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Sensors, Volume 14, Issue 8 (August 2014) , Pages 13308-15640

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Open AccessCorrection
Correction: Supuk, T.G., et al. Design, Development and Testing of a Low-Cost sEMG System and Its Use in Recording Muscle Activity in Human Gait. Sensors 2014, 14, 8235–8258
Sensors 2014, 14(8), 15639-15640; https://doi.org/10.3390/s140815639
Received: 25 July 2014 / Accepted: 4 August 2014 / Published: 22 August 2014
Viewed by 2770 | PDF Full-text (620 KB) | HTML Full-text | XML Full-text
Abstract
The authors wish to make the following correction to this paper [1]. Due to an error Figure 15 was a duplicate of Figure 13, the former Figure 15 (labelled here as Previous Figure 15) should be replaced by the new version shown below [...] Read more.
The authors wish to make the following correction to this paper [1]. Due to an error Figure 15 was a duplicate of Figure 13, the former Figure 15 (labelled here as Previous Figure 15) should be replaced by the new version shown below (labeled here as New Figure 15):[...] Full article
(This article belongs to the Special Issue Biomedical Sensors and Systems)
Open AccessArticle
Analytical Model of Large Data Transactions in CoAP Networks
Sensors 2014, 14(8), 15610-15638; https://doi.org/10.3390/s140815610
Received: 26 June 2014 / Revised: 7 August 2014 / Accepted: 13 August 2014 / Published: 22 August 2014
Cited by 2 | Viewed by 2885 | PDF Full-text (5298 KB) | HTML Full-text | XML Full-text
Abstract
We propose a novel analytical model to study fragmentation methods in wireless sensor networks adopting the Constrained Application Protocol (CoAP) and the IEEE 802.15.4 standard for medium access control (MAC). The blockwise transfer technique proposed in CoAP and the 6LoWPAN fragmentation are included [...] Read more.
We propose a novel analytical model to study fragmentation methods in wireless sensor networks adopting the Constrained Application Protocol (CoAP) and the IEEE 802.15.4 standard for medium access control (MAC). The blockwise transfer technique proposed in CoAP and the 6LoWPAN fragmentation are included in the analysis. The two techniques are compared in terms of reliability and delay, depending on the traffic, the number of nodes and the parameters of the IEEE 802.15.4 MAC. The results are validated trough Monte Carlo simulations. To the best of our knowledge this is the first study that evaluates and compares analytically the performance of CoAP blockwise transfer and 6LoWPAN fragmentation. A major contribution is the possibility to understand the behavior of both techniques with different network conditions. Our results show that 6LoWPAN fragmentation is preferable for delay-constrained applications. For highly congested networks, the blockwise transfer slightly outperforms 6LoWPAN fragmentation in terms of reliability. Full article
(This article belongs to the Special Issue Wireless Sensor Networks and the Internet of Things)
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Graphical abstract

Open AccessArticle
Use of Temperature and Humidity Sensors to Determine Moisture Content of Oolong Tea
Sensors 2014, 14(8), 15593-15609; https://doi.org/10.3390/s140815593
Received: 22 June 2014 / Revised: 19 August 2014 / Accepted: 20 August 2014 / Published: 22 August 2014
Cited by 9 | Viewed by 2480 | PDF Full-text (755 KB) | HTML Full-text | XML Full-text
Abstract
The measurement of tea moisture content is important for processing and storing tea. The moisture content of tea affects the quality and durability of the product. Some electrical devices have been proposed to measure the moisture content of tea leaves but are not [...] Read more.
The measurement of tea moisture content is important for processing and storing tea. The moisture content of tea affects the quality and durability of the product. Some electrical devices have been proposed to measure the moisture content of tea leaves but are not practical. Their performance is influenced by material density and packing. The official oven method is time-consuming. In this study, the moisture content of Oolong tea was measured by the equilibrium relative humidity technique. The equilibrium relative humidity, and temperature, of tea materials were measured by using temperature and relative humidity sensors. Sensors were calibrated, and calibration equations were established to improve accuracy. The moisture content was calculated by using an equilibrium moisture content model. The error of the moisture content determined with this method was within 0.5% w.b. at moisture <15% w.b. Uncertainty analysis revealed that the performance of the humidity sensor had a significant effect on the accuracy of moisture determination. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle
Energy-Efficient ZigBee-Based Wireless Sensor Network for Track Bicycle Performance Monitoring
Sensors 2014, 14(8), 15573-15592; https://doi.org/10.3390/s140815573
Received: 12 July 2014 / Revised: 11 August 2014 / Accepted: 13 August 2014 / Published: 22 August 2014
Cited by 23 | Viewed by 2933 | PDF Full-text (880 KB) | HTML Full-text | XML Full-text
Abstract
In a wireless sensor network (WSN), saving power is a vital requirement. In this paper, a simple point-to-point bike WSN was considered. The data of bike parameters, speed and cadence, were monitored and transmitted via a wireless communication based on the ZigBee protocol. [...] Read more.
In a wireless sensor network (WSN), saving power is a vital requirement. In this paper, a simple point-to-point bike WSN was considered. The data of bike parameters, speed and cadence, were monitored and transmitted via a wireless communication based on the ZigBee protocol. Since the bike parameters are monitored and transmitted on every bike wheel rotation, this means the sensor node does not sleep for a long time, causing power consumption to rise. Therefore, a newly proposed algorithm, known as the Redundancy and Converged Data (RCD) algorithm, was implemented for this application to put the sensor node into sleep mode while maintaining the performance measurements. This is achieved by minimizing the data packets transmitted as much as possible and fusing the data of speed and cadence by utilizing the correlation measurements between them to minimize the number of sensor nodes in the network to one node, which results in reduced power consumption, cost, and size, in addition to simpler hardware implementation. Execution of the proposed RCD algorithm shows that this approach can reduce the current consumption to 1.69 mA, and save 95% of the sensor node energy. Also, the comparison results with different wireless standard technologies demonstrate minimal current consumption in the sensor node. Full article
(This article belongs to the Section Sensor Networks)
Open AccessArticle
Application of Service Oriented Architecture for Sensors and Actuators in District Heating Substations
Sensors 2014, 14(8), 15553-15572; https://doi.org/10.3390/s140815553
Received: 7 March 2014 / Revised: 12 August 2014 / Accepted: 13 August 2014 / Published: 21 August 2014
Cited by 6 | Viewed by 2537 | PDF Full-text (503 KB) | HTML Full-text | XML Full-text
Abstract
Hardwired sensor installations using proprietary protocols found in today’s district heating substations limit the potential usability of the sensors in and around the substations. If sensor resources can be shared and re-used in a variety of applications, the cost of sensors and installation [...] Read more.
Hardwired sensor installations using proprietary protocols found in today’s district heating substations limit the potential usability of the sensors in and around the substations. If sensor resources can be shared and re-used in a variety of applications, the cost of sensors and installation can be reduced, and their functionality and operability can be increased. In this paper, we present a new concept of district heating substation control and monitoring, where a service oriented architecture (SOA) is deployed in a wireless sensor network (WSN), which is integrated with the substation. IP-networking is exclusively used from sensor to server; hence, no middleware is needed for Internet integration. Further, by enabling thousands of sensors with SOA capabilities, a System of Systems approach can be applied. The results of this paper show that it is possible to utilize SOA solutions with heavily resource-constrained embedded devices in contexts where the real-time constrains are limited, such as in a district heating substation. Full article
(This article belongs to the Section Sensor Networks)
Open AccessArticle
Efficient Sensor Placement Optimization Using Gradient Descent and Probabilistic Coverage
Sensors 2014, 14(8), 15525-15552; https://doi.org/10.3390/s140815525
Received: 20 June 2014 / Revised: 8 August 2014 / Accepted: 14 August 2014 / Published: 21 August 2014
Cited by 10 | Viewed by 2595 | PDF Full-text (3886 KB) | HTML Full-text | XML Full-text
Abstract
We are proposing an adaptation of the gradient descent method to optimize the position and orientation of sensors for the sensor placement problem. The novelty of the proposed method lies in the combination of gradient descent optimization with a realistic model, which considers [...] Read more.
We are proposing an adaptation of the gradient descent method to optimize the position and orientation of sensors for the sensor placement problem. The novelty of the proposed method lies in the combination of gradient descent optimization with a realistic model, which considers both the topography of the environment and a set of sensors with directional probabilistic sensing. The performance of this approach is compared with two other black box optimization methods over area coverage and processing time. Results show that our proposed method produces competitive results on smaller maps and superior results on larger maps, while requiring much less computation than the other optimization methods to which it has been compared. Full article
(This article belongs to the Special Issue State-of-the-Art Sensors in Canada 2014)
Open AccessArticle
Lab-on-Chip Cytometry Based on Magnetoresistive Sensors for Bacteria Detection in Milk
Sensors 2014, 14(8), 15496-15524; https://doi.org/10.3390/s140815496
Received: 23 May 2014 / Revised: 14 July 2014 / Accepted: 1 August 2014 / Published: 21 August 2014
Cited by 29 | Viewed by 4233 | PDF Full-text (4767 KB) | HTML Full-text | XML Full-text
Abstract
Flow cytometers have been optimized for use in portable platforms, where cell separation, identification and counting can be achieved in a compact and modular format. This feature can be combined with magnetic detection, where magnetoresistive sensors can be integrated within microfluidic channels to [...] Read more.
Flow cytometers have been optimized for use in portable platforms, where cell separation, identification and counting can be achieved in a compact and modular format. This feature can be combined with magnetic detection, where magnetoresistive sensors can be integrated within microfluidic channels to detect magnetically labelled cells. This work describes a platform for in-flow detection of magnetically labelled cells with a magneto-resistive based cell cytometer. In particular, we present an example for the validation of the platform as a magnetic counter that identifies and quantifies Streptococcus agalactiae in milk. Full article
(This article belongs to the Special Issue Biomedical Sensors and Systems)
Open AccessArticle
A High-Pressure Bi-Directional Cycloid Rotor Flowmeter
Sensors 2014, 14(8), 15480-15495; https://doi.org/10.3390/s140815480
Received: 27 June 2014 / Revised: 5 August 2014 / Accepted: 6 August 2014 / Published: 21 August 2014
Cited by 4 | Viewed by 2291 | PDF Full-text (2496 KB) | HTML Full-text | XML Full-text
Abstract
The measurement of the flow rate of various liquids and gases is critical in industrial automation. Rotary positive displacement meters (rotary PD meters) are highly accurate flowmeters that are widely employed in engineering applications, especially in custody transfer operations and hydraulic control systems. [...] Read more.
The measurement of the flow rate of various liquids and gases is critical in industrial automation. Rotary positive displacement meters (rotary PD meters) are highly accurate flowmeters that are widely employed in engineering applications, especially in custody transfer operations and hydraulic control systems. This paper presents a high pressure rotary PD meter containing a pair of internal cycloid rotors. It has the advantages of concise structure, low pressure loss, high accuracy and low noise. The curve of the internal rotor is designed as an equidistant curtate epicycloid curve with the external rotor curve as its conjugate. The calculation method used to determine the displacement of the cycloid rotor flowmeter is discussed. A prototype was fabricated, and experiments were performed to confirm measurements over a flow range of 1–100 L/min with relative errors of less than ±0.5%. The pressure loss through the flowmeter was about 3 bar at a flow rate of 100 L/min. Full article
(This article belongs to the Section Physical Sensors)
Open AccessReview
Recent Developments in Optical Detection Technologies in Lab-on-a-Chip Devices for Biosensing Applications
Sensors 2014, 14(8), 15458-15479; https://doi.org/10.3390/s140815458
Received: 15 July 2014 / Revised: 14 August 2014 / Accepted: 15 August 2014 / Published: 21 August 2014
Cited by 84 | Viewed by 5046 | PDF Full-text (1092 KB) | HTML Full-text | XML Full-text
Abstract
The field of microfluidics has yet to develop practical devices that provide real clinical value. One of the main reasons for this is the difficulty in realizing low-cost, sensitive, reproducible, and portable analyte detection microfluidic systems. Previous research has addressed two main approaches [...] Read more.
The field of microfluidics has yet to develop practical devices that provide real clinical value. One of the main reasons for this is the difficulty in realizing low-cost, sensitive, reproducible, and portable analyte detection microfluidic systems. Previous research has addressed two main approaches for the detection technologies in lab-on-a-chip devices: (a) study of the compatibility of conventional instrumentation with microfluidic structures, and (b) integration of innovative sensors contained within the microfluidic system. Despite the recent advances in electrochemical and mechanical based sensors, their drawbacks pose important challenges to their application in disposable microfluidic devices. Instead, optical detection remains an attractive solution for lab-on-a-chip devices, because of the ubiquity of the optical methods in the laboratory. Besides, robust and cost-effective devices for use in the field can be realized by integrating proper optical detection technologies on chips. This review examines the recent developments in detection technologies applied to microfluidic biosensors, especially addressing several optical methods, including fluorescence, chemiluminescence, absorbance and surface plasmon resonance. Full article
(This article belongs to the Special Issue Opto-Microfluidics for Bio Applications)
Open AccessArticle
Estimation of Spatial-Temporal Gait Parameters Using a Low-Cost Ultrasonic Motion Analysis System
Sensors 2014, 14(8), 15434-15457; https://doi.org/10.3390/s140815434
Received: 28 May 2014 / Revised: 14 August 2014 / Accepted: 15 August 2014 / Published: 20 August 2014
Cited by 8 | Viewed by 2364 | PDF Full-text (1191 KB) | HTML Full-text | XML Full-text
Abstract
In this paper, a low-cost motion analysis system using a wireless ultrasonic sensor network is proposed and investigated. A methodology has been developed to extract spatial-temporal gait parameters including stride length, stride duration, stride velocity, stride cadence, and stride symmetry from 3D foot [...] Read more.
In this paper, a low-cost motion analysis system using a wireless ultrasonic sensor network is proposed and investigated. A methodology has been developed to extract spatial-temporal gait parameters including stride length, stride duration, stride velocity, stride cadence, and stride symmetry from 3D foot displacements estimated by the combination of spherical positioning technique and unscented Kalman filter. The performance of this system is validated against a camera-based system in the laboratory with 10 healthy volunteers. Numerical results show the feasibility of the proposed system with average error of 2.7% for all the estimated gait parameters. The influence of walking speed on the measurement accuracy of proposed system is also evaluated. Statistical analysis demonstrates its capability of being used as a gait assessment tool for some medical applications. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle
A Kalman Filter-Based Short Baseline RTK Algorithm for Single-Frequency Combination of GPS and BDS
Sensors 2014, 14(8), 15415-15433; https://doi.org/10.3390/s140815415
Received: 25 June 2014 / Revised: 11 August 2014 / Accepted: 13 August 2014 / Published: 20 August 2014
Cited by 29 | Viewed by 2986 | PDF Full-text (1445 KB) | HTML Full-text | XML Full-text
Abstract
The emerging Global Navigation Satellite Systems (GNSS) including the BeiDou Navigation Satellite System (BDS) offer more visible satellites for positioning users. To employ those new satellites in a real-time kinematic (RTK) algorithm to enhance positioning precision and availability, a data processing model for [...] Read more.
The emerging Global Navigation Satellite Systems (GNSS) including the BeiDou Navigation Satellite System (BDS) offer more visible satellites for positioning users. To employ those new satellites in a real-time kinematic (RTK) algorithm to enhance positioning precision and availability, a data processing model for the dual constellation of GPS and BDS is proposed and analyzed. A Kalman filter-based algorithm is developed to estimate the float ambiguities for short baseline scenarios. The entire work process of the high-precision algorithm based on the proposed model is deeply investigated in detail. The model is validated with real GPS and BDS data recorded from one zero and two short baseline experiments. Results show that the proposed algorithm can generate fixed baseline output with the same precision level as that of either a single GPS or BDS RTK algorithm. The significantly improved fixed rate and time to first fix of the proposed method demonstrates a better availability and effectiveness on processing multi-GNSSs. Full article
(This article belongs to the Special Issue Positioning and Tracking Sensors and Technologies in Road Transport)
Open AccessArticle
Rapid, Single-Molecule Assays in Nano/Micro-Fluidic Chips with Arrays of Closely Spaced Parallel Channels Fabricated by Femtosecond Laser Machining
Sensors 2014, 14(8), 15400-15414; https://doi.org/10.3390/s140815400
Received: 16 July 2014 / Revised: 8 August 2014 / Accepted: 18 August 2014 / Published: 20 August 2014
Cited by 1 | Viewed by 2374 | PDF Full-text (523 KB) | HTML Full-text | XML Full-text
Abstract
Cost-effective pharmaceutical drug discovery depends on increasing assay throughput while reducing reagent needs. To this end, we are developing an ultrasensitive, fluorescence-based platform that incorporates a nano/micro-fluidic chip with an array of closely spaced channels for parallelized optical readout of single-molecule assays. Here [...] Read more.
Cost-effective pharmaceutical drug discovery depends on increasing assay throughput while reducing reagent needs. To this end, we are developing an ultrasensitive, fluorescence-based platform that incorporates a nano/micro-fluidic chip with an array of closely spaced channels for parallelized optical readout of single-molecule assays. Here we describe the use of direct femtosecond laser machining to fabricate several hundred closely spaced channels on the surfaces of fused silica substrates. The channels are sealed by bonding to a microscope cover slip spin-coated with a thin film of poly(dimethylsiloxane). Single-molecule detection experiments are conducted using a custom-built, wide-field microscope. The array of channels is epi-illuminated by a line-generating red diode laser, resulting in a line focus just a few microns thick across a 500 micron field of view. A dilute aqueous solution of fluorescently labeled biomolecules is loaded into the device and fluorescence is detected with an electron-multiplying CCD camera, allowing acquisition rates up to 7 kHz for each microchannel. Matched digital filtering based on experimental parameters is used to perform an initial, rapid assessment of detected fluorescence. More detailed analysis is obtained through fluorescence correlation spectroscopy. Simulated fluorescence data is shown to agree well with experimental values. Full article
(This article belongs to the Special Issue Opto-Microfluidics for Bio Applications)
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Open AccessArticle
Directional Navigation Improves Opportunistic Communication for Emergencies
Sensors 2014, 14(8), 15387-15399; https://doi.org/10.3390/s140815387
Received: 2 May 2014 / Revised: 1 June 2014 / Accepted: 14 August 2014 / Published: 20 August 2014
Cited by 5 | Viewed by 2085 | PDF Full-text (494 KB) | HTML Full-text | XML Full-text
Abstract
We present a novel direction based shortest path search algorithm to guide evacuees during an emergency. It uses opportunistic communications (oppcomms) with low-cost wearable mobile nodes that can exchange packets at close range of a few to some tens of meters without help [...] Read more.
We present a novel direction based shortest path search algorithm to guide evacuees during an emergency. It uses opportunistic communications (oppcomms) with low-cost wearable mobile nodes that can exchange packets at close range of a few to some tens of meters without help of an infrastructure. The algorithm seeks the shortest path to exits which are safest with regard to a hazard, and is integrated into an autonomous Emergency Support System (ESS) to guide evacuees in a built environment. The algorithm proposed that ESSs are evaluated with the DBES (Distributed Building Evacuation Simulator) by simulating a shopping centre where fire is spreading. The results show that the directional path finding algorithm can offer significant improvements for the evacuees. Full article
(This article belongs to the Section Sensor Networks)
Open AccessArticle
An Ultrasonic Contactless Sensor for Breathing Monitoring
Sensors 2014, 14(8), 15371-15386; https://doi.org/10.3390/s140815371
Received: 10 June 2014 / Revised: 2 August 2014 / Accepted: 5 August 2014 / Published: 20 August 2014
Cited by 17 | Viewed by 4112 | PDF Full-text (1587 KB) | HTML Full-text | XML Full-text
Abstract
The monitoring of human breathing activity during a long period has multiple fundamental applications in medicine. In breathing sleep disorders such as apnea, the diagnosis is based on events during which the person stops breathing for several periods during sleep. In polysomnography, the [...] Read more.
The monitoring of human breathing activity during a long period has multiple fundamental applications in medicine. In breathing sleep disorders such as apnea, the diagnosis is based on events during which the person stops breathing for several periods during sleep. In polysomnography, the standard for sleep disordered breathing analysis, chest movement and airflow are used to monitor the respiratory activity. However, this method has serious drawbacks. Indeed, as the subject should sleep overnight in a laboratory and because of sensors being in direct contact with him, artifacts modifying sleep quality are often observed. This work investigates an analysis of the viability of an ultrasonic device to quantify the breathing activity, without contact and without any perception by the subject. Based on a low power ultrasonic active source and transducer, the device measures the frequency shift produced by the velocity difference between the exhaled air flow and the ambient environment, i.e., the Doppler effect. After acquisition and digitization, a specific signal processing is applied to separate the effects of breath from those due to subject movements from the Doppler signal. The distance between the source and the sensor, about 50 cm, and the use of ultrasound frequency well above audible frequencies, 40 kHz, allow monitoring the breathing activity without any perception by the subject, and therefore without any modification of the sleep quality which is very important for sleep disorders diagnostic applications. This work is patented (patent pending 2013-7-31 number FR.13/57569). Full article
Open AccessArticle
Intra-and-Inter Species Biomass Prediction in a Plantation Forest: Testing the Utility of High Spatial Resolution Spaceborne Multispectral RapidEye Sensor and Advanced Machine Learning Algorithms
Sensors 2014, 14(8), 15348-15370; https://doi.org/10.3390/s140815348
Received: 26 April 2014 / Revised: 14 June 2014 / Accepted: 6 August 2014 / Published: 20 August 2014
Cited by 52 | Viewed by 2841 | PDF Full-text (827 KB) | HTML Full-text | XML Full-text
Abstract
The quantification of aboveground biomass using remote sensing is critical for better understanding the role of forests in carbon sequestration and for informed sustainable management. Although remote sensing techniques have been proven useful in assessing forest biomass in general, more is required to [...] Read more.
The quantification of aboveground biomass using remote sensing is critical for better understanding the role of forests in carbon sequestration and for informed sustainable management. Although remote sensing techniques have been proven useful in assessing forest biomass in general, more is required to investigate their capabilities in predicting intra-and-inter species biomass which are mainly characterised by non-linear relationships. In this study, we tested two machine learning algorithms, Stochastic Gradient Boosting (SGB) and Random Forest (RF) regression trees to predict intra-and-inter species biomass using high resolution RapidEye reflectance bands as well as the derived vegetation indices in a commercial plantation. The results showed that the SGB algorithm yielded the best performance for intra-and-inter species biomass prediction; using all the predictor variables as well as based on the most important selected variables. For example using the most important variables the algorithm produced an R2 of 0.80 and RMSE of 16.93 t·ha−1 for E. grandis; R2 of 0.79, RMSE of 17.27 t·ha−1 for P. taeda and R2 of 0.61, RMSE of 43.39 t·ha−1 for the combined species data sets. Comparatively, RF yielded plausible results only for E. dunii (R2 of 0.79; RMSE of 7.18 t·ha−1). We demonstrated that although the two statistical methods were able to predict biomass accurately, RF produced weaker results as compared to SGB when applied to combined species dataset. The result underscores the relevance of stochastic models in predicting biomass drawn from different species and genera using the new generation high resolution RapidEye sensor with strategically positioned bands. Full article
(This article belongs to the Section Remote Sensors, Control, and Telemetry)
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Open AccessArticle
Preceding Vehicle Detection and Tracking Adaptive to Illumination Variation in Night Traffic Scenes Based on Relevance Analysis
Sensors 2014, 14(8), 15325-15347; https://doi.org/10.3390/s140815325
Received: 29 May 2014 / Revised: 14 July 2014 / Accepted: 12 August 2014 / Published: 19 August 2014
Cited by 10 | Viewed by 3477 | PDF Full-text (765 KB) | HTML Full-text | XML Full-text
Abstract
Preceding vehicle detection and tracking at nighttime are challenging problems due to the disturbance of other extraneous illuminant sources coexisting with the vehicle lights. To improve the detection accuracy and robustness of vehicle detection, a novel method for vehicle detection and tracking at [...] Read more.
Preceding vehicle detection and tracking at nighttime are challenging problems due to the disturbance of other extraneous illuminant sources coexisting with the vehicle lights. To improve the detection accuracy and robustness of vehicle detection, a novel method for vehicle detection and tracking at nighttime is proposed in this paper. The characteristics of taillights in the gray level are applied to determine the lower boundary of the threshold for taillights segmentation, and the optimal threshold for taillight segmentation is calculated using the OTSU algorithm between the lower boundary and the highest grayscale of the region of interest. The candidate taillight pairs are extracted based on the similarity between left and right taillights, and the non-vehicle taillight pairs are removed based on the relevance analysis of vehicle location between frames. To reduce the false negative rate of vehicle detection, a vehicle tracking method based on taillights estimation is applied. The taillight spot candidate is sought in the region predicted by Kalman filtering, and the disturbed taillight is estimated based on the symmetry and location of the other taillight of the same vehicle. Vehicle tracking is completed after estimating its location according to the two taillight spots. The results of experiments on a vehicle platform indicate that the proposed method could detect vehicles quickly, correctly and robustly in the actual traffic environments with illumination variation. Full article
(This article belongs to the Special Issue Positioning and Tracking Sensors and Technologies in Road Transport)
Open AccessArticle
A Novel Approach for Weed Type Classification Based on Shape Descriptors and a Fuzzy Decision-Making Method
Sensors 2014, 14(8), 15304-15324; https://doi.org/10.3390/s140815304
Received: 5 March 2014 / Revised: 7 July 2014 / Accepted: 8 August 2014 / Published: 19 August 2014
Cited by 21 | Viewed by 2538 | PDF Full-text (1403 KB) | HTML Full-text | XML Full-text
Abstract
An important objective in weed management is the discrimination between grasses (monocots) and broad-leaved weeds (dicots), because these two weed groups can be appropriately controlled by specific herbicides. In fact, efficiency is higher if selective treatment is performed for each type of infestation [...] Read more.
An important objective in weed management is the discrimination between grasses (monocots) and broad-leaved weeds (dicots), because these two weed groups can be appropriately controlled by specific herbicides. In fact, efficiency is higher if selective treatment is performed for each type of infestation instead of using a broadcast herbicide on the whole surface. This work proposes a strategy where weeds are characterised by a set of shape descriptors (the seven Hu moments and six geometric shape descriptors). Weeds appear in outdoor field images which display real situations obtained from a RGB camera. Thus, images present a mixture of both weed species under varying conditions of lighting. In the presented approach, four decision-making methods were adapted to use the best shape descriptors as attributes and a choice was taken. This proposal establishes a novel methodology with a high success rate in weed species discrimination. Full article
(This article belongs to the Special Issue Agriculture and Forestry: Sensors, Technologies and Procedures)
Open AccessEditorial
Sensors and Technologies in Spain: State-of-the-Art
Sensors 2014, 14(8), 15282-15303; https://doi.org/10.3390/s140815282
Received: 14 August 2014 / Accepted: 19 August 2014 / Published: 19 August 2014
Cited by 4 | Viewed by 2467 | PDF Full-text (231 KB) | HTML Full-text | XML Full-text
Abstract
The aim of this special issue was to provide a comprehensive view on the state-of-the-art sensor technology in Spain. Different problems cause the appearance and development of new sensor technologies and vice versa, the emergence of new sensors facilitates the solution of [...] Read more.
The aim of this special issue was to provide a comprehensive view on the state-of-the-art sensor technology in Spain. Different problems cause the appearance and development of new sensor technologies and vice versa, the emergence of new sensors facilitates the solution of existing real problems. [...] Full article
Open AccessArticle
Particle Swarm Inspired Underwater Sensor Self-Deployment
Sensors 2014, 14(8), 15262-15281; https://doi.org/10.3390/s140815262
Received: 9 June 2014 / Revised: 27 July 2014 / Accepted: 8 August 2014 / Published: 19 August 2014
Cited by 23 | Viewed by 2204 | PDF Full-text (1341 KB) | HTML Full-text | XML Full-text
Abstract
Underwater sensor networks (UWSNs) can be applied in sea resource reconnaissance, pollution monitoring and assistant navigation, etc., and have become a hot research field in wireless sensor networks. In open and complicated underwater environments, targets (events) tend to be highly dynamic and [...] Read more.
Underwater sensor networks (UWSNs) can be applied in sea resource reconnaissance, pollution monitoring and assistant navigation, etc., and have become a hot research field in wireless sensor networks. In open and complicated underwater environments, targets (events) tend to be highly dynamic and uncertain. It is important to deploy sensors to cover potential events in an optimal manner. In this paper, the underwater sensor deployment problem and its performance evaluation metrics are introduced. Furthermore, a particle swarm inspired sensor self-deployment algorithm is presented. By simulating the flying behavior of particles and introducing crowd control, the proposed algorithm can drive sensors to cover almost all the events, and make the distribution of sensors match that of events. Through extensive simulations, we demonstrate that it can solve the underwater sensor deployment problem effectively, with fast convergence rate, and amiable to distributed implementation. Full article
(This article belongs to the Section Sensor Networks)
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Graphical abstract

Open AccessArticle
Optimization of a Cell Counting Algorithm for Mobile Point-of-Care Testing Platforms
Sensors 2014, 14(8), 15244-15261; https://doi.org/10.3390/s140815244
Received: 26 May 2014 / Revised: 4 August 2014 / Accepted: 8 August 2014 / Published: 19 August 2014
Cited by 3 | Viewed by 2363 | PDF Full-text (2735 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
In a point-of-care (POC) setting, it is critically important to reliably count the number of specific cells in a blood sample. Software-based cell counting, which is far faster than manual counting, while much cheaper than hardware-based counting, has emerged as an attractive solution [...] Read more.
In a point-of-care (POC) setting, it is critically important to reliably count the number of specific cells in a blood sample. Software-based cell counting, which is far faster than manual counting, while much cheaper than hardware-based counting, has emerged as an attractive solution potentially applicable to mobile POC testing. However, the existing software-based algorithm based on the normalized cross-correlation (NCC) method is too time- and, thus, energy-consuming to be deployed for battery-powered mobile POC testing platforms. In this paper, we identify inefficiencies in the NCC-based algorithm and propose two synergistic optimization techniques that can considerably reduce the runtime and, thus, energy consumption of the original algorithm with negligible impact on counting accuracy. We demonstrate that an AndroidTM smart phone running the optimized algorithm consumes 11.5× less runtime than the original algorithm. Full article
(This article belongs to the Section Biosensors)
Open AccessArticle
Simultaneous Electrochemical Detection of Dopamine and Ascorbic Acid Using an Iron Oxide/Reduced Graphene Oxide Modified Glassy Carbon Electrode
Sensors 2014, 14(8), 15227-15243; https://doi.org/10.3390/s140815227
Received: 28 April 2014 / Revised: 2 July 2014 / Accepted: 11 July 2014 / Published: 19 August 2014
Cited by 68 | Viewed by 4638 | PDF Full-text (1268 KB) | HTML Full-text | XML Full-text
Abstract
The fabrication of an electrochemical sensor based on an iron oxide/graphene modified glassy carbon electrode (Fe3O4/rGO/GCE) and its simultaneous detection of dopamine (DA) and ascorbic acid (AA) is described here. The Fe3O4/rGO nanocomposite was synthesized [...] Read more.
The fabrication of an electrochemical sensor based on an iron oxide/graphene modified glassy carbon electrode (Fe3O4/rGO/GCE) and its simultaneous detection of dopamine (DA) and ascorbic acid (AA) is described here. The Fe3O4/rGO nanocomposite was synthesized via a simple, one step in-situ wet chemical method and characterized by different techniques. The presence of Fe3O4 nanoparticles on the surface of rGO sheets was confirmed by FESEM and TEM images. The electrochemical behavior of Fe3O4/rGO/GCE towards electrocatalytic oxidation of DA was investigated by cyclic voltammetry (CV) and differential pulse voltammetry (DPV) analysis. The electrochemical studies revealed that the Fe3O4/rGO/GCE dramatically increased the current response against the DA, due to the synergistic effect emerged between Fe3O4 and rGO. This implies that Fe3O4/rGO/GCE could exhibit excellent electrocatalytic activity and remarkable electron transfer kinetics towards the oxidation of DA. Moreover, the modified sensor electrode portrayed sensitivity and selectivity for simultaneous determination of AA and DA. The observed DPVs response linearly depends on AA and DA concentration in the range of 1–9 mM and 0.5–100 µM, with correlation coefficients of 0.995 and 0.996, respectively. The detection limit of (S/N = 3) was found to be 0.42 and 0.12 µM for AA and DA, respectively. Full article
(This article belongs to the Section Biosensors)
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Open AccessArticle
Focal-Plane Sensing-Processing: A Power-Efficient Approach for the Implementation of Privacy-Aware Networked Visual Sensors
Sensors 2014, 14(8), 15203-15226; https://doi.org/10.3390/s140815203
Received: 10 July 2014 / Revised: 12 August 2014 / Accepted: 14 August 2014 / Published: 19 August 2014
Cited by 12 | Viewed by 2829 | PDF Full-text (3636 KB) | HTML Full-text | XML Full-text
Abstract
The capture, processing and distribution of visual information is one of the major challenges for the paradigm of the Internet of Things. Privacy emerges as a fundamental barrier to overcome. The idea of networked image sensors pervasively collecting data generates social rejection in [...] Read more.
The capture, processing and distribution of visual information is one of the major challenges for the paradigm of the Internet of Things. Privacy emerges as a fundamental barrier to overcome. The idea of networked image sensors pervasively collecting data generates social rejection in the face of sensitive information being tampered by hackers or misused by legitimate users. Power consumption also constitutes a crucial aspect. Images contain a massive amount of data to be processed under strict timing requirements, demanding high-performance vision systems. In this paper, we describe a hardware-based strategy to concurrently address these two key issues. By conveying processing capabilities to the focal plane in addition to sensing, we can implement privacy protection measures just at the point where sensitive data are generated. Furthermore, such measures can be tailored for efficiently reducing the computational load of subsequent processing stages. As a proof of concept, a full-custom QVGA vision sensor chip is presented. It incorporates a mixed-signal focal-plane sensing-processing array providing programmable pixelation of multiple image regions in parallel. In addition to this functionality, the sensor exploits reconfigurability to implement other processing primitives, namely block-wise dynamic range adaptation, integral image computation and multi-resolution filtering. The proposed circuitry is also suitable to build a granular space, becoming the raw material for subsequent feature extraction and recognition of categorized objects. Full article
(This article belongs to the Special Issue Wireless Sensor Networks and the Internet of Things)
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Open AccessArticle
The Open Service Signal in Space Navigation Data Comparison of the Global Positioning System and the BeiDou Navigation Satellite System
Sensors 2014, 14(8), 15182-15202; https://doi.org/10.3390/s140815182
Received: 17 June 2014 / Revised: 24 July 2014 / Accepted: 15 August 2014 / Published: 19 August 2014
Cited by 8 | Viewed by 2370 | PDF Full-text (974 KB) | HTML Full-text | XML Full-text
Abstract
More and more Global Navigation Satellite Systems (GNSSs) have been developed and are in operation. Before integrating information on various GNSSs, the differences between the various systems must be studied first. This research focuses on analyzing the navigation data differences between the Chinese [...] Read more.
More and more Global Navigation Satellite Systems (GNSSs) have been developed and are in operation. Before integrating information on various GNSSs, the differences between the various systems must be studied first. This research focuses on analyzing the navigation data differences between the Chinese BeiDou Navigation Satellite System (BDS) and the United States’ Global Positioning System (GPS). In addition to explaining the impact caused by these two different coordinate and time systems, this research uses an actual open service signal in space (SIS) for both GPS and BDS to analyze their current system performance. Five data quality analysis (DQA) mechanisms are proposed in this research to validate both systems’ SIS navigation data. These five DQAs evaluate the differences in ephemeris and almanac messages from both systems for stability and accuracy. After all of the DQAs, the different issues related to GPS and BDS satellite information are presented. Finally, based on these DQA results, this research provides suggested resolutions for the combined use of GPS and BDS for navigation and guidance. Full article
(This article belongs to the Special Issue Sensor Innovations for Spacecraft Guidance, Navigation, and Control)
Open AccessArticle
An Energy Efficient Distance-Aware Routing Algorithm with Multiple Mobile Sinks for Wireless Sensor Networks
Sensors 2014, 14(8), 15163-15181; https://doi.org/10.3390/s140815163
Received: 20 June 2014 / Revised: 7 August 2014 / Accepted: 13 August 2014 / Published: 18 August 2014
Cited by 13 | Viewed by 2899 | PDF Full-text (479 KB) | HTML Full-text | XML Full-text
Abstract
Traffic patterns in wireless sensor networks (WSNs) usually follow a many-to-one model. Sensor nodes close to static sinks will deplete their limited energy more rapidly than other sensors, since they will have more data to forward during multihop transmission. This will cause network [...] Read more.
Traffic patterns in wireless sensor networks (WSNs) usually follow a many-to-one model. Sensor nodes close to static sinks will deplete their limited energy more rapidly than other sensors, since they will have more data to forward during multihop transmission. This will cause network partition, isolated nodes and much shortened network lifetime. Thus, how to balance energy consumption for sensor nodes is an important research issue. In recent years, exploiting sink mobility technology in WSNs has attracted much research attention because it can not only improve energy efficiency, but prolong network lifetime. In this paper, we propose an energy efficient distance-aware routing algorithm with multiple mobile sink for WSNs, where sink nodes will move with a certain speed along the network boundary to collect monitored data. We study the influence of multiple mobile sink nodes on energy consumption and network lifetime, and we mainly focus on the selection of mobile sink node number and the selection of parking positions, as well as their impact on performance metrics above. We can see that both mobile sink node number and the selection of parking position have important influence on network performance. Simulation results show that our proposed routing algorithm has better performance than traditional routing ones in terms of energy consumption. Full article
(This article belongs to the Section Sensor Networks)
Open AccessArticle
Emergency Navigation without an Infrastructure
Sensors 2014, 14(8), 15142-15162; https://doi.org/10.3390/s140815142
Received: 6 May 2014 / Revised: 3 July 2014 / Accepted: 8 August 2014 / Published: 18 August 2014
Cited by 17 | Viewed by 2786 | PDF Full-text (289 KB) | HTML Full-text | XML Full-text
Abstract
Emergency navigation systems for buildings and other built environments, such as sport arenas or shopping centres, typically rely on simple sensor networks to detect emergencies and, then, provide automatic signs to direct the evacuees. The major drawbacks of such static wireless sensor network [...] Read more.
Emergency navigation systems for buildings and other built environments, such as sport arenas or shopping centres, typically rely on simple sensor networks to detect emergencies and, then, provide automatic signs to direct the evacuees. The major drawbacks of such static wireless sensor network (WSN)-based emergency navigation systems are the very limited computing capacity, which makes adaptivity very difficult, and the restricted battery power, due to the low cost of sensor nodes for unattended operation. If static wireless sensor networks and cloud-computing can be integrated, then intensive computations that are needed to determine optimal evacuation routes in the presence of time-varying hazards can be offloaded to the cloud, but the disadvantages of limited battery life-time at the client side, as well as the high likelihood of system malfunction during an emergency still remain. By making use of the powerful sensing ability of smart phones, which are increasingly ubiquitous, this paper presents a cloud-enabled indoor emergency navigation framework to direct evacuees in a coordinated fashion and to improve the reliability and resilience for both communication and localization. By combining social potential fields (SPF) and a cognitive packet network (CPN)-based algorithm, evacuees are guided to exits in dynamic loose clusters. Rather than relying on a conventional telecommunications infrastructure, we suggest an ad hoc cognitive packet network (AHCPN)-based protocol to adaptively search optimal communication routes between portable devices and the network egress nodes that provide access to cloud servers, in a manner that spares the remaining battery power of smart phones and minimizes the time latency. Experimental results through detailed simulations indicate that smart human motion and smart network management can increase the survival rate of evacuees and reduce the number of drained smart phones in an evacuation process. Full article
(This article belongs to the Section Sensor Networks)
Open AccessArticle
Genetic Algorithm with Maximum-Minimum Crossover (GA-MMC) Applied in Optimization of Radiation Pattern Control of Phased-Array Radars for Rocket Tracking Systems
Sensors 2014, 14(8), 15113-15141; https://doi.org/10.3390/s140815113
Received: 23 January 2014 / Revised: 20 June 2014 / Accepted: 9 July 2014 / Published: 18 August 2014
Cited by 1 | Viewed by 2845 | PDF Full-text (902 KB) | HTML Full-text | XML Full-text
Abstract
In launching operations, Rocket Tracking Systems (RTS) process the trajectory data obtained by radar sensors. In order to improve functionality and maintenance, radars can be upgraded by replacing antennas with parabolic reflectors (PRs) with phased arrays (PAs). These arrays enable the electronic control [...] Read more.
In launching operations, Rocket Tracking Systems (RTS) process the trajectory data obtained by radar sensors. In order to improve functionality and maintenance, radars can be upgraded by replacing antennas with parabolic reflectors (PRs) with phased arrays (PAs). These arrays enable the electronic control of the radiation pattern by adjusting the signal supplied to each radiating element. However, in projects of phased array radars (PARs), the modeling of the problem is subject to various combinations of excitation signals producing a complex optimization problem. In this case, it is possible to calculate the problem solutions with optimization methods such as genetic algorithms (GAs). For this, the Genetic Algorithm with Maximum-Minimum Crossover (GA-MMC) method was developed to control the radiation pattern of PAs. The GA-MMC uses a reconfigurable algorithm with multiple objectives, differentiated coding and a new crossover genetic operator. This operator has a different approach from the conventional one, because it performs the crossover of the fittest individuals with the least fit individuals in order to enhance the genetic diversity. Thus, GA-MMC was successful in more than 90% of the tests for each application, increased the fitness of the final population by more than 20% and reduced the premature convergence. Full article
(This article belongs to the Section Remote Sensors, Control, and Telemetry)
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Open AccessArticle
Stability Analysis for a Multi-Camera Photogrammetric System
Sensors 2014, 14(8), 15084-15112; https://doi.org/10.3390/s140815084
Received: 6 June 2014 / Revised: 7 August 2014 / Accepted: 11 August 2014 / Published: 18 August 2014
Cited by 16 | Viewed by 2772 | PDF Full-text (1262 KB) | HTML Full-text | XML Full-text
Abstract
Consumer-grade digital cameras suffer from geometrical instability that may cause problems when used in photogrammetric applications. This paper provides a comprehensive review of this issue of interior orientation parameter variation over time, it explains the common ways used for coping with the issue, [...] Read more.
Consumer-grade digital cameras suffer from geometrical instability that may cause problems when used in photogrammetric applications. This paper provides a comprehensive review of this issue of interior orientation parameter variation over time, it explains the common ways used for coping with the issue, and describes the existing methods for performing stability analysis for a single camera. The paper then points out the lack of coverage of stability analysis for multi-camera systems, suggests a modification of the collinearity model to be used for the calibration of an entire photogrammetric system, and proposes three methods for system stability analysis. The proposed methods explore the impact of the changes in interior orientation and relative orientation/mounting parameters on the reconstruction process. Rather than relying on ground truth in real datasets to check the system calibration stability, the proposed methods are simulation-based. Experiment results are shown, where a multi-camera photogrammetric system was calibrated three times, and stability analysis was performed on the system calibration parameters from the three sessions. The proposed simulation-based methods provided results that were compatible with a real-data based approach for evaluating the impact of changes in the system calibration parameters on the three-dimensional reconstruction. Full article
(This article belongs to the Special Issue State-of-the-Art Sensors in Canada 2014)
Open AccessArticle
Wave Dispersion and Attenuation on Human Femur Tissue
Sensors 2014, 14(8), 15067-15083; https://doi.org/10.3390/s140815067
Received: 30 May 2014 / Revised: 27 July 2014 / Accepted: 6 August 2014 / Published: 15 August 2014
Cited by 7 | Viewed by 2508 | PDF Full-text (1529 KB) | HTML Full-text | XML Full-text
Abstract
Cortical bone is a highly heterogeneous material at the microscale and has one of the most complex structures among materials. Application of elastic wave techniques to this material is thus very challenging. In such media the initial excitation energy goes into the formation [...] Read more.
Cortical bone is a highly heterogeneous material at the microscale and has one of the most complex structures among materials. Application of elastic wave techniques to this material is thus very challenging. In such media the initial excitation energy goes into the formation of elastic waves of different modes. Due to “dispersion”, these modes tend to separate according to the velocities of the frequency components. This work demonstrates elastic wave measurements on human femur specimens. The aim of the study is to measure parameters like wave velocity, dispersion and attenuation by using broadband acoustic emission sensors. First, four sensors were placed at small intervals on the surface of the bone to record the response after pencil lead break excitations. Next, the results were compared to measurements on a bulk steel block which does not exhibit heterogeneity at the same wave lengths. It can be concluded that the microstructure of the tissue imposes a dispersive behavior for frequencies below 1 MHz and care should be taken for interpretation of the signals. Of particular interest are waveform parameters like the duration, rise time and average frequency, since in the next stage of research the bone specimens will be fractured with concurrent monitoring of acoustic emission. Full article
Open AccessEditorial
Polymeric Micro Sensors and Actuators
Sensors 2014, 14(8), 15065-15066; https://doi.org/10.3390/s140815065
Received: 13 August 2014 / Accepted: 15 August 2014 / Published: 15 August 2014
Cited by 1 | Viewed by 2013 | PDF Full-text (70 KB) | HTML Full-text | XML Full-text
Abstract
Sensors and actuators using polymeric systems, constitute one of the most promising fields of “smart polymers”, and it is becoming ever more important to associate artificial sensing and actuating systems with living organisms. [...] Full article
(This article belongs to the Special Issue Polymeric Micro Sensors and Actuators)
Open AccessArticle
An Intelligent Space for Mobile Robot Localization Using a Multi-Camera System
Sensors 2014, 14(8), 15039-15064; https://doi.org/10.3390/s140815039
Received: 9 July 2014 / Revised: 1 August 2014 / Accepted: 7 August 2014 / Published: 15 August 2014
Cited by 13 | Viewed by 3157 | PDF Full-text (17065 KB) | HTML Full-text | XML Full-text
Abstract
This paper describes an intelligent space, whose objective is to localize and control robots or robotic wheelchairs to help people. Such an intelligent space has 11 cameras distributed in two laboratories and a corridor. The cameras are fixed in the environment, and image [...] Read more.
This paper describes an intelligent space, whose objective is to localize and control robots or robotic wheelchairs to help people. Such an intelligent space has 11 cameras distributed in two laboratories and a corridor. The cameras are fixed in the environment, and image capturing is done synchronously. The system was programmed as a client/server with TCP/IP connections, and a communication protocol was defined. The client coordinates the activities inside the intelligent space, and the servers provide the information needed for that. Once the cameras are used for localization, they have to be properly calibrated. Therefore, a calibration method for a multi-camera network is also proposed in this paper. A robot is used to move a calibration pattern throughout the field of view of the cameras. Then, the captured images and the robot odometry are used for calibration. As a result, the proposed algorithm provides a solution for multi-camera calibration and robot localization at the same time. The intelligent space and the calibration method were evaluated under different scenarios using computer simulations and real experiments. The results demonstrate the proper functioning of the intelligent space and validate the multi-camera calibration method, which also improves robot localization. Full article
(This article belongs to the Section Sensor Networks)
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