Next Issue
Previous Issue

E-Mail Alert

Add your e-mail address to receive forthcoming issues of this journal:

Journal Browser

Journal Browser

Table of Contents

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

  • Issues are regarded as officially published after their release is announced to the table of contents alert mailing list.
  • You may sign up for e-mail alerts to receive table of contents of newly released issues.
  • PDF is the official format for papers published in both, html and pdf forms. To view the papers in pdf format, click on the "PDF Full-text" link, and use the free Adobe Readerexternal link to open them.
View options order results:
result details:
Displaying articles 1-98
Export citation of selected articles as:
Open AccessArticle
A Multi-Resolution Approach for an Automated Fusion of Different Low-Cost 3D Sensors
Sensors 2014, 14(4), 7563-7579; https://doi.org/10.3390/s140407563
Received: 24 January 2014 / Revised: 8 April 2014 / Accepted: 15 April 2014 / Published: 24 April 2014
Cited by 6 | Viewed by 3475 | PDF Full-text (17230 KB) | HTML Full-text | XML Full-text
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)
Open AccessArticle
The Enhanced Locating Performance of an Integrated Cross-Correlation and Genetic Algorithm for Radio Monitoring Systems
Sensors 2014, 14(4), 7541-7562; https://doi.org/10.3390/s140407541
Received: 14 March 2014 / Revised: 20 April 2014 / Accepted: 21 April 2014 / Published: 24 April 2014
Cited by 2 | Viewed by 3004 | PDF Full-text (1580 KB) | HTML Full-text | XML Full-text
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
Open AccessArticle
Floor Sensing System Using Laser Reflectivity for Localizing Everyday Objects and Robot
Sensors 2014, 14(4), 7524-7540; https://doi.org/10.3390/s140407524
Received: 31 December 2013 / Revised: 14 April 2014 / Accepted: 15 April 2014 / Published: 24 April 2014
Cited by 7 | Viewed by 3481 | PDF Full-text (1251 KB) | HTML Full-text | XML Full-text
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)
Open AccessArticle
Model Parameter Adaption-Based Multi-Model Algorithm for Extended Object Tracking Using a Random Matrix
Sensors 2014, 14(4), 7505-7523; https://doi.org/10.3390/s140407505
Received: 20 January 2014 / Revised: 31 March 2014 / Accepted: 21 April 2014 / Published: 24 April 2014
Cited by 2 | Viewed by 2767 | PDF Full-text (793 KB) | HTML Full-text | XML Full-text
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)
Open AccessArticle
Non-Destructive Quality Evaluation of Pepper (Capsicum annuum L.) Seeds Using LED-Induced Hyperspectral Reflectance Imaging
Sensors 2014, 14(4), 7489-7504; https://doi.org/10.3390/s140407489
Received: 17 March 2014 / Revised: 21 April 2014 / Accepted: 21 April 2014 / Published: 24 April 2014
Cited by 14 | Viewed by 3190 | PDF Full-text (864 KB) | HTML Full-text | XML Full-text
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, Control, and Telemetry)
Open AccessReview
Chronology of Fabry-Perot Interferometer Fiber-Optic Sensors and Their Applications: A Review
Sensors 2014, 14(4), 7451-7488; https://doi.org/10.3390/s140407451
Received: 30 December 2013 / Revised: 29 March 2014 / Accepted: 18 April 2014 / Published: 24 April 2014
Cited by 78 | Viewed by 4836 | PDF Full-text (1213 KB) | HTML Full-text | XML Full-text
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)
Open AccessArticle
First-Principles Surface Stress Calculations and Multiscale Deformation Analysis of a Self-Assembled Monolayer Adsorbed on a Micro-Cantilever
Sensors 2014, 14(4), 7435-7450; https://doi.org/10.3390/s140407435
Received: 29 September 2013 / Revised: 26 February 2014 / Accepted: 18 April 2014 / Published: 23 April 2014
Cited by 5 | Viewed by 3137 | PDF Full-text (1343 KB) | HTML Full-text | XML Full-text
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)
Figures

Graphical abstract

Open AccessArticle
Calibration-Free Pulse Oximetry Based on Two Wavelengths in the Infrared — A Preliminary Study
Sensors 2014, 14(4), 7420-7434; https://doi.org/10.3390/s140407420
Received: 23 January 2014 / Revised: 9 April 2014 / Accepted: 14 April 2014 / Published: 23 April 2014
Cited by 14 | Viewed by 4463 | PDF Full-text (709 KB) | HTML Full-text | XML Full-text
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)
Open AccessReview
Fiber Bragg Grating Sensors toward Structural Health Monitoring in Composite Materials: Challenges and Solutions
Sensors 2014, 14(4), 7394-7419; https://doi.org/10.3390/s140407394
Received: 10 February 2014 / Revised: 4 April 2014 / Accepted: 18 April 2014 / Published: 23 April 2014
Cited by 169 | Viewed by 5477 | PDF Full-text (991 KB) | HTML Full-text | XML Full-text
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)
Figures

Graphical abstract

Open AccessArticle
An Accurate and Computationally Efficient Model for Membrane-Type Circular-Symmetric Micro-Hotplates
Sensors 2014, 14(4), 7374-7393; https://doi.org/10.3390/s140407374
Received: 11 February 2014 / Revised: 15 April 2014 / Accepted: 17 April 2014 / Published: 23 April 2014
Cited by 5 | Viewed by 2602 | PDF Full-text (828 KB) | HTML Full-text | XML Full-text
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)
Open AccessArticle
Development of a Sweetness Sensor for Aspartame, a Positively Charged High-Potency Sweetener
Sensors 2014, 14(4), 7359-7373; https://doi.org/10.3390/s140407359
Received: 12 March 2014 / Revised: 14 April 2014 / Accepted: 21 April 2014 / Published: 23 April 2014
Cited by 18 | Viewed by 3604 | PDF Full-text (415 KB) | HTML Full-text | XML Full-text
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)
Open AccessArticle
Using Massive Vehicle Positioning Data to Improve Control and Planning of Public Road Transport
Sensors 2014, 14(4), 7342-7358; https://doi.org/10.3390/s140407342
Received: 13 March 2014 / Revised: 15 April 2014 / Accepted: 17 April 2014 / Published: 23 April 2014
Cited by 5 | Viewed by 2539 | PDF Full-text (654 KB) | HTML Full-text | XML Full-text
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
Figures

Graphical abstract

Open AccessArticle
Optical Sensor Based on a Single CdS Nanobelt
Sensors 2014, 14(4), 7332-7341; https://doi.org/10.3390/s140407332
Received: 3 March 2014 / Revised: 18 April 2014 / Accepted: 18 April 2014 / Published: 23 April 2014
Cited by 5 | Viewed by 2818 | PDF Full-text (532 KB) | HTML Full-text | XML Full-text
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)
Figures

Graphical abstract

Open AccessArticle
Quantitative Damage Detection and Sparse Sensor Array Optimization of Carbon Fiber Reinforced Resin Composite Laminates for Wind Turbine Blade Structural Health Monitoring
Sensors 2014, 14(4), 7312-7331; https://doi.org/10.3390/s140407312
Received: 10 March 2014 / Revised: 14 April 2014 / Accepted: 18 April 2014 / Published: 23 April 2014
Cited by 11 | Viewed by 3330 | PDF Full-text (1038 KB) | HTML Full-text | XML Full-text
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)
Figures

Graphical abstract

Open AccessArticle
Experience in Evaluating AAL Solutions in Living Labs
Sensors 2014, 14(4), 7277-7311; https://doi.org/10.3390/s140407277
Received: 17 March 2014 / Revised: 15 April 2014 / Accepted: 18 April 2014 / Published: 23 April 2014
Cited by 6 | Viewed by 3376 | PDF Full-text (7920 KB) | HTML Full-text | XML Full-text
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
Open AccessReview
Recent Developments in Hyperspectral Imaging for Assessment of Food Quality and Safety
Sensors 2014, 14(4), 7248-7276; https://doi.org/10.3390/s140407248
Received: 25 September 2013 / Revised: 7 April 2014 / Accepted: 8 April 2014 / Published: 22 April 2014
Cited by 95 | Viewed by 4371 | PDF Full-text (617 KB) | HTML Full-text | XML Full-text
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)
Open AccessArticle
An Interactive Control Algorithm Used for Equilateral Triangle Formation with Robotic Sensors
Sensors 2014, 14(4), 7229-7247; https://doi.org/10.3390/s140407229
Received: 1 February 2014 / Revised: 16 April 2014 / Accepted: 16 April 2014 / Published: 22 April 2014
Cited by 2 | Viewed by 2424 | PDF Full-text (357 KB) | HTML Full-text | XML Full-text
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)
Open AccessArticle
Tracking and Recognition of Multiple Human Targets Moving in a Wireless Pyroelectric Infrared Sensor Network
Sensors 2014, 14(4), 7209-7228; https://doi.org/10.3390/s140407209
Received: 17 March 2014 / Revised: 16 April 2014 / Accepted: 17 April 2014 / Published: 22 April 2014
Cited by 17 | Viewed by 2900 | PDF Full-text (1080 KB) | HTML Full-text | XML Full-text
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)
Open AccessReview
Smartphone-Based Solutions for Fall Detection and Prevention: Challenges and Open Issues
Sensors 2014, 14(4), 7181-7208; https://doi.org/10.3390/s140407181
Received: 4 March 2014 / Revised: 10 April 2014 / Accepted: 11 April 2014 / Published: 22 April 2014
Cited by 84 | Viewed by 6516 | PDF Full-text (674 KB) | HTML Full-text | XML Full-text
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
Open AccessArticle
Angular Rate Optimal Design for the Rotary Strapdown Inertial Navigation System
Sensors 2014, 14(4), 7156-7180; https://doi.org/10.3390/s140407156
Received: 2 February 2014 / Revised: 28 March 2014 / Accepted: 2 April 2014 / Published: 22 April 2014
Cited by 13 | Viewed by 3218 | PDF Full-text (2208 KB) | HTML Full-text | XML Full-text
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)
Open AccessArticle
An Affordable Open-Source Turbidimeter
Sensors 2014, 14(4), 7142-7155; https://doi.org/10.3390/s140407142
Received: 22 February 2014 / Revised: 4 April 2014 / Accepted: 8 April 2014 / Published: 22 April 2014
Cited by 29 | Viewed by 8101 | PDF Full-text (392 KB) | HTML Full-text | XML Full-text | Supplementary Files
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)
Open AccessArticle
Wearable Biomedical Measurement Systems for Assessment of Mental Stress of Combatants in Real Time
Sensors 2014, 14(4), 7120-7141; https://doi.org/10.3390/s140407120
Received: 2 January 2014 / Revised: 31 March 2014 / Accepted: 15 April 2014 / Published: 22 April 2014
Cited by 50 | Viewed by 4675 | PDF Full-text (1092 KB) | HTML Full-text | XML Full-text
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
Open AccessArticle
WiSPH: A Wireless Sensor Network-Based Home Care Monitoring System
Sensors 2014, 14(4), 7096-7119; https://doi.org/10.3390/s140407096
Received: 19 March 2014 / Revised: 11 April 2014 / Accepted: 11 April 2014 / Published: 22 April 2014
Cited by 22 | Viewed by 5249 | PDF Full-text (1969 KB) | HTML Full-text | XML Full-text
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
Figures

Graphical abstract

Open AccessArticle
A Method for Measuring the Volume of Transdermally Extracted Interstitial Fluid by a Three-Electrode Skin Resistance Sensor
Sensors 2014, 14(4), 7084-7095; https://doi.org/10.3390/s140407084
Received: 14 November 2013 / Revised: 31 March 2014 / Accepted: 9 April 2014 / Published: 22 April 2014
Cited by 2 | Viewed by 3260 | PDF Full-text (570 KB) | HTML Full-text | XML Full-text
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)
Figures

Graphical abstract

Open AccessArticle
Setup of Galvanic Sensors for the Monitoring of Gilded Bronzes
Sensors 2014, 14(4), 7066-7083; https://doi.org/10.3390/s140407066
Received: 17 March 2014 / Revised: 14 April 2014 / Accepted: 14 April 2014 / Published: 22 April 2014
Cited by 3 | Viewed by 2753 | PDF Full-text (1624 KB) | HTML Full-text | XML Full-text
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)
Figures

Graphical abstract

Open AccessArticle
Novel Paradigm for Constructing Masses in Dempster-Shafer Evidence Theory for Wireless Sensor Network’s Multisource Data Fusion
Sensors 2014, 14(4), 7049-7065; https://doi.org/10.3390/s140407049
Received: 23 January 2014 / Revised: 12 April 2014 / Accepted: 15 April 2014 / Published: 22 April 2014
Cited by 7 | Viewed by 2627 | PDF Full-text (987 KB) | HTML Full-text | XML Full-text
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)
Open AccessArticle
Effect of Angular Velocity on Sensors Based on Morphology Dependent Resonances
Sensors 2014, 14(4), 7041-7048; https://doi.org/10.3390/s140407041
Received: 13 February 2014 / Revised: 7 April 2014 / Accepted: 14 April 2014 / Published: 22 April 2014
Cited by 24 | Viewed by 3100 | PDF Full-text (360 KB) | HTML Full-text | XML Full-text
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)
Figures

Graphical abstract

Open AccessArticle
Quorum Sensing Activity of Aeromonas Caviae Strain YL12, A Bacterium Isolated from Compost
Sensors 2014, 14(4), 7026-7040; https://doi.org/10.3390/s140407026
Received: 4 March 2014 / Revised: 6 April 2014 / Accepted: 10 April 2014 / Published: 22 April 2014
Cited by 17 | Viewed by 2981 | PDF Full-text (932 KB) | HTML Full-text | XML Full-text
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)
Figures

Graphical abstract

Open AccessArticle
Measurement of Cerenkov Radiation Induced by the Gamma-Rays of Co-60 Therapy Units Using Wavelength Shifting Fiber
Sensors 2014, 14(4), 7013-7025; https://doi.org/10.3390/s140407013
Received: 31 December 2013 / Revised: 18 March 2014 / Accepted: 15 April 2014 / Published: 21 April 2014
Cited by 9 | Viewed by 3345 | PDF Full-text (414 KB) | HTML Full-text | XML Full-text
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)
Open AccessArticle
An Internet of Things Example: Classrooms Access Control over Near Field Communication
Sensors 2014, 14(4), 6998-7012; https://doi.org/10.3390/s140406998
Received: 28 January 2014 / Revised: 19 March 2014 / Accepted: 9 April 2014 / Published: 21 April 2014
Cited by 20 | Viewed by 6087 | PDF Full-text (736 KB) | HTML Full-text | XML Full-text
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)
Figures

Graphical abstract

Sensors EISSN 1424-8220 Published by MDPI AG, Basel, Switzerland RSS E-Mail Table of Contents Alert
Back to Top