Sensors

17 pages, 424 KiB

Open AccessArticle

High Resolution Direction of Arrival (DOA) Estimation Based on Improved Orthogonal Matching Pursuit (OMP) Algorithm by Iterative Local Searching

by Wenyi Wang^* and Renbiao Wu

Tianjin Key Lab for Advanced Signal Processing, Civil Aviation University of China, Tianjin 300300, China

Sensors 2013, 13(9), 11167-11183; https://doi.org/10.3390/s130911167 - 22 Aug 2013

Cited by 38 | Viewed by 8588

Abstract

DOA (Direction of Arrival) estimation is a major problem in array signal processing applications. Recently, compressive sensing algorithms, including convex relaxation algorithms and greedy algorithms, have been recognized as a kind of novel DOA estimation algorithm. However, the success of these algorithms is [...] Read more.

DOA (Direction of Arrival) estimation is a major problem in array signal processing applications. Recently, compressive sensing algorithms, including convex relaxation algorithms and greedy algorithms, have been recognized as a kind of novel DOA estimation algorithm. However, the success of these algorithms is limited by the RIP (Restricted Isometry Property) condition or the mutual coherence of measurement matrix. In the DOA estimation problem, the columns of measurement matrix are steering vectors corresponding to different DOAs. Thus, it violates the mutual coherence condition. The situation gets worse when there are two sources from two adjacent DOAs. In this paper, an algorithm based on OMP (Orthogonal Matching Pursuit), called ILS-OMP (Iterative Local Searching-Orthogonal Matching Pursuit), is proposed to improve DOA resolution by Iterative Local Searching. Firstly, the conventional OMP algorithm is used to obtain initial estimated DOAs. Then, in each iteration, a local searching process for every estimated DOA is utilized to find a new DOA in a given DOA set to further decrease the residual. Additionally, the estimated DOAs are updated by substituting the initial DOA with the new one. The simulation results demonstrate the advantages of the proposed algorithm. Full article

(This article belongs to the Section Physical Sensors)

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12 pages, 1044 KiB

Open AccessArticle

Identification of Capacitive MEMS Accelerometer Structure Parameters for Human Body Dynamics Measurements

by Vincas Benevicius, Vytautas Ostasevicius^* and Rimvydas Gaidys

Institute for Hi-Tech Development, Faculty of Mechanical Engineering and Mechatronics, Kaunas University of Technology, Studentu 65-209, Kaunas LT-51369, Lithuania

Sensors 2013, 13(9), 11184-11195; https://doi.org/10.3390/s130911184 - 22 Aug 2013

Cited by 21 | Viewed by 11465

Abstract

Due to their small size, low weight, low cost and low energy consumption, MEMS accelerometers have achieved great commercial success in recent decades. The aim of this research work is to identify a MEMS accelerometer structure for human body dynamics measurements. Photogrammetry was [...] Read more.

Due to their small size, low weight, low cost and low energy consumption, MEMS accelerometers have achieved great commercial success in recent decades. The aim of this research work is to identify a MEMS accelerometer structure for human body dynamics measurements. Photogrammetry was used in order to measure possible maximum accelerations of human body parts and the bandwidth of the digital acceleration signal. As the primary structure the capacitive accelerometer configuration is chosen in such a way that sensing part measures on all three axes as it is 3D accelerometer and sensitivity on each axis is equal. Hill climbing optimization was used to find the structure parameters. Proof-mass displacements were simulated for all the acceleration range that was given by the optimization problem constraints. The final model was constructed in Comsol Multiphysics. Eigenfrequencies were calculated and model’s response was found, when vibration stand displacement data was fed into the model as the base excitation law. Model output comparison with experimental data was conducted for all excitation frequencies used during the experiments. Full article

(This article belongs to the Special Issue Modeling, Testing and Reliability Issues in MEMS Engineering 2013)

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33 pages, 882 KiB

Open AccessReview

Cognitive Radio Wireless Sensor Networks: Applications, Challenges and Research Trends

by Gyanendra Prasad Joshi

, Seung Yeob Nam and Sung Won Kim^*

Department of Information and Communication Engineering, Yeungnam University, 214-1 Dae-dong, Gyeongsan-si, Kyongsan 712-749, Gyeongsangbuk-do, Korea

Sensors 2013, 13(9), 11196-11228; https://doi.org/10.3390/s130911196 - 22 Aug 2013

Cited by 249 | Viewed by 30069

Abstract

A cognitive radio wireless sensor network is one of the candidate areas where cognitive techniques can be used for opportunistic spectrum access. Research in this area is still in its infancy, but it is progressing rapidly. The aim of this study is to [...] Read more.

A cognitive radio wireless sensor network is one of the candidate areas where cognitive techniques can be used for opportunistic spectrum access. Research in this area is still in its infancy, but it is progressing rapidly. The aim of this study is to classify the existing literature of this fast emerging application area of cognitive radio wireless sensor networks, highlight the key research that has already been undertaken, and indicate open problems. This paper describes the advantages of cognitive radio wireless sensor networks, the difference between ad hoc cognitive radio networks, wireless sensor networks, and cognitive radio wireless sensor networks, potential application areas of cognitive radio wireless sensor networks, challenges and research trend in cognitive radio wireless sensor networks. The sensing schemes suited for cognitive radio wireless sensor networks scenarios are discussed with an emphasis on cooperation and spectrum access methods that ensure the availability of the required QoS. Finally, this paper lists several open research challenges aimed at drawing the attention of the readers toward the important issues that need to be addressed before the vision of completely autonomous cognitive radio wireless sensor networks can be realized. Full article

(This article belongs to the Section Sensor Networks)

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14 pages, 726 KiB

Open AccessArticle

Polycarbonate as an Elasto-Plastic Material Model for Simulation of the Microstructure Hot Imprint Process

by Birutė Narijauskaitė¹, Arvydas Palevičius¹, Rimvydas Gaidys², Giedrius Janušas^1,*

and Rokas Šakalys¹

¹ International Studies Centre, Kaunas University of Technology, A. Mickevičiaus Gatvė 37, Kaunas 44244, Lithuania

² Department of Engineering Design, Kaunas University of Technology, Kęstučio Gatvė 27, Kaunas 44025, Lithuania

Sensors 2013, 13(9), 11229-11242; https://doi.org/10.3390/s130911229 - 22 Aug 2013

Cited by 10 | Viewed by 9144

Abstract

The thermal imprint process of polymer micro-patterning is widely applied in areas such as manufacturing of optical parts, solar energy, bio-mechanical devices and chemical chips. Polycarbonate (PC), as an amorphous polymer, is often used in thermoforming processes because of its good replication characteristics. [...] Read more.

The thermal imprint process of polymer micro-patterning is widely applied in areas such as manufacturing of optical parts, solar energy, bio-mechanical devices and chemical chips. Polycarbonate (PC), as an amorphous polymer, is often used in thermoforming processes because of its good replication characteristics. In order to obtain replicas of the best quality, the imprint parameters (e.g., pressure, temperature, time, etc.) must be determined. Therefore finite element model of the hot imprint process of lamellar periodical microstructure into PC has been created using COMSOL Multiphysics. The mathematical model of the hot imprint process includes three steps: heating, imprinting and demolding. The material properties of amorphous PC strongly depend on the imprint temperature and loading pressure. Polycarbonate was modelled as an elasto-plastic material, since it was analyzed below the glass transition temperature. The hot imprint model was solved using the heat transfer and the solid stress-strain application modes with thermal contact problem between the mold and polycarbonate. It was used for the evaluation of temperature and stress distributions in the polycarbonate during the hot imprint process. The quality of the replica, by means of lands filling ratio, was determined as well. Full article

(This article belongs to the Special Issue Modeling, Testing and Reliability Issues in MEMS Engineering 2013)

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17 pages, 905 KiB

Open AccessArticle

Finger Vein Recognition with Personalized Feature Selection

by Xiaoming Xi, Gongping Yang^*, Yilong Yin and Xianjing Meng

School of Computer Science and Technology, Shandong University, Jinan 250101, China

Sensors 2013, 13(9), 11243-11259; https://doi.org/10.3390/s130911243 - 22 Aug 2013

Cited by 41 | Viewed by 8602

Abstract

Finger veins are a promising biometric pattern for personalized identification in terms of their advantages over existing biometrics. Based on the spatial pyramid representation and the combination of more effective information such as gray, texture and shape, this paper proposes a simple but [...] Read more.

Finger veins are a promising biometric pattern for personalized identification in terms of their advantages over existing biometrics. Based on the spatial pyramid representation and the combination of more effective information such as gray, texture and shape, this paper proposes a simple but powerful feature, called Pyramid Histograms of Gray, Texture and Orientation Gradients (PHGTOG). For a finger vein image, PHGTOG can reflect the global spatial layout and local details of gray, texture and shape. To further improve the recognition performance and reduce the computational complexity, we select a personalized subset of features from PHGTOG for each subject by using the sparse weight vector, which is trained by using LASSO and called PFS-PHGTOG. We conduct extensive experiments to demonstrate the promise of the PHGTOG and PFS-PHGTOG, experimental results on our databases show that PHGTOG outperforms the other existing features. Moreover, PFS-PHGTOG can further boost the performance in comparison with PHGTOG. Full article

(This article belongs to the Section Physical Sensors)

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11 pages, 399 KiB

Open AccessArticle

A Refractive Index Sensor Based on the Resonant Coupling to Cladding Modes in a Fiber Loop

by Mauricio Reyes¹, David Monzón-Hernández^2,*, Alejandro Martínez-Ríos², Enrique Silvestre³

, Antonio Díez¹, José Luis Cruz¹ and Miguel V. Andrés¹

¹ Departamento de Física Aplicada, Instituto de Ciencia de los Materiales, Universidad de Valencia, Burjassot 46100, Spain

² Grupo de Sensores Ópticos y Microdispositivos, Centro de Investigaciones en Óptica A.C., Loma del Bosque 115, col. Lomas del Campestre, Leon, Guanajuato 37150, Mexico

³ Departamento de Óptica, Universidad de Valencia, Burjassot 46100, Spain

Sensors 2013, 13(9), 11260-11270; https://doi.org/10.3390/s130911260 - 23 Aug 2013

Cited by 15 | Viewed by 7793

Abstract

We report an easy-to-build, compact, and low-cost optical fiber refractive index sensor. It consists of a single fiber loop whose transmission spectra exhibit a series of notches produced by the resonant coupling between the fundamental mode and the cladding modes in a uniformly [...] Read more.

We report an easy-to-build, compact, and low-cost optical fiber refractive index sensor. It consists of a single fiber loop whose transmission spectra exhibit a series of notches produced by the resonant coupling between the fundamental mode and the cladding modes in a uniformly bent fiber. The wavelength of the notches, distributed in a wavelength span from 1,400 to 1,700 nm, can be tuned by adjusting the diameter of the fiber loop and are sensitive to refractive index changes of the external medium. Sensitivities of 170 and 800 nm per refractive index unit for water solutions and for the refractive index interval 1.40–1.442, respectively, are demonstrated. We estimate a long range resolution of 3 × 10⁻⁴ and a short range resolution of 2 × 10⁻⁵ for water solutions. Full article

(This article belongs to the Special Issue Optomechatronics)

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9 pages, 412 KiB

Open AccessArticle

Fetal Electrocardiogram (fECG) Gated MRI

by Martyn N.J. Paley^*, Janet E. Morris, Debbie Jarvis and Paul D. Griffiths

Academic Radiology, Department of Cardiovascular Science, University of Sheffield, Sheffield S10 2JF, UK

Sensors 2013, 13(9), 11271-11279; https://doi.org/10.3390/s130911271 - 23 Aug 2013

Cited by 10 | Viewed by 10515

Abstract

We have developed a Magnetic Resonance Imaging (MRI)-compatible system to enable gating of a scanner to the heartbeat of a foetus for cardiac, umbilical cord flow and other possible imaging applications. We performed radiofrequency safety testing prior to a fetal electrocardiogram (fECG) gated [...] Read more.

We have developed a Magnetic Resonance Imaging (MRI)-compatible system to enable gating of a scanner to the heartbeat of a foetus for cardiac, umbilical cord flow and other possible imaging applications. We performed radiofrequency safety testing prior to a fetal electrocardiogram (fECG) gated imaging study in pregnant volunteers (n = 3). A compact monitoring device with advanced software capable of reliably detecting both the maternal electrocardiogram (mECG) and fECG simultaneously was modified by the manufacturer (Monica Healthcare, Nottingham, UK) to provide an external TTL trigger signal from the detected fECG which could be used to trigger a standard 1.5 T MR (GE Healthcare, Milwaukee, WI, USA) gating system with suitable attenuation. The MR scanner was tested by triggering rapidly during image acquisition at a typical fetal heart rate (123 beats per minute) using a simulated fECG waveform fed into the gating system. Gated MR images were also acquired from volunteers who were attending for a repeat fetal Central Nervous System (CNS) examination using an additional rapid cardiac imaging sequence triggered from the measured fECG. No adverse safety effects were encountered. This is the first time fECG gating has been used with MRI and opens up a range of new possibilities to study a developing foetus. Full article

(This article belongs to the Special Issue Magnetic Resonance Sensors)

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9 pages, 797 KiB

Open AccessArticle

GPS/MEMS INS Data Fusion and Map Matching in Urban Areas

by Hone-Jay Chu, Guang-Je Tsai, Kai-Wei Chiang and Thanh-Trung Duong^*

Department of Geomatics, National Cheng Kung University, No.1, University Road, Tainan 701, Taiwan

Sensors 2013, 13(9), 11280-11288; https://doi.org/10.3390/s130911280 - 23 Aug 2013

Cited by 53 | Viewed by 10462

Abstract

This paper presents an evaluation of the map-matching scheme of an integrated GPS/INS system in urban areas. Data fusion using a Kalman filter and map matching are effective approaches to improve the performance of navigation system applications based on GPS/MEMS IMUs. The study [...] Read more.

This paper presents an evaluation of the map-matching scheme of an integrated GPS/INS system in urban areas. Data fusion using a Kalman filter and map matching are effective approaches to improve the performance of navigation system applications based on GPS/MEMS IMUs. The study considers the curve-to-curve matching algorithm after Kalman filtering to correct mismatch and eliminate redundancy. By applying data fusion and map matching, the study easily accomplished mapping of a GPS/INS trajectory onto the road network. The results demonstrate the effectiveness of the algorithms in controlling the INS drift error and indicate the potential of low-cost MEMS IMUs in navigation applications. Full article

(This article belongs to the Special Issue Modeling, Testing and Reliability Issues in MEMS Engineering 2013)

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25 pages, 648 KiB

Open AccessArticle

Human Body Parts Tracking and Kinematic Features Assessment Based on RSSI and Inertial Sensor Measurements

by Gaddi Blumrosen^*,† and Ami Luttwak^†

¹ School of Computer Science & Engineering, Hebrew University of Jerusalem, Jerusalem 91904, Israel

^† These authors contributed equally to this work.

Sensors 2013, 13(9), 11289-11313; https://doi.org/10.3390/s130911289 - 23 Aug 2013

Cited by 16 | Viewed by 11875

Abstract

Acquisition of patient kinematics in different environments plays an important role in the detection of risk situations such as fall detection in elderly patients, in rehabilitation of patients with injuries, and in the design of treatment plans for patients with neurological diseases. Received [...] Read more.

Acquisition of patient kinematics in different environments plays an important role in the detection of risk situations such as fall detection in elderly patients, in rehabilitation of patients with injuries, and in the design of treatment plans for patients with neurological diseases. Received Signal Strength Indicator (RSSI) measurements in a Body Area Network (BAN), capture the signal power on a radio link. The main aim of this paper is to demonstrate the potential of utilizing RSSI measurements in assessment of human kinematic features, and to give methods to determine these features. RSSI measurements can be used for tracking different body parts’ displacements on scales of a few centimeters, for classifying motion and gait patterns instead of inertial sensors, and to serve as an additional reference to other sensors, in particular inertial sensors. Criteria and analytical methods for body part tracking, kinematic motion feature extraction, and a Kalman filter model for aggregation of RSSI and inertial sensor were derived. The methods were verified by a set of experiments performed in an indoor environment. In the future, the use of RSSI measurements can help in continuous assessment of various kinematic features of patients during their daily life activities and enhance medical diagnosis accuracy with lower costs. Full article

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

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22 pages, 842 KiB

Open AccessArticle

Lightweight Filter Architecture for Energy Efficient Mobile Vehicle Localization Based on a Distributed Acoustic Sensor Network

by Keonwook Kim

Division of Electronics & Electrical Engineering, Dongguk University-Seoul, Seoul 100-715, Korea

Sensors 2013, 13(9), 11314-11335; https://doi.org/10.3390/s130911314 - 23 Aug 2013

Cited by 10 | Viewed by 6147

Abstract

The generic properties of an acoustic signal provide numerous benefits for localization by applying energy-based methods over a deployed wireless sensor network (WSN). However, the signal generated by a stationary target utilizes a significant amount of bandwidth and power in the system without [...] Read more.

The generic properties of an acoustic signal provide numerous benefits for localization by applying energy-based methods over a deployed wireless sensor network (WSN). However, the signal generated by a stationary target utilizes a significant amount of bandwidth and power in the system without providing further position information. For vehicle localization, this paper proposes a novel proximity velocity vector estimator (PVVE) node architecture in order to capture the energy from a moving vehicle and reject the signal from motionless automobiles around the WSN node. A cascade structure between analog envelope detector and digital exponential smoothing filter presents the velocity vector-sensitive output with low analog circuit and digital computation complexity. The optimal parameters in the exponential smoothing filter are obtained by analytical and mathematical methods for maximum variation over the vehicle speed. For stationary targets, the derived simulation based on the acoustic field parameters demonstrates that the system significantly reduces the communication requirements with low complexity and can be expected to extend the operation time considerably. Full article

(This article belongs to the Section Sensor Networks)

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14 pages, 748 KiB

Open AccessArticle

Fluidic Automation of Nitrate and Nitrite Bioassays in Whole Blood by Dissolvable-Film Based Centrifugo-Pneumatic Actuation

by Charles E. Nwankire¹, Di-Sien S. Chan¹, Jennifer Gaughran¹, Robert Burger^1,2, Robert Gorkin III^1,3 and Jens Ducrée^1,*

¹ Biomedical Diagnostics Institute, National Centre for Sensor Research, School of Physical Sciences, Dublin City University, Glasnevin, Dublin 9, Ireland

² Department of Micro- and Nanotechnology, Technical University of Denmark, Ørsteds Plads 345Ø, DK2800 Kgs, Lyngby, Denmark

³ Intelligent Polymer Research Institute, ARC Centre of Excellence for Electromaterials Science, AIIM Facility, Innovation Campus, University of Wollongong, Wollongong, NSW 2522, Australia

Sensors 2013, 13(9), 11336-11349; https://doi.org/10.3390/s130911336 - 26 Aug 2013

Cited by 22 | Viewed by 9429

Abstract

This paper demonstrates the full centrifugal microfluidic integration and automation of all liquid handling steps of a 7-step fluorescence-linked immunosorbent assay (FLISA) for quantifying nitrate and nitrite levels in whole blood within about 15 min. The assay protocol encompasses the extraction of metered [...] Read more.

This paper demonstrates the full centrifugal microfluidic integration and automation of all liquid handling steps of a 7-step fluorescence-linked immunosorbent assay (FLISA) for quantifying nitrate and nitrite levels in whole blood within about 15 min. The assay protocol encompasses the extraction of metered plasma, the controlled release of sample and reagents (enzymes, co-factors and fluorescent labels), and incubation and detection steps. Flow control is implemented by a rotationally actuated dissolvable film (DF) valving scheme. In the valves, the burst pressure is primarily determined by the radial position, geometry and volume of the valve chamber and its inlet channel and can thus be individually tuned over an extraordinarily wide range of equivalent spin rates between 1,000 RPM and 5,500 RPM. Furthermore, the vapour barrier properties of the DF valves are investigated in this paper in order to further show the potential for commercially relevant on-board storage of liquid reagents during shelf-life of bioanalytical, ready-to-use discs. Full article

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

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12 pages, 567 KiB

Open AccessArticle

Narrow and Deep Fano Resonances in a Rod and Concentric Square Ring-Disk Nanostructures

by Yanyan Huo, Tianqing Jia^*, Yi Zhang, Hua Zhao, Shian Zhang, Donghai Feng and Zhenrong Sun

State Key Laboratory of Precision Spectroscopy, Department of Physics, East China Normal University, Shanghai 200062, China

Sensors 2013, 13(9), 11350-11361; https://doi.org/10.3390/s130911350 - 26 Aug 2013

Cited by 25 | Viewed by 7509

Abstract

Localized surface plasmon resonances (LSPRs) in metallic nanostructures have been studied intensely in the last decade. Fano interference is an important way to decrease the resonance linewidth and enhance the spectral detection resolution, but realizing a Fano lineshape with both a narrow linewidth [...] Read more.

Localized surface plasmon resonances (LSPRs) in metallic nanostructures have been studied intensely in the last decade. Fano interference is an important way to decrease the resonance linewidth and enhance the spectral detection resolution, but realizing a Fano lineshape with both a narrow linewidth and high spectral contrast-ratio is still challenging. Here we propose a metallic nanostructure consisting of a concentric square ring-disk (CSRD) nanostructure and an outside nanorod. Fano linewidth and spectral contrast ratio can be actively manipulated by adjusting the gap between the nanorod and CSRD, and by adjusting the gap between the ring and disk in CSRD. When the gap size in CSRD is reduced to 5 nm, the quadrupolar Fano linewidth is of 0.025 eV, with a contrast ratio of 80%, and the figure of merit reaches 15. Full article

(This article belongs to the Section Physical Sensors)

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23 pages, 6373 KiB

Open AccessArticle

Measuring Accurate Body Parameters of Dressed Humans with Large-Scale Motion Using a Kinect Sensor

by Huanghao Xu, Yao Yu^*, Yu Zhou^*, Yang Li and Sidan Du^*

School of Electronic Science and Engineering, Nanjing University, Nanjing 210046, China

Sensors 2013, 13(9), 11362-11384; https://doi.org/10.3390/s130911362 - 26 Aug 2013

Cited by 32 | Viewed by 17881

Abstract

Non-contact human body measurement plays an important role in surveillance, physical healthcare, on-line business and virtual fitting. Current methods for measuring the human body without physical contact usually cannot handle humans wearing clothes, which limits their applicability in public environments. In this paper, [...] Read more.

Non-contact human body measurement plays an important role in surveillance, physical healthcare, on-line business and virtual fitting. Current methods for measuring the human body without physical contact usually cannot handle humans wearing clothes, which limits their applicability in public environments. In this paper, we propose an effective solution that can measure accurate parameters of the human body with large-scale motion from a Kinect sensor, assuming that the people are wearing clothes. Because motion can drive clothes attached to the human body loosely or tightly, we adopt a space-time analysis to mine the information across the posture variations. Using this information, we recover the human body, regardless of the effect of clothes, and measure the human body parameters accurately. Experimental results show that our system can perform more accurate parameter estimation on the human body than state-of-the-art methods. Full article

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

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22 pages, 1020 KiB

Open AccessArticle

An Oil Fraction Neural Sensor Developed Using Electrical Capacitance Tomography Sensor Data

by Khursiah Zainal-Mokhtar and Junita Mohamad-Saleh^*

School of Electrical and Electronic Engineering, Engineering Campus, Universiti Sains Malaysia, Nibong Tebal, Penang 14300, Malaysia

Sensors 2013, 13(9), 11385-11406; https://doi.org/10.3390/s130911385 - 26 Aug 2013

Cited by 23 | Viewed by 7795

Abstract

This paper presents novel research on the development of a generic intelligent oil fraction sensor based on Electrical Capacitance Tomography (ECT) data. An artificial Neural Network (ANN) has been employed as the intelligent system to sense and estimate oil fractions from the cross-sections [...] Read more.

This paper presents novel research on the development of a generic intelligent oil fraction sensor based on Electrical Capacitance Tomography (ECT) data. An artificial Neural Network (ANN) has been employed as the intelligent system to sense and estimate oil fractions from the cross-sections of two-component flows comprising oil and gas in a pipeline. Previous works only focused on estimating the oil fraction in the pipeline based on fixed ECT sensor parameters. With fixed ECT design sensors, an oil fraction neural sensor can be trained to deal with ECT data based on the particular sensor parameters, hence the neural sensor is not generic. This work focuses on development of a generic neural oil fraction sensor based on training a Multi-Layer Perceptron (MLP) ANN with various ECT sensor parameters. On average, the proposed oil fraction neural sensor has shown to be able to give a mean absolute error of 3.05% for various ECT sensor sizes. Full article

(This article belongs to the Section Physical Sensors)

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17 pages, 1063 KiB

Open AccessArticle

Study of the Effect of the Strategy of Heating on the Mudejar Church of Santa Maria in Ateca (Spain) for Preventive Conservation of the Altarpiece Surroundings

by Fernando-Juan García-Diego^1,2,*,†

, Ángel Fernández-Navajas^1,†, Pedro Beltrán^1,† and Paloma Merello^1,3,†

¹ Departamento de Física Aplicada. (U.D. Industriales), Universitat Politècnica de València, Av. de los Naranjos s/n, Valencia 46022, Spain

² Centro de Tecnologías Físicas, Unidad Asociada ICMM- CSIC/UPV., Universitat Politècnica de València, Av. de los Naranjos s/n., Valencia 46022, Spain

³ Instituto Valenciano de Conservación y Restauración de Bienes Culturales (IVC+R), Complejo Socio-Educativo de Penyeta Roja s/n., Castellón 12080, Spain

^† All authors contributed equally to this work.

Sensors 2013, 13(9), 11407-11423; https://doi.org/10.3390/s130911407 - 26 Aug 2013

Cited by 15 | Viewed by 6732

Abstract

The mudéjar church of Santa María (Ateca) is valuable for its architecture and the altarpiece contained inside. Ateca is a village with continental climate characterized by cold winters and hot summers. In this paper we are interested in analysing the effect of temperature [...] Read more.

The mudéjar church of Santa María (Ateca) is valuable for its architecture and the altarpiece contained inside. Ateca is a village with continental climate characterized by cold winters and hot summers. In this paper we are interested in analysing the effect of temperature and relative humidity (RH) changes produced by the heating system on the altarpiece. Therefore, a monitoring system of 15 temperature and 15 relative humidity sensors was installed with a recording frequency of a data point per minute. The main contribution of this paper is the quantitative study of the effect of the heating system on the thermo-hygrometric parameters using statistical techniques such as ANOVA, mean daily trajectories or bivariate plots, and the proposal of an innovative dynamic contour plot. As results, the heating system produces a substantial increase (decrease) of temperature (RH) causing an hourly variation of these physical parameters detrimental to the conservation of the altarpiece, especially in its higher areas. Full article

(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Spain 2013)

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15 pages, 643 KiB

Open AccessArticle

Spectral-Domain Measurements of Birefringence and Sensing Characteristics of a Side-Hole Microstructured Fiber

by Petr Hlubina^1,*

, Tadeusz Martynkien², Jacek Olszewski², Pawel Mergo³, Mariusz Makara³, Krzysztof Poturaj³ and Waclaw Urbańczyk²

¹ Department of Physics, Technical University Ostrava, 17. listopadu 15, Ostrava-Poruba 708 33, Czech Republic

² Institute of Physics, Wroclaw University of Technology, Wybrze˙ze Wyspiańskiego 27, Wroclaw 50-370, Poland

³ Laboratory of Optical Fibre Technology, Maria Curie-Sklodowska University, Pl. M. Curie-Sklodowskiej 3, Lublin 20-031, Poland

Sensors 2013, 13(9), 11424-11438; https://doi.org/10.3390/s130911424 - 28 Aug 2013

Cited by 19 | Viewed by 7094

Abstract

We experimentally characterized a birefringent side-hole microstructured fiber in the visible wavelength region. The spectral dependence of the group and phase modal birefringence was measured using the methods of spectral interferometry. The phase modal birefringence of the investigated fiber increases with wavelength, but [...] Read more.

We experimentally characterized a birefringent side-hole microstructured fiber in the visible wavelength region. The spectral dependence of the group and phase modal birefringence was measured using the methods of spectral interferometry. The phase modal birefringence of the investigated fiber increases with wavelength, but its positive sign is opposite to the sign of the group modal birefringence. We also measured the sensing characteristics of the fiber using a method of tandem spectral interferometry. Spectral interferograms corresponding to different values of a physical parameter were processed to retrieve the spectral phase functions and to determine the spectral dependence of polarimetric sensitivity to strain, temperature and hydrostatic pressure. A negative sign of the polarimetric sensitivity was deduced from the simulation results utilizing the known modal birefringence dispersion of the fiber. Our experimental results show that the investigated fiber has a very high polarimetric sensitivity to hydrostatic pressure, reaching –200 rad x MPa^–1 x m^–1 at 750 nm. Full article

(This article belongs to the Special Issue Optomechatronics)

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14 pages, 500 KiB

Open AccessArticle

A Linearization Time-Domain CMOS Smart Temperature Sensor Using a Curvature Compensation Oscillator

by Chun-Chi Chen^*

and Hao-Wen Chen

Department of Electronic Engineering, National Kaohsiung First University of Science and Technology, Kaohsiung, 811, Taiwan

Sensors 2013, 13(9), 11439-11452; https://doi.org/10.3390/s130911439 - 28 Aug 2013

Cited by 15 | Viewed by 8340

Abstract

This paper presents an area-efficient time-domain CMOS smart temperature sensor using a curvature compensation oscillator for linearity enhancement with a −40 to 120 °C temperature range operability. The inverter-based smart temperature sensors can substantially reduce the cost and circuit complexity of integrated temperature [...] Read more.

This paper presents an area-efficient time-domain CMOS smart temperature sensor using a curvature compensation oscillator for linearity enhancement with a −40 to 120 °C temperature range operability. The inverter-based smart temperature sensors can substantially reduce the cost and circuit complexity of integrated temperature sensors. However, a large curvature exists on the temperature-to-time transfer curve of the inverter-based delay line and results in poor linearity of the sensor output. For cost reduction and error improvement, a temperature-to-pulse generator composed of a ring oscillator and a time amplifier was used to generate a thermal sensing pulse with a sufficient width proportional to the absolute temperature (PTAT). Then, a simple but effective on-chip curvature compensation oscillator is proposed to simultaneously count and compensate the PTAT pulse with curvature for linearization. With such a simple structure, the proposed sensor possesses an extremely small area of 0.07 mm² in a TSMC 0.35-mm CMOS 2P4M digital process. By using an oscillator-based scheme design, the proposed sensor achieves a fine resolution of 0.045 °C without significantly increasing the circuit area. With the curvature compensation, the inaccuracy of −1.2 to 0.2 °C is achieved in an operation range of −40 to 120 °C after two-point calibration for 14 packaged chips. The power consumption is measured as 23 mW at a sample rate of 10 samples/s. Full article

(This article belongs to the Section Physical Sensors)

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23 pages, 1894 KiB

Open AccessArticle

A Sparse Representation-Based Deployment Method for Optimizing the Observation Quality of Camera Networks

by Chang Wang^*, Fei Qi^*, Guangming Shi and Xiaotian Wang

School of Electronic Engineering, Xidian University, Xi'an, Shaanxi, 710071, China

Sensors 2013, 13(9), 11453-11475; https://doi.org/10.3390/s130911453 - 28 Aug 2013

Cited by 6 | Viewed by 6503

Abstract

Deployment is a critical issue affecting the quality of service of camera networks. The deployment aims at adopting the least number of cameras to cover the whole scene, which may have obstacles to occlude the line of sight, with expected observation quality. This [...] Read more.

Deployment is a critical issue affecting the quality of service of camera networks. The deployment aims at adopting the least number of cameras to cover the whole scene, which may have obstacles to occlude the line of sight, with expected observation quality. This is generally formulated as a non-convex optimization problem, which is hard to solve in polynomial time. In this paper, we propose an efficient convex solution for deployment optimizing the observation quality based on a novel anisotropic sensing model of cameras, which provides a reliable measurement of the observation quality. The deployment is formulated as the selection of a subset of nodes from a redundant initial deployment with numerous cameras, which is an ℓ0 minimization problem. Then, we relax this non-convex optimization to a convex ℓ1 minimization employing the sparse representation. Therefore, the high quality deployment is efficiently obtained via convex optimization. Simulation results confirm the effectiveness of the proposed camera deployment algorithms. Full article

(This article belongs to the Section Sensor Networks)

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Graphical abstract

14 pages, 830 KiB

Open AccessArticle

A Noncontact Force Sensor Based on a Fiber Bragg Grating and Its Application for Corrosion Measurement

by Clara J. Pacheco and Antonio C. Bruno^*

Departamento de Física, Pontifícia Universidade Católica do Rio de Janeiro, Rua Marquês de São Vicente 225, Rio de Janeiro, RJ 22451-900, Brazil

Sensors 2013, 13(9), 11476-11489; https://doi.org/10.3390/s130911476 - 29 Aug 2013

Cited by 29 | Viewed by 8928

Abstract

A simple noncontact force sensor based on an optical fiber Bragg grating attached to a small magnet has been proposed and built. The sensor measures the force between the magnet and any ferromagnetic material placed within a few millimeters of the sensor. Maintaining [...] Read more.

A simple noncontact force sensor based on an optical fiber Bragg grating attached to a small magnet has been proposed and built. The sensor measures the force between the magnet and any ferromagnetic material placed within a few millimeters of the sensor. Maintaining the sensor at a constant standoff distance, material loss due to corrosion increases the distance between the magnet and the corroded surface, which decreases the magnetic force. This will decrease the strain in the optical fiber shifting the reflected Bragg wavelength. The measured shift for the optical fiber used was 1.36 nm per Newton. Models were developed to optimize the magnet geometry for a specific sensor standoff distance and for particular corrosion pit depths. The sensor was able to detect corrosion pits on a fuel storage tank bottom with depths in the sub-millimeter range. Full article

(This article belongs to the Special Issue Photonic Sensors for Industrial, Environmental and Health Monitoring)

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8 pages, 244 KiB

Open AccessArticle

Covariance-Based Direction-of-Arrival Estimation of Wideband Coherent Chirp Signals via Sparse Representation

by Zhichao Sha^*, Zhengmeng Liu, Zhitao Huang and Yiyu Zhou

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

Sensors 2013, 13(9), 11490-11497; https://doi.org/10.3390/s130911490 - 29 Aug 2013

Cited by 10 | Viewed by 5610

Abstract

This paper addresses the problem of direction-of-arrival (DOA) estimation of multiple wideband coherent chirp signals, and a new method is proposed. The new method is based on signal component analysis of the array output covariance, instead of the complicated time-frequency analysis used in [...] Read more.

This paper addresses the problem of direction-of-arrival (DOA) estimation of multiple wideband coherent chirp signals, and a new method is proposed. The new method is based on signal component analysis of the array output covariance, instead of the complicated time-frequency analysis used in previous literatures, and thus is more compact and effectively avoids possible signal energy loss during the hyper-processes. Moreover, the a priori information of signal number is no longer a necessity for DOA estimation in the new method. Simulation results demonstrate the performance superiority of the new method over previous ones. Full article

(This article belongs to the Section Physical Sensors)

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9 pages, 223 KiB

Open AccessArticle

An Acetylcholinesterase-Based Chronoamperometric Biosensor for Fast and Reliable Assay of Nerve Agents

by Miroslav Pohanka^1,2,*

, Vojtech Adam^3,4 and Rene Kizek^3,4

¹ Faculty of Military Health Sciences, University of Defence, Trebesska 1575, CZ-500 01 Hradec Kralove, Czech Republic

² Karel English College in Brno, Sujanovo namesti 356/1, CZ-602 00 Brno, Czech Republic

³ Central European Institute of Technology, Brno University of Technology, Technicka 3058/10, CZ-616 00 Brno, Czech Republic

⁴ Department of Chemistry and Biochemistry, Faculty of Agronomy, Mendel University in Brno, Zemedelska 1, CZ-613 00 Brno, Czech Republic

Sensors 2013, 13(9), 11498-11506; https://doi.org/10.3390/s130911498 - 30 Aug 2013

Cited by 31 | Viewed by 9901

Abstract

The enzyme acetylcholinesterase (AChE) is an important part of cholinergic nervous system, where it stops neurotransmission by hydrolysis of the neurotransmitter acetylcholine. It is sensitive to inhibition by organophosphate and carbamate insecticides, some Alzheimer disease drugs, secondary metabolites such as aflatoxins and nerve [...] Read more.

The enzyme acetylcholinesterase (AChE) is an important part of cholinergic nervous system, where it stops neurotransmission by hydrolysis of the neurotransmitter acetylcholine. It is sensitive to inhibition by organophosphate and carbamate insecticides, some Alzheimer disease drugs, secondary metabolites such as aflatoxins and nerve agents used in chemical warfare. When immobilized on a sensor (physico-chemical transducer), it can be used for assay of these inhibitors. In the experiments described herein, an AChE- based electrochemical biosensor using screen printed electrode systems was prepared. The biosensor was used for assay of nerve agents such as sarin, soman, tabun and VX. The limits of detection achieved in a measuring protocol lasting ten minutes were 7.41 × 10⁻¹² mol/L for sarin, 6.31 × 10⁻¹² mol /L for soman, 6.17 × 10⁻¹¹ mol/L for tabun, and 2.19 × 10⁻¹¹ mol/L for VX, respectively. The assay was reliable, with minor interferences caused by the organic solvents ethanol, methanol, isopropanol and acetonitrile. Isopropanol was chosen as suitable medium for processing lipophilic samples. Full article

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

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15 pages, 1888 KiB

Open AccessArticle

Mutational Analysis of a Red Fluorescent Protein-Based Calcium Ion Indicator

by Haley J. Carlson and Robert E. Campbell^*

Department of Chemistry, University of Alberta, Edmonton, AB T6G 2G2, Canada

Sensors 2013, 13(9), 11507-11521; https://doi.org/10.3390/s130911507 - 2 Sep 2013

Cited by 9 | Viewed by 9614

Abstract

As part of an ongoing effort to develop genetically encoded calcium ion (Ca²⁺) indicators we recently described a new variant, designated CH-GECO2.1, that is a genetic chimera of the red fluorescent protein (FP) mCherry, calmodulin (CaM), and a peptide that binds [...] Read more.

As part of an ongoing effort to develop genetically encoded calcium ion (Ca²⁺) indicators we recently described a new variant, designated CH-GECO2.1, that is a genetic chimera of the red fluorescent protein (FP) mCherry, calmodulin (CaM), and a peptide that binds to Ca²⁺-bound CaM. In contrast to the closely related Ca²⁺ indicator R-GECO1, CH-GECO2.1 is characterized by a much higher affinity for Ca²⁺ and a sensing mechanism that does not involve direct modulation of the chromophore pK_a. To probe the structural basis underlying the differences between CH-GECO2.1 and R-GECO1, and to gain a better understanding of the mechanism of CH-GECO2.1, we have constructed, purified, and characterized a large number of variants with strategic amino acid substitutions. This effort led us to identify Gln163 as the key residue involved in the conformational change that transduces the Ca²⁺ binding event into a change in the chromophore environment. In addition, we demonstrate that many of the substitutions that differentiate CH-GECO2.1 and R-GECO1 have little influence on both the K_d for Ca²⁺ and the sensing mechanism, and that the interdomain linkers and interfaces play important roles. Full article

(This article belongs to the Special Issue Fluorescent Biosensors)

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17 pages, 2367 KiB

Open AccessArticle

Microseismic Monitoring of CO₂ Injection at the Penn West Enhanced Oil Recovery Pilot Project, Canada: Implications for Detection of Wellbore Leakage

by Patricia Martínez-Garzón^1,*, Marco Bohnhoff^1,2, Grzegorz Kwiatek¹, Gonzalo Zambrano-Narváez³ and Rick Chalaturnyk³

¹ Helmholtz Centre Potsdam GFZ German Research Centre for Geosciences, Section 3.2 Geomechanics and Rheology, Telegrafenberg, Potsdam 14473, Germany

² Institute of Geological Sciences, Free University of Berlin, Berlin 14195, Germany

³ Department of Civil and Environmental Engineering, University of Alberta, Edmonton, AB T6G 2W2, Canada

Sensors 2013, 13(9), 11522-11538; https://doi.org/10.3390/s130911522 - 2 Sep 2013

Cited by 18 | Viewed by 12826

Abstract

A passive seismic monitoring campaign was carried out in the frame of a CO₂-Enhanced Oil Recovery (EOR) pilot project in Alberta, Canada. Our analysis focuses on a two-week period during which prominent downhole pressure fluctuations in the reservoir were accompanied by [...] Read more.

A passive seismic monitoring campaign was carried out in the frame of a CO₂-Enhanced Oil Recovery (EOR) pilot project in Alberta, Canada. Our analysis focuses on a two-week period during which prominent downhole pressure fluctuations in the reservoir were accompanied by a leakage of CO₂ and CH₄ along the monitoring well equipped with an array of short-period borehole geophones. We applied state of the art seismological processing schemes to the continuous seismic waveform recordings. During the analyzed time period we did not find evidence of induced micro-seismicity associated with CO₂ injection. Instead, we identified signals related to the leakage of CO₂ and CH₄, in that seven out of the eight geophones show a clearly elevated noise level framing the onset time of leakage along the monitoring well. Our results confirm that micro-seismic monitoring of reservoir treatment can contribute towards improved reservoir monitoring and leakage detection. Full article

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

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14 pages, 749 KiB

Open AccessArticle

Research on the Dynamic Hysteresis Loop Model of the Residence Times Difference (RTD)-Fluxgate

by Yanzhang Wang^1,2, Shujun Wu^1,2,*, Zhijian Zhou^1,2, Defu Cheng^1,2, Na Pang^1,2 and Yunxia Wan^1,2

¹ College of Instrumentation & Electrical Engineering, Jilin University, No.938 Ximinzhu Street, Changchun 130026, China

² Key Laboratory of Geo-Exploration Instrumentation, Ministry of Education, Jilin University, No.938 Ximinzhu Street, Changchun 130026, China

Sensors 2013, 13(9), 11539-11552; https://doi.org/10.3390/s130911539 - 2 Sep 2013

Cited by 24 | Viewed by 8210

Abstract

Based on the core hysteresis features, the RTD-fluxgate core, while working, is repeatedly saturated with excitation field. When the fluxgate simulates, the accurate characteristic model of the core may provide a precise simulation result. As the shape of the ideal hysteresis loop model [...] Read more.

Based on the core hysteresis features, the RTD-fluxgate core, while working, is repeatedly saturated with excitation field. When the fluxgate simulates, the accurate characteristic model of the core may provide a precise simulation result. As the shape of the ideal hysteresis loop model is fixed, it cannot accurately reflect the actual dynamic changing rules of the hysteresis loop. In order to improve the fluxgate simulation accuracy, a dynamic hysteresis loop model containing the parameters which have actual physical meanings is proposed based on the changing rule of the permeability parameter when the fluxgate is working. Compared with the ideal hysteresis loop model, this model has considered the dynamic features of the hysteresis loop, which makes the simulation results closer to the actual output. In addition, other hysteresis loops of different magnetic materials can be explained utilizing the described model for an example of amorphous magnetic material in this manuscript. The model has been validated by the output response comparison between experiment results and fitting results using the model. Full article

(This article belongs to the Section Physical Sensors)

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33 pages, 502 KiB

Open AccessArticle

A Security Analysis of the 802.11s Wireless Mesh Network Routing Protocol and Its Secure Routing Protocols

by Whye Kit Tan¹, Sang-Gon Lee^1,*

, Jun Huy Lam¹ and Seong-Moo Yoo²

¹ Department of Ubiquitous IT, Division of Computer & Information Engineering, Dongseo University, Busan 617-716, Korea

² Department of Electrical and Computer Engineering, The University of Alabama in Huntsville, Huntsville, AL 35899, USA

Sensors 2013, 13(9), 11553-11585; https://doi.org/10.3390/s130911553 - 2 Sep 2013

Cited by 15 | Viewed by 8583

Abstract

Wireless mesh networks (WMNs) can act as a scalable backbone by connecting separate sensor networks and even by connecting WMNs to a wired network. The Hybrid Wireless Mesh Protocol (HWMP) is the default routing protocol for the 802.11s WMN. The routing protocol is [...] Read more.

Wireless mesh networks (WMNs) can act as a scalable backbone by connecting separate sensor networks and even by connecting WMNs to a wired network. The Hybrid Wireless Mesh Protocol (HWMP) is the default routing protocol for the 802.11s WMN. The routing protocol is one of the most important parts of the network, and it requires protection, especially in the wireless environment. The existing security protocols, such as the Broadcast Integrity Protocol (BIP), Counter with cipher block chaining message authentication code protocol (CCMP), Secure Hybrid Wireless Mesh Protocol (SHWMP), Identity Based Cryptography HWMP (IBC-HWMP), Elliptic Curve Digital Signature Algorithm HWMP (ECDSA-HWMP), and Watchdog-HWMP aim to protect the HWMP frames. In this paper, we have analyzed the vulnerabilities of the HWMP and developed security requirements to protect these identified vulnerabilities. We applied the security requirements to analyze the existing secure schemes for HWMP. The results of our analysis indicate that none of these protocols is able to satisfy all of the security requirements. We also present a quantitative complexity comparison among the protocols and an example of a security scheme for HWMP to demonstrate how the result of our research can be utilized. Our research results thus provide a tool for designing secure schemes for the HWMP. Full article

(This article belongs to the Section Sensor Networks)

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17 pages, 898 KiB

Open AccessArticle

Oriented Immobilization of His-Tagged Protein on a Redox Active Thiol Derivative of DPTA-Cu(II) Layer Deposited on a Gold Electrode—The Base of Electrochemical Biosensors

by Edyta Mikuła¹, Magdalena Sulima², Ilona Marszałek², Aleksandra Wysłouch-Cieszyńska², Peter Verwilst³, Wim Dehaen³

, Jerzy Radecki¹ and Hanna Radecka^1,*

¹ Institute of Animal Reproduction and Food Research of Polish Academy of Sciences, Tuwima 10, Olsztyn 10-748, Poland

² Institute of Biochemistry and Biophysics of Polish Academy of Sciences, Pawińskiego 5a, Warsaw 02-106, Poland

³ Chemistry Department, University of Leuven, Celestijnenlaan 200F, Leuven B-3001, Belgium

Sensors 2013, 13(9), 11586-11602; https://doi.org/10.3390/s130911586 - 3 Sep 2013

Cited by 24 | Viewed by 7448

Abstract

This paper concerns the development of an electrochemical biosensor for the determination of Aβ16–23' and Aβ1–40 peptides. The His-tagged V and VC1 domains of Receptor for Advanced Glycation end Products (RAGE) immobilized on a gold electrode surface were used as analytically active molecules. [...] Read more.

This paper concerns the development of an electrochemical biosensor for the determination of Aβ16–23' and Aβ1–40 peptides. The His-tagged V and VC1 domains of Receptor for Advanced Glycation end Products (RAGE) immobilized on a gold electrode surface were used as analytically active molecules. The immobilization of His6–RAGE domains consists of: (i) formation of a mixed layer of N-acetylcysteamine (NAC) and the thiol derivative of pentetic acid (DPTA); (ii) complexation of Cu(II) by DPTA; (iii) oriented immobilization of His6–RAGE domains via coordination bonds between Cu(II) sites from DPTA–Cu(II) complex and imidazole nitrogen atoms of a histidine tag. Each modification step was controlled by cyclic voltammetry (CV), Osteryoung square-wave voltammetry (OSWV), and atomic force microscopy (AFM). The applicability of the proposed biosensor was tested in the presence of human plasma, which had no influence on its performance. The detection limits for Aβ1–40 determination were 1.06 nM and 0.80 nM, in the presence of buffer and human plasma, respectively. These values reach the concentration level of Aβ1–40 which is relevant for determination of its soluble form in human plasma, as well as in brain. This indicates the promising future application of biosensor presented for early diagnosis of neurodegenerative diseases. Full article

(This article belongs to the Section Biosensors)

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33 pages, 3478 KiB

Open AccessArticle

Human Detection from a Mobile Robot Using Fusion of Laser and Vision Information

by Efstathios P. Fotiadis^*, Mario Garzón and Antonio Barrientos

Centro de Automática y Robótica, UPM-CSIC. Calle José Gutiérrez Abascal, 2. Madrid 28006, Spain

Sensors 2013, 13(9), 11603-11635; https://doi.org/10.3390/s130911603 - 4 Sep 2013

Cited by 37 | Viewed by 13524

Abstract

This paper presents a human detection system that can be employed on board a mobile platform for use in autonomous surveillance of large outdoor infrastructures. The prediction is based on the fusion of two detection modules, one for the laser and another for [...] Read more.

This paper presents a human detection system that can be employed on board a mobile platform for use in autonomous surveillance of large outdoor infrastructures. The prediction is based on the fusion of two detection modules, one for the laser and another for the vision data. In the laser module, a novel feature set that better encapsulates variations due to noise, distance and human pose is proposed. This enhances the generalization of the system, while at the same time, increasing the outdoor performance in comparison with current methods. The vision module uses the combination of the histogram of oriented gradients descriptor and the linear support vector machine classifier. Current approaches use a fixed-size projection to define regions of interest on the image data using the range information from the laser range finder. When applied to small size unmanned ground vehicles, these techniques suffer from misalignment, due to platform vibrations and terrain irregularities. This is effectively addressed in this work by using a novel adaptive projection technique, which is based on a probabilistic formulation of the classifier performance. Finally, a probability calibration step is introduced in order to optimally fuse the information from both modules. Experiments in real world environments demonstrate the robustness of the proposed method. Full article

(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Spain 2013)

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Graphical abstract

17 pages, 8508 KiB

Open AccessArticle

Robust Depth Estimation and Image Fusion Based on Optimal Area Selection

by Ik-Hyun Lee¹, Muhammad Tariq Mahmood²

and Tae-Sun Choi^1,*

¹ School of Mechatronics, Gwangju Institute of Science and Technology (GIST), 123 Cheomdan gwagiro, Buk-Gu, Gwangju 500-712, Korea

² School of Computer Science and Engineering, Korea University of Technology and Education, 1600 Chungjeolno, Byeogchunmyun, Cheonan, Chungnam 330-708, Korea

Sensors 2013, 13(9), 11636-11652; https://doi.org/10.3390/s130911636 - 4 Sep 2013

Cited by 6 | Viewed by 6292

Abstract

Mostly, 3D cameras having depth sensing capabilities employ active depth estimation techniques, such as stereo, the triangulation method or time-of-flight. However, these methods are expensive. The cost can be reduced by applying optical passive methods, as they are inexpensive and efficient. In this [...] Read more.

Mostly, 3D cameras having depth sensing capabilities employ active depth estimation techniques, such as stereo, the triangulation method or time-of-flight. However, these methods are expensive. The cost can be reduced by applying optical passive methods, as they are inexpensive and efficient. In this paper, we suggest the use of one of the passive optical methods named shape from focus (SFF) for 3D cameras. In the proposed scheme, first, an adaptive window is computed through an iterative process using a criterion. Then, the window is divided into four regions. In the next step, the best focused area among the four regions is selected based on variation in the data. The effectiveness of the proposed scheme is validated using image sequences of synthetic and real objects. Comparative analysis based on statistical metrics correlation, mean square error (MSE), universal image quality index (UIQI) and structural similarity (SSIM) shows the effectiveness of the proposed scheme. Full article

(This article belongs to the Section Physical Sensors)

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7 pages, 481 KiB

Open AccessArticle

A High-Temperature Fiber Sensor Using a Low Cost Interrogation Scheme

by David Barrera^* and Salvador Sales

Optical and Quantum Communications Group, Institute of Telecommunications and Multimedia Applications (iTEAM), Universitat Politècnica de València, Valencia, 46022, Spain

Sensors 2013, 13(9), 11653-11659; https://doi.org/10.3390/s130911653 - 4 Sep 2013

Cited by 8 | Viewed by 6209

Abstract

Regenerated Fibre Bragg Gratings have the potential for high-temperature monitoring. In this paper, the inscription of Fibre Bragg Gratings (FBGs) and the later regeneration process to obtain Regenerated Fiber Bragg Gratings (RFBGs) in high-birefringence optical fiber is reported. The obtained RFBGs show two [...] Read more.

Regenerated Fibre Bragg Gratings have the potential for high-temperature monitoring. In this paper, the inscription of Fibre Bragg Gratings (FBGs) and the later regeneration process to obtain Regenerated Fiber Bragg Gratings (RFBGs) in high-birefringence optical fiber is reported. The obtained RFBGs show two Bragg resonances corresponding to the slow and fast axis that are characterized in temperature terms. As the temperature increases the separation between the two Bragg resonances is reduced, which can be used for low cost interrogation. The proposed interrogation setup is based in the use of optical filters in order to convert the wavelength shift of each of the Bragg resonances into optical power changes. The design of the optical filters is also studied in this article. In first place, the ideal filter is calculated using a recursive method and defining the boundary conditions. This ideal filter linearizes the output of the interrogation setup but is limited by the large wavelength shift of the RFBG with temperature and the maximum attenuation. The response of modal interferometers as optical filters is also analyzed. They can be easily tuned shifting the optical spectrum. The output of the proposed interrogation scheme is simulated in these conditions improving the sensitivity. Full article

(This article belongs to the Special Issue Optomechatronics)

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27 pages, 3463 KiB

Open AccessArticle

Video-Based Fingerprint Verification

by Wei Qin, Yilong Yin^* and Lili Liu

School of Computer Science and Technology, Shandong University, Jinan 250101, Shandong, China

Sensors 2013, 13(9), 11660-11686; https://doi.org/10.3390/s130911660 - 4 Sep 2013

Cited by 4 | Viewed by 6231

Abstract

Conventional fingerprint verification systems use only static information. In this paper, fingerprint videos, which contain dynamic information, are utilized for verification. Fingerprint videos are acquired by the same capture device that acquires conventional fingerprint images, and the user experience of providing a fingerprint [...] Read more.

Conventional fingerprint verification systems use only static information. In this paper, fingerprint videos, which contain dynamic information, are utilized for verification. Fingerprint videos are acquired by the same capture device that acquires conventional fingerprint images, and the user experience of providing a fingerprint video is the same as that of providing a single impression. After preprocessing and aligning processes, “inside similarity” and “outside similarity” are defined and calculated to take advantage of both dynamic and static information contained in fingerprint videos. Match scores between two matching fingerprint videos are then calculated by combining the two kinds of similarity. Experimental results show that the proposed video-based method leads to a relative reduction of 60 percent in the equal error rate (EER) in comparison to the conventional single impression-based method. We also analyze the time complexity of our method when different combinations of strategies are used. Our method still outperforms the conventional method, even if both methods have the same time complexity. Finally, experimental results demonstrate that the proposed video-based method can lead to better accuracy than the multiple impressions fusion method, and the proposed method has a much lower false acceptance rate (FAR) when the false rejection rate (FRR) is quite low. Full article

(This article belongs to the Section Physical Sensors)

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22 pages, 1209 KiB

Open AccessArticle

Distributed Pedestrian Detection Alerts Based on Data Fusion with Accurate Localization

by Fernando García^1,*

, Felipe Jiménez²

, José Javier Anaya²

, José María Armingol¹, José Eugenio Naranjo²

and Arturo De la Escalera¹

¹ Intelligent Systems Laboratory, Universidad Carlos III de Madrid, Avda de la Universidad 30, Leganés 28911, Madrid, Spain

² INSIA, Technical University of Madrid, Carretera de Valencia, km.7, Madrid 28031, Spain

Sensors 2013, 13(9), 11687-11708; https://doi.org/10.3390/s130911687 - 4 Sep 2013

Cited by 31 | Viewed by 9496

Abstract

Among Advanced Driver Assistance Systems (ADAS) pedestrian detection is a common issue due to the vulnerability of pedestrians in the event of accidents. In the present work, a novel approach for pedestrian detection based on data fusion is presented. Data fusion helps to [...] Read more.

Among Advanced Driver Assistance Systems (ADAS) pedestrian detection is a common issue due to the vulnerability of pedestrians in the event of accidents. In the present work, a novel approach for pedestrian detection based on data fusion is presented. Data fusion helps to overcome the limitations inherent to each detection system (computer vision and laser scanner) and provides accurate and trustable tracking of any pedestrian movement. The application is complemented by an efficient communication protocol, able to alert vehicles in the surroundings by a fast and reliable communication. The combination of a powerful location, based on a GPS with inertial measurement, and accurate obstacle localization based on data fusion has allowed locating the detected pedestrians with high accuracy. Tests proved the viability of the detection system and the efficiency of the communication, even at long distances. By the use of the alert communication, dangerous situations such as occlusions or misdetections can be avoided. Full article

(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Spain 2013)

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19 pages, 1073 KiB

Open AccessArticle

Design and Implementation of a New Real-Time Frequency Sensor Used as Hardware Countermeasure

by Raúl Jiménez-Naharro^*, Juan Antonio Gómez-Galán

, Manuel Sánchez-Raya, Fernando Gómez-Bravo and Manuel Pedro-Carrasco

Department of Electronic Engineering, Computers, and Automatic, University of Huelva, Ctra Huelva-La Rábida, s/n, 21819 Huelva, Spain

Sensors 2013, 13(9), 11709-11727; https://doi.org/10.3390/s130911709 - 4 Sep 2013

Cited by 3 | Viewed by 7472

Abstract

A new digital countermeasure against attacks related to the clock frequency is presented. This countermeasure, known as frequency sensor, consists of a local oscillator, a transition detector, a measurement element and an output block. The countermeasure has been designed using a full-custom technique [...] Read more.

A new digital countermeasure against attacks related to the clock frequency is presented. This countermeasure, known as frequency sensor, consists of a local oscillator, a transition detector, a measurement element and an output block. The countermeasure has been designed using a full-custom technique implemented in an Application-Specific Integrated Circuit (ASIC), and the implementation has been verified and characterized with an integrated design using a 0.35 mm standard Complementary Metal Oxide Semiconductor (CMOS) technology (Very Large Scale Implementation—VLSI implementation). The proposed solution is configurable in resolution time and allowed range of period, achieving a minimum resolution time of only 1.91 ns and an initialization time of 5.84 ns. The proposed VLSI implementation shows better results than other solutions, such as digital ones based on semi-custom techniques and analog ones based on band pass filters, all design parameters considered. Finally, a counter has been used to verify the good performance of the countermeasure in avoiding the success of an attack. Full article

(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Spain 2013)

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22 pages, 1035 KiB

Open AccessArticle

A Telemetry System Embedded in Clothes for Indoor Localization and Elderly Health Monitoring

by Yoann Charlon^1,2,*, Nicolas Fourty³ and Eric Campo^1,2

¹ CNRS, LAAS, 7 Avenue du Colonel Roche, Toulouse F-31400, France

² Univ de Toulouse, UPS, UTM, LAAS, Toulouse F-31400, France

³ LCIS, Grenoble-INP, Université Pierre Mendès, 50, rue Barthélémy de Laffemas BP54–F-26902 Valence, France

Sensors 2013, 13(9), 11728-11749; https://doi.org/10.3390/s130911728 - 4 Sep 2013

Cited by 15 | Viewed by 9851

Abstract

This paper presents a telemetry system used in a combined trilateration method for the precise indoor localization of the elderly who need health monitoring. The system is based on the association of two wireless technologies: ultrasonic and 802.15.4. The use of the 802.15.4 [...] Read more.

This paper presents a telemetry system used in a combined trilateration method for the precise indoor localization of the elderly who need health monitoring. The system is based on the association of two wireless technologies: ultrasonic and 802.15.4. The use of the 802.15.4 RF signal gives the reference starting time of the ultrasonic emission (time difference of arrival method). A time of flight measurement of the ultrasonic pulses provides the distances between the mobile node and three anchor points. These distance measurements are then used to locate the mobile node using the trilateration method with an accuracy of a few centimetres. The originality of our work lies in embedding the mobile node in clothes. The system is embedded in clothes in two ways: on a shoe in order to form a “smart” shoe and in a hat in order to form a “smart” hat. Both accessories allow movements, gait speed and distance covered to be monitored for health applications. Experiments in a test room are presented to show the effectiveness of our system. Full article

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

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22 pages, 963 KiB

Open AccessArticle

SIVEH: Numerical Computing Simulation of Wireless Energy-Harvesting Sensor Nodes

by Antonio Sanchez^1,*, Sara Blanc², Salvador Climent¹, Pedro Yuste² and Rafael Ors²

¹ ITACA Institute, Universitat Politècnica de València, Valencia 46022, Spain

² DISCA Department, Universitat Politècnica de València, Valencia 46022, Spain

Sensors 2013, 13(9), 11750-11771; https://doi.org/10.3390/s130911750 - 4 Sep 2013

Cited by 11 | Viewed by 6856

Abstract

The paper presents a numerical energy harvesting model for sensor nodes, SIVEH (Simulator I–V for EH), based on I–V hardware tracking. I–V tracking is demonstrated to be more accurate than traditional energy modeling techniques when some of the components present different power dissipation [...] Read more.

The paper presents a numerical energy harvesting model for sensor nodes, SIVEH (Simulator I–V for EH), based on I–V hardware tracking. I–V tracking is demonstrated to be more accurate than traditional energy modeling techniques when some of the components present different power dissipation at either different operating voltages or drawn currents. SIVEH numerical computing allows fast simulation of long periods of time—days, weeks, months or years—using real solar radiation curves. Moreover, SIVEH modeling has been enhanced with sleep time rate dynamic adjustment, while seeking energy-neutral operation. This paper presents the model description, a functional verification and a critical comparison with the classic energy approach. Full article

(This article belongs to the Section Sensor Networks)

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10 pages, 334 KiB

Open AccessArticle

Surface Roughness Measurement on a Wing Aircraft by Speckle Correlation

by Félix Salazar^* and Alberto Barrientos

Departamento de Física Aplicada (FARN), ETSI Minas, Universidad Politécnica de Madrid, C/Ríos Rosas 21, 28003 Madrid, Spain

Sensors 2013, 13(9), 11772-11781; https://doi.org/10.3390/s130911772 - 5 Sep 2013

Cited by 23 | Viewed by 8408

Abstract

The study of the damage of aeronautical materials is important because it may change the microscopic surface structure profiles. The modification of geometrical surface properties can cause small instabilities and then a displacement of the boundary layer. One of the irregularities we can [...] Read more.

The study of the damage of aeronautical materials is important because it may change the microscopic surface structure profiles. The modification of geometrical surface properties can cause small instabilities and then a displacement of the boundary layer. One of the irregularities we can often find is surface roughness. Due to an increase of roughness and other effects, there may be extra momentum losses in the boundary layer and a modification in the parasite drag. In this paper we present a speckle method for measuring the surface roughness on an actual unmanned aircraft wing. The results show an inhomogeneous roughness distribution on the wing, as expected according to the anisotropic influence of the winds over the entire wing geometry. A calculation of the uncertainty of the technique is given. Full article

(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Spain 2013)

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15 pages, 537 KiB

Open AccessEditorial

Underwater Sensor Nodes and Networks

by Jaime Lloret

Instituto de Investigación para la Gestión Integrada de Zonas Costeras (IGIC), Universidad Politécnica de Valencia, Camino Vera s/n, Valencia 46022, Spain

Sensors 2013, 13(9), 11782-11796; https://doi.org/10.3390/s130911782 - 5 Sep 2013

Cited by 117 | Viewed by 12601

Abstract

Sensor technology has matured enough to be used in any type of environment. The appearance of new physical sensors has increased the range of environmental parameters for gathering data. Because of the huge amount of unexploited resources in the ocean environment, there is [...] Read more.

Sensor technology has matured enough to be used in any type of environment. The appearance of new physical sensors has increased the range of environmental parameters for gathering data. Because of the huge amount of unexploited resources in the ocean environment, there is a need of new research in the field of sensors and sensor networks. This special issue is focused on collecting recent advances on underwater sensors and underwater sensor networks in order to measure, monitor, surveillance of and control of underwater environments. On the one hand, from the sensor node perspective, we will see works related with the deployment of physical sensors, development of sensor nodes and transceivers for sensor nodes, sensor measurement analysis and several issues such as layer 1 and 2 protocols for underwater communication and sensor localization and positioning systems. On the other hand, from the sensor network perspective, we will see several architectures and protocols for underwater environments and analysis concerning sensor network measurements. Both sides will provide us a complete view of last scientific advances in this research field. Full article

(This article belongs to the Special Issue Underwater Sensor Nodes and Underwater Sensor Networks)

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21 pages, 1903 KiB

Open AccessArticle

Automatic Determination of Validity of Input Data Used in Ellipsoid Fitting MARG Calibration Algorithms

by Alberto Olivares^1,*, Gonzalo Ruiz-Garcia², Gonzalo Olivares², Juan Manuel Górriz¹ and Javier Ramirez¹

¹ Department of Signal Theory, Telematics and Communications, CITIC-University of Granada,Calle Periodista Rafael Gómez Montero, 2, E-18071 Granada, Spain

² Department of Computer Architecture and Computer Technology, CITIC-University of Granada, Calle Periodista Rafael Gómez Montero, 2, E-18071 Granada, Spain

Sensors 2013, 13(9), 11797-11817; https://doi.org/10.3390/s130911797 - 5 Sep 2013

Cited by 32 | Viewed by 10334

Abstract

Ellipsoid fitting algorithms are widely used to calibrate Magnetic Angular Rate and Gravity (MARG) sensors. These algorithms are based on the minimization of an error function that optimizes the parameters of a mathematical sensor model that is subsequently applied to calibrate the raw [...] Read more.

Ellipsoid fitting algorithms are widely used to calibrate Magnetic Angular Rate and Gravity (MARG) sensors. These algorithms are based on the minimization of an error function that optimizes the parameters of a mathematical sensor model that is subsequently applied to calibrate the raw data. The convergence of this kind of algorithms to a correct solution is very sensitive to input data. Input calibration datasets must be properly distributed in space so data can be accurately fitted to the theoretical ellipsoid model. Gathering a well distributed set is not an easy task as it is difficult for the operator carrying out the maneuvers to keep a visual record of all the positions that have already been covered, as well as the remaining ones. It would be then desirable to have a system that gives feedback to the operator when the dataset is ready, or to enable the calibration process in auto-calibrated systems. In this work, we propose two different algorithms that analyze the goodness of the distributions by computing four different indicators. The first approach is based on a thresholding algorithm that uses only one indicator as its input and the second one is based on a Fuzzy Logic System (FLS) that estimates the calibration error for a given calibration set using a weighted combination of two indicators. Very accurate classification between valid and invalid datasets is achieved with average Area Under Curve (AUC) of up to 0.98. Full article

(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Spain 2013)

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24 pages, 2057 KiB

Open AccessArticle

Low-Cost Ultrasonic Distance Sensor Arrays with Networked Error Correction

by Hongjun Dai^1,*, Shulin Zhao¹, Zhiping Jia¹ and Tianzhou Chen²

¹ Department of Computer Science and Technology, Shandong University, No. 1500, Shunhua Road,Jinan 276023, China

² Department of Computer Science and Technology, Zhejiang University, No. 38, Zheda Road, Hangzhou 310027, China

Sensors 2013, 13(9), 11818-11841; https://doi.org/10.3390/s130911818 - 5 Sep 2013

Cited by 5 | Viewed by 6873

Abstract

Distance has been one of the basic factors in manufacturing and control fields, and ultrasonic distance sensors have been widely used as a low-cost measuring tool. However, the propagation of ultrasonic waves is greatly affected by environmental factors such as temperature, humidity and [...] Read more.

Distance has been one of the basic factors in manufacturing and control fields, and ultrasonic distance sensors have been widely used as a low-cost measuring tool. However, the propagation of ultrasonic waves is greatly affected by environmental factors such as temperature, humidity and atmospheric pressure. In order to solve the problem of inaccurate measurement, which is significant within industry, this paper presents a novel ultrasonic distance sensor model using networked error correction (NEC) trained on experimental data. This is more accurate than other existing approaches because it uses information from indirect association with neighboring sensors, which has not been considered before. The NEC technique, focusing on optimization of the relationship of the topological structure of sensor arrays, is implemented for the compensation of erroneous measurements caused by the environment. We apply the maximum likelihood method to determine the optimal fusion data set and use a neighbor discovery algorithm to identify neighbor nodes at the top speed. Furthermore, we adopt the NEC optimization algorithm, which takes full advantage of the correlation coefficients for neighbor sensors. The experimental results demonstrate that the ranging errors of the NEC system are within 2.20%; furthermore, the mean absolute percentage error is reduced to 0.01% after three iterations of this method, which means that the proposed method performs extremely well. The optimized method of distance measurement we propose, with the capability of NEC, would bring a significant advantage for intelligent industrial automation. Full article

(This article belongs to the Section Physical Sensors)

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19 pages, 4396 KiB

Open AccessArticle

Human-Computer Interaction Based on Hand Gestures Using RGB-D Sensors

by José Manuel Palacios^1,*, Carlos Sagüés¹, Eduardo Montijano² and Sergio Llorente³

¹ Departamento de Informática e Ingeniería de Sistemas (DIIS) and Instituto de Investigación en Ingeniería de Aragón (I3A), Universidad de Zaragoza, Zaragoza 50018, Spain

² Centro Universitario de la Defensa (CUD) and Instituto de Investigación en Ingeniería de Aragón(I3A), Zaragoza 50090, Spain

³ Research and Development Department, Induction Technology, Product Division Cookers, BSH Home Appliances Group, Zaragoza 50016, Spain

Sensors 2013, 13(9), 11842-11860; https://doi.org/10.3390/s130911842 - 6 Sep 2013

Cited by 76 | Viewed by 12345

Abstract

In this paper we present a new method for hand gesture recognition based on an RGB-D sensor. The proposed approach takes advantage of depth information to cope with the most common problems of traditional video-based hand segmentation methods: cluttered backgrounds and occlusions. The [...] Read more.

In this paper we present a new method for hand gesture recognition based on an RGB-D sensor. The proposed approach takes advantage of depth information to cope with the most common problems of traditional video-based hand segmentation methods: cluttered backgrounds and occlusions. The algorithm also uses colour and semantic information to accurately identify any number of hands present in the image. Ten different static hand gestures are recognised, including all different combinations of spread fingers. Additionally, movements of an open hand are followed and 6 dynamic gestures are identified. The main advantage of our approach is the freedom of the user’s hands to be at any position of the image without the need of wearing any specific clothing or additional devices. Besides, the whole method can be executed without any initial training or calibration. Experiments carried out with different users and in different environments prove the accuracy and robustness of the method which, additionally, can be run in real-time. Full article

(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Spain 2013)

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38 pages, 3026 KiB

Open AccessArticle

Theoretical Analysis of Interferometer Wave Front Tilt and Fringe Radiant Flux on a Rectangular Photodetector

by Robert Smith^* and Franz Konstantin Fuss

School of Aerospace, Mechanical and Manufacturing Engineering, RMIT University, Plenty Road, Melbourne 3083, Australia

Sensors 2013, 13(9), 11861-11898; https://doi.org/10.3390/s130911861 - 6 Sep 2013

Cited by 6 | Viewed by 9199

Abstract

This paper is a theoretical analysis of mirror tilt in a Michelson interferometer and its effect on the radiant flux over the active area of a rectangular photodetector or image sensor pixel. It is relevant to sensor applications using homodyne interferometry where these [...] Read more.

This paper is a theoretical analysis of mirror tilt in a Michelson interferometer and its effect on the radiant flux over the active area of a rectangular photodetector or image sensor pixel. It is relevant to sensor applications using homodyne interferometry where these opto-electronic devices are employed for partial fringe counting. Formulas are derived for radiant flux across the detector for variable location within the fringe pattern and with varying wave front angle. The results indicate that the flux is a damped sine function of the wave front angle, with a decay constant of the ratio of wavelength to detector width. The modulation amplitude of the dynamic fringe pattern reduces to zero at wave front angles that are an integer multiple of this ratio and the results show that the polarity of the radiant flux changes exclusively at these multiples. Varying tilt angle causes radiant flux oscillations under an envelope curve, the frequency of which is dependent on the location of the detector with the fringe pattern. It is also shown that a fringe count of zero can be obtained for specific photodetector locations and wave front angles where the combined effect of fringe contraction and fringe tilt can have equal and opposite effects. Fringe tilt as a result of a wave front angle of 0.05° can introduce a phase measurement difference of 16° between a photodetector/pixel located 20 mm and one located 100 mm from the optical origin. Full article

(This article belongs to the Special Issue Photodetectors)

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14 pages, 792 KiB

Open AccessArticle

Application of a Novel Tool for Diagnosing Bile Acid Diarrhoea

by James A. Covington^1,*

, Eric W. Westenbrink¹, Nathalie Ouaret¹, Ruth Harbord², Catherine Bailey³, Nicola O'Connell³, James Cullis⁴, Nigel Williams⁴, Chuka U. Nwokolo³, Karna D. Bardhan^5,6 and Ramesh P. Arasaradnam^3,6

¹ School of Engineering, University of Warwick, Coventry CV4 7AL, UK

² MOAC Doctoral Training Centre, University of Warwick, Coventry CV4 7AL, UK

³ Department of Gastroenterology, University Hospital Coventry & Warwickshire, Coventry CV2 2DX, UK

⁴ Department of Nuclear Medicine, University Hospital Coventry & Warwickshire, Coventry CV2 2DX, UK

⁵ Department of Gastroenterology, Rotherham General Hospital, Rotherham S60 2UD, UK

⁶ Clinical Sciences Research Institute, University of Warwick, Coventry CV2 2DX, UK

Sensors 2013, 13(9), 11899-11912; https://doi.org/10.3390/s130911899 - 6 Sep 2013

Cited by 69 | Viewed by 10252

Abstract

Bile acid diarrhoea (BAD) is a common disease that requires expensive imaging to diagnose. We have tested the efficacy of a new method to identify BAD, based on the detection of differences in volatile organic compounds (VOC) in urine headspace of BAD vs [...] Read more.

Bile acid diarrhoea (BAD) is a common disease that requires expensive imaging to diagnose. We have tested the efficacy of a new method to identify BAD, based on the detection of differences in volatile organic compounds (VOC) in urine headspace of BAD vs. ulcerative colitis and healthy controls. A total of 110 patients were recruited; 23 with BAD, 42 with ulcerative colitis (UC) and 45 controls. Patients with BAD also received standard imaging (Se75HCAT) for confirmation. Urine samples were collected and the headspace analysed using an AlphaMOS Fox 4000 electronic nose in combination with an Owlstone Lonestar Field Asymmetric Ion Mobility Spectrometer (FAIMS). A subset was also tested by gas chromatography, mass spectrometry (GCMS). Linear Discriminant Analysis (LDA) was used to explore both the electronic nose and FAIMS data. LDA showed statistical differences between the groups, with reclassification success rates (using an n-1 approach) at typically 83%. GCMS experiments confirmed these results and showed that patients with BAD had two chemical compounds, 2-propanol and acetamide, that were either not present or were in much reduced quantities in the ulcerative colitis and control samples. We believe that this work may lead to a new tool to diagnose BAD, which is cheaper, quicker and easier that current methods. Full article

(This article belongs to the Special Issue Sensing of Scent, Fragrance, Smell, and Odor Emissions from Biota Sources)

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10 pages, 614 KiB

Open AccessArticle

ABO Blood-Typing Using an Antibody Array Technique Based on Surface Plasmon Resonance Imaging

by Nongluck Houngkamhang¹, Apirom Vongsakulyanon², Patjaree Peungthum¹, Krisda Sudprasert¹, Pimpun Kitpoka², Mongkol Kunakorn², Boonsong Sutapun³, Ratthasart Amarit⁴, Armote Somboonkaew⁴ and Toemsak Srikhirin^1,5,*

¹ Materials Science and Engineering Programme, Faculty of Science, Mahidol University, Rama 6 Rd., Phayathai, Rajathavee, Bangkok 10400, Thailand

² Department of Pathology, Faculty of Medicine, Ramathibodi Hospital, Mahidol University Rama 6 Rd., Phayathai, Rajathavee, Bangkok 10400, Thailand

³ School of Electronic Engineering and School of Telecommunications Engineering, Suranaree University of Technology, 111 University Avenue, Muang District, Nakhon Ratchasima 30000, Thailand

⁴ Photonics Technology Laboratory, National Electronics and Computer Technology Center (NECTEC), Pathumthani 12120, Thailand

⁵ Physics Department, Faculty of Science, Mahidol University, Rama 6 Rd., Phayathai, Rajathavee, Bangkok 10400, Thailand

Sensors 2013, 13(9), 11913-11922; https://doi.org/10.3390/s130911913 - 9 Sep 2013

Cited by 40 | Viewed by 9914

Abstract

In this study, readily available antibodies that are used in standard agglutination tests were evaluated for their use in ABO blood typing by a surface plasmon resonance imaging (SPR imaging) technique. Five groups of antibodies, including mixed clones of anti-A, anti-B, and anti-AB, [...] Read more.

In this study, readily available antibodies that are used in standard agglutination tests were evaluated for their use in ABO blood typing by a surface plasmon resonance imaging (SPR imaging) technique. Five groups of antibodies, including mixed clones of anti-A, anti-B, and anti-AB, and single clones of anti-A and anti-B, were used to construct the five-line detection arrays using a multichannel flow cell in the SPR imager. The red blood cell (RBC) samples were applied to a multichannel flow cell that was orthogonal to the detection line arrays for blood group typing. We found that the blood samples were correctly grouped in less than 12 min by the SPR imaging technique, and the results were consistent with those of the standard agglutination technique for all 60 samples. We found that mixed clones of antibodies provided 33%–68% greater change in the SPR signal than the single-clone antibodies. Applying the SPR imaging technique using readily available antibodies may reduce the costs of the antibodies, shorten the measurement time, and increase the throughput. Full article

(This article belongs to the Special Issue Plasmonics and Nanoplasmonics Biosensors)

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33 pages, 936 KiB

Open AccessReview

PTR-MS in Italy: A Multipurpose Sensor with Applications in Environmental, Agri-Food and Health Science

by Luca Cappellin¹, Francesco Loreto^2,*, Eugenio Aprea¹

, Andrea Romano¹, José Sánchez Del Pulgar¹, Flavia Gasperi¹ and Franco Biasioli¹

¹ Research and Innovation Centre, Fondazione Edmund Mach (FEM), Via E. Mach 1, San Michele all'Adige 38010, Italy

² Institute of Agro-Environmental and Forest Biology, National Research Council, Via Salaria km 29, 300-00015 Monterotondo Scalo, Roma, Italy

Sensors 2013, 13(9), 11923-11955; https://doi.org/10.3390/s130911923 - 9 Sep 2013

Cited by 42 | Viewed by 10278

Abstract

Proton Transfer Reaction Mass Spectrometry (PTR-MS) has evolved in the last decade as a fast and high sensitivity sensor for the real-time monitoring of volatile compounds. Its applications range from environmental sciences to medical sciences, from food technology to bioprocess monitoring. Italian scientists [...] Read more.

Proton Transfer Reaction Mass Spectrometry (PTR-MS) has evolved in the last decade as a fast and high sensitivity sensor for the real-time monitoring of volatile compounds. Its applications range from environmental sciences to medical sciences, from food technology to bioprocess monitoring. Italian scientists and institutions participated from the very beginning in fundamental and applied research aiming at exploiting the potentialities of this technique and providing relevant methodological advances and new fundamental indications. In this review we describe this activity on the basis of the available literature. The Italian scientific community has been active mostly in food science and technology, plant physiology and environmental studies and also pioneered the applications of the recently released PTR-ToF-MS (Proton Transfer Reaction-Time of Flight-Mass Spectrometry) in food science and in plant physiology. In the very last years new results related to bioprocess monitoring and health science have been published as well. PTR-MS data analysis, particularly in the case of the ToF based version, and the application of advanced chemometrics and data mining are also aspects characterising the activity of the Italian community. Full article

(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Italy 2012)

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13 pages, 769 KiB

Open AccessArticle

Characterization of Flexible Copolymer Optical Fibers for Force Sensing Applications

by Marek Krehel^1,2, René M. Rossi¹

, Gian-Luca Bona^1,2 and Lukas J. Scherer^1,*

¹ Empa, Swiss Federal Laboratories for Materials Science and Technology, Laboratory for Protection and Physiology, Lerchenfeldstrasse 5, St. Gallen 9014, Switzerland

² ETH Zurich, Swiss Federal Institute of Technology, Department of Information Technology and Electrical Engineering, Gloriastrasse 35, Zurich 8092, Switzerland

Sensors 2013, 13(9), 11956-11968; https://doi.org/10.3390/s130911956 - 9 Sep 2013

Cited by 33 | Viewed by 13451

Abstract

In this paper, different polymer optical fibres for applications in force sensing systems in textile fabrics are reported. The proposed method is based on the deflection of the light in fibre waveguides. Applying a force on the fibre changes the geometry and affects [...] Read more.

In this paper, different polymer optical fibres for applications in force sensing systems in textile fabrics are reported. The proposed method is based on the deflection of the light in fibre waveguides. Applying a force on the fibre changes the geometry and affects the wave guiding properties and hence induces light loss in the optical fibre. Fibres out of three different elastic and transparent copolymer materials were successfully produced and tested. Moreover, the influence of the diameter on the sensing properties was studied. The detectable force ranges from 0.05 N to 40 N (applied on 3 cm of fibre length), which can be regulated with the material and the diameter of the fibre. The detected signal loss varied from 0.6% to 78.3%. The fibres have attenuation parameters between 0.16–0.25 dB/cm at 652 nm. We show that the cross-sensitivies to temperature, strain and bends are low. Moreover, the high yield strength (0.0039–0.0054 GPa) and flexibility make these fibres very attractive candidates for integration into textiles to form wearable sensors, medical textiles or even computing systems. Full article

(This article belongs to the Special Issue Photonic Sensors for Industrial, Environmental and Health Monitoring)

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29 pages, 1426 KiB

Open AccessArticle

Through-the-Wall Localization of a Moving Target by Two Independent Ultra Wideband (UWB) Radar Systems

by Dušan Kocur^*, Mária Švecová and Jana Rovňáková^*

Department of Electronics and Multimedia Communications, Technical University of Košice, Park Komenského 13, Košice 04120, Slovakia

Sensors 2013, 13(9), 11969-11997; https://doi.org/10.3390/s130911969 - 9 Sep 2013

Cited by 48 | Viewed by 9070

Abstract

In the case of through-the-wall localization of moving targets by ultra wideband (UWB) radars, there are applications in which handheld sensors equipped only with one transmitting and two receiving antennas are applied. Sometimes, the radar using such a small antenna array is not [...] Read more.

In the case of through-the-wall localization of moving targets by ultra wideband (UWB) radars, there are applications in which handheld sensors equipped only with one transmitting and two receiving antennas are applied. Sometimes, the radar using such a small antenna array is not able to localize the target with the required accuracy. With a view to improve through-the-wall target localization, cooperative positioning based on a fusion of data retrieved from two independent radar systems can be used. In this paper, the novel method of the cooperative localization referred to as joining intersections of the ellipses is introduced. This method is based on a geometrical interpretation of target localization where the target position is estimated using a properly created cluster of the ellipse intersections representing potential positions of the target. The performance of the proposed method is compared with the direct calculation method and two alternative methods of cooperative localization using data obtained by measurements with the M-sequence UWB radars. The direct calculation method is applied for the target localization by particular radar systems. As alternative methods of cooperative localization, the arithmetic average of the target coordinates estimated by two single independent UWB radars and the Taylor series method is considered. Full article

(This article belongs to the Section Remote Sensors)

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14 pages, 1461 KiB

Open AccessArticle

Proof of Concept of Impact Detection in Composites Using Fiber Bragg Grating Arrays

by Javier Gomez^1,*, Iagoba Jorge², Gaizka Durana¹, Jon Arrue¹, Joseba Zubia¹

, Gerardo Aranguren¹

, Ander Montero² and Ion López²

¹ Department of Communications Engineering, Faculty of Engineering, University of the Basque Country, Alda Urquijo, s/n. Bilbao 48013, Spain

² Aeronautical Technologies Center, Technologic Park of Alava, C/Juan de la Cierva 1, Miñano 01510, Alava, Spain

Sensors 2013, 13(9), 11998-12011; https://doi.org/10.3390/s130911998 - 9 Sep 2013

Cited by 12 | Viewed by 6992

Abstract

Impact detection in aeronautical structures allows predicting their future reliability and performance. An impact can produce microscopic fissures that could evolve into fractures or even the total collapse of the structure, so it is important to know the location and severity of each [...] Read more.

Impact detection in aeronautical structures allows predicting their future reliability and performance. An impact can produce microscopic fissures that could evolve into fractures or even the total collapse of the structure, so it is important to know the location and severity of each impact. For this purpose, optical fibers with Bragg gratings are used to analyze each impact and the vibrations generated by them. In this paper it is proven that optical fibers with Bragg gratings can be used to detect impacts, and also that a high-frequency interrogator is necessary to collect valuable information about the impacts. The use of two interrogators constitutes the main novelty of this paper. Full article

(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Spain 2013)

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18 pages, 1074 KiB

Open AccessArticle

Practical Strategies for Stable Operation of HFF-QCM in Continuous Air Flow

by Alexander Wessels¹, Bernhard Klöckner¹, Carsten Siering² and Siegfried R. Waldvogel^2,*

¹ Chemische Institute, Abteilung Elektronik, Rheinische Friedrich-Wilhelm-Universität Bonn, Gerhard-Domagk-Str. 1, Bonn D-55121, Germany

² Institut für Organische Chemie, Johannes Gutenberg-Universität Mainz, Duesbergweg 10-14, Mainz D-55128, Germany

Sensors 2013, 13(9), 12012-12029; https://doi.org/10.3390/s130912012 - 9 Sep 2013

Cited by 22 | Viewed by 8355

Abstract

Currently there are a few fields of application using quartz crystal microbalances (QCM). Because of environmental conditions and insufficient resolution of the microbalance, chemical sensing of volatile organic compounds in an open system was as yet not possible. In this study we present [...] Read more.

Currently there are a few fields of application using quartz crystal microbalances (QCM). Because of environmental conditions and insufficient resolution of the microbalance, chemical sensing of volatile organic compounds in an open system was as yet not possible. In this study we present strategies on how to use 195 MHz fundamental quartz resonators for a mobile sensor platform to detect airborne analytes. Commonly the use of devices with a resonant frequency of about 10 MHz is standard. By increasing the frequency to 195 MHz the frequency shift increases by a factor of almost 400. Unfortunately, such kinds of quartz crystals tend to exhibit some challenges to obtain a reasonable signal-to-noise ratio. It was possible to reduce the noise in frequency in a continuous air flow of 7.5 m/s to 0.4 Hz [i.e., σ(τ) = 2 × 10⁻⁹] by elucidating the major source of noise. The air flow in the vicinity of the quartz was analyzed to reduce turbulences. Furthermore, we found a dependency between the acceleration sensitivity and mechanical stress induced by an internal thermal gradient. By reducing this gradient, we achieved reduction of the sensitivity to acceleration by more than one decade. Hence, the resulting sensor is more robust to environmental conditions such as temperature, acceleration and air flow. Full article

(This article belongs to the Section Chemical Sensors)

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14 pages, 689 KiB

Open AccessArticle

A Study on Rational Function Model Generation for TerraSAR-X Imagery

by Akram Eftekhari^1,*, Mohammad Saadatseresht¹ and Mahdi Motagh²

¹ Department of Surveying and Geomatics Engineering, University of Tehran, Tehran 14395-515, Iran

² Helmholtz Centre Potsdam, GFZ German Research Centre for Geosciences, Potsdam 14473, Germany

Sensors 2013, 13(9), 12030-12043; https://doi.org/10.3390/s130912030 - 9 Sep 2013

Cited by 12 | Viewed by 7848

Abstract

The Rational Function Model (RFM) has been widely used as an alternative to rigorous sensor models of high-resolution optical imagery in photogrammetry and remote sensing geometric processing. However, not much work has been done to evaluate the applicability of the RF model for [...] Read more.

The Rational Function Model (RFM) has been widely used as an alternative to rigorous sensor models of high-resolution optical imagery in photogrammetry and remote sensing geometric processing. However, not much work has been done to evaluate the applicability of the RF model for Synthetic Aperture Radar (SAR) image processing. This paper investigates how to generate a Rational Polynomial Coefficient (RPC) for high-resolution TerraSAR-X imagery using an independent approach. The experimental results demonstrate that the RFM obtained using the independent approach fits the Range-Doppler physical sensor model with an accuracy of greater than 10⁻³ pixel. Because independent RPCs indicate absolute errors in geolocation, two methods can be used to improve the geometric accuracy of the RFM. In the first method, Ground Control Points (GCPs) are used to update SAR sensor orientation parameters, and the RPCs are calculated using the updated parameters. Our experiment demonstrates that by using three control points in the corners of the image, an accuracy of 0.69 pixels in range and 0.88 pixels in the azimuth direction is achieved. For the second method, we tested the use of an affine model for refining RPCs. In this case, by applying four GCPs in the corners of the image, the accuracy reached 0.75 pixels in range and 0.82 pixels in the azimuth direction. Full article

(This article belongs to the Section Remote Sensors)

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26 pages, 2388 KiB

Open AccessArticle

Five Years of Designing Wireless Sensor Networks in the Doñana Biological Reserve (Spain): An Applications Approach

by Diego F. Larios^1,*

, Julio Barbancho¹

, José L. Sevillano²

, Gustavo Rodríguez¹, Francisco J. Molina¹, Virginia G. Gasull¹, Javier M. Mora-Merchan¹ and Carlos León¹

¹ Departamento de Tecnología Electrónica, Universidad de Sevilla, Seville 41011, Spain

² Departamento de Arquitectura de Computadores, Universidad de Sevilla, Seville 41012, Spain

Sensors 2013, 13(9), 12044-12069; https://doi.org/10.3390/s130912044 - 10 Sep 2013

Cited by 16 | Viewed by 8451

Abstract

Wireless Sensor Networks (WSNs) are a technology that is becoming very popular for many applications, and environmental monitoring is one of its most important application areas. This technology solves the lack of flexibility of wired sensor installations and, at the same time, reduces [...] Read more.

Wireless Sensor Networks (WSNs) are a technology that is becoming very popular for many applications, and environmental monitoring is one of its most important application areas. This technology solves the lack of flexibility of wired sensor installations and, at the same time, reduces the deployment costs. To demonstrate the advantages of WSN technology, for the last five years we have been deploying some prototypes in the Doñana Biological Reserve, which is an important protected area in Southern Spain. These prototypes not only evaluate the technology, but also solve some of the monitoring problems that have been raised by biologists working in Doñana. This paper presents a review of the work that has been developed during these five years. Here, we demonstrate the enormous potential of using machine learning in wireless sensor networks for environmental and animal monitoring because this approach increases the amount of useful information and reduces the effort that is required by biologists in an environmental monitoring task. Full article

(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Spain 2013)

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23 pages, 1325 KiB

Open AccessArticle

Strontium-Doped Hematite as a Possible Humidity Sensing Material for Soil Water Content Determination

by Jean-Marc Tulliani^1,*

, Chiara Baroni¹, Laura Zavattaro² and Carlo Grignani²

¹ Department of Applied Science and Technology, Politecnico di Torino, C.so Duca degli Abruzzi 24, 10129 Torino, Italy

² Department of Agricultural, Forest and Food Sciences, Università di Torino, Via Leonardo da Vinci, 44, 10095 Grugliasco, Italy

Sensors 2013, 13(9), 12070-12092; https://doi.org/10.3390/s130912070 - 10 Sep 2013

Cited by 25 | Viewed by 7984

Abstract

The aim of this work is to study the sensing behavior of Sr-doped hematite for soil water content measurement. The material was prepared by solid state reaction from commercial hematite and strontium carbonate heat treated at 900 °C. X-Ray diffraction, scanning electron microscopy [...] Read more.

The aim of this work is to study the sensing behavior of Sr-doped hematite for soil water content measurement. The material was prepared by solid state reaction from commercial hematite and strontium carbonate heat treated at 900 °C. X-Ray diffraction, scanning electron microscopy and mercury intrusion porosimetry were used for microstructural characterization of the synthesized powder. Sensors were then prepared by uniaxially pressing and by screen-printing, on an alumina substrate, the prepared powder and subsequent firing in the 800–1,000 °C range. These sensors were first tested in a laboratory apparatus under humid air and then in an homogenized soil and finally in field. The results evidenced that the screen printed film was able to give a response for a soil matric potential from about 570 kPa, that is to say well below the wilting point in the used soil. Full article

(This article belongs to the Section Chemical Sensors)

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20 pages, 534 KiB

Open AccessArticle

Finger Vein Recognition Based on Personalized Weight Maps

by Gongping Yang, Rongyang Xiao, Yilong Yin^* and Lu Yang

School of Computer Science and Technology, Shandong University, Jinan 250101, China

Sensors 2013, 13(9), 12093-12112; https://doi.org/10.3390/s130912093 - 10 Sep 2013

Cited by 30 | Viewed by 7284

Abstract

Finger vein recognition is a promising biometric recognition technology, which verifies identities via the vein patterns in the fingers. Binary pattern based methods were thoroughly studied in order to cope with the difficulties of extracting the blood vessel network. However, current binary pattern [...] Read more.

Finger vein recognition is a promising biometric recognition technology, which verifies identities via the vein patterns in the fingers. Binary pattern based methods were thoroughly studied in order to cope with the difficulties of extracting the blood vessel network. However, current binary pattern based finger vein matching methods treat every bit of feature codes derived from different image of various individuals as equally important and assign the same weight value to them. In this paper, we propose a finger vein recognition method based on personalized weight maps (PWMs). The different bits have different weight values according to their stabilities in a certain number of training samples from an individual. Firstly we present the concept of PWM, and then propose the finger vein recognition framework, which mainly consists of preprocessing, feature extraction, and matching. Finally, we design extensive experiments to evaluate the effectiveness of our proposal. Experimental results show that PWM achieves not only better performance, but also high robustness and reliability. In addition, PWM can be used as a general framework for binary pattern based recognition. Full article

(This article belongs to the Section Physical Sensors)

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19 pages, 3442 KiB

Open AccessArticle

Improving Pyroelectric Energy Harvesting Using a Sandblast Etching Technique

by Chun-Ching Hsiao^*

and An-Shen Siao

Department of Mechanical Design Engineering, National Formosa University, No. 64, Wunhua Rd., Huwei Township, Yunlin County 632, Taiwan,

Sensors 2013, 13(9), 12113-12131; https://doi.org/10.3390/s130912113 - 10 Sep 2013

Cited by 38 | Viewed by 7584

Abstract

Large amounts of low-grade heat are emitted by various industries and exhausted into the environment. This heat energy can be used as a free source for pyroelectric power generation. A three-dimensional pattern helps to improve the temperature variation rates in pyroelectric elements by [...] Read more.

Large amounts of low-grade heat are emitted by various industries and exhausted into the environment. This heat energy can be used as a free source for pyroelectric power generation. A three-dimensional pattern helps to improve the temperature variation rates in pyroelectric elements by means of lateral temperature gradients induced on the sidewalls of the responsive elements. A novel method using sandblast etching is successfully applied in fabricating the complex pattern of a vortex-like electrode. Both experiment and simulation show that the proposed design of the vortex-like electrode improved the electrical output of the pyroelectric cells and enhanced the efficiency of pyroelectric harvesting converters. A three-dimensional finite element model is generated by commercial software for solving the transient temperature fields and exploring the temperature variation rate in the PZT pyroelectric cells with various designs. The vortex-like type has a larger temperature variation rate than the fully covered type, by about 53.9%.The measured electrical output of the vortex-like electrode exhibits an obvious increase in the generated charge and the measured current, as compared to the fully covered electrode, by of about 47.1% and 53.1%, respectively. Full article

(This article belongs to the Section Physical Sensors)

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8 pages, 118 KiB

Open AccessEditorial

Sensors in Agriculture and Forestry

by Gonzalo Pajares^1,*

, Andrea Peruzzi^2,* and Pablo Gonzalez-de-Santos^3,*

¹ Department of Software Engineering and Artificial Intelligence, Faculty of Informatics, University Complutense of Madrid, 28040 Madrid, Spain

² Department of Agriculture, Food and Environment, University of Pisa, Via S. Michele degli Scalzi 2, 56124 Pisa, Italy

³ Centre for Automation and Robotics (UPM-CSIC), Arganda del Rey 28500, Madrid, Spain

Sensors 2013, 13(9), 12132-12139; https://doi.org/10.3390/s130912132 - 10 Sep 2013

Cited by 33 | Viewed by 9385

Abstract

Agriculture and Forestry are two broad and promising areas demanding technological solutions with the aim of increasing production or accurate inventories for sustainability while the environmental impact is minimized by reducing the application of agro-chemicals and increasing the use of environmental friendly agronomical [...] Read more.

Agriculture and Forestry are two broad and promising areas demanding technological solutions with the aim of increasing production or accurate inventories for sustainability while the environmental impact is minimized by reducing the application of agro-chemicals and increasing the use of environmental friendly agronomical practices. In addition, the immediate consequence of this “trend” is the reduction of production costs. [...] Full article

(This article belongs to the Special Issue Sensor-Based Technologies and Processes in Agriculture and Forestry)

9 pages, 427 KiB

Open AccessArticle

An Experimental Study on Fabricating an Inverted Mesa-Type Quartz Crystal Resonator Using a Cheap Wet Etching Process

by Jinxing Liang^1,*, Jia Huang¹, Tian Zhang¹, Jing Zhang¹, Xuefeng Li² and Toshitsugu Ueda³

¹ Key Laboratory of Micro-Inertial Instrument and Advanced Navigation Technology, Ministry of Education, School of Instrument Science and Engineering, Southeast University, Nanjing 210096, China

² School of Electronics and Information Engineering, Tongji University, Shanghai 201804, China

³ Graduate School of Information, Production and System, Waseda University, Kitakyushu 808-0135, Japan

Sensors 2013, 13(9), 12140-12148; https://doi.org/10.3390/s130912140 - 10 Sep 2013

Cited by 15 | Viewed by 7616

Abstract

In this study, a miniaturized high fundamental frequency quartz crystal microbalance (QCM) is fabricated for sensor applications using a wet etching technique. The vibration area is reduced in the fabrication of the high frequency QCM with an inverted mesa structure. To reduce the [...] Read more.

In this study, a miniaturized high fundamental frequency quartz crystal microbalance (QCM) is fabricated for sensor applications using a wet etching technique. The vibration area is reduced in the fabrication of the high frequency QCM with an inverted mesa structure. To reduce the complexity of the side wall profile that results from anisotropic quartz etching, a rectangular vibration area is used instead of the conventional circular structure. QCMs with high Q values exceeding 25,000 at 47 MHz, 27,000 at 60 MHz, 24,000 at 73 MHz and 25,000 at 84 MHz are fabricated on 4 × 4 mm² chips with small vibration areas of 1.2 × 1.4 mm². A PMMA-based flow cell is designed and manufactured to characterize the behavior of the fabricated QCM chip in a liquid. Q values as high as 1,006 at 47 MHz, 904 at 62 MHz, 867 at 71 MHz and 747 at 84 MHz are obtained when one side of the chip is exposed to pure water. These results show that fabricated QCM chips can be used for bio- and chemical sensor applications in liquids. Full article

(This article belongs to the Section Chemical Sensors)

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17 pages, 536 KiB

Open AccessArticle

A Self-Sensing Active Magnetic Bearing Based on a Direct Current Measurement Approach

by Andries C. Niemann, George Van Schoor and Carel P. Du Rand^*

School of Electrical, Electronic and Computer Engineering, North-West University, 11 Hoffman Street, Potchefstroom 2531, South Africa

Sensors 2013, 13(9), 12149-12165; https://doi.org/10.3390/s130912149 - 11 Sep 2013

Cited by 25 | Viewed by 8839

Abstract

Active magnetic bearings (AMBs) have become a key technology in various industrial applications. Self-sensing AMBs provide an integrated sensorless solution for position estimation, consolidating the sensing and actuating functions into a single electromagnetic transducer. The approach aims to reduce possible hardware failure points, [...] Read more.

Active magnetic bearings (AMBs) have become a key technology in various industrial applications. Self-sensing AMBs provide an integrated sensorless solution for position estimation, consolidating the sensing and actuating functions into a single electromagnetic transducer. The approach aims to reduce possible hardware failure points, production costs, and system complexity. Despite these advantages, self-sensing methods must address various technical challenges to maximize the performance thereof. This paper presents the direct current measurement (DCM) approach for self-sensing AMBs, denoting the direct measurement of the current ripple component. In AMB systems, switching power amplifiers (PAs) modulate the rotor position information onto the current waveform. Demodulation self-sensing techniques then use bandpass and lowpass filters to estimate the rotor position from the voltage and current signals. However, the additional phase-shift introduced by these filters results in lower stability margins. The DCM approach utilizes a novel PA switching method that directly measures the current ripple to obtain duty-cycle invariant position estimates. Demodulation filters are largely excluded to minimize additional phase-shift in the position estimates. Basic functionality and performance of the proposed self-sensing approach are demonstrated via a transient simulation model as well as a high current (10 A) experimental system. A digital implementation of amplitude modulation self-sensing serves as a comparative estimator. Full article

(This article belongs to the Section Physical Sensors)

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9 pages, 3571 KiB

Open AccessArticle

Temperature Stability of the Sky Quality Meter

by Sabrina Schnitt¹, Thomas Ruhtz¹, Jürgen Fischer¹, Franz Hölker² and Christopher C.M. Kyba^1,2,*

¹ Institute for Space Sciences, Freie Universität Berlin, Carl-Heinrich-Becker-Weg 6-10, Berlin 12165, Germany

² Leibniz-Institute of Freshwater Ecology and Inland Fisheries, Müggelseedamm 310, Berlin 12587, Germany

Sensors 2013, 13(9), 12166-12174; https://doi.org/10.3390/s130912166 - 11 Sep 2013

Cited by 24 | Viewed by 9285

Abstract

The stability of radiance measurements taken by the Sky Quality Meter (SQM)was tested under rapidly changing temperature conditions during exposure to a stable lightfield in the laboratory. The reported radiance was found to be negatively correlated withtemperature, but remained within 7% of the [...] Read more.

The stability of radiance measurements taken by the Sky Quality Meter (SQM)was tested under rapidly changing temperature conditions during exposure to a stable lightfield in the laboratory. The reported radiance was found to be negatively correlated withtemperature, but remained within 7% of the initial reported radiance over a temperaturerange of -15 °C to 35 °C, and during temperature changes of -33 °C/h and +70 °C/h.This is smaller than the manufacturer’s quoted unit-to-unit systematic uncertainty of 10%,indicating that the temperature compensation of the SQM is adequate under expected outdoor operating conditions. Full article

(This article belongs to the Section Physical Sensors)

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17 pages, 1054 KiB

Open AccessArticle

Determination of the Elastic Properties of Tomato Fruit Cells with an Atomic Force Microscope

by Artur Zdunek^* and Andrzej Kurenda

Institute of Agrophysics, Polish Academy of Sciences, Doswiadczalna 4, Lublin 20-290, Poland

Sensors 2013, 13(9), 12175-12191; https://doi.org/10.3390/s130912175 - 11 Sep 2013

Cited by 74 | Viewed by 11864

Abstract

Since the mechanical properties of single cells together with the intercellular adhesive properties determine the macro-mechanical properties of plants, a method for evaluation of the cell elastic properties is needed to help explanation of the behavior of fruits and vegetables in handling and [...] Read more.

Since the mechanical properties of single cells together with the intercellular adhesive properties determine the macro-mechanical properties of plants, a method for evaluation of the cell elastic properties is needed to help explanation of the behavior of fruits and vegetables in handling and food processing. For this purpose, indentation of tomato mesocarp cells with an atomic force microscope was used. The Young’s modulus of a cell using the Hertz and Sneddon models, and stiffness were calculated from force-indentation curves. Use of two probes of distinct radius of curvature (20 nm and 10,000 nm) showed that the measured elastic properties were significantly affected by tip geometry. The Young’s modulus was about 100 kPa ± 35 kPa and 20 kPa ± 14 kPa for the sharper tip and a bead tip, respectively. Moreover, large variability regarding elastic properties (>100%) among cells sampled from the same region in the fruit was observed. We showed that AFM provides the possibility of combining nano-mechanical properties with topography imaging, which could be very useful for the study of structure-related properties of fruits and vegetables at the cellular and sub-cellular scale. Full article

(This article belongs to the Special Issue Nanomechanical Sensors)

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26 pages, 1197 KiB

Open AccessArticle

Fast Thermal Calibration of Low-Grade Inertial Sensors and Inertial Measurement Units

by Xiaoji Niu, You Li, Hongping Zhang^*, Qingjiang Wang and Yalong Ban

GNSS Research Center, Wuhan University, No.129, Luoyu Rd., Wuhan 430079, Hubei, China

Sensors 2013, 13(9), 12192-12217; https://doi.org/10.3390/s130912192 - 12 Sep 2013

Cited by 100 | Viewed by 13151

Abstract

The errors of low-cost inertial sensors, especially Micro-Electro Mechanical Systems (MEMS) ones, are highly dependent on environmental conditions such as the temperature. Thus, there is a need for the development of accurate and reliable thermal compensation models to reduce the impact of such [...] Read more.

The errors of low-cost inertial sensors, especially Micro-Electro Mechanical Systems (MEMS) ones, are highly dependent on environmental conditions such as the temperature. Thus, there is a need for the development of accurate and reliable thermal compensation models to reduce the impact of such thermal drift of the sensors. Since the conventional thermal calibration methods are typically time-consuming and costly, an efficient thermal calibration method to investigate the thermal drift of a full set of gyroscope and accelerometer errors (i.e., biases, scale factor errors and non-orthogonalities) over the entire temperature range in a few hours is proposed. The proposed method uses the idea of the Ramp method, which removes the time-consuming process of stabilizing the sensor temperature, and addresses its inherent problems with several improvements. We change the temperature linearly for a complete cycle and take a balanced strategy by making comprehensive use of the sensor measurements during both heating and cooling processes. Besides, an efficient 8-step rotate-and-static scheme is designed to further improve the calibration accuracy and efficiency. Real calibration tests showed that the proposed method is suitable for low-grade IMUs and for both lab and factory calibration due to its efficiency and sufficient accuracy. Full article

(This article belongs to the Special Issue Modeling, Testing and Reliability Issues in MEMS Engineering 2013)

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26 pages, 5646 KiB

Open AccessArticle

MARS, a Multi-Agent System for Assessing Rowers’ Coordination via Motion-Based Stigmergy

by Marco Avvenuti, Daniel Cesarini and Mario G. C. A. Cimino^*

Department of Information Engineering, University of Pisa, Largo Lucio Lazzarino 1, Pisa 56122, Italy

Sensors 2013, 13(9), 12218-12243; https://doi.org/10.3390/s130912218 - 12 Sep 2013

Cited by 26 | Viewed by 8640

Abstract

A crucial aspect in rowing is having a synchronized, highly-efficient stroke. This is very difficult to obtain, due to the many interacting factors that each rower of the crew must perceive. Having a system that monitors and represents the crew coordination would be [...] Read more.

A crucial aspect in rowing is having a synchronized, highly-efficient stroke. This is very difficult to obtain, due to the many interacting factors that each rower of the crew must perceive. Having a system that monitors and represents the crew coordination would be of great help to the coach during training sessions. In the literature, some methods already employ wireless sensors for capturing motion patterns that affect rowing performance. A challenging problem is to support the coach’s decisions at his same level of knowledge, using a limited number of sensors and avoiding the complexity of the biomechanical analysis of human movements. In this paper, we present a multi-agent information-processing system for on-water measuring of both the overall crew asynchrony and the individual rower asynchrony towards the crew. More specifically, in the system, the first level of processing is managed by marking agents, which release marks in a sensing space, according to the rowers’ motion. The accumulation of marks enables a stigmergic cooperation mechanism, generating collective marks, i.e., short-term memory structures in the sensing space. At the second level of processing, information provided by marks is observed by similarity agents, which associate a similarity degree with respect to optimal marks. Finally, the third level is managed by granulation agents, which extract asynchrony indicators for different purposes. The effectiveness of the system has been experimented on real-world scenarios. The study includes the problem statement and its characterization in the literature, as well as the proposed solving approach and initial experimental setting. Full article

(This article belongs to the Section Sensor Networks)

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22 pages, 294 KiB

Open AccessArticle

Analytic Performance Prediction of Track-to-Track Association with Biased Data in Multi-Sensor Multi-Target Tracking Scenarios

by Wei Tian^1,2,*, Yue Wang¹, Xiuming Shan¹ and Jian Yang¹

¹ Department of Electronic Engineering, Tsinghua University, Beijing 100084, China

² Unit 91715, Navy, People's Liberation Army, Guangzhou 510450, China

Sensors 2013, 13(9), 12244-12265; https://doi.org/10.3390/s130912244 - 12 Sep 2013

Cited by 26 | Viewed by 7073

Abstract

An analytic method for predicting the performance of track-to-track association (TTTA) with biased data in multi-sensor multi-target tracking scenarios is proposed in this paper. The proposed method extends the existing results of the bias-free situation by accounting for the impact of sensor biases. [...] Read more.

An analytic method for predicting the performance of track-to-track association (TTTA) with biased data in multi-sensor multi-target tracking scenarios is proposed in this paper. The proposed method extends the existing results of the bias-free situation by accounting for the impact of sensor biases. Since little insight of the intrinsic relationship between scenario parameters and the performance of TTTA can be obtained by numerical simulations, the proposed analytic approach is a potential substitute for the costly Monte Carlo simulation method. Analytic expressions are developed for the global nearest neighbor (GNN) association algorithm in terms of correct association probability. The translational biases of sensors are incorporated in the expressions, which provide good insight into how the TTTA performance is affected by sensor biases, as well as other scenario parameters, including the target spatial density, the extraneous track density and the average association uncertainty error. To show the validity of the analytic predictions, we compare them with the simulation results, and the analytic predictions agree reasonably well with the simulations in a large range of normally anticipated scenario parameters. Full article

(This article belongs to the Section Sensor Networks)

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11 pages, 273 KiB

Open AccessArticle

Visible Light Communication System Using an Organic Bulk Heterojunction Photodetector

by Belén Arredondo^1,*, Beatriz Romero¹, José Manuel Sánchez Pena²

, Agustín Fernández-Pacheco², Eduardo Alonso², Ricardo Vergaz²

and Cristina De Dios²

¹ Electronic Technology Department, University Rey Juan Carlos, Calle Tulipán s/n, Móstoles 28933, Madrid, Spain

² Electronic Technology Department, University Carlos III de Madrid, Avda. de la Universidad, 30, Leganés 28911, Madrid, Spain

Sensors 2013, 13(9), 12266-12276; https://doi.org/10.3390/s130912266 - 12 Sep 2013

Cited by 61 | Viewed by 10629

Abstract

A visible light communication (VLC) system using an organic bulk heterojunction photodetector (OPD) is presented. The system has been successfully proven indoors with an audio signal. The emitter consists of three commercial high-power white LEDs connected in parallel. The receiver is based on [...] Read more.

A visible light communication (VLC) system using an organic bulk heterojunction photodetector (OPD) is presented. The system has been successfully proven indoors with an audio signal. The emitter consists of three commercial high-power white LEDs connected in parallel. The receiver is based on an organic photodetector having as active layer a blend of poly(3-hexylthiophene) (P3HT) and phenyl C61-butyric acid methyl ester (PCBM). The OPD is opto-electrically characterized, showing a responsivity of 0.18 A/W and a modulation response of 790 kHz at −6 V. Full article

(This article belongs to the Special Issue Photodetectors)

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18 pages, 484 KiB

Open AccessArticle

Optimal Sensor Arrangements in Angle of Arrival (AoA) and Range Based Localization with Linear Sensor Arrays

by Sanvidha C. K. Herath^* and Pubudu N. Pathirana

Networked Sensing and Control Laboratory, School of Engineering, Deakin University, Pigdons Road, Geelong, Victoria 3217, Australia

Sensors 2013, 13(9), 12277-12294; https://doi.org/10.3390/s130912277 - 12 Sep 2013

Cited by 28 | Viewed by 7217

Abstract

This paper investigates the linear separation requirements for Angle-of-Arrival (AoA) and range sensors, in order to achieve the optimal performance in estimating the position of a target from multiple and typically noisy sensor measurements. We analyse the sensor-target geometry in terms of the [...] Read more.

This paper investigates the linear separation requirements for Angle-of-Arrival (AoA) and range sensors, in order to achieve the optimal performance in estimating the position of a target from multiple and typically noisy sensor measurements. We analyse the sensor-target geometry in terms of the Cramer–Rao inequality and the corresponding Fisher information matrix, in order to characterize localization performance with respect to the linear spatial distribution of sensors. Here in this paper, we consider both fixed and adjustable linear sensor arrays. Full article

(This article belongs to the Section Physical Sensors)

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34 pages, 907 KiB

Open AccessArticle

Currents Induced by Injected Charge in Junction Detectors

by Eugenijus Gaubas^*, Tomas Ceponis and Vidas Kalesinskas

Institute of Applied Research, Vilnius University, Sauletekio av. 9-III, LT-10223, Vilnius, Lithuania

Sensors 2013, 13(9), 12295-12328; https://doi.org/10.3390/s130912295 - 12 Sep 2013

Cited by 10 | Viewed by 6266

Abstract

The problem of drifting charge-induced currents is considered in order to predict the pulsed operational characteristics in photo-and particle-detectors with a junction controlled active area. The direct analysis of the field changes induced by drifting charge in the abrupt junction devices with a [...] Read more.

The problem of drifting charge-induced currents is considered in order to predict the pulsed operational characteristics in photo-and particle-detectors with a junction controlled active area. The direct analysis of the field changes induced by drifting charge in the abrupt junction devices with a plane-parallel geometry of finite area electrodes is presented. The problem is solved using the one-dimensional approach. The models of the formation of the induced pulsed currents have been analyzed for the regimes of partial and full depletion. The obtained solutions for the current density contain expressions of a velocity field dependence on the applied voltage, location of the injected surface charge domain and carrier capture parameters. The drift component of this current coincides with Ramo’s expression. It has been illustrated, that the synchronous action of carrier drift, trapping, generation and diffusion can lead to a vast variety of possible current pulse waveforms. Experimental illustrations of the current pulse variations determined by either the rather small or large carrier density within the photo-injected charge domain are presented, based on a study of Si detectors. Full article

(This article belongs to the Special Issue Photodetectors)

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16 pages, 1003 KiB

Open AccessArticle

A New Position Measurement System Using a Motion-Capture Camera for Wind Tunnel Tests

by Hyo Seon Park¹, Ji Young Kim², Jin Gi Kim¹, Se Woon Choi³ and Yousok Kim^3,*

¹ Department of Architectural Engineering, Yonsei University, 134 Shinchon-dong, Seoul 110-732, Korea

² Disaster Prevention Research Team, Daewoo Institute of Construction Technology, 60, Songjuk-dong, Jangan-gu, Kyounggi-do 440-800, Korea

³ Center for Structural Health Care Technology in Buildings, Yonsei University, 134 Shinchon-dong, Seoul 110-732, Korea

Sensors 2013, 13(9), 12329-12344; https://doi.org/10.3390/s130912329 - 13 Sep 2013

Cited by 38 | Viewed by 9345

Abstract

Considering the characteristics of wind tunnel tests, a position measurement system that can minimize the effects on the flow of simulated wind must be established. In this study, a motion-capture camera was used to measure the displacement responses of structures in a wind [...] Read more.

Considering the characteristics of wind tunnel tests, a position measurement system that can minimize the effects on the flow of simulated wind must be established. In this study, a motion-capture camera was used to measure the displacement responses of structures in a wind tunnel test, and the applicability of the system was tested. A motion-capture system (MCS) could output 3D coordinates using two-dimensional image coordinates obtained from the camera. Furthermore, this remote sensing system had some flexibility regarding lab installation because of its ability to measure at relatively long distances from the target structures. In this study, we performed wind tunnel tests on a pylon specimen and compared the measured responses of the MCS with the displacements measured with a laser displacement sensor (LDS). The results of the comparison revealed that the time-history displacement measurements from the MCS slightly exceeded those of the LDS. In addition, we confirmed the measuring reliability of the MCS by identifying the dynamic properties (natural frequency, damping ratio, and mode shape) of the test specimen using system identification methods (frequency domain decomposition, FDD). By comparing the mode shape obtained using the aforementioned methods with that obtained using the LDS, we also confirmed that the MCS could construct a more accurate mode shape (bending-deflection mode shape) with the 3D measurements. Full article

(This article belongs to the Section Physical Sensors)

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30 pages, 9527 KiB

Open AccessArticle

Sensors Systems for the Automation of Operations in the Ship Repair Industry

by Pedro Javier Navarro¹

, Juan Suardíaz Muro², Pedro María Alcover^1,*

and Carlos Fernández-Isla¹

¹ Universidad Politécnica de Cartagena, TIC, Plaza del Hospital, 1, Cartagena 30202, Spain

² Universidad Politécnica de Cartagena, DTE, C/ Doctor Fleming,s/n, Cartagena 30202, Spain

Sensors 2013, 13(9), 12345-12374; https://doi.org/10.3390/s130912345 - 13 Sep 2013

Cited by 9 | Viewed by 10016

Abstract

Hull cleaning before repainting is a key operation in the maintenance of ships. For years, a method to improve such operation has been sought by means of the robotization of techniques such as grit blasting and ultra high pressure water jetting. Despite this, [...] Read more.

Hull cleaning before repainting is a key operation in the maintenance of ships. For years, a method to improve such operation has been sought by means of the robotization of techniques such as grit blasting and ultra high pressure water jetting. Despite this, it continues to be standard practice in shipyards that this process is carried out manually because the developed robotized systems are too expensive to be widely accepted by shipyards. We have chosen to apply a more conservative and realistic approach to this problem, which has resulted in the development of several solutions that have been designed with different automation and operation range degrees. These solutions are fitted with most of the elements already available in many shipyards, so the installation of additional machinery in the workplace would not be necessary. This paper describes the evolutionary development of sensor systems for the automation of the preparation process of ship hull surfaces before the painting process is performed. Such evolution has given rise to the development of new technologies for coating removal. Full article

(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Spain 2013)

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17 pages, 408 KiB

Open AccessArticle

Crack Orientation and Depth Estimation in a Low-Pressure Turbine Disc Using a Phased Array Ultrasonic Transducer and an Artificial Neural Network

by Xiaoxia Yang^*, Shili Chen^*, Shijiu Jin and Wenshuang Chang

State Key Laboratory of Precision Measurement Technology and Instrument, Tianjin University, Tianjin 300072, China

Sensors 2013, 13(9), 12375-12391; https://doi.org/10.3390/s130912375 - 13 Sep 2013

Cited by 26 | Viewed by 7751

Abstract

Stress corrosion cracks (SCC) in low-pressure steam turbine discs are serious hidden dangers to production safety in the power plants, and knowing the orientation and depth of the initial cracks is essential for the evaluation of the crack growth rate, propagation direction and [...] Read more.

Stress corrosion cracks (SCC) in low-pressure steam turbine discs are serious hidden dangers to production safety in the power plants, and knowing the orientation and depth of the initial cracks is essential for the evaluation of the crack growth rate, propagation direction and working life of the turbine disc. In this paper, a method based on phased array ultrasonic transducer and artificial neural network (ANN), is proposed to estimate both the depth and orientation of initial cracks in the turbine discs. Echo signals from cracks with different depths and orientations were collected by a phased array ultrasonic transducer, and the feature vectors were extracted by wavelet packet, fractal technology and peak amplitude methods. The radial basis function (RBF) neural network was investigated and used in this application. The final results demonstrated that the method presented was efficient in crack estimation tasks. Full article

(This article belongs to the Section Physical Sensors)

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14 pages, 621 KiB

Open AccessArticle

A Dry Membrane Protection Technique to Allow Surface Acoustic Wave Biosensor Measurements of Biological Model Membrane Approaches

by Katrin Reder-Christ^1,*, Patrick Schmitz¹, Marian Bota², Ursula Gerber¹, Hildegard Falkenstein-Paul¹, Christian Fuss¹, Marius Enachescu^2,3 and Gerd Bendas¹

¹ Pharmaceutical Chemistry, Rheinische Friedrich-Wilhelms-Universität Bonn, An der Immenburg 4, Bonn D-53121, Germany

² Center for Surface Science and Nanotechnology, University Politehnica of Bucharest, 313 Splaiul Independentei, Bucharest, RO-060042, Romania

³ Academy of Romanian Scientists, 54 Splaiul Independentei, Bucharest, RO-050094, Romania

Sensors 2013, 13(9), 12392-12405; https://doi.org/10.3390/s130912392 - 13 Sep 2013

Cited by 8 | Viewed by 7934

Abstract

Model membrane approaches have attracted much attention in biomedical sciences to investigate and simulate biological processes. The application of model membrane systems for biosensor measurements is partly restricted by the fact that the integrity of membranes critically depends on the maintenance of an [...] Read more.

Model membrane approaches have attracted much attention in biomedical sciences to investigate and simulate biological processes. The application of model membrane systems for biosensor measurements is partly restricted by the fact that the integrity of membranes critically depends on the maintenance of an aqueous surrounding, while various biosensors require a preconditioning of dry sensors. This is for example true for the well-established surface acoustic wave (SAW) biosensor SAM^®5 blue. Here, a simple drying procedure of sensor-supported model membranes is introduced using the protective disaccharide trehalose. Highly reproducible model membranes were prepared by the Langmuir-Blodgett technique, transferred to SAW sensors and supplemented with a trehalose solution. Membrane rehydration after dry incorporation into the SAW device becomes immediately evident by phase changes. Reconstituted model membranes maintain their full functionality, as indicated by biotin/avidin binding experiments. Atomic force microscopy confirmed the morphological invariability of dried and rehydrated membranes. Approximating to more physiological recognition phenomena, the site-directed immobilization of the integrin VLA-4 into the reconstituted model membrane and subsequent VCAM-1 ligand binding with nanomolar affinity were illustrated. This simple drying procedure is a novel way to combine the model membrane generation by Langmuir-Blodgett technique with SAW biosensor measurements, which extends the applicability of SAM^®5 blue in biomedical sciences. Full article

(This article belongs to the Section Biosensors)

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25 pages, 24130 KiB

Open AccessArticle

Teaching Human Poses Interactively to a Social Robot

by Victor Gonzalez-Pacheco^1,*, Maria Malfaz¹, Fernando Fernandez² and Miguel A. Salichs¹

¹ Robotics Lab, Systems Engineering and Automation Department, Universidad Carlos III de Madrid, Av. Universidad 30, Leganés 28911, Spain

² Computer Science Department, Universidad Carlos III de Madrid, Av. Universidad 30, Leganés 28911, Spain

Sensors 2013, 13(9), 12406-12430; https://doi.org/10.3390/s130912406 - 17 Sep 2013

Cited by 15 | Viewed by 11082

Abstract

The main activity of social robots is to interact with people. In order to do that, the robot must be able to understand what the user is saying or doing. Typically, this capability consists of pre-programmed behaviors or is acquired through controlled learning [...] Read more.

The main activity of social robots is to interact with people. In order to do that, the robot must be able to understand what the user is saying or doing. Typically, this capability consists of pre-programmed behaviors or is acquired through controlled learning processes, which are executed before the social interaction begins. This paper presents a software architecture that enables a robot to learn poses in a similar way as people do. That is, hearing its teacher’s explanations and acquiring new knowledge in real time. The architecture leans on two main components: an RGB-D (Red-, Green-, Blue- Depth) -based visual system, which gathers the user examples, and an Automatic Speech Recognition (ASR) system, which processes the speech describing those examples. The robot is able to naturally learn the poses the teacher is showing to it by maintaining a natural interaction with the teacher. We evaluate our system with 24 users who teach the robot a predetermined set of poses. The experimental results show that, with a few training examples, the system reaches high accuracy and robustness. This method shows how to combine data from the visual and auditory systems for the acquisition of new knowledge in a natural manner. Such a natural way of training enables robots to learn from users, even if they are not experts in robotics. Full article

(This article belongs to the Section Physical Sensors)

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Graphical abstract

36 pages, 1288 KiB

Open AccessReview

Surface Electromyography Signal Processing and Classification Techniques

by Rubana H. Chowdhury^1,*, Mamun B. I. Reaz¹, Mohd Alauddin Bin Mohd Ali¹, Ashrif A. A. Bakar¹, Kalaivani Chellappan¹ and Tae G. Chang²

¹ Department of Electrical, Electronic and Systems Engineering, Universiti Kebangsaan Malaysia, Bangi, Selangor 43600, Malaysia

² School of Electrical and Electronics Engineering, Chung Ang University, 221 Hueksuk-Dong, Dongjak-Gu, Seoul 156-756, Korea

Sensors 2013, 13(9), 12431-12466; https://doi.org/10.3390/s130912431 - 17 Sep 2013

Cited by 791 | Viewed by 49531

Abstract

Electromyography (EMG) signals are becoming increasingly important in many applications, including clinical/biomedical, prosthesis or rehabilitation devices, human machine interactions, and more. However, noisy EMG signals are the major hurdles to be overcome in order to achieve improved performance in the above applications. Detection, [...] Read more.

Electromyography (EMG) signals are becoming increasingly important in many applications, including clinical/biomedical, prosthesis or rehabilitation devices, human machine interactions, and more. However, noisy EMG signals are the major hurdles to be overcome in order to achieve improved performance in the above applications. Detection, processing and classification analysis in electromyography (EMG) is very desirable because it allows a more standardized and precise evaluation of the neurophysiological, rehabitational and assistive technological findings. This paper reviews two prominent areas; first: the pre-processing method for eliminating possible artifacts via appropriate preparation at the time of recording EMG signals, and second: a brief explanation of the different methods for processing and classifying EMG signals. This study then compares the numerous methods of analyzing EMG signals, in terms of their performance. The crux of this paper is to review the most recent developments and research studies related to the issues mentioned above. Full article

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

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15 pages, 2047 KiB

Open AccessArticle

NO and NO₂ Sensing Properties of WO₃ and Co₃O₄ Based Gas Sensors

by Takafumi Akamatsu^*, Toshio Itoh, Noriya Izu and Woosuck Shin

National Institute of Advanced Industrial Science and Technology (AIST), Advanced Manufacturing Research Institute, 2266-98 Anagahora, Shimo-Shidami, Moriyama-ku, Nagoya 463-8560, Japan

Sensors 2013, 13(9), 12467-12481; https://doi.org/10.3390/s130912467 - 17 Sep 2013

Cited by 111 | Viewed by 10216

Abstract

Semiconductor-based gas sensors that use n-type WO₃ or p-type Co₃O₄ powder were fabricated and their gas sensing properties toward NO₂ or NO (0.5–5 ppm in air) were investigated at 100 °C or 200 °C. The resistance of the [...] Read more.

Semiconductor-based gas sensors that use n-type WO₃ or p-type Co₃O₄ powder were fabricated and their gas sensing properties toward NO₂ or NO (0.5–5 ppm in air) were investigated at 100 °C or 200 °C. The resistance of the WO₃-based sensor increased on exposure to NO₂ and NO. On the other hand, the resistance of the Co₃O₄-based sensor varied depending on the operating temperature and the gas species. The chemical states of the surface of WO₃ or those of the Co₃O₄ powder on exposure to 1 ppm NO₂ and NO were investigated by diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy. No clear differences between the chemical states of the metal oxide surface exposed to NO₂ or NO could be detected from the DRIFT spectra. Full article

(This article belongs to the Section Chemical Sensors)

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15 pages, 1750 KiB

Open AccessArticle

A Multi-Fork Z-Axis Quartz Micromachined Gyroscope

by Lihui Feng^*, Ke Zhao, Yunan Sun, Jianmin Cui, Fang Cui and Aiying Yang

School of Optoelectronics, Beijing Institute of Technology, Beijing 100081, China

Sensors 2013, 13(9), 12482-12496; https://doi.org/10.3390/s130912482 - 17 Sep 2013

Cited by 8 | Viewed by 8418

Abstract

A novel multi-fork z-axis gyroscope is presented in this paper. Different from traditional quartz gyroscopes, the lateral electrodes of the sense beam can be arranged in simple patterns; as a result, the fabrication is simplified. High sensitivity is achieved by the multi-fork design. [...] Read more.

A novel multi-fork z-axis gyroscope is presented in this paper. Different from traditional quartz gyroscopes, the lateral electrodes of the sense beam can be arranged in simple patterns; as a result, the fabrication is simplified. High sensitivity is achieved by the multi-fork design. The working principles are introduced, while the finite element method (FEM) is used to simulate the modal and sensitivity. A quartz fork is fabricated, and a prototype is assembled. Impedance testing shows that the drive frequency and sense frequency are similar to the simulations, and the quality factor is approximately 10,000 in air. The scale factor is measured to be 18.134 mV/(°/s) and the nonlinearity is 0.40% in a full-scale input range of ±250 °/s. Full article

(This article belongs to the Special Issue Modeling, Testing and Reliability Issues in MEMS Engineering 2013)

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19 pages, 1652 KiB

Open AccessArticle

Data Processing and Quality Evaluation of a Boat-Based Mobile Laser Scanning System

by Matti Vaaja^1,*

, Antero Kukko², Harri Kaartinen², Matti Kurkela¹, Elina Kasvi³, Claude Flener³

, Hannu Hyyppä^1,4, Juha Hyyppä², Juha Järvelä⁵ and Petteri Alho^1,3

¹ Department of Real Estate, Planning and Geoinformatics, Aalto University, Aalto FI-00076, Finland

² Department of Remote Sensing and Photogrammetry, Finnish Geodetic Institute, P.O. Box 15, Masala FI-02431, Finland

³ Department of Geography and Geology, University of Turku, Turku FI-20014, Finland

⁴ Civil Engineering and Building Services, Helsinki Metropolia University of Applied Sciences, Metropolia FI-00079, Finland

⁵ Department of Civil and Environmental Engineering, Aalto University, Aalto FI-00076, Finland

Sensors 2013, 13(9), 12497-12515; https://doi.org/10.3390/s130912497 - 17 Sep 2013

Cited by 37 | Viewed by 9889

Abstract

Mobile mapping systems (MMSs) are used for mapping topographic and urban features which are difficult and time consuming to measure with other instruments. The benefits of MMSs include efficient data collection and versatile usability. This paper investigates the data processing steps and quality [...] Read more.

Mobile mapping systems (MMSs) are used for mapping topographic and urban features which are difficult and time consuming to measure with other instruments. The benefits of MMSs include efficient data collection and versatile usability. This paper investigates the data processing steps and quality of a boat-based mobile mapping system (BoMMS) data for generating terrain and vegetation points in a river environment. Our aim in data processing was to filter noise points, detect shorelines as well as points below water surface and conduct ground point classification. Previous studies of BoMMS have investigated elevation accuracies and usability in detection of fluvial erosion and deposition areas. The new findings concerning BoMMS data are that the improved data processing approach allows for identification of multipath reflections and shoreline delineation. We demonstrate the possibility to measure bathymetry data in shallow (0–1 m) and clear water. Furthermore, we evaluate for the first time the accuracy of the BoMMS ground points classification compared to manually classified data. We also demonstrate the spatial variations of the ground point density and assess elevation and vertical accuracies of the BoMMS data. Full article

(This article belongs to the Section Remote Sensors)

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11 pages, 543 KiB

Open AccessArticle

Stem Cell Enrichment with Selectin Receptors: Mimicking the pH Environment of Trauma

by Thong M. Cao^1,†, Michael J. Mitchell^1,†, Jane Liesveld² and Michael R. King^1,*

¹ Department of Biomedical Engineering, Cornell University, Ithaca, NY 14850, USA

² School of Medicine and Dentistry, University of Rochester Medical Center, Rochester, NY 14642, USA

^† These authors contributed equally to this work.

Sensors 2013, 13(9), 12516-12526; https://doi.org/10.3390/s130912516 - 17 Sep 2013

Cited by 16 | Viewed by 7924

Abstract

The isolation of hematopoietic stem and progenitor cells (HSPCs) is critical for transplantation therapy and HSPC research, however current isolation techniques can be prohibitively expensive, time-consuming, and produce variable results. Selectin-coated microtubes have shown promise in rapidly isolating HSPCs from human bone marrow, [...] Read more.

The isolation of hematopoietic stem and progenitor cells (HSPCs) is critical for transplantation therapy and HSPC research, however current isolation techniques can be prohibitively expensive, time-consuming, and produce variable results. Selectin-coated microtubes have shown promise in rapidly isolating HSPCs from human bone marrow, but further purification of HSPCs remains a challenge. Herein, a biomimetic device for HSPC isolation is presented to mimic the acidic vascular microenvironment during trauma, which can enhance the binding frequency between L-selectin and its counter-receptor PSGL-1 and HSPCs. Under acidic pH conditions, L-selectin coated microtubes enhanced CD34+ HSPC adhesion, as evidenced by decreased cell rolling velocity and increased rolling flux. Dynamic light scattering was utilized as a novel sensor to confirm an L-selectin conformational change under acidic conditions, as previously predicted by molecular dynamics. These results suggest that mimicking the acidic conditions of trauma can induce a conformational extension of L-selectin, which can be utilized for flow-based, clinical isolation of HSPCs. Full article

(This article belongs to the Special Issue Biomimetic Receptors and Sensors)

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9 pages, 391 KiB

Open AccessArticle

Quantitative Assessment of Birefringent Skin Structures in Scattered Light Confocal Imaging Using Radially Polarized Light

by Babu Varghese^*, Rieko Verhagen, Altaf Hussain, Clemence Boudot, Qiangqiang Tai, Siqi Ding, Jasmin Alexandra Holz and Natallia Eduarda Uzunbajakava

Care & Health Applications Group, Philips Research Europe, High Tech Campus 34, 5656AE Eindhoven, The Netherlands

Sensors 2013, 13(9), 12527-12535; https://doi.org/10.3390/s130912527 - 17 Sep 2013

Cited by 5 | Viewed by 8413

Abstract

The polarization characteristics of birefringent tissues could be only partially obtained using linearly polarized light in polarization sensitive optical imaging. Here we analyze the change in polarization of backscattered light from birefringent structures versus the orientations of the incident polarizations using linearly, circularly [...] Read more.

The polarization characteristics of birefringent tissues could be only partially obtained using linearly polarized light in polarization sensitive optical imaging. Here we analyze the change in polarization of backscattered light from birefringent structures versus the orientations of the incident polarizations using linearly, circularly and radially polarized light in a cross-polarized confocal microscope. A spatially variable retardation plate composed of eight sectors of λ/2 wave plates was used to transform linearly polarized light into a radially polarized light. Based on the experimental data obtained from ex-vivo measurements on human scalp hairs and in-vivo measurements on hair and skin, we exemplify that the underestimation of the birefringence content resulting from the orientation related effects associated with the use of linearly polarized light for imaging tissues containing wavy birefringent structures could be minimized by using radially polarized light. Full article

(This article belongs to the Special Issue Photonic Sensors for Industrial, Environmental and Health Monitoring)

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12 pages, 399 KiB

Open AccessArticle

Model-Based Spike Detection of Epileptic EEG Data

by Yung-Chun Liu^1,2, Chou-Ching K. Lin³, Jing-Jane Tsai³ and Yung-Nien Sun^1,2,*

¹ Department of Computer Science and Information Engineering, National Cheng Kung University, No. 1, University Road, Tainan City 701, Taiwan

² Medical Device Innovation Center, National Cheng Kung University, No. 1, University Road, Tainan City 701, Taiwan

³ Department of Neurology, National Cheng Kung University Hospital, No. 138, Sheng Li Road, Tainan City 704, Taiwan

Sensors 2013, 13(9), 12536-12547; https://doi.org/10.3390/s130912536 - 17 Sep 2013

Cited by 57 | Viewed by 10120

Abstract

Accurate automatic spike detection is highly beneficial to clinical assessment of epileptic electroencephalogram (EEG) data. In this paper, a new two-stage approach is proposed for epileptic spike detection. First, the k-point nonlinear energy operator (k-NEO) is adopted to detect all possible spike candidates, [...] Read more.

Accurate automatic spike detection is highly beneficial to clinical assessment of epileptic electroencephalogram (EEG) data. In this paper, a new two-stage approach is proposed for epileptic spike detection. First, the k-point nonlinear energy operator (k-NEO) is adopted to detect all possible spike candidates, then a newly proposed spike model with slow wave features is applied to these candidates for spike classification. Experimental results show that the proposed system, using the AdaBoost classifier, outperforms the conventional method in both two- and three-class EEG pattern classification problems. The proposed system not only achieves better accuracy for spike detection, but also provides new ability to differentiate between spikes and spikes with slow waves. Though spikes with slow waves occur frequently in epileptic EEGs, they are not used in conventional spike detection. Identifying spikes with slow waves allows the proposed system to have better capability for assisting clinical neurologists in routine EEG examinations and epileptic diagnosis. Full article

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

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16 pages, 463 KiB

Open AccessArticle

Experimental Investigation on Centrifugal Compressor Blade Crack Classification Using the Squared Envelope Spectrum

by Hongkun Li^*, Xuefeng Zhang and Fujian Xu

School of Mechanical Engineering, Dalian University of Technology, No. 2 Linggong Road, Dalian 116024, China

Sensors 2013, 13(9), 12548-12563; https://doi.org/10.3390/s130912548 - 18 Sep 2013

Cited by 21 | Viewed by 9001

Abstract

Centrifugal compressors are a key piece of equipment for modern production. Among the components of the centrifugal compressor, the impeller is a pivotal part as it is used to transform kinetic energy into pressure energy. Blade crack condition monitoring and classification has been [...] Read more.

Centrifugal compressors are a key piece of equipment for modern production. Among the components of the centrifugal compressor, the impeller is a pivotal part as it is used to transform kinetic energy into pressure energy. Blade crack condition monitoring and classification has been broadly investigated in the industrial and academic area. In this research, a pressure pulsation (PP) sensor arranged in close vicinity to the crack area and the corresponding casing vibration signals are used to monitor blade crack information. As these signals cannot directly demonstrate the blade crack, the method employed in this research is based on the extraction of weak signal characteristics that are induced by blade cracking. A method for blade crack classification based on the signals monitored by using a squared envelope spectrum (SES) is presented. Experimental investigations on blade crack classification are carried out to verify the effectiveness of this method. The results show that it is an effective tool for blade crack classification in centrifugal compressors. Full article

(This article belongs to the Section Physical Sensors)

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17 pages, 577 KiB

Open AccessArticle

Analysis and Design of a 3rd Order Velocity-Controlled Closed-Loop for MEMS Vibratory Gyroscopes

by Huan-ming Wu^1,2, Hai-gang Yang^1,*, Tao Yin¹ and Ji-wei Jiao³

¹ Institute of Electronics, Chinese Academy of Sciences, Beijing 100190, China

² Ningbo High-tech Institute, Ningbo University, Ningbo 315211, China

³ Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050, China

Sensors 2013, 13(9), 12564-12580; https://doi.org/10.3390/s130912564 - 18 Sep 2013

Cited by 6 | Viewed by 8803

Abstract

The time-average method currently available is limited to analyzing the specific performance of the automatic gain control-proportional and integral (AGC-PI) based velocity-controlled closed-loop in a micro-electro-mechanical systems (MEMS) vibratory gyroscope, since it is hard to solve nonlinear functions in the time domain when [...] Read more.

The time-average method currently available is limited to analyzing the specific performance of the automatic gain control-proportional and integral (AGC-PI) based velocity-controlled closed-loop in a micro-electro-mechanical systems (MEMS) vibratory gyroscope, since it is hard to solve nonlinear functions in the time domain when the control loop reaches to 3rd order. In this paper, we propose a linearization design approach to overcome this limitation by establishing a 3rd order linear model of the control loop and transferring the analysis to the frequency domain. Order reduction is applied on the built linear model’s transfer function by constructing a zero-pole doublet, and therefore mathematical expression of each control loop’s performance specification is obtained. Then an optimization methodology is summarized, which reveals that a robust, stable and swift control loop can be achieved by carefully selecting the system parameters following a priority order. Closed-loop drive circuits are designed and implemented using 0.35 μm complementary metal oxide semiconductor (CMOS) process, and experiments carried out on a gyroscope prototype verify the optimization methodology that an optimized stability of the control loop can be achieved by constructing the zero-pole doublet, and disturbance rejection capability (D.R.C) of the control loop can be improved by increasing the integral term. Full article

(This article belongs to the Special Issue Modeling, Testing and Reliability Issues in MEMS Engineering 2011)

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24 pages, 370 KiB

Open AccessArticle

Ontology Alignment Architecture for Semantic Sensor Web Integration

by Susel Fernandez^*

, Ivan Marsa-Maestre

, Juan R. Velasco

and Bernardo Alarcos

Department of Computing Engineering, University of Alcala, Superior Polytechnic School, University Campus, Alcalá de Henares 28805, Madrid, Spain

Sensors 2013, 13(9), 12581-12604; https://doi.org/10.3390/s130912581 - 18 Sep 2013

Cited by 31 | Viewed by 8702

Abstract

Sensor networks are a concept that has become very popular in data acquisition and processing for multiple applications in different fields such as industrial, medicine, home automation, environmental detection, etc. Today, with the proliferation of small communication devices with sensors that collect environmental [...] Read more.

Sensor networks are a concept that has become very popular in data acquisition and processing for multiple applications in different fields such as industrial, medicine, home automation, environmental detection, etc. Today, with the proliferation of small communication devices with sensors that collect environmental data, semantic Web technologies are becoming closely related with sensor networks. The linking of elements from Semantic Web technologies with sensor networks has been called Semantic Sensor Web and has among its main features the use of ontologies. One of the key challenges of using ontologies in sensor networks is to provide mechanisms to integrate and exchange knowledge from heterogeneous sources (that is, dealing with semantic heterogeneity). Ontology alignment is the process of bringing ontologies into mutual agreement by the automatic discovery of mappings between related concepts. This paper presents a system for ontology alignment in the Semantic Sensor Web which uses fuzzy logic techniques to combine similarity measures between entities of different ontologies. The proposed approach focuses on two key elements: the terminological similarity, which takes into account the linguistic and semantic information of the context of the entity’s names, and the structural similarity, based on both the internal and relational structure of the concepts. This work has been validated using sensor network ontologies and the Ontology Alignment Evaluation Initiative (OAEI) tests. The results show that the proposed techniques outperform previous approaches in terms of precision and recall. Full article

(This article belongs to the Section Sensor Networks)

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27 pages, 3040 KiB

Open AccessArticle

Detection of Upscale-Crop and Partial Manipulation in Surveillance Video Based on Sensor Pattern Noise

by Dai-Kyung Hyun¹, Seung-Jin Ryu¹, Hae-Yeoun Lee² and Heung-Kyu Lee^1,*

¹ Department of Computer Science, Korea Advanced Institute of Science and Technology, 291 Daehak-Ro, Yuseong-Gu, Daejon, Korea

² Department of Computer and Software Engineering, Kumoh National Institute of Technology, Yangho-dong, Gumi, Gyeongbuk, Korea

Sensors 2013, 13(9), 12605-12631; https://doi.org/10.3390/s130912605 - 18 Sep 2013

Cited by 28 | Viewed by 8065

Abstract

In many court cases, surveillance videos are used as significant court evidence. As these surveillance videos can easily be forged, it may cause serious social issues, such as convicting an innocent person. Nevertheless, there is little research being done on forgery of surveillance [...] Read more.

In many court cases, surveillance videos are used as significant court evidence. As these surveillance videos can easily be forged, it may cause serious social issues, such as convicting an innocent person. Nevertheless, there is little research being done on forgery of surveillance videos. This paper proposes a forensic technique to detect forgeries of surveillance video based on sensor pattern noise (SPN). We exploit the scaling invariance of the minimum average correlation energy Mellin radial harmonic (MACE-MRH) correlation filter to reliably unveil traces of upscaling in videos. By excluding the high-frequency components of the investigated video and adaptively choosing the size of the local search window, the proposed method effectively localizes partially manipulated regions. Empirical evidence from a large database of test videos, including RGB (Red, Green, Blue)/infrared video, dynamic-/static-scene video and compressed video, indicates the superior performance of the proposed method. Full article

(This article belongs to the Section Physical Sensors)

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16 pages, 2117 KiB

Open AccessArticle

Laser Doppler Blood Flow Imaging Using a CMOS Imaging Sensor with On-Chip Signal Processing

by Diwei He¹, Hoang C. Nguyen¹, Barrie R. Hayes-Gill¹, Yiqun Zhu¹, John A. Crowe¹, Cally Gill², Geraldine F. Clough² and Stephen P. Morgan^1,*

¹ Electrical Systems and Optics Research Division, Faculty of Engineering, University of Nottingham, University Park, Nottingham NG7 2RD, UK

² School of Medicine, University of Southampton, University Road, Southampton SO17 1BJ, UK

Sensors 2013, 13(9), 12632-12647; https://doi.org/10.3390/s130912632 - 18 Sep 2013

Cited by 17 | Viewed by 12529

Abstract

The first fully integrated 2D CMOS imaging sensor with on-chip signal processing for applications in laser Doppler blood flow (LDBF) imaging has been designed and tested. To obtain a space efficient design over 64 × 64 pixels means that standard processing electronics used [...] Read more.

The first fully integrated 2D CMOS imaging sensor with on-chip signal processing for applications in laser Doppler blood flow (LDBF) imaging has been designed and tested. To obtain a space efficient design over 64 × 64 pixels means that standard processing electronics used off-chip cannot be implemented. Therefore the analog signal processing at each pixel is a tailored design for LDBF signals with balanced optimization for signal-to-noise ratio and silicon area. This custom made sensor offers key advantages over conventional sensors, viz. the analog signal processing at the pixel level carries out signal normalization; the AC amplification in combination with an anti-aliasing filter allows analog-to-digital conversion with a low number of bits; low resource implementation of the digital processor enables on-chip processing and the data bottleneck that exists between the detector and processing electronics has been overcome. The sensor demonstrates good agreement with simulation at each design stage. The measured optical performance of the sensor is demonstrated using modulated light signals and in vivo blood flow experiments. Images showing blood flow changes with arterial occlusion and an inflammatory response to a histamine skin-prick demonstrate that the sensor array is capable of detecting blood flow signals from tissue. Full article

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

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15 pages, 1813 KiB

Open AccessArticle

A 0.0016 mm² 0.64 nJ Leakage-Based CMOS Temperature Sensor

by Pablo Ituero^*, Marisa López-Vallejo

and Carlos López-Barrio

Departamento de Ingeniería Electrónica, ETSI Telecomunicación, Universidad Politécnica de Madrid, Avenida Complutense 30, 28040 Madrid, Spain

Sensors 2013, 13(9), 12648-12662; https://doi.org/10.3390/s130912648 - 18 Sep 2013

Cited by 14 | Viewed by 7306

Abstract

This paper presents a CMOS temperature sensor based on the thermal dependencies of the leakage currents targeting the 65 nm node. To compensate for the effect of process fluctuations, the proposed sensor realizes the ratio of two measures of the time it takes [...] Read more.

This paper presents a CMOS temperature sensor based on the thermal dependencies of the leakage currents targeting the 65 nm node. To compensate for the effect of process fluctuations, the proposed sensor realizes the ratio of two measures of the time it takes a capacitor to discharge through a transistor in the subthreshold regime. Furthermore, a novel charging mechanism for the capacitor is proposed to further increase the robustness against fabrication variability. The sensor, including digitization and interfacing, occupies 0.0016 mm2 and has an energy consumption of 47.7–633 pJ per sample. The resolution of the sensor is 0.28 °C, and the 3σ inaccuracy over the range 40–110 °C is 1.17 °C. Full article

(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Spain 2013)

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24 pages, 697 KiB

Open AccessArticle

A Relevance Vector Machine-Based Approach with Application to Oil Sand Pump Prognostics

by Jinfei Hu and Peter W. Tse^*

The Smart Engineering Asset Management Laboratory (SEAM), Department of Systems Engineering and Engineering Management (SEEM), City University of Hong Kong, Tat Chee Avenue, Kowloon, 999077 Hong Kong

Sensors 2013, 13(9), 12663-12686; https://doi.org/10.3390/s130912663 - 18 Sep 2013

Cited by 48 | Viewed by 7736

Abstract

Oil sand pumps are widely used in the mining industry for the delivery of mixtures of abrasive solids and liquids. Because they operate under highly adverse conditions, these pumps usually experience significant wear. Consequently, equipment owners are quite often forced to invest substantially [...] Read more.

Oil sand pumps are widely used in the mining industry for the delivery of mixtures of abrasive solids and liquids. Because they operate under highly adverse conditions, these pumps usually experience significant wear. Consequently, equipment owners are quite often forced to invest substantially in system maintenance to avoid unscheduled downtime. In this study, an approach combining relevance vector machines (RVMs) with a sum of two exponential functions was developed to predict the remaining useful life (RUL) of field pump impellers. To handle field vibration data, a novel feature extracting process was proposed to arrive at a feature varying with the development of damage in the pump impellers. A case study involving two field datasets demonstrated the effectiveness of the developed method. Compared with standalone exponential fitting, the proposed RVM-based model was much better able to predict the remaining useful life of pump impellers. Full article

(This article belongs to the Section Physical Sensors)

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11 pages, 279 KiB

Open AccessArticle

Static Hyperspectral Fluorescence Imaging of Viscous Materials Based on a Linear Variable Filter Spectrometer

by Patrik J. Murr^*, Michael Schardt and Alexander W. Koch

Institute for Measurement Systems and Sensor Technology, Technische Universität München, Theresienstrasse 90/N5, Munich 80333, Germany

Sensors 2013, 13(9), 12687-12697; https://doi.org/10.3390/s130912687 - 23 Sep 2013

Cited by 14 | Viewed by 8431

Abstract

This paper presents a low-cost hyperspectral measurement setup in a new application based on fluorescence detection in the visible (Vis) wavelength range. The aim of the setup is to take hyperspectral fluorescence images of viscous materials. Based on these images, fluorescent and non-fluorescent [...] Read more.

This paper presents a low-cost hyperspectral measurement setup in a new application based on fluorescence detection in the visible (Vis) wavelength range. The aim of the setup is to take hyperspectral fluorescence images of viscous materials. Based on these images, fluorescent and non-fluorescent impurities in the viscous materials can be detected. For the illumination of the measurement object, a narrow-band high-power light-emitting diode (LED) with a center wavelength of 370 nm was used. The low-cost acquisition unit for the imaging consists of a linear variable filter (LVF) and a complementary metal oxide semiconductor (CMOS) 2D sensor array. The translucent wavelength range of the LVF is from 400 nm to 700 nm. For the confirmation of the concept, static measurements of fluorescent viscous materials with a non-fluorescent impurity have been performed and analyzed. With the presented setup, measurement surfaces in the micrometer range can be provided. The measureable minimum particle size of the impurities is in the nanometer range. The recording rate for the measurements depends on the exposure time of the used CMOS 2D sensor array and has been found to be in the microsecond range. Full article

(This article belongs to the Special Issue Optomechatronics)

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