Sensors

19 pages, 1113 KiB

Open AccessArticle

New Lower-Limb Gait Asymmetry Indices Based on a Depth Camera

by Edouard Auvinet^1,2,*, Franck Multon^1,3 and Jean Meunier²

¹ University Rennes 2, ENS Rennes, Campus de Ker lann, Avenue Robert Schuman, Bruz 35170, France

² Université de Montréal, C.P. 6128, succ. Centre-ville, Montréal H3C 3J7, QC, Canada

³ Inria, Campus Universitaire de Beaulieu, Rennes 35052, France

Sensors 2015, 15(3), 4605-4623; https://doi.org/10.3390/s150304605 - 24 Feb 2015

Cited by 35 | Viewed by 10250

Abstract

Background: Various asymmetry indices have been proposed to compare the spatiotemporal, kinematic and kinetic parameters of lower limbs during the gait cycle. However, these indices rely on gait measurement systems that are costly and generally require manual examination, calibration procedures and the precise [...] Read more.

Background: Various asymmetry indices have been proposed to compare the spatiotemporal, kinematic and kinetic parameters of lower limbs during the gait cycle. However, these indices rely on gait measurement systems that are costly and generally require manual examination, calibration procedures and the precise placement of sensors/markers on the body of the patient. Methods: To overcome these issues, this paper proposes a new asymmetry index, which uses an inexpensive, easy-to-use and markerless depth camera (Microsoft Kinect™) output. This asymmetry index directly uses depth images provided by the Kinect™ without requiring joint localization. It is based on the longitudinal spatial difference between lower-limb movements during the gait cycle. To evaluate the relevance of this index, fifteen healthy subjects were tested on a treadmill walking normally and then via an artificially-induced gait asymmetry with a thick sole placed under one shoe. The gait movement was simultaneously recorded using a Kinect™ placed in front of the subject and a motion capture system. Results: The proposed longitudinal index distinguished asymmetrical gait (p < 0.001), while other symmetry indices based on spatiotemporal gait parameters failed using such Kinect™ skeleton measurements. Moreover, the correlation coefficient between this index measured by Kinect™ and the ground truth of this index measured by motion capture is 0.968. Conclusion: This gait asymmetry index measured with a Kinect™ is low cost, easy to use and is a promising development for clinical gait analysis. Full article

(This article belongs to the Collection Sensors for Globalized Healthy Living and Wellbeing)

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19 pages, 407 KiB

Open AccessArticle

Distance Measurement Error in Time-of-Flight Sensors Due to Shot Noise

by Julio Illade-Quinteiro^1,*, Víctor M. Brea¹, Paula López¹, Diego Cabello¹ and Gines Doménech-Asensi²

¹ Centro de Investigación en Tecnoloxías da Información (CITIUS), University of Santiago de Compostela, 15782-Santiago de Compostela, Spain

² Department of Electronics, Computer Technologies and Projects, Universidad Politécnica de Cartagena, 30202-Cartagena, Spain

Sensors 2015, 15(3), 4624-4642; https://doi.org/10.3390/s150304624 - 25 Feb 2015

Cited by 36 | Viewed by 9041

Abstract

Unlike other noise sources, which can be reduced or eliminated by different signal processing techniques, shot noise is an ever-present noise component in any imaging system. In this paper, we present an in-depth study of the impact of shot noise on time-of-flight sensors [...] Read more.

Unlike other noise sources, which can be reduced or eliminated by different signal processing techniques, shot noise is an ever-present noise component in any imaging system. In this paper, we present an in-depth study of the impact of shot noise on time-of-flight sensors in terms of the error introduced in the distance estimation. The paper addresses the effect of parameters, such as the size of the photosensor, the background and signal power or the integration time, and the resulting design trade-offs. The study is demonstrated with different numerical examples, which show that, in general, the phase shift determination technique with two background measurements approach is the most suitable for pixel arrays of large resolution. Full article

(This article belongs to the Special Issue Silicon Based Optical Sensors)

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15 pages, 6557 KiB

Open AccessArticle

Fast and Flexible Movable Vision Measurement for the Surface of a Large-Sized Object

by Zhen Liu, Xiaojing Li, Fengjiao Li, Xinguo Wei^* and Guanjun Zhang

Ministry of Education Key Laboratory of Precision Opto-Mechatronics Technology, Beihang University, No.37 Xueyuan Rd., Haidian District, Beijing 100191, China

Sensors 2015, 15(3), 4643-4657; https://doi.org/10.3390/s150304643 - 25 Feb 2015

Cited by 17 | Viewed by 6417

Abstract

The presented movable vision measurement for the three-dimensional (3D) surface of a large-sized object has the advantages of system simplicity, low cost, and high accuracy. Aiming at addressing the problems of existing movable vision measurement methods, a more suitable method for large-sized products [...] Read more.

The presented movable vision measurement for the three-dimensional (3D) surface of a large-sized object has the advantages of system simplicity, low cost, and high accuracy. Aiming at addressing the problems of existing movable vision measurement methods, a more suitable method for large-sized products on industrial sites is introduced in this paper. A raster binocular vision sensor and a wide-field camera are combined to form a 3D scanning sensor. During measurement, several planar targets are placed around the object to be measured. With the planar target as an intermediary, the local 3D data measured by the scanning sensor are integrated into the global coordinate system. The effectiveness of the proposed method is verified through physical experiments. Full article

(This article belongs to the Section Physical Sensors)

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19 pages, 2729 KiB

Open AccessArticle

Development of a Passive Liquid Valve (PLV) Utilizing a Pressure Equilibrium Phenomenon on the Centrifugal Microfluidic Platform

by Wisam Al-Faqheri^1,2, Fatimah Ibrahim^1,2,*, Tzer Hwai Gilbert Thio^1,2,3, Norulain Bahari^1,2, Hamzah Arof^1,2,4, Hussin A. Rothan⁷, Rohana Yusof⁷ and Marc Madou^1,2,5,6

¹ Centre for Innovation in Medical Engineering (CIME), Faculty of Engineering, University of Malaya, 50603 Kuala Lumpur, Malaysia

² Department of Biomedical Engineering, Faculty of Engineering, University of Malaya, 50603 Kuala Lumpur, Malaysia

³ Faculty of Science, Technology, Engineering and Mathematics, INTI International University, Persiaran Perdana BBN, Putra Nilai, 71800 Nilai, Negeri Sembilan, Malaysia

⁴ Department of Electrical Engineering, Faculty of Engineering, University of Malaya, 50603 Kuala Lumpur, Malaysia

⁵ Department of Biomedical Engineering, University of California, Irvine, 92697 CA, USA

⁶ Department of Mechanical and Aerospace Engineering, University of California, Irvine, 92697 CA, USA

⁷ Department of Molecular Medicine, Faculty of Medicine, University of Malaya, 50603 Kuala Lumpur, Malaysia

Sensors 2015, 15(3), 4658-4676; https://doi.org/10.3390/s150304658 - 25 Feb 2015

Cited by 15 | Viewed by 9023

Abstract

In this paper, we propose an easy-to-implement passive liquid valve (PLV) for the microfluidic compact-disc (CD). This valve can be implemented by introducing venting chambers to control the air flow of the source and destination chambers. The PLV mechanism is based on equalizing [...] Read more.

In this paper, we propose an easy-to-implement passive liquid valve (PLV) for the microfluidic compact-disc (CD). This valve can be implemented by introducing venting chambers to control the air flow of the source and destination chambers. The PLV mechanism is based on equalizing the main forces acting on the microfluidic CD (i.e., the centrifugal and capillary forces) to control the burst frequency of the source chamber liquid. For a better understanding of the physics behind the proposed PLV, an analytical model is described. Moreover, three parameters that control the effectiveness of the proposed valve, i.e., the liquid height, liquid density, and venting chamber position with respect to the CD center, are tested experimentally. To demonstrate the ability of the proposed PLV valve, microfluidic liquid switching and liquid metering are performed. In addition, a Bradford assay is performed to measure the protein concentration and evaluated in comparison to the benchtop procedure. The result shows that the proposed valve can be implemented in any microfluidic process that requires simplicity and accuracy. Moreover, the developed valve increases the flexibility of the centrifugal CD platform for passive control of the liquid flow without the need for an external force or trigger. Full article

(This article belongs to the Special Issue On-Chip Sensors)

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23 pages, 1737 KiB

Open AccessArticle

Symphony: A Framework for Accurate and Holistic WSN Simulation

by Laurynas Riliskis^1,* and Evgeny Osipov²

¹ Computer Science Department, Stanford University, 353 Serra Mall, Stanford, CA 94305, USA

² Department of Computer Science, Electrical and Space Engineering , Luleå University of Technology, Luleå 971-87, Sweden

Sensors 2015, 15(3), 4677-4699; https://doi.org/10.3390/s150304677 - 25 Feb 2015

Cited by 5 | Viewed by 6951

Abstract

Research on wireless sensor networks has progressed rapidly over the last decade, and these technologies have been widely adopted for both industrial and domestic uses. Several operating systems have been developed, along with a multitude of network protocols for all layers of the [...] Read more.

Research on wireless sensor networks has progressed rapidly over the last decade, and these technologies have been widely adopted for both industrial and domestic uses. Several operating systems have been developed, along with a multitude of network protocols for all layers of the communication stack. Industrial Wireless Sensor Network (WSN) systems must satisfy strict criteria and are typically more complex and larger in scale than domestic systems. Together with the non-deterministic behavior of network hardware in real settings, this greatly complicates the debugging and testing of WSN functionality. To facilitate the testing, validation, and debugging of large-scale WSN systems, we have developed a simulation framework that accurately reproduces the processes that occur inside real equipment, including both hardware- and software-induced delays. The core of the framework consists of a virtualized operating system and an emulated hardware platform that is integrated with the general purpose network simulator ns-3. Our framework enables the user to adjust the real code base as would be done in real deployments and also to test the boundary effects of different hardware components on the performance of distributed applications and protocols. Additionally we have developed a clock emulator with several different skew models and a component that handles sensory data feeds. The new framework should substantially shorten WSN application development cycles. Full article

(This article belongs to the Special Issue Cyber-Physical Systems)

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34 pages, 2338 KiB

Open AccessArticle

Distributed Sensor Architecture for Intelligent Control that Supports Quality of Control and Quality of Service

by Jose-Luis Poza-Lujan^*, Juan-Luis Posadas-Yagüe, José-Enrique Simó-Ten, Raúl Simarro and Ginés Benet

University Institute of Control Systems and Industrial Computing (ai2), Polytechnic University of Valencia (UPV), Camino de Vera, Valencia 46022 , Spain

Sensors 2015, 15(3), 4700-4733; https://doi.org/10.3390/s150304700 - 25 Feb 2015

Cited by 4 | Viewed by 7166

Abstract

This paper is part of a study of intelligent architectures for distributed control and communications systems. The study focuses on optimizing control systems by evaluating the performance of middleware through quality of service (QoS) parameters and the optimization of control using Quality of [...] Read more.

This paper is part of a study of intelligent architectures for distributed control and communications systems. The study focuses on optimizing control systems by evaluating the performance of middleware through quality of service (QoS) parameters and the optimization of control using Quality of Control (QoC) parameters. The main aim of this work is to study, design, develop, and evaluate a distributed control architecture based on the Data-Distribution Service for Real-Time Systems (DDS) communication standard as proposed by the Object Management Group (OMG). As a result of the study, an architecture called Frame-Sensor-Adapter to Control (FSACtrl) has been developed. FSACtrl provides a model to implement an intelligent distributed Event-Based Control (EBC) system with support to measure QoS and QoC parameters. The novelty consists of using, simultaneously, the measured QoS and QoC parameters to make decisions about the control action with a new method called Event Based Quality Integral Cycle. To validate the architecture, the first five Braitenberg vehicles have been implemented using the FSACtrl architecture. The experimental outcomes, demonstrate the convenience of using jointly QoS and QoC parameters in distributed control systems. Full article

(This article belongs to the Section Sensor Networks)

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15 pages, 1487 KiB

Open AccessArticle

Development of an NDIR CO₂ Sensor-Based System for Assessing Soil Toxicity Using Substrate-Induced Respiration

by Jasmeen Kaur¹, Viacheslav I. Adamchuk^1,*, Joann K. Whalen²

and Ashraf A. Ismail³

¹ Department of Bioresource Engineering, McGill University, 21111 Lakeshore Road, Ste-Anne-de-Bellevue, QC H9X 3V9, Canada

² Department of Natural Resource Sciences, McGill University, 21111 Lakeshore Road, Ste-Anne-de-Bellevue, QC H9X 3V9, Canada

³ Department of Food Science and Agricultural Chemistry, McGill University, 21111 Lakeshore Road, Ste-Anne-de-Bellevue, QC H9X 3V9, Canada

Sensors 2015, 15(3), 4734-4748; https://doi.org/10.3390/s150304734 - 26 Feb 2015

Cited by 25 | Viewed by 11266

Abstract

The eco-toxicological indicators used to evaluate soil quality complement the physico-chemical criteria employed in contaminated site remediation, but their cost, time, sophisticated analytical methods and in-situ inapplicability pose a major challenge to rapidly detect and map the extent of soil contamination. This paper [...] Read more.

The eco-toxicological indicators used to evaluate soil quality complement the physico-chemical criteria employed in contaminated site remediation, but their cost, time, sophisticated analytical methods and in-situ inapplicability pose a major challenge to rapidly detect and map the extent of soil contamination. This paper describes a sensor-based approach for measuring potential (substrate-induced) microbial respiration in diesel-contaminated and non-contaminated soil and hence, indirectly evaluates their microbial activity. A simple CO₂ sensing system was developed using an inexpensive non-dispersive infrared (NDIR) CO₂ sensor and was successfully deployed to differentiate the control and diesel-contaminated soils in terms of CO₂ emission after glucose addition. Also, the sensor system distinguished glucose-induced CO₂ emission from sterile and control soil samples (p ≤ 0.0001). Significant effects of diesel contamination (p ≤ 0.0001) and soil type (p ≤ 0.0001) on glucose-induced CO₂ emission were also found. The developed sensing system can provide in-situ evaluation of soil microbial activity, an indicator of soil quality. The system can be a promising tool for the initial screening of contaminated environmental sites to create high spatial density maps at a relatively low cost. Full article

(This article belongs to the Section Biosensors)

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17 pages, 2091 KiB

Open AccessArticle

Development of a Hydrogen Gas Sensor Using a Double Saw Resonator System at Room Temperature

by Zainab Yunusa^1,2, Mohd Nizar Hamidon^1,*, Alyani Ismail³, Maryam Mohd Isa⁴, Mohd Hanif Yaacob³, Saeed Rahmanian⁵, Siti Azlida Ibrahim^3,6 and Arafat A.A Shabaneh³

¹ Institute of Advanced Technology, Universiti Putra Malaysia, 43400 Serdang, Selangor, Malaysia

² Department of Electrical Engineering, Bayero University Kano, P.M.B 3011 Kano, Nigeria

³ Department of Computer and Communications, Universiti Putra Malaysia, 43400 Serdang, Selangor, Malaysia

⁴ Department of Electrical and Electronics Engineering, Faculty of Engineering, Universiti Putra Malaysia 43400 Serdang, Selangor, Malaysia

⁵ Department of Mechanical and Manufacturing Engineering, Faculty of Engineering Universiti Putra Malaysia, 43400 Serdang, Selangor, Malaysia

⁶ Faculty of Engineering, Multimedia University, 63100 Cyberjaya, Selangor, Malaysia

Sensors 2015, 15(3), 4749-4765; https://doi.org/10.3390/s150304749 - 26 Feb 2015

Cited by 20 | Viewed by 8392

Abstract

A double SAW resonator system was developed as a novel method for gas sensing applications. The proposed system was investigated for hydrogen sensing. Commercial Surface Acoustic Wave (SAW) resonators with resonance frequencies of 433.92 MHz and 433.42 MHz were employed in the double [...] Read more.

A double SAW resonator system was developed as a novel method for gas sensing applications. The proposed system was investigated for hydrogen sensing. Commercial Surface Acoustic Wave (SAW) resonators with resonance frequencies of 433.92 MHz and 433.42 MHz were employed in the double SAW resonator system configuration. The advantages of using this configuration include its ability for remote measurements, and insensitivity to vibrations and other external disturbances. The sensitive layer is composed of functionalized multiwalled carbon nanotubes and polyaniline nanofibers which were deposited on pre-patterned platinum metal electrodes fabricated on a piezoelectric substrate. This was mounted into the DSAWR circuit and connected in parallel. The sensor response was measured as the difference between the resonance frequencies of the SAW resonators, which is a measure of the gas concentration. The sensor showed good response towards hydrogen with a minimum detection limit of 1%. Full article

(This article belongs to the Special Issue Acoustic Waveguide Sensors)

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15 pages, 1147 KiB

Open AccessArticle

Design and Test of a Low-Cost RGB Sensor for Online Measurement of Microalgae Concentration within a Photo-Bioreactor

by Micaela Benavides¹, Johan Mailier¹, Anne-Lise Hantson¹, Gerardo Muñoz², Alejandro Vargas², Jan Van Impe³ and Alain Vande Wouwer^1,*

¹ BioSys, University of Mons, Boulevard Dolez 31, 7000 Mons, Belgium

² Unidad Académica Juriquilla, Instituto de Ingeniería, Universidad Nacional Autónoma de México, Blvd. Juriquilla 3001, Querétaro 76230, Mexico

³ Department of Chemical Engineering, Catholic University of Leuven, 3001 Leuven, Belgium

Sensors 2015, 15(3), 4766-4780; https://doi.org/10.3390/s150304766 - 26 Feb 2015

Cited by 39 | Viewed by 10484

Abstract

In this study, a low-cost RGB sensor is developed to measure online the microalgae concentration within a photo-bioreactor. Two commercially available devices, i.e., a spectrophotometer for offline measurements and an immersed probe for online measurements, are used for calibration and comparison purposes. [...] Read more.

In this study, a low-cost RGB sensor is developed to measure online the microalgae concentration within a photo-bioreactor. Two commercially available devices, i.e., a spectrophotometer for offline measurements and an immersed probe for online measurements, are used for calibration and comparison purposes. Furthermore, the potential of such a sensor for estimating other variables is illustrated with the design of an extended Luenberger observer. Full article

(This article belongs to the Special Issue Sensors for Bioprocess Monitoring and Control)

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15 pages, 1599 KiB

Open AccessArticle

Refrigerated Fruit Storage Monitoring Combining Two Different Wireless Sensing Technologies: RFID and WSN

by Ricardo Badia-Melis^1,*, Luis Ruiz-Garcia¹

, Javier Garcia-Hierro² and Jose I. Robla Villalba²

¹ Departamento de Ingeniería Agroforestal, ETSI Agrónomos, Universidad Politécnica de Madrid, 28040 Madrid, Spain

² Sensors Technology Laboratory, Centro Nacional de Investigaciones Metalúrgicas, Consejo Superior de Investigaciones Científicas (CENIM-CSIC), Avenida Gregorio del Amo 8, 28040 Madrid, Spain

Sensors 2015, 15(3), 4781-4795; https://doi.org/10.3390/s150304781 - 26 Feb 2015

Cited by 83 | Viewed by 11495

Abstract

Every day, millions of tons of temperature-sensitive goods are produced, transported, stored or distributed worldwide, thus making their temperature and humidity control essential. Quality control and monitoring of goods during the cold chain is an increasing concern for producers, suppliers, logistic decision makers [...] Read more.

Every day, millions of tons of temperature-sensitive goods are produced, transported, stored or distributed worldwide, thus making their temperature and humidity control essential. Quality control and monitoring of goods during the cold chain is an increasing concern for producers, suppliers, logistic decision makers and consumers. In this paper we present the results of a combination of RFID and WSN devices in a set of studies performed in three commercial wholesale chambers of 1848 m³ with different set points and products. Up to 90 semi-passive RFID temperature loggers were installed simultaneously together with seven motes, during one week in each chamber. 3D temperature mapping charts were obtained and also the psychrometric data model from ASABE was implemented for the calculation of enthalpy changes and the absolute water content of air. Thus thank to the feedback of data, between RFID and WSN it is possible to estimate energy consumption in the cold room, water loss from the products and detect any condensation over the stored commodities. Full article

(This article belongs to the Special Issue Wireless Sensor Networks and the Internet of Things)

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Graphical abstract

14 pages, 1814 KiB

Open AccessArticle

Role of Edge Inclination in an Optical Microdisk Resonator for Label-Free Sensing

by Davide Gandolfi^1,*, Fernando Ramiro-Manzano¹, Francisco Javier Aparicio Rebollo¹, Mher Ghulinyan², Georg Pucker² and Lorenzo Pavesi¹

¹ Nanoscience Laboratory, Dept. Physics, University of Trento, Via Sommarive 14, I-38123 Trento, Italy

² Center for Materials and Microsystems, Fondazione Bruno Kessler, via Sommarive 18,I-38123 Trento, Italy

Sensors 2015, 15(3), 4796-4809; https://doi.org/10.3390/s150304796 - 26 Feb 2015

Cited by 20 | Viewed by 7691

Abstract

In this paper, we report on the measurement and modeling of enhanced optical refractometric sensors based on whispering gallery modes. The devices under test are optical microresonators made of silicon nitride on silicon oxide, which differ in their sidewall inclination angle. In our [...] Read more.

In this paper, we report on the measurement and modeling of enhanced optical refractometric sensors based on whispering gallery modes. The devices under test are optical microresonators made of silicon nitride on silicon oxide, which differ in their sidewall inclination angle. In our approach, these microresonators are vertically coupled to a buried waveguide with the aim of creating integrated and cost-effective devices. Device modeling shows that the optimization of the device is a delicate balance of the resonance quality factor and evanescent field overlap with the surrounding environment to analyze. By numerical simulations, we show that the microdisk thickness is critical to yield a high figure of merit for the sensor and that edge inclination should be kept as high as possible. We also show that bulk-sensing figures of merit as high as 1600 RIU^-1 (refractive index unit) are feasible. Full article

(This article belongs to the Special Issue Advances in Optical Biosensors)

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13 pages, 10933 KiB

Open AccessArticle

Calculation of the Electronic Parameters of an Al/DNA/p-Si Schottky Barrier Diode Influenced by Alpha Radiation

by Hassan Maktuff Jaber Al-Ta'ii^1,2,*, Yusoff Mohd Amin¹ and Vengadesh Periasamy^1,*

¹ Department of Physics, Faculty of Science, University of Malaya, 50603 Kuala Lumpur, Malaysia

² Department of Physics, Faculty of Science, University of Al-Muthanna, Samawah 66001, Iraq

Sensors 2015, 15(3), 4810-4822; https://doi.org/10.3390/s150304810 - 26 Feb 2015

Cited by 24 | Viewed by 7425

Abstract

Many types of materials such as inorganic semiconductors have been employed as detectors for nuclear radiation, the importance of which has increased significantly due to recent nuclear catastrophes. Despite the many advantages of this type of materials, the ability to measure direct cellular [...] Read more.

Many types of materials such as inorganic semiconductors have been employed as detectors for nuclear radiation, the importance of which has increased significantly due to recent nuclear catastrophes. Despite the many advantages of this type of materials, the ability to measure direct cellular or biological responses to radiation might improve detector sensitivity. In this context, semiconducting organic materials such as deoxyribonucleic acid or DNA have been studied in recent years. This was established by studying the varying electronic properties of DNA-metal or semiconductor junctions when exposed to radiation. In this work, we investigated the electronics of aluminium (Al)/DNA/silicon (Si) rectifying junctions using their current-voltage (I-V) characteristics when exposed to alpha radiation. Diode parameters such as ideality factor, barrier height and series resistance were determined for different irradiation times. The observed results show significant changes with exposure time or total dosage received. An increased deviation from ideal diode conditions (7.2 to 18.0) was observed when they were bombarded with alpha particles for up to 40 min. Using the conventional technique, barrier height values were observed to generally increase after 2, 6, 10, 20 and 30 min of radiation. The same trend was seen in the values of the series resistance (0.5889–1.423 Ω for 2–8 min). These changes in the electronic properties of the DNA/Si junctions could therefore be utilized in the construction of sensitive alpha particle detectors. Full article

(This article belongs to the Special Issue Next-Generation Nucleic Acid Sensors)

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14 pages, 4909 KiB

Open AccessArticle

An Automated Field Phenotyping Pipeline for Application in Grapevine Research

by Anna Kicherer^1,*, Katja Herzog¹, Michael Pflanz^2,3, Markus Wieland⁴, Philipp Rüger⁵, Steffen Kecke⁶, Heiner Kuhlmann⁴ and Reinhard Töpfer¹

¹ Julius Kühn-Institut, Federal Research Centre of Cultivated Plants, Institute for Grapevine Breeding Geilweilerhof, 76833 Siebeldingen, Germany

² Julius Kühn-Institut, Federal Research Centre for Cultivated Plants, Institute for Plant Protection in Field Crops and Grassland, Messeweg 11-12, 38104 Braunschweig, Germany

³ Leibniz Institute for Agricultural Engineering Potsdam-Bornim, Department Horticultural Engineering, Max-Eyth-Allee 100, 14469 Potsdam, Germany

⁴ University of Bonn, Department of Geodesy, Institute for Geodesy and Geoinformation (IGG), Nussallee 17, 53115 Bonn, Germany

⁵ Geisenheim University, Department of Viticultural Engineering, Brentanostraße 9, 65366 Geisenheim, Germany

⁶ Julius Kühn-Institut, Federal Research Centre for Cultivated Plants, Department of Data Processing, Erwin-Baur-Str. 27, 06484 Quedlinburg, Germany

Sensors 2015, 15(3), 4823-4836; https://doi.org/10.3390/s150304823 - 26 Feb 2015

Cited by 56 | Viewed by 9476

Abstract

Due to its perennial nature and size, the acquisition of phenotypic data in grapevine research is almost exclusively restricted to the field and done by visual estimation. This kind of evaluation procedure is limited by time, cost and the subjectivity of records. As [...] Read more.

Due to its perennial nature and size, the acquisition of phenotypic data in grapevine research is almost exclusively restricted to the field and done by visual estimation. This kind of evaluation procedure is limited by time, cost and the subjectivity of records. As a consequence, objectivity, automation and more precision of phenotypic data evaluation are needed to increase the number of samples, manage grapevine repositories, enable genetic research of new phenotypic traits and, therefore, increase the efficiency in plant research. In the present study, an automated field phenotyping pipeline was setup and applied in a plot of genetic resources. The application of the PHENObot allows image acquisition from at least 250 individual grapevines per hour directly in the field without user interaction. Data management is handled by a database (IMAGEdata). The automatic image analysis tool BIVcolor (Berries in Vineyards-color) permitted the collection of precise phenotypic data of two important fruit traits, berry size and color, within a large set of plants. The application of the PHENObot represents an automated tool for high-throughput sampling of image data in the field. The automated analysis of these images facilitates the generation of objective and precise phenotypic data on a larger scale. Full article

(This article belongs to the Section Physical Sensors)

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33 pages, 298 KiB

Open AccessReview

The Past, Present and Future of Cyber-Physical Systems: A Focus on Models

by Edward A. Lee

EECS Department, University of California, Berkeley, CA 94720-1770, USA

Sensors 2015, 15(3), 4837-4869; https://doi.org/10.3390/s150304837 - 26 Feb 2015

Cited by 548 | Viewed by 34538

Abstract

This paper is about better engineering of cyber-physical systems (CPSs) through better models. Deterministic models have historically proven extremely useful and arguably form the kingpin of the industrial revolution and the digital and information technology revolutions. Key deterministic models that have proven successful [...] Read more.

This paper is about better engineering of cyber-physical systems (CPSs) through better models. Deterministic models have historically proven extremely useful and arguably form the kingpin of the industrial revolution and the digital and information technology revolutions. Key deterministic models that have proven successful include differential equations, synchronous digital logic and single-threaded imperative programs. Cyber-physical systems, however, combine these models in such a way that determinism is not preserved. Two projects show that deterministic CPS models with faithful physical realizations are possible and practical. The first project is PRET, which shows that the timing precision of synchronous digital logic can be practically made available at the software level of abstraction. The second project is Ptides (programming temporally-integrated distributed embedded systems), which shows that deterministic models for distributed cyber-physical systems have practical faithful realizations. These projects are existence proofs that deterministic CPS models are possible and practical. Full article

(This article belongs to the Special Issue Cyber-Physical Systems)

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20 pages, 1495 KiB

Open AccessArticle

Electropolymerized Molecularly Imprinted Polypyrrole Film for Sensing of Clofibric Acid

by Bianca Schweiger¹, Jungtae Kim¹, Young Jun Kim^1,*

and Mathias Ulbricht²

¹ KIST Europe Forschungsgesellschaft mbH, Campus E 7.1, 66123 Saarbrücken, Germany

² Lehrstuhl für Technische Chemie II, Universität Duisburg-Essen, Universitätsstraße 7, 45141 Essen, Germany

Sensors 2015, 15(3), 4870-4889; https://doi.org/10.3390/s150304870 - 26 Feb 2015

Cited by 66 | Viewed by 9308

Abstract

Piezoelectric quartz crystals and analogous gold substrates were electrochemically coated with molecularly imprinted polypyrrole films for pulsed amperometric detection (PAD) of clofibric acid, a metabolite of clofibrate. Cyclic voltammetry data obtained during polymerization and deposited weight estimations revealed a decrease of the polymerization [...] Read more.

Piezoelectric quartz crystals and analogous gold substrates were electrochemically coated with molecularly imprinted polypyrrole films for pulsed amperometric detection (PAD) of clofibric acid, a metabolite of clofibrate. Cyclic voltammetry data obtained during polymerization and deposited weight estimations revealed a decrease of the polymerization rate with increasing clofibric acid concentration. XPS measurements indicated that clofibric acid could be removed after imprinting with an aqueous ethanol solution, which was further optimized by using PAD. Zeta potential and contact angle measurements revealed differences between molecularly imprinted (MIP) and non-imprinted polymer (NIP) layers. Binding experiments with clofibric acid and other substances showed a pronounced selectivity of the MIP for clofibric acid vs. carbamazepine, but the response of MIP and NIP to 2,4-dichlorophenoxyacetic acid was higher than that for clofibric acid. A smooth surface, revealed by AFM measurements, with roughness of 6–8 nm for imprinted and non-imprinted layers, might be a reason for an excessively low density of specific binding sites for clofibric acid. Furthermore, the decreased polymerization rate in the presence of clofibric acid might not result in well-defined polymer structures, which could be the reason for the lower sensitivity. Full article

(This article belongs to the Special Issue Mass-Sensitive Sensors Based on Biomimetic Recognition)

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9 pages, 1738 KiB

Open AccessCommunication

Ultra-Sensitive Nanofiber Fluorescence Detection in a Microfluidic Chip

by Zhiyong Li, Yingxin Xu, Wei Fang, Limin Tong and Lei Zhang^*

State Key Laboratory of Modern Optical Instrumentation, Department of Optical Engineering, Zhejiang University, Hangzhou 310027, China

Sensors 2015, 15(3), 4890-4898; https://doi.org/10.3390/s150304890 - 26 Feb 2015

Cited by 40 | Viewed by 9266

Abstract

We report an ultra-sensitive and robust fluorescence sensor made by using a biconical taper with a waist diameter of 720 nm for both excitation and fluorescence collection. To enhance the stability of the fluorescence sensor, the biconical taper has been embedded in a [...] Read more.

We report an ultra-sensitive and robust fluorescence sensor made by using a biconical taper with a waist diameter of 720 nm for both excitation and fluorescence collection. To enhance the stability of the fluorescence sensor, the biconical taper has been embedded in a 125 µm wide microchannel with a detection length of 2.5 cm. Investigated by measuring the fluorescence intensity of rhodamine 6G (R6G), the sensor shows a detection limit down to 100 pM, with excellent reversibility in a concentration range of 0–10 nM. The sensor has also been applied to quantum dot (QD)-labeled streptavidin measurements, yielding a detection sensitivity down to 10 pM for QDs. In addition, the small sample volume (ca. 500 nL), high sampling throughput, and seamless connection between the biconical taper and standard optical fibers offer a number of attractive advantages for chemical and biosensing applications. Full article

(This article belongs to the Special Issue On-Chip Sensors)

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14 pages, 1033 KiB

Open AccessArticle

A New Open-Loop Fiber Optic Gyro Error Compensation Method Based on Angular Velocity Error Modeling

by Yanshun Zhang¹, Yajing Guo^1,*, Chunyu Li¹, Yixin Wang¹ and Zhanqing Wang²

¹ School of Instrumentation and Optoelectronic Engineering, Beihang University, Beijing 100191, China

² School of Automation, Beijing Institute of Technology, Beijing 100081, China

Sensors 2015, 15(3), 4899-4912; https://doi.org/10.3390/s150304899 - 27 Feb 2015

Cited by 13 | Viewed by 7711

Abstract

With the open-loop fiber optic gyro (OFOG) model, output voltage and angular velocity can effectively compensate OFOG errors. However, the model cannot reflect the characteristics of OFOG errors well when it comes to pretty large dynamic angular velocities. This paper puts forward a [...] Read more.

With the open-loop fiber optic gyro (OFOG) model, output voltage and angular velocity can effectively compensate OFOG errors. However, the model cannot reflect the characteristics of OFOG errors well when it comes to pretty large dynamic angular velocities. This paper puts forward a modeling scheme with OFOG output voltage and temperature as the input variables and angular velocity error as the output variable. Firstly, the angular velocity error is extracted from OFOG output signals, and then the output voltage , temperature and angular velocity error are used as the learning samples to train a Radial-Basis-Function (RBF) neural network model. Then the nonlinear mapping model over T, and is established and thus can be calculated automatically to compensate OFOG errors according to and . The results of the experiments show that the established model can be used to compensate the nonlinear OFOG errors. The maximum, the minimum and the mean square error of OFOG angular velocity are decreased by , and relative to their initial values, respectively. Compared with the direct modeling of gyro angular velocity, which we researched before, the experimental results of the compensating method proposed in this paper are further reduced by , and , respectively, so the performance of this method is better than that of the direct modeling for gyro angular velocity. Full article

(This article belongs to the Special Issue Optical Gyroscopes and Navigation Systems)

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12 pages, 1797 KiB

Open AccessArticle

Engineering a Ca⁺⁺-Sensitive (Bio)Sensor from the Pore-Module of a Potassium Channel

by Mattia Lorenzo DiFrancesco^1,†, Sabrina Gazzarrini¹, Cristina Arrigoni¹, Giulia Romani², Gerhard Thiel³ and Anna Moroni^1,2,*

¹ Department of Biosciences, University of Milan, Via Celoria 26, Milano 20133, Italy

² Institute of Biophysics-Milan section, National Research Council, Via Celoria 26, Milano 20133, Italy

³ Department of Biology, Technische Universität Darmstadt, Schnittspahnstrasse 3, Darmstadt 64287, Germany

^† Present Addresses: CNRS UMR-5203, Institut de Génomique Fonctionnelle, Départment de Physiologie, LabEx ICST, 141 rue de la Cardonille, 34094 Montpellier cedex 5, France; INSERM U1191, F-34094 Montpellier, France; Université de Montpellier, F-34094 Montpellier, France

Sensors 2015, 15(3), 4913-4924; https://doi.org/10.3390/s150304913 - 27 Feb 2015

Cited by 4 | Viewed by 6752

Abstract

Signals recorded at the cell membrane are meaningful indicators of the physiological vs. pathological state of a cell and will become useful diagnostic elements in nanomedicine. In this project we present a coherent strategy for the design and fabrication of a bio-nano-sensor that [...] Read more.

Signals recorded at the cell membrane are meaningful indicators of the physiological vs. pathological state of a cell and will become useful diagnostic elements in nanomedicine. In this project we present a coherent strategy for the design and fabrication of a bio-nano-sensor that monitors changes in intracellular cell calcium concentration and allows an easy read out by converting the calcium signal into an electrical current in the range of microampere that can be easily measured by conventional cell electrophysiology apparatus. Full article

(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Italy 2014)

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22 pages, 2510 KiB

Open AccessArticle

Sensor Data Fusion for Body State Estimation in a Bipedal Robot and Its Feedback Control Application for Stable Walking

by Ching-Pei Chen, Jing-Yi Chen, Chun-Kai Huang, Jau-Ching Lu and Pei-Chun Lin^*

Department of Mechanical Engineering, National Taiwan University, No. 1, Sec. 4, Roosevelt Road, Taipei 10617, Taiwan

Sensors 2015, 15(3), 4925-4946; https://doi.org/10.3390/s150304925 - 27 Feb 2015

Cited by 11 | Viewed by 8981

Abstract

We report on a sensor data fusion algorithm via an extended Kalman filter for estimating the spatial motion of a bipedal robot. Through fusing the sensory information from joint encoders, a 6-axis inertial measurement unit and a 2-axis inclinometer, the robot’s [...] Read more.

We report on a sensor data fusion algorithm via an extended Kalman filter for estimating the spatial motion of a bipedal robot. Through fusing the sensory information from joint encoders, a 6-axis inertial measurement unit and a 2-axis inclinometer, the robot’s body state at a specific fixed position can be yielded. This position is also equal to the CoM when the robot is in the standing posture suggested by the detailed CAD model of the robot. In addition, this body state is further utilized to provide sensory information for feedback control on a bipedal robot with walking gait. The overall control strategy includes the proposed body state estimator as well as the damping controller, which regulates the body position state of the robot in real-time based on instant and historical position tracking errors. Moreover, a posture corrector for reducing unwanted torque during motion is addressed. The body state estimator and the feedback control structure are implemented in a child-size bipedal robot and the performance is experimentally evaluated. Full article

(This article belongs to the Section Physical Sensors)

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11 pages, 3337 KiB

Open AccessReview

The Utility and Limitations of Contrast-Enhanced Ultrasound for the Diagnosis and Treatment of Prostate Cancer

by Futoshi Sano and Hiroji Uemura^*

Department of Urology, Yokohama City University Graduate School of Medicine, 3–9, Fukuura, Kanazawa-ku, Yokohama 236-0004, Japan

Sensors 2015, 15(3), 4947-4957; https://doi.org/10.3390/s150304947 - 27 Feb 2015

Cited by 33 | Viewed by 9006

Abstract

In association with the widespread use of prostate specific antigen (PSA) screening, the numbers of men identified with early-stage prostate cancer (PCa) are increasing in the developed countries, including Japan. However, the accurate localization of PCa lesions in diagnostic imaging is still difficult [...] Read more.

In association with the widespread use of prostate specific antigen (PSA) screening, the numbers of men identified with early-stage prostate cancer (PCa) are increasing in the developed countries, including Japan. However, the accurate localization of PCa lesions in diagnostic imaging is still difficult because PCa has a tendency to be multifocal in the prostate gland. Contrast-enhanced ultrasound (CEUS) improves the detection of PCa by visualizing cancerous lesions in order to target a needle biopsy. CEUS has the potential to enable not only accurate diagnoses but also novel treatments such as focal therapy. The combination of CEUS and other modalities is expected to improve the diagnosis of PCa and its treatment. Full article

(This article belongs to the Special Issue Ultrasonic Sensors and Transducers for Applications in Biology, Medicine and NDT)

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17 pages, 2842 KiB

Open AccessArticle

Feasibility of Multiple Micro-Particle Trapping—A Simulation Study

by Yanyan Yu¹, Weibao Qiu², Bernard Chiu¹ and Lei Sun^3,*

¹ Department of Electronic Engineering, City University of Hong Kong, Hong Kong, China

² Paul C. Lauterbur Research Center for Biomedical Imaging, Institute of Biomedical and Health Engineering, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen 518055, China

³ Interdisciplinary Division of Biomedical Engineering, the Hong Kong Polytechnic University, Hong Kong, China

Sensors 2015, 15(3), 4958-4974; https://doi.org/10.3390/s150304958 - 27 Feb 2015

Cited by 1 | Viewed by 7066

Abstract

Both optical tweezers and acoustic tweezers have been demonstrated for trapping small particles in diverse biomedical applications. Compared to the optical tweezers, acoustic tweezers have deeper penetration, lower intensity, and are more useful in light opaque media. These advantages enable the potential utility [...] Read more.

Both optical tweezers and acoustic tweezers have been demonstrated for trapping small particles in diverse biomedical applications. Compared to the optical tweezers, acoustic tweezers have deeper penetration, lower intensity, and are more useful in light opaque media. These advantages enable the potential utility of acoustic tweezers in biological science. Since the first demonstration of acoustic tweezers, various applications have required the trapping of not only one, but more particles simultaneously in both the axial and lateral direction. In this research, a method is proposed to create multiple trapping patterns, to prove the feasibility of trapping micro-particles. It has potential ability to electronically control the location and movement of the particles in real-time. A multiple-focus acoustic field can be generated by controlling the excitation of the transducer elements. The pressure and intensity of the field are obtained by modeling phased array transducer. Moreover, scattering force and gradient force at various positions are also evaluated to analyze their relative components to the effect of the acoustic tweezers. Besides, the axial and lateral radiation force and the trapping trajectory are computed based on ray acoustic approach. The results obtained demonstrate that the acoustic tweezers are capable of multiple trapping in both the axial and lateral directions. Full article

(This article belongs to the Special Issue Ultrasonic Sensors and Transducers for Applications in Biology, Medicine and NDT)

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21 pages, 9751 KiB

Open AccessArticle

A Robust Kalman Framework with Resampling and Optimal Smoothing

by Thomas Kautz^* and Bjoern M. Eskofier

Digital Sports Group, Pattern Recognition Lab, Friedrich-Alexander University Erlangen-Nürnberg (FAU), Haberstr. 2, 91058 Erlangen, Germany

Sensors 2015, 15(3), 4975-4995; https://doi.org/10.3390/s150304975 - 27 Feb 2015

Cited by 14 | Viewed by 6265

Abstract

The Kalman filter (KF) is an extremely powerful and versatile tool for signal processing that has been applied extensively in various fields. We introduce a novel Kalman-based analysis procedure that encompasses robustness towards outliers, Kalman smoothing and real-time conversion from non-uniformly sampled inputs [...] Read more.

The Kalman filter (KF) is an extremely powerful and versatile tool for signal processing that has been applied extensively in various fields. We introduce a novel Kalman-based analysis procedure that encompasses robustness towards outliers, Kalman smoothing and real-time conversion from non-uniformly sampled inputs to a constant output rate. These features have been mostly treated independently, so that not all of their benefits could be exploited at the same time. Here, we present a coherent analysis procedure that combines the aforementioned features and their benefits. To facilitate utilization of the proposed methodology and to ensure optimal performance, we also introduce a procedure to calculate all necessary parameters. Thereby, we substantially expand the versatility of one of the most widely-used filtering approaches, taking full advantage of its most prevalent extensions. The applicability and superior performance of the proposed methods are demonstrated using simulated and real data. The possible areas of applications for the presented analysis procedure range from movement analysis over medical imaging, brain-computer interfaces to robot navigation or meteorological studies. Full article

(This article belongs to the Section Physical Sensors)

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24 pages, 940 KiB

Open AccessArticle

Sensor4PRI: A Sensor Platform for the Protection of Railway Infrastructures

by Eduardo Cañete^*, Jaime Chen, Manuel Díaz, Luis Llopis and Bartolomé Rubio

Department of Languages and Computer Science, University of Málaga, Boulevar Louis Pasteur 35, 29071 Málaga, Spain

Sensors 2015, 15(3), 4996-5019; https://doi.org/10.3390/s150304996 - 27 Feb 2015

Cited by 18 | Viewed by 10544

Abstract

Wireless Sensor Networks constitute pervasive and distributed computing systems and are potentially one of the most important technologies of this century. They have been specifically identified as a good candidate to become an integral part of the protection of critical infrastructures. In this [...] Read more.

Wireless Sensor Networks constitute pervasive and distributed computing systems and are potentially one of the most important technologies of this century. They have been specifically identified as a good candidate to become an integral part of the protection of critical infrastructures. In this paper we focus on railway infrastructure protection and we present the details of a sensor platform designed to be integrated into a slab track system in order to carry out both installation and maintenance monitoring activities. In the installation phase, the platform helps operators to install the slab tracks in the right position. In the maintenance phase, the platform collects information about the structural health and behavior of the infrastructure when a train travels along it and relays the readings to a base station. The base station uses trains as data mules to upload the information to the internet. The use of a train as a data mule is especially suitable for collecting information from remote or inaccessible places which do not have a direct connection to the internet and require less network infrastructure. The overall aim of the system is to deploy a permanent economically viable monitoring system to improve the safety of railway infrastructures. Full article

(This article belongs to the Special Issue Sensors in New Road Vehicles)

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12 pages, 1431 KiB

Open AccessArticle

A Wind Energy Powered Wireless Temperature Sensor Node

by Chuang Zhang¹, Xue-Feng He^1,2,*, Si-Yu Li¹, Yao-Qing Cheng² and Yang Rao¹

¹ Key Laboratory of Optoelectronic Technology and Systems of the Education Ministry of China, Chongqing University, Chongqing 400044, China

² Microsystem Research Center, Chongqing University, Chongqing 400044, China

Sensors 2015, 15(3), 5020-5031; https://doi.org/10.3390/s150305020 - 27 Feb 2015

Cited by 36 | Viewed by 10979

Abstract

A wireless temperature sensor node composed of a piezoelectric wind energy harvester, a temperature sensor, a microcontroller, a power management circuit and a wireless transmitting module was developed. The wind-induced vibration energy harvester with a cuboid chamber of 62 mm × 19.6 mm [...] Read more.

A wireless temperature sensor node composed of a piezoelectric wind energy harvester, a temperature sensor, a microcontroller, a power management circuit and a wireless transmitting module was developed. The wind-induced vibration energy harvester with a cuboid chamber of 62 mm × 19.6 mm × 10 mm converts ambient wind energy into electrical energy to power the sensor node. A TMP102 temperature sensor and the MSP430 microcontroller are used to measure the temperature. The power management module consists of LTC3588-1 and LT3009 units. The measured temperature is transmitted by the nRF24l01 transceiver. Experimental results show that the critical wind speed of the harvester was about 5.4 m/s and the output power of the harvester was about 1.59 mW for the electrical load of 20 kΩ at wind speed of 11.2 m/s, which was sufficient to power the wireless sensor node to measure and transmit the temperature every 13 s. When the wind speed increased from 6 m/s to 11.5 m/s, the self-powered wireless sensor node worked normally. Full article

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

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26 pages, 1659 KiB

Open AccessArticle

Vector Graph Assisted Pedestrian Dead Reckoning Using an Unconstrained Smartphone

by Jiuchao Qian, Ling Pei^*, Jiabin Ma, Rendong Ying and Peilin Liu

Shanghai Key Laboratory of Navigation and Location-based Services, School of Electronic Information and Electrical Engineering, Shanghai Jiao Tong University, Shanghai 200240, China

Sensors 2015, 15(3), 5032-5057; https://doi.org/10.3390/s150305032 - 2 Mar 2015

Cited by 61 | Viewed by 12221

Abstract

The paper presents a hybrid indoor positioning solution based on a pedestrian dead reckoning (PDR) approach using built-in sensors on a smartphone. To address the challenges of flexible and complex contexts of carrying a phone while walking, a robust step detection algorithm based [...] Read more.

The paper presents a hybrid indoor positioning solution based on a pedestrian dead reckoning (PDR) approach using built-in sensors on a smartphone. To address the challenges of flexible and complex contexts of carrying a phone while walking, a robust step detection algorithm based on motion-awareness has been proposed. Given the fact that step length is influenced by different motion states, an adaptive step length estimation algorithm based on motion recognition is developed. Heading estimation is carried out by an attitude acquisition algorithm, which contains a two-phase filter to mitigate the distortion of magnetic anomalies. In order to estimate the heading for an unconstrained smartphone, principal component analysis (PCA) of acceleration is applied to determine the offset between the orientation of smartphone and the actual heading of a pedestrian. Moreover, a particle filter with vector graph assisted particle weighting is introduced to correct the deviation in step length and heading estimation. Extensive field tests, including four contexts of carrying a phone, have been conducted in an office building to verify the performance of the proposed algorithm. Test results show that the proposed algorithm can achieve sub-meter mean error in all contexts. Full article

(This article belongs to the Special Issue Sensors for Indoor Mapping and Navigation)

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23 pages, 725 KiB

Open AccessArticle

Sub-Sampling Framework Comparison for Low-Power Data Gathering: A Comparative Analysis

by Bojan Milosevic^1,2,*, Carlo Caione¹, Elisabetta Farella^1,2, Davide Brunelli³

and Luca Benini^1,4

¹ DEI, University of Bologna, 40123 Bologna, Italy

² DA, Fondazione Bruno Kessler, I-38123 Trento, Italy

³ DII, University of Trento, I-38123 Trento, Italy

⁴ IIS, ETH, 8092 Zurich, Switzerland

Sensors 2015, 15(3), 5058-5080; https://doi.org/10.3390/s150305058 - 2 Mar 2015

Cited by 21 | Viewed by 7090

Abstract

A key design challenge for successful wireless sensor network (WSN) deployment is a good balance between the collected data resolution and the overall energy consumption. In this paper, we present a WSN solution developed to efficiently satisfy the requirements for long-term monitoring of [...] Read more.

A key design challenge for successful wireless sensor network (WSN) deployment is a good balance between the collected data resolution and the overall energy consumption. In this paper, we present a WSN solution developed to efficiently satisfy the requirements for long-term monitoring of a historical building. The hardware of the sensor nodes and the network deployment are described and used to collect the data. To improve the network’s energy efficiency, we developed and compared two approaches, sharing similar sub-sampling strategies and data reconstruction assumptions: one is based on compressive sensing (CS) and the second is a custom data-driven latent variable-based statistical model (LV). Both approaches take advantage of the multivariate nature of the data collected by a heterogeneous sensor network and reduce the sampling frequency at sub-Nyquist levels. Our comparative analysis highlights the advantages and limitations: signal reconstruction performance is assessed jointly with network-level energy reduction. The performed experiments include detailed performance and energy measurements on the deployed network and explore how the different parameters can affect the overall data accuracy and the energy consumption. The results show how the CS approach achieves better reconstruction accuracy and overall efficiency, with the exception of cases with really aggressive sub-sampling policies. Full article

(This article belongs to the Special Issue Wireless Sensor Networks and the Internet of Things)

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15 pages, 3795 KiB

Open AccessArticle

A High Speed CMOS Image Sensor with a Novel Digital Correlated Double Sampling and a Differential Difference Amplifier

by Daehyeok Kim, Jaeyoung Bae and Minkyu Song^*

Department of Semiconductor Science, Dongguk University, Seoul 100-715, Korea

Sensors 2015, 15(3), 5081-5095; https://doi.org/10.3390/s150305081 - 2 Mar 2015

Cited by 8 | Viewed by 12624

Abstract

In order to increase the operating speed of a CMOS image sensor (CIS), a new technique of digital correlated double sampling (CDS) is described. In general, the fixed pattern noise (FPN) of a CIS has been reduced with the subtraction algorithm between the [...] Read more.

In order to increase the operating speed of a CMOS image sensor (CIS), a new technique of digital correlated double sampling (CDS) is described. In general, the fixed pattern noise (FPN) of a CIS has been reduced with the subtraction algorithm between the reset signal and pixel signal. This is because a single-slope analog-to-digital converter (ADC) has been normally adopted in the conventional digital CDS with the reset ramp and signal ramp. Thus, the operating speed of a digital CDS is much slower than that of an analog CDS. In order to improve the operating speed, we propose a novel digital CDS based on a differential difference amplifier (DDA) that compares the reset signal and the pixel signal using only one ramp. The prototype CIS has been fabricated with 0.13 µm CIS technology and it has the VGA resolution of 640 × 480. The measured conversion time is 16 µs, and a high frame rate of 131 fps is achieved at the VGA resolution. Full article

(This article belongs to the Section Physical Sensors)

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16 pages, 8100 KiB

Open AccessArticle

Detection of Bird Nests during Mechanical Weeding by Incremental Background Modeling and Visual Saliency

by Kim Arild Steen^1,*, Ole Roland Therkildsen², Ole Green³ and Henrik Karstoft¹

¹ Department of Engineering, Aarhus University, Finlandsgade 22, 8200 Aarhus N, Denmark

² Department of Bioscience, Aarhus University, Grenåvej 14, 8410 Rønde, Denmark

³ Kongskilde Industries, Strategic Development, Niels Pedersens Allé 2, 8830 Tjele, Denmark

Sensors 2015, 15(3), 5096-5111; https://doi.org/10.3390/s150305096 - 2 Mar 2015

Cited by 10 | Viewed by 7046

Abstract

Mechanical weeding is an important tool in organic farming. However, the use of mechanical weeding in conventional agriculture is increasing, due to public demands to lower the use of pesticides and an increased number of pesticide-resistant weeds. Ground nesting birds are highly susceptible [...] Read more.

Mechanical weeding is an important tool in organic farming. However, the use of mechanical weeding in conventional agriculture is increasing, due to public demands to lower the use of pesticides and an increased number of pesticide-resistant weeds. Ground nesting birds are highly susceptible to farming operations, like mechanical weeding, which may destroy the nests and reduce the survival of chicks and incubating females. This problem has limited focus within agricultural engineering. However, when the number of machines increases, destruction of nests will have an impact on various species. It is therefore necessary to explore and develop new technology in order to avoid these negative ethical consequences. This paper presents a vision-based approach to automated ground nest detection. The algorithm is based on the fusion of visual saliency, which mimics human attention, and incremental background modeling, which enables foreground detection with moving cameras. The algorithm achieves a good detection rate, as it detects 28 of 30 nests at an average distance of 3.8 m, with a true positive rate of 0.75. Full article

(This article belongs to the Special Issue Agriculture and Forestry: Sensors, Technologies and Procedures)

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24 pages, 2087 KiB

Open AccessArticle

Opportunistic Mobility Support for Resource Constrained Sensor Devices in Smart Cities

by Daniel Granlund^*, Patrik Holmlund and Christer Åhlund

Luleå University of Technology, Skellefteå, SE-93187, Sweden

Sensors 2015, 15(3), 5112-5135; https://doi.org/10.3390/s150305112 - 2 Mar 2015

Cited by 7 | Viewed by 7503

Abstract

A multitude of wireless sensor devices and technologies are being developed and deployed in cities all over the world. Sensor applications in city environments may include highly mobile installations that span large areas which necessitates sensor mobility support. This paper presents and validates [...] Read more.

A multitude of wireless sensor devices and technologies are being developed and deployed in cities all over the world. Sensor applications in city environments may include highly mobile installations that span large areas which necessitates sensor mobility support. This paper presents and validates two mechanisms for supporting sensor mobility between different administrative domains. Firstly, EAP-Swift, an Extensible Authentication Protocol (EAP)-based sensor authentication protocol is proposed that enables light-weight sensor authentication and key generation. Secondly, a mechanism for handoffs between wireless sensor gateways is proposed. We validate both mechanisms in a real-life study that was conducted in a smart city environment with several fixed sensors and moving gateways. We conduct similar experiments in an industry-based anechoic Long Term Evolution (LTE) chamber with an ideal radio environment. Further, we validate our results collected from the smart city environment against the results produced under ideal conditions to establish best and real-life case scenarios. Our results clearly validate that our proposed mechanisms can facilitate efficient sensor authentication and handoffs while sensors are roaming in a smart city environment. Full article

(This article belongs to the Special Issue Sensors and Smart Cities)

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15 pages, 1271 KiB

Open AccessArticle

Biosignal Analysis to Assess Mental Stress in Automatic Driving of Trucks: Palmar Perspiration and Masseter Electromyography

by Rencheng Zheng^1,*

, Shigeyuki Yamabe², Kimihiko Nakano³ and Yoshihiro Suda¹

¹ Institute of Industrial Science, The University of Tokyo, Tokyo 153-8505, Japan

² New Industry Creation Hatchery Center, Tohoku University, Sendai 980-8579, Japan

³ Interfaculty Initiative in Information Studies, The University of Tokyo, Tokyo 153-8505, Japan

Sensors 2015, 15(3), 5136-5150; https://doi.org/10.3390/s150305136 - 2 Mar 2015

Cited by 68 | Viewed by 8554

Abstract

Nowadays insight into human-machine interaction is a critical topic with the large-scale development of intelligent vehicles. Biosignal analysis can provide a deeper understanding of driver behaviors that may indicate rationally practical use of the automatic technology. Therefore, this study concentrates on biosignal analysis [...] Read more.

Nowadays insight into human-machine interaction is a critical topic with the large-scale development of intelligent vehicles. Biosignal analysis can provide a deeper understanding of driver behaviors that may indicate rationally practical use of the automatic technology. Therefore, this study concentrates on biosignal analysis to quantitatively evaluate mental stress of drivers during automatic driving of trucks, with vehicles set at a closed gap distance apart to reduce air resistance to save energy consumption. By application of two wearable sensor systems, a continuous measurement was realized for palmar perspiration and masseter electromyography, and a biosignal processing method was proposed to assess mental stress levels. In a driving simulator experiment, ten participants completed automatic driving with 4, 8, and 12 m gap distances from the preceding vehicle, and manual driving with about 25 m gap distance as a reference. It was found that mental stress significantly increased when the gap distances decreased, and an abrupt increase in mental stress of drivers was also observed accompanying a sudden change of the gap distance during automatic driving, which corresponded to significantly higher ride discomfort according to subjective reports. Full article

(This article belongs to the Special Issue HCI In Smart Environments)

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12 pages, 3184 KiB

Open AccessArticle

A Guided Wave Sensor Based on the Inverse Magnetostrictive Effect for Distinguishing Symmetric from Asymmetric Features in Pipes

by Jiang Xu^*

, Xinjun Wu, Dongying Kong and Pengfei Sun

School of Mechanical Science and Engineering, Huazhong University of Science and Technology, Wuhan 430074, China

Sensors 2015, 15(3), 5151-5162; https://doi.org/10.3390/s150305151 - 2 Mar 2015

Cited by 12 | Viewed by 6944

Abstract

The magnetostrictive guided wave sensor with a single induced winding cannot distinguish axially symmetric from non-axially symmetric features in a pipe, because it is impossible for the sensor to detect the non-axially symmetric mode waves. When we study the effect of the change [...] Read more.

The magnetostrictive guided wave sensor with a single induced winding cannot distinguish axially symmetric from non-axially symmetric features in a pipe, because it is impossible for the sensor to detect the non-axially symmetric mode waves. When we study the effect of the change of the magnetic field in the air zone for receiving the longitudinal guided wave mode, we find that the change of the magnetic flux in the air zone is almost equivalent to the change of the flux in the pipe wall, but in opposite directions. Based on this phenomenon, we present a sensor that can detect the flexural-mode waves in pipes based on the inverse magnetostrictive effect. The sensor is composed of several coils that are arranged evenly on the outside of pipes. The coils induce a change in magnetic flux in the air to detect the flexural-mode waves. The waves can be determined by adding a phase delay to the induced signals. The symmetric and asymmetric features of a pipe can be distinguished using the sensor. A prototype sensor that can detect F(1,3) and F(2,3) mode waves is presented. The function of the sensor is verified by experiments. Full article

(This article belongs to the Section Physical Sensors)

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34 pages, 1596 KiB

Open AccessArticle

Low Energy Physical Activity Recognition System on Smartphones

by Luis Miguel Soria Morillo^1,*, Luis Gonzalez-Abril², Juan Antonio Ortega Ramirez¹ and Miguel Angel Alvarez De la Concepcion¹

¹ Computer Languages and Systems Department, University of Seville, 41012 Seville, Spain

² Applied Economics I Department, University of Seville, 41018 Seville, Spain

Sensors 2015, 15(3), 5163-5196; https://doi.org/10.3390/s150305163 - 3 Mar 2015

Cited by 46 | Viewed by 7984

Abstract

An innovative approach to physical activity recognition based on the use of discrete variables obtained from accelerometer sensors is presented. The system first performs a discretization process for each variable, which allows efficient recognition of activities performed by users using as little energy [...] Read more.

An innovative approach to physical activity recognition based on the use of discrete variables obtained from accelerometer sensors is presented. The system first performs a discretization process for each variable, which allows efficient recognition of activities performed by users using as little energy as possible. To this end, an innovative discretization and classification technique is presented based on the χ² distribution. Furthermore, the entire recognition process is executed on the smartphone, which determines not only the activity performed, but also the frequency at which it is carried out. These techniques and the new classification system presented reduce energy consumption caused by the activity monitoring system. The energy saved increases smartphone usage time to more than 27 h without recharging while maintaining accuracy. Full article

(This article belongs to the Section Sensor Networks)

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31 pages, 3552 KiB

Open AccessArticle

Continuous Human Action Recognition Using Depth-MHI-HOG and a Spotter Model

by Hyukmin Eum¹, Changyong Yoon², Heejin Lee³ and Mignon Park^1,*

¹ School of Electrical and Electronic Engineering, Yonsei University, 134 Shinchon-Dong, Seodaemun-Gu, Seoul 120-749, Korea

² Department of Electrical Engineering, Suwon Science College, Hwaseong 445-742, Korea

³ Department of Electrical, Electronic and Control Engineering, Hankyong National University, Anseong 456-749, Korea

Sensors 2015, 15(3), 5197-5227; https://doi.org/10.3390/s150305197 - 3 Mar 2015

Cited by 35 | Viewed by 8391

Abstract

In this paper, we propose a new method for spotting and recognizing continuous human actions using a vision sensor. The method is comprised of depth-MHI-HOG (DMH), action modeling, action spotting, and recognition. First, to effectively separate the foreground from background, we propose a [...] Read more.

In this paper, we propose a new method for spotting and recognizing continuous human actions using a vision sensor. The method is comprised of depth-MHI-HOG (DMH), action modeling, action spotting, and recognition. First, to effectively separate the foreground from background, we propose a method called DMH. It includes a standard structure for segmenting images and extracting features by using depth information, MHI, and HOG. Second, action modeling is performed to model various actions using extracted features. The modeling of actions is performed by creating sequences of actions through k-means clustering; these sequences constitute HMM input. Third, a method of action spotting is proposed to filter meaningless actions from continuous actions and to identify precise start and end points of actions. By employing the spotter model, the proposed method improves action recognition performance. Finally, the proposed method recognizes actions based on start and end points. We evaluate recognition performance by employing the proposed method to obtain and compare probabilities by applying input sequences in action models and the spotter model. Through various experiments, we demonstrate that the proposed method is efficient for recognizing continuous human actions in real environments. Full article

(This article belongs to the Section Physical Sensors)

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23 pages, 2544 KiB

Open AccessArticle

Human Computer Interactions in Next-Generation of Aircraft Smart Navigation Management Systems: Task Analysis and Architecture under an Agent-Oriented Methodological Approach

by José M. Canino-Rodríguez^1,*, Jesús García-Herrero², Juan Besada-Portas³, Antonio G. Ravelo-García¹, Carlos Travieso-González¹

and Jesús B. Alonso-Hernández¹

¹ Signals and Communications Department, University of Las Palmas de Gran Canaria, Las Palmas de Gran Canaria 35001, Spain

² Computer Science Department, University of Carlos III, Madrid 28903, Spain

³ Signal, Systems and Radio-communications Department, Polytechnic University of Madrid, Madrid 28040, Spain

Sensors 2015, 15(3), 5228-5250; https://doi.org/10.3390/s150305228 - 4 Mar 2015

Cited by 9 | Viewed by 10830

Abstract

The limited efficiency of current air traffic systems will require a next-generation of Smart Air Traffic System (SATS) that relies on current technological advances. This challenge means a transition toward a new navigation and air-traffic procedures paradigm, where pilots and air traffic controllers [...] Read more.

The limited efficiency of current air traffic systems will require a next-generation of Smart Air Traffic System (SATS) that relies on current technological advances. This challenge means a transition toward a new navigation and air-traffic procedures paradigm, where pilots and air traffic controllers perform and coordinate their activities according to new roles and technological supports. The design of new Human-Computer Interactions (HCI) for performing these activities is a key element of SATS. However efforts for developing such tools need to be inspired on a parallel characterization of hypothetical air traffic scenarios compatible with current ones. This paper is focused on airborne HCI into SATS where cockpit inputs came from aircraft navigation systems, surrounding traffic situation, controllers’ indications, etc. So the HCI is intended to enhance situation awareness and decision-making through pilot cockpit. This work approach considers SATS as a system distributed on a large-scale with uncertainty in a dynamic environment. Therefore, a multi-agent systems based approach is well suited for modeling such an environment. We demonstrate that current methodologies for designing multi-agent systems are a useful tool to characterize HCI. We specifically illustrate how the selected methodological approach provides enough guidelines to obtain a cockpit HCI design that complies with future SATS specifications. Full article

(This article belongs to the Special Issue HCI In Smart Environments)

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30 pages, 1098 KiB

Open AccessArticle

Dynamic Reconfiguration of Security Policies in Wireless Sensor Networks

by Mónica Pinto^*, Nadia Gámez, Lidia Fuentes, Mercedes Amor, José Miguel Horcas and Inmaculada Ayala

Departamento de Lenguajes y Ciencias de la Computación, University of Málaga, Andalucía Tech, Málaga 29071, Spain

Sensors 2015, 15(3), 5251-5280; https://doi.org/10.3390/s150305251 - 4 Mar 2015

Cited by 12 | Viewed by 7740

Abstract

Providing security and privacy to wireless sensor nodes (WSNs) is very challenging, due to the heterogeneity of sensor nodes and their limited capabilities in terms of energy, processing power and memory. The applications for these systems run in a myriad of sensors with [...] Read more.

Providing security and privacy to wireless sensor nodes (WSNs) is very challenging, due to the heterogeneity of sensor nodes and their limited capabilities in terms of energy, processing power and memory. The applications for these systems run in a myriad of sensors with different low-level programming abstractions, limited capabilities and different routing protocols. This means that applications for WSNs need mechanisms for self-adaptation and for self-protection based on the dynamic adaptation of the algorithms used to provide security. Dynamic software product lines (DSPLs) allow managing both variability and dynamic software adaptation, so they can be considered a key technology in successfully developing self-protected WSN applications. In this paper, we propose a self-protection solution for WSNs based on the combination of the INTER-TRUST security framework (a solution for the dynamic negotiation and deployment of security policies) and the FamiWare middleware (a DSPL approach to automatically configure and reconfigure instances of a middleware for WSNs).We evaluate our approach using a case study from the intelligent transportation system domain. Full article

(This article belongs to the Special Issue Wireless Sensor Networks and the Internet of Things)

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12 pages, 1730 KiB

Open AccessArticle

A Highly Sensitive ELISA and Immunochromatographic Strip for the Detection of Salmonella typhimurium in Milk Samples

by Wenbin Wang, Liqiang Liu, Shanshan Song, Lijuan Tang, Hua Kuang and Chuanlai Xu^*

State Key Lab of Food Science and Technology, School of Food Science and Technology, Jiangnan University, Wuxi 214122, China

Sensors 2015, 15(3), 5281-5292; https://doi.org/10.3390/s150305281 - 4 Mar 2015

Cited by 77 | Viewed by 8042

Abstract

Murine monoclonal antibodies to target Salmonella typhimurium flagellin and lipopolysaccharide (LPS) were prepared and characterized. For the immunological detection of S. typhimurium, different pairs of monoclonal antibodies (MAbs) were tested in a sandwich enzyme linked immunosorbent assay (ELISA) format. After comparison, a [...] Read more.

Murine monoclonal antibodies to target Salmonella typhimurium flagellin and lipopolysaccharide (LPS) were prepared and characterized. For the immunological detection of S. typhimurium, different pairs of monoclonal antibodies (MAbs) were tested in a sandwich enzyme linked immunosorbent assay (ELISA) format. After comparison, a sandwich ELISA and immunochromatographic strip based on LPS MAbs was established to detect S. typhimurium. The determination limits of the immunochromatographic strip in phosphate-buffered saline (PBS) containing 0.1% Tween 20 (PBST) and pure milk sample were found to be 1.25 × 10⁵ colony-forming units (cfu)/mL and 1.25 × 10⁶ cfu/mL S. typhimurium, respectively. Results can be obtained with the naked eye in 10 min. Cross-reactivity was observed with Salmonella paratyphi B, but not S. paratyphi A or Salmonella enteritidis. The LPS MAbs based immunochromatographic strip is rapid and convenient to detect S. typhimurium in milk samples. Full article

(This article belongs to the Section Biosensors)

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18 pages, 1932 KiB

Open AccessArticle

Magnetometer-Augmented IMU Simulator: In-Depth Elaboration

by Thomas Brunner^1,2,*, Jean-Philippe Lauffenburger², Sébastien Changey¹ and Michel Basset²

¹ French-German Research Institute of Saint-Louis (ISL, Guidance, Navigation and Control (GNC) Department), 5 rue du Général Cassagnou, Saint-Louis 68300, France

² Laboratoire MIPS - EA2332, Université de Haute-Alsace, 12 rue des Frères Lumière, Mulhouse Cedex 68093, France

Sensors 2015, 15(3), 5293-5310; https://doi.org/10.3390/s150305293 - 4 Mar 2015

Cited by 25 | Viewed by 10061

Abstract

The location of objects is a growing research topic due, for instance, to the expansion of civil drones or intelligent vehicles. This expansion was made possible through the development of microelectromechanical systems (MEMS), inexpensive and miniaturized inertial sensors. In this context, this article [...] Read more.

The location of objects is a growing research topic due, for instance, to the expansion of civil drones or intelligent vehicles. This expansion was made possible through the development of microelectromechanical systems (MEMS), inexpensive and miniaturized inertial sensors. In this context, this article describes the development of a new simulator which generates sensor measurements, giving a specific input trajectory. This will allow the comparison of pose estimation algorithms. To develop this simulator, the measurement equations of every type of sensor have to be analytically determined. To achieve this objective, classical kinematic equations are used for the more common sensors, i.e., accelerometers and rate gyroscopes. As nowadays, the MEMS inertial measurement units (IMUs) are generally magnetometer-augmented, an absolute world magnetic model is implemented. After the determination of the perfect measurement (through the error-free sensor models), realistic error models are developed to simulate real IMU behavior. Finally, the developed simulator is subjected to different validation tests. Full article

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

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20 pages, 4549 KiB

Open AccessArticle

Fast Fingerprint Database Maintenance for Indoor Positioning Based on UGV SLAM

by Jian Tang^1,2, Yuwei Chen^2,*

, Liang Chen³, Jingbin Liu², Juha Hyyppä², Antero Kukko²

, Harri Kaartinen²

, Hannu Hyyppä⁴ and Ruizhi Chen⁵

¹ GNSS Research Center, Wuhan University, 129 Luoyu Road, Wuhan 430000, China

² Department of Remote Sensing and Photogrammetry, Finnish Geospatial Research Institute, Geodeetinrinne 2, Kirkkonummi FI-02431, Finland

³ Department of Navigation and Positioning, Finnish Geospatial Research Institute, Geodeetinrine 2, Kirkkonummi FI-02431, Finland

⁴ Department of Real Estate, Planning and Geoinformatics, Aalto University, P.O. Box 11000, Espoo FI-00076, Finland

⁵ Conrad Blucher Institute of Surveying & Science, Texas A&M University at Corpus Christi, Corpus Christi, TX 77843-3577, USA

Sensors 2015, 15(3), 5311-5330; https://doi.org/10.3390/s150305311 - 4 Mar 2015

Cited by 50 | Viewed by 10587

Abstract

Indoor positioning technology has become more and more important in the last two decades. Utilizing Received Signal Strength Indicator (RSSI) fingerprints of Signals of OPportunity (SOP) is a promising alternative navigation solution. However, as the RSSIs vary during operation due to their physical [...] Read more.

Indoor positioning technology has become more and more important in the last two decades. Utilizing Received Signal Strength Indicator (RSSI) fingerprints of Signals of OPportunity (SOP) is a promising alternative navigation solution. However, as the RSSIs vary during operation due to their physical nature and are easily affected by the environmental change, one challenge of the indoor fingerprinting method is maintaining the RSSI fingerprint database in a timely and effective manner. In this paper, a solution for rapidly updating the fingerprint database is presented, based on a self-developed Unmanned Ground Vehicles (UGV) platform NAVIS. Several SOP sensors were installed on NAVIS for collecting indoor fingerprint information, including a digital compass collecting magnetic field intensity, a light sensor collecting light intensity, and a smartphone which collects the access point number and RSSIs of the pre-installed WiFi network. The NAVIS platform generates a map of the indoor environment and collects the SOPs during processing of the mapping, and then the SOP fingerprint database is interpolated and updated in real time. Field tests were carried out to evaluate the effectiveness and efficiency of the proposed method. The results showed that the fingerprint databases can be quickly created and updated with a higher sampling frequency (5Hz) and denser reference points compared with traditional methods, and the indoor map can be generated without prior information. Moreover, environmental changes could also be detected quickly for fingerprint indoor positioning. Full article

(This article belongs to the Special Issue Sensors for Indoor Mapping and Navigation)

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13 pages, 1648 KiB

Open AccessArticle

Hydrodynamic Voltammetry as a Rapid and Simple Method for Evaluating Soil Enzyme Activities

by Kazuto Sazawa^1,* and Hideki Kuramitz²

¹ Center for Far Eastern Studies, University of Toyama, Gofuku 3190, 930-8555 Toyama, Japan

² Department of Environmental Biology and Chemistry, Graduate School of Science and Engineering for Research, University of Toyama, Gofuku 3190, 930-8555 Toyama, Japan

Sensors 2015, 15(3), 5331-5343; https://doi.org/10.3390/s150305331 - 4 Mar 2015

Cited by 12 | Viewed by 9113

Abstract

Soil enzymes play essential roles in catalyzing reactions necessary for nutrient cycling in the biosphere. They are also sensitive indicators of ecosystem stress, therefore their evaluation is very important in assessing soil health and quality. The standard soil enzyme assay method based on [...] Read more.

Soil enzymes play essential roles in catalyzing reactions necessary for nutrient cycling in the biosphere. They are also sensitive indicators of ecosystem stress, therefore their evaluation is very important in assessing soil health and quality. The standard soil enzyme assay method based on spectroscopic detection is a complicated operation that requires the removal of soil particles. The purpose of this study was to develop a new soil enzyme assay based on hydrodynamic electrochemical detection using a rotating disk electrode in a microliter droplet. The activities of enzymes were determined by measuring the electrochemical oxidation of p-aminophenol (PAP), following the enzymatic conversion of substrate-conjugated PAP. The calibration curves of β-galactosidase (β-gal), β-glucosidase (β-glu) and acid phosphatase (AcP) showed good linear correlation after being spiked in soils using chronoamperometry. We also performed electrochemical detection using real soils. Hydrodynamic chronoamperometry can be used to assess the AcP in soils, with a detection time of only 90 s. Linear sweep voltammetry was used to measure the amount of PAP released from β-gal and β-glu by enzymatic reaction after 60 min. For the assessment of soil enzymes, the results of hydrodynamic voltammetry assay compared favorably to those using a standard assay procedure, but this new procedure is more user-friendly, rapid and simple. Full article

(This article belongs to the Special Issue Modern Technologies for Sensing Pollution in Air, Water, and Soil)

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32 pages, 1284 KiB

Open AccessArticle

A Framework for Mining Actionable Navigation Patterns from In-Store RFID Datasets via Indoor Mapping

by Bin Shen¹, Qiuhua Zheng², Xingsen Li¹ and Libo Xu^1,*

¹ Ningbo Institute of Technology, Zhejiang University, Ningbo 315100, China

² School of Computer Science and Technology, Hangzhou Dianzi University, Hangzhou 310018, China

Sensors 2015, 15(3), 5344-5375; https://doi.org/10.3390/s150305344 - 5 Mar 2015

Cited by 18 | Viewed by 7110

Abstract

With the quick development of RFID technology and the decreasing prices of RFID devices, RFID is becoming widely used in various intelligent services. Especially in the retail application domain, RFID is increasingly adopted to capture the shopping tracks and behavior of in-store customers. [...] Read more.

With the quick development of RFID technology and the decreasing prices of RFID devices, RFID is becoming widely used in various intelligent services. Especially in the retail application domain, RFID is increasingly adopted to capture the shopping tracks and behavior of in-store customers. To further enhance the potential of this promising application, in this paper, we propose a unified framework for RFID-based path analytics, which uses both in-store shopping paths and RFID-based purchasing data to mine actionable navigation patterns. Four modules of this framework are discussed, which are: (1) mapping from the physical space to the cyber space, (2) data preprocessing, (3) pattern mining and (4) knowledge understanding and utilization. In the data preprocessing module, the critical problem of how to capture the mainstream shopping path sequences while wiping out unnecessary redundant and repeated details is addressed in detail. To solve this problem, two types of redundant patterns, i.e., loop repeat pattern and palindrome-contained pattern are recognized and the corresponding processing algorithms are proposed. The experimental results show that the redundant pattern filtering functions are effective and scalable. Overall, this work builds a bridge between indoor positioning and advanced data mining technologies, and provides a feasible way to study customers’ shopping behaviors via multi-source RFID data. Full article

(This article belongs to the Special Issue Sensors for Indoor Mapping and Navigation)

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14 pages, 2067 KiB

Open AccessArticle

A Portable Automatic Endpoint Detection System for Amplicons of Loop Mediated Isothermal Amplification on Microfluidic Compact Disk Platform

by Shah Mukim Uddin^1,2

, Fatimah Ibrahim^1,2,*, Abkar Ahmed Sayad^1,2, Aung Thiha^1,2, Koh Xiu Pei³, Mas S. Mohktar^1,2, Uda Hashim⁴, Jongman Cho^1,2,5 and Kwai Lin Thong^2,3

¹ Department of Biomedical Engineering, Faculty of Engineering, University of Malaya, 50603 Kuala Lumpur, Malaysia

² Centre for Innovation in Medical Engineering (CIME), Faculty of Engineering, University of Malaya, 50603 Kuala Lumpur, Malaysia

³ Microbiology Unit, Institute of Biological Sciences, Faculty of Science, University of Malaya 50603 Kuala Lumpur, Malaysia

⁴ Institute of Nano Electronic Engineering (INEE), Universiti Malaysia Perlis, 01000 Kangar, Perlis, Malaysia

⁵ Department of Biomedical Engineering, Inje University, Gimhae 621-749, South Korea

Sensors 2015, 15(3), 5376-5389; https://doi.org/10.3390/s150305376 - 5 Mar 2015

Cited by 32 | Viewed by 11059

Abstract

In recent years, many improvements have been made in foodborne pathogen detection methods to reduce the impact of food contamination. Several rapid methods have been developed with biosensor devices to improve the way of performing pathogen detection. This paper presents an automated endpoint [...] Read more.

In recent years, many improvements have been made in foodborne pathogen detection methods to reduce the impact of food contamination. Several rapid methods have been developed with biosensor devices to improve the way of performing pathogen detection. This paper presents an automated endpoint detection system for amplicons generated by loop mediated isothermal amplification (LAMP) on a microfluidic compact disk platform. The developed detection system utilizes a monochromatic ultraviolet (UV) emitter for excitation of fluorescent labeled LAMP amplicons and a color sensor to detect the emitted florescence from target. Then it processes the sensor output and displays the detection results on liquid crystal display (LCD). The sensitivity test has been performed with detection limit up to 2.5 × 10⁻³ ng/µL with different DNA concentrations of Salmonella bacteria. This system allows a rapid and automatic endpoint detection which could lead to the development of a point-of-care diagnosis device for foodborne pathogens detection in a resource-limited environment. Full article

(This article belongs to the Special Issue Biosensors for Pathogen Detection)

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12 pages, 16732 KiB

Open AccessArticle

A Bio-Inspired Two-Layer Sensing Structure of Polypeptide and Multiple-Walled Carbon Nanotube to Sense Small Molecular Gases

by Li-Chun Wang¹, Tseng-Hsiung Su¹, Cheng-Long Ho¹, Shang-Ren Yang¹, Shih-Wen Chiu², Han-Wen Kuo³ and Kea-Tiong Tang^2,*

¹ Analytical Chemistry Section, Chung-Shan Institute of Science & Technology, Hsinchu 30325, Taiwan

² Department of Electrical Engineering, National Tsing Hua University, No. 101, Sec. 2, Kuang-Fu Road, Hsinchu 30013, Taiwan

³ Department of Chemistry, National Central University, Taoyuan 32001, Taiwan

Sensors 2015, 15(3), 5390-5401; https://doi.org/10.3390/s150305390 - 5 Mar 2015

Cited by 7 | Viewed by 6378

Abstract

In this paper, we propose a bio-inspired, two-layer, multiple-walled carbon nanotube (MWCNT)-polypeptide composite sensing device. The MWCNT serves as a responsive and conductive layer, and the nonselective polypeptide (40 mer) coating the top of the MWCNT acts as a filter into which small [...] Read more.

In this paper, we propose a bio-inspired, two-layer, multiple-walled carbon nanotube (MWCNT)-polypeptide composite sensing device. The MWCNT serves as a responsive and conductive layer, and the nonselective polypeptide (40 mer) coating the top of the MWCNT acts as a filter into which small molecular gases pass. Instead of using selective peptides to sense specific odorants, we propose using nonselective, peptide-based sensors to monitor various types of volatile organic compounds. In this study, depending on gas interaction and molecular sizes, the randomly selected polypeptide enabled the recognition of certain polar volatile chemical vapors, such as amines, and the improved discernment of low-concentration gases. The results of our investigation demonstrated that the polypeptide-coated sensors can detect ammonia at a level of several hundred ppm and barely responded to triethylamine. Full article

(This article belongs to the Special Issue Modern Technologies for Sensing Pollution in Air, Water, and Soil)

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27 pages, 1801 KiB

Open AccessArticle

Distributed Multi-Level Supervision to Effectively Monitor the Operations of a Fleet of Autonomous Vehicles in Agricultural Tasks

by Jesús Conesa-Muñoz

, Mariano Gonzalez-de-Soto

, Pablo Gonzalez-de-Santos

and Angela Ribeiro^*

Centre for Automation and Robotics, (CSIC-UPM), Arganda del Rey, 28500 Madrid, Spain

Sensors 2015, 15(3), 5402-5428; https://doi.org/10.3390/s150305402 - 5 Mar 2015

Cited by 38 | Viewed by 10565

Abstract

This paper describes a supervisor system for monitoring the operation of automated agricultural vehicles. The system analyses all of the information provided by the sensors and subsystems on the vehicles in real time and notifies the user when a failure or potentially dangerous [...] Read more.

This paper describes a supervisor system for monitoring the operation of automated agricultural vehicles. The system analyses all of the information provided by the sensors and subsystems on the vehicles in real time and notifies the user when a failure or potentially dangerous situation is detected. In some situations, it is even able to execute a neutralising protocol to remedy the failure. The system is based on a distributed and multi-level architecture that divides the supervision into different subsystems, allowing for better management of the detection and repair of failures. The proposed supervision system was developed to perform well in several scenarios, such as spraying canopy treatments against insects and diseases and selective weed treatments, by either spraying herbicide or burning pests with a mechanical-thermal actuator. Results are presented for selective weed treatment by the spraying of herbicide. The system successfully supervised the task; it detected failures such as service disruptions, incorrect working speeds, incorrect implement states, and potential collisions. Moreover, the system was able to prevent collisions between vehicles by taking action to avoid intersecting trajectories. The results show that the proposed system is a highly useful tool for managing fleets of autonomous vehicles. In particular, it can be used to manage agricultural vehicles during treatment operations. Full article

(This article belongs to the Special Issue Agriculture and Forestry: Sensors, Technologies and Procedures)

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45 pages, 3310 KiB

Open AccessArticle

Simulations of Operation Dynamics of Different Type GaN Particle Sensors

by Eugenijus Gaubas^*, Tomas Ceponis, Vidas Kalesinskas, Jevgenij Pavlov and Juozas Vysniauskas

Institute of Applied Research and Faculty of Physics, Vilnius University, Sauletekio av. 9-III, LT-10222 Vilnius, Lithuania

Sensors 2015, 15(3), 5429-5473; https://doi.org/10.3390/s150305429 - 5 Mar 2015

Cited by 12 | Viewed by 5460

Abstract

The operation dynamics of the capacitor-type and PIN diode type detectors based on GaN have been simulated using the dynamic and drift-diffusion models. The drift-diffusion current simulations have been implemented by employing the software package Synopsys TCAD Sentaurus. The monopolar and bipolar drift [...] Read more.

The operation dynamics of the capacitor-type and PIN diode type detectors based on GaN have been simulated using the dynamic and drift-diffusion models. The drift-diffusion current simulations have been implemented by employing the software package Synopsys TCAD Sentaurus. The monopolar and bipolar drift regimes have been analyzed by using dynamic models based on the Shockley-Ramo theorem. The carrier multiplication processes determined by impact ionization have been considered in order to compensate carrier lifetime reduction due to introduction of radiation defects into GaN detector material. Full article

(This article belongs to the Section Physical Sensors)

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30 pages, 1107 KiB

Open AccessArticle

Distributed Efficient Similarity Search Mechanism in Wireless Sensor Networks

by Khandakar Ahmed^*,† and Mark A. Gregory^†

¹ School of Electrical and Computer Engineering, RMIT University, Melbourne, VIC 3000, Australia

^† These authors contributed equally to this work.

Sensors 2015, 15(3), 5474-5503; https://doi.org/10.3390/s150305474 - 5 Mar 2015

Cited by 6 | Viewed by 5065

Abstract

The Wireless Sensor Network similarity search problem has received considerable research attention due to sensor hardware imprecision and environmental parameter variations. Most of the state-of-the-art distributed data centric storage (DCS) schemes lack optimization for similarity queries of events. In this paper, a DCS [...] Read more.

The Wireless Sensor Network similarity search problem has received considerable research attention due to sensor hardware imprecision and environmental parameter variations. Most of the state-of-the-art distributed data centric storage (DCS) schemes lack optimization for similarity queries of events. In this paper, a DCS scheme with metric based similarity searching (DCSMSS) is proposed. DCSMSS takes motivation from vector distance index, called iDistance, in order to transform the issue of similarity searching into the problem of an interval search in one dimension. In addition, a sector based distance routing algorithm is used to efficiently route messages. Extensive simulation results reveal that DCSMSS is highly efficient and significantly outperforms previous approaches in processing similarity search queries. Full article

(This article belongs to the Section Sensor Networks)

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14 pages, 5272 KiB

Open AccessArticle

An Approach to Precise Nitrogen Management Using Hand-Held Crop Sensor Measurements and Winter Wheat Yield Mapping in a Mediterranean Environment

by Lucía Quebrajo¹, Manuel Pérez-Ruiz^1,*, Antonio Rodriguez-Lizana¹ and Juan Agüera²

¹ Aerospace Engineering and Fluids Mechanics Department, University of Seville, Ctra. Sevilla-Utrera km. 1, Seville 41013, Spain

² Rural Engineering Department, University of Cordoba, Córdoba 14071, Spain

Sensors 2015, 15(3), 5504-5517; https://doi.org/10.3390/s150305504 - 6 Mar 2015

Cited by 28 | Viewed by 9018

Abstract

Regardless of the crop production system, nutrients inputs must be controlled at or below a certain economic threshold to achieve an acceptable level of profitability. The use of management zones and variable-rate fertilizer applications is gaining popularity in precision agriculture. Many researchers have [...] Read more.

Regardless of the crop production system, nutrients inputs must be controlled at or below a certain economic threshold to achieve an acceptable level of profitability. The use of management zones and variable-rate fertilizer applications is gaining popularity in precision agriculture. Many researchers have evaluated the application of final yield maps and geo-referenced geophysical measurements (e.g., apparent soil electrical conductivity-ECa) as a method of establishing relatively homogeneous management zones within the same plot. Yield estimation models based on crop conditions at certain growth stages, soil nutrient statuses, agronomic factors, moisture statuses, and weed/pest pressures are a primary goal in precision agriculture. This study attempted to achieve the following objectives: (1) to investigate the potential for predicting winter wheat yields using vegetation measurements (the Normalized Difference Vegetation Index—NDVI) at the beginning of the season, thereby allowing for a yield response to nitrogen (N) fertilizer; and (2) evaluate the feasibility of using inexpensive optical sensor measurements in a Mediterranean environment. A field experiment was conducted in two commercial wheat fields near Seville, in southwestern Spain. Yield data were collected at harvest using a yield monitoring system (RDS Ceres II-volumetric meter) installed on a combine. Wheat yield and NDVI values of 3498 ± 481 kg ha⁻¹ and 0.67 ± 0.04 nm nm⁻¹ (field 1) and 3221 ± 531 kg ha⁻¹ and 0.68 ± 0.05 nm nm⁻¹ (field 2) were obtained. In both fields, the yield and NDVI exhibited a strong Pearson correlation, with r_xy = 0.64 and p < 10⁻⁴ in field 1 and r_xy = 0.78 and p < 10⁻⁴ in field 2. The preliminary results indicate that hand-held crop sensor-based N management can be applied to wheat production in Spain and has the potential to increase agronomic N-use efficiency on a long-term basis. Full article

(This article belongs to the Special Issue Agriculture and Forestry: Sensors, Technologies and Procedures)

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13 pages, 2148 KiB

Open AccessArticle

Design of a Mobile Brain Computer Interface-Based Smart Multimedia Controller

by Kevin C. Tseng^1,2, Bor-Shing Lin³

, Alice May-Kuen Wong⁴ and Bor-Shyh Lin^5,6,*

¹ Department of Industrial Design, Chang-Gung University, Taoyuan 333, Taiwan

² Healthy Aging Research Centre, Chang Gung University, Taoyuan 333, Taiwan

³ Department of Computer Science and Information Engineering, National Taipei University, New Taipei 237, Taiwan

⁴ Department of Physical Medicine and Rehabilitation, Chang Gung Medical Foundation, Taoyuan 333, Taiwan

⁵ Institute of Imaging and Biomedical Photonics, National Chiao Tung University, Tainan 711, Taiwan

⁶ Department of Medical Research, Chi-Mei Medical Center, Tainan 710, Taiwan

Sensors 2015, 15(3), 5518-5530; https://doi.org/10.3390/s150305518 - 6 Mar 2015

Cited by 16 | Viewed by 9374

Abstract

Music is a way of expressing our feelings and emotions. Suitable music can positively affect people. However, current multimedia control methods, such as manual selection or automatic random mechanisms, which are now applied broadly in MP3 and CD players, cannot adaptively select suitable [...] Read more.

Music is a way of expressing our feelings and emotions. Suitable music can positively affect people. However, current multimedia control methods, such as manual selection or automatic random mechanisms, which are now applied broadly in MP3 and CD players, cannot adaptively select suitable music according to the user’s physiological state. In this study, a brain computer interface-based smart multimedia controller was proposed to select music in different situations according to the user’s physiological state. Here, a commercial mobile tablet was used as the multimedia platform, and a wireless multi-channel electroencephalograph (EEG) acquisition module was designed for real-time EEG monitoring. A smart multimedia control program built in the multimedia platform was developed to analyze the user’s EEG feature and select music according his/her state. The relationship between the user’s state and music sorted by listener’s preference was also examined in this study. The experimental results show that real-time music biofeedback according a user’s EEG feature may positively improve the user’s attention state. Full article

(This article belongs to the Special Issue HCI In Smart Environments)

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24 pages, 1526 KiB

Open AccessArticle

An Ultra-Low Power CMOS Image Sensor with On-Chip Energy Harvesting and Power Management Capability

by Ismail Cevik¹, Xiwei Huang², Hao Yu³, Mei Yan³ and Suat U. Ay^1,*

¹ Department of Electrical and Computer Engineering, University Idaho, 875 Perimeter Drive MS 1023 Moscow, ID 83844-1023, USA

² School of Electronics and Information, Hangzhou Dianzi University, No.1 Avenue, 2 Xiasha, Hangzhou 310018, China

³ Electrical and Electronic Engineering Department, Nanyang Technological University (NTU), 50 Nanyang Avenue, 639798, Singapore

Sensors 2015, 15(3), 5531-5554; https://doi.org/10.3390/s150305531 - 6 Mar 2015

Cited by 46 | Viewed by 17331

Abstract

An ultra-low power CMOS image sensor with on-chip energy harvesting and power management capability is introduced in this paper. The photodiode pixel array can not only capture images but also harvest solar energy. As such, the CMOS image sensor chip is able to [...] Read more.

An ultra-low power CMOS image sensor with on-chip energy harvesting and power management capability is introduced in this paper. The photodiode pixel array can not only capture images but also harvest solar energy. As such, the CMOS image sensor chip is able to switch between imaging and harvesting modes towards self-power operation. Moreover, an on-chip maximum power point tracking (MPPT)-based power management system (PMS) is designed for the dual-mode image sensor to further improve the energy efficiency. A new isolated P-well energy harvesting and imaging (EHI) pixel with very high fill factor is introduced. Several ultra-low power design techniques such as reset and select boosting techniques have been utilized to maintain a wide pixel dynamic range. The chip was designed and fabricated in a 1.8 V, 1P6M 0.18 µm CMOS process. Total power consumption of the imager is 6.53 µW for a 96 × 96 pixel array with 1 V supply and 5 fps frame rate. Up to 30 μW of power could be generated by the new EHI pixels. The PMS is capable of providing 3× the power required during imaging mode with 50% efficiency allowing energy autonomous operation with a 72.5% duty cycle. Full article

(This article belongs to the Special Issue On-Chip Sensors)

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28 pages, 3839 KiB

Open AccessArticle

SEnviro: A Sensorized Platform Proposal Using Open Hardware and Open Standards

by Sergio Trilles^*

, Alejandro Luján, Óscar Belmonte, Raúl Montoliu

, Joaquín Torres-Sospedra

and Joaquín Huerta

Institute of New Imaging Technologies, Universitat Jaume I, Av. Vicente Sos Baynat s/n, 12071, Castellón de la Plana, Spain

Sensors 2015, 15(3), 5555-5582; https://doi.org/10.3390/s150305555 - 6 Mar 2015

Cited by 42 | Viewed by 11895

Abstract

The need for constant monitoring of environmental conditions has produced an increase in the development of wireless sensor networks (WSN). The drive towards smart cities has produced the need for smart sensors to be able to monitor what is happening in our cities. [...] Read more.

The need for constant monitoring of environmental conditions has produced an increase in the development of wireless sensor networks (WSN). The drive towards smart cities has produced the need for smart sensors to be able to monitor what is happening in our cities. This, combined with the decrease in hardware component prices and the increase in the popularity of open hardware, has favored the deployment of sensor networks based on open hardware. The new trends in Internet Protocol (IP) communication between sensor nodes allow sensor access via the Internet, turning them into smart objects (Internet of Things and Web of Things). Currently, WSNs provide data in different formats. There is a lack of communication protocol standardization, which turns into interoperability issues when connecting different sensor networks or even when connecting different sensor nodes within the same network. This work presents a sensorized platform proposal that adheres to the principles of the Internet of Things and theWeb of Things. Wireless sensor nodes were built using open hardware solutions, and communications rely on the HTTP/IP Internet protocols. The Open Geospatial Consortium (OGC) SensorThings API candidate standard was used as a neutral format to avoid interoperability issues. An environmental WSN developed following the proposed architecture was built as a proof of concept. Details on how to build each node and a study regarding energy concerns are presented. Full article

(This article belongs to the Special Issue Wireless Sensor Networks and the Internet of Things)

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11 pages, 1161 KiB

Open AccessArticle

Interstitial Photoacoustic Sensor for the Measurement of Tissue Temperature during Interstitial Laser Phototherapy

by Zhifang Li^1,*, Haiyu Chen², Feifan Zhou³, Hui Li^1,* and Wei R. Chen^1,3,*

¹ Fujian Provincial Key Laboratory of Photonic Technology, Key Laboratory of Optoelectronic Science and Technology for Medicine, Ministry of Education, College of Photonic and Electronic Engineering, Fujian Normal University, Fuzhou 350007, China

² Department of Cardiovascular Surgery, Fujian Provincial Hospital, Fujian Medical University, Fuzhou 350000, China

³ Biophotonics Research Laboratory, Center for Interdisciplinary Biomedical Education and Research, University of Central Oklahoma, Edmond, OK 73034, USA

Sensors 2015, 15(3), 5583-5593; https://doi.org/10.3390/s150305583 - 6 Mar 2015

Cited by 24 | Viewed by 6205

Abstract

Photothermal therapy is an effective means to induce tumor cell death, since tumor tissue is more sensitive to temperature increases than normal tissue. Biological responses depend on tissue temperature; target tissue temperature needs to be precisely measured and controlled to achieve desired thermal [...] Read more.

Photothermal therapy is an effective means to induce tumor cell death, since tumor tissue is more sensitive to temperature increases than normal tissue. Biological responses depend on tissue temperature; target tissue temperature needs to be precisely measured and controlled to achieve desired thermal effects. In this work, a unique photoacoustic (PA) sensor is proposed for temperature measurement during interstitial laser phototherapy. A continuous-wave laser light and a pulsed laser light, for photothermal irradiation and photoacoustic temperature measurement, respectively, were delivered to the target tissue through a fiber coupler. During laser irradiation, the PA amplitude was measured. The Grüneisen parameter and the bioheat equation were used to determine the temperature in strategic positions in the target tissue. Our results demonstrate that the interstitial PA amplitude is a linear function of temperature in the range of 22 to 55 °C, as confirmed by thermocouple measurement. Furthermore, by choosing appropriate laser parameters, the maximum temperature surrounding the active diffuse fiber tip in tissue can be controlled in the range of 41 to 55 °C. Thus, this sensor could potentially be used for fast, accurate, and convenient three-dimensional temperature measurement, and for real-time feedback and control of interstitial laser phototherapy in cancer treatment. Full article

(This article belongs to the Section Physical Sensors)

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15 pages, 919 KiB

Open AccessArticle

Temperature-Phase Converter Based on a LC Cell as a Variable Capacitance

by Juan Carlos Torres^*, Braulio García-Cámara, Isabel Pérez, Virginia Urruchi and José Manuel Sánchez-Pena

Displays and Photonic Applications Group, Department of Electronic Technology, Carlos III University of Madrid, Avenida de la Universidad 30, Leganés E28911, Spain

Sensors 2015, 15(3), 5594-5608; https://doi.org/10.3390/s150305594 - 6 Mar 2015

Cited by 4 | Viewed by 5980

Abstract

The main characteristic of liquid crystals is that their properties, both electrical and optical, can be modified through a convenient applied signal, for instance a certain voltage. This tunable behavior of liquid crystals is directly related to the orientation of their nanometric components [...] Read more.

The main characteristic of liquid crystals is that their properties, both electrical and optical, can be modified through a convenient applied signal, for instance a certain voltage. This tunable behavior of liquid crystals is directly related to the orientation of their nanometric components with respect to a director direction. However, the initial alignment is a fabrication-dependent parameter and may be either planar or homeotropic. In addition, the strong dependence of the properties of liquid crystals with the temperature is well known and widely used for several temperature sensors. This dependence is produced by the influence of the temperature on the ordering of the molecules. In this work, we have studied the temperature dependence of the electric properties of a liquid crystal cell, in particular the dielectric permittivity, with the temperature as a function of the initial alignment set during the fabrication process. Starting from experimental measurements, an equivalent circuit model including the temperature dependence has been proposed. We have observed that a good linearity in a wide temperature range is provided at a suitable exciting frequency. Finally, a proper conditioner circuit is proposed as a powerful tool for linear and high sensibility temperature measurement. Full article

(This article belongs to the Section Physical Sensors)

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18 pages, 5992 KiB

Open AccessArticle

Quantifying Efficacy and Limits of Unmanned Aerial Vehicle (UAV) Technology for Weed Seedling Detection as Affected by Sensor Resolution

by José M. Peña^*, Jorge Torres-Sánchez

, Angélica Serrano-Pérez, Ana I. De Castro

and Francisca López-Granados

Institute for Sustainable Agriculture, IAS-CSIC, P.O. Box 4084, 14080 Córdoba, Spain

Sensors 2015, 15(3), 5609-5626; https://doi.org/10.3390/s150305609 - 6 Mar 2015

Cited by 168 | Viewed by 17355

Abstract

In order to optimize the application of herbicides in weed-crop systems, accurate and timely weed maps of the crop-field are required. In this context, this investigation quantified the efficacy and limitations of remote images collected with an unmanned aerial vehicle (UAV) for early [...] Read more.

In order to optimize the application of herbicides in weed-crop systems, accurate and timely weed maps of the crop-field are required. In this context, this investigation quantified the efficacy and limitations of remote images collected with an unmanned aerial vehicle (UAV) for early detection of weed seedlings. The ability to discriminate weeds was significantly affected by the imagery spectral (type of camera), spatial (flight altitude) and temporal (the date of the study) resolutions. The colour-infrared images captured at 40 m and 50 days after sowing (date 2), when plants had 5–6 true leaves, had the highest weed detection accuracy (up to 91%). At this flight altitude, the images captured before date 2 had slightly better results than the images captured later. However, this trend changed in the visible-light images captured at 60 m and higher, which had notably better results on date 3 (57 days after sowing) because of the larger size of the weed plants. Our results showed the requirements on spectral and spatial resolutions needed to generate a suitable weed map early in the growing season, as well as the best moment for the UAV image acquisition, with the ultimate objective of applying site-specific weed management operations. Full article

(This article belongs to the Collection Sensors in Agriculture and Forestry)

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22 pages, 993 KiB

Open AccessArticle

An SVM-Based Solution for Fault Detection in Wind Turbines

by Pedro Santos¹, Luisa F. Villa², Aníbal Reñones², Andres Bustillo^1,* and Jesús Maudes¹

¹ Department of Civil Engineering, University of Burgos, C/ Francisco de Vitoria s/n, Burgos 09006, Spain

² CARTIF Foundation, Parque Tecnológico de Boecillo, Boecillo 47151, Spain

Sensors 2015, 15(3), 5627-5648; https://doi.org/10.3390/s150305627 - 9 Mar 2015

Cited by 205 | Viewed by 12695

Abstract

Research into fault diagnosis in machines with a wide range of variable loads and speeds, such as wind turbines, is of great industrial interest. Analysis of the power signals emitted by wind turbines for the diagnosis of mechanical faults in their mechanical transmission [...] Read more.

Research into fault diagnosis in machines with a wide range of variable loads and speeds, such as wind turbines, is of great industrial interest. Analysis of the power signals emitted by wind turbines for the diagnosis of mechanical faults in their mechanical transmission chain is insufficient. A successful diagnosis requires the inclusion of accelerometers to evaluate vibrations. This work presents a multi-sensory system for fault diagnosis in wind turbines, combined with a data-mining solution for the classification of the operational state of the turbine. The selected sensors are accelerometers, in which vibration signals are processed using angular resampling techniques and electrical, torque and speed measurements. Support vector machines (SVMs) are selected for the classification task, including two traditional and two promising new kernels. This multi-sensory system has been validated on a test-bed that simulates the real conditions of wind turbines with two fault typologies: misalignment and imbalance. Comparison of SVM performance with the results of artificial neural networks (ANNs) shows that linear kernel SVM outperforms other kernels and ANNs in terms of accuracy, training and tuning times. The suitability and superior performance of linear SVM is also experimentally analyzed, to conclude that this data acquisition technique generates linearly separable datasets. Full article

(This article belongs to the Section Physical Sensors)

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17 pages, 11993 KiB

Open AccessArticle

An Efficient Mosaic Algorithm Considering Seasonal Variation: Application to KOMPSAT-2 Satellite Images

by Jaewon Choi¹, Hyung-Sup Jung^1,*

and Sang-Ho Yun²

¹ The Department of Geoinformatics, The University of Seoul, Seoul 130-743, Korea

² The Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA

Sensors 2015, 15(3), 5649-5665; https://doi.org/10.3390/s150305649 - 9 Mar 2015

Cited by 9 | Viewed by 6715

Abstract

As the aerospace industry grows, images obtained from Earth observation satellites have been successfully used in various fields. Specifically, the demand for a high-resolution (HR) optical images is gradually increasing, and hence the generation of a high-quality mosaic image is being magnified as [...] Read more.

As the aerospace industry grows, images obtained from Earth observation satellites have been successfully used in various fields. Specifically, the demand for a high-resolution (HR) optical images is gradually increasing, and hence the generation of a high-quality mosaic image is being magnified as an interesting issue. In this paper, we have proposed an efficient mosaic algorithm for HR optical images that are significantly different due to seasonal change. The algorithm includes main steps such as: (1) seamline extraction from gradient magnitude and seam images; (2) histogram matching; and (3) image feathering. Eleven Kompsat-2 images characterized by seasonal variations are used for the performance validation of the proposed method. The results of the performance test show that the proposed method effectively mosaics Kompsat-2 adjacent images including severe seasonal changes. Moreover, the results reveal that the proposed method is applicable to HR optic images such as GeoEye, IKONOS, QuickBird, RapidEye, SPOT, WorldView, etc. Full article

(This article belongs to the Section Remote Sensors)

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21 pages, 1986 KiB

Open AccessArticle

A Trajectory and Orientation Reconstruction Method for Moving Objects Based on a Moving Monocular Camera

by Jian Zhou¹, Yang Shang², Xiaohu Zhang² and Wenxian Yu^3,*

¹ Shanghai Key Laboratory of Navigation and Location Based Services, Shanghai Jiao Tong University, Shanghai 200240, China

² College of Aerospace Science and Engineering, National University of Defense Technology, Changsha 410073, China

³ Shanghai Key Laboratory of Intelligent Sensing and Recognition, Shanghai Jiao Tong University, Shanghai 200240, China

Sensors 2015, 15(3), 5666-5686; https://doi.org/10.3390/s150305666 - 9 Mar 2015

Cited by 3 | Viewed by 4979

Abstract

We propose a monocular trajectory intersection method to solve the problem that a monocular moving camera cannot be used for three-dimensional reconstruction of a moving object point. The necessary and sufficient condition of when this method has the unique solution is provided. An [...] Read more.

We propose a monocular trajectory intersection method to solve the problem that a monocular moving camera cannot be used for three-dimensional reconstruction of a moving object point. The necessary and sufficient condition of when this method has the unique solution is provided. An extended application of the method is to not only achieve the reconstruction of the 3D trajectory, but also to capture the orientation of the moving object, which would not be obtained by PnP problem methods due to lack of features. It is a breakthrough improvement that develops the intersection measurement from the traditional “point intersection” to “trajectory intersection” in videometrics. The trajectory of the object point can be obtained by using only linear equations without any initial value or iteration; the orientation of the object with poor conditions can also be calculated. The required condition for the existence of definite solution of this method is derived from equivalence relations of the orders of the moving trajectory equations of the object, which specifies the applicable conditions of the method. Simulation and experimental results show that it not only applies to objects moving along a straight line, or a conic and another simple trajectory, but also provides good result for more complicated trajectories, making it widely applicable. Full article

(This article belongs to the Section Physical Sensors)

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10 pages, 2169 KiB

Open AccessArticle

Magnetization Reversal and Magnetic Anisotropy in Ordered CoNiP Nanowire Arrays: Effects of Wire Diameter

by Luu Van Thiem^1,2, Le Tuan Tu^3,* and Manh-Huong Phan^4,*

¹ Faculty of Engineering Physics and Nanotechnology, VNU University of Engineering Technology, Vietnam National University, 144 Xuan Thuy, Cau Giay, Hanoi, Vietnam

² Faculty of Basic Science, Hanoi Industrial College for Textile, Garment and Fashion Le Chi, Gia Lam, Hanoi, Vietnam

³ Faculty of Physics, VNU University of Science, Vietnam National University, 334 Nguyen Trai, Thanh Xuan, Hanoi, Vietnam

⁴ Department of Physics, University of South Florida, Tampa, FL 33620, USA

Sensors 2015, 15(3), 5687-5696; https://doi.org/10.3390/s150305687 - 9 Mar 2015

Cited by 22 | Viewed by 7063

Abstract

Ordered CoNiP nanowires with the same length of 4 µm and varying diameters (d = 100 nm–600 nm) were fabricated by electrodeposition of CoNiP onto polycarbonate templates. X-ray diffraction, scanning electron microscopy, and high-resolution transmission electron microscopy confirmed the quality of the [...] Read more.

Ordered CoNiP nanowires with the same length of 4 µm and varying diameters (d = 100 nm–600 nm) were fabricated by electrodeposition of CoNiP onto polycarbonate templates. X-ray diffraction, scanning electron microscopy, and high-resolution transmission electron microscopy confirmed the quality of the fabricated nanowires. Magnetic measurements and theoretical analysis revealed that the magnetization reversal and magnetic anisotropy were significantly influenced by varying of the diameters of the nanowires. There existed a critical wire diameter (d_c ≈ 276 nm), below which the magnetization reversal occurred via a coherent rotation mode, and above which the magnetization reversal occurred via a curling rotation mode. The easy axis of the magnetization tended to change in direction from parallel to perpendicular with respect to the wire axis as the wire diameter exceeded d_c ≈ 276 nm. With increasing wire diameter, the coercive field (H_c) and the remanent to saturation magnetization ratio (M_r/M_s) were also found to rapidly decrease in the range d = 100–400 nm and gradually decrease for d > 400 nm. Full article

(This article belongs to the Special Issue Functional Nanomaterials and Devices for Biomedical Engineering and Sensing Applications' Papers Selected from the Energy Materials Nanotechnology (EMN) Fall Meeting, November 22–25, 2014, Orlando, USA)

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13 pages, 1215 KiB

Open AccessArticle

Use of a Modified Vector Model for Odor Intensity Prediction of Odorant Mixtures

by Luchun Yan, Jiemin Liu^* and Di Fang

School of Chemistry and Biological Engineering, University of Science and Technology Beijing, Xueyuan Road 30, Haidian District, Beijing 100083, China

Sensors 2015, 15(3), 5697-5709; https://doi.org/10.3390/s150305697 - 9 Mar 2015

Cited by 30 | Viewed by 6392

Abstract

Odor intensity (OI) indicates the perceived intensity of an odor by the human nose, and it is usually rated by specialized assessors. In order to avoid restrictions on assessor participation in OI evaluations, the Vector Model which calculates the OI of a mixture [...] Read more.

Odor intensity (OI) indicates the perceived intensity of an odor by the human nose, and it is usually rated by specialized assessors. In order to avoid restrictions on assessor participation in OI evaluations, the Vector Model which calculates the OI of a mixture as the vector sum of its unmixed components’ odor intensities was modified. Based on a detected linear relation between the OI and the logarithm of odor activity value (OAV—a ratio between chemical concentration and odor threshold) of individual odorants, OI of the unmixed component was replaced with its corresponding logarithm of OAV. The interaction coefficient (cosα) which represented the degree of interaction between two constituents was also measured in a simplified way. Through a series of odor intensity matching tests for binary, ternary and quaternary odor mixtures, the modified Vector Model provided an effective way of relating the OI of an odor mixture with the lnOAV values of its constituents. Thus, OI of an odor mixture could be directly predicted by employing the modified Vector Model after usual quantitative analysis. Besides, it was considered that the modified Vector Model was applicable for odor mixtures which consisted of odorants with the same chemical functional groups and similar molecular structures. Full article

(This article belongs to the Section Chemical Sensors)

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12 pages, 3192 KiB

Open AccessArticle

Optical Sensing of the Fatigue Damage State of CFRP under Realistic Aeronautical Load Sequences

by Pablo Zuluaga-Ramírez^1,2,*, Álvaro Arconada², Malte Frövel¹, Tomás Belenguer¹ and Félix Salazar²

¹ Instituto Nacional de Técnica Aeroespacial (INTA), Carretera de Ajalvir Km 4, 28850 Torrejón de Ardoz, Spain

² Department of Applied Physics, ETSI Minas, Universidad Politécnica de Madrid, C/Ríos Rosas 21, 28003 Madrid, Spain

Sensors 2015, 15(3), 5710-5721; https://doi.org/10.3390/s150305710 - 9 Mar 2015

Cited by 8 | Viewed by 5710

Abstract

We present an optical sensing methodology to estimate the fatigue damage state of structures made of carbon fiber reinforced polymer (CFRP), by measuring variations on the surface roughness. Variable amplitude loads (VAL), which represent realistic loads during aeronautical missions of fighter aircraft (FALSTAFF) [...] Read more.

We present an optical sensing methodology to estimate the fatigue damage state of structures made of carbon fiber reinforced polymer (CFRP), by measuring variations on the surface roughness. Variable amplitude loads (VAL), which represent realistic loads during aeronautical missions of fighter aircraft (FALSTAFF) have been applied to coupons until failure. Stiffness degradation and surface roughness variations have been measured during the life of the coupons obtaining a Pearson correlation of 0.75 between both variables. The data were compared with a previous study for Constant Amplitude Load (CAL) obtaining similar results. Conclusions suggest that the surface roughness measured in strategic zones is a useful technique for structural health monitoring of CFRP structures, and that it is independent of the type of load applied. Surface roughness can be measured in the field by optical techniques such as speckle, confocal perfilometers and interferometry, among others. Full article

(This article belongs to the Special Issue Novel Sensors for Non-Destructive Testing and Structural Health Monitoring)

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25 pages, 2224 KiB

Open AccessArticle

A Performance Improvement Method for Low-Cost Land Vehicle GPS/MEMS-INS Attitude Determination

by Li Cong^1,*, Ercui Li¹, Honglei Qin¹, Keck Voon Ling² and Rui Xue¹

¹ School of Electronic and Information Engineering, Beihang University, 37 Xueyuan Road, Haidian District, Beijing 100191, China

² School of Electrical and Electronic Engineering, Nanyang Technological University, 50 Nangyang Avenue 639798, Singapore

Sensors 2015, 15(3), 5722-5746; https://doi.org/10.3390/s150305722 - 9 Mar 2015

Cited by 42 | Viewed by 7645

Abstract

Global positioning system (GPS) technology is well suited for attitude determination. However, in land vehicle application, low-cost single frequency GPS receivers which have low measurement quality are often used, and external factors such as multipath and low satellite visibility in the densely built-up [...] Read more.

Global positioning system (GPS) technology is well suited for attitude determination. However, in land vehicle application, low-cost single frequency GPS receivers which have low measurement quality are often used, and external factors such as multipath and low satellite visibility in the densely built-up urban environment further degrade the quality of the GPS measurements. Due to the low-quality receivers used and the challenging urban environment, the success rate of the single epoch ambiguity resolution for dynamic attitude determination is usually quite low. In this paper, a micro-electro-mechanical system (MEMS)—inertial navigation system (INS)-aided ambiguity resolution method is proposed to improve the GPS attitude determination performance, which is particularly suitable for land vehicle attitude determination. First, the INS calculated baseline vector is augmented with the GPS carrier phase and code measurements. This improves the ambiguity dilution of precision (ADOP), resulting in better quality of the unconstrained float solution. Second, the undesirable float solutions caused by large measurement errors are further filtered and replaced using the INS-aided ambiguity function method (AFM). The fixed solutions are then obtained by the constrained least squares ambiguity decorrelation (CLAMBDA) algorithm. Finally, the GPS/MEMS-INS integration is realized by the use of a Kalman filter. Theoretical analysis of the ADOP is given and experimental results demonstrate that our proposed method can significantly improve the quality of the float ambiguity solution, leading to high success rate and better accuracy of attitude determination. Full article

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

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16 pages, 13934 KiB

Open AccessArticle

Sensor-Based Auto-Focusing System Using Multi-Scale Feature Extraction and Phase Correlation Matching

by Jinbeum Jang¹, Yoonjong Yoo¹, Jongheon Kim² and Joonki Paik^1,*

¹ Image Processing and Intelligent System Laboratory Graduate School of Advanced Imaging Science, and Film Chung-Ang University, Seoul 156-756, Korea

² Digital Design Team, SK Hynix, Gyeonggi-do 463-844, Korea

Sensors 2015, 15(3), 5747-5762; https://doi.org/10.3390/s150305747 - 10 Mar 2015

Cited by 40 | Viewed by 14637

Abstract

This paper presents a novel auto-focusing system based on a CMOS sensor containing pixels with different phases. Robust extraction of features in a severely defocused image is the fundamental problem of a phase-difference auto-focusing system. In order to solve this problem, a multi-resolution [...] Read more.

This paper presents a novel auto-focusing system based on a CMOS sensor containing pixels with different phases. Robust extraction of features in a severely defocused image is the fundamental problem of a phase-difference auto-focusing system. In order to solve this problem, a multi-resolution feature extraction algorithm is proposed. Given the extracted features, the proposed auto-focusing system can provide the ideal focusing position using phase correlation matching. The proposed auto-focusing (AF) algorithm consists of four steps: (i) acquisition of left and right images using AF points in the region-of-interest; (ii) feature extraction in the left image under low illumination and out-of-focus blur; (iii) the generation of two feature images using the phase difference between the left and right images; and (iv) estimation of the phase shifting vector using phase correlation matching. Since the proposed system accurately estimates the phase difference in the out-of-focus blurred image under low illumination, it can provide faster, more robust auto focusing than existing systems. Full article

(This article belongs to the Section Physical Sensors)

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20 pages, 3206 KiB

Open AccessArticle

DCPVP: Distributed Clustering Protocol Using Voting and Priority for Wireless Sensor Networks

by Hooman Hematkhah and Yousef S. Kavian^*

Faculty of Engineering, Shahid Chamran University of Ahvaz, Ahvaz 61639, Iran

Sensors 2015, 15(3), 5763-5782; https://doi.org/10.3390/s150305763 - 10 Mar 2015

Cited by 14 | Viewed by 6159

Abstract

This paper presents a new clustering protocol for designing energy-efficient hierarchical wireless sensor networks (WSNs) by dividing the distributed sensor network into virtual sensor groups to satisfy the scalability and prolong the network lifetime in large-scale applications. The proposed approach is a distributed [...] Read more.

This paper presents a new clustering protocol for designing energy-efficient hierarchical wireless sensor networks (WSNs) by dividing the distributed sensor network into virtual sensor groups to satisfy the scalability and prolong the network lifetime in large-scale applications. The proposed approach is a distributed clustering protocol called DCPVP, which is based on voting and priority ideas. In the DCPVP protocol, the size of clusters is based on the distance of nodes from the data link such as base station (BS) and the local node density. The cluster heads are elected based on the mean distance from neighbors, remaining energy and the times of being elected as cluster head. The performance of the DCPVP protocol is compared with some well-known clustering protocols in literature such as the LEACH, HEED, WCA, GCMRA and TCAC protocols. The simulation results confirm that the prioritizing- and voting-based election ideas decrease the construction time and the energy consumption of clustering progress in sensor networks and consequently improve the lifetime of networks with limited resources and battery powered nodes in harsh and inaccessible environments. Full article

(This article belongs to the Section Sensor Networks)

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20 pages, 2507 KiB

Open AccessArticle

Tightly Coupled Integration of Ionosphere-Constrained Precise Point Positioning and Inertial Navigation Systems

by Zhouzheng Gao^1,2,3, Hongping Zhang^2,*, Maorong Ge³, Xiaoji Niu², Wenbin Shen¹, Jens Wickert³

and Harald Schuh³

¹ School of Geodesy and Geomatics, Wuhan University, 129 Luoyu Road, Wuhan 430079, China

² GNSS Research Center, Wuhan University, 129 Luoyu Road, Wuhan 430079, China

³ German Research Centre for Geosciences (GFZ), Telegrafenberg, Potsdam 14473, Germany

Sensors 2015, 15(3), 5783-5802; https://doi.org/10.3390/s150305783 - 10 Mar 2015

Cited by 33 | Viewed by 8211

Abstract

The continuity and reliability of precise GNSS positioning can be seriously limited by severe user observation environments. The Inertial Navigation System (INS) can overcome such drawbacks, but its performance is clearly restricted by INS sensor errors over time. Accordingly, the tightly coupled integration [...] Read more.

The continuity and reliability of precise GNSS positioning can be seriously limited by severe user observation environments. The Inertial Navigation System (INS) can overcome such drawbacks, but its performance is clearly restricted by INS sensor errors over time. Accordingly, the tightly coupled integration of GPS and INS can overcome the disadvantages of each individual system and together form a new navigation system with a higher accuracy, reliability and availability. Recently, ionosphere-constrained (IC) precise point positioning (PPP) utilizing raw GPS observations was proven able to improve both the convergence and positioning accuracy of the conventional PPP using ionosphere-free combined observations (LC-PPP). In this paper, a new mode of tightly coupled integration, in which the IC-PPP instead of LC-PPP is employed, is implemented to further improve the performance of the coupled system. We present the detailed mathematical model and the related algorithm of the new integration of IC-PPP and INS. To evaluate the performance of the new tightly coupled integration, data of both airborne and vehicle experiments with a geodetic GPS receiver and tactical grade inertial measurement unit are processed and the results are analyzed. The statistics show that the new approach can further improve the positioning accuracy compared with both IC-PPP and the tightly coupled integration of the conventional PPP and INS. Full article

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

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17 pages, 4773 KiB

Open AccessArticle

Fracture of Human Femur Tissue Monitored by Acoustic Emission Sensors

by Dimitrios. G. Aggelis^1,*

, Maria Strantza^1,†, Olivia Louis^2,†, Frans Boulpaep^1,†, Demosthenes Polyzos^3,† and Danny Van Hemelrijck^1,†

¹ Department of Mechanics of Materials and Constructions, Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussels, Belgium

² Department of Radiology, UZ Brussel, Vrije Universiteit Brussel, Laarbeeklaan 101, 1090 Brussels, Belgium

³ Department of Mechanical Engineering and Aeronautics, University of Patras, Panepistimioupolis Rion, 26500 Patra, Greece

^† These authors contributed equally to this work.

Sensors 2015, 15(3), 5803-5819; https://doi.org/10.3390/s150305803 - 10 Mar 2015

Cited by 22 | Viewed by 7677

Abstract

The study describes the acoustic emission (AE) activity during human femur tissue fracture. The specimens were fractured in a bending-torsion loading pattern with concurrent monitoring by two AE sensors. The number of recorded signals correlates well with the applied load providing the onset [...] Read more.

The study describes the acoustic emission (AE) activity during human femur tissue fracture. The specimens were fractured in a bending-torsion loading pattern with concurrent monitoring by two AE sensors. The number of recorded signals correlates well with the applied load providing the onset of micro-fracture at approximately one sixth of the maximum load. Furthermore, waveform frequency content and rise time are related to the different modes of fracture (bending of femur neck or torsion of diaphysis). The importance of the study lies mainly in two disciplines. One is that, although femurs are typically subjects of surgical repair in humans, detailed monitoring of the fracture with AE will enrich the understanding of the process in ways that cannot be achieved using only the mechanical data. Additionally, from the point of view of monitoring techniques, applying sensors used for engineering materials and interpreting the obtained data pose additional difficulties due to the uniqueness of the bone structure. Full article

(This article belongs to the Section Physical Sensors)

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45 pages, 2279 KiB

Open AccessArticle

Fortified Anonymous Communication Protocol for Location Privacy in WSN: A Modular Approach

by Abdel-Shakour Abuzneid^1,*, Tarek Sobh¹

, Miad Faezipour¹

, Ausif Mahmood¹ and John James²

¹ Computer Science and Engineering Department, University of Bridgeport, Bridgeport, CT 06604, USA

² Department of Electrical Engineering & Computer Science, United States Military Academy, West Point, NY 10996, USA

Sensors 2015, 15(3), 5820-5864; https://doi.org/10.3390/s150305820 - 10 Mar 2015

Cited by 18 | Viewed by 6740

Abstract

Wireless sensor network (WSN) consists of many hosts called sensors. These sensors can sense a phenomenon (motion, temperature, humidity, average, max, min, etc.) and represent what they sense in a form of data. There are many applications for WSNs including object tracking [...] Read more.

Wireless sensor network (WSN) consists of many hosts called sensors. These sensors can sense a phenomenon (motion, temperature, humidity, average, max, min, etc.) and represent what they sense in a form of data. There are many applications for WSNs including object tracking and monitoring where in most of the cases these objects need protection. In these applications, data privacy itself might not be as important as the privacy of source location. In addition to the source location privacy, sink location privacy should also be provided. Providing an efficient end-to-end privacy solution would be a challenging task to achieve due to the open nature of the WSN. The key schemes needed for end-to-end location privacy are anonymity, observability, capture likelihood, and safety period. We extend this work to allow for countermeasures against multi-local and global adversaries. We present a network model protected against a sophisticated threat model: passive /active and local/multi-local/global attacks. This work provides a solution for end-to-end anonymity and location privacy as well. We will introduce a framework called fortified anonymous communication (FAC) protocol for WSN. Full article

(This article belongs to the Section Sensor Networks)

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19 pages, 1174 KiB

Open AccessArticle

Accurate Calibration and Uncertainty Estimation of the Normal Spring Constant of Various AFM Cantilevers

by Yunpeng Song, Sen Wu, Linyan Xu^* and Xing Fu

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

Sensors 2015, 15(3), 5865-5883; https://doi.org/10.3390/s150305865 - 10 Mar 2015

Cited by 21 | Viewed by 8669

Abstract

Measurement of force on a micro- or nano-Newton scale is important when exploring the mechanical properties of materials in the biophysics and nanomechanical fields. The atomic force microscope (AFM) is widely used in microforce measurement. The cantilever probe works as an AFM force [...] Read more.

Measurement of force on a micro- or nano-Newton scale is important when exploring the mechanical properties of materials in the biophysics and nanomechanical fields. The atomic force microscope (AFM) is widely used in microforce measurement. The cantilever probe works as an AFM force sensor, and the spring constant of the cantilever is of great significance to the accuracy of the measurement results. This paper presents a normal spring constant calibration method with the combined use of an electromagnetic balance and a homemade AFM head. When the cantilever presses the balance, its deflection is detected through an optical lever integrated in the AFM head. Meanwhile, the corresponding bending force is recorded by the balance. Then the spring constant can be simply calculated using Hooke’s law. During the calibration, a feedback loop is applied to control the deflection of the cantilever. Errors that may affect the stability of the cantilever could be compensated rapidly. Five types of commercial cantilevers with different shapes, stiffness, and operating modes were chosen to evaluate the performance of our system. Based on the uncertainty analysis, the expanded relative standard uncertainties of the normal spring constant of most measured cantilevers are believed to be better than 2%. Full article

(This article belongs to the Section Physical Sensors)

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11 pages, 1289 KiB

Open AccessArticle

Study of the Interaction of Trastuzumab and SKOV3 Epithelial Cancer Cells Using a Quartz Crystal Microbalance Sensor

by Louise Elmlund¹, Camilla Käck², Teodor Aastrup² and Ian A. Nicholls^1,3,*

¹ Bioorganic & Biophysical Chemistry Laboratory, Linnæus University Centre for Biomaterials Chemistry, Department of Chemistry & Biomedical Sciences, Linnæus University, SE-39182 Kalmar, Sweden

² Attana AB, Björnnäsvägen 21, SE-11419 Stockholm, Sweden

³ Department of Chemistry–BMC, Uppsala University, Box 576, SE-75123 Uppsala, Sweden

Sensors 2015, 15(3), 5884-5894; https://doi.org/10.3390/s150305884 - 10 Mar 2015

Cited by 27 | Viewed by 8565

Abstract

Analytical methods founded upon whole cell-based assays are of importance in early stage drug development and in fundamental studies of biomolecular recognition. Here we have studied the binding of the monoclonal antibody trastuzumab to human epidermal growth factor receptor 2 (HER2) on human [...] Read more.

Analytical methods founded upon whole cell-based assays are of importance in early stage drug development and in fundamental studies of biomolecular recognition. Here we have studied the binding of the monoclonal antibody trastuzumab to human epidermal growth factor receptor 2 (HER2) on human ovary adenocarcinoma epithelial cancer cells (SKOV3) using quartz crystal microbalance (QCM) technology. An optimized procedure for immobilizing the cells on the chip surface was established with respect to fixation procedure and seeding density. Trastuzumab binding to the cell decorated sensor surface was studied, revealing a mean dissociation constant, K_D, value of 7 ± 1 nM (standard error of the mean). This study provides a new perspective on the affinity of the antibody-receptor complex presented a more natural context compared to purified receptors. These results demonstrate the potential for using whole cell-based QCM assay in drug development, the screening of HER2 selective antibody-based drug candidates, and for the study of biomolecular recognition. This real time, label free approach for studying interactions with target receptors present in their natural environment afforded sensitive and detailed kinetic information about the binding of the analyte to the target. Full article

(This article belongs to the Special Issue Mass-Sensitive Sensors Based on Biomimetic Recognition)

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19 pages, 7048 KiB

Open AccessArticle

An Evaluation of Skylight Polarization Patterns for Navigation

by Tao Ma, Xiaoping Hu^*, Lilian Zhang, Junxiang Lian, Xiaofeng He, Yujie Wang and Zhiwen Xian

College of Mechatronic Engineering and Automation, National University of Defense Technology, Changsha 410073, Hunan, China

Sensors 2015, 15(3), 5895-5913; https://doi.org/10.3390/s150305895 - 10 Mar 2015

Cited by 45 | Viewed by 9005

Abstract

Skylight polarization provides a significant navigation cue for certain polarization-sensitive animals. However, the precision of the angle of polarization (AOP) of skylight for vehicle orientation is not clear. An evaluation of AOP must be performed before it is utilized. This paper reports an [...] Read more.

Skylight polarization provides a significant navigation cue for certain polarization-sensitive animals. However, the precision of the angle of polarization (AOP) of skylight for vehicle orientation is not clear. An evaluation of AOP must be performed before it is utilized. This paper reports an evaluation of AOP of skylight by measuring the skylight polarization patterns of clear and cloudy skies using a full-sky imaging polarimetry system. AOP measurements of skylight are compared with the pattern calculated by the single-scattering Rayleigh model and these differences are quantified. The relationship between the degree of polarization (DOP) and the deviation of AOP of skylight is thoroughly studied. Based on these, a solar meridian extracted method is presented. The results of experiments reveal that the DOP is a key parameter to indicate the accuracy of AOP measurements, and all the output solar meridian orientations extracted by our method in both clear and cloudy skies can achieve a high accuracy for vehicle orientation. Full article

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

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21 pages, 889 KiB

Open AccessArticle

Proactive and Reactive Transmission Power Control for Energy-Efficient On-Body Communications

by Mónica Vallejo^1,*, Joaquín Recas² and José L. Ayala²

¹ Facultad de Minas, Departamento de Energía Eléctrica y Automática, Gaunal, Universidad Nacional de Colombia, Medellín, Carrera 80 No.65-223, Núcleo Robledo, Medellín, 4-72, Colombia

² Department of Computer Architecture and Automation, Complutense University of Madrid, C/ Profesor José García Santesmases, Madrid s/n. 28040, Spain

Sensors 2015, 15(3), 5914-5934; https://doi.org/10.3390/s150305914 - 11 Mar 2015

Cited by 8 | Viewed by 7388

Abstract

In wireless body sensor network (WBSNs), the human body has an important effect on the performance of the communication due to the temporal variations caused and the attenuation and fluctuation of the path loss. This fact suggests that the transmission power must adapt [...] Read more.

In wireless body sensor network (WBSNs), the human body has an important effect on the performance of the communication due to the temporal variations caused and the attenuation and fluctuation of the path loss. This fact suggests that the transmission power must adapt to the current state of the link in a way that it ensures a balance between energy consumption and packet loss. In this paper, we validate our two transmission power level policies (reactive and predictive approaches) using the Castalia simulator. The integration of our experimental measurements in the simulator allows us to easily evaluate complex scenarios, avoiding the difficulties associated with a practical realization. Our results show that both schemes perform satisfactorily, providing overall energy savings of 24% and 22% for a case of study, as compared to the maximum transmission power mode. Full article

(This article belongs to the Section Sensor Networks)

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47 pages, 17328 KiB

Open AccessArticle

A New Gaze Estimation Method Considering External Light

by Jong Man Lee¹, Hyeon Chang Lee¹, Su Yeong Gwon¹, Dongwook Jung¹, Weiyuan Pan¹, Chul Woo Cho¹, Kang Ryoung Park^1,*, Hyun-Cheol Kim² and Jihun Cha²

¹ Division of Electronics and Electrical Engineering, Dongguk University, 26 Pil-dong 3-ga, Jung-gu, Seoul 100-715, Korea

² Electronics and Telecommunications Research Institute, 218 Gajeong-ro, Yuseong-gu, Daejeon 305-700, Korea

Sensors 2015, 15(3), 5935-5981; https://doi.org/10.3390/s150305935 - 11 Mar 2015

Cited by 4 | Viewed by 6664

Abstract

Gaze tracking systems usually utilize near-infrared (NIR) lights and NIR cameras, and the performance of such systems is mainly affected by external light sources that include NIR components. This is ascribed to the production of additional (imposter) corneal specular reflection (SR) caused by [...] Read more.

Gaze tracking systems usually utilize near-infrared (NIR) lights and NIR cameras, and the performance of such systems is mainly affected by external light sources that include NIR components. This is ascribed to the production of additional (imposter) corneal specular reflection (SR) caused by the external light, which makes it difficult to discriminate between the correct SR as caused by the NIR illuminator of the gaze tracking system and the imposter SR. To overcome this problem, a new method is proposed for determining the correct SR in the presence of external light based on the relationship between the corneal SR and the pupil movable area with the relative position of the pupil and the corneal SR. The experimental results showed that the proposed method makes the gaze tracking system robust to the existence of external light. Full article

(This article belongs to the Section Physical Sensors)

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27 pages, 3523 KiB

Open AccessArticle

Comparison of the Detection Characteristics of Trace Species Using Laser-Induced Breakdown Spectroscopy and Laser Breakdown Time-of-Flight Mass Spectrometry

by Zhenzhen Wang^1,2, Yoshihiro Deguchi^2,*, Junjie Yan¹ and Jiping Liu¹

¹ State Key Laboratory of Multiphase Flow in Power Engineering, Xi'an Jiaotong University, No.28, Xianning West Road, Xi'an 710049, China

² Graduate School of Advanced Technology and Science, the University of Tokushima, 2-1, Minamijyosanjima, Tokushima 770-8506, Japan

Sensors 2015, 15(3), 5982-6008; https://doi.org/10.3390/s150305982 - 11 Mar 2015

Cited by 15 | Viewed by 8635

Abstract

The rapid and precise element measurement of trace species, such as mercury, iodine, strontium, cesium, etc. is imperative for various applications, especially for industrial needs. The elements mercury and iodine were measured by two detection methods for comparison of the corresponding detection features. [...] Read more.

The rapid and precise element measurement of trace species, such as mercury, iodine, strontium, cesium, etc. is imperative for various applications, especially for industrial needs. The elements mercury and iodine were measured by two detection methods for comparison of the corresponding detection features. A laser beam was focused to induce plasma. Emission and ion signals were detected using laser-induced breakdown spectroscopy (LIBS) and laser breakdown time-of-flight mass spectrometry (LB-TOFMS). Multi-photon ionization and electron impact ionization in the plasma generation process can be controlled by the pressure and pulse width. The effect of electron impact ionization on continuum emission, coexisting molecular and atomic emissions became weakened in low pressure condition. When the pressure was less than 1 Pa, the plasma was induced by laser dissociation and multi-photon ionization in LB-TOFMS. According to the experimental results, the detection limits of mercury and iodine in N₂ were 3.5 ppb and 60 ppb using low pressure LIBS. The mercury and iodine detection limits using LB-TOFMS were 1.2 ppb and 9.0 ppb, which were enhanced due to different detection features. The detection systems of LIBS and LB-TOFMS can be selected depending on the condition of each application. Full article

(This article belongs to the Special Issue Modern Technologies for Sensing Pollution in Air, Water, and Soil)

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24 pages, 1518 KiB

Open AccessArticle

Color Filtering Localization for Three-Dimensional Underwater Acoustic Sensor Networks

by Zhihua Liu¹, Han Gao², Wuling Wang¹, Shuai Chang² and Jiaxing Chen^2,*

¹ College of Information Technology, Hebei Normal University, Shijiazhuang 050024, China

² College of Mathematics and Information Science, Hebei Normal University, Shijiazhuang 050024, China

Sensors 2015, 15(3), 6009-6032; https://doi.org/10.3390/s150306009 - 12 Mar 2015

Cited by 19 | Viewed by 6344

Abstract

Accurate localization of mobile nodes has been an important and fundamental problem in underwater acoustic sensor networks (UASNs). The detection information returned from a mobile node is meaningful only if its location is known. In this paper, we propose two localization algorithms based [...] Read more.

Accurate localization of mobile nodes has been an important and fundamental problem in underwater acoustic sensor networks (UASNs). The detection information returned from a mobile node is meaningful only if its location is known. In this paper, we propose two localization algorithms based on color filtering technology called PCFL and ACFL. PCFL and ACFL aim at collaboratively accomplishing accurate localization of underwater mobile nodes with minimum energy expenditure. They both adopt the overlapping signal region of task anchors which can communicate with the mobile node directly as the current sampling area. PCFL employs the projected distances between each of the task projections and the mobile node, while ACFL adopts the direct distance between each of the task anchors and the mobile node. The proportion factor of distance is also proposed to weight the RGB values. By comparing the nearness degrees of the RGB sequences between the samples and the mobile node, samples can be filtered out. The normalized nearness degrees are considered as the weighted standards to calculate the coordinates of the mobile nodes. The simulation results show that the proposed methods have excellent localization performance and can localize the mobile node in a timely way. The average localization error of PCFL is decreased by about 30.4% compared to the AFLA method. Full article

(This article belongs to the Special Issue Wireless Sensor Networks and the Internet of Things)

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33 pages, 8536 KiB

Open AccessArticle

Omnidirectional Underwater Camera Design and Calibration

by Josep Bosch^*

, Nuno Gracias

, Pere Ridao and David Ribas

Computer Vision and Robotics Group, Centre d’Investigació en Robòtica Submarina, Parc Científic i Tecnològic, Universitat de Girona, 17003 Girona, Spain

Sensors 2015, 15(3), 6033-6065; https://doi.org/10.3390/s150306033 - 12 Mar 2015

Cited by 39 | Viewed by 10506

Abstract

This paper presents the development of an underwater omnidirectional multi-camera system (OMS) based on a commercially available six-camera system, originally designed for land applications. A full calibration method is presented for the estimation of both the intrinsic and extrinsic parameters, which is able [...] Read more.

This paper presents the development of an underwater omnidirectional multi-camera system (OMS) based on a commercially available six-camera system, originally designed for land applications. A full calibration method is presented for the estimation of both the intrinsic and extrinsic parameters, which is able to cope with wide-angle lenses and non-overlapping cameras simultaneously. This method is valid for any OMS in both land or water applications. For underwater use, a customized housing is required, which often leads to strong image distortion due to refraction among the different media. This phenomena makes the basic pinhole camera model invalid for underwater cameras, especially when using wide-angle lenses, and requires the explicit modeling of the individual optical rays. To address this problem, a ray tracing approach has been adopted to create a field-of-view (FOV) simulator for underwater cameras. The simulator allows for the testing of different housing geometries and optics for the cameras to ensure a complete hemisphere coverage in underwater operation. This paper describes the design and testing of a compact custom housing for a commercial off-the-shelf OMS camera (Ladybug 3) and presents the first results of its use. A proposed three-stage calibration process allows for the estimation of all of the relevant camera parameters. Experimental results are presented, which illustrate the performance of the calibration method and validate the approach. Full article

(This article belongs to the Section Physical Sensors)

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25 pages, 1120 KiB

Open AccessArticle

Data Fault Detection in Medical Sensor Networks

by Yang Yang^*, Qian Liu, Zhipeng Gao, Xuesong Qiu and Luoming Meng

State Key Laboratory of Networking and Switching Technology, Beijing University of Posts and Telecommunications, No.10 Xitucheng Road, Haidian District, Beijing 100876, China

Sensors 2015, 15(3), 6066-6090; https://doi.org/10.3390/s150306066 - 12 Mar 2015

Cited by 24 | Viewed by 5875

Abstract

Medical body sensors can be implanted or attached to the human body to monitor the physiological parameters of patients all the time. Inaccurate data due to sensor faults or incorrect placement on the body will seriously influence clinicians’ diagnosis, therefore detecting sensor data [...] Read more.

Medical body sensors can be implanted or attached to the human body to monitor the physiological parameters of patients all the time. Inaccurate data due to sensor faults or incorrect placement on the body will seriously influence clinicians’ diagnosis, therefore detecting sensor data faults has been widely researched in recent years. Most of the typical approaches to sensor fault detection in the medical area ignore the fact that the physiological indexes of patients aren’t changing synchronously at the same time, and fault values mixed with abnormal physiological data due to illness make it difficult to determine true faults. Based on these facts, we propose a Data Fault Detection mechanism in Medical sensor networks (DFD-M). Its mechanism includes: (1) use of a dynamic-local outlier factor (D-LOF) algorithm to identify outlying sensed data vectors; (2) use of a linear regression model based on trapezoidal fuzzy numbers to predict which readings in the outlying data vector are suspected to be faulty; (3) the proposal of a novel judgment criterion of fault state according to the prediction values. The simulation results demonstrate the efficiency and superiority of DFD-M. Full article

(This article belongs to the Section Sensor Networks)

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14 pages, 8153 KiB

Open AccessArticle

Low-Cost Photolithographic Fabrication of Nanowires and Microfilters for Advanced Bioassay Devices

by Nhi M. Doan^1,†, Liangliang Qiang^1,†, Zhe Li¹, Santhisagar Vaddiraju^1,2, Gregory W. Bishop³, James F. Rusling^3,4,5,6

and Fotios Papadimitrakopoulos^1,3,4,*

¹ Nanomaterials Optoelectronics Laboratory, Polymer Program, University of Connecticut, Storrs, CT 06269, USA

² Biorasis Inc., 23 Fellen Road, Storrs, CT 06268, USA

³ Department of Chemistry, University of Connecticut, Storrs, CT 06269, USA

⁴ Institute of Materials Science, University of Connecticut, Storrs, CT 06269, USA

⁵ Department of Cell Biology, University of Connecticut Health Center, Farmington, CT 062032, USA

⁶ School of Chemistry, National University of Ireland, Galway, Ireland

^† These authors contributed equally to this work.

Sensors 2015, 15(3), 6091-6104; https://doi.org/10.3390/s150306091 - 12 Mar 2015

Cited by 7 | Viewed by 8741

Abstract

Integrated microfluidic devices with nanosized array electrodes and microfiltration capabilities can greatly increase sensitivity and enhance automation in immunoassay devices. In this contribution, we utilize the edge-patterning method of thin aluminum (Al) films in order to form nano- to micron-sized gaps. Evaporation of [...] Read more.

Integrated microfluidic devices with nanosized array electrodes and microfiltration capabilities can greatly increase sensitivity and enhance automation in immunoassay devices. In this contribution, we utilize the edge-patterning method of thin aluminum (Al) films in order to form nano- to micron-sized gaps. Evaporation of high work-function metals (i.e., Au, Ag, etc.) on these gaps, followed by Al lift-off, enables the formation of electrical uniform nanowires from low-cost, plastic-based, photomasks. By replacing Al with chromium (Cr), the formation of high resolution, custom-made photomasks that are ideal for low-cost fabrication of a plurality of array devices were realized. To demonstrate the feasibility of such Cr photomasks, SU-8 micro-pillar masters were formed and replicated into PDMS to produce micron-sized filters with 3–4 µm gaps and an aspect ratio of 3. These microfilters were capable of retaining 6 µm beads within a localized site, while allowing solvent flow. The combination of nanowire arrays and micro-pillar filtration opens new perspectives for rapid R&D screening of various microfluidic-based immunoassay geometries, where analyte pre-concentration and highly sensitive, electrochemical detection can be readily co-localized. Full article

(This article belongs to the Special Issue Electrochemical Sensors and Biosensors: From Bench-Top to Point-of-Care)

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28 pages, 1216 KiB

Open AccessArticle

In-Network Processing of an Iceberg Join Query in Wireless Sensor Networks Based on 2-Way Fragment Semijoins

by Hyunchul Kang

School of Computer Science and Engineering, Chung-Ang University, Seoul 156-756, Korea

Sensors 2015, 15(3), 6105-6132; https://doi.org/10.3390/s150306105 - 12 Mar 2015

Cited by 3 | Viewed by 4765

Abstract

We investigate the in-network processing of an iceberg join query in wireless sensor networks (WSNs). An iceberg join is a special type of join where only those joined tuples whose cardinality exceeds a certain threshold (called iceberg threshold) are qualified for the result. [...] Read more.

We investigate the in-network processing of an iceberg join query in wireless sensor networks (WSNs). An iceberg join is a special type of join where only those joined tuples whose cardinality exceeds a certain threshold (called iceberg threshold) are qualified for the result. Processing such a join involves the value matching for the join predicate as well as the checking of the cardinality constraint for the iceberg threshold. In the previous scheme, the value matching is carried out as the main task for filtering non-joinable tuples while the iceberg threshold is treated as an additional constraint. We take an alternative approach, meeting the cardinality constraint first and matching values next. In this approach, with a logical fragmentation of the join operand relations on the aggregate counts of the joining attribute values, the optimal sequence of 2-way fragment semijoins is generated, where each fragment semijoin employs a Bloom filter as a synopsis of the joining attribute values. This sequence filters non-joinable tuples in an energy-efficient way in WSNs. Through implementation and a set of detailed experiments, we show that our alternative approach considerably outperforms the previous one. Full article

(This article belongs to the Section Sensor Networks)

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19 pages, 1347 KiB

Open AccessArticle

Validation of Five Minimally Obstructive Methods to Estimate Physical Activity Energy Expenditure in Young Adults in Semi-Standardized Settings

by Mikkel B. Schneller^1,2, Mogens T. Pedersen¹, Nidhi Gupta², Mette Aadahl³ and Andreas Holtermann^2,*

¹ Department of Nutrition, Exercise and Sports, University of Copenhagen, DK-2200 Copenhagen, Denmark

² National Research Centre for the Working Environment, DK-2100 Copenhagen, Denmark

³ Research Centre for Prevention and Health, the Capital Region of Denmark, Glostrup University Hospital, DK-2600 Glostrup, Denmark

Sensors 2015, 15(3), 6133-6151; https://doi.org/10.3390/s150306133 - 13 Mar 2015

Cited by 26 | Viewed by 7947

Abstract

We compared the accuracy of five objective methods, including two newly developed methods combining accelerometry and activity type recognition (Acti4), against indirect calorimetry, to estimate total energy expenditure (EE) of different activities in semi-standardized settings. Fourteen participants performed a standardized and semi-standardized protocol [...] Read more.

We compared the accuracy of five objective methods, including two newly developed methods combining accelerometry and activity type recognition (Acti4), against indirect calorimetry, to estimate total energy expenditure (EE) of different activities in semi-standardized settings. Fourteen participants performed a standardized and semi-standardized protocol including seven daily life activity types, while having their EE measured by indirect calorimetry. Simultaneously, physical activity was quantified by an ActivPAL³, two ActiGraph GT3X+’s and an Actiheart. EE was estimated by the standard ActivPAL³ software (ActivPAL), ActiGraph GT3X+ (ActiGraph) and Actiheart (Actiheart), and by a combination of activity type recognition via Acti4 software and activity counts per minute (CPM) of either a hip- or thigh-worn ActiGraph GT3X+ (AGhip + Acti4 and AGthigh + Acti4). At group level, estimated physical activities EE by Actiheart (MSE = 2.05) and AGthigh + Acti4 (MSE = 0.25) were not significantly different from measured EE by indirect calorimetry, while significantly underestimated by ActiGraph, ActivPAL and AGhip + Acti4. AGthigh + Acti4 and Actiheart explained 77% and 45%, of the individual variations in measured physical activity EE by indirect calorimetry, respectively. This study concludes that combining accelerometer data from a thigh-worn ActiGraph GT3X+ with activity type recognition improved the accuracy of activity specific EE estimation against indirect calorimetry in semi-standardized settings compared to previously validated methods using CPM only. Full article

(This article belongs to the Section Physical Sensors)

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22 pages, 1075 KiB

Open AccessArticle

Expected Improvements in the Quantitative Remote Sensing of Optically Complex Waters with the Use of an Optically Fast Hyperspectral Spectrometer—A Modeling Study

by Wesley J. Moses^*, Jeffrey H. Bowles and Michael R. Corson

Remote Sensing Division, Naval Research Laboratory, 4555 Overlook Ave. SW, Washington, DC 20375, USA

Sensors 2015, 15(3), 6152-6173; https://doi.org/10.3390/s150306152 - 13 Mar 2015

Cited by 23 | Viewed by 7037

Abstract

Using simulated data, we investigated the effect of noise in a spaceborne hyperspectral sensor on the accuracy of the atmospheric correction of at-sensor radiances and the consequent uncertainties in retrieved water quality parameters. Specifically, we investigated the improvement expected as the F-number of [...] Read more.

Using simulated data, we investigated the effect of noise in a spaceborne hyperspectral sensor on the accuracy of the atmospheric correction of at-sensor radiances and the consequent uncertainties in retrieved water quality parameters. Specifically, we investigated the improvement expected as the F-number of the sensor is changed from 3.5, which is the smallest among existing operational spaceborne hyperspectral sensors, to 1.0, which is foreseeable in the near future. With the change in F-number, the uncertainties in the atmospherically corrected reflectance decreased by more than 90% across the visible-near-infrared spectrum, the number of pixels with negative reflectance (caused by over-correction) decreased to almost one-third, and the uncertainties in the retrieved water quality parameters decreased by more than 50% and up to 92%. The analysis was based on the sensor model of the Hyperspectral Imager for the Coastal Ocean (HICO) but using a 30-m spatial resolution instead of HICO’s 96 m. Atmospheric correction was performed using Tafkaa. Water quality parameters were retrieved using a numerical method and a semi-analytical algorithm. The results emphasize the effect of sensor noise on water quality parameter retrieval and the need for sensors with high Signal-to-Noise Ratio for quantitative remote sensing of optically complex waters. Full article

(This article belongs to the Section Remote Sensors)

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22 pages, 2488 KiB

Open AccessArticle

Digital Control Analysis and Design of a Field-Sensed Magnetic Suspension System

by Jen-Hsing Li¹ and Juing-Shian Chiou^2,*

¹ Department of Electrical Engineering, Kun Shan University, 195 Kunda Road, Yongkang District, Tainan City 710, Taiwan

² Department of Electrical Engineering, Southern Taiwan University of Science and Technology, 1 Nan Ti Street, Yongkang District, Tainan City 710, Taiwan

Sensors 2015, 15(3), 6174-6195; https://doi.org/10.3390/s150306174 - 13 Mar 2015

Cited by 4 | Viewed by 7429

Abstract

Magnetic suspension systems are mechatronic systems and crucial in several engineering applications, such as the levitation of high-speed trains, frictionless bearings, and wind tunnels. Magnetic suspension systems are nonlinear and unstable systems; therefore, they are suitable educational benchmarks for testing various modeling and [...] Read more.

Magnetic suspension systems are mechatronic systems and crucial in several engineering applications, such as the levitation of high-speed trains, frictionless bearings, and wind tunnels. Magnetic suspension systems are nonlinear and unstable systems; therefore, they are suitable educational benchmarks for testing various modeling and control methods. This paper presents the digital modeling and control of magnetic suspension systems. First, the magnetic suspension system is stabilized using a digital proportional-derivative controller. Subsequently, the digital model is identified using recursive algorithms. Finally, a digital mixed linear quadratic regulator (LQR)/H∞ control is adopted to stabilize the magnetic suspension system robustly. Simulation examples and a real-world example are provided to demonstrate the practicality of the study results. In this study, a digital magnetic suspension system model was developed and reviewed. In addition, equivalent state and output feedback controls for magnetic suspension systems were developed. Using this method, the controller design for magnetic suspension systems was simplified, which is the novel contribution of this study. In addition, this paper proposes a complete digital controller design procedure for magnetic suspension systems. Full article

(This article belongs to the Special Issue Magnetic Sensor Device-Part 1)

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21 pages, 2694 KiB

Open AccessArticle

Evaluation and Intercomparison of MODIS and GEOV1 Global Leaf Area Index Products over Four Sites in North China

by Zhenwang Li

, Huan Tang, Baohui Zhang, Guixia Yang and Xiaoping Xin^*

National Hulunber Grassland Ecosystem Observation and Research Station, Institute of Agricultural Resources and Regional Planning, Chinese Academy of Agricultural Sciences, Beijing 100081, China

Sensors 2015, 15(3), 6196-6216; https://doi.org/10.3390/s150306196 - 13 Mar 2015

Cited by 20 | Viewed by 6116

Abstract

This study investigated the performances of the Moderate Resolution Imaging Spectroradiometer (MODIS) and GEOLAND2 Version 1 (GEOV1) Leaf Area Index (LAI) products using ground measurements and LAI reference maps over four sites in North China for 2011–2013. The Terra + Aqua MODIS and [...] Read more.

This study investigated the performances of the Moderate Resolution Imaging Spectroradiometer (MODIS) and GEOLAND2 Version 1 (GEOV1) Leaf Area Index (LAI) products using ground measurements and LAI reference maps over four sites in North China for 2011–2013. The Terra + Aqua MODIS and Terra MODIS LAI retrieved by the main algorithm and GEOV1 LAI within the valid range were evaluated and intercompared using LAI reference maps to assess their uncertainty and seasonal variability The results showed that GEOV1 LAI is the most similar product with the LAI reference maps (R² = 0.78 and RMSE = 0.59). The MODIS products performed well for biomes with low LAI values, but considerable uncertainty arose when the LAI was larger than 3. Terra + Aqua MODIS (R² = 0.72 and RMSE = 0.68) was slightly more accurate than Terra MODIS (R² = 0.57 and RMSE = 0.90) for producing slightly more successful observations. Both MODIS and GEOV1 products effectively followed the seasonal trajectory of the reference maps, and GEOV1 exhibited a smoother seasonal trajectory than MODIS. MODIS anomalies mainly occurred during summer and likely occurred because of surface reflectance uncertainty, shorter temporal resolutions and inconsistency between simulated and MODIS surface reflectances. This study suggests that further improvements of the MODIS LAI products should focus on finer algorithm inputs and improved seasonal variation modeling of MODIS observations. Future field work considering finer biome maps and better generation of LAI reference maps is still needed. Full article

(This article belongs to the Section Remote Sensors)

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4 pages, 142 KiB

Open AccessLetter

Remarks on Peinado et al.’s Analysis of J3Gen

by Joaquin Garcia-Alfaro^1,*

, Jordi Herrera-Joancomartí² and Joan Melià-Seguí³

¹ Institut Mines-Telecom, Telecom SudParis, CNRS Samovar UMR 5157, 9 Rue Charles Fourier, 91000 Evry, France

² Department of Information and Communications Engineering, Universitat Autònoma de Barcelona, Edifici Q, Campus de Bellaterra, 08193 Bellaterra, Spain

³ Internet Interdisciplinary Institute, Universitat Oberta de Catalunya, Roc Boronat 117, 08018 Barcelona, Spain

Sensors 2015, 15(3), 6217-6220; https://doi.org/10.3390/s150306217 - 13 Mar 2015

Cited by 2 | Viewed by 5476

Abstract

Peinado et al. analyzed the security of the J3Gen pseudorandom number generator proposed by Melià-Seguí et al., and claimed weaknesses regarding its security properties. They also presented a deterministic attack based on the decimation of the J3Gen output sequences. We show that [...] Read more.

Peinado et al. analyzed the security of the J3Gen pseudorandom number generator proposed by Melià-Seguí et al., and claimed weaknesses regarding its security properties. They also presented a deterministic attack based on the decimation of the J3Gen output sequences. We show that the assumptions made by Peinado et al. are not correct and that the proposed deterministic attack against J3Gen does not hold in practice. Full article

(This article belongs to the Section Sensor Networks)

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20 pages, 1483 KiB

Open AccessArticle

Adjusting Spectral Indices for Spectral Response Function Differences of Very High Spatial Resolution Sensors Simulated from Field Spectra

by Sharon L. Cundill^*, Harald M. A. Van der Werff

and Mark Van der Meijde

Faculty of Geo-Information Science and Earth Observation (ITC), University of Twente, PO Box 217, 7500 AE Enschede, The Netherlands

Sensors 2015, 15(3), 6221-6240; https://doi.org/10.3390/s150306221 - 13 Mar 2015

Cited by 30 | Viewed by 7149

Abstract

The use of data from multiple sensors is often required to ensure data coverage and continuity, but differences in the spectral characteristics of sensors result in spectral index values being different. This study investigates spectral response function effects on 48 spectral indices for [...] Read more.

The use of data from multiple sensors is often required to ensure data coverage and continuity, but differences in the spectral characteristics of sensors result in spectral index values being different. This study investigates spectral response function effects on 48 spectral indices for cultivated grasslands using simulated data of 10 very high spatial resolution sensors, convolved from field reflectance spectra of a grass covered dike (with varying vegetation condition). Index values for 48 indices were calculated for original narrow-band spectra and convolved data sets, and then compared. The indices Difference Vegetation Index (DVI), Global Environmental Monitoring Index (GEMI), Enhanced Vegetation Index (EVI), Modified Soil-Adjusted Vegetation Index (MSAVI₂) and Soil-Adjusted Vegetation Index (SAVI), which include the difference between the near-infrared and red bands, have values most similar to those of the original spectra across all 10 sensors (1:1 line mean _1:1R² > 0.960 and linear trend mean ccR² > 0.997). Additionally, relationships between the indices’ values and two quality indicators for grass covered dikes were compared to those of the original spectra. For the soil moisture indicator, indices that ratio bands performed better across sensors than those that difference bands, while for the dike cover quality indicator, both the choice of bands and their formulation are important. Full article

(This article belongs to the Section Remote Sensors)

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9 pages, 1387 KiB

Open AccessArticle

Study of the Relationship between Taste Sensor Response and the Amount of Epigallocatechin Gallate Adsorbed Onto a Lipid-Polymer Membrane

by Yuhei Harada¹, Yusuke Tahara^1,* and Kiyoshi Toko^1,2

¹ Graduate School of Information Science and Electrical Engineering, Kyushu University, Nishi-ku, Fukuoka 819-0395, Japan

² Research and Development Center for Taste and Odor Sensing, Kyushu University, Nishi-ku, Fukuoka 819-0395, Japan

Sensors 2015, 15(3), 6241-6249; https://doi.org/10.3390/s150306241 - 13 Mar 2015

Cited by 15 | Viewed by 7409

Abstract

A taste sensor using lipid-polymer membranes has been developed to evaluate the taste of foods, beverages and medicines. The response of the taste sensor, measured as a change in the membrane potential caused by adsorption (CPA), corresponds to the aftertaste felt by humans. [...] Read more.

A taste sensor using lipid-polymer membranes has been developed to evaluate the taste of foods, beverages and medicines. The response of the taste sensor, measured as a change in the membrane potential caused by adsorption (CPA), corresponds to the aftertaste felt by humans. The relationships between the CPA value and the amount of adsorbed taste substances, quinine and iso-α acid (bitterness), and tannic acid (astringency), have been studied so far. However, that of epigallocatechin gallate (EGCg) has not been clarified, although EGCg is abundantly present in green tea as one of its astringent substances. This study aimed at clarifying the response of the taste sensor to EGCg and its relationship with the amount of EGCg adsorbed onto lipid-polymer membranes. The lipid concentration dependence of the CPA value was similar to that of the amount of adsorbed EGCg, indicating a high correlation between the CPA value and the amount of adsorbed EGCg. The CPA value increased with increasing amount of adsorbed EGCg; however, the CPA value showed a tendency of leveling off when the amount of adsorbed EGCg further increased. Full article

(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Japan 2015)

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20 pages, 2662 KiB

Open AccessArticle

The Design and Implementation of the Leaf Area Index Sensor

by Xiuhong Li^1,2,3, Qiang Liu^1,2

, Rongjin Yang^4,*, Haijing Zhang¹, Jialin Zhang¹ and Erli Cai¹

¹ College of Global Change and Earth System Science, Beijing Normal University, No.19, XinJieKou Wai Street, HaiDian District, Beijing 100875, China

² Joint Center for Global Change Studies, Beijing 100875, China

³ State Key Laboratory of Remote Sensing Science, Jointly Sponsored by the Institute of Remote Sensing and Digital Earth of Chinese Academy of Sciences and Beijing Normal University, No. 20 Nouth, DaTun Road, ChaoYang District, Beijing 100101, China

⁴ Chinese Research Academy of Environment Sciences, No.8, DaYangFang, AnWai, ChaoYang District, Beijing 100012, China

Sensors 2015, 15(3), 6250-6269; https://doi.org/10.3390/s150306250 - 13 Mar 2015

Cited by 19 | Viewed by 7626

Abstract

The quick and accurate acquisition of crop growth parameters on a large scale is important for agricultural management and food security. The combination of photographic and wireless sensor network (WSN) techniques can be used to collect agricultural information, such as leaf area index [...] Read more.

The quick and accurate acquisition of crop growth parameters on a large scale is important for agricultural management and food security. The combination of photographic and wireless sensor network (WSN) techniques can be used to collect agricultural information, such as leaf area index (LAI), over long distances and in real time. Such acquisition not only provides farmers with photographs of crops and suggestions for farmland management, but also the collected quantitative parameters, such as LAI, can be used to support large scale research in ecology, hydrology, remote sensing, etc. The present research developed a Leaf Area Index Sensor (LAIS) to continuously monitor the growth of crops in several sampling points, and applied 3G/WIFI communication technology to remotely collect (and remotely setup and upgrade) crop photos in real-time. Then the crop photos are automatically processed and LAI is estimated based on the improved leaf area index of Lang and Xiang (LAILX) algorithm in LAIS. The research also constructed a database of images and other information relating to crop management. The leaf length and width method (LAILLW) can accurately measure LAI through direct field harvest. The LAIS has been tested in several exemplary applications, and validation with LAI from LAILLW. The LAI acquired by LAIS had been proved reliable. Full article

(This article belongs to the Special Issue Agriculture and Forestry: Sensors, Technologies and Procedures)

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36 pages, 7554 KiB

Open AccessArticle

The Optimization Based Dynamic and Cyclic Working Strategies for Rechargeable Wireless Sensor Networks with Multiple Base Stations and Wireless Energy Transfer Devices

by Xu Ding^†, Jianghong Han^*,† and Lei Shi^†

¹ School of Computer and Information, Hefei University of Technology, No.193 Tunxi Road, Hefei 230009, China

^† These authors contributed equally to this work.

Sensors 2015, 15(3), 6270-6305; https://doi.org/10.3390/s150306270 - 16 Mar 2015

Cited by 7 | Viewed by 6843

Abstract

In this paper, the optimal working schemes for wireless sensor networks with multiple base stations and wireless energy transfer devices are proposed. The wireless energy transfer devices also work as data gatherers while charging sensor nodes. The wireless sensor network is firstly divided [...] Read more.

In this paper, the optimal working schemes for wireless sensor networks with multiple base stations and wireless energy transfer devices are proposed. The wireless energy transfer devices also work as data gatherers while charging sensor nodes. The wireless sensor network is firstly divided into sub networks according to the concept of Voronoi diagram. Then, the entire energy replenishing procedure is split into the pre-normal and normal energy replenishing stages. With the objective of maximizing the sojourn time ratio of the wireless energy transfer device, a continuous time optimization problem for the normal energy replenishing cycle is formed according to constraints with which sensor nodes and wireless energy transfer devices should comply. Later on, the continuous time optimization problem is reshaped into a discrete multi-phased optimization problem, which yields the identical optimality. After linearizing it, we obtain a linear programming problem that can be solved efficiently. The working strategies of both sensor nodes and wireless energy transfer devices in the pre-normal replenishing stage are also discussed in this paper. The intensive simulations exhibit the dynamic and cyclic working schemes for the entire energy replenishing procedure. Additionally, a way of eliminating “bottleneck” sensor nodes is also developed in this paper. Full article

(This article belongs to the Special Issue Wireless Sensor Networks and the Internet of Things)

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18 pages, 2502 KiB

Open AccessArticle

Bio-Optics Based Sensation Imaging for Breast Tumor Detection Using Tissue Characterization

by Jong-Ha Lee^1,*

, Yoon Nyun Kim² and Hee-Jun Park¹

¹ Department of Biomedical Engineering, School of Medicine, Keimyung University, 1095, Dalgubeol-daero, Daegu 704-701, Korea

² Department of Internal Medicine, Dongsan Medical Center, Keimyung University, 1095, Dalgubeol-daero, Daegu 704-701, Korea

Sensors 2015, 15(3), 6306-6323; https://doi.org/10.3390/s150306306 - 16 Mar 2015

Cited by 6 | Viewed by 5942

Abstract

The tissue inclusion parameter estimation method is proposed to measure the stiffness as well as geometric parameters. The estimation is performed based on the tactile data obtained at the surface of the tissue using an optical tactile sensation imaging system (TSIS). A forward [...] Read more.

The tissue inclusion parameter estimation method is proposed to measure the stiffness as well as geometric parameters. The estimation is performed based on the tactile data obtained at the surface of the tissue using an optical tactile sensation imaging system (TSIS). A forward algorithm is designed to comprehensively predict the tactile data based on the mechanical properties of tissue inclusion using finite element modeling (FEM). This forward information is used to develop an inversion algorithm that will be used to extract the size, depth, and Young's modulus of a tissue inclusion from the tactile data. We utilize the artificial neural network (ANN) for the inversion algorithm. The proposed estimation method was validated by a realistic tissue phantom with stiff inclusions. The experimental results showed that the proposed estimation method can measure the size, depth, and Young's modulus of a tissue inclusion with 0.58%, 3.82%, and 2.51% relative errors, respectively. The obtained results prove that the proposed method has potential to become a useful screening and diagnostic method for breast cancer. Full article

(This article belongs to the Special Issue Optical Sensors for Chemical, Biological and Industrial Applications)

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18 pages, 1870 KiB

Open AccessArticle

Label-Free, Single Molecule Resonant Cavity Detection: A Double-Blind Experimental Study

by Maria V. Chistiakova^†, Ce Shi^† and Andrea M. Armani^*

¹ Mork Family Department of Chemical Engineering and Materials Science, University of Southern California, 3651 Watt Way, Los Angeles, CA 90089, USA

^† These authors contributed equally to this work.

Sensors 2015, 15(3), 6324-6341; https://doi.org/10.3390/s150306324 - 16 Mar 2015

Cited by 5 | Viewed by 7603

Abstract

Optical resonant cavity sensors are gaining increasing interest as a potential diagnostic method for a range of applications, including medical prognostics and environmental monitoring. However, the majority of detection demonstrations to date have involved identifying a “known” analyte, and the more rigorous double-blind [...] Read more.

Optical resonant cavity sensors are gaining increasing interest as a potential diagnostic method for a range of applications, including medical prognostics and environmental monitoring. However, the majority of detection demonstrations to date have involved identifying a “known” analyte, and the more rigorous double-blind experiment, in which the experimenter must identify unknown solutions, has yet to be performed. This scenario is more representative of a real-world situation. Therefore, before these devices can truly transition, it is necessary to demonstrate this level of robustness. By combining a recently developed surface chemistry with integrated silica optical sensors, we have performed a double-blind experiment to identify four unknown solutions. The four unknown solutions represented a subset or complete set of four known solutions; as such, there were 256 possible combinations. Based on the single molecule detection signal, we correctly identified all solutions. In addition, as part of this work, we developed noise reduction algorithms. Full article

(This article belongs to the Special Issue Advances in Optical Biosensors)

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18 pages, 1022 KiB

Open AccessArticle

Robust Optimization of a MEMS Accelerometer Considering Temperature Variations

by Guangjun Liu, Feng Yang, Xiaofan Bao and Tao Jiang^*

School of Mechanical Engineering, Tongji University, Shanghai 200092, China

Sensors 2015, 15(3), 6342-6359; https://doi.org/10.3390/s150306342 - 16 Mar 2015

Cited by 29 | Viewed by 7919

Abstract

A robust optimization approach for a MEMS accelerometer to minimize the effects of temperature variations is presented. The mathematical model of the accelerometer is built. The effects of temperature variations on the output performance of the accelerometer are determined, and thermal deformation of [...] Read more.

A robust optimization approach for a MEMS accelerometer to minimize the effects of temperature variations is presented. The mathematical model of the accelerometer is built. The effects of temperature variations on the output performance of the accelerometer are determined, and thermal deformation of the accelerometer is analyzed. The deviations of the output capacitance and resonance frequency due to temperature fluctuations are calculated and discussed. The sensitivity analysis method is employed to determine the design variables for robust optimization and find out the key structural parameters that have most significant influence on the output capacitance and resonance frequency of the accelerometer. The mathematical model and procedure for the robust optimization of the accelerometer are proposed. The robust optimization problem is solved and discussed. The robust optimization results show that an optimized accelerometer with high sensitivity, high temperature robustness and decoupling structure is finally obtained. Full article

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

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23 pages, 4098 KiB

Open AccessArticle

A Model-Based 3D Template Matching Technique for Pose Acquisition of an Uncooperative Space Object

by Roberto Opromolla^*

, Giancarmine Fasano

, Giancarlo Rufino

and Michele Grassi

Department of Industrial Engineering, University of Naples Federico II, Piazzale Tecchio 80, Naples 80125, Italy

Sensors 2015, 15(3), 6360-6382; https://doi.org/10.3390/s150306360 - 16 Mar 2015

Cited by 77 | Viewed by 8962

Abstract

This paper presents a customized three-dimensional template matching technique for autonomous pose determination of uncooperative targets. This topic is relevant to advanced space applications, like active debris removal and on-orbit servicing. The proposed technique is model-based and produces estimates of the target pose [...] Read more.

This paper presents a customized three-dimensional template matching technique for autonomous pose determination of uncooperative targets. This topic is relevant to advanced space applications, like active debris removal and on-orbit servicing. The proposed technique is model-based and produces estimates of the target pose without any prior pose information, by processing three-dimensional point clouds provided by a LIDAR. These estimates are then used to initialize a pose tracking algorithm. Peculiar features of the proposed approach are the use of a reduced number of templates and the idea of building the database of templates on-line, thus significantly reducing the amount of on-board stored data with respect to traditional techniques. An algorithm variant is also introduced aimed at further accelerating the pose acquisition time and reducing the computational cost. Technique performance is investigated within a realistic numerical simulation environment comprising a target model, LIDAR operation and various target-chaser relative dynamics scenarios, relevant to close-proximity flight operations. Specifically, the capability of the proposed techniques to provide a pose solution suitable to initialize the tracking algorithm is demonstrated, as well as their robustness against highly variable pose conditions determined by the relative dynamics. Finally, a criterion for autonomous failure detection of the presented techniques is presented. Full article

(This article belongs to the Special Issue Sensor Innovations for Spacecraft Guidance, Navigation, and Control)

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16 pages, 1369 KiB

Open AccessArticle

Assessment of Human Respiration Patterns via Noncontact Sensing Using Doppler Multi-Radar System

by Changzhan Gu^1,2 and Changzhi Li^2,*

¹ Marvell Technology Group Ltd., 5488 Marvell Lane, Santa Clara, CA 95054, USA

² Department of Electrical and Computer Engineering, Texas Tech University, Lubbock, TX 79409, USA

Sensors 2015, 15(3), 6383-6398; https://doi.org/10.3390/s150306383 - 16 Mar 2015

Cited by 73 | Viewed by 10200

Abstract

Human respiratory patterns at chest and abdomen are associated with both physical and emotional states. Accurate measurement of the respiratory patterns provides an approach to assess and analyze the physical and emotional states of the subject persons. Not many research efforts have been [...] Read more.

Human respiratory patterns at chest and abdomen are associated with both physical and emotional states. Accurate measurement of the respiratory patterns provides an approach to assess and analyze the physical and emotional states of the subject persons. Not many research efforts have been made to wirelessly assess different respiration patterns, largely due to the inaccuracy of the conventional continuous-wave radar sensor to track the original signal pattern of slow respiratory movements. This paper presents the accurate assessment of different respiratory patterns based on noncontact Doppler radar sensing. This paper evaluates the feasibility of accurately monitoring different human respiration patterns via noncontact radar sensing. A 2.4 GHz DC coupled multi-radar system was used for accurate measurement of the complete respiration patterns without any signal distortion. Experiments were carried out in the lab environment to measure the different respiration patterns when the subject person performed natural breathing, chest breathing and diaphragmatic breathing. The experimental results showed that accurate assessment of different respiration patterns is feasible using the proposed noncontact radar sensing technique. Full article

(This article belongs to the Section Physical Sensors)

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20 pages, 947 KiB

Open AccessArticle

Improved Local Ternary Patterns for Automatic Target Recognition in Infrared Imagery

by Xiaosheng Wu¹, Junding Sun^1,*, Guoliang Fan² and Zhiheng Wang¹

¹ School of Computer Science and Technology, Henan Polytechnic University, 2001 Century Avenue, Jiaozuo 454000, China

² School of Electrical and Computer Engineering, Oklahoma State University, 202 Engineering South, Stillwater, OK 74078, USA

Sensors 2015, 15(3), 6399-6418; https://doi.org/10.3390/s150306399 - 16 Mar 2015

Cited by 23 | Viewed by 7810

Abstract

This paper presents an improved local ternary pattern (LTP) for automatic target recognition (ATR) in infrared imagery. Firstly, a robust LTP (RLTP) scheme is proposed to overcome the limitation of the original LTP for achieving the invariance with respect to the illumination transformation. [...] Read more.

This paper presents an improved local ternary pattern (LTP) for automatic target recognition (ATR) in infrared imagery. Firstly, a robust LTP (RLTP) scheme is proposed to overcome the limitation of the original LTP for achieving the invariance with respect to the illumination transformation. Then, a soft concave-convex partition (SCCP) is introduced to add some flexibility to the original concave-convex partition (CCP) scheme. Referring to the orthogonal combination of local binary patterns (OC_LBP), the orthogonal combination of LTP (OC_LTP) is adopted to reduce the dimensionality of the LTP histogram. Further, a novel operator, called the soft concave-convex orthogonal combination of robust LTP (SCC_OC_RLTP), is proposed by combing RLTP, SCCP and OC_LTP. Finally, the new operator is used for ATR along with a blocking schedule to improve its discriminability and a feature selection technique to enhance its efficiency. Experimental results on infrared imagery show that the proposed features can achieve competitive ATR results compared with the state-of-the-art methods. Full article

(This article belongs to the Section Physical Sensors)

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22 pages, 1620 KiB

Open AccessArticle

Stride Segmentation during Free Walk Movements Using Multi-Dimensional Subsequence Dynamic Time Warping on Inertial Sensor Data

by Jens Barth^1,2,3, Cäcilia Oberndorfer^1,2, Cristian Pasluosta^2,3, Samuel Schülein⁴, Heiko Gassner³, Samuel Reinfelder², Patrick Kugler², Dominik Schuldhaus², Jürgen Winkler³, Jochen Klucken^3,† and Björn M. Eskofier^2,*,†

¹ ASTRUM IT GmbH, Am Wolfsmantel 2, Erlangen D-91058, Germany

² Digital Sports Group, Pattern Recognition Lab, Department of Computer Science, Friedrich-Alexander University Erlangen-Nürnberg (FAU), Martensstraße 3, Erlangen D-91058, Germany

³ Department of Molecular Neurology, Universitätsklinikum Erlangen, Friedrich-Alexander University Erlangen-Nürnberg (FAU), Schwabachanlage 6, Erlangen D-91054, Germany

⁴ Geriatrics Centre Erlangen, Waldkrankenhaus St. Marien, Rathsberger Straße 57, Erlangen D-91054, Germany

^† These authors contributed equally to this work.

Sensors 2015, 15(3), 6419-6440; https://doi.org/10.3390/s150306419 - 17 Mar 2015

Cited by 159 | Viewed by 14458

Abstract

Changes in gait patterns provide important information about individuals’ health. To perform sensor based gait analysis, it is crucial to develop methodologies to automatically segment single strides from continuous movement sequences. In this study we developed an algorithm based on time-invariant template matching [...] Read more.

Changes in gait patterns provide important information about individuals’ health. To perform sensor based gait analysis, it is crucial to develop methodologies to automatically segment single strides from continuous movement sequences. In this study we developed an algorithm based on time-invariant template matching to isolate strides from inertial sensor signals. Shoe-mounted gyroscopes and accelerometers were used to record gait data from 40 elderly controls, 15 patients with Parkinson’s disease and 15 geriatric patients. Each stride was manually labeled from a straight 40 m walk test and from a video monitored free walk sequence. A multi-dimensional subsequence Dynamic Time Warping (msDTW) approach was used to search for patterns matching a pre-defined stride template constructed from 25 elderly controls. F-measure of 98% (recall 98%, precision 98%) for 40 m walk tests and of 97% (recall 97%, precision 97%) for free walk tests were obtained for the three groups. Compared to conventional peak detection methods up to 15% F-measure improvement was shown. The msDTW proved to be robust for segmenting strides from both standardized gait tests and free walks. This approach may serve as a platform for individualized stride segmentation during activities of daily living. Full article

(This article belongs to the Special Issue Sensor Systems for Motion Capture and Interpretation)

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28 pages, 754 KiB

Open AccessReview

MEMS Sensor Technologies for Human Centred Applications in Healthcare, Physical Activities, Safety and Environmental Sensing: A Review on Research Activities in Italy

by Gastone Ciuti^*, Leonardo Ricotti, Arianna Menciassi and Paolo Dario

The BioRobotics Institute, Scuola Superiore Sant'Anna, Pisa 56025, Italy

Sensors 2015, 15(3), 6441-6468; https://doi.org/10.3390/s150306441 - 17 Mar 2015

Cited by 144 | Viewed by 22923

Abstract

Over the past few decades the increased level of public awareness concerning healthcare, physical activities, safety and environmental sensing has created an emerging need for smart sensor technologies and monitoring devices able to sense, classify, and provide feedbacks to users’ health status and [...] Read more.

Over the past few decades the increased level of public awareness concerning healthcare, physical activities, safety and environmental sensing has created an emerging need for smart sensor technologies and monitoring devices able to sense, classify, and provide feedbacks to users’ health status and physical activities, as well as to evaluate environmental and safety conditions in a pervasive, accurate and reliable fashion. Monitoring and precisely quantifying users’ physical activity with inertial measurement unit-based devices, for instance, has also proven to be important in health management of patients affected by chronic diseases, e.g., Parkinson’s disease, many of which are becoming highly prevalent in Italy and in the Western world. This review paper will focus on MEMS sensor technologies developed in Italy in the last three years describing research achievements for healthcare and physical activity, safety and environmental sensing, in addition to smart systems integration. Innovative and smart integrated solutions for sensing devices, pursued and implemented in Italian research centres, will be highlighted, together with specific applications of such technologies. Finally, the paper will depict the future perspective of sensor technologies and corresponding exploitation opportunities, again with a specific focus on Italy. Full article

(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Italy 2014)

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14 pages, 1345 KiB

Open AccessArticle

A Solid-State Thin-Film Ag/AgCl Reference Electrode Coated with Graphene Oxide and Its Use in a pH Sensor

by Tae Yong Kim¹, Sung A Hong¹ and Sung Yang^1,2,*

¹ Department of Medical System Engineering, Gwangju Institute of Science and Technology (GIST), Gwangju 500-712, Korea

² School of Mechatronics, Gwangju Institute of Science and Technology (GIST), Gwangju 500-712, Korea

Sensors 2015, 15(3), 6469-6482; https://doi.org/10.3390/s150306469 - 17 Mar 2015

Cited by 66 | Viewed by 16782

Abstract

In this study, we describe a novel solid-state thin-film Ag/AgCl reference electrode (SSRE) that was coated with a protective layer of graphene oxide (GO). This layer was prepared by drop casting a solution of GO on the Ag/AgCl thin film. The potential differences [...] Read more.

In this study, we describe a novel solid-state thin-film Ag/AgCl reference electrode (SSRE) that was coated with a protective layer of graphene oxide (GO). This layer was prepared by drop casting a solution of GO on the Ag/AgCl thin film. The potential differences exhibited by the SSRE were less than 2 mV for 26 days. The cyclic voltammograms of the SSRE were almost similar to those of a commercial reference electrode, while the diffusion coefficient of Fe(CN)₆³⁻ as calculated from the cathodic peaks of the SSRE was 6.48 × 10⁻⁶ cm²/s. The SSRE was used in conjunction with a laboratory-made working electrode to determine its suitability for practical use. The average pH sensitivity of this combined sensor was 58.5 mV/pH in the acid-to-base direction; the correlation coefficient was greater than 0.99. In addition, an integrated pH sensor that included the SSRE was packaged in a secure digital (SD) card and tested. The average sensitivity of the chip was 56.8 mV/pH, with the correlation coefficient being greater than 0.99. In addition, a pH sensing test was also performed by using a laboratory-made potentiometer, which showed a sensitivity of 55.4 mV/pH, with the correlation coefficient being greater than 0.99. Full article

(This article belongs to the Section Chemical Sensors)

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14 pages, 1961 KiB

Open AccessArticle

Cooperative Environment Scans Based on a Multi-Robot System

by Ji-Wook Kwon

Yonsei Institute of Convergence Technology, Yonsei University, Songdogwahak-ro, Yeonsu-gu, Incheon 406-840, Korea

Sensors 2015, 15(3), 6483-6496; https://doi.org/10.3390/s150306483 - 17 Mar 2015

Cited by 5 | Viewed by 6707

Abstract

This paper proposes a cooperative environment scan system (CESS) using multiple robots, where each robot has low-cost range finders and low processing power. To organize and maintain the CESS, a base robot monitors the positions of the child robots, controls them, and builds [...] Read more.

This paper proposes a cooperative environment scan system (CESS) using multiple robots, where each robot has low-cost range finders and low processing power. To organize and maintain the CESS, a base robot monitors the positions of the child robots, controls them, and builds a map of the unknown environment, while the child robots with low performance range finders provide obstacle information. Even though each child robot provides approximated and limited information of the obstacles, CESS replaces the single LRF, which has a high cost, because much of the information is acquired and accumulated by a number of the child robots. Moreover, the proposed CESS extends the measurement boundaries and detects obstacles hidden behind others. To show the performance of the proposed system and compare this with the numerical models of the commercialized 2D and 3D laser scanners, simulation results are included. Full article

(This article belongs to the Section Physical Sensors)

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23 pages, 1421 KiB

Open AccessArticle

Sparse Component Analysis Using Time-Frequency Representations for Operational Modal Analysis

by Shaoqian Qin, Jie Guo^*

and Changan Zhu

Department of Precision Machinery and Precision Instrumentation, University of Science and Technology of China (USTC), Hefei 230027, China

Sensors 2015, 15(3), 6497-6519; https://doi.org/10.3390/s150306497 - 17 Mar 2015

Cited by 32 | Viewed by 7310

Abstract

Sparse component analysis (SCA) has been widely used for blind source separation(BSS) for many years. Recently, SCA has been applied to operational modal analysis (OMA), which is also known as output-only modal identification. This paper considers the sparsity of sources’ time-frequency (TF) representation [...] Read more.

Sparse component analysis (SCA) has been widely used for blind source separation(BSS) for many years. Recently, SCA has been applied to operational modal analysis (OMA), which is also known as output-only modal identification. This paper considers the sparsity of sources’ time-frequency (TF) representation and proposes a new TF-domain SCA under the OMA framework. First, the measurements from the sensors are transformed to the TF domain to get a sparse representation. Then, single-source-points (SSPs) are detected to better reveal the hyperlines which correspond to the columns of the mixing matrix. The K-hyperline clustering algorithm is used to identify the direction vectors of the hyperlines and then the mixing matrix is calculated. Finally, basis pursuit de-noising technique is used to recover the modal responses, from which the modal parameters are computed. The proposed method is valid even if the number of active modes exceed the number of sensors. Numerical simulation and experimental verification demonstrate the good performance of the proposed method. Full article

(This article belongs to the Section Physical Sensors)

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29 pages, 3901 KiB

Open AccessArticle

Game Design to Measure Reflexes and Attention Based on Biofeedback Multi-Sensor Interaction

by Inigo De Loyola Ortiz-Vigon Uriarte^*, Begonya Garcia-Zapirain

and Yolanda Garcia-Chimeno

Deusto-Tech-LIFE Department, University of Deusto, Bilbao 48007, Spain

Sensors 2015, 15(3), 6520-6548; https://doi.org/10.3390/s150306520 - 17 Mar 2015

Cited by 15 | Viewed by 9269

Abstract

This paper presents a multi-sensor system for implementing biofeedback as a human-computer interaction technique in a game involving driving cars in risky situations. The sensors used are: Eye Tracker, Kinect, pulsometer, respirometer, electromiography (EMG) and galvanic skin resistance (GSR). An algorithm has been [...] Read more.

This paper presents a multi-sensor system for implementing biofeedback as a human-computer interaction technique in a game involving driving cars in risky situations. The sensors used are: Eye Tracker, Kinect, pulsometer, respirometer, electromiography (EMG) and galvanic skin resistance (GSR). An algorithm has been designed which gives rise to an interaction logic with the game according to the set of physiological constants obtained from the sensors. The results reflect a 72.333 response to the System Usability Scale (SUS), a significant difference of p = 0.026 in GSR values in terms of the difference between the start and end of the game, and an r = 0.659 and p = 0.008 correlation while playing with the Kinect between the breathing level and the energy and joy factor. All the sensors used had an impact on the end results, whereby none of them should be disregarded in future lines of research, even though it would be interesting to obtain separate breathing values from that of the cardio. Full article

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

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11 pages, 1586 KiB

Open AccessArticle

Single- and Two-Phase Flow Characterization Using Optical Fiber Bragg Gratings

by Virgínia H.V. Baroncini¹, Cicero Martelli^1,*, Marco José Da Silva¹ and Rigoberto E.M. Morales²

¹ Graduate School of Electrical Engineering and Computer Science, Federal University of Technology-Paraná (UTFPR), Curitiba 80230-901, Brazil

² Graduate School of Mechanical and Materials Engineering, Federal University of Technology-Paraná (UTFPR), Curitiba 80230-901, Brazil

Sensors 2015, 15(3), 6549-6559; https://doi.org/10.3390/s150306549 - 17 Mar 2015

Cited by 22 | Viewed by 6501

Abstract

Single- and two-phase flow characterization using optical fiber Bragg gratings (FBGs) is presented. The sensor unit consists of the optical fiber Bragg grating positioned transversely to the flow and fixed in the pipe walls. The hydrodynamic pressure applied by the liquid or air/liquid [...] Read more.

Single- and two-phase flow characterization using optical fiber Bragg gratings (FBGs) is presented. The sensor unit consists of the optical fiber Bragg grating positioned transversely to the flow and fixed in the pipe walls. The hydrodynamic pressure applied by the liquid or air/liquid flow to the optical fiber induces deformation that can be detected by the FBG. Given that the applied pressure is directly related to the mass flow, it is possible to establish a relationship using the grating resonance wavelength shift to determine the mass flow when the flow velocity is well known. For two phase flows of air and liquid, there is a significant change in the force applied to the fiber that accounts for the very distinct densities of these substances. As a consequence, the optical fiber deformation and the correspondent grating wavelength shift as a function of the flow will be very different for an air bubble or a liquid slug, allowing their detection as they flow through the pipe. A quasi-distributed sensing tool with 18 sensors evenly spread along the pipe is developed and characterized, making possible the characterization of the flow, as well as the tracking of the bubbles over a large section of the test bed. Results show good agreement with standard measurement methods and open up plenty of opportunities to both laboratory measurement tools and field applications. Full article

(This article belongs to the Section Physical Sensors)

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26 pages, 8337 KiB

Open AccessArticle

New Calibration Method Using Low Cost MEM IMUs to Verify the Performance of UAV-Borne MMS Payloads

by Kai-Wei Chiang¹, Meng-Lun Tsai¹, El-Sheimy Naser^2,†, Ayman Habib^3,†

and Chien-Hsun Chu^1,*

¹ Department of Geomatics, National Cheng-Kung University, No.1, Daxue Rd., Tainan 70101, Taiwan

² Department of Geomatics Engineering, University of Calgary, Calgary City, AB T2N 1N4, Canada

³ Lyles School of Civil Engineering, Purdue University, Lafayette city, IN 47907, USA

^† These authors contributed equally to this work

Sensors 2015, 15(3), 6560-6585; https://doi.org/10.3390/s150306560 - 19 Mar 2015

Cited by 33 | Viewed by 9116

Abstract

Spatial information plays a critical role in remote sensing and mapping applications such as environment surveying and disaster monitoring. An Unmanned Aerial Vehicle (UAV)-borne mobile mapping system (MMS) can accomplish rapid spatial information acquisition under limited sky conditions with better mobility and flexibility [...] Read more.

Spatial information plays a critical role in remote sensing and mapping applications such as environment surveying and disaster monitoring. An Unmanned Aerial Vehicle (UAV)-borne mobile mapping system (MMS) can accomplish rapid spatial information acquisition under limited sky conditions with better mobility and flexibility than other means. This study proposes a long endurance Direct Geo-referencing (DG)-based fixed-wing UAV photogrammetric platform and two DG modules that each use different commercial Micro-Electro Mechanical Systems’ (MEMS) tactical grade Inertial Measurement Units (IMUs). Furthermore, this study develops a novel kinematic calibration method which includes lever arms, boresight angles and camera shutter delay to improve positioning accuracy. The new calibration method is then compared with the traditional calibration approach. The results show that the accuracy of the DG can be significantly improved by flying at a lower altitude using the new higher specification hardware. The new proposed method improves the accuracy of DG by about 20%. The preliminary results show that two-dimensional (2D) horizontal DG positioning accuracy is around 5.8 m at a flight height of 300 m using the newly designed tactical grade integrated Positioning and Orientation System (POS). The positioning accuracy in three-dimensions (3D) is less than 8 m. Full article

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

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21 pages, 4074 KiB

Open AccessArticle

Tracking Systems for Virtual Rehabilitation: Objective Performance vs. Subjective Experience. A Practical Scenario

by Roberto Lloréns^1,2,*, Enrique Noé^2,†, Valery Naranjo^1,†, Adrián Borrego^1,†, Jorge Latorre^1,† and Mariano Alcañiz^1,3,†

¹ Instituto Interuniversitario de Investigación en Bioingeniería y Tecnología Orientada al Ser Humano, Universitat Politècnica de València, Camino de Vera s/n, 46022 Valencia, Spain

² Servicio de Neurorrehabilitación y Daño Cerebral de los Hospitales NISA, Fundación Hospitales NISA, 46022 Valencia, Spain

³ Ciber, Fisiopatología Obesidad y Nutrición, CB06/03 Instituto de Salud Carlos III, Av. Sos Baynat s/n, Univesity of Jaume I, 12071 Castellón, Spain

^† These authors contributed equally to this work.

Sensors 2015, 15(3), 6586-6606; https://doi.org/10.3390/s150306586 - 19 Mar 2015

Cited by 23 | Viewed by 9353

Abstract

Motion tracking systems are commonly used in virtual reality-based interventions to detect movements in the real world and transfer them to the virtual environment. There are different tracking solutions based on different physical principles, which mainly define their performance parameters. However, special requirements [...] Read more.

Motion tracking systems are commonly used in virtual reality-based interventions to detect movements in the real world and transfer them to the virtual environment. There are different tracking solutions based on different physical principles, which mainly define their performance parameters. However, special requirements have to be considered for rehabilitation purposes. This paper studies and compares the accuracy and jitter of three tracking solutions (optical, electromagnetic, and skeleton tracking) in a practical scenario and analyzes the subjective perceptions of 19 healthy subjects, 22 stroke survivors, and 14 physical therapists. The optical tracking system provided the best accuracy (1.074 ± 0.417 cm) while the electromagnetic device provided the most inaccurate results (11.027 ± 2.364 cm). However, this tracking solution provided the best jitter values (0.324 ± 0.093 cm), in contrast to the skeleton tracking, which had the worst results (1.522 ± 0.858 cm). Healthy individuals and professionals preferred the skeleton tracking solution rather than the optical and electromagnetic solution (in that order). Individuals with stroke chose the optical solution over the other options. Our results show that subjective perceptions and preferences are far from being constant among different populations, thus suggesting that these considerations, together with the performance parameters, should be also taken into account when designing a rehabilitation system. Full article

(This article belongs to the Collection Sensors for Globalized Healthy Living and Wellbeing)

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26 pages, 909 KiB

Open AccessArticle

Sensing in the Collaborative Internet of Things

by João B. Borges Neto^1,2,*, Thiago H. Silva¹, Renato Martins Assunção¹, Raquel A. F. Mini³ and Antonio A. F. Loureiro¹

¹ Department of Computer Science, Universidade Federal de Minas Gerais, Belo Horizonte 31270-901, Brazil

² Department of Computing and Technology, Universidade Federal do Rio Grande do Norte, Caicó 59300-000, Brazil

³ Department of Computer Science, Pontifícia Universidade Católica de Minas Gerais, Belo Horizonte 30535-901, Brazil

Sensors 2015, 15(3), 6607-6632; https://doi.org/10.3390/s150306607 - 19 Mar 2015

Cited by 27 | Viewed by 9146

Abstract

We are entering a new era of computing technology, the era of Internet of Things (IoT). An important element for this popularization is the large use of off-the-shelf sensors. Most of those sensors will be deployed by different owners, generally common users, creating [...] Read more.

We are entering a new era of computing technology, the era of Internet of Things (IoT). An important element for this popularization is the large use of off-the-shelf sensors. Most of those sensors will be deployed by different owners, generally common users, creating what we call the Collaborative IoT. This collaborative IoT helps to increase considerably the amount and availability of collected data for different purposes, creating new interesting opportunities, but also several challenges. For example, it is very challenging to search for and select a desired sensor or a group of sensors when there is no description about the provided sensed data or when it is imprecise. Given that, in this work we characterize the properties of the sensed data in the Internet of Things, mainly the sensed data contributed by several sources, including sensors from common users. We conclude that, in order to safely use data available in the IoT, we need a filtering process to increase the data reliability. In this direction, we propose a new simple and powerful approach that helps to select reliable sensors. We tested our method for different types of sensed data, and the results reveal the effectiveness in the correct selection of sensor data. Full article

(This article belongs to the Special Issue Wireless Sensor Networks and the Internet of Things)

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19 pages, 21391 KiB

Open AccessArticle

Wavelength-Adaptive Dehazing Using Histogram Merging-Based Classification for UAV Images

by Inhye Yoon¹, Seokhwa Jeong¹, Jaeheon Jeong², Doochun Seo² and Joonki Paik^1,*

¹ Department of Image, Chung-Ang University, 84 Heukseok-ro, Dongjak-gu, Seoul 156-756, Korea

² Department of Satellite Data Cal/Val Team, Korea Aerospace Research Institute, 115 Gwahangbo,Yusung-Gu, Daejon 305-806, Korea

Sensors 2015, 15(3), 6633-6651; https://doi.org/10.3390/s150306633 - 19 Mar 2015

Cited by 32 | Viewed by 7928

Abstract

Since incoming light to an unmanned aerial vehicle (UAV) platform can be scattered by haze and dust in the atmosphere, the acquired image loses the original color and brightness of the subject. Enhancement of hazy images is an important task in improving the [...] Read more.

Since incoming light to an unmanned aerial vehicle (UAV) platform can be scattered by haze and dust in the atmosphere, the acquired image loses the original color and brightness of the subject. Enhancement of hazy images is an important task in improving the visibility of various UAV images. This paper presents a spatially-adaptive dehazing algorithm that merges color histograms with consideration of the wavelength-dependent atmospheric turbidity. Based on the wavelength-adaptive hazy image acquisition model, the proposed dehazing algorithm consists of three steps: (i) image segmentation based on geometric classes; (ii) generation of the context-adaptive transmission map; and (iii) intensity transformation for enhancing a hazy UAV image. The major contribution of the research is a novel hazy UAV image degradation model by considering the wavelength of light sources. In addition, the proposed transmission map provides a theoretical basis to differentiate visually important regions from others based on the turbidity and merged classification results. Full article

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

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16 pages, 3719 KiB

Open AccessArticle

Water Area Extraction Using RADARSAT SAR Imagery Combined with Landsat Imagery and Terrain Information

by Seunghwan Hong

, Hyoseon Jang, Namhoon Kim and Hong-Gyoo Sohn^*

School of Civil and Environmental Engineering, Yonsei University, Seodaemun-gu, Seoul 120-749, Korea

Sensors 2015, 15(3), 6652-6667; https://doi.org/10.3390/s150306652 - 19 Mar 2015

Cited by 77 | Viewed by 8168

Abstract

This paper exploits an effective water extraction method using SAR imagery in preparation for flood mapping in unpredictable flood situations. The proposed method is based on the thresholding method using SAR amplitude, terrain information, and object-based classification techniques for noise removal. Since the [...] Read more.

This paper exploits an effective water extraction method using SAR imagery in preparation for flood mapping in unpredictable flood situations. The proposed method is based on the thresholding method using SAR amplitude, terrain information, and object-based classification techniques for noise removal. Since the water areas in SAR images have the lowest amplitude value, the thresholding method using SAR amplitude could effectively extract water bodies. However, the reflective properties of water areas in SAR imagery cannot distinguish the occluded areas caused by steep relief and they can be eliminated with terrain information. In spite of the thresholding method using SAR amplitude and terrain information, noises which interfered with users’ interpretation of water maps still remained and the object-based classification using an object size criterion was applied for the noise removal and the criterion was determined by a histogram-based technique. When only using SAR amplitude information, the overall accuracy was 83.67%. However, using SAR amplitude, terrain information and the noise removal technique, the overall classification accuracy over the study area turned out to be 96.42%. In particular, user accuracy was improved by 46.00%. Full article

(This article belongs to the Section Remote Sensors)

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20 pages, 1504 KiB

Open AccessArticle

Beamforming and Power Control in Sensor Arrays Using Reinforcement Learning

by Náthalee C. Almeida^1,*, Marcelo A.C. Fernandes^2,†

and Adrião D.D. Neto^2,†

¹ UFERSA—Federal Rural University of the Semi-Árido, Pau dos Ferros 59900-000, Brazil

² DCA-CT-UFRN, Federal University of Rio Grande do Norte, Natal 59072-970, Brazil

^† These authors contributed equally to this work.

Sensors 2015, 15(3), 6668-6687; https://doi.org/10.3390/s150306668 - 19 Mar 2015

Cited by 6 | Viewed by 6815

Abstract

The use of beamforming and power control, combined or separately, has advantages and disadvantages, depending on the application. The combined use of beamforming and power control has been shown to be highly effective in applications involving the suppression of interference signals from different [...] Read more.

The use of beamforming and power control, combined or separately, has advantages and disadvantages, depending on the application. The combined use of beamforming and power control has been shown to be highly effective in applications involving the suppression of interference signals from different sources. However, it is necessary to identify efficient methodologies for the combined operation of these two techniques. The most appropriate technique may be obtained by means of the implementation of an intelligent agent capable of making the best selection between beamforming and power control. The present paper proposes an algorithm using reinforcement learning (RL) to determine the optimal combination of beamforming and power control in sensor arrays. The RL algorithm used was Q-learning, employing an ε-greedy policy, and training was performed using the offline method. The simulations showed that RL was effective for implementation of a switching policy involving the different techniques, taking advantage of the positive characteristics of each technique in terms of signal reception. Full article

(This article belongs to the Section Physical Sensors)

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11 pages, 2273 KiB

Open AccessArticle

Development of a Capacitive Ice Sensor to Measure Ice Growth in Real Time

by Xiang Zhi¹, Hyo Chang Cho¹, Bo Wang¹, Cheol Hee Ahn¹, Hyeong Soon Moon² and Jeung Sang Go^1,*

¹ School of Mechanical Engineering, Pusan National University, 2, Busandaehak-ro 63beon-gil, Geumjeong-gu, Busan 609-735, Korea

² Korea Institute of Industrial Technology, 60beon-gil, Gangseo-gu, Busan 618-230, Korea

Sensors 2015, 15(3), 6688-6698; https://doi.org/10.3390/s150306688 - 19 Mar 2015

Cited by 28 | Viewed by 10087

Abstract

This paper presents the development of the capacitive sensor to measure the growth of ice on a fuel pipe surface in real time. The ice sensor consists of pairs of electrodes to detect the change in capacitance and a thermocouple temperature sensor to [...] Read more.

This paper presents the development of the capacitive sensor to measure the growth of ice on a fuel pipe surface in real time. The ice sensor consists of pairs of electrodes to detect the change in capacitance and a thermocouple temperature sensor to examine the ice formation situation. In addition, an environmental chamber was specially designed to control the humidity and temperature to simulate the ice formation conditions. From the humidity, a water film is formed on the ice sensor, which results in an increase in capacitance. Ice nucleation occurs, followed by the rapid formation of frost ice that decreases the capacitance suddenly. The capacitance is saturated. The developed ice sensor explains the ice growth providing information about the icing temperature in real time. Full article

(This article belongs to the Section Physical Sensors)

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20 pages, 4424 KiB

Open AccessArticle

Soil Water Content Assessment: Critical Issues Concerning the Operational Application of the Triangle Method

by Antonino Maltese^*

, Fulvio Capodici^†

, Giuseppe Ciraolo^†

and Goffredo La Loggia^†

¹ Department of Civil, Environmental, Aerospace, Materials Engineering, Università degli Studi di Palermo, Viale delle Scienze Ed. 8, 90128 Palermo, Italy

^† These authors contributed equally to this work.

Sensors 2015, 15(3), 6699-6718; https://doi.org/10.3390/s150306699 - 19 Mar 2015

Cited by 29 | Viewed by 6731

Abstract

Knowledge of soil water content plays a key role in water management efforts to improve irrigation efficiency. Among the indirect estimation methods of soil water content via Earth Observation data is the triangle method, used to analyze optical and thermal features because these [...] Read more.

Knowledge of soil water content plays a key role in water management efforts to improve irrigation efficiency. Among the indirect estimation methods of soil water content via Earth Observation data is the triangle method, used to analyze optical and thermal features because these are primarily controlled by water content within the near-surface evaporation layer and root zone in bare and vegetated soils. Although the soil-vegetation-atmosphere transfer theory describes the ongoing processes, theoretical models reveal limits for operational use. When applying simplified empirical formulations, meteorological forcing could be replaced with alternative variables when the above-canopy temperature is unknown, to mitigate the effects of calibration inaccuracies or to account for the temporal admittance of the soil. However, if applied over a limited area, a characterization of both dry and wet edges could not be properly achieved; thus, a multi-temporal analysis can be exploited to include outer extremes in soil water content. A diachronic empirical approach introduces the need to assume a constancy of other meteorological forcing variables that control thermal features. Airborne images were acquired on a Sicilian vineyard during most of an entire irrigation period (fruit-set to ripening stages, vintage 2008), during which in situ soil water content was measured to set up the triangle method. Within this framework, we tested the triangle method by employing alternative thermal forcing. The results were inaccurate when air temperature at airborne acquisition was employed. Sonic and aerodynamic air temperatures confirmed and partially explained the limits of simultaneous meteorological forcing, and the use of proxy variables improved model accuracy. The analysis indicates that high spatial resolution does not necessarily imply higher accuracies. Full article

(This article belongs to the Section Remote Sensors)

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21 pages, 2047 KiB

Open AccessArticle

Multi-Layer Sparse Representation for Weighted LBP-Patches Based Facial Expression Recognition

by Qi Jia, Xinkai Gao, He Guo^*, Zhongxuan Luo and Yi Wang

School of Software, Dalian University of Technology, Dalian 116621, China

Sensors 2015, 15(3), 6719-6739; https://doi.org/10.3390/s150306719 - 19 Mar 2015

Cited by 23 | Viewed by 7774

Abstract

In this paper, a novel facial expression recognition method based on sparse representation is proposed. Most contemporary facial expression recognition systems suffer from limited ability to handle image nuisances such as low resolution and noise. Especially for low intensity expression, most of the [...] Read more.

In this paper, a novel facial expression recognition method based on sparse representation is proposed. Most contemporary facial expression recognition systems suffer from limited ability to handle image nuisances such as low resolution and noise. Especially for low intensity expression, most of the existing training methods have quite low recognition rates. Motivated by sparse representation, the problem can be solved by finding sparse coefficients of the test image by the whole training set. Deriving an effective facial representation from original face images is a vital step for successful facial expression recognition. We evaluate facial representation based on weighted local binary patterns, and Fisher separation criterion is used to calculate the weighs of patches. A multi-layer sparse representation framework is proposed for multi-intensity facial expression recognition, especially for low-intensity expressions and noisy expressions in reality, which is a critical problem but seldom addressed in the existing works. To this end, several experiments based on low-resolution and multi-intensity expressions are carried out. Promising results on publicly available databases demonstrate the potential of the proposed approach. Full article

(This article belongs to the Section Physical Sensors)

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23 pages, 2138 KiB

Open AccessArticle

Location Detection and Tracking of Moving Targets by a 2D IR-UWB Radar System

by Van-Han Nguyen^1,2 and Jae-Young Pyun^1,*

¹ Department of Information and Communication Engineering, Chosun University, 375 Susuk-Dong, Dong-gu, Gwangju 501-759, Korea

² Department of Electronic and Automation Engineering, Nha Trang University, 02 Nguyen Dinh Chieu, Nha Trang 625080, Khanh Hoa, Vietnam

Sensors 2015, 15(3), 6740-6762; https://doi.org/10.3390/s150306740 - 19 Mar 2015

Cited by 94 | Viewed by 14693

Abstract

In indoor environments, the Global Positioning System (GPS) and long-range tracking radar systems are not optimal, because of signal propagation limitations in the indoor environment. In recent years, the use of ultra-wide band (UWB) technology has become a possible solution for object detection, [...] Read more.

In indoor environments, the Global Positioning System (GPS) and long-range tracking radar systems are not optimal, because of signal propagation limitations in the indoor environment. In recent years, the use of ultra-wide band (UWB) technology has become a possible solution for object detection, localization and tracking in indoor environments, because of its high range resolution, compact size and low cost. This paper presents improved target detection and tracking techniques for moving objects with impulse-radio UWB (IR-UWB) radar in a short-range indoor area. This is achieved through signal-processing steps, such as clutter reduction, target detection, target localization and tracking. In this paper, we introduce a new combination consisting of our proposed signal-processing procedures. In the clutter-reduction step, a filtering method that uses a Kalman filter (KF) is proposed. Then, in the target detection step, a modification of the conventional CLEAN algorithm which is used to estimate the impulse response from observation region is applied for the advanced elimination of false alarms. Then, the output is fed into the target localization and tracking step, in which the target location and trajectory are determined and tracked by using unscented KF in two-dimensional coordinates. In each step, the proposed methods are compared to conventional methods to demonstrate the differences in performance. The experiments are carried out using actual IR-UWB radar under different scenarios. The results verify that the proposed methods can improve the probability and efficiency of target detection and tracking. Full article

(This article belongs to the Special Issue Sensors for Indoor Mapping and Navigation)

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26 pages, 2658 KiB

Open AccessArticle

Human Detection Based on the Generation of a Background Image by Using a Far-Infrared Light Camera

by Eun Som Jeon, Jong-Suk Choi, Ji Hoon Lee, Kwang Yong Shin, Yeong Gon Kim, Toan Thanh Le and Kang Ryoung Park^*

Division of Electronics and Electrical Engineering, Dongguk University, 26 Pil-dong 3-ga, Jung-gu, Seoul 100-715, Korea

Sensors 2015, 15(3), 6763-6788; https://doi.org/10.3390/s150306763 - 19 Mar 2015

Cited by 47 | Viewed by 13261

Abstract

The need for computer vision-based human detection has increased in fields, such as security, intelligent surveillance and monitoring systems. However, performance enhancement of human detection based on visible light cameras is limited, because of factors, such as nonuniform illumination, shadows and low external [...] Read more.

The need for computer vision-based human detection has increased in fields, such as security, intelligent surveillance and monitoring systems. However, performance enhancement of human detection based on visible light cameras is limited, because of factors, such as nonuniform illumination, shadows and low external light in the evening and night. Consequently, human detection based on thermal (far-infrared light) cameras has been considered as an alternative. However, its performance is influenced by the factors, such as low image resolution, low contrast and the large noises of thermal images. It is also affected by the high temperature of backgrounds during the day. To solve these problems, we propose a new method for detecting human areas in thermal camera images. Compared to previous works, the proposed research is novel in the following four aspects. One background image is generated by median and average filtering. Additional filtering procedures based on maximum gray level, size filtering and region erasing are applied to remove the human areas from the background image. Secondly, candidate human regions in the input image are located by combining the pixel and edge difference images between the input and background images. The thresholds for the difference images are adaptively determined based on the brightness of the generated background image. Noise components are removed by component labeling, a morphological operation and size filtering. Third, detected areas that may have more than two human regions are merged or separated based on the information in the horizontal and vertical histograms of the detected area. This procedure is adaptively operated based on the brightness of the generated background image. Fourth, a further procedure for the separation and removal of the candidate human regions is performed based on the size and ratio of the height to width information of the candidate regions considering the camera viewing direction and perspective projection. Experimental results with two types of databases confirm that the proposed method outperforms other methods. Full article

(This article belongs to the Special Issue Frontiers in Infrared Photodetection)

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18 pages, 4143 KiB

Open AccessArticle

Development of a Microfluidic-Based Optical Sensing Device for Label-Free Detection of Circulating Tumor Cells (CTCs) Through Their Lactic Acid Metabolism

by Tzu-Keng Chiu^1,†, Kin-Fong Lei^2,3,†

, Chia-Hsun Hsieh^1,4

, Hung-Bo Hsiao⁵, Hung-Ming Wang⁶ and Min-Hsien Wu^5,*

¹ Department of Chemical and Materials Engineering, Chang Gung University, Taoyuan 33302, Taiwan

² Graduate Institute of Medical Mechatronics, Chang Gung University, Taoyuan 33302, Taiwan

³ Department of Mechanical Engineering, Chang Gung University, Taoyuan 33302, Taiwan

⁴ Division of Hematology-Oncology, Department of Internal Medicine, Chang Gung Memorial Hospital at Linkuo, Taoyuan 33302, Taiwan

⁵ Graduate Institute of Biochemical and Biomedical Engineering, Chang Gung University, Taoyuan 33302, Taiwan

⁶ Division of Hematology-Oncology, Department of Internal Medicine, Chang Gung Memorial Hospital, Chang Gung University, Taoyuan 33302, Taiwan

^† These authors contributed equally to this work.

Sensors 2015, 15(3), 6789-6806; https://doi.org/10.3390/s150306789 - 19 Mar 2015

Cited by 33 | Viewed by 9083

Abstract

This study reports a microfluidic-based optical sensing device for label-free detection of circulating tumor cells (CTCs), a rare cell species in blood circulation. Based on the metabolic features of cancer cells, live CTCs can be quantified indirectly through their lactic acid production. Compared [...] Read more.

This study reports a microfluidic-based optical sensing device for label-free detection of circulating tumor cells (CTCs), a rare cell species in blood circulation. Based on the metabolic features of cancer cells, live CTCs can be quantified indirectly through their lactic acid production. Compared with the conventional schemes for CTC detection, this label-free approach could prevent the biological bias due to the heterogeneity of the surface antigens on cancer cells. In this study, a microfluidic device was proposed to generate uniform water-in-oil cell-encapsulating micro-droplets, followed by the fluorescence-based optical detection of lactic acid produced within the micro-droplets. To test its feasibility to quantify cancer cells, experiments were carried out. Results showed that the detection signals were proportional to the number of cancer cells within the micro-droplets, whereas such signals were insensitive to the existence and number of leukocytes within. To further demonstrate its feasibility for cancer cell detection, the cancer cells with known cell number in a cell suspension was detected based on the method. Results revealed that there was no significant difference between the detected number and the real number of cancer cells. As a whole, the proposed method opens up a new route to detect live CTCs in a label-free manner. Full article

(This article belongs to the Special Issue On-Chip Sensors)

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11 pages, 1911 KiB

Open AccessArticle

Broadband and High Sensitive Time-of-Flight Diffraction Ultrasonic Transducers Based on PMNT/Epoxy 1–3 Piezoelectric Composite

by Dongxu Liu^1,2, Qingwen Yue^1,2, Ji Deng^1,2, Di Lin¹, Xiaobing Li¹, Wenning Di¹, Xi'an Wang¹, Xiangyong Zhao¹ and Haosu Luo^1,*

¹ Key Laboratory of Inorganic Functional Materials and Devices, Shanghai Institute of Ceramics, University of Chinese Academy of Sciences, 215 Chengbei Road, Jiading, Shanghai 201800, China

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

Sensors 2015, 15(3), 6807-6817; https://doi.org/10.3390/s150306807 - 19 Mar 2015

Cited by 33 | Viewed by 9531

Abstract

5–6 MHz PMNT/epoxy 1–3 composites were prepared by a modified dice-and-fill method. They exhibit excellent properties for ultrasonic transducer applications, such as ultrahigh thickness electromechanical coupling coefficient k_t (85.7%), large piezoelectric coefficient d₃₃ (1209 pC/N), and relatively low acoustic impedance Z [...] Read more.

5–6 MHz PMNT/epoxy 1–3 composites were prepared by a modified dice-and-fill method. They exhibit excellent properties for ultrasonic transducer applications, such as ultrahigh thickness electromechanical coupling coefficient k_t (85.7%), large piezoelectric coefficient d₃₃ (1209 pC/N), and relatively low acoustic impedance Z (1.82 × 10⁷ kg/(m²·s)). Besides, two types of Time-of-Flight Diffraction (TOFD) ultrasonic transducers have been designed, fabricated, and characterized, which have different matching layer schemes with the acoustic impedance of 4.8 and 5.7 × 10⁶ kg/(m²·s), respectively. In the detection on a backwall of 12.7 mm polystyrene, the former exhibits higher detectivity, the relative pulse-echo sensitivity and −6 dB relative bandwidth are −21.93 dB and 102.7%, respectively, while the later exhibits broader bandwidth, the relative pulse-echo sensitivity and −6 dB relative bandwidth are −24.08 dB and 117.3%, respectively. These TOFD ultrasonic transducers based on PMNT/epoxy 1–3 composite exhibit considerably improved performance over the commercial PZT/epoxy 1–3 composite TOFD ultrasonic transducer. Full article

(This article belongs to the Special Issue Acoustic Waveguide Sensors)

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27 pages, 1746 KiB

Open AccessArticle

Open Hardware: A Role to Play in Wireless Sensor Networks?

by Roy Fisher^1,2,*, Lehlogonolo Ledwaba³, Gerhard Hancke²

and Carel Kruger^1,3

¹ Advanced Sensor Networks Research Group, University of Pretoria, Lynwood Road, Pretoria 0083, South Africa

² Department of Computer Science, City University of Hong Kong, 83 Tat Chee Avenue,Kowloon Tong, Hong Kong

³ Meraka Institute, Council for Scientific and Industrial Research South Africa, Meiring Naude Road,Pretoria 0184, South Africa

Sensors 2015, 15(3), 6818-6844; https://doi.org/10.3390/s150306818 - 20 Mar 2015

Cited by 78 | Viewed by 10621

Abstract

The concept of the Internet of Things is rapidly becoming a reality, with many applications being deployed within industrial and consumer sectors. At the ‘thing’ level—devices and inter-device network communication—the core technical building blocks are generally the same as those found in wireless [...] Read more.

The concept of the Internet of Things is rapidly becoming a reality, with many applications being deployed within industrial and consumer sectors. At the ‘thing’ level—devices and inter-device network communication—the core technical building blocks are generally the same as those found in wireless sensor network implementations. For the Internet of Things to continue growing, we need more plentiful resources for building intelligent devices and sensor networks. Unfortunately, current commercial devices, e.g., sensor nodes and network gateways, tend to be expensive and proprietary, which presents a barrier to entry and arguably slows down further development. There are, however, an increasing number of open embedded platforms available and also a wide selection of off-the-shelf components that can quickly and easily be built into device and network gateway solutions. The question is whether these solutions measure up to built-for-purpose devices. In the paper, we provide a comparison of existing built-for-purpose devices against open source devices. For comparison, we have also designed and rapidly prototyped a sensor node based on off-the-shelf components. We show that these devices compare favorably to built-for-purpose devices in terms of performance, power and cost. Using open platforms and off-the-shelf components would allow more developers to build intelligent devices and sensor networks, which could result in a better overall development ecosystem, lower barriers to entry and rapid growth in the number of IoT applications. Full article

(This article belongs to the Special Issue Wireless Sensor Networks and the Internet of Things)

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27 pages, 7652 KiB

Open AccessArticle

Global Coverage Measurement Planning Strategies for Mobile Robots Equipped with a Remote Gas Sensor

by Muhammad Asif Arain^*, Marco Trincavelli, Marcello Cirillo, Erik Schaffernicht and Achim J. Lilienthal

Mobile Robotics & Olfaction Lab, Center of Applied Autonomous Sensor Systems (AASS), School of Science & Technology, Örebro University, Örebro SE-70182, Sweden

Sensors 2015, 15(3), 6845-6871; https://doi.org/10.3390/s150306845 - 20 Mar 2015

Cited by 16 | Viewed by 9407

Abstract

The problem of gas detection is relevant to many real-world applications, such as leak detection in industrial settings and landfill monitoring. In this paper, we address the problem of gas detection in large areas with a mobile robotic platform equipped with a remote [...] Read more.

The problem of gas detection is relevant to many real-world applications, such as leak detection in industrial settings and landfill monitoring. In this paper, we address the problem of gas detection in large areas with a mobile robotic platform equipped with a remote gas sensor. We propose an algorithm that leverages a novel method based on convex relaxation for quickly solving sensor placement problems, and for generating an efficient exploration plan for the robot. To demonstrate the applicability of our method to real-world environments, we performed a large number of experimental trials, both on randomly generated maps and on the map of a real environment. Our approach proves to be highly efficient in terms of computational requirements and to provide nearly-optimal solutions. Full article

(This article belongs to the Section Physical Sensors)

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13 pages, 1008 KiB

Open AccessArticle

A CMOS Pressure Sensor Tag Chip for Passive Wireless Applications

by Fangming Deng^1,2,*, Yigang He², Bing Li², Lei Zuo², Xiang Wu¹ and Zhihui Fu¹

¹ School of Electrical and Electronic Engineering, East China Jiao Tong University, Nanchang 330013, China

² School of Electrical Engineering and Automation, Hefei University of Technology, Hefei 230009, China

Sensors 2015, 15(3), 6872-6884; https://doi.org/10.3390/s150306872 - 23 Mar 2015

Cited by 20 | Viewed by 7842

Abstract

This paper presents a novel monolithic pressure sensor tag for passive wireless applications. The proposed pressure sensor tag is based on an ultra-high frequency RFID system. The pressure sensor element is implemented in the 0.18 µm CMOS process and the membrane gap is [...] Read more.

This paper presents a novel monolithic pressure sensor tag for passive wireless applications. The proposed pressure sensor tag is based on an ultra-high frequency RFID system. The pressure sensor element is implemented in the 0.18 µm CMOS process and the membrane gap is formed by sacrificial layer release, resulting in a sensitivity of 1.2 fF/kPa within the range from 0 to 600 kPa. A three-stage rectifier adopts a chain of auxiliary floating rectifier cells to boost the gate voltage of the switching transistors, resulting in a power conversion efficiency of 53% at the low input power of −20 dBm. The capacitive sensor interface, using phase-locked loop archietcture, employs fully-digital blocks, which results in a 7.4 bits resolution and 0.8 µW power dissipation at 0.8 V supply voltage. The proposed passive wireless pressure sensor tag costs a total 3.2 µW power dissipation. Full article

(This article belongs to the Section Physical Sensors)

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20 pages, 2439 KiB

Open AccessArticle

A Novel Abandoned Object Detection System Based on Three-Dimensional Image Information

by Yiliang Zeng¹, Jinhui Lan^1,*, Bin Ran², Jing Gao¹ and Jinlin Zou¹

¹ School of Automation and Electrical Engineering, University of Science and Technology Beijing, Beijing 100083, China

² School of Transportation, Southeast University, Nanjing 210096, Jiangsu Province, China

Sensors 2015, 15(3), 6885-6904; https://doi.org/10.3390/s150306885 - 23 Mar 2015

Cited by 19 | Viewed by 8405

Abstract

A new idea of an abandoned object detection system for road traffic surveillance systems based on three-dimensional image information is proposed in this paper to prevent traffic accidents. A novel Binocular Information Reconstruction and Recognition (BIRR) algorithm is presented to implement the new [...] Read more.

A new idea of an abandoned object detection system for road traffic surveillance systems based on three-dimensional image information is proposed in this paper to prevent traffic accidents. A novel Binocular Information Reconstruction and Recognition (BIRR) algorithm is presented to implement the new idea. As initial detection, suspected abandoned objects are detected by the proposed static foreground region segmentation algorithm based on surveillance video from a monocular camera. After detection of suspected abandoned objects, three-dimensional (3D) information of the suspected abandoned object is reconstructed by the proposed theory about 3D object information reconstruction with images from a binocular camera. To determine whether the detected object is hazardous to normal road traffic, road plane equation and height of suspected-abandoned object are calculated based on the three-dimensional information. Experimental results show that this system implements fast detection of abandoned objects and this abandoned object system can be used for road traffic monitoring and public area surveillance. Full article

(This article belongs to the Section Physical Sensors)

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19 pages, 771 KiB

Open AccessArticle

Radar Imaging of Non-Uniformly Rotating Targets via a Novel Approach for Multi-Component AM-FM Signal Parameter Estimation

by Yong Wang

Research Institute of Electronic Engineering Technology, Harbin Institute of Technology, Harbin 150001, China

Sensors 2015, 15(3), 6905-6923; https://doi.org/10.3390/s150306905 - 23 Mar 2015

Cited by 7 | Viewed by 5709

Abstract

A novel radar imaging approach for non-uniformly rotating targets is proposed in this study. It is assumed that the maneuverability of the non-cooperative target is severe, and the received signal in a range cell can be modeled as multi-component amplitude-modulated and frequency-modulated (AM-FM) [...] Read more.

A novel radar imaging approach for non-uniformly rotating targets is proposed in this study. It is assumed that the maneuverability of the non-cooperative target is severe, and the received signal in a range cell can be modeled as multi-component amplitude-modulated and frequency-modulated (AM-FM) signals after motion compensation. Then, the modified version of Chirplet decomposition (MCD) based on the integrated high order ambiguity function (IHAF) is presented for the parameter estimation of AM-FM signals, and the corresponding high quality instantaneous ISAR images can be obtained from the estimated parameters. Compared with the MCD algorithm based on the generalized cubic phase function (GCPF) in the authors’ previous paper, the novel algorithm presented in this paper is more accurate and efficient, and the results with simulated and real data demonstrate the superiority of the proposed method. Full article

(This article belongs to the Section Remote Sensors)

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23 pages, 7664 KiB

Open AccessArticle

Bayesian Deconvolution for Angular Super-Resolution in Forward-Looking Scanning Radar

by Yuebo Zha^*, Yulin Huang, Zhichao Sun

, Yue Wang and Jianyu Yang

School of Electronic Engineering, University of Electronic Science and Technology of China, 2006 Xiyuan Road, Gaoxin Western District, Chengdu 611731, China

Sensors 2015, 15(3), 6924-6946; https://doi.org/10.3390/s150306924 - 23 Mar 2015

Cited by 87 | Viewed by 8150

Abstract

Scanning radar is of notable importance for ground surveillance, terrain mapping and disaster rescue. However, the angular resolution of a scanning radar image is poor compared to the achievable range resolution. This paper presents a deconvolution algorithm for angular super-resolution in scanning radar [...] Read more.

Scanning radar is of notable importance for ground surveillance, terrain mapping and disaster rescue. However, the angular resolution of a scanning radar image is poor compared to the achievable range resolution. This paper presents a deconvolution algorithm for angular super-resolution in scanning radar based on Bayesian theory, which states that the angular super-resolution can be realized by solving the corresponding deconvolution problem with the maximum a posteriori (MAP) criterion. The algorithm considers that the noise is composed of two mutually independent parts, i.e., a Gaussian signal-independent component and a Poisson signal-dependent component. In addition, the Laplace distribution is used to represent the prior information about the targets under the assumption that the radar image of interest can be represented by the dominant scatters in the scene. Experimental results demonstrate that the proposed deconvolution algorithm has higher precision for angular super-resolution compared with the conventional algorithms, such as the Tikhonov regularization algorithm, the Wiener filter and the Richardson–Lucy algorithm. Full article

(This article belongs to the Section Remote Sensors)

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49 pages, 3030 KiB

Open AccessReview

The Application of Biomedical Engineering Techniques to the Diagnosis and Management of Tropical Diseases: A Review

by Fatimah Ibrahim^1,2,*,†, Tzer Hwai Gilbert Thio^1,2,3,†, Tarig Faisal^1,2,4,† and Michael Neuman⁵

¹ Department of Biomedical Engineering, Faculty of Engineering, University of Malaya, 50603 Kuala Lumpur, Malaysia

² Centre for Innovation in Medical Engineering (CIME), Faculty of Engineering, University of Malaya, 50603 Kuala Lumpur, Malaysia

³ Faculty of Science, Technology, Engineering and Mathematics, INTI International University, 71800 Nilai, Negeri Sembilan, Malaysia

⁴ Faculty-Electronics Engineering, Ruwais College, Higher Colleges of Technology, Ruwais, P.O Box 12389, UAE

⁵ Department of Biomedical Engineering, Michigan Technological University, Houghton, MI 49931, USA

^† These authors contributed equally to this work.

Sensors 2015, 15(3), 6947-6995; https://doi.org/10.3390/s150306947 - 23 Mar 2015

Cited by 34 | Viewed by 14327

Abstract

This paper reviews a number of biomedical engineering approaches to help aid in the detection and treatment of tropical diseases such as dengue, malaria, cholera, schistosomiasis, lymphatic filariasis, ebola, leprosy, leishmaniasis, and American trypanosomiasis (Chagas). Many different forms of non-invasive approaches such as [...] Read more.

This paper reviews a number of biomedical engineering approaches to help aid in the detection and treatment of tropical diseases such as dengue, malaria, cholera, schistosomiasis, lymphatic filariasis, ebola, leprosy, leishmaniasis, and American trypanosomiasis (Chagas). Many different forms of non-invasive approaches such as ultrasound, echocardiography and electrocardiography, bioelectrical impedance, optical detection, simplified and rapid serological tests such as lab-on-chip and micro-/nano-fluidic platforms and medical support systems such as artificial intelligence clinical support systems are discussed. The paper also reviewed the novel clinical diagnosis and management systems using artificial intelligence and bioelectrical impedance techniques for dengue clinical applications. Full article

(This article belongs to the Section Biosensors)

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20 pages, 1297 KiB

Open AccessArticle

Degradation Prediction Model Based on a Neural Network with Dynamic Windows

by Xinghui Zhang¹, Lei Xiao^2,3,* and Jianshe Kang¹

¹ Mechanical Engineering College, Shijiazhuang 050003, China

² The State Key Lab of Mechanical Transmission, Chongqing University, Chongqing 400030, China

³ Department of Industrial and Systems Engineering, Rutgers University, Piscataway, NJ 08854, USA

Sensors 2015, 15(3), 6996-7015; https://doi.org/10.3390/s150306996 - 23 Mar 2015

Cited by 25 | Viewed by 8034

Abstract

Tracking degradation of mechanical components is very critical for effective maintenance decision making. Remaining useful life (RUL) estimation is a widely used form of degradation prediction. RUL prediction methods when enough run-to-failure condition monitoring data can be used have been fully researched, but [...] Read more.

Tracking degradation of mechanical components is very critical for effective maintenance decision making. Remaining useful life (RUL) estimation is a widely used form of degradation prediction. RUL prediction methods when enough run-to-failure condition monitoring data can be used have been fully researched, but for some high reliability components, it is very difficult to collect run-to-failure condition monitoring data, i.e., from normal to failure. Only a certain number of condition indicators in certain period can be used to estimate RUL. In addition, some existing prediction methods have problems which block RUL estimation due to poor extrapolability. The predicted value converges to a certain constant or fluctuates in certain range. Moreover, the fluctuant condition features also have bad effects on prediction. In order to solve these dilemmas, this paper proposes a RUL prediction model based on neural network with dynamic windows. This model mainly consists of three steps: window size determination by increasing rate, change point detection and rolling prediction. The proposed method has two dominant strengths. One is that the proposed approach does not need to assume the degradation trajectory is subject to a certain distribution. The other is it can adapt to variation of degradation indicators which greatly benefits RUL prediction. Finally, the performance of the proposed RUL prediction model is validated by real field data and simulation data. Full article

(This article belongs to the Section Physical Sensors)

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24 pages, 6395 KiB

Open AccessArticle

Improving the Precision and Speed of Euler Angles Computation from Low-Cost Rotation Sensor Data

by Aleš Janota^*, Vojtech Šimák, Dušan Nemec and Jozef Hrbček

Department of Control & Information Systems, Faculty of Electrical Engineering, University of Žilina, Univerzitná 8215/1, Žilina 010 26, Slovakia

Sensors 2015, 15(3), 7016-7039; https://doi.org/10.3390/s150307016 - 23 Mar 2015

Cited by 62 | Viewed by 16627

Abstract

This article compares three different algorithms used to compute Euler angles from data obtained by the angular rate sensor (e.g., MEMS gyroscope)—the algorithms based on a rotational matrix, on transforming angular velocity to time derivations of the Euler angles and on unit quaternion [...] Read more.

This article compares three different algorithms used to compute Euler angles from data obtained by the angular rate sensor (e.g., MEMS gyroscope)—the algorithms based on a rotational matrix, on transforming angular velocity to time derivations of the Euler angles and on unit quaternion expressing rotation. Algorithms are compared by their computational efficiency and accuracy of Euler angles estimation. If attitude of the object is computed only from data obtained by the gyroscope, the quaternion-based algorithm seems to be most suitable (having similar accuracy as the matrix-based algorithm, but taking approx. 30% less clock cycles on the 8-bit microcomputer). Integration of the Euler angles’ time derivations has a singularity, therefore is not accurate at full range of object’s attitude. Since the error in every real gyroscope system tends to increase with time due to its offset and thermal drift, we also propose some measures based on compensation by additional sensors (a magnetic compass and accelerometer). Vector data of mentioned secondary sensors has to be transformed into the inertial frame of reference. While transformation of the vector by the matrix is slightly faster than doing the same by quaternion, the compensated sensor system utilizing a matrix-based algorithm can be approximately 10% faster than the system utilizing quaternions (depending on implementation and hardware). Full article

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

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22 pages, 864 KiB

Open AccessArticle

A Robust Trust Establishment Scheme for Wireless Sensor Networks

by Farruh Ishmanov¹, Sung Won Kim^2,*

and Seung Yeob Nam²

¹ Department of Electronics and Communication Engineering, Kwangwoon University, 447-1 Wolgye-dong, Nowon-gu, Seoul 139-701, Korea

² Department of Information and Communication Engineering, Yeungnam University, 280 Daehak-Ro, Gyeongsan-si 712-749, Gyeongsangbuk-do, Korea

Sensors 2015, 15(3), 7040-7061; https://doi.org/10.3390/s150307040 - 23 Mar 2015

Cited by 46 | Viewed by 6074

Abstract

Security techniques like cryptography and authentication can fail to protect a network once a node is compromised. Hence, trust establishment continuously monitors and evaluates node behavior to detect malicious and compromised nodes. However, just like other security schemes, trust establishment is also vulnerable [...] Read more.

Security techniques like cryptography and authentication can fail to protect a network once a node is compromised. Hence, trust establishment continuously monitors and evaluates node behavior to detect malicious and compromised nodes. However, just like other security schemes, trust establishment is also vulnerable to attack. Moreover, malicious nodes might misbehave intelligently to trick trust establishment schemes. Unfortunately, attack-resistance and robustness issues with trust establishment schemes have not received much attention from the research community. Considering the vulnerability of trust establishment to different attacks and the unique features of sensor nodes in wireless sensor networks, we propose a lightweight and robust trust establishment scheme. The proposed trust scheme is lightweight thanks to a simple trust estimation method. The comprehensiveness and flexibility of the proposed trust estimation scheme make it robust against different types of attack and misbehavior. Performance evaluation under different types of misbehavior and on-off attacks shows that the detection rate of the proposed trust mechanism is higher and more stable compared to other trust mechanisms. Full article

(This article belongs to the Section Sensor Networks)

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