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Sensors, Volume 14, Issue 4 (April 2014) – 98 articles , Pages 5742-7579

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17230 KiB  
Article
A Multi-Resolution Approach for an Automated Fusion of Different Low-Cost 3D Sensors
by Jan Dupuis, Stefan Paulus, Jan Behmann, Lutz Plümer and Heiner Kuhlmann
Sensors 2014, 14(4), 7563-7579; https://doi.org/10.3390/s140407563 - 24 Apr 2014
Cited by 13 | Viewed by 8812
Abstract
The 3D acquisition of object structures has become a common technique in many fields of work, e.g., industrial quality management, cultural heritage or crime scene documentation. The requirements on the measuring devices are versatile, because spacious scenes have to be imaged with a [...] Read more.
The 3D acquisition of object structures has become a common technique in many fields of work, e.g., industrial quality management, cultural heritage or crime scene documentation. The requirements on the measuring devices are versatile, because spacious scenes have to be imaged with a high level of detail for selected objects. Thus, the used measuring systems are expensive and require an experienced operator. With the rise of low-cost 3D imaging systems, their integration into the digital documentation process is possible. However, common low-cost sensors have the limitation of a trade-off between range and accuracy, providing either a low resolution of single objects or a limited imaging field. Therefore, the use of multiple sensors is desirable. We show the combined use of two low-cost sensors, the Microsoft Kinect and the David laserscanning system, to achieve low-resolved scans of the whole scene and a high level of detail for selected objects, respectively. Afterwards, the high-resolved David objects are automatically assigned to their corresponding Kinect object by the use of surface feature histograms and SVM-classification. The corresponding objects are fitted using an ICP-implementation to produce a multi-resolution map. The applicability is shown for a fictional crime scene and the reconstruction of a ballistic trajectory. Full article
(This article belongs to the Section Physical Sensors)
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<p>The low-cost sensors, Kinect (<b>A</b>) with the IR emitter (i), the RGB camera (ii) and the IR camera (iii), as well as the David system (<b>B</b>) with the camera (iv), the calibration corner (v) and the laser line (vi). Corresponding point-clouds (<b>C,D</b>) from the Kinect sensor and the David system, respectively.</p> Full article ">
<p>Dataflow chart that describes the main steps of the automated registration approach. CoG, center of gravity.</p> Full article ">
<p>Results of the segmentation work-flow: (<b>A</b>) original point-cloud; (<b>B</b>) the ground-plane was removed and the point-cloud was rotated into the xy-plane; (<b>C</b>) segmented binary image; (<b>D</b>) segmented point-cloud retransformed into the origin space.</p> Full article ">
<p>Distinct surfaces generate distinct histogram manifestations. A pistol (<b>A</b>) with the corresponding mean histogram (<b>B</b>) is shown, as well as a can imitation (<b>C</b>) with the mean histogram (<b>D</b>).</p> Full article ">
<p>(<b>A</b>) The results of the object assignment using SVM classification; (<b>B</b>) point-clouds of the pre-aligned objects; (<b>C</b>) point-clouds after final ICP registration; (<b>D</b>) deviation map of registered point-clouds.</p> Full article ">
<p>Result of a reconstruction of a ballistic trajectory.</p> Full article ">
1580 KiB  
Article
The Enhanced Locating Performance of an Integrated Cross-Correlation and Genetic Algorithm for Radio Monitoring Systems
by Yao-Tang Chang, Chi-Lin Wu and Hsu-Chih Cheng
Sensors 2014, 14(4), 7541-7562; https://doi.org/10.3390/s140407541 - 24 Apr 2014
Cited by 6 | Viewed by 7605
Abstract
The rapid development of wireless broadband communication technology has affected the location accuracy of worldwide radio monitoring stations that employ time-difference-of-arrival (TDOA) location technology. In this study, TDOA-based location technology was implemented in Taiwan for the first time according to International Telecommunications Union [...] Read more.
The rapid development of wireless broadband communication technology has affected the location accuracy of worldwide radio monitoring stations that employ time-difference-of-arrival (TDOA) location technology. In this study, TDOA-based location technology was implemented in Taiwan for the first time according to International Telecommunications Union Radiocommunication (ITU-R) recommendations regarding monitoring and location applications. To improve location accuracy, various scenarios, such as a three-dimensional environment (considering an unequal locating antenna configuration), were investigated. Subsequently, the proposed integrated cross-correlation and genetic algorithm was evaluated in the metropolitan area of Tainan. The results indicated that the location accuracy at a circular error probability of 50% was less than 60 m when a multipath effect was present in the area. Moreover, compared with hyperbolic algorithms that have been applied in conventional TDOA-based location systems, the proposed algorithm yielded 17-fold and 19-fold improvements in the mean difference when the location position of the interference station was favorable and unfavorable, respectively. Hence, the various forms of radio interference, such as low transmission power, burst and weak signals, and metropolitan interference, was proved to be easily identified, located, and removed. Full article
(This article belongs to the Special Issue Selected Papers from 2014 International Symposium on Computer, Consumer and Control (IS3C 2014))
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<p>The major installation processing consist of below step in current proposed TDOA-based monitoring station.</p> Full article ">
<p>The proposed TDOA monitoring/locating system (<b>a</b>) system architecture (<b>b</b>) physical configuration in current experiments.</p> Full article ">
<p>The proposed interface of the TDOA-based monitoring/locating system by selecting the sampling time, filter, bandwidth, <span class="html-italic">etc</span>.</p> Full article ">
<p>The proposed user interface on integrating the monitoring power spectrum density and locating position by indicating hyperbolic curve.</p> Full article ">
<p>The experimental processing of proposed and conventional TDOA-based monitoring/location system.</p> Full article ">
<p>The 88.3 MHz experimental evaluation of (<b>a</b>) time difference and (<b>b</b>) distance difference using cross-correlation algorithm in TDOA-based monitoring/locating system.</p> Full article ">
<p>The proposed experiment configuration for investigating the TDOA limitation of location performance in multi-path effect of metropolitan area.</p> Full article ">
<p>The procedure of proposed genetic algorithm applied in TDOA-based locating system.</p> Full article ">
<p>The simulated configuration of various scenarios on (<b>a</b>) inside coverage area (<b>b</b>) outside coverage area (<b>c</b>) spreading (extending) locating networks of TDOA-based locating system.</p> Full article ">
1251 KiB  
Article
Floor Sensing System Using Laser Reflectivity for Localizing Everyday Objects and Robot
by Yoonseok Pyo, Tsutomu Hasegawa, Tokuo Tsuji, Ryo Kurazume and Ken'ichi Morooka
Sensors 2014, 14(4), 7524-7540; https://doi.org/10.3390/s140407524 - 24 Apr 2014
Cited by 12 | Viewed by 8933
Abstract
This paper describes a new method of measuring the position of everyday objects and a robot on the floor using distance and reflectance acquired by laser range finder (LRF). The information obtained by this method is important for a service robot working in [...] Read more.
This paper describes a new method of measuring the position of everyday objects and a robot on the floor using distance and reflectance acquired by laser range finder (LRF). The information obtained by this method is important for a service robot working in a human daily life environment. Our method uses only one LRF together with a mirror installed on the wall. Moreover, since the area of sensing is limited to a LRF scanning plane parallel to the floor and just a few centimeters above the floor, the scanning covers the whole room with minimal invasion of privacy of a resident, and occlusion problem is mitigated by using mirror. We use the reflection intensity and position information obtained from the target surface. Although it is not possible to identify all objects by additionally using reflection values, it would be easier to identify unknown objects if we can eliminate easily identifiable objects by reflectance. In addition, we propose a method for measuring the robot’s pose using the tag which has the encoded reflection pattern optically identified by the LRF. Our experimental results validate the effectiveness of the proposed method. Full article
(This article belongs to the Section Physical Sensors)
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<p>Diffuse feature of laser beam.</p> Full article ">
<p>Position measurement using reflected laser beam and diffused laser beam: (<b>a</b>) position measurement using reflected laser beam, (<b>b</b>) position measurement using diffused laser beam.</p> Full article ">
<p>Objects in daily environment.</p> Full article ">
<p>Experiment results of reflection intensity <span class="html-italic">vs.</span> distance and angle of incidence.</p> Full article ">
<p>Experiment setups.</p> Full article ">
<p>Reflection intensity value of each object.</p> Full article ">
<p>Normalized reflection intensity value of each object.</p> Full article ">
<p>Reflection intensity value of retroreflective material.</p> Full article ">
<p>Attaching retroreflective materials and position measurement using reflected laser beam and diffused laser beam: (<b>a</b>) position of retroreflective material, (<b>b</b>) distinctly different intensity compared to the other objects.</p> Full article ">
793 KiB  
Article
Model Parameter Adaption-Based Multi-Model Algorithm for Extended Object Tracking Using a Random Matrix
by Borui Li, Chundi Mu, Shuli Han and Tianming Bai
Sensors 2014, 14(4), 7505-7523; https://doi.org/10.3390/s140407505 - 24 Apr 2014
Cited by 4 | Viewed by 6706
Abstract
Traditional object tracking technology usually regards the target as a point source object. However, this approximation is no longer appropriate for tracking extended objects such as large targets and closely spaced group objects. Bayesian extended object tracking (EOT) using a random symmetrical positive [...] Read more.
Traditional object tracking technology usually regards the target as a point source object. However, this approximation is no longer appropriate for tracking extended objects such as large targets and closely spaced group objects. Bayesian extended object tracking (EOT) using a random symmetrical positive definite (SPD) matrix is a very effective method to jointly estimate the kinematic state and physical extension of the target. The key issue in the application of this random matrix-based EOT approach is to model the physical extension and measurement noise accurately. Model parameter adaptive approaches for both extension dynamic and measurement noise are proposed in this study based on the properties of the SPD matrix to improve the performance of extension estimation. An interacting multi-model algorithm based on model parameter adaptive filter using random matrix is also presented. Simulation results demonstrate the effectiveness of the proposed adaptive approaches and multi-model algorithm. The estimation performance of physical extension is better than the other algorithms, especially when the target maneuvers. The kinematic state estimation error is lower than the others as well. Full article
(This article belongs to the Section Physical Sensors)
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<p>Description by ellipses of the target's physical extension. A large ship (<b>left</b>) and an aircraft formation (<b>right</b>).</p> Full article ">
<p>Target trajectory of simulation scenario 1.</p> Full article ">
<p>Average <math display="inline"> <semantics id="sm128"> <mrow> <msubsup> <mi>θ</mi> <mi>k</mi> <mi>A</mi></msubsup></mrow></semantics></math> in simulation scenario 1.</p> Full article ">
<p>RMSE of physical extension in simulation scenario 1.</p> Full article ">
<p>Target trajectory of simulation scenario 2.</p> Full article ">
<p>Average <math display="inline"> <semantics id="sm129"> <mrow> <msubsup> <mi>θ</mi> <mi>k</mi> <mi>A</mi></msubsup></mrow></semantics></math> of model 3 in simulation scenario 2.</p> Full article ">
<p>RMSE of position in simulation scenario 2.</p> Full article ">
<p>RMSE of velocity in simulation scenario 2.</p> Full article ">
<p>RMSE of physical extension in simulation scenario 2.</p> Full article ">
864 KiB  
Article
Non-Destructive Quality Evaluation of Pepper (Capsicum annuum L.) Seeds Using LED-Induced Hyperspectral Reflectance Imaging
by Changyeun Mo, Giyoung Kim, Kangjin Lee, Moon S. Kim, Byoung-Kwan Cho, Jongguk Lim and Sukwon Kang
Sensors 2014, 14(4), 7489-7504; https://doi.org/10.3390/s140407489 - 24 Apr 2014
Cited by 39 | Viewed by 8323
Abstract
In this study, we developed a viability evaluation method for pepper (Capsicum annuum L.) seeds based on hyperspectral reflectance imaging. The reflectance spectra of pepper seeds in the 400–700 nm range are collected from hyperspectral reflectance images obtained using blue, green, [...] Read more.
In this study, we developed a viability evaluation method for pepper (Capsicum annuum L.) seeds based on hyperspectral reflectance imaging. The reflectance spectra of pepper seeds in the 400–700 nm range are collected from hyperspectral reflectance images obtained using blue, green, and red LED illumination. A partial least squares–discriminant analysis (PLS-DA) model is developed to classify viable and non-viable seeds. Four spectral ranges generated with four types of LEDs (blue, green, red, and RGB), which were pretreated using various methods, are investigated to develop the classification models. The optimal PLS-DA model based on the standard normal variate for RGB LED illumination (400–700 nm) yields discrimination accuracies of 96.7% and 99.4% for viable seeds and nonviable seeds, respectively. The use of images based on the PLS-DA model with the first-order derivative of a 31.5-nm gap for red LED illumination (600–700 nm) yields 100% discrimination accuracy for both viable and nonviable seeds. The results indicate that a hyperspectral imaging technique based on LED light can be potentially applied to high-quality pepper seed sorting. Full article
(This article belongs to the Section Remote Sensors)
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<p>(<b>a</b>) Schematic diagram and (<b>b</b>) photograph of the hyperspectral reflectance imaging system.</p> Full article ">
<p>Spectra of the reference panel with blue, green, and red LED illumination.</p> Full article ">
<p>Average spectra with pretreated maximum normalization extracted from images of viable and nonviable pepper seeds illuminated by BL, GL, and RL.</p> Full article ">
<p>(<b>a</b>) Regression coefficients plot of the PLS-DA model, and (<b>b</b>) the PLS-DA prediction results obtained using the first-order derivative with a gap of 13.5 nm to discriminate between viable and nonviable pepper seeds based on the reflectance spectra produced under BL (400–500 nm).</p> Full article ">
<p>(<b>a</b>) Regression coefficients of the PLS-DA model, and (<b>b</b>) the PLS-DA prediction results obtained using SNV to discriminate between viable and nonviable pepper seeds based on the reflectance spectra produced under GL (500–600 nm).</p> Full article ">
<p>(<b>a</b>) Regression coefficients of the PLS-DA model, and (<b>b</b>) the PLS-DA prediction results obtained using the first-order derivative with a 31.5 nm interval to discriminate between viable and nonviable pepper seeds based on the reflectance spectra under RL (600–700 nm).</p> Full article ">
<p>(<b>a</b>) Regression coefficients of the PLS-DA model, and (<b>b</b>) the PLS-DA prediction results obtained using SNV to discriminate between viable and nonviable pepper seeds based on the reflectance spectra under RGB LED (400–700 nm).</p> Full article ">
<p>PLS image processing to classify viable and nonviable pepper seeds.</p> Full article ">
<p>PLS image prediction results obtained when discriminating between viable and nonviable pepper seeds using spectral images of seeds illuminated by: (<b>a</b>) BL (400–500 nm), (<b>b</b>) GL (500–600 nm), (<b>c</b>) RL (600–700 nm), and (<b>d</b>) a RGB LED (400–700 nm), where the PLS-DA was applied.</p> Full article ">
1213 KiB  
Review
Chronology of Fabry-Perot Interferometer Fiber-Optic Sensors and Their Applications: A Review
by Md. Rajibul Islam, Muhammad Mahmood Ali, Man-Hong Lai, Kok-Sing Lim and Harith Ahmad
Sensors 2014, 14(4), 7451-7488; https://doi.org/10.3390/s140407451 - 24 Apr 2014
Cited by 325 | Viewed by 27110
Abstract
Optical fibers have been involved in the area of sensing applications for more than four decades. Moreover, interferometric optical fiber sensors have attracted broad interest for their prospective applications in sensing temperature, refractive index, strain measurement, pressure, acoustic wave, vibration, magnetic field, and [...] Read more.
Optical fibers have been involved in the area of sensing applications for more than four decades. Moreover, interferometric optical fiber sensors have attracted broad interest for their prospective applications in sensing temperature, refractive index, strain measurement, pressure, acoustic wave, vibration, magnetic field, and voltage. During this time, numerous types of interferometers have been developed such as Fabry-Perot, Michelson, Mach-Zehnder, Sagnac Fiber, and Common-path interferometers. Fabry-Perot interferometer (FPI) fiber-optic sensors have been extensively investigated for their exceedingly effective, simple fabrication as well as low cost aspects. In this study, a wide variety of FPI sensors are reviewed in terms of fabrication methods, principle of operation and their sensing applications. The chronology of the development of FPI sensors and their implementation in various applications are discussed. Full article
(This article belongs to the Special Issue Photonic Sensors for Industrial, Environmental and Health Monitoring)
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<p>Experimental arrangement of the coherence multiplexing technique for remote sensing based on Fabry-Perot interferometers [<a href="#b4-sensors-14-07451" class="html-bibr">4</a>]. The abbreviations used in figure are light emitting diode (LED), fiber directional coupler (DC), fiber Fabry-Perot (FFP), beam splitter (BSD), photodiode (PD), integrator (mittpiezoelectric transducer (PZT).</p> Full article ">
<p>Schematic of a sensor structure. The light is sent and received through the 100 μm core fiber. The cavity length is about 7 μm and the thickness of the membrane is 8 μm [<a href="#b56-sensors-14-07451" class="html-bibr">56</a>].</p> Full article ">
<p>Schematic diagram of an EFPI ultrasound sensor [<a href="#b59-sensors-14-07451" class="html-bibr">59</a>].</p> Full article ">
<p>Experimental humidity sensor system design [<a href="#b15-sensors-14-07451" class="html-bibr">15</a>].</p> Full article ">
<p>Illustration of the Langmuir-Blodgett method. (<b>a</b>) Formation of a monolayer film of aliphatic molecules on the surface of water, represented by hydrophilic circles and hydrophobic rods; (<b>b</b>) deposition of one layer on the optical fiber by passing up through the film; (<b>c</b>) after depositing the six layers on the fiber end through the film, deposition of a 7th layer; (<b>d</b>) formation of the cavity at the fiber end of the fiber with patterned refractive indices [<a href="#b65-sensors-14-07451" class="html-bibr">65</a>].</p> Full article ">
<p>Detail of a Fabry-Perot strain gauge placed on the surface of a cantilever beam [<a href="#b68-sensors-14-07451" class="html-bibr">68</a>].</p> Full article ">
<p>The model diagram for the chitosan-coated FPI, RH sensor [<a href="#b75-sensors-14-07451" class="html-bibr">75</a>].</p> Full article ">
<p>Illustration of fabrication of a FPI cavity inside the fiber [<a href="#b77-sensors-14-07451" class="html-bibr">77</a>]. (<b>a</b>) The creation of microholes, on the order of ∼1 μm using a femtosecond laser, through the center of the fiber core. (<b>b</b>) Splicing of the two fiber ends with microholes. (<b>c</b>) Formation of the FP cavity. (<b>d</b>) Introducing the vertical cross-through microcavity for the fabrication of microchannels.</p> Full article ">
<p>Percentages of the FPI fabrication studies in two categories are presented through some considered time ranges.</p> Full article ">
1343 KiB  
Article
First-Principles Surface Stress Calculations and Multiscale Deformation Analysis of a Self-Assembled Monolayer Adsorbed on a Micro-Cantilever
by Yu-Ching Shih, Chuin-Shan Chen and Kuang-Chong Wu
Sensors 2014, 14(4), 7435-7450; https://doi.org/10.3390/s140407435 - 23 Apr 2014
Cited by 6 | Viewed by 9134
Abstract
Micro-cantilever sensors are widely used to detect biomolecules, chemical gases, and ionic species. However, the theoretical descriptions and predictive modeling of these devices are not well developed, and lag behind advances in fabrication and applications. In this paper, we present a novel multiscale [...] Read more.
Micro-cantilever sensors are widely used to detect biomolecules, chemical gases, and ionic species. However, the theoretical descriptions and predictive modeling of these devices are not well developed, and lag behind advances in fabrication and applications. In this paper, we present a novel multiscale simulation framework for nanomechanical sensors. This framework, combining density functional theory (DFT) calculations and finite element method (FEM) analysis, is capable of analyzing molecular adsorption-induced deformation and stress fields in the sensors from the molecular scale to the device scale. Adsorption of alkanethiolate self-assembled monolayer (SAM) on the Au(111) surface of the micro-cantilever sensor is studied in detail to demonstrate the applicability of this framework. DFT calculations are employed to investigate the molecular adsorption-induced surface stress upon the gold surface. The 3D shell elements with initial stresses obtained from the DFT calculations serve as SAM domains in the adsorption layer, while FEM is employed to analyze the deformation and stress of the sensor devices. We find that the micro-cantilever tip deflection has a linear relationship with the coverage of the SAM domains. With full coverage, the tip deflection decreases as the molecular chain length increases. The multiscale simulation framework provides a quantitative analysis of the displacement and stress fields, and can be used to predict the response of nanomechanical sensors subjected to complex molecular adsorption. Full article
(This article belongs to the Special Issue Nanomechanical Sensors)
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Graphical abstract

Graphical abstract
Full article ">
<p>(<b>a</b>) Multiscale simulation framework: bridging the molecular simulation with adsorption-induced deformation of nanomechanical sensors; (<b>b</b>) The link between DFT and FEM. The DFT surface stresses (g<sub>11</sub> and g<sub>22</sub>) are substituted as initial stresses in a section of film depicted as a 2D circle. The thickness <span class="html-italic">h<sub>s</sub></span> of the substrate (illustrated as a cylinder but could be any shape) is much greater than that of the film. The thin film and substrate parts of the sensors are simulated together in the FEM analysis.</p> Full article ">
<p>(<b>a</b>) Multiscale simulation framework: bridging the molecular simulation with adsorption-induced deformation of nanomechanical sensors; (<b>b</b>) The link between DFT and FEM. The DFT surface stresses (g<sub>11</sub> and g<sub>22</sub>) are substituted as initial stresses in a section of film depicted as a 2D circle. The thickness <span class="html-italic">h<sub>s</sub></span> of the substrate (illustrated as a cylinder but could be any shape) is much greater than that of the film. The thin film and substrate parts of the sensors are simulated together in the FEM analysis.</p> Full article ">
<p>An illustration of the supercell model for a clean gold surface.</p> Full article ">
<p>(<b>a</b>) An illustration of 30% coverage of randomly dispersed SAM domains; (<b>b</b>) An arbitrary angle θ is used to convert the principal stress into normal stress and shear stress components; (<b>c</b>) A normalized histogram plot of the uniformly distributed angles.</p> Full article ">
<p>(<b>a</b>) Top view of the hexanethiolates on the Au(111) surface. Solid lines represent a <math display="inline"> <semantics id="sm14"> <mrow> <mrow> <mo>(</mo> <mrow> <msqrt> <mn>3</mn></msqrt> <mo>×</mo> <msqrt> <mn>3</mn></msqrt></mrow> <mo>)</mo></mrow> <mtext>R</mtext> <mn>30</mn> <mo>°</mo> <mtext>Au</mtext> <mo>(</mo> <mn>111</mn> <mo>)</mo></mrow></semantics></math> surface unit cell. The gray, white, yellow, and orange spheres indicate carbon, hydrogen, gold, and sulfur atoms, respectively; (<b>b</b>) A 3D view of the DFT unit cell indicated in (a).</p> Full article ">
<p>(<b>a</b>) Finite element models of the micro-cantilever. The upper part is the shell element section and the lower part is the solid element section. For clarity, the two parts are separated, the number of surface elements is reduced, and the direction of the surface normal is scaled for clarity. The colors blue, red, green, and yellow indicate the surface, gold, silicon nitride, and silicon sections, respectively. The beam has a length, <span class="html-italic">L</span>, of 206 μm and a width, <span class="html-italic">W</span>, of 60 μm. The support block has a length, <span class="html-italic">B</span>, of 20 μm and a width of 100 μm; (<b>b</b>) A mesh convergence study: the relative error <span class="html-italic">versus</span> the number of shell elements used in the model.</p> Full article ">
<p>(<b>a</b>) Top view of the S<sub>11</sub> (MPa) stress contour of the shell surface subjected to a 30% coverage of hexanethiolate SAMs on Au(111). The white color indicates no initial stress; (<b>b</b>) The Z-component of the displacement (μm) of the micro-cantilever subjected to full coverage of hexanethiolate SAMs on the gold surface.</p> Full article ">
<p>Top view of the S<sub>11</sub> stress distribution of the silicon nitride layer in the micro-cantilever subjected to a full coverage of hexanethiolate SAMs on Au(111).</p> Full article ">
<p>(<b>a</b>) Average tip deflection as a function of the coverage of alkanethiolate SAM domains. The error bars indicate the range of the maximum and minimum tip deflections at each sample at the same coverage; (<b>b</b>) Average tip deflections as a function of alkanethiolate chain length at full coverage.</p> Full article ">
709 KiB  
Article
Calibration-Free Pulse Oximetry Based on Two Wavelengths in the Infrared — A Preliminary Study
by Meir Nitzan, Salman Noach, Elias Tobal, Yair Adar, Yaacov Miller, Eran Shalom and Shlomo Engelberg
Sensors 2014, 14(4), 7420-7434; https://doi.org/10.3390/s140407420 - 23 Apr 2014
Cited by 39 | Viewed by 12230
Abstract
The assessment of oxygen saturation in arterial blood by pulse oximetry (SpO2) is based on the different light absorption spectra for oxygenated and deoxygenated hemoglobin and the analysis of photoplethysmographic (PPG) signals acquired at two wavelengths. Commercial pulse oximeters use two [...] Read more.
The assessment of oxygen saturation in arterial blood by pulse oximetry (SpO2) is based on the different light absorption spectra for oxygenated and deoxygenated hemoglobin and the analysis of photoplethysmographic (PPG) signals acquired at two wavelengths. Commercial pulse oximeters use two wavelengths in the red and infrared regions which have different pathlengths and the relationship between the PPG-derived parameters and oxygen saturation in arterial blood is determined by means of an empirical calibration. This calibration results in an inherent error, and pulse oximetry thus has an error of about 4%, which is too high for some clinical problems. We present calibration-free pulse oximetry for measurement of SpO2, based on PPG pulses of two nearby wavelengths in the infrared. By neglecting the difference between the path-lengths of the two nearby wavelengths, SpO2 can be derived from the PPG parameters with no need for calibration. In the current study we used three laser diodes of wavelengths 780, 785 and 808 nm, with narrow spectral line-width. SaO2 was calculated by using each pair of PPG signals selected from the three wavelengths. In measurements on healthy subjects, SpO2 values, obtained by the 780–808 nm wavelength pair were found to be in the normal range. The measurement of SpO2 by two nearby wavelengths in the infrared with narrow line-width enables the assessment of SpO2 without calibration. Full article
(This article belongs to the Special Issue Biomedical Sensors and Systems)
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<p>Molar extinction coefficients of oxygenated (HbO<sub>2</sub>) and deoxygenated (Hb) hemoglobin as a function of the wavelength. Prepared by Dr. Scott Prahl from a variety of sources [<a href="#b7-sensors-14-07420" class="html-bibr">7</a>]. Used with permission from Dr. Prahl.</p> Full article ">
<p>The PPG pulse. The transmitted light through the tissue decreases during systole and increases during diastole. I<sub>D</sub> and I<sub>S</sub> represent the maximal and minimal light transmission through the tissue.</p> Full article ">
<p>Schematics of the optical setup. The three laser diodes were coupled to a trifurcated fiber bundle. The common bundle was attached to the finger probe parallel to the finger surface. The reflecting prism is opposite to the detector.</p> Full article ">
<p>Photograph of the finger probe. Light is delivered to one side of the finger and the transmitted light is collected by the detector.</p> Full article ">
<p>Block diagram of the measurement system.</p> Full article ">
<p>Schematic presentation of the time division of the laser diode activation between the three diodes.</p> Full article ">
<p>The extrapolated values of I<sub>D</sub>, and the determination of the pulse amplitude as the difference between the extrapolated values of I<sub>D</sub> and the measured value of I<sub>S</sub>.</p> Full article ">
<p>The extinction coefficients of Hb and HbO<sub>2</sub> in the near infrared region as obtained by Zijlstra <span class="html-italic">et al.</span> (red), Cope (blue) and Prahl (Black) [<a href="#b25-sensors-14-07420" class="html-bibr">25</a>]. The red lines represent values derived from the experimental measurements of Zijlstra by means of interpolation (using the pchip command in MATLAB).</p> Full article ">
<p>SpO<sub>2</sub> values for the three pairs of wavelengths, determined by using the extinction coefficient data obtained by Zijlstra (red) Prahl (black) and Cope (blue).</p> Full article ">
991 KiB  
Review
Fiber Bragg Grating Sensors toward Structural Health Monitoring in Composite Materials: Challenges and Solutions
by Damien Kinet, Patrice Mégret, Keith W. Goossen, Liang Qiu, Dirk Heider and Christophe Caucheteur
Sensors 2014, 14(4), 7394-7419; https://doi.org/10.3390/s140407394 - 23 Apr 2014
Cited by 442 | Viewed by 21096
Abstract
Nowadays, smart composite materials embed miniaturized sensors for structural health monitoring (SHM) in order to mitigate the risk of failure due to an overload or to unwanted inhomogeneity resulting from the fabrication process. Optical fiber sensors, and more particularly fiber Bragg grating (FBG) [...] Read more.
Nowadays, smart composite materials embed miniaturized sensors for structural health monitoring (SHM) in order to mitigate the risk of failure due to an overload or to unwanted inhomogeneity resulting from the fabrication process. Optical fiber sensors, and more particularly fiber Bragg grating (FBG) sensors, outperform traditional sensor technologies, as they are lightweight, small in size and offer convenient multiplexing capabilities with remote operation. They have thus been extensively associated to composite materials to study their behavior for further SHM purposes. This paper reviews the main challenges arising from the use of FBGs in composite materials. The focus will be made on issues related to temperature-strain discrimination, demodulation of the amplitude spectrum during and after the curing process as well as connection between the embedded optical fibers and the surroundings. The main strategies developed in each of these three topics will be summarized and compared, demonstrating the large progress that has been made in this field in the past few years. Full article
(This article belongs to the Section Physical Sensors)
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<p>Reflected amplitude spectrum of a 1 cm long uniform FBG.</p> Full article ">
<p>Bragg wavelength shift as a function of a temperature change (<b>a</b>) and a mechanical axial strain (<b>b</b>).</p> Full article ">
<p>Bragg wavelength shifts as a function of strain and temperature for both FBGs integrated into the composite material sample.</p> Full article ">
<p>Bragg wavelength shifts of both grating types as a function of strain and temperature.</p> Full article ">
<p>Wavelength shifts as a function of strain and temperature for the Bragg and ghost mode resonances.</p> Full article ">
<p>Operating principle of the edge filter (<b>a</b>) and tunable filter (<b>b</b>) techniques.</p> Full article ">
<p>OFDR trace for 10 identical FBGs cascaded in an optical fiber embedded into a composite material fabric and corresponding photon-counting OTDR trace.</p> Full article ">
<p>Protective loose tube in Teflon around the optical fiber.</p> Full article ">
<p>Main steps towards the integration of surface-mounted connector, from [<a href="#b113-sensors-14-07394" class="html-bibr">113</a>].</p> Full article ">
828 KiB  
Article
An Accurate and Computationally Efficient Model for Membrane-Type Circular-Symmetric Micro-Hotplates
by Usman Khan and Christian Falconi
Sensors 2014, 14(4), 7374-7393; https://doi.org/10.3390/s140407374 - 23 Apr 2014
Cited by 5 | Viewed by 7061
Abstract
Ideally, the design of high-performance micro-hotplates would require a large number of simulations because of the existence of many important design parameters as well as the possibly crucial effects of both spread and drift. However, the computational cost of FEM simulations, which are [...] Read more.
Ideally, the design of high-performance micro-hotplates would require a large number of simulations because of the existence of many important design parameters as well as the possibly crucial effects of both spread and drift. However, the computational cost of FEM simulations, which are the only available tool for accurately predicting the temperature in micro-hotplates, is very high. As a result, micro-hotplate designers generally have no effective simulation-tools for the optimization. In order to circumvent these issues, here, we propose a model for practical circular-symmetric micro-hot-plates which takes advantage of modified Bessel functions, computationally efficient matrix-approach for considering the relevant boundary conditions, Taylor linearization for modeling the Joule heating and radiation losses, and external-region-segmentation strategy in order to accurately take into account radiation losses in the entire micro-hotplate. The proposed model is almost as accurate as FEM simulations and two to three orders of magnitude more computationally efficient (e.g., 45 s versus more than 8 h). The residual errors, which are mainly associated to the undesired heating in the electrical contacts, are small (e.g., few degrees Celsius for an 800 °C operating temperature) and, for important analyses, almost constant. Therefore, we also introduce a computationally-easy single-FEM-compensation strategy in order to reduce the residual errors to about 1 °C. As illustrative examples of the power of our approach, we report the systematic investigation of a spread in the membrane thermal conductivity and of combined variations of both ambient and bulk temperatures. Our model enables a much faster characterization of micro-hotplates and, thus, a much more effective optimization prior to fabrication. Full article
(This article belongs to the Section Physical Sensors)
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<p>Schematic diagram for a circular-symmetric micro-hotplate and the corresponding heat flows. Perspective view of the micro-hot-plate structure showing different parts (<b>a</b>); Cross-sectional view of the micro-hotplate structure with the description of the three heat transfer mechanisms (<b>b</b>).</p> Full article ">
<p>Heat flows for a thin cylindrical ring.</p> Full article ">
<p>Perspective (<b>a</b>) and cross-sectional (<b>b</b>) views of a circular-symmetric micro-hotplate with N ring-shaped-heaters.</p> Full article ">
<p>Micro-hotplate with three-heater geometry (<b>top</b>) and zoom of the central part of micro-hotplate (<b>bottom</b>) (not to scale).</p> Full article ">
<p>Micro-heater (<b>a</b>) and FEM results for the surface temperature distribution (°C) within the hot-region (<b>b</b>).</p> Full article ">
<p>Temperature distribution in the micro-hotplate; <span class="html-italic">T<sub>h</sub></span> is the average temperature in the hot-region and Δ<span class="html-italic">T<sub>h</sub></span> is maximum temperature difference in the hot region; at the edge of the hot region (which extends up to 0.216 mm), there is a sharp decrease of the temperature which is responsible for the larger values of Δ<span class="html-italic">T<sub>h</sub></span>.</p> Full article ">
<p>Error in the model in comparison with the FEM simulation.</p> Full article ">
<p>Influence of a spread in the thermal conductivity of the membrane, k<sub>m</sub>, on the average temperature, <span class="html-italic">T<sub>h</sub></span> (<b>left</b>); and on the maximum temperature difference, Δ<span class="html-italic">T<sub>h</sub></span> (<b>right</b>), in the hot region.</p> Full article ">
<p>Model results (<b>a, b</b>) and FEM results (<b>c, d</b>) for the influence of a variation of the bulk temperature, <span class="html-italic">T<sub>b</sub></span>, and ambient temperature, <span class="html-italic">T<sub>a</sub></span>, on the average temperature in the hot region, <span class="html-italic">T<sub>h</sub></span> (<b>a, c</b>), and maximum temperature difference in the hot region, Δ<span class="html-italic">T<sub>h</sub></span> (<b>b, d</b>).</p> Full article ">
415 KiB  
Article
Development of a Sweetness Sensor for Aspartame, a Positively Charged High-Potency Sweetener
by Masato Yasuura, Yusuke Tahara, Hidekazu Ikezaki and Kiyoshi Toko
Sensors 2014, 14(4), 7359-7373; https://doi.org/10.3390/s140407359 - 23 Apr 2014
Cited by 30 | Viewed by 10318
Abstract
Taste evaluation technology has been developed by several methods, such as sensory tests, electronic tongues and a taste sensor based on lipid/polymer membranes. In particular, the taste sensor can individually quantify five basic tastes without multivariate analysis. However, it has proven difficult to [...] Read more.
Taste evaluation technology has been developed by several methods, such as sensory tests, electronic tongues and a taste sensor based on lipid/polymer membranes. In particular, the taste sensor can individually quantify five basic tastes without multivariate analysis. However, it has proven difficult to develop a sweetness sensor, because sweeteners are classified into three types according to the electric charges in an aqueous solution; that is, no charge, negative charge and positive charge. Using membrane potential measurements, the taste-sensing system needs three types of sensor membrane for each electric charge type of sweetener. Since the commercially available sweetness sensor was only intended for uncharged sweeteners, a sweetness sensor for positively charged high-potency sweeteners such as aspartame was developed in this study. Using a lipid and plasticizers, we fabricated various lipid/polymer membranes for the sweetness sensor to identify the suitable components of the sensor membranes. As a result, one of the developed sensors showed responses of more than 20 mV to 10 mM aspartame and less than 5 mV to any other taste. The responses of the sensor depended on the concentration of aspartame. These results suggested that the developed sweetness sensor had high sensitivity to and high selectivity for aspartame. Full article
(This article belongs to the Special Issue Biomimetic Receptors and Sensors)
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<p>Four typical high-potency sweeteners. They are classified in three types by the electric charge under acidic conditions. (<b>a</b>) Negatively charged high-potency sweeteners; (<b>b</b>) Positively charged high-potency sweeteners; (<b>c</b>) No electrical charge high-potency sweeteners.</p> Full article ">
<p>Two kinds of electrode are used in the taste-sensing system. (<b>a</b>) Sensor electrode; (<b>b</b>) Reference electrode.</p> Full article ">
<p>Measurement procedure of taste sensing.</p> Full article ">
<p>Phosphoric acid di(2-ethylhexyl) ester (PAEE). PAEE is often used in lipid/polymer membranes for taste sensor as a lipid.</p> Full article ">
<p>Plasticizers: eight plasticizers were used in this study.</p> Full article ">
<p>Relative values: basic taste samples were measured using eight kinds of lipid/polymer membrane (parameter of membranes: type of plasticizer).</p> Full article ">
<p>CPA values: basic taste samples were measured using 8 kinds of lipid/polymer membrane (parameter of membranes: type of plasticizer).</p> Full article ">
<p>The responsivity in terms of CPA values of the membranes comprising PAEE, PVC and one of the eight types of plasticizer to 10 mM aspartame. Aspartame sample was measured using 8 kinds of lipid/polymer membrane (parameter: type of plasticizer)</p> Full article ">
<p>The selectivity of the membranes comprising PAEE, PVC and one of the eight types of plasticizer in terms of CPA values. Bitterness (+) and aspartame samples were measured using eight kinds of lipid/polymer membrane (parameter: type of plasticizer).</p> Full article ">
654 KiB  
Article
Using Massive Vehicle Positioning Data to Improve Control and Planning of Public Road Transport
by Gabino Padrón, Carmelo R. García, A. Quesada-Arencibia, Francisco Alayón and Ricardo Pérez
Sensors 2014, 14(4), 7342-7358; https://doi.org/10.3390/s140407342 - 23 Apr 2014
Cited by 8 | Viewed by 6445
Abstract
This study describes a system for the automatic recording of positioning data for public transport vehicles used on roads. With the data provided by this system, transportation-regulatory authorities can control, verify and improve the routes that vehicles use, while also providing new data [...] Read more.
This study describes a system for the automatic recording of positioning data for public transport vehicles used on roads. With the data provided by this system, transportation-regulatory authorities can control, verify and improve the routes that vehicles use, while also providing new data to improve the representation of the transportation network and providing new services in the context of intelligent metropolitan areas. The system is executed autonomously in the vehicles, by recording their massive positioning data and transferring them to remote data banks for subsequent processing. To illustrate the utility of the system, we present a case of application that consists of identifying the points at which vehicles stop systematically, which may be points of scheduled stops or points at which traffic signals or road topology force the vehicle to stop. This identification is performed using pattern recognition techniques. The system has been applied under real operating conditions, providing the results discussed in the present study. Full article
(This article belongs to the Special Issue Select Papers from UCAmI & IWAAL 2013 - the 7th International Conference on Ubiquitous Computing and Ambient Intelligence & the 5th International Workshop on Ambient Assisted Living (UCAmI & IWAAL 2013: Pervasive Sensing Solutions)
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<p>General view of the system.</p> Full article ">
<p>Aerial view of the geographic area of the route being studied. The green tags represent vehicle position readings with a velocity of zero. The orange markings represent the centroids of the groups of readings with a velocity of zero. The yellow icons represent scheduled bus stops of the route.</p> Full article ">
<p>Aerial view of a cluster of type G1. Tag NL28 represents the centroid of the group of readings obtained when the vehicle stopped. Tag 227011 represents the position of the stop.</p> Full article ">
<p>Aerial view of a type G2 cluster. The orange markings represent position readings of the vehicle with zero velocity at a location where no stop is programmed. The vehicle stops because it reaches a road with greater circulation priority. The yellow marking is the centroid of the cluster.</p> Full article ">
<p>Cluster of type G3. The orange markings are position readings of the vehicle with a velocity of zero. There are two scheduled stop points in the area shown; however, all the readings have been grouped into one cluster, with a centroid at a distance of more than 15 m from the two scheduled stops.</p> Full article ">
<p>Close-up aerial view of the same cluster presented in <a href="#f5-sensors-14-07342" class="html-fig">Figure 5</a>. Result of the first iteration of the method. Tags 175031 and 175041 are scheduled stop points, and tag NL14 is the centroid obtained in the first iteration of the method. The readings have been grouped in a single cluster because there is a roundabout between the two scheduled stop points where the vehicle stops.</p> Full article ">
<p>Result after applying a second iteration of the method to the cluster shown in <a href="#f5-sensors-14-07342" class="html-fig">Figures 5</a> and <a href="#f6-sensors-14-07342" class="html-fig">6</a>. The method obtains three clusters, two associated with the stops and another one associated with the singular point, which is a roundabout. As the scatter of the clusters is less than 15 m, the identification process is considered to be complete.</p> Full article ">
532 KiB  
Article
Optical Sensor Based on a Single CdS Nanobelt
by Lei Li, Shuming Yang, Feng Han, Liangjun Wang, Xiaotong Zhang, Zhuangde Jiang and Anlian Pan
Sensors 2014, 14(4), 7332-7341; https://doi.org/10.3390/s140407332 - 23 Apr 2014
Cited by 16 | Viewed by 8472
Abstract
In this paper, an optical sensor based on a cadmium sulfide (CdS) nanobelt has been developed. The CdS nanobelt was synthesized by the vapor phase transportation (VPT) method. X-Ray Diffraction (XRD) and Transmission Electron Microscopy (TEM) results revealed that the nanobelt had a [...] Read more.
In this paper, an optical sensor based on a cadmium sulfide (CdS) nanobelt has been developed. The CdS nanobelt was synthesized by the vapor phase transportation (VPT) method. X-Ray Diffraction (XRD) and Transmission Electron Microscopy (TEM) results revealed that the nanobelt had a hexagonal wurtzite structure of CdS and presented good crystal quality. A single nanobelt Schottky contact optical sensor was fabricated by the electron beam lithography (EBL) technique, and the device current-voltage results showed back-to-back Schottky diode characteristics. The photosensitivity, dark current and the decay time of the sensor were 4 × 104, 31 ms and 0.2 pA, respectively. The high photosensitivity and the short decay time were because of the exponential dependence of photocurrent on the number of the surface charges and the configuration of the back to back Schottky junctions. Full article
(This article belongs to the Section Physical Sensors)
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<p>The SEM image of the finished single nanobelt optical sensor, the upper right insert was the optical microscope image of the device.</p> Full article ">
<p>The SEM image of the as-grown CdS nanobelts.</p> Full article ">
<p>XRD pattern of the CdS nanobelt.</p> Full article ">
<p>TEM, HRTEM and SAED image of the single CdS nanobelt.</p> Full article ">
<p>I-V curves of the device: (<b>a</b>) was the I-V curve without light illumination; (<b>b</b>) was the I-V curve with light illumination; the lower right insert of b was the schematic diagram of the device.</p> Full article ">
<p>(<b>a</b>) The light response of the sensor; (<b>b</b>) the detailed decay curve and the decay time calculated from the curve was about 31 ms.</p> Full article ">
<p>The Schottky barrier energy band diagram and the photoresponse mechanism: when light was on, the photo generated holes will recombine with the adsorbed oxygen on the nanobelt surface. The surface depletion layer thickness and the Schottky barrier E<sub>B</sub> were reduced. E<sub>Cs</sub> and E<sub>Vs</sub> were the conductance band and valance band of the CdS nanowire; E<sub>fm</sub> and E<sub>Cm</sub> were the Fermi level and conductance band of the metal. E<sub>B</sub> was the Schottky barrier.</p> Full article ">
1038 KiB  
Article
Quantitative Damage Detection and Sparse Sensor Array Optimization of Carbon Fiber Reinforced Resin Composite Laminates for Wind Turbine Blade Structural Health Monitoring
by Xiang Li, Zhibo Yang and Xuefeng Chen
Sensors 2014, 14(4), 7312-7331; https://doi.org/10.3390/s140407312 - 23 Apr 2014
Cited by 24 | Viewed by 10406
Abstract
The active structural health monitoring (SHM) approach for the complex composite laminate structures of wind turbine blades (WTBs), addresses the important and complicated problem of signal noise. After illustrating the wind energy industry’s development perspectives and its crucial requirement for SHM, an improved [...] Read more.
The active structural health monitoring (SHM) approach for the complex composite laminate structures of wind turbine blades (WTBs), addresses the important and complicated problem of signal noise. After illustrating the wind energy industry’s development perspectives and its crucial requirement for SHM, an improved redundant second generation wavelet transform (IRSGWT) pre-processing algorithm based on neighboring coefficients is introduced for feeble signal denoising. The method can avoid the drawbacks of conventional wavelet methods that lose information in transforms and the shortcomings of redundant second generation wavelet (RSGWT) denoising that can lead to error propagation. For large scale WTB composites, how to minimize the number of sensors while ensuring accuracy is also a key issue. A sparse sensor array optimization of composites for WTB applications is proposed that can reduce the number of transducers that must be used. Compared to a full sixteen transducer array, the optimized eight transducer configuration displays better accuracy in identifying the correct position of simulated damage (mass of load) on composite laminates with anisotropic characteristics than a non-optimized array. It can help to guarantee more flexible and qualified monitoring of the areas that more frequently suffer damage. The proposed methods are verified experimentally on specimens of carbon fiber reinforced resin composite laminates. Full article
(This article belongs to the Section Physical Sensors)
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<p>System architecture of SHM [<a href="#b34-sensors-14-07312" class="html-bibr">34</a>].</p> Full article ">
<p>Distribution of wind power generator damage types.</p> Full article ">
<p>A view of some of the damage types found during the examination of the downwind skin of test section subjected to a compressive load [<a href="#b38-sensors-14-07312" class="html-bibr">38</a>]. Damages to the adhesive layers: Types 1 (skin/adhesive debonding) and 2 (adhesive joint failure between skins) at the leading as well as the trailing edge. Damage to the downwind skin under compressive load: Types 4 (delamination driven by a buckling load), 5 (laminate failure in compression) and 7 (gel-coat cracking and gel-coat/skin debonding).</p> Full article ">
<p>The spanwise location of a wind turbine blade that is likely to damage [<a href="#b39-sensors-14-07312" class="html-bibr">39</a>].</p> Full article ">
<p>The forward and inverse transform of IRSGWT.</p> Full article ">
<p>The scheme of the sparse sensor optimization method. (<b>a</b>) 8 Transducers not optimized; (<b>b</b>) Full 16 transducers; (<b>c</b>) Top 8 transducers optimized.</p> Full article ">
<p>The flowchart of a PZT pitch-catch configuration for Lamb waves.</p> Full article ">
<p>Schematic of damage detection using the proposed monitoring system with active sensor network. (<b>a</b>) Block diagram of the experimental system; (<b>b</b>) 16 PZT actuator and sensor layout on CFRRCL specimen (unit: mm); (<b>c</b>) Overall view of experiment setup.</p> Full article ">
<p>Denoising signals via actuator–sensor path P2-P10. (<b>a</b>) Raw Lamb wave damage signal via path P2-P10; (<b>b</b>) RSGWT Denoising of Lamb wave damage signal via path P2-P10; (<b>c</b>) IRSGWT Denoising of Lamb wave damage signal via path P2-P10.</p> Full article ">
7920 KiB  
Article
Experience in Evaluating AAL Solutions in Living Labs
by Juan Bautista Montalvá Colomer, Dario Salvi, Maria Fernanda Cabrera-Umpierrez, Maria Teresa Arredondo, Patricia Abril, Viveca Jimenez-Mixco, Rebeca García-Betances, Alessio Fioravanti, Matteo Pastorino, Jorge Cancela and Alejandro Medrano
Sensors 2014, 14(4), 7277-7311; https://doi.org/10.3390/s140407277 - 23 Apr 2014
Cited by 21 | Viewed by 9095
Abstract
Ambient assisted living (AAL) is a complex field, where different technologies are integrated to offer solutions for the benefit of different stakeholders. Several evaluation techniques are commonly applied that tackle specific aspects of AAL; however, holistic evaluation approaches are lacking when addressing the [...] Read more.
Ambient assisted living (AAL) is a complex field, where different technologies are integrated to offer solutions for the benefit of different stakeholders. Several evaluation techniques are commonly applied that tackle specific aspects of AAL; however, holistic evaluation approaches are lacking when addressing the needs of both developers and end-users. Living labs have been often used as real-life test and experimentation environments for co-designing AAL technologies and validating them with relevant stakeholders. During the last five years, we have been evaluating AAL systems and services in the framework of various research projects. This paper presents the lessons learned in this experience and proposes a set of harmonized guidelines to conduct evaluations in living labs. Full article
(This article belongs to the Special Issue Ambient Assisted Living (AAL): Sensors, Architectures and Applications)
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<p>The Smart House Living Lab.</p> Full article ">
<p>The overall view of the user area of the Smart House Living Lab.</p> Full article ">
<p>The overall view of the observation area of the Smart House Living Lab.</p> Full article ">
<p>The virtual reality facilities of the Smart House Living Lab. (<b>a</b>) View of the virtual reality (VR) room; (<b>b</b>) VR wheelchair adaptation.</p> Full article ">
<p>Map of the Smart House Living Lab.</p> Full article ">
<p>The test settings of the CogWatch system. (<b>a</b>) The CogWatch test workspace; (<b>b</b>) An example of the CogWatch smart tool.</p> Full article ">
<p>User testing ParKinect in the Smart House Living Lab.</p> Full article ">
<p>Segment used for signaling the path to the actor.</p> Full article ">
<p>Actor moving on a path during a benchmark.</p> Full article ">
617 KiB  
Review
Recent Developments in Hyperspectral Imaging for Assessment of Food Quality and Safety
by Hui Huang, Li Liu and Michael O. Ngadi
Sensors 2014, 14(4), 7248-7276; https://doi.org/10.3390/s140407248 - 22 Apr 2014
Cited by 281 | Viewed by 18735
Abstract
Hyperspectral imaging which combines imaging and spectroscopic technology is rapidly gaining ground as a non-destructive, real-time detection tool for food quality and safety assessment. Hyperspectral imaging could be used to simultaneously obtain large amounts of spatial and spectral information on the objects being [...] Read more.
Hyperspectral imaging which combines imaging and spectroscopic technology is rapidly gaining ground as a non-destructive, real-time detection tool for food quality and safety assessment. Hyperspectral imaging could be used to simultaneously obtain large amounts of spatial and spectral information on the objects being studied. This paper provides a comprehensive review on the recent development of hyperspectral imaging applications in food and food products. The potential and future work of hyperspectral imaging for food quality and safety control is also discussed. Full article
(This article belongs to the Special Issue Spectral Imaging at the Microscale and Beyond)
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<p>The number of publications about hyperspectral imaging applications in food.</p> Full article ">
<p>Configuration of a hyperspectral imaging system.</p> Full article ">
<p>QE of typical Si based camera.</p> Full article ">
<p>QE comparison of InGaAs detectors and Si-based cameras.</p> Full article ">
<p>Flow diagram of hyperspectral data analysis process.</p> Full article ">
<p>Gabor filter for extracting texture features from a ROI of a pork image. (<b>a</b>) Selected ROI of pork, (<b>b</b>) applied Gabor filter, (<b>c</b>) Gabor filtered image, (<b>d</b>) extracted texture features.</p> Full article ">
<p>Wide line detector for extracting line feature from red, green, and blue images of pork.</p> Full article ">
357 KiB  
Article
An Interactive Control Algorithm Used for Equilateral Triangle Formation with Robotic Sensors
by Xiang Li and Hongcai Chen
Sensors 2014, 14(4), 7229-7247; https://doi.org/10.3390/s140407229 - 22 Apr 2014
Cited by 5 | Viewed by 6234
Abstract
This paper describes an interactive control algorithm, called Triangle Formation Algorithm (TFA), used for three neighboring robotic sensors which are distributed randomly to self-organize into and equilateral triangle (E) formation. The algorithm is proposed based on the triangular geometry and considering the actual [...] Read more.
This paper describes an interactive control algorithm, called Triangle Formation Algorithm (TFA), used for three neighboring robotic sensors which are distributed randomly to self-organize into and equilateral triangle (E) formation. The algorithm is proposed based on the triangular geometry and considering the actual sensors used in robotics. In particular, the stability of the TFA, which can be executed by robotic sensors independently and asynchronously for E formation, is analyzed in details based on Lyapunov stability theory. Computer simulations are carried out for verifying the effectiveness of the TFA. The analytical results and simulation studies indicate that three neighboring robots employing conventional sensors can self-organize into E formations successfully regardless of their initial distribution using the same TFAs. Full article
(This article belongs to the Section Physical Sensors)
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<p>The state transition model of a robotic sensor.</p> Full article ">
<p>The detection of neighbor's local position information</p> Full article ">
<p>The calculation methods of specific <span class="html-italic">p<sub>ig</sub></span> for R<sub>i</sub>. (<b>a</b>) The case where two possible destinations for <span class="html-italic">p<sub>i</sub></span>. (<b>b</b>) <span class="html-italic">p<sub>i</sub></span><sub>1</sub><span class="html-italic">p<sub>i</sub></span><sub>2</sub> is parallel to axis <span class="html-italic">y</span>. (<b>c</b>) <span class="html-italic">p<sub>i</sub></span><sub>1</sub><span class="html-italic">p<sub>i</sub></span><sub>2</sub> is parallel to axis <span class="html-italic">x</span>. (<b>d</b>) <span class="html-italic">p<sub>c</sub></span> under line <span class="html-italic">l</span>. (<b>e</b>) <span class="html-italic">p<sub>c</sub></span> above (on) line <span class="html-italic">l</span>.</p> Full article ">
<p>The calculation methods of specific <span class="html-italic">p<sub>ig</sub></span> for R<sub>i</sub>. (<b>a</b>) The case where two possible destinations for <span class="html-italic">p<sub>i</sub></span>. (<b>b</b>) <span class="html-italic">p<sub>i</sub></span><sub>1</sub><span class="html-italic">p<sub>i</sub></span><sub>2</sub> is parallel to axis <span class="html-italic">y</span>. (<b>c</b>) <span class="html-italic">p<sub>i</sub></span><sub>1</sub><span class="html-italic">p<sub>i</sub></span><sub>2</sub> is parallel to axis <span class="html-italic">x</span>. (<b>d</b>) <span class="html-italic">p<sub>c</sub></span> under line <span class="html-italic">l</span>. (<b>e</b>) <span class="html-italic">p<sub>c</sub></span> above (on) line <span class="html-italic">l</span>.</p> Full article ">
<p>A position distribution and the <span class="html-italic">p<sub>ig</sub></span> of R<sub>i</sub>.</p> Full article ">
<p>The execution procedures of basic CA and AA algorithms for R<sub>i</sub>.</p> Full article ">
<p>The execution procedure of the TFA algorithm for R<sub>i</sub>.</p> Full article ">
<p>The collinear distribution of three robotic sensors.</p> Full article ">
<p>The detail of modified sub-algorithm in <a href="#f6-sensors-14-07229" class="html-fig">Figure 6</a>.</p> Full article ">
<p>The critical formation necessary for CF transforming into AF.</p> Full article ">
1080 KiB  
Article
Tracking and Recognition of Multiple Human Targets Moving in a Wireless Pyroelectric Infrared Sensor Network
by Ji Xiong, Fangmin Li, Ning Zhao and Na Jiang
Sensors 2014, 14(4), 7209-7228; https://doi.org/10.3390/s140407209 - 22 Apr 2014
Cited by 29 | Viewed by 7973
Abstract
With characteristics of low-cost and easy deployment, the distributed wireless pyroelectric infrared sensor network has attracted extensive interest, which aims to make it an alternate infrared video sensor in thermal biometric applications for tracking and identifying human targets. In these applications, effectively processing [...] Read more.
With characteristics of low-cost and easy deployment, the distributed wireless pyroelectric infrared sensor network has attracted extensive interest, which aims to make it an alternate infrared video sensor in thermal biometric applications for tracking and identifying human targets. In these applications, effectively processing signals collected from sensors and extracting the features of different human targets has become crucial. This paper proposes the application of empirical mode decomposition and the Hilbert-Huang transform to extract features of moving human targets both in the time domain and the frequency domain. Moreover, the support vector machine is selected as the classifier. The experimental results demonstrate that by using this method the identification rates of multiple moving human targets are around 90%. Full article
(This article belongs to the Section Sensor Networks)
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<p>Setup of the distributed wireless pyroelectric infrared sensor system.</p> Full article ">
<p>A pyroelectric infrared (PIR) sensor node covered by a Fresnel lens.</p> Full article ">
<p>Human thermal infrared signal processing in sensor node.</p> Full article ">
<p>The composition module of one sensor MASK.</p> Full article ">
<p>Mask sensor module.</p> Full article ">
<p>The module composition of the wireless gateway.</p> Full article ">
<p>The wireless gateway module.</p> Full article ">
<p>Coded mask sensor module.</p> Full article ">
<p>Division of the detection area of the system.</p> Full article ">
674 KiB  
Review
Smartphone-Based Solutions for Fall Detection and Prevention: Challenges and Open Issues
by Mohammad Ashfak Habib, Mas S. Mohktar, Shahrul Bahyah Kamaruzzaman, Kheng Seang Lim, Tan Maw Pin and Fatimah Ibrahim
Sensors 2014, 14(4), 7181-7208; https://doi.org/10.3390/s140407181 - 22 Apr 2014
Cited by 176 | Viewed by 23148
Abstract
This paper presents a state-of-the-art survey of smartphone (SP)-based solutions for fall detection and prevention. Falls are considered as major health hazards for both the elderly and people with neurodegenerative diseases. To mitigate the adverse consequences of falling, a great deal of research [...] Read more.
This paper presents a state-of-the-art survey of smartphone (SP)-based solutions for fall detection and prevention. Falls are considered as major health hazards for both the elderly and people with neurodegenerative diseases. To mitigate the adverse consequences of falling, a great deal of research has been conducted, mainly focused on two different approaches, namely, fall detection and fall prevention. Required hardware for both fall detection and prevention are also available in SPs. Consequently, researchers’ interest in finding SP-based solutions has increased dramatically over recent years. To the best of our knowledge, there has been no published review on SP-based fall detection and prevention. Thus in this paper, we present the taxonomy for SP-based fall detection and prevention solutions and systematic comparisons of existing studies. We have also identified three challenges and three open issues for future research, after reviewing the existing articles. Our time series analysis demonstrates a trend towards the integration of external sensing units with SPs for improvement in usability of the systems. Full article
(This article belongs to the Special Issue Ambient Assisted Living (AAL): Sensors, Architectures and Applications)
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<p>Common basic architecture of fall detection and fall prevention systems.</p> Full article ">
<p>Taxonomy of smartphone-based systems based on sensing mechanism and sensor placement.</p> Full article ">
<p>Taxonomy of smartphone based fall detection and prevention algorithms.</p> Full article ">
<p>Taxonomy of communication patterns in smartphone-based fall detection and prevention systems.</p> Full article ">
<p>Estimation of the number of SP based fall detection and prevention studies.</p> Full article ">
2208 KiB  
Article
Angular Rate Optimal Design for the Rotary Strapdown Inertial Navigation System
by Fei Yu and Qian Sun
Sensors 2014, 14(4), 7156-7180; https://doi.org/10.3390/s140407156 - 22 Apr 2014
Cited by 25 | Viewed by 7912
Abstract
Due to the characteristics of high precision for a long duration, the rotary strapdown inertial navigation system (RSINS) has been widely used in submarines and surface ships. Nowadays, the core technology, the rotating scheme, has been studied by numerous researchers. It is well [...] Read more.
Due to the characteristics of high precision for a long duration, the rotary strapdown inertial navigation system (RSINS) has been widely used in submarines and surface ships. Nowadays, the core technology, the rotating scheme, has been studied by numerous researchers. It is well known that as one of the key technologies, the rotating angular rate seriously influences the effectiveness of the error modulating. In order to design the optimal rotating angular rate of the RSINS, the relationship between the rotating angular rate and the velocity error of the RSINS was analyzed in detail based on the Laplace transform and the inverse Laplace transform in this paper. The analysis results showed that the velocity error of the RSINS depends on not only the sensor error, but also the rotating angular rate. In order to minimize the velocity error, the rotating angular rate of the RSINS should match the sensor error. One optimal design method for the rotating rate of the RSINS was also proposed in this paper. Simulation and experimental results verified the validity and superiority of this optimal design method for the rotating rate of the RSINS. Full article
(This article belongs to the Section Physical Sensors)
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<p>Schematic of the rotary strapdown inertial navigation system (RSINS).</p> Full article ">
<p>The geometrical relationship between <span class="html-italic">x<sub>s</sub>y<sub>s</sub>z<sub>s</sub></span> and <span class="html-italic">X<sub>b</sub>Y<sub>b</sub>Z<sub>b</sub></span>.</p> Full article ">
<p>The relationship curve of the amplitude of the velocity error, the constant bias of the gyroscope and the rotating angular rate.</p> Full article ">
<p>The relationship curve of the amplitude of the velocity error, the constant bias of the accelerometer and the rotating angular rate.</p> Full article ">
<p>The relationship curve of the amplitude of the velocity error, the scale factor error and the rotating angular rate.</p> Full article ">
<p>The relationship curve of the amplitude of the velocity error, the installation error and the rotating angular rate.</p> Full article ">
<p>The relationship curves between the velocity errors and the rotating rates.</p> Full article ">
<p>IMU rotating scheme.</p> Full article ">
<p>Simulation results of Group 1.</p> Full article ">
392 KiB  
Article
An Affordable Open-Source Turbidimeter
by Christopher D. Kelley, Alexander Krolick, Logan Brunner, Alison Burklund, Daniel Kahn, William P. Ball and Monroe Weber-Shirk
Sensors 2014, 14(4), 7142-7155; https://doi.org/10.3390/s140407142 - 22 Apr 2014
Cited by 78 | Viewed by 24353
Abstract
Turbidity is an internationally recognized criterion for assessing drinking water quality, because the colloidal particles in turbid water may harbor pathogens, chemically reduce oxidizing disinfectants, and hinder attempts to disinfect water with ultraviolet radiation. A turbidimeter is an electronic/optical instrument that assesses turbidity [...] Read more.
Turbidity is an internationally recognized criterion for assessing drinking water quality, because the colloidal particles in turbid water may harbor pathogens, chemically reduce oxidizing disinfectants, and hinder attempts to disinfect water with ultraviolet radiation. A turbidimeter is an electronic/optical instrument that assesses turbidity by measuring the scattering of light passing through a water sample containing such colloidal particles. Commercial turbidimeters cost hundreds or thousands of dollars, putting them beyond the reach of low-resource communities around the world. An affordable open-source turbidimeter based on a single light-to-frequency sensor was designed and constructed, and evaluated against a portable commercial turbidimeter. The final product, which builds on extensive published research, is intended to catalyze further developments in affordable water and sanitation monitoring. Full article
(This article belongs to the Section Physical Sensors)
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<p>Common turbidimeter design patterns: (<b>a</b>) single-beam, (<b>b</b>) ratio, (<b>c</b>) modulated four-beam. Components: light source (trapezoid), liquid sample (circle), detector (rectangle), transmitted light (large arrow), scattered light (small arrow).</p> Full article ">
<p>Open-Source Turbidimeter: (<b>a</b>) external view, (<b>b</b>) image of cuvette holder.</p> Full article ">
<p>Wiring diagram for the open-source turbidimeter.</p> Full article ">
<p>Comparison of averaged open-source turbidimeter and commercial turbidimeter measurements of 25 cutting oil suspensions, overall (<b>a</b>) and in four sub-regions: (<b>b</b>) 0–0.5 NTU; (<b>c</b>) 0.5–30 NTU; (<b>d</b>) 30–300 NTU; (<b>e</b>) 300–1,100 NTU.</p> Full article ">
<p>Commercial and open-source turbidimeter measurements of five non-formazin turbidity standards.</p> Full article ">
1092 KiB  
Article
Wearable Biomedical Measurement Systems for Assessment of Mental Stress of Combatants in Real Time
by Fernando Seoane, Inmaculada Mohino-Herranz, Javier Ferreira, Lorena Alvarez, Ruben Buendia, David Ayllón, Cosme Llerena and Roberto Gil-Pita
Sensors 2014, 14(4), 7120-7141; https://doi.org/10.3390/s140407120 - 22 Apr 2014
Cited by 126 | Viewed by 17519
Abstract
The Spanish Ministry of Defense, through its Future Combatant program, has sought to develop technology aids with the aim of extending combatants’ operational capabilities. Within this framework the ATREC project funded by the “Coincidente” program aims at analyzing diverse biometrics to assess by [...] Read more.
The Spanish Ministry of Defense, through its Future Combatant program, has sought to develop technology aids with the aim of extending combatants’ operational capabilities. Within this framework the ATREC project funded by the “Coincidente” program aims at analyzing diverse biometrics to assess by real time monitoring the stress levels of combatants. This project combines multidisciplinary disciplines and fields, including wearable instrumentation, textile technology, signal processing, pattern recognition and psychological analysis of the obtained information. In this work the ATREC project is described, including the different execution phases, the wearable biomedical measurement systems, the experimental setup, the biomedical signal analysis and speech processing performed. The preliminary results obtained from the data analysis collected during the first phase of the project are presented, indicating the good classification performance exhibited when using features obtained from electrocardiographic recordings and electrical bioimpedance measurements from the thorax. These results suggest that cardiac and respiration activity offer better biomarkers for assessment of stress than speech, galvanic skin response or skin temperature when recorded with wearable biomedical measurement systems. Full article
(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Spain 2013)
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<p>System overview of the full system aimed to be implemented during the ATREC project integrating sensorized garments, wireless communication and wearable computing for real-time assessment.</p> Full article ">
<p>GSR device with a drawing of the connection with the sensorized glove.</p> Full article ">
<p>Drawing of the ECG/ICG measuring device indicating the connection with the biopotential and the TEB textrodes placed on the torso for performing ECG and respiration measurements.</p> Full article ">
<p>Drawing of the sensorized glove. (<b>a</b>) Upper view of the glove. (<b>b</b>) Cross-sectional view of the glove at the proximal phalanx in a perpendicular plane to the palm. (<b>c</b>) Palm view.</p> Full article ">
<p>Sensorized glove connected to the measuring unit fasten to the wristband.</p> Full article ">
<p>Drawing of the confectioned sensorized upper arm strap. (<b>a</b>) Inside view, showing the sensors. (<b>b</b>) Outside side, where the sensing device is placed and connected. (<b>c</b>) Detail of the textile-electronic interconnection achieved by using conductive fabrics, yarn and sewing them through a ring-shaped end.</p> Full article ">
<p>(<b>a</b>) Confectioned upper arm strap. (<b>b</b>) Measuring device and strap worn on the upper arm.</p> Full article ">
<p>(<b>a</b>) Chest straps system confectioned for placement of ECG and TEB electrodes. (<b>b</b>) Detail of the elastic perforated band. (<b>c</b>) Fixation between straps through chef jacket button.</p> Full article ">
<p>(<b>a</b>) Schematic of the repositionable textrode. Notice that when folded the electrode is clamped using its male and female press-studs, thus creating an electrical and mechanical connection. (<b>b</b>) Confectioned repositionable textrode.</p> Full article ">
1969 KiB  
Article
WiSPH: A Wireless Sensor Network-Based Home Care Monitoring System
by Pedro Magaña-Espinoza, Raúl Aquino-Santos, Néstor Cárdenas-Benítez, José Aguilar-Velasco, César Buenrostro-Segura, Arthur Edwards-Block and Aldo Medina-Cass
Sensors 2014, 14(4), 7096-7119; https://doi.org/10.3390/s140407096 - 22 Apr 2014
Cited by 56 | Viewed by 13805
Abstract
This paper presents a system based on WSN technology capable of monitoring heart rate and the rate of motion of seniors within their homes. The system is capable of remotely alerting specialists, caretakers or family members via a smartphone of rapid physiological changes [...] Read more.
This paper presents a system based on WSN technology capable of monitoring heart rate and the rate of motion of seniors within their homes. The system is capable of remotely alerting specialists, caretakers or family members via a smartphone of rapid physiological changes due to falls, tachycardia or bradycardia. This work was carried out using our workgroup’s WiSe platform, which we previously developed for use in WSNs. The proposed WSN architecture is flexible, allowing for greater scalability to better allow event-based monitoring. The architecture also provides security mechanisms to assure that the monitored and/or stored data can only be accessed by authorized individuals or devices. The aforementioned characteristics provide the network versatility and solidity required for use in health applications. Full article
(This article belongs to the Special Issue Ambient Assisted Living (AAL): Sensors, Architectures and Applications)
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<p>The proposed system architecture.</p> Full article ">
<p>Block diagram of the Mobile Monitoring Node.</p> Full article ">
<p>(<b>a</b>) Fall detection algorithm (part 1); (<b>b</b>) Fall detection algorithm (part 2).</p> Full article ">
<p>(<b>a</b>) Routing Algorithm (part 1); (<b>b</b>) Routing Algorithm (part 2).</p> Full article ">
<p>(<b>a</b>) Routing Algorithm (part 1); (<b>b</b>) Routing Algorithm (part 2).</p> Full article ">
<p>SINK processing algorithm.</p> Full article ">
<p>Web interface and alerts flow chart.</p> Full article ">
<p>Fall tests.</p> Full article ">
<p>Proof of concept scenario.</p> Full article ">
<p>(<b>a</b>) Results from backwards falls; (<b>b</b>) Results from side falls; (<b>c</b>) Results from forward falls; (<b>d</b>) Results from knee falls.</p> Full article ">
<p>(<b>a</b>) Results from backwards falls; (<b>b</b>) Results from side falls; (<b>c</b>) Results from forward falls; (<b>d</b>) Results from knee falls.</p> Full article ">
570 KiB  
Article
A Method for Measuring the Volume of Transdermally Extracted Interstitial Fluid by a Three-Electrode Skin Resistance Sensor
by Dachao Li, Ridong Wang, Haixia Yu, Guoqing Li, Yue Sun, Wenshuai Liang and Kexin Xu
Sensors 2014, 14(4), 7084-7095; https://doi.org/10.3390/s140407084 - 22 Apr 2014
Cited by 6 | Viewed by 8260
Abstract
It is difficult to accurately measure the volume of transdermally extracted interstitial fluid (ISF), which is important for improving blood glucose prediction accuracy. Skin resistance, which is a good indicator of skin permeability, can be used to determine the volume of extracted ISF. [...] Read more.
It is difficult to accurately measure the volume of transdermally extracted interstitial fluid (ISF), which is important for improving blood glucose prediction accuracy. Skin resistance, which is a good indicator of skin permeability, can be used to determine the volume of extracted ISF. However, it is a challenge to realize in vivo longitudinal skin resistance measurements of microareas. In this study, a three-electrode sensor was presented for measuring single-point skin resistance in vivo, and a method for determining the volume of transdermally extracted ISF using this sensor was proposed. Skin resistance was measured under static and dynamic conditions. The correlation between the skin resistance and the permeation rate of transdermally extracted ISF was proven. The volume of transdermally extracted ISF was determined using skin resistance. Factors affecting the volume prediction accuracy of transdermally extracted ISF were discussed. This method is expected to improve the accuracy of blood glucose prediction, and is of great significance for the clinical application of minimally invasive blood glucose measurement. Full article
(This article belongs to the Special Issue On-Chip Sensors)
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<p>Three-electrode sensor.</p> Full article ">
<p>Skin resistance measuring system.</p> Full article ">
<p>Skin resistance measurement based on a three-electrode system (static measurement).</p> Full article ">
<p>Electrode used for the dynamic measurement of skin resistance.</p> Full article ">
<p>Results of six static skin resistance measurements. The time interval between each two measurement results was over 10 min.</p> Full article ">
<p>Results of six dynamic skin resistance measurements. The time interval between each two measurement results was over 10 min.</p> Full article ">
<p>Relation between the glucose concentration of the sample solution and skin conductance.</p> Full article ">
1624 KiB  
Article
Setup of Galvanic Sensors for the Monitoring of Gilded Bronzes
by Sara Goidanich, Davide Gulotta, Laura Brambilla, Ruben Beltrami, Paola Fermo and Lucia Toniolo
Sensors 2014, 14(4), 7066-7083; https://doi.org/10.3390/s140407066 - 22 Apr 2014
Cited by 10 | Viewed by 8204
Abstract
Traditional electrochemical techniques, such as linear polarization resistance (Rp), and electrochemical impedance spectroscopy (EIS), cannot be applied to gilded bronzes, as it may not be possible to interpret the results obtained due to the bimetallic nature of the studied material. The measurement of [...] Read more.
Traditional electrochemical techniques, such as linear polarization resistance (Rp), and electrochemical impedance spectroscopy (EIS), cannot be applied to gilded bronzes, as it may not be possible to interpret the results obtained due to the bimetallic nature of the studied material. The measurement of the macrocouple current generated by the gold/bronze galvanic couple can be used as an indicator of degradation processes. Nevertheless, this measurement cannot be performed directly on the original artifacts due to the systematic presence of short-circuits between the two metals. In the present work the use of galvanic sensors is proposed as a possible solution for the monitoring of gilded bronze artefacts. The sensors have been designed to simulate real gilded bronze surfaces in terms of composition and stratigraphy and have proved to be a reliable diagnostic tool for the in situ monitoring of the rates of deterioration of gilded bronze surfaces and to test new conservation treatments. Their set-up and application is reported and their performances discussed. Full article
(This article belongs to the Special Issue Sensors for Cultural Heritage Diagnostics)
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<p>The galvanic sensors of the seventies [<a href="#b48-sensors-14-07066" class="html-bibr">48</a>,<a href="#b49-sensors-14-07066" class="html-bibr">49</a>]: macrocouple current as a function of time and relative humidity.</p> Full article ">
<p>General model of a galvanic sensor (<b>a</b>) with detail of the gold leaf overlapped (<b>b</b>).The complete stratigraphy of the sensor includes: (1) metallic substrate; (2) cuprite layer; (3) patina of corrosion products; (4) gilding; (5) electric insulation cover.</p> Full article ">
<p>Photographic documentation of the different types of patina: S&amp;C (<b>A</b>); BCC (<b>B</b>); BrocChal (<b>C</b>); BrocNan (<b>D</b>); BrocNan+Broc (<b>E</b>) (specimens dimensions: 60 × 20 mm).</p> Full article ">
<p>Photographic documentation of galvanic sensors with increasing thickness of the patina realized on copper substrate and with a S&amp;C patina: single layer (<b>A</b>), double layer (<b>B</b>) and triple layer (<b>C</b>) (sensors dimensions: 60 × 50 mm).</p> Full article ">
<p>Brochantite patinas with increasing thickness (<b>A</b>) &gt; (<b>B</b>) &gt; (<b>C</b>) &gt; (<b>D</b>) (sensors max. length: 60 mm).</p> Full article ">
<p>SEM documentation of the characteristic porosity of the gold leaf.</p> Full article ">
<p>Macroscopic (sensor dimensions: 60 × 50 mm) (<b>a</b>) and microscopic (<b>b</b>) documentation of a galvanic sensors resulting from the too early application of the gold leaf on a highly moistened patina.</p> Full article ">
<p>Macroscopic (sensors max. length: 60 mm) (<b>a</b>) and microscopic documentation (<b>b</b>,<b>c</b>) of a galvanic sensors showing a lack of adhesion of the gold leaf.</p> Full article ">
<p>Macrocouple current as a function of time for three galvanic sensors with bronze substrate and double or triple layer of S&amp;C artificial patina.</p> Full article ">
987 KiB  
Article
Novel Paradigm for Constructing Masses in Dempster-Shafer Evidence Theory for Wireless Sensor Network’s Multisource Data Fusion
by Zhenjiang Zhang, Tonghuan Liu and Wenyu Zhang
Sensors 2014, 14(4), 7049-7065; https://doi.org/10.3390/s140407049 - 22 Apr 2014
Cited by 15 | Viewed by 6539
Abstract
Dempster-Shafer evidence theory (DSET) is a flexible and popular paradigm for multisource data fusion in wireless sensor networks (WSNs). This paper presents a novel and easy implementing method computing masses from the hundreds of pieces of data collected by a WSN. The transfer [...] Read more.
Dempster-Shafer evidence theory (DSET) is a flexible and popular paradigm for multisource data fusion in wireless sensor networks (WSNs). This paper presents a novel and easy implementing method computing masses from the hundreds of pieces of data collected by a WSN. The transfer model is based on the Mahalanobis distance (MD), which is an effective method to measure the similarity between an object and a sample. Compared to the existing methods, the proposed method concerns the statistical features of the observed data and it is good at transferring multi-dimensional data to belief assignment correctly and effectively. The main processes of the proposed method, which include the calculation of the intersection classes of the power set and the algorithm mapping MDs to masses, are described in detail. Experimental results in transformer fault diagnosis show that the proposed method has a high accuracy in constructing masses from multidimensional data for DSET. Additionally, the results also prove that higher dimensional data brings higher accuracy in transferring data to mass. Full article
(This article belongs to the Section Sensor Networks)
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<p>Common method used to transfer observed data into a belief assignment.</p> Full article ">
<p>Difference between ED and MD in metric distance. (<b>a</b>) Distance defined by ED. (<b>b</b>) Distance Defined by MD.</p> Full article ">
<p>Calculation of intersection scope with one dimensional data. (<b>a</b>) Intersection interval of X and Y is null set. (<b>b</b>) Intersection interval of X and Y. (<b>c</b>) Intersection interval of X and Y when Y’s interval is contained in X.</p> Full article ">
<p>Calculation of intersection scope with 2-dimensional data. (<b>a</b>) Intersection scope of A and B. (<b>b</b>) Intersection scope of A and B when B’s scope is contained in A.</p> Full article ">
<p>Curve of transfer function with different k. (<b>a</b>) k = 1. (<b>b</b>) k = 2.</p> Full article ">
<p>Process of proposed mass constructing method.</p> Full article ">
<p>The distribution of the sample data, which includes (<b>a</b>): the original samples collected in the 3 conditions; (<b>b</b>): the all calculated sample sets of the power set.</p> Full article ">
<p>The distribution map of the validate data.</p> Full article ">
<p>The obtained masses from the validate data. (<b>a</b>) masses obtained under CWA; (<b>b</b>) masses obtained under OWA.</p> Full article ">
360 KiB  
Article
Effect of Angular Velocity on Sensors Based on Morphology Dependent Resonances
by Amir R. Ali and Tindaro Ioppolo
Sensors 2014, 14(4), 7041-7048; https://doi.org/10.3390/s140407041 - 22 Apr 2014
Cited by 39 | Viewed by 7655
Abstract
We carried out an analysis to investigate the morphology dependent optical resonances shift (MDR) of a rotating spherical resonator. The spinning resonator experiences an elastic deformation due to the centrifugal force acting on it, leading to a shift in its MDR. Experiments are [...] Read more.
We carried out an analysis to investigate the morphology dependent optical resonances shift (MDR) of a rotating spherical resonator. The spinning resonator experiences an elastic deformation due to the centrifugal force acting on it, leading to a shift in its MDR. Experiments are also carried out to demonstrate the MDR shifts of a spinning polydimethylsiloxane (PDMS) microsphere. The experimental results agree well with the analytical prediction. These studies demonstrated that spinning sensor based on MDR may experience sufficient shift in the optical resonances, therefore interfering with its desirable operational sensor design. Also the results show that angular velocity sensors could be designed using this principle. Full article
(This article belongs to the Section Physical Sensors)
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<p>Ray optics description of MDR in a sphere.</p> Full article ">
<p>(<b>a</b>) Schematic of sensor system and (<b>b</b>) observed transmission spectrum.</p> Full article ">
<p>Geometry of a rotating sphere.</p> Full article ">
<p>MDR shift using <a href="#FD7" class="html-disp-formula">Equation (7)</a> for silica, PMMA and PDMS 10:1 and 60:1 resonators.</p> Full article ">
<p>(<b>a</b>) Schematic and (<b>b</b>) photograph of the experimental setup.</p> Full article ">
<p>Comparison of experimental results with analytical prediction for a (10:1) PDMS microsphere.</p> Full article ">
<p>Transmission spectrum of MDR for a (60:1) PDMS microsphere.</p> Full article ">
<p>Comparison of experimental results with analytical prediction for a (60:1) PDMS resonator.</p> Full article ">
932 KiB  
Article
Quorum Sensing Activity of Aeromonas Caviae Strain YL12, A Bacterium Isolated from Compost
by Yan-Lue Lim, Robson Ee, Wai-Fong Yin and Kok-Gan Chan
Sensors 2014, 14(4), 7026-7040; https://doi.org/10.3390/s140407026 - 22 Apr 2014
Cited by 24 | Viewed by 7926
Abstract
Quorum sensing is a well-studied cell-to-cell communication method that involves a cell-density dependent regulation of genes expression mediated by signalling molecules. In this study, a bacterium isolated from a plant material compost pile was found to possess quorum sensing activity based on bioassay [...] Read more.
Quorum sensing is a well-studied cell-to-cell communication method that involves a cell-density dependent regulation of genes expression mediated by signalling molecules. In this study, a bacterium isolated from a plant material compost pile was found to possess quorum sensing activity based on bioassay screening. Isolate YL12 was identified using matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectrometry and molecular typing using rpoD gene which identified the isolate as Aeromonas caviae. High resolution tandem mass spectrometry was subsequently employed to identify the N-acyl homoserine lactone profile of Aeromonas caviae YL12 and confirmed that this isolate produced two short chain N-acyl homoserine lactones, namely C4-HSL and C6, and the production was observed to be cell density-dependent. Using the thin layer chromatography (TLC) bioassay, both AHLs were found to activate C. violaceum CV026, whereas only C6-HSL was revealed to induce bioluminescence expression of E. coli [pSB401]. The data presented in this study will be the leading steps in understanding the role of quorum sensing in Aeromonas caviae strain YL12. Full article
(This article belongs to the Section Biosensors)
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<p>Cross-streaking of strain YL12 with <span class="html-italic">C. violaceum</span> CV026 was observed to trigger violacein production in the biosensor. <span class="html-italic">E. carotovora</span> GS101 and <span class="html-italic">E. carotovora</span> PNP22 were used as positive and negative controls, respectively.</p> Full article ">
<p>Detection of AHL production by strain YL12 by bioluminescent reporter assay with <span class="html-italic">E. coli</span> [pSB401] as biosensor. Graph was plotted as RLU/OD<sub>495</sub> against time. Increment of RLU/OD<sub>495</sub> value which was observed to occur exponentially within 13 h confirmed the AHL-producing activity of strain YL12 (circle). Negative control (square) was blank LB broth extract that did not show any detectable activity. Data are presented as means of SEM values from triplicate experiments.</p> Full article ">
<p>MALDI-TOF MS identification of strain YL12. The different colours of the branches represent distinct clusters among the microorganisms in the database.</p> Full article ">
<p>The Phylogenetic Analysis of Strain YL12.</p> Full article ">
<p>Mass spectrometry analysis of extracted AHL from spent supernatant of YL12 harvested at the 24th hour incubation. (<b>a</b>) C4-HSL (<span class="html-italic">m</span>/<span class="html-italic">z</span> 172.100; retention time: 0.732 min; abundance: 1643.48) and (<b>b</b>) C6-HSL (<span class="html-italic">m</span>/<span class="html-italic">z</span> 200.200; rentention time: 1.882 min; abundance: 261.54).</p> Full article ">
<p>Abundance value of C4-HSL (●) and C6-HSL (▪) collected from culture harvested at three separate time points (8 h, 16 h, 24 h;. C4-HSL were found to increase exponentially from 8 h to 24 h whereas C6-HSL shows a relatively slight increment during the same incubation period. Data are presented as means of SEM values from triplicate experiments.</p> Full article ">
<p>TLC bioassay of spent supernatants extracts of YL12. (<b>a</b>) TLC/CV026 bioassay shows that YL12 extracts (lane 2) were chromatographed into two distinct spots with R<span class="html-italic"><sub>f</sub></span> value of 0.4 and 0.6, which corresponds to the R<span class="html-italic"><sub>f</sub></span> values of the synthetic standards (lane 1) used, namely C4-HSL (R<span class="html-italic"><sub>f</sub></span> value of 0.6) and C6-HSL(R<span class="html-italic"><sub>f</sub></span> value of 0.4). (<b>b</b>) TLC/ <span class="html-italic">E. coli</span> [pSB401] bioassay showed only one bioluminescent spot in both lane 2 (YL12 extracts) and lane 1 (synthetic standard) with R<span class="html-italic"><sub>f</sub></span> value of 0.4 following incubation at 37 °C.</p> Full article ">
414 KiB  
Article
Measurement of Cerenkov Radiation Induced by the Gamma-Rays of Co-60 Therapy Units Using Wavelength Shifting Fiber
by Kyoung Won Jang, Sang Hun Shin, Seon Geun Kim, Jae Seok Kim, Wook Jae Yoo, Young Hoon Ji and Bongsoo Lee
Sensors 2014, 14(4), 7013-7025; https://doi.org/10.3390/s140407013 - 21 Apr 2014
Cited by 17 | Viewed by 8631
Abstract
In this study, a wavelength shifting fiber that shifts ultra-violet and blue light to green light was employed as a sensor probe of a fiber-optic Cerenkov radiation sensor. In order to characterize Cerenkov radiation generated in the developed wavelength shifting fiber and a [...] Read more.
In this study, a wavelength shifting fiber that shifts ultra-violet and blue light to green light was employed as a sensor probe of a fiber-optic Cerenkov radiation sensor. In order to characterize Cerenkov radiation generated in the developed wavelength shifting fiber and a plastic optical fiber, spectra and intensities of Cerenkov radiation were measured with a spectrometer. The spectral peaks of light outputs from the wavelength shifting fiber and the plastic optical fiber were measured at wavelengths of 500 and 510 nm, respectively, and the intensity of transmitted light output of the wavelength shifting fiber was 22.2 times higher than that of the plastic optical fiber. Also, electron fluxes and total energy depositions of gamma-ray beams generated from a Co-60 therapy unit were calculated according to water depths using the Monte Carlo N-particle transport code. The relationship between the fluxes of electrons over the Cerenkov threshold energy and the energy depositions of gamma-ray beams from the Co-60 unit is a near-identity function. Finally, percentage depth doses for the gamma-ray beams were obtained using the fiber-optic Cerenkov radiation sensor, and the results were compared with those obtained by an ionization chamber. The average dose difference between the results of the fiber-optic Cerenkov radiation sensor and those of the ionization chamber was about 2.09%. Full article
(This article belongs to the Special Issue Photonic Sensors for Industrial, Environmental and Health Monitoring)
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<p>Transmission characteristic of the PMMA based optical fiber.</p> Full article ">
<p>Cerenkov threshold energies of electrons according to refractive indices.</p> Full article ">
<p>Structure of fiber-optic Cerenkov radiation sensors and experimental setup.</p> Full article ">
<p>MCNPX scheme.</p> Full article ">
<p>Average energies of electrons generated in polystyrene according to depths of a water phantom.</p> Full article ">
<p>Relationship between fluxes of electrons over the CTE and energy depositions of the gamma-ray beams.</p> Full article ">
<p>The response of the FOCRS incorporating the WSF for 88 keV gamma-rays emitted from a Cd-109.</p> Full article ">
<p>Spectra of light outputs generated in FOCRSs.</p> Full article ">
<p>Transmission of light signals generated in a POF and a WSF.</p> Full article ">
736 KiB  
Article
An Internet of Things Example: Classrooms Access Control over Near Field Communication
by Daniel Palma, Juan Enrique Agudo, Héctor Sánchez and Miguel Macías Macías
Sensors 2014, 14(4), 6998-7012; https://doi.org/10.3390/s140406998 - 21 Apr 2014
Cited by 47 | Viewed by 13837
Abstract
The Internet of Things is one of the ideas that has become increasingly relevant in recent years. It involves connecting things to the Internet in order to retrieve information from them at any time and from anywhere. In the Internet of Things, sensor [...] Read more.
The Internet of Things is one of the ideas that has become increasingly relevant in recent years. It involves connecting things to the Internet in order to retrieve information from them at any time and from anywhere. In the Internet of Things, sensor networks that exchange information wirelessly via Wi-Fi, Bluetooth, Zigbee or RF are common. In this sense, our paper presents a way in which each classroom control is accessed through Near Field Communication (NFC) and the information is shared via radio frequency. These data are published on the Web and could easily be used for building applications from the data collected. As a result, our application collects information from the classroom to create a control classroom tool that displays access to and the status of all the classrooms graphically and also connects this data with social networks. Full article
(This article belongs to the Section Sensor Networks)
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Graphical abstract

Graphical abstract
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<p>Arduino UNO and Ethernet shield.</p> Full article ">
<p>System communication scheme.</p> Full article ">
<p>Overall system.</p> Full article ">
<p>Classroom node hardware prototype: (<b>a</b>) outside (<b>b</b>) inside.</p> Full article ">
<p>Master node hardware prototype: (<b>a</b>) outside (<b>b</b>) inside.</p> Full article ">
<p>System flowchart diagram (<b>a</b>) reading cards (<b>b</b>) uploading data to cloud.</p> Full article ">
<p>Processing data.</p> Full article ">
<p>Putting data in the cloud.</p> Full article ">
<p>Data in the map.</p> Full article ">
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