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Sensors, Volume 12, Issue 6 (June 2012), Pages 6764-8437

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Open AccessArticle Enhancing Positioning Accuracy in Urban Terrain by Fusing Data from a GPS Receiver, Inertial Sensors, Stereo-Camera and Digital Maps for Pedestrian Navigation
Sensors 2012, 12(6), 6764-6801; doi:10.3390/s120606764
Received: 6 March 2012 / Revised: 19 April 2012 / Accepted: 29 April 2012 / Published: 25 May 2012
Cited by 13 | PDF Full-text (1856 KB) | HTML Full-text | XML Full-text
Abstract
The paper presents an algorithm for estimating a pedestrian location in an urban environment. The algorithm is based on the particle filter and uses different data sources: a GPS receiver, inertial sensors, probability maps and a stereo camera. Inertial sensors are used to
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The paper presents an algorithm for estimating a pedestrian location in an urban environment. The algorithm is based on the particle filter and uses different data sources: a GPS receiver, inertial sensors, probability maps and a stereo camera. Inertial sensors are used to estimate a relative displacement of a pedestrian. A gyroscope estimates a change in the heading direction. An accelerometer is used to count a pedestrian’s steps and their lengths. The so-called probability maps help to limit GPS inaccuracy by imposing constraints on pedestrian kinematics, e.g., it is assumed that a pedestrian cannot cross buildings, fences etc. This limits position inaccuracy to ca. 10 m. Incorporation of depth estimates derived from a stereo camera that are compared to the 3D model of an environment has enabled further reduction of positioning errors. As a result, for 90% of the time, the algorithm is able to estimate a pedestrian location with an error smaller than 2 m, compared to an error of 6.5 m for a navigation based solely on GPS. Full article
(This article belongs to the Special Issue New Trends towards Automatic Vehicle Control and Perception Systems)
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Open AccessArticle Meeting People’s Needs in a Fully Interoperable Domotic Environment
Sensors 2012, 12(6), 6802-6824; doi:10.3390/s120606802
Received: 8 April 2012 / Revised: 11 May 2012 / Accepted: 22 May 2012 / Published: 25 May 2012
Cited by 3 | PDF Full-text (437 KB) | HTML Full-text | XML Full-text
Abstract
The key idea underlying many Ambient Intelligence (AmI) projects and applications is context awareness, which is based mainly on their capacity to identify users and their locations. The actual computing capacity should remain in the background, in the periphery of our awareness, and
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The key idea underlying many Ambient Intelligence (AmI) projects and applications is context awareness, which is based mainly on their capacity to identify users and their locations. The actual computing capacity should remain in the background, in the periphery of our awareness, and should only move to the center if and when necessary. Computing thus becomes ‘invisible’, as it is embedded in the environment and everyday objects. The research project described herein aims to realize an Ambient Intelligence-based environment able to improve users’ quality of life by learning their habits and anticipating their needs. This environment is part of an adaptive, context-aware framework designed to make today’s incompatible heterogeneous domotic systems fully interoperable, not only for connecting sensors and actuators, but for providing comprehensive connections of devices to users. The solution is a middleware architecture based on open and widely recognized standards capable of abstracting the peculiarities of underlying heterogeneous technologies and enabling them to co-exist and interwork, without however eliminating their differences. At the highest level of this infrastructure, the Ambient Intelligence framework, integrated with the domotic sensors, can enable the system to recognize any unusual or dangerous situations and anticipate health problems or special user needs in a technological living environment, such as a house or a public space. Full article
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Open AccessArticle Analysis of Airborne Particulate Matter (PM2.5) over Hong Kong Using Remote Sensing and GIS
Sensors 2012, 12(6), 6825-6836; doi:10.3390/s120606825
Received: 26 March 2012 / Revised: 25 April 2012 / Accepted: 8 May 2012 / Published: 25 May 2012
Cited by 14 | PDF Full-text (422 KB) | HTML Full-text | XML Full-text
Abstract
Airborne fine particulates (PM2.5; particulate matter with diameter less than 2.5 µm) are receiving increasing attention for their potential toxicities and roles in visibility and health. In this study, we interpreted the behavior of PM2.5 and its correlation with meteorological
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Airborne fine particulates (PM2.5; particulate matter with diameter less than 2.5 µm) are receiving increasing attention for their potential toxicities and roles in visibility and health. In this study, we interpreted the behavior of PM2.5 and its correlation with meteorological parameters in Hong Kong, during 2007–2008. Significant diurnal variations of PM2.5 concentrations were observed and showed a distinctive bimodal pattern with two marked peaks during the morning and evening rush hour times, due to dense traffic. The study observed higher PM2.5 concentrations in winter when the northerly and northeasterly winds bring pollutants from the Chinese mainland, whereas southerly monsoon winds from the sea bring fresh air to the city in summer. In addition, higher concentrations of PM2.5 were observed in rush hours on weekdays compared to weekends, suggesting the influence of anthropogenic activities on fine particulate levels, e.g., traffic-related local PM2.5 emissions. To understand the spatial pattern of PM2.5 concentrations in the context of the built-up environment of Hong Kong, we utilized MODerate Resolution Imaging Spectroradiometer (MODIS) Aerosol Optical Thickness (AOT) 500 m data and visibility data to derive aerosol extinction profile, then converted to aerosol and PM2.5 vertical profiles. A Geographic Information Systems (GIS) prototype was developed to integrate atmospheric PM2.5 vertical profiles with 3D GIS data. An example of the query function in GIS prototype is given. The resulting 3D database of PM2.5 concentrations provides crucial information to air quality regulators and decision makers to comply with air quality standards and in devising control strategies. Full article
(This article belongs to the Section Remote Sensors)
Open AccessArticle An Ultra-Low Power and Flexible Acoustic Modem Design to Develop Energy-Efficient Underwater Sensor Networks
Sensors 2012, 12(6), 6837-6856; doi:10.3390/s120606837
Received: 3 April 2012 / Revised: 8 May 2012 / Accepted: 16 May 2012 / Published: 25 May 2012
Cited by 19 | PDF Full-text (645 KB) | HTML Full-text | XML Full-text
Abstract
This paper is focused on the description of the physical layer of a new acoustic modem called ITACA. The modem architecture includes as a major novelty an ultra-low power asynchronous wake-up system implementation for underwater acoustic transmission that is based on a low-cost
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This paper is focused on the description of the physical layer of a new acoustic modem called ITACA. The modem architecture includes as a major novelty an ultra-low power asynchronous wake-up system implementation for underwater acoustic transmission that is based on a low-cost off-the-shelf RFID peripheral integrated circuit. This feature enables a reduced power dissipation of 10 µW in stand-by mode and registers very low power values during reception and transmission. The modem also incorporates clear channel assessment (CCA) to support CSMA-based medium access control (MAC) layer protocols. The design is part of a compact platform for a long-life short/medium range underwater wireless sensor network. Full article
(This article belongs to the Special Issue Underwater Sensor Nodes and Underwater Sensor Networks)
Open AccessArticle Prediction of Gap Asymmetry in Differential Micro Accelerometers
Sensors 2012, 12(6), 6857-6868; doi:10.3390/s120606857
Received: 16 April 2012 / Revised: 13 May 2012 / Accepted: 22 May 2012 / Published: 25 May 2012
Cited by 8 | PDF Full-text (641 KB) | HTML Full-text | XML Full-text
Abstract
Gap asymmetry in differential capacitors is the primary source of the zero bias output of force-balanced micro accelerometers. It is also used to evaluate the applicability of differential structures in MEMS manufacturing. Therefore, determining the asymmetry level has considerable significance for the design
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Gap asymmetry in differential capacitors is the primary source of the zero bias output of force-balanced micro accelerometers. It is also used to evaluate the applicability of differential structures in MEMS manufacturing. Therefore, determining the asymmetry level has considerable significance for the design of MEMS devices. This paper proposes an experimental-theoretical method for predicting gap asymmetry in differential sensing capacitors of micro accelerometers. The method involves three processes: first, bi-directional measurement, which can sharply reduce the influence of the feedback circuit on bias output, is proposed. Experiments are then carried out on a centrifuge to obtain the input and output data of an accelerometer. Second, the analytical input-output relationship of the accelerometer with gap asymmetry and circuit error is theoretically derived. Finally, the prediction methodology combines the measurement results and analytical derivation to identify the asymmetric error of 30 accelerometers fabricated by DRIE. Results indicate that the level of asymmetry induced by fabrication uncertainty is about ±5 × 10−2, and that the absolute error is about ±0.2 µm under a 4 µm gap. Full article
(This article belongs to the Special Issue Modeling, Testing and Reliability Issues in MEMS Engineering 2011)
Open AccessArticle Joint Torque Reduction of a Three Dimensional Redundant Planar Manipulator
Sensors 2012, 12(6), 6869-6892; doi:10.3390/s120606869
Received: 1 April 2012 / Revised: 2 May 2012 / Accepted: 22 May 2012 / Published: 25 May 2012
Cited by 3 | PDF Full-text (1790 KB) | HTML Full-text | XML Full-text
Abstract
Research on joint torque reduction in robot manipulators has received considerable attention in recent years. Minimizing the computational complexity of torque optimization and the ability to calculate the magnitude of the joint torque accurately will result in a safe operation without overloading the
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Research on joint torque reduction in robot manipulators has received considerable attention in recent years. Minimizing the computational complexity of torque optimization and the ability to calculate the magnitude of the joint torque accurately will result in a safe operation without overloading the joint actuators. This paper presents a mechanical design for a three dimensional planar redundant manipulator with the advantage of the reduction in the number of motors needed to control the joint angle, leading to a decrease in the weight of the manipulator. Many efforts have been focused on decreasing the weight of manipulators, such as using lightweight joints design or setting the actuators at the base of the manipulator and using tendons for the transmission of power to these joints. By using the design of this paper, only three motors are needed to control any n degrees of freedom in a three dimensional planar redundant manipulator instead of n motors. Therefore this design is very effective to decrease the weight of the manipulator as well as the number of motors needed to control the manipulator. In this paper, the torque of all the joints are calculated for the proposed manipulator (with three motors) and the conventional three dimensional planar manipulator (with one motor for each degree of freedom) to show the effectiveness of the proposed manipulator for decreasing the weight of the manipulator and minimizing driving joint torques. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle Geometric and Colour Data Fusion for Outdoor 3D Models
Sensors 2012, 12(6), 6893-6919; doi:10.3390/s120606893
Received: 29 February 2012 / Revised: 15 May 2012 / Accepted: 17 May 2012 / Published: 25 May 2012
Cited by 2 | PDF Full-text (2574 KB) | HTML Full-text | XML Full-text
Abstract
This paper deals with the generation of accurate, dense and coloured 3D models of outdoor scenarios from scanners. This is a challenging research field in which several problems still remain unsolved. In particular, the process of 3D model creation in outdoor scenes may
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This paper deals with the generation of accurate, dense and coloured 3D models of outdoor scenarios from scanners. This is a challenging research field in which several problems still remain unsolved. In particular, the process of 3D model creation in outdoor scenes may be inefficient if the scene is digitalized under unsuitable technical (specific scanner on-board camera) and environmental (rain, dampness, changing illumination) conditions. We address our research towards the integration of images and range data to produce photorealistic models. Our proposal is based on decoupling the colour integration and geometry reconstruction stages, making them independent and controlled processes. This issue is approached from two different viewpoints. On the one hand, given a complete model (geometry plus texture), we propose a method to modify the original texture provided by the scanner on-board camera with the colour information extracted from external images taken at given moments and under specific environmental conditions. On the other hand, we propose an algorithm to directly assign external images onto the complete geometric model, thus avoiding tedious on-line calibration processes. We present the work conducted on two large Roman archaeological sites dating from the first century A.D., namely, the Theatre of Segobriga and the Fori Porticus of Emerita Augusta, both in Spain. The results obtained demonstrate that our approach could be useful in the digitalization and 3D modelling fields. Full article
Open AccessArticle Ultra-Fast Displaying Spectral Domain Optical Doppler Tomography System Using a Graphics Processing Unit
Sensors 2012, 12(6), 6920-6929; doi:10.3390/s120606920
Received: 22 March 2012 / Revised: 2 May 2012 / Accepted: 21 May 2012 / Published: 25 May 2012
Cited by 20 | PDF Full-text (478 KB) | HTML Full-text | XML Full-text
Abstract
We demonstrate an ultrafast displaying Spectral Domain Optical Doppler Tomography system using Graphics Processing Unit (GPU) computing. The calculation of FFT and the Doppler frequency shift is accelerated by the GPU. Our system can display processed OCT and ODT images simultaneously in real
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We demonstrate an ultrafast displaying Spectral Domain Optical Doppler Tomography system using Graphics Processing Unit (GPU) computing. The calculation of FFT and the Doppler frequency shift is accelerated by the GPU. Our system can display processed OCT and ODT images simultaneously in real time at 120 fps for 1,024 pixels × 512 lateral A-scans. The computing time for the Doppler information was dependent on the size of the moving average window, but with a window size of 32 pixels the ODT computation time is only 8.3 ms, which is comparable to the data acquisition time. Also the phase noise decreases significantly with the window size. Since the performance of a real-time display for OCT/ODT is very important for clinical applications that need immediate diagnosis for screening or biopsy. Intraoperative surgery can take much benefit from the real-time display flow rate information from the technology. Moreover, the GPU is an attractive tool for clinical and commercial systems for functional OCT features as well. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle On the Impact of Localization and Density Control Algorithms in Target Tracking Applications for Wireless Sensor Networks
Sensors 2012, 12(6), 6930-6952; doi:10.3390/s120606930
Received: 29 March 2012 / Revised: 26 April 2012 / Accepted: 26 April 2012 / Published: 25 May 2012
Cited by 8 | PDF Full-text (4903 KB) | HTML Full-text | XML Full-text
Abstract
Target tracking is an important application of wireless sensor networks. The networks’ ability to locate and track an object is directed linked to the nodes’ ability to locate themselves. Consequently, localization systems are essential for target tracking applications. In addition, sensor networks are
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Target tracking is an important application of wireless sensor networks. The networks’ ability to locate and track an object is directed linked to the nodes’ ability to locate themselves. Consequently, localization systems are essential for target tracking applications. In addition, sensor networks are often deployed in remote or hostile environments. Therefore, density control algorithms are used to increase network lifetime while maintaining its sensing capabilities. In this work, we analyze the impact of localization algorithms (RPE and DPE) and density control algorithms (GAF, A3 and OGDC) on target tracking applications. We adapt the density control algorithms to address the k-coverage problem. In addition, we analyze the impact of network density, residual integration with density control, and k-coverage on both target tracking accuracy and network lifetime. Our results show that DPE is a better choice for target tracking applications than RPE. Moreover, among the evaluated density control algorithms, OGDC is the best option among the three. Although the choice of the density control algorithm has little impact on the tracking precision, OGDC outperforms GAF and A3 in terms of tracking time. Full article
(This article belongs to the Special Issue Ubiquitous Sensing)
Open AccessArticle Sensoring Fusion Data from the Optic and Acoustic Emissions of Electric Arcs in the GMAW-S Process for Welding Quality Assessment
Sensors 2012, 12(6), 6953-6966; doi:10.3390/s120606953
Received: 31 March 2012 / Revised: 17 May 2012 / Accepted: 17 May 2012 / Published: 25 May 2012
Cited by 2 | PDF Full-text (1378 KB) | HTML Full-text | XML Full-text
Abstract
The present study shows the relationship between welding quality and optical-acoustic emissions from electric arcs, during welding runs, in the GMAW-S process. Bead on plate welding tests was carried out with pre-set parameters chosen from manufacturing standards. During the welding runs interferences were
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The present study shows the relationship between welding quality and optical-acoustic emissions from electric arcs, during welding runs, in the GMAW-S process. Bead on plate welding tests was carried out with pre-set parameters chosen from manufacturing standards. During the welding runs interferences were induced on the welding path using paint, grease or gas faults. In each welding run arc voltage, welding current, infrared and acoustic emission values were acquired and parameters such as arc power, acoustic peaks rate and infrared radiation rate computed. Data fusion algorithms were developed by assessing known welding quality parameters from arc emissions. These algorithms have showed better responses when they are based on more than just one sensor. Finally, it was concluded that there is a close relation between arc emissions and quality in welding and it can be measured from arc emissions sensing and data fusion algorithms. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle Single-Cell Electric Lysis on an Electroosmotic-Driven Microfluidic Chip with Arrays of Microwells
Sensors 2012, 12(6), 6967-6977; doi:10.3390/s120606967
Received: 16 April 2012 / Revised: 15 May 2012 / Accepted: 21 May 2012 / Published: 25 May 2012
Cited by 9 | PDF Full-text (456 KB) | HTML Full-text | XML Full-text
Abstract
Accurate analysis at the single-cell level has become a highly attractive tool for investigating cellular content. An electroosmotic-driven microfluidic chip with arrays of 30-µm-diameter microwells was developed for single-cell electric lysis in the present study. The cellular occupancy in the microwells when the
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Accurate analysis at the single-cell level has become a highly attractive tool for investigating cellular content. An electroosmotic-driven microfluidic chip with arrays of 30-µm-diameter microwells was developed for single-cell electric lysis in the present study. The cellular occupancy in the microwells when the applied voltage was 5 V (82.4%) was slightly higher than that at an applied voltage of 10 V (81.8%). When the applied voltage was increased to 15 V, the cellular occupancy in the microwells dropped to 64.3%. More than 50% of the occupied microwells contain individual cells. The results of electric lysis experiments at the single-cell level indicate that the cells were gradually lysed as the DC voltage of 30 V was applied; the cell was fully lysed after 25 s. Single-cell electric lysis was demonstrated in the proposed microfluidic chip, which is suitable for high-throughput cell lysis. Full article
(This article belongs to the Special Issue Biochips)
Open AccessArticle Use of Finite Elements Analysis for a Weigh-in-Motion Sensor Design
Sensors 2012, 12(6), 6978-6994; doi:10.3390/s120606978
Received: 4 April 2012 / Revised: 14 May 2012 / Accepted: 14 May 2012 / Published: 25 May 2012
PDF Full-text (3327 KB) | HTML Full-text | XML Full-text
Abstract
High speed weigh-in-motion (WIM) sensors are utilized as components of complex traffic monitoring and measurement systems. They should be able to determine the weights on wheels, axles and vehicle gross weights, and to help the classification of vehicles (depending on the number of
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High speed weigh-in-motion (WIM) sensors are utilized as components of complex traffic monitoring and measurement systems. They should be able to determine the weights on wheels, axles and vehicle gross weights, and to help the classification of vehicles (depending on the number of axles). WIM sensors must meet the following main requirements: good accuracy, high endurance, low price and easy installation in the road structure. It is not advisable to use cheap materials in constructing these devices for lower prices, since the sensors are normally working in harsh environmental conditions such as temperatures between –40 °C and +70 °C, dust, temporary water immersion, shocks and vibrations. Consequently, less expensive manufacturing technologies are recommended. Because the installation cost in the road structure is high and proportional to the WIM sensor cross section (especially with its thickness), the device needs to be made as flat as possible. The WIM sensor model presented and analyzed in this paper uses a spring element equipped with strain gages. Using Finite Element Analysis (FEA), the authors have attempted to obtain a more sensitive, reliable, lower profile and overall cheaper elastic element for a new WIM sensor. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle Ubiquitous Mobile Knowledge Construction in Collaborative Learning Environments
Sensors 2012, 12(6), 6995-7014; doi:10.3390/s120606995
Received: 19 March 2012 / Revised: 18 May 2012 / Accepted: 18 May 2012 / Published: 25 May 2012
Cited by 9 | PDF Full-text (615 KB) | HTML Full-text | XML Full-text
Abstract
Knowledge management is a critical activity for any organization. It has been said to be a differentiating factor and an important source of competitiveness if this knowledge is constructed and shared among its members, thus creating a learning organization. Knowledge construction is critical
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Knowledge management is a critical activity for any organization. It has been said to be a differentiating factor and an important source of competitiveness if this knowledge is constructed and shared among its members, thus creating a learning organization. Knowledge construction is critical for any collaborative organizational learning environment. Nowadays workers must perform knowledge creation tasks while in motion, not just in static physical locations; therefore it is also required that knowledge construction activities be performed in ubiquitous scenarios, and supported by mobile and pervasive computational systems. These knowledge creation systems should help people in or outside organizations convert their tacit knowledge into explicit knowledge, thus supporting the knowledge construction process. Therefore in our understanding, we consider highly relevant that undergraduate university students learn about the knowledge construction process supported by mobile and ubiquitous computing. This has been a little explored issue in this field. This paper presents the design, implementation, and an evaluation of a system called MCKC for Mobile Collaborative Knowledge Construction, supporting collaborative face-to-face tacit knowledge construction and sharing in ubiquitous scenarios. The MCKC system can be used by undergraduate students to learn how to construct knowledge, allowing them anytime and anywhere to create, make explicit and share their knowledge with their co-learners, using visual metaphors, gestures and sketches to implement the human-computer interface of mobile devices (PDAs). Full article
Open AccessArticle Electrochemical Determination of Pentachlorophenol in Water on a Multi-Wall Carbon Nanotubes-Epoxy Composite Electrode
Sensors 2012, 12(6), 7033-7046; doi:10.3390/s120607033
Received: 30 March 2012 / Revised: 18 April 2012 / Accepted: 26 April 2012 / Published: 25 May 2012
Cited by 11 | PDF Full-text (790 KB) | HTML Full-text | XML Full-text
Abstract
The aim of this study was the preparation, characterization, and application of a multi-wall carbon nanotubes-epoxy composite electrode (MWCNT-EP) with 25%, wt. MWCNTs loading for the voltammetric/amperometric determination of pentachlorophenol (PCP) in aqueous solutions. The structural and morphological aspects of the MWCNT-EP composite
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The aim of this study was the preparation, characterization, and application of a multi-wall carbon nanotubes-epoxy composite electrode (MWCNT-EP) with 25%, wt. MWCNTs loading for the voltammetric/amperometric determination of pentachlorophenol (PCP) in aqueous solutions. The structural and morphological aspects of the MWCNT-EP composite electrode were examined by scanning electron microscopy. The electrical properties were characterized by direct-current conductivity measurements in relation with the percolation threshold. The electrochemical behavior of PCP at the MWCNT-EP composite electrode was investigated using cyclic voltammetry in 0.1 M Na2SO4 supporting electrolyte in order to establish the parameters for amperometric/voltammetric determination of PCP. The linear dependence of current vs. PCP concentrations was reached in a wide concentration range from 0.2 to 12 μM PCP using cyclic voltammetry, differential-pulsed voltammetry, square-wave voltammetry, chronoamperometry, and multiple-pulsed amperometry techniques. The best electroanalytical performances of this composite electrode were achieved using a pre-concentration/square-wave voltammetric technique and also multiple-pulsed amperometry techniques envisaging the practical applications. The ease of preparation, high sensitivity, and stability of this composite electrode should open novel avenues and applications for fabricating robust sensors for detection of many important species. Full article
(This article belongs to the Section Chemical Sensors)
Open AccessArticle CMEIAS-Aided Microscopy of the Spatial Ecology of Individual Bacterial Interactions Involving Cell-to-Cell Communication within Biofilms
Sensors 2012, 12(6), 7047-7062; doi:10.3390/s120607047
Received: 29 March 2012 / Revised: 17 April 2012 / Accepted: 22 May 2012 / Published: 29 May 2012
Cited by 4 | PDF Full-text (1274 KB) | HTML Full-text | XML Full-text
Abstract
This paper describes how the quantitative analytical tools of CMEIAS image analysis software can be used to investigate in situ microbial interactions involving cell-to-cell communication within biofilms. Various spatial pattern analyses applied to the data extracted from the 2-dimensional coordinate positioning of individual
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This paper describes how the quantitative analytical tools of CMEIAS image analysis software can be used to investigate in situ microbial interactions involving cell-to-cell communication within biofilms. Various spatial pattern analyses applied to the data extracted from the 2-dimensional coordinate positioning of individual bacterial cells at single-cell resolution indicate that microbial colonization within natural biofilms is not a spatially random process, but rather involves strong positive interactions between communicating cells that influence their neighbors’ aggregated colonization behavior. Geostatistical analysis of the data provide statistically defendable estimates of the micrometer scale and interpolation maps of the spatial heterogeneity and local intensity at which these microbial interactions autocorrelate with their spatial patterns of distribution. Including in situ image analysis in cell communication studies fills an important gap in understanding the spatially dependent microbial ecophysiology that governs the intensity of biofilm colonization and its unique architecture. Full article
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Open AccessArticle RGB Color Calibration for Quantitative Image Analysis: The “3D Thin-Plate Spline” Warping Approach
Sensors 2012, 12(6), 7063-7079; doi:10.3390/s120607063
Received: 12 April 2012 / Revised: 14 May 2012 / Accepted: 22 May 2012 / Published: 29 May 2012
Cited by 22 | PDF Full-text (389 KB) | HTML Full-text | XML Full-text
Abstract
In the last years the need to numerically define color by its coordinates in n-dimensional space has increased strongly. Colorimetric calibration is fundamental in food processing and other biological disciplines to quantitatively compare samples’ color during workflow with many devices. Several software programmes
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In the last years the need to numerically define color by its coordinates in n-dimensional space has increased strongly. Colorimetric calibration is fundamental in food processing and other biological disciplines to quantitatively compare samples’ color during workflow with many devices. Several software programmes are available to perform standardized colorimetric procedures, but they are often too imprecise for scientific purposes. In this study, we applied the Thin-Plate Spline interpolation algorithm to calibrate colours in sRGB space (the corresponding Matlab code is reported in the Appendix). This was compared with other two approaches. The first is based on a commercial calibration system (ProfileMaker) and the second on a Partial Least Square analysis. Moreover, to explore device variability and resolution two different cameras were adopted and for each sensor, three consecutive pictures were acquired under four different light conditions. According to our results, the Thin-Plate Spline approach reported a very high efficiency of calibration allowing the possibility to create a revolution in the in-field applicative context of colour quantification not only in food sciences, but also in other biological disciplines. These results are of great importance for scientific color evaluation when lighting conditions are not controlled. Moreover, it allows the use of low cost instruments while still returning scientifically sound quantitative data. Full article
(This article belongs to the Section Physical Sensors)
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Open AccessArticle Quartz Crystal Microbalance Aptasensor for Sensitive Detection of Mercury(II) Based on Signal Amplification with Gold Nanoparticles
Sensors 2012, 12(6), 7080-7094; doi:10.3390/s120607080
Received: 18 April 2012 / Revised: 14 May 2012 / Accepted: 23 May 2012 / Published: 29 May 2012
Cited by 23 | PDF Full-text (709 KB) | HTML Full-text | XML Full-text
Abstract
We show that a short mercury-specific aptamer (MSA) along with gold nanoparticles (Au-NPs) can be used to determine Hg(II) ion by a combination of a QCM-based sensor and a flow system. The MSA binds specifically to Hg(II), and the Au-NPs can amplify the
[...] Read more.
We show that a short mercury-specific aptamer (MSA) along with gold nanoparticles (Au-NPs) can be used to determine Hg(II) ion by a combination of a QCM-based sensor and a flow system. The MSA binds specifically to Hg(II), and the Au-NPs can amplify the signal to enhance sensitivity. Specifically, the short thiolated MSAs are immobilized on the surface of the QCM as the capture probe, and the MSAs are linked to the Au-NPs as the linking probe. The two components can form a sandwich structure of the T-Hg(II)-T type in the presence of Hg(II) ions. This leads to change in the mass on the QCM and a change in the resonance frequency. Hg(II) can be determined with a detection limit of 0.24 ± 0.06 nM which is better by three orders of magnitude than previous methods. The sensor can be regenerated by disrupting the T-Hg(II)-T base pairs with a solution of cysteine. Full article
(This article belongs to the Section Biosensors)
Open AccessArticle Passive Fluidic Chip Composed of Integrated Vertical Capillary Tubes Developed for On-Site SPR Immunoassay Analysis Targeting Real Samples
Sensors 2012, 12(6), 7095-7108; doi:10.3390/s120607095
Received: 15 April 2012 / Revised: 21 May 2012 / Accepted: 22 May 2012 / Published: 29 May 2012
Cited by 6 | PDF Full-text (444 KB) | HTML Full-text | XML Full-text
Abstract
We have successfully developed a surface plasmon resonance (SPR) measurement system for the on-site immunoassay of real samples. The system is composed of a portable SPR instrument (290 mm(W) x 160 mm(D) x 120 mm(H)) and a microfluidic immunoassay chip (16 mm(W) x
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We have successfully developed a surface plasmon resonance (SPR) measurement system for the on-site immunoassay of real samples. The system is composed of a portable SPR instrument (290 mm(W) x 160 mm(D) x 120 mm(H)) and a microfluidic immunoassay chip (16 mm(W) x 16 mm(D) x 4 mm(H)) that needs no external pump system. An integrated vertical capillary tube functions as a large volume (150 μL ) passive pump and a waste reservoir that has sufficient capacity for several refill operations. An immunoassay was carried out that employed the direct injection of a buffer and a test sample in sequence into a microfluidic chip that included 9 antibody bands and 10 reference reagent bands immobilized in the flow channel. By subtracting a reliable averaged reference sensorgram from the antibody, we effectively reduced the influence of the non-specific binding, and then our chip successfully detected the specific binding of spiked IgG in non-homogeneous milk. IgG is a model antigen that is certain not to be present in non-homogeneous milk, and non-homogeneous milk is a model of real sample that includes many interfering foreign substances that induce non-specific binding. The direct injection of a real sample with no pretreatment enabled us to complete the entire immunoassay in several minutes. This ease of operation and short measuring time are acceptable for on-site agricultural, environmentaland medical testing. Full article
(This article belongs to the Section Biosensors)
Open AccessArticle Personal Pervasive Environments: Practice and Experience
Sensors 2012, 12(6), 7109-7125; doi:10.3390/s120607109
Received: 1 April 2012 / Revised: 8 May 2012 / Accepted: 23 May 2012 / Published: 29 May 2012
Cited by 2 | PDF Full-text (1208 KB) | HTML Full-text | XML Full-text
Abstract
In this paper we present our experience designing and developing two different systems to enable personal pervasive computing environments, Plan B and the Octopus. These systems were fully implemented and have been used on a daily basis for years. Both are based on
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In this paper we present our experience designing and developing two different systems to enable personal pervasive computing environments, Plan B and the Octopus. These systems were fully implemented and have been used on a daily basis for years. Both are based on synthetic (virtual) file system interfaces and provide mechanisms to adapt to changes in the context and reconfigure the system to support pervasive applications. We also present the main differences between them, focusing on architectural and reconfiguration aspects. Finally, we analyze the pitfalls and successes of both systems and review the lessons we learned while designing, developing, and using them. Full article
Open AccessArticle A Sub-ppm Acetone Gas Sensor for Diabetes Detection Using 10 nm Thick Ultrathin InN FETs
Sensors 2012, 12(6), 7157-7168; doi:10.3390/s120607157
Received: 16 April 2012 / Revised: 15 May 2012 / Accepted: 21 May 2012 / Published: 29 May 2012
Cited by 30 | PDF Full-text (532 KB) | HTML Full-text | XML Full-text
Abstract
An indium nitride (InN) gas sensor of 10 nm in thickness has achieved detection limit of 0.4 ppm acetone. The sensor has a size of 1 mm by 2.5 mm, while its sensing area is 0.25 mm by 2 mm. Detection of such
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An indium nitride (InN) gas sensor of 10 nm in thickness has achieved detection limit of 0.4 ppm acetone. The sensor has a size of 1 mm by 2.5 mm, while its sensing area is 0.25 mm by 2 mm. Detection of such a low acetone concentration in exhaled breath could enable early diagnosis of diabetes for portable physiological applications. The ultrathin InN epilayer extensively enhances sensing sensitivity due to its strong electron accumulation on roughly 5–10 nm deep layers from the surface. Platinum as catalyst can increase output current signals by 2.5-fold (94 vs. 37.5 μA) as well as reduce response time by 8.4-fold (150 vs. 1,260 s) in comparison with bare InN. More, the effect of 3% oxygen consumption due to breath inhalation and exhalation on 2.4 ppm acetone gas detection was investigated, indicating that such an acetone concentration can be analyzed in air. Full article
(This article belongs to the Section Chemical Sensors)
Open AccessArticle The Camera Itself as a Calibration Pattern: A Novel Self-Calibration Method for Non-Central Catadioptric Cameras
Sensors 2012, 12(6), 7299-7317; doi:10.3390/s120607299
Received: 30 April 2012 / Revised: 14 May 2012 / Accepted: 14 May 2012 / Published: 30 May 2012
Cited by 7 | PDF Full-text (1046 KB) | HTML Full-text | XML Full-text
Abstract
A novel and practical self-calibration method for misaligned non-central catadioptric cameras is proposed in this paper. Without the aid of any special calibration patterns in the scene, the developed method is able to automatically estimate the pose parameters of the mirror with respect
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A novel and practical self-calibration method for misaligned non-central catadioptric cameras is proposed in this paper. Without the aid of any special calibration patterns in the scene, the developed method is able to automatically estimate the pose parameters of the mirror with respect to the perspective camera. First it uses the ellipse corresponding to the mirror boundary in the image to compute the possible solutions for mirror postures. With two pose candidates, thereafter we propose a novel selection method to find the correct solution by using the image of the lens boundary. The whole calibration process is automatic and convenient to carry out since nothing more than a single image acquired from the catadioptric camera is needed. Experimental results both on synthesized and real images prove our success. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle A Hybrid LPG/CFBG for Highly Sensitive Refractive Index Measurements
Sensors 2012, 12(6), 7318-7325; doi:10.3390/s120607318
Received: 28 March 2012 / Revised: 18 April 2012 / Accepted: 28 April 2012 / Published: 30 May 2012
Cited by 5 | PDF Full-text (229 KB) | HTML Full-text | XML Full-text
Abstract
A simple and high sensitive method employing a hybrid long period grating (LPG)/chirped fiber Bragg grating (CFBG) for refractive index (RI) measurements is proposed and investigated experimentally. The wide wavelength range of backward cladding modes are excited through the coupling and recoupling between
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A simple and high sensitive method employing a hybrid long period grating (LPG)/chirped fiber Bragg grating (CFBG) for refractive index (RI) measurements is proposed and investigated experimentally. The wide wavelength range of backward cladding modes are excited through the coupling and recoupling between LPG and CFBG. Experimental results indicate that the recoupled cladding modes between LPG and CFBG and core mode are modulated by the surrounding RI and highly sensitive RI measurements can be achieved by simply measuring the reflected intensity changes of the recoupled cladding modes and core mode. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle A Vision-Based Dynamic Rotational Angle Measurement System for Large Civil Structures
Sensors 2012, 12(6), 7326-7336; doi:10.3390/s120607326
Received: 2 May 2012 / Revised: 28 May 2012 / Accepted: 28 May 2012 / Published: 30 May 2012
Cited by 15 | PDF Full-text (675 KB) | HTML Full-text | XML Full-text
Abstract
In this paper, we propose a vision-based rotational angle measurement system for large-scale civil structures. Despite the fact that during the last decade several rotation angle measurement systems were introduced, they however often required complex and expensive equipment. Therefore, alternative effective solutions with
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In this paper, we propose a vision-based rotational angle measurement system for large-scale civil structures. Despite the fact that during the last decade several rotation angle measurement systems were introduced, they however often required complex and expensive equipment. Therefore, alternative effective solutions with high resolution are in great demand. The proposed system consists of commercial PCs, commercial camcorders, low-cost frame grabbers, and a wireless LAN router. The calculation of rotation angle is obtained by using image processing techniques with pre-measured calibration parameters. Several laboratory tests were conducted to verify the performance of the proposed system. Compared with the commercial rotation angle measurement, the results of the system showed very good agreement with an error of less than 1.0% in all test cases. Furthermore, several tests were conducted on the five-story modal testing tower with a hybrid mass damper to experimentally verify the feasibility of the proposed system. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle Temperature Effects on the Propagation Characteristics of Love Waves along Multi-Guide Layers of Sio2/Su-8 on St-90°X Quartz
Sensors 2012, 12(6), 7337-7349; doi:10.3390/s120607337
Received: 6 April 2012 / Revised: 21 May 2012 / Accepted: 22 May 2012 / Published: 30 May 2012
Cited by 2 | PDF Full-text (857 KB) | HTML Full-text | XML Full-text
Abstract
Theoretical calculations have been performed on the temperature effects on the propagation characteristics of Love waves in layered structures by solving the coupled electromechanical field equations, and the optimal design parameters were extracted for temperature stability improvement. Based on the theoretical analysis, excellent
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Theoretical calculations have been performed on the temperature effects on the propagation characteristics of Love waves in layered structures by solving the coupled electromechanical field equations, and the optimal design parameters were extracted for temperature stability improvement. Based on the theoretical analysis, excellent temperature coefficient of frequency (Tcf) of the fabricated Love wave devices with guide layers of SU-8/SiO2 on ST-90°X quartz substrate is evaluated experimentally as only 2.16 ppm. Full article
(This article belongs to the Section Chemical Sensors)
Open AccessArticle A Kernel Gabor-Based Weighted Region Covariance Matrix for Face Recognition
Sensors 2012, 12(6), 7410-7422; doi:10.3390/s120607410
Received: 6 May 2012 / Revised: 16 May 2012 / Accepted: 17 May 2012 / Published: 31 May 2012
Cited by 10 | PDF Full-text (452 KB) | HTML Full-text | XML Full-text
Abstract
This paper proposes a novel image region descriptor for face recognition, named kernel Gabor-based weighted region covariance matrix (KGWRCM). As different parts are different effectual in characterizing and recognizing faces, we construct a weighting matrix by computing the similarity of each pixel within
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This paper proposes a novel image region descriptor for face recognition, named kernel Gabor-based weighted region covariance matrix (KGWRCM). As different parts are different effectual in characterizing and recognizing faces, we construct a weighting matrix by computing the similarity of each pixel within a face sample to emphasize features. We then incorporate the weighting matrices into a region covariance matrix, named weighted region covariance matrix (WRCM), to obtain the discriminative features of faces for recognition. Finally, to further preserve discriminative features in higher dimensional space, we develop the kernel Gabor-based weighted region covariance matrix (KGWRCM). Experimental results show that the KGWRCM outperforms other algorithms including the kernel Gabor-based region covariance matrix (KGCRM). Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle A Urinary Bcl-2 Surface Acoustic Wave Biosensor for Early Ovarian Cancer Detection
Sensors 2012, 12(6), 7423-7437; doi:10.3390/s120607423
Received: 31 March 2012 / Revised: 22 May 2012 / Accepted: 28 May 2012 / Published: 31 May 2012
Cited by 11 | PDF Full-text (1112 KB) | HTML Full-text | XML Full-text
Abstract
In this study, the design, fabrication, surface functionalization and experimental characterization of an ultrasonic MEMS biosensor for urinary anti-apoptotic protein B-cell lymphoma 2 (Bcl-2) detection with sub ng/mL sensitivity is presented. It was previously shown that urinary Bcl-2 levels are reliably elevated during
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In this study, the design, fabrication, surface functionalization and experimental characterization of an ultrasonic MEMS biosensor for urinary anti-apoptotic protein B-cell lymphoma 2 (Bcl-2) detection with sub ng/mL sensitivity is presented. It was previously shown that urinary Bcl-2 levels are reliably elevated during early and late stages of ovarian cancer. Our biosensor uses shear horizontal (SH) surface acoustic waves (SAWs) on surface functionalized ST-cut Quartz to quantify the mass loading change by protein adhesion to the delay path. SH-SAWs were generated and received by a pair of micro-fabricated interdigital transducers (IDTs) separated by a judiciously designed delay path. The delay path was surface-functionalized with monoclonal antibodies, ODMS, Protein A/G and Pluronic F127 for optimal Bcl-2 capture with minimal non-specific adsorption. Bcl-2 concentrations were quantified by the resulting resonance frequency shift detected by a custom designed resonator circuit. The target sensitivity for diagnosis and identifying the stage of ovarian cancer was successfully achieved with demonstrated Bcl-2 detection capability of 500 pg/mL. It was also shown that resonance frequency shift increases linearly with increasing Bcl-2 concentration. Full article
(This article belongs to the Special Issue BioMEMS and Advanced Analytical Sensors for Biological Applications)
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Open AccessArticle Aquatic Acoustic Metrics Interface Utility for Underwater Sound Monitoring and Analysis
Sensors 2012, 12(6), 7438-7450; doi:10.3390/s120607438
Received: 9 April 2012 / Revised: 23 May 2012 / Accepted: 24 May 2012 / Published: 31 May 2012
Cited by 2 | PDF Full-text (890 KB) | HTML Full-text | XML Full-text
Abstract
Fishes and marine mammals may suffer a range of potential effects from exposure to intense underwater sound generated by anthropogenic activities such as pile driving, shipping, sonars, and underwater blasting. Several underwater sound recording (USR) devices have been built to acquire samples of
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Fishes and marine mammals may suffer a range of potential effects from exposure to intense underwater sound generated by anthropogenic activities such as pile driving, shipping, sonars, and underwater blasting. Several underwater sound recording (USR) devices have been built to acquire samples of the underwater sound generated by anthropogenic activities. Software becomes indispensable for processing and analyzing the audio files recorded by these USRs. In this paper, we provide a detailed description of a new software package, the Aquatic Acoustic Metrics Interface (AAMI), specifically designed for analysis of underwater sound recordings to provide data in metrics that facilitate evaluation of the potential impacts of the sound on aquatic animals. In addition to the basic functions, such as loading and editing audio files recorded by USRs and batch processing of sound files, the software utilizes recording system calibration data to compute important parameters in physical units. The software also facilitates comparison of the noise sound sample metrics with biological measures such as audiograms of the sensitivity of aquatic animals to the sound, integrating various components into a single analytical frame. The features of the AAMI software are discussed, and several case studies are presented to illustrate its functionality. Full article
(This article belongs to the Section Physical Sensors)
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Open AccessArticle Intelligent Emergency Stop Algorithm for a Manipulator Using a New Regression Method
Sensors 2012, 12(6), 7451-7467; doi:10.3390/s120607451
Received: 2 May 2012 / Revised: 25 May 2012 / Accepted: 28 May 2012 / Published: 31 May 2012
Cited by 1 | PDF Full-text (1486 KB) | HTML Full-text | XML Full-text
Abstract
In working environments with large manipulators, accidental collisions can cause severe personal injuries and can seriously damage manipulators, necessitating the development of an emergency stop algorithm to prevent such occurrences. In this paper, we propose an emergency stop system for the efficient and
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In working environments with large manipulators, accidental collisions can cause severe personal injuries and can seriously damage manipulators, necessitating the development of an emergency stop algorithm to prevent such occurrences. In this paper, we propose an emergency stop system for the efficient and safe operation of a manipulator by applying an intelligent emergency stop algorithm. Our proposed intelligent algorithm considers the direction of motion of the manipulator. In addition, using a new regression method, the algorithm includes a decision step that determines whether a detected object is a collision-causing obstacle or a part of the manipulator. We apply our emergency stop system to a two-link manipulator and assess the performance of our intelligent emergency stop algorithm as compared with other models. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle Bluetooth Based Chaos Synchronization Using Particle Swarm Optimization and Its Applications to Image Encryption
Sensors 2012, 12(6), 7468-7484; doi:10.3390/s120607468
Received: 18 April 2012 / Revised: 25 May 2012 / Accepted: 31 May 2012 / Published: 1 June 2012
Cited by 5 | PDF Full-text (2481 KB) | HTML Full-text | XML Full-text
Abstract
This study used the complex dynamic characteristics of chaotic systems and Bluetooth to explore the topic of wireless chaotic communication secrecy and develop a communication security system. The PID controller for chaos synchronization control was applied, and the optimum parameters of this PID
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This study used the complex dynamic characteristics of chaotic systems and Bluetooth to explore the topic of wireless chaotic communication secrecy and develop a communication security system. The PID controller for chaos synchronization control was applied, and the optimum parameters of this PID controller were obtained using a Particle Swarm Optimization (PSO) algorithm. Bluetooth was used to realize wireless transmissions, and a chaotic wireless communication security system was developed in the design concept of a chaotic communication security system. The experimental results show that this scheme can be used successfully in image encryption. Full article
(This article belongs to the Section Sensor Networks)
Open AccessArticle A Sensing Element Based on a Bent and Elongated Grooved Polymer Optical Fiber
Sensors 2012, 12(6), 7485-7495; doi:10.3390/s120607485
Received: 27 April 2012 / Revised: 28 May 2012 / Accepted: 28 May 2012 / Published: 1 June 2012
Cited by 3 | PDF Full-text (433 KB) | HTML Full-text | XML Full-text
Abstract
An experimental and numerical investigation is performed into the power loss induced in grooved polymer optical fibers (POFs) subjected to combined bending and elongation deformations. The power loss is examined as a function of both the groove depth and the bend radius. An
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An experimental and numerical investigation is performed into the power loss induced in grooved polymer optical fibers (POFs) subjected to combined bending and elongation deformations. The power loss is examined as a function of both the groove depth and the bend radius. An elastic-plastic three-dimensional finite element model is constructed to simulate the deformation in the grooved region of the deformed specimens. The results indicate that the power loss increases significantly with an increasing bending displacement or groove depth. Specifically, the power loss increases to as much as 12% given a groove depth of 1.1 mm and a bending displacement of 10 mm. Based on the experimental results, an empirical expression is formulated to relate the power loss with the bending displacement for a given groove depth. It is shown that the difference between the estimated power loss and the actual power loss is less than 2%. Full article
(This article belongs to the Special Issue Optical Fiber Sensors 2012)
Open AccessArticle Study of LZ-Based Location Prediction and Its Application to Transportation Recommender Systems
Sensors 2012, 12(6), 7496-7517; doi:10.3390/s120607496
Received: 20 April 2012 / Revised: 21 May 2012 / Accepted: 30 May 2012 / Published: 4 June 2012
Cited by 7 | PDF Full-text (765 KB) | HTML Full-text | XML Full-text
Abstract
Predicting users’ next location allows to anticipate their future context, thus providing additional time to be ready for that context and react consequently. This work is focused on a set of LZ-based algorithms (LZ, LeZi Update and Active LeZi) capable of learning mobility
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Predicting users’ next location allows to anticipate their future context, thus providing additional time to be ready for that context and react consequently. This work is focused on a set of LZ-based algorithms (LZ, LeZi Update and Active LeZi) capable of learning mobility patterns and estimating the next location with low resource needs, which makes it possible to execute them on mobile devices. The original algorithms have been divided into two phases, thus being possible to mix them and check which combination is the best one to obtain better prediction accuracy or lower resource consumption. To make such comparisons, a set of GSM-based mobility traces of 95 different users is considered. Finally, a prototype for mobile devices that integrates the predictors in a public transportation recommender system is described in order to show an example of how to take advantage of location prediction in an ubiquitous computing environment. Full article
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Open AccessArticle Satellite- and Epoch Differenced Precise Point Positioning Based on a Regional Augmentation Network
Sensors 2012, 12(6), 7518-7528; doi:10.3390/s120607518
Received: 30 March 2012 / Revised: 29 May 2012 / Accepted: 30 May 2012 / Published: 4 June 2012
Cited by 6 | PDF Full-text (635 KB) | HTML Full-text | XML Full-text
Abstract
Precise Point Positioning (PPP) has been demonstrated as a simple and effective approach for user positioning. The key issue in PPP is how to shorten convergence time and improve positioning efficiency. Recent researches mainly focus on the ambiguity resolution by correcting residual phase
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Precise Point Positioning (PPP) has been demonstrated as a simple and effective approach for user positioning. The key issue in PPP is how to shorten convergence time and improve positioning efficiency. Recent researches mainly focus on the ambiguity resolution by correcting residual phase errors at a single station. The success of this approach (referred to hereafter as NORM-PPP) is subject to how rapidly one can fix wide-lane and narrow-lane ambiguities to achieve the first ambiguity-fixed solution. The convergence time of NORM-PPP is receiver type dependent, and normally takes 15–20 min. Different from the general algorithm and theory by which the float ambiguities are estimated and the integer ambiguities are fixed, we concentrate on a differential PPP approach: the satellite- and epoch differenced (SDED) approach. In general, the SDED approach eliminates receiver clocks and ambiguity parameters and thus avoids the complicated residual phase modeling procedure. As a further development of the SDED approach, we use a regional augmentation network to derive tropospheric delay and remaining un-modeled errors at user sites. By adding these corrections and applying the Robust estimation, the weak mathematic properties due to the ED operation is much improved. Implementing this new approach, we need only two epochs of data to achieve PPP positioning converging to centimeter-positioning accuracy. Using seven days of GPS data at six CORS stations in Shanghai, we demonstrate the success rate, defined as the case when three directions converging to desired positioning accuracy of 10 cm, reaches 100% when the interval between the two epochs is longer than 15 min. Comparing the results of 15 min’ interval to that of 10 min’, it is observed that the position RMS improves from 2.47, 3.95, 5.78 cm to 2.21, 3.93, 4.90 cm in the North, East and Up directions, respectively. Combining the SDED coordinates at the starting point and the ED relative coordinates thereafter, we demonstrate the performance of RTK PPP with standard deviation of 0.80, 1.34, 0.97 cm in the North, East and Up directions. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle Estimating Sugarcane Yield Potential Using an In-Season Determination of Normalized Difference Vegetative Index
Sensors 2012, 12(6), 7529-7547; doi:10.3390/s120607529
Received: 13 April 2012 / Revised: 24 May 2012 / Accepted: 27 May 2012 / Published: 4 June 2012
Cited by 17 | PDF Full-text (532 KB) | HTML Full-text | XML Full-text
Abstract
Estimating crop yield using remote sensing techniques has proven to be successful. However, sugarcane possesses unique characteristics; such as, a multi-year cropping cycle and plant height-limiting for midseason fertilizer application timing. Our study objective was to determine if sugarcane yield potential could be
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Estimating crop yield using remote sensing techniques has proven to be successful. However, sugarcane possesses unique characteristics; such as, a multi-year cropping cycle and plant height-limiting for midseason fertilizer application timing. Our study objective was to determine if sugarcane yield potential could be estimated using an in-season estimation of normalized difference vegetative index (NDVI). Sensor readings were taken using the GreenSeeker® handheld sensor from 2008 to 2011 in St. Gabriel and Jeanerette, LA, USA. In-season estimates of yield (INSEY) values were calculated by dividing NDVI by thermal variables. Optimum timing for estimating sugarcane yield was between 601–750 GDD. In-season estimated yield values improved the yield potential (YP) model compared to using NDVI. Generally, INSEY value showed a positive exponential relationship with yield (r2 values 0.48 and 0.42 for cane tonnage and sugar yield, respectively). When models were separated based on canopy structure there was an increase the strength of the relationship for the erectophile varieties (r2 0.53 and 0.47 for cane tonnage and sugar yield, respectively); however, the model for planophile varieties weakened slightly. Results of this study indicate using an INSEY value for predicting sugarcane yield shows potential of being a valuable management tool for sugarcane producers in Louisiana. Full article
(This article belongs to the Special Issue Sensor-Based Technologies and Processes in Agriculture and Forestry)
Open AccessArticle A Neural Networks-Based Hybrid Routing Protocol for Wireless Mesh Networks
Sensors 2012, 12(6), 7548-7575; doi:10.3390/s120607548
Received: 13 March 2012 / Revised: 28 May 2012 / Accepted: 29 May 2012 / Published: 7 June 2012
Cited by 8 | PDF Full-text (817 KB) | HTML Full-text | XML Full-text
Abstract
The networking infrastructure of wireless mesh networks (WMNs) is decentralized and relatively simple, but they can display reliable functioning performance while having good redundancy. WMNs provide Internet access for fixed and mobile wireless devices. Both in urban and rural areas they provide users
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The networking infrastructure of wireless mesh networks (WMNs) is decentralized and relatively simple, but they can display reliable functioning performance while having good redundancy. WMNs provide Internet access for fixed and mobile wireless devices. Both in urban and rural areas they provide users with high-bandwidth networks over a specific coverage area. The main problems affecting these networks are changes in network topology and link quality. In order to provide regular functioning, the routing protocol has the main influence in WMN implementations. In this paper we suggest a new routing protocol for WMN, based on good results of a proactive and reactive routing protocol, and for that reason it can be classified as a hybrid routing protocol. The proposed solution should avoid flooding and creating the new routing metric. We suggest the use of artificial logic—i.e., neural networks (NNs). This protocol is based on mobile agent technologies controlled by a Hopfield neural network. In addition to this, our new routing metric is based on multicriteria optimization in order to minimize delay and blocking probability (rejected packets or their retransmission). The routing protocol observes real network parameters and real network environments. As a result of artificial logic intelligence, the proposed routing protocol should maximize usage of network resources and optimize network performance. Full article
(This article belongs to the Section Sensor Networks)
Open AccessArticle Detection of miRNA in Cell Cultures by Using Microchip Electrophoresis with a Fluorescence-Labeled Riboprobe
Sensors 2012, 12(6), 7576-7586; doi:10.3390/s120607576
Received: 28 March 2012 / Revised: 28 May 2012 / Accepted: 31 May 2012 / Published: 7 June 2012
Cited by 3 | PDF Full-text (307 KB) | HTML Full-text | XML Full-text
Abstract
The analysis of a microRNA (miRNA), miR-222 isolated from the PC12 cell line, was performed by use of the ribonuclease (RNase) protection assay, cyanine 5 (Cy5)-labeled miR-222 riboprobe, and a Hitachi SV1210 microchip electrophoresis system, which can be used to evaluate the integrity
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The analysis of a microRNA (miRNA), miR-222 isolated from the PC12 cell line, was performed by use of the ribonuclease (RNase) protection assay, cyanine 5 (Cy5)-labeled miR-222 riboprobe, and a Hitachi SV1210 microchip electrophoresis system, which can be used to evaluate the integrity of total RNA. The fluorescence intensity corresponding to the protected RNA fragment increased in a dose-dependent manner with respect to the complementary-strand RNA. More highly sensitive detection of miRNA by microchip electrophoresis than by conventional method using fluorescence-labeled riboprobe could be obtained in 180 s. An obvious increase in miR-222 expression induced by nerve growth factor in PC12 cells could be observed. These results clearly indicate the potential of microchip electrophoresis for the analysis of miRNA using RNase protection assay with a fluorescence-labeled riboprobe. Full article
Open AccessArticle Automatic Detection of Animals in Mowing Operations Using Thermal Cameras
Sensors 2012, 12(6), 7587-7597; doi:10.3390/s120607587
Received: 27 April 2012 / Revised: 30 May 2012 / Accepted: 4 June 2012 / Published: 7 June 2012
Cited by 7 | PDF Full-text (7158 KB) | HTML Full-text | XML Full-text
Abstract
During the last decades, high-efficiency farming equipment has been developed in the agricultural sector. This has also included efficiency improvement of moving techniques, which include increased working speeds and widths. Therefore, the risk of wild animals being accidentally injured or killed during routine
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During the last decades, high-efficiency farming equipment has been developed in the agricultural sector. This has also included efficiency improvement of moving techniques, which include increased working speeds and widths. Therefore, the risk of wild animals being accidentally injured or killed during routine farming operations has increased dramatically over the years. In particular, the nests of ground nesting bird species like grey partridge (Perdix perdix) or pheasant (Phasianus colchicus) are vulnerable to farming operations in their breeding habitat, whereas in mammals, the natural instinct of e.g., leverets of brown hare (Lepus europaeus) and fawns of roe deer (Capreolus capreolus) to lay low and still in the vegetation to avoid predators increase their risk of being killed or injured in farming operations. Various methods and approaches have been used to reduce wildlife mortality resulting from farming operations. However, since wildlife-friendly farming often results in lower efficiency, attempts have been made to develop automatic systems capable of detecting wild animals in the crop. Here we assessed the suitability of thermal imaging in combination with digital image processing to automatically detect a chicken (Gallus domesticus) and a rabbit (Oryctolagus cuniculus) in a grassland habitat. Throughout the different test scenarios, our study animals were detected with a high precision, although the most dense grass cover reduced the detection rate. We conclude that thermal imaging and digital imaging processing may be an important tool for the improvement of wildlife-friendly farming practices in the future. Full article
(This article belongs to the Special Issue Sensor-Based Technologies and Processes in Agriculture and Forestry)
Open AccessArticle Analysis of the Air Flow Generated by an Air-Assisted Sprayer Equipped with Two Axial Fans Using a 3D Sonic Anemometer
Sensors 2012, 12(6), 7598-7613; doi:10.3390/s120607598
Received: 19 April 2012 / Revised: 29 May 2012 / Accepted: 1 June 2012 / Published: 7 June 2012
Cited by 8 | PDF Full-text (522 KB) | HTML Full-text | XML Full-text
Abstract
The flow of air generated by a new design of air assisted sprayer equipped with two axial fans of reversed rotation was analyzed. For this goal, a 3D sonic anemometer has been used (accuracy: 1.5%; measurement range: 0 to 45 m/s). The study
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The flow of air generated by a new design of air assisted sprayer equipped with two axial fans of reversed rotation was analyzed. For this goal, a 3D sonic anemometer has been used (accuracy: 1.5%; measurement range: 0 to 45 m/s). The study was divided into a static test and a dynamic test. During the static test, the air velocity in the working vicinity of the sprayer was measured considering the following machine configurations: (1) one activated fan regulated at three air flows (machine working as a traditional sprayer); (2) two activated fans regulated at three air flows for each fan. In the static test 72 measurement points were considered. The location of the measurement points was as follow: left and right sides of the sprayer; three sections of measurement (A, B and C); three measurement distances from the shaft of the machine (1.5 m, 2.5 m and 3.5 m); and four measurement heights (1 m, 2 m, 3 m and 4 m). The static test results have shown significant differences in the module and the vertical angle of the air velocity vector in function of the regulations of the sprayer. In the dynamic test, the air velocity was measured at 2.5 m from the axis of the sprayer considering four measurement heights (1 m, 2 m, 3 m and 4 m). In this test, the sprayer regulations were: one or two activated fans; one air flow for each fan; forward speed of 2.8 km/h. The use of one fan (back) or two fans (back and front) produced significant differences on the duration of the presence of wind in the measurement point and on the direction of the air velocity vector. The module of the air velocity vector was not affected by the number of activated fans. Full article
(This article belongs to the Special Issue Sensor-Based Technologies and Processes in Agriculture and Forestry)
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Open AccessArticle An Intelligent Sensor Array Distributed System for Vibration Analysis and Acoustic Noise Characterization of a Linear Switched Reluctance Actuator
Sensors 2012, 12(6), 7614-7633; doi:10.3390/s120607614
Received: 15 May 2012 / Revised: 1 June 2012 / Accepted: 1 June 2012 / Published: 7 June 2012
PDF Full-text (1111 KB) | HTML Full-text | XML Full-text
Abstract
This paper proposes a distributed system for analysis and monitoring (DSAM) of vibrations and acoustic noise, which consists of an array of intelligent modules, sensor modules, communication bus and a host PC acting as data center. The main advantages of the DSAM are
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This paper proposes a distributed system for analysis and monitoring (DSAM) of vibrations and acoustic noise, which consists of an array of intelligent modules, sensor modules, communication bus and a host PC acting as data center. The main advantages of the DSAM are its modularity, scalability, and flexibility for use of different type of sensors/transducers, with analog or digital outputs, and for signals of different nature. Its final cost is also significantly lower than other available commercial solutions. The system is reconfigurable, can operate either with synchronous or asynchronous modes, with programmable sampling frequencies, 8-bit or 12-bit resolution and a memory buffer of 15 kbyte. It allows real-time data-acquisition for signals of different nature, in applications that require a large number of sensors, thus it is suited for monitoring of vibrations in Linear Switched Reluctance Actuators (LSRAs). The acquired data allows the full characterization of the LSRA in terms of its response to vibrations of structural origins, and the vibrations and acoustic noise emitted under normal operation. The DSAM can also be used for electrical machine condition monitoring, machine fault diagnosis, structural characterization and monitoring, among other applications. Full article
(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Portugal)
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Open AccessArticle A New Inertial Aid Method for High Dynamic Compass Signal Tracking Based on a Nonlinear Tracking Differentiator
Sensors 2012, 12(6), 7634-7647; doi:10.3390/s120607634
Received: 14 May 2012 / Revised: 1 June 2012 / Accepted: 1 June 2012 / Published: 7 June 2012
Cited by 7 | PDF Full-text (462 KB) | HTML Full-text | XML Full-text
Abstract
In Compass/INS integrated navigation systems, feedback inertial navigation solutions to baseband tracking loops may eliminate receiver dynamic effects, and effectively improve the tracking accuracy and sensitivity. In the conventional inertially-aided tracking loop, the satellite-receiver line-of-sight velocity is used directly to adjust local carrier
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In Compass/INS integrated navigation systems, feedback inertial navigation solutions to baseband tracking loops may eliminate receiver dynamic effects, and effectively improve the tracking accuracy and sensitivity. In the conventional inertially-aided tracking loop, the satellite-receiver line-of-sight velocity is used directly to adjust local carrier frequency. However, if the inertial solution drifts, the phase tracking error will be enlarged. By using Kalman filter based carrier phase tracking loop, this paper introduces a new inertial aid method, in which the line-of-sight jerk obtained from inertial acceleration by a nonlinear tracking differentiator is used to adjust relevant parameters of the Kalman filter’s process noise matrix. Validation is achieved through high dynamic Compass B3 signal with line-of-sight jerk of 10 g/s collected by a GNSS simulator. Experimental results indicate that the new inertial aid method proposed in this paper is free of the impact of the receiver dynamic and inertial errors. Therefore, when the integrated navigation system is starting or re-tracking after losing lock, the inertial error is absent from the navigation solution correction that induces large drift, and the new aid method proposed in this paper can track highly dynamic signals. Full article
(This article belongs to the Section Physical Sensors)
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Open AccessArticle A Communication Model to Integrate the Request-Response and the Publish-Subscribe Paradigms into Ubiquitous Systems
Sensors 2012, 12(6), 7648-7668; doi:10.3390/s120607648
Received: 9 May 2012 / Revised: 31 May 2012 / Accepted: 4 June 2012 / Published: 7 June 2012
Cited by 11 | PDF Full-text (1502 KB) | HTML Full-text | XML Full-text
Abstract
The Request-Response (RR) paradigm is widely used in ubiquitous systems to exchange information in a secure, reliable and timely manner. Nonetheless, there is also an emerging need for adopting the Publish-Subscribe (PubSub) paradigm in this kind of systems, due to the advantages that
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The Request-Response (RR) paradigm is widely used in ubiquitous systems to exchange information in a secure, reliable and timely manner. Nonetheless, there is also an emerging need for adopting the Publish-Subscribe (PubSub) paradigm in this kind of systems, due to the advantages that this paradigm offers in supporting mobility by means of asynchronous, non-blocking and one-to-many message distribution semantics for event notification. This paper analyzes the strengths and weaknesses of both the RR and PubSub paradigms to support communications in ubiquitous systems and proposes an abstract communication model in order to enable their seamless integration. Thus, developers will be focused on communication semantics and the required quality properties, rather than be concerned about specific communication mechanisms. The aim is to provide developers with abstractions intended to decrease the complexity of integrating different communication paradigms commonly needed in ubiquitous systems. The proposal has been applied to implement a middleware and a real home automation system to show its applicability and benefits. Full article
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Open AccessArticle Multichannel Boron Doped Nanocrystalline Diamond Ultramicroelectrode Arrays: Design, Fabrication and Characterization
Sensors 2012, 12(6), 7669-7681; doi:10.3390/s120607669
Received: 24 April 2012 / Revised: 23 May 2012 / Accepted: 4 June 2012 / Published: 7 June 2012
Cited by 21 | PDF Full-text (367 KB) | HTML Full-text | XML Full-text
Abstract
We report on the fabrication and characterization of an 8 × 8 multichannel Boron Doped Diamond (BDD) ultramicro-electrode array (UMEA). The device combines both the assets of microelectrodes, resulting from conditions in mass transport from the bulk solution toward the electrode, and of
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We report on the fabrication and characterization of an 8 × 8 multichannel Boron Doped Diamond (BDD) ultramicro-electrode array (UMEA). The device combines both the assets of microelectrodes, resulting from conditions in mass transport from the bulk solution toward the electrode, and of BDD’s remarkable intrinsic electrochemical properties. The UMEAs were fabricated using an original approach relying on the selective growth of diamond over pre-processed 4 inches silicon substrates. The prepared UMEAs were characterized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The results demonstrated that the electrodes have exhibited a very fast electrode transfer rate (k0) up to 0.05 cm∙s−1 (in a fast redox couple) and on average, a steady state limiting current (in a 0.5 M potassium chloride aqueous solution containing 1 mM Fe(CN)64− ion at 100 mV∙s−1) of 1.8 nA. The UMEAs are targeted for electrophysiological as well as analytical applications. Full article
(This article belongs to the Section Biosensors)
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Open AccessArticle An Accurately Controlled Antagonistic Shape Memory Alloy Actuator with Self-Sensing
Sensors 2012, 12(6), 7682-7700; doi:10.3390/s120607682
Received: 10 April 2012 / Revised: 21 May 2012 / Accepted: 30 May 2012 / Published: 7 June 2012
Cited by 19 | PDF Full-text (1070 KB) | HTML Full-text | XML Full-text
Abstract
With the progress of miniaturization, shape memory alloy (SMA) actuators exhibit high energy density, self-sensing ability and ease of fabrication, which make them well suited for practical applications. This paper presents a self-sensing controlled actuator drive that was designed using antagonistic pairs of
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With the progress of miniaturization, shape memory alloy (SMA) actuators exhibit high energy density, self-sensing ability and ease of fabrication, which make them well suited for practical applications. This paper presents a self-sensing controlled actuator drive that was designed using antagonistic pairs of SMA wires. Under a certain pre-strain and duty cycle, the stress between two wires becomes constant. Meanwhile, the strain to resistance curve can minimize the hysteresis gap between the heating and the cooling paths. The curves of both wires are then modeled by fitting polynomials such that the measured resistance can be used directly to determine the difference between the testing values and the target strain. The hysteresis model of strains to duty cycle difference has been used as compensation. Accurate control is demonstrated through step response and sinusoidal tracking. The experimental results show that, under a combination control program, the root-mean-square error can be reduced to 1.093%. The limited bandwidth of the frequency is estimated to be 0.15 Hz. Two sets of instruments with three degrees of freedom are illustrated to show how this type actuator could be potentially implemented. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle Definition of Linear Color Models in the RGB Vector Color Space to Detect Red Peaches in Orchard Images Taken under Natural Illumination
Sensors 2012, 12(6), 7701-7718; doi:10.3390/s120607701
Received: 19 April 2012 / Revised: 28 May 2012 / Accepted: 1 June 2012 / Published: 7 June 2012
Cited by 15 | PDF Full-text (1251 KB) | HTML Full-text | XML Full-text
Abstract
This work proposes the detection of red peaches in orchard images based on the definition of different linear color models in the RGB vector color space. The classification and segmentation of the pixels of the image is then performed by comparing the color
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This work proposes the detection of red peaches in orchard images based on the definition of different linear color models in the RGB vector color space. The classification and segmentation of the pixels of the image is then performed by comparing the color distance from each pixel to the different previously defined linear color models. The methodology proposed has been tested with images obtained in a real orchard under natural light. The peach variety in the orchard was the paraguayo (Prunus persica var. platycarpa) peach with red skin. The segmentation results showed that the area of the red peaches in the images was detected with an average error of 11.6%; 19.7% in the case of bright illumination; 8.2% in the case of low illumination; 8.6% for occlusion up to 33%; 12.2% in the case of occlusion between 34 and 66%; and 23% for occlusion above 66%. Finally, a methodology was proposed to estimate the diameter of the fruits based on an ellipsoidal fitting. A first diameter was obtained by using all the contour pixels and a second diameter was obtained by rejecting some pixels of the contour. This approach enables a rough estimate of the fruit occlusion percentage range by comparing the two diameter estimates. Full article
(This article belongs to the Special Issue Sensor-Based Technologies and Processes in Agriculture and Forestry)
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Open AccessArticle Managing RFID Sensors Networks with a General Purpose RFID Middleware
Sensors 2012, 12(6), 7719-7737; doi:10.3390/s120607719
Received: 27 February 2012 / Revised: 29 May 2012 / Accepted: 4 June 2012 / Published: 7 June 2012
Cited by 8 | PDF Full-text (526 KB) | HTML Full-text | XML Full-text
Abstract
RFID middleware is anticipated to one of the main research areas in the field of RFID applications in the near future. The Data EPC Acquisition System (DEPCAS) is an original proposal designed by our group to transfer and apply fundamental ideas from System
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RFID middleware is anticipated to one of the main research areas in the field of RFID applications in the near future. The Data EPC Acquisition System (DEPCAS) is an original proposal designed by our group to transfer and apply fundamental ideas from System and Data Acquisition (SCADA) systems into the areas of RFID acquisition, processing and distribution systems. In this paper we focus on how to organize and manage generic RFID sensors (edge readers, readers, PLCs, etc…) inside the DEPCAS middleware. We denote by RFID Sensors Networks Management (RSNM) this part of DEPCAS, which is built on top of two new concepts introduced and developed in this work: MARC (Minimum Access Reader Command) and RRTL (RFID Reader Topology Language). MARC is an abstraction layer used to hide heterogeneous devices inside a homogeneous acquisition network. RRTL is a language to define RFID Reader networks and to describe the relationship between them (concentrator, peer to peer, master/submaster). Full article
Open AccessArticle PAU-SA: A Synthetic Aperture Interferometric Radiometer Test Bed for Potential Improvements in Future Missions
Sensors 2012, 12(6), 7738-7777; doi:10.3390/s120607738
Received: 4 April 2012 / Revised: 23 May 2012 / Accepted: 30 May 2012 / Published: 7 June 2012
Cited by 2 | PDF Full-text (8987 KB) | XML Full-text | Supplementary Files
Abstract
The Soil Moisture and Ocean Salinity (SMOS) mission is an Earth Explorer Opportunity mission from the European Space Agency (ESA). Its goal is to produce global maps of soil moisture and ocean salinity using the Microwave Imaging Radiometer by Aperture Synthesis (MIRAS). The
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The Soil Moisture and Ocean Salinity (SMOS) mission is an Earth Explorer Opportunity mission from the European Space Agency (ESA). Its goal is to produce global maps of soil moisture and ocean salinity using the Microwave Imaging Radiometer by Aperture Synthesis (MIRAS). The purpose of the Passive Advanced Unit Synthetic Aperture (PAU-SA) instrument is to study and test some potential improvements that could eventually be implemented in future missions using interferometric radiometers such as the Geoestacionary Atmosferic Sounder (GAS), the Precipitation and All-weather Temperature and Humidity (PATH) and the Geostationary Interferometric Microwave Sounder (GIMS). Both MIRAS and PAU-SA are Y-shaped arrays with uniformly distributed antennas, but the receiver topology and the processing unit are quite different. The purpose of this work is to identify the elements in the MIRAS’s design susceptible of improvement and apply them in the PAU-SA instrument demonstrator, to test them in view of these future interferometric radiometer missions. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle Personalized Alert Notifications and Evacuation Routes in Indoor Environments
Sensors 2012, 12(6), 7804-7827; doi:10.3390/s120607804
Received: 7 May 2012 / Revised: 4 June 2012 / Accepted: 5 June 2012 / Published: 8 June 2012
Cited by 12 | PDF Full-text (5449 KB) | HTML Full-text | XML Full-text
Abstract
The preparedness phase is crucial in the emergency management process for reaching an adequate level of readiness to react to potential threats and hazards. During this phase, emergency plans are developed to establish, among other procedures, evacuation and emergency escape routes. Information and
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The preparedness phase is crucial in the emergency management process for reaching an adequate level of readiness to react to potential threats and hazards. During this phase, emergency plans are developed to establish, among other procedures, evacuation and emergency escape routes. Information and Communication Technologies (ICT) can support and improve these procedures providing appropriate, updated and accessible information to all people in the affected zone. Current emergency management and evacuation systems do not adapt information to the context and the profile of each person, so messages received in the emergency might be useless. In this paper, we propose a set of criteria that ICT-based systems could achieve in order to avoid this problem adapting emergency alerts and evacuation routes to different situations and people. Moreover, in order to prove the applicability of such criteria, we define a mechanism that can be used as a complement of traditional evacuation systems to provide personalized alerts and evacuation routes to all kinds of people during emergency situations in working places. This mechanism is composed by three main components: CAP-ONES for notifying emergency alerts, NERES for defining emergency plans and generating personalized evacuation routes, and iNeres as the interface to receive and visualize these routes on smartphones. The usability and understandability of proposed interface has been assessed through a user study performed in a fire simulation in an indoor environment. This evaluation demonstrated that users considered iNeres easy to understand, to learn and to use, and they also found very innovative the idea to use smartphones as a support for escaping instead of static signals on walls and doors. Full article
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Open AccessArticle A Novel Human Autonomy Assessment System
Sensors 2012, 12(6), 7828-7854; doi:10.3390/s120607828
Received: 11 May 2012 / Revised: 31 May 2012 / Accepted: 4 June 2012 / Published: 8 June 2012
Cited by 3 | PDF Full-text (2916 KB) | HTML Full-text | XML Full-text
Abstract
This article presents a novel human autonomy assessment system for generating context and discovering the behaviors of older people who use ambulant services. Our goal is to assist caregivers in assessing possibly abnormal health conditions in their clients concerning their level of autonomy,
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This article presents a novel human autonomy assessment system for generating context and discovering the behaviors of older people who use ambulant services. Our goal is to assist caregivers in assessing possibly abnormal health conditions in their clients concerning their level of autonomy, thus enabling caregivers to take countermeasures as soon as possible. Full article
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Open AccessArticle The UspIC: Performing Scan Matching Localization Using an Imaging Sonar
Sensors 2012, 12(6), 7855-7885; doi:10.3390/s120607855
Received: 27 April 2012 / Revised: 31 May 2012 / Accepted: 5 June 2012 / Published: 8 June 2012
Cited by 8 | PDF Full-text (5719 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents a novel approach to localize an underwater mobile robot based on scan matching using a Mechanically Scanned Imaging Sonar (MSIS). When used to perform scan matching, this sensor presents some problems such as significant uncertainty in the measurements or large
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This paper presents a novel approach to localize an underwater mobile robot based on scan matching using a Mechanically Scanned Imaging Sonar (MSIS). When used to perform scan matching, this sensor presents some problems such as significant uncertainty in the measurements or large scan times, which lead to a motion induced distortion. This paper presents the uspIC, which deals with these problems by adopting a probabilistic scan matching strategy and by defining a method to strongly alleviate the motion induced distortion. Experimental results evaluating our approach and comparing it to previously existing methods are provided. Full article
(This article belongs to the Section Physical Sensors)
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Open AccessArticle A Temperature-Insensitive Cladding-Etched Fiber Bragg Grating Using a Liquid Mixture with a Negative Thermo-Optic Coefficient
Sensors 2012, 12(6), 7886-7892; doi:10.3390/s120607886
Received: 28 April 2012 / Revised: 30 May 2012 / Accepted: 31 May 2012 / Published: 8 June 2012
Cited by 11 | PDF Full-text (469 KB) | HTML Full-text | XML Full-text
Abstract
To compensate for the temperature dependency of a standard FBG, a cladding-etched FBG immersed with a liquid mixture having a negative thermo-optic coefficient is presented, and its characteristics are investigated. The Bragg wavelength of the cladding-etched FBG is shifted counter to the direction
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To compensate for the temperature dependency of a standard FBG, a cladding-etched FBG immersed with a liquid mixture having a negative thermo-optic coefficient is presented, and its characteristics are investigated. The Bragg wavelength of the cladding-etched FBG is shifted counter to the direction of the Bragg wavelength shift of a conventional FBG according to the mixing ratio of glycerin to water; thus, the temperature-dependent Bragg wavelength shift was almost compensated by using a liquid mixture of water (50%) and glycerin (50%) having the negative thermo-optic coefficient of −5 × 10−4 °C−1. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle Acetylcholinesterase Immobilized on Magnetic Beads for Pesticides Detection: Application to Olive Oil Analysis
Sensors 2012, 12(6), 7893-7904; doi:10.3390/s120607893
Received: 4 May 2012 / Revised: 24 May 2012 / Accepted: 4 June 2012 / Published: 8 June 2012
Cited by 15 | PDF Full-text (282 KB) | HTML Full-text | XML Full-text
Abstract
This work presents the development of bioassays and biosensors for the detection of insecticides widely used in the treatment of olive trees. The systems are based on the covalent immobilisation of acetylcholinesterase on magnetic microbeads using either colorimetry or amperometry as detection technique.
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This work presents the development of bioassays and biosensors for the detection of insecticides widely used in the treatment of olive trees. The systems are based on the covalent immobilisation of acetylcholinesterase on magnetic microbeads using either colorimetry or amperometry as detection technique. The magnetic beads were immobilised on screen-printed electrodes or microtitration plates and tested using standard solutions and real samples. The developed devices showed good analytical performances with limits of detection much lower than the maximum residue limit tolerated by international regulations, as well as a good reproducibility and stability. Full article
(This article belongs to the Section Biosensors)
Open AccessArticle Design and Theoretical Analysis of a Resonant Sensor for Liquid Density Measurement
Sensors 2012, 12(6), 7905-7916; doi:10.3390/s120607905
Received: 5 May 2012 / Revised: 16 May 2012 / Accepted: 21 May 2012 / Published: 8 June 2012
Cited by 3 | PDF Full-text (581 KB) | HTML Full-text | XML Full-text
Abstract
In order to increase the accuracy of on-line liquid density measurements, a sensor equipped with a tuning fork as the resonant sensitive component is designed in this paper. It is a quasi-digital sensor with simple structure and high precision. The sensor is based
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In order to increase the accuracy of on-line liquid density measurements, a sensor equipped with a tuning fork as the resonant sensitive component is designed in this paper. It is a quasi-digital sensor with simple structure and high precision. The sensor is based on resonance theory and composed of a sensitive unit and a closed-loop control unit, where the sensitive unit consists of the actuator, the resonant tuning fork and the detector and the closed-loop control unit comprises precondition circuit, digital signal processing and control unit, analog-to-digital converter and digital-to-analog converter. An approximate parameters model of the tuning fork is established and the impact of liquid density, position of the tuning fork, temperature and structural parameters on the natural frequency of the tuning fork are also analyzed. On this basis, a tuning fork liquid density measurement sensor is developed. In addition, experimental testing on the sensor has been carried out on standard calibration facilities under constant 20 °C, and the sensor coefficients are calibrated. The experimental results show that the repeatability error is about 0.03% and the accuracy is about 0.4 kg/m3. The results also confirm that the method to increase the accuracy of liquid density measurement is feasible. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle Ultra Low Power Signal Oriented Approach for Wireless Health Monitoring
Sensors 2012, 12(6), 7917-7937; doi:10.3390/s120607917
Received: 27 March 2012 / Revised: 29 May 2012 / Accepted: 29 May 2012 / Published: 8 June 2012
Cited by 12 | PDF Full-text (1019 KB) | HTML Full-text | XML Full-text
Abstract
In recent years there is growing pressure on the medical sector to reduce costs while maintaining or even improving the quality of care. A potential solution to this problem is real time and/or remote patient monitoring by using mobile devices. To achieve this,
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In recent years there is growing pressure on the medical sector to reduce costs while maintaining or even improving the quality of care. A potential solution to this problem is real time and/or remote patient monitoring by using mobile devices. To achieve this, medical sensors with wireless communication, computational and energy harvesting capabilities are networked on, or in, the human body forming what is commonly called a Wireless Body Area Network (WBAN). We present the implementation of a novel Wake Up Receiver (WUR) in the context of standardised wireless protocols, in a signal-oriented WBAN environment and present a novel protocol intended for wireless health monitoring (WhMAC). WhMAC is a TDMA-based protocol with very low power consumption. It utilises WBAN-specific features and a novel ultra low power wake up receiver technology, to achieve flexible and at the same time very low power wireless data transfer of physiological signals. As the main application is in the medical domain, or personal health monitoring, the protocol caters for different types of medical sensors. We define four sensor modes, in which the sensors can transmit data, depending on the sensor type and emergency level. A full power dissipation model is provided for the protocol, with individual hardware and application parameters. Finally, an example application shows the reduction in the power consumption for different data monitoring scenarios. Full article
(This article belongs to the Special Issue Body Sensor Networks for Healthcare and Pervasive Applications)
Open AccessArticle Palmprint Recognition across Different Devices
Sensors 2012, 12(6), 7938-7964; doi:10.3390/s120607938
Received: 17 April 2012 / Revised: 21 May 2012 / Accepted: 22 May 2012 / Published: 8 June 2012
Cited by 7 | PDF Full-text (1615 KB) | HTML Full-text | XML Full-text
Abstract
In this paper, the problem of Palmprint Recognition Across Different Devices (PRADD) is investigated, which has not been well studied so far. Since there is no publicly available PRADD image database, we created a non-contact PRADD image database containing 12,000 grayscale captured from
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In this paper, the problem of Palmprint Recognition Across Different Devices (PRADD) is investigated, which has not been well studied so far. Since there is no publicly available PRADD image database, we created a non-contact PRADD image database containing 12,000 grayscale captured from 100 subjects using three devices, i.e., one digital camera and two smart-phones. Due to the non-contact image acquisition used, rotation and scale changes between different images captured from a same palm are inevitable. We propose a robust method to calculate the palm width, which can be effectively used for scale normalization of palmprints. On this PRADD image database, we evaluate the recognition performance of three different methods, i.e., subspace learning method, correlation method, and orientation coding based method, respectively. Experiments results show that orientation coding based methods achieved promising recognition performance for PRADD. Full article
(This article belongs to the Special Issue Hand-Based Biometrics Sensors and Systems)
Open AccessArticle Synergistic Effects in the Gas Sensitivity of Polypyrrole/Single Wall Carbon Nanotube Composites
Sensors 2012, 12(6), 7965-7974; doi:10.3390/s120607965
Received: 19 April 2012 / Revised: 24 May 2012 / Accepted: 25 May 2012 / Published: 8 June 2012
Cited by 23 | PDF Full-text (681 KB) | HTML Full-text | XML Full-text
Abstract
Polypyrrole/single wall carbon nanotube composites were synthesized by in-situ chemical polymerization using pyrrole (PPy) as precursor and single wall carbon nanotubes (SWNTs) as additive component. Electron microscope images reveal that SWNTs component acts as nucleation sites for PPy growth in the form of
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Polypyrrole/single wall carbon nanotube composites were synthesized by in-situ chemical polymerization using pyrrole (PPy) as precursor and single wall carbon nanotubes (SWNTs) as additive component. Electron microscope images reveal that SWNTs component acts as nucleation sites for PPy growth in the form of spherical and cylindrical core-shell structures. The SWNTs/PPy core-shell results in thin n-p junctions which modify the PPy bandgap and reduce the work function of electrons. As a result of the strong coupling, Raman and IR spectra show that the PPy undergoes a transition from polaron to bipolaron state, i.e., indicating an increase in the conductivity. In the UV-Vis spectra, the 340 nm adsorption band (π*-π transition) exhibits a red shift, while the 460 nm adsorption band (bipolaron transition) experiences a blue shift indicating a change in electronic structure and a relocation of polaron levels in the band gap of PPy. The modification in PPy electronic structure brings in a synergistic effect in sensing feature. Upon exposure to oxygen (an oxidizing agent) and NH3 gas (a reducing agent), the PPy/SWNTs nanocomposite shows an enhancement in sensitivity exceeding ten folds in comparison with those of PPy or SWNTs. Full article
(This article belongs to the Section Chemical Sensors)
Open AccessArticle Reliable Finite Frequency Filter Design for Networked Control Systems with Sensor Faults
Sensors 2012, 12(6), 7975-7993; doi:10.3390/s120607975
Received: 6 April 2012 / Revised: 17 May 2012 / Accepted: 21 May 2012 / Published: 8 June 2012
PDF Full-text (154 KB) | HTML Full-text | XML Full-text
Abstract
This paper is concerned with the reliable finite frequency filter design for networked control systems (NCSs) subject to quantization and data missing. Taking into account quantization, possible data missing and sensor stuck faults, NCSs are modeled in the framework of discrete time-delay switched
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This paper is concerned with the reliable finite frequency filter design for networked control systems (NCSs) subject to quantization and data missing. Taking into account quantization, possible data missing and sensor stuck faults, NCSs are modeled in the framework of discrete time-delay switched systems, and the finite frequency l2 gain is adopted for the filter design of discrete time-delay switched systems, which is converted into a set of linear matrix inequality (LMI) conditions. By the virtues of the derived conditions, a procedure of reliable filter synthesis is presented. Further, the filter gains are characterized in terms of solutions to a convex optimization problem which can be solved by using the semi-definite programme method. Finally, an example is given to illustrate the effectiveness of the proposed method. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle Compiler Optimizations as a Countermeasure against Side-Channel Analysis in MSP430-Based Devices
Sensors 2012, 12(6), 7994-8012; doi:10.3390/s120607994
Received: 16 May 2012 / Revised: 4 June 2012 / Accepted: 4 June 2012 / Published: 8 June 2012
PDF Full-text (2125 KB) | HTML Full-text | XML Full-text
Abstract
Ambient Intelligence (AmI) requires devices everywhere, dynamic and massively distributed networks of low-cost nodes that, among other data, manage private information or control restricted operations. MSP430, a 16-bit microcontroller, is used in WSN platforms, as the TelosB. Physical access to devices cannot be
[...] Read more.
Ambient Intelligence (AmI) requires devices everywhere, dynamic and massively distributed networks of low-cost nodes that, among other data, manage private information or control restricted operations. MSP430, a 16-bit microcontroller, is used in WSN platforms, as the TelosB. Physical access to devices cannot be restricted, so attackers consider them a target of their malicious attacks in order to obtain access to the network. Side-channel analysis (SCA) easily exploits leakages from the execution of encryption algorithms that are dependent on critical data to guess the key value. In this paper we present an evaluation framework that facilitates the analysis of the effects of compiler and backend optimizations on the resistance against statistical SCA. We propose an optimization-based software countermeasure that can be used in current low-cost devices to radically increase resistance against statistical SCA, analyzed with the new framework. Full article
Open AccessArticle Selective Detection of NO2 Using Cr-Doped CuO Nanorods
Sensors 2012, 12(6), 8013-8025; doi:10.3390/s120608013
Received: 24 April 2012 / Revised: 18 May 2012 / Accepted: 1 June 2012 / Published: 11 June 2012
Cited by 18 | PDF Full-text (797 KB) | HTML Full-text | XML Full-text
Abstract
CuO nanosheets, Cr-doped CuO nanosheets, and Cr-doped CuO nanorods were prepared by heating a slurry containing Cu-hydroxide/Cr-hydroxide. Their responses to 100 ppm NO2, C2H5OH, NH3, trimethylamine, C3H8, and CO were measured.
[...] Read more.
CuO nanosheets, Cr-doped CuO nanosheets, and Cr-doped CuO nanorods were prepared by heating a slurry containing Cu-hydroxide/Cr-hydroxide. Their responses to 100 ppm NO2, C2H5OH, NH3, trimethylamine, C3H8, and CO were measured. For 2.2 at% Cr-doped CuO nanorods, the response (Ra/Rg, Ra: resistance in air, Rg: resistance in gas) to 100 ppm NO2 was 134.2 at 250 °C, which was significantly higher than that of pure CuO nano-sheets (Ra/Rg = 7.5) and 0.76 at% Cr-doped CuO nanosheets (Ra/Rg = 19.9). In addition, the sensitivity for NO2 was also markedly enhanced by Cr doping. Highly sensitive and selective detection of NO2 in 2.2 at% Cr-doped CuO nanorods is explained in relation to Cr-doping induced changes in donor density, morphology, and catalytic effects. Full article
(This article belongs to the Section Chemical Sensors)
Open AccessArticle An Annular Mechanical Temperature Compensation Structure for Gas-Sealed Capacitive Pressure Sensor
Sensors 2012, 12(6), 8026-8038; doi:10.3390/s120608026
Received: 24 April 2012 / Revised: 2 May 2012 / Accepted: 4 June 2012 / Published: 11 June 2012
Cited by 4 | PDF Full-text (1391 KB) | HTML Full-text | XML Full-text
Abstract
A novel gas-sealed capacitive pressure sensor with a temperature compensation structure is reported. The pressure sensor is sealed by Au-Au diffusion bonding under a nitrogen ambient with a pressure of 100 kPa and integrated with a platinum resistor-based temperature sensor for human activity
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A novel gas-sealed capacitive pressure sensor with a temperature compensation structure is reported. The pressure sensor is sealed by Au-Au diffusion bonding under a nitrogen ambient with a pressure of 100 kPa and integrated with a platinum resistor-based temperature sensor for human activity monitoring applications. The capacitance-pressure and capacitance-temperature characteristics of the gas-sealed capacitive pressure sensor without temperature compensation structure are calculated. It is found by simulation that a ring-shaped structure on the diaphragm of the pressure sensor can mechanically suppress the thermal expansion effect of the sealed gas in the cavity. Pressure sensors without/with temperature compensation structures are fabricated and measured. Through measured results, it is verified that the calculation model is accurate. Using the compensation structures with a 900 μm inner radius, the measured temperature coefficient is much reduced as compared to that of the pressure sensor without compensation. The sensitivities of the pressure sensor before and after compensation are almost the same in the pressure range from 80 kPa to 100 kPa. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle On the Use of Sensor Fusion to Reduce the Impact of Rotational and Additive Noise in Human Activity Recognition
Sensors 2012, 12(6), 8039-8054; doi:10.3390/s120608039
Received: 19 March 2012 / Revised: 5 June 2012 / Accepted: 6 June 2012 / Published: 11 June 2012
Cited by 18 | PDF Full-text (561 KB) | HTML Full-text | XML Full-text
Abstract
The main objective of fusion mechanisms is to increase the individual reliability of the systems through the use of the collectivity knowledge. Moreover, fusion models are also intended to guarantee a certain level of robustness. This is particularly required for problems such as
[...] Read more.
The main objective of fusion mechanisms is to increase the individual reliability of the systems through the use of the collectivity knowledge. Moreover, fusion models are also intended to guarantee a certain level of robustness. This is particularly required for problems such as human activity recognition where runtime changes in the sensor setup seriously disturb the reliability of the initial deployed systems. For commonly used recognition systems based on inertial sensors, these changes are primarily characterized as sensor rotations, displacements or faults related to the batteries or calibration. In this work we show the robustness capabilities of a sensor-weighted fusion model when dealing with such disturbances under different circumstances. Using the proposed method, up to 60% outperformance is obtained when a minority of the sensors are artificially rotated or degraded, independent of the level of disturbance (noise) imposed. These robustness capabilities also apply for any number of sensors affected by a low to moderate noise level. The presented fusion mechanism compensates the poor performance that otherwise would be obtained when just a single sensor is considered. Full article
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Open AccessArticle Electronic Nose Based on Independent Component Analysis Combined with Partial Least Squares and Artificial Neural Networks for Wine Prediction
Sensors 2012, 12(6), 8055-8072; doi:10.3390/s120608055
Received: 10 April 2012 / Revised: 25 May 2012 / Accepted: 5 June 2012 / Published: 11 June 2012
Cited by 14 | PDF Full-text (2473 KB) | HTML Full-text | XML Full-text
Abstract
The aim of this work is to propose an alternative way for wine classification and prediction based on an electronic nose (e-nose) combined with Independent Component Analysis (ICA) as a dimensionality reduction technique, Partial Least Squares (PLS) to predict sensorial descriptors and Artificial
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The aim of this work is to propose an alternative way for wine classification and prediction based on an electronic nose (e-nose) combined with Independent Component Analysis (ICA) as a dimensionality reduction technique, Partial Least Squares (PLS) to predict sensorial descriptors and Artificial Neural Networks (ANNs) for classification purpose. A total of 26 wines from different regions, varieties and elaboration processes have been analyzed with an e-nose and tasted by a sensory panel. Successful results have been obtained in most cases for prediction and classification. Full article
Open AccessArticle Robust Feedback Zoom Tracking for Digital Video Surveillance
Sensors 2012, 12(6), 8073-8099; doi:10.3390/s120608073
Received: 9 April 2012 / Revised: 31 May 2012 / Accepted: 1 June 2012 / Published: 11 June 2012
Cited by 3 | PDF Full-text (3480 KB) | HTML Full-text | XML Full-text
Abstract
Zoom tracking is an important function in video surveillance, particularly in traffic management and security monitoring. It involves keeping an object of interest in focus during the zoom operation. Zoom tracking is typically achieved by moving the zoom and focus motors in lenses
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Zoom tracking is an important function in video surveillance, particularly in traffic management and security monitoring. It involves keeping an object of interest in focus during the zoom operation. Zoom tracking is typically achieved by moving the zoom and focus motors in lenses following the so-called “trace curve”, which shows the in-focus motor positions versus the zoom motor positions for a specific object distance. The main task of a zoom tracking approach is to accurately estimate the trace curve for the specified object. Because a proportional integral derivative (PID) controller has historically been considered to be the best controller in the absence of knowledge of the underlying process and its high-quality performance in motor control, in this paper, we propose a novel feedback zoom tracking (FZT) approach based on the geometric trace curve estimation and PID feedback controller. The performance of this approach is compared with existing zoom tracking methods in digital video surveillance. The real-time implementation results obtained on an actual digital video platform indicate that the developed FZT approach not only solves the traditional one-to-many mapping problem without pre-training but also improves the robustness for tracking moving or switching objects which is the key challenge in video surveillance. Full article
(This article belongs to the Section Physical Sensors)
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Open AccessArticle Novel Biochip Platform for Nucleic Acid Analysis
Sensors 2012, 12(6), 8100-8111; doi:10.3390/s120608100
Received: 25 April 2012 / Revised: 21 May 2012 / Accepted: 31 May 2012 / Published: 11 June 2012
Cited by 12 | PDF Full-text (938 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
This manuscript describes the use of a novel biochip platform for the rapid analysis/identification of nucleic acids, including DNA and microRNAs, with very high specificity. This approach combines a unique dynamic chemistry approach for nucleic acid testing and analysis developed by DestiNA Genomics
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This manuscript describes the use of a novel biochip platform for the rapid analysis/identification of nucleic acids, including DNA and microRNAs, with very high specificity. This approach combines a unique dynamic chemistry approach for nucleic acid testing and analysis developed by DestiNA Genomics with the STMicroelectronics In-Check platform, which comprises two microfluidic optimized and independent PCR reaction chambers, and a sequential microarray area for nucleic acid capture and identification by fluorescence. With its compact bench-top “footprint” requiring only a single technician to operate, the biochip system promises to transform and expand routine clinical diagnostic testing and screening for genetic diseases, cancers, drug toxicology and heart disease, as well as employment in the emerging companion diagnostics market. Full article
(This article belongs to the Special Issue Biomarkers and Nanosensors: New Approaches for Biology and Medicine)
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Open AccessArticle Process-in-Network: A Comprehensive Network Processing Approach
Sensors 2012, 12(6), 8112-8134; doi:10.3390/s120608112
Received: 23 April 2012 / Revised: 30 May 2012 / Accepted: 4 June 2012 / Published: 12 June 2012
PDF Full-text (741 KB) | HTML Full-text | XML Full-text
Abstract
A solid and versatile communications platform is very important in modern Ambient Intelligence (AmI) applications, which usually require the transmission of large amounts of multimedia information over a highly heterogeneous network. This article focuses on the concept of Process-in-Network (PIN), which is defined
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A solid and versatile communications platform is very important in modern Ambient Intelligence (AmI) applications, which usually require the transmission of large amounts of multimedia information over a highly heterogeneous network. This article focuses on the concept of Process-in-Network (PIN), which is defined as the possibility that the network processes information as it is being transmitted, and introduces a more comprehensive approach than current network processing technologies. PIN can take advantage of waiting times in queues of routers, idle processing capacity in intermediate nodes, and the information that passes through the network. Full article
Open AccessArticle Novel Platform Development Using an Assembly of Carbon Nanotube, Nanogold and Immobilized RNA Capture Element towards Rapid, Selective Sensing of Bacteria
Sensors 2012, 12(6), 8135-8144; doi:10.3390/s120608135
Received: 1 May 2012 / Revised: 29 May 2012 / Accepted: 1 June 2012 / Published: 12 June 2012
Cited by 10 | PDF Full-text (871 KB) | HTML Full-text | XML Full-text
Abstract
This study examines the creation of a nano-featured biosensor platform designed for the rapid and selective detection of the bacterium Escherichia coli. The foundation of this sensor is carbon nanotubes decorated with gold nanoparticles that are modified with a specific, surface adherent
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This study examines the creation of a nano-featured biosensor platform designed for the rapid and selective detection of the bacterium Escherichia coli. The foundation of this sensor is carbon nanotubes decorated with gold nanoparticles that are modified with a specific, surface adherent ribonucleiuc acid (RNA) sequence element. The multi-step sensor assembly was accomplished by growing carbon nanotubes on a graphite substrate, the direct synthesis of gold nanoparticles on the nanotube surface, and the attachment of thiolated RNA to the bound nanoparticles. The application of the compounded nano-materials for sensor development has the distinct advantage of retaining the electrical behavior property of carbon nanotubes and, through the gold nanoparticles, incorporating an increased surface area for additional analyte attachment sites, thus increasing sensitivity. We successfully demonstrated that the coating of gold nanoparticles with a selective RNA sequence increased the capture of E. coli by 189% when compared to uncoated particles. The approach to sensor formation detailed in this study illustrates the great potential of unique composite structures in the development of a multi-array, electrochemical sensor for the fast and sensitive detection of pathogens. Full article
(This article belongs to the Special Issue Nano-Biosensors)
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Open AccessArticle Accuracy and Precision of Equine Gait Event Detection during Walking with Limb and Trunk Mounted Inertial Sensors
Sensors 2012, 12(6), 8145-8156; doi:10.3390/s120608145
Received: 12 April 2012 / Revised: 4 June 2012 / Accepted: 7 June 2012 / Published: 12 June 2012
Cited by 13 | PDF Full-text (337 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
The increased variations of temporal gait events when pathology is present are good candidate features for objective diagnostic tests. We hypothesised that the gait events hoof-on/off and stance can be detected accurately and precisely using features from trunk and distal limb-mounted Inertial Measurement
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The increased variations of temporal gait events when pathology is present are good candidate features for objective diagnostic tests. We hypothesised that the gait events hoof-on/off and stance can be detected accurately and precisely using features from trunk and distal limb-mounted Inertial Measurement Units (IMUs). Four IMUs were mounted on the distal limb and five IMUs were attached to the skin over the dorsal spinous processes at the withers, fourth lumbar vertebrae and sacrum as well as left and right tuber coxae. IMU data were synchronised to a force plate array and a motion capture system. Accuracy (bias) and precision (SD of bias) was calculated to compare force plate and IMU timings for gait events. Data were collected from seven horses. One hundred and twenty three (123) front limb steps were analysed; hoof-on was detected with a bias (SD) of −7 (23) ms, hoof-off with 0.7 (37) ms and front limb stance with −0.02 (37) ms. A total of 119 hind limb steps were analysed; hoof-on was found with a bias (SD) of −4 (25) ms, hoof-off with 6 (21) ms and hind limb stance with 0.2 (28) ms. IMUs mounted on the distal limbs and sacrum can detect gait events accurately and precisely. Full article
(This article belongs to the Section Physical Sensors)
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Open AccessArticle Improved Iterative Calibration for Triaxial Accelerometers Based on the Optimal Observation
Sensors 2012, 12(6), 8157-8175; doi:10.3390/s120608157
Received: 2 April 2012 / Revised: 25 May 2012 / Accepted: 31 May 2012 / Published: 12 June 2012
Cited by 3 | PDF Full-text (596 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents an improved iterative nonlinear calibration method in the gravitational field for both low-grade and high-grade triaxial accelerometers. This calibration method assumes the probability density function of a Gaussian distribution for the raw outputs of triaxial accelerometers. A nonlinear criterion function
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This paper presents an improved iterative nonlinear calibration method in the gravitational field for both low-grade and high-grade triaxial accelerometers. This calibration method assumes the probability density function of a Gaussian distribution for the raw outputs of triaxial accelerometers. A nonlinear criterion function is derived as the maximum likelihood estimation for the calibration parameters and inclination vectors, which is solved by the iterative estimation. First, the calibration parameters, including the scale factors, misalignments, biases and squared coefficients are estimated by the linear least squares method according to the multi-position raw outputs of triaxial accelerometers and the initial inclination vectors. Second, the sequence quadric program method is utilized to solve the nonlinear constrained optimization to update the inclination vectors according to the estimated calibration parameters and raw outputs of the triaxial accelerometers. The initial inclination vectors are supplied by normalizing raw outputs of triaxial accelerometers at different positions without any a priori knowledge. To overcome the imperfections of models, the optimal observation scheme is designed according to some maximum sensitivity principle. Simulation and experiments show good estimation accuracy for calibration parameters and inclination vectors. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle Long-Term Outdoor Reliability Assessment of a Wireless Unit for Air-Quality Monitoring Based on Nanostructured Films Integrated on Micromachined Platforms
Sensors 2012, 12(6), 8176-8192; doi:10.3390/s120608176
Received: 15 March 2012 / Revised: 31 May 2012 / Accepted: 8 June 2012 / Published: 13 June 2012
Cited by 3 | PDF Full-text (1254 KB) | HTML Full-text | XML Full-text
Abstract
We have fabricated and tested in long-term field operating conditions a wireless unit for outdoor air quality monitoring. The unit is equipped with two multiparametric sensors, one miniaturized thermo-hygrometer, front-end analogical and digital electronics, and an IEEE 802.15.4 based module for wireless data
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We have fabricated and tested in long-term field operating conditions a wireless unit for outdoor air quality monitoring. The unit is equipped with two multiparametric sensors, one miniaturized thermo-hygrometer, front-end analogical and digital electronics, and an IEEE 802.15.4 based module for wireless data transmission. Micromachined platforms were functionalized with nanoporous metal-oxides to obtain multiparametric sensors, hosting gas-sensitive, anemometric and temperature transducers. Nanoporous metal-oxide layer was directly deposited on gas sensing regions of micromachined platform batches by hard-mask patterned supersonic cluster beam deposition. An outdoor, roadside experiment was arranged in downtown Milan (Italy), where one wireless sensing unit was continuously operated side by side with standard gas chromatographic instrumentation for air quality measurements. By means of a router PC, data from sensing unit and other instrumentation were collected, merged, and sent to a remote data storage server, through an UMTS device. The whole-system robustness as well as sensor dataset characteristics were continuously characterized over a run-time period of 18 months. Full article
(This article belongs to the Section Physical Sensors)
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Open AccessArticle A Novel Sensor for Monitoring of Iron(III) Ions Based on Porphyrins
Sensors 2012, 12(6), 8193-8203; doi:10.3390/s120608193
Received: 9 April 2012 / Revised: 27 May 2012 / Accepted: 8 June 2012 / Published: 13 June 2012
Cited by 22 | PDF Full-text (202 KB) | HTML Full-text | XML Full-text
Abstract
Three A3B porphyrins with mixed carboxy-, phenoxy-, pyridyl- and dimethoxy-substituent functionalization on the meso-phenyl groups were obtained by multicomponent synthesis, fully characterized and used as ionophores for preparing PVC-based membrane sensors selective to iron(III). The membranes have an ionophore:PVC:plasticizer composition
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Three A3B porphyrins with mixed carboxy-, phenoxy-, pyridyl- and dimethoxy-substituent functionalization on the meso-phenyl groups were obtained by multicomponent synthesis, fully characterized and used as ionophores for preparing PVC-based membrane sensors selective to iron(III). The membranes have an ionophore:PVC:plasticizer composition ratio of 1:33:66. Sodium tetraphenylborate was used as additive (20 mol% relative to ionophore). The performance characteristics (linear concentration range, slope and selectivity) of the sensors were investigated. The best results were obtained for the membrane based on 5-(4-carboxyphenyl)-10,15,20-tris(4-phenoxyphenyl)-porphyrin plasticized with bis(2-ethylhexyl)sebacate, in a linear range from 1 × 10−7–1 × 10−1 M with a slope of 21.6 mV/decade. The electrode showed high selectivity with respect to alkaline and heavy metal ions and a response time of 20 s. The influence of pH on the sensor response was studied. The sensor was used for a period of six weeks and the utility has been tested for the quantitative determination of Fe(III) in recovered solutions from spent lithium ion batteries and for the quantitative determination of Fe(III) in tap water samples. Full article
(This article belongs to the Section Chemical Sensors)
Open AccessArticle Open-WiSe: A Solar Powered Wireless Sensor Network Platform
Sensors 2012, 12(6), 8204-8217; doi:10.3390/s120608204
Received: 1 May 2012 / Revised: 4 June 2012 / Accepted: 8 June 2012 / Published: 13 June 2012
Cited by 11 | PDF Full-text (738 KB) | HTML Full-text | XML Full-text
Abstract
Because battery-powered nodes are required in wireless sensor networks and energy consumption represents an important design consideration, alternate energy sources are needed to provide more effective and optimal function. The main goal of this work is to present an energy harvesting wireless sensor
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Because battery-powered nodes are required in wireless sensor networks and energy consumption represents an important design consideration, alternate energy sources are needed to provide more effective and optimal function. The main goal of this work is to present an energy harvesting wireless sensor network platform, the Open Wireless Sensor node (WiSe). The design and implementation of the solar powered wireless platform is described including the hardware architecture, firmware, and a POSIX Real-Time Kernel. A sleep and wake up strategy was implemented to prolong the lifetime of the wireless sensor network. This platform was developed as a tool for researchers investigating Wireless sensor network or system integrators. Full article
Open AccessArticle A Fast MEANSHIFT Algorithm-Based Target Tracking System
Sensors 2012, 12(6), 8218-8235; doi:10.3390/s120608218
Received: 13 April 2012 / Revised: 9 May 2012 / Accepted: 22 May 2012 / Published: 13 June 2012
Cited by 3 | PDF Full-text (3880 KB) | HTML Full-text | XML Full-text
Abstract
Tracking moving targets in complex scenes using an active video camera is a challenging task. Tracking accuracy and efficiency are two key yet generally incompatible aspects of a Target Tracking System (TTS). A compromise scheme will be studied in this paper. A fast
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Tracking moving targets in complex scenes using an active video camera is a challenging task. Tracking accuracy and efficiency are two key yet generally incompatible aspects of a Target Tracking System (TTS). A compromise scheme will be studied in this paper. A fast mean-shift-based Target Tracking scheme is designed and realized, which is robust to partial occlusion and changes in object appearance. The physical simulation shows that the image signal processing speed is > 50 frame/s. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle An Indoor Navigation System for the Visually Impaired
Sensors 2012, 12(6), 8236-8258; doi:10.3390/s120608236
Received: 27 April 2012 / Revised: 29 May 2012 / Accepted: 31 May 2012 / Published: 13 June 2012
Cited by 39 | PDF Full-text (873 KB) | HTML Full-text | XML Full-text
Abstract
Navigation in indoor environments is highly challenging for the severely visually impaired, particularly in spaces visited for the first time. Several solutions have been proposed to deal with this challenge. Although some of them have shown to be useful in real scenarios, they
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Navigation in indoor environments is highly challenging for the severely visually impaired, particularly in spaces visited for the first time. Several solutions have been proposed to deal with this challenge. Although some of them have shown to be useful in real scenarios, they involve an important deployment effort or use artifacts that are not natural for blind users. This paper presents an indoor navigation system that was designed taking into consideration usability as the quality requirement to be maximized. This solution enables one to identify the position of a person and calculates the velocity and direction of his movements. Using this information, the system determines the user’s trajectory, locates possible obstacles in that route, and offers navigation information to the user. The solution has been evaluated using two experimental scenarios. Although the results are still not enough to provide strong conclusions, they indicate that the system is suitable to guide visually impaired people through an unknown built environment. Full article
Open AccessArticle Experimental Artifacts for Morphological Tweaking of Chemical Sensor Materials: Studies on ZnO
Sensors 2012, 12(6), 8259-8277; doi:10.3390/s120608259
Received: 2 May 2012 / Revised: 29 May 2012 / Accepted: 6 June 2012 / Published: 13 June 2012
PDF Full-text (1864 KB) | HTML Full-text | XML Full-text
Abstract
Sensing mechanisms of gases on solid structures are predominantly surface-dominated. Benign surface features in terms of small grain size, high aspect ratio, large surface area and open and connected porosity, are required to realize a successful sensor material. Such morphological artifacts are a
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Sensing mechanisms of gases on solid structures are predominantly surface-dominated. Benign surface features in terms of small grain size, high aspect ratio, large surface area and open and connected porosity, are required to realize a successful sensor material. Such morphological artifacts are a function of the fabrication and processing techniques employed. In this paper, we describe the fabrication of monoshaped and monosized zinc oxide (ZnO) particles by a homogeneous precipitation method, using urea and/or hexmethyltetraamine as the reductant. The effect of operating conditions and experimental variables, such as the relative concentration of the precursors, temperature, and the aging time on the morphology of the resulting particles was studied systematically. These experimental parameters were optimized in order to achieve particles of uniform morphology and of narrow size distribution. Some of these particles were employed for the detection of ammonia gas at room temperature. Full article
(This article belongs to the Special Issue Sensing at the Nano-Scale: Chemical and Bio-Sensing)
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Open AccessArticle Intelligent Lead: A Novel HRI Sensor for Guide Robots
Sensors 2012, 12(6), 8301-8318; doi:10.3390/s120608301
Received: 23 May 2012 / Revised: 6 June 2012 / Accepted: 6 June 2012 / Published: 14 June 2012
Cited by 15 | PDF Full-text (1313 KB) | HTML Full-text | XML Full-text
Abstract
This paper addresses the introduction of a new Human Robot Interaction (HRI) sensor for guide robots. Guide robots for geriatric patients or the visually impaired should follow user’s control command, keeping a certain desired distance allowing the user to work freely. Therefore, it
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This paper addresses the introduction of a new Human Robot Interaction (HRI) sensor for guide robots. Guide robots for geriatric patients or the visually impaired should follow user’s control command, keeping a certain desired distance allowing the user to work freely. Therefore, it is necessary to acquire control commands and a user’s position on a real-time basis. We suggest a new sensor fusion system to achieve this objective and we will call this sensor the “intelligent lead”. The objective of the intelligent lead is to acquire a stable distance from the user to the robot, speed-control volume and turn-control volume, even when the robot platform with the intelligent lead is shaken on uneven ground. In this paper we explain a precise Extended Kalman Filter (EKF) procedure for this. The intelligent lead physically consists of a Kinect sensor, the serial linkage attached with eight rotary encoders, and an IMU (Inertial Measurement Unit) and their measurements are fused by the EKF. A mobile robot was designed to test the performance of the proposed sensor system. After installing the intelligent lead in the mobile robot, several tests are conducted to verify that the mobile robot with the intelligent lead is capable of achieving its goal points while maintaining the appropriate distance between the robot and the user. The results show that we can use the intelligent lead proposed in this paper as a new HRI sensor joined a joystick and a distance measure in the mobile environments such as the robot and the user are moving at the same time. Full article
(This article belongs to the Section Physical Sensors)
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Open AccessArticle A Miniature Integrated Multimodal Sensor for Measuring pH, EC and Temperature for Precision Agriculture
Sensors 2012, 12(6), 8338-8354; doi:10.3390/s120608338
Received: 30 April 2012 / Revised: 30 May 2012 / Accepted: 1 June 2012 / Published: 15 June 2012
Cited by 11 | PDF Full-text (1140 KB) | HTML Full-text | XML Full-text
Abstract
Making several simultaneous measurements with different kinds of sensors at the same location in a solution is difficult because of crosstalk between the sensors. In addition, because the conditions at different locations in plant beds differ, in situ measurements in agriculture need to
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Making several simultaneous measurements with different kinds of sensors at the same location in a solution is difficult because of crosstalk between the sensors. In addition, because the conditions at different locations in plant beds differ, in situ measurements in agriculture need to be done in small localized areas. We have fabricated a multimodal sensor on a small Si chip in which a pH sensor was integrated with electrical conductivity (EC) and temperature sensors. An ISFET with a Si3N4 membrane was used for the pH sensor. For the EC sensor, the electrical conductivity between platinum electrodes was measured, and the temperature sensor was a p-n junction diode. These are some of the most important measurements required for controlling the conditions in plant beds. The multimodal sensor can be inserted into a plant bed for in situ monitoring. To confirm the absence of crosstalk between the sensors, we made simultaneous measurements of pH, EC, and temperature of a pH buffer solution in a plant bed. When the solution was diluted with hot or cold water, the real time measurements showed changes to the EC and temperature, but no change in pH. We also demonstrated that our sensor was capable of simultaneous in situ measurements in rock wool without being affected by crosstalk. Full article
(This article belongs to the Special Issue Ultra-Small Sensor Systems and Components)
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Open AccessArticle License Plate Recognition Algorithm for Passenger Cars in Chinese Residential Areas
Sensors 2012, 12(6), 8355-8370; doi:10.3390/s120608355
Received: 20 March 2012 / Revised: 7 June 2012 / Accepted: 7 June 2012 / Published: 15 June 2012
Cited by 13 | PDF Full-text (783 KB) | XML Full-text
Abstract
This paper presents a solution for the license plate recognition problem in residential community administrations in China. License plate images are pre-processed through gradation, middle value filters and edge detection. In the license plate localization module the number of edge points, the length
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This paper presents a solution for the license plate recognition problem in residential community administrations in China. License plate images are pre-processed through gradation, middle value filters and edge detection. In the license plate localization module the number of edge points, the length of license plate area and the number of each line of edge points are used for localization. In the recognition module, the paper applies a statistical character method combined with a structure character method to obtain the characters. In addition, more models and template library for the characters which have less difference between each other are built. A character classifier is designed and a fuzzy recognition method is proposed based on the fuzzy decision-making method. Experiments show that the recognition accuracy rate is up to 92%. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle Direct Measurement of Mammographic X-Ray Spectra with a Digital CdTe Detection System
Sensors 2012, 12(6), 8390-8404; doi:10.3390/s120608390
Received: 8 May 2012 / Revised: 11 June 2012 / Accepted: 12 June 2012 / Published: 18 June 2012
Cited by 14 | PDF Full-text (487 KB) | HTML Full-text | XML Full-text
Abstract
In this work we present a detection system, based on a CdTe detector and an innovative digital pulse processing (DPP) system, for high-rate X-ray spectroscopy in mammography (1–30 keV). The DPP system performs a height and shape analysis of the detector pulses, sampled
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In this work we present a detection system, based on a CdTe detector and an innovative digital pulse processing (DPP) system, for high-rate X-ray spectroscopy in mammography (1–30 keV). The DPP system performs a height and shape analysis of the detector pulses, sampled and digitized by a 14-bit, 100 MHz ADC. We show the results of the characterization of the detection system both at low and high photon counting rates by using monoenergetic X-ray sources and a nonclinical X-ray tube. The detection system exhibits excellent performance up to 830 kcps with an energy resolution of 4.5% FWHM at 22.1 keV. Direct measurements of clinical molybdenum X-ray spectra were carried out by using a pinhole collimator and a custom alignment device. A comparison with the attenuation curves and the half value layer values, obtained from the measured and simulated spectra, from an ionization chamber and from a solid state dosimeter, also shows the accuracy of the measurements. These results make the proposed detection system a very attractive tool for both laboratory research, calibration of dosimeters and advanced quality controls in mammography. Full article
(This article belongs to the Special Issue Ultra-Small Sensor Systems and Components)
Open AccessArticle Evaluation of Complexation Ability Using a Sensor Electrode Chip Equipped with a Wireless Screening System
Sensors 2012, 12(6), 8405-8425; doi:10.3390/s120608405
Received: 12 April 2012 / Revised: 30 May 2012 / Accepted: 11 June 2012 / Published: 19 June 2012
PDF Full-text (591 KB) | HTML Full-text | XML Full-text
Abstract
We fabricated an electrode chip with a structure coated by an insulation layer that contains dispersed SiO2 adsorbent particles modified by an amino-group on a source-drain electrode. Voltage changes caused by chelate molecule adsorption onto electrode surfaces and by specific cation interactions
[...] Read more.
We fabricated an electrode chip with a structure coated by an insulation layer that contains dispersed SiO2 adsorbent particles modified by an amino-group on a source-drain electrode. Voltage changes caused by chelate molecule adsorption onto electrode surfaces and by specific cation interactions were investigated. The detection of specific cations without the presence of chelate molecules on the free electrode was also examined. By comparing both sets of results the complexation ability of the studied chelate molecules onto the electrode was evaluated. Five pairs of source-drain electrodes (×8 arrays) were fabricated on a glass substrate of 20 × 30 mm in size. The individual Au/Cr (1.0/0.1 μm thickness) electrodes had widths of 50 μm and an inter-electrode interval of 100 μm. The fabricated source-drain electrodes were further coated with an insulation layer comprising a porous SiO2 particle modified amino-group to adsorb the chelate molecules. The electrode chip was equipped with a handy-type sensor signal analyzer that was mounted on an amplifier circuit using a MinishipTM or a system in a packaged LSI device. For electrode surfaces containing different adsorbed chelate molecules an increase in the sensor voltage depended on a combination of host-guest reactions and generally decreased in the following order: 5,10,15,20-tetrakis(N-methylpyridinium-4-yl)-21H,23H-porphine, tetrakis(p-toluenesulfonate) (TMPyP) as a Cu2+ chelator and Cu2+ > 2-nitroso-5-[N-n-propyl-N-(3-sulfopropyl)amino]phenol (nitroso-PSAP) as an Fe2+ chelator and Fe2+ > 4,7-diphenyl-1,10-phenanthrolinedisulfonic acid, disodium salt (BPDSA) as an Fe2+ chelator and Fe2+ > 3-[3-(2,4-dimethylphenylcarbamoyl)-2-hydroxynaphthalene-1-yl-azo]-4-hydroxybenzenesulfonic acid, sodium salt (XB-1) as a Mg2+ chelator and Mg2+ > 2,9-dimethyl-4,7-diphenyl-1,10-phenanthrolinedisulfonic acid, disodium salt (BCIDSA) as a Cu2+ chelator and Cu2+, respectively. In contrast, for the electrode surfaces with adsorbed O,O'-bis(2-aminoethyl)ethyleneglycol-N,N,N',N'-tetraacetic acid (GEDTA) or O,O'-bis(2-aminophenyl)ethyleneglycol-N,N,N',N'-tetraacetic acid, tetrapotassium salt, hydrate (BAPTA) as a Ca2+ chelator no increase in the detection voltage was found for all the electrode tests conducted in the presence of Ca2+. To determine the differences in electrode detection, molecular orbital (MO) calculations of the chelate molecules and surface molecular modeling of the adsorbents were carried out. In accordance with frontier orbital theory, the lowest unoccupied MO (LUMO) of the chelate molecules can accept two lone pair electrons at the highest occupied MO (HOMO) of the amino group on the model surface structure of the SiO2 particle. As a result, a good correlation was obtained between the LUMO-HOMO difference and the ion response of all the electrodes tested. Based on the results obtained, the order of adsorbed chelate molecules on adsorption particles reflects the different metal ion detection abilities of the electrode chips. Full article
(This article belongs to the Special Issue Selective Chelating Agents)
Open AccessArticle Multiplex Immunoassay Platforms Based on Shape-Coded Poly(ethylene glycol) Hydrogel Microparticles Incorporating Acrylic Acid
Sensors 2012, 12(6), 8426-8436; doi:10.3390/s120608426
Received: 3 May 2012 / Revised: 25 May 2012 / Accepted: 5 June 2012 / Published: 20 June 2012
Cited by 9 | PDF Full-text (621 KB) | HTML Full-text | XML Full-text
Abstract
A suspension protein microarray was developed using shape-coded poly(ethylene glycol) (PEG) hydrogel microparticles for potential applications in multiplex and high-throughput immunoassays. A simple photopatterning process produced various shapes of hydrogel micropatterns that were weakly bound to poly(dimethylsiloxane) (PDMS)-coated substrates. These micropatterns were easily
[...] Read more.
A suspension protein microarray was developed using shape-coded poly(ethylene glycol) (PEG) hydrogel microparticles for potential applications in multiplex and high-throughput immunoassays. A simple photopatterning process produced various shapes of hydrogel micropatterns that were weakly bound to poly(dimethylsiloxane) (PDMS)-coated substrates. These micropatterns were easily detached from substrates during the washing process and were collected as non-spherical microparticles. Acrylic acids were incorporated into hydrogels, which could covalently immobilize proteins onto their surfaces due to the presence of carboxyl groups. The amount of immobilized protein increased with the amount of acrylic acid due to more available carboxyl groups. Saturation was reached at 25% v/v of acrylic acid. Immunoassays with IgG and IgM immobilized onto hydrogel microparticles were successfully performed with a linear concentration range from 0 to 500 ng/mL of anti-IgG and anti-IgM, respectively. Finally, a mixture of two different shapes of hydrogel microparticles immobilizing IgG (circle) and IgM (square) was prepared and it was demonstrated that simultaneous detection of two different target proteins was possible without cross-talk using same fluorescence indicator because each immunoassay was easily identified by the shapes of hydrogel microparticles. Full article
(This article belongs to the Special Issue Micro and Nano Technologies for Point-of-Care Diagnosis)

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Open AccessReview Optical Oxygen Micro- and Nanosensors for Plant Applications
Sensors 2012, 12(6), 7015-7032; doi:10.3390/s120607015
Received: 15 March 2012 / Revised: 1 May 2012 / Accepted: 14 May 2012 / Published: 25 May 2012
Cited by 20 | PDF Full-text (344 KB) | HTML Full-text | XML Full-text
Abstract
Pioneered by Clark’s microelectrode more than half a century ago, there has been substantial interest in developing new, miniaturized optical methods to detect molecular oxygen inside cells. While extensively used for animal tissue measurements, applications of intracellular optical oxygen biosensors are still scarce
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Pioneered by Clark’s microelectrode more than half a century ago, there has been substantial interest in developing new, miniaturized optical methods to detect molecular oxygen inside cells. While extensively used for animal tissue measurements, applications of intracellular optical oxygen biosensors are still scarce in plant science. A critical aspect is the strong autofluorescence of the green plant tissue that interferes with optical signals of commonly used oxygen probes. A recently developed dual-frequency phase modulation technique can overcome this limitation, offering new perspectives for plant research. This review gives an overview on the latest optical sensing techniques and methods based on phosphorescence quenching in diverse tissues and discusses the potential pitfalls for applications in plants. The most promising oxygen sensitive probes are reviewed plus different oxygen sensing structures ranging from micro-optodes to soluble nanoparticles. Moreover, the applicability of using heterologously expressed oxygen binding proteins and fluorescent proteins to determine changes in the cellular oxygen concentration are discussed as potential non-invasive cellular oxygen reporters. Full article
(This article belongs to the Special Issue Biomarkers and Nanosensors: New Approaches for Biology and Medicine)
Open AccessReview Advancements in Transmitters and Sensors for Biological Tissue Imaging in Magnetic Induction Tomography
Sensors 2012, 12(6), 7126-7156; doi:10.3390/s120607126
Received: 9 April 2012 / Revised: 2 May 2012 / Accepted: 9 May 2012 / Published: 29 May 2012
Cited by 21 | PDF Full-text (1475 KB) | HTML Full-text | XML Full-text
Abstract
Magnetic Induction Tomography (MIT), which is also known as Electromagnetic Tomography (EMT) or Mutual Inductance Tomography, is among the imaging modalities of interest to many researchers around the world. This noninvasive modality applies an electromagnetic field and is sensitive to all three passive
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Magnetic Induction Tomography (MIT), which is also known as Electromagnetic Tomography (EMT) or Mutual Inductance Tomography, is among the imaging modalities of interest to many researchers around the world. This noninvasive modality applies an electromagnetic field and is sensitive to all three passive electromagnetic properties of a material that are conductivity, permittivity and permeability. MIT is categorized under the passive imaging family with an electrodeless technique through the use of excitation coils to induce an electromagnetic field in the material, which is then measured at the receiving side by sensors. The aim of this review is to discuss the challenges of the MIT technique and summarize the recent advancements in the transmitters and sensors, with a focus on applications in biological tissue imaging. It is hoped that this review will provide some valuable information on the MIT for those who have interest in this modality. The need of this knowledge may speed up the process of adopted of MIT as a medical imaging technology. Full article
(This article belongs to the Section Physical Sensors)
Open AccessReview On-Chip Cellomics Assay Enabling Algebraic and Geometric Understanding of Epigenetic Information in Cellular Networks of Living Systems. 1. Temporal Aspects of Epigenetic Information in Bacteria
Sensors 2012, 12(6), 7169-7206; doi:10.3390/s120607169
Received: 1 May 2012 / Revised: 24 May 2012 / Accepted: 24 May 2012 / Published: 30 May 2012
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Abstract
A series of studies aimed at developing methods and systems of analyzing epigenetic information in cells and in cell networks, as well as that of genetic information, was examined to expand our understanding of how living systems are determined. Because cells are minimum
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A series of studies aimed at developing methods and systems of analyzing epigenetic information in cells and in cell networks, as well as that of genetic information, was examined to expand our understanding of how living systems are determined. Because cells are minimum units reflecting epigenetic information, which is considered to map the history of a parallel-processing recurrent network of biochemical reactions, their behaviors cannot be explained by considering only conventional DNA information-processing events. The role of epigenetic information on cells, which complements their genetic information, was inferred by comparing predictions from genetic information with cell behaviour observed under conditions chosen to reveal adaptation processes, population effects and community effects. A system of analyzing epigenetic information was developed starting from the twin complementary viewpoints of cell regulation as an “algebraic” system (emphasis on temporal aspects) and as a “geometric” system (emphasis on spatial aspects). Exploiting the combination of latest microfabrication technology and measurement technologies, which we call on-chip cellomics assay, we can control and re-construct the environments and interaction of cells from “algebraic” and “geometric” viewpoints. In this review, temporal viewpoint of epigenetic information, a part of the series of single-cell-based “algebraic” and “geometric” studies of celluler systems in our research groups, are summerized and reported. The knowlege acquired from this study may lead to the use of cells that fully control practical applications like cell-based drug screening and the regeneration of organs. Full article
(This article belongs to the Special Issue Live Cell-Based Sensors)
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Open AccessReview Gas Sensors Based on One Dimensional Nanostructured Metal-Oxides: A Review
Sensors 2012, 12(6), 7207-7258; doi:10.3390/s120607207
Received: 2 April 2012 / Revised: 18 April 2012 / Accepted: 11 May 2012 / Published: 30 May 2012
Cited by 164 | PDF Full-text (1384 KB) | HTML Full-text | XML Full-text
Abstract
Recently one dimensional (1-D) nanostructured metal-oxides have attracted much attention because of their potential applications in gas sensors. 1-D nanostructured metal-oxides provide high surface to volume ratio, while maintaining good chemical and thermal stabilities with minimal power consumption and low weight. In recent
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Recently one dimensional (1-D) nanostructured metal-oxides have attracted much attention because of their potential applications in gas sensors. 1-D nanostructured metal-oxides provide high surface to volume ratio, while maintaining good chemical and thermal stabilities with minimal power consumption and low weight. In recent years, various processing routes have been developed for the synthesis of 1-D nanostructured metal-oxides such as hydrothermal, ultrasonic irradiation, electrospinning, anodization, sol-gel, molten-salt, carbothermal reduction, solid-state chemical reaction, thermal evaporation, vapor-phase transport, aerosol, RF sputtering, molecular beam epitaxy, chemical vapor deposition, gas-phase assisted nanocarving, UV lithography and dry plasma etching. A variety of sensor fabrication processing routes have also been developed. Depending on the materials, morphology and fabrication process the performance of the sensor towards a specific gas shows a varying degree of success. This article reviews and evaluates the performance of 1-D nanostructured metal-oxide gas sensors based on ZnO, SnO2, TiO2, In2O3, WOx, AgVO3, CdO, MoO3, CuO, TeO2 and Fe2O3. Advantages and disadvantages of each sensor are summarized, along with the associated sensing mechanism. Finally, the article concludes with some future directions of research. Full article
(This article belongs to the Special Issue Sensing at the Nano-Scale: Chemical and Bio-Sensing)
Open AccessReview Single Molecule Electronics and Devices
Sensors 2012, 12(6), 7259-7298; doi:10.3390/s120607259
Received: 16 April 2012 / Revised: 15 May 2012 / Accepted: 17 May 2012 / Published: 30 May 2012
Cited by 52 | PDF Full-text (663 KB) | HTML Full-text | XML Full-text
Abstract
The manufacture of integrated circuits with single-molecule building blocks is a goal of molecular electronics. While research in the past has been limited to bulk experiments on self-assembled monolayers, advances in technology have now enabled us to fabricate single-molecule junctions. This has led
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The manufacture of integrated circuits with single-molecule building blocks is a goal of molecular electronics. While research in the past has been limited to bulk experiments on self-assembled monolayers, advances in technology have now enabled us to fabricate single-molecule junctions. This has led to significant progress in understanding electron transport in molecular systems at the single-molecule level and the concomitant emergence of new device concepts. Here, we review recent developments in this field. We summarize the methods currently used to form metal-molecule-metal structures and some single-molecule techniques essential for characterizing molecular junctions such as inelastic electron tunnelling spectroscopy. We then highlight several important achievements, including demonstration of single-molecule diodes, transistors, and switches that make use of electrical, photo, and mechanical stimulation to control the electron transport. We also discuss intriguing issues to be addressed further in the future such as heat and thermoelectric transport in an individual molecule. Full article
(This article belongs to the Special Issue Molecular Devices and Machines: Cooperativity and Multifunctionality)
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Open AccessReview A Survey on the Taxonomy of Cluster-Based Routing Protocols for Homogeneous Wireless Sensor Networks
Sensors 2012, 12(6), 7350-7409; doi:10.3390/s120607350
Received: 30 March 2012 / Revised: 14 May 2012 / Accepted: 20 May 2012 / Published: 30 May 2012
Cited by 34 | PDF Full-text (959 KB) | HTML Full-text | XML Full-text
Abstract
The past few years have witnessed increased interest among researchers in cluster-based protocols for homogeneous networks because of their better scalability and higher energy efficiency than other routing protocols. Given the limited capabilities of sensor nodes in terms of energy resources, processing and
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The past few years have witnessed increased interest among researchers in cluster-based protocols for homogeneous networks because of their better scalability and higher energy efficiency than other routing protocols. Given the limited capabilities of sensor nodes in terms of energy resources, processing and communication range, the cluster-based protocols should be compatible with these constraints in either the setup state or steady data transmission state. With focus on these constraints, we classify routing protocols according to their objectives and methods towards addressing the shortcomings of clustering process on each stage of cluster head selection, cluster formation, data aggregation and data communication. We summarize the techniques and methods used in these categories, while the weakness and strength of each protocol is pointed out in details. Furthermore, taxonomy of the protocols in each phase is given to provide a deeper understanding of current clustering approaches. Ultimately based on the existing research, a summary of the issues and solutions of the attributes and characteristics of clustering approaches and some open research areas in cluster-based routing protocols that can be further pursued are provided. Full article
(This article belongs to the Section Sensor Networks)
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Open AccessReview Satellite Remote Sensing of Harmful Algal Blooms (HABs) and a Potential Synthesized Framework
Sensors 2012, 12(6), 7778-7803; doi:10.3390/s120607778
Received: 16 May 2012 / Revised: 31 May 2012 / Accepted: 31 May 2012 / Published: 7 June 2012
Cited by 16 | PDF Full-text (375 KB) | HTML Full-text | XML Full-text
Abstract
Harmful algal blooms (HABs) are severe ecological disasters threatening aquatic systems throughout the World, which necessitate scientific efforts in detecting and monitoring them. Compared with traditional in situ point observations, satellite remote sensing is considered as a promising technique for studying HABs due
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Harmful algal blooms (HABs) are severe ecological disasters threatening aquatic systems throughout the World, which necessitate scientific efforts in detecting and monitoring them. Compared with traditional in situ point observations, satellite remote sensing is considered as a promising technique for studying HABs due to its advantages of large-scale, real-time, and long-term monitoring. The present review summarizes the suitability of current satellite data sources and different algorithms for detecting HABs. It also discusses the spatial scale issue of HABs. Based on the major problems identified from previous literature, including the unsystematic understanding of HABs, the insufficient incorporation of satellite remote sensing, and a lack of multiple oceanographic explanations of the mechanisms causing HABs, this review also attempts to provide a comprehensive understanding of the complicated mechanism of HABs impacted by multiple oceanographic factors. A potential synthesized framework can be established by combining multiple accessible satellite remote sensing approaches including visual interpretation, spectra analysis, parameters retrieval and spatial-temporal pattern analysis. This framework aims to lead to a systematic and comprehensive monitoring of HABs based on satellite remote sensing from multiple oceanographic perspectives. Full article
(This article belongs to the Section Remote Sensors)
Open AccessReview Atomic Force Microscopy as a Tool Applied to Nano/Biosensors
Sensors 2012, 12(6), 8278-8300; doi:10.3390/s120608278
Received: 5 April 2012 / Revised: 1 June 2012 / Accepted: 5 June 2012 / Published: 14 June 2012
Cited by 20 | PDF Full-text (731 KB) | HTML Full-text | XML Full-text
Abstract
This review article discusses and documents the basic concepts and principles of nano/biosensors. More specifically, we comment on the use of Chemical Force Microscopy (CFM) to study various aspects of architectural and chemical design details of specific molecules and polymers and its influence
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This review article discusses and documents the basic concepts and principles of nano/biosensors. More specifically, we comment on the use of Chemical Force Microscopy (CFM) to study various aspects of architectural and chemical design details of specific molecules and polymers and its influence on the control of chemical interactions between the Atomic Force Microscopy (AFM) tip and the sample. This technique is based on the fabrication of nanomechanical cantilever sensors (NCS) and microcantilever-based biosensors (MC-B), which can provide, depending on the application, rapid, sensitive, simple and low-cost in situ detection. Besides, it can provide high repeatability and reproducibility. Here, we review the applications of CFM through some application examples which should function as methodological questions to understand and transform this tool into a reliable source of data. This section is followed by a description of the theoretical principle and usage of the functionalized NCS and MC-B technique in several fields, such as agriculture, biotechnology and immunoassay. Finally, we hope this review will help the reader to appreciate how important the tools CFM, NCS and MC-B are for characterization and understanding of systems on the atomic scale. Full article
(This article belongs to the Section Chemical Sensors)
Open AccessReview Diagnostic Devices for Isothermal Nucleic Acid Amplification
Sensors 2012, 12(6), 8319-8337; doi:10.3390/s120608319
Received: 2 May 2012 / Revised: 29 May 2012 / Accepted: 7 June 2012 / Published: 14 June 2012
Cited by 41 | PDF Full-text (3895 KB) | HTML Full-text | XML Full-text
Abstract
Since the development of the polymerase chain reaction (PCR) technique, genomic information has been retrievable from lesser amounts of DNA than previously possible. PCR-based amplifications require high-precision instruments to perform temperature cycling reactions; further, they are cumbersome for routine clinical use. However, the
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Since the development of the polymerase chain reaction (PCR) technique, genomic information has been retrievable from lesser amounts of DNA than previously possible. PCR-based amplifications require high-precision instruments to perform temperature cycling reactions; further, they are cumbersome for routine clinical use. However, the use of isothermal approaches can eliminate many complications associated with thermocycling. The application of diagnostic devices for isothermal DNA amplification has recently been studied extensively. In this paper, we describe the basic concepts of several isothermal amplification approaches and review recent progress in diagnostic device development. Full article
(This article belongs to the Special Issue Biomarkers and Nanosensors: New Approaches for Biology and Medicine)
Open AccessReview Fiber Optic-Based Refractive Index Sensing at INESC Porto
Sensors 2012, 12(6), 8371-8389; doi:10.3390/s120608371
Received: 2 May 2012 / Revised: 4 June 2012 / Accepted: 6 June 2012 / Published: 18 June 2012
Cited by 10 | PDF Full-text (430 KB) | HTML Full-text | XML Full-text
Abstract
A review of refractive index measurement based on different types of optical fiber sensor configurations and techniques is presented. It addresses the main developments in the area, with particular focus on results obtained at INESC Porto, Portugal. The optical fiber sensing structures studied
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A review of refractive index measurement based on different types of optical fiber sensor configurations and techniques is presented. It addresses the main developments in the area, with particular focus on results obtained at INESC Porto, Portugal. The optical fiber sensing structures studied include those based on Bragg and long period gratings, on micro-interferometers, on plasmonic effects in fibers and on multimode interference in a large spectrum of standard and microstructured optical fibers. Full article
(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Portugal)
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Open AccessCorrection Correction: Renaudin, V. et al. Use of Earth’s Magnetic Field for Mitigating Gyroscope Errors Regardless of Magnetic Perturbation. Sensors 2011, 11, 11390-11414
Sensors 2012, 12(6), 8437; doi:10.3390/s120608437
Received: 1 June 2012 / Accepted: 20 June 2012 / Published: 20 June 2012
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Abstract Although the equations’ derivation in our paper published in Sensors 2011 [1] is correct, a typo has been found in the summarizing Equations (48) and (49). The dot on the B in the skew matrix should be removed. [...] Full article
(This article belongs to the Section Physical Sensors)

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