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Sensors, Volume 16, Issue 10 (October 2016)

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Open AccessArticle Graphene Nanogrids FET Immunosensor: Signal to Noise Ratio Enhancement
Sensors 2016, 16(10), 1481; doi:10.3390/s16101481
Received: 11 May 2016 / Revised: 11 August 2016 / Accepted: 19 August 2016 / Published: 8 October 2016
Cited by 2 | PDF Full-text (2903 KB) | HTML Full-text | XML Full-text
Abstract
Recently, a reproducible and scalable chemical method for fabrication of smooth graphene nanogrids has been reported which addresses the challenges of graphene nanoribbons (GNR). These nanogrids have been found to be capable of attomolar detection of biomolecules in field effect transistor (FET) mode.
[...] Read more.
Recently, a reproducible and scalable chemical method for fabrication of smooth graphene nanogrids has been reported which addresses the challenges of graphene nanoribbons (GNR). These nanogrids have been found to be capable of attomolar detection of biomolecules in field effect transistor (FET) mode. However, for detection of sub-femtomolar concentrations of target molecule in complex mixtures with reasonable accuracy, it is not sufficient to only explore the steady state sensitivities, but is also necessary to investigate the flicker noise which dominates at frequencies below 100 kHz. This low frequency noise is dependent on the exposure time of the graphene layer in the buffer solution and concentration of charged impurities at the surface. In this paper, the functionalization strategy of graphene nanogrids has been optimized with respect to concentration and incubation time of the cross linker for an enhancement in signal to noise ratio (SNR). It has been interestingly observed that as the sensitivity and noise power change at different rates with the functionalization parameters, SNR does not vary monotonically but is maximum corresponding to a particular parameter. The optimized parameter has improved the SNR by 50% which has enabled a detection of 0.05 fM Hep-B virus molecules with a sensitivity of around 30% and a standard deviation within 3%. Further, the SNR enhancement has resulted in improvement of quantification accuracy by five times and selectivity by two orders of magnitude. Full article
(This article belongs to the Special Issue Carbon MEMS and NEMS for Sensor Applications)
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Open AccessArticle Adaptive Connectivity Restoration from Node Failure(s) in Wireless Sensor Networks
Sensors 2016, 16(10), 1487; doi:10.3390/s16101487
Received: 19 June 2016 / Revised: 29 August 2016 / Accepted: 8 September 2016 / Published: 28 September 2016
Cited by 4 | PDF Full-text (5436 KB) | HTML Full-text | XML Full-text
Abstract
Recently, there is a growing interest in the applications of wireless sensor networks (WSNs). A set of sensor nodes is deployed in order to collectively survey an area of interest and/or perform specific surveillance tasks in some of the applications, such as battlefield
[...] Read more.
Recently, there is a growing interest in the applications of wireless sensor networks (WSNs). A set of sensor nodes is deployed in order to collectively survey an area of interest and/or perform specific surveillance tasks in some of the applications, such as battlefield reconnaissance. Due to the harsh deployment environments and limited energy supply, nodes may fail, which impacts the connectivity of the whole network. Since a single node failure (cut-vertex) will destroy the connectivity and divide the network into disjoint blocks, most of the existing studies focus on the problem of single node failure. However, the failure of multiple nodes would be a disaster to the whole network and must be repaired effectively. Only few studies are proposed to handle the problem of multiple cut-vertex failures, which is a special case of multiple node failures. Therefore, this paper proposes a comprehensive solution to address the problems of node failure (single and multiple). Collaborative Single Node Failure Restoration algorithm (CSFR) is presented to solve the problem of single node failure only with cooperative communication, but CSFR-M, which is the extension of CSFR, handles the single node failure problem more effectively with node motion. Moreover, Collaborative Connectivity Restoration Algorithm (CCRA) is proposed on the basis of cooperative communication and node maneuverability to restore network connectivity after multiple nodes fail. CSFR-M and CCRA are reactive methods that initiate the connectivity restoration after detecting the node failure(s). In order to further minimize the energy dissipation, CCRA opts to simplify the recovery process by gridding. Moreover, the distance that an individual node needs to travel during recovery is reduced by choosing the nearest suitable candidates. Finally, extensive simulations validate the performance of CSFR, CSFR-M and CCRA. Full article
(This article belongs to the Section Sensor Networks)
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Open AccessArticle Phosphor-Doped Thermal Barrier Coatings Deposited by Air Plasma Spray for In-Depth Temperature Sensing
Sensors 2016, 16(10), 1490; doi:10.3390/s16101490
Received: 19 July 2016 / Revised: 28 August 2016 / Accepted: 29 August 2016 / Published: 28 September 2016
Cited by 1 | PDF Full-text (2632 KB) | HTML Full-text | XML Full-text
Abstract
Yttria-stabilized zirconia (YSZ)-based thermal barrier coating (TBC) has been integrated with thermographic phosphors through air plasma spray (APS) for in-depth; non-contact temperature sensing. This coating consisted of a thin layer of Dy-doped YSZ (about 40 µm) on the bottom and a regular YSZ
[...] Read more.
Yttria-stabilized zirconia (YSZ)-based thermal barrier coating (TBC) has been integrated with thermographic phosphors through air plasma spray (APS) for in-depth; non-contact temperature sensing. This coating consisted of a thin layer of Dy-doped YSZ (about 40 µm) on the bottom and a regular YSZ layer with a thickness up to 300 µm on top. A measurement system has been established; which included a portable; low-cost diode laser (405 nm); a photo-multiplier tube (PMT) and the related optics. Coating samples with different topcoat thickness were calibrated in a high-temperature furnace from room temperature to around 900 °C. The results convincingly showed that the current sensor and the measurement system was capable of in-depth temperature sensing over 800 °C with a YSZ top layer up to 300 µm. The topcoat thickness was found to have a strong effect on the luminescent signal level. Therefore; the measurement accuracy at high temperatures was reduced for samples with thick topcoats due to strong light attenuation. However; it seemed that the light transmissivity of YSZ topcoat increased with temperature; which would improve the sensor’s performance at high temperatures. The current sensor and the measurement technology have shown great potential in on-line monitoring of TBC interface temperature. Full article
(This article belongs to the Special Issue The Use of New and/or Improved Materials for Sensing Applications)
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Open AccessArticle An Online Gravity Modeling Method Applied for High Precision Free-INS
Sensors 2016, 16(10), 1541; doi:10.3390/s16101541
Received: 14 May 2016 / Revised: 31 August 2016 / Accepted: 6 September 2016 / Published: 23 September 2016
Cited by 2 | PDF Full-text (8023 KB) | HTML Full-text | XML Full-text
Abstract
For real-time solution of inertial navigation system (INS), the high-degree spherical harmonic gravity model (SHM) is not applicable because of its time and space complexity, in which traditional normal gravity model (NGM) has been the dominant technique for gravity compensation. In this paper,
[...] Read more.
For real-time solution of inertial navigation system (INS), the high-degree spherical harmonic gravity model (SHM) is not applicable because of its time and space complexity, in which traditional normal gravity model (NGM) has been the dominant technique for gravity compensation. In this paper, a two-dimensional second-order polynomial model is derived from SHM according to the approximate linear characteristic of regional disturbing potential. Firstly, deflections of vertical (DOVs) on dense grids are calculated with SHM in an external computer. And then, the polynomial coefficients are obtained using these DOVs. To achieve global navigation, the coefficients and applicable region of polynomial model are both updated synchronously in above computer. Compared with high-degree SHM, the polynomial model takes less storage and computational time at the expense of minor precision. Meanwhile, the model is more accurate than NGM. Finally, numerical test and INS experiment show that the proposed method outperforms traditional gravity models applied for high precision free-INS. Full article
(This article belongs to the Special Issue Inertial Sensors and Systems 2016)
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Open AccessArticle Secure Nearest Neighbor Query on Crowd-Sensing Data
Sensors 2016, 16(10), 1545; doi:10.3390/s16101545
Received: 19 July 2016 / Revised: 5 September 2016 / Accepted: 14 September 2016 / Published: 22 September 2016
Cited by 1 | PDF Full-text (4162 KB) | HTML Full-text | XML Full-text
Abstract
Nearest neighbor queries are fundamental in location-based services, and secure nearest neighbor queries mainly focus on how to securely and quickly retrieve the nearest neighbor in the outsourced cloud server. However, the previous big data system structure has changed because of the crowd-sensing
[...] Read more.
Nearest neighbor queries are fundamental in location-based services, and secure nearest neighbor queries mainly focus on how to securely and quickly retrieve the nearest neighbor in the outsourced cloud server. However, the previous big data system structure has changed because of the crowd-sensing data. On the one hand, sensing data terminals as the data owner are numerous and mistrustful, while, on the other hand, in most cases, the terminals find it difficult to finish many safety operation due to computation and storage capability constraints. In light of they Multi Owners and Multi Users (MOMU) situation in the crowd-sensing data cloud environment, this paper presents a secure nearest neighbor query scheme based on the proxy server architecture, which is constructed by protocols of secure two-party computation and secure Voronoi diagram algorithm. It not only preserves the data confidentiality and query privacy but also effectively resists the collusion between the cloud server and the data owners or users. Finally, extensive theoretical and experimental evaluations are presented to show that our proposed scheme achieves a superior balance between the security and query performance compared to other schemes. Full article
(This article belongs to the Special Issue Big Data and Cloud Computing for Sensor Networks)
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Open AccessArticle An Online Dictionary Learning-Based Compressive Data Gathering Algorithm in Wireless Sensor Networks
Sensors 2016, 16(10), 1547; doi:10.3390/s16101547
Received: 30 May 2016 / Revised: 19 August 2016 / Accepted: 14 September 2016 / Published: 22 September 2016
Cited by 1 | PDF Full-text (3855 KB) | HTML Full-text | XML Full-text
Abstract
To adapt to sense signals of enormous diversities and dynamics, and to decrease the reconstruction errors caused by ambient noise, a novel online dictionary learning method-based compressive data gathering (ODL-CDG) algorithm is proposed. The proposed dictionary is learned from a two-stage iterative procedure,
[...] Read more.
To adapt to sense signals of enormous diversities and dynamics, and to decrease the reconstruction errors caused by ambient noise, a novel online dictionary learning method-based compressive data gathering (ODL-CDG) algorithm is proposed. The proposed dictionary is learned from a two-stage iterative procedure, alternately changing between a sparse coding step and a dictionary update step. The self-coherence of the learned dictionary is introduced as a penalty term during the dictionary update procedure. The dictionary is also constrained with sparse structure. It’s theoretically demonstrated that the sensing matrix satisfies the restricted isometry property (RIP) with high probability. In addition, the lower bound of necessary number of measurements for compressive sensing (CS) reconstruction is given. Simulation results show that the proposed ODL-CDG algorithm can enhance the recovery accuracy in the presence of noise, and reduce the energy consumption in comparison with other dictionary based data gathering methods. Full article
(This article belongs to the Section Sensor Networks)
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Open AccessArticle Reference Beam Pattern Design for Frequency Invariant Beamforming Based on Fast Fourier Transform
Sensors 2016, 16(10), 1554; doi:10.3390/s16101554
Received: 31 May 2016 / Revised: 23 August 2016 / Accepted: 14 September 2016 / Published: 22 September 2016
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Abstract
In the field of fast Fourier transform (FFT)-based frequency invariant beamforming (FIB), there is still an unsolved problem. That is the selection of the reference beam to make the designed wideband pattern frequency invariant (FI) over a given frequency range. This problem is
[...] Read more.
In the field of fast Fourier transform (FFT)-based frequency invariant beamforming (FIB), there is still an unsolved problem. That is the selection of the reference beam to make the designed wideband pattern frequency invariant (FI) over a given frequency range. This problem is studied in this paper. The research shows that for a given array, the selection of the reference beam pattern is determined by the number of sensors and the ratio of the highest frequency to the lowest frequency of the signal (RHL). The length of the weight vector corresponding to a given reference beam pattern depends on the reference frequency. In addition, the upper bound of the weight length to ensure the FI property over the whole frequency band of interest is also given. When the constraints are added to the reference beam, it does not affect the FI property of the designed wideband beam as long as the symmetry of the reference beam is ensured. Based on this conclusion, a scheme for reference beam design is proposed. Full article
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Open AccessArticle Performance Evaluation of Analog Beamforming with Hardware Impairments for mmW Massive MIMO Communication in an Urban Scenario
Sensors 2016, 16(10), 1555; doi:10.3390/s16101555
Received: 7 April 2016 / Revised: 14 September 2016 / Accepted: 16 September 2016 / Published: 22 September 2016
Cited by 2 | PDF Full-text (1557 KB) | HTML Full-text | XML Full-text
Abstract
The use of massive multiple-input multiple-output (MIMO) techniques for communication at millimeter-Wave (mmW) frequency bands has become a key enabler to meet the data rate demands of the upcoming fifth generation (5G) cellular systems. In particular, analog and hybrid beamforming solutions are receiving
[...] Read more.
The use of massive multiple-input multiple-output (MIMO) techniques for communication at millimeter-Wave (mmW) frequency bands has become a key enabler to meet the data rate demands of the upcoming fifth generation (5G) cellular systems. In particular, analog and hybrid beamforming solutions are receiving increasing attention as less expensive and more power efficient alternatives to fully digital precoding schemes. Despite their proven good performance in simple setups, their suitability for realistic cellular systems with many interfering base stations and users is still unclear. Furthermore, the performance of massive MIMO beamforming and precoding methods are in practice also affected by practical limitations and hardware constraints. In this sense, this paper assesses the performance of digital precoding and analog beamforming in an urban cellular system with an accurate mmW channel model under both ideal and realistic assumptions. The results show that analog beamforming can reach the performance of fully digital maximum ratio transmission under line of sight conditions and with a sufficient number of parallel radio-frequency (RF) chains, especially when the practical limitations of outdated channel information and per antenna power constraints are considered. This work also shows the impact of the phase shifter errors and combiner losses introduced by real phase shifter and combiner implementations over analog beamforming, where the former ones have minor impact on the performance, while the latter ones determine the optimum number of RF chains to be used in practice. Full article
(This article belongs to the Special Issue Millimeter Wave Wireless Communications and Networks)
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Open AccessArticle Analysis of Uncertainty in a Middle-Cost Device for 3D Measurements in BIM Perspective
Sensors 2016, 16(10), 1557; doi:10.3390/s16101557
Received: 19 April 2016 / Revised: 16 September 2016 / Accepted: 19 September 2016 / Published: 22 September 2016
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Abstract
Medium-cost devices equipped with sensors are being developed to get 3D measurements. Some allow for generating geometric models and point clouds. Nevertheless, the accuracy of these measurements should be evaluated, taking into account the requirements of the Building Information Model (BIM). This paper
[...] Read more.
Medium-cost devices equipped with sensors are being developed to get 3D measurements. Some allow for generating geometric models and point clouds. Nevertheless, the accuracy of these measurements should be evaluated, taking into account the requirements of the Building Information Model (BIM). This paper analyzes the uncertainty in outdoor/indoor three-dimensional coordinate measures and point clouds (using Spherical Accuracy Standard (SAS) methods) for Eyes Map, a medium-cost tablet manufactured by e-Capture Research & Development Company, Mérida, Spain. To achieve it, in outdoor tests, by means of this device, the coordinates of targets were measured from 1 to 6 m and cloud points were obtained. Subsequently, these were compared to the coordinates of the same targets measured by a Total Station. The Euclidean average distance error was 0.005–0.027 m for measurements by Photogrammetry and 0.013–0.021 m for the point clouds. All of them satisfy the tolerance for point cloud acquisition (0.051 m) according to the BIM Guide for 3D Imaging (General Services Administration); similar results are obtained in the indoor tests, with values of 0.022 m. In this paper, we establish the optimal distances for the observations in both, Photogrammetry and 3D Photomodeling modes (outdoor) and point out some working conditions to avoid in indoor environments. Finally, the authors discuss some recommendations for improving the performance and working methods of the device. Full article
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Open AccessArticle ReliefF-Based EEG Sensor Selection Methods for Emotion Recognition
Sensors 2016, 16(10), 1558; doi:10.3390/s16101558
Received: 29 April 2016 / Revised: 13 September 2016 / Accepted: 14 September 2016 / Published: 22 September 2016
Cited by 4 | PDF Full-text (1839 KB) | HTML Full-text | XML Full-text
Abstract
Electroencephalogram (EEG) signals recorded from sensor electrodes on the scalp can directly detect the brain dynamics in response to different emotional states. Emotion recognition from EEG signals has attracted broad attention, partly due to the rapid development of wearable computing and the needs
[...] Read more.
Electroencephalogram (EEG) signals recorded from sensor electrodes on the scalp can directly detect the brain dynamics in response to different emotional states. Emotion recognition from EEG signals has attracted broad attention, partly due to the rapid development of wearable computing and the needs of a more immersive human-computer interface (HCI) environment. To improve the recognition performance, multi-channel EEG signals are usually used. A large set of EEG sensor channels will add to the computational complexity and cause users inconvenience. ReliefF-based channel selection methods were systematically investigated for EEG-based emotion recognition on a database for emotion analysis using physiological signals (DEAP). Three strategies were employed to select the best channels in classifying four emotional states (joy, fear, sadness and relaxation). Furthermore, support vector machine (SVM) was used as a classifier to validate the performance of the channel selection results. The experimental results showed the effectiveness of our methods and the comparison with the similar strategies, based on the F-score, was given. Strategies to evaluate a channel as a unity gave better performance in channel reduction with an acceptable loss of accuracy. In the third strategy, after adjusting channels’ weights according to their contribution to the classification accuracy, the number of channels was reduced to eight with a slight loss of accuracy (58.51% ± 10.05% versus the best classification accuracy 59.13% ± 11.00% using 19 channels). In addition, the study of selecting subject-independent channels, related to emotion processing, was also implemented. The sensors, selected subject-independently from frontal, parietal lobes, have been identified to provide more discriminative information associated with emotion processing, and are distributed symmetrically over the scalp, which is consistent with the existing literature. The results will make a contribution to the realization of a practical EEG-based emotion recognition system. Full article
(This article belongs to the Special Issue Security and Privacy in Sensor Networks)
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Open AccessArticle Micro-Doppler Signal Time-Frequency Algorithm Based on STFRFT
Sensors 2016, 16(10), 1559; doi:10.3390/s16101559
Received: 15 July 2016 / Revised: 12 September 2016 / Accepted: 19 September 2016 / Published: 24 September 2016
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Abstract
This paper proposes a time-frequency algorithm based on short-time fractional order Fourier transformation (STFRFT) for identification of a complicated movement targets. This algorithm, consisting of a STFRFT order-changing and quick selection method, is effective in reducing the computation load. A multi-order STFRFT time-frequency
[...] Read more.
This paper proposes a time-frequency algorithm based on short-time fractional order Fourier transformation (STFRFT) for identification of a complicated movement targets. This algorithm, consisting of a STFRFT order-changing and quick selection method, is effective in reducing the computation load. A multi-order STFRFT time-frequency algorithm is also developed that makes use of the time-frequency feature of each micro-Doppler component signal. This algorithm improves the estimation accuracy of time-frequency curve fitting through multi-order matching. Finally, experiment data were used to demonstrate STFRFT’s performance in micro-Doppler time-frequency analysis. The results validated the higher estimate accuracy of the proposed algorithm. It may be applied to an LFM (Linear frequency modulated) pulse radar, SAR (Synthetic aperture radar), or ISAR (Inverse synthetic aperture radar), for improving the probability of target recognition. Full article
(This article belongs to the Section Physical Sensors)
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Open AccessArticle Gateway-Assisted Retransmission for Lightweight and Reliable IoT Communications
Sensors 2016, 16(10), 1560; doi:10.3390/s16101560
Received: 28 May 2016 / Revised: 14 September 2016 / Accepted: 20 September 2016 / Published: 22 September 2016
PDF Full-text (1163 KB) | HTML Full-text | XML Full-text
Abstract
Message Queuing Telemetry Transport for Sensor Networks (MQTT-SN) and Constrained Application Protocol (CoAP) are two protocols supporting publish/subscribe models for IoT devices to publish messages to interested subscribers. Retransmission mechanisms are introduced to compensate for the lack of data reliability. If the device
[...] Read more.
Message Queuing Telemetry Transport for Sensor Networks (MQTT-SN) and Constrained Application Protocol (CoAP) are two protocols supporting publish/subscribe models for IoT devices to publish messages to interested subscribers. Retransmission mechanisms are introduced to compensate for the lack of data reliability. If the device does not receive the acknowledgement (ACK) before retransmission timeout (RTO) expires, the device will retransmit data. Setting an appropriate RTO is important because the delay may be large or retransmission may be too frequent when the RTO is inappropriate. We propose a Gateway-assisted CoAP (GaCoAP) to dynamically compute RTO for devices. Simulation models are proposed to investigate the performance of GaCoAP compared with four other methods. The experiment results show that GaCoAP is more suitable for IoT devices. Full article
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Open AccessArticle A MoS2 Nanosheet-Based Fluorescence Biosensor for Simple and Quantitative Analysis of DNA Methylation
Sensors 2016, 16(10), 1561; doi:10.3390/s16101561
Received: 4 May 2016 / Revised: 24 June 2016 / Accepted: 6 July 2016 / Published: 22 September 2016
PDF Full-text (1720 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
MoS2 nanomaterial has unique properties, including innate affinity with ss-DNA and quenching ability for fluorescence dyes. Here, we present the development of a simple fluorescence biosensor based on water-soluble MoS2 nanosheets and restriction endonuclease BstUI for methylation analysis of p16 promoter.
[...] Read more.
MoS2 nanomaterial has unique properties, including innate affinity with ss-DNA and quenching ability for fluorescence dyes. Here, we present the development of a simple fluorescence biosensor based on water-soluble MoS2 nanosheets and restriction endonuclease BstUI for methylation analysis of p16 promoter. The biosensing platform exhibited excellent sensitivity in detecting DNA with a linear range of 100 pM~20 nM and a detection limit of 140 pM. More importantly, our method could distinguish as low as 1% difference in methylation level. Compared with previous methylation analysis, our design is both time saving and simple to operate, avoiding the limitations of PCR-based assays without compromising performance. Full article
(This article belongs to the Section Biosensors)
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Open AccessArticle An Off-Grid Turbo Channel Estimation Algorithm for Millimeter Wave Communications
Sensors 2016, 16(10), 1562; doi:10.3390/s16101562
Received: 31 May 2016 / Revised: 3 September 2016 / Accepted: 7 September 2016 / Published: 22 September 2016
Cited by 1 | PDF Full-text (689 KB) | HTML Full-text | XML Full-text
Abstract
The bandwidth shortage has motivated the exploration of the millimeter wave (mmWave) frequency spectrum for future communication networks. To compensate for the severe propagation attenuation in the mmWave band, massive antenna arrays can be adopted at both the transmitter and receiver to provide
[...] Read more.
The bandwidth shortage has motivated the exploration of the millimeter wave (mmWave) frequency spectrum for future communication networks. To compensate for the severe propagation attenuation in the mmWave band, massive antenna arrays can be adopted at both the transmitter and receiver to provide large array gains via directional beamforming. To achieve such array gains, channel estimation (CE) with high resolution and low latency is of great importance for mmWave communications. However, classic super-resolution subspace CE methods such as multiple signal classification (MUSIC) and estimation of signal parameters via rotation invariant technique (ESPRIT) cannot be applied here due to RF chain constraints. In this paper, an enhanced CE algorithm is developed for the off-grid problem when quantizing the angles of mmWave channel in the spatial domain where off-grid problem refers to the scenario that angles do not lie on the quantization grids with high probability, and it results in power leakage and severe reduction of the CE performance. A new model is first proposed to formulate the off-grid problem. The new model divides the continuously-distributed angle into a quantized discrete grid part, referred to as the integral grid angle, and an offset part, termed fractional off-grid angle. Accordingly, an iterative off-grid turbo CE (IOTCE) algorithm is proposed to renew and upgrade the CE between the integral grid part and the fractional off-grid part under the Turbo principle. By fully exploiting the sparse structure of mmWave channels, the integral grid part is estimated by a soft-decoding based compressed sensing (CS) method called improved turbo compressed channel sensing (ITCCS). It iteratively updates the soft information between the linear minimum mean square error (LMMSE) estimator and the sparsity combiner. Monte Carlo simulations are presented to evaluate the performance of the proposed method, and the results show that it enhances the angle detection resolution greatly. Full article
(This article belongs to the Special Issue Millimeter Wave Wireless Communications and Networks)
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Open AccessArticle Indoor-Outdoor Detection Using a Smart Phone Sensor
Sensors 2016, 16(10), 1563; doi:10.3390/s16101563
Received: 27 June 2016 / Revised: 12 September 2016 / Accepted: 19 September 2016 / Published: 22 September 2016
Cited by 1 | PDF Full-text (12638 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
In the era of mobile internet, Location Based Services (LBS) have developed dramatically. Seamless Indoor and Outdoor Navigation and Localization (SNAL) has attracted a lot of attention. No single positioning technology was capable of meeting the various positioning requirements in different environments. Selecting
[...] Read more.
In the era of mobile internet, Location Based Services (LBS) have developed dramatically. Seamless Indoor and Outdoor Navigation and Localization (SNAL) has attracted a lot of attention. No single positioning technology was capable of meeting the various positioning requirements in different environments. Selecting different positioning techniques for different environments is an alternative method. Detecting the users’ current environment is crucial for this technique. In this paper, we proposed to detect the indoor/outdoor environment automatically without high energy consumption. The basic idea was simple: we applied a machine learning algorithm to classify the neighboring Global System for Mobile (GSM) communication cellular base station’s signal strength in different environments, and identified the users’ current context by signal pattern recognition. We tested the algorithm in four different environments. The results showed that the proposed algorithm was capable of identifying open outdoors, semi-outdoors, light indoors and deep indoors environments with 100% accuracy using the signal strength of four nearby GSM stations. The required hardware and signal are widely available in our daily lives, implying its high compatibility and availability. Full article
(This article belongs to the Section Physical Sensors)
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Open AccessArticle Strain Sharing Assessment in Woven Fiber Reinforced Concrete Beams Using Fiber Bragg Grating Sensors
Sensors 2016, 16(10), 1564; doi:10.3390/s16101564
Received: 28 July 2016 / Revised: 9 September 2016 / Accepted: 19 September 2016 / Published: 22 September 2016
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Abstract
Embedded fiber Bragg grating sensors have been extensively used worldwide for health monitoring of smart structures. In civil engineering, they provide a powerful method for monitoring the performance of composite reinforcements used for concrete structure rehabilitation and retrofitting. This paper discusses the problem
[...] Read more.
Embedded fiber Bragg grating sensors have been extensively used worldwide for health monitoring of smart structures. In civil engineering, they provide a powerful method for monitoring the performance of composite reinforcements used for concrete structure rehabilitation and retrofitting. This paper discusses the problem of investigating the strain transfer mechanism in composite strengthened concrete beams subjected to three-point bending tests. Fiber Bragg grating sensors were embedded both in the concrete tensioned surface and in the woven fiber reinforcement. It has been shown that, if interface decoupling occurs, strain in the concrete can be up to 3.8 times higher than that developed in the reinforcement. A zero friction slipping model was developed which fitted very well the experimental data. Full article
(This article belongs to the Section Physical Sensors)
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Open AccessArticle Characterization of Biosensors Based on Recombinant Glutamate Oxidase: Comparison of Crosslinking Agents in Terms of Enzyme Loading and Efficiency Parameters
Sensors 2016, 16(10), 1565; doi:10.3390/s16101565
Received: 28 July 2016 / Revised: 7 September 2016 / Accepted: 18 September 2016 / Published: 23 September 2016
Cited by 1 | PDF Full-text (1448 KB) | HTML Full-text | XML Full-text
Abstract
Amperometric l-glutamate (Glu) biosensors, based on both wild-type and a recombinant form of l-glutamate oxidase (GluOx), were designed and characterized in terms of enzyme-kinetic, sensitivity and stability parameters in attempts to fabricate a real-time Glu monitoring device suitable for future long-term
[...] Read more.
Amperometric l-glutamate (Glu) biosensors, based on both wild-type and a recombinant form of l-glutamate oxidase (GluOx), were designed and characterized in terms of enzyme-kinetic, sensitivity and stability parameters in attempts to fabricate a real-time Glu monitoring device suitable for future long-term detection of this amino acid in biological and other complex media. A comparison of the enzyme from these two sources showed that they were similar in terms of biosensor performance. Optimization of the loading of the polycationic stabilization agent, polyethyleneimine (PEI), was established before investigating a range of crosslinking agents under different conditions: glutaraldehyde (GA), polyethylene glycol (PEG), and polyethylene glycol diglycidyl ether (PEGDE). Whereas PEI-free biosensor designs lost most of their meager Glu sensitivity after one or two days, configurations with a 2:5 ratio of dip-evaporation applications of PEI(1%):GluOx(400 U/mL) displayed a 20-fold increase in their initial sensitivity, and a decay half-life extended to 10 days. All the crosslinkers studied had no effect on initial Glu sensitivity, but enhanced biosensor stability, provided the crosslinking procedure was carried out under well-defined conditions. The resulting biosensor design based on the recombinant enzyme deposited on a permselective layer of poly-(ortho-phenylenediamine), PoPD/PEI2/GluOx5/PEGDE, displayed good sensitivity (LOD < 0.2 μM), response time (t90% < 1 s) and stability over a 90-day period, making it an attractive candidate for future long-term monitoring of Glu concentration dynamics in complex media. Full article
(This article belongs to the Section Biosensors)
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Open AccessArticle Estimation of Energy Expenditure Using a Patch-Type Sensor Module with an Incremental Radial Basis Function Neural Network
Sensors 2016, 16(10), 1566; doi:10.3390/s16101566
Received: 13 June 2016 / Revised: 8 September 2016 / Accepted: 20 September 2016 / Published: 22 September 2016
PDF Full-text (2145 KB) | HTML Full-text | XML Full-text
Abstract
Conventionally, indirect calorimetry has been used to estimate oxygen consumption in an effort to accurately measure human body energy expenditure. However, calorimetry requires the subject to wear a mask that is neither convenient nor comfortable. The purpose of our study is to develop
[...] Read more.
Conventionally, indirect calorimetry has been used to estimate oxygen consumption in an effort to accurately measure human body energy expenditure. However, calorimetry requires the subject to wear a mask that is neither convenient nor comfortable. The purpose of our study is to develop a patch-type sensor module with an embedded incremental radial basis function neural network (RBFNN) for estimating the energy expenditure. The sensor module contains one ECG electrode and a three-axis accelerometer, and can perform real-time heart rate (HR) and movement index (MI) monitoring. The embedded incremental network includes linear regression (LR) and RBFNN based on context-based fuzzy c-means (CFCM) clustering. This incremental network is constructed by building a collection of information granules through CFCM clustering that is guided by the distribution of error of the linear part of the LR model. Full article
(This article belongs to the collection Sensors for Globalized Healthy Living and Wellbeing)
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Open AccessArticle A Geographical Heuristic Routing Protocol for VANETs
Sensors 2016, 16(10), 1567; doi:10.3390/s16101567
Received: 9 June 2016 / Revised: 14 September 2016 / Accepted: 18 September 2016 / Published: 23 September 2016
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Abstract
Vehicular ad hoc networks (VANETs) leverage the communication system of Intelligent Transportation Systems (ITS). Recently, Delay-Tolerant Network (DTN) routing protocols have increased their popularity among the research community for being used in non-safety VANET applications and services like traffic reporting. Vehicular DTN protocols
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Vehicular ad hoc networks (VANETs) leverage the communication system of Intelligent Transportation Systems (ITS). Recently, Delay-Tolerant Network (DTN) routing protocols have increased their popularity among the research community for being used in non-safety VANET applications and services like traffic reporting. Vehicular DTN protocols use geographical and local information to make forwarding decisions. However, current proposals only consider the selection of the best candidate based on a local-search. In this paper, we propose a generic Geographical Heuristic Routing (GHR) protocol that can be applied to any DTN geographical routing protocol that makes forwarding decisions hop by hop. GHR includes in its operation adaptations simulated annealing and Tabu-search meta-heuristics, which have largely been used to improve local-search results in discrete optimization. We include a complete performance evaluation of GHR in a multi-hop VANET simulation scenario for a reporting service. Our study analyzes all of the meaningful configurations of GHR and offers a statistical analysis of our findings by means of MANOVA tests. Our results indicate that the use of a Tabu list contributes to improving the packet delivery ratio by around 5% to 10%. Moreover, if Tabu is used, then the simulated annealing routing strategy gets a better performance than the selection of the best node used with carry and forwarding (default operation). Full article
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Open AccessArticle A Wireless and Batteryless Intelligent Carbon Monoxide Sensor
Sensors 2016, 16(10), 1568; doi:10.3390/s16101568
Received: 29 May 2016 / Revised: 15 September 2016 / Accepted: 19 September 2016 / Published: 23 September 2016
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Abstract
Carbon monoxide (CO) poisoning from natural gas water heaters is a common household accident in Taiwan. We propose a wireless and batteryless intelligent CO sensor for improving the safety of operating natural gas water heaters. A micro-hydropower generator supplies power to a CO
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Carbon monoxide (CO) poisoning from natural gas water heaters is a common household accident in Taiwan. We propose a wireless and batteryless intelligent CO sensor for improving the safety of operating natural gas water heaters. A micro-hydropower generator supplies power to a CO sensor without battery (COSWOB) (2.5 W at a flow rate of 4.2 L/min), and the power consumption of the COSWOB is only ~13 mW. The COSWOB monitors the CO concentration in ambient conditions around natural gas water heaters and transmits it to an intelligent gateway. When the CO level reaches a dangerous level, the COSWOB alarm sounds loudly. Meanwhile, the intelligent gateway also sends a trigger to activate Wi-Fi alarms and sends notifications to the mobile device through the Internet. Our strategy can warn people indoors and outdoors, thereby reducing CO poisoning accidents. We also believe that our technique not only can be used for home security but also can be used in industrial applications (for example, to monitor leak occurrence in a pipeline). Full article
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Open AccessArticle Assessment of Receiver Signal Strength Sensing for Location Estimation Based on Fisher Information
Sensors 2016, 16(10), 1570; doi:10.3390/s16101570
Received: 28 July 2016 / Revised: 9 September 2016 / Accepted: 15 September 2016 / Published: 24 September 2016
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Abstract
Currently there is almost ubiquitous availability of wireless signaling for data communications within commercial building complexes resulting in receiver signal strength (RSS) observables that are typically sufficient for generating viable location estimates of mobile wireless devices. However, while RSS observables are generally plentiful,
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Currently there is almost ubiquitous availability of wireless signaling for data communications within commercial building complexes resulting in receiver signal strength (RSS) observables that are typically sufficient for generating viable location estimates of mobile wireless devices. However, while RSS observables are generally plentiful, achieving an accurate estimation of location is difficult due to several factors affecting the electromagnetic coupling between the mobile antenna and the building access points that are not modeled and hence contribute to the overall estimation uncertainty. Such uncertainty is typically mitigated with a moderate redundancy of RSS sensor observations in combination with other constraints imposed on the mobile trajectory. In this paper, the Fisher Information (FI) of a set of RSS sensor observations in the context of variables related to the mobile location is developed. This provides a practical method of determining the potential location accuracy for the given set of wireless signals available. Furthermore, the information value of individual RSS measurements can be quantified and the RSS observables weighted accordingly in estimation combining algorithms. The practical utility of using FI in this context was demonstrated experimentally with an extensive set of RSS measurements recorded in an office complex. The resulting deviation of the mobile location estimation based on application of weighted likelihood processing to the experimental RSS data was shown to agree closely with the Cramer Rao bound determined from the FI analysis. Full article
(This article belongs to the Section Physical Sensors)
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Open AccessArticle A Novel Petri Nets-Based Modeling Method for the Interaction between the Sensor and the Geographic Environment in Emerging Sensor Networks
Sensors 2016, 16(10), 1571; doi:10.3390/s16101571
Received: 1 July 2016 / Revised: 11 September 2016 / Accepted: 19 September 2016 / Published: 25 September 2016
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Abstract
The service of sensor device in Emerging Sensor Networks (ESNs) is the extension of traditional Web services. Through the sensor network, the service of sensor device can communicate directly with the entity in the geographic environment, and even impact the geographic entity directly.
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The service of sensor device in Emerging Sensor Networks (ESNs) is the extension of traditional Web services. Through the sensor network, the service of sensor device can communicate directly with the entity in the geographic environment, and even impact the geographic entity directly. The interaction between the sensor device in ESNs and geographic environment is very complex, and the interaction modeling is a challenging problem. This paper proposed a novel Petri Nets-based modeling method for the interaction between the sensor device and the geographic environment. The feature of the sensor device service in ESNs is more easily affected by the geographic environment than the traditional Web service. Therefore, the response time, the fault-tolerant ability and the resource consumption become important factors in the performance of the whole sensor application system. Thus, this paper classified IoT services as Sensing services and Controlling services according to the interaction between IoT service and geographic entity, and classified GIS services as data services and processing services. Then, this paper designed and analyzed service algebra and Colored Petri Nets model to modeling the geo-feature, IoT service, GIS service and the interaction process between the sensor and the geographic enviroment. At last, the modeling process is discussed by examples. Full article
(This article belongs to the Special Issue Topology Control in Emerging Sensor Networks)
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Open AccessArticle A Low Power Digital Accumulation Technique for Digital-Domain CMOS TDI Image Sensor
Sensors 2016, 16(10), 1572; doi:10.3390/s16101572
Received: 13 July 2016 / Revised: 18 September 2016 / Accepted: 19 September 2016 / Published: 23 September 2016
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Abstract
In this paper, an accumulation technique suitable for digital domain CMOS time delay integration (TDI) image sensors is proposed to reduce power consumption without degrading the rate of imaging. In terms of the slight variations of quantization codes among different pixel exposures towards
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In this paper, an accumulation technique suitable for digital domain CMOS time delay integration (TDI) image sensors is proposed to reduce power consumption without degrading the rate of imaging. In terms of the slight variations of quantization codes among different pixel exposures towards the same object, the pixel array is divided into two groups: one is for coarse quantization of high bits only, and the other one is for fine quantization of low bits. Then, the complete quantization codes are composed of both results from the coarse-and-fine quantization. The equivalent operation comparably reduces the total required bit numbers of the quantization. In the 0.18 µm CMOS process, two versions of 16-stage digital domain CMOS TDI image sensor chains based on a 10-bit successive approximate register (SAR) analog-to-digital converter (ADC), with and without the proposed technique, are designed. The simulation results show that the average power consumption of slices of the two versions are 6 . 47 × 10 - 8 J/line and 7 . 4 × 10 - 8 J/line, respectively. Meanwhile, the linearity of the two versions are 99.74% and 99.99%, respectively. Full article
(This article belongs to the Special Issue Imaging: Sensors and Technologies) Printed Edition available
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Open AccessArticle Design and Evaluation of Novel Textile Wearable Systems for the Surveillance of Vital Signals
Sensors 2016, 16(10), 1573; doi:10.3390/s16101573
Received: 30 June 2016 / Revised: 16 September 2016 / Accepted: 20 September 2016 / Published: 24 September 2016
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Abstract
This article addresses the design, development, and evaluation of T-shirt prototypes that embed novel textile sensors for the capture of cardio and respiratory signals. The sensors are connected through textile interconnects to either an embedded custom-designed data acquisition and transmission unit or to
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This article addresses the design, development, and evaluation of T-shirt prototypes that embed novel textile sensors for the capture of cardio and respiratory signals. The sensors are connected through textile interconnects to either an embedded custom-designed data acquisition and transmission unit or to snap fastener terminals for connection to external monitoring devices. The performance of the T-shirt prototype is evaluated in terms of signal-to-noise ratio amplitude and signal interference caused by baseline wander and motion artefacts, through laboratory tests with subjects in standing and walking conditions. Performance tests were also conducted in a hospital environment using a T-shirt prototype connected to a commercial three-channel Holter monitoring device. The textile sensors and interconnects were realized with the assistance of an industrial six-needle digital embroidery tool and their resistance to wear addressed with normalized tests of laundering and abrasion. The performance of these wearable systems is discussed, and pathways and methods for their optimization are highlighted. Full article
(This article belongs to the Special Issue Flexible Electronics and Sensors)
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Open AccessArticle Data Analytics for Smart Parking Applications
Sensors 2016, 16(10), 1575; doi:10.3390/s16101575
Received: 9 August 2016 / Revised: 15 September 2016 / Accepted: 20 September 2016 / Published: 23 September 2016
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Abstract
We consider real-life smart parking systems where parking lot occupancy data are collected from field sensor devices and sent to backend servers for further processing and usage for applications. Our objective is to make these data useful to end users, such as parking
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We consider real-life smart parking systems where parking lot occupancy data are collected from field sensor devices and sent to backend servers for further processing and usage for applications. Our objective is to make these data useful to end users, such as parking managers, and, ultimately, to citizens. To this end, we concoct and validate an automated classification algorithm having two objectives: (1) outlier detection: to detect sensors with anomalous behavioral patterns, i.e., outliers; and (2) clustering: to group the parking sensors exhibiting similar patterns into distinct clusters. We first analyze the statistics of real parking data, obtaining suitable simulation models for parking traces. We then consider a simple classification algorithm based on the empirical complementary distribution function of occupancy times and show its limitations. Hence, we design a more sophisticated algorithm exploiting unsupervised learning techniques (self-organizing maps). These are tuned following a supervised approach using our trace generator and are compared against other clustering schemes, namely expectation maximization, k-means clustering and DBSCAN, considering six months of data from a real sensor deployment. Our approach is found to be superior in terms of classification accuracy, while also being capable of identifying all of the outliers in the dataset. Full article
(This article belongs to the Special Issue Smart City: Vision and Reality)
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Open AccessArticle A Cluster-Based Dual-Adaptive Topology Control Approach in Wireless Sensor Networks
Sensors 2016, 16(10), 1576; doi:10.3390/s16101576
Received: 22 July 2016 / Revised: 11 September 2016 / Accepted: 21 September 2016 / Published: 25 September 2016
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Abstract
Multi-Input Multi-Output (MIMO) can improve wireless network performance. Sensors are usually single-antenna devices due to the high hardware complexity and cost, so several sensors are used to form virtual MIMO array, which is a desirable approach to efficiently take advantage of MIMO gains.
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Multi-Input Multi-Output (MIMO) can improve wireless network performance. Sensors are usually single-antenna devices due to the high hardware complexity and cost, so several sensors are used to form virtual MIMO array, which is a desirable approach to efficiently take advantage of MIMO gains. Also, in large Wireless Sensor Networks (WSNs), clustering can improve the network scalability, which is an effective topology control approach. The existing virtual MIMO-based clustering schemes do not either fully explore the benefits of MIMO or adaptively determine the clustering ranges. Also, clustering mechanism needs to be further improved to enhance the cluster structure life. In this paper, we propose an improved clustering scheme for virtual MIMO-based topology construction (ICV-MIMO), which can determine adaptively not only the inter-cluster transmission modes but also the clustering ranges. Through the rational division of cluster head function and the optimization of cluster head selection criteria and information exchange process, the ICV-MIMO scheme effectively reduces the network energy consumption and improves the lifetime of the cluster structure when compared with the existing typical virtual MIMO-based scheme. Moreover, the message overhead and time complexity are still in the same order of magnitude. Full article
(This article belongs to the Special Issue Topology Control in Emerging Sensor Networks)
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Open AccessArticle Real-Time Performance of Mechatronic PZT Module Using Active Vibration Feedback Control
Sensors 2016, 16(10), 1577; doi:10.3390/s16101577
Received: 30 June 2016 / Revised: 7 September 2016 / Accepted: 14 September 2016 / Published: 25 September 2016
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Abstract
This paper proposes an innovative mechatronic piezo-actuated module to control vibrations in modern machine tools. Vibrations represent one of the main issues that seriously compromise the quality of the workpiece. The active vibration control (AVC) device is composed of a host part integrated
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This paper proposes an innovative mechatronic piezo-actuated module to control vibrations in modern machine tools. Vibrations represent one of the main issues that seriously compromise the quality of the workpiece. The active vibration control (AVC) device is composed of a host part integrated with sensors and actuators synchronized by a regulator; it is able to make a self-assessment and adjust to alterations in the environment. In particular, an innovative smart actuator has been designed and developed to satisfy machining requirements during active vibration control. This study presents the mechatronic model based on the kinematic and dynamic analysis of the AVC device. To ensure a real time performance, a H2-LQG controller has been developed and validated by simulations involving a machine tool, PZT actuator and controller models. The Hardware in the Loop (HIL) architecture is adopted to control and attenuate the vibrations. A set of experimental tests has been performed to validate the AVC module on a commercial machine tool. The feasibility of the real time vibration damping is demonstrated and the simulation accuracy is evaluated. Full article
(This article belongs to the Special Issue Advanced Robotics and Mechatronics Devices)
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Open AccessArticle A Novel Zero Velocity Interval Detection Algorithm for Self-Contained Pedestrian Navigation System with Inertial Sensors
Sensors 2016, 16(10), 1578; doi:10.3390/s16101578
Received: 14 July 2016 / Revised: 3 September 2016 / Accepted: 21 September 2016 / Published: 24 September 2016
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Abstract
Zero velocity update (ZUPT) plays an important role in pedestrian navigation algorithms with the premise that the zero velocity interval (ZVI) should be detected accurately and effectively. A novel adaptive ZVI detection algorithm based on a smoothed pseudo Wigner–Ville distribution to remove multiple
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Zero velocity update (ZUPT) plays an important role in pedestrian navigation algorithms with the premise that the zero velocity interval (ZVI) should be detected accurately and effectively. A novel adaptive ZVI detection algorithm based on a smoothed pseudo Wigner–Ville distribution to remove multiple frequencies intelligently (SPWVD-RMFI) is proposed in this paper. The novel algorithm adopts the SPWVD-RMFI method to extract the pedestrian gait frequency and to calculate the optimal ZVI detection threshold in real time by establishing the function relationships between the thresholds and the gait frequency; then, the adaptive adjustment of thresholds with gait frequency is realized and improves the ZVI detection precision. To put it into practice, a ZVI detection experiment is carried out; the result shows that compared with the traditional fixed threshold ZVI detection method, the adaptive ZVI detection algorithm can effectively reduce the false and missed detection rate of ZVI; this indicates that the novel algorithm has high detection precision and good robustness. Furthermore, pedestrian trajectory positioning experiments at different walking speeds are carried out to evaluate the influence of the novel algorithm on positioning precision. The results show that the ZVI detected by the adaptive ZVI detection algorithm for pedestrian trajectory calculation can achieve better performance. Full article
(This article belongs to the Special Issue Inertial Sensors and Systems 2016)
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Open AccessArticle Gait Phase Recognition for Lower-Limb Exoskeleton with Only Joint Angular Sensors
Sensors 2016, 16(10), 1579; doi:10.3390/s16101579
Received: 28 June 2016 / Revised: 18 September 2016 / Accepted: 20 September 2016 / Published: 27 September 2016
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Abstract
Gait phase is widely used for gait trajectory generation, gait control and gait evaluation on lower-limb exoskeletons. So far, a variety of methods have been developed to identify the gait phase for lower-limb exoskeletons. Angular sensors on lower-limb exoskeletons are essential for joint
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Gait phase is widely used for gait trajectory generation, gait control and gait evaluation on lower-limb exoskeletons. So far, a variety of methods have been developed to identify the gait phase for lower-limb exoskeletons. Angular sensors on lower-limb exoskeletons are essential for joint closed-loop controlling; however, other types of sensors, such as plantar pressure, attitude or inertial measurement unit, are not indispensable.Therefore, to make full use of existing sensors, we propose a novel gait phase recognition method for lower-limb exoskeletons using only joint angular sensors. The method consists of two procedures. Firstly, the gait deviation distances during walking are calculated and classified by Fisher’s linear discriminant method, and one gait cycle is divided into eight gait phases. The validity of the classification results is also verified based on large gait samples. Secondly, we build a gait phase recognition model based on multilayer perceptron and train it with the phase-labeled gait data. The experimental result of cross-validation shows that the model has a 94.45% average correct rate of set (CRS) and an 87.22% average correct rate of phase (CRP) on the testing set, and it can predict the gait phase accurately. The novel method avoids installing additional sensors on the exoskeleton or human body and simplifies the sensory system of the lower-limb exoskeleton. Full article
(This article belongs to the Special Issue Wearable Biomedical Sensors)
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Open AccessArticle Analysis of Abnormal Intra-QRS Potentials in Signal-Averaged Electrocardiograms Using a Radial Basis Function Neural Network
Sensors 2016, 16(10), 1580; doi:10.3390/s16101580
Received: 27 June 2016 / Revised: 31 August 2016 / Accepted: 19 September 2016 / Published: 27 September 2016
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Abstract
Abnormal intra-QRS potentials (AIQPs) are commonly observed in patients at high risk for ventricular tachycardia. We present a method for approximating a measured QRS complex using a non-linear neural network with all radial basis functions having the same smoothness. We extracted the high
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Abnormal intra-QRS potentials (AIQPs) are commonly observed in patients at high risk for ventricular tachycardia. We present a method for approximating a measured QRS complex using a non-linear neural network with all radial basis functions having the same smoothness. We extracted the high frequency, but low amplitude intra-QRS potentials using the approximation error to identify possible ventricular tachycardia. With a specified number of neurons, we performed an orthogonal least squares algorithm to determine the center of each Gaussian radial basis function. We found that the AIQP estimation error arising from part of the normal QRS complex could cause clinicians to misjudge patients with ventricular tachycardia. Our results also show that it is possible to correct this misjudgment by combining multiple AIQP parameters estimated using various spread parameters and numbers of neurons. Clinical trials demonstrate that higher AIQP-to-QRS ratios in the X, Y and Z leads are visible in patients with ventricular tachycardia than in normal subjects. A linear combination of 60 AIQP-to-QRS ratios can achieve 100% specificity, 90% sensitivity, and 95.8% total prediction accuracy for diagnosing ventricular tachycardia. Full article
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Open AccessCommunication A Human Serum-Based Enzyme-Free Continuous Glucose Monitoring Technique Using a Needle-Type Bio-Layer Interference Sensor
Sensors 2016, 16(10), 1581; doi:10.3390/s16101581
Received: 4 July 2016 / Revised: 13 September 2016 / Accepted: 21 September 2016 / Published: 24 September 2016
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Abstract
The incidence of diabetes is continually increasing, and by 2030, it is expected to have increased by 69% and 20% in underdeveloped and developed countries, respectively. Therefore, glucose sensors are likely to remain in high demand in medical device markets. For the current
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The incidence of diabetes is continually increasing, and by 2030, it is expected to have increased by 69% and 20% in underdeveloped and developed countries, respectively. Therefore, glucose sensors are likely to remain in high demand in medical device markets. For the current study, we developed a needle-type bio-layer interference (BLI) sensor that can continuously monitor glucose levels. Using dialysis procedures, we were able to obtain hypoglycemic samples from commercial human serum. These dialysis-derived samples, alongside samples of normal human serum were used to evaluate the utility of the sensor for the detection of the clinical interest range of glucose concentrations (70–200 mg/dL), revealing high system performance for a wide glycemic state range (45–500 mg/dL). Reversibility and reproducibility were also tested over a range of time spans. Combined with existing BLI system technology, this sensor holds great promise for use as a wearable online continuous glucose monitoring system for patients in a hospital setting. Full article
(This article belongs to the Special Issue Glucose Sensors: Revolution in Diabetes Management 2016)
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Open AccessArticle A Wireless 32-Channel Implantable Bidirectional Brain Machine Interface
Sensors 2016, 16(10), 1582; doi:10.3390/s16101582
Received: 20 July 2016 / Revised: 17 September 2016 / Accepted: 21 September 2016 / Published: 24 September 2016
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Abstract
All neural information systems (NIS) rely on sensing neural activity to supply commands and control signals for computers, machines and a variety of prosthetic devices. Invasive systems achieve a high signal-to-noise ratio (SNR) by eliminating the volume conduction problems caused by tissue and
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All neural information systems (NIS) rely on sensing neural activity to supply commands and control signals for computers, machines and a variety of prosthetic devices. Invasive systems achieve a high signal-to-noise ratio (SNR) by eliminating the volume conduction problems caused by tissue and bone. An implantable brain machine interface (BMI) using intracortical electrodes provides excellent detection of a broad range of frequency oscillatory activities through the placement of a sensor in direct contact with cortex. This paper introduces a compact-sized implantable wireless 32-channel bidirectional brain machine interface (BBMI) to be used with freely-moving primates. The system is designed to monitor brain sensorimotor rhythms and present current stimuli with a configurable duration, frequency and amplitude in real time to the brain based on the brain activity report. The battery is charged via a novel ultrasonic wireless power delivery module developed for efficient delivery of power into a deeply-implanted system. The system was successfully tested through bench tests and in vivo tests on a behaving primate to record the local field potential (LFP) oscillation and stimulate the target area at the same time. Full article
(This article belongs to the Special Issue Sensing Technology for Healthcare System)
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Open AccessArticle Strain Modal Analysis of Small and Light Pipes Using Distributed Fibre Bragg Grating Sensors
Sensors 2016, 16(10), 1583; doi:10.3390/s16101583
Received: 29 July 2016 / Revised: 3 September 2016 / Accepted: 13 September 2016 / Published: 25 September 2016
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Abstract
Vibration fatigue failure is a critical problem of hydraulic pipes under severe working conditions. Strain modal testing of small and light pipes is a good option for dynamic characteristic evaluation, structural health monitoring and damage identification. Unique features such as small size, light
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Vibration fatigue failure is a critical problem of hydraulic pipes under severe working conditions. Strain modal testing of small and light pipes is a good option for dynamic characteristic evaluation, structural health monitoring and damage identification. Unique features such as small size, light weight, and high multiplexing capability enable Fibre Bragg Grating (FBG) sensors to measure structural dynamic responses where sensor size and placement are critical. In this paper, experimental strain modal analysis of pipes using distributed FBG sensors ispresented. Strain modal analysis and parameter identification methods are introduced. Experimental strain modal testing and finite element analysis for a cantilever pipe have been carried out. The analysis results indicate that the natural frequencies and strain mode shapes of the tested pipe acquired by FBG sensors are in good agreement with the results obtained by a reference accelerometer and simulation outputs. The strain modal parameters of a hydraulic pipe were obtained by the proposed strain modal testing method. FBG sensors have been shown to be useful in the experimental strain modal analysis of small and light pipes in mechanical, aeronautic and aerospace applications. Full article
(This article belongs to the Special Issue Recent Advances in Fiber Bragg Grating Sensing)
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Open AccessArticle Electrocardiogram Signal Denoising Using Extreme-Point Symmetric Mode Decomposition and Nonlocal Means
Sensors 2016, 16(10), 1584; doi:10.3390/s16101584
Received: 24 April 2016 / Revised: 8 September 2016 / Accepted: 20 September 2016 / Published: 25 September 2016
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Abstract
Electrocardiogram (ECG) signals contain a great deal of essential information which can be utilized by physicians for the diagnosis of heart diseases. Unfortunately, ECG signals are inevitably corrupted by noise which will severely affect the accuracy of cardiovascular disease diagnosis. Existing ECG signal
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Electrocardiogram (ECG) signals contain a great deal of essential information which can be utilized by physicians for the diagnosis of heart diseases. Unfortunately, ECG signals are inevitably corrupted by noise which will severely affect the accuracy of cardiovascular disease diagnosis. Existing ECG signal denoising methods based on wavelet shrinkage, empirical mode decomposition and nonlocal means (NLM) cannot provide sufficient noise reduction or well-detailed preservation, especially with high noise corruption. To address this problem, we have proposed a hybrid ECG signal denoising scheme by combining extreme-point symmetric mode decomposition (ESMD) with NLM. In the proposed method, the noisy ECG signals will first be decomposed into several intrinsic mode functions (IMFs) and adaptive global mean using ESMD. Then, the first several IMFs will be filtered by the NLM method according to the frequency of IMFs while the QRS complex detected from these IMFs as the dominant feature of the ECG signal and the remaining IMFs will be left unprocessed. The denoised IMFs and unprocessed IMFs are combined to produce the final denoised ECG signals. Experiments on both simulated ECG signals and real ECG signals from the MIT-BIH database demonstrate that the proposed method can suppress noise in ECG signals effectively while preserving the details very well, and it outperforms several state-of-the-art ECG signal denoising methods in terms of signal-to-noise ratio (SNR), root mean squared error (RMSE), percent root mean square difference (PRD) and mean opinion score (MOS) error index. Full article
(This article belongs to the Special Issue Noninvasive Biomedical Sensors)
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Open AccessArticle Inferring Human Activity Recognition with Ambient Sound on Wireless Sensor Nodes
Sensors 2016, 16(10), 1586; doi:10.3390/s16101586
Received: 10 May 2016 / Revised: 19 September 2016 / Accepted: 20 September 2016 / Published: 27 September 2016
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Abstract
A wireless sensor network that consists of nodes with a sound sensor can be used to obtain context awareness in home environments. However, the limited processing power of wireless nodes offers a challenge when extracting features from the signal, and subsequently, classifying the
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A wireless sensor network that consists of nodes with a sound sensor can be used to obtain context awareness in home environments. However, the limited processing power of wireless nodes offers a challenge when extracting features from the signal, and subsequently, classifying the source. Although multiple papers can be found on different methods of sound classification, none of these are aimed at limited hardware or take the efficiency of the algorithms into account. In this paper, we compare and evaluate several classification methods on a real sensor platform using different feature types and classifiers, in order to find an approach that results in a good classifier that can run on limited hardware. To be as realistic as possible, we trained our classifiers using sound waves from many different sources. We conclude that despite the fact that the classifiers are often of low quality due to the highly restricted hardware resources, sufficient performance can be achieved when (1) the window length for our classifiers is increased, and (2) if we apply a two-step approach that uses a refined classification after a global classification has been performed. Full article
(This article belongs to the Section Physical Sensors)
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Open AccessArticle Design of a Piezoelectric Accelerometer with High Sensitivity and Low Transverse Effect
Sensors 2016, 16(10), 1587; doi:10.3390/s16101587
Received: 19 July 2016 / Revised: 20 September 2016 / Accepted: 21 September 2016 / Published: 26 September 2016
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Abstract
In order to meet the requirements of cable fault detection, a new structure of piezoelectric accelerometer was designed and analyzed in detail. The structure was composed of a seismic mass, two sensitive beams, and two added beams. Then, simulations including the maximum stress,
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In order to meet the requirements of cable fault detection, a new structure of piezoelectric accelerometer was designed and analyzed in detail. The structure was composed of a seismic mass, two sensitive beams, and two added beams. Then, simulations including the maximum stress, natural frequency, and output voltage were carried out. Moreover, comparisons with traditional structures of piezoelectric accelerometer were made. To verify which vibration mode is the dominant one on the acceleration and the space between the mass and glass, mode analysis and deflection analysis were carried out. Fabricated on an n-type single crystal silicon wafer, the sensor chips were wire-bonged to printed circuit boards (PCBs) and simply packaged for experiments. Finally, a vibration test was conducted. The results show that the proposed piezoelectric accelerometer has high sensitivity, low resonance frequency, and low transverse effect. Full article
(This article belongs to the Special Issue Inertial Sensors and Systems 2016)
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Open AccessArticle Effect of Nanoparticles on Modified Screen Printed Inhibition Superoxide Dismutase Electrodes for Aluminum
Sensors 2016, 16(10), 1588; doi:10.3390/s16101588
Received: 26 July 2016 / Revised: 10 September 2016 / Accepted: 20 September 2016 / Published: 26 September 2016
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Abstract
A novel amperometric biosensor for the determination of Al(III) based on the inhibition of the enzyme superoxide dismutase has been developed. The oxidation signal of epinephrine substrate was affected by the presence of Al(III) ions leading to a decrease in its amperometric current.
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A novel amperometric biosensor for the determination of Al(III) based on the inhibition of the enzyme superoxide dismutase has been developed. The oxidation signal of epinephrine substrate was affected by the presence of Al(III) ions leading to a decrease in its amperometric current. The immobilization of the enzyme was performed with glutaraldehyde on screen-printed carbon electrodes modifiedwith tetrathiofulvalene (TTF) and different types ofnanoparticles. Nanoparticles of gold, platinum, rhodium and palladium were deposited on screen printed carbon electrodes by means of two electrochemical procedures. Nanoparticles were characterized trough scanning electronic microscopy, X-rays fluorescence, and atomic force microscopy. Palladium nanoparticles showed lower atomic force microscopy parameters and higher slope of aluminum calibration curves and were selected to perform sensor validation. The developed biosensor has a detection limit of 2.0 ± 0.2 μM for Al(III), with a reproducibility of 7.9% (n = 5). Recovery of standard reference material spiked to buffer solution was 103.8% with a relative standard deviation of 4.8% (n = 5). Recovery of tap water spiked with the standard reference material was 100.5 with a relative standard deviation of 3.4% (n = 3). The study of interfering ions has also been carried out. Full article
(This article belongs to the Special Issue Amperometric Biosensors)
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Open AccessArticle Enhanced RGB-D Mapping Method for Detailed 3D Indoor and Outdoor Modeling
Sensors 2016, 16(10), 1589; doi:10.3390/s16101589
Received: 30 April 2016 / Revised: 12 September 2016 / Accepted: 20 September 2016 / Published: 27 September 2016
Cited by 4 | PDF Full-text (3910 KB) | HTML Full-text | XML Full-text
Abstract
RGB-D sensors (sensors with RGB camera and Depth camera) are novel sensing systems that capture RGB images along with pixel-wise depth information. Although they are widely used in various applications, RGB-D sensors have significant drawbacks including limited measurement ranges (e.g., within 3 m)
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RGB-D sensors (sensors with RGB camera and Depth camera) are novel sensing systems that capture RGB images along with pixel-wise depth information. Although they are widely used in various applications, RGB-D sensors have significant drawbacks including limited measurement ranges (e.g., within 3 m) and errors in depth measurement increase with distance from the sensor with respect to 3D dense mapping. In this paper, we present a novel approach to geometrically integrate the depth scene and RGB scene to enlarge the measurement distance of RGB-D sensors and enrich the details of model generated from depth images. First, precise calibration for RGB-D Sensors is introduced. In addition to the calibration of internal and external parameters for both, IR camera and RGB camera, the relative pose between RGB camera and IR camera is also calibrated. Second, to ensure poses accuracy of RGB images, a refined false features matches rejection method is introduced by combining the depth information and initial camera poses between frames of the RGB-D sensor. Then, a global optimization model is used to improve the accuracy of the camera pose, decreasing the inconsistencies between the depth frames in advance. In order to eliminate the geometric inconsistencies between RGB scene and depth scene, the scale ambiguity problem encountered during the pose estimation with RGB image sequences can be resolved by integrating the depth and visual information and a robust rigid-transformation recovery method is developed to register RGB scene to depth scene. The benefit of the proposed joint optimization method is firstly evaluated with the publicly available benchmark datasets collected with Kinect. Then, the proposed method is examined by tests with two sets of datasets collected in both outside and inside environments. The experimental results demonstrate the feasibility and robustness of the proposed method. Full article
(This article belongs to the Section Remote Sensors)
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Open AccessArticle Effective Waterline Detection of Unmanned Surface Vehicles Based on Optical Images
Sensors 2016, 16(10), 1590; doi:10.3390/s16101590
Received: 14 July 2016 / Revised: 18 September 2016 / Accepted: 20 September 2016 / Published: 27 September 2016
PDF Full-text (16314 KB) | HTML Full-text | XML Full-text
Abstract
Real-time and accurate detection of the sailing or water area will help realize unmanned surface vehicle (USV) systems. Although there are some methods for using optical images in USV-oriented environmental modeling, both the robustness and precision of these published waterline detection methods are
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Real-time and accurate detection of the sailing or water area will help realize unmanned surface vehicle (USV) systems. Although there are some methods for using optical images in USV-oriented environmental modeling, both the robustness and precision of these published waterline detection methods are comparatively low for a real USV system moving in a complicated environment. This paper proposes an efficient waterline detection method based on structure extraction and texture analysis with respect to optical images and presents a practical application to a USV system for validation. First, the basic principles of local binary patterns (LBPs) and gray level co-occurrence matrix (GLCM) were analyzed, and their advantages were integrated to calculate the texture information of river images. Then, structure extraction was introduced to preprocess the original river images so that the textures resulting from USV motion, wind, and illumination are removed. In the practical application, the waterlines of many images captured by the USV system moving along an inland river were detected with the proposed method, and the results were compared with those of edge detection and super pixel segmentation. The experimental results showed that the proposed algorithm is effective and robust. The average error of the proposed method was 1.84 pixels, and the mean square deviation was 4.57 pixels. Full article
(This article belongs to the Section Physical Sensors)
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Open AccessArticle Infrared LED Enhanced Spectroscopic CdZnTe Detector Working under High Fluxes of X-rays
Sensors 2016, 16(10), 1591; doi:10.3390/s16101591
Received: 18 July 2016 / Revised: 2 September 2016 / Accepted: 6 September 2016 / Published: 27 September 2016
Cited by 1 | PDF Full-text (2752 KB) | HTML Full-text | XML Full-text
Abstract
This paper describes an application of infrared light-induced de-polarization applied on a polarized CdZnTe detector working under high radiation fluxes. We newly demonstrate the influence of a high flux of X-rays and simultaneous 1200-nm LED illumination on the spectroscopic properties of a CdZnTe
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This paper describes an application of infrared light-induced de-polarization applied on a polarized CdZnTe detector working under high radiation fluxes. We newly demonstrate the influence of a high flux of X-rays and simultaneous 1200-nm LED illumination on the spectroscopic properties of a CdZnTe detector. CdZnTe detectors operating under high radiation fluxes usually suffer from the polarization effect, which occurs due to a screening of the internal electric field by a positive space charge caused by photogenerated holes trapped at a deep level. Polarization results in the degradation of detector charge collection efficiency. We studied the spectroscopic behavior of CdZnTe under various X-ray fluxes ranging between 5 × 10 5 and 8 × 10 6 photons per mm 2 per second. It was observed that polarization occurs at an X-ray flux higher than 3 × 10 6 mm 2 ·s 1 . Using simultaneous illumination of the detector by a de-polarizing LED at 1200 nm, it was possible to recover X-ray spectra originally deformed by the polarization effect. Full article
(This article belongs to the Section Physical Sensors)
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Open AccessArticle The Design and Analysis of Split Row-Column Addressing Array for 2-D Transducer
Sensors 2016, 16(10), 1592; doi:10.3390/s16101592
Received: 11 April 2016 / Revised: 7 September 2016 / Accepted: 9 September 2016 / Published: 27 September 2016
PDF Full-text (5307 KB) | HTML Full-text | XML Full-text
Abstract
For 3-D ultrasound imaging, the row-column addressing (RCA) with 2N connections for an N × N 2-D array makes the fabrication and interconnection simpler than the fully addressing with N2 connections. However, RCA degrades the image quality because of defocusing in
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For 3-D ultrasound imaging, the row-column addressing (RCA) with 2N connections for an N × N 2-D array makes the fabrication and interconnection simpler than the fully addressing with N2 connections. However, RCA degrades the image quality because of defocusing in signal channel direction in the transmit event. To solve this problem, a split row-column addressing scheme (SRCA) is proposed in this paper. Rather than connecting all the elements in the signal channel direction together, this scheme divides the elements in the signal channel direction into several disconnected blocks, thus enables focusing beam access in both signal channel and switch channel directions. Selecting an appropriate split scheme is the key for SRCA to maintaining a reasonable tradeoff between the image quality and the number of connections. Various split schemes for a 32 × 32 array are fully investigated with point spread function (PSF) analysis and imaging simulation. The result shows the split scheme with five blocks (4, 6, 12, 6, and 4 elements of each block) can provide similar image quality to fully addressing. The splitting schemes for different array sizes from 16 × 16 to 96 × 96 are also discussed. Full article
(This article belongs to the Section Physical Sensors)
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Open AccessArticle Design of a Sub-Picosecond Jitter with Adjustable-Range CMOS Delay-Locked Loop for High-Speed and Low-Power Applications
Sensors 2016, 16(10), 1593; doi:10.3390/s16101593
Received: 28 July 2016 / Revised: 5 September 2016 / Accepted: 5 September 2016 / Published: 28 September 2016
Cited by 1 | PDF Full-text (6168 KB) | HTML Full-text | XML Full-text
Abstract
A Delay-Locked Loop (DLL) with a modified charge pump circuit is proposed for generating high-resolution linear delay steps with sub-picosecond jitter performance and adjustable delay range. The small-signal model of the modified charge pump circuit is analyzed to bring forth the relationship between
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A Delay-Locked Loop (DLL) with a modified charge pump circuit is proposed for generating high-resolution linear delay steps with sub-picosecond jitter performance and adjustable delay range. The small-signal model of the modified charge pump circuit is analyzed to bring forth the relationship between the DLL’s internal control voltage and output time delay. Circuit post-layout simulation shows that a 0.97 ps delay step within a 69 ps delay range with 0.26 ps Root-Mean Square (RMS) jitter performance is achievable using a standard 0.13 µm Complementary Metal-Oxide Semiconductor (CMOS) process. The post-layout simulation results show that the power consumption of the proposed DLL architecture’s circuit is 0.1 mW when the DLL is operated at 2 GHz. Full article
(This article belongs to the Special Issue Imaging: Sensors and Technologies) Printed Edition available
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Open AccessArticle Multi-Frequency Target Detection Techniques for DVB-T Based Passive Radar Sensors
Sensors 2016, 16(10), 1594; doi:10.3390/s16101594
Received: 13 July 2016 / Revised: 6 September 2016 / Accepted: 7 September 2016 / Published: 28 September 2016
Cited by 2 | PDF Full-text (4288 KB) | HTML Full-text | XML Full-text
Abstract
This paper investigates the possibility to improve target detection capability in a DVB-T- based passive radar sensor by jointly exploiting multiple digital television channels broadcast by the same transmitter of opportunity. Based on the remarkable results obtained by such a multi-frequency approach using
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This paper investigates the possibility to improve target detection capability in a DVB-T- based passive radar sensor by jointly exploiting multiple digital television channels broadcast by the same transmitter of opportunity. Based on the remarkable results obtained by such a multi-frequency approach using other signals of opportunity (i.e., FM radio broadcast transmissions), we propose appropriate modifications to the previously devised signal processing techniques for them to be effective in the newly considered scenarios. The resulting processing schemes are extensively applied against experimental DVB-T-based passive radar data pertaining to different surveillance applications. The obtained results clearly show the effectiveness of the proposed multi-frequency approaches and demonstrate their suitability for application in the considered scenarios. Full article
(This article belongs to the Special Issue Non-Contact Sensing)
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Open AccessArticle Home Automation System Based on Intelligent Transducer Enablers
Sensors 2016, 16(10), 1595; doi:10.3390/s16101595
Received: 9 June 2016 / Revised: 13 September 2016 / Accepted: 20 September 2016 / Published: 28 September 2016
Cited by 5 | PDF Full-text (10326 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents a novel home automation system named HASITE (Home Automation System based on Intelligent Transducer Enablers), which has been specifically designed to identify and configure transducers easily and quickly. These features are especially useful in situations where many transducers are deployed,
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This paper presents a novel home automation system named HASITE (Home Automation System based on Intelligent Transducer Enablers), which has been specifically designed to identify and configure transducers easily and quickly. These features are especially useful in situations where many transducers are deployed, since their setup becomes a cumbersome task that consumes a significant amount of time and human resources. HASITE simplifies the deployment of a home automation system by using wireless networks and both self-configuration and self-registration protocols. Thanks to the application of these three elements, HASITE is able to add new transducers by just powering them up. According to the tests performed in different realistic scenarios, a transducer is ready to be used in less than 13 s. Moreover, all HASITE functionalities can be accessed through an API, which also allows for the integration of third-party systems. As an example, an Android application based on the API is presented. Remote users can use it to interact with transducers by just using a regular smartphone or a tablet. Full article
(This article belongs to the Special Issue Intelligent Internet of Things (IoT) Networks)
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Open AccessArticle A Real-Time Web of Things Framework with Customizable Openness Considering Legacy Devices
Sensors 2016, 16(10), 1596; doi:10.3390/s16101596
Received: 7 July 2016 / Revised: 17 September 2016 / Accepted: 23 September 2016 / Published: 28 September 2016
Cited by 2 | PDF Full-text (6484 KB) | HTML Full-text | XML Full-text
Abstract
With the development of the Internet of Things (IoT), resources and applications based on it have emerged on a large scale. However, most efforts are “silo” solutions where devices and applications are tightly coupled. Infrastructures are needed to connect sensors to the Internet,
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With the development of the Internet of Things (IoT), resources and applications based on it have emerged on a large scale. However, most efforts are “silo” solutions where devices and applications are tightly coupled. Infrastructures are needed to connect sensors to the Internet, open up and break the current application silos and move to a horizontal application mode. Based on the concept of Web of Things (WoT), many infrastructures have been proposed to integrate the physical world with the Web. However, issues such as no real-time guarantee, lack of fine-grained control of data, and the absence of explicit solutions for integrating heterogeneous legacy devices, hinder their widespread and practical use. To address these issues, this paper proposes a WoT resource framework that provides the infrastructures for the customizable openness and sharing of users’ data and resources under the premise of ensuring the real-time behavior of their own applications. The proposed framework is validated by actual systems and experimental evaluations. Full article
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Open AccessCommunication The Usability of a Pressure-Indicating Film to Measure the Teat Load Caused by a Collapsing Liner
Sensors 2016, 16(10), 1597; doi:10.3390/s16101597
Received: 8 August 2016 / Revised: 13 September 2016 / Accepted: 23 September 2016 / Published: 28 September 2016
Cited by 1 | PDF Full-text (1812 KB) | HTML Full-text | XML Full-text
Abstract
Prevention of damage to the teat and mastitis requires determination of the teat load caused by a collapsing liner. The aim of this study was to test a pressure-indicating film designed to measure the pressure between a collapsing liner and artificial teats. The
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Prevention of damage to the teat and mastitis requires determination of the teat load caused by a collapsing liner. The aim of this study was to test a pressure-indicating film designed to measure the pressure between a collapsing liner and artificial teats. The Ultra Super Low and the Extreme Low pressure-indicating films were tested on two types of artificial teat. The experiments were performed with a conventional milking cluster equipped with round silicone liners. For each teat and film type, 30 repetitions were performed. Each repetition was performed with a new piece of film. Kruskal-Wallis tests were performed to detect differences between the pressure values for the different teats. The area of regions where pressure-indication color developed was calculated to determine the most suitable film type. Both film types measured the pressure applied to both artificial teats by the teat cup liner. Thus, the pressure-indicating films can be used to measure the pressure between a collapsing liner and an artificial teat. Based on the results of the present investigation, a pressure-indicating film with the measurement ranges of both film types combined would be an optimal tool to measure the overall pressure between an artificial teat and a collapsing liner. Full article
(This article belongs to the Section Physical Sensors)
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Open AccessArticle Fast Industrial Inspection of Optical Thin Film Using Optical Coherence Tomography
Sensors 2016, 16(10), 1598; doi:10.3390/s16101598
Received: 1 June 2016 / Revised: 19 September 2016 / Accepted: 22 September 2016 / Published: 28 September 2016
Cited by 5 | PDF Full-text (7934 KB) | HTML Full-text | XML Full-text
Abstract
An application of spectral domain optical coherence tomography (SD-OCT) was demonstrated for a fast industrial inspection of an optical thin film panel. An optical thin film sample similar to a liquid crystal display (LCD) panel was examined. Two identical SD-OCT systems were utilized
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An application of spectral domain optical coherence tomography (SD-OCT) was demonstrated for a fast industrial inspection of an optical thin film panel. An optical thin film sample similar to a liquid crystal display (LCD) panel was examined. Two identical SD-OCT systems were utilized for parallel scanning of a complete sample in half time. Dual OCT inspection heads were utilized for transverse (fast) scanning, while a stable linear motorized translational stage was used for lateral (slow) scanning. The cross-sectional and volumetric images of an optical thin film sample were acquired to detect the defects in glass and other layers that are difficult to observe using visual inspection methods. The rapid inspection enabled by this setup led to the early detection of product defects on the manufacturing line, resulting in a significant improvement in the quality assurance of industrial products. Full article
(This article belongs to the Special Issue Non-Contact Sensing)
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Open AccessArticle Characterization of Screen-Printed Organic Electrochemical Transistors to Detect Cations of Different Sizes
Sensors 2016, 16(10), 1599; doi:10.3390/s16101599
Received: 5 July 2016 / Revised: 9 September 2016 / Accepted: 14 September 2016 / Published: 28 September 2016
Cited by 1 | PDF Full-text (2846 KB) | HTML Full-text | XML Full-text
Abstract
A novel screen-printing fabrication method was used to prepare organic electrochemical transistors (OECTs) based on poly(3,4-ethylenedioxythiophene) doped with polysterene sulfonate (PEDOT:PSS). Initially, three types of these screen-printed OECTs with a different channel and gate areas ratio were compared in terms of output characteristics,
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A novel screen-printing fabrication method was used to prepare organic electrochemical transistors (OECTs) based on poly(3,4-ethylenedioxythiophene) doped with polysterene sulfonate (PEDOT:PSS). Initially, three types of these screen-printed OECTs with a different channel and gate areas ratio were compared in terms of output characteristics, transfer characteristics, and current modulation in a phosphate buffered saline (PBS) solution. Results confirm that transistors with a gate electrode larger than the channel exhibit higher modulation. OECTs with this geometry were therefore chosen to investigate their ion-sensitive properties in aqueous solutions of cations of different sizes (sodium and rhodamine B). The effect of the gate electrode was additionally studied by comparing these all-PEDOT:PSS transistors with OECTs with the same geometry but with a non-polarizable metal gate (Ag). The operation of the all-PEDOT:PSS OECTs yields a response that is not dependent on a Na+ or rhodamine concentration. The weak modulation of these transistors can be explained assuming that PEDOT:PSS behaves like a supercapacitor. In contrast, the operation of Ag-Gate OECTs yields a response that is dependent on ion concentration due to the redox reaction taking place at the gate electrode with Cl counter-ions. This indicates that, for cation detection, the response is maximized in OECTs with non-polarizable gate electrodes. Full article
(This article belongs to the Section Chemical Sensors)
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Open AccessArticle Colorimetric Integrated PCR Protocol for Rapid Detection of Vibrio parahaemolyticus
Sensors 2016, 16(10), 1600; doi:10.3390/s16101600
Received: 9 August 2016 / Revised: 7 September 2016 / Accepted: 12 September 2016 / Published: 28 September 2016
Cited by 5 | PDF Full-text (2210 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Rapid detection of pathogens is of great significance for food safety and disease diagnosis. A new colorimetric method for rapid and easy detection of Vibrio parahaemolyticus (V. parahaemolyticus or Vp) has been developed in this research. A specific sequence was designed and
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Rapid detection of pathogens is of great significance for food safety and disease diagnosis. A new colorimetric method for rapid and easy detection of Vibrio parahaemolyticus (V. parahaemolyticus or Vp) has been developed in this research. A specific sequence was designed and integrated with the forward primer for molecular detection of Vp. This specific sequence was tested and treated as the horseradish peroxidase (HRP)-mimicking DNAzyme and could be amplified during the polymerase chain reaction (PCR) process. The products of PCR including the sequence of HRP-mimicking DNAzyme could produce the distinguished color in the presence of catalysis substrates. The optical signal of the catalysis reaction, which is in a linear relationship with the initial template of Vp, could be determined with the naked eye or measured with Ultraviolet-visible (UV-vis) for qualitative and quantitative detections, respectively. Based on the optical signal intensity, rapid and easy detection of Vp was successfully achieved with satisfied sensitivity and specificity. Furthermore, the detection of tdh, trh, tlh and toxR virulence genes of two Vp species (Vp 33847 and Vp 17802) were all performed successfully with this developed colorimetric integrated PCR protocol, which demonstrated potential applicability for the rapid detection of other bacteria. Full article
(This article belongs to the Special Issue Nanobiosensing for Sensors)
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Open AccessArticle Temporal Data-Driven Sleep Scheduling and Spatial Data-Driven Anomaly Detection for Clustered Wireless Sensor Networks
Sensors 2016, 16(10), 1601; doi:10.3390/s16101601
Received: 18 July 2016 / Revised: 18 September 2016 / Accepted: 22 September 2016 / Published: 28 September 2016
Cited by 1 | PDF Full-text (3999 KB) | HTML Full-text | XML Full-text
Abstract
The spatial–temporal correlation is an important feature of sensor data in wireless sensor networks (WSNs). Most of the existing works based on the spatial–temporal correlation can be divided into two parts: redundancy reduction and anomaly detection. These two parts are pursued separately in
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The spatial–temporal correlation is an important feature of sensor data in wireless sensor networks (WSNs). Most of the existing works based on the spatial–temporal correlation can be divided into two parts: redundancy reduction and anomaly detection. These two parts are pursued separately in existing works. In this work, the combination of temporal data-driven sleep scheduling (TDSS) and spatial data-driven anomaly detection is proposed, where TDSS can reduce data redundancy. The TDSS model is inspired by transmission control protocol (TCP) congestion control. Based on long and linear cluster structure in the tunnel monitoring system, cooperative TDSS and spatial data-driven anomaly detection are then proposed. To realize synchronous acquisition in the same ring for analyzing the situation of every ring, TDSS is implemented in a cooperative way in the cluster. To keep the precision of sensor data, spatial data-driven anomaly detection based on the spatial correlation and Kriging method is realized to generate an anomaly indicator. The experiment results show that cooperative TDSS can realize non-uniform sensing effectively to reduce the energy consumption. In addition, spatial data-driven anomaly detection is quite significant for maintaining and improving the precision of sensor data. Full article
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Open AccessArticle Broadband Cooperative Spectrum Sensing Based on Distributed Modulated Wideband Converter
Sensors 2016, 16(10), 1602; doi:10.3390/s16101602
Received: 9 July 2016 / Revised: 3 September 2016 / Accepted: 23 September 2016 / Published: 28 September 2016
Cited by 4 | PDF Full-text (1722 KB) | HTML Full-text | XML Full-text
Abstract
The modulated wideband converter (MWC) is a kind of sub-Nyquist sampling system which is developed from compressed sensing theory. It accomplishes highly accurate broadband sparse signal recovery by multichannel sub-Nyquist sampling sequences. However, when the number of sparse sub-bands becomes large, the amount
[...] Read more.
The modulated wideband converter (MWC) is a kind of sub-Nyquist sampling system which is developed from compressed sensing theory. It accomplishes highly accurate broadband sparse signal recovery by multichannel sub-Nyquist sampling sequences. However, when the number of sparse sub-bands becomes large, the amount of sampling channels increases proportionally. Besides, it is very hard to adjust the number of sampling channels when the sparsity changes, because its undersampling board is designed by a given sparsity. Such hardware cost and inconvenience are unacceptable in practical applications. This paper proposes a distributed modulated wideband converter (DMWC) scheme innovatively, which regards one sensor node as one sampling channel and combines MWC technology with a broadband cooperative spectrum sensing network perfectly. Being different from the MWC scheme, DMWC takes phase shift and transmission loss into account in the input terminal, which are unavoidable in practical application. Our scheme is not only able to recover the support of broadband sparse signals quickly and accurately, but also reduces the hardware cost of the single node drastically. Theoretical analysis and numerical simulations show that phase shift has no influence on the recovery of frequency support, but transmission loss degrades the recovery performance to a different extent. Nevertheless, we can increase the amount of cooperative nodes and select satisfactory nodes by a different transmission distance to improve the recovery performance. Furthermore, we can adjust the amount of cooperative nodes flexibly when the sparsity changes. It indicates DMWC is extremely effective in the broadband cooperative spectrum sensing network. Full article
(This article belongs to the Section Sensor Networks)
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Open AccessArticle An Impedance-Based Mold Sensor with on-Chip Optical Reference
Sensors 2016, 16(10), 1603; doi:10.3390/s16101603
Received: 28 July 2016 / Revised: 12 September 2016 / Accepted: 23 September 2016 / Published: 28 September 2016
Cited by 2 | PDF Full-text (3561 KB) | HTML Full-text | XML Full-text
Abstract
A new miniaturized sensor system with an internal optical reference for the detection of mold growth is presented. The sensor chip comprises a reaction chamber provided with a culture medium that promotes the growth of mold species from mold spores. The mold detection
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A new miniaturized sensor system with an internal optical reference for the detection of mold growth is presented. The sensor chip comprises a reaction chamber provided with a culture medium that promotes the growth of mold species from mold spores. The mold detection is performed by measuring impedance changes with integrated electrodes fabricated inside the reaction chamber. The impedance change in the culture medium is caused by shifts in the pH (i.e., from 5.5 to 8) as the mold grows. In order to determine the absolute pH value without the need for calibration, a methyl red indicator dye has been added to the culture medium. It changes the color of the medium as the pH passes specific values. This colorimetric principle now acts as a reference measurement. It also allows the sensitivity of the impedance sensor to be established in terms of impedance change per pH unit. Major mold species that are involved in the contamination of food, paper and indoor environments, like Fusarium oxysporum, Fusarium incarnatum, Eurotium amstelodami, Aspergillus penicillioides and Aspergillus restrictus, have been successfully analyzed on-chip. Full article
(This article belongs to the Section Biosensors)
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Open AccessArticle A Toolbox of Genetically Encoded FRET-Based Biosensors for Rapid l-Lysine Analysis
Sensors 2016, 16(10), 1604; doi:10.3390/s16101604
Received: 2 August 2016 / Revised: 15 September 2016 / Accepted: 20 September 2016 / Published: 28 September 2016
Cited by 1 | PDF Full-text (4616 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Background: The fast development of microbial production strains for basic and fine chemicals is increasingly carried out in small scale cultivation systems to allow for higher throughput. Such parallelized systems create a need for new rapid online detection systems to quantify the respective
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Background: The fast development of microbial production strains for basic and fine chemicals is increasingly carried out in small scale cultivation systems to allow for higher throughput. Such parallelized systems create a need for new rapid online detection systems to quantify the respective target compound. In this regard, biosensors, especially genetically encoded Förster resonance energy transfer (FRET)-based biosensors, offer tremendous opportunities. As a proof-of-concept, we have created a toolbox of FRET-based biosensors for the ratiometric determination of l-lysine in fermentation broth. Methods: The sensor toolbox was constructed based on a sensor that consists of an optimized central lysine-/arginine-/ornithine-binding protein (LAO-BP) flanked by two fluorescent proteins (enhanced cyan fluorescent protein (ECFP), Citrine). Further sensor variants with altered affinity and sensitivity were obtained by circular permutation of the binding protein as well as the introduction of flexible and rigid linkers between the fluorescent proteins and the LAO-BP, respectively. Results: The sensor prototype was applied to monitor the extracellular l-lysine concentration of the l-lysine producing Corynebacterium glutamicum (C. glutamicum) strain DM1933 in a BioLector® microscale cultivation device. The results matched well with data obtained by HPLC analysis and the Ninhydrin assay, demonstrating the high potential of FRET-based biosensors for high-throughput microbial bioprocess optimization. Full article
(This article belongs to the Special Issue FRET Biosensors)
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Open AccessArticle Towards Enhanced Gas Sensor Performance with Fluoropolymer Membranes
Sensors 2016, 16(10), 1605; doi:10.3390/s16101605
Received: 12 July 2016 / Revised: 12 September 2016 / Accepted: 19 September 2016 / Published: 28 September 2016
Cited by 1 | PDF Full-text (4237 KB) | HTML Full-text | XML Full-text
Abstract
In this paper we report on how to increase the selectivity of gas sensors by using fluoropolymer membranes. The mass transport of polar and non-polar gases through a polymer membrane matrix was studied by systematic selection of polymers with different degrees of fluorination,
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In this paper we report on how to increase the selectivity of gas sensors by using fluoropolymer membranes. The mass transport of polar and non-polar gases through a polymer membrane matrix was studied by systematic selection of polymers with different degrees of fluorination, as well as polymers whose monomers have ether groups (-O-) in addition to fluorine groups (-F). For the study, a set of application-relevant gases including H2, CO, CO2, NO2, methane, ethanol, acetone, and acetaldehyde as well as various concentrations of relative humidity were used. These gases have different functional groups and polarities, yet have a similar kinetic diameter and are therefore typically difficult to separate. The concentrations of the gases were chosen according to international indicative limit values (TWA, STEL). To measure the concentration in the feed and permeate, we used tin-dioxide-based metal oxide gas sensors with palladium catalyst (SnO2:Pd), catalytic sensors (also SnO2:Pd-based) and thermal conductivity sensors. This allows a close examination of the interdependence of diffusion and physicochemical operating principle of the sensor. Our goal is to increase the selectivity of gas sensors by using inexpensive fluoropolymer membranes. The measurements showed that through membranes with low polarity, preferably non-polar gases are transported. Furthermore, the degree of crystallization influences the permeability and selectivity of a polymer membrane. Basically the polar polymers showed a higher permeability to water vapor and polar substances than non-polar polymer membranes. Full article
(This article belongs to the Special Issue Gas Nanosensors)
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Open AccessArticle A Hybrid Secure Scheme for Wireless Sensor Networks against Timing Attacks Using Continuous-Time Markov Chain and Queueing Model
Sensors 2016, 16(10), 1606; doi:10.3390/s16101606
Received: 14 April 2016 / Revised: 3 September 2016 / Accepted: 5 September 2016 / Published: 28 September 2016
PDF Full-text (1378 KB) | HTML Full-text | XML Full-text
Abstract
Wireless sensor networks (WSNs) have recently gained popularity for a wide spectrum of applications. Monitoring tasks can be performed in various environments. This may be beneficial in many scenarios, but it certainly exhibits new challenges in terms of security due to increased data
[...] Read more.
Wireless sensor networks (WSNs) have recently gained popularity for a wide spectrum of applications. Monitoring tasks can be performed in various environments. This may be beneficial in many scenarios, but it certainly exhibits new challenges in terms of security due to increased data transmission over the wireless channel with potentially unknown threats. Among possible security issues are timing attacks, which are not prevented by traditional cryptographic security. Moreover, the limited energy and memory resources prohibit the use of complex security mechanisms in such systems. Therefore, balancing between security and the associated energy consumption becomes a crucial challenge. This paper proposes a secure scheme for WSNs while maintaining the requirement of the security-performance tradeoff. In order to proceed to a quantitative treatment of this problem, a hybrid continuous-time Markov chain (CTMC) and queueing model are put forward, and the tradeoff analysis of the security and performance attributes is carried out. By extending and transforming this model, the mean time to security attributes failure is evaluated. Through tradeoff analysis, we show that our scheme can enhance the security of WSNs, and the optimal rekeying rate of the performance and security tradeoff can be obtained. Full article
(This article belongs to the Special Issue Security and Privacy in Sensor Networks)
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Open AccessArticle Analysis on Target Detection and Classification in LTE Based Passive Forward Scattering Radar
Sensors 2016, 16(10), 1607; doi:10.3390/s16101607
Received: 21 April 2016 / Revised: 18 July 2016 / Accepted: 16 August 2016 / Published: 29 September 2016
Cited by 1 | PDF Full-text (5250 KB) | HTML Full-text | XML Full-text
Abstract
The passive bistatic radar (PBR) system can utilize the illuminator of opportunity to enhance radar capability. By utilizing the forward scattering technique and procedure into the specific mode of PBR can provide an improvement in target detection and classification. The system is known
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The passive bistatic radar (PBR) system can utilize the illuminator of opportunity to enhance radar capability. By utilizing the forward scattering technique and procedure into the specific mode of PBR can provide an improvement in target detection and classification. The system is known as passive Forward Scattering Radar (FSR). The passive FSR system can exploit the peculiar advantage of the enhancement in forward scatter radar cross section (FSRCS) for target detection. Thus, the aim of this paper is to show the feasibility of passive FSR for moving target detection and classification by experimental analysis and results. The signal source is coming from the latest technology of 4G Long-Term Evolution (LTE) base station. A detailed explanation on the passive FSR receiver circuit, the detection scheme and the classification algorithm are given. In addition, the proposed passive FSR circuit employs the self-mixing technique at the receiver; hence the synchronization signal from the transmitter is not required. The experimental results confirm the passive FSR system’s capability for ground target detection and classification. Furthermore, this paper illustrates the first classification result in the passive FSR system. The great potential in the passive FSR system provides a new research area in passive radar that can be used for diverse remote monitoring applications. Full article
(This article belongs to the Section Remote Sensors)
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Open AccessArticle Atmospheric Measurements by Ultra-Light SpEctrometer (AMULSE) Dedicated to Vertical Profile in Situ Measurements of Carbon Dioxide (CO2) Under Weather Balloons: Instrumental Development and Field Application
Sensors 2016, 16(10), 1609; doi:10.3390/s16101609
Received: 9 May 2016 / Revised: 20 September 2016 / Accepted: 24 September 2016 / Published: 29 September 2016
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Abstract
The concentration of greenhouse gases in the atmosphere plays an important role in the radiative effects in the Earth’s climate system. Therefore, it is crucial to increase the number of atmospheric observations in order to quantify the natural sinks and emission sources. We
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The concentration of greenhouse gases in the atmosphere plays an important role in the radiative effects in the Earth’s climate system. Therefore, it is crucial to increase the number of atmospheric observations in order to quantify the natural sinks and emission sources. We report in this paper the development of a new compact lightweight spectrometer (1.8 kg) called AMULSE based on near infrared laser technology at 2.04 µm coupled to a 6-m open-path multipass cell. The measurements were made using the Wavelength Modulation Spectroscopy (WMS) technique and the spectrometer is hence dedicated to in situ measuring the vertical profiles of the CO2 at high precision levels (σAllan = 0.96 ppm in 1 s integration time (1σ)) and with high temporal/spatial resolution (1 Hz/5 m) using meteorological balloons. The instrument is compact, robust, cost-effective, fully autonomous, has low-power consumption, a non-intrusive probe and is plug & play. It was first calibrated and validated in the laboratory and then used for 17 successful flights up to 10 km altitude in the region Champagne—Ardenne, France in 2014. A rate of 100% of instrument recovery was validated due to the pre-localization prediction of the Météo—France based on the flight simulation software. Full article
(This article belongs to the Special Issue Autonomous Sensors)
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Open AccessArticle Integration of Error Compensation of Coordinate Measuring Machines into Feature Measurement: Part I—Model Development
Sensors 2016, 16(10), 1610; doi:10.3390/s16101610
Received: 7 August 2016 / Revised: 15 September 2016 / Accepted: 22 September 2016 / Published: 29 September 2016
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Abstract
The development of an error compensation model for coordinate measuring machines (CMMs) and its integration into feature measurement is presented. CMMs are widespread and dependable instruments in industry and laboratories for dimensional measurement. From the tip probe sensor to the machine display, there
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The development of an error compensation model for coordinate measuring machines (CMMs) and its integration into feature measurement is presented. CMMs are widespread and dependable instruments in industry and laboratories for dimensional measurement. From the tip probe sensor to the machine display, there is a complex transformation of probed point coordinates through the geometrical feature model that makes the assessment of accuracy and uncertainty measurement results difficult. Therefore, error compensation is not standardized, conversely to other simpler instruments. Detailed coordinate error compensation models are generally based on CMM as a rigid-body and it requires a detailed mapping of the CMM’s behavior. In this paper a new model type of error compensation is proposed. It evaluates the error from the vectorial composition of length error by axis and its integration into the geometrical measurement model. The non-explained variability by the model is incorporated into the uncertainty budget. Model parameters are analyzed and linked to the geometrical errors and uncertainty of CMM response. Next, the outstanding measurement models of flatness, angle, and roundness are developed. The proposed models are useful for measurement improvement with easy integration into CMM signal processing, in particular in industrial environments where built-in solutions are sought. A battery of implementation tests are presented in Part II, where the experimental endorsement of the model is included. Full article
(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Spain 2016)
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Open AccessArticle A Fourier Transform Spectrometer Based on an Electrothermal MEMS Mirror with Improved Linear Scan Range
Sensors 2016, 16(10), 1611; doi:10.3390/s16101611
Received: 21 August 2016 / Revised: 20 September 2016 / Accepted: 26 September 2016 / Published: 29 September 2016
Cited by 1 | PDF Full-text (4982 KB) | HTML Full-text | XML Full-text
Abstract
A Fourier transform spectrometer (FTS) that incorporates a closed-loop controlled, electrothermally actuated microelectromechanical systems (MEMS) micromirror is proposed and experimentally verified. The scan range and the tilting angle of the mirror plate are the two critical parameters for MEMS-based FTS. In this work,
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A Fourier transform spectrometer (FTS) that incorporates a closed-loop controlled, electrothermally actuated microelectromechanical systems (MEMS) micromirror is proposed and experimentally verified. The scan range and the tilting angle of the mirror plate are the two critical parameters for MEMS-based FTS. In this work, the MEMS mirror with a footprint of 4.3 mm × 3.1 mm is based on a modified lateral-shift-free (LSF) bimorph actuator design with large piston and reduced tilting. Combined with a position-sensitive device (PSD) for tilt angle sensing, the feedback controlled MEMS mirror generates a 430 µm stable linear piston scan with the mirror plate tilting angle less than ±0.002°. The usable piston scan range is increased to 78% of the MEMS mirror’s full scan capability, and a spectral resolution of 0.55 nm at 531.9 nm wavelength, has been achieved. It is a significant improvement compared to the prior work. Full article
(This article belongs to the collection Modeling, Testing and Reliability Issues in MEMS Engineering)
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Open AccessArticle Planar Indium Tin Oxide Heater for Improved Thermal Distribution for Metal Oxide Micromachined Gas Sensors
Sensors 2016, 16(10), 1612; doi:10.3390/s16101612
Received: 18 July 2016 / Revised: 22 September 2016 / Accepted: 23 September 2016 / Published: 29 September 2016
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Abstract
Metal oxide gas sensors with integrated micro-hotplate structures are widely used in the industry and they are still being investigated and developed. Metal oxide gas sensors have the advantage of being sensitive to a wide range of organic and inorganic volatile compounds, although
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Metal oxide gas sensors with integrated micro-hotplate structures are widely used in the industry and they are still being investigated and developed. Metal oxide gas sensors have the advantage of being sensitive to a wide range of organic and inorganic volatile compounds, although they lack selectivity. To introduce selectivity, the operating temperature of a single sensor is swept, and the measurements are fed to a discriminating algorithm. The efficiency of those data processing methods strongly depends on temperature uniformity across the active area of the sensor. To achieve this, hot plate structures with complex resistor geometries have been designed and additional heat-spreading structures have been introduced. In this work we designed and fabricated a metal oxide gas sensor integrated with a simple square planar indium tin oxide (ITO) heating element, by using conventional micromachining and thin-film deposition techniques. Power consumption–dependent surface temperature measurements were performed. A 420 °C working temperature was achieved at 120 mW power consumption. Temperature distribution uniformity was measured and a 17 °C difference between the hottest and the coldest points of the sensor at an operating temperature of 290 °C was achieved. Transient heat-up and cool-down cycle durations are measured as 40 ms and 20 ms, respectively. Full article
(This article belongs to the Special Issue Chemiresistive Sensors)
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Open AccessArticle Development of a Flexible Non-Metal Electrode for Cell Stimulation and Recording
Sensors 2016, 16(10), 1613; doi:10.3390/s16101613
Received: 6 August 2016 / Revised: 21 September 2016 / Accepted: 23 September 2016 / Published: 29 September 2016
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Abstract
This study presents a method of producing flexible electrodes for potentially simultaneously stimulating and measuring cellular signals in retinal cells. Currently, most multi-electrode applications rely primarily on etching, but the metals involved have a certain degree of brittleness, leaving them prone to cracking
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This study presents a method of producing flexible electrodes for potentially simultaneously stimulating and measuring cellular signals in retinal cells. Currently, most multi-electrode applications rely primarily on etching, but the metals involved have a certain degree of brittleness, leaving them prone to cracking under prolonged pressure. This study proposes using silver chloride ink as a conductive metal, and polydimethysiloxane (PDMS) as the substrate to provide electrodes with an increased degree of flexibility to allow them to bend. This structure is divided into the electrode layer made of PDMS and silver chloride ink, and a PDMS film coating layer. PDMS can be mixed in different proportions to modify the degree of rigidity. The proposed method involved three steps. The first segment entailed the manufacturing of the electrode, using silver chloride ink as the conductive material, and using computer software to define the electrode size and micro-engraving mechanisms to produce the electrode pattern. The resulting uniform PDMS pattern was then baked onto the model, and the flow channel was filled with the conductive material before air drying to produce the required electrode. In the second stage, we tested the electrode, using an impedance analyzer to measure electrode cyclic voltammetry and impedance. In the third phase, mechanical and biocompatibility tests were conducted to determine electrode properties. This study aims to produce a flexible, non-metallic sensing electrode which fits snugly for use in a range of measurement applications. Full article
(This article belongs to the Section Biosensors)
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Open AccessArticle Spectral Skyline Separation: Extended Landmark Databases and Panoramic Imaging
Sensors 2016, 16(10), 1614; doi:10.3390/s16101614
Received: 9 August 2016 / Revised: 20 September 2016 / Accepted: 26 September 2016 / Published: 29 September 2016
Cited by 2 | PDF Full-text (5132 KB) | HTML Full-text | XML Full-text
Abstract
Evidence from behavioral experiments suggests that insects use the skyline as a cue for visual navigation. However, changes of lighting conditions, over hours, days or possibly seasons, significantly affect the appearance of the sky and ground objects. One possible solution to this problem
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Evidence from behavioral experiments suggests that insects use the skyline as a cue for visual navigation. However, changes of lighting conditions, over hours, days or possibly seasons, significantly affect the appearance of the sky and ground objects. One possible solution to this problem is to extract the “skyline” by an illumination-invariant classification of the environment into two classes, ground objects and sky. In a previous study (Insect models of illumination-invariant skyline extraction from UV (ultraviolet) and green channels), we examined the idea of using two different color channels available for many insects (UV and green) to perform this segmentation. We found out that for suburban scenes in temperate zones, where the skyline is dominated by trees and artificial objects like houses, a “local” UV segmentation with adaptive thresholds applied to individual images leads to the most reliable classification. Furthermore, a “global” segmentation with fixed thresholds (trained on an image dataset recorded over several days) using UV-only information is only slightly worse compared to using both the UV and green channel. In this study, we address three issues: First, to enhance the limited range of environments covered by the dataset collected in the previous study, we gathered additional data samples of skylines consisting of minerals (stones, sand, earth) as ground objects. We could show that also for mineral-rich environments, UV-only segmentation achieves a quality comparable to multi-spectral (UV and green) segmentation. Second, we collected a wide variety of ground objects to examine their spectral characteristics under different lighting conditions. On the one hand, we found that the special case of diffusely-illuminated minerals increases the difficulty to reliably separate ground objects from the sky. On the other hand, the spectral characteristics of this collection of ground objects covers well with the data collected in the skyline databases, increasing, due to the increased variety of ground objects, the validity of our findings for novel environments. Third, we collected omnidirectional images, as often used for visual navigation tasks, of skylines using an UV-reflective hyperbolic mirror. We could show that “local” separation techniques can be adapted to the use of panoramic images by splitting the image into segments and finding individual thresholds for each segment. Contrarily, this is not possible for ‘global’ separation techniques. Full article
(This article belongs to the Section Physical Sensors)
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Open AccessArticle A Mechatronic Loading Device to Stimulate Bone Growth via a Human Knee
Sensors 2016, 16(10), 1615; doi:10.3390/s16101615
Received: 30 June 2016 / Revised: 31 August 2016 / Accepted: 22 September 2016 / Published: 29 September 2016
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Abstract
This paper presents the design of an innovative device that applies dynamic mechanical load to human knee joints. Dynamic loading is employed by applying cyclic and periodic force on a target area. The repeated force loading was considered to be an effective modality
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This paper presents the design of an innovative device that applies dynamic mechanical load to human knee joints. Dynamic loading is employed by applying cyclic and periodic force on a target area. The repeated force loading was considered to be an effective modality for repair and rehabilitation of long bones that are subject to ailments like fractures, osteoporosis, osteoarthritis, etc. The proposed device design builds on the knowledge gained in previous animal and mechanical studies. It employs a modified slider-crank linkage mechanism actuated by a brushless Direct Current (DC) motor and provides uniform and cyclic force. The functionality of the device was simulated in a software environment and the structural integrity was analyzed using a finite element method for the prototype construction. The device is controlled by a microcontroller that is programmed to provide the desired loading force at a predetermined frequency and for a specific duration. The device was successfully tested in various experiments for its usability and full functionality. The results reveal that the device works according to the requirements of force magnitude and operational frequency. This device is considered ready to be used for a clinical study to examine whether controlled knee-loading could be an effective regimen for treating the stated bone-related ailments. Full article
(This article belongs to the Special Issue Advanced Robotics and Mechatronics Devices)
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Open AccessArticle Arbitrarily Accessible 3D Microfluidic Device for Combinatorial High-Throughput Drug Screening
Sensors 2016, 16(10), 1616; doi:10.3390/s16101616
Received: 26 August 2016 / Revised: 19 September 2016 / Accepted: 23 September 2016 / Published: 29 September 2016
Cited by 3 | PDF Full-text (2677 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Microfluidics-based drug-screening systems have enabled efficient and high-throughput drug screening, but their routine uses in ordinary labs are limited due to the complexity involved in device fabrication and system setup. In this work, we report an easy-to-use and low-cost arbitrarily accessible 3D microfluidic
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Microfluidics-based drug-screening systems have enabled efficient and high-throughput drug screening, but their routine uses in ordinary labs are limited due to the complexity involved in device fabrication and system setup. In this work, we report an easy-to-use and low-cost arbitrarily accessible 3D microfluidic device that can be easily adopted by various labs to perform combinatorial assays for high-throughput drug screening. The device is capable of precisely performing automatic and simultaneous reagent loading and aliquoting tasks and performing multistep assays with arbitrary sequences. The device is not intended to compete with other microfluidic technologies regarding ultra-low reaction volume. Instead, its freedom from tubing or pumping systems and easy operation makes it an ideal platform for routine high-throughput drug screening outside traditional microfluidic labs. The functionality and quantitative reliability of the 3D microfluidic device were demonstrated with a histone acetyltransferase-based drug-screening assay using the recombinant Plasmodium falciparum GCN5 enzyme, benchmarked with a traditional microtiter plate-based method. This arbitrarily accessible, multistep capable, low-cost, and easy-to-use device can be widely adopted in various combinatorial assays beyond high-throughput drug screening. Full article
(This article belongs to the Special Issue Microfluidics-Based Microsystem Integration Research)
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Open AccessArticle Ontology-Based High-Level Context Inference for Human Behavior Identification
Sensors 2016, 16(10), 1617; doi:10.3390/s16101617
Received: 30 April 2016 / Revised: 21 September 2016 / Accepted: 22 September 2016 / Published: 29 September 2016
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Abstract
Recent years have witnessed a huge progress in the automatic identification of individual primitives of human behavior, such as activities or locations. However, the complex nature of human behavior demands more abstract contextual information for its analysis. This work presents an ontology-based method
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Recent years have witnessed a huge progress in the automatic identification of individual primitives of human behavior, such as activities or locations. However, the complex nature of human behavior demands more abstract contextual information for its analysis. This work presents an ontology-based method that combines low-level primitives of behavior, namely activity, locations and emotions, unprecedented to date, to intelligently derive more meaningful high-level context information. The paper contributes with a new open ontology describing both low-level and high-level context information, as well as their relationships. Furthermore, a framework building on the developed ontology and reasoning models is presented and evaluated. The proposed method proves to be robust while identifying high-level contexts even in the event of erroneously-detected low-level contexts. Despite reasonable inference times being obtained for a relevant set of users and instances, additional work is required to scale to long-term scenarios with a large number of users. Full article
(This article belongs to the Special Issue Selected Papers from UCAmI, IWAAL and AmIHEALTH 2015)
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Open AccessArticle Vehicle Maneuver Detection with Accelerometer-Based Classification
Sensors 2016, 16(10), 1618; doi:10.3390/s16101618
Received: 12 July 2016 / Revised: 14 September 2016 / Accepted: 23 September 2016 / Published: 29 September 2016
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Abstract
In the mobile computing era, smartphones have become instrumental tools to develop innovative mobile context-aware systems. In that sense, their usage in the vehicular domain eases the development of novel and personal transportation solutions. In this frame, the present work introduces an innovative
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In the mobile computing era, smartphones have become instrumental tools to develop innovative mobile context-aware systems. In that sense, their usage in the vehicular domain eases the development of novel and personal transportation solutions. In this frame, the present work introduces an innovative mechanism to perceive the current kinematic state of a vehicle on the basis of the accelerometer data from a smartphone mounted in the vehicle. Unlike previous proposals, the introduced architecture targets the computational limitations of such devices to carry out the detection process following an incremental approach. For its realization, we have evaluated different classification algorithms to act as agents within the architecture. Finally, our approach has been tested with a real-world dataset collected by means of the ad hoc mobile application developed. Full article
(This article belongs to the Section Physical Sensors)
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Open AccessArticle Ensemble of One-Class Classifiers for Personal Risk Detection Based on Wearable Sensor Data
Sensors 2016, 16(10), 1619; doi:10.3390/s16101619
Received: 30 June 2016 / Revised: 24 September 2016 / Accepted: 24 September 2016 / Published: 29 September 2016
Cited by 1 | PDF Full-text (399 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
This study introduces the One-Class K-means with Randomly-projected features Algorithm (OCKRA). OCKRA is an ensemble of one-class classifiers built over multiple projections of a dataset according to random feature subsets. Algorithms found in the literature spread over a wide range of applications where
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This study introduces the One-Class K-means with Randomly-projected features Algorithm (OCKRA). OCKRA is an ensemble of one-class classifiers built over multiple projections of a dataset according to random feature subsets. Algorithms found in the literature spread over a wide range of applications where ensembles of one-class classifiers have been satisfactorily applied; however, none is oriented to the area under our study: personal risk detection. OCKRA has been designed with the aim of improving the detection performance in the problem posed by the Personal RIsk DEtection(PRIDE) dataset. PRIDE was built based on 23 test subjects, where the data for each user were captured using a set of sensors embedded in a wearable band. The performance of OCKRA was compared against support vector machine and three versions of the Parzen window classifier. On average, experimental results show that OCKRA outperformed the other classifiers for at least 0.53% of the area under the curve (AUC). In addition, OCKRA achieved an AUC above 90% for more than 57% of the users. Full article
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Open AccessArticle Monitoring Heritage Buildings with Open Source Hardware Sensors: A Case Study of the Mosque-Cathedral of Córdoba
Sensors 2016, 16(10), 1620; doi:10.3390/s16101620
Received: 12 July 2016 / Revised: 11 September 2016 / Accepted: 25 September 2016 / Published: 29 September 2016
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Abstract
A number of physical factors can adversely affect cultural heritage. Therefore, monitoring parameters involved in the deterioration process, principally temperature and relative humidity, is useful for preventive conservation. In this study, a total of 15 microclimate stations using open source hardware were developed
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A number of physical factors can adversely affect cultural heritage. Therefore, monitoring parameters involved in the deterioration process, principally temperature and relative humidity, is useful for preventive conservation. In this study, a total of 15 microclimate stations using open source hardware were developed and stationed at the Mosque-Cathedral of Córdoba, which is registered with UNESCO for its outstanding universal value, to assess the behavior of interior temperature and relative humidity in relation to exterior weather conditions, public hours and interior design. Long-term monitoring of these parameters is of interest in terms of preservation and reducing the costs of future conservation strategies. Results from monitoring are presented to demonstrate the usefulness of this system. Full article
(This article belongs to the Section Remote Sensors)
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Open AccessArticle Assessment of Data Fusion Algorithms for Earth Observation Change Detection Processes
Sensors 2016, 16(10), 1621; doi:10.3390/s16101621
Received: 22 July 2016 / Revised: 16 September 2016 / Accepted: 22 September 2016 / Published: 30 September 2016
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Abstract
In this work a parametric multi-sensor Bayesian data fusion approach and a Support Vector Machine (SVM) are used for a Change Detection problem. For this purpose two sets of SPOT5-PAN images have been used, which are in turn used for Change Detection Indices
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In this work a parametric multi-sensor Bayesian data fusion approach and a Support Vector Machine (SVM) are used for a Change Detection problem. For this purpose two sets of SPOT5-PAN images have been used, which are in turn used for Change Detection Indices (CDIs) calculation. For minimizing radiometric differences, a methodology based on zonal “invariant features” is suggested. The choice of one or the other CDI for a change detection process is a subjective task as each CDI is probably more or less sensitive to certain types of changes. Likewise, this idea might be employed to create and improve a “change map”, which can be accomplished by means of the CDI’s informational content. For this purpose, information metrics such as the Shannon Entropy and “Specific Information” have been used to weight the changes and no-changes categories contained in a certain CDI and thus introduced in the Bayesian information fusion algorithm. Furthermore, the parameters of the probability density functions (pdf’s) that best fit the involved categories have also been estimated. Conversely, these considerations are not necessary for mapping procedures based on the discriminant functions of a SVM. This work has confirmed the capabilities of probabilistic information fusion procedure under these circumstances. Full article
(This article belongs to the Special Issue Advances in Multi-Sensor Information Fusion: Theory and Applications)
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Open AccessArticle Analysis of Aggregation Delay for Multisource Sensor Data with On-Off Traffic Pattern in Wireless Body Area Networks
Sensors 2016, 16(10), 1622; doi:10.3390/s16101622
Received: 1 July 2016 / Revised: 21 September 2016 / Accepted: 26 September 2016 / Published: 30 September 2016
PDF Full-text (2351 KB) | HTML Full-text | XML Full-text
Abstract
Data aggregation plays an important role to improve the transmission efficiency in wireless body area networks (WBANs); however, it inherently induces additional aggregation delay. Therefore, the effect of packet aggregation on WBAN applications, which are vulnerable to delay, must be analyzed rigorously. In
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Data aggregation plays an important role to improve the transmission efficiency in wireless body area networks (WBANs); however, it inherently induces additional aggregation delay. Therefore, the effect of packet aggregation on WBAN applications, which are vulnerable to delay, must be analyzed rigorously. In this paper, we analyze the packet aggregation delay for multisource sensor data with an on-off traffic pattern in WBANs. Considering two operational parameters of the aggregation threshold and aggregation timer, we calculate the probability that a packet aggregation occurs during a unit time and then derive the average aggregation delay in closed-form. The analysis results show that the aggregation delay increases as the aggregation timer or aggregation threshold increases, but is bounded below a certain level according to the number of active sensors and their on-off traffic attribute. This implies that the data aggregation technique can maximize the transmission efficiency while satisfying a given delay requirement in the WBAN system. Full article
(This article belongs to the Special Issue Advances in Body Sensor Networks: Sensors, Systems, and Applications)
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Open AccessArticle Amplitude Dispersion Compensation for Damage Detection Using Ultrasonic Guided Waves
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