone antibiotic, is widely used for the treatment of bacterial infection in humans due to its broad antibacterial spectrum. An excessive use or overdose of ciprofloxacin on the other hand can cause several adverse effects not only to humans but also [...] Read more.

Ciprofloxacin, a fluoroquinolone antibiotic, is widely used for the treatment of bacterial infection in humans due to its broad antibacterial spectrum. An excessive use or overdose of ciprofloxacin on the other hand can cause several adverse effects not only to humans but also to microorganisms. Unabsorbed ciprofloxacin in the body is mostly excreted through urine and finally goes to the environment, providing a drug resistance pressure on bacteria. Hence a simple and efficient detection method of ciprofloxacin is necessary, which, for example, can be used to analyze ciprofloxacin content in urine. Although ciprofloxacin itself shows inherent fluorescence, direct fluorescent detection of ciprofloxacin in raw urine sample is difficult due to autofluorescence of urine by other components. Herein we report that a Tb(III) complex of DO3A (1,4,7,10-tetraazacyclododecane-1,4,7-triacetic acid) can be efficiently sensitized by ciprofloxacin to emit luminescence separately from the urine autofluorescence wavelength region. Tb-DO3A shows excellent sensitivity with a detection limit of three parts per billion in aqueous buffer solution. Further, Tb-DO3A is used to detect ciprofloxacin with high sensitivity and selectivity in a raw urine sample without any purification or separation procedures in the concentrations ranging from 1 µg·mL⁻¹ to 50 µg·mL⁻¹. The direct measurement of ciprofloxacin excreted in urine may be used to control overdose of the drug. Full article

(This article belongs to the Special Issue Colorimetric and Fluorescent Sensor)

► Show Figures

Figure 1

12 pages, 2913 KiB

Open AccessArticle

A Robust Range Grating Lobe Suppression Method Based on Image Contrast for Stepped-Frequency SAR

by Wen-Bin Gao, Teng Long, Ze-Gang Ding and Yi-Rong Wu

Sensors 2016, 16(12), 2066; https://doi.org/10.3390/s16122066 - 6 Dec 2016

Cited by 2 | Viewed by 4607

Abstract

The magnitude error and phase error (MEPE) in the transfer function of a stepped-frequency synthetic aperture radar (SAR) system results in a periodic MEPE in the synthesized wideband waveform (SWW), which induces the grating lobes in the high-resolution range profile (HRRP). In this [...] Read more.

The magnitude error and phase error (MEPE) in the transfer function of a stepped-frequency synthetic aperture radar (SAR) system results in a periodic MEPE in the synthesized wideband waveform (SWW), which induces the grating lobes in the high-resolution range profile (HRRP). In this paper, a robust data-driven grating lobe suppression (GLS) method is proposed. Based on a contrast-based error estimation method and the grating lobes of the brightest scatterers in the SAR image, the periodic MEPE can be robustly estimated using the proposed method. By compensating the estimated periodic MEPE, the range grating lobes can be suppressed to the background level of the SAR image. Simulation results and real data processing have demonstrated the superiority of the proposed method. Full article

(This article belongs to the Section Remote Sensors)

► Show Figures

Figure 1

18 pages, 13780 KiB

Open AccessArticle

Rapid Detection Methods for Asphalt Pavement Thicknesses and Defects by a Vehicle-Mounted Ground Penetrating Radar (GPR) System

by Zehua Dong, Shengbo Ye, Yunze Gao, Guangyou Fang, Xiaojuan Zhang, Zhongjun Xue and Tao Zhang

Sensors 2016, 16(12), 2067; https://doi.org/10.3390/s16122067 - 6 Dec 2016

Cited by 83 | Viewed by 13558

Abstract

The thickness estimation of the top surface layer and surface layer, as well as the detection of road defects, are of great importance to the quality conditions of asphalt pavement. Although ground penetrating radar (GPR) methods have been widely used in non-destructive detection [...] Read more.

The thickness estimation of the top surface layer and surface layer, as well as the detection of road defects, are of great importance to the quality conditions of asphalt pavement. Although ground penetrating radar (GPR) methods have been widely used in non-destructive detection of pavements, the thickness estimation of the thin top surface layer is still a difficult problem due to the limitations of GPR resolution and the similar permittivity of asphalt sub-layers. Besides, the detection of some road defects, including inadequate compaction and delamination at interfaces, require further practical study. In this paper, a newly-developed vehicle-mounted GPR detection system is introduced. We used a horizontal high-pass filter and a modified layer localization method to extract the underground layers. Besides, according to lab experiments and simulation analysis, we proposed theoretical methods for detecting the degree of compaction and delamination at the interface, respectively. Moreover, a field test was carried out and the estimated results showed a satisfactory accuracy of the system and methods. Full article

(This article belongs to the Special Issue Urban Remote Sensing: Monitoring, Synthesis and Modeling in the Urban Environment)

► Show Figures

Figure 1

11 pages, 3560 KiB

Open AccessArticle

Electrical Impedance Monitoring of C2C12 Myoblast Differentiation on an Indium Tin Oxide Electrode

by Ilhwan Park, Yeonhee Hong, Young-Hoo Jun, Ga-Yeon Lee, Hee-Sook Jun, Jae-Chul Pyun, Jeong-Woo Choi and Sungbo Cho

Sensors 2016, 16(12), 2068; https://doi.org/10.3390/s16122068 - 5 Dec 2016

Cited by 19 | Viewed by 9195

Abstract

Electrical cell-substrate impedance sensing is increasingly being used for label-free and real-time monitoring of changes in cell morphology and number during cell growth, drug screening, and differentiation. In this study, we evaluated the feasibility of using ECIS to monitor C2C12 myoblast differentiation using [...] Read more.

Electrical cell-substrate impedance sensing is increasingly being used for label-free and real-time monitoring of changes in cell morphology and number during cell growth, drug screening, and differentiation. In this study, we evaluated the feasibility of using ECIS to monitor C2C12 myoblast differentiation using a fabricated indium tin oxide (ITO) electrode-based chip. C2C12 myoblast differentiation on the ITO electrode was validated based on decreases in the mRNA level of MyoD and increases in the mRNA levels of myogenin and myosin heavy chain (MHC). Additionally, MHC expression and morphological changes in myoblasts differentiated on the ITO electrode were comparable to those in cells in the control culture dish. From the monitoring the integration of the resistance change at 21.5 kHz, the cell differentiation was label-free and real-time detectable in 30 h of differentiation (p < 0.05). Full article

(This article belongs to the Special Issue Whole Cell-Based Biosensors and Application)

► Show Figures

Figure 1

21 pages, 633 KiB

Open AccessArticle

Fault Detection Using the Clustering-kNN Rule for Gas Sensor Arrays

by Jingli Yang, Zhen Sun and Yinsheng Chen

Sensors 2016, 16(12), 2069; https://doi.org/10.3390/s16122069 - 6 Dec 2016

Cited by 51 | Viewed by 7364

Abstract

The k-nearest neighbour (kNN) rule, which naturally handles the possible non-linearity of data, is introduced to solve the fault detection problem of gas sensor arrays. In traditional fault detection methods based on the kNN rule, the detection process of each new test sample [...] Read more.

The k-nearest neighbour (kNN) rule, which naturally handles the possible non-linearity of data, is introduced to solve the fault detection problem of gas sensor arrays. In traditional fault detection methods based on the kNN rule, the detection process of each new test sample involves all samples in the entire training sample set. Therefore, these methods can be computation intensive in monitoring processes with a large volume of variables and training samples and may be impossible for real-time monitoring. To address this problem, a novel clustering-kNN rule is presented. The landmark-based spectral clustering (LSC) algorithm, which has low computational complexity, is employed to divide the entire training sample set into several clusters. Further, the kNN rule is only conducted in the cluster that is nearest to the test sample; thus, the efficiency of the fault detection methods can be enhanced by reducing the number of training samples involved in the detection process of each test sample. The performance of the proposed clustering-kNN rule is fully verified in numerical simulations with both linear and non-linear models and a real gas sensor array experimental system with different kinds of faults. The results of simulations and experiments demonstrate that the clustering-kNN rule can greatly enhance both the accuracy and efficiency of fault detection methods and provide an excellent solution to reliable and real-time monitoring of gas sensor arrays. Full article

(This article belongs to the Section Physical Sensors)

► Show Figures

Figure 1

13 pages, 3143 KiB

Open AccessArticle

An Improved Zero Potential Circuit for Readout of a Two-Dimensional Resistive Sensor Array

by Jian-Feng Wu, Feng Wang, Qi Wang, Jian-Qing Li and Ai-Guo Song

Sensors 2016, 16(12), 2070; https://doi.org/10.3390/s16122070 - 6 Dec 2016

Cited by 12 | Viewed by 6219

Abstract

With one operational amplifier (op-amp) in negative feedback, the traditional zero potential circuit could access one element in the two-dimensional (2-D) resistive sensor array with the shared row-column fashion but it suffered from the crosstalk problem for the non-scanned elements’ bypass currents, which [...] Read more.

With one operational amplifier (op-amp) in negative feedback, the traditional zero potential circuit could access one element in the two-dimensional (2-D) resistive sensor array with the shared row-column fashion but it suffered from the crosstalk problem for the non-scanned elements’ bypass currents, which were injected into array’s non-scanned electrodes from zero potential. Firstly, for suppressing the crosstalk problem, we designed a novel improved zero potential circuit with one more op-amp in negative feedback to sample the total bypass current and calculate the precision resistance of the element being tested (EBT) with it. The improved setting non-scanned-electrode zero potential circuit (S-NSE-ZPC) was given as an example for analyzing and verifying the performance of the improved zero potential circuit. Secondly, in the S-NSE-ZPC and the improved S-NSE-ZPC, the effects of different parameters of the resistive sensor arrays and their readout circuits on the EBT’s measurement accuracy were simulated with the NI Multisim 12. Thirdly, part features of the improved circuit were verified with the experiments of a prototype circuit. Followed, the results were discussed and the conclusions were given. The experiment results show that the improved circuit, though it requires one more op-amp, one more resistor and one more sampling channel, can access the EBT in the 2-D resistive sensor array more accurately. Full article

(This article belongs to the Special Issue Smart Sensor Interface Circuits and Systems)

► Show Figures

Figure 1

20 pages, 4759 KiB

Open AccessArticle

A Height Estimation Approach for Terrain Following Flights from Monocular Vision

by Igor S. G. Campos, Erickson R. Nascimento, Gustavo M. Freitas and Luiz Chaimowicz

Sensors 2016, 16(12), 2071; https://doi.org/10.3390/s16122071 - 6 Dec 2016

Cited by 16 | Viewed by 8858

Abstract

In this paper, we present a monocular vision-based height estimation algorithm for terrain following flights. The impressive growth of Unmanned Aerial Vehicle (UAV) usage, notably in mapping applications, will soon require the creation of new technologies to enable these systems to better perceive [...] Read more.

In this paper, we present a monocular vision-based height estimation algorithm for terrain following flights. The impressive growth of Unmanned Aerial Vehicle (UAV) usage, notably in mapping applications, will soon require the creation of new technologies to enable these systems to better perceive their surroundings. Specifically, we chose to tackle the terrain following problem, as it is still unresolved for consumer available systems. Virtually every mapping aircraft carries a camera; therefore, we chose to exploit this in order to use presently available hardware to extract the height information toward performing terrain following flights. The proposed methodology consists of using optical flow to track features from videos obtained by the UAV, as well as its motion information to estimate the flying height. To determine if the height estimation is reliable, we trained a decision tree that takes the optical flow information as input and classifies whether the output is trustworthy or not. The classifier achieved accuracies of

80 %

for positives and

90 %

for negatives, while the height estimation algorithm presented good accuracy. Full article

(This article belongs to the Special Issue Vision-Based Sensors in Field Robotics)

► Show Figures

Figure 1

17 pages, 676 KiB

Open AccessArticle

Cramer-Rao Lower Bound Evaluation for Linear Frequency Modulation Based Active Radar Networks Operating in a Rice Fading Environment

by Chenguang Shi, Sana Salous, Fei Wang and Jianjiang Zhou

Sensors 2016, 16(12), 2072; https://doi.org/10.3390/s16122072 - 6 Dec 2016

Cited by 10 | Viewed by 7113

Abstract

This paper investigates the joint target parameter (delay and Doppler) estimation performance of linear frequency modulation (LFM)-based radar networks in a Rice fading environment. The active radar networks are composed of multiple radar transmitters and multichannel receivers placed on moving platforms. First, the [...] Read more.

This paper investigates the joint target parameter (delay and Doppler) estimation performance of linear frequency modulation (LFM)-based radar networks in a Rice fading environment. The active radar networks are composed of multiple radar transmitters and multichannel receivers placed on moving platforms. First, the log-likelihood function of the received signal for a Rician target is derived, where the received signal scattered off the target comprises of dominant scatterer (DS) component and weak isotropic scatterers (WIS) components. Then, the analytically closed-form expressions of the Cramer-Rao lower bounds (CRLBs) on the Cartesian coordinates of target position and velocity are calculated, which can be adopted as a performance metric to access the target parameter estimation accuracy for LFM-based radar network systems in a Rice fading environment. It is found that the cumulative Fisher information matrix (FIM) is a linear combination of both DS component and WIS components, and it also demonstrates that the joint CRLB is a function of signal-to-noise ratio (SNR), target’s radar cross section (RCS) and transmitted waveform parameters, as well as the relative geometry between the target and the radar network architectures. Finally, numerical results are provided to indicate that the joint target parameter estimation performance of active radar networks can be significantly improved with the exploitation of DS component. Full article

(This article belongs to the Special Issue UAV-Based Remote Sensing)

► Show Figures

Figure 1

13 pages, 5936 KiB

Open AccessArticle

Disposable, Paper-Based, Inkjet-Printed Humidity and H₂S Gas Sensor for Passive Sensing Applications

by Abdul Quddious, Shuai Yang, Munawar M. Khan, Farooq A. Tahir, Atif Shamim, Khaled N. Salama and Hammad M. Cheema

Sensors 2016, 16(12), 2073; https://doi.org/10.3390/s16122073 - 6 Dec 2016

Cited by 58 | Viewed by 10288

Abstract

An inkjet-printed, fully passive sensor capable of either humidity or gas sensing is presented herein. The sensor is composed of an interdigitated electrode, a customized printable gas sensitive ink and a specialized dipole antenna for wireless sensing. The interdigitated electrode printed on a [...] Read more.

An inkjet-printed, fully passive sensor capable of either humidity or gas sensing is presented herein. The sensor is composed of an interdigitated electrode, a customized printable gas sensitive ink and a specialized dipole antenna for wireless sensing. The interdigitated electrode printed on a paper substrate provides the base conductivity that varies during the sensing process. Aided by the porous nature of the substrate, a change in relative humidity from 18% to 88% decreases the electrode resistance from a few Mega-ohms to the kilo-ohm range. For gas sensing, an additional copper acetate-based customized ink is printed on top of the electrode, which, upon reaction with hydrogen sulphide gas (H₂S) changes, both the optical and the electrical properties of the electrode. A fast response time of 3 min is achieved at room temperature for a H₂S concentration of 10 ppm at a relative humidity (RH) of 45%. The passive wireless sensing is enabled through an antenna in which the inner loop takes care of conductivity changes in the 4–5 GHz band, whereas the outer-dipole arm is used for chipless identification in the 2–3 GHz band. Full article

(This article belongs to the Special Issue Gas Nanosensors)

► Show Figures

Figure 1

22 pages, 8322 KiB

Open AccessArticle

A Self-Adaptive Model-Based Wi-Fi Indoor Localization Method

by Jure Tuta and Matjaz B. Juric

Sensors 2016, 16(12), 2074; https://doi.org/10.3390/s16122074 - 6 Dec 2016

Cited by 19 | Viewed by 6200

Abstract

This paper presents a novel method for indoor localization, developed with the main aim of making it useful for real-world deployments. Many indoor localization methods exist, yet they have several disadvantages in real-world deployments—some are static, which is not suitable for long-term usage; [...] Read more.

This paper presents a novel method for indoor localization, developed with the main aim of making it useful for real-world deployments. Many indoor localization methods exist, yet they have several disadvantages in real-world deployments—some are static, which is not suitable for long-term usage; some require costly human recalibration procedures; and others require special hardware such as Wi-Fi anchors and transponders. Our method is self-calibrating and self-adaptive thus maintenance free and based on Wi-Fi only. We have employed two well-known propagation models—free space path loss and ITU models—which we have extended with additional parameters for better propagation simulation. Our self-calibrating procedure utilizes one propagation model to infer parameters of the space and the other to simulate the propagation of the signal without requiring any additional hardware beside Wi-Fi access points, which is suitable for real-world usage. Our method is also one of the few model-based Wi-Fi only self-adaptive approaches that do not require the mobile terminal to be in the access-point mode. The only input requirements of the method are Wi-Fi access point positions, and positions and properties of the walls. Our method has been evaluated in single- and multi-room environments, with measured mean error of 2–3 and 3–4 m, respectively, which is similar to existing methods. The evaluation has proven that usable localization accuracy can be achieved in real-world environments solely by the proposed Wi-Fi method that relies on simple hardware and software requirements. Full article

(This article belongs to the Special Issue Scalable Localization in Wireless Sensor Networks)

► Show Figures

Figure 1

14 pages, 3391 KiB

Open AccessArticle

Chlorophyll-a Estimation Around the Antarctica Peninsula Using Satellite Algorithms: Hints from Field Water Leaving Reflectance

by Chen Zeng, Huiping Xu and Andrew M. Fischer

Sensors 2016, 16(12), 2075; https://doi.org/10.3390/s16122075 - 7 Dec 2016

Cited by 23 | Viewed by 6586

Abstract

Ocean color remote sensing significantly contributes to our understanding of phytoplankton distribution and abundance and primary productivity in the Southern Ocean (SO). However, the current SO in situ optical database is still insufficient and unevenly distributed. This limits the ability to produce robust [...] Read more.

Ocean color remote sensing significantly contributes to our understanding of phytoplankton distribution and abundance and primary productivity in the Southern Ocean (SO). However, the current SO in situ optical database is still insufficient and unevenly distributed. This limits the ability to produce robust and accurate measurements of satellite-based chlorophyll. Based on data collected on cruises around the Antarctica Peninsula (AP) on January 2014 and 2016, this research intends to enhance our knowledge of SO water and atmospheric optical characteristics and address satellite algorithm deficiency of ocean color products. We collected high resolution in situ water leaving reflectance (±1 nm band resolution), simultaneous in situ chlorophyll-a concentrations and satellite (MODIS and VIIRS) water leaving reflectance. Field samples show that clouds have a great impact on the visible green bands and are difficult to detect because NASA protocols apply the NIR band as a cloud contamination threshold. When compared to global case I water, water around the AP has lower water leaving reflectance and a narrower blue-green band ratio, which explains chlorophyll-a underestimation in high chlorophyll-a regions and overestimation in low chlorophyll-a regions. VIIRS shows higher spatial coverage and detection accuracy than MODIS. After coefficient improvement, VIIRS is able to predict chlorophyll a with 53% accuracy. Full article

(This article belongs to the Special Issue Sensors and Sensing in Water Quality Assessment and Monitoring)

► Show Figures

Figure 1

12 pages, 7836 KiB

Open AccessArticle

Bio-Photonic Detection and Quantitative Evaluation Method for the Progression of Dental Caries Using Optical Frequency-Domain Imaging Method

by Ruchire Eranga Wijesinghe, Nam Hyun Cho, Kibeom Park, Mansik Jeon and Jeehyun Kim

Sensors 2016, 16(12), 2076; https://doi.org/10.3390/s16122076 - 6 Dec 2016

Cited by 36 | Viewed by 6510

Abstract

The initial detection of dental caries is an essential biomedical requirement to barricade the progression of caries and tooth demineralization. The objective of this study is to introduce an optical frequency-domain imaging technique based quantitative evaluation method to calculate the volume and thickness [...] Read more.

The initial detection of dental caries is an essential biomedical requirement to barricade the progression of caries and tooth demineralization. The objective of this study is to introduce an optical frequency-domain imaging technique based quantitative evaluation method to calculate the volume and thickness of enamel residual, and a quantification method was developed to evaluate the total intensity fluctuation in depth direction owing to carious lesions, which can be favorable to identify the progression of dental caries in advance. The cross-sectional images of the ex vivo tooth samples were acquired using 1.3 μm spectral domain optical coherence tomography system (SD-OCT). Moreover, the advantages of the proposed method over the conventional dental inspection methods were compared to highlight the potential capability of OCT. As a consequence, the threshold parameters obtained through the developed method can be used as an efficient investigating technique for the initial detection of demineralization. Full article

(This article belongs to the Special Issue Optical Methods in Sensing and Imaging for Medical and Biological Applications)

► Show Figures

Figure 1

24 pages, 2955 KiB

Open AccessArticle

Enabling SDN in VANETs: What is the Impact on Security?

by Antonio Di Maio, Maria Rita Palattella, Ridha Soua, Luca Lamorte, Xavier Vilajosana, Jesus Alonso-Zarate and Thomas Engel

Sensors 2016, 16(12), 2077; https://doi.org/10.3390/s16122077 - 6 Dec 2016

Cited by 40 | Viewed by 12322

Abstract

The demand for safe and secure journeys over roads and highways has been growing at a tremendous pace over recent decades. At the same time, the smart city paradigm has emerged to improve citizens’ quality of life by developing the smart mobility concept. [...] Read more.

The demand for safe and secure journeys over roads and highways has been growing at a tremendous pace over recent decades. At the same time, the smart city paradigm has emerged to improve citizens’ quality of life by developing the smart mobility concept. Vehicular Ad hoc NETworks (VANETs) are widely recognized to be instrumental in realizing such concept, by enabling appealing safety and infotainment services. Such networks come with their own set of challenges, which range from managing high node mobility to securing data and user privacy. The Software Defined Networking (SDN) paradigm has been identified as a suitable solution for dealing with the dynamic network environment, the increased number of connected devices, and the heterogeneity of applications. While some preliminary investigations have been already conducted to check the applicability of the SDN paradigm to VANETs, and its presumed benefits for managing resources and mobility, it is still unclear what impact SDN will have on security and privacy. Security is a relevant issue in VANETs, because of the impact that threats can have on drivers’ behavior and quality of life. This paper opens a discussion on the security threats that future SDN-enabled VANETs will have to face, and investigates how SDN could be beneficial in building new countermeasures. The analysis is conducted in real use cases (smart parking, smart grid of electric vehicles, platooning, and emergency services), which are expected to be among the vehicular applications that will most benefit from introducing an SDN architecture. Full article

(This article belongs to the Special Issue Smart City: Vision and Reality)

► Show Figures

Figure 1

18 pages, 4288 KiB

Open AccessArticle

Application of Fast Dynamic Allan Variance for the Characterization of FOGs-Based Measurement While Drilling

by Lu Wang, Chunxi Zhang, Shuang Gao, Tao Wang, Tie Lin and Xianmu Li

Sensors 2016, 16(12), 2078; https://doi.org/10.3390/s16122078 - 7 Dec 2016

Cited by 18 | Viewed by 7888

Abstract

The stability of a fiber optic gyroscope (FOG) in measurement while drilling (MWD) could vary with time because of changing temperature, high vibration, and sudden power failure. The dynamic Allan variance (DAVAR) is a sliding version of the Allan variance. It is a [...] Read more.

The stability of a fiber optic gyroscope (FOG) in measurement while drilling (MWD) could vary with time because of changing temperature, high vibration, and sudden power failure. The dynamic Allan variance (DAVAR) is a sliding version of the Allan variance. It is a practical tool that could represent the non-stationary behavior of the gyroscope signal. Since the normal DAVAR takes too long to deal with long time series, a fast DAVAR algorithm has been developed to accelerate the computation speed. However, both the normal DAVAR algorithm and the fast algorithm become invalid for discontinuous time series. What is worse, the FOG-based MWD underground often keeps working for several days; the gyro data collected aboveground is not only very time-consuming, but also sometimes discontinuous in the timeline. In this article, on the basis of the fast algorithm for DAVAR, we make a further advance in the fast algorithm (improved fast DAVAR) to extend the fast DAVAR to discontinuous time series. The improved fast DAVAR and the normal DAVAR are used to responsively characterize two sets of simulation data. The simulation results show that when the length of the time series is short, the improved fast DAVAR saves 78.93% of calculation time. When the length of the time series is long (

6 \times 10^{5}

samples), the improved fast DAVAR reduces calculation time by 97.09%. Another set of simulation data with missing data is characterized by the improved fast DAVAR. Its simulation results prove that the improved fast DAVAR could successfully deal with discontinuous data. In the end, a vibration experiment with FOGs-based MWD has been implemented to validate the good performance of the improved fast DAVAR. The results of the experience testify that the improved fast DAVAR not only shortens computation time, but could also analyze discontinuous time series. Full article

(This article belongs to the Section Physical Sensors)

► Show Figures

Figure 1

13 pages, 9470 KiB

Open AccessArticle

Standardization, Calibration, and Evaluation of Tantalum-Nano rGO-SnO₂ Composite as a Possible Candidate Material in Humidity Sensors

by Subbiah Karthick, Han-Seung Lee, Seung-Jun Kwon, Rethinam Natarajan and Velu Saraswathy

Sensors 2016, 16(12), 2079; https://doi.org/10.3390/s16122079 - 7 Dec 2016

Cited by 38 | Viewed by 7985

Abstract

The present study focuses the development and the evaluation of humidity sensors based on reduced graphene oxide—tin oxide (rGO-SnO₂) nanocomposites, synthesized by a simple redox reaction between GO and SnCl₂. The physico-chemical characteristics of the nanocomposites were analyzed by [...] Read more.

The present study focuses the development and the evaluation of humidity sensors based on reduced graphene oxide—tin oxide (rGO-SnO₂) nanocomposites, synthesized by a simple redox reaction between GO and SnCl₂. The physico-chemical characteristics of the nanocomposites were analyzed by XRD, TEM, FTIR, and Raman spectroscopy. The formation of SnO₂ crystal phase was observed through XRD. The SnO₂ crystal phase anchoring to the graphene sheet was confirmed through TEM images. For the preparation of the sensors, tantalum substrates were coated with the sensing material. The sensitivity of the fabricated sensor was studied by varying the relative humidity (RH) from 11% to 95% over a period of 30 days. The dependence of the impedance and of the capacitance with RH of the sensor was measured with varying frequency ranging from 1 kHz to 100 Hz. The long-term stability of the sensor was measured at 95% RH over a period of 30 days. The results proved that rGO-SnO₂ nanocomposites are an ideal conducting material for humidity sensors due to their high sensitivity, rapid response and recovery times, as well as their good long-term stability. Full article

(This article belongs to the Special Issue Humidity Sensors)

► Show Figures

Figure 1

13 pages, 4678 KiB

Open AccessArticle

Modeling of a Robust Confidence Band for the Power Curve of a Wind Turbine

by Wilmar Hernandez, Alfredo Méndez, Jorge L. Maldonado-Correa and Francisco Balleteros

Sensors 2016, 16(12), 2080; https://doi.org/10.3390/s16122080 - 7 Dec 2016

Cited by 9 | Viewed by 5220

Abstract

Having an accurate model of the power curve of a wind turbine allows us to better monitor its operation and planning of storage capacity. Since wind speed and direction is of a highly stochastic nature, the forecasting of the power generated by the [...] Read more.

Having an accurate model of the power curve of a wind turbine allows us to better monitor its operation and planning of storage capacity. Since wind speed and direction is of a highly stochastic nature, the forecasting of the power generated by the wind turbine is of the same nature as well. In this paper, a method for obtaining a robust confidence band containing the power curve of a wind turbine under test conditions is presented. Here, the confidence band is bound by two curves which are estimated using parametric statistical inference techniques. However, the observations that are used for carrying out the statistical analysis are obtained by using the binning method, and in each bin, the outliers are eliminated by using a censorship process based on robust statistical techniques. Then, the observations that are not outliers are divided into observation sets. Finally, both the power curve of the wind turbine and the two curves that define the robust confidence band are estimated using each of the previously mentioned observation sets. Full article

(This article belongs to the Section Physical Sensors)

► Show Figures

Figure 1

18 pages, 3082 KiB

Open AccessArticle

Aerodynamic Drag Analysis of 3-DOF Flex-Gimbal GyroWheel System in the Sense of Ground Test

by Xin Huo, Sizhao Feng, Kangzhi Liu, Libin Wang and Weishan Chen

Sensors 2016, 16(12), 2081; https://doi.org/10.3390/s16122081 - 7 Dec 2016

Cited by 5 | Viewed by 5654

Abstract

GyroWheel is an innovative device that combines the actuating capabilities of a control moment gyro with the rate sensing capabilities of a tuned rotor gyro by using a spinning flex-gimbal system. However, in the process of the ground test, the existence of aerodynamic [...] Read more.

GyroWheel is an innovative device that combines the actuating capabilities of a control moment gyro with the rate sensing capabilities of a tuned rotor gyro by using a spinning flex-gimbal system. However, in the process of the ground test, the existence of aerodynamic disturbance is inevitable, which hinders the improvement of the specification performance and control accuracy. A vacuum tank test is a possible candidate but is sometimes unrealistic due to the substantial increase in costs and complexity involved. In this paper, the aerodynamic drag problem with respect to the 3-DOF flex-gimbal GyroWheel system is investigated by simulation analysis and experimental verification. Concretely, the angular momentum envelope property of the spinning rotor system is studied and its integral dynamical model is deduced based on the physical configuration of the GyroWheel system with an appropriately defined coordinate system. In the sequel, the fluid numerical model is established and the model geometries are checked with FLUENT software. According to the diversity and time-varying properties of the rotor motions in three-dimensions, the airflow field around the GyroWheel rotor is analyzed by simulation with respect to its varying angular velocity and tilt angle. The IPC-based experimental platform is introduced, and the properties of aerodynamic drag in the ground test condition are obtained through comparing the simulation with experimental results. Full article

(This article belongs to the Section Physical Sensors)

► Show Figures

Figure 1

11 pages, 1931 KiB

Open AccessArticle

An Ionic 1,4-Bis(styryl)benzene-Based Fluorescent Probe for Mercury(II) Detection in Water via Deprotection of the Thioacetal Group

by Van Sang Le, Ji-Eun Jeong, Huy Tuan Huynh, Jiae Lee and Han Young Woo

Sensors 2016, 16(12), 2082; https://doi.org/10.3390/s16122082 - 7 Dec 2016

Cited by 8 | Viewed by 6867

Abstract

Highly sensitive and selective mercury detection in aqueous media is urgently needed because mercury poisoning usually results from exposure to water-soluble forms of mercury by inhalation and/or ingesting. An ionic conjugated oligoelectrolye (M1Q) based on 1,4-bis(styryl)benzene was synthesized as a fluorescent mercury(II) probe. [...] Read more.

Highly sensitive and selective mercury detection in aqueous media is urgently needed because mercury poisoning usually results from exposure to water-soluble forms of mercury by inhalation and/or ingesting. An ionic conjugated oligoelectrolye (M1Q) based on 1,4-bis(styryl)benzene was synthesized as a fluorescent mercury(II) probe. The thioacetal moiety and quaternized ammonium group were incorporated for Hg²⁺ recognition and water solubility. A neutral Hg²⁺ probe (M1) was also prepared based on the same molecular backbone, and their sensor characteristics were investigated in a mixture of acetonitrile/water and in water. In the presence of Hg²⁺, the thioacetal group was converted to aldehyde functionality, and the resulting photoluminescence intensity decreased. In water, M1Q successfully demonstrated highly sensitive detection, showing a binding toward Hg²⁺ that was ~15 times stronger and a signal on/off ratio twice as high, compared to M1 in acetonitrile/water. The thioacetal deprotection by Hg²⁺ ions was substantially facilitated in water without an organic cosolvent. The limit of detection was measured to be 7 nM with a detection range of 10–180 nM in 100% aqueous medium. Full article

(This article belongs to the Special Issue Colorimetric and Fluorescent Sensor)

► Show Figures

Figure 1

11 pages, 5057 KiB

Open AccessArticle

Concrete Infill Monitoring in Concrete-Filled FRP Tubes Using a PZT-Based Ultrasonic Time-of-Flight Method

by Mingzhang Luo, Weijie Li, Chuang Hei and Gangbing Song

Sensors 2016, 16(12), 2083; https://doi.org/10.3390/s16122083 - 7 Dec 2016

Cited by 87 | Viewed by 5313

Abstract

Concrete-filled fiber-reinforced polymer tubes (CFFTs) have attracted interest for their structural applications in corrosive environments. However, a weak interfacial strength between the fiber-reinforced polymer (FRP) tube and the concrete infill may develop due to concrete shrinkage and inadequate concrete compaction during concrete casting, [...] Read more.

Concrete-filled fiber-reinforced polymer tubes (CFFTs) have attracted interest for their structural applications in corrosive environments. However, a weak interfacial strength between the fiber-reinforced polymer (FRP) tube and the concrete infill may develop due to concrete shrinkage and inadequate concrete compaction during concrete casting, which will destroy the confinement effect and thereby reduce the load bearing capacity of a CFFT. In this paper, the lead zirconate titanate (PZT)-based ultrasonic time-of-flight (TOF) method was adopted to assess the concrete infill condition of CFFTs. The basic idea of this method is that the velocity of the ultrasonic wave propagation in the FRP material is about half of that in concrete material. Any voids or debonding created along the interface between the FRP tube and the concrete will delay the arrival time between the pairs of PZT transducers. A comparison of the arrival times of the PZT pairs between the intact and the defected CFFT was made to assess the severity of the voids or the debonding. The feasibility of the methodology was analyzed using a finite-difference time-domain-based numerical simulation. Experiments were setup to validate the numerical results, which showed good agreement with the numerical findings. The results showed that the ultrasonic time-of-flight method is able to detect the concrete infill condition of CFFTs. Full article

(This article belongs to the Section Physical Sensors)

► Show Figures

Figure 1

21 pages, 5360 KiB

Open AccessArticle

A Low Cost VLSI Architecture for Spike Sorting Based on Feature Extraction with Peak Search

by Yuan-Jyun Chang, Wen-Jyi Hwang and Chih-Chang Chen

Sensors 2016, 16(12), 2084; https://doi.org/10.3390/s16122084 - 7 Dec 2016

Cited by 3 | Viewed by 5078

Abstract

The goal of this paper is to present a novel VLSI architecture for spike sorting with high classification accuracy, low area costs and low power consumption. A novel feature extraction algorithm with low computational complexities is proposed for the design of the architecture. [...] Read more.

The goal of this paper is to present a novel VLSI architecture for spike sorting with high classification accuracy, low area costs and low power consumption. A novel feature extraction algorithm with low computational complexities is proposed for the design of the architecture. In the feature extraction algorithm, a spike is separated into two portions based on its peak value. The area of each portion is then used as a feature. The algorithm is simple to implement and less susceptible to noise interference. Based on the algorithm, a novel architecture capable of identifying peak values and computing spike areas concurrently is proposed. To further accelerate the computation, a spike can be divided into a number of segments for the local feature computation. The local features are subsequently merged with the global ones by a simple hardware circuit. The architecture can also be easily operated in conjunction with the circuits for commonly-used spike detection algorithms, such as the Non-linear Energy Operator (NEO). The architecture has been implemented by an Application-Specific Integrated Circuit (ASIC) with 90-nm technology. Comparisons to the existing works show that the proposed architecture is well suited for real-time multi-channel spike detection and feature extraction requiring low hardware area costs, low power consumption and high classification accuracy. Full article

(This article belongs to the Special Issue Integrated Sensor Arrays and Array Signal Processing)

► Show Figures

Figure 1

17 pages, 6140 KiB

Open AccessArticle

A Target-Less Vision-Based Displacement Sensor Based on Image Convex Hull Optimization for Measuring the Dynamic Response of Building Structures

by Insub Choi, JunHee Kim and Donghyun Kim

Sensors 2016, 16(12), 2085; https://doi.org/10.3390/s16122085 - 8 Dec 2016

Cited by 30 | Viewed by 7045

Abstract

Existing vision-based displacement sensors (VDSs) extract displacement data through changes in the movement of a target that is identified within the image using natural or artificial structure markers. A target-less vision-based displacement sensor (hereafter called “TVDS”) is proposed. It can extract displacement data [...] Read more.

Existing vision-based displacement sensors (VDSs) extract displacement data through changes in the movement of a target that is identified within the image using natural or artificial structure markers. A target-less vision-based displacement sensor (hereafter called “TVDS”) is proposed. It can extract displacement data without targets, which then serve as feature points in the image of the structure. The TVDS can extract and track the feature points without the target in the image through image convex hull optimization, which is done to adjust the threshold values and to optimize them so that they can have the same convex hull in every image frame and so that the center of the convex hull is the feature point. In addition, the pixel coordinates of the feature point can be converted to physical coordinates through a scaling factor map calculated based on the distance, angle, and focal length between the camera and target. The accuracy of the proposed scaling factor map was verified through an experiment in which the diameter of a circular marker was estimated. A white-noise excitation test was conducted, and the reliability of the displacement data obtained from the TVDS was analyzed by comparing the displacement data of the structure measured with a laser displacement sensor (LDS). The dynamic characteristics of the structure, such as the mode shape and natural frequency, were extracted using the obtained displacement data, and were compared with the numerical analysis results. TVDS yielded highly reliable displacement data and highly accurate dynamic characteristics, such as the natural frequency and mode shape of the structure. As the proposed TVDS can easily extract the displacement data even without artificial or natural markers, it has the advantage of extracting displacement data from any portion of the structure in the image. Full article

(This article belongs to the Section Physical Sensors)

► Show Figures

Figure 1

17 pages, 4868 KiB

Open AccessReview

A Review on Microfluidic Paper-Based Analytical Devices for Glucose Detection

by Shuopeng Liu, Wenqiong Su and Xianting Ding

Sensors 2016, 16(12), 2086; https://doi.org/10.3390/s16122086 - 8 Dec 2016

Cited by 104 | Viewed by 15198

Abstract

Glucose, as an essential substance directly involved in metabolic processes, is closely related to the occurrence of various diseases such as glucose metabolism disorders and islet cell carcinoma. Therefore, it is crucial to develop sensitive, accurate, rapid, and cost effective methods for frequent [...] Read more.

Glucose, as an essential substance directly involved in metabolic processes, is closely related to the occurrence of various diseases such as glucose metabolism disorders and islet cell carcinoma. Therefore, it is crucial to develop sensitive, accurate, rapid, and cost effective methods for frequent and convenient detections of glucose. Microfluidic Paper-based Analytical Devices (μPADs) not only satisfying the above requirements but also occupying the advantages of portability and minimal sample consumption, have exhibited great potential in the field of glucose detection. This article reviews and summarizes the most recent improvements in glucose detection in two aspects of colorimetric and electrochemical μPADs. The progressive techniques for fabricating channels on μPADs are also emphasized in this article. With the growth of diabetes and other glucose indication diseases in the underdeveloped and developing countries, low-cost and reliably commercial μPADs for glucose detection will be in unprecedentedly demand. Full article

(This article belongs to the Special Issue Glucose Sensors: Revolution in Diabetes Management 2016)

► Show Figures

Figure 1

15 pages, 8289 KiB

Open AccessArticle

A Portable Array-Type Optical Fiber Sensing Instrument for Real-Time Gas Detection

by San-Shan Hung, Hsing-Cheng Chang and I-Nan Chang

Sensors 2016, 16(12), 2087; https://doi.org/10.3390/s16122087 - 8 Dec 2016

Cited by 16 | Viewed by 7709

Abstract

A novel optical fiber array-type of sensing instrument with temperature compensation for real-time detection was developed to measure oxygen, carbon dioxide, and ammonia simultaneously. The proposed instrument is multi-sensing array integrated with real-time measurement module for portable applications. The sensing optical fibers were [...] Read more.

A novel optical fiber array-type of sensing instrument with temperature compensation for real-time detection was developed to measure oxygen, carbon dioxide, and ammonia simultaneously. The proposed instrument is multi-sensing array integrated with real-time measurement module for portable applications. The sensing optical fibers were etched and polished before coating to increase sensitivities. The ammonia and temperature sensors were each composed of a dye-coated single-mode fiber with constructing a fiber Bragg grating and a long-period filter grating for detecting light intensity. Both carbon dioxide and oxygen sensing structures use multimode fibers where 1-hydroxy-3,6,8-pyrene trisulfonic acid trisodium salt is coated for carbon dioxide sensing and Tris(2,2′-bipyridyl) dichlororuthenium(II) hexahydrate and Tris(bipyridine)ruthenium(II) chloride are coated for oxygen sensing. Gas-induced fluorescent light intensity variation was applied to detect gas concentration. The portable gas sensing array was set up by integrating with photo-electronic measurement modules and a human-machine interface to detect gases in real time. The measured data have been processed using piecewise-linear method. The sensitivity of the oxygen sensor were 1.54%/V and 9.62%/V for concentrations less than 1.5% and for concentrations between 1.5% and 6%, respectively. The sensitivity of the carbon dioxide sensor were 8.33%/V and 9.62%/V for concentrations less than 2% and for concentrations between 2% and 5%, respectively. For the ammonia sensor, the sensitivity was 27.78%/V, while ammonia concentration was less than 2%. Full article

(This article belongs to the Section Chemical Sensors)

► Show Figures

Figure 1

22 pages, 8124 KiB

Open AccessArticle

An Open Platform for Seamless Sensor Support in Healthcare for the Internet of Things

by Jorge Miranda, Jorge Cabral, Stefan Rahr Wagner, Christian Fischer Pedersen, Blaise Ravelo, Mukhtiar Memon and Morten Mathiesen

Sensors 2016, 16(12), 2089; https://doi.org/10.3390/s16122089 - 8 Dec 2016

Cited by 39 | Viewed by 9304

Abstract

Population aging and increasing pressure on health systems are two issues that demand solutions. Involving and empowering citizens as active managers of their health represents a desirable shift from the current culture mainly focused on treatment of disease, to one also focused on [...] Read more.

Population aging and increasing pressure on health systems are two issues that demand solutions. Involving and empowering citizens as active managers of their health represents a desirable shift from the current culture mainly focused on treatment of disease, to one also focused on continuous health management and well-being. Current developments in technological areas such as the Internet of Things (IoT), lead to new technological solutions that can aid this shift in the healthcare sector. This study presents the design, development, implementation and evaluation of a platform called Common Recognition and Identification Platform (CRIP), a part of the CareStore project, which aims at supporting caregivers and citizens to manage health routines in a seamless way. Specifically, the CRIP offers sensor-based support for seamless identification of users and health devices. A set of initial requirements was defined with a focus on usability limitations and current sensor technologies. The CRIP was designed and implemented using several technologies that enable seamless integration and interaction of sensors and people, namely Near Field Communication and fingerprint biometrics for identification and authentication, Bluetooth for communication with health devices and web services for wider integration with other platforms. Two CRIP prototypes were implemented and evaluated in laboratory during a period of eight months. The evaluations consisted of identifying users and devices, as well as seamlessly configure and acquire vital data from the last. Also, the entire Carestore platform was deployed in a nursing home where its usability was evaluated with caregivers. The evaluations helped assess that seamless identification of users and seamless configuration and communication with health devices is feasible and can help enable the IoT on healthcare applications. Therefore, the CRIP and similar platforms could be transformed into a valuable enabling technology for secure and reliable IoT deployments on the healthcare sector. Full article

(This article belongs to the Special Issue Sensing Technology for Healthcare System)

► Show Figures

Figure 1

17 pages, 2442 KiB

Open AccessArticle

An IMU-to-Body Alignment Method Applied to Human Gait Analysis

by Laura Susana Vargas-Valencia, Arlindo Elias, Eduardo Rocon, Teodiano Bastos-Filho and Anselmo Frizera

Sensors 2016, 16(12), 2090; https://doi.org/10.3390/s16122090 - 10 Dec 2016

Cited by 88 | Viewed by 16199

Abstract

This paper presents a novel calibration procedure as a simple, yet powerful, method to place and align inertial sensors with body segments. The calibration can be easily replicated without the need of any additional tools. The proposed method is validated in three different [...] Read more.

This paper presents a novel calibration procedure as a simple, yet powerful, method to place and align inertial sensors with body segments. The calibration can be easily replicated without the need of any additional tools. The proposed method is validated in three different applications: a computer mathematical simulation; a simplified joint composed of two semi-spheres interconnected by a universal goniometer; and a real gait test with five able-bodied subjects. Simulation results demonstrate that, after the calibration method is applied, the joint angles are correctly measured independently of previous sensor placement on the joint, thus validating the proposed procedure. In the cases of a simplified joint and a real gait test with human volunteers, the method also performs correctly, although secondary plane errors appear when compared with the simulation results. We believe that such errors are caused by limitations of the current inertial measurement unit (IMU) technology and fusion algorithms. In conclusion, the presented calibration procedure is an interesting option to solve the alignment problem when using IMUs for gait analysis. Full article

(This article belongs to the Section Physical Sensors)

► Show Figures

Figure 1

24 pages, 4181 KiB

Open AccessArticle

Adjustable Trajectory Design Based on Node Density for Mobile Sink in WSNs

by Guisong Yang, Shuai Liu, Xingyu He, Naixue Xiong and Chunxue Wu

Sensors 2016, 16(12), 2091; https://doi.org/10.3390/s16122091 - 9 Dec 2016

Cited by 13 | Viewed by 4838

Abstract

The design of movement trajectories for mobile sink plays an important role in data gathering for Wireless Sensor Networks (WSNs), as it affects the network coverage, and packet delivery ratio, as well as the network lifetime. In some scenarios, the whole network can [...] Read more.

The design of movement trajectories for mobile sink plays an important role in data gathering for Wireless Sensor Networks (WSNs), as it affects the network coverage, and packet delivery ratio, as well as the network lifetime. In some scenarios, the whole network can be divided into subareas where the nodes are randomly deployed. The node densities of these subareas are quite different, which may result in a decreased packet delivery ratio and network lifetime if the movement trajectory of the mobile sink cannot adapt to these differences. To address these problems, we propose an adjustable trajectory design method based on node density for mobile sink in WSNs. The movement trajectory of the mobile sink in each subarea follows the Hilbert space-filling curve. Firstly, the trajectory is constructed based on network size. Secondly, the adjustable trajectory is established based on node density in specific subareas. Finally, the trajectories in each subarea are combined to acquire the whole network’s movement trajectory for the mobile sink. In addition, an adaptable power control scheme is designed to adjust nodes’ transmitting range dynamically according to the movement trajectory of the mobile sink in each subarea. The simulation results demonstrate that the proposed trajectories can adapt to network changes flexibly, thus outperform both in packet delivery ratio and in energy consumption the trajectories designed only based on the network size and the whole network node density. Full article

(This article belongs to the Special Issue Topology Control in Emerging Sensor Networks)

► Show Figures

Figure 1

14 pages, 11367 KiB

Open AccessArticle

Resonance-Based Reflector and Its Application in Unidirectional Antenna with Low-Profile and Broadband Characteristics for Wireless Applications

by Lin Peng, Ji-yang Xie, Kai Sun, Xing Jiang and Si-min Li

Sensors 2016, 16(12), 2092; https://doi.org/10.3390/s16122092 - 9 Dec 2016

Cited by 13 | Viewed by 6070

Abstract

In this research, the novel concept of a resonance-based reflector (RBR) was proposed, and a ring-shaped RBR was utilized to design a unidirectional antenna with low-profile and broadband characteristics. Research found the ring operates as two half-wavelength (λ/2) resonators. Then, the [...] Read more.

In this research, the novel concept of a resonance-based reflector (RBR) was proposed, and a ring-shaped RBR was utilized to design a unidirectional antenna with low-profile and broadband characteristics. Research found the ring operates as two half-wavelength (λ/2) resonators. Then, the resonance effect transforms the reflection phase of the ring RBR, and achieves a reflection phase of 0° < ϕ < 180° in a wide frequency range above the resonance. Then, the in-phase reflection characteristic (−90° < ϕ < 90°) can be obtained in the wide frequency band by placing an antenna above the RBR with a distance smaller than λ/4. Two unidirectional antennas, named Case 1 and Case 2, were designed with the ring-shaped RBRs and bowtie antennas (RBR-BAs). The impedance bandwidths of Case 1 and the Case 2 are 2.04–5.12 GHz (86.3%) and 1.97–5.01 GHz (87.1%), respectively. The front-to-back ratio (FBR, an important parameter to measure the unidirectional radiation) of Case 1 ranges from 5–9.9 dB for frequencies 2.04–2.42 GHz, and the FBR of Case 2 ranges from 5–16 dB for frequencies 2.16–3.15 GHz. The proposed concept of RBR is desirable in wideband unidirectional antenna design, and the designing antennas can be used at the front end of wireless systems—such as indoors communication, remote sensing, and wireless sensor systems—for signal receiving or transmitting. Full article

(This article belongs to the Section Physical Sensors)

► Show Figures

Figure 1

12 pages, 888 KiB

Open AccessArticle

Continuous Glucose Monitoring Sensors: Past, Present and Future Algorithmic Challenges

by Andrea Facchinetti

Sensors 2016, 16(12), 2093; https://doi.org/10.3390/s16122093 - 9 Dec 2016

Cited by 134 | Viewed by 16466

Abstract

Continuous glucose monitoring (CGM) sensors are portable devices that allow measuring and visualizing the glucose concentration in real time almost continuously for several days and are provided with hypo/hyperglycemic alerts and glucose trend information. CGM sensors have revolutionized Type 1 diabetes (T1D) management, [...] Read more.

Continuous glucose monitoring (CGM) sensors are portable devices that allow measuring and visualizing the glucose concentration in real time almost continuously for several days and are provided with hypo/hyperglycemic alerts and glucose trend information. CGM sensors have revolutionized Type 1 diabetes (T1D) management, improving glucose control when used adjunctively to self-monitoring blood glucose systems. Furthermore, CGM devices have stimulated the development of applications that were impossible to create without a continuous-time glucose signal, e.g., real-time predictive alerts of hypo/hyperglycemic episodes based on the prediction of future glucose concentration, automatic basal insulin attenuation methods for hypoglycemia prevention, and the artificial pancreas. However, CGM sensors’ lack of accuracy and reliability limited their usability in the clinical practice, calling upon the academic community for the development of suitable signal processing methods to improve CGM performance. The aim of this paper is to review the past and present algorithmic challenges of CGM sensors, to show how they have been tackled by our research group, and to identify the possible future ones. Full article

(This article belongs to the Special Issue Glucose Sensors: Revolution in Diabetes Management 2016)

► Show Figures

Figure 1

11 pages, 1992 KiB

Open AccessArticle

Bent Fiber Sensor for Preservative Detection in Milk

by Omer Galip Saracoglu and Sekip Esat Hayber

Sensors 2016, 16(12), 2094; https://doi.org/10.3390/s16122094 - 9 Dec 2016

Cited by 23 | Viewed by 7744

Abstract

A fiber optic sensor sensitive to refractive index changes of the outer region of the fiber cladding is presented. The sensor uses bent plastic optical fibers in different bending lengths to increase sensitivity. Measurements were made for low-fat milk, the refractive index of [...] Read more.

A fiber optic sensor sensitive to refractive index changes of the outer region of the fiber cladding is presented. The sensor uses bent plastic optical fibers in different bending lengths to increase sensitivity. Measurements were made for low-fat milk, the refractive index of which is altered by some preservatives such as formaldehyde, hydrogen peroxide, and sodium carbonate. Concentrations of the preservatives in the milk were changed between 0% and 14.3% while the refractive indices occurred between 1.34550 and 1.35093 for the minimum (0%) and maximum (14.286%) concentrations of sodium carbonate, respectively. Due to bending-induced sensitivity, the sensor is able to detect refractive index changes less of than 0.4%. The results show that there is excellent linearity between the concentration and normalized response of the sensor. Full article

(This article belongs to the Special Issue Sensors for Biomedical, Environmental and Food Monitoring Applications)

► Show Figures

Figure 1

17 pages, 2659 KiB

Open AccessArticle

A Wide-Swath Spaceborne TOPS SAR Image Formation Algorithm Based on Chirp Scaling and Chirp-Z Transform

by Wei Yang, Jie Chen, Hong Cheng Zeng, Peng Bo Wang and Wei Liu

Sensors 2016, 16(12), 2095; https://doi.org/10.3390/s16122095 - 9 Dec 2016

Cited by 8 | Viewed by 6087

Abstract

Based on the terrain observation by progressive scans (TOPS) mode, an efficient full-aperture image formation algorithm for focusing wide-swath spaceborne TOPS data is proposed. First, to overcome the Doppler frequency spectrum aliasing caused by azimuth antenna steering, the range-independent derotation operation is adopted, [...] Read more.

Based on the terrain observation by progressive scans (TOPS) mode, an efficient full-aperture image formation algorithm for focusing wide-swath spaceborne TOPS data is proposed. First, to overcome the Doppler frequency spectrum aliasing caused by azimuth antenna steering, the range-independent derotation operation is adopted, and the signal properties after derotation are derived in detail. Then, the azimuth deramp operation is performed to resolve image folding in azimuth. The traditional dermap function will introduce a time shift, resulting in appearance of ghost targets and azimuth resolution reduction at the scene edge, especially in the wide-swath coverage case. To avoid this, a novel solution is provided using a modified range-dependent deramp function combined with the chirp-z transform. Moreover, range scaling and azimuth scaling are performed to provide the same azimuth and range sampling interval for all sub-swaths, instead of the interpolation operation for the sub-swath image mosaic. Simulation results are provided to validate the proposed algorithm. Full article

(This article belongs to the Section Remote Sensors)

► Show Figures

Graphical abstract

23 pages, 11280 KiB

Open AccessArticle

Node Deployment with k-Connectivity in Sensor Networks for Crop Information Full Coverage Monitoring

by Naisen Liu, Weixing Cao, Yan Zhu, Jingchao Zhang, Fangrong Pang and Jun Ni

Sensors 2016, 16(12), 2096; https://doi.org/10.3390/s16122096 - 9 Dec 2016

Cited by 11 | Viewed by 6892

Abstract

Wireless sensor networks (WSNs) are suitable for the continuous monitoring of crop information in large-scale farmland. The information obtained is great for regulation of crop growth and achieving high yields in precision agriculture (PA). In order to realize full coverage and k-connectivity [...] Read more.

Wireless sensor networks (WSNs) are suitable for the continuous monitoring of crop information in large-scale farmland. The information obtained is great for regulation of crop growth and achieving high yields in precision agriculture (PA). In order to realize full coverage and k-connectivity WSN deployment for monitoring crop growth information of farmland on a large scale and to ensure the accuracy of the monitored data, a new WSN deployment method using a genetic algorithm (GA) is here proposed. The fitness function of GA was constructed based on the following WSN deployment criteria: (1) nodes must be located in the corresponding plots; (2) WSN must have k-connectivity; (3) WSN must have no communication silos; (4) the minimum distance between node and plot boundary must be greater than a specific value to prevent each node from being affected by the farmland edge effect. The deployment experiments were performed on natural farmland and on irregular farmland divided based on spatial differences of soil nutrients. Results showed that both WSNs gave full coverage, there were no communication silos, and the minimum connectivity of nodes was equal to k. The deployment was tested for different values of k and transmission distance (d) to the node. The results showed that, when d was set to 200 m, as k increased from 2 to 4 the minimum connectivity of nodes increases and is equal to k. When k was set to 2, the average connectivity of all nodes increased in a linear manner with the increase of d from 140 m to 250 m, and the minimum connectivity does not change. Full article

(This article belongs to the Special Issue Topology Control in Emerging Sensor Networks)

► Show Figures

Figure 1

18 pages, 1795 KiB

Open AccessArticle

An Accurate Non-Cooperative Method for Measuring Textureless Spherical Target Based on Calibrated Lasers

by Fei Wang, Hang Dong, Yanan Chen and Nanning Zheng

Sensors 2016, 16(12), 2097; https://doi.org/10.3390/s16122097 - 9 Dec 2016

Cited by 10 | Viewed by 5257

Abstract

Strong demands for accurate non-cooperative target measurement have been arising recently for the tasks of assembling and capturing. Spherical objects are one of the most common targets in these applications. However, the performance of the traditional vision-based reconstruction method was limited for practical [...] Read more.

Strong demands for accurate non-cooperative target measurement have been arising recently for the tasks of assembling and capturing. Spherical objects are one of the most common targets in these applications. However, the performance of the traditional vision-based reconstruction method was limited for practical use when handling poorly-textured targets. In this paper, we propose a novel multi-sensor fusion system for measuring and reconstructing textureless non-cooperative spherical targets. Our system consists of four simple lasers and a visual camera. This paper presents a complete framework of estimating the geometric parameters of textureless spherical targets: (1) an approach to calibrate the extrinsic parameters between a camera and simple lasers; and (2) a method to reconstruct the 3D position of the laser spots on the target surface and achieve the refined results via an optimized scheme. The experiment results show that our proposed calibration method can obtain a fine calibration result, which is comparable to the state-of-the-art LRF-based methods, and our calibrated system can estimate the geometric parameters with high accuracy in real time. Full article

(This article belongs to the Section Physical Sensors)

► Show Figures

Figure 1

20 pages, 14652 KiB

Open AccessArticle

Robust Grape Cluster Detection in a Vineyard by Combining the AdaBoost Framework and Multiple Color Components

by Lufeng Luo, Yunchao Tang, Xiangjun Zou, Chenglin Wang, Po Zhang and Wenxian Feng

Sensors 2016, 16(12), 2098; https://doi.org/10.3390/s16122098 - 10 Dec 2016

Cited by 89 | Viewed by 8735

Abstract

The automatic fruit detection and precision picking in unstructured environments was always a difficult and frontline problem in the harvesting robots field. To realize the accurate identification of grape clusters in a vineyard, an approach for the automatic detection of ripe grape by [...] Read more.

The automatic fruit detection and precision picking in unstructured environments was always a difficult and frontline problem in the harvesting robots field. To realize the accurate identification of grape clusters in a vineyard, an approach for the automatic detection of ripe grape by combining the AdaBoost framework and multiple color components was developed by using a simple vision sensor. This approach mainly included three steps: (1) the dataset of classifier training samples was obtained by capturing the images from grape planting scenes using a color digital camera, extracting the effective color components for grape clusters, and then constructing the corresponding linear classification models using the threshold method; (2) based on these linear models and the dataset, a strong classifier was constructed by using the AdaBoost framework; and (3) all the pixels of the captured images were classified by the strong classifier, the noise was eliminated by the region threshold method and morphological filtering, and the grape clusters were finally marked using the enclosing rectangle method. Nine hundred testing samples were used to verify the constructed strong classifier, and the classification accuracy reached up to 96.56%, higher than other linear classification models. Moreover, 200 images captured under three different illuminations in the vineyard were selected as the testing images on which the proposed approach was applied, and the average detection rate was as high as 93.74%. The experimental results show that the approach can partly restrain the influence of the complex background such as the weather condition, leaves and changing illumination. Full article

(This article belongs to the Section Physical Sensors)

► Show Figures

Figure 1

21 pages, 39184 KiB

Open AccessArticle

Crop Phenology Detection Using High Spatio-Temporal Resolution Data Fused from SPOT5 and MODIS Products

by Yang Zheng, Bingfang Wu, Miao Zhang and Hongwei Zeng

Sensors 2016, 16(12), 2099; https://doi.org/10.3390/s16122099 - 10 Dec 2016

Cited by 61 | Viewed by 8215

Abstract

Timely and efficient monitoring of crop phenology at a high spatial resolution are crucial for the precise and effective management of agriculture. Recently, satellite-derived vegetation indices (VIs), such as the Normalized Difference Vegetation Index (NDVI), have been widely used for the phenology detection [...] Read more.

Timely and efficient monitoring of crop phenology at a high spatial resolution are crucial for the precise and effective management of agriculture. Recently, satellite-derived vegetation indices (VIs), such as the Normalized Difference Vegetation Index (NDVI), have been widely used for the phenology detection of terrestrial ecosystems. In this paper, a framework is proposed to detect crop phenology using high spatio-temporal resolution data fused from Systeme Probatoire d'Observation de la Tarre5 (SPOT5) and Moderate Resolution Imaging Spectroradiometer (MODIS) images. The framework consists of a data fusion method to produce a synthetic NDVI dataset at SPOT5’s spatial resolution and at MODIS’s temporal resolution and a phenology extraction algorithm based on NDVI time-series analysis. The feasibility of our phenology detection approach was evaluated at the county scale in Shandong Province, China. The results show that (1) the Spatial and Temporal Adaptive Reflectance Fusion Model (STARFM) algorithm can accurately blend SPOT5 and MODIS NDVI, with an R² of greater than 0.69 and an root mean square error (RMSE) of less than 0.11 between the predicted and referenced data; and that (2) the estimated phenology parameters, such as the start and end of season (SOS and EOS), were closely correlated with the field-observed data with an R² of the SOS ranging from 0.68 to 0.86 and with an R² of the EOS ranging from 0.72 to 0.79. Our research provides a reliable approach for crop phenology mapping in areas with high fragmented farmland, which is meaningful for the implementation of precision agriculture. Full article

(This article belongs to the Special Issue Precision Agriculture and Remote Sensing Data Fusion)

► Show Figures

Figure 1

24 pages, 1473 KiB

Open AccessArticle

Wi-Fi/MARG Integration for Indoor Pedestrian Localization

by Zengshan Tian, Yue Jin, Mu Zhou, Zipeng Wu and Ze Li

Sensors 2016, 16(12), 2100; https://doi.org/10.3390/s16122100 - 10 Dec 2016

Cited by 51 | Viewed by 5874

Abstract

With the wide deployment of Wi-Fi networks, Wi-Fi based indoor localization systems that are deployed without any special hardware have caught significant attention and have become a currently practical technology. At the same time, the Magnetic, Angular Rate, and Gravity (MARG) sensors installed [...] Read more.

With the wide deployment of Wi-Fi networks, Wi-Fi based indoor localization systems that are deployed without any special hardware have caught significant attention and have become a currently practical technology. At the same time, the Magnetic, Angular Rate, and Gravity (MARG) sensors installed in commercial mobile devices can achieve highly-accurate localization in short time. Based on this, we design a novel indoor localization system by using built-in MARG sensors and a Wi-Fi module. The innovative contributions of this paper include the enhanced Pedestrian Dead Reckoning (PDR) and Wi-Fi localization approaches, and an Extended Kalman Particle Filter (EKPF) based fusion algorithm. A new Wi-Fi/MARG indoor localization system, including an Android based mobile client, a Web page for remote control, and a location server, is developed for real-time indoor pedestrian localization. The extensive experimental results show that the proposed system is featured with better localization performance, with the average error 0.85 m, than the one achieved by using the Wi-Fi module or MARG sensors solely. Full article

(This article belongs to the Section Sensor Networks)

► Show Figures

Figure 1

11 pages, 6733 KiB

Open AccessArticle

Non-Uniform Microstrip Antenna Array for DSRC in Single-Lane Structures

by Tiago Varum, João N. Matos and Pedro Pinho

Sensors 2016, 16(12), 2101; https://doi.org/10.3390/s16122101 - 11 Dec 2016

Cited by 5 | Viewed by 5772

Abstract

Vehicular communications have been subject to a great development in recent years, with multiple applications, such as electronic payments, improving the convenience and comfort of drivers. Its communication network is supported by dedicated short range communications (DSRC), a system composed of onboard units [...] Read more.

Vehicular communications have been subject to a great development in recent years, with multiple applications, such as electronic payments, improving the convenience and comfort of drivers. Its communication network is supported by dedicated short range communications (DSRC), a system composed of onboard units (OBU) and roadside units (RSU). A recently conceived different set-up for the tolling infrastructures consists of placing them in highway access roads, allowing a number of benefits over common gateway infrastructures, divided into several lanes and using complex systems. This paper presents an antenna array whose characteristics are according to the DSRC standards. Additionally, the array holds an innovative radiation pattern adjusted to the new approach requirements, with an almost uniform wide beamwidth along the road width, negligible side lobes, and operating in a significant bandwidth. Full article

(This article belongs to the Special Issue Vehicular Sensor Networks: Technical Challenges, Supports, and Application Experiences)

► Show Figures

Figure 1

12 pages, 6502 KiB

Open AccessArticle

Velocity-Aided Attitude Estimation for Helicopter Aircraft Using Microelectromechanical System Inertial-Measurement Units

by Sang Cheol Lee and Sung Kyung Hong

Sensors 2016, 16(12), 2102; https://doi.org/10.3390/s16122102 - 11 Dec 2016

Cited by 9 | Viewed by 7377

Abstract

This paper presents an algorithm for velocity-aided attitude estimation for helicopter aircraft using a microelectromechanical system inertial-measurement unit. In general, high- performance gyroscopes are used for estimating the attitude of a helicopter, but this type of sensor is very expensive. When designing a [...] Read more.

This paper presents an algorithm for velocity-aided attitude estimation for helicopter aircraft using a microelectromechanical system inertial-measurement unit. In general, high- performance gyroscopes are used for estimating the attitude of a helicopter, but this type of sensor is very expensive. When designing a cost-effective attitude system, attitude can be estimated by fusing a low cost accelerometer and a gyro, but the disadvantage of this method is its relatively low accuracy. The accelerometer output includes a component that occurs primarily as the aircraft turns, as well as the gravitational acceleration. When estimating attitude, the accelerometer measurement terms other than gravitational ones can be considered as disturbances. Therefore, errors increase in accordance with the flight dynamics. The proposed algorithm is designed for using velocity as an aid for high accuracy at low cost. It effectively eliminates the disturbances of accelerometer measurements using the airspeed. The algorithm was verified using helicopter experimental data. The algorithm performance was confirmed through a comparison with an attitude estimate obtained from an attitude heading reference system based on a high accuracy optic gyro, which was employed as core attitude equipment in the helicopter. Full article

(This article belongs to the Collection Modeling, Testing and Reliability Issues in MEMS Engineering)

► Show Figures

Figure 1

18 pages, 5044 KiB

Open AccessArticle

A High-Efficiency Uneven Cluster Deployment Algorithm Based on Network Layered for Event Coverage in UWSNs

by Shanen Yu, Shuai Liu and Peng Jiang

Sensors 2016, 16(12), 2103; https://doi.org/10.3390/s16122103 - 12 Dec 2016

Cited by 13 | Viewed by 4738

Abstract

Most existing deployment algorithms for event coverage in underwater wireless sensor networks (UWSNs) usually do not consider that network communication has non-uniform characteristics on three-dimensional underwater environments. Such deployment algorithms ignore that the nodes are distributed at different depths and have different probabilities [...] Read more.

Most existing deployment algorithms for event coverage in underwater wireless sensor networks (UWSNs) usually do not consider that network communication has non-uniform characteristics on three-dimensional underwater environments. Such deployment algorithms ignore that the nodes are distributed at different depths and have different probabilities for data acquisition, thereby leading to imbalances in the overall network energy consumption, decreasing the network performance, and resulting in poor and unreliable late network operation. Therefore, in this study, we proposed an uneven cluster deployment algorithm based network layered for event coverage. First, according to the energy consumption requirement of the communication load at different depths of the underwater network, we obtained the expected value of deployment nodes and the distribution density of each layer network after theoretical analysis and deduction. Afterward, the network is divided into multilayers based on uneven clusters, and the heterogeneous communication radius of nodes can improve the network connectivity rate. The recovery strategy is used to balance the energy consumption of nodes in the cluster and can efficiently reconstruct the network topology, which ensures that the network has a high network coverage and connectivity rate in a long period of data acquisition. Simulation results show that the proposed algorithm improves network reliability and prolongs network lifetime by significantly reducing the blind movement of overall network nodes while maintaining a high network coverage and connectivity rate. Full article

(This article belongs to the Special Issue Sensing Technologies for Autonomy and Cooperation in Underwater Networked Robot Systems)

► Show Figures

Figure 1

27 pages, 2046 KiB

Open AccessArticle

Conceptual Design of a Nano-Networking Device

by Sebastian Canovas-Carrasco, Antonio-Javier Garcia-Sanchez, Felipe Garcia-Sanchez and Joan Garcia-Haro

Sensors 2016, 16(12), 2104; https://doi.org/10.3390/s16122104 - 11 Dec 2016

Cited by 35 | Viewed by 7731

Abstract

Nanotechnology is an emerging scientific area whose advances, among many others, have a positive direct impact on the miniaturization of electronics. This unique technology enables the possibility to design and build electronic components as well as complete devices (called nanomachines or nanodevices) at [...] Read more.

Nanotechnology is an emerging scientific area whose advances, among many others, have a positive direct impact on the miniaturization of electronics. This unique technology enables the possibility to design and build electronic components as well as complete devices (called nanomachines or nanodevices) at the nano scale. A nanodevice is expected to be an essential element able to operate in a nanonetwork, where a huge number of them would coordinate to acquire data, process the information gathered, and wirelessly transmit those data to end-points providing innovative services in many key scenarios, such as the human body or the environment. This paper is aimed at studying the feasibility of this type of device by carefully examining their main component parts, namely the nanoprocessor, nanomemory, nanoantenna, and nanogenerator. To this end, a thorough state-of-the-art review is conveyed to discuss, substantiate, and select the most suitable current technology (commercial or pre-commercial) for each component. Then, we further contribute by developing a complete conceptual nanodevice layout taking into consideration its ultra-small size (similar to a blood cell) and its very restricted capabilities (e.g., processing, memory storage, telecommunication, and energy management). The required resources as well as the power consumption are realistically estimated. Full article

(This article belongs to the Section Sensor Networks)

► Show Figures

Graphical abstract

15 pages, 2594 KiB

Open AccessArticle

Performance Evaluation of State of the Art Systems for Physical Activity Classification of Older Subjects Using Inertial Sensors in a Real Life Scenario: A Benchmark Study

by Muhammad Awais, Luca Palmerini, Alan K. Bourke, Espen A.F. Ihlen, Jorunn L. Helbostad and Lorenzo Chiari

Sensors 2016, 16(12), 2105; https://doi.org/10.3390/s16122105 - 11 Dec 2016

Cited by 27 | Viewed by 6744

Abstract

The popularity of using wearable inertial sensors for physical activity classification has dramatically increased in the last decade due to their versatility, low form factor, and low power requirements. Consequently, various systems have been developed to automatically classify daily life activities. However, the [...] Read more.

The popularity of using wearable inertial sensors for physical activity classification has dramatically increased in the last decade due to their versatility, low form factor, and low power requirements. Consequently, various systems have been developed to automatically classify daily life activities. However, the scope and implementation of such systems is limited to laboratory-based investigations. Furthermore, these systems are not directly comparable, due to the large diversity in their design (e.g., number of sensors, placement of sensors, data collection environments, data processing techniques, features set, classifiers, cross-validation methods). Hence, the aim of this study is to propose a fair and unbiased benchmark for the field-based validation of three existing systems, highlighting the gap between laboratory and real-life conditions. For this purpose, three representative state-of-the-art systems are chosen and implemented to classify the physical activities of twenty older subjects (76.4 ± 5.6 years). The performance in classifying four basic activities of daily life (sitting, standing, walking, and lying) is analyzed in controlled and free living conditions. To observe the performance of laboratory-based systems in field-based conditions, we trained the activity classification systems using data recorded in a laboratory environment and tested them in real-life conditions in the field. The findings show that the performance of all systems trained with data in the laboratory setting highly deteriorates when tested in real-life conditions, thus highlighting the need to train and test the classification systems in the real-life setting. Moreover, we tested the sensitivity of chosen systems to window size (from 1 s to 10 s) suggesting that overall accuracy decreases with increasing window size. Finally, to evaluate the impact of the number of sensors on the performance, chosen systems are modified considering only the sensing unit worn at the lower back. The results, similarly to the multi-sensor setup, indicate substantial degradation of the performance when laboratory-trained systems are tested in the real-life setting. This degradation is higher than in the multi-sensor setup. Still, the performance provided by the single-sensor approach, when trained and tested with real data, can be acceptable (with an accuracy above 80%). Full article

(This article belongs to the Special Issue Body Worn Behavior Sensing)

► Show Figures

Figure 1

24 pages, 7284 KiB

Open AccessArticle

Integrated Fault Diagnosis Algorithm for Motor Sensors of In-Wheel Independent Drive Electric Vehicles

by Namju Jeon and Hyeongcheol Lee

Sensors 2016, 16(12), 2106; https://doi.org/10.3390/s16122106 - 12 Dec 2016

Cited by 19 | Viewed by 6080

Abstract

An integrated fault-diagnosis algorithm for a motor sensor of in-wheel independent drive electric vehicles is presented. This paper proposes a method that integrates the high- and low-level fault diagnoses to improve the robustness and performance of the system. For the high-level fault diagnosis [...] Read more.

An integrated fault-diagnosis algorithm for a motor sensor of in-wheel independent drive electric vehicles is presented. This paper proposes a method that integrates the high- and low-level fault diagnoses to improve the robustness and performance of the system. For the high-level fault diagnosis of vehicle dynamics, a planar two-track non-linear model is first selected, and the longitudinal and lateral forces are calculated. To ensure redundancy of the system, correlation between the sensor and residual in the vehicle dynamics is analyzed to detect and separate the fault of the drive motor system of each wheel. To diagnose the motor system for low-level faults, the state equation of an interior permanent magnet synchronous motor is developed, and a parity equation is used to diagnose the fault of the electric current and position sensors. The validity of the high-level fault-diagnosis algorithm is verified using Carsim and Matlab/Simulink co-simulation. The low-level fault diagnosis is verified through Matlab/Simulink simulation and experiments. Finally, according to the residuals of the high- and low-level fault diagnoses, fault-detection flags are defined. On the basis of this information, an integrated fault-diagnosis strategy is proposed. Full article

(This article belongs to the Section Physical Sensors)

► Show Figures

Figure 1

10 pages, 815 KiB

Open AccessArticle

Acoustical Direction Finding with Time-Modulated Arrays

by Ben Clark and James A. Flint

Sensors 2016, 16(12), 2107; https://doi.org/10.3390/s16122107 - 11 Dec 2016

Cited by 15 | Viewed by 6631

Abstract

Time-Modulated Linear Arrays (TMLAs) offer useful efficiency savings over conventional phased arrays when applied in parameter estimation applications. The present paper considers the application of TMLAs to acoustic systems and proposes an algorithm for efficiently deriving the arrival angle of a signal. The [...] Read more.

Time-Modulated Linear Arrays (TMLAs) offer useful efficiency savings over conventional phased arrays when applied in parameter estimation applications. The present paper considers the application of TMLAs to acoustic systems and proposes an algorithm for efficiently deriving the arrival angle of a signal. The proposed technique is applied in the frequency domain, where the signal and harmonic content is captured. Using a weighted average method on harmonic amplitudes and their respective main beam angles, it is possible to determine an estimate for the signal’s direction of arrival. The method is demonstrated and evaluated using results from both numerical and practical implementations and performance data is provided. The use of Micro-Electromechanical Systems (MEMS) sensors allows time-modulation techniques to be applied at ultrasonic frequencies. Theoretical predictions for an array of five isotropic elements with half-wavelength spacing and 1000 data samples suggest an accuracy of

\pm 1^{\circ}

within an angular range of approximately

\pm 50^{\circ}

. In experiments of a 40 kHz five-element microphone array, a Direction of Arrival (DoA) estimation within

\pm 2 . 5^{\circ}

of the target signal is readily achieved inside a

\pm 45^{\circ}

range using a single switched input stage and a simple hardware setup. Full article

(This article belongs to the Special Issue Integrated Sensor Arrays and Array Signal Processing)

► Show Figures

Figure 1

12 pages, 2343 KiB

Open AccessArticle

Development and Characterization a Single-Active-Chamber Piezoelectric Membrane Pump with Multiple Passive Check Valves

by Ronghui Zhang, Feng You, Zhihan Lv, Zhaocheng He, Haiwei Wang and Ling Huang

Sensors 2016, 16(12), 2108; https://doi.org/10.3390/s16122108 - 12 Dec 2016

Cited by 35 | Viewed by 7460

Abstract

In order to prevent the backward flow of piezoelectric pumps, this paper presents a single-active-chamber piezoelectric membrane pump with multiple passive check valves. Under the condition of a fixed total number of passive check valves, by means of changing the inlet valves and [...] Read more.

In order to prevent the backward flow of piezoelectric pumps, this paper presents a single-active-chamber piezoelectric membrane pump with multiple passive check valves. Under the condition of a fixed total number of passive check valves, by means of changing the inlet valves and outlet valves’ configuration, the pumping characteristics in terms of flow rate and backpressure are experimentally investigated. Like the maximum flow rate and backpressure, the testing results show that the optimal frequencies are significantly affected by changes in the number inlet valves and outlet valves. The variation ratios of the maximum flow rate and the maximum backpressure are up to 66% and less than 20%, respectively. Furthermore, the piezoelectric pump generally demonstrates very similar flow rate and backpressure characteristics when the number of inlet valves in one kind of configuration is the same as that of outlet valves in another configuration. The comparison indicates that the backflow from the pumping chamber to inlet is basically the same as the backflow from the outlet to the pumping chamber. No matter whether the number of inlet valves or the number of outlet valves is increased, the backflow can be effectively reduced. In addition, the backpressure fluctuation can be significantly suppressed with an increase of either inlet valves or outlet valves. It also means that the pump can prevent the backflow more effectively at the cost of power consumption. The pump is very suitable for conditions where more accurate flow rates are needed and wear and fatigue of check valves often occur. Full article

(This article belongs to the Special Issue Enabling the Move from Wireless Sensor Networks to Internet of Things and Cyber-Physical Systems)

► Show Figures

Figure 1

20 pages, 2373 KiB

Open AccessArticle

DOA and Polarization Estimation Using an Electromagnetic Vector Sensor Uniform Circular Array Based on the ESPRIT Algorithm

by Na Wu, Zhiyu Qu, Weijian Si and Shuhong Jiao

Sensors 2016, 16(12), 2109; https://doi.org/10.3390/s16122109 - 13 Dec 2016

Cited by 22 | Viewed by 6430

Abstract

In array signal processing systems, the direction of arrival (DOA) and polarization of signals based on uniform linear or rectangular sensor arrays are generally obtained by rotational invariance techniques (ESPRIT). However, since the ESPRIT algorithm relies on the rotational invariant structure of the [...] Read more.

In array signal processing systems, the direction of arrival (DOA) and polarization of signals based on uniform linear or rectangular sensor arrays are generally obtained by rotational invariance techniques (ESPRIT). However, since the ESPRIT algorithm relies on the rotational invariant structure of the received data, it cannot be applied to electromagnetic vector sensor arrays (EVSAs) featuring uniform circular patterns. To overcome this limitation, a fourth-order cumulant-based ESPRIT algorithm is proposed in this paper, for joint estimation of DOA and polarization based on a uniform circular EVSA. The proposed algorithm utilizes the fourth-order cumulant to obtain a virtual extended array of a uniform circular EVSA, from which the pairs of rotation invariant sub-arrays are obtained. The ESPRIT algorithm and parameter pair matching are then utilized to estimate the DOA and polarization of the incident signals. The closed-form parameter estimation algorithm can effectively reduce the computational complexity of the joint estimation, which has been demonstrated by numerical simulations. Full article

(This article belongs to the Section Physical Sensors)

► Show Figures

Figure 1

8 pages, 2686 KiB

Open AccessCommunication

Airborne Transducer Integrity under Operational Environment for Structural Health Monitoring

by Mohammad Saleh Salmanpour, Zahra Sharif Khodaei and Mohammad Hossein Aliabadi

Sensors 2016, 16(12), 2110; https://doi.org/10.3390/s16122110 - 12 Dec 2016

Cited by 46 | Viewed by 5683

Abstract

This paper investigates the robustness of permanently mounted transducers used in airborne structural health monitoring systems, when exposed to the operational environment. Typical airliners operate in a range of conditions, hence, structural health monitoring (SHM) transducer robustness and integrity must be demonstrated for [...] Read more.

This paper investigates the robustness of permanently mounted transducers used in airborne structural health monitoring systems, when exposed to the operational environment. Typical airliners operate in a range of conditions, hence, structural health monitoring (SHM) transducer robustness and integrity must be demonstrated for these environments. A set of extreme temperature, altitude and vibration environment test profiles are developed using the existing Radio Technical Commission for Aeronautics (RTCA)/DO-160 test methods. Commercially available transducers and manufactured versions bonded to carbon fibre reinforced polymer (CFRP) composite materials are tested. It was found that the DuraAct transducer is robust to environmental conditions tested, while the other transducer types degrade under the same conditions. Full article

(This article belongs to the Special Issue Ultrasonic Sensors)

► Show Figures

Figure 1

12 pages, 5072 KiB

Open AccessArticle

Evaluation of Laser-Assisted Trans-Nail Drug Delivery with Optical Coherence Tomography

by Meng-Tsan Tsai, Ting-Yen Tsai, Su-Chin Shen, Chau Yee Ng, Ya-Ju Lee, Jiann-Der Lee and Chih-Hsun Yang

Sensors 2016, 16(12), 2111; https://doi.org/10.3390/s16122111 - 12 Dec 2016

Cited by 23 | Viewed by 6223

Abstract

The nail provides a functional protection to the fingertips and surrounding tissue from external injuries. The nail plate consists of three layers including dorsal, intermediate, and ventral layers. The dorsal layer consists of compact, hard keratins, limiting topical drug delivery through the nail. [...] Read more.

The nail provides a functional protection to the fingertips and surrounding tissue from external injuries. The nail plate consists of three layers including dorsal, intermediate, and ventral layers. The dorsal layer consists of compact, hard keratins, limiting topical drug delivery through the nail. In this study, we investigate the application of fractional CO₂ laser that produces arrays of microthermal ablation zones (MAZs) to facilitate drug delivery in the nails. We utilized optical coherence tomography (OCT) for real-time monitoring of the laser–skin tissue interaction, sparing the patient from an invasive surgical sampling procedure. The time-dependent OCT intensity variance was used to observe drug diffusion through an induced MAZ array. Subsequently, nails were treated with cream and liquid topical drugs to investigate the feasibility and diffusion efficacy of laser-assisted drug delivery. Our results show that fractional CO₂ laser improves the effectiveness of topical drug delivery in the nail plate and that OCT could potentially be used for in vivo monitoring of the depth of laser penetration as well as real-time observations of drug delivery. Full article

(This article belongs to the Special Issue Optical Methods in Sensing and Imaging for Medical and Biological Applications)

► Show Figures

Figure 1

18 pages, 7000 KiB

Open AccessArticle

Application of Template Matching for Improving Classification of Urban Railroad Point Clouds

by Mostafa Arastounia and Sander Oude Elberink

Sensors 2016, 16(12), 2112; https://doi.org/10.3390/s16122112 - 12 Dec 2016

Cited by 32 | Viewed by 6760

Abstract

This study develops an integrated data-driven and model-driven approach (template matching) that clusters the urban railroad point clouds into three classes of rail track, contact cable, and catenary cable. The employed dataset covers 630 m of the Dutch urban railroad corridors in which [...] Read more.

This study develops an integrated data-driven and model-driven approach (template matching) that clusters the urban railroad point clouds into three classes of rail track, contact cable, and catenary cable. The employed dataset covers 630 m of the Dutch urban railroad corridors in which there are four rail tracks, two contact cables, and two catenary cables. The dataset includes only geometrical information (three dimensional (3D) coordinates of the points) with no intensity data and no RGB data. The obtained results indicate that all objects of interest are successfully classified at the object level with no false positives and no false negatives. The results also show that an average 97.3% precision and an average 97.7% accuracy at the point cloud level are achieved. The high precision and high accuracy of the rail track classification (both greater than 96%) at the point cloud level stems from the great impact of the employed template matching method on excluding the false positives. The cables also achieve quite high average precision (96.8%) and accuracy (98.4%) due to their high sampling and isolated position in the railroad corridor. Full article

(This article belongs to the Special Issue Urban Remote Sensing: Monitoring, Synthesis and Modeling in the Urban Environment)

► Show Figures

Graphical abstract

18 pages, 1964 KiB

Open AccessArticle

A New Continuous Rotation IMU Alignment Algorithm Based on Stochastic Modeling for Cost Effective North-Finding Applications

by Yun Li, Wenqi Wu, Qingan Jiang and Jinling Wang

Sensors 2016, 16(12), 2113; https://doi.org/10.3390/s16122113 - 13 Dec 2016

Cited by 5 | Viewed by 5661

Abstract

Based on stochastic modeling of Coriolis vibration gyros by the Allan variance technique, this paper discusses Angle Random Walk (ARW), Rate Random Walk (RRW) and Markov process gyroscope noises which have significant impacts on the North-finding accuracy. A new continuous rotation alignment algorithm [...] Read more.

Based on stochastic modeling of Coriolis vibration gyros by the Allan variance technique, this paper discusses Angle Random Walk (ARW), Rate Random Walk (RRW) and Markov process gyroscope noises which have significant impacts on the North-finding accuracy. A new continuous rotation alignment algorithm for a Coriolis vibration gyroscope Inertial Measurement Unit (IMU) is proposed in this paper, in which the extended observation equations are used for the Kalman filter to enhance the estimation of gyro drift errors, thus improving the north-finding accuracy. Theoretical and numerical comparisons between the proposed algorithm and the traditional ones are presented. The experimental results show that the new continuous rotation alignment algorithm using the extended observation equations in the Kalman filter is more efficient than the traditional two-position alignment method. Using Coriolis vibration gyros with bias instability of 0.1°/h, a north-finding accuracy of 0.1° (1σ) is achieved by the new continuous rotation alignment algorithm, compared with 0.6° (1σ) north-finding accuracy for the two-position alignment and 1° (1σ) for the fixed-position alignment. Full article

(This article belongs to the Special Issue Inertial Sensors and Systems 2016)

► Show Figures

Figure 1

20 pages, 4968 KiB

Open AccessArticle

An Extensive Unified Thermo-Electric Module Characterization Method

by Filippo Attivissimo, Carlo Guarnieri Calò Carducci, Anna Maria Lucia Lanzolla and Maurizio Spadavecchia

Sensors 2016, 16(12), 2114; https://doi.org/10.3390/s16122114 - 13 Dec 2016

Cited by 25 | Viewed by 5239

Abstract

Thermo-Electric Modules (TEMs) are being increasingly used in power generation as a valid alternative to batteries, providing autonomy to sensor nodes or entire Wireless Sensor Networks, especially for energy harvesting applications. Often, manufacturers provide some essential parameters under determined conditions, like for example, [...] Read more.

Thermo-Electric Modules (TEMs) are being increasingly used in power generation as a valid alternative to batteries, providing autonomy to sensor nodes or entire Wireless Sensor Networks, especially for energy harvesting applications. Often, manufacturers provide some essential parameters under determined conditions, like for example, maximum temperature difference between the surfaces of the TEM or for maximum heat absorption, but in many cases, a TEM-based system is operated under the best conditions only for a fraction of the time, thus, when dynamic working conditions occur, the performance estimation of TEMs is crucial to determine their actual efficiency. The focus of this work is on using a novel procedure to estimate the parameters of both the electrical and thermal equivalent model and investigate their relationship with the operating temperature and the temperature gradient. The novelty of the method consists in the use of a simple test configuration to stimulate the modules and simultaneously acquire electrical and thermal data to obtain all parameters in a single test. Two different current profiles are proposed as possible stimuli, which use depends on the available test instrumentation, and relative performance are compared both quantitatively and qualitatively, in terms of standard deviation and estimation uncertainty. Obtained results, besides agreeing with both technical literature and a further estimation method based on module specifications, also provides the designer a detailed description of the module behavior, useful to simulate its performance in different scenarios. Full article

(This article belongs to the Section Sensor Networks)

► Show Figures

Figure 1

13 pages, 808 KiB

Open AccessArticle

Greedy Successive Anchorization for Localizing Machine Type Communication Devices

by Mian Imtiaz Ul Haq and Dongwoo Kim

Sensors 2016, 16(12), 2115; https://doi.org/10.3390/s16122115 - 13 Dec 2016

Cited by 3 | Viewed by 4060

Abstract

Localization of machine type communication (MTC) devices is essential for various types of location-based applications. In this paper, we investigate a distributed localization problem in noisy networks, where an estimated position of blind MTC machines (BMs) is obtained by using noisy measurements of [...] Read more.

Localization of machine type communication (MTC) devices is essential for various types of location-based applications. In this paper, we investigate a distributed localization problem in noisy networks, where an estimated position of blind MTC machines (BMs) is obtained by using noisy measurements of distance between BM and anchor machines (AMs). We allow positioned BMs also to work as anchors that are referred to as virtual AMs (VAMs) in this paper. VAMs usually have greater position errors than (original) AMs, and, if used as anchors, the error propagates through the whole network. However, VAMs are necessary, especially when many BMs are distributed in a large area with an insufficient number of AMs. To overcome the error propagation, we propose a greedy successive anchorization process (GSAP). A round of GSAP consists of consecutive two steps. In the first step, a greedy selection of anchors among AMs and VAMs is done by which GSAP considers only those three anchors that possibly pertain to the localization accuracy. In the second step, each BM that can select three anchors in its neighbor determines its location with a proposed distributed localization algorithm. Iterative rounds of GSAP terminate when every BM in the network finds its location. To examine the performance of GSAP, a root mean square error (RMSE) metric is used and the corresponding Cramér–Rao lower bound (CRLB) is provided. By numerical investigation, RMSE performance of GSAP is shown to be better than existing localization methods with and without an anchor selection method and mostly close to the CRLB. Full article

(This article belongs to the Section Sensor Networks)

► Show Figures

Figure 1

16 pages, 2728 KiB

Open AccessArticle

A Small Leak Detection Method Based on VMD Adaptive De-Noising and Ambiguity Correlation Classification Intended for Natural Gas Pipelines

by Qiyang Xiao, Jian Li, Zhiliang Bai, Jiedi Sun, Nan Zhou and Zhoumo Zeng

Sensors 2016, 16(12), 2116; https://doi.org/10.3390/s16122116 - 13 Dec 2016

Cited by 55 | Viewed by 6290

Abstract

In this study, a small leak detection method based on variational mode decomposition (VMD) and ambiguity correlation classification (ACC) is proposed. The signals acquired from sensors were decomposed using the VMD, and numerous components were obtained. According to the probability density function (PDF), [...] Read more.

In this study, a small leak detection method based on variational mode decomposition (VMD) and ambiguity correlation classification (ACC) is proposed. The signals acquired from sensors were decomposed using the VMD, and numerous components were obtained. According to the probability density function (PDF), an adaptive de-noising algorithm based on VMD is proposed for noise component processing and de-noised components reconstruction. Furthermore, the ambiguity function image was employed for analysis of the reconstructed signals. Based on the correlation coefficient, ACC is proposed to detect the small leak of pipeline. The analysis of pipeline leakage signals, using 1 mm and 2 mm leaks, has shown that proposed detection method can detect a small leak accurately and effectively. Moreover, the experimental results have shown that the proposed method achieved better performances than support vector machine (SVM) and back propagation neural network (BP) methods. Full article

(This article belongs to the Section Physical Sensors)

► Show Figures

Figure 1

23 pages, 4693 KiB

Open AccessArticle

Detecting Target Objects by Natural Language Instructions Using an RGB-D Camera

by Jiatong Bao, Yunyi Jia, Yu Cheng, Hongru Tang and Ning Xi

Sensors 2016, 16(12), 2117; https://doi.org/10.3390/s16122117 - 13 Dec 2016

Cited by 3 | Viewed by 6976

Abstract

Controlling robots by natural language (NL) is increasingly attracting attention for its versatility, convenience and no need of extensive training for users. Grounding is a crucial challenge of this problem to enable robots to understand NL instructions from humans. This paper mainly explores [...] Read more.

Controlling robots by natural language (NL) is increasingly attracting attention for its versatility, convenience and no need of extensive training for users. Grounding is a crucial challenge of this problem to enable robots to understand NL instructions from humans. This paper mainly explores the object grounding problem and concretely studies how to detect target objects by the NL instructions using an RGB-D camera in robotic manipulation applications. In particular, a simple yet robust vision algorithm is applied to segment objects of interest. With the metric information of all segmented objects, the object attributes and relations between objects are further extracted. The NL instructions that incorporate multiple cues for object specifications are parsed into domain-specific annotations. The annotations from NL and extracted information from the RGB-D camera are matched in a computational state estimation framework to search all possible object grounding states. The final grounding is accomplished by selecting the states which have the maximum probabilities. An RGB-D scene dataset associated with different groups of NL instructions based on different cognition levels of the robot are collected. Quantitative evaluations on the dataset illustrate the advantages of the proposed method. The experiments of NL controlled object manipulation and NL-based task programming using a mobile manipulator show its effectiveness and practicability in robotic applications. Full article

(This article belongs to the Special Issue Video Analysis and Tracking Using State-of-the-Art Sensors)

► Show Figures

Figure 1

29 pages, 12843 KiB

Open AccessArticle

Vision-Based Corrosion Detection Assisted by a Micro-Aerial Vehicle in a Vessel Inspection Application

by Alberto Ortiz, Francisco Bonnin-Pascual, Emilio Garcia-Fidalgo and Joan P. Company-Corcoles

Sensors 2016, 16(12), 2118; https://doi.org/10.3390/s16122118 - 14 Dec 2016

Cited by 71 | Viewed by 14328

Abstract

Vessel maintenance requires periodic visual inspection of the hull in order to detect typical defective situations of steel structures such as, among others, coating breakdown and corrosion. These inspections are typically performed by well-trained surveyors at great cost because of the need for [...] Read more.

Vessel maintenance requires periodic visual inspection of the hull in order to detect typical defective situations of steel structures such as, among others, coating breakdown and corrosion. These inspections are typically performed by well-trained surveyors at great cost because of the need for providing access means (e.g., scaffolding and/or cherry pickers) that allow the inspector to be at arm’s reach from the structure under inspection. This paper describes a defect detection approach comprising a micro-aerial vehicle which is used to collect images from the surfaces under inspection, particularly focusing on remote areas where the surveyor has no visual access, and a coating breakdown/corrosion detector based on a three-layer feed-forward artificial neural network. As it is discussed in the paper, the success of the inspection process depends not only on the defect detection software but also on a number of assistance functions provided by the control architecture of the aerial platform, whose aim is to improve picture quality. Both aspects of the work are described along the different sections of the paper, as well as the classification performance attained. Full article

(This article belongs to the Special Issue Vision-Based Sensors in Field Robotics)

► Show Figures

Figure 1

11 pages, 2687 KiB

Open AccessArticle

Refractive Index Sensing with D-Shaped Plastic Optical Fibers for Chemical and Biochemical Applications

by Filipa Sequeira, Daniel Duarte, Lúcia Bilro, Alisa Rudnitskaya, Maria Pesavento, Luigi Zeni and Nunzio Cennamo

Sensors 2016, 16(12), 2119; https://doi.org/10.3390/s16122119 - 13 Dec 2016

Cited by 65 | Viewed by 9316

Abstract

We report the optimization of the length of a D-shaped plastic optical fiber (POF) sensor for refractive index (RI) sensing from a numerical and experimental point of view. The sensing principle is based on total internal reflection (TIR). POFs with 1 mm in [...] Read more.

We report the optimization of the length of a D-shaped plastic optical fiber (POF) sensor for refractive index (RI) sensing from a numerical and experimental point of view. The sensing principle is based on total internal reflection (TIR). POFs with 1 mm in diameter were embedded in grooves, realized in planar supports with different lengths, and polished to remove the cladding and part of the core. All D-shaped POF sensors were tested using aqueous medium with different refractive indices (from 1.332 to 1.471) through intensity-based configuration. Results showed two different responses. Considering the refractive index (RI) range (1.33–1.39), the sensitivity and the resolution of the sensor were strongly dependent on the sensing region length. The highest sensitivity (resolution of 6.48 × 10⁻³ refractive index units, RIU) was obtained with 6 cm sensing length. In the RI range (1.41–1.47), the length of the sensing region was not a critical aspect to obtain the best resolution. These results enable the application of this optical platform for chemical and biochemical evanescent field sensing. The sensor production procedure is very simple, fast, and low-cost. Full article

(This article belongs to the Special Issue Specialty Optical Fibers for Chemical and Biochemical Sensing: From Evanescent Waves to Plasmonic Interaction)

► Show Figures

Figure 1

10 pages, 5620 KiB

Open AccessArticle

Efficient Terahertz Wide-Angle NUFFT-Based Inverse Synthetic Aperture Imaging Considering Spherical Wavefront

by Jingkun Gao, Bin Deng, Yuliang Qin, Hongqiang Wang and Xiang Li

Sensors 2016, 16(12), 2120; https://doi.org/10.3390/s16122120 - 14 Dec 2016

Cited by 12 | Viewed by 5421

Abstract

An efficient wide-angle inverse synthetic aperture imaging method considering the spherical wavefront effects and suitable for the terahertz band is presented. Firstly, the echo signal model under spherical wave assumption is established, and the detailed wavefront curvature compensation method accelerated by 1D fast [...] Read more.

An efficient wide-angle inverse synthetic aperture imaging method considering the spherical wavefront effects and suitable for the terahertz band is presented. Firstly, the echo signal model under spherical wave assumption is established, and the detailed wavefront curvature compensation method accelerated by 1D fast Fourier transform (FFT) is discussed. Then, to speed up the reconstruction procedure, the fast Gaussian gridding (FGG)-based nonuniform FFT (NUFFT) is employed to focus the image. Finally, proof-of-principle experiments are carried out and the results are compared with the ones obtained by the convolution back-projection (CBP) algorithm. The results demonstrate the effectiveness and the efficiency of the presented method. This imaging method can be directly used in the field of nondestructive detection and can also be used to provide a solution for the calculation of the far-field RCSs (Radar Cross Section) of targets in the terahertz regime. Full article

(This article belongs to the Special Issue Advances in Applied Remote Sensing and Decision Making: Transforming Hazard Assessment and Environmental Management)

► Show Figures

Figure 1

15 pages, 3296 KiB

Open AccessArticle

Design and Optimization of a Hybrid-Driven Waist Rehabilitation Robot

by Bin Zi, Guangcai Yin and Dan Zhang

Sensors 2016, 16(12), 2121; https://doi.org/10.3390/s16122121 - 14 Dec 2016

Cited by 32 | Viewed by 7430

Abstract

In this paper a waist rehabilitation robot driven by cables and pneumatic artificial muscles (PAMs) has been conceptualized and designed. In the process of mechanism design, the human body structure, the waist movement characteristics, and the actuators’ driving characteristics are the main considerable [...] Read more.

In this paper a waist rehabilitation robot driven by cables and pneumatic artificial muscles (PAMs) has been conceptualized and designed. In the process of mechanism design, the human body structure, the waist movement characteristics, and the actuators’ driving characteristics are the main considerable factors to make the hybrid-driven waist rehabilitation robot (HWRR) cost-effective, safe, flexible, and well-adapted. A variety of sensors are chosen to measure the position and orientation of the recovery patient to ensure patient safety at the same time as the structure design. According to the structure specialty and function, the HWRR is divided into two independent parallel robots: the waist twist device and the lower limb traction device. Then these two devices are analyzed and evaluated, respectively. Considering the characters of the human body in the HWRR, the inverse kinematics and statics are studied when the waist and the lower limb are considered as a spring and link, respectively. Based on the inverse kinematics and statics, the effect of the contraction parameter of the PAM is considered in the optimization of the waist twist device, and the lower limb traction device is optimized using particle swarm optimization (PSO) to minimize the global conditioning number over the feasible workspace. As a result of the optimization, an optimal rehabilitation robot design is obtained and the condition number of the Jacobian matrix over the feasible workspace is also calculated. Full article

(This article belongs to the Special Issue Advanced Robotics and Mechatronics Devices)

► Show Figures

Figure 1

21 pages, 6739 KiB

Open AccessArticle

Urban Growth Modeling Using Cellular Automata with Multi-Temporal Remote Sensing Images Calibrated by the Artificial Bee Colony Optimization Algorithm

by Fereydoun Naghibi, Mahmoud Reza Delavar and Bryan Pijanowski

Sensors 2016, 16(12), 2122; https://doi.org/10.3390/s16122122 - 14 Dec 2016

Cited by 32 | Viewed by 7563

Abstract

Cellular Automata (CA) is one of the most common techniques used to simulate the urbanization process. CA-based urban models use transition rules to deliver spatial patterns of urban growth and urban dynamics over time. Determining the optimum transition rules of the CA is [...] Read more.

Cellular Automata (CA) is one of the most common techniques used to simulate the urbanization process. CA-based urban models use transition rules to deliver spatial patterns of urban growth and urban dynamics over time. Determining the optimum transition rules of the CA is a critical step because of the heterogeneity and nonlinearities existing among urban growth driving forces. Recently, new CA models integrated with optimization methods based on swarm intelligence algorithms were proposed to overcome this drawback. The Artificial Bee Colony (ABC) algorithm is an advanced meta-heuristic swarm intelligence-based algorithm. Here, we propose a novel CA-based urban change model that uses the ABC algorithm to extract optimum transition rules. We applied the proposed ABC-CA model to simulate future urban growth in Urmia (Iran) with multi-temporal Landsat images from 1997, 2006 and 2015. Validation of the simulation results was made through statistical methods such as overall accuracy, the figure of merit and total operating characteristics (TOC). Additionally, we calibrated the CA model by ant colony optimization (ACO) to assess the performance of our proposed model versus similar swarm intelligence algorithm methods. We showed that the overall accuracy and the figure of merit of the ABC-CA model are 90.1% and 51.7%, which are 2.9% and 8.8% higher than those of the ACO-CA model, respectively. Moreover, the allocation disagreement of the simulation results for the ABC-CA model is 9.9%, which is 2.9% less than that of the ACO-CA model. Finally, the ABC-CA model also outperforms the ACO-CA model with fewer quantity and allocation errors and slightly more hits. Full article

(This article belongs to the Special Issue Urban Remote Sensing: Monitoring, Synthesis and Modeling in the Urban Environment)

► Show Figures

Figure 1

17 pages, 1212 KiB

Open AccessArticle

Three-Factor User Authentication and Key Agreement Using Elliptic Curve Cryptosystem in Wireless Sensor Networks

by YoHan Park and YoungHo Park

Sensors 2016, 16(12), 2123; https://doi.org/10.3390/s16122123 - 14 Dec 2016

Cited by 89 | Viewed by 5466

Abstract

Secure communication is a significant issue in wireless sensor networks. User authentication and key agreement are essential for providing a secure system, especially in user-oriented mobile services. It is also necessary to protect the identity of each individual in wireless environments to avoid [...] Read more.

Secure communication is a significant issue in wireless sensor networks. User authentication and key agreement are essential for providing a secure system, especially in user-oriented mobile services. It is also necessary to protect the identity of each individual in wireless environments to avoid personal privacy concerns. Many authentication and key agreement schemes utilize a smart card in addition to a password to support security functionalities. However, these schemes often fail to provide security along with privacy. In 2015, Chang et al. analyzed the security vulnerabilities of previous schemes and presented the two-factor authentication scheme that provided user privacy by using dynamic identities. However, when we cryptanalyzed Chang et al.’s scheme, we found that it does not provide sufficient security for wireless sensor networks and fails to provide accurate password updates. This paper proposes a security-enhanced authentication and key agreement scheme to overcome these security weaknesses using biometric information and an elliptic curve cryptosystem. We analyze the security of the proposed scheme against various attacks and check its viability in the mobile environment. Full article

(This article belongs to the Section Sensor Networks)

► Show Figures

Figure 1

28 pages, 3297 KiB

Open AccessArticle

Looking inside the Ocean: Toward an Autonomous Imaging System for Monitoring Gelatinous Zooplankton

by Lorenzo Corgnati, Simone Marini, Luca Mazzei, Ennio Ottaviani, Stefano Aliani, Alessandra Conversi and Annalisa Griffa

Sensors 2016, 16(12), 2124; https://doi.org/10.3390/s16122124 - 14 Dec 2016

Cited by 36 | Viewed by 7706

Abstract

Marine plankton abundance and dynamics in the open and interior ocean is still an unknown field. The knowledge of gelatinous zooplankton distribution is especially challenging, because this type of plankton has a very fragile structure and cannot be directly sampled using traditional net [...] Read more.

Marine plankton abundance and dynamics in the open and interior ocean is still an unknown field. The knowledge of gelatinous zooplankton distribution is especially challenging, because this type of plankton has a very fragile structure and cannot be directly sampled using traditional net based techniques. To overcome this shortcoming, Computer Vision techniques can be successfully used for the automatic monitoring of this group.This paper presents the GUARD1 imaging system, a low-cost stand-alone instrument for underwater image acquisition and recognition of gelatinous zooplankton, and discusses the performance of three different methodologies, Tikhonov Regularization, Support Vector Machines and Genetic Programming, that have been compared in order to select the one to be run onboard the system for the automatic recognition of gelatinous zooplankton. The performance comparison results highlight the high accuracy of the three methods in gelatinous zooplankton identification, showing their good capability in robustly selecting relevant features. In particular, Genetic Programming technique achieves the same performances of the other two methods by using a smaller set of features, thus being the most efficient in avoiding computationally consuming preprocessing stages, that is a crucial requirement for running on an autonomous imaging system designed for long lasting deployments, like the GUARD1. The Genetic Programming algorithm has been installed onboard the system, that has been operationally tested in a two-months survey in the Ligurian Sea, providing satisfactory results in terms of monitoring and recognition performances. Full article

(This article belongs to the Special Issue Sensing Technologies for Autonomy and Cooperation in Underwater Networked Robot Systems)

► Show Figures

Figure 1

10 pages, 3662 KiB

Open AccessArticle

High-Frequency Fiber-Optic Ultrasonic Sensor Using Air Micro-Bubble for Imaging of Seismic Physical Models

by Tingting Gang, Manli Hu, Qiangzhou Rong, Xueguang Qiao, Lei Liang, Nan Liu, Rongxin Tong, Xiaobo Liu and Ce Bian

Sensors 2016, 16(12), 2125; https://doi.org/10.3390/s16122125 - 14 Dec 2016

Cited by 27 | Viewed by 7200

Abstract

A micro-fiber-optic Fabry-Perot interferometer (FPI) is proposed and demonstrated experimentally for ultrasonic imaging of seismic physical models. The device consists of a micro-bubble followed by the end of a single-mode fiber (SMF). The micro-structure is formed by the discharging operation on a short [...] Read more.

A micro-fiber-optic Fabry-Perot interferometer (FPI) is proposed and demonstrated experimentally for ultrasonic imaging of seismic physical models. The device consists of a micro-bubble followed by the end of a single-mode fiber (SMF). The micro-structure is formed by the discharging operation on a short segment of hollow-core fiber (HCF) that is spliced to the SMF. This micro FPI is sensitive to ultrasonic waves (UWs), especially to the high-frequency (up to 10 MHz) UW, thanks to its ultra-thin cavity wall and micro-diameter. A side-band filter technology is employed for the UW interrogation, and then the high signal-to-noise ratio (SNR) UW signal is achieved. Eventually the sensor is used for lateral imaging of the physical model by scanning UW detection and two-dimensional signal reconstruction. Full article

(This article belongs to the Section Physical Sensors)

► Show Figures

Figure 1

14 pages, 2028 KiB

Open AccessArticle

Performance Prediction of a MongoDB-Based Traceability System in Smart Factory Supply Chains

by Yong-Shin Kang, Il-Ha Park and Sekyoung Youm

Sensors 2016, 16(12), 2126; https://doi.org/10.3390/s16122126 - 14 Dec 2016

Cited by 27 | Viewed by 7967

Abstract

In the future, with the advent of the smart factory era, manufacturing and logistics processes will become more complex, and the complexity and criticality of traceability will further increase. This research aims at developing a performance assessment method to verify scalability when implementing [...] Read more.

In the future, with the advent of the smart factory era, manufacturing and logistics processes will become more complex, and the complexity and criticality of traceability will further increase. This research aims at developing a performance assessment method to verify scalability when implementing traceability systems based on key technologies for smart factories, such as Internet of Things (IoT) and BigData. To this end, based on existing research, we analyzed traceability requirements and an event schema for storing traceability data in MongoDB, a document-based Not Only SQL (NoSQL) database. Next, we analyzed the algorithm of the most representative traceability query and defined a query-level performance model, which is composed of response times for the components of the traceability query algorithm. Next, this performance model was solidified as a linear regression model because the response times increase linearly by a benchmark test. Finally, for a case analysis, we applied the performance model to a virtual automobile parts logistics. As a result of the case study, we verified the scalability of a MongoDB-based traceability system and predicted the point when data node servers should be expanded in this case. The traceability system performance assessment method proposed in this research can be used as a decision-making tool for hardware capacity planning during the initial stage of construction of traceability systems and during their operational phase. Full article

(This article belongs to the Special Issue Big Data and Cloud Computing for Sensor Networks)

► Show Figures

Figure 1

16 pages, 2498 KiB

Open AccessArticle

A New Adaptive H-Infinity Filtering Algorithm for the GPS/INS Integrated Navigation

by Chen Jiang, Shu-Bi Zhang and Qiu-Zhao Zhang

Sensors 2016, 16(12), 2127; https://doi.org/10.3390/s16122127 - 19 Dec 2016

Cited by 40 | Viewed by 6863

Abstract

The Kalman filter is an optimal estimator with numerous applications in technology, especially in systems with Gaussian distributed noise. Moreover, the adaptive Kalman filtering algorithms, based on the Kalman filter, can control the influence of dynamic model errors. In contrast to the adaptive [...] Read more.

The Kalman filter is an optimal estimator with numerous applications in technology, especially in systems with Gaussian distributed noise. Moreover, the adaptive Kalman filtering algorithms, based on the Kalman filter, can control the influence of dynamic model errors. In contrast to the adaptive Kalman filtering algorithms, the H-infinity filter is able to address the interference of the stochastic model by minimization of the worst-case estimation error. In this paper, a novel adaptive H-infinity filtering algorithm, which integrates the adaptive Kalman filter and the H-infinity filter in order to perform a comprehensive filtering algorithm, is presented. In the proposed algorithm, a robust estimation method is employed to control the influence of outliers. In order to verify the proposed algorithm, experiments with real data of the Global Positioning System (GPS) and Inertial Navigation System (INS) integrated navigation, were conducted. The experimental results have shown that the proposed algorithm has multiple advantages compared to the other filtering algorithms. Full article

(This article belongs to the Section Remote Sensors)

► Show Figures

Figure 1

16 pages, 4759 KiB

Open AccessArticle

Fabrication of a Horizontal and a Vertical Large Surface Area Nanogap Electrochemical Sensor

by Jules L. Hammond, Mark C. Rosamond, Siva Sivaraya, Frank Marken and Pedro Estrela

Sensors 2016, 16(12), 2128; https://doi.org/10.3390/s16122128 - 14 Dec 2016

Cited by 9 | Viewed by 7786

Abstract

Nanogap sensors have a wide range of applications as they can provide accurate direct detection of biomolecules through impedimetric or amperometric signals. Signal response from nanogap sensors is dependent on both the electrode spacing and surface area. However, creating large surface area nanogap [...] Read more.

Nanogap sensors have a wide range of applications as they can provide accurate direct detection of biomolecules through impedimetric or amperometric signals. Signal response from nanogap sensors is dependent on both the electrode spacing and surface area. However, creating large surface area nanogap sensors presents several challenges during fabrication. We show two different approaches to achieve both horizontal and vertical coplanar nanogap geometries. In the first method we use electron-beam lithography (EBL) to pattern an 11 mm long serpentine nanogap (215 nm) between two electrodes. For the second method we use inductively-coupled plasma (ICP) reactive ion etching (RIE) to create a channel in a silicon substrate, optically pattern a buried 1.0 mm × 1.5 mm electrode before anodically bonding a second identical electrode, patterned on glass, directly above. The devices have a wide range of applicability in different sensing techniques with the large area nanogaps presenting advantages over other devices of the same family. As a case study we explore the detection of peptide nucleic acid (PNA)−DNA binding events using dielectric spectroscopy with the horizontal coplanar device. Full article

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

► Show Figures

Figure 1

15 pages, 1150 KiB

Open AccessArticle

Novel Resistance Measurement Method: Analysis of Accuracy and Thermal Dependence with Applications in Fiber Materials

by Silvia Casans, Alfredo Rosado-Muñoz and Taras Iakymchuk

Sensors 2016, 16(12), 2129; https://doi.org/10.3390/s16122129 - 14 Dec 2016

Cited by 7 | Viewed by 6111

Abstract

Material resistance is important since different physicochemical properties can be extracted from it. This work describes a novel resistance measurement method valid for a wide range of resistance values up to 100 GΩ at a low powered, small sized, digitally controlled and wireless [...] Read more.

Material resistance is important since different physicochemical properties can be extracted from it. This work describes a novel resistance measurement method valid for a wide range of resistance values up to 100 GΩ at a low powered, small sized, digitally controlled and wireless communicated device. The analog and digital circuits of the design are described, analysing the main error sources affecting the accuracy. Accuracy and extended uncertainty are obtained for a pattern decade box, showing a maximum of

1 %

accuracy for temperatures below 30

^{\circ}

C in the range from 1 MΩ to 100 GΩ. Thermal analysis showed stability up to 50

^{\circ}

C for values below 10 GΩ and systematic deviations for higher values. Power supply

V_{i}

applied to the measurement probes is also analysed, showing no differences in case of the pattern decade box, except for resistance values above 10 GΩ and temperatures above 35

^{\circ}

C. To evaluate the circuit behaviour under fiber materials, an 11-day drying process in timber from four species (Oregon pine-Pseudotsuga menziesii, cedar-Cedrus atlantica, ash-Fraxinus excelsior, chestnut-Castanea sativa) was monitored. Results show that the circuit, as expected, provides different resistance values (they need individual conversion curves) for different species and the same ambient conditions. Additionally, it was found that, contrary to the decade box analysis,

V_{i}

affects the resistance value due to material properties. In summary, the proposed circuit is able to accurately measure material resistance that can be further related to material properties. Full article

(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Spain 2016)

► Show Figures

Figure 1

11 pages, 2115 KiB

Open AccessArticle

Contactless Measurement of Magnetic Nanoparticles on Lateral Flow Strips Using Tunneling Magnetoresistance (TMR) Sensors in Differential Configuration

by Huaming Lei, Kan Wang, Xiaojun Ji and Daxiang Cui

Sensors 2016, 16(12), 2130; https://doi.org/10.3390/s16122130 - 14 Dec 2016

Cited by 52 | Viewed by 8263

Abstract

Magnetic nanoparticles (MNPs) are commonly used in biomedical detection due to their capability to bind with some specific antibodies. Quantification of biological entities could be realized by measuring the magnetic response of MNPs after the binding process. This paper presents a contactless scanning [...] Read more.

Magnetic nanoparticles (MNPs) are commonly used in biomedical detection due to their capability to bind with some specific antibodies. Quantification of biological entities could be realized by measuring the magnetic response of MNPs after the binding process. This paper presents a contactless scanning prototype based on tunneling magnetoresistance (TMR) sensors for quantification of MNPs present in lateral flow strips (LFSs). The sensing unit of the prototype composes of two active TMR elements, which are parallel and closely arranged to form a differential sensing configuration in a perpendicular magnetic field. Geometrical parameters of the configuration are optimized according to theoretical analysis of the stray magnetic field produced by the test line (T-line) while strips being scanned. A brief description of our prototype and the sample preparation is presented. Experimental results show that the prototype exhibits the performance of high sensitivity and strong anti-interference ability. Meanwhile, the detection speed has been improved compared with existing similar techniques. The proposed prototype demonstrates a good sensitivity for detecting samples containing human chorionic gonadotropin (hCG) at a concentration of 25 mIU/mL. The T-line produced by the sample with low concentration is almost beyond the visual limit and produces a maximum stray magnetic field some 0.247 mOe at the sensor in the x direction. Full article

(This article belongs to the Section Physical Sensors)

► Show Figures

Figure 1

9 pages, 2648 KiB

Open AccessArticle

Flexible Pressure Sensor with Ag Wrinkled Electrodes Based on PDMS Substrate

by Jianli Cui, Binzhen Zhang, Junping Duan, Hao Guo and Jun Tang

Sensors 2016, 16(12), 2131; https://doi.org/10.3390/s16122131 - 14 Dec 2016

Cited by 86 | Viewed by 11584

Abstract

Flexible pressure sensors are essential components of electronic skins for future attractive applications ranging from human healthcare monitoring to biomedical diagnostics, robotic skins, and prosthetic limbs. Here we report a new kind of flexible pressure sensor. The sensors are capacitive, and composed of [...] Read more.

Flexible pressure sensors are essential components of electronic skins for future attractive applications ranging from human healthcare monitoring to biomedical diagnostics, robotic skins, and prosthetic limbs. Here we report a new kind of flexible pressure sensor. The sensors are capacitive, and composed of two Ag wrinkled electrodes separated by a carbon nanotubes (CNTs)/polydimethylsiloxane (PDMS) composite deformable dielectric layer. Ag wrinkled electrodes were formed by vacuum deposition on top of pre-strained and relaxed PDMS substrates which were treated using an O₂ plasma, a surface functionalization process, and a magnetron sputtering process. Ultimately, the developed sensor exhibits a maximum sensitivity of 19.80% kPa⁻¹ to capacitance, great durability over 500 cycles, and rapid mechanical responses (<200 ms). We also demonstrate that our sensor can be used to effectively detect the location and distribution of finger pressure. Full article

(This article belongs to the Collection Modeling, Testing and Reliability Issues in MEMS Engineering)

► Show Figures

Figure 1

25 pages, 2865 KiB

Open AccessArticle

Assessing Motor Fluctuations in Parkinson’s Disease Patients Based on a Single Inertial Sensor

by Carlos Pérez-López, Albert Samà, Daniel Rodríguez-Martín, Andreu Català, Joan Cabestany, Juan Manuel Moreno-Arostegui, Eva De Mingo and Alejandro Rodríguez-Molinero

Sensors 2016, 16(12), 2132; https://doi.org/10.3390/s16122132 - 15 Dec 2016

Cited by 42 | Viewed by 8365

Abstract

Altered movement control is typically the first noticeable symptom manifested by Parkinson’s disease (PD) patients. Once under treatment, the effect of the medication is very patent and patients often recover correct movement control over several hours. Nonetheless, as the disease advances, patients present [...] Read more.

Altered movement control is typically the first noticeable symptom manifested by Parkinson’s disease (PD) patients. Once under treatment, the effect of the medication is very patent and patients often recover correct movement control over several hours. Nonetheless, as the disease advances, patients present motor complications. Obtaining precise information on the long-term evolution of these motor complications and their short-term fluctuations is crucial to provide optimal therapy to PD patients and to properly measure the outcome of clinical trials. This paper presents an algorithm based on the accelerometer signals provided by a waist sensor that has been validated in the automatic assessment of patient’s motor fluctuations (ON and OFF motor states) during their activities of daily living. A total of 15 patients have participated in the experiments in ambulatory conditions during 1 to 3 days. The state recognised by the algorithm and the motor state annotated by patients in standard diaries are contrasted. Results show that the average specificity and sensitivity are higher than 90%, while their values are higher than 80% of all patients, thereby showing that PD motor status is able to be monitored through a single sensor during daily life of patients in a precise and objective way. Full article

(This article belongs to the Special Issue Body Worn Behavior Sensing)

► Show Figures

Figure 1

11 pages, 2019 KiB

Open AccessArticle

Investigating Effects of Proteasome Inhibitor on Multiple Myeloma Cells Using Confocal Raman Microscopy

by Jeon Woong Kang, Surya P. Singh, Freddy T. Nguyen, Niyom Lue, Yongjin Sung, Peter T. C. So and Ramachandra R. Dasari

Sensors 2016, 16(12), 2133; https://doi.org/10.3390/s16122133 - 14 Dec 2016

Cited by 17 | Viewed by 6710

Abstract

Due to its label-free and non-destructive nature, applications of Raman spectroscopic imaging in monitoring therapeutic responses at the cellular level are growing. We have recently developed a high-speed confocal Raman microscopy system to image living biological specimens with high spatial resolution and sensitivity. [...] Read more.

Due to its label-free and non-destructive nature, applications of Raman spectroscopic imaging in monitoring therapeutic responses at the cellular level are growing. We have recently developed a high-speed confocal Raman microscopy system to image living biological specimens with high spatial resolution and sensitivity. In the present study, we have applied this system to monitor the effects of Bortezomib, a proteasome inhibitor drug, on multiple myeloma cells. Cluster imaging followed by spectral profiling suggest major differences in the nuclear and cytoplasmic contents of cells due to drug treatment that can be monitored with Raman spectroscopy. Spectra were also acquired from group of cells and feasibility of discrimination among treated and untreated cells using principal component analysis (PCA) was accessed. Findings support the feasibility of Raman technologies as an alternate, novel method for monitoring live cell dynamics with minimal external perturbation. Full article

(This article belongs to the Special Issue Label-Free Optical Biosensors)

► Show Figures

Figure 1

17 pages, 1649 KiB

Open AccessReview

A Review of Wearable Sensor Systems for Monitoring Body Movements of Neonates

by Hongyu Chen, Mengru Xue, Zhenning Mei, Sidarto Bambang Oetomo and Wei Chen

Sensors 2016, 16(12), 2134; https://doi.org/10.3390/s16122134 - 14 Dec 2016

Cited by 80 | Viewed by 12789

Abstract

Characteristics of physical movements are indicative of infants’ neuro-motor development and brain dysfunction. For instance, infant seizure, a clinical signal of brain dysfunction, could be identified and predicted by monitoring its physical movements. With the advance of wearable sensor technology, including the miniaturization [...] Read more.

Characteristics of physical movements are indicative of infants’ neuro-motor development and brain dysfunction. For instance, infant seizure, a clinical signal of brain dysfunction, could be identified and predicted by monitoring its physical movements. With the advance of wearable sensor technology, including the miniaturization of sensors, and the increasing broad application of micro- and nanotechnology, and smart fabrics in wearable sensor systems, it is now possible to collect, store, and process multimodal signal data of infant movements in a more efficient, more comfortable, and non-intrusive way. This review aims to depict the state-of-the-art of wearable sensor systems for infant movement monitoring. We also discuss its clinical significance and the aspect of system design. Full article

(This article belongs to the Special Issue Sensing Technology for Healthcare System)

► Show Figures

Figure 1

17 pages, 877 KiB

Open AccessArticle

An Indoor Positioning Method for Smartphones Using Landmarks and PDR

by Xi Wang, Mingxing Jiang, Zhongwen Guo, Naijun Hu, Zhongwei Sun and Jing Liu

Sensors 2016, 16(12), 2135; https://doi.org/10.3390/s16122135 - 15 Dec 2016

Cited by 48 | Viewed by 7465

Abstract

Recently location based services (LBS) have become increasingly popular in indoor environments. Among these indoor positioning techniques providing LBS, a fusion approach combining WiFi-based and pedestrian dead reckoning (PDR) techniques is drawing more and more attention of researchers. Although this fusion method performs [...] Read more.

Recently location based services (LBS) have become increasingly popular in indoor environments. Among these indoor positioning techniques providing LBS, a fusion approach combining WiFi-based and pedestrian dead reckoning (PDR) techniques is drawing more and more attention of researchers. Although this fusion method performs well in some cases, it still has some limitations, such as heavy computation and inconvenience for real-time use. In this work, we study map information of a given indoor environment, analyze variations of WiFi received signal strength (RSS), define several kinds of indoor landmarks, and then utilize these landmarks to correct accumulated errors derived from PDR. This fusion scheme, called Landmark-aided PDR (LaP), is proved to be light-weight and suitable for real-time implementation by running an Android application designed for the experiment. We compared LaP with other PDR-based fusion approaches. Experimental results show that the proposed scheme can achieve a significant improvement with an average accuracy of 2.17 m. Full article

(This article belongs to the Special Issue Advanced Algorithms for Mobile Sensing: from Wireless Sensor Networks to Mobile Crowd Sensing)

► Show Figures

Figure 1

25 pages, 17533 KiB

Open AccessArticle

Towards Automated Large-Scale 3D Phenotyping of Vineyards under Field Conditions

by Johann Christian Rose, Anna Kicherer, Markus Wieland, Lasse Klingbeil, Reinhard Töpfer and Heiner Kuhlmann

Sensors 2016, 16(12), 2136; https://doi.org/10.3390/s16122136 - 15 Dec 2016

Cited by 58 | Viewed by 9870

Abstract

In viticulture, phenotypic data are traditionally collected directly in the field via visual and manual means by an experienced person. This approach is time consuming, subjective and prone to human errors. In recent years, research therefore has focused strongly on developing automated and [...] Read more.

In viticulture, phenotypic data are traditionally collected directly in the field via visual and manual means by an experienced person. This approach is time consuming, subjective and prone to human errors. In recent years, research therefore has focused strongly on developing automated and non-invasive sensor-based methods to increase data acquisition speed, enhance measurement accuracy and objectivity and to reduce labor costs. While many 2D methods based on image processing have been proposed for field phenotyping, only a few 3D solutions are found in the literature. A track-driven vehicle consisting of a camera system, a real-time-kinematic GPS system for positioning, as well as hardware for vehicle control, image storage and acquisition is used to visually capture a whole vine row canopy with georeferenced RGB images. In the first post-processing step, these images were used within a multi-view-stereo software to reconstruct a textured 3D point cloud of the whole grapevine row. A classification algorithm is then used in the second step to automatically classify the raw point cloud data into the semantic plant components, grape bunches and canopy. In the third step, phenotypic data for the semantic objects is gathered using the classification results obtaining the quantity of grape bunches, berries and the berry diameter. Full article

(This article belongs to the Collection Sensors in Agriculture and Forestry)

► Show Figures

Graphical abstract

22 pages, 11323 KiB

Open AccessArticle

GridiLoc: A Backtracking Grid Filter for Fusing the Grid Model with PDR Using Smartphone Sensors

by Jianga Shang, Xuke Hu, Wen Cheng and Hongchao Fan

Sensors 2016, 16(12), 2137; https://doi.org/10.3390/s16122137 - 15 Dec 2016

Cited by 11 | Viewed by 6786

Abstract

Although map filtering-aided Pedestrian Dead Reckoning (PDR) is capable of largely improving indoor localization accuracy, it becomes less efficient when coping with highly complex indoor spaces. For instance, indoor spaces with a few close corners or neighboring passages can lead to particles entering [...] Read more.

Although map filtering-aided Pedestrian Dead Reckoning (PDR) is capable of largely improving indoor localization accuracy, it becomes less efficient when coping with highly complex indoor spaces. For instance, indoor spaces with a few close corners or neighboring passages can lead to particles entering erroneous passages, which can further cause the failure of subsequent tracking. To address this problem, we propose GridiLoc, a reliable and accurate pedestrian indoor localization method through the fusion of smartphone sensors and a grid model. The key novelty of GridiLoc is the utilization of a backtracking grid filter for improving localization accuracy and for handling dead ending issues. In order to reduce the time consumption of backtracking, a topological graph is introduced for representing candidate backtracking points, which are the expected locations at the starting time of the dead ending. Furthermore, when the dead ending is caused by the erroneous step length model of PDR, our solution can automatically calibrate the model by using the historical tracking data. Our experimental results show that GridiLoc achieves a higher localization accuracy and reliability compared with the commonly-used map filtering approach. Meanwhile, it maintains an acceptable computational complexity. Full article

(This article belongs to the Special Issue Advanced Algorithms for Mobile Sensing: from Wireless Sensor Networks to Mobile Crowd Sensing)

► Show Figures

Figure 1

17 pages, 606 KiB

Open AccessArticle

Estimation of Full-Body Poses Using Only Five Inertial Sensors: An Eager or Lazy Learning Approach?

by Frank J. Wouda, Matteo Giuberti, Giovanni Bellusci and Peter H. Veltink

Sensors 2016, 16(12), 2138; https://doi.org/10.3390/s16122138 - 15 Dec 2016

Cited by 49 | Viewed by 10660

Abstract

Human movement analysis has become easier with the wide availability of motion capture systems. Inertial sensing has made it possible to capture human motion without external infrastructure, therefore allowing measurements in any environment. As high-quality motion capture data is available in large quantities, [...] Read more.

Human movement analysis has become easier with the wide availability of motion capture systems. Inertial sensing has made it possible to capture human motion without external infrastructure, therefore allowing measurements in any environment. As high-quality motion capture data is available in large quantities, this creates possibilities to further simplify hardware setups, by use of data-driven methods to decrease the number of body-worn sensors. In this work, we contribute to this field by analyzing the capabilities of using either artificial neural networks (eager learning) or nearest neighbor search (lazy learning) for such a problem. Sparse orientation features, resulting from sensor fusion of only five inertial measurement units with magnetometers, are mapped to full-body poses. Both eager and lazy learning algorithms are shown to be capable of constructing this mapping. The full-body output poses are visually plausible with an average joint position error of approximately 7 cm, and average joint angle error of 7

^{\circ}

. Additionally, the effects of magnetic disturbances typical in orientation tracking on the estimation of full-body poses was also investigated, where nearest neighbor search showed better performance for such disturbances. Full article

(This article belongs to the Special Issue Body Worn Behavior Sensing)

► Show Figures

Figure 1

21 pages, 7101 KiB

Open AccessArticle

A Real-Time Marker-Based Visual Sensor Based on a FPGA and a Soft Core Processor

by Hilal Tayara, Woonchul Ham and Kil To Chong

Sensors 2016, 16(12), 2139; https://doi.org/10.3390/s16122139 - 15 Dec 2016

Cited by 10 | Viewed by 5894

Abstract

This paper introduces a real-time marker-based visual sensor architecture for mobile robot localization and navigation. A hardware acceleration architecture for post video processing system was implemented on a field-programmable gate array (FPGA). The pose calculation algorithm was implemented in a System on Chip [...] Read more.

This paper introduces a real-time marker-based visual sensor architecture for mobile robot localization and navigation. A hardware acceleration architecture for post video processing system was implemented on a field-programmable gate array (FPGA). The pose calculation algorithm was implemented in a System on Chip (SoC) with an Altera Nios II soft-core processor. For every frame, single pass image segmentation and Feature Accelerated Segment Test (FAST) corner detection were used for extracting the predefined markers with known geometries in FPGA. Coplanar PosIT algorithm was implemented on the Nios II soft-core processor supplied with floating point hardware for accelerating floating point operations. Trigonometric functions have been approximated using Taylor series and cubic approximation using Lagrange polynomials. Inverse square root method has been implemented for approximating square root computations. Real time results have been achieved and pixel streams have been processed on the fly without any need to buffer the input frame for further implementation. Full article

(This article belongs to the Section Physical Sensors)

► Show Figures

Figure 1

16 pages, 4550 KiB

Open AccessArticle

Low-Cost GNSS Receivers for Local Monitoring: Experimental Simulation, and Analysis of Displacements

by Ludovico Biagi, Florin Cătălin Grec and Marco Negretti

Sensors 2016, 16(12), 2140; https://doi.org/10.3390/s16122140 - 15 Dec 2016

Cited by 59 | Viewed by 7397

Abstract

The geodetic monitoring of local displacements and deformations is often needed for civil engineering structures and natural phenomena like, for example, landslides. A local permanent GNSS (Global Navigation Satellite Systems) network can be installed: receiver positions in the interest area are estimated and [...] Read more.

The geodetic monitoring of local displacements and deformations is often needed for civil engineering structures and natural phenomena like, for example, landslides. A local permanent GNSS (Global Navigation Satellite Systems) network can be installed: receiver positions in the interest area are estimated and monitored with respect to reference stations. Usually, GNSS geodetic receivers are adopted and provide results with accuracies at the millimeter level: however, they are very expensive and the initial cost and the risk of damage and loss can discourage this approach. In this paper the accuracy and the reliability of low-cost u-blox GNSS receivers are experimentally investigated for local monitoring. Two experiments are analyzed. In the first, a baseline (65 m long) between one geodetic reference receiver and one u-blox is continuously observed for one week: the data are processed by hourly sessions and the results provide comparisons between two processing packages and a preliminary accuracy assessment. Then, a network composed of one geodetic and two u-blox receivers is set up. One u-blox is installed on a device (slide) that allows to apply controlled displacements. The geodetic and the other u-blox (at about 130 m) act as references. The experiment lasts about two weeks. The data are again processed by hourly sessions. The estimated displacements of the u-blox on the slide are analyzed and compared with the imposed displacements. All of the results are encouraging: in the first experiment the standard deviations of the residuals are smaller than 5 mm both in the horizontal and vertical; in the second, they are slightly worse but still satisfactory (5 mm in the horizontal and 13 mm in vertical) and the imposed displacements are almost correctly identified. Full article

(This article belongs to the Section Remote Sensors)

► Show Figures

Figure 1

19 pages, 2497 KiB

Open AccessArticle

Node Immunization with Time-Sensitive Restrictions

by Wen Cui, Xiaoqing Gong, Chen Liu, Dan Xu, Xiaojiang Chen, Dingyi Fang, Shaojie Tang, Fan Wu and Guihai Chen

Sensors 2016, 16(12), 2141; https://doi.org/10.3390/s16122141 - 15 Dec 2016

Cited by 6 | Viewed by 5293

Abstract

When we encounter a malicious rumor or an infectious disease outbreak, immunizing k nodes of the relevant network with limited resources is always treated as an extremely effective method. The key challenge is how we can insulate limited nodes to minimize the propagation [...] Read more.

When we encounter a malicious rumor or an infectious disease outbreak, immunizing k nodes of the relevant network with limited resources is always treated as an extremely effective method. The key challenge is how we can insulate limited nodes to minimize the propagation of those contagious things. In previous works, the best k immunised nodes are selected by learning the initial status of nodes and their strategies even if there is no feedback in the propagation process, which eventually leads to ineffective performance of their solutions. In this paper, we design a novel vaccines placement strategy for protecting much more healthy nodes from being infected by infectious nodes. The main idea of our solution is that we are not only utilizing the status of changing nodes as auxiliary knowledge to adjust our scheme, but also comparing the performance of vaccines in various transmission slots. Thus, our solution has a better chance to get more benefit from these limited vaccines. Extensive experiments have been conducted on several real-world data sets and the results have shown that our algorithm has a better performance than previous works. Full article

(This article belongs to the Special Issue New Paradigms in Cyber-Physical Social Sensing)

► Show Figures

Figure 1

12 pages, 352 KiB

Open AccessArticle

Evaluation of Google Glass Technical Limitations on Their Integration in Medical Systems

by Antonio Martinez-Millana, Jose-Luis Bayo-Monton, Aroa Lizondo, Carlos Fernandez-Llatas and Vicente Traver

Sensors 2016, 16(12), 2142; https://doi.org/10.3390/s16122142 - 15 Dec 2016

Cited by 29 | Viewed by 10927

Abstract

Google Glass is a wearable sensor presented to facilitate access to information and assist while performing complex tasks. Despite the withdrawal of Google in supporting the product, today there are multiple applications and much research analyzing the potential impact of this technology in [...] Read more.

Google Glass is a wearable sensor presented to facilitate access to information and assist while performing complex tasks. Despite the withdrawal of Google in supporting the product, today there are multiple applications and much research analyzing the potential impact of this technology in different fields of medicine. Google Glass satisfies the need of managing and having rapid access to real-time information in different health care scenarios. Among the most common applications are access to electronic medical records, display monitorizations, decision support and remote consultation in specialties ranging from ophthalmology to surgery and teaching. The device enables a user-friendly hands-free interaction with remote health information systems and broadcasting medical interventions and consultations from a first-person point of view. However, scientific evidence highlights important technical limitations in its use and integration, such as failure in connectivity, poor reception of images and automatic restart of the device. This article presents a technical study on the aforementioned limitations (specifically on the latency, reliability and performance) on two standard communication schemes in order to categorize and identify the sources of the problems. Results have allowed us to obtain a basis to define requirements for medical applications to prevent network, computational and processing failures associated with the use of Google Glass. Full article

(This article belongs to the Special Issue Sensing Technology for Healthcare System)

► Show Figures

Figure 1

11 pages, 3685 KiB

Open AccessArticle

Thermal Property Analysis of Axle Load Sensors for Weighing Vehicles in Weigh-in-Motion System

by Piotr Burnos and Janusz Gajda

Sensors 2016, 16(12), 2143; https://doi.org/10.3390/s16122143 - 15 Dec 2016

Cited by 51 | Viewed by 11500

Abstract

Systems which permit the weighing of vehicles in motion are called dynamic Weigh-in-Motion scales. In such systems, axle load sensors are embedded in the pavement. Among the influencing factors that negatively affect weighing accuracy is the pavement temperature. This paper presents a detailed [...] Read more.

Systems which permit the weighing of vehicles in motion are called dynamic Weigh-in-Motion scales. In such systems, axle load sensors are embedded in the pavement. Among the influencing factors that negatively affect weighing accuracy is the pavement temperature. This paper presents a detailed analysis of this phenomenon and describes the properties of polymer, quartz and bending plate load sensors. The studies were conducted in two ways: at roadside Weigh-in-Motion sites and at a laboratory using a climate chamber. For accuracy assessment of roadside systems, the reference vehicle method was used. The pavement temperature influence on the weighing error was experimentally investigated as well as a non-uniform temperature distribution along and across the Weigh-in-Motion site. Tests carried out in the climatic chamber allowed the influence of temperature on the sensor intrinsic error to be determined. The results presented clearly show that all kinds of sensors are temperature sensitive. This is a new finding, as up to now the quartz and bending plate sensors were considered insensitive to this factor. Full article

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

► Show Figures

Graphical abstract

24 pages, 7971 KiB

Open AccessArticle

Representing Geospatial Environment Observation Capability Information: A Case Study of Managing Flood Monitoring Sensors in the Jinsha River Basin

by Chuli Hu, Qingfeng Guan, Jie Li, Ke Wang and Nengcheng Chen

Sensors 2016, 16(12), 2144; https://doi.org/10.3390/s16122144 - 16 Dec 2016

Cited by 6 | Viewed by 5383

Abstract

Sensor inquirers cannot understand comprehensive or accurate observation capability information because current observation capability modeling does not consider the union of multiple sensors nor the effect of geospatial environmental features on the observation capability of sensors. These limitations result in a failure to [...] Read more.

Sensor inquirers cannot understand comprehensive or accurate observation capability information because current observation capability modeling does not consider the union of multiple sensors nor the effect of geospatial environmental features on the observation capability of sensors. These limitations result in a failure to discover credible sensors or plan for their collaboration for environmental monitoring. The Geospatial Environmental Observation Capability (GEOC) is proposed in this study and can be used as an information basis for the reliable discovery and collaborative planning of multiple environmental sensors. A field-based GEOC (GEOCF) information representation model is built. Quintuple GEOCF feature components and two GEOCF operations are formulated based on the geospatial field conceptual framework. The proposed GEOCF markup language is used to formalize the proposed GEOCF. A prototype system called GEOCapabilityManager is developed, and a case study is conducted for flood observation in the lower reaches of the Jinsha River Basin. The applicability of the GEOCF is verified through the reliable discovery of flood monitoring sensors and planning for the collaboration of these sensors. Full article

(This article belongs to the Section Remote Sensors)

► Show Figures

Figure 1

8 pages, 3916 KiB

Open AccessArticle

The Influence of Different Partial Pressure on the Fabrication of InGaO Ultraviolet Photodetectors

by Sheng-Po Chang, Li-Yang Chang and Jyun-Yi Li

Sensors 2016, 16(12), 2145; https://doi.org/10.3390/s16122145 - 15 Dec 2016

Cited by 18 | Viewed by 5986

Abstract

A metal–semiconductor–metal ultraviolet photodetector has been fabricated with a radiofrequency (RF)-sputtered InGaO thin film. Results for the devices fabricated under different oxygen partial pressure are here in discussed. Under low oxygen partial pressure, the devices work in the photoconductive mode because of the [...] Read more.

A metal–semiconductor–metal ultraviolet photodetector has been fabricated with a radiofrequency (RF)-sputtered InGaO thin film. Results for the devices fabricated under different oxygen partial pressure are here in discussed. Under low oxygen partial pressure, the devices work in the photoconductive mode because of the large number of subgap states. Therefore, the devices exhibit internal gain. These defects in the films result in slow switching times and lower photo/dark current ratios. A higher flow ratio of oxygen during the sputtering process can effectively restrain the oxygen vacancies in the film. The responsivity of the photodetector fabricated under an oxygen flow ratio of 20% can reach 0.31 A/W. The rise time and decay time can reach 21 s and 27 s, respectively. Full article

(This article belongs to the Special Issue Materials and Applications for Sensors and Transducers)

► Show Figures

Figure 1

16 pages, 9390 KiB

Open AccessArticle

Data Field Modeling and Spectral-Spatial Feature Fusion for Hyperspectral Data Classification

by Da Liu and Jianxun Li

Sensors 2016, 16(12), 2146; https://doi.org/10.3390/s16122146 - 16 Dec 2016

Cited by 9 | Viewed by 4488

Abstract

Classification is a significant subject in hyperspectral remote sensing image processing. This study proposes a spectral-spatial feature fusion algorithm for the classification of hyperspectral images (HSI). Unlike existing spectral-spatial classification methods, the influences and interactions of the surroundings on each measured pixel were [...] Read more.

Classification is a significant subject in hyperspectral remote sensing image processing. This study proposes a spectral-spatial feature fusion algorithm for the classification of hyperspectral images (HSI). Unlike existing spectral-spatial classification methods, the influences and interactions of the surroundings on each measured pixel were taken into consideration in this paper. Data field theory was employed as the mathematical realization of the field theory concept in physics, and both the spectral and spatial domains of HSI were considered as data fields. Therefore, the inherent dependency of interacting pixels was modeled. Using data field modeling, spatial and spectral features were transformed into a unified radiation form and further fused into a new feature by using a linear model. In contrast to the current spectral-spatial classification methods, which usually simply stack spectral and spatial features together, the proposed method builds the inner connection between the spectral and spatial features, and explores the hidden information that contributed to classification. Therefore, new information is included for classification. The final classification result was obtained using a random forest (RF) classifier. The proposed method was tested with the University of Pavia and Indian Pines, two well-known standard hyperspectral datasets. The experimental results demonstrate that the proposed method has higher classification accuracies than those obtained by the traditional approaches. Full article

(This article belongs to the Special Issue Multi-Sensor Integration and Fusion)

► Show Figures

Figure 1

12 pages, 1360 KiB

Open AccessArticle

Design and Sensitivity Analysis Simulation of a Novel 3D Force Sensor Based on a Parallel Mechanism

by Eileen Chih-Ying Yang

Sensors 2016, 16(12), 2147; https://doi.org/10.3390/s16122147 - 16 Dec 2016

Cited by 17 | Viewed by 6847

Abstract

Automated force measurement is one of the most important technologies in realizing intelligent automation systems. However, while many methods are available for micro-force sensing, measuring large three-dimensional (3D) forces and loads remains a significant challenge. Accordingly, the present study proposes a novel 3D [...] Read more.

Automated force measurement is one of the most important technologies in realizing intelligent automation systems. However, while many methods are available for micro-force sensing, measuring large three-dimensional (3D) forces and loads remains a significant challenge. Accordingly, the present study proposes a novel 3D force sensor based on a parallel mechanism. The transformation function and sensitivity index of the proposed sensor are analytically derived. The simulation results show that the sensor has a larger effective measuring capability than traditional force sensors. Moreover, the sensor has a greater measurement sensitivity for horizontal forces than for vertical forces over most of the measurable force region. In other words, compared to traditional force sensors, the proposed sensor is more sensitive to shear forces than normal forces. Full article

(This article belongs to the Section Physical Sensors)

► Show Figures

Figure 1

18 pages, 9070 KiB

Open AccessArticle

A Flexible and Highly Sensitive Pressure Sensor Based on a PDMS Foam Coated with Graphene Nanoplatelets

by Andrea Rinaldi, Alessio Tamburrano, Marco Fortunato and Maria Sabrina Sarto

Sensors 2016, 16(12), 2148; https://doi.org/10.3390/s16122148 - 16 Dec 2016

Cited by 170 | Viewed by 17173

Abstract

The demand for high performance multifunctional wearable devices is more and more pushing towards the development of novel low-cost, soft and flexible sensors with high sensitivity. In the present work, we describe the fabrication process and the properties of new polydimethylsiloxane (PDMS) foams [...] Read more.

The demand for high performance multifunctional wearable devices is more and more pushing towards the development of novel low-cost, soft and flexible sensors with high sensitivity. In the present work, we describe the fabrication process and the properties of new polydimethylsiloxane (PDMS) foams loaded with multilayer graphene nanoplatelets (MLGs) for application as high sensitive piezoresistive pressure sensors. The effective DC conductivity of the produced foams is measured as a function of MLG loading. The piezoresistive response of the MLG-PDMS foam-based sensor at different strain rates is assessed through quasi-static pressure tests. The results of the experimental investigations demonstrated that sensor loaded with 0.96 wt.% of MLGs is characterized by a highly repeatable pressure-dependent conductance after a few stabilization cycles and it is suitable for detecting compressive stresses as low as 10 kPa, with a sensitivity of 0.23 kPa⁻¹, corresponding to an applied pressure of 70 kPa. Moreover, it is estimated that the sensor is able to detect pressure variations of ~1 Pa. Therefore, the new graphene-PDMS composite foam is a lightweight cost-effective material, suitable for sensing applications in the subtle or low and medium pressure ranges. Full article

(This article belongs to the Section Physical Sensors)

► Show Figures

Figure 1

14 pages, 4749 KiB

Open AccessArticle

Tapered Polymer Fiber Sensors for Reinforced Concrete Beam Vibration Detection

by Dong Luo, Zainah Ibrahim, Jianxun Ma, Zubaidah Ismail and David Thomas Iseley

Sensors 2016, 16(12), 2149; https://doi.org/10.3390/s16122149 - 16 Dec 2016

Cited by 5 | Viewed by 7031

Abstract

In this study, tapered polymer fiber sensors (TPFSs) have been employed to detect the vibration of a reinforced concrete beam (RC beam). The sensing principle was based on transmission modes theory. The natural frequency of an RC beam was theoretically analyzed. Experiments were [...] Read more.

In this study, tapered polymer fiber sensors (TPFSs) have been employed to detect the vibration of a reinforced concrete beam (RC beam). The sensing principle was based on transmission modes theory. The natural frequency of an RC beam was theoretically analyzed. Experiments were carried out with sensors mounted on the surface or embedded in the RC beam. Vibration detection results agreed well with Kistler accelerometers. The experimental results found that both the accelerometer and TPFS detected the natural frequency function of a vibrated RC beam well. The mode shapes of the RC beam were also found by using the TPFSs. The proposed vibration detection method provides a cost-comparable solution for a structural health monitoring (SHM) system in civil engineering. Full article

(This article belongs to the Special Issue Optical Fiber Sensors 2016)

► Show Figures

Figure 1

18 pages, 85894 KiB

Open AccessArticle

A Visualization Method for Corrosion Damage on Aluminum Plates Using an Nd:YAG Pulsed Laser Scanning System

by Inbok Lee, Aoqi Zhang, Changgil Lee and Seunghee Park

Sensors 2016, 16(12), 2150; https://doi.org/10.3390/s16122150 - 16 Dec 2016

Cited by 7 | Viewed by 5655

Abstract

This paper proposes a non-contact nondestructive evaluation (NDE) technique that uses laser-induced ultrasonic waves to visualize corrosion damage in aluminum alloy plate structures. The non-contact, pulsed-laser ultrasonic measurement system generates ultrasonic waves using a galvanometer-based Q-switched Nd:YAG laser and measures the ultrasonic waves [...] Read more.

This paper proposes a non-contact nondestructive evaluation (NDE) technique that uses laser-induced ultrasonic waves to visualize corrosion damage in aluminum alloy plate structures. The non-contact, pulsed-laser ultrasonic measurement system generates ultrasonic waves using a galvanometer-based Q-switched Nd:YAG laser and measures the ultrasonic waves using a piezoelectric (PZT) sensor. During scanning, a wavefield can be acquired by changing the excitation location of the laser point and measuring waves using the PZT sensor. The corrosion damage can be detected in the wavefield snapshots using the scattering characteristics of the waves that encounter corrosion. The structural damage is visualized by calculating the logarithmic values of the root mean square (RMS), with a weighting parameter to compensate for the attenuation caused by geometrical spreading and dispersion of the waves. An intact specimen is used to conduct a comparison with corrosion at different depths and sizes in other specimens. Both sides of the plate are scanned with the same scanning area to observe the effect of the location where corrosion has formed. The results show that the damage can be successfully visualized for almost all cases using the RMS-based functions, whether it formed on the front or back side. Also, the system is confirmed to have distinguished corroded areas at different depths. Full article

(This article belongs to the Section Physical Sensors)

► Show Figures

Figure 1

19 pages, 2769 KiB

Open AccessArticle

Accelerometry-Based Activity Recognition and Assessment in Rheumatic and Musculoskeletal Diseases

by Lieven Billiet, Thijs Willem Swinnen, Rene Westhovens, Kurt De Vlam and Sabine Van Huffel

Sensors 2016, 16(12), 2151; https://doi.org/10.3390/s16122151 - 16 Dec 2016

Cited by 10 | Viewed by 5258

Abstract

One of the important aspects to be considered in rheumatic and musculoskeletal diseases is the patient’s activity capacity (or performance), defined as the ability to perform a task. Currently, it is assessed by physicians or health professionals mainly by means of a patient-reported [...] Read more.

One of the important aspects to be considered in rheumatic and musculoskeletal diseases is the patient’s activity capacity (or performance), defined as the ability to perform a task. Currently, it is assessed by physicians or health professionals mainly by means of a patient-reported questionnaire, sometimes combined with the therapist’s judgment on performance-based tasks. This work introduces an approach to assess the activity capacity at home in a more objective, yet interpretable way. It offers a pilot study on 28 patients suffering from axial spondyloarthritis (axSpA) to demonstrate its efficacy. Firstly, a protocol is introduced to recognize a limited set of six transition activities in the home environment using a single accelerometer. To this end, a hierarchical classifier with the rejection of non-informative activity segments has been developed drawing on both direct pattern recognition and statistical signal features. Secondly, the recognized activities should be assessed, similarly to the scoring performed by patients themselves. This is achieved through the interval coded scoring (ICS) system, a novel method to extract an interpretable scoring system from data. The activity recognition reaches an average accuracy of 93.5%; assessment is currently 64.3% accurate. These results indicate the potential of the approach; a next step should be its validation in a larger patient study. Full article

(This article belongs to the Special Issue Wearable Biomedical Sensors)

► Show Figures

Figure 1

30 pages, 664 KiB

Open AccessArticle

Secure Distributed Detection under Energy Constraint in IoT-Oriented Sensor Networks

by Guomei Zhang and Hao Sun

Sensors 2016, 16(12), 2152; https://doi.org/10.3390/s16122152 - 16 Dec 2016

Cited by 7 | Viewed by 4861

Abstract

We study the secure distributed detection problems under energy constraint for IoT-oriented sensor networks. The conventional channel-aware encryption (CAE) is an efficient physical-layer secure distributed detection scheme in light of its energy efficiency, good scalability and robustness over diverse eavesdropping scenarios. However, in [...] Read more.

We study the secure distributed detection problems under energy constraint for IoT-oriented sensor networks. The conventional channel-aware encryption (CAE) is an efficient physical-layer secure distributed detection scheme in light of its energy efficiency, good scalability and robustness over diverse eavesdropping scenarios. However, in the CAE scheme, it remains an open problem of how to optimize the key thresholds for the estimated channel gain, which are used to determine the sensor’s reporting action. Moreover, the CAE scheme does not jointly consider the accuracy of local detection results in determining whether to stay dormant for a sensor. To solve these problems, we first analyze the error probability and derive the optimal thresholds in the CAE scheme under a specified energy constraint. These results build a convenient mathematic framework for our further innovative design. Under this framework, we propose a hybrid secure distributed detection scheme. Our proposal can satisfy the energy constraint by keeping some sensors inactive according to the local detection confidence level, which is characterized by likelihood ratio. In the meanwhile, the security is guaranteed through randomly flipping the local decisions forwarded to the fusion center based on the channel amplitude. We further optimize the key parameters of our hybrid scheme, including two local decision thresholds and one channel comparison threshold. Performance evaluation results demonstrate that our hybrid scheme outperforms the CAE under stringent energy constraints, especially in the high signal-to-noise ratio scenario, while the security is still assured. Full article

(This article belongs to the Special Issue Enabling the Move from Wireless Sensor Networks to Internet of Things and Cyber-Physical Systems)

► Show Figures

Figure 1

15 pages, 2954 KiB

Open AccessArticle

Classification of Clouds in Satellite Imagery Using Adaptive Fuzzy Sparse Representation

by Wei Jin, Fei Gong, Xingbin Zeng and Randi Fu

Sensors 2016, 16(12), 2153; https://doi.org/10.3390/s16122153 - 16 Dec 2016

Cited by 16 | Viewed by 6333

Abstract

Automatic cloud detection and classification using satellite cloud imagery have various meteorological applications such as weather forecasting and climate monitoring. Cloud pattern analysis is one of the research hotspots recently. Since satellites sense the clouds remotely from space, and different cloud types often [...] Read more.

Automatic cloud detection and classification using satellite cloud imagery have various meteorological applications such as weather forecasting and climate monitoring. Cloud pattern analysis is one of the research hotspots recently. Since satellites sense the clouds remotely from space, and different cloud types often overlap and convert into each other, there must be some fuzziness and uncertainty in satellite cloud imagery. Satellite observation is susceptible to noises, while traditional cloud classification methods are sensitive to noises and outliers; it is hard for traditional cloud classification methods to achieve reliable results. To deal with these problems, a satellite cloud classification method using adaptive fuzzy sparse representation-based classification (AFSRC) is proposed. Firstly, by defining adaptive parameters related to attenuation rate and critical membership, an improved fuzzy membership is introduced to accommodate the fuzziness and uncertainty of satellite cloud imagery; secondly, by effective combination of the improved fuzzy membership function and sparse representation-based classification (SRC), atoms in training dictionary are optimized; finally, an adaptive fuzzy sparse representation classifier for cloud classification is proposed. Experiment results on FY-2G satellite cloud image show that, the proposed method not only improves the accuracy of cloud classification, but also has strong stability and adaptability with high computational efficiency. Full article

(This article belongs to the Special Issue Earth Observation for Biodiversity and Ecosystem Services: Remote Sensing Data Handling and Analysis)

► Show Figures

Figure 1

10 pages, 11108 KiB

Open AccessArticle

Development of Lateral Flow Assay Based on Size-Controlled Gold Nanoparticles for Detection of Hepatitis B Surface Antigen

by Dong Seok Kim, Yong Tae Kim, Seok Bok Hong, Jinwoon Kim, Nam Su Heo, Moon-Keun Lee, Seok Jae Lee, Byeong Il Kim, In Soo Kim, Yun Suk Huh and Bong Gill Choi

Sensors 2016, 16(12), 2154; https://doi.org/10.3390/s16122154 - 16 Dec 2016

Cited by 83 | Viewed by 10523

Abstract

In this study, we developed lateral flow assay (LFA) biosensors for the detection of hepatitis B surface antigens using well-controlled gold nanoparticles (AuNPs). To enhance colorimetric signals, a seeded growth method was used for the preparation of size-controlled AuNPs with a narrow size [...] Read more.

In this study, we developed lateral flow assay (LFA) biosensors for the detection of hepatitis B surface antigens using well-controlled gold nanoparticles (AuNPs). To enhance colorimetric signals, a seeded growth method was used for the preparation of size-controlled AuNPs with a narrow size distribution. Different sizes of AuNPs in the range of 342–137.8 nm were conjugated with antibodies and then optimized for the efficient detection of LFA biosensors. The conjugation stability was investigated by UV-vis spectroscopy of AuNP dispersion at various pH values and concentrations of antibody. Based on optimized conjugation conditions, the use of 42.7 ± 0.8 nm AuNPs exhibited superior performance for the detection of LFAs relative to other sizes of AuNPs. Full article

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

► Show Figures

Figure 1

8 pages, 2787 KiB

Open AccessArticle

A Sensitive and Label-Free Pb(II) Fluorescence Sensor Based on a DNAzyme Controlled G-Quadruplex/Thioflavin T Conformation

by Yanli Wen, Lele Wang, Lanying Li, Li Xu and Gang Liu

Sensors 2016, 16(12), 2155; https://doi.org/10.3390/s16122155 - 16 Dec 2016

Cited by 22 | Viewed by 7374

Abstract

Pb(II) can cause serious damaging effects to human health, and thus, the study of Pb²⁺ detection methods to sensitively and selectively monitor Pb(II) pollution has significant importance. In this work, we have developed a label-free fluorescence sensing strategy based on a Pb(II) [...] Read more.

Pb(II) can cause serious damaging effects to human health, and thus, the study of Pb²⁺ detection methods to sensitively and selectively monitor Pb(II) pollution has significant importance. In this work, we have developed a label-free fluorescence sensing strategy based on a Pb(II) DNAzyme cleavage and the ThT/G-quadruplex complex. In the presence of Pb(II), a G-rich tail was cut and released from the substrate strand, which then would form a G-quadruplex structure by combination with ThT dye. The fluorescence signal increase was then measured for sensitive Pb(II) quantification with a limit of detection of 0.06 nM. Our sensor also demonstrated high selectivity against six different metal ions, which is very important for the analysis of complex samples. Full article

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

► Show Figures

Figure 1

9 pages, 1723 KiB

Open AccessArticle

Bi-Directional Brillouin Optical Time Domain Analyzer System for Long Range Distributed Sensing

by Nan Guo, Liang Wang, Jie Wang, Chao Jin, Hwa-Yaw Tam, A. Ping Zhang and Chao Lu

Sensors 2016, 16(12), 2156; https://doi.org/10.3390/s16122156 - 16 Dec 2016

Cited by 1 | Viewed by 4776

Abstract

We propose and experimentally demonstrate a novel scheme of bi-directional Brillouin time domain analyzer (BD-BOTDA) to extend the sensing range. By deploying two pump-probe pairs at two different wavelengths, the Brillouin frequency shift (BFS) distribution over each half of the whole fiber can [...] Read more.

We propose and experimentally demonstrate a novel scheme of bi-directional Brillouin time domain analyzer (BD-BOTDA) to extend the sensing range. By deploying two pump-probe pairs at two different wavelengths, the Brillouin frequency shift (BFS) distribution over each half of the whole fiber can be obtained with the simultaneous detection of Brillouin signals in both channels. Compared to the conventional unidirectional BOTDA system of the same sensing range, the proposed BD-BOTDA scheme enables distributed sensing with a performance level comparable to the conventional one with half of the sensing range and a spatial resolution of 2 m, while maintaining the Brillouin signal-to-noise ratio (SNR) and the BFS uncertainty. Based on this technique, we have achieved distributed temperature sensing with a measurement range of 81.9 km fiber at a spatial resolution of 2 m and BFS uncertainty of ~0.44 MHz without introducing any complicated components or schemes. Full article

(This article belongs to the Section Physical Sensors)

► Show Figures

Figure 1

8 pages, 3368 KiB

Open AccessArticle

A Photonic Crystal Magnetic Field Sensor Using a Shoulder-Coupled Resonant Cavity Infiltrated with Magnetic Fluid

by Delong Su, Shengli Pu, Lianmin Mao, Zhaofang Wang and Kai Qian

Sensors 2016, 16(12), 2157; https://doi.org/10.3390/s16122157 - 16 Dec 2016

Cited by 25 | Viewed by 5471

Abstract

A kind of photonic crystal magnetic field sensor is proposed and investigated numerically. The shoulder-coupled resonant cavity is introduced in the photonic crystal, which is infiltrated with magnetic fluid. Through monitoring the shift of resonant wavelength, the magnetic field sensing is realized. According [...] Read more.

A kind of photonic crystal magnetic field sensor is proposed and investigated numerically. The shoulder-coupled resonant cavity is introduced in the photonic crystal, which is infiltrated with magnetic fluid. Through monitoring the shift of resonant wavelength, the magnetic field sensing is realized. According to the designed infiltration schemes, both the magnetic field sensitivity and full width at half maximum increase with the number of infiltrated air holes. The figure of merit of the structure is defined to evaluate the sensing performance comprehensively. The best structure corresponding to the optimal infiltration scheme with eight air holes infiltrated with magnetic fluid is obtained. Full article

(This article belongs to the Section Physical Sensors)

► Show Figures

Figure 1

20 pages, 1818 KiB

Open AccessReview

MB-OFDM-UWB Based Wireless Multimedia Sensor Networks for Underground Coalmine: A Survey

by Ruisong Han, Wei Yang and Kaiming You

Sensors 2016, 16(12), 2158; https://doi.org/10.3390/s16122158 - 16 Dec 2016

Cited by 22 | Viewed by 6797

Abstract

Safety production of coalmines is a task of top priority which plays an important role in guaranteeing, supporting and promoting the continuous development of the coal industry. Since traditional wireless sensor networks (WSNs) cannot fully meet the requirements of comprehensive environment monitoring of [...] Read more.

Safety production of coalmines is a task of top priority which plays an important role in guaranteeing, supporting and promoting the continuous development of the coal industry. Since traditional wireless sensor networks (WSNs) cannot fully meet the requirements of comprehensive environment monitoring of underground coalmines, wireless multimedia sensor networks (WMSNs), enabling the retrieval of multimedia information, are introduced to realize fine-grained and precise environment surveillance. In this paper, a framework for designing underground coalmine WMSNs based on Multi-Band Orthogonal Frequency-Division Multiplexing Ultra-wide Band (MB-OFDM-UWB) is presented. The selection of MB-OFDM-UWB wireless transmission solution is based on the characteristics of underground coalmines. Network structure and design challenges are analyzed first, which is the foundation for further discussion. Then, key supporting technologies and open research areas in different layers are surveyed, and we provide a detailed literature review of the state of the art strategies, algorithms and general solutions in these issues. Finally, other research issues like localization, information processing, and network management are discussed. Full article

(This article belongs to the Section Sensor Networks)

► Show Figures

Figure 1

16 pages, 12795 KiB

Open AccessArticle

Recognition of Damaged Arrow-Road Markings by Visible Light Camera Sensor Based on Convolutional Neural Network

by Husan Vokhidov, Hyung Gil Hong, Jin Kyu Kang, Toan Minh Hoang and Kang Ryoung Park

Sensors 2016, 16(12), 2160; https://doi.org/10.3390/s16122160 - 16 Dec 2016

Cited by 43 | Viewed by 10621

Abstract

Automobile driver information as displayed on marked road signs indicates the state of the road, traffic conditions, proximity to schools, etc. These signs are important to insure the safety of the driver and pedestrians. They are also important input to the automated advanced [...] Read more.

Automobile driver information as displayed on marked road signs indicates the state of the road, traffic conditions, proximity to schools, etc. These signs are important to insure the safety of the driver and pedestrians. They are also important input to the automated advanced driver assistance system (ADAS), installed in many automobiles. Over time, the arrow-road markings may be eroded or otherwise damaged by automobile contact, making it difficult for the driver to correctly identify the marking. Failure to properly identify an arrow-road marker creates a dangerous situation that may result in traffic accidents or pedestrian injury. Very little research exists that studies the problem of automated identification of damaged arrow-road marking painted on the road. In this study, we propose a method that uses a convolutional neural network (CNN) to recognize six types of arrow-road markings, possibly damaged, by visible light camera sensor. Experimental results with six databases of Road marking dataset, KITTI dataset, Málaga dataset 2009, Málaga urban dataset, Naver street view dataset, and Road/Lane detection evaluation 2013 dataset, show that our method outperforms conventional methods. Full article

(This article belongs to the Special Issue Sensors for Autonomous Road Vehicles)

► Show Figures

Figure 1

22 pages, 10238 KiB

Open AccessReview

Review of the Usefulness of Various Rotational Seismometers with Laboratory Results of Fibre-Optic Ones Tested for Engineering Applications

by Leszek R. Jaroszewicz, Anna Kurzych, Zbigniew Krajewski, Paweł Marć, Jerzy K. Kowalski, Piotr Bobra, Zbigniew Zembaty, Bartosz Sakowicz and Robert Jankowski

Sensors 2016, 16(12), 2161; https://doi.org/10.3390/s16122161 - 16 Dec 2016

Cited by 69 | Viewed by 8543

Abstract

Starting with descriptions of rotational seismology, areas of interest and historical field measurements, the fundamental requirements for rotational seismometers for seismological and engineering application are formulated. On the above basis, a review of all existing rotational seismometers is presented with a description of [...] Read more.

Starting with descriptions of rotational seismology, areas of interest and historical field measurements, the fundamental requirements for rotational seismometers for seismological and engineering application are formulated. On the above basis, a review of all existing rotational seismometers is presented with a description of the principles of their operation as well as possibilities to fulfill formulated requirements. This review includes mechanical, acoustical, electrochemical and optical devices and shows that the last of these types are the most promising. It is shown that optical rotational seismometer based on the ring-laser gyroscope concept is the best for seismological applications, whereas systems based on fiber-optic gyroscopes demonstrate parameters which are also required for engineering applications. Laboratory results of the Fibre-Optic System for Rotational Events & Phenomena Monitoring using a small 1-D shaking table modified to generate rotational excitations are presented. The harmonic and time-history tests demonstrate its usefulness for recording rotational motions with rates up to 0.25 rad/s. Full article

(This article belongs to the Special Issue Optical Fiber Sensors 2016)

► Show Figures

Figure 1

14 pages, 17086 KiB

Open AccessArticle

Synthesis, Characterization, and Sensor Applications of Spinel ZnCo₂O₄ Nanoparticles

by Juan Pablo Morán-Lázaro, Florentino López-Urías, Emilio Muñoz-Sandoval, Oscar Blanco-Alonso, Marciano Sanchez-Tizapa, Alejandra Carreon-Alvarez, Héctor Guillén-Bonilla, María De la Luz Olvera-Amador, Alex Guillén-Bonilla and Verónica María Rodríguez-Betancourtt

Sensors 2016, 16(12), 2162; https://doi.org/10.3390/s16122162 - 17 Dec 2016

Cited by 37 | Viewed by 9721

Abstract

Spinel ZnCo₂O₄ nanoparticles were synthesized by means of the microwave-assisted colloidal method. A solution containing ethanol, Co-nitrate, Zn-nitrate, and dodecylamine was stirred for 24 h and evaporated by a microwave oven. The resulting solid material was dried at 200 °C [...] Read more.

Spinel ZnCo₂O₄ nanoparticles were synthesized by means of the microwave-assisted colloidal method. A solution containing ethanol, Co-nitrate, Zn-nitrate, and dodecylamine was stirred for 24 h and evaporated by a microwave oven. The resulting solid material was dried at 200 °C and subsequently calcined at 500 °C for 5 h. The samples were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and Raman spectroscopy, confirming the formation of spinel ZnCo₂O₄ nanoparticles with average sizes between 49 and 75 nm. It was found that the average particle size decreased when the dodecylamine concentration increased. Pellets containing ZnCo₂O₄ nanoparticles were fabricated and tested as sensors in carbon monoxide (CO) and propane (C₃H₈) gases at different concentrations and temperatures. Sensor performance tests revealed an extremely high response to 300 ppm of CO at an operating temperature of 200 °C. Full article

(This article belongs to the Special Issue Gas Nanosensors)

► Show Figures

Figure 1

9 pages, 543 KiB

Open AccessArticle

A Smartphone Application for Personal Assessments of Body Composition and Phenotyping

by Gian Luca Farina, Fabrizio Spataro, Antonino De Lorenzo and Henry Lukaski

Sensors 2016, 16(12), 2163; https://doi.org/10.3390/s16122163 - 17 Dec 2016

Cited by 24 | Viewed by 13396 | Correction

Abstract

Personal assessments of body phenotype can enhance success in weight management but are limited by the lack of availability of practical methods. We describe a novel smart phone application of digital photography (DP) and determine its validity to estimate fat mass (FM). This [...] Read more.

Personal assessments of body phenotype can enhance success in weight management but are limited by the lack of availability of practical methods. We describe a novel smart phone application of digital photography (DP) and determine its validity to estimate fat mass (FM). This approach utilizes the percent (%) occupancy of an individual lateral whole-body digital image and regions indicative of adipose accumulation associated with increased risk of cardio-metabolic disease. We measured 117 healthy adults (63 females and 54 males aged 19 to 65 years) with DP and dual X-ray absorptiometry (DXA) and report here the development and validation of this application. Inter-observer variability of the determination of % occupancy was 0.02%. Predicted and reference FM values were significantly related in females (R² = 0.949, SEE = 2.83) and males (R² = 0.907, SEE = 2.71). Differences between predicted and measured FM values were small (0.02 kg, p = 0.96 and 0.07 kg, p = 0.96) for females and males, respectively. No significant bias was found; limits of agreement ranged from 5.6 to −5.4 kg for females and from 5.6 to −5.7 kg for males. These promising results indicate that DP is a practical and valid method for personal body composition assessments. Full article

(This article belongs to the Special Issue Smartphone-Based Sensors for Non-Invasive Physiological Monitoring)

► Show Figures

Figure 1

26 pages, 7546 KiB

Open AccessArticle

Differential GNSS and Vision-Based Tracking to Improve Navigation Performance in Cooperative Multi-UAV Systems

by Amedeo Rodi Vetrella, Giancarmine Fasano, Domenico Accardo and Antonio Moccia

Sensors 2016, 16(12), 2164; https://doi.org/10.3390/s16122164 - 17 Dec 2016

Cited by 70 | Viewed by 9870

Abstract

Autonomous navigation of micro-UAVs is typically based on the integration of low cost Global Navigation Satellite System (GNSS) receivers and Micro-Electro-Mechanical Systems (MEMS)-based inertial and magnetic sensors to stabilize and control the flight. The resulting navigation performance in terms of position and attitude [...] Read more.

Autonomous navigation of micro-UAVs is typically based on the integration of low cost Global Navigation Satellite System (GNSS) receivers and Micro-Electro-Mechanical Systems (MEMS)-based inertial and magnetic sensors to stabilize and control the flight. The resulting navigation performance in terms of position and attitude accuracy may not suffice for other mission needs, such as the ones relevant to fine sensor pointing. In this framework, this paper presents a cooperative UAV navigation algorithm that allows a chief vehicle, equipped with inertial and magnetic sensors, a Global Positioning System (GPS) receiver, and a vision system, to improve its navigation performance (in real time or in the post processing phase) exploiting formation flying deputy vehicles equipped with GPS receivers. The focus is set on outdoor environments and the key concept is to exploit differential GPS among vehicles and vision-based tracking (DGPS/Vision) to build a virtual additional navigation sensor whose information is then integrated in a sensor fusion algorithm based on an Extended Kalman Filter. The developed concept and processing architecture are described, with a focus on DGPS/Vision attitude determination algorithm. Performance assessment is carried out on the basis of both numerical simulations and flight tests. In the latter ones, navigation estimates derived from the DGPS/Vision approach are compared with those provided by the onboard autopilot system of a customized quadrotor. The analysis shows the potential of the developed approach, mainly deriving from the possibility to exploit magnetic- and inertial-independent accurate attitude information. Full article

(This article belongs to the Special Issue UAV-Based Remote Sensing)

► Show Figures

Figure 1

12 pages, 2603 KiB

Open AccessArticle

Visualization of Fluoride Ions In Vivo Using a Gadolinium(III)-Coumarin Complex-Based Fluorescence/MRI Dual-Modal Probe

by Yue Wang, Renfeng Song, Huan Feng, Ke Guo, Qingtao Meng, Haijun Chi, Run Zhang and Zhiqiang Zhang

Sensors 2016, 16(12), 2165; https://doi.org/10.3390/s16122165 - 16 Dec 2016

Cited by 13 | Viewed by 7760

Abstract

A new Gadolinium(III)–coumarin complex, DO3A-Gd-CA, was designed and prepared as a dual-modal probe for simultaneous fluorescence and relaxivity responses to fluoride ions (F⁻) in aqueous media and mice. DO3A-Gd-CA was designed by using Gd(III) center as an MRI [...] Read more.

A new Gadolinium(III)–coumarin complex, DO3A-Gd-CA, was designed and prepared as a dual-modal probe for simultaneous fluorescence and relaxivity responses to fluoride ions (F⁻) in aqueous media and mice. DO3A-Gd-CA was designed by using Gd(III) center as an MRI signal output unit and fluoride binding site, and the 4-(diethylamino)-coumarin-3-carboxylic acid (CA) as a fluorescence reporter. Upon the addition of fluoride ions to the solution of DO3A-Gd-CA, the liberation of the coordinated CA ligand led to a 5.7-fold fluorescence enhancement and a 75% increase in the longitudinal relaxivity (r₁). The fluorescent detection limit for fluoride ions was determined to be 8 μM based on a 3σ/slope. The desirable features of the proposed DO3A-Gd-CA, such as high sensitivity and specificity, reliability at physiological pH and low cytotoxicity enable its application in visualization of fluoride ion in mice. The successful in vivo imaging indicates that DO3A-Gd-CA could be potentially used in biomedical diagnosis fields. Full article

(This article belongs to the Special Issue Colorimetric and Fluorescent Sensor)

► Show Figures

Figure 1

17 pages, 3000 KiB

Open AccessArticle

High Accuracy Acquisition of 3-D Flight Trajectory of Individual Insect Based on Phase Measurement

by Cheng Hu, Yunkai Deng, Rui Wang, Changjiang Liu and Teng Long

Sensors 2016, 16(12), 2166; https://doi.org/10.3390/s16122166 - 17 Dec 2016

Cited by 4 | Viewed by 4655

Abstract

Accurate acquisition of 3-D flight trajectory of individual insect could be of benefit to the research of insect migration behaviors and the development of migratory entomology. This paper proposes a novel method to acquire 3-D flight trajectory of individual insect. First, based on [...] Read more.

Accurate acquisition of 3-D flight trajectory of individual insect could be of benefit to the research of insect migration behaviors and the development of migratory entomology. This paper proposes a novel method to acquire 3-D flight trajectory of individual insect. First, based on the high range resolution synthesizing and the Doppler coherent processing, insects can be detected effectively, and the range resolution and velocity resolution are combined together to discriminate insects. Then, high accuracy range measurement with the carrier phase is proposed. The range measurement accuracy can reach millimeter level and benefits the acquisition of 3-D trajectory information significantly. Finally, based on the multi-baselines interferometry theory, the azimuth and elevation angles can be obtained with high accuracy. Simulation results prove that the retrieval accuracy of a simulated target’s 3-D coordinates can reach centimeter level. Experiments utilizing S-band radar in an anechoic chamber were taken and results showed that the insects’ flight behaviors and 3-D coordinates’ variation matched the practical cases well. In conclusion, both the simulated and experimental datasets validate the feasibility of the proposed method, which could be a novel measurement way of monitoring flight trajectory of aerial free-fly insects. Full article

(This article belongs to the Section Remote Sensors)

► Show Figures

Figure 1

18 pages, 4327 KiB

Open AccessArticle

Estimation of Temporal Gait Parameters Using a Wearable Microphone-Sensor-Based System

by Cheng Wang, Xiangdong Wang, Zhou Long, Jing Yuan, Yueliang Qian and Jintao Li

Sensors 2016, 16(12), 2167; https://doi.org/10.3390/s16122167 - 17 Dec 2016

Cited by 23 | Viewed by 5924

Abstract

Most existing wearable gait analysis methods focus on the analysis of data obtained from inertial sensors. This paper proposes a novel, low-cost, wireless and wearable gait analysis system which uses microphone sensors to collect footstep sound signals during walking. This is the first [...] Read more.

Most existing wearable gait analysis methods focus on the analysis of data obtained from inertial sensors. This paper proposes a novel, low-cost, wireless and wearable gait analysis system which uses microphone sensors to collect footstep sound signals during walking. This is the first time a microphone sensor is used as a wearable gait analysis device as far as we know. Based on this system, a gait analysis algorithm for estimating the temporal parameters of gait is presented. The algorithm fully uses the fusion of two feet footstep sound signals and includes three stages: footstep detection, heel-strike event and toe-on event detection, and calculation of gait temporal parameters. Experimental results show that with a total of 240 data sequences and 1732 steps collected using three different gait data collection strategies from 15 healthy subjects, the proposed system achieves an average 0.955 F1-measure for footstep detection, an average 94.52% accuracy rate for heel-strike detection and 94.25% accuracy rate for toe-on detection. Using these detection results, nine temporal related gait parameters are calculated and these parameters are consistent with their corresponding normal gait temporal parameters and labeled data calculation results. The results verify the effectiveness of our proposed system and algorithm for temporal gait parameter estimation. Full article

(This article belongs to the Section Physical Sensors)

► Show Figures

Figure 1

13 pages, 5191 KiB

Open AccessArticle

A Modified Magnetic Gradient Contraction Based Method for Ferromagnetic Target Localization

by Chen Wang, Xiaojuan Zhang, Xiaodong Qu, Xiao Pan, Guangyou Fang and Luzhao Chen

Sensors 2016, 16(12), 2168; https://doi.org/10.3390/s16122168 - 17 Dec 2016

Cited by 41 | Viewed by 6284

Abstract

The Scalar Triangulation and Ranging (STAR) method, which is based upon the unique properties of magnetic gradient contraction, is a high real-time ferromagnetic target localization method. Only one measurement point is required in the STAR method and it is not sensitive to changes [...] Read more.

The Scalar Triangulation and Ranging (STAR) method, which is based upon the unique properties of magnetic gradient contraction, is a high real-time ferromagnetic target localization method. Only one measurement point is required in the STAR method and it is not sensitive to changes in sensing platform orientation. However, the localization accuracy of the method is limited by the asphericity errors and the inaccurate value of position leads to larger errors in the estimation of magnetic moment. To improve the localization accuracy, a modified STAR method is proposed. In the proposed method, the asphericity errors of the traditional STAR method are compensated with an iterative algorithm. The proposed method has a fast convergence rate which meets the requirement of high real-time localization. Simulations and field experiments have been done to evaluate the performance of the proposed method. The results indicate that target parameters estimated by the modified STAR method are more accurate than the traditional STAR method. Full article

(This article belongs to the Special Issue Advances in Applied Remote Sensing and Decision Making: Transforming Hazard Assessment and Environmental Management)

► Show Figures

Figure 1

19 pages, 9121 KiB

Open AccessArticle

Autonomous Aeromagnetic Surveys Using a Fluxgate Magnetometer

by Douglas G. Macharet, Héctor I. A. Perez-Imaz, Paulo A. F. Rezeck, Guilherme A. Potje, Luiz C. C. Benyosef, André Wiermann, Gustavo M. Freitas, Luis G. U. Garcia and Mario F. M. Campos

Sensors 2016, 16(12), 2169; https://doi.org/10.3390/s16122169 - 17 Dec 2016

Cited by 39 | Viewed by 12740

Abstract

Recent advances in the research of autonomous vehicles have showed a vast range of applications, such as exploration, surveillance and environmental monitoring. Considering the mining industry, it is possible to use such vehicles in the prospection of minerals of commercial interest beneath the [...] Read more.

Recent advances in the research of autonomous vehicles have showed a vast range of applications, such as exploration, surveillance and environmental monitoring. Considering the mining industry, it is possible to use such vehicles in the prospection of minerals of commercial interest beneath the ground. However, tasks such as geophysical surveys are highly dependent on specific sensors, which mostly are not designed to be used in these new range of autonomous vehicles. In this work, we propose a novel magnetic survey pipeline that aims to increase versatility, speed and robustness by using autonomous rotary-wing Unmanned Aerial Vehicles (UAVs). We also discuss the development of a state-of-the-art three-axis fluxgate, where our goal in this work was to refine and adjust the sensor topology and coupled electronics specifically for this type of vehicle and application. The sensor was built with two ring-cores using a specially developed stress-annealed CoFeSiB amorphous ribbon, in order to get sufficient resolution to detect concentrations of small ferrous minerals. Finally, we report on the results of experiments performed with a real UAV in an outdoor environment, showing the efficacy of the methodology in detecting an artificial ferrous anomaly. Full article

(This article belongs to the Special Issue UAV-Based Remote Sensing)

► Show Figures

Figure 1

16 pages, 441 KiB

Open AccessArticle

A Mathematical Model of a Novel 3D Fractal-Inspired Piezoelectric Ultrasonic Transducer

by Sara Canning, Alan J. Walker and Paul A. Roach

Sensors 2016, 16(12), 2170; https://doi.org/10.3390/s16122170 - 17 Dec 2016

Cited by 4 | Viewed by 6228

Abstract

Piezoelectric ultrasonic transducers have the potential to operate as both a sensor and as an actuator of ultrasonic waves. Currently, manufactured transducers operate effectively over narrow bandwidths as a result of their regular structures which incorporate a single length scale. To increase the [...] Read more.

Piezoelectric ultrasonic transducers have the potential to operate as both a sensor and as an actuator of ultrasonic waves. Currently, manufactured transducers operate effectively over narrow bandwidths as a result of their regular structures which incorporate a single length scale. To increase the operational bandwidth of these devices, consideration has been given in the literature to the implementation of designs which contain a range of length scales. In this paper, a mathematical model of a novel Sierpinski tetrix fractal-inspired transducer for sensor applications is presented. To accompany the growing body of research based on fractal-inspired transducers, this paper offers the first sensor design based on a three-dimensional fractal. The three-dimensional model reduces to an effective one-dimensional model by allowing for a number of assumptions of the propagating wave in the fractal lattice. The reception sensitivity of the sensor is investigated. Comparisons of reception force response (RFR) are performed between this novel design along with a previously investigated Sierpinski gasket-inspired device and standard Euclidean design. The results indicate that the proposed device surpasses traditional design sensors. Full article

(This article belongs to the Special Issue Ultrasonic Sensors)

► Show Figures

Figure 1

22 pages, 4126 KiB

Open AccessArticle

Adaptive Local Spatiotemporal Features from RGB-D Data for One-Shot Learning Gesture Recognition

by Jia Lin, Xiaogang Ruan, Naigong Yu and Yee-Hong Yang

Sensors 2016, 16(12), 2171; https://doi.org/10.3390/s16122171 - 17 Dec 2016

Cited by 6 | Viewed by 5821

Abstract

Noise and constant empirical motion constraints affect the extraction of distinctive spatiotemporal features from one or a few samples per gesture class. To tackle these problems, an adaptive local spatiotemporal feature (ALSTF) using fused RGB-D data is proposed. First, motion regions of interest [...] Read more.

Noise and constant empirical motion constraints affect the extraction of distinctive spatiotemporal features from one or a few samples per gesture class. To tackle these problems, an adaptive local spatiotemporal feature (ALSTF) using fused RGB-D data is proposed. First, motion regions of interest (MRoIs) are adaptively extracted using grayscale and depth velocity variance information to greatly reduce the impact of noise. Then, corners are used as keypoints if their depth, and velocities of grayscale and of depth meet several adaptive local constraints in each MRoI. With further filtering of noise, an accurate and sufficient number of keypoints is obtained within the desired moving body parts (MBPs). Finally, four kinds of multiple descriptors are calculated and combined in extended gradient and motion spaces to represent the appearance and motion features of gestures. The experimental results on the ChaLearn gesture, CAD-60 and MSRDailyActivity3D datasets demonstrate that the proposed feature achieves higher performance compared with published state-of-the-art approaches under the one-shot learning setting and comparable accuracy under the leave-one-out cross validation. Full article

(This article belongs to the Special Issue Video Analysis and Tracking Using State-of-the-Art Sensors)

► Show Figures

Figure 1

11 pages, 1880 KiB

Open AccessArticle

Development of a Wearable Instrumented Vest for Posture Monitoring and System Usability Verification Based on the Technology Acceptance Model

by Wen-Yen Lin, Wen-Cheng Chou, Tsai-Hsuan Tsai, Chung-Chih Lin and Ming-Yih Lee

Sensors 2016, 16(12), 2172; https://doi.org/10.3390/s16122172 - 17 Dec 2016

Cited by 48 | Viewed by 10510

Abstract

Body posture and activity are important indices for assessing health and quality of life, especially for elderly people. Therefore, an easily wearable device or instrumented garment would be valuable for monitoring elderly people’s postures and activities to facilitate healthy aging. In particular, such [...] Read more.

Body posture and activity are important indices for assessing health and quality of life, especially for elderly people. Therefore, an easily wearable device or instrumented garment would be valuable for monitoring elderly people’s postures and activities to facilitate healthy aging. In particular, such devices should be accepted by elderly people so that they are willing to wear it all the time. This paper presents the design and development of a novel, textile-based, intelligent wearable vest for real-time posture monitoring and emergency warnings. The vest provides a highly portable and low-cost solution that can be used both indoors and outdoors in order to provide long-term care at home, including health promotion, healthy aging assessments, and health abnormality alerts. The usability of the system was verified using a technology acceptance model-based study of 50 elderly people. The results indicated that although elderly people are anxious about some newly developed wearable technologies, they look forward to wearing this instrumented posture-monitoring vest in the future. Full article

(This article belongs to the Special Issue Wearable Biomedical Sensors)

► Show Figures

Figure 1

15 pages, 13077 KiB

Open AccessArticle

Robust and Accurate Vision-Based Pose Estimation Algorithm Based on Four Coplanar Feature Points

by Zimiao Zhang, Shihai Zhang and Qiu Li

Sensors 2016, 16(12), 2173; https://doi.org/10.3390/s16122173 - 17 Dec 2016

Cited by 8 | Viewed by 5661

Abstract

Vision-based pose estimation is an important application of machine vision. Currently, analytical and iterative methods are used to solve the object pose. The analytical solutions generally take less computation time. However, the analytical solutions are extremely susceptible to noise. The iterative solutions minimize [...] Read more.

Vision-based pose estimation is an important application of machine vision. Currently, analytical and iterative methods are used to solve the object pose. The analytical solutions generally take less computation time. However, the analytical solutions are extremely susceptible to noise. The iterative solutions minimize the distance error between feature points based on 2D image pixel coordinates. However, the non-linear optimization needs a good initial estimate of the true solution, otherwise they are more time consuming than analytical solutions. Moreover, the image processing error grows rapidly with measurement range increase. This leads to pose estimation errors. All the reasons mentioned above will cause accuracy to decrease. To solve this problem, a novel pose estimation method based on four coplanar points is proposed. Firstly, the coordinates of feature points are determined according to the linear constraints formed by the four points. The initial coordinates of feature points acquired through the linear method are then optimized through an iterative method. Finally, the coordinate system of object motion is established and a method is introduced to solve the object pose. The growing image processing error causes pose estimation errors the measurement range increases. Through the coordinate system, the pose estimation errors could be decreased. The proposed method is compared with two other existing methods through experiments. Experimental results demonstrate that the proposed method works efficiently and stably. Full article

(This article belongs to the Special Issue Video Analysis and Tracking Using State-of-the-Art Sensors)

► Show Figures

Figure 1

13 pages, 2213 KiB

Open AccessArticle

Development and Application of a Synthetically-Derived Lead Biosensor Construct for Use in Gram-Negative Bacteria

by Lara Bereza-Malcolm, Sanja Aracic and Ashley E. Franks

Sensors 2016, 16(12), 2174; https://doi.org/10.3390/s16122174 - 18 Dec 2016

Cited by 51 | Viewed by 6513

Abstract

The use of lead in manufacturing has decreased significantly over the last few decades. However, previous widespread use of lead-containing products and their incorrect disposal has resulted in environmental contamination. Accumulation of harmful quantities of lead pose a threat to all living organisms, [...] Read more.

The use of lead in manufacturing has decreased significantly over the last few decades. However, previous widespread use of lead-containing products and their incorrect disposal has resulted in environmental contamination. Accumulation of harmful quantities of lead pose a threat to all living organisms, through inhalation, ingestion, or direct contact, resulting in lead poisoning. This study utilized synthetic biology principles to develop plasmid-based whole-cell bacterial biosensors for detection of lead. The genetic element of the lead biosensor construct consists of pbrR, which encodes the regulatory protein, together with its divergent promoter region and a promoterless gfp. GFP expression is controlled by PbrR in response to the presence of lead. The lead biosensor genetic element was cloned onto a low-copy number broad host range plasmid, which can stably exist in a range of laboratory and environmental isolates, including Pseudomonas, Shewanella, and Enterobacter. The biosensors constructed were found to be sensitive, rapid, and specific and could, as such, serve as monitoring tools for lead-contaminated water. Full article

(This article belongs to the Special Issue Sensors for Environmental Monitoring 2016)

► Show Figures

Graphical abstract

20 pages, 1050 KiB

Open AccessArticle

A Cooperative Traffic Control of Vehicle–Intersection (CTCVI) for the Reduction of Traffic Delays and Fuel Consumption

by Jinjian Li, Mahjoub Dridi and Abdellah El-Moudni

Sensors 2016, 16(12), 2175; https://doi.org/10.3390/s16122175 - 17 Dec 2016

Cited by 15 | Viewed by 5260

Abstract

The problem of reducing traffic delays and decreasing fuel consumption simultaneously in a network of intersections without traffic lights is solved by a cooperative traffic control algorithm, where the cooperation is executed based on the connection of Vehicle-to-Infrastructure (V2I). This resolution of the [...] Read more.

The problem of reducing traffic delays and decreasing fuel consumption simultaneously in a network of intersections without traffic lights is solved by a cooperative traffic control algorithm, where the cooperation is executed based on the connection of Vehicle-to-Infrastructure (V2I). This resolution of the problem contains two main steps. The first step concerns the itinerary of which intersections are chosen by vehicles to arrive at their destination from their starting point. Based on the principle of minimal travel distance, each vehicle chooses its itinerary dynamically based on the traffic loads in the adjacent intersections. The second step is related to the following proposed cooperative procedures to allow vehicles to pass through each intersection rapidly and economically: on one hand, according to the real-time information sent by vehicles via V2I in the edge of the communication zone, each intersection applies Dynamic Programming (DP) to cooperatively optimize the vehicle passing sequence with minimal traffic delays so that the vehicles may rapidly pass the intersection under the relevant safety constraints; on the other hand, after receiving this sequence, each vehicle finds the optimal speed profiles with the minimal fuel consumption by an exhaustive search. The simulation results reveal that the proposed algorithm can significantly reduce both travel delays and fuel consumption compared with other papers under different traffic volumes. Full article

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

► Show Figures

Figure 1

18 pages, 473 KiB

Open AccessArticle

Underwater Electromagnetic Sensor Networks, Part II: Localization and Network Simulations

by Javier Zazo, Sergio Valcarcel Macua, Santiago Zazo, Marina Pérez, Iván Pérez-Álvarez, Eugenio Jiménez, Laura Cardona, Joaquín Hernández Brito and Eduardo Quevedo

Sensors 2016, 16(12), 2176; https://doi.org/10.3390/s16122176 - 17 Dec 2016

Cited by 14 | Viewed by 6701

Abstract

In the first part of the paper, we modeled and characterized the underwater radio channel in shallowwaters. In the second part,we analyze the application requirements for an underwaterwireless sensor network (U-WSN) operating in the same environment and perform detailed simulations. We consider two [...] Read more.

In the first part of the paper, we modeled and characterized the underwater radio channel in shallowwaters. In the second part,we analyze the application requirements for an underwaterwireless sensor network (U-WSN) operating in the same environment and perform detailed simulations. We consider two localization applications, namely self-localization and navigation aid, and propose algorithms that work well under the specific constraints associated with U-WSN, namely low connectivity, low data rates and high packet loss probability. We propose an algorithm where the sensor nodes collaboratively estimate their unknown positions in the network using a low number of anchor nodes and distance measurements from the underwater channel. Once the network has been self-located, we consider a node estimating its position for underwater navigation communicating with neighboring nodes. We also propose a communication system and simulate the whole electromagnetic U-WSN in the Castalia simulator to evaluate the network performance, including propagation impairments (e.g., noise, interference), radio parameters (e.g., modulation scheme, bandwidth, transmit power), hardware limitations (e.g., clock drift, transmission buffer) and complete MAC and routing protocols. We also explain the changes that have to be done to Castalia in order to perform the simulations. In addition, we propose a parametric model of the communication channel that matches well with the results from the first part of this paper. Finally, we provide simulation results for some illustrative scenarios. Full article

(This article belongs to the Special Issue Sensing Technologies for Autonomy and Cooperation in Underwater Networked Robot Systems)

► Show Figures

Figure 1

17 pages, 5857 KiB

Open AccessArticle

Gravity Compensation Using EGM2008 for High-Precision Long-Term Inertial Navigation Systems

by Ruonan Wu, Qiuping Wu, Fengtian Han, Tianyi Liu, Peida Hu and Haixia Li

Sensors 2016, 16(12), 2177; https://doi.org/10.3390/s16122177 - 18 Dec 2016

Cited by 23 | Viewed by 6076

Abstract

The gravity disturbance vector is one of the major error sources in high-precision and long-term inertial navigation applications. Specific to the inertial navigation systems (INSs) with high-order horizontal damping networks, analyses of the error propagation show that the gravity-induced errors exist almost exclusively [...] Read more.

The gravity disturbance vector is one of the major error sources in high-precision and long-term inertial navigation applications. Specific to the inertial navigation systems (INSs) with high-order horizontal damping networks, analyses of the error propagation show that the gravity-induced errors exist almost exclusively in the horizontal channels and are mostly caused by deflections of the vertical (DOV). Low-frequency components of the DOV propagate into the latitude and longitude errors at a ratio of 1:1 and time-varying fluctuations in the DOV excite Schuler oscillation. This paper presents two gravity compensation methods using the Earth Gravitational Model 2008 (EGM2008), namely, interpolation from the off-line database and computing gravity vectors directly using the spherical harmonic model. Particular attention is given to the error contribution of the gravity update interval and computing time delay. It is recommended for the marine navigation that a gravity vector should be calculated within 1 s and updated every 100 s at most. To meet this demand, the time duration of calculating the current gravity vector using EGM2008 has been reduced to less than 1 s by optimizing the calculation procedure. A few off-line experiments were conducted using the data of a shipborne INS collected during an actual sea test. With the aid of EGM2008, most of the low-frequency components of the position errors caused by the gravity disturbance vector have been removed and the Schuler oscillation has been attenuated effectively. In the rugged terrain, the horizontal position error could be reduced at best 48.85% of its regional maximum. The experimental results match with the theoretical analysis and indicate that EGM2008 is suitable for gravity compensation of the high-precision and long-term INSs. Full article

(This article belongs to the Special Issue Inertial Sensors and Systems 2016)

► Show Figures

Figure 1

21 pages, 2566 KiB

Open AccessReview

Label-Free Aptasensors for the Detection of Mycotoxins

by Amina Rhouati, Gaelle Catanante, Gilvanda Nunes, Akhtar Hayat and Jean-Louis Marty

Sensors 2016, 16(12), 2178; https://doi.org/10.3390/s16122178 - 18 Dec 2016

Cited by 87 | Viewed by 11485

Abstract

Various methodologies have been reported in the literature for the qualitative and quantitative monitoring of mycotoxins in food and feed samples. Based on their enhanced specificity, selectivity and versatility, bio-affinity assays have inspired many researchers to develop sensors by exploring bio-recognition phenomena. However, [...] Read more.

Various methodologies have been reported in the literature for the qualitative and quantitative monitoring of mycotoxins in food and feed samples. Based on their enhanced specificity, selectivity and versatility, bio-affinity assays have inspired many researchers to develop sensors by exploring bio-recognition phenomena. However, a significant problem in the fabrication of these devices is that most of the biomolecules do not generate an easily measurable signal upon binding to the target analytes, and signal-generating labels are required to perform the measurements. In this context, aptamers have been emerged as a potential and attractive bio-recognition element to design label-free aptasensors for various target analytes. Contrary to other bioreceptor-based approaches, the aptamer-based assays rely on antigen binding-induced conformational changes or oligomerization states rather than binding-assisted changes in adsorbed mass or charge. This review will focus on current designs in label-free conformational switchable design strategies, with a particular focus on applications in the detection of mycotoxins. Full article

(This article belongs to the Special Issue Aptasensors 2016)

► Show Figures

Figure 1

8 pages, 2551 KiB

Open AccessArticle

Vision Marker-Based In Situ Examination of Bacterial Growth in Liquid Culture Media

by Kyukwang Kim, Duckyu Choi, Hwijoon Lim, Hyeongkeun Kim and Jessie S. Jeon

Sensors 2016, 16(12), 2179; https://doi.org/10.3390/s16122179 - 18 Dec 2016

Cited by 5 | Viewed by 7139

Abstract

The detection of bacterial growth in liquid media is an essential process in determining antibiotic susceptibility or the level of bacterial presence for clinical or research purposes. We have developed a system, which enables simplified and automated detection using a camera and a [...] Read more.

The detection of bacterial growth in liquid media is an essential process in determining antibiotic susceptibility or the level of bacterial presence for clinical or research purposes. We have developed a system, which enables simplified and automated detection using a camera and a striped pattern marker. The quantification of bacterial growth is possible as the bacterial growth in the culturing vessel blurs the marker image, which is placed on the back of the vessel, and the blurring results in a decrease in the high-frequency spectrum region of the marker image. The experiment results show that the FFT (fast Fourier transform)-based growth detection method is robust to the variations in the type of bacterial carrier and vessels ranging from the culture tubes to the microfluidic devices. Moreover, the automated incubator and image acquisition system are developed to be used as a comprehensive in situ detection system. We expect that this result can be applied in the automation of biological experiments, such as the Antibiotics Susceptibility Test or toxicity measurement. Furthermore, the simple framework of the proposed growth measurement method may be further utilized as an effective and convenient method for building point-of-care devices for developing countries. Full article

(This article belongs to the Special Issue Microfluidics-Based Microsystem Integration Research)

► Show Figures

Figure 1

12 pages, 5671 KiB

Open AccessArticle

A Novel Probabilistic Data Association for Target Tracking in a Cluttered Environment

by Xiao Chen, Yaan Li, Yuxing Li, Jing Yu and Xiaohua Li

Sensors 2016, 16(12), 2180; https://doi.org/10.3390/s16122180 - 18 Dec 2016

Cited by 30 | Viewed by 6967

Abstract

The problem of data association for target tracking in a cluttered environment is discussed. In order to improve the real-time processing and accuracy of target tracking, based on a probabilistic data association algorithm, a novel data association algorithm using distance weighting was proposed, [...] Read more.

The problem of data association for target tracking in a cluttered environment is discussed. In order to improve the real-time processing and accuracy of target tracking, based on a probabilistic data association algorithm, a novel data association algorithm using distance weighting was proposed, which can enhance the association probability of measurement originated from target, and then using a Kalman filter to estimate the target state more accurately. Thus, the tracking performance of the proposed algorithm when tracking non-maneuvering targets in a densely cluttered environment has improved, and also does better when two targets are parallel to each other, or at a small-angle crossing in a densely cluttered environment. As for maneuvering target issues, usually with an interactive multi-model framework, combined with the improved probabilistic data association method, we propose an improved algorithm using a combined interactive multiple model probabilistic data association algorithm to track a maneuvering target in a densely cluttered environment. Through Monte Carlo simulation, the results show that the proposed algorithm can be more effective and reliable for different scenarios of target tracking in a densely cluttered environment. Full article

(This article belongs to the Special Issue Video Analysis and Tracking Using State-of-the-Art Sensors)

► Show Figures

Figure 1

9 pages, 2300 KiB

Open AccessCommunication

Annealing Effects of Parylene-Caulked Polydimethylsiloxane as a Substrate of Electrodes

by Jinmo Jeong, Namsun Chou, Gihyun Lee and Sohee Kim

Sensors 2016, 16(12), 2181; https://doi.org/10.3390/s16122181 - 18 Dec 2016

Cited by 2 | Viewed by 7523

Abstract

This paper investigates the effects of annealing of the electrodes based on parylene-caulked polydimethylsiloxane (pc-PDMS) in terms of mechanical strength and long-term electrical property. Previously, the electrodes based on pc-PDMS showed a better ability to withstand in vivo environments because of the low [...] Read more.

This paper investigates the effects of annealing of the electrodes based on parylene-caulked polydimethylsiloxane (pc-PDMS) in terms of mechanical strength and long-term electrical property. Previously, the electrodes based on pc-PDMS showed a better ability to withstand in vivo environments because of the low water absorption and beneficial mechanical properties of the substrate, compared to native PDMS. Moreover, annealing is expected to even strengthen the mechanical strength and lower the water absorption of the pc-PDMS substrate. To characterize the mechanical strength and water absorption of the annealed pc-PDMS, tensile tests were carried out and infrared (IR) spectra were measured using Fourier transform infrared spectroscopy over a month. The results showed that annealed pc-PDMS had higher mechanical strength and lower water absorption than non-annealed pc-PDMS. Then, electrochemical impedance spectroscopy was measured to evaluate the electrical stability of the electrodes based on annealed pc-PDMS in phosphate-buffered saline solution at 36.5 °C. The impedance magnitude of the electrodes on annealed pc-PDMS was twice higher than that of the electrodes on non-annealed pc-PDMS in the initial days, but the impedance magnitude of the electrodes based on two different substrates converged to a similar value after eight months, indicating that the annealing effects disappear after a certain period of time in a physiological environment. Full article

(This article belongs to the Collection Modeling, Testing and Reliability Issues in MEMS Engineering)

► Show Figures

Figure 1

16 pages, 3528 KiB

Open AccessArticle

Monitoring Building Deformation with InSAR: Experiments and Validation

by Kui Yang, Li Yan, Guoman Huang, Chu Chen and Zhengpeng Wu

Sensors 2016, 16(12), 2182; https://doi.org/10.3390/s16122182 - 20 Dec 2016

Cited by 55 | Viewed by 9519

Abstract

Synthetic Aperture Radar Interferometry (InSAR) techniques are increasingly applied for monitoring land subsidence. The advantages of InSAR include high accuracy and the ability to cover large areas; nevertheless, research validating the use of InSAR on building deformation is limited. In this paper, we [...] Read more.

Synthetic Aperture Radar Interferometry (InSAR) techniques are increasingly applied for monitoring land subsidence. The advantages of InSAR include high accuracy and the ability to cover large areas; nevertheless, research validating the use of InSAR on building deformation is limited. In this paper, we test the monitoring capability of the InSAR in experiments using two landmark buildings; the Bohai Building and the China Theater, located in Tianjin, China. They were selected as real examples to compare InSAR and leveling approaches for building deformation. Ten TerraSAR-X images spanning half a year were used in Permanent Scatterer InSAR processing. These extracted InSAR results were processed considering the diversity in both direction and spatial distribution, and were compared with true leveling values in both Ordinary Least Squares (OLS) regression and measurement of error analyses. The detailed experimental results for the Bohai Building and the China Theater showed a high correlation between InSAR results and the leveling values. At the same time, the two Root Mean Square Error (RMSE) indexes had values of approximately 1 mm. These analyses show that a millimeter level of accuracy can be achieved by means of InSAR technique when measuring building deformation. We discuss the differences in accuracy between OLS regression and measurement of error analyses, and compare the accuracy index of leveling in order to propose InSAR accuracy levels appropriate for monitoring buildings deformation. After assessing the advantages and limitations of InSAR techniques in monitoring buildings, further applications are evaluated. Full article

(This article belongs to the Section Remote Sensors)

► Show Figures

Figure 1

15 pages, 1210 KiB

Open AccessArticle

Local Coverage Optimization Strategy Based on Voronoi for Directional Sensor Networks

by Guanglin Zhang, Shan You, Jiajie Ren, Demin Li and Lin Wang

Sensors 2016, 16(12), 2183; https://doi.org/10.3390/s16122183 - 18 Dec 2016

Cited by 28 | Viewed by 7159

Abstract

In this paper, we study the area coverage of directional sensor networks (DSNs) with random node distribution. The coverage of DSNs depends on the sensor’s locations, the sensing radiuses, and the working directions, as well as the angle of view (AoV), which is [...] Read more.

In this paper, we study the area coverage of directional sensor networks (DSNs) with random node distribution. The coverage of DSNs depends on the sensor’s locations, the sensing radiuses, and the working directions, as well as the angle of view (AoV), which is challenging to analyze. We transform the network area coverage problem into cell coverage problems by exploiting the Voronoi diagram, which only needs to optimize local coverage for each cell in a decentralized way. To address the cell coverage problem, we propose three local coverage optimization algorithms to improve the cell coverage, namely Move Inside Cell Algorithm (MIC), Rotate Working Direction Algorithm (RWD) and Rotation based on boundary (RB), respectively. Extensive simulations are performed to prove the effectiveness of our proposed algorithms in terms of the coverage ratio. Full article

(This article belongs to the Special Issue Advanced Algorithms for Mobile Sensing: from Wireless Sensor Networks to Mobile Crowd Sensing)

► Show Figures

Figure 1

10 pages, 4870 KiB

Open AccessArticle

The Longitudinal Force Measurement of CWR Tracks with Hetero-Cladding FBG Sensors: A Proof of Concept

by Li-Yang Shao, Meng Zhang, Kaize Xie, Xinpu Zhang, Ping Wang and Lianshan Yan

Sensors 2016, 16(12), 2184; https://doi.org/10.3390/s16122184 - 18 Dec 2016

Cited by 14 | Viewed by 5373

Abstract

A new method has been proposed to accurately determine longitudinal additional force in continuous welded rail (CWR) on bridges via hetero-cladding fiber Bragg grating (HC-FBG) sensors. The HC-FBG sensor consists of two FBGs written in the same type of fiber but with different [...] Read more.

A new method has been proposed to accurately determine longitudinal additional force in continuous welded rail (CWR) on bridges via hetero-cladding fiber Bragg grating (HC-FBG) sensors. The HC-FBG sensor consists of two FBGs written in the same type of fiber but with different cladding diameters. The HC-FBGs have the same temperature sensitivity but different strain sensitivity because of the different areas of the cross section. The differential strain coefficient is defined as the relative wavelength differences of two FBGs with the change of applied longitudinal force. In the verification experiment in the lab, the HC-FBGs were attached on a section of rail model of which the material property is the same as that of rail on line. The temperature and differential strain sensitivity were calibrated using a universal testing machine. As shown by the test results, the linearity between the relative wavelength difference and the longitudinal additional force is greater than 0.9999. The differential strain sensitivity is 4.85 × 10⁻⁶/N. Moreover, the relative wavelength difference is not affected by the temperature change. Compared to the theoretical results, the accumulated error is controlled within 5.0%. Full article

(This article belongs to the Special Issue Recent Advances in Fiber Bragg Grating Sensing)

► Show Figures

Figure 1

15 pages, 4380 KiB

Open AccessArticle

A Novel Fisheye-Lens-Based Photoacoustic System

by Hojong Choi, Jaemyung Ryu and Jungsuk Kim

Sensors 2016, 16(12), 2185; https://doi.org/10.3390/s16122185 - 19 Dec 2016

Cited by 18 | Viewed by 8365

Abstract

This paper presents a novel fisheye-lens-based photoacoustic (PA) system. In conventional PA systems, mechanical motors are utilized to obtain the target information due to the small fields of view of such systems. The use of such motors introduces mechanical noise, which is difficult [...] Read more.

This paper presents a novel fisheye-lens-based photoacoustic (PA) system. In conventional PA systems, mechanical motors are utilized to obtain the target information due to the small fields of view of such systems. The use of such motors introduces mechanical noise, which is difficult to remove when processing the echo signals. A fisheye lens system offering a wide field of view would effectively reduce the motor effects (i.e., the noise) and enable the system to have a wide field of view. Therefore, in this work, we propose a novel fisheye lens scheme and describe a PA system based on the developed lens scheme. In addition, to confirm the feasibility of the fisheye-lens-based PA system, we present the typical pulse-echo responses obtained using a 20 MHz single element immersion transducer and the echo signals measured from bull’s eye tissue samples separated by approximately 4, 6, 8, and 10 cm diagonally and 2 cm vertically from the fisheye lens. The experimental results demonstrate that the echo signal amplitudes, their center frequencies, and the −6 dB bandwidths obtained using red, green, and blue lights and a fisheye lens are acceptable when the fisheye lens is separated from a sample both diagonally and vertically. Therefore, fisheye-lens-based PA systems could be a potential method of achieving wide fields of view while reducing the mechanical motor effects. Full article

(This article belongs to the Special Issue Ultrasonic Sensors)

► Show Figures

Figure 1

43 pages, 12407 KiB

Open AccessArticle

Smart Pipe System for a Shipyard 4.0

by Paula Fraga-Lamas, Diego Noceda-Davila, Tiago M. Fernández-Caramés, Manuel A. Díaz-Bouza and Miguel Vilar-Montesinos

Sensors 2016, 16(12), 2186; https://doi.org/10.3390/s16122186 - 20 Dec 2016

Cited by 51 | Viewed by 16289

Abstract

As a result of the progressive implantation of the Industry 4.0 paradigm, many industries are experimenting a revolution that shipyards cannot ignore. Therefore, the application of the principles of Industry 4.0 to shipyards are leading to the creation of Shipyards 4.0. Due to [...] Read more.

As a result of the progressive implantation of the Industry 4.0 paradigm, many industries are experimenting a revolution that shipyards cannot ignore. Therefore, the application of the principles of Industry 4.0 to shipyards are leading to the creation of Shipyards 4.0. Due to this, Navantia, one of the 10 largest shipbuilders in the world, is updating its whole inner workings to keep up with the near-future challenges that a Shipyard 4.0 will have to face. Such challenges can be divided into three groups: the vertical integration of production systems, the horizontal integration of a new generation of value creation networks, and the re-engineering of the entire production chain, making changes that affect the entire life cycle of each piece of a ship. Pipes, which exist in a huge number and varied typology on a ship, are one of the key pieces, and its monitoring constitutes a prospective cyber-physical system. Their improved identification, traceability, and indoor location, from production and through their life, can enhance shipyard productivity and safety. In order to perform such tasks, this article first conducts a thorough analysis of the shipyard environment. From this analysis, the essential hardware and software technical requirements are determined. Next, the concept of smart pipe is presented and defined as an object able to transmit signals periodically that allows for providing enhanced services in a shipyard. In order to build a smart pipe system, different technologies are selected and evaluated, concluding that passive and active RFID (Radio Frequency Identification) are currently the most appropriate technologies to create it. Furthermore, some promising indoor positioning results obtained in a pipe workshop are presented, showing that multi-antenna algorithms and Kalman filtering can help to stabilize Received Signal Strength (RSS) and improve the overall accuracy of the system. Full article

(This article belongs to the Special Issue Enabling the Move from Wireless Sensor Networks to Internet of Things and Cyber-Physical Systems)

► Show Figures

Figure 1

18 pages, 677 KiB

Open AccessArticle

A Method of Detections’ Fusion for GNSS Anti-Spoofing

by Huiqi Tao, Hong Li and Mingquan Lu

Sensors 2016, 16(12), 2187; https://doi.org/10.3390/s16122187 - 19 Dec 2016

Cited by 15 | Viewed by 4882

Abstract

The spoofing attack is one of the security threats of systems depending on the Global Navigation Satellite System (GNSS). There have been many GNSS spoofing detection methods, and each of them focuses on a characteristic of the GNSS signal or a measurement that [...] Read more.

The spoofing attack is one of the security threats of systems depending on the Global Navigation Satellite System (GNSS). There have been many GNSS spoofing detection methods, and each of them focuses on a characteristic of the GNSS signal or a measurement that the receiver has obtained. The method based on a single detector is insufficient against spoofing attacks in some scenarios. How to fuse multiple detections together is a problem that concerns the performance of GNSS anti-spoofing. Scholars have put forward a model to fuse different detection results based on the Dempster-Shafer theory (DST) of evidence combination. However, there are some problems in the application. The main challenge is the valuation of the belief function, which is a key issue in DST. This paper proposes a practical method of detections’ fusion based on an approach to assign the belief function for spoofing detections. The frame of discernment is simplified, and the hard decision of hypothesis testing is replaced by the soft decision; then, the belief functions for some detections can be evaluated. The method is discussed in detail, and a performance evaluation is provided, as well. Detections’ fusion reduces false alarms of detection and makes the result more reliable. Experimental results based on public test datasets demonstrate the performance of the proposed method. Full article

(This article belongs to the Section Physical Sensors)

► Show Figures

Figure 1

16 pages, 340 KiB

Open AccessArticle

A Novel Modification of PSO Algorithm for SML Estimation of DOA

by Haihua Chen, Shibao Li, Jianhang Liu, Fen Liu and Masakiyo Suzuki

Sensors 2016, 16(12), 2188; https://doi.org/10.3390/s16122188 - 19 Dec 2016

Cited by 15 | Viewed by 4731

Abstract

This paper addresses the issue of reducing the computational complexity of Stochastic Maximum Likelihood (SML) estimation of Direction-of-Arrival (DOA). The SML algorithm is well-known for its high accuracy of DOA estimation in sensor array signal processing. However, its computational complexity is very high [...] Read more.

This paper addresses the issue of reducing the computational complexity of Stochastic Maximum Likelihood (SML) estimation of Direction-of-Arrival (DOA). The SML algorithm is well-known for its high accuracy of DOA estimation in sensor array signal processing. However, its computational complexity is very high because the estimation of SML criteria is a multi-dimensional non-linear optimization problem. As a result, it is hard to apply the SML algorithm to real systems. The Particle Swarm Optimization (PSO) algorithm is considered as a rather efficient method for multi-dimensional non-linear optimization problems in DOA estimation. However, the conventional PSO algorithm suffers two defects, namely, too many particles and too many iteration times. Therefore, the computational complexity of SML estimation using conventional PSO algorithm is still a little high. To overcome these two defects and to reduce computational complexity further, this paper proposes a novel modification of the conventional PSO algorithm for SML estimation and we call it Joint-PSO algorithm. The core idea of the modification lies in that it uses the solution of Estimation of Signal Parameters via Rotational Invariance Techniques (ESPRIT) and stochastic Cramer-Rao bound (CRB) to determine a novel initialization space. Since this initialization space is already close to the solution of SML, fewer particles and fewer iteration times are needed. As a result, the computational complexity can be greatly reduced. In simulation, we compare the proposed algorithm with the conventional PSO algorithm, the classic Altering Minimization (AM) algorithm and Genetic algorithm (GA). Simulation results show that our proposed algorithm is one of the most efficient solving algorithms and it shows great potential for the application of SML in real systems. Full article

(This article belongs to the Section Sensor Networks)

► Show Figures

Figure 1

14 pages, 5020 KiB

Open AccessArticle

Omni-Directional Scanning Localization Method of a Mobile Robot Based on Ultrasonic Sensors

by Wei-Yi Mu, Guang-Peng Zhang, Yu-Mei Huang, Xin-Gang Yang, Hong-Yan Liu and Wen Yan

Sensors 2016, 16(12), 2189; https://doi.org/10.3390/s16122189 - 20 Dec 2016

Cited by 12 | Viewed by 6802

Abstract

Improved ranging accuracy is obtained by the development of a novel ultrasonic sensor ranging algorithm, unlike the conventional ranging algorithm, which considers the divergence angle and the incidence angle of the ultrasonic sensor synchronously. An ultrasonic sensor scanning method is developed based on [...] Read more.

Improved ranging accuracy is obtained by the development of a novel ultrasonic sensor ranging algorithm, unlike the conventional ranging algorithm, which considers the divergence angle and the incidence angle of the ultrasonic sensor synchronously. An ultrasonic sensor scanning method is developed based on this algorithm for the recognition of an inclined plate and to obtain the localization of the ultrasonic sensor relative to the inclined plate reference frame. The ultrasonic sensor scanning method is then leveraged for the omni-directional localization of a mobile robot, where the ultrasonic sensors are installed on a mobile robot and follow the spin of the robot, the inclined plate is recognized and the position and posture of the robot are acquired with respect to the coordinate system of the inclined plate, realizing the localization of the robot. Finally, the localization method is implemented into an omni-directional scanning localization experiment with the independently researched and developed mobile robot. Localization accuracies of up to ±3.33 mm for the front, up to ±6.21 for the lateral and up to ±0.20° for the posture are obtained, verifying the correctness and effectiveness of the proposed localization method. Full article

(This article belongs to the Special Issue Ultrasonic Sensors)

► Show Figures

Figure 1

17 pages, 1299 KiB

Open AccessArticle

An Interference-Aware Traffic-Priority-Based Link Scheduling Algorithm for Interference Mitigation in Multiple Wireless Body Area Networks

by Thien T. T. Le and Sangman Moh

Sensors 2016, 16(12), 2190; https://doi.org/10.3390/s16122190 - 20 Dec 2016

Cited by 18 | Viewed by 5357

Abstract

Currently, wireless body area networks (WBANs) are effectively used for health monitoring services. However, in cases where WBANs are densely deployed, interference among WBANs can cause serious degradation of network performance and reliability. Inter-WBAN interference can be reduced by scheduling the communication links [...] Read more.

Currently, wireless body area networks (WBANs) are effectively used for health monitoring services. However, in cases where WBANs are densely deployed, interference among WBANs can cause serious degradation of network performance and reliability. Inter-WBAN interference can be reduced by scheduling the communication links of interfering WBANs. In this paper, we propose an interference-aware traffic-priority-based link scheduling (ITLS) algorithm to overcome inter-WBAN interference in densely deployed WBANs. First, we model a network with multiple WBANs as an interference graph where node-level interference and traffic priority are taken into account. Second, we formulate link scheduling for multiple WBANs as an optimization model where the objective is to maximize the throughput of the entire network while ensuring the traffic priority of sensor nodes. Finally, we propose the ITLS algorithm for multiple WBANs on the basis of the optimization model. High spatial reuse is also achieved in the proposed ITLS algorithm. The proposed ITLS achieves high spatial reuse while considering traffic priority, packet length, and the number of interfered sensor nodes. Our simulation results show that the proposed ITLS significantly increases spatial reuse and network throughput with lower delay by mitigating inter-WBAN interference. Full article

(This article belongs to the Section Sensor Networks)

► Show Figures

Figure 1

13 pages, 814 KiB

Open AccessArticle

A Sum-of-Squares and Semidefinite Programming Approach for Maximum Likelihood DOA Estimation

by Shu Cai, Quan Zhou and Hongbo Zhu

Sensors 2016, 16(12), 2191; https://doi.org/10.3390/s16122191 - 20 Dec 2016

Cited by 2 | Viewed by 4684

Abstract

Direction of arrival (DOA) estimation using a uniform linear array (ULA) is a classical problem in array signal processing. In this paper, we focus on DOA estimation based on the maximum likelihood (ML) criterion, transform the estimation problem into a novel formulation, named [...] Read more.

Direction of arrival (DOA) estimation using a uniform linear array (ULA) is a classical problem in array signal processing. In this paper, we focus on DOA estimation based on the maximum likelihood (ML) criterion, transform the estimation problem into a novel formulation, named as sum-of-squares (SOS), and then solve it using semidefinite programming (SDP). We first derive the SOS and SDP method for DOA estimation in the scenario of a single source and then extend it under the framework of alternating projection for multiple DOA estimation. The simulations demonstrate that the SOS- and SDP-based algorithms can provide stable and accurate DOA estimation when the number of snapshots is small and the signal-to-noise ratio (SNR) is low. Moveover, it has a higher spatial resolution compared to existing methods based on the ML criterion. Full article

(This article belongs to the Section Physical Sensors)

► Show Figures

Figure 1

14 pages, 1895 KiB

Open AccessArticle

BDS Precise Point Positioning for Seismic Displacements Monitoring: Benefit from the High-Rate Satellite Clock Corrections

by Tao Geng, Xing Su, Rongxin Fang, Xin Xie, Qile Zhao and Jingnan Liu

Sensors 2016, 16(12), 2192; https://doi.org/10.3390/s16122192 - 20 Dec 2016

Cited by 16 | Viewed by 5928

Abstract

In order to satisfy the requirement of high-rate high-precision applications, 1 Hz BeiDou Navigation Satellite System (BDS) satellite clock corrections are generated based on precise orbit products, and the quality of the generated clock products is assessed by comparing with those from the [...] Read more.

In order to satisfy the requirement of high-rate high-precision applications, 1 Hz BeiDou Navigation Satellite System (BDS) satellite clock corrections are generated based on precise orbit products, and the quality of the generated clock products is assessed by comparing with those from the other analysis centers. The comparisons show that the root mean square (RMS) of clock errors of geostationary Earth orbits (GEO) is about 0.63 ns, whereas those of inclined geosynchronous orbits (IGSO) and medium Earth orbits (MEO) are about 0.2–0.3 ns and 0.1 ns, respectively. Then, the 1 Hz clock products are used for BDS precise point positioning (PPP) to retrieve seismic displacements of the 2015 Mw 7.8 Gorkha, Nepal, earthquake. The derived seismic displacements from BDS PPP are consistent with those from the Global Positioning System (GPS) PPP, with RMS of 0.29, 0.38, and 1.08 cm in east, north, and vertical components, respectively. In addition, the BDS PPP solutions with different clock intervals of 1 s, 5 s, 30 s, and 300 s are processed and compared with each other. The results demonstrate that PPP with 300 s clock intervals is the worst and that with 1 s clock interval is the best. For the scenario of 5 s clock intervals, the precision of PPP solutions is almost the same to 1 s results. Considering the time consumption of clock estimates, we suggest that 5 s clock interval is competent for high-rate BDS solutions. Full article

(This article belongs to the Section Remote Sensors)

► Show Figures

Figure 1

14 pages, 1104 KiB

Open AccessArticle

A Novel Sensor Selection and Power Allocation Algorithm for Multiple-Target Tracking in an LPI Radar Network

by Ji She, Fei Wang and Jianjiang Zhou

Sensors 2016, 16(12), 2193; https://doi.org/10.3390/s16122193 - 21 Dec 2016

Cited by 27 | Viewed by 5592

Abstract

Radar networks are proven to have numerous advantages over traditional monostatic and bistatic radar. With recent developments, radar networks have become an attractive platform due to their low probability of intercept (LPI) performance for target tracking. In this paper, a joint sensor selection [...] Read more.

Radar networks are proven to have numerous advantages over traditional monostatic and bistatic radar. With recent developments, radar networks have become an attractive platform due to their low probability of intercept (LPI) performance for target tracking. In this paper, a joint sensor selection and power allocation algorithm for multiple-target tracking in a radar network based on LPI is proposed. It is found that this algorithm can minimize the total transmitted power of a radar network on the basis of a predetermined mutual information (MI) threshold between the target impulse response and the reflected signal. The MI is required by the radar network system to estimate target parameters, and it can be calculated predictively with the estimation of target state. The optimization problem of sensor selection and power allocation, which contains two variables, is non-convex and it can be solved by separating power allocation problem from sensor selection problem. To be specific, the optimization problem of power allocation can be solved by using the bisection method for each sensor selection scheme. Also, the optimization problem of sensor selection can be solved by a lower complexity algorithm based on the allocated powers. According to the simulation results, it can be found that the proposed algorithm can effectively reduce the total transmitted power of a radar network, which can be conducive to improving LPI performance. Full article

(This article belongs to the Special Issue Advances in Multi-Sensor Information Fusion: Theory and Applications)

► Show Figures

Figure 1

25 pages, 13353 KiB

Open AccessArticle

Sci-Fin: Visual Mining Spatial and Temporal Behavior Features from Social Media

by Jiansu Pu, Zhiyao Teng, Rui Gong, Changjiang Wen and Yang Xu

Sensors 2016, 16(12), 2194; https://doi.org/10.3390/s16122194 - 20 Dec 2016

Cited by 8 | Viewed by 6282

Abstract

Check-in records are usually available in social services, which offer us the opportunity to capture and analyze users’ spatial and temporal behaviors. Mining such behavior features is essential to social analysis and business intelligence. However, the complexity and incompleteness of check-in records bring [...] Read more.

Check-in records are usually available in social services, which offer us the opportunity to capture and analyze users’ spatial and temporal behaviors. Mining such behavior features is essential to social analysis and business intelligence. However, the complexity and incompleteness of check-in records bring challenges to achieve such a task. Different from the previous work on social behavior analysis, in this paper, we present a visual analytics system, Social Check-in Fingerprinting (Sci-Fin), to facilitate the analysis and visualization of social check-in data. We focus on three major components of user check-in data: location, activity, and profile. Visual fingerprints for location, activity, and profile are designed to intuitively represent the high-dimensional attributes. To visually mine and demonstrate the behavior features, we integrate WorldMapper and Voronoi Treemap into our glyph-like designs. Such visual fingerprint designs offer us the opportunity to summarize the interesting features and patterns from different check-in locations, activities and users (groups). We demonstrate the effectiveness and usability of our system by conducting extensive case studies on real check-in data collected from a popular microblogging service. Interesting findings are reported and discussed at last. Full article

(This article belongs to the Special Issue Big Data and Cloud Computing for Sensor Networks)

► Show Figures

Figure 1

11 pages, 3393 KiB

Open AccessArticle

Configurations of Splitter/Combiner Microstrip Sections Loaded with Stepped Impedance Resonators (SIRs) for Sensing Applications

by Lijuan Su, Javier Mata-Contreras, Paris Vélez and Ferran Martín

Sensors 2016, 16(12), 2195; https://doi.org/10.3390/s16122195 - 20 Dec 2016

Cited by 53 | Viewed by 7071

Abstract

In this paper, several configurations of splitter/combiner microstrip sections loaded with stepped impedance resonators (SIRs) are analyzed. Such structures are useful as sensors and comparators, and the main aim of the paper is to show that the proposed configurations are useful for the [...] Read more.

In this paper, several configurations of splitter/combiner microstrip sections loaded with stepped impedance resonators (SIRs) are analyzed. Such structures are useful as sensors and comparators, and the main aim of the paper is to show that the proposed configurations are useful for the optimization of sensitivity and discrimination. Specifically, for comparison purposes, i.e., to determine anomalies, abnormalities or defects of a sample under test (SUT) in comparison to a reference sample, it is shown that up to three samples can be simultaneously tested. Simple models of the proposed structures are presented, and these models are validated through electromagnetic simulation and experiment. Finally, the principle of operation is validated through a proof-of-concept demonstrator. Full article

(This article belongs to the Special Issue Advanced Technologies and Techniques for Microwave and Wireless Sensors)

► Show Figures

Figure 1

15 pages, 5370 KiB

Open AccessArticle

Nondestructive In Situ Measurement Method for Kernel Moisture Content in Corn Ear

by Han-Lin Zhang, Qin Ma, Li-Feng Fan, Peng-Fei Zhao, Jian-Xu Wang, Xiao-Dong Zhang, De-Hai Zhu, Lan Huang, Dong-Jie Zhao and Zhong-Yi Wang

Sensors 2016, 16(12), 2196; https://doi.org/10.3390/s16122196 - 20 Dec 2016

Cited by 23 | Viewed by 6951

Abstract

Moisture content is an important factor in corn breeding and cultivation. A corn breed with low moisture at harvest is beneficial for mechanical operations, reduces drying and storage costs after harvesting and, thus, reduces energy consumption. Nondestructive measurement of kernel moisture in an [...] Read more.

Moisture content is an important factor in corn breeding and cultivation. A corn breed with low moisture at harvest is beneficial for mechanical operations, reduces drying and storage costs after harvesting and, thus, reduces energy consumption. Nondestructive measurement of kernel moisture in an intact corn ear allows us to select corn varieties with seeds that have high dehydration speeds in the mature period. We designed a sensor using a ring electrode pair for nondestructive measurement of the kernel moisture in a corn ear based on a high-frequency detection circuit. Through experiments using the effective scope of the electrodes’ electric field, we confirmed that the moisture in the corn cob has little effect on corn kernel moisture measurement. Before the sensor was applied in practice, we investigated temperature and conductivity effects on the output impedance. Results showed that the temperature was linearly related to the output impedance (both real and imaginary parts) of the measurement electrodes and the detection circuit’s output voltage. However, the conductivity has a non-monotonic dependence on the output impedance (both real and imaginary parts) of the measurement electrodes and the output voltage of the high-frequency detection circuit. Therefore, we reduced the effect of conductivity on the measurement results through measurement frequency selection. Corn moisture measurement results showed a quadric regression between corn ear moisture and the imaginary part of the output impedance, and there is also a quadric regression between corn kernel moisture and the high-frequency detection circuit output voltage at 100 MHz. In this study, two corn breeds were measured using our sensor and gave R² values for the quadric regression equation of 0.7853 and 0.8496. Full article

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

► Show Figures

Figure 1

11 pages, 1405 KiB

Open AccessArticle

Feasibility of a Gelatin Temperature Sensor Based on Electrical Capacitance

by Fernando Teixeira Silva, Brice Sorli, Veronica Calado, Carole Guillaume and Nathalie Gontard

Sensors 2016, 16(12), 2197; https://doi.org/10.3390/s16122197 - 20 Dec 2016

Cited by 15 | Viewed by 5689

Abstract

The innovative use of gelatin as a temperature sensor based on capacitance was studied at a temperature range normally used for meat cooking (20–80 °C). Interdigital electrodes coated by gelatin solution and two sensors of different thicknesses (38 and 125 µm) were studied [...] Read more.

The innovative use of gelatin as a temperature sensor based on capacitance was studied at a temperature range normally used for meat cooking (20–80 °C). Interdigital electrodes coated by gelatin solution and two sensors of different thicknesses (38 and 125 µm) were studied between 300 MHz and 900 MHz. At 38 µm, the capacitance was adequately measured, but for 125 µm the slope capacitance versus temperature curve decreased before 900 MHz due to the electrothermal breakdown between 60 °C and 80 °C. Thus, for 125 µm, the capacitance was studied applying 600 MHz. Sensitivity at 38 µm at 868 MHz (0.045 pF/°C) was lower than 125 µm at 600 MHz (0.14 pF/°C), influencing the results in the simulation (temperature range versus time) of meat cooking; at 125 µm, the sensitivity was greater, mainly during chilling steps. The potential of gelatin as a temperature sensor was demonstrated, and a balance between thickness and frequency should be considered to increase the sensitivity. Full article

(This article belongs to the Section Physical Sensors)

► Show Figures

Figure 1

20 pages, 4794 KiB

Open AccessArticle

Diverse Planning for UAV Control and Remote Sensing

by Jan Tožička and Antonín Komenda

Sensors 2016, 16(12), 2199; https://doi.org/10.3390/s16122199 - 21 Dec 2016

Cited by 3 | Viewed by 6332

Abstract

Unmanned aerial vehicles (UAVs) are suited to various remote sensing missions, such as measuring air quality. The conventional method of UAV control is by human operators. Such an approach is limited by the ability of cooperation among the operators controlling larger fleets of [...] Read more.

Unmanned aerial vehicles (UAVs) are suited to various remote sensing missions, such as measuring air quality. The conventional method of UAV control is by human operators. Such an approach is limited by the ability of cooperation among the operators controlling larger fleets of UAVs in a shared area. The remedy for this is to increase autonomy of the UAVs in planning their trajectories by considering other UAVs and their plans. To provide such improvement in autonomy, we need better algorithms for generating alternative trajectory variants that the UAV coordination algorithms can utilize. In this article, we define a novel family of multi-UAV sensing problems, solving task allocation of huge number of tasks (tens of thousands) to a group of configurable UAVs with non-zero weight of equipped sensors (comprising the air quality measurement as well) together with two base-line solvers. To solve the problem efficiently, we use an algorithm for diverse trajectory generation and integrate it with a solver for the multi-UAV coordination problem. Finally, we experimentally evaluate the multi-UAV sensing problem solver. The evaluation is done on synthetic and real-world-inspired benchmarks in a multi-UAV simulator. Results show that diverse planning is a valuable method for remote sensing applications containing multiple UAVs. Full article

(This article belongs to the Special Issue UAV-Based Remote Sensing)

► Show Figures

Figure 1

25 pages, 2211 KiB

Open AccessArticle

Semantic Agent-Based Service Middleware and Simulation for Smart Cities

by Ming Liu, Yang Xu, Haixiao Hu and Abdul-Wahid Mohammed

Sensors 2016, 16(12), 2200; https://doi.org/10.3390/s16122200 - 21 Dec 2016

Cited by 12 | Viewed by 6263

Abstract

With the development of Machine-to-Machine (M2M) technology, a variety of embedded and mobile devices is integrated to interact via the platform of the Internet of Things, especially in the domain of smart cities. One of the primary challenges is that selecting the appropriate [...] Read more.

With the development of Machine-to-Machine (M2M) technology, a variety of embedded and mobile devices is integrated to interact via the platform of the Internet of Things, especially in the domain of smart cities. One of the primary challenges is that selecting the appropriate services or service combination for upper layer applications is hard, which is due to the absence of a unified semantical service description pattern, as well as the service selection mechanism. In this paper, we define a semantic service representation model from four key properties: Capability (C), Deployment (D), Resource (R) and IOData (IO). Based on this model, an agent-based middleware is built to support semantic service enablement. In this middleware, we present an efficient semantic service discovery and matching approach for a service combination process, which calculates the semantic similarity between services, and a heuristic algorithm to search the service candidates for a specific service request. Based on this design, we propose a simulation of virtual urban fire fighting, and the experimental results manifest the feasibility and efficiency of our design. Full article

(This article belongs to the Special Issue Smart City: Vision and Reality)

► Show Figures

Figure 1

15 pages, 3218 KiB

Open AccessArticle

Smart Device-Supported BDS/GNSS Real-Time Kinematic Positioning for Sub-Meter-Level Accuracy in Urban Location-Based Services

by Liang Wang, Zishen Li, Jiaojiao Zhao, Kai Zhou, Zhiyu Wang and Hong Yuan

Sensors 2016, 16(12), 2201; https://doi.org/10.3390/s16122201 - 21 Dec 2016

Cited by 43 | Viewed by 9209

Abstract

Using mobile smart devices to provide urban location-based services (LBS) with sub-meter-level accuracy (around 0.5 m) is a major application field for future global navigation satellite system (GNSS) development. Real-time kinematic (RTK) positioning, which is a widely used GNSS-based positioning approach, can improve [...] Read more.

Using mobile smart devices to provide urban location-based services (LBS) with sub-meter-level accuracy (around 0.5 m) is a major application field for future global navigation satellite system (GNSS) development. Real-time kinematic (RTK) positioning, which is a widely used GNSS-based positioning approach, can improve the accuracy from about 10–20 m (achieved by the standard positioning services) to about 3–5 cm based on the geodetic receivers. In using the smart devices to achieve positioning with sub-meter-level accuracy, a feasible solution of combining the low-cost GNSS module and the smart device is proposed in this work and a user-side GNSS RTK positioning software was developed from scratch based on the Android platform. Its real-time positioning performance was validated by BeiDou Navigation Satellite System/Global Positioning System (BDS/GPS) combined RTK positioning under the conditions of a static and kinematic (the velocity of the rover was 50–80 km/h) mode in a real urban environment with a SAMSUNG Galaxy A7 smartphone. The results show that the fixed-rates of ambiguity resolution (the proportion of epochs of ambiguities fixed) for BDS/GPS combined RTK in the static and kinematic tests were about 97% and 90%, respectively, and the average positioning accuracies (RMS) were better than 0.15 m (horizontal) and 0.25 m (vertical) for the static test, and 0.30 m (horizontal) and 0.45 m (vertical) for the kinematic test. Full article

(This article belongs to the Section Remote Sensors)

► Show Figures

Figure 1

15 pages, 3853 KiB

Open AccessArticle

Development and Validation of a UAV Based System for Air Pollution Measurements

by Tommaso Francesco Villa, Farhad Salimi, Kye Morton, Lidia Morawska and Felipe Gonzalez

Sensors 2016, 16(12), 2202; https://doi.org/10.3390/s16122202 - 21 Dec 2016

Cited by 185 | Viewed by 16141

Abstract

Air quality data collection near pollution sources is difficult, particularly when sites are complex, have physical barriers, or are themselves moving. Small Unmanned Aerial Vehicles (UAVs) offer new approaches to air pollution and atmospheric studies. However, there are a number of critical design [...] Read more.

Air quality data collection near pollution sources is difficult, particularly when sites are complex, have physical barriers, or are themselves moving. Small Unmanned Aerial Vehicles (UAVs) offer new approaches to air pollution and atmospheric studies. However, there are a number of critical design decisions which need to be made to enable representative data collection, in particular the location of the air sampler or air sensor intake. The aim of this research was to establish the best mounting point for four gas sensors and a Particle Number Concentration (PNC) monitor, onboard a hexacopter, so to develop a UAV system capable of measuring point source emissions. The research included two different tests: (1) evaluate the air flow behavior of a hexacopter, its downwash and upwash effect, by measuring air speed along three axes to determine the location where the sensors should be mounted; (2) evaluate the use of gas sensors for CO₂, CO, NO₂ and NO, and the PNC monitor (DISCmini) to assess the efficiency and performance of the UAV based system by measuring emissions from a diesel engine. The air speed behavior map produced by test 1 shows the best mounting point for the sensors to be alongside the UAV. This position is less affected by the propeller downwash effect. Test 2 results demonstrated that the UAV propellers cause a dispersion effect shown by the decrease of gas and PN concentration measured in real time. A Linear Regression model was used to estimate how the sensor position, relative to the UAV center, affects pollutant concentration measurements when the propellers are turned on. This research establishes guidelines on how to develop a UAV system to measure point source emissions. Such research should be undertaken before any UAV system is developed for real world data collection. Full article

(This article belongs to the Special Issue UAV-Based Remote Sensing)

► Show Figures

Figure 1

15 pages, 5070 KiB

Open AccessArticle

Topological Path Planning in GPS Trajectory Data

by Padraig Corcoran

Sensors 2016, 16(12), 2203; https://doi.org/10.3390/s16122203 - 21 Dec 2016

Cited by 2 | Viewed by 5170

Abstract

This paper proposes a novel solution to the problem of computing a set of topologically inequivalent paths between two points in a space given a set of samples drawn from that space. Specifically, these paths are homotopy inequivalent where homotopy is a topological [...] Read more.

This paper proposes a novel solution to the problem of computing a set of topologically inequivalent paths between two points in a space given a set of samples drawn from that space. Specifically, these paths are homotopy inequivalent where homotopy is a topological equivalence relation. This is achieved by computing a basis for the group of homology inequivalent loops in the space. An additional distinct element is then computed where this element corresponds to a loop which passes through the points in question. The set of paths is subsequently obtained by taking the orbit of this element acted on by the group of homology inequivalent loops. Using a number of spaces, including a street network where the samples are GPS trajectories, the proposed method is demonstrated to accurately compute a set of homotopy inequivalent paths. The applications of this method include path and coverage planning. Full article

(This article belongs to the Section Remote Sensors)

► Show Figures

Figure 1

19 pages, 11932 KiB

Open AccessArticle

Secure and Efficient Key Coordination Algorithm for Line Topology Network Maintenance for Use in Maritime Wireless Sensor Networks

by Walid Elgenaidi, Thomas Newe, Eoin O’Connell, Daniel Toal and Gerard Dooly

Sensors 2016, 16(12), 2204; https://doi.org/10.3390/s16122204 - 21 Dec 2016

Cited by 7 | Viewed by 5382

Abstract

There has been a significant increase in the proliferation and implementation of Wireless Sensor Networks (WSNs) in different disciplines, including the monitoring of maritime environments, healthcare systems, and industrial sectors. It has now become critical to address the security issues of data communication [...] Read more.

There has been a significant increase in the proliferation and implementation of Wireless Sensor Networks (WSNs) in different disciplines, including the monitoring of maritime environments, healthcare systems, and industrial sectors. It has now become critical to address the security issues of data communication while considering sensor node constraints. There are many proposed schemes, including the scheme being proposed in this paper, to ensure that there is a high level of security in WSNs. This paper presents a symmetric security scheme for a maritime coastal environment monitoring WSN. The scheme provides security for travelling packets via individually encrypted links between authenticated neighbors, thus avoiding a reiteration of a global rekeying process. Furthermore, this scheme proposes a dynamic update key based on a trusted node configuration, called a leader node, which works as a trusted third party. The technique has been implemented in real time on a Waspmote test bed sensor platform and the results from both field testing and indoor bench testing environments are discussed in this paper. Full article

(This article belongs to the Section Sensor Networks)

► Show Figures

Figure 1

9 pages, 2770 KiB

Open AccessArticle

An Ultrasensitive Long-Period Fiber Grating-Based Refractive Index Sensor with Long Wavelengths

by Qiu-Shun Li, Xu-Lin Zhang, Jian-Guo Shi, Dong Xiang, Lan Zheng, Yan Yang, Jun-Hui Yang, Dong Feng and Wen-Fei Dong

Sensors 2016, 16(12), 2205; https://doi.org/10.3390/s16122205 - 21 Dec 2016

Cited by 26 | Viewed by 5997

Abstract

The response of a novel long-period fiber grating (LPFG) with a period of 180 µm to a surrounding refractive index (RI) was investigated. The results displayed that, with the increase in RI of the surrounding media of cladding glass in the grating region, [...] Read more.

The response of a novel long-period fiber grating (LPFG) with a period of 180 µm to a surrounding refractive index (RI) was investigated. The results displayed that, with the increase in RI of the surrounding media of cladding glass in the grating region, the resonant peak located at 1336.4 nm in the transmission spectrum gradually shifts towards a shorter wavelength, while the resonant peak located at 1618 nm gradually shifted towards a longer wavelength. Moreover, the resonant peak at 1618 nm is much more sensitive to the surrounding RI than that of the one at 1336.4 nm. Compared with the conventional LPFG and other types of wavelength-interrogated RI sensors, such as ring resonators, surface plasmon resonance sensors, and Fabry–Perot interferometric sensors, this novel LPFG possesses a higher sensitivity, which achieved 10,792.45 nm/RIU (RI unit) over a RI range of 1.4436–1.4489. Full article

(This article belongs to the Section Physical Sensors)

► Show Figures

Figure 1

17 pages, 3033 KiB

Open AccessArticle

Ambulatory Assessment of Instantaneous Velocity during Walking Using Inertial Sensor Measurements

by Angelo Maria Sabatini and Andrea Mannini

Sensors 2016, 16(12), 2206; https://doi.org/10.3390/s16122206 - 21 Dec 2016

Cited by 12 | Viewed by 6504

Abstract

A novel approach for estimating the instantaneous velocity of the pelvis during walking was developed based on Inertial Measurement Units (IMUs). The instantaneous velocity was modeled by the sum of a cyclical component, decomposed in the Medio-Lateral (ML), VerTical (VT) and Antero-Posterior (AP) [...] Read more.

A novel approach for estimating the instantaneous velocity of the pelvis during walking was developed based on Inertial Measurement Units (IMUs). The instantaneous velocity was modeled by the sum of a cyclical component, decomposed in the Medio-Lateral (ML), VerTical (VT) and Antero-Posterior (AP) directions, and the Average Progression Velocity (APV) over each gait cycle. The proposed method required the availability of two IMUs, attached to the pelvis and one shank. Gait cycles were identified from the shank angular velocity; for each cycle, the Fourier series coefficients of the pelvis and shank acceleration signals were computed. The cyclical component was estimated by Fourier-based time-integration of the pelvis acceleration. A Bayesian Linear Regression (BLR) with Automatic Relevance Determination (ARD) predicted the APV from the stride time, the stance duration, and the Fourier series coefficients of the shank acceleration. Healthy subjects performed tasks of Treadmill Walking (TW) and Overground Walking (OW), and an optical motion capture system (OMCS) was used as reference for algorithm performance assessment. The widths of the limits of agreements (±1.96 standard deviation) were computed between the proposed method and the reference OMCS, yielding, for the cyclical component in the different directions: ML: ±0.07 m/s (±0.10 m/s); VT: ±0.03 m/s (±0.05 m/s); AP: ±0.06 m/s (±0.10 m/s), in TW (OW) conditions. The ARD-BLR achieved an APV root mean square error of 0.06 m/s (0.07 m/s) in the same conditions. Full article

(This article belongs to the Section Physical Sensors)

► Show Figures

Figure 1

Journal Menu

Journal Browser

Sensors, Volume 16, Issue 12 (December 2016) – 224 articles

Further Information

Guidelines

MDPI Initiatives

Follow MDPI