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

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Editorial

Jump to: Research, Review

Open AccessEditorial Latest Trends in Acoustic Sensing
Sensors 2014, 14(4), 5781-5784; doi:10.3390/s140405781
Received: 18 March 2014 / Accepted: 19 March 2014 / Published: 25 March 2014
Cited by 1 | PDF Full-text (79 KB) | HTML Full-text | XML Full-text
Abstract
Acoustics-based methods offer a powerful tool for sensing applications. Acoustic sensors can be applied in many fields ranging from materials characterization, structural health monitoring, acoustic imaging, defect characterization, etc., to name just a few. A proper selection of the acoustic wave [...] Read more.
Acoustics-based methods offer a powerful tool for sensing applications. Acoustic sensors can be applied in many fields ranging from materials characterization, structural health monitoring, acoustic imaging, defect characterization, etc., to name just a few. A proper selection of the acoustic wave frequency over a wide spectrum that extends from infrasound (<20 Hz) up to ultrasound (in the GHz–band), together with a number of different propagating modes, including bulk longitudinal and shear waves, surface waves, plate modes, etc., allow acoustic tools to be successfully applied to the characterization of gaseous, solid and liquid environments. The purpose of this special issue is to provide an overview of the research trends in acoustic wave sensing through some cases that are representative of specific applications in different sensing fields. [...] Full article
(This article belongs to the Special Issue Last Trends in Acoustic Sensing)
Open AccessEditorial Introduction to the Special Issue on “Optomechatronics”
Sensors 2014, 14(4), 6302-6304; doi:10.3390/s140406302
Received: 15 March 2014 / Accepted: 28 March 2014 / Published: 31 March 2014
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Abstract
The field of optomechatronics combines the synergistic effects of optics, mechanics and electronics for efficient sensor development. Optical sensors for the measurement of mechanical quantities, equipped with appropriate electronic signal (pre)processing have a wide range of applications, from surface testing, stress monitoring, [...] Read more.
The field of optomechatronics combines the synergistic effects of optics, mechanics and electronics for efficient sensor development. Optical sensors for the measurement of mechanical quantities, equipped with appropriate electronic signal (pre)processing have a wide range of applications, from surface testing, stress monitoring, and thin film analysis to biochemical sensing. The aim of this special issue is to provide an overview of current research and innovative applications of optomechatronics in sensors. [...] Full article
(This article belongs to the Special Issue Optomechatronics) Print Edition available
Open AccessEditorial Sensing of Scent, Fragrance, Smell, and Odor Emissions from Biota Sources
Sensors 2014, 14(4), 6567-6570; doi:10.3390/s140406567
Received: 2 April 2014 / Accepted: 8 April 2014 / Published: 9 April 2014
PDF Full-text (75 KB) | HTML Full-text | XML Full-text
Abstract
People encounter enormous numbers of chemicals present in the outdoor atmosphere and/or in the various facilities they use daily. Despite such diversity, not many of them have necessarily the potential to draw human’s nasal attraction if their perception thresholds are in general [...] Read more.
People encounter enormous numbers of chemicals present in the outdoor atmosphere and/or in the various facilities they use daily. Despite such diversity, not many of them have necessarily the potential to draw human’s nasal attraction if their perception thresholds are in general not sufficiently low enough, regardless of abundance. In this sense, many types of scents, musks, fragrances, smells, odors, and pheromones are unique enough to draw a great deal of attention mainly by their presence at or near threshold levels which are far lower than those of common chemicals with poor odorant characteristics. It is known that most of the diverse characters of odor-related ingredients or expressions are commonly produced from various biota sources present in the biosphere, e.g., fauna, flora, bacteria, fruits, flowers, trees, meats, fresh/decaying foods, etc. [...] Full article

Research

Jump to: Editorial, Review

Open AccessArticle Context-Aware Personal Navigation Using Embedded Sensor Fusion in Smartphones
Sensors 2014, 14(4), 5742-5767; doi:10.3390/s140405742
Received: 1 October 2013 / Revised: 14 March 2014 / Accepted: 14 March 2014 / Published: 25 March 2014
Cited by 11 | PDF Full-text (1671 KB) | HTML Full-text | XML Full-text
Abstract
Context-awareness is an interesting topic in mobile navigation scenarios where the context of the application is highly dynamic. Using context-aware computing, navigation services consider the situation of user, not only in the design process, but in real time while the device is [...] Read more.
Context-awareness is an interesting topic in mobile navigation scenarios where the context of the application is highly dynamic. Using context-aware computing, navigation services consider the situation of user, not only in the design process, but in real time while the device is in use. The basic idea is that mobile navigation services can provide different services based on different contexts—where contexts are related to the user’s activity and the device placement. Context-aware systems are concerned with the following challenges which are addressed in this paper: context acquisition, context understanding, and context-aware application adaptation. The proposed approach in this paper is using low-cost sensors in a multi-level fusion scheme to improve the accuracy and robustness of context-aware navigation system. The experimental results demonstrate the capabilities of the context-aware Personal Navigation Systems (PNS) for outdoor personal navigation using a smartphone. Full article
(This article belongs to the Section Sensor Networks)
Open AccessArticle Derivation of Land Surface Temperature for Landsat-8 TIRS Using a Split Window Algorithm
Sensors 2014, 14(4), 5768-5780; doi:10.3390/s140405768
Received: 7 January 2014 / Revised: 10 February 2014 / Accepted: 15 March 2014 / Published: 25 March 2014
Cited by 27 | PDF Full-text (810 KB) | HTML Full-text | XML Full-text | Correction
Abstract
Land surface temperature (LST) is one of the most important variables measured by satellite remote sensing. Public domain data are available from the newly operational Landsat-8 Thermal Infrared Sensor (TIRS). This paper presents an adjustment of the split window algorithm (SWA) for [...] Read more.
Land surface temperature (LST) is one of the most important variables measured by satellite remote sensing. Public domain data are available from the newly operational Landsat-8 Thermal Infrared Sensor (TIRS). This paper presents an adjustment of the split window algorithm (SWA) for TIRS that uses atmospheric transmittance and land surface emissivity (LSE) as inputs. Various alternatives for estimating these SWA inputs are reviewed, and a sensitivity analysis of the SWA to misestimating the input parameters is performed. The accuracy of the current development was assessed using simulated Modtran data. The root mean square error (RMSE) of the simulated LST was calculated as 0.93 °C. This SWA development is leading to progress in the determination of LST by Landsat-8 TIRS. Full article
(This article belongs to the Section Remote Sensors)
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Open AccessArticle Minimal Camera Networks for 3D Image Based Modeling of Cultural Heritage Objects
Sensors 2014, 14(4), 5785-5804; doi:10.3390/s140405785
Received: 7 January 2014 / Revised: 10 February 2014 / Accepted: 14 March 2014 / Published: 25 March 2014
Cited by 8 | PDF Full-text (2337 KB) | HTML Full-text | XML Full-text
Abstract
3D modeling of cultural heritage objects like artifacts, statues and buildings is nowadays an important tool for virtual museums, preservation and restoration. In this paper, we introduce a method to automatically design a minimal imaging network for the 3D modeling of cultural [...] Read more.
3D modeling of cultural heritage objects like artifacts, statues and buildings is nowadays an important tool for virtual museums, preservation and restoration. In this paper, we introduce a method to automatically design a minimal imaging network for the 3D modeling of cultural heritage objects. This becomes important for reducing the image capture time and processing when documenting large and complex sites. Moreover, such a minimal camera network design is desirable for imaging non-digitally documented artifacts in museums and other archeological sites to avoid disturbing the visitors for a long time and/or moving delicate precious objects to complete the documentation task. The developed method is tested on the Iraqi famous statue “Lamassu”. Lamassu is a human-headed winged bull of over 4.25 m in height from the era of Ashurnasirpal II (883–859 BC). Close-range photogrammetry is used for the 3D modeling task where a dense ordered imaging network of 45 high resolution images were captured around Lamassu with an object sample distance of 1 mm. These images constitute a dense network and the aim of our study was to apply our method to reduce the number of images for the 3D modeling and at the same time preserve pre-defined point accuracy. Temporary control points were fixed evenly on the body of Lamassu and measured by using a total station for the external validation and scaling purpose. Two network filtering methods are implemented and three different software packages are used to investigate the efficiency of the image orientation and modeling of the statue in the filtered (reduced) image networks. Internal and external validation results prove that minimal image networks can provide highly accurate records and efficiency in terms of visualization, completeness, processing time (>60% reduction) and the final accuracy of 1 mm. Full article
(This article belongs to the Special Issue Sensors for Cultural Heritage Diagnostics)
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Open AccessArticle Contact Region Estimation Based on a Vision-Based Tactile Sensor Using a Deformable Touchpad
Sensors 2014, 14(4), 5805-5822; doi:10.3390/s140405805
Received: 30 January 2014 / Revised: 10 March 2014 / Accepted: 20 March 2014 / Published: 25 March 2014
PDF Full-text (861 KB) | HTML Full-text | XML Full-text
Abstract
A new method is proposed to estimate the contact region between a sensor and an object using a deformable tactile sensor. The sensor consists of a charge-coupled device (CCD) camera, light-emitting diode (LED) lights and a deformable touchpad. The sensor can obtain [...] Read more.
A new method is proposed to estimate the contact region between a sensor and an object using a deformable tactile sensor. The sensor consists of a charge-coupled device (CCD) camera, light-emitting diode (LED) lights and a deformable touchpad. The sensor can obtain a variety of tactile information, such as the contact region, multi-axis contact force, slippage, shape, position and orientation of an object in contact with the touchpad. The proposed method is based on the movements of dots printed on the surface of the touchpad and classifies the contact state of dots into three types—A non-contacting dot, a sticking dot and a slipping dot. Considering the movements of the dots with noise and errors, equations are formulated to discriminate between the contacting dots and the non-contacting dots. A set of the contacting dots discriminated by the formulated equations can construct the contact region. Next, a method is developed to detect the dots in images of the surface of the touchpad captured by the CCD camera. A method to assign numbers to dots for calculating the displacements of the dots is also proposed. Finally, the proposed methods are validated by experimental results. Full article
(This article belongs to the Special Issue Tactile Sensors and Sensing Systems)
Open AccessArticle Use of an Activity Monitor and GPS Device to Assess Community Activity and Participation in Transtibial Amputees
Sensors 2014, 14(4), 5845-5859; doi:10.3390/s140405845
Received: 17 January 2014 / Revised: 12 March 2014 / Accepted: 15 March 2014 / Published: 25 March 2014
Cited by 2 | PDF Full-text (204 KB) | HTML Full-text | XML Full-text
Abstract
This study characterized measures of community activity and participation of transtibial amputees based on combined data from separate accelerometer and GPS devices. The relationship between community activity and participation and standard clinical measures was assessed. Forty-seven participants were recruited (78% male, mean [...] Read more.
This study characterized measures of community activity and participation of transtibial amputees based on combined data from separate accelerometer and GPS devices. The relationship between community activity and participation and standard clinical measures was assessed. Forty-seven participants were recruited (78% male, mean age 60.5 years). Participants wore the accelerometer and GPS devices for seven consecutive days. Data were linked to assess community activity (community based step counts) and community participation (number of community visits). Community activity and participation were compared across amputee K-level groups. Forty-six participants completed the study. On average each participant completed 16,645 (standard deviation (SD) 13,274) community steps and 16 (SD 10.9) community visits over seven days. There were differences between K-level groups for measures of community activity (F(2,45) = 9.4, p < 0.001) and participation (F(2,45) = 6.9, p = 0.002) with lower functioning K1/2 amputees demonstrating lower levels of community activity and participation than K3 and K4 amputees. There was no significant difference between K3 and K4 for community activity (p = 0.28) or participation (p = 0.43). This study demonstrated methodology to link accelerometer and GPS data to assess community activity and participation in a group of transtibial amputees. Differences in K-levels do not appear to accurately reflect actual community activity or participation in higher functioning transtibial amputees. Full article
(This article belongs to the Special Issue Wearable Gait Sensors)
Open AccessArticle A Fast and Accurate Sparse Continuous Signal Reconstruction by Homotopy DCD with Non-Convex Regularization
Sensors 2014, 14(4), 5929-5951; doi:10.3390/s140405929
Received: 26 January 2014 / Revised: 10 March 2014 / Accepted: 24 March 2014 / Published: 26 March 2014
Cited by 1 | PDF Full-text (856 KB) | HTML Full-text | XML Full-text
Abstract
In recent years, various applications regarding sparse continuous signal recovery such as source localization, radar imaging, communication channel estimation, etc., have been addressed from the perspective of compressive sensing (CS) theory. However, there are two major defects that need to be [...] Read more.
In recent years, various applications regarding sparse continuous signal recovery such as source localization, radar imaging, communication channel estimation, etc., have been addressed from the perspective of compressive sensing (CS) theory. However, there are two major defects that need to be tackled when considering any practical utilization. The first issue is off-grid problem caused by the basis mismatch between arbitrary located unknowns and the pre-specified dictionary, which would make conventional CS reconstruction methods degrade considerably. The second important issue is the urgent demand for low-complexity algorithms, especially when faced with the requirement of real-time implementation. In this paper, to deal with these two problems, we have presented three fast and accurate sparse reconstruction algorithms, termed as HR-DCD, Hlog-DCD and Hlp-DCD, which are based on homotopy, dichotomous coordinate descent (DCD) iterations and non-convex regularizations, by combining with the grid refinement technique. Experimental results are provided to demonstrate the effectiveness of the proposed algorithms and related analysis. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle Locatable-Body Temperature Monitoring Based on Semi-Active UHF RFID Tags
Sensors 2014, 14(4), 5952-5966; doi:10.3390/s140405952
Received: 22 January 2014 / Revised: 6 March 2014 / Accepted: 17 March 2014 / Published: 26 March 2014
Cited by 3 | PDF Full-text (690 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents the use of radio-frequency identification (RFID) technology for the real-time remote monitoring of body temperature, while an associated program can determine the location of the body carrying the respective sensor. The RFID chip’s internal integrated temperature sensor is used [...] Read more.
This paper presents the use of radio-frequency identification (RFID) technology for the real-time remote monitoring of body temperature, while an associated program can determine the location of the body carrying the respective sensor. The RFID chip’s internal integrated temperature sensor is used for both the human-body temperature detection and as a measurement device, while using radio-frequency communication to broadcast the temperature information. The adopted RFID location technology makes use of reference tags together with a nearest neighbor localization algorithm and a multiple-antenna time-division multiplexing location system. A graphical user interface (GUI) was developed for collecting temperature and location data for the data fusion by using RFID protocols. With a puppy as test object, temperature detection and localization experiments were carried out. The measured results show that the applied method, when using a mercury thermometer for comparison in terms of measuring the temperature of the dog, has a good consistency, with an average temperature error of 0.283 °C. When using the associated program over the area of 12.25 m2, the average location error is of 0.461 m, which verifies the feasibility of the sensor-carrier location by using the proposed program. Full article
(This article belongs to the Section Physical Sensors)
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Open AccessArticle A Novel Approach to ECG Classification Based upon Two-Layered HMMs in Body Sensor Networks
Sensors 2014, 14(4), 5994-6011; doi:10.3390/s140405994
Received: 18 December 2013 / Revised: 24 February 2014 / Accepted: 18 March 2014 / Published: 27 March 2014
Cited by 4 | PDF Full-text (957 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents a novel approach to ECG signal filtering and classification. Unlike the traditional techniques which aim at collecting and processing the ECG signals with the patient being still, lying in bed in hospitals, our proposed algorithm is intentionally designed for [...] Read more.
This paper presents a novel approach to ECG signal filtering and classification. Unlike the traditional techniques which aim at collecting and processing the ECG signals with the patient being still, lying in bed in hospitals, our proposed algorithm is intentionally designed for monitoring and classifying the patient’s ECG signals in the free-living environment. The patients are equipped with wearable ambulatory devices the whole day, which facilitates the real-time heart attack detection. In ECG preprocessing, an integral-coefficient-band-stop (ICBS) filter is applied, which omits time-consuming floating-point computations. In addition, two-layered Hidden Markov Models (HMMs) are applied to achieve ECG feature extraction and classification. The periodic ECG waveforms are segmented into ISO intervals, P subwave, QRS complex and T subwave respectively in the first HMM layer where expert-annotation assisted Baum-Welch algorithm is utilized in HMM modeling. Then the corresponding interval features are selected and applied to categorize the ECG into normal type or abnormal type (PVC, APC) in the second HMM layer. For verifying the effectiveness of our algorithm on abnormal signal detection, we have developed an ECG body sensor network (BSN) platform, whereby real-time ECG signals are collected, transmitted, displayed and the corresponding classification outcomes are deduced and shown on the BSN screen. Full article
(This article belongs to the Section Sensor Networks)
Open AccessArticle A Novel Teaching System for Industrial Robots
Sensors 2014, 14(4), 6012-6031; doi:10.3390/s140406012
Received: 18 October 2013 / Revised: 19 March 2014 / Accepted: 24 March 2014 / Published: 27 March 2014
Cited by 2 | PDF Full-text (871 KB) | HTML Full-text | XML Full-text
Abstract
The most important tool for controlling an industrial robotic arm is a teach pendant, which controls the robotic arm movement in work spaces and accomplishes teaching tasks. A good teaching tool should be easy to operate and can complete teaching tasks rapidly [...] Read more.
The most important tool for controlling an industrial robotic arm is a teach pendant, which controls the robotic arm movement in work spaces and accomplishes teaching tasks. A good teaching tool should be easy to operate and can complete teaching tasks rapidly and effortlessly. In this study, a new teaching system is proposed for enabling users to operate robotic arms and accomplish teaching tasks easily. The proposed teaching system consists of the teach pen, optical markers on the pen, a motion capture system, and the pen tip estimation algorithm. With the marker positions captured by the motion capture system, the pose of the teach pen is accurately calculated by the pen tip algorithm and used to control the robot tool frame. In addition, Fitts’ Law is adopted to verify the usefulness of this new system, and the results show that the system provides high accuracy, excellent operation performance, and a stable error rate. In addition, the system maintains superior performance, even when users work on platforms with different inclination angles. Full article
(This article belongs to the Section Physical Sensors)
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Open AccessArticle Fruit Detectability Analysis for Different Camera Positions in Sweet-Pepper
Sensors 2014, 14(4), 6032-6044; doi:10.3390/s140406032
Received: 6 December 2013 / Revised: 14 March 2014 / Accepted: 20 March 2014 / Published: 27 March 2014
Cited by 4 | PDF Full-text (573 KB) | HTML Full-text | XML Full-text
Abstract
For robotic harvesting of sweet-pepper fruits in greenhouses a sensor system is required to detect and localize the fruits on the plants. Due to the complex structure of the plant, most fruits are (partially) occluded when an image is taken from one [...] Read more.
For robotic harvesting of sweet-pepper fruits in greenhouses a sensor system is required to detect and localize the fruits on the plants. Due to the complex structure of the plant, most fruits are (partially) occluded when an image is taken from one viewpoint only. In this research the effect of multiple camera positions and viewing angles on fruit visibility and detectability was investigated. A recording device was built which allowed to place the camera under different azimuth and zenith angles and to move the camera horizontally along the crop row. Fourteen camera positions were chosen and the fruit visibility in the recorded images was manually determined for each position. For images taken from one position only with the criterion of maximum 50% occlusion per fruit, the fruit detectability (FD) was in no case higher than 69%. The best single positions were the front views and looking with a zenith angle of 60° upwards. The FD increased when a combination was made of multiple viewpoint positions. With a combination of five favourite positions the maximum FD was 90%. Full article
(This article belongs to the Section Physical Sensors)
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Open AccessArticle Ambient Intelligence Application Based on Environmental Measurements Performed with an Assistant Mobile Robot
Sensors 2014, 14(4), 6045-6055; doi:10.3390/s140406045
Received: 13 March 2014 / Revised: 21 March 2014 / Accepted: 25 March 2014 / Published: 27 March 2014
Cited by 6 | PDF Full-text (347 KB) | HTML Full-text | XML Full-text
Abstract
This paper proposes the use of an autonomous assistant mobile robot in order to monitor the environmental conditions of a large indoor area and develop an ambient intelligence application. The mobile robot uses single high performance embedded sensors in order to collect [...] Read more.
This paper proposes the use of an autonomous assistant mobile robot in order to monitor the environmental conditions of a large indoor area and develop an ambient intelligence application. The mobile robot uses single high performance embedded sensors in order to collect and geo-reference environmental information such as ambient temperature, air velocity and orientation and gas concentration. The data collected with the assistant mobile robot is analyzed in order to detect unusual measurements or discrepancies and develop focused corrective ambient actions. This paper shows an example of the measurements performed in a research facility which have enabled the detection and location of an uncomfortable temperature profile inside an office of the research facility. The ambient intelligent application has been developed by performing some localized ambient measurements that have been analyzed in order to propose some ambient actuations to correct the uncomfortable temperature profile. Full article
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Open AccessArticle Electroless Deposition and Nanolithography Can Control the Formation of Materials at the Nano-Scale for Plasmonic Applications
Sensors 2014, 14(4), 6056-6083; doi:10.3390/s140406056
Received: 20 December 2013 / Revised: 10 March 2014 / Accepted: 21 March 2014 / Published: 27 March 2014
Cited by 10 | PDF Full-text (1056 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
The new revolution in materials science is being driven by our ability to manipulate matter at the molecular level to create structures with novel functions and properties. The aim of this paper is to explore new strategies to obtain plasmonic metal nanostructures [...] Read more.
The new revolution in materials science is being driven by our ability to manipulate matter at the molecular level to create structures with novel functions and properties. The aim of this paper is to explore new strategies to obtain plasmonic metal nanostructures through the combination of a top down method, that is electron beam lithography, and a bottom up technique, that is the chemical electroless deposition. This technique allows a tight control over the shape and size of bi- and three-dimensional metal patterns at the nano scale. The resulting nanostructures can be used as constituents of Surface Enhanced Raman Spectroscopy (SERS) substrates, where the electromagnetic field is strongly amplified. Our results indicate that, in electroless growth, high quality metal nanostructures with sizes below 50 nm may be easily obtained. These findings were explained within the framework of a diffusion limited aggregation (DLA) model, that is a simulation model that makes it possible to decipher, at an atomic level, the rules governing the evolution of the growth front; moreover, we give a description of the physical mechanisms of growth at a basic level. In the discussion, we show how these findings can be utilized to fabricate dimers of silver nanospheres where the size and shape of those spheres is controlled with extreme precision and can be used for very large area SERS substrates and nano-optics, for single molecule detection. Full article
(This article belongs to the Special Issue Single Biomolecule Detection)
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Open AccessArticle A Pseudolite-Based Positioning System for Legacy GNSS Receivers
Sensors 2014, 14(4), 6104-6123; doi:10.3390/s140406104
Received: 2 December 2013 / Revised: 17 March 2014 / Accepted: 18 March 2014 / Published: 27 March 2014
Cited by 2 | PDF Full-text (1677 KB) | HTML Full-text | XML Full-text
Abstract
The ephemeris data format of legacy GPS receivers is improper for positioning stationary pseudolites on the ground. Therefore, to utilize pseudolites for navigation, GPS receivers must be modified so that they can handle the modified data formats of the pseudolites. Because of [...] Read more.
The ephemeris data format of legacy GPS receivers is improper for positioning stationary pseudolites on the ground. Therefore, to utilize pseudolites for navigation, GPS receivers must be modified so that they can handle the modified data formats of the pseudolites. Because of this problem, the practical use of pseudolites has so far been limited. This paper proposes a pseudolite-based positioning system that can be used with unmodified legacy GPS receivers. In the proposed system, pseudolites transmit simulated GPS signals. The signals use standard GPS ephemeris data format and contain ephemeris data of simulated GPS satellites, not those of pseudolites. The use of the standard format enables the GPS receiver to process pseudolite signals without any modification. However, the position output of the GPS receiver is not the correct position in this system, because there are additional signal delays from each pseudolite to the receiver. A post-calculation process was added to obtain the correct receiver position using GPS receiver output. This re-estimation is possible because it is based on known information about the simulated signals, pseudolites, and positioning process of the GPS receiver. Simulations using generated data and live GPS data are conducted for various geometries to verify the proposed system. The test results show that the proposed system provides the desired user position using pseudolite signals without requiring any modifications to the legacy GPS receiver. In this initial study, a pseudolite-only indoor system was assumed. However, it can be expanded to a GPS-pseudolite system outdoors. Full article
(This article belongs to the Section Remote Sensors)
Open AccessArticle 2.5D Multi-View Gait Recognition Based on Point Cloud Registration
Sensors 2014, 14(4), 6124-6143; doi:10.3390/s140406124
Received: 14 January 2014 / Revised: 24 March 2014 / Accepted: 24 March 2014 / Published: 28 March 2014
Cited by 9 | PDF Full-text (1108 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents a method for modeling a 2.5-dimensional (2.5D) human body and extracting the gait features for identifying the human subject. To achieve view-invariant gait recognition, a multi-view synthesizing method based on point cloud registration (MVSM) to generate multi-view training galleries [...] Read more.
This paper presents a method for modeling a 2.5-dimensional (2.5D) human body and extracting the gait features for identifying the human subject. To achieve view-invariant gait recognition, a multi-view synthesizing method based on point cloud registration (MVSM) to generate multi-view training galleries is proposed. The concept of a density and curvature-based Color Gait Curvature Image is introduced to map 2.5D data onto a 2D space to enable data dimension reduction by discrete cosine transform and 2D principle component analysis. Gait recognition is achieved via a 2.5D view-invariant gait recognition method based on point cloud registration. Experimental results on the in-house database captured by a Microsoft Kinect camera show a significant performance gain when using MVSM. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle A New Approach to Integrate Internet-of-Things and Software-as-a-Service Model for Logistic Systems: A Case Study
Sensors 2014, 14(4), 6144-6164; doi:10.3390/s140406144
Received: 5 January 2014 / Revised: 16 March 2014 / Accepted: 25 March 2014 / Published: 28 March 2014
Cited by 10 | PDF Full-text (637 KB) | HTML Full-text | XML Full-text
Abstract
Cloud computing is changing the ways software is developed and managed in enterprises, which is changing the way of doing business in that dynamically scalable and virtualized resources are regarded as services over the Internet. Traditional manufacturing systems such as supply chain [...] Read more.
Cloud computing is changing the ways software is developed and managed in enterprises, which is changing the way of doing business in that dynamically scalable and virtualized resources are regarded as services over the Internet. Traditional manufacturing systems such as supply chain management (SCM), customer relationship management (CRM), and enterprise resource planning (ERP) are often developed case by case. However, effective collaboration between different systems, platforms, programming languages, and interfaces has been suggested by researchers. In cloud-computing-based systems, distributed resources are encapsulated into cloud services and centrally managed, which allows high automation, flexibility, fast provision, and ease of integration at low cost. The integration between physical resources and cloud services can be improved by combining Internet of things (IoT) technology and Software-as-a-Service (SaaS) technology. This study proposes a new approach for developing cloud-based manufacturing systems based on a four-layer SaaS model. There are three main contributions of this paper: (1) enterprises can develop their own cloud-based logistic management information systems based on the approach proposed in this paper; (2) a case study based on literature reviews with experimental results is proposed to verify that the system performance is remarkable; (3) challenges encountered and feedback collected from T Company in the case study are discussed in this paper for the purpose of enterprise deployment. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle Enhancement of the Wear Particle Monitoring Capability of Oil Debris Sensors Using a Maximal Overlap Discrete Wavelet Transform with Optimal Decomposition Depth
Sensors 2014, 14(4), 6207-6228; doi:10.3390/s140406207
Received: 26 January 2014 / Revised: 11 March 2014 / Accepted: 13 March 2014 / Published: 28 March 2014
Cited by 4 | PDF Full-text (580 KB) | HTML Full-text | XML Full-text
Abstract
Oil debris sensors are effective tools to monitor wear particles in lubricants. For in situ applications, surrounding noise and vibration interferences often distort the oil debris signature of the sensor. Hence extracting oil debris signatures from sensor signals is a challenging task [...] Read more.
Oil debris sensors are effective tools to monitor wear particles in lubricants. For in situ applications, surrounding noise and vibration interferences often distort the oil debris signature of the sensor. Hence extracting oil debris signatures from sensor signals is a challenging task for wear particle monitoring. In this paper we employ the maximal overlap discrete wavelet transform (MODWT) with optimal decomposition depth to enhance the wear particle monitoring capability. The sensor signal is decomposed by the MODWT into different depths for detecting the wear particle existence. To extract the authentic particle signature with minimal distortion, the root mean square deviation of kurtosis value of the segmented signal residue is adopted as a criterion to obtain the optimal decomposition depth for the MODWT. The proposed approach is evaluated using both simulated and experimental wear particles. The results show that the present method can improve the oil debris monitoring capability without structural upgrade requirements. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle A Wearable System for Gait Training in Subjects with Parkinson’s Disease
Sensors 2014, 14(4), 6229-6246; doi:10.3390/s140406229
Received: 8 January 2014 / Revised: 20 March 2014 / Accepted: 24 March 2014 / Published: 28 March 2014
Cited by 13 | PDF Full-text (1541 KB) | HTML Full-text | XML Full-text
Abstract
In this paper, a system for gait training and rehabilitation for Parkinson’s disease (PD) patients in a daily life setting is presented. It is based on a wearable architecture aimed at the provision of real-time auditory feedback. Recent studies have, in fact, [...] Read more.
In this paper, a system for gait training and rehabilitation for Parkinson’s disease (PD) patients in a daily life setting is presented. It is based on a wearable architecture aimed at the provision of real-time auditory feedback. Recent studies have, in fact, shown that PD patients can receive benefit from a motor therapy based on auditory cueing and feedback, as happens in traditional rehabilitation contexts with verbal instructions given by clinical operators. To this extent, a system based on a wireless body sensor network and a smartphone has been developed. The system enables real-time extraction of gait spatio-temporal features and their comparison with a patient’s reference walking parameters captured in the lab under clinical operator supervision. Feedback is returned to the user in form of vocal messages, encouraging the user to keep her/his walking behavior or to correct it. This paper describes the overall concept, the proposed usage scenario and the parameters estimated for the gait analysis. It also presents, in detail, the hardware-software architecture of the system and the evaluation of system reliability by testing it on a few subjects. Full article
(This article belongs to the Special Issue Wearable Gait Sensors)
Open AccessArticle Random-Profiles-Based 3D Face Recognition System
Sensors 2014, 14(4), 6279-6301; doi:10.3390/s140406279
Received: 22 January 2014 / Revised: 10 March 2014 / Accepted: 24 March 2014 / Published: 31 March 2014
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Abstract
In this paper, a noble nonintrusive three-dimensional (3D) face modeling system for random-profile-based 3D face recognition is presented. Although recent two-dimensional (2D) face recognition systems can achieve a reliable recognition rate under certain conditions, their performance is limited by internal and external [...] Read more.
In this paper, a noble nonintrusive three-dimensional (3D) face modeling system for random-profile-based 3D face recognition is presented. Although recent two-dimensional (2D) face recognition systems can achieve a reliable recognition rate under certain conditions, their performance is limited by internal and external changes, such as illumination and pose variation. To address these issues, 3D face recognition, which uses 3D face data, has recently received much attention. However, the performance of 3D face recognition highly depends on the precision of acquired 3D face data, while also requiring more computational power and storage capacity than 2D face recognition systems. In this paper, we present a developed nonintrusive 3D face modeling system composed of a stereo vision system and an invisible near-infrared line laser, which can be directly applied to profile-based 3D face recognition. We further propose a novel random-profile-based 3D face recognition method that is memory-efficient and pose-invariant. The experimental results demonstrate that the reconstructed 3D face data consists of more than 50 k 3D point clouds and a reliable recognition rate against pose variation. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle Measurement of Entrance Surface Dose on an Anthropomorphic Thorax Phantom Using a Miniature Fiber-Optic Dosimeter
Sensors 2014, 14(4), 6305-6316; doi:10.3390/s140406305
Received: 24 December 2013 / Revised: 26 March 2014 / Accepted: 27 March 2014 / Published: 1 April 2014
Cited by 4 | PDF Full-text (1077 KB) | HTML Full-text | XML Full-text
Abstract
A miniature fiber-optic dosimeter (FOD) system was fabricated using a plastic scintillating fiber, a plastic optical fiber, and a multi-pixel photon counter to measure real-time entrance surface dose (ESD) during radiation diagnosis. Under varying exposure parameters of a digital radiography (DR) system, [...] Read more.
A miniature fiber-optic dosimeter (FOD) system was fabricated using a plastic scintillating fiber, a plastic optical fiber, and a multi-pixel photon counter to measure real-time entrance surface dose (ESD) during radiation diagnosis. Under varying exposure parameters of a digital radiography (DR) system, we measured the scintillating light related to the ESD using the sensing probe of the FOD, which was placed at the center of the beam field on an anthropomorphic thorax phantom. Also, we obtained DR images using a flat panel detector of the DR system to evaluate the effects of the dosimeter on image artifacts during posteroanterior (PA) chest radiography. From the experimental results, the scintillation output signals of the FOD were similar to the ESDs including backscatter simultaneously obtained using a semiconductor dosimeter. We demonstrated that the proposed miniature FOD can be used to measure real-time ESDs with minimization of DR image artifacts in the X-ray energy range of diagnostic radiology. Full article
(This article belongs to the Special Issue Photonic Sensors for Industrial, Environmental and Health Monitoring)
Open AccessArticle Monocular SLAM for Autonomous Robots with Enhanced Features Initialization
Sensors 2014, 14(4), 6317-6337; doi:10.3390/s140406317
Received: 6 January 2014 / Revised: 19 March 2014 / Accepted: 26 March 2014 / Published: 2 April 2014
Cited by 9 | PDF Full-text (1703 KB) | HTML Full-text | XML Full-text
Abstract
This work presents a variant approach to the monocular SLAM problem focused in exploiting the advantages of a human-robot interaction (HRI) framework. Based upon the delayed inverse-depth feature initialization SLAM (DI-D SLAM), a known monocular technique, several but crucial modifications are introduced [...] Read more.
This work presents a variant approach to the monocular SLAM problem focused in exploiting the advantages of a human-robot interaction (HRI) framework. Based upon the delayed inverse-depth feature initialization SLAM (DI-D SLAM), a known monocular technique, several but crucial modifications are introduced taking advantage of data from a secondary monocular sensor, assuming that this second camera is worn by a human. The human explores an unknown environment with the robot, and when their fields of view coincide, the cameras are considered a pseudo-calibrated stereo rig to produce estimations for depth through parallax. These depth estimations are used to solve a related problem with DI-D monocular SLAM, namely, the requirement of a metric scale initialization through known artificial landmarks. The same process is used to improve the performance of the technique when introducing new landmarks into the map. The convenience of the approach taken to the stereo estimation, based on SURF features matching, is discussed. Experimental validation is provided through results from real data with results showing the improvements in terms of more features correctly initialized, with reduced uncertainty, thus reducing scale and orientation drift. Additional discussion in terms of how a real-time implementation could take advantage of this approach is provided. Full article
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Open AccessArticle Time-Resolved Photoluminescence Spectroscopy and Imaging: New Approaches to the Analysis of Cultural Heritage and Its Degradation
Sensors 2014, 14(4), 6338-6355; doi:10.3390/s140406338
Received: 11 March 2014 / Revised: 31 March 2014 / Accepted: 31 March 2014 / Published: 2 April 2014
Cited by 6 | PDF Full-text (583 KB) | HTML Full-text | XML Full-text
Abstract
Applications of time-resolved photoluminescence spectroscopy (TRPL) and fluorescence lifetime imaging (FLIM) to the analysis of cultural heritage are presented. Examples range from historic wall paintings and stone sculptures to 20th century iconic design objects. A detailed description of the instrumentation developed and [...] Read more.
Applications of time-resolved photoluminescence spectroscopy (TRPL) and fluorescence lifetime imaging (FLIM) to the analysis of cultural heritage are presented. Examples range from historic wall paintings and stone sculptures to 20th century iconic design objects. A detailed description of the instrumentation developed and employed for analysis in the laboratory or in situ is given. Both instruments rely on a pulsed laser source coupled to a gated detection system, but differ in the type of information they provide. Applications of FLIM to the analysis of model samples and for the in-situ monitoring of works of art range from the analysis of organic materials and pigments in wall paintings, the detection of trace organic substances on stone sculptures, to the mapping of luminescence in late 19th century paintings. TRPL and FLIM are employed as sensors for the detection of the degradation of design objects made in plastic. Applications and avenues for future research are suggested. Full article
(This article belongs to the Special Issue Sensors for Cultural Heritage Diagnostics)
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Open AccessArticle Dielectrophoretic Manipulation and Separation of Microparticles Using Microarray Dot Electrodes
Sensors 2014, 14(4), 6356-6369; doi:10.3390/s140406356
Received: 15 November 2013 / Revised: 7 March 2014 / Accepted: 14 March 2014 / Published: 3 April 2014
Cited by 8 | PDF Full-text (1457 KB) | HTML Full-text | XML Full-text
Abstract
This paper introduces a dielectrophoretic system for the manipulation and separation of microparticles. The system is composed of five layers and utilizes microarray dot electrodes. We validated our system by conducting size-dependent manipulation and separation experiments on 1, 5 and 15 μm [...] Read more.
This paper introduces a dielectrophoretic system for the manipulation and separation of microparticles. The system is composed of five layers and utilizes microarray dot electrodes. We validated our system by conducting size-dependent manipulation and separation experiments on 1, 5 and 15 μm polystyrene particles. Our findings confirm the capability of the proposed device to rapidly and efficiently manipulate and separate microparticles of various dimensions, utilizing positive and negative dielectrophoresis (DEP) effects. Larger size particles were repelled and concentrated in the center of the dot by negative DEP, while the smaller sizes were attracted and collected by the edge of the dot by positive DEP. Full article
(This article belongs to the Special Issue Microarray Sensors)
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Open AccessArticle Video-Based Human Activity Recognition Using Multilevel Wavelet Decomposition and Stepwise Linear Discriminant Analysis
Sensors 2014, 14(4), 6370-6392; doi:10.3390/s140406370
Received: 19 February 2014 / Revised: 26 March 2014 / Accepted: 26 March 2014 / Published: 4 April 2014
Cited by 5 | PDF Full-text (829 KB) | HTML Full-text | XML Full-text
Abstract
Video-based human activity recognition (HAR) means the analysis of motions and behaviors of human from the low level sensors. Over the last decade, automatic HAR is an exigent research area and is considered a significant concern in the field of computer vision [...] Read more.
Video-based human activity recognition (HAR) means the analysis of motions and behaviors of human from the low level sensors. Over the last decade, automatic HAR is an exigent research area and is considered a significant concern in the field of computer vision and pattern recognition. In this paper, we have presented a robust and an accurate activity recognition system called WS-HAR that consists of wavelet transform coupled with stepwise linear discriminant analysis (SWLDA) followed by hidden Markov model (HMM). Symlet wavelet has been employed in order to extract the features from the activity frames. The most prominent features were selected by proposing a robust technique called stepwise linear discriminant analysis (SWLDA) that focuses on selecting the localized features from the activity frames and discriminating their class based on regression values (i.e., partial F-test values). Finally, we applied a well-known sequential classifier called hidden Markov model (HMM) to give the appropriate labels to the activities. In order to validate the performance of the WS-HAR, we utilized two publicly available standard datasets under two different experimental settings, n??fold cross validation scheme based on subjects; and a set of experiments was performed in order to show the effectiveness of each approach. The weighted average recognition rate for the WS-HAR was 97% across the two different datasets that is a significant improvement in classication accuracy compared to the existing well-known statistical and state-of-the-art methods. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle Surface Roughness Model Based on Force Sensors for the Prediction of the Tool Wear
Sensors 2014, 14(4), 6393-6408; doi:10.3390/s140406393
Received: 7 February 2014 / Revised: 12 March 2014 / Accepted: 28 March 2014 / Published: 4 April 2014
Cited by 4 | PDF Full-text (470 KB) | HTML Full-text | XML Full-text
Abstract
In this study, a methodology has been developed with the objective of evaluating the surface roughness obtained during turning processes by measuring the signals detected by a force sensor under the same cutting conditions. In this way, the surface quality achieved along [...] Read more.
In this study, a methodology has been developed with the objective of evaluating the surface roughness obtained during turning processes by measuring the signals detected by a force sensor under the same cutting conditions. In this way, the surface quality achieved along the process is correlated to several parameters of the cutting forces (thrust forces, feed forces and cutting forces), so the effect that the tool wear causes on the surface roughness is evaluated. In a first step, the best cutting conditions (cutting parameters and radius of tool) for a certain quality surface requirement were found for pieces of UNS A97075. Next, with this selection a model of surface roughness based on the cutting forces was developed for different states of wear that simulate the behaviour of the tool throughout its life. The validation of this model reveals that it was effective for approximately 70% of the surface roughness values obtained. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle Inflammable Gas Mixture Detection with a Single Catalytic Sensor Based on the Electric Field Effect
Sensors 2014, 14(4), 6409-6418; doi:10.3390/s140406409
Received: 3 March 2014 / Revised: 27 March 2014 / Accepted: 1 April 2014 / Published: 8 April 2014
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Abstract
This paper introduces a new way to analyze mixtures of inflammable gases with a single catalytic sensor. The analysis technology was based on a new finding that an electric field on the catalytic sensor can change the output sensitivity of the sensor. [...] Read more.
This paper introduces a new way to analyze mixtures of inflammable gases with a single catalytic sensor. The analysis technology was based on a new finding that an electric field on the catalytic sensor can change the output sensitivity of the sensor. The analysis of mixed inflammable gases results from processing the output signals obtained by adjusting the electric field parameter of the catalytic sensor. For the signal process, we designed a group of equations based on the heat balance of catalytic sensor expressing the relationship between the output signals and the concentration of gases. With these equations and the outputs of different electric fields, the gas concentration in a mixture could be calculated. In experiments, a mixture of methane, butane and ethane was analyzed by this new method, and the results showed that the concentration of each gas in the mixture could be detected with a single catalytic sensor, and the maximum relative error was less than 5%. Full article
(This article belongs to the Section Chemical Sensors)
Open AccessArticle CPAC: Energy-Efficient Data Collection through Adaptive Selection of Compression Algorithms for Sensor Networks
Sensors 2014, 14(4), 6419-6442; doi:10.3390/s140406419
Received: 10 February 2014 / Revised: 24 March 2014 / Accepted: 3 April 2014 / Published: 9 April 2014
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Abstract
We propose a technique to optimize the energy efficiency of data collection in sensor networks by exploiting a selective data compression. To achieve such an aim, we need to make optimal decisions regarding two aspects: (1) which sensor nodes should execute compression; [...] Read more.
We propose a technique to optimize the energy efficiency of data collection in sensor networks by exploiting a selective data compression. To achieve such an aim, we need to make optimal decisions regarding two aspects: (1) which sensor nodes should execute compression; and (2) which compression algorithm should be used by the selected sensor nodes. We formulate this problem into binary integer programs, which provide an energy-optimal solution under the given latency constraint. Our simulation results show that the optimization algorithm significantly reduces the overall network-wide energy consumption for data collection. In the environment having a stationary sink from stationary sensor nodes, the optimized data collection shows 47% energy savings compared to the state-of-the-art collection protocol (CTP). More importantly, we demonstrate that our optimized data collection provides the best performance in an intermittent network under high interference. In such networks, we found that the selective compression for frequent packet retransmissions saves up to 55% energy compared to the best known protocol. Full article
(This article belongs to the Section Sensor Networks)
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Open AccessArticle Security Analysis and Improvements of Two-Factor Mutual Authentication with Key Agreement in Wireless Sensor Networks
Sensors 2014, 14(4), 6443-6462; doi:10.3390/s140406443
Received: 22 January 2014 / Revised: 30 March 2014 / Accepted: 31 March 2014 / Published: 9 April 2014
Cited by 15 | PDF Full-text (665 KB) | HTML Full-text | XML Full-text
Abstract
User authentication and key management are two important security issues in WSNs (Wireless Sensor Networks). In WSNs, for some applications, the user needs to obtain real-time data directly from sensors and several user authentication schemes have been recently proposed for this case. [...] Read more.
User authentication and key management are two important security issues in WSNs (Wireless Sensor Networks). In WSNs, for some applications, the user needs to obtain real-time data directly from sensors and several user authentication schemes have been recently proposed for this case. We found that a two-factor mutual authentication scheme with key agreement in WSNs is vulnerable to gateway node bypassing attacks and user impersonation attacks using secret data stored in sensor nodes or an attacker’s own smart card. In this paper, we propose an improved scheme to overcome these security weaknesses by storing secret data in unique ciphertext form in each node. In addition, our proposed scheme should provide not only security, but also efficiency since sensors in a WSN operate with resource constraints such as limited power, computation, and storage space. Therefore, we also analyze the performance of the proposed scheme by comparing its computation and communication costs with those of other schemes. Full article
(This article belongs to the Section Sensor Networks)
Open AccessArticle Rhodotorula Mucilaginosa, a Quorum Quenching Yeast Exhibiting Lactonase Activity Isolated from a Tropical Shoreline
Sensors 2014, 14(4), 6463-6473; doi:10.3390/s140406463
Received: 26 January 2014 / Revised: 19 March 2014 / Accepted: 21 March 2014 / Published: 9 April 2014
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Abstract
Two microbial isolates from a Malaysian shoreline were found to be capable of degrading N-acylhomoserine lactones. Both Matrix Assisted Laser Desorption Ionization-Time of Flight-Mass Spectrometry and 18S rDNA phylogenetic analyses confirmed that these isolates are Rhodotorula mucilaginosa. Quorum quenching activities [...] Read more.
Two microbial isolates from a Malaysian shoreline were found to be capable of degrading N-acylhomoserine lactones. Both Matrix Assisted Laser Desorption Ionization-Time of Flight-Mass Spectrometry and 18S rDNA phylogenetic analyses confirmed that these isolates are Rhodotorula mucilaginosa. Quorum quenching activities were detected by a series of bioassays and rapid resolution liquid chromatography analysis. The isolates were able to degrade various quorum sensing molecules namely N-hexanoyl-L-homoserine lactone (C6-HSL), N-(3-oxo-hexanoyl)-L-homoserine lactone (3-oxo-C6-HSL) and N-(3-hydroxyhexanoyl)-L-homoserine lactone (3-hydroxy-C6-HSL). Using a relactonisation assay to verify the quorum quenching mechanism, it is confirmed that Rh. mucilaginosa degrades the quorum sensing molecules via lactonase activity. To the best of our knowledge, this is the first documentation of the fact that Rh. mucilaginosa has activity against a broad range of AHLs namely C6-HSL, 3-oxo-C6-HSL and 3-hydroxy-C6-HSL. Full article
(This article belongs to the Section Biosensors)
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Open AccessArticle Window Size Impact in Human Activity Recognition
Sensors 2014, 14(4), 6474-6499; doi:10.3390/s140406474
Received: 10 December 2013 / Revised: 19 March 2014 / Accepted: 26 March 2014 / Published: 9 April 2014
Cited by 26 | PDF Full-text (1047 KB) | HTML Full-text | XML Full-text
Abstract
Signal segmentation is a crucial stage in the activity recognition process; however, this has been rarely and vaguely characterized so far. Windowing approaches are normally used for segmentation, but no clear consensus exists on which window size should be preferably employed. In [...] Read more.
Signal segmentation is a crucial stage in the activity recognition process; however, this has been rarely and vaguely characterized so far. Windowing approaches are normally used for segmentation, but no clear consensus exists on which window size should be preferably employed. In fact, most designs normally rely on figures used in previous works, but with no strict studies that support them. Intuitively, decreasing the window size allows for a faster activity detection, as well as reduced resources and energy needs. On the contrary, large data windows are normally considered for the recognition of complex activities. In this work, we present an extensive study to fairly characterize the windowing procedure, to determine its impact within the activity recognition process and to help clarify some of the habitual assumptions made during the recognition system design. To that end, some of the most widely used activity recognition procedures are evaluated for a wide range of window sizes and activities. From the evaluation, the interval 1–2 s proves to provide the best trade-off between recognition speed and accuracy. The study, specifically intended for on-body activity recognition systems, further provides designers with a set of guidelines devised to facilitate the system definition and configuration according to the particular application requirements and target activities. Full article
(This article belongs to the Special Issue Wearable Gait Sensors)
Open AccessArticle EPCGen2 Pseudorandom Number Generators: Analysis of J3Gen
Sensors 2014, 14(4), 6500-6515; doi:10.3390/s140406500
Received: 18 December 2013 / Revised: 1 April 2014 / Accepted: 2 April 2014 / Published: 9 April 2014
Cited by 5 | PDF Full-text (429 KB) | HTML Full-text | XML Full-text
Abstract
This paper analyzes the cryptographic security of J3Gen, a promising pseudo random number generator for low-cost passive Radio Frequency Identification (RFID) tags. Although J3Gen has been shown to fulfill the randomness criteria set by the EPCglobal Gen2 standard and is intended for [...] Read more.
This paper analyzes the cryptographic security of J3Gen, a promising pseudo random number generator for low-cost passive Radio Frequency Identification (RFID) tags. Although J3Gen has been shown to fulfill the randomness criteria set by the EPCglobal Gen2 standard and is intended for security applications, we describe here two cryptanalytic attacks that question its security claims: (i) a probabilistic attack based on solving linear equation systems; and (ii) a deterministic attack based on the decimation of the output sequence. Numerical results, supported by simulations, show that for the specific recommended values of the configurable parameters, a low number of intercepted output bits are enough to break J3Gen. We then make some recommendations that address these issues. Full article
(This article belongs to the Section Sensor Networks)
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Open AccessArticle New System for Tracking a Device for Diagnosing Scalp Skin
Sensors 2014, 14(4), 6516-6534; doi:10.3390/s140406516
Received: 13 November 2013 / Revised: 13 March 2014 / Accepted: 30 March 2014 / Published: 9 April 2014
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Abstract
In scalp skin examinations, it is difficult to find a previously treated region on a patient’s scalp through images captured by a camera attached to a diagnostic device because the zoom lens on camera has a small field of view. Thus, doctors [...] Read more.
In scalp skin examinations, it is difficult to find a previously treated region on a patient’s scalp through images captured by a camera attached to a diagnostic device because the zoom lens on camera has a small field of view. Thus, doctors manually record the region on a chart or manually mark the region. However, this process is slow and inconveniences the patient. Thus, we propose a new system for tracking the diagnostic device for the scalp skin of patients. Our research is novel in four ways. First, our proposed system consists of two cameras to capture the face and the diagnostic device. Second, the user can easily set the position of camera to capture the diagnostic device by manually moving a frame to which the camera is attached. Third, the position of patient’s nostrils and corners of the eyes are detected to align the position of his/her head more accurately with the recorded position from previous sessions. Fourth, the position of the diagnostic device is continuously tracked during the examination through images that help detect the position of the color marker attached to the device. Experimental results show that our system has a higher performance than conventional method. Full article
(This article belongs to the Special Issue Biomedical Sensors and Systems)
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Open AccessArticle Low-Power Wearable Respiratory Sound Sensing
Sensors 2014, 14(4), 6535-6566; doi:10.3390/s140406535
Received: 24 December 2013 / Revised: 19 March 2014 / Accepted: 30 March 2014 / Published: 9 April 2014
Cited by 8 | PDF Full-text (2135 KB) | HTML Full-text | XML Full-text
Abstract
Building upon the findings from the field of automated recognition of respiratory sound patterns, we propose a wearable wireless sensor implementing on-board respiratory sound acquisition and classification, to enable continuous monitoring of symptoms, such as asthmatic wheezing. Low-power consumption of such a [...] Read more.
Building upon the findings from the field of automated recognition of respiratory sound patterns, we propose a wearable wireless sensor implementing on-board respiratory sound acquisition and classification, to enable continuous monitoring of symptoms, such as asthmatic wheezing. Low-power consumption of such a sensor is required in order to achieve long autonomy. Considering that the power consumption of its radio is kept minimal if transmitting only upon (rare) occurrences of wheezing, we focus on optimizing the power consumption of the digital signal processor (DSP). Based on a comprehensive review of asthmatic wheeze detection algorithms, we analyze the computational complexity of common features drawn from short-time Fourier transform (STFT) and decision tree classification. Four algorithms were implemented on a low-power TMS320C5505 DSP. Their classification accuracies were evaluated on a dataset of prerecorded respiratory sounds in two operating scenarios of different detection fidelities. The execution times of all algorithms were measured. The best classification accuracy of over 92%, while occupying only 2.6% of the DSP’s processing time, is obtained for the algorithm featuring the time-frequency tracking of shapes of crests originating from wheezing, with spectral features modeled using energy. Full article
(This article belongs to the Special Issue Biomedical Sensors and Systems)
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Open AccessArticle A Novel High-Sensitivity, Low-Power, Liquid Crystal Temperature Sensor
Sensors 2014, 14(4), 6571-6583; doi:10.3390/s140406571
Received: 13 March 2014 / Revised: 2 April 2014 / Accepted: 3 April 2014 / Published: 9 April 2014
Cited by 4 | PDF Full-text (1113 KB) | HTML Full-text | XML Full-text
Abstract
A novel temperature sensor based on nematic liquid crystal permittivity as a sensing magnitude, is presented. This sensor consists of a specific micrometric structure that gives considerable advantages from other previous related liquid crystal (LC) sensors. The analytical study reveals that permittivity [...] Read more.
A novel temperature sensor based on nematic liquid crystal permittivity as a sensing magnitude, is presented. This sensor consists of a specific micrometric structure that gives considerable advantages from other previous related liquid crystal (LC) sensors. The analytical study reveals that permittivity change with temperature is introduced in a hyperbolic cosine function, increasing the sensitivity term considerably. The experimental data has been obtained for ranges from −6 °C to 100 °C. Despite this, following the LC datasheet, theoretical ranges from −40 °C to 109 °C could be achieved. These results have revealed maximum sensitivities of 33 mVrms/°C for certain temperature ranges; three times more than of most silicon temperature sensors. As it was predicted by the analytical study, the micrometric size of the proposed structure produces a high output voltage. Moreover the voltage’s sensitivity to temperature response can be controlled by the applied voltage. This response allows temperature measurements to be carried out without any amplification or conditioning circuitry, with very low power consumption. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle Uncertain Data Clustering-Based Distance Estimation in Wireless Sensor Networks
Sensors 2014, 14(4), 6584-6605; doi:10.3390/s140406584
Received: 19 December 2013 / Revised: 24 March 2014 / Accepted: 28 March 2014 / Published: 9 April 2014
Cited by 8 | PDF Full-text (578 KB) | HTML Full-text | XML Full-text
Abstract
For communication distance estimations in Wireless Sensor Networks (WSNs), the RSSI (Received Signal Strength Indicator) value is usually assumed to have a linear relationship with the logarithm of the communication distance. However, this is not always true in reality because there are [...] Read more.
For communication distance estimations in Wireless Sensor Networks (WSNs), the RSSI (Received Signal Strength Indicator) value is usually assumed to have a linear relationship with the logarithm of the communication distance. However, this is not always true in reality because there are always uncertainties in RSSI readings due to obstacles, wireless interferences, etc. In this paper, we specifically propose a novel RSSI-based communication distance estimation method based on the idea of interval data clustering. We first use interval data, combined with statistical information of RSSI values, to interpret the distribution characteristics of RSSI. We then use interval data hard clustering and soft clustering to overcome different levels of RSSI uncertainties, respectively. We have used real RSSI measurements to evaluate our communication distance estimation method in three representative wireless environments. Extensive experimental results show that our communication distance estimation method can effectively achieve promising estimation accuracy with high efficiency when compared to other state-of-art approaches. Full article
(This article belongs to the Section Sensor Networks)
Open AccessArticle Luminescent Measurement Systems for the Investigation of a Scramjet Inlet-Isolator
Sensors 2014, 14(4), 6606-6632; doi:10.3390/s140406606
Received: 14 November 2013 / Revised: 28 March 2014 / Accepted: 2 April 2014 / Published: 9 April 2014
Cited by 3 | PDF Full-text (7339 KB) | HTML Full-text | XML Full-text
Abstract
Scramjets have become a main focus of study for many researchers, due to their application as propulsive devices in hypersonic flight. This entails a detailed understanding of the fluid mechanics involved to be able to design and operate these engines with maximum [...] Read more.
Scramjets have become a main focus of study for many researchers, due to their application as propulsive devices in hypersonic flight. This entails a detailed understanding of the fluid mechanics involved to be able to design and operate these engines with maximum efficiency even at their off-design conditions. It is the objective of the present cold-flow investigation to study and analyse experimentally the mechanics of the fluid structures encountered within a generic scramjet inlet at M = 5. Traditionally, researchers have to rely on stream-thrust analysis, which requires the complex setup of a mass flow meter, a force balance and a heat transducer in order to measure inlet-isolator performance. Alternatively, the pitot rake could be positioned at inlet-isolator exit plane, but this method is intrusive to the flow, and the number of pitot tubes is limited by the model size constraint. Thus, this urgent need for a better flow diagnostics method is addressed in this paper. Pressure-sensitive paint (PSP) has been applied to investigate the flow characteristics on the compression ramp, isolator surface and isolator sidewall. Numerous shock-shock interactions, corner and shoulder separation regions, as well as shock trains were captured by the luminescent system. The performance of the scramjet inlet-isolator has been shown to improve when operated in a modest angle of attack. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle Thermal-Infrared Pedestrian ROI Extraction through Thermal and Motion Information Fusion
Sensors 2014, 14(4), 6666-6676; doi:10.3390/s140406666
Received: 14 March 2014 / Revised: 2 April 2014 / Accepted: 4 April 2014 / Published: 10 April 2014
Cited by 10 | PDF Full-text (420 KB) | HTML Full-text | XML Full-text
Abstract
This paper investigates the robustness of a new thermal-infrared pedestrian detection system under different outdoor environmental conditions. In first place the algorithm for pedestrian ROI extraction in thermal-infrared video based on both thermal and motion information is introduced. Then, the evaluation of [...] Read more.
This paper investigates the robustness of a new thermal-infrared pedestrian detection system under different outdoor environmental conditions. In first place the algorithm for pedestrian ROI extraction in thermal-infrared video based on both thermal and motion information is introduced. Then, the evaluation of the proposal is detailed after describing the complete thermal and motion information fusion. In this sense, the environment chosen for evaluation is described, and the twelve test sequences are specified. For each of the sequences captured from a forward-looking infrared FLIR A-320 camera, the paper explains the weather and light conditions under which it was captured. The results allow us to draw firm conclusions about the conditions under which it can be affirmed that it is efficient to use our thermal-infrared proposal to robustly extract human ROIs. Full article
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Open AccessArticle An Upper-Limb Power-Assist Exoskeleton Using Proportional Myoelectric Control
Sensors 2014, 14(4), 6677-6694; doi:10.3390/s140406677
Received: 12 November 2013 / Revised: 17 February 2014 / Accepted: 20 March 2014 / Published: 10 April 2014
Cited by 11 | PDF Full-text (3286 KB) | HTML Full-text | XML Full-text
Abstract
We developed an upper-limb power-assist exoskeleton actuated by pneumatic muscles. The exoskeleton included two metal links: a nylon joint, four size-adjustable carbon fiber bracers, a potentiometer and two pneumatic muscles. The proportional myoelectric control method was proposed to control the exoskeleton according [...] Read more.
We developed an upper-limb power-assist exoskeleton actuated by pneumatic muscles. The exoskeleton included two metal links: a nylon joint, four size-adjustable carbon fiber bracers, a potentiometer and two pneumatic muscles. The proportional myoelectric control method was proposed to control the exoskeleton according to the user’s motion intention in real time. With the feature extraction procedure and the classification (back-propagation neural network), an electromyogram (EMG)-angle model was constructed to be used for pattern recognition. Six healthy subjects performed elbow flexion-extension movements under four experimental conditions: (1) holding a 1-kg load, wearing the exoskeleton, but with no actuation and for different periods (2-s, 4-s and 8-s periods); (2) holding a 1-kg load, without wearing the exoskeleton, for a fixed period; (3) holding a 1-kg load, wearing the exoskeleton, but with no actuation, for a fixed period; (4) holding a 1-kg load, wearing the exoskeleton under proportional myoelectric control, for a fixed period. The EMG signals of the biceps brachii, the brachioradialis, the triceps brachii and the anconeus and the angle of the elbow were collected. The control scheme’s reliability and power-assist effectiveness were evaluated in the experiments. The results indicated that the exoskeleton could be controlled by the user’s motion intention in real time and that it was useful for augmenting arm performance with neurological signal control, which could be applied to assist in elbow rehabilitation after neurological injury. Full article
(This article belongs to the Special Issue Biomedical Sensors and Systems)
Open AccessCommunication Optimization of Dengue Immunoassay by Label-Free Interferometric Optical Detection Method
Sensors 2014, 14(4), 6695-6700; doi:10.3390/s140406695
Received: 29 December 2013 / Revised: 10 March 2014 / Accepted: 3 April 2014 / Published: 10 April 2014
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Abstract
In this communication we report a direct immunoassay for detecting dengue virus by means of a label-free interferometric optical detection method. We also demonstrate how we can optimize this sensing response by adding a blocking step able to significantly enhance the optical [...] Read more.
In this communication we report a direct immunoassay for detecting dengue virus by means of a label-free interferometric optical detection method. We also demonstrate how we can optimize this sensing response by adding a blocking step able to significantly enhance the optical sensing response. The blocking reagent used for this optimization is a dry milk diluted in phosphate buffered saline. The recognition curve of dengue virus over the proposed surface sensor demonstrates the capacity of this method to be applied in Point of Care technology. Full article
(This article belongs to the Special Issue Photonic Sensors for Industrial, Environmental and Health Monitoring)
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Open AccessArticle A Secure-Enhanced Data Aggregation Based on ECC in Wireless Sensor Networks
Sensors 2014, 14(4), 6701-6721; doi:10.3390/s140406701
Received: 16 December 2013 / Revised: 24 March 2014 / Accepted: 8 April 2014 / Published: 11 April 2014
Cited by 5 | PDF Full-text (622 KB) | HTML Full-text | XML Full-text
Abstract
Data aggregation is an important technique for reducing the energy consumption of sensor nodes in wireless sensor networks (WSNs). However, compromised aggregators may forge false values as the aggregated results of their child nodes in order to conduct stealthy attacks or steal [...] Read more.
Data aggregation is an important technique for reducing the energy consumption of sensor nodes in wireless sensor networks (WSNs). However, compromised aggregators may forge false values as the aggregated results of their child nodes in order to conduct stealthy attacks or steal other nodes’ privacy. This paper proposes a Secure-Enhanced Data Aggregation based on Elliptic Curve Cryptography (SEDA-ECC). The design of SEDA-ECC is based on the principles of privacy homomorphic encryption (PH) and divide-and-conquer. An aggregation tree disjoint method is first adopted to divide the tree into three subtrees of similar sizes, and a PH-based aggregation is performed in each subtree to generate an aggregated subtree result. Then the forged result can be identified by the base station (BS) by comparing the aggregated count value. Finally, the aggregated result can be calculated by the BS according to the remaining results that have not been forged. Extensive analysis and simulations show that SEDA-ECC can achieve the highest security level on the aggregated result with appropriate energy consumption compared with other asymmetric schemes. Full article
(This article belongs to the Section Sensor Networks)
Open AccessArticle Modeling and Manufacturing of a Micromachined Magnetic Sensor Using the CMOS Process without Any Post-Process
Sensors 2014, 14(4), 6722-6733; doi:10.3390/s140406722
Received: 18 February 2014 / Revised: 31 March 2014 / Accepted: 8 April 2014 / Published: 11 April 2014
Cited by 1 | PDF Full-text (722 KB) | HTML Full-text | XML Full-text
Abstract
The modeling and fabrication of a magnetic microsensor based on a magneto-transistor were presented. The magnetic sensor is fabricated by the commercial 0.18 mm complementary metal oxide semiconductor (CMOS) process without any post-process. The finite element method (FEM) software Sentaurus TCAD is [...] Read more.
The modeling and fabrication of a magnetic microsensor based on a magneto-transistor were presented. The magnetic sensor is fabricated by the commercial 0.18 mm complementary metal oxide semiconductor (CMOS) process without any post-process. The finite element method (FEM) software Sentaurus TCAD is utilized to analyze the electrical properties and carriers motion path of the magneto-transistor. A readout circuit is used to amplify the voltage difference of the bases into the output voltage. Experiments show that the sensitivity of the magnetic sensor is 354 mV/T at the supply current of 4 mA. Full article
Open AccessArticle Object Detection Techniques Applied on Mobile Robot Semantic Navigation
Sensors 2014, 14(4), 6734-6757; doi:10.3390/s140406734
Received: 20 January 2014 / Revised: 22 March 2014 / Accepted: 27 March 2014 / Published: 11 April 2014
Cited by 5 | PDF Full-text (6388 KB) | HTML Full-text | XML Full-text
Abstract
The future of robotics predicts that robots will integrate themselves more every day with human beings and their environments. To achieve this integration, robots need to acquire information about the environment and its objects. There is a big need for algorithms to [...] Read more.
The future of robotics predicts that robots will integrate themselves more every day with human beings and their environments. To achieve this integration, robots need to acquire information about the environment and its objects. There is a big need for algorithms to provide robots with these sort of skills, from the location where objects are needed to accomplish a task up to where these objects are considered as information about the environment. This paper presents a way to provide mobile robots with the ability-skill to detect objets for semantic navigation. This paper aims to use current trends in robotics and at the same time, that can be exported to other platforms. Two methods to detect objects are proposed, contour detection and a descriptor based technique, and both of them are combined to overcome their respective limitations. Finally, the code is tested on a real robot, to prove its accuracy and efficiency. Full article
Open AccessArticle Spatial Estimation of Sub-Hour Global Horizontal Irradiance Based on Official Observations and Remote Sensors
Sensors 2014, 14(4), 6758-6787; doi:10.3390/s140406758
Received: 5 November 2013 / Revised: 24 March 2014 / Accepted: 3 April 2014 / Published: 11 April 2014
Cited by 4 | PDF Full-text (1623 KB) | HTML Full-text | XML Full-text
Abstract
This study was motivated by the need to improve densification of Global Horizontal Irradiance (GHI) observations, increasing the number of surface weather stations that observe it, using sensors with a sub-hour periodicity and examining the methods of spatial GHI estimation (by interpolation) [...] Read more.
This study was motivated by the need to improve densification of Global Horizontal Irradiance (GHI) observations, increasing the number of surface weather stations that observe it, using sensors with a sub-hour periodicity and examining the methods of spatial GHI estimation (by interpolation) with that periodicity in other locations. The aim of the present research project is to analyze the goodness of 15-minute GHI spatial estimations for five methods in the territory of Spain (three geo-statistical interpolation methods, one deterministic method and the HelioSat2 method, which is based on satellite images). The research concludes that, when the work area has adequate station density, the best method for estimating GHI every 15 min is Regression Kriging interpolation using GHI estimated from satellite images as one of the input variables. On the contrary, when station density is low, the best method is estimating GHI directly from satellite images. A comparison between the GHI observed by volunteer stations and the estimation model applied concludes that 67% of the volunteer stations analyzed present values within the margin of error (average of ±2 standard deviations). Full article
(This article belongs to the Section Remote Sensors)
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Open AccessArticle Quorum Sensing Activity of Hafnia alvei Isolated from Packed Food
Sensors 2014, 14(4), 6788-6796; doi:10.3390/s140406788
Received: 2 March 2014 / Revised: 2 April 2014 / Accepted: 8 April 2014 / Published: 14 April 2014
Cited by 2 | PDF Full-text (363 KB) | HTML Full-text | XML Full-text
Abstract
Quorum sensing (QS) is a mechanism adopted by bacteria to regulate expression of genes according to population density. N-acylhomoserine lactones (AHLs) are a type of QS signalling molecules commonly found in Gram-negative bacteria which have been reported to play a role [...] Read more.
Quorum sensing (QS) is a mechanism adopted by bacteria to regulate expression of genes according to population density. N-acylhomoserine lactones (AHLs) are a type of QS signalling molecules commonly found in Gram-negative bacteria which have been reported to play a role in microbial spoilage of foods and pathogenesis. In this study, we isolated an AHL-producing Hafnia alvei strain (FB1) from spherical fish pastes. Analysis via high resolution triple quadrupole liquid chromatography/mass spectrometry (LC/MS) on extracts from the spent supernatant of H. alvei FB1 revealed the existence of two short chain AHLs: N-(3-oxohexanoyl) homoserine lactone (3-oxo-C6-HSL) and N-(3-oxo- octanoyl) homoserine lactone (3-oxo-C8-HSL). To our knowledge, this is the first report of the production of AHLs, especially 3-oxo-C8-HSL, by H. alvei. Full article
(This article belongs to the Section Biosensors)
Open AccessArticle Degradation of Phosphate Ester Hydraulic Fluid in Power Station Turbines Investigated by a Three-Magnet Unilateral Magnet Array
Sensors 2014, 14(4), 6797-6805; doi:10.3390/s140406797
Received: 3 December 2013 / Revised: 25 March 2014 / Accepted: 28 March 2014 / Published: 14 April 2014
Cited by 4 | PDF Full-text (537 KB) | HTML Full-text | XML Full-text
Abstract
A three-magnet array unilateral NMR sensor with a homogeneous sensitive spot was employed for assessing aging of the turbine oils used in two different power stations. The Carr-Purcell-Meiboom-Gill (CPMG) sequence and Inversion Recovery-prepared CPMG were employed for measuring the 1H-NMR transverse [...] Read more.
A three-magnet array unilateral NMR sensor with a homogeneous sensitive spot was employed for assessing aging of the turbine oils used in two different power stations. The Carr-Purcell-Meiboom-Gill (CPMG) sequence and Inversion Recovery-prepared CPMG were employed for measuring the 1H-NMR transverse and longitudinal relaxation times of turbine oils with different service status. Two signal components with different lifetimes were obtained by processing the transverse relaxation curves with a numeric program based on the Inverse Laplace Transformation. The long lifetime components of the transverse relaxation time T2eff and longitudinal relaxation time T1 were chosen to monitor the hydraulic fluid aging. The results demonstrate that an increase of the service time of the turbine oils clearly results in a decrease of T2eff,long and T1,long. This indicates that the T2eff,long and T1,long relaxation times, obtained from the unilateral magnetic resonance measurements, can be applied as indices for degradation of the hydraulic fluid in power station turbines. Full article
(This article belongs to the Special Issue Magnetic Resonance Sensors) Print Edition available
Open AccessArticle Ozone Sensing Based on Palladium Decorated Carbon Nanotubes
Sensors 2014, 14(4), 6806-6818; doi:10.3390/s140406806
Received: 20 February 2014 / Revised: 4 April 2014 / Accepted: 8 April 2014 / Published: 14 April 2014
Cited by 8 | PDF Full-text (343 KB) | HTML Full-text | XML Full-text
Abstract
Multiwall carbon nanotubes (MWCNTs) were easily and efficiently decorated with Pd nanoparticles through a vapor-phase impregnation-decomposition method starting from palladium acetylacetonates. The sensor device consisted on a film of sensitive material (MWCNTs-Pd) deposited by drop coating on platinum interdigitated electrodes on a [...] Read more.
Multiwall carbon nanotubes (MWCNTs) were easily and efficiently decorated with Pd nanoparticles through a vapor-phase impregnation-decomposition method starting from palladium acetylacetonates. The sensor device consisted on a film of sensitive material (MWCNTs-Pd) deposited by drop coating on platinum interdigitated electrodes on a SiO2 substrate. The sensor exhibited a resistance change to ozone (O3) with a response time of 60 s at different temperatures and the capability of detecting concentrations up to 20 ppb. The sensor shows the best response when exposed to O3 at 120 °C. The device shows a very reproducible sensor performance, with high repeatability, full recovery and efficient response. Full article
(This article belongs to the Section Chemical Sensors)
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Open AccessArticle Detection of Freezing of Gait in Parkinson Disease: Preliminary Results
Sensors 2014, 14(4), 6819-6827; doi:10.3390/s140406819
Received: 23 December 2013 / Revised: 9 April 2014 / Accepted: 10 April 2014 / Published: 15 April 2014
Cited by 12 | PDF Full-text (421 KB) | HTML Full-text | XML Full-text
Abstract
Freezing of gait (FOG) is a common symptom in Parkinsonism, which affects the gait pattern and is associated to a fall risk. Automatized FOG episode detection would allow systematic assessment of patient state and objective evaluation of the clinical effects of treatments. [...] Read more.
Freezing of gait (FOG) is a common symptom in Parkinsonism, which affects the gait pattern and is associated to a fall risk. Automatized FOG episode detection would allow systematic assessment of patient state and objective evaluation of the clinical effects of treatments. Techniques have been proposed in the literature to identify FOG episodes based on the frequency properties of inertial sensor signals. Our objective here is to adapt and extend these FOG detectors in order to include other associated gait pattern changes, like festination. The proposed approach is based on a single wireless inertial sensor placed on the patient’s lower limbs. The preliminary experimental results show that existing frequency-based freezing detectors are not sufficient to detect all FOG and festination episodes and that the observation of some gait parameters such as stride length and cadence are valuable inputs to anticipate the occurrence of upcoming FOG events. Full article
(This article belongs to the Special Issue Wearable Gait Sensors)
Open AccessArticle Design of a Broadband Electrical Impedance Matching Network for Piezoelectric Ultrasound Transducers Based on a Genetic Algorithm
Sensors 2014, 14(4), 6828-6843; doi:10.3390/s140406828
Received: 6 January 2014 / Revised: 8 February 2014 / Accepted: 10 April 2014 / Published: 16 April 2014
PDF Full-text (687 KB) | HTML Full-text | XML Full-text
Abstract
An improved method based on a genetic algorithm (GA) is developed to design a broadband electrical impedance matching network for piezoelectric ultrasound transducer. A key feature of the new method is that it can optimize both the topology of the matching network [...] Read more.
An improved method based on a genetic algorithm (GA) is developed to design a broadband electrical impedance matching network for piezoelectric ultrasound transducer. A key feature of the new method is that it can optimize both the topology of the matching network and perform optimization on the components. The main idea of this method is to find the optimal matching network in a set of candidate topologies. Some successful experiences of classical algorithms are absorbed to limit the size of the set of candidate topologies and greatly simplify the calculation process. Both binary-coded GA and real-coded GA are used for topology optimization and components optimization, respectively. Some calculation strategies, such as elitist strategy and clearing niche method, are adopted to make sure that the algorithm can converge to the global optimal result. Simulation and experimental results prove that matching networks with better performance might be achieved by this improved method. Full article
(This article belongs to the Section Sensor Networks)
Open AccessArticle Response Mechanism for Surface Acoustic Wave Gas Sensors Based on Surface-Adsorption
Sensors 2014, 14(4), 6844-6853; doi:10.3390/s140406844
Received: 20 February 2014 / Revised: 12 March 2014 / Accepted: 27 March 2014 / Published: 16 April 2014
Cited by 6 | PDF Full-text (419 KB) | HTML Full-text | XML Full-text
Abstract
A theoretical model is established to describe the response mechanism of surface acoustic wave (SAW) gas sensors based on physical adsorption on the detector surface. Wohljent’s method is utilized to describe the relationship of sensor output (frequency shift of SAW oscillator) and [...] Read more.
A theoretical model is established to describe the response mechanism of surface acoustic wave (SAW) gas sensors based on physical adsorption on the detector surface. Wohljent’s method is utilized to describe the relationship of sensor output (frequency shift of SAW oscillator) and the mass loaded on the detector surface. The Brunauer-Emmett-Teller (BET) formula and its improved form are introduced to depict the adsorption behavior of gas on the detector surface. By combining the two methods, we obtain a theoretical model for the response mechanism of SAW gas sensors. By using a commercial SAW gas chromatography (GC) analyzer, an experiment is performed to measure the frequency shifts caused by different concentration of dimethyl methylphosphonate (DMMP). The parameters in the model are given by fitting the experimental results and the theoretical curve agrees well with the experimental data. Full article
(This article belongs to the Section Chemical Sensors)
Open AccessArticle Integration of Fiber-Optic Sensor Arrays into a Multi-Modal Tactile Sensor Processing System for Robotic End-Effectors
Sensors 2014, 14(4), 6854-6876; doi:10.3390/s140406854
Received: 7 January 2014 / Revised: 1 April 2014 / Accepted: 11 April 2014 / Published: 16 April 2014
Cited by 3 | PDF Full-text (4952 KB) | HTML Full-text | XML Full-text
Abstract
With the increasing complexity of robotic missions and the development towards long-term autonomous systems, the need for multi-modal sensing of the environment increases. Until now, the use of tactile sensor systems has been mostly based on sensing one modality of forces in [...] Read more.
With the increasing complexity of robotic missions and the development towards long-term autonomous systems, the need for multi-modal sensing of the environment increases. Until now, the use of tactile sensor systems has been mostly based on sensing one modality of forces in the robotic end-effector. The use of a multi-modal tactile sensory system is motivated, which combines static and dynamic force sensor arrays together with an absolute force measurement system. This publication is focused on the development of a compact sensor interface for a fiber-optic sensor array, as optic measurement principles tend to have a bulky interface. Mechanical, electrical and software approaches are combined to realize an integrated structure that provides decentralized data pre-processing of the tactile measurements. Local behaviors are implemented using this setup to show the effectiveness of this approach. Full article
(This article belongs to the Special Issue Tactile Sensors and Sensing Systems)
Open AccessArticle Enhance the Pyroelectricity of Polyvinylidene Fluoride by Graphene-Oxide Doping
Sensors 2014, 14(4), 6877-6890; doi:10.3390/s140406877
Received: 13 January 2014 / Revised: 2 April 2014 / Accepted: 4 April 2014 / Published: 16 April 2014
Cited by 8 | PDF Full-text (873 KB) | HTML Full-text | XML Full-text
Abstract
The high quality properties and benefits of graphene-oxide have generated an active area of research where many investigations have shown potential applications in various technological fields. This paper proposes a methodology for enhancing the pyro-electricity of PVDF by graphene-oxide doping. The PVDF [...] Read more.
The high quality properties and benefits of graphene-oxide have generated an active area of research where many investigations have shown potential applications in various technological fields. This paper proposes a methodology for enhancing the pyro-electricity of PVDF by graphene-oxide doping. The PVDF film with graphene-oxide is prepared by the sol-gel method. Firstly, PVDF and graphene-oxide powders are dispersed into dimethylformamide as solvent to form a sol solution. Secondly, the sol solution is deposited on a flexible ITO/PET substrate by spin-coating. Thirdly, the particles in the sol solution are polymerized through baking off the solvent to produce a gel in a state of a continuous network of PVDF and graphene-oxide. The final annealing process pyrolyzes the gel and form a β-phase PVDF film with graphene-oxide doping. A complete study on the process of the graphene oxide doping of PVDF is accomplished. Some key points about the process are addressed based on experiments. The solutions to some key issues are found in this work, such as the porosity of film, the annealing temperature limitation by the use of flexible PET substrate, and the concentrations of PVDF and graphene-oxide. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle IMU-Based Joint Angle Measurement for Gait Analysis
Sensors 2014, 14(4), 6891-6909; doi:10.3390/s140406891
Received: 20 November 2013 / Revised: 20 March 2014 / Accepted: 10 April 2014 / Published: 16 April 2014
Cited by 37 | PDF Full-text (2776 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
This contribution is concerned with joint angle calculation based on inertial measurement data in the context of human motion analysis. Unlike most robotic devices, the human body lacks even surfaces and right angles. Therefore, we focus on methods that avoid assuming certain [...] Read more.
This contribution is concerned with joint angle calculation based on inertial measurement data in the context of human motion analysis. Unlike most robotic devices, the human body lacks even surfaces and right angles. Therefore, we focus on methods that avoid assuming certain orientations in which the sensors are mounted with respect to the body segments. After a review of available methods that may cope with this challenge, we present a set of new methods for: (1) joint axis and position identification; and (2) flexion/extension joint angle measurement. In particular, we propose methods that use only gyroscopes and accelerometers and, therefore, do not rely on a homogeneous magnetic field. We provide results from gait trials of a transfemoral amputee in which we compare the inertial measurement unit (IMU)-based methods to an optical 3D motion capture system. Unlike most authors, we place the optical markers on anatomical landmarks instead of attaching them to the IMUs. Root mean square errors of the knee flexion/extension angles are found to be less than 1° on the prosthesis and about 3° on the human leg. For the plantar/dorsiflexion of the ankle, both deviations are about 1°. Full article
(This article belongs to the Special Issue Wearable Gait Sensors)
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Open AccessArticle Novel Piezoelectric Effect and Surface Plasmon Resonance-Based Elements for MEMS Applications
Sensors 2014, 14(4), 6910-6921; doi:10.3390/s140406910
Received: 30 December 2013 / Revised: 1 April 2014 / Accepted: 11 April 2014 / Published: 17 April 2014
Cited by 2 | PDF Full-text (494 KB) | HTML Full-text | XML Full-text
Abstract
This paper covers research on novel thin films with periodical microstructure—optical elements, exhibiting a combination of piezoelectric and surface plasmon resonance effects. The research results showed that incorporation of Ag nanoparticles in novel piezoelectric—plasmonic elements shift a dominating peak in the visible [...] Read more.
This paper covers research on novel thin films with periodical microstructure—optical elements, exhibiting a combination of piezoelectric and surface plasmon resonance effects. The research results showed that incorporation of Ag nanoparticles in novel piezoelectric—plasmonic elements shift a dominating peak in the visible light spectrum. This optical window is essential in the design of optical elements for sensing systems. Novel optical elements can be tunable under defined bias and change its main grating parameters (depth and width) influencing the response of diffraction efficiencies. These elements allow opening new avenues in the design of more sensitive and multifunctional microdevices. Full article
(This article belongs to the Special Issue Polymeric Micro Sensors and Actuators)
Open AccessArticle An Enhanced Sensing Application Based on a Flexible Projected Capacitive-Sensing Mattress
Sensors 2014, 14(4), 6922-6937; doi:10.3390/s140406922
Received: 24 January 2014 / Revised: 11 April 2014 / Accepted: 14 April 2014 / Published: 17 April 2014
Cited by 3 | PDF Full-text (796 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents a cost-effective sensor system for mattresses that can classify the sleeping posture of an individual and prevent pressure ulcers. This system applies projected capacitive sensing to the field of health care. The charge time (CT) method was used to [...] Read more.
This paper presents a cost-effective sensor system for mattresses that can classify the sleeping posture of an individual and prevent pressure ulcers. This system applies projected capacitive sensing to the field of health care. The charge time (CT) method was used to sensitively and accurately measure the capacitance of the projected electrodes. The required characteristics of the projected capacitor were identified to develop large-area applications for sensory mattresses. The area of the electrodes, the use of shielding, and the increased length of the transmission line were calibrated to more accurately measure the capacitance of the electrodes in large-size applications. To offer the users comfort in the prone position, a flexible substrate was selected and covered with 16 × 20 electrodes. Compared with the static charge sensitive bed (SCSB), our proposed system-flexible projected capacitive-sensing mattress (FPCSM) comes with more electrodes to increase the resolution of posture identification. As for the body pressure system (BPS), the FPCSM has advantages such as lower cost, higher aging-resistance capability, and the ability to sense the capacitance of the covered regions without physical contact. The proposed guard ring design effectively absorbs the noise and interrupts leakage paths. The projected capacitive electrode is suitable for proximity-sensing applications and succeeds at quickly recognizing the sleeping pattern of the user. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle A Discriminant Distance Based Composite Vector Selection Method for Odor Classification
Sensors 2014, 14(4), 6938-6951; doi:10.3390/s140406938
Received: 9 January 2014 / Revised: 25 March 2014 / Accepted: 9 April 2014 / Published: 17 April 2014
Cited by 2 | PDF Full-text (6478 KB) | HTML Full-text | XML Full-text
Abstract
We present a composite vector selection method for an effective electronic nose system that performs well even in noisy environments. Each composite vector generated from a electronic nose data sample is evaluated by computing the discriminant distance. By quantitatively measuring the amount [...] Read more.
We present a composite vector selection method for an effective electronic nose system that performs well even in noisy environments. Each composite vector generated from a electronic nose data sample is evaluated by computing the discriminant distance. By quantitatively measuring the amount of discriminative information in each composite vector, composite vectors containing informative variables can be distinguished and the final composite features for odor classification are extracted using the selected composite vectors. Using the only informative composite vectors can be also helpful to extract better composite features instead of using all the generated composite vectors. Experimental results with different volatile organic compound data show that the proposed system has good classification performance even in a noisy environment compared to other methods. Full article
(This article belongs to the Section Chemical Sensors)
Open AccessArticle Response of a New Low-Coherence Fabry-Perot Sensor to Hematocrit Levels in Human Blood
Sensors 2014, 14(4), 6965-6976; doi:10.3390/s140406965
Received: 6 February 2014 / Revised: 8 April 2014 / Accepted: 10 April 2014 / Published: 21 April 2014
Cited by 9 | PDF Full-text (666 KB) | HTML Full-text | XML Full-text
Abstract
In this paper, a low-coherence Fabry-Perot sensor with a spectrally measured signal processing response to the refractive index of liquids is presented. Optical fiber sensors are potentially capable of continuous measuring hematocrit levels in blood. Low-coherence Fabry-Perot interferometric sensors offer a robust [...] Read more.
In this paper, a low-coherence Fabry-Perot sensor with a spectrally measured signal processing response to the refractive index of liquids is presented. Optical fiber sensors are potentially capable of continuous measuring hematocrit levels in blood. Low-coherence Fabry-Perot interferometric sensors offer a robust solution, where information about the measurand is encoded in the full spectrum of light reflected from the sensing interferometer. The first step in the research on such sensor is the assessment of its performance under favorable conditions, i.e., using blood samples from healthy volunteers tested in vitro. Such an experiment was conducted using a sensor comprising a superluminescent diode source, an optical spectrum analyzer working as the detection setup and a sensing Fabry-Perot interferometer providing high interference contrast. The response of this sensor was recorded for several samples and compared with the reference laboratory method. The coefficient of determination (R2) for a linear relationship between the results given by both methods was 0.978 and the difference between these results was less than 1%. The presented results suggest that further research into the performance of the sensor is merited. Full article
(This article belongs to the Section Biosensors)
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Open AccessArticle Applications of Nuclear Magnetic Resonance Sensors to Cultural Heritage
Sensors 2014, 14(4), 6977-6997; doi:10.3390/s140406977
Received: 3 March 2014 / Revised: 8 April 2014 / Accepted: 15 April 2014 / Published: 21 April 2014
Cited by 4 | PDF Full-text (1114 KB) | HTML Full-text | XML Full-text
Abstract
In recent years nuclear magnetic resonance (NMR) sensors have been increasingly applied to investigate, characterize and monitor objects of cultural heritage interest. NMR is not confined to a few specific applications, but rather its use can be successfully extended to a wide [...] Read more.
In recent years nuclear magnetic resonance (NMR) sensors have been increasingly applied to investigate, characterize and monitor objects of cultural heritage interest. NMR is not confined to a few specific applications, but rather its use can be successfully extended to a wide number of different cultural heritage issues. A breakthrough has surely been the recent development of portable NMR sensors which can be applied in situ for non-destructive and non-invasive investigations. In this paper three studies illustrating the potential of NMR sensors in this field of research are reported. Full article
(This article belongs to the Special Issue Sensors for Cultural Heritage Diagnostics)
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Open AccessArticle An Internet of Things Example: Classrooms Access Control over Near Field Communication
Sensors 2014, 14(4), 6998-7012; doi:10.3390/s140406998
Received: 28 January 2014 / Revised: 19 March 2014 / Accepted: 9 April 2014 / Published: 21 April 2014
Cited by 8 | 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, [...] 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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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; doi:10.3390/s140407013
Received: 31 December 2013 / Revised: 18 March 2014 / Accepted: 15 April 2014 / Published: 21 April 2014
Cited by 3 | 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 [...] 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 Quorum Sensing Activity of Aeromonas Caviae Strain YL12, A Bacterium Isolated from Compost
Sensors 2014, 14(4), 7026-7040; doi:10.3390/s140407026
Received: 4 March 2014 / Revised: 6 April 2014 / Accepted: 10 April 2014 / Published: 22 April 2014
Cited by 6 | 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 [...] 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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Open AccessArticle Effect of Angular Velocity on Sensors Based on Morphology Dependent Resonances
Sensors 2014, 14(4), 7041-7048; doi:10.3390/s140407041
Received: 13 February 2014 / Revised: 7 April 2014 / Accepted: 14 April 2014 / Published: 22 April 2014
Cited by 3 | 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 [...] 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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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; doi:10.3390/s140407049
Received: 23 January 2014 / Revised: 12 April 2014 / Accepted: 15 April 2014 / Published: 22 April 2014
Cited by 2 | 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 [...] 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 Setup of Galvanic Sensors for the Monitoring of Gilded Bronzes
Sensors 2014, 14(4), 7066-7083; doi:10.3390/s140407066
Received: 17 March 2014 / Revised: 14 April 2014 / Accepted: 14 April 2014 / Published: 22 April 2014
Cited by 2 | 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 [...] 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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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; doi:10.3390/s140407084
Received: 14 November 2013 / Revised: 31 March 2014 / Accepted: 9 April 2014 / Published: 22 April 2014
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 [...] 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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Open AccessArticle WiSPH: A Wireless Sensor Network-Based Home Care Monitoring System
Sensors 2014, 14(4), 7096-7119; doi:10.3390/s140407096
Received: 19 March 2014 / Revised: 11 April 2014 / Accepted: 11 April 2014 / Published: 22 April 2014
Cited by 9 | 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 [...] 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
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Open AccessArticle Wearable Biomedical Measurement Systems for Assessment of Mental Stress of Combatants in Real Time
Sensors 2014, 14(4), 7120-7141; doi:10.3390/s140407120
Received: 2 January 2014 / Revised: 31 March 2014 / Accepted: 15 April 2014 / Published: 22 April 2014
Cited by 17 | 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 [...] 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 An Affordable Open-Source Turbidimeter
Sensors 2014, 14(4), 7142-7155; doi:10.3390/s140407142
Received: 22 February 2014 / Revised: 4 April 2014 / Accepted: 8 April 2014 / Published: 22 April 2014
Cited by 6 | 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 [...] 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 Angular Rate Optimal Design for the Rotary Strapdown Inertial Navigation System
Sensors 2014, 14(4), 7156-7180; doi:10.3390/s140407156
Received: 2 February 2014 / Revised: 28 March 2014 / Accepted: 2 April 2014 / Published: 22 April 2014
Cited by 3 | 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 [...] 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 Tracking and Recognition of Multiple Human Targets Moving in a Wireless Pyroelectric Infrared Sensor Network
Sensors 2014, 14(4), 7209-7228; doi:10.3390/s140407209
Received: 17 March 2014 / Revised: 16 April 2014 / Accepted: 17 April 2014 / Published: 22 April 2014
Cited by 5 | 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 [...] 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 AccessArticle An Interactive Control Algorithm Used for Equilateral Triangle Formation with Robotic Sensors
Sensors 2014, 14(4), 7229-7247; doi:10.3390/s140407229
Received: 1 February 2014 / Revised: 16 April 2014 / Accepted: 16 April 2014 / Published: 22 April 2014
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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 [...] 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 Experience in Evaluating AAL Solutions in Living Labs
Sensors 2014, 14(4), 7277-7311; doi:10.3390/s140407277
Received: 17 March 2014 / Revised: 15 April 2014 / Accepted: 18 April 2014 / Published: 23 April 2014
Cited by 1 | 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 [...] 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 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; doi:10.3390/s140407312
Received: 10 March 2014 / Revised: 14 April 2014 / Accepted: 18 April 2014 / Published: 23 April 2014
Cited by 4 | 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 [...] 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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Open AccessArticle Optical Sensor Based on a Single CdS Nanobelt
Sensors 2014, 14(4), 7332-7341; doi:10.3390/s140407332
Received: 3 March 2014 / Revised: 18 April 2014 / Accepted: 18 April 2014 / Published: 23 April 2014
Cited by 3 | 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 [...] 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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Open AccessArticle Using Massive Vehicle Positioning Data to Improve Control and Planning of Public Road Transport
Sensors 2014, 14(4), 7342-7358; doi:10.3390/s140407342
Received: 13 March 2014 / Revised: 15 April 2014 / Accepted: 17 April 2014 / Published: 23 April 2014
Cited by 2 | 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 [...] 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
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Open AccessArticle Development of a Sweetness Sensor for Aspartame, a Positively Charged High-Potency Sweetener
Sensors 2014, 14(4), 7359-7373; doi:10.3390/s140407359
Received: 12 March 2014 / Revised: 14 April 2014 / Accepted: 21 April 2014 / Published: 23 April 2014
Cited by 8 | 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 [...] 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 An Accurate and Computationally Efficient Model for Membrane-Type Circular-Symmetric Micro-Hotplates
Sensors 2014, 14(4), 7374-7393; doi:10.3390/s140407374
Received: 11 February 2014 / Revised: 15 April 2014 / Accepted: 17 April 2014 / Published: 23 April 2014
Cited by 1 | 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 [...] 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 Calibration-Free Pulse Oximetry Based on Two Wavelengths in the Infrared — A Preliminary Study
Sensors 2014, 14(4), 7420-7434; doi:10.3390/s140407420
Received: 23 January 2014 / Revised: 9 April 2014 / Accepted: 14 April 2014 / Published: 23 April 2014
Cited by 1 | 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 [...] 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 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; doi:10.3390/s140407435
Received: 29 September 2013 / Revised: 26 February 2014 / Accepted: 18 April 2014 / Published: 23 April 2014
Cited by 2 | 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 [...] 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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Open AccessArticle Non-Destructive Quality Evaluation of Pepper (Capsicum annuum L.) Seeds Using LED-Induced Hyperspectral Reflectance Imaging
Sensors 2014, 14(4), 7489-7504; doi:10.3390/s140407489
Received: 17 March 2014 / Revised: 21 April 2014 / Accepted: 21 April 2014 / Published: 24 April 2014
Cited by 3 | 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, [...] 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)
Open AccessArticle Model Parameter Adaption-Based Multi-Model Algorithm for Extended Object Tracking Using a Random Matrix
Sensors 2014, 14(4), 7505-7523; doi:10.3390/s140407505
Received: 20 January 2014 / Revised: 31 March 2014 / Accepted: 21 April 2014 / Published: 24 April 2014
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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 [...] 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 Floor Sensing System Using Laser Reflectivity for Localizing Everyday Objects and Robot
Sensors 2014, 14(4), 7524-7540; doi:10.3390/s140407524
Received: 31 December 2013 / Revised: 14 April 2014 / Accepted: 15 April 2014 / Published: 24 April 2014
Cited by 5 | 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 [...] 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 The Enhanced Locating Performance of an Integrated Cross-Correlation and Genetic Algorithm for Radio Monitoring Systems
Sensors 2014, 14(4), 7541-7562; doi:10.3390/s140407541
Received: 14 March 2014 / Revised: 20 April 2014 / Accepted: 21 April 2014 / Published: 24 April 2014
Cited by 2 | 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 [...] 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 A Multi-Resolution Approach for an Automated Fusion of Different Low-Cost 3D Sensors
Sensors 2014, 14(4), 7563-7579; doi:10.3390/s140407563
Received: 24 January 2014 / Revised: 8 April 2014 / Accepted: 15 April 2014 / Published: 24 April 2014
Cited by 2 | 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 [...] 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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Open AccessReview Microfiber Optical Sensors: A Review
Sensors 2014, 14(4), 5823-5844; doi:10.3390/s140405823
Received: 6 January 2014 / Revised: 17 February 2014 / Accepted: 19 February 2014 / Published: 25 March 2014
Cited by 18 | PDF Full-text (1159 KB) | HTML Full-text | XML Full-text
Abstract
With diameter close to or below the wavelength of guided light and high index contrast between the fiber core and the surrounding, an optical microfiber shows a variety of interesting waveguiding properties, including widely tailorable optical confinement, evanescent fields and waveguide dispersion. [...] Read more.
With diameter close to or below the wavelength of guided light and high index contrast between the fiber core and the surrounding, an optical microfiber shows a variety of interesting waveguiding properties, including widely tailorable optical confinement, evanescent fields and waveguide dispersion. Among various microfiber applications, optical sensing has been attracting increasing research interest due to its possibilities of realizing miniaturized fiber optic sensors with small footprint, high sensitivity, fast response, high flexibility and low optical power consumption. Here we review recent progress in microfiber optical sensors regarding their fabrication, waveguide properties and sensing applications. Typical microfiber-based sensing structures, including biconical tapers, optical gratings, circular cavities, Mach-Zehnder interferometers and functionally coated/doped microfibers, are summarized. Categorized by sensing structures, microfiber optical sensors for refractive index, concentration, temperature, humidity, strain and current measurement in gas or liquid environments are reviewed. Finally, we conclude with an outlook for challenges and opportunities of microfiber optical sensors. Full article
(This article belongs to the Special Issue Photonic Sensors for Industrial, Environmental and Health Monitoring)
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Open AccessReview Synthesis of Silver Nanostructures by Multistep Methods
Sensors 2014, 14(4), 5860-5889; doi:10.3390/s140405860
Received: 13 January 2014 / Revised: 16 March 2014 / Accepted: 18 March 2014 / Published: 25 March 2014
Cited by 16 | PDF Full-text (1252 KB) | HTML Full-text | XML Full-text
Abstract
The shape of plasmonic nanostructures such as silver and gold is vital to their physical and chemical properties and potential applications. Recently, preparation of complex nanostructures with rich function by chemical multistep methods is the hotspot of research. In this review we [...] Read more.
The shape of plasmonic nanostructures such as silver and gold is vital to their physical and chemical properties and potential applications. Recently, preparation of complex nanostructures with rich function by chemical multistep methods is the hotspot of research. In this review we introduce three typical multistep methods to prepare silver nanostructures with well-controlled shapes, including the double reductant method, etching technique and construction of core-shell nanostructures. The growth mechanism of double the reductant method is that different favorable facets of silver nanocrystals are produced in different reductants, which can be used to prepare complex nanostructures such as nanoflags with ultranarrow resonant band bandwidth or some silver nanostructures which are difficult to prepare using other methods. The etching technique can selectively remove nanoparticles to achieve the aim of shape control and is widely used for the synthesis of nanoflowers and hollow nanostructures. Construction of core-shell nanostructures is another tool to control shape and size. The three methods can not only prepare various silver nanostructures with well-controlled shapes, which exhibit unique optical properties, such as strong surface-enhanced Raman scattering (SERS) signal and localized surface plasmon resonance (LSPR) effect, but also have potential application in many areas. Full article
(This article belongs to the Special Issue Plasmonics and Nanoplasmonics Biosensors)
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Open AccessReview Hybrid Integrated Label-Free Chemical and Biological Sensors
Sensors 2014, 14(4), 5890-5928; doi:10.3390/s140405890
Received: 11 February 2014 / Revised: 10 March 2014 / Accepted: 14 March 2014 / Published: 26 March 2014
Cited by 17 | PDF Full-text (1030 KB) | HTML Full-text | XML Full-text
Abstract
Label-free sensors based on electrical, mechanical and optical transduction methods have potential applications in numerous areas of society, ranging from healthcare to environmental monitoring. Initial research in the field focused on the development and optimization of various sensor platforms fabricated from a [...] Read more.
Label-free sensors based on electrical, mechanical and optical transduction methods have potential applications in numerous areas of society, ranging from healthcare to environmental monitoring. Initial research in the field focused on the development and optimization of various sensor platforms fabricated from a single material system, such as fiber-based optical sensors and silicon nanowire-based electrical sensors. However, more recent research efforts have explored designing sensors fabricated from multiple materials. For example, synthetic materials and/or biomaterials can also be added to the sensor to improve its response toward analytes of interest. By leveraging the properties of the different material systems, these hybrid sensing devices can have significantly improved performance over their single-material counterparts (better sensitivity, specificity, signal to noise, and/or detection limits). This review will briefly discuss some of the methods for creating these multi-material sensor platforms and the advances enabled by this design approach. Full article
(This article belongs to the Special Issue Inorganic-Organic Hybrid Biological and Chemical Sensors)
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Open AccessReview Language Model Applications to Spelling with Brain-Computer Interfaces
Sensors 2014, 14(4), 5967-5993; doi:10.3390/s140405967
Received: 23 December 2013 / Revised: 17 February 2014 / Accepted: 24 February 2014 / Published: 26 March 2014
Cited by 4 | PDF Full-text (955 KB) | HTML Full-text | XML Full-text
Abstract
Within the Ambient Assisted Living (AAL) community, Brain-Computer Interfaces (BCIs) have raised great hopes as they provide alternative communication means for persons with disabilities bypassing the need for speech and other motor activities. Although significant advancements have been realized in the last [...] Read more.
Within the Ambient Assisted Living (AAL) community, Brain-Computer Interfaces (BCIs) have raised great hopes as they provide alternative communication means for persons with disabilities bypassing the need for speech and other motor activities. Although significant advancements have been realized in the last decade, applications of language models (e.g., word prediction, completion) have only recently started to appear in BCI systems. The main goal of this article is to review the language model applications that supplement non-invasive BCI-based communication systems by discussing their potential and limitations, and to discern future trends. First, a brief overview of the most prominent BCI spelling systems is given, followed by an in-depth discussion of the language models applied to them. These language models are classified according to their functionality in the context of BCI-based spelling: the static/dynamic nature of the user interface, the use of error correction and predictive spelling, and the potential to improve their classification performance by using language models. To conclude, the review offers an overview of the advantages and challenges when implementing language models in BCI-based communication systems when implemented in conjunction with other AAL technologies. Full article
Open AccessReview Oxygen Sensing for Industrial Safety — Evolution and New Approaches
Sensors 2014, 14(4), 6084-6103; doi:10.3390/s140406084
Received: 20 December 2013 / Revised: 20 March 2014 / Accepted: 21 March 2014 / Published: 27 March 2014
Cited by 3 | PDF Full-text (783 KB) | HTML Full-text | XML Full-text
Abstract
The requirement for the detection of oxygen in industrial safety applications has historically been met by electrochemical technologies based on the consumption of metal anodes. Products using this approach have been technically and commercially successful for more than three decades. However, a [...] Read more.
The requirement for the detection of oxygen in industrial safety applications has historically been met by electrochemical technologies based on the consumption of metal anodes. Products using this approach have been technically and commercially successful for more than three decades. However, a combination of new requirements is driving the development of alternative approaches offering fresh opportunities and challenges. This paper reviews some key aspects in the evolution of consumable anode products and highlights recent developments in alternative technologies aimed at meeting current and anticipated future needs in this important application. Full article
(This article belongs to the Special Issue Gas Sensors - 2013)
Open AccessReview Quartz-Enhanced Photoacoustic Spectroscopy: A Review
Sensors 2014, 14(4), 6165-6206; doi:10.3390/s140406165
Received: 29 November 2013 / Revised: 18 February 2014 / Accepted: 21 March 2014 / Published: 28 March 2014
Cited by 53 | PDF Full-text (1852 KB) | HTML Full-text | XML Full-text
Abstract
A detailed review on the development of quartz-enhanced photoacoustic sensors (QEPAS) for the sensitive and selective quantification of molecular trace gas species with resolved spectroscopic features is reported. The basis of the QEPAS technique, the technology available to support this field in [...] Read more.
A detailed review on the development of quartz-enhanced photoacoustic sensors (QEPAS) for the sensitive and selective quantification of molecular trace gas species with resolved spectroscopic features is reported. The basis of the QEPAS technique, the technology available to support this field in terms of key components, such as light sources and quartz-tuning forks and the recent developments in detection methods and performance limitations will be discussed. Furthermore, different experimental QEPAS methods such as: on-beam and off-beam QEPAS, quartz-enhanced evanescent wave photoacoustic detection, modulation-cancellation approach and mid-IR single mode fiber-coupled sensor systems will be reviewed and analysed. A QEPAS sensor operating in the THz range, employing a custom-made quartz-tuning fork and a THz quantum cascade laser will be also described. Finally, we evaluated data reported during the past decade and draw relevant and useful conclusions from this analysis. Full article
(This article belongs to the Special Issue Gas Sensors - 2013)
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Open AccessReview A Survey on FPGA-Based Sensor Systems: Towards Intelligent and Reconfigurable Low-Power Sensors for Computer Vision, Control and Signal Processing
Sensors 2014, 14(4), 6247-6278; doi:10.3390/s140406247
Received: 30 December 2013 / Revised: 20 March 2014 / Accepted: 21 March 2014 / Published: 31 March 2014
Cited by 9 | PDF Full-text (1209 KB) | HTML Full-text | XML Full-text
Abstract
The current trend in the evolution of sensor systems seeks ways to provide more accuracy and resolution, while at the same time decreasing the size and power consumption. The use of Field Programmable Gate Arrays (FPGAs) provides specific reprogrammable hardware technology that [...] Read more.
The current trend in the evolution of sensor systems seeks ways to provide more accuracy and resolution, while at the same time decreasing the size and power consumption. The use of Field Programmable Gate Arrays (FPGAs) provides specific reprogrammable hardware technology that can be properly exploited to obtain a reconfigurable sensor system. This adaptation capability enables the implementation of complex applications using the partial reconfigurability at a very low-power consumption. For highly demanding tasks FPGAs have been favored due to the high efficiency provided by their architectural flexibility (parallelism, on-chip memory, etc.), reconfigurability and superb performance in the development of algorithms. FPGAs have improved the performance of sensor systems and have triggered a clear increase in their use in new fields of application. A new generation of smarter, reconfigurable and lower power consumption sensors is being developed in Spain based on FPGAs. In this paper, a review of these developments is presented, describing as well the FPGA technologies employed by the different research groups and providing an overview of future research within this field. Full article
Open AccessReview Advances in Bio-Tactile Sensors for Minimally Invasive Surgery Using the Fibre Bragg Grating Force Sensor Technique: A Survey
Sensors 2014, 14(4), 6633-6665; doi:10.3390/s140406633
Received: 23 December 2013 / Revised: 7 March 2014 / Accepted: 13 March 2014 / Published: 9 April 2014
Cited by 13 | PDF Full-text (1320 KB) | HTML Full-text | XML Full-text
Abstract
The large interest in utilising fibre Bragg grating (FBG) strain sensors for minimally invasive surgery (MIS) applications to replace conventional electrical tactile sensors has grown in the past few years. FBG strain sensors offer the advantages of optical fibre sensors, such as [...] Read more.
The large interest in utilising fibre Bragg grating (FBG) strain sensors for minimally invasive surgery (MIS) applications to replace conventional electrical tactile sensors has grown in the past few years. FBG strain sensors offer the advantages of optical fibre sensors, such as high sensitivity, immunity to electromagnetic noise, electrical passivity and chemical inertness, but are not limited by phase discontinuity or intensity fluctuations. FBG sensors feature a wavelength-encoding sensing signal that enables distributed sensing that utilises fewer connections. In addition, their flexibility and lightness allow easy insertion into needles and catheters, thus enabling localised measurements inside tissues and blood. Two types of FBG tactile sensors have been emphasised in the literature: single-point and array FBG tactile sensors. This paper describes the current design, development and research of the optical fibre tactile techniques that are based on FBGs to enhance the performance of MIS procedures in general. Providing MIS or microsurgery surgeons with accurate and precise measurements and control of the contact forces during tissues manipulation will benefit both surgeons and patients. Full article
(This article belongs to the Section Physical Sensors)
Open AccessReview Applications of Micro/Nanoparticles in Microfluidic Sensors: A Review
Sensors 2014, 14(4), 6952-6964; doi:10.3390/s140406952
Received: 8 February 2014 / Revised: 4 April 2014 / Accepted: 10 April 2014 / Published: 21 April 2014
Cited by 5 | PDF Full-text (755 KB) | HTML Full-text | XML Full-text
Abstract
This paper reviews the applications of micro/nanoparticles in microfluidics device fabrication and analytical processing. In general, researchers have focused on two properties of particles—electric behavior and magnetic behavior. The applications of micro/nanoparticles could be summarized on the chip fabrication level and on [...] Read more.
This paper reviews the applications of micro/nanoparticles in microfluidics device fabrication and analytical processing. In general, researchers have focused on two properties of particles—electric behavior and magnetic behavior. The applications of micro/nanoparticles could be summarized on the chip fabrication level and on the processing level. In the fabrication of microfluidic chips (chip fabrication level), particles are good additives in polydimethylsiloxane (PDMS) to prepare conductive or magnetic composites which have wide applications in sensors, valves and actuators. On the other hand, particles could be manipulated according to their electric and magnetic properties under external electric and magnetic fields when they are travelling in microchannels (processing level). Researchers have made a great progress in preparing modified PDMS and investigating the behaviors of particles in microchannels. This article attempts to present a discussion on the basis of particles applications in microfluidics. Full article
(This article belongs to the Special Issue On-Chip Sensors)
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Open AccessReview Smartphone-Based Solutions for Fall Detection and Prevention: Challenges and Open Issues
Sensors 2014, 14(4), 7181-7208; doi:10.3390/s140407181
Received: 4 March 2014 / Revised: 10 April 2014 / Accepted: 11 April 2014 / Published: 22 April 2014
Cited by 29 | 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 [...] 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 AccessReview Recent Developments in Hyperspectral Imaging for Assessment of Food Quality and Safety
Sensors 2014, 14(4), 7248-7276; doi:10.3390/s140407248
Received: 25 September 2013 / Revised: 7 April 2014 / Accepted: 8 April 2014 / Published: 22 April 2014
Cited by 26 | 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 [...] 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 AccessReview Fiber Bragg Grating Sensors toward Structural Health Monitoring in Composite Materials: Challenges and Solutions
Sensors 2014, 14(4), 7394-7419; doi:10.3390/s140407394
Received: 10 February 2014 / Revised: 4 April 2014 / Accepted: 18 April 2014 / Published: 23 April 2014
Cited by 42 | 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 [...] 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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Open AccessReview Chronology of Fabry-Perot Interferometer Fiber-Optic Sensors and Their Applications: A Review
Sensors 2014, 14(4), 7451-7488; doi:10.3390/s140407451
Received: 30 December 2013 / Revised: 29 March 2014 / Accepted: 18 April 2014 / Published: 24 April 2014
Cited by 20 | 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, [...] 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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