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Sensors, Volume 11, Issue 9 (September 2011) , Pages 8203-9120

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Open AccessArticle
Impact of the Excitation Source and Plasmonic Material on Cylindrical Active Coated Nano-Particles
Sensors 2011, 11(9), 9109-9120; https://doi.org/10.3390/s110909109
Received: 23 July 2011 / Revised: 23 August 2011 / Accepted: 20 September 2011 / Published: 21 September 2011
Cited by 17 | Viewed by 4026 | PDF Full-text (1202 KB) | HTML Full-text | XML Full-text
Abstract
Electromagnetic properties of cylindrical active coated nano-particles comprised of a silica nano-cylinder core layered with a plasmonic concentric nano-shell are investigated for potential nano-sensor applications. Particular attention is devoted to the near-field properties of these particles, as well as to their far-field radiation [...] Read more.
Electromagnetic properties of cylindrical active coated nano-particles comprised of a silica nano-cylinder core layered with a plasmonic concentric nano-shell are investigated for potential nano-sensor applications. Particular attention is devoted to the near-field properties of these particles, as well as to their far-field radiation characteristics, in the presence of an electric or a magnetic line source. A constant frequency canonical gain model is used to account for the gain introduced in the dielectric part of the nano-particle, whereas three different plasmonic materials (silver, gold, and copper) are employed and compared for the nano-shell layers. Full article
(This article belongs to the Special Issue Metamaterials for Sensing)
Open AccessArticle
Direction-of-Arrival Estimation Based on Joint Sparsity
Sensors 2011, 11(9), 9098-9108; https://doi.org/10.3390/s110909098
Received: 16 August 2011 / Revised: 17 September 2011 / Accepted: 18 September 2011 / Published: 21 September 2011
Cited by 6 | Viewed by 3259 | PDF Full-text (311 KB) | HTML Full-text | XML Full-text
Abstract
We present a DOA estimation algorithm, called Joint-Sparse DOA to address the problem of Direction-of-Arrival (DOA) estimation using sensor arrays. Firstly, DOA estimation is cast as the joint-sparse recovery problem. Then, norm is approximated by an arctan function to represent joint sparsity and [...] Read more.
We present a DOA estimation algorithm, called Joint-Sparse DOA to address the problem of Direction-of-Arrival (DOA) estimation using sensor arrays. Firstly, DOA estimation is cast as the joint-sparse recovery problem. Then, norm is approximated by an arctan function to represent joint sparsity and DOA estimation can be obtained by minimizing the approximate norm. Finally, the minimization problem is solved by a quasi-Newton method to estimate DOA. Simulation results show that our algorithm has some advantages over most existing methods: it needs a small number of snapshots to estimate DOA, while the number of sources need not be known a priori. Besides, it improves the resolution, and it can also handle the coherent sources well. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle
Geometric Calibration and Radiometric Correction of LiDAR Data and Their Impact on the Quality of Derived Products
Sensors 2011, 11(9), 9069-9097; https://doi.org/10.3390/s110909069
Received: 22 June 2011 / Revised: 1 September 2011 / Accepted: 3 September 2011 / Published: 21 September 2011
Cited by 24 | Viewed by 4926 | PDF Full-text (1136 KB) | HTML Full-text | XML Full-text
Abstract
LiDAR (Light Detection And Ranging) systems are capable of providing 3D positional and spectral information (in the utilized spectrum range) of the mapped surface. Due to systematic errors in the system parameters and measurements, LiDAR systems require geometric calibration and radiometric correction of [...] Read more.
LiDAR (Light Detection And Ranging) systems are capable of providing 3D positional and spectral information (in the utilized spectrum range) of the mapped surface. Due to systematic errors in the system parameters and measurements, LiDAR systems require geometric calibration and radiometric correction of the intensity data in order to maximize the benefit from the collected positional and spectral information. This paper presents a practical approach for the geometric calibration of LiDAR systems and radiometric correction of collected intensity data while investigating their impact on the quality of the derived products. The proposed approach includes the use of a quasi-rigorous geometric calibration and the radar equation for the radiometric correction of intensity data. The proposed quasi-rigorous calibration procedure requires time-tagged point cloud and trajectory position data, which are available to most of the data users. The paper presents a methodology for evaluating the impact of the geometric calibration on the relative and absolute accuracy of the LiDAR point cloud. Furthermore, the impact of the geometric calibration and radiometric correction on land cover classification accuracy is investigated. The feasibility of the proposed methods and their impact on the derived products are demonstrated through experimental results using real data. Full article
(This article belongs to the Section Remote Sensors, Control, and Telemetry)
Open AccessArticle
A Framework for UWB-Based Communication and Location Tracking Systems for Wireless Sensor Networks
Sensors 2011, 11(9), 9045-9068; https://doi.org/10.3390/s110909045
Received: 10 August 2011 / Revised: 10 September 2011 / Accepted: 20 September 2011 / Published: 21 September 2011
Cited by 13 | Viewed by 4367 | PDF Full-text (559 KB) | HTML Full-text | XML Full-text
Abstract
Ultra wideband (UWB) radio technology is nowadays one of the most promising technologies for medium-short range communications. It has a wide range of applications including Wireless Sensor Networks (WSN) with simultaneous data transmission and location tracking. The combination of location and data transmission [...] Read more.
Ultra wideband (UWB) radio technology is nowadays one of the most promising technologies for medium-short range communications. It has a wide range of applications including Wireless Sensor Networks (WSN) with simultaneous data transmission and location tracking. The combination of location and data transmission is important in order to increase flexibility and reduce the cost and complexity of the system deployment. In this scenario, accuracy is not the only evaluation criteria, but also the amount of resources associated to the location service, as it has an impact not only on the location capacity of the system but also on the sensor data transmission capacity. Although several studies can be found in the literature addressing UWB-based localization, these studies mainly focus on distance estimation and position calculation algorithms. Practical aspects such as the design of the functional architecture, the procedure for the transmission of the associated information between the different elements of the system, and the need of tracking multiple terminals simultaneously in various application scenarios, are generally omitted. This paper provides a complete system level evaluation of a UWB-based communication and location system for Wireless Sensor Networks, including aspects such as UWB-based ranging, tracking algorithms, latency, target mobility and MAC layer design. With this purpose, a custom simulator has been developed, and results with real UWB equipment are presented too. Full article
(This article belongs to the Section Physical Sensors)
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Open AccessArticle
The Design of RFID Conveyor Belt Gate Systems Using an Antenna Control Unit
Sensors 2011, 11(9), 9033-9044; https://doi.org/10.3390/s110909033
Received: 21 August 2011 / Revised: 13 September 2011 / Accepted: 20 September 2011 / Published: 21 September 2011
Cited by 3 | Viewed by 5090 | PDF Full-text (466 KB) | HTML Full-text | XML Full-text
Abstract
This paper proposes an efficient management system utilizing a Radio Frequency Identification (RFID) antenna control unit which is moving along with the path of boxes of materials on the conveyor belt by manipulating a motor. The proposed antenna control unit, which is driven [...] Read more.
This paper proposes an efficient management system utilizing a Radio Frequency Identification (RFID) antenna control unit which is moving along with the path of boxes of materials on the conveyor belt by manipulating a motor. The proposed antenna control unit, which is driven by a motor and is located on top of the gate, has an array structure of two antennas with parallel connection. The array structure helps improve the directivity of antenna beam pattern and the readable RFID distance due to its configuration. In the experiments, as the control unit follows moving materials, the reading time has been improved by almost three-fold compared to an RFID system employing conventional fixed antennas. The proposed system also has a recognition rate of over 99% without additional antennas for detecting the sides of a box of materials. The recognition rate meets the conditions recommended by the Electronic Product Code glbal network (EPC)global for commercializing the system, with three antennas at a 20 dBm power of reader and a conveyor belt speed of 3.17 m/s. This will enable a host of new RFID conveyor belt gate systems with increased performance. Full article
(This article belongs to the Special Issue Selected Papers from FGIT 2010)
Open AccessArticle
A Programmable Plug & Play Sensor Interface for WSN Applications
Sensors 2011, 11(9), 9009-9032; https://doi.org/10.3390/s110909009
Received: 4 August 2011 / Revised: 6 September 2011 / Accepted: 15 September 2011 / Published: 21 September 2011
Cited by 1 | Viewed by 4001 | PDF Full-text (1218 KB) | HTML Full-text | XML Full-text
Abstract
Cost reduction in wireless sensor networks (WSN) becomes a priority when extending their application to fields where a great number of sensors is needed, such as habitat monitoring, precision agriculture or diffuse greenhouse emission measurement. In these cases, the use of smart sensors [...] Read more.
Cost reduction in wireless sensor networks (WSN) becomes a priority when extending their application to fields where a great number of sensors is needed, such as habitat monitoring, precision agriculture or diffuse greenhouse emission measurement. In these cases, the use of smart sensors is expensive, consequently requiring the use of low-cost sensors. The solution to convert such generic low-cost sensors into intelligent ones leads to the implementation of a versatile system with enhanced processing and storage capabilities to attain a plug and play electronic interface able to adapt to all the sensors used. This paper focuses on this issue and presents a low-voltage plug & play reprogrammable interface capable of adapting to different sensor types and achieving an optimum reading performance for every sensor. The proposed interface, which includes both electronic and software elements so that it can be easily integrated in WSN nodes, is described and experimental test results to validate its performance are given. Full article
(This article belongs to the Section Physical Sensors)
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Open AccessArticle
Integrating Millimeter Wave Radar with a Monocular Vision Sensor for On-Road Obstacle Detection Applications
Sensors 2011, 11(9), 8992-9008; https://doi.org/10.3390/s110908992
Received: 19 August 2011 / Revised: 15 September 2011 / Accepted: 15 September 2011 / Published: 21 September 2011
Cited by 42 | Viewed by 5402 | PDF Full-text (2218 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents a systematic scheme for fusing millimeter wave (MMW) radar and a monocular vision sensor for on-road obstacle detection. As a whole, a three-level fusion strategy based on visual attention mechanism and driver’s visual consciousness is provided for MMW radar and [...] Read more.
This paper presents a systematic scheme for fusing millimeter wave (MMW) radar and a monocular vision sensor for on-road obstacle detection. As a whole, a three-level fusion strategy based on visual attention mechanism and driver’s visual consciousness is provided for MMW radar and monocular vision fusion so as to obtain better comprehensive performance. Then an experimental method for radar-vision point alignment for easy operation with no reflection intensity of radar and special tool requirements is put forward. Furthermore, a region searching approach for potential target detection is derived in order to decrease the image processing time. An adaptive thresholding algorithm based on a new understanding of shadows in the image is adopted for obstacle detection, and edge detection is used to assist in determining the boundary of obstacles. The proposed fusion approach is verified through real experimental examples of on-road vehicle/pedestrian detection. In the end, the experimental results show that the proposed method is simple and feasible. Full article
(This article belongs to the Section Physical Sensors)
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Open AccessArticle
A Real-Time Capable Software-Defined Receiver Using GPU for Adaptive Anti-Jam GPS Sensors
Sensors 2011, 11(9), 8966-8991; https://doi.org/10.3390/s110908966
Received: 22 July 2011 / Revised: 14 September 2011 / Accepted: 16 September 2011 / Published: 19 September 2011
Cited by 26 | Viewed by 6282 | PDF Full-text (995 KB) | HTML Full-text | XML Full-text
Abstract
Due to their weak received signal power, Global Positioning System (GPS) signals are vulnerable to radio frequency interference. Adaptive beam and null steering of the gain pattern of a GPS antenna array can significantly increase the resistance of GPS sensors to signal interference [...] Read more.
Due to their weak received signal power, Global Positioning System (GPS) signals are vulnerable to radio frequency interference. Adaptive beam and null steering of the gain pattern of a GPS antenna array can significantly increase the resistance of GPS sensors to signal interference and jamming. Since adaptive array processing requires intensive computational power, beamsteering GPS receivers were usually implemented using hardware such as field-programmable gate arrays (FPGAs). However, a software implementation using general-purpose processors is much more desirable because of its flexibility and cost effectiveness. This paper presents a GPS software-defined radio (SDR) with adaptive beamsteering capability for anti-jam applications. The GPS SDR design is based on an optimized desktop parallel processing architecture using a quad-core Central Processing Unit (CPU) coupled with a new generation Graphics Processing Unit (GPU) having massively parallel processors. This GPS SDR demonstrates sufficient computational capability to support a four-element antenna array and future GPS L5 signal processing in real time. After providing the details of our design and optimization schemes for future GPU-based GPS SDR developments, the jamming resistance of our GPS SDR under synthetic wideband jamming is presented. Since the GPS SDR uses commercial-off-the-shelf hardware and processors, it can be easily adopted in civil GPS applications requiring anti-jam capabilities. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle
A Guided Mode Resonance Aptasensor for Thrombin Detection
Sensors 2011, 11(9), 8953-8965; https://doi.org/10.3390/s110908953
Received: 21 July 2011 / Revised: 27 August 2011 / Accepted: 15 September 2011 / Published: 19 September 2011
Cited by 18 | Viewed by 3837 | PDF Full-text (791 KB) | HTML Full-text | XML Full-text
Abstract
Recent developments in aptamers have led to their widespread use in analytical and diagnostic applications, particularly for biosensing. Previous studies have combined aptamers as ligands with various sensors for numerous applications. However, merging the aptamer developments with guided mode resonance (GMR) devices has [...] Read more.
Recent developments in aptamers have led to their widespread use in analytical and diagnostic applications, particularly for biosensing. Previous studies have combined aptamers as ligands with various sensors for numerous applications. However, merging the aptamer developments with guided mode resonance (GMR) devices has not been attempted. This study reports an aptasensor based home built GMR device. The 29-mer thrombin aptamer was immobilized on the surface of a GMR device as a recognizing ligand for thrombin detection. The sensitivity reported in this first trial study is 0.04 nm/μM for thrombin detection in the concentration range from 0.25 to 1 μM and the limit of detection (LOD) is 0.19 μM. Furthermore, the binding affinity constant (Ka) measured is in the range of 106 M−1. The investigation has demonstrated that such a GMR aptasensor has the required sensitivity for the real time, label-free, in situ detection of thrombin and provides kinetic information related to the binding. Full article
(This article belongs to the Special Issue Aptamer-Based Sensors)
Open AccessArticle
A Novel Design of an Automatic Lighting Control System for a Wireless Sensor Network with Increased Sensor Lifetime and Reduced Sensor Numbers
Sensors 2011, 11(9), 8933-8952; https://doi.org/10.3390/s110908933
Received: 2 August 2011 / Revised: 26 August 2011 / Accepted: 26 August 2011 / Published: 16 September 2011
Cited by 11 | Viewed by 4854 | PDF Full-text (2946 KB) | HTML Full-text | XML Full-text
Abstract
Wireless sensor networks (WSN) are currently being applied to energy conservation applications such as light control. We propose a design for such a system called a Lighting Automatic Control System (LACS). The LACS system contains a centralized or distributed architecture determined by application [...] Read more.
Wireless sensor networks (WSN) are currently being applied to energy conservation applications such as light control. We propose a design for such a system called a Lighting Automatic Control System (LACS). The LACS system contains a centralized or distributed architecture determined by application requirements and space usage. The system optimizes the calculations and communications for lighting intensity, incorporates user illumination requirements according to their activities and performs adjustments based on external lighting effects in external sensor and external sensor-less architectures. Methods are proposed for reducing the number of sensors required and increasing the lifetime of those used, for considerably reduced energy consumption. Additionally we suggest methods for improving uniformity of illuminance distribution on a workplane’s surface, which improves user satisfaction. Finally simulation results are presented to verify the effectiveness of our design. Full article
(This article belongs to the Section Physical Sensors)
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Open AccessEditorial
Advances in Sensors Applied to Agriculture and Forestry
Sensors 2011, 11(9), 8930-8932; https://doi.org/10.3390/s110908930
Received: 14 September 2011 / Accepted: 15 September 2011 / Published: 15 September 2011
Cited by 11 | Viewed by 4980 | PDF Full-text (119 KB) | HTML Full-text | XML Full-text
Abstract
In agriculture and forestry, the need to increase production and the simultaneous efforts to minimize the environmental impact of agricultural production processes and save costs find in sensor systems the best allied tool. The use of sensors helps exploit all available resources appropriately [...] Read more.
In agriculture and forestry, the need to increase production and the simultaneous efforts to minimize the environmental impact of agricultural production processes and save costs find in sensor systems the best allied tool. The use of sensors helps exploit all available resources appropriately and to apply hazardous products moderately. When nutrients in the soil, humidity, solar radiation, density of weeds and a broad set of factors and data affecting the production are known, this situation improves and the use of chemical products such as fertilizers, herbicides and other pollutants can be reduced considerably. Part of this knowledge allows also monitoring photosynthetic parameters of high relevance for photosynthesis. Most of the associated activities fall within the scope of what it is called Precision Agriculture, an emerging area receiving special attention in recent years. [...] Full article
(This article belongs to the Special Issue Sensors in Agriculture and Forestry)
Open AccessArticle
Organic Pollution in Surface Waters from the Fuglebekken Basin in Svalbard, Norwegian Arctic
Sensors 2011, 11(9), 8910-8929; https://doi.org/10.3390/s110908910
Received: 8 August 2011 / Revised: 4 September 2011 / Accepted: 8 September 2011 / Published: 15 September 2011
Cited by 23 | Viewed by 4414 | PDF Full-text (631 KB) | HTML Full-text | XML Full-text
Abstract
The Fuglebekken basin is situated in the southern part of the island of Spitsbergen (Norwegian Arctic), on the Hornsund fjord (Wedel Jarlsberg Land). Surface water was collected from 24 tributaries (B1–B24) and from the main stream water in the Fuglebekken basin (25) between [...] Read more.
The Fuglebekken basin is situated in the southern part of the island of Spitsbergen (Norwegian Arctic), on the Hornsund fjord (Wedel Jarlsberg Land). Surface water was collected from 24 tributaries (B1–B24) and from the main stream water in the Fuglebekken basin (25) between 10 July 2009 and 30 July 2009. The present investigation reveals the results of the analysis of these samples for their PAH and PCB content. Twelve of 16 PAHs and seven PCBs were determined in the surface waters from 24 tributaries and the main stream. Total PAH and PCB concentrations in the surface waters ranged from 4 to 600 ng/L and from 2 to 400 ng/L respectively. The highest concentrations of an individual PCB (138–308 ng/L and 123 ng/L) were found in samples from tributaries B9 and B5. The presence in the basin (thousands of kilometres distant from industrial centres) of PAHs and PCBs is testimony to the fact that these compounds are transported over vast distances with air masses and deposited in regions devoid of any human pressure. Full article
(This article belongs to the Special Issue Sensing of Organic Pollution in Soil, Air, Water and Food)
Open AccessArticle
Reconstruction of Self-Sparse 2D NMR Spectra from Undersampled Data in the Indirect Dimension
Sensors 2011, 11(9), 8888-8909; https://doi.org/10.3390/s110908888
Received: 31 July 2011 / Revised: 31 August 2011 / Accepted: 5 September 2011 / Published: 15 September 2011
Cited by 23 | Viewed by 5394 | PDF Full-text (2868 KB) | HTML Full-text | XML Full-text
Abstract
Reducing the acquisition time for two-dimensional nuclear magnetic resonance (2D NMR) spectra is important. One way to achieve this goal is reducing the acquired data. In this paper, within the framework of compressed sensing, we proposed to undersample the data in the indirect [...] Read more.
Reducing the acquisition time for two-dimensional nuclear magnetic resonance (2D NMR) spectra is important. One way to achieve this goal is reducing the acquired data. In this paper, within the framework of compressed sensing, we proposed to undersample the data in the indirect dimension for a type of self-sparse 2D NMR spectra, that is, only a few meaningful spectral peaks occupy partial locations, while the rest of locations have very small or even no peaks. The spectrum is reconstructed by enforcing its sparsity in an identity matrix domain with p (p = 0.5) norm optimization algorithm. Both theoretical analysis and simulation results show that the proposed method can reduce the reconstruction errors compared with the wavelet-based 1 norm optimization. Full article
(This article belongs to the Section Chemical Sensors)
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Open AccessArticle
A Semantic Sensor Web for Environmental Decision Support Applications
Sensors 2011, 11(9), 8855-8887; https://doi.org/10.3390/s110908855
Received: 26 July 2011 / Revised: 29 August 2011 / Accepted: 29 August 2011 / Published: 14 September 2011
Cited by 23 | Viewed by 8792 | PDF Full-text (2275 KB) | HTML Full-text | XML Full-text
Abstract
Sensing devices are increasingly being deployed to monitor the physical world around us. One class of application for which sensor data is pertinent is environmental decision support systems, e.g., flood emergency response. For these applications, the sensor readings need to be put in [...] Read more.
Sensing devices are increasingly being deployed to monitor the physical world around us. One class of application for which sensor data is pertinent is environmental decision support systems, e.g., flood emergency response. For these applications, the sensor readings need to be put in context by integrating them with other sources of data about the surrounding environment. Traditional systems for predicting and detecting floods rely on methods that need significant human resources. In this paper we describe a semantic sensor web architecture for integrating multiple heterogeneous datasets, including live and historic sensor data, databases, and map layers. The architecture provides mechanisms for discovering datasets, defining integrated views over them, continuously receiving data in real-time, and visualising on screen and interacting with the data. Our approach makes extensive use of web service standards for querying and accessing data, and semantic technologies to discover and integrate datasets. We demonstrate the use of our semantic sensor web architecture in the context of a flood response planning web application that uses data from sensor networks monitoring the sea-state around the coast of England. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle
Detailed Study of Amplitude Nonlinearity in Piezoresistive Force Sensors
Sensors 2011, 11(9), 8836-8854; https://doi.org/10.3390/s110908836
Received: 28 July 2011 / Revised: 8 September 2011 / Accepted: 9 September 2011 / Published: 14 September 2011
Cited by 12 | Viewed by 4034 | PDF Full-text (1507 KB) | HTML Full-text | XML Full-text
Abstract
This article upgrades the RC linear model presented for piezoresistive force sensors. Amplitude nonlinearity is found in sensor conductance, and a characteristic equation is formulated for modeling its response under DC-driving voltages below 1 V. The feasibility of such equation is tested on [...] Read more.
This article upgrades the RC linear model presented for piezoresistive force sensors. Amplitude nonlinearity is found in sensor conductance, and a characteristic equation is formulated for modeling its response under DC-driving voltages below 1 V. The feasibility of such equation is tested on four FlexiForce model A201-100 piezoresistive sensors by varying the sourcing voltage and the applied forces. Since the characteristic equation proves to be valid, a method is presented for obtaining a specific sensitivity in sensor response by calculating the appropriate sourcing voltage and feedback resistor in the driving circuit; this provides plug-and-play capabilities to the device and reduces the start-up time of new applications where piezoresistive devices are to be used. Finally, a method for bypassing the amplitude nonlinearity is presented with the aim of reading sensor capacitance. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle
A High-Precision Micropipette Sensor for Cellular-Level Real-Time Thermal Characterization
Sensors 2011, 11(9), 8826-8835; https://doi.org/10.3390/s110908826
Received: 5 August 2011 / Revised: 7 September 2011 / Accepted: 7 September 2011 / Published: 13 September 2011
Cited by 13 | Viewed by 3139 | PDF Full-text (593 KB) | HTML Full-text | XML Full-text
Abstract
We report herein development of a novel glass micropipette thermal sensor fabricated in a cost-effective manner, which is capable of measuring steady thermal fluctuation at spatial resolution of ~2 µm with an accuracy of ±0.01 °C. We produced and tested various micrometer-sized sensors, [...] Read more.
We report herein development of a novel glass micropipette thermal sensor fabricated in a cost-effective manner, which is capable of measuring steady thermal fluctuation at spatial resolution of ~2 µm with an accuracy of ±0.01 °C. We produced and tested various micrometer-sized sensors, ranging from 2 µm to 30 µm. The sensor comprises unleaded low-melting-point solder alloy (Sn-based) as a core metal inside a pulled borosilicate glass pipette and a thin film of nickel coating outside, creating a thermocouple junction at the tip. The sensor was calibrated using a thermally insulated calibration chamber, the temperature of which can be controlled with an accuracy of ±0.01 °C, and the thermoelectric power (Seebeck coefficient) of the sensor was recorded from 8.46 to 8.86 µV/°C. We have demonstrated the capability of measuring temperatures at a cellular level by inserting our temperature sensor into the membrane of a live retinal pigment epithelium cell subjected to a laser beam with a focal spot of 6 μm. We measured transient temperature profiles and the maximum temperatures were in the range of 38–55 ± 0.5 °C. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle
Use of a New Ziprasidone-Selective Electrode in Mixed Solvents and Its Application in the Analysis of Pharmaceuticals and Biological Fluids
Sensors 2011, 11(9), 8813-8825; https://doi.org/10.3390/s110908813
Received: 4 August 2011 / Revised: 7 September 2011 / Accepted: 8 September 2011 / Published: 13 September 2011
Cited by 3 | Viewed by 3704 | PDF Full-text (265 KB) | HTML Full-text | XML Full-text
Abstract
The construction and characterization of a new ion-selective electrode for the determination of the antipsychotic ziprasidone in mixed solvents is presented. The electrode contains a plasticized polymeric membrane based on a ziprasidone-tetraphenylborate ion-exchanger. The influence of membrane composition on the electrode response towards [...] Read more.
The construction and characterization of a new ion-selective electrode for the determination of the antipsychotic ziprasidone in mixed solvents is presented. The electrode contains a plasticized polymeric membrane based on a ziprasidone-tetraphenylborate ion-exchanger. The influence of membrane composition on the electrode response towards ziprasidone in hydroalcoholic solutions was studied. The electrode displayed a stable response in a 2:3 (v/v) methanol/water medium from a ziprasidone concentration of 3 × 10−6 M with a fast response time of less than 20 s. The electrode also showed good selectivity towards ziprasidone over common inorganic and organic compounds and several species with pharmacological activity. The electrode was successfully applied to the determination of ziprasidone in pharmaceuticals and human urine and serum. Full article
(This article belongs to the Section Chemical Sensors)
Open AccessArticle
An Approach to a Comprehensive Test Framework for Analysis and Evaluation of Text Line Segmentation Algorithms
Sensors 2011, 11(9), 8782-8812; https://doi.org/10.3390/s110908782
Received: 1 August 2011 / Revised: 2 September 2011 / Accepted: 5 September 2011 / Published: 13 September 2011
Cited by 8 | Viewed by 3953 | PDF Full-text (1648 KB) | HTML Full-text | XML Full-text
Abstract
The paper introduces a testing framework for the evaluation and validation of text line segmentation algorithms. Text line segmentation represents the key action for correct optical character recognition. Many of the tests for the evaluation of text line segmentation algorithms deal with text [...] Read more.
The paper introduces a testing framework for the evaluation and validation of text line segmentation algorithms. Text line segmentation represents the key action for correct optical character recognition. Many of the tests for the evaluation of text line segmentation algorithms deal with text databases as reference templates. Because of the mismatch, the reliable testing framework is required. Hence, a new approach to a comprehensive experimental framework for the evaluation of text line segmentation algorithms is proposed. It consists of synthetic multi-like text samples and real handwritten text as well. Although the tests are mutually independent, the results are cross-linked. The proposed method can be used for different types of scripts and languages. Furthermore, two different procedures for the evaluation of algorithm efficiency based on the obtained error type classification are proposed. The first is based on the segmentation line error description, while the second one incorporates well-known signal detection theory. Each of them has different capabilities and convenience, but they can be used as supplements to make the evaluation process efficient. Overall the proposed procedure based on the segmentation line error description has some advantages, characterized by five measures that describe measurement procedures. Full article
(This article belongs to the Section Physical Sensors)
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Open AccessArticle
Gamma-Ray Sterilization Effects in Silica Nanoparticles/γ-APTES Nanocomposite-Based pH-Sensitive Polysilicon Wire Sensors
Sensors 2011, 11(9), 8769-8781; https://doi.org/10.3390/s110908769
Received: 13 August 2011 / Revised: 7 September 2011 / Accepted: 8 September 2011 / Published: 13 September 2011
Cited by 6 | Viewed by 4015 | PDF Full-text (1904 KB) | HTML Full-text | XML Full-text
Abstract
In this paper, we report the γ-ray sterilization effects in pH-sensitive polysilicon wire (PSW) sensors using a mixture of 3-aminopropyltriethoxysilane (γ-APTES) and polydimethylsiloxane (PDMS)-treated hydrophobic fumed silica nanoparticles (NPs) as a sensing membrane. pH analyses showed that the γ-ray irradiation-induced sensitivity degradation of [...] Read more.
In this paper, we report the γ-ray sterilization effects in pH-sensitive polysilicon wire (PSW) sensors using a mixture of 3-aminopropyltriethoxysilane (γ-APTES) and polydimethylsiloxane (PDMS)-treated hydrophobic fumed silica nanoparticles (NPs) as a sensing membrane. pH analyses showed that the γ-ray irradiation-induced sensitivity degradation of the PSW pH sensor covered with γ-APTES/silica NPs nanocomposite (γ-APTES+NPs) could be restored to a condition even better than prior to γ-ray irradiation by 40-min of post-sterilization room-temperature UV annealing. We found that the trapping charges caused by γ-ray sterilization primarily concentrated in the native oxide layer for the pH sensor covered with γ-APTES, but accumulated in the γ-APTES+NPs layer for the γ-APTES+NPs-covered sensor. It is believed that mixing the PDMS-treated silica NPs into g-APTES provides many g-APTES/SiO2 interfaces for the accumulation of trapping charges and for post-sterilization UV oxidation, thus restoring γ-ray-induced sensor degradation. The PDMS-treated silica NPs not only enhance the sensitivity of the pH-sensitive PSW sensors but are also able to withstand the two-step sterilization resulting from γ-ray and UV irradiations. This investigation suggests γ-ray irradiation could be used as a highly-efficient sterilization method for γ-APTES-based pH-sensitive biosensors. Full article
(This article belongs to the Section Chemical Sensors)
Open AccessArticle
Simultaneous Intrinsic and Extrinsic Parameter Identification of a Hand-Mounted Laser-Vision Sensor
Sensors 2011, 11(9), 8751-8768; https://doi.org/10.3390/s110908751
Received: 18 August 2011 / Revised: 5 September 2011 / Accepted: 6 September 2011 / Published: 9 September 2011
Cited by 3 | Viewed by 3666 | PDF Full-text (868 KB) | HTML Full-text | XML Full-text
Abstract
In this paper, we propose a simultaneous intrinsic and extrinsic parameter identification of a hand-mounted laser-vision sensor (HMLVS). A laser-vision sensor (LVS), consisting of a camera and a laser stripe projector, is used as a sensor component of the robotic measurement system, and [...] Read more.
In this paper, we propose a simultaneous intrinsic and extrinsic parameter identification of a hand-mounted laser-vision sensor (HMLVS). A laser-vision sensor (LVS), consisting of a camera and a laser stripe projector, is used as a sensor component of the robotic measurement system, and it measures the range data with respect to the robot base frame using the robot forward kinematics and the optical triangulation principle. For the optimal estimation of the model parameters, we applied two optimization techniques: a nonlinear least square optimizer and a particle swarm optimizer. Best-fit parameters, including both the intrinsic and extrinsic parameters of the HMLVS, are simultaneously obtained based on the least-squares criterion. From the simulation and experimental results, it is shown that the parameter identification problem considered was characterized by a highly multimodal landscape; thus, the global optimization technique such as a particle swarm optimization can be a promising tool to identify the model parameters for a HMLVS, while the nonlinear least square optimizer often failed to find an optimal solution even when the initial candidate solutions were selected close to the true optimum. The proposed optimization method does not require good initial guesses of the system parameters to converge at a very stable solution and it could be applied to a kinematically dissimilar robot system without loss of generality. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle
Power Loss Characteristics of a Sensing Element Based on a Polymer Optical Fiber under Cyclic Tensile Elongation
Sensors 2011, 11(9), 8741-8750; https://doi.org/10.3390/s110908741
Received: 4 August 2011 / Revised: 29 August 2011 / Accepted: 1 September 2011 / Published: 8 September 2011
Cited by 5 | Viewed by 3686 | PDF Full-text (456 KB) | HTML Full-text | XML Full-text
Abstract
In this study, power losses in polymer optical fiber (POF) subjected to cyclic tensile loadings are studied experimentally. The parameters discussed are the cyclic load level and the number of cycles. The results indicate that the power loss in POF specimens increases with [...] Read more.
In this study, power losses in polymer optical fiber (POF) subjected to cyclic tensile loadings are studied experimentally. The parameters discussed are the cyclic load level and the number of cycles. The results indicate that the power loss in POF specimens increases with increasing load level or number of cycles. The power loss can reach as high as 18.3% after 100 cyclic loadings. Based on the experimental results, a linear equation is proposed to estimate the relationship between the power loss and the number of cycles. The difference between the estimated results and the experimental results is found to be less than 3%. Full article
(This article belongs to the Special Issue Optical Fiber Sensors 2012)
Open AccessArticle
Range Camera Self-Calibration Based on Integrated Bundle Adjustment via Joint Setup with a 2D Digital Camera
Sensors 2011, 11(9), 8721-8740; https://doi.org/10.3390/s110908721
Received: 15 July 2011 / Revised: 12 August 2011 / Accepted: 15 August 2011 / Published: 8 September 2011
Cited by 17 | Viewed by 4647 | PDF Full-text (1038 KB) | HTML Full-text | XML Full-text
Abstract
Time-of-flight cameras, based on Photonic Mixer Device (PMD) technology, are capable of measuring distances to objects at high frame rates, however, the measured ranges and the intensity data contain systematic errors that need to be corrected. In this paper, a new integrated range [...] Read more.
Time-of-flight cameras, based on Photonic Mixer Device (PMD) technology, are capable of measuring distances to objects at high frame rates, however, the measured ranges and the intensity data contain systematic errors that need to be corrected. In this paper, a new integrated range camera self-calibration method via joint setup with a digital (RGB) camera is presented. This method can simultaneously estimate the systematic range error parameters as well as the interior and external orientation parameters of the camera. The calibration approach is based on photogrammetric bundle adjustment of observation equations originating from collinearity condition and a range errors model. Addition of a digital camera to the calibration process overcomes the limitations of small field of view and low pixel resolution of the range camera. The tests are performed on a dataset captured by a PMD[vision]-O3 camera from a multi-resolution test field of high contrast targets. An average improvement of 83% in RMS of range error and 72% in RMS of coordinate residual, over that achieved with basic calibration, was realized in an independent accuracy assessment. Our proposed calibration method also achieved 25% and 36% improvement on RMS of range error and coordinate residual, respectively, over that obtained by integrated calibration of the single PMD camera. Full article
(This article belongs to the Section Physical Sensors)
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Open AccessArticle
Remote (250 km) Fiber Bragg Grating Multiplexing System
Sensors 2011, 11(9), 8711-8720; https://doi.org/10.3390/s110908711
Received: 4 July 2011 / Revised: 1 September 2011 / Accepted: 7 September 2011 / Published: 8 September 2011
Cited by 20 | Viewed by 5169 | PDF Full-text (301 KB) | HTML Full-text | XML Full-text
Abstract
We propose and demonstrate two ultra-long range fiber Bragg grating (FBG) sensor interrogation systems. In the first approach four FBGs are located 200 km from the monitoring station and a signal to noise ratio of 20 dB is obtained. The second improved version [...] Read more.
We propose and demonstrate two ultra-long range fiber Bragg grating (FBG) sensor interrogation systems. In the first approach four FBGs are located 200 km from the monitoring station and a signal to noise ratio of 20 dB is obtained. The second improved version is able to detect the four multiplexed FBGs placed 250 km away, offering a signal to noise ratio of 6–8 dB. Consequently, this last system represents the longest range FBG sensor system reported so far that includes fiber sensor multiplexing capability. Both simple systems are based on a wavelength swept laser to scan the reflection spectra of the FBGs, and they are composed by two identical-lengths optical paths: the first one intended to launch the amplified laser signal by means of Raman amplification and the other one is employed to guide the reflection signal to the reception system. Full article
(This article belongs to the Special Issue Optical Fiber Sensors 2012)
Open AccessArticle
Long-Term Monitoring of Fresco Paintings in the Cathedral of Valencia (Spain) Through Humidity and Temperature Sensors in Various Locations for Preventive Conservation
Sensors 2011, 11(9), 8685-8710; https://doi.org/10.3390/s110908685
Received: 11 August 2011 / Revised: 2 September 2011 / Accepted: 6 September 2011 / Published: 8 September 2011
Cited by 25 | Viewed by 5329 | PDF Full-text (5242 KB) | HTML Full-text | XML Full-text | Correction | Supplementary Files
Abstract
We describe the performance of a microclimate monitoring system that was implemented for the preventive conservation of the Renaissance frescoes in the apse vault of the Cathedral of Valencia, that were restored in 2006. This system comprises 29 relative humidity (RH) [...] Read more.
We describe the performance of a microclimate monitoring system that was implemented for the preventive conservation of the Renaissance frescoes in the apse vault of the Cathedral of Valencia, that were restored in 2006. This system comprises 29 relative humidity (RH) and temperature sensors: 10 of them inserted into the plaster layer supporting the fresco paintings, 10 sensors in the walls close to the frescoes and nine sensors measuring the indoor microclimate at different points of the vault. Principal component analysis was applied to RH data recorded in 2007. The analysis was repeated with data collected in 2008 and 2010. The resulting loading plots revealed that the similarities and dissimilarities among sensors were approximately maintained along the three years. A physical interpretation was provided for the first and second principal components. Interestingly, sensors recording the highest RH values correspond to zones where humidity problems are causing formation of efflorescence. Recorded data of RH and temperature are discussed according to Italian Standard UNI 10829 (1999). Full article
(This article belongs to the Section Physical Sensors)
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Open AccessArticle
Real-Time Remote Monitoring of Temperature and Humidity Within a Proton Exchange Membrane Fuel Cell Using Flexible Sensors
Sensors 2011, 11(9), 8674-8684; https://doi.org/10.3390/s110908674
Received: 15 July 2011 / Revised: 19 August 2011 / Accepted: 5 September 2011 / Published: 8 September 2011
Cited by 7 | Viewed by 4301 | PDF Full-text (653 KB) | HTML Full-text | XML Full-text
Abstract
This study developed portable, non-invasive flexible humidity and temperature microsensors and an in situ wireless sensing system for a proton exchange membrane fuel cell (PEMFC). The system integrated three parts: a flexible capacitive humidity microsensor, a flexible resistive temperature microsensor, and a radio [...] Read more.
This study developed portable, non-invasive flexible humidity and temperature microsensors and an in situ wireless sensing system for a proton exchange membrane fuel cell (PEMFC). The system integrated three parts: a flexible capacitive humidity microsensor, a flexible resistive temperature microsensor, and a radio frequency (RF) module for signal transmission. The results show that the capacitive humidity microsensor has a high sensitivity of 0.83 pF%RH−1 and the resistive temperature microsensor also exhibits a high sensitivity of 2.94 × 10−3 °C−1. The established RF module transmits the signals from the two microsensors. The transmission distance can reach 4 m and the response time is less than 0.25 s. The performance measurements demonstrate that the maximum power density of the fuel cell with and without these microsensors are 14.76 mW·cm−2 and 15.90 mW·cm−2, with only 7.17% power loss. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle
A Fiber Bragg Grating—Bimetal Temperature Sensor for Solar Panel Inverters
Sensors 2011, 11(9), 8665-8673; https://doi.org/10.3390/s110908665
Received: 27 July 2011 / Revised: 27 August 2011 / Accepted: 5 September 2011 / Published: 6 September 2011
Cited by 9 | Viewed by 4142 | PDF Full-text (488 KB) | HTML Full-text | XML Full-text
Abstract
This paper reports the design, characterization and implementation of a Fiber Bragg Grating (FBG)-based temperature sensor for an Insulted-Gate Bipolar Transistor (IGBT) in a solar panel inverter. The FBG is bonded to the higher Coefficient of Thermal Expansion (CTE) side of a bimetallic [...] Read more.
This paper reports the design, characterization and implementation of a Fiber Bragg Grating (FBG)-based temperature sensor for an Insulted-Gate Bipolar Transistor (IGBT) in a solar panel inverter. The FBG is bonded to the higher Coefficient of Thermal Expansion (CTE) side of a bimetallic strip to increase its sensitivity. Characterization results show a linear relationship between increasing temperature and the wavelength shift. It is found that the sensitivity of the sensor can be categorized into three characterization temperature regions between 26 °C and 90 °C. The region from 41 °C to 90 °C shows the highest sensitivity, with a value of 14 pm/°C. A new empirical model that considers both temperature and strain effects has been developed for the sensor. Finally, the FBG-bimetal temperature sensor is placed in a solar panel inverter and results confirm that it can be used for real-time monitoring of the IGBT temperature. Full article
(This article belongs to the Section Physical Sensors)
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Open AccessArticle
A Surface Plasmon Resonance Sensor for the Detection of Deoxynivalenol Using a Molecularly Imprinted Polymer
Sensors 2011, 11(9), 8654-8664; https://doi.org/10.3390/s110908654
Received: 15 July 2011 / Revised: 30 August 2011 / Accepted: 30 August 2011 / Published: 5 September 2011
Cited by 25 | Viewed by 3755 | PDF Full-text (599 KB) | HTML Full-text | XML Full-text
Abstract
The aim of the present work was to investigate the feasibility of applying the molecular imprinting polymer technique to the detection of the mycotoxin deoxynivalenol (DON) using a surface plasmon resonance (SPR) transducer. A molecularly imprinted polypyrrole (MIPPy) film was prepared via electropolymerization [...] Read more.
The aim of the present work was to investigate the feasibility of applying the molecular imprinting polymer technique to the detection of the mycotoxin deoxynivalenol (DON) using a surface plasmon resonance (SPR) transducer. A molecularly imprinted polypyrrole (MIPPy) film was prepared via electropolymerization of pyrrole onto a bare Au chip in the presence of a template DON molecule. Atomic force microscope SPR analysis showed that the MIPPy film was deposited homogeneously on the Au surface, with a thickness of 5 nm. The MIPPy–SPR sensor exhibited a linear response for the detection of DON in the range of 0.1–100 ng/mL (R2 = 0.988). The selectivity efficiency of the MIPPy film for DON and its acetylated analogs 3-ADON and 15-ADON was 100, 19, and 44%, respectively. The limit of detection for DON with the MIPPy–SPR for a standard solution was estimated at >1 ng/mL. These results suggest that the combination of SPR sensing with a MIPPy film as a synthetic receptor can be used to detect DON. Full article
(This article belongs to the Section Chemical Sensors)
Open AccessArticle
Ethanol Vapor Sensing Properties of Triangular Silver Nanostructures Based on Localized Surface Plasmon Resonance
Sensors 2011, 11(9), 8643-8653; https://doi.org/10.3390/s110908643
Received: 25 July 2011 / Revised: 28 August 2011 / Accepted: 31 August 2011 / Published: 5 September 2011
Cited by 32 | Viewed by 4255 | PDF Full-text (1286 KB) | HTML Full-text | XML Full-text
Abstract
A sensitive volatile organic vapor sensor based on the LSPR properties of silver triangular nanoprisms is proposed in this paper. The triangular nanoprisms were fabricated by a nanosphere lithography (NSL) method. They have sharp vertices and edges, and are arranged in an ideal [...] Read more.
A sensitive volatile organic vapor sensor based on the LSPR properties of silver triangular nanoprisms is proposed in this paper. The triangular nanoprisms were fabricated by a nanosphere lithography (NSL) method. They have sharp vertices and edges, and are arranged in an ideal hexangular array. These characteristics ensure that they exhibit an excellent LSPR spectrum and a high sensitivity to the exterior environment changes. The LSPR spectra responding to ethanol vapor and four other volatile organic vapors—acetone, benzene, hexane and propanol—were measured with a UV-vis spectrometer in real time. Compared with the other four vapors, ethanol exhibits the highest sensitivity (~0.1 nm/mg L−1) and the lowest detection limit (~10 mg/L) in the spectral tests. The ethanol vapor test process is also fast (~4 s) and reversible. These insights demonstrate that the triangular nanoprism based nano-sensor can be used in ethanol vapor detection applications. Full article
(This article belongs to the Section Chemical Sensors)
Open AccessArticle
Artificial Skin Ridges Enhance Local Tactile Shape Discrimination
Sensors 2011, 11(9), 8626-8642; https://doi.org/10.3390/s110908626
Received: 9 August 2011 / Revised: 31 August 2011 / Accepted: 2 September 2011 / Published: 5 September 2011
Cited by 20 | Viewed by 4849 | PDF Full-text (443 KB) | HTML Full-text | XML Full-text
Abstract
One of the fundamental requirements for an artificial hand to successfully grasp and manipulate an object is to be able to distinguish different objects’ shapes and, more specifically, the objects’ surface curvatures. In this study, we investigate the possibility of enhancing the curvature [...] Read more.
One of the fundamental requirements for an artificial hand to successfully grasp and manipulate an object is to be able to distinguish different objects’ shapes and, more specifically, the objects’ surface curvatures. In this study, we investigate the possibility of enhancing the curvature detection of embedded tactile sensors by proposing a ridged fingertip structure, simulating human fingerprints. In addition, a curvature detection approach based on machine learning methods is proposed to provide the embedded sensors with the ability to discriminate the surface curvature of different objects. For this purpose, a set of experiments were carried out to collect tactile signals from a 2 × 2 tactile sensor array, then the signals were processed and used for learning algorithms. To achieve the best possible performance for our machine learning approach, three different learning algorithms of Naïve Bayes (NB), Artificial Neural Networks (ANN), and Support Vector Machines (SVM) were implemented and compared for various parameters. Finally, the most accurate method was selected to evaluate the proposed skin structure in recognition of three different curvatures. The results showed an accuracy rate of 97.5% in surface curvature discrimination. Full article
(This article belongs to the Special Issue Biomimetic Sensors, Actuators and Integrated Systems)
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Open AccessArticle
Conductometric Sensors for Monitoring Degradation of Automotive Engine Oil
Sensors 2011, 11(9), 8611-8625; https://doi.org/10.3390/s110908611
Received: 16 July 2011 / Revised: 31 August 2011 / Accepted: 1 September 2011 / Published: 5 September 2011
Cited by 22 | Viewed by 4184 | PDF Full-text (1019 KB) | HTML Full-text | XML Full-text
Abstract
Conductometric sensors have been fabricated by applying imprinted polymers as receptors for monitoring engine oil quality. Titania and silica layers are synthesized via the sol-gel technique and used as recognition materials for acidic components present in used lubricating oil. Thin-film gold electrodes forming [...] Read more.
Conductometric sensors have been fabricated by applying imprinted polymers as receptors for monitoring engine oil quality. Titania and silica layers are synthesized via the sol-gel technique and used as recognition materials for acidic components present in used lubricating oil. Thin-film gold electrodes forming an interdigitated structure are used as transducers to measure the conductance of polymer coatings. Optimization of layer composition is carried out by varying the precursors, e.g., dimethylaminopropyltrimethoxysilane (DMAPTMS), and aminopropyl-triethoxysilane (APTES). Characterization of these sensitive materials is performed by testing against oil oxidation products, e.g., carbonic acids. The results depict that imprinted aminopropyltriethoxysilane (APTES) polymer is a promising candidate for detecting the age of used lubricating oil. In the next strategy, polyurethane-nanotubes composite as sensitive material is synthesized, producing appreciable differentiation pattern between fresh and used oils at elevated temperature with enhanced sensitivity. Full article
(This article belongs to the Section Chemical Sensors)
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