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Sensors, Volume 10, Issue 5 (May 2010) , Pages 4180-5293

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Open AccessArticle A Bayesian Framework for Human Body Pose Tracking from Depth Image Sequences
Sensors 2010, 10(5), 5280-5293; https://doi.org/10.3390/s100505280
Received: 7 April 2010 / Revised: 19 May 2010 / Accepted: 20 May 2010 / Published: 25 May 2010
Cited by 29 | Viewed by 6840 | PDF Full-text (1855 KB) | HTML Full-text | XML Full-text
Abstract
This paper addresses the problem of accurate and robust tracking of 3D human body pose from depth image sequences. Recovering the large number of degrees of freedom in human body movements from a depth image sequence is challenging due to the need to [...] Read more.
This paper addresses the problem of accurate and robust tracking of 3D human body pose from depth image sequences. Recovering the large number of degrees of freedom in human body movements from a depth image sequence is challenging due to the need to resolve the depth ambiguity caused by self-occlusions and the difficulty to recover from tracking failure. Human body poses could be estimated through model fitting using dense correspondences between depth data and an articulated human model (local optimization method). Although it usually achieves a high accuracy due to dense correspondences, it may fail to recover from tracking failure. Alternately, human pose may be reconstructed by detecting and tracking human body anatomical landmarks (key-points) based on low-level depth image analysis. While this method (key-point based method) is robust and recovers from tracking failure, its pose estimation accuracy depends solely on image-based localization accuracy of key-points. To address these limitations, we present a flexible Bayesian framework for integrating pose estimation results obtained by methods based on key-points and local optimization. Experimental results are shown and performance comparison is presented to demonstrate the effectiveness of the proposed approach. Full article
(This article belongs to the Special Issue Motion Detectors)
Open AccessArticle Basic Test Framework for the Evaluation of Text Line Segmentation and Text Parameter Extraction
Sensors 2010, 10(5), 5263-5279; https://doi.org/10.3390/s100505263
Received: 9 April 2010 / Revised: 13 May 2010 / Accepted: 14 May 2010 / Published: 25 May 2010
Cited by 21 | Viewed by 5690 | PDF Full-text (360 KB) | HTML Full-text | XML Full-text
Abstract
Text line segmentation is an essential stage in off-line optical character recognition (OCR) systems. It is a key because inaccurately segmented text lines will lead to OCR failure. Text line segmentation of handwritten documents is a complex and diverse problem, complicated by the [...] Read more.
Text line segmentation is an essential stage in off-line optical character recognition (OCR) systems. It is a key because inaccurately segmented text lines will lead to OCR failure. Text line segmentation of handwritten documents is a complex and diverse problem, complicated by the nature of handwriting. Hence, text line segmentation is a leading challenge in handwritten document image processing. Due to inconsistencies in measurement and evaluation of text segmentation algorithm quality, some basic set of measurement methods is required. Currently, there is no commonly accepted one and all algorithm evaluation is custom oriented. In this paper, a basic test framework for the evaluation of text feature extraction algorithms is proposed. This test framework consists of a few experiments primarily linked to text line segmentation, skew rate and reference text line evaluation. Although they are mutually independent, the results obtained are strongly cross linked. In the end, its suitability for different types of letters and languages as well as its adaptability are its main advantages. Thus, the paper presents an efficient evaluation method for text analysis algorithms. Full article
(This article belongs to the Section Chemical Sensors)
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Open AccessArticle NEURON: Enabling Autonomicity in Wireless Sensor Networks
Sensors 2010, 10(5), 5233-5262; https://doi.org/10.3390/s100505233
Received: 1 February 2010 / Revised: 1 April 2010 / Accepted: 14 May 2010 / Published: 25 May 2010
Cited by 7 | Viewed by 10049 | PDF Full-text (991 KB) | HTML Full-text | XML Full-text
Abstract
Future Wireless Sensor Networks (WSNs) will be ubiquitous, large-scale networks interconnected with the existing IP infrastructure. Autonomic functionalities have to be designed in order to reduce the complexity of their operation and management, and support the dissemination of knowledge within a WSN. In [...] Read more.
Future Wireless Sensor Networks (WSNs) will be ubiquitous, large-scale networks interconnected with the existing IP infrastructure. Autonomic functionalities have to be designed in order to reduce the complexity of their operation and management, and support the dissemination of knowledge within a WSN. In this paper a novel protocol for energy efficient deployment, clustering and routing in WSNs is proposed that focuses on the incorporation of autonomic functionalities in the existing approaches. The design of the protocol facilitates the design of innovative applications and services that are based on overlay topologies created through cooperation among the sensor nodes. Full article
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Open AccessArticle Estimation of Visual Maps with a Robot Network Equipped with Vision Sensors
Sensors 2010, 10(5), 5209-5232; https://doi.org/10.3390/s100505209
Received: 11 February 2010 / Revised: 31 March 2010 / Accepted: 14 April 2010 / Published: 25 May 2010
Cited by 19 | Viewed by 7385 | PDF Full-text (2746 KB) | HTML Full-text | XML Full-text
Abstract
In this paper we present an approach to the Simultaneous Localization and Mapping (SLAM) problem using a team of autonomous vehicles equipped with vision sensors. The SLAM problem considers the case in which a mobile robot is equipped with a particular sensor, moves [...] Read more.
In this paper we present an approach to the Simultaneous Localization and Mapping (SLAM) problem using a team of autonomous vehicles equipped with vision sensors. The SLAM problem considers the case in which a mobile robot is equipped with a particular sensor, moves along the environment, obtains measurements with its sensors and uses them to construct a model of the space where it evolves. In this paper we focus on the case where several robots, each equipped with its own sensor, are distributed in a network and view the space from different vantage points. In particular, each robot is equipped with a stereo camera that allow the robots to extract visual landmarks and obtain relative measurements to them. We propose an algorithm that uses the measurements obtained by the robots to build a single accurate map of the environment. The map is represented by the three-dimensional position of the visual landmarks. In addition, we consider that each landmark is accompanied by a visual descriptor that encodes its visual appearance. The solution is based on a Rao-Blackwellized particle filter that estimates the paths of the robots and the position of the visual landmarks. The validity of our proposal is demonstrated by means of experiments with a team of real robots in a office-like indoor environment. Full article
(This article belongs to the Special Issue Intelligent Sensors - 2010)
Open AccessArticle A Reusable PZT Transducer for Monitoring Initial Hydration and Structural Health of Concrete
Sensors 2010, 10(5), 5193-5208; https://doi.org/10.3390/s100505193
Received: 19 March 2010 / Revised: 18 May 2010 / Accepted: 18 May 2010 / Published: 25 May 2010
Cited by 54 | Viewed by 5628 | PDF Full-text (827 KB) | HTML Full-text | XML Full-text
Abstract
During the construction of a concrete structure, strength monitoring is important to ensure the safety of both personnel and the structure. Furthermore, to increase the efficiency of in situ casting or precast of concrete, determining the optimal time of demolding is important for [...] Read more.
During the construction of a concrete structure, strength monitoring is important to ensure the safety of both personnel and the structure. Furthermore, to increase the efficiency of in situ casting or precast of concrete, determining the optimal time of demolding is important for concrete suppliers. Surface bonded lead zirconate titanate (PZT) transducers have been used for damage detection and parameter identification for various engineering structures over the last two decades. In this work, a reusable PZT transducer setup for monitoring initial hydration of concrete and structural health is developed, where a piece of PZT is bonded to an enclosure with two bolts tightened inside the holes drilled in the enclosure. An impedance analyzer is used to acquire the admittance signatures of the PZT. Root mean square deviation (RMSD) is employed to associate the change in concrete strength with changes in the PZT admittance signatures. The results show that the reusable setup is able to effectively monitor the initial hydration of concrete and the structural health. It can also be detached from the concrete for future re-use. Full article
(This article belongs to the Special Issue Advances in Transducers)
Open AccessReview Location Estimation in Wireless Sensor Networks Using Spring-Relaxation Technique
Sensors 2010, 10(5), 5171-5192; https://doi.org/10.3390/s100505171
Received: 25 March 2010 / Revised: 15 April 2010 / Accepted: 10 May 2010 / Published: 25 May 2010
Cited by 15 | Viewed by 10525 | PDF Full-text (327 KB) | HTML Full-text | XML Full-text
Abstract
Accurate and low-cost autonomous self-localization is a critical requirement of various applications of a large-scale distributed wireless sensor network (WSN). Due to its massive deployment of sensors, explicit measurements based on specialized localization hardware such as the Global Positioning System (GPS) is not [...] Read more.
Accurate and low-cost autonomous self-localization is a critical requirement of various applications of a large-scale distributed wireless sensor network (WSN). Due to its massive deployment of sensors, explicit measurements based on specialized localization hardware such as the Global Positioning System (GPS) is not practical. In this paper, we propose a low-cost WSN localization solution. Our design uses received signal strength indicators for ranging, light weight distributed algorithms based on the spring-relaxation technique for location computation, and the cooperative approach to achieve certain location estimation accuracy with a low number of nodes with known locations. We provide analysis to show the suitability of the spring-relaxation technique for WSN localization with cooperative approach, and perform simulation experiments to illustrate its accuracy in localization. Full article
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Open AccessArticle A Highly Sensitive Enzyme-Amplified Immunosensor Based on a Nanoporous Niobium Oxide (Nb2O5) Electrode
Sensors 2010, 10(5), 5160-5170; https://doi.org/10.3390/s100505160
Received: 26 March 2010 / Revised: 13 April 2010 / Accepted: 10 May 2010 / Published: 25 May 2010
Cited by 11 | Viewed by 5593 | PDF Full-text (1033 KB) | HTML Full-text | XML Full-text
Abstract
We report on the development of an enzyme-amplified sandwich-type immunosensor based on a thin gold film sputtered on an anodic nanoporous niobium oxide ([email protected]2O5) electrode. The electrocatalytic activity of enzymatically amplified electroactive species and a stable electrode consisting of [...] Read more.
We report on the development of an enzyme-amplified sandwich-type immunosensor based on a thin gold film sputtered on an anodic nanoporous niobium oxide ([email protected]2O5) electrode. The electrocatalytic activity of enzymatically amplified electroactive species and a stable electrode consisting of [email protected]2O5 were used to obtain a powerful signal amplification of the electrochemical immunobiosensor. The method using this electrochemical biosensor based on an [email protected]2O5 electrode provides a much better performance than those based on conventional bulk gold or niobium oxide electrodes. Our novel approach does not require any time-consuming cleaning steps to yield reproducible electrochemical signals. In addition, the strong adhesion of gold films on the niobium oxide electrodes offers a very stable substrate during electrochemical biosensing. Cyclic voltammetry measurements indicate that non-specific binding of proteins to the modified [email protected]2O5 surface is sufficiently low to be ignored in the case of our novel system. Finally, we demonstrated the ability of the biosensor based on an [email protected]2O5 offering the enhanced performance with a high resolution and sensitivity. Therefore, it is expected that the biosensor based on an [email protected]2O5 has great potential for highly efficient biological devices. Full article
(This article belongs to the Special Issue Immunosensors)
Open AccessReview Carbon Nanostructure-Based Field-Effect Transistors for Label-Free Chemical/Biological Sensors
Sensors 2010, 10(5), 5133-5159; https://doi.org/10.3390/s100505133
Received: 23 March 2010 / Revised: 15 April 2010 / Accepted: 5 May 2010 / Published: 25 May 2010
Cited by 97 | Viewed by 10649 | PDF Full-text (887 KB) | HTML Full-text | XML Full-text
Abstract
Over the past decade, electrical detection of chemical and biological species using novel nanostructure-based devices has attracted significant attention for chemical, genomics, biomedical diagnostics, and drug discovery applications. The use of nanostructured devices in chemical/biological sensors in place of conventional sensing technologies has [...] Read more.
Over the past decade, electrical detection of chemical and biological species using novel nanostructure-based devices has attracted significant attention for chemical, genomics, biomedical diagnostics, and drug discovery applications. The use of nanostructured devices in chemical/biological sensors in place of conventional sensing technologies has advantages of high sensitivity, low decreased energy consumption and potentially highly miniaturized integration. Owing to their particular structure, excellent electrical properties and high chemical stability, carbon nanotube and graphene based electrical devices have been widely developed for high performance label-free chemical/biological sensors. Here, we review the latest developments of carbon nanostructure-based transistor sensors in ultrasensitive detection of chemical/biological entities, such as poisonous gases, nucleic acids, proteins and cells. Full article
(This article belongs to the Special Issue State-of-the-Art Sensors Technology in the UK)
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Open AccessReview Sonochemically Fabricated Microelectrode Arrays for Use as Sensing Platforms
Sensors 2010, 10(5), 5090-5132; https://doi.org/10.3390/s100505090
Received: 26 January 2010 / Revised: 15 April 2010 / Accepted: 27 April 2010 / Published: 25 May 2010
Cited by 8 | Viewed by 7955 | PDF Full-text (1301 KB) | HTML Full-text | XML Full-text
Abstract
The development, manufacture, modification and subsequent utilisation of sonochemically-formed microelectrode arrays is described for a range of applications. Initial fabrication of the sensing platform utilises ultrasonic ablation of electrochemically insulating polymers deposited upon conductive carbon substrates, forming an array of up to 70,000 [...] Read more.
The development, manufacture, modification and subsequent utilisation of sonochemically-formed microelectrode arrays is described for a range of applications. Initial fabrication of the sensing platform utilises ultrasonic ablation of electrochemically insulating polymers deposited upon conductive carbon substrates, forming an array of up to 70,000 microelectrode pores cm–2. Electrochemical and optical analyses using these arrays, their enhanced signal response and stir-independence area are all discussed. The growth of conducting polymeric “mushroom” protrusion arrays with entrapped biological entities, thereby forming biosensors is detailed. The simplicity and inexpensiveness of this approach, lending itself ideally to mass fabrication coupled with unrivalled sensitivity and stir independence makes commercial viability of this process a reality. Application of microelectrode arrays as functional components within sensors include devices for detection of chlorine, glucose, ethanol and pesticides. Immunosensors based on microelectrode arrays are described within this monograph for antigens associated with prostate cancer and transient ischemic attacks (strokes). Full article
(This article belongs to the Special Issue State-of-the-Art Sensors Technology in the UK)
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Open AccessArticle Characterization of Mixed xWO3(1-x)Y2O3 Nanoparticle Thick Film for Gas Sensing Application
Sensors 2010, 10(5), 5074-5089; https://doi.org/10.3390/s100505074
Received: 29 March 2010 / Revised: 27 April 2010 / Accepted: 28 April 2010 / Published: 25 May 2010
Cited by 14 | Viewed by 6377 | PDF Full-text (889 KB) | HTML Full-text | XML Full-text
Abstract
Microstructural, topology, inner morphology, and gas-sensitivity of mixed xWO3(1-x)Y2O3 nanoparticles (x = 1, 0.95, 0.9, 0.85, 0.8) thick-film semiconductor gas sensors were studied. The surface topography and inner morphological properties of the mixed powder [...] Read more.
Microstructural, topology, inner morphology, and gas-sensitivity of mixed xWO3(1-x)Y2O3 nanoparticles (x = 1, 0.95, 0.9, 0.85, 0.8) thick-film semiconductor gas sensors were studied. The surface topography and inner morphological properties of the mixed powder and sensing film were characterized with X-ray diffraction (XRD), atomic force microscopy (AFM), transmission electron microscopy (TEM), and scanning electron microscopy (SEM). Also, gas sensitivity properties of the printed films were evaluated in the presence of methane (CH4) and butane (C4H10) at up to 500 °C operating temperature of the sensor. The results show that the doping agent can modify some structural properties and gas sensitivity of the mixed powder. Full article
(This article belongs to the Section Chemical Sensors)
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Open AccessArticle Novel Microwave-Assisted Synthesis of Poly(D,L-lactide): The Influence of Monomer/Initiator Molar Ratio on the Product Properties
Sensors 2010, 10(5), 5063-5073; https://doi.org/10.3390/s100505063
Received: 29 March 2010 / Revised: 26 April 2010 / Accepted: 28 April 2010 / Published: 20 May 2010
Cited by 34 | Viewed by 6617 | PDF Full-text (894 KB) | HTML Full-text | XML Full-text
Abstract
Poly(D,L-lactide) synthesis using tin(II) 2-ethylhexanoate initiated ring-opening polymerization (ROP) takes over 30 hours in bulk at 120 °C. The use of microwave makes the same bulk polymerization process with the same initiator much faster and energy saving, with a reaction time of about [...] Read more.
Poly(D,L-lactide) synthesis using tin(II) 2-ethylhexanoate initiated ring-opening polymerization (ROP) takes over 30 hours in bulk at 120 °C. The use of microwave makes the same bulk polymerization process with the same initiator much faster and energy saving, with a reaction time of about 30 minutes at 100 °C. Here, the poly(lactide) synthesis was done in a microwave reactor, using frequency of 2.45 GHz and maximal power of 150 W. The reaction temperature was controlled via infra-red system for in-bulk-measuring, and was maintained at 100 °C. Different molar ratios of monomer and initiator, [M]/[I], of 1,000, 5,000 and 10,000 were used. The achieved average molar masses for the obtained polymers (determined by gel permeation chromatography) were in the interval from 26,700 to 112,500 g/mol. The polydispersion index was from 2.436 to 3.425. For applicative purposes, the obtained material was purified during the procedure of microsphere preparation. Microspheres were obtained by spraying a fine fog of polymer (D,L-lactide) solution in tetrahydrofuran into the water solution of poly(vinyl alcohol) with intensive stirring. Full article
(This article belongs to the Section Chemical Sensors)
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Open AccessArticle A Flexible Proximity Sensor Fully Fabricated by Inkjet Printing
Sensors 2010, 10(5), 5054-5062; https://doi.org/10.3390/s100505054
Received: 9 March 2010 / Revised: 11 May 2010 / Accepted: 14 May 2010 / Published: 19 May 2010
Cited by 46 | Viewed by 9673 | PDF Full-text (398 KB) | HTML Full-text | XML Full-text
Abstract
A flexible proximity sensor fully fabricated by inkjet printing is proposed in this paper. The flexible proximity sensor is composed of a ZnO layer sandwiched in between a flexible aluminum sheet and a web-shaped top electrode layer. The flexible aluminum sheet serves as [...] Read more.
A flexible proximity sensor fully fabricated by inkjet printing is proposed in this paper. The flexible proximity sensor is composed of a ZnO layer sandwiched in between a flexible aluminum sheet and a web-shaped top electrode layer. The flexible aluminum sheet serves as the bottom electrode. The material of the top electrode layer is nano silver. Both the ZnO and top electrode layers are deposited by inkjet printing. The fully inkjet printing process possesses the advantages of direct patterning and low-cost. It does not require photolithography and etching processes since the pattern is directly printed on the flexible aluminum sheet. The prototype demonstrates that the presented flexible sensor is sensitive to the human body. It may be applied to proximity sensing or thermal eradiation sensing. Full article
(This article belongs to the Section Chemical Sensors)
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Open AccessReview Transcriptional Regulation of Glucose Sensors in Pancreatic β-Cells and Liver: An Update
Sensors 2010, 10(5), 5031-5053; https://doi.org/10.3390/s100505031
Received: 1 February 2010 / Revised: 7 May 2010 / Accepted: 13 May 2010 / Published: 19 May 2010
Cited by 19 | Viewed by 7263 | PDF Full-text (709 KB) | HTML Full-text | XML Full-text
Abstract
Pancreatic β-cells and the liver play a key role in glucose homeostasis. After a meal or in a state of hyperglycemia, glucose is transported into the β-cells or hepatocytes where it is metabolized. In the β-cells, glucose is metabolized to increase the ATP:ADP [...] Read more.
Pancreatic β-cells and the liver play a key role in glucose homeostasis. After a meal or in a state of hyperglycemia, glucose is transported into the β-cells or hepatocytes where it is metabolized. In the β-cells, glucose is metabolized to increase the ATP:ADP ratio, resulting in the secretion of insulin stored in the vesicle. In the hepatocytes, glucose is metabolized to CO2, fatty acids or stored as glycogen. In these cells, solute carrier family 2 (SLC2A2) and glucokinase play a key role in sensing and uptaking glucose. Dysfunction of these proteins results in the hyperglycemia which is one of the characteristics of type 2 diabetes mellitus (T2DM). Thus, studies on the molecular mechanisms of their transcriptional regulations are important in understanding pathogenesis and combating T2DM. In this paper, we will review a recent update on the progress of gene regulation of glucose sensors in the liver and β-cells. Full article
(This article belongs to the Section Biosensors)
Open AccessEditorial Sensors: New Challenges in Spain
Sensors 2010, 10(5), 5028-5030; https://doi.org/10.3390/s100505028
Received: 6 April 2010 / Published: 19 May 2010
Viewed by 4840 | PDF Full-text (47 KB) | HTML Full-text | XML Full-text
Abstract
The main goal of this special issue was to explore sensor technology and its applications in Spain. It is well-known that a reciprocal interrelation exists between sensor technology and the demand for solutions to different problems. Indeed, when a new sensor is developed, [...] Read more.
The main goal of this special issue was to explore sensor technology and its applications in Spain. It is well-known that a reciprocal interrelation exists between sensor technology and the demand for solutions to different problems. Indeed, when a new sensor is developed, it offers a solution to a problem, but also if a problem requires a solution perhaps new sensors or technologies based on existing sensors could be developed. [...] Full article
(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Spain)
Open AccessArticle Low Light CMOS Contact Imager with an Integrated Poly-Acrylic Emission Filter for Fluorescence Detection
Sensors 2010, 10(5), 5014-5027; https://doi.org/10.3390/s100505014
Received: 18 March 2010 / Revised: 2 May 2010 / Accepted: 4 May 2010 / Published: 19 May 2010
Cited by 17 | Viewed by 7777 | PDF Full-text (281 KB) | HTML Full-text | XML Full-text
Abstract
This study presents the fabrication of a low cost poly-acrylic acid (PAA) based emission filter integrated with a low light CMOS contact imager for fluorescence detection. The process involves the use of PAA as an adhesive for the emission filter. The poly-acrylic solution [...] Read more.
This study presents the fabrication of a low cost poly-acrylic acid (PAA) based emission filter integrated with a low light CMOS contact imager for fluorescence detection. The process involves the use of PAA as an adhesive for the emission filter. The poly-acrylic solution was chosen due its optical transparent properties, adhesive properties, miscibility with polar protic solvents and most importantly its bio-compatibility with a biological environment. The emission filter, also known as an absorption filter, involves dissolving an absorbing specimen in a polar protic solvent and mixing it with the PAA to uniformly bond the absorbing specimen and harden the filter. The PAA is optically transparent in solid form and therefore does not contribute to the absorbance of light in the visible spectrum. Many combinations of absorbing specimen and polar protic solvents can be derived, yielding different filter characteristics in different parts of the spectrum. We report a specific combination as a first example of implementation of our technology. The filter reported has excitation in the green spectrum and emission in the red spectrum, utilizing the increased quantum efficiency of the photo sensitive sensor array. The thickness of the filter (20 μm) was chosen by calculating the desired SNR using Beer-Lambert’s law for liquids, Quantum Yield of the fluorophore and the Quantum Efficiency of the sensor array. The filters promising characteristics make it suitable for low light fluorescence detection. The filter was integrated with a fully functional low noise, low light CMOS contact imager and experimental results using fluorescence polystyrene micro-spheres are presented. Full article
(This article belongs to the Section Chemical Sensors)
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Open AccessArticle Diffused Matrix Format: A New Storage and Processing Format for Airborne Hyperspectral Sensor Images
Sensors 2010, 10(5), 4996-5013; https://doi.org/10.3390/s100504996
Received: 12 March 2010 / Revised: 27 April 2010 / Accepted: 6 May 2010 / Published: 18 May 2010
Cited by 4 | Viewed by 8584 | PDF Full-text (1305 KB) | HTML Full-text | XML Full-text
Abstract
At present, hyperspectral images are mainly obtained with airborne sensors that are subject to turbulences while the spectrometer is acquiring the data. Therefore, geometric corrections are required to produce spatially correct images for visual interpretation and change detection analysis. This paper analyzes the [...] Read more.
At present, hyperspectral images are mainly obtained with airborne sensors that are subject to turbulences while the spectrometer is acquiring the data. Therefore, geometric corrections are required to produce spatially correct images for visual interpretation and change detection analysis. This paper analyzes the data acquisition process of airborne sensors. The main objective is to propose a new data format called Diffused Matrix Format (DMF) adapted to the sensor's characteristics including its spectral and spatial information. The second objective is to compare the accuracy of the quantitative maps derived by using the DMF data structure with those obtained from raster images based on traditional data structures. Results show that DMF processing is more accurate and straightforward than conventional image processing of remotely sensed data with the advantage that the DMF file structure requires less storage space than other data formats. In addition the data processing time does not increase when DMF is used. Full article
(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Spain)
Open AccessArticle Detecting Nano-Scale Vibrations in Rotating Devices by Using Advanced Computational Methods
Sensors 2010, 10(5), 4983-4995; https://doi.org/10.3390/s100504983
Received: 3 March 2010 / Revised: 27 April 2010 / Accepted: 6 May 2010 / Published: 18 May 2010
Cited by 2 | Viewed by 6654 | PDF Full-text (730 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents a computational method for detecting vibrations related to eccentricity in ultra precision rotation devices used for nano-scale manufacturing. The vibration is indirectly measured via a frequency domain analysis of the signal from a piezoelectric sensor attached to the stationary component [...] Read more.
This paper presents a computational method for detecting vibrations related to eccentricity in ultra precision rotation devices used for nano-scale manufacturing. The vibration is indirectly measured via a frequency domain analysis of the signal from a piezoelectric sensor attached to the stationary component of the rotating device. The algorithm searches for particular harmonic sequences associated with the eccentricity of the device rotation axis. The detected sequence is quantified and serves as input to a regression model that estimates the eccentricity. A case study presents the application of the computational algorithm during precision manufacturing processes. Full article
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Open AccessArticle Testing ZigBee Motes for Monitoring Refrigerated Vegetable Transportation under Real Conditions
Sensors 2010, 10(5), 4968-4982; https://doi.org/10.3390/s100504968
Received: 23 March 2010 / Revised: 7 April 2010 / Accepted: 30 April 2010 / Published: 18 May 2010
Cited by 27 | Viewed by 9633 | PDF Full-text (639 KB) | HTML Full-text | XML Full-text
Abstract
Quality control and monitoring of perishable goods during transportation and delivery services is an increasing concern for producers, suppliers, transport decision makers and consumers. The major challenge is to ensure a continuous ‘cold chain’ from producer to consumer in order to guaranty prime [...] Read more.
Quality control and monitoring of perishable goods during transportation and delivery services is an increasing concern for producers, suppliers, transport decision makers and consumers. The major challenge is to ensure a continuous ‘cold chain’ from producer to consumer in order to guaranty prime condition of goods. In this framework, the suitability of ZigBee protocol for monitoring refrigerated transportation has been proposed by several authors. However, up to date there was not any experimental work performed under real conditions. Thus, the main objective of our experiment was to test wireless sensor motes based in the ZigBee/IEEE 802.15.4 protocol during a real shipment. The experiment was conducted in a refrigerated truck traveling through two countries (Spain and France) which means a journey of 1,051 kilometers. The paper illustrates the great potential of this type of motes, providing information about several parameters such as temperature, relative humidity, door openings and truck stops. Psychrometric charts have also been developed for improving the knowledge about water loss and condensation on the product during shipments. Full article
(This article belongs to the Section Chemical Sensors)
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Open AccessArticle Level Set Approach to Anisotropic Wet Etching of Silicon
Sensors 2010, 10(5), 4950-4967; https://doi.org/10.3390/s100504950
Received: 31 December 2009 / Revised: 8 April 2010 / Accepted: 13 April 2010 / Published: 17 May 2010
Cited by 23 | Viewed by 6980 | PDF Full-text (743 KB) | HTML Full-text | XML Full-text
Abstract
In this paper a methodology for the three dimensional (3D) modeling and simulation of the profile evolution during anisotropic wet etching of silicon based on the level set method is presented. Etching rate anisotropy in silicon is modeled taking into account full silicon [...] Read more.
In this paper a methodology for the three dimensional (3D) modeling and simulation of the profile evolution during anisotropic wet etching of silicon based on the level set method is presented. Etching rate anisotropy in silicon is modeled taking into account full silicon symmetry properties, by means of the interpolation technique using experimentally obtained values for the etching rates along thirteen principal and high index directions in KOH solutions. The resulting level set equations are solved using an open source implementation of the sparse field method (ITK library, developed in medical image processing community), extended for the case of non-convex Hamiltonians. Simulation results for some interesting initial 3D shapes, as well as some more practical examples illustrating anisotropic etching simulation in the presence of masks (simple square aperture mask, convex corner undercutting and convex corner compensation, formation of suspended structures) are shown also. The obtained results show that level set method can be used as an effective tool for wet etching process modeling, and that is a viable alternative to the Cellular Automata method which now prevails in the simulations of the wet etching process. Full article
(This article belongs to the Special Issue Modeling, Testing and Reliability Issues in MEMS Engineering - 2009)
Open AccessArticle Comparative Laser Spectroscopy Diagnostics for Ancient Metallic Artefacts Exposed to Environmental Pollution
Sensors 2010, 10(5), 4926-4949; https://doi.org/10.3390/s100504926
Received: 3 February 2010 / Revised: 29 April 2010 / Accepted: 4 May 2010 / Published: 14 May 2010
Cited by 18 | Viewed by 7267 | PDF Full-text (2048 KB) | HTML Full-text | XML Full-text
Abstract
Metal artworks are subjected to corrosion and oxidation processes due to reactive agents present in the air, water and in the ground that these objects have been in contact with for hundreds of years. This is the case for archaeological metals that are [...] Read more.
Metal artworks are subjected to corrosion and oxidation processes due to reactive agents present in the air, water and in the ground that these objects have been in contact with for hundreds of years. This is the case for archaeological metals that are recovered from excavation sites, as well as artefacts exposed to polluted air. Stabilization of the conservation state of these objects needs precise diagnostics of the accrued surface layers and identification of original, historical materials before further protective treatments, including safe laser cleaning of unwanted layers. This paper presents analyses of the chemical composition and stratigraphy of corrosion products with the use of laser induced breakdown spectroscopy (LIBS) and Raman spectroscopy. The discussion of the results is supported by material studies (SEM-EDS, XRF, ion-analyses). The tests were performed on several samples taken from original objects, including copper roofing from Wilanów Palace in Warsaw and Karol Poznański Palace in Łódź, bronze decorative figures from the Wilanów Palace gardens, and four archaeological examples of old jewellery (different copper alloys). Work has been performed as a part of the MATLAS project in the frames of EEA and Norway Grants (www.matlas.eu) and the results enable the comparison of the methodology and to elaborate the joint diagnostic procedures of the three project partner independent laboratories. Full article
(This article belongs to the Special Issue Laser Spectroscopy and Sensing)
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Open AccessReview Effect of Atmospheric Conditions on LIBS Spectra
Sensors 2010, 10(5), 4907-4925; https://doi.org/10.3390/s100504907
Received: 30 March 2010 / Revised: 4 May 2010 / Accepted: 10 May 2010 / Published: 14 May 2010
Cited by 91 | Viewed by 9744 | PDF Full-text (1294 KB) | HTML Full-text | XML Full-text
Abstract
Laser-induced breakdown spectroscopy (LIBS) is typically performed at ambient Earth atmospheric conditions. However, interest in LIBS in other atmospheric conditions has increased in recent years, especially for use in space exploration (e.g., Mars and Lunar) or to improve resolution for isotopic signatures. This [...] Read more.
Laser-induced breakdown spectroscopy (LIBS) is typically performed at ambient Earth atmospheric conditions. However, interest in LIBS in other atmospheric conditions has increased in recent years, especially for use in space exploration (e.g., Mars and Lunar) or to improve resolution for isotopic signatures. This review focuses on what has been reported about the performance of LIBS in reduced pressure environments as well as in various gases other than air. Full article
(This article belongs to the Special Issue Laser Spectroscopy and Sensing)
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Open AccessCommunication High Sensitivity Carbon Nanotubes Flow-Rate Sensors and Their Performance Improvement by Coating
Sensors 2010, 10(5), 4898-4906; https://doi.org/10.3390/s100504898
Received: 26 March 2010 / Revised: 17 April 2010 / Accepted: 25 April 2010 / Published: 14 May 2010
Cited by 8 | Viewed by 5683 | PDF Full-text (473 KB) | HTML Full-text | XML Full-text
Abstract
A new type of hot-wire flow-rate sensor (HWFS) with a sensing element made of a macro-sized carbon nanotube (CNT) strand is presented in this study. An effective way to improve repeatability of the CNT flow-rate sensor by coating a layer of Al2 [...] Read more.
A new type of hot-wire flow-rate sensor (HWFS) with a sensing element made of a macro-sized carbon nanotube (CNT) strand is presented in this study. An effective way to improve repeatability of the CNT flow-rate sensor by coating a layer of Al2O3 on the CNT surface is proposed. Experimental results show that due to the large surface-to-volume ratio and thin coated Al2O3 layer, the CNT flow-rate sensor has higher sensitivity and faster response than a conventional platinum (Pt) HWFS. It is also demonstrated that the covered CNT flow-rate sensor has better repeatability than its bare counterpart due to insulation from the surrounding environment. The proposed CNT flow-rate sensor shows application potential for high-sensitivity measurement of flow rate. Full article
(This article belongs to the Section Chemical Sensors)
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Open AccessArticle Solvent Vapour Detection with Cholesteric Liquid Crystals—Optical and Mass-Sensitive Evaluation of the Sensor Mechanism
Sensors 2010, 10(5), 4887-4897; https://doi.org/10.3390/s100504887
Received: 18 March 2010 / Revised: 4 May 2010 / Accepted: 6 May 2010 / Published: 12 May 2010
Cited by 40 | Viewed by 6234 | PDF Full-text (203 KB) | HTML Full-text | XML Full-text
Abstract
Cholesteric liquid crystals (CLCs) are used as sensitive coatings for the detection of organic solvent vapours for both polar and non-polar substances. The incorporation of different analyte vapours in the CLC layers disturbs the pitch length which changes the optical properties, i.e., [...] Read more.
Cholesteric liquid crystals (CLCs) are used as sensitive coatings for the detection of organic solvent vapours for both polar and non-polar substances. The incorporation of different analyte vapours in the CLC layers disturbs the pitch length which changes the optical properties, i.e., shifting the absorption band. The engulfing of CLCs around non-polar solvent vapours such as tetrahedrofuran (THF), chloroform and tetrachloroethylene is favoured in comparison to polar ones, i.e., methanol and ethanol. Increasing solvent vapour concentrations shift the absorbance maximumto smaller wavelengths, e.g., as observed for THF. Additionally, CLCs have been coated on acoustic devices such as the quartz crystal microbalance (QCM) to measure the frequency shift of analyte samples at similar concentration levels. The mass effect for tetrachloroethylene was about six times higher than chloroform. Thus, optical response can be correlated with intercalation in accordance to mass detection. The mechanical stability was gained by combining CLCs with imprinted polymers. Therefore, pre-concentration of solvent vapours was performed leading to an additional selectivity. Full article
(This article belongs to the Section Chemical Sensors)
Open AccessReview A Comprehensive Review of Glucose Biosensors Based on Nanostructured Metal-Oxides
Sensors 2010, 10(5), 4855-4886; https://doi.org/10.3390/s100504855
Received: 11 March 2010 / Revised: 7 April 2010 / Accepted: 15 April 2010 / Published: 12 May 2010
Cited by 364 | Viewed by 16062 | PDF Full-text (656 KB) | HTML Full-text | XML Full-text
Abstract
Nanotechnology has opened new and exhilarating opportunities for exploring glucose biosensing applications of the newly prepared nanostructured materials. Nanostructured metal-oxides have been extensively explored to develop biosensors with high sensitivity, fast response times, and stability for the determination of glucose by electrochemical oxidation. [...] Read more.
Nanotechnology has opened new and exhilarating opportunities for exploring glucose biosensing applications of the newly prepared nanostructured materials. Nanostructured metal-oxides have been extensively explored to develop biosensors with high sensitivity, fast response times, and stability for the determination of glucose by electrochemical oxidation. This article concentrates mainly on the development of different nanostructured metal-oxide [such as ZnO, Cu(I)/(II) oxides, MnO2, TiO2, CeO2, SiO2, ZrO2, and other metal-oxides] based glucose biosensors. Additionally, we devote our attention to the operating principles (i.e., potentiometric, amperometric, impedimetric and conductometric) of these nanostructured metal-oxide based glucose sensors. Finally, this review concludes with a personal prospective and some challenges of these nanoscaled sensors. Full article
(This article belongs to the Special Issue Metal-Oxide Based Nanosensors)
Open AccessArticle Novel Feature Modelling the Prediction and Detection of sEMG Muscle Fatigue towards an Automated Wearable System
Sensors 2010, 10(5), 4838-4854; https://doi.org/10.3390/s100504838
Received: 22 April 2010 / Revised: 28 April 2010 / Accepted: 7 May 2010 / Published: 12 May 2010
Cited by 16 | Viewed by 6729 | PDF Full-text (1389 KB) | HTML Full-text | XML Full-text
Abstract
Surface Electromyography (sEMG) activity of the biceps muscle was recorded from ten subjects performing isometric contraction until fatigue. A novel feature (1D spectro_std) was used to extract the feature that modeled three classes of fatigue, which enabled the prediction and detection of fatigue. [...] Read more.
Surface Electromyography (sEMG) activity of the biceps muscle was recorded from ten subjects performing isometric contraction until fatigue. A novel feature (1D spectro_std) was used to extract the feature that modeled three classes of fatigue, which enabled the prediction and detection of fatigue. Initial results of class separation were encouraging, discriminating between the three classes of fatigue, a longitudinal classification on Non-Fatigue and Transition-to-Fatigue shows 81.58% correct classification with accuracy 0.74 of correct predictions while the longitudinal classification on Transition-to-Fatigue and Fatigue showed lower average correct classification of 66.51% with a positive classification accuracy 0.73 of correct prediction. Comparison of the 1D spectro_std with other sEMG fatigue features on the same dataset show a significant improvement in classification, where results show a significant 20.58% (p < 0.01) improvement when using the 1D spectro_std to classify Non-Fatigue and Transition-to-Fatigue. In classifying Transition-to-Fatigue and Fatigue results also show a significant improvement over the other features giving 8.14% (p < 0.05) on average of all compared features. Full article
(This article belongs to the Section Chemical Sensors)
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Open AccessArticle GPCA vs. PCA in Recognition and 3-D Localization of Ultrasound Reflectors
Sensors 2010, 10(5), 4825-4837; https://doi.org/10.3390/s100504825
Received: 25 February 2010 / Revised: 20 April 2010 / Accepted: 7 May 2010 / Published: 11 May 2010
Cited by 3 | Viewed by 7887 | PDF Full-text (341 KB) | HTML Full-text | XML Full-text
Abstract
In this paper, a new method of classification and localization of reflectors, using the time-of-flight (TOF) data obtained from ultrasonic transducers, is presented. The method of classification and localization is based on Generalized Principal Component Analysis (GPCA) applied to the TOF values obtained [...] Read more.
In this paper, a new method of classification and localization of reflectors, using the time-of-flight (TOF) data obtained from ultrasonic transducers, is presented. The method of classification and localization is based on Generalized Principal Component Analysis (GPCA) applied to the TOF values obtained from a sensor that contains four ultrasound emitters and 16 receivers. Since PCA works with vectorized representations of TOF, it does not take into account the spatial locality of receivers. The GPCA works with two-dimensional representations of TOF, taking into account information on the spatial position of the receivers. This report includes a detailed description of the method of classification and localization and the results of achieved tests with three types of reflectors in 3-D environments: planes, edges, and corners. The results in terms of processing time, classification and localization were very satisfactory for the reflectors located in the range of 50–350 cm. Full article
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Open AccessArticle Real Time Speed Estimation of Moving Vehicles from Side View Images from an Uncalibrated Video Camera
Sensors 2010, 10(5), 4805-4824; https://doi.org/10.3390/s100504805
Received: 28 December 2009 / Revised: 12 April 2010 / Accepted: 22 April 2010 / Published: 11 May 2010
Cited by 31 | Viewed by 9001 | PDF Full-text (575 KB) | HTML Full-text | XML Full-text
Abstract
In order to estimate the speed of a moving vehicle with side view camera images, velocity vectors of a sufficient number of reference points identified on the vehicle must be found using frame images. This procedure involves two main steps. In the first [...] Read more.
In order to estimate the speed of a moving vehicle with side view camera images, velocity vectors of a sufficient number of reference points identified on the vehicle must be found using frame images. This procedure involves two main steps. In the first step, a sufficient number of points from the vehicle is selected, and these points must be accurately tracked on at least two successive video frames. In the second step, by using the displacement vectors of the tracked points and passed time, the velocity vectors of those points are computed. Computed velocity vectors are defined in the video image coordinate system and displacement vectors are measured by the means of pixel units. Then the magnitudes of the computed vectors in image space should be transformed to the object space to find the absolute values of these magnitudes. This transformation requires an image to object space information in a mathematical sense that is achieved by means of the calibration and orientation parameters of the video frame images. This paper presents proposed solutions for the problems of using side view camera images mentioned here. Full article
(This article belongs to the Section Chemical Sensors)
Open AccessArticle A Multi-D-Shaped Optical Fiber for Refractive Index Sensing
Sensors 2010, 10(5), 4794-4804; https://doi.org/10.3390/s100504794
Received: 10 March 2010 / Revised: 29 March 2010 / Accepted: 14 April 2010 / Published: 11 May 2010
Cited by 51 | Viewed by 8158 | PDF Full-text (630 KB) | HTML Full-text | XML Full-text
Abstract
A novel class of multi-D-shaped optical fiber suited for refractive index measurements is presented. The multi-D-shaped optical fiber was constructed by forming several D-sections in a multimode optical fiber at localized regions with femtosecond laser pulses. The total number of D-shaped zones fabricated [...] Read more.
A novel class of multi-D-shaped optical fiber suited for refractive index measurements is presented. The multi-D-shaped optical fiber was constructed by forming several D-sections in a multimode optical fiber at localized regions with femtosecond laser pulses. The total number of D-shaped zones fabricated could range from three to seven. Each D-shaped zone covered a sensor volume of 100 μm depth, 250 μm width, and 1 mm length. The mean roughness of the core surface obtained by the AFM images was 231.7 nm, which is relatively smooth. Results of the tensile test indicated that the fibers have sufficient mechanical strength to resist damage from further processing. The multi-D-shaped optical fiber as a high sensitive refractive-index sensor to detect changes in the surrounding refractive index was studied. The results for different concentrations of sucrose solution show that a resolution of 1.27 × 103–3.13 × 10−4 RIU is achieved for refractive indices in the range of 1.333 to 1.403, suggesting that the multi-D-shaped fibers are attractive for chemical, biological, and biochemical sensing with aqueous solutions. Full article
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Open AccessArticle A Power-Efficient Bio-Potential Acquisition Device with DS-MDE Sensors for Long-Term Healthcare Monitoring Applications
Sensors 2010, 10(5), 4777-4793; https://doi.org/10.3390/s100504777
Received: 2 March 2010 / Revised: 21 April 2010 / Accepted: 27 April 2010 / Published: 11 May 2010
Cited by 15 | Viewed by 7773 | PDF Full-text (522 KB) | HTML Full-text | XML Full-text
Abstract
This work describes a power-efficient bio-potential acquisition device for long-term healthcare applications that is implemented using novel microelectromechanical dry electrodes (MDE) and a low power bio-potential processing chip. Using micromachining technology, an attempt is also made to enhance the sensing reliability and stability [...] Read more.
This work describes a power-efficient bio-potential acquisition device for long-term healthcare applications that is implemented using novel microelectromechanical dry electrodes (MDE) and a low power bio-potential processing chip. Using micromachining technology, an attempt is also made to enhance the sensing reliability and stability by fabricating a diamond-shaped MDE (DS-MDE) that has a satisfactory self-stability capability and superior electric conductivity when attached onto skin without any extra skin tissue injury technology. To acquire differential bio-potentials such as ECG signals, the proposed processing chip fabricated in a standard CMOS process has a high common mode rejection ratio (C.M.R.R.) differential amplifier and a 12-bit analog-to-digital converter (ADC). Use of the proposed system and integrate simple peripheral commercial devices can obtain the ECG signal efficiently without additional skin tissue injury and ensure continuous monitoring more than 70 hours with a 400 mAh battery. Full article
Open AccessArticle Fiber Bragg Grating Sensor to Monitor Stress Kinetics in Drying Process of Commercial Latex Paints
Sensors 2010, 10(5), 4761-4776; https://doi.org/10.3390/s100504761
Received: 3 February 2010 / Revised: 25 April 2010 / Accepted: 28 April 2010 / Published: 11 May 2010
Cited by 6 | Viewed by 6349 | PDF Full-text (565 KB) | HTML Full-text | XML Full-text
Abstract
In this paper, we report a study about the application of packaged fiber Bragg gratings used as strain sensors to monitor the stress kinetics during the drying process of commercial latex paints. Three stages of drying with distinct mechanical deformation and temporal behaviors [...] Read more.
In this paper, we report a study about the application of packaged fiber Bragg gratings used as strain sensors to monitor the stress kinetics during the drying process of commercial latex paints. Three stages of drying with distinct mechanical deformation and temporal behaviors were identified for the samples, with mechanical deformation from 15 μm to 21 μm in the longitudinal film dimension on time intervals from 370 to 600 minutes. Drying time tests based on human sense technique described by the Brazilian Technical Standards NBR 9558 were also done. The results obtained shows that human sense technique has a limited perception of the drying process and that the optical measurement system proposed can be used to characterize correctly the dry-through stage of paint. The influence of solvent (water) addition in the drying process was also investigated. The paint was diluted with four parts paint and one part water (80% paint), and one part paint and one part water (50% paint). It was observed that the increase of the water ratio mixed into the paint decreases both the mechanical deformation magnitude and the paint dry-through time. Contraction of 5.2 μm and 10.4 μm were measured for concentrations of 50% and 80% of paint in the mixture, respectively. For both diluted paints the dry-through time was approximately 170 minutes less than undiluted paint. The optical technique proposed in this work can contribute to the development of new standards to specify the drying time of paint coatings. Full article
(This article belongs to the Special Issue Advances in Transducers)
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