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Sensors, Volume 11, Issue 11 (November 2011), Pages 10010-11035

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Editorial

Jump to: Research, Review, Other

Open AccessEditorial Bioinspired Sensor Systems
Sensors 2011, 11(11), 10180-10186; doi:10.3390/s111110180
Received: 21 October 2011 / Accepted: 21 October 2011 / Published: 26 October 2011
Cited by 7 | PDF Full-text (263 KB) | HTML Full-text | XML Full-text
Abstract
This editorial summarizes and classifies the contributions presented by different authors to the special issue of the journal Sensors dedicated to Bioinspired Sensor Systems. From the coupling of sensor arrays or networks, plus computer processing abilities, new applications to mimic or to [...] Read more.
This editorial summarizes and classifies the contributions presented by different authors to the special issue of the journal Sensors dedicated to Bioinspired Sensor Systems. From the coupling of sensor arrays or networks, plus computer processing abilities, new applications to mimic or to complement human senses are arising in the context of ambient intelligence. Principles used, and illustrative study cases have been presented permitting readers to grasp the current status of the field. Full article
(This article belongs to the Special Issue Bioinspired Sensor Systems)
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Research

Jump to: Editorial, Review, Other

Open AccessArticle Improving Prediction Accuracy for WSN Data Reduction by Applying Multivariate Spatio-Temporal Correlation
Sensors 2011, 11(11), 10010-10037; doi:10.3390/s111110010
Received: 18 August 2011 / Revised: 13 October 2011 / Accepted: 19 October 2011 / Published: 25 October 2011
Cited by 18 | PDF Full-text (637 KB) | HTML Full-text | XML Full-text
Abstract
This paper proposes a method based on multivariate spatial and temporal correlation to improve prediction accuracy in data reduction for Wireless Sensor Networks (WSN). Prediction of data not sent to the sink node is a technique used to save energy in WSNs [...] Read more.
This paper proposes a method based on multivariate spatial and temporal correlation to improve prediction accuracy in data reduction for Wireless Sensor Networks (WSN). Prediction of data not sent to the sink node is a technique used to save energy in WSNs by reducing the amount of data traffic. However, it may not be very accurate. Simulations were made involving simple linear regression and multiple linear regression functions to assess the performance of the proposed method. The results show a higher correlation between gathered inputs when compared to time, which is an independent variable widely used for prediction and forecasting. Prediction accuracy is lower when simple linear regression is used, whereas multiple linear regression is the most accurate one. In addition to that, our proposal outperforms some current solutions by about 50% in humidity prediction and 21% in light prediction. To the best of our knowledge, we believe that we are probably the first to address prediction based on multivariate correlation for WSN data reduction. Full article
(This article belongs to the Special Issue Collaborative Sensors)
Open AccessArticle Line-Monitoring, Hyperspectral Fluorescence Setup for Simultaneous Multi-Analyte Biosensing    
Sensors 2011, 11(11), 10038-10047; doi:10.3390/s111110038
Received: 5 September 2011 / Revised: 5 October 2011 / Accepted: 17 October 2011 / Published: 25 October 2011
Cited by 5 | PDF Full-text (626 KB) | HTML Full-text | XML Full-text
Abstract
Conventional fluorescence scanners utilize multiple filters to distinguish different fluorescent labels, and problems arise because of this filter-based mechanism. In this work we propose a line-monitoring, hyperspectral fluorescence technique which is designed and optimized for applications in multi-channel microfluidic systems. In contrast [...] Read more.
Conventional fluorescence scanners utilize multiple filters to distinguish different fluorescent labels, and problems arise because of this filter-based mechanism. In this work we propose a line-monitoring, hyperspectral fluorescence technique which is designed and optimized for applications in multi-channel microfluidic systems. In contrast to the filter-based mechanism, which only records fluorescent intensities, the hyperspectral technique records the full spectrum for every point on the sample plane. Multivariate data exploitation is then applied to spectra analysis to determine ratios of different fluorescent labels and eliminate unwanted artifacts. This sensor is designed to monitor multiple fluidic channels simultaneously, providing the potential for multi-analyte biosensing. The detection sensitivity is approximately 0.81 fluors/μm2, and this sensor is proved to act with a good homogeneity. Finally, a model experiment of detecting short oligonucleotides has demonstrated the biomedical application of this hyperspectral fluorescence biosensor. Full article
(This article belongs to the Special Issue Biochips)
Open AccessArticle A Grid-Based Distributed Event Detection Scheme for Wireless Sensor Networks
Sensors 2011, 11(11), 10048-10062; doi:10.3390/s111110048
Received: 18 August 2011 / Revised: 11 October 2011 / Accepted: 19 October 2011 / Published: 25 October 2011
Cited by 2 | PDF Full-text (258 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents a grid-based distributed event detection scheme for wireless sensor networks. The network is divided into square-shaped grids of predefined grid size, where sensor nodes in each grid form a cluster with a cluster head. Event detection at each grid [...] Read more.
This paper presents a grid-based distributed event detection scheme for wireless sensor networks. The network is divided into square-shaped grids of predefined grid size, where sensor nodes in each grid form a cluster with a cluster head. Event detection at each grid alone based on the readings of its member nodes is limited in event detection performance, especially for a small event region compared to the grid size. To improve the performance, each grid is further divided into 2 × 2 sub-grids of equal size. The decision on an event is made by finding a square region of 2 × 2 sub-grids, not necessarily in the same grid, that passed a predefined threshold. This process is conducted at each cluster head in a distributed manner by inter-cluster communications. Event detection is initiated when a cluster head receives an alarm from its member nodes. The cluster-head communicates with its neighboring cluster heads to exchange the number of nodes reporting an alarm. The threshold for event detection can be dynamically adjusted to reflect the number of sensor nodes in a grid and event size, if known. High event detection accuracy is achieved with a relatively low threshold without sacrificing false alarm rate by filtering most errors due to transient faults and isolating nodes with permanent faults. Experimental results show that the proposed scheme can achieve high detection accuracy, while maintaining low false alarm rate. Full article
(This article belongs to the Special Issue Collaborative Sensors)
Open AccessArticle Solid Phase Biosensors for Arsenic or Cadmium Composed of A trans Factor and cis Element Complex
Sensors 2011, 11(11), 10063-10073; doi:10.3390/s111110063
Received: 16 September 2011 / Revised: 18 October 2011 / Accepted: 24 October 2011 / Published: 25 October 2011
Cited by 7 | PDF Full-text (432 KB) | HTML Full-text | XML Full-text
Abstract
The presence of toxic metals in drinking water has hazardous effects on human health. This study was conducted to develop GFP-based-metal-binding biosensors for on-site assay of toxic metal ions. GFP-tagged ArsR and CadC proteins bound to a cis element, and lost the [...] Read more.
The presence of toxic metals in drinking water has hazardous effects on human health. This study was conducted to develop GFP-based-metal-binding biosensors for on-site assay of toxic metal ions. GFP-tagged ArsR and CadC proteins bound to a cis element, and lost the capability of binding to it in their As- and Cd-binding conformational states, respectively. Water samples containing toxic metals were incubated on a complex of GFP-tagged ArsR or CadC and cis element which was immobilized on a solid surface. Metal concentrations were quantified with fluorescence intensity of the metal-binding states released from the cis element. Fluorescence intensity obtained with the assay significantly increased with increasing concentrations of toxic metals. Detection limits of 1 μg/L for Cd(II) and 5 μg/L for As(III) in purified water and 10 µg/L for Cd(II) and As(III) in tap water and bottled mineral water were achieved by measurement with a battery-powered portable fluorometer after 15-min and 30-min incubation, respectively. A complex of freeze dried GFP-tagged ArsR or CadC binding to cis element was stable at 4 °C and responded to 5 μg/L As(III) or Cd(II). The solid phase biosensors are sensitive, less time-consuming, portable, and could offer a protocol for on-site evaluation of the toxic metals in drinking water. Full article
(This article belongs to the Section Biosensors)
Open AccessArticle Historical Building Monitoring Using an Energy-Efficient Scalable Wireless Sensor Network Architecture
Sensors 2011, 11(11), 10074-10093; doi:10.3390/s111110074
Received: 8 September 2011 / Revised: 18 October 2011 / Accepted: 24 October 2011 / Published: 25 October 2011
Cited by 7 | PDF Full-text (1384 KB) | HTML Full-text | XML Full-text
Abstract
We present a set of novel low power wireless sensor nodes designed for monitoring wooden masterpieces and historical buildings, in order to perform an early detection of pests. Although our previous star-based system configuration has been in operation for more than 13 [...] Read more.
We present a set of novel low power wireless sensor nodes designed for monitoring wooden masterpieces and historical buildings, in order to perform an early detection of pests. Although our previous star-based system configuration has been in operation for more than 13 years, it does not scale well for sensorization of large buildings or when deploying hundreds of nodes. In this paper we demonstrate the feasibility of a cluster-based dynamic-tree hierarchical Wireless Sensor Network (WSN) architecture where realistic assumptions of radio frequency data transmission are applied to cluster construction, and a mix of heterogeneous nodes are used to minimize economic cost of the whole system and maximize power saving of the leaf nodes. Simulation results show that the specialization of a fraction of the nodes by providing better antennas and some energy harvesting techniques can dramatically extend the life of the entire WSN and reduce the cost of the whole system. A demonstration of the proposed architecture with a new routing protocol and applied to termite pest detection has been implemented on a set of new nodes and should last for about 10 years, but it provides better scalability, reliability and deployment properties. Full article
(This article belongs to the Special Issue Microprocessors and System-on-Chip)
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Open AccessArticle A Novel Sensor-Assisted RFID-Based Indoor Tracking System for the Elderly Living Alone
Sensors 2011, 11(11), 10094-10113; doi:10.3390/s111110094
Received: 17 August 2011 / Revised: 18 October 2011 / Accepted: 21 October 2011 / Published: 25 October 2011
Cited by 9 | PDF Full-text (1022 KB) | HTML Full-text | XML Full-text
Abstract
The population of elderly people is increasing rapidly in many developed nations. Providing safe and comfortable care to aging people is an important social goal. Moreover, obtaining correct activity and location information for an elderly person is an important research goal. This [...] Read more.
The population of elderly people is increasing rapidly in many developed nations. Providing safe and comfortable care to aging people is an important social goal. Moreover, obtaining correct activity and location information for an elderly person is an important research goal. This work proposes a novel intelligent RFID-based indoor tracking system for elderly people living alone. The proposed system uses environment information for inhabitants and received signal strength of an RFID reader to estimate the probable location of an inhabitant. The proposed system then coordinates with the wireless sensor node of a three-axis accelerometer and uses a genetic algorithm to compute the location of the inhabitant. The proposed system also uses context and gait information to improve inhabitant-tracking accuracy. Experiment results show that the accuracy of the proposed system is better than that of existing RFID-based systems. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle Development of a Rapid Soil Water Content Detection Technique Using Active Infrared Thermal Methods for In-Field Applications
Sensors 2011, 11(11), 10114-10128; doi:10.3390/s111110114
Received: 8 September 2011 / Revised: 13 October 2011 / Accepted: 21 October 2011 / Published: 25 October 2011
Cited by 14 | PDF Full-text (451 KB) | HTML Full-text | XML Full-text
Abstract
The aim of this study was to investigate the suitability of active infrared thermography and thermometry in combination with multivariate statistical partial least squares analysis as rapid soil water content detection techniques both in the laboratory and the field. Such techniques allow [...] Read more.
The aim of this study was to investigate the suitability of active infrared thermography and thermometry in combination with multivariate statistical partial least squares analysis as rapid soil water content detection techniques both in the laboratory and the field. Such techniques allow fast soil water content measurements helpful in both agricultural and environmental fields. These techniques, based on the theory of heat dissipation, were tested by directly measuring temperature dynamic variation of samples after heating. For the assessment of temperature dynamic variations data were collected during three intervals (3, 6 and 10 s). To account for the presence of specific heats differences between water and soil, the analyses were regulated using slopes to linearly describe their trends. For all analyses, the best model was achieved for a 10 s slope. Three different approaches were considered, two in the laboratory and one in the field. The first laboratory-based one was centred on active infrared thermography, considered measurement of temperature variation as independent variable and reported r = 0.74. The second laboratory–based one was focused on active infrared thermometry, added irradiation as independent variable and reported r = 0.76. The in-field experiment was performed by active infrared thermometry, heating bare soil by solar irradiance after exposure due to primary tillage. Some meteorological parameters were inserted as independent variables in the prediction model, which presented r = 0.61. In order to obtain more general and wide estimations in-field a Partial Least Squares Discriminant Analysis on three classes of percentage of soil water content was performed obtaining a high correct classification in the test (88.89%). The prediction error values were lower in the field with respect to laboratory analyses. Both techniques could be used in conjunction with a Geographic Information System for obtaining detailed information on soil heterogeneity. Full article
(This article belongs to the Section Remote Sensors)
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Open AccessArticle Electrostatic Excitation for the Force Amplification of Microcantilever Sensors
Sensors 2011, 11(11), 10129-10142; doi:10.3390/s111110129
Received: 21 September 2011 / Revised: 17 October 2011 / Accepted: 17 October 2011 / Published: 25 October 2011
Cited by 2 | PDF Full-text (381 KB) | HTML Full-text | XML Full-text
Abstract
This paper describes an electrostatic excited microcantilever sensor operating in static mode that is more sensitive than traditional microcantilevers. The proposed sensor comprises a simple microcantilever with electrostatic excitation ability and an optical or piezoresistive detector. Initially the microcantilever is excited by [...] Read more.
This paper describes an electrostatic excited microcantilever sensor operating in static mode that is more sensitive than traditional microcantilevers. The proposed sensor comprises a simple microcantilever with electrostatic excitation ability and an optical or piezoresistive detector. Initially the microcantilever is excited by electrostatic force to near pull-in voltage. The nonlinear behavior of the microcantilever in near pull-in voltage i.e., the inverse-square relation between displacement and electrostatic force provides a novel method for force amplification. In this situation, any external load applied to the sensor will be amplified by electrostatic force leading to more displacement. We prove that the proposed microcantilever sensor can be 2 to 100 orders more sensitive compared with traditional microcantilevers sensors of the same dimensions. The results for surface stress and the free-end point force load are discussed. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle Unconstrained and Contactless Hand Geometry Biometrics
Sensors 2011, 11(11), 10143-10164; doi:10.3390/s111110143
Received: 6 September 2011 / Revised: 14 October 2011 / Accepted: 14 October 2011 / Published: 25 October 2011
Cited by 10 | PDF Full-text (1198 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents a hand biometric system for contact-less, platform-free scenarios, proposing innovative methods in feature extraction, template creation and template matching. The evaluation of the proposed method considers both the use of three contact-less publicly available hand databases, and the comparison [...] Read more.
This paper presents a hand biometric system for contact-less, platform-free scenarios, proposing innovative methods in feature extraction, template creation and template matching. The evaluation of the proposed method considers both the use of three contact-less publicly available hand databases, and the comparison of the performance to two competitive pattern recognition techniques existing in literature: namely Support Vector Machines (SVM) and k-Nearest Neighbour (k-NN). Results highlight the fact that the proposed method outcomes existing approaches in literature in terms of computational cost, accuracy in human identification, number of extracted features and number of samples for template creation. The proposed method is a suitable solution for human identification in contact-less scenarios based on hand biometrics, providing a feasible solution to devices with limited hardware requirements like mobile devices. Full article
(This article belongs to the Special Issue Hand-Based Biometrics Sensors and Systems)
Open AccessArticle Electrocatalytic Oxidation of Ascorbic Acid Using a Poly(aniline-co-m-ferrocenylaniline) Modified Glassy Carbon Electrode
Sensors 2011, 11(11), 10166-10179; doi:10.3390/s111110166
Received: 10 August 2011 / Revised: 19 September 2011 / Accepted: 24 October 2011 / Published: 26 October 2011
Cited by 6 | PDF Full-text (1433 KB) | HTML Full-text | XML Full-text
Abstract
A poly(aniline-co-m-ferrocenylaniline) was successfully synthesized on a glassy carbon electrode (GCE) by electrochemical copolymerization using a scan potential range from −0.3 to +0.9 V (vs. Ag/AgCl) in 0.5 M H2SO4 containing 30% acetonitrile (ACN), 0.1 [...] Read more.
A poly(aniline-co-m-ferrocenylaniline) was successfully synthesized on a glassy carbon electrode (GCE) by electrochemical copolymerization using a scan potential range from −0.3 to +0.9 V (vs. Ag/AgCl) in 0.5 M H2SO4 containing 30% acetonitrile (ACN), 0.1 M aniline (Ani) and 0.005 M m-ferrocenyaniline (m-FcAni). The field emission scanning electron microscope (FESEM) and electrochemical methods were used to characterize the poly(Ani-co-m-FcAni) modified electrode. The poly(Ani-co-m-FcAni)/GCE exhibited excellent electrocatalytic oxidation of ascorbic acid (AA) in citrate buffer solution (CBS, pH 5.0). The anodic peak potential of AA was shifted from +0.55 V at the bare GCE to +0.25 V at the poly(Ani-co-m-FcAni)/GCE with higher current responses than those seen on the bare GCE. The scan number at the 10th cycle was selected as the maximum scan cycle in electrochemical polymerization. The limit of detection (LOD) was estimated to be 2.0 mM based on the signal-to-noise ratio (S/N = 3). The amperometric responses demonstrated an excellent selectivity for AA determination over glucose (Glu) and dopamine (DA). Full article
(This article belongs to the Section Chemical Sensors)
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Open AccessArticle A Highly Sensitive and Selective Competition Assay for the Detection of Cysteine Using Mercury-Specific DNA, Hg2+ and Sybr Green I
Sensors 2011, 11(11), 10187-10196; doi:10.3390/s111110187
Received: 3 September 2011 / Revised: 18 October 2011 / Accepted: 23 October 2011 / Published: 26 October 2011
Cited by 5 | PDF Full-text (838 KB) | HTML Full-text | XML Full-text
Abstract
We here report a rapid, sensitive, selective and label-free fluorescence detection method for cysteine (Cys). The conformation of mercury-specific DNA (MSD) changes from a random coil form to a hairpin structure in the presence of Hg2+ due to the formation of [...] Read more.
We here report a rapid, sensitive, selective and label-free fluorescence detection method for cysteine (Cys). The conformation of mercury-specific DNA (MSD) changes from a random coil form to a hairpin structure in the presence of Hg2+ due to the formation of a thymine-Hg2+-thymine (T-Hg2+-T) complex. Cys can selectively coordinate with Hg2+ and extract it from the thymine-Hg2+-thymine complex. The hairpin structure dehybridizes and the fluorescence intensity of Sybr Green I (SG) decreases upon addition of Cys because SG efficiently discriminates mercury-specific DNA and mercury-specific DNA/Hg2+ complex. The detection can be finished within 5 min with high sensitivity and selectivity. In addition, we can obtain variable dynamic ranges for Cys by changing the concentration of MSD/Hg2+. Full article
(This article belongs to the Section Biosensors)
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Open AccessArticle A Novel Combined SLAM Based on RBPF-SLAM and EIF-SLAM for Mobile System Sensing in a Large Scale Environment
Sensors 2011, 11(11), 10197-10219; doi:10.3390/s111110197
Received: 11 August 2011 / Revised: 27 September 2011 / Accepted: 27 October 2011 / Published: 28 October 2011
Cited by 6 | PDF Full-text (1144 KB) | HTML Full-text | XML Full-text
Abstract
Mobile autonomous systems are very important for marine scientific investigation and military applications. Many algorithms have been studied to deal with the computational efficiency problem required for large scale Simultaneous Localization and Mapping (SLAM) and its related accuracy and consistency. Among these [...] Read more.
Mobile autonomous systems are very important for marine scientific investigation and military applications. Many algorithms have been studied to deal with the computational efficiency problem required for large scale Simultaneous Localization and Mapping (SLAM) and its related accuracy and consistency. Among these methods, submap-based SLAM is a more effective one. By combining the strength of two popular mapping algorithms, the Rao-Blackwellised particle filter (RBPF) and extended information filter (EIF), this paper presents a Combined SLAM—an efficient submap-based solution to the SLAM problem in a large scale environment. RBPF-SLAM is used to produce local maps, which are periodically fused into an EIF-SLAM algorithm. RBPF-SLAM can avoid linearization of the robot model during operating and provide a robust data association, while EIF-SLAM can improve the whole computational speed, and avoid the tendency of RBPF-SLAM to be over-confident. In order to further improve the computational speed in a real time environment, a binary-tree-based decision-making strategy is introduced. Simulation experiments show that the proposed Combined SLAM algorithm significantly outperforms currently existing algorithms in terms of accuracy and consistency, as well as the computing efficiency. Finally, the Combined SLAM algorithm is experimentally validated in a real environment by using the Victoria Park dataset. Full article
(This article belongs to the Section Sensor Networks)
Open AccessArticle Improved Kalman Filter Method for Measurement Noise Reduction in Multi Sensor RFID Systems
Sensors 2011, 11(11), 10266-10282; doi:10.3390/s111110266
Received: 12 October 2011 / Revised: 24 October 2011 / Accepted: 24 October 2011 / Published: 28 October 2011
Cited by 5 | PDF Full-text (2595 KB) | HTML Full-text | XML Full-text
Abstract
Recently, the range of available Radio Frequency Identification (RFID) tags has been widened to include smart RFID tags which can monitor their varying surroundings. One of the most important factors for better performance of smart RFID system is accurate measurement from various [...] Read more.
Recently, the range of available Radio Frequency Identification (RFID) tags has been widened to include smart RFID tags which can monitor their varying surroundings. One of the most important factors for better performance of smart RFID system is accurate measurement from various sensors. In the multi-sensing environment, some noisy signals are obtained because of the changing surroundings. We propose in this paper an improved Kalman filter method to reduce noise and obtain correct data. Performance of Kalman filter is determined by a measurement and system noise covariance which are usually called the R and Q variables in the Kalman filter algorithm. Choosing a correct R and Q variable is one of the most important design factors for better performance of the Kalman filter. For this reason, we proposed an improved Kalman filter to advance an ability of noise reduction of the Kalman filter. The measurement noise covariance was only considered because the system architecture is simple and can be adjusted by the neural network. With this method, more accurate data can be obtained with smart RFID tags. In a simulation the proposed improved Kalman filter has 40.1%, 60.4% and 87.5% less Mean Squared Error (MSE) than the conventional Kalman filter method for a temperature sensor, humidity sensor and oxygen sensor, respectively. The performance of the proposed method was also verified with some experiments. Full article
(This article belongs to the Special Issue Selected Papers from FGIT 2010)
Open AccessArticle Skyline Query Processing in Sensor Network Based on Data Centric Storage
Sensors 2011, 11(11), 10283-10292; doi:10.3390/s111110283
Received: 1 October 2011 / Revised: 27 October 2011 / Accepted: 28 October 2011 / Published: 28 October 2011
Cited by 1 | PDF Full-text (201 KB) | HTML Full-text | XML Full-text
Abstract
Data centric storages for sensor networks have been proposed to efficiently process multi-dimensional range queries as well as exact matches. Usually, a sensor network does not process only one type of the query, but processes various types of queries such as range [...] Read more.
Data centric storages for sensor networks have been proposed to efficiently process multi-dimensional range queries as well as exact matches. Usually, a sensor network does not process only one type of the query, but processes various types of queries such as range queries, exact matches and skyline queries. Therefore, a sensor network based on a data centric storage for range queries and exact matches should process skyline queries efficiently. However, existing algorithms for skyline queries have not considered the features of data centric storages. Some of the data centric storages store similar data in sensor nodes that are placed on geographically similar locations. Consequently, all data are ordered in a sensor network. In this paper, we propose a new skyline query processing algorithm that exploits the above features of data centric storages. Full article
(This article belongs to the Special Issue Selected Papers from FGIT 2010)
Open AccessArticle An Optical Wavefront Sensor Based on a Double Layer Microlens Array
Sensors 2011, 11(11), 10293-10307; doi:10.3390/s111110293
Received: 25 August 2011 / Revised: 13 October 2011 / Accepted: 18 October 2011 / Published: 31 October 2011
Cited by 10 | PDF Full-text (2333 KB) | HTML Full-text | XML Full-text
Abstract
In order to determine light aberrations, Shack-Hartmann optical wavefront sensors make use of microlens arrays (MLA) to divide the incident light into small parts and focus them onto image planes. In this paper, we present the design and fabrication of long focal [...] Read more.
In order to determine light aberrations, Shack-Hartmann optical wavefront sensors make use of microlens arrays (MLA) to divide the incident light into small parts and focus them onto image planes. In this paper, we present the design and fabrication of long focal length MLA with various shapes and arrangements based on a double layer structure for optical wavefront sensing applications. A longer focal length MLA could provide high sensitivity in determining the average slope across each microlens under a given wavefront, and spatial resolution of a wavefront sensor is increased by numbers of microlenses across a detector. In order to extend focal length, we used polydimethysiloxane (PDMS) above MLA on a glass substrate. Because of small refractive index difference between PDMS and MLA interface (UV-resin), the incident light is less refracted and focused in further distance. Other specific focal lengths could also be realized by modifying the refractive index difference without changing the MLA size. Thus, the wavefront sensor could be improved with better sensitivity and higher spatial resolution. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle Chip Implementation with a Combined Wireless Temperature Sensor and Reference Devices Based on the DZTC Principle
Sensors 2011, 11(11), 10308-10325; doi:10.3390/s111110308
Received: 16 September 2011 / Revised: 24 October 2011 / Accepted: 25 October 2011 / Published: 31 October 2011
Cited by 2 | PDF Full-text (2191 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents a novel CMOS wireless temperature sensor design in order to improve the sensitivity and linearity of our previous work on such devices. Based on the principle of CMOS double zero temperature coefficient (DZTC) points, a combined device is first [...] Read more.
This paper presents a novel CMOS wireless temperature sensor design in order to improve the sensitivity and linearity of our previous work on such devices. Based on the principle of CMOS double zero temperature coefficient (DZTC) points, a combined device is first created at the chip level with two voltage references, one current reference, and one temperature sensor. It was successfully fabricated using the 0.35 μm CMOS process. According to the chip results in a wide temperature range from −20 °C to 120 °C, two voltage references can provide temperature-stable outputs of 823 mV and 1,265 mV with maximum deviations of 0.2 mV and 8.9 mV, respectively. The result for the current reference gives a measurement of 23.5 µA, with a maximum deviation of 1.2 µA. The measurements also show that the wireless temperature sensor has good sensitivity of 9.55 mV/°C and high linearity of 97%. The proposed temperature sensor has 4.15-times better sensitivity than the previous design. Moreover, to facilitate temperature data collection, standard wireless data transmission is chosen; therefore, an 8-bit successive-approximation-register (SAR) analog-to-digital converter (ADC) and a 433 MHz wireless transmitter are also integrated in this chip. Sensing data from different places can be collected remotely avoiding the need for complex wire lines. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle Measuring Time-of-Flight in an Ultrasonic LPS System Using Generalized Cross-Correlation
Sensors 2011, 11(11), 10326-10342; doi:10.3390/s111110326
Received: 14 August 2011 / Revised: 28 September 2011 / Accepted: 24 October 2011 / Published: 31 October 2011
Cited by 10 | PDF Full-text (661 KB) | HTML Full-text | XML Full-text
Abstract
In this article, a time-of-flight detection technique in the frequency domain is described for an ultrasonic Local Positioning System (LPS) based on encoded beacons. Beacon transmissions have been synchronized and become simultaneous by means of the DS-CDMA (Direct-Sequence Code Division Multiple Access) [...] Read more.
In this article, a time-of-flight detection technique in the frequency domain is described for an ultrasonic Local Positioning System (LPS) based on encoded beacons. Beacon transmissions have been synchronized and become simultaneous by means of the DS-CDMA (Direct-Sequence Code Division Multiple Access) technique. Every beacon has been associated to a 255-bit Kasami code. The detection of signal arrival instant at the receiver, from which the distance to each beacon can be obtained, is based on the application of the Generalized Cross-Correlation (GCC), by using the cross-spectral density between the received signal and the sequence to be detected. Prior filtering to enhance the frequency components around the carrier frequency (40 kHz) has improved estimations when obtaining the correlation function maximum, which implies an improvement in distance measurement precision. Positioning has been achieved by using hyperbolic trilateration, based on the Time Differences of Arrival (TDOA) between a reference beacon and the others. Full article
(This article belongs to the Special Issue Sensorial Systems Applied to Intelligent Spaces)
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Open AccessArticle SOMM: A New Service Oriented Middleware for Generic Wireless Multimedia Sensor Networks Based on Code Mobility
Sensors 2011, 11(11), 10343-10371; doi:10.3390/s111110343
Received: 1 October 2011 / Revised: 26 October 2011 / Accepted: 27 October 2011 / Published: 31 October 2011
Cited by 4 | PDF Full-text (591 KB) | HTML Full-text | XML Full-text
Abstract
Although much research in the area of Wireless Multimedia Sensor Networks (WMSNs) has been done in recent years, the programming of sensor nodes is still time-consuming and tedious. It requires expertise in low-level programming, mainly because of the use of resource constrained [...] Read more.
Although much research in the area of Wireless Multimedia Sensor Networks (WMSNs) has been done in recent years, the programming of sensor nodes is still time-consuming and tedious. It requires expertise in low-level programming, mainly because of the use of resource constrained hardware and also the low level API provided by current operating systems. The code of the resulting systems has typically no clear separation between application and system logic. This minimizes the possibility of reusing code and often leads to the necessity of major changes when the underlying platform is changed. In this paper, we present a service oriented middleware named SOMM to support application development for WMSNs. The main goal of SOMM is to enable the development of modifiable and scalable WMSN applications. A network which uses the SOMM is capable of providing multiple services to multiple clients at the same time with the specified Quality of Service (QoS). SOMM uses a virtual machine with the ability to support mobile agents. Services in SOMM are provided by mobile agents and SOMM also provides a t space on each node which agents can use to communicate with each other. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle Fabrication and Characterization of Electrospun Semiconductor Nanoparticle—Polyelectrolyte Ultra-Fine Fiber Composites for Sensing Applications
Sensors 2011, 11(11), 10372-10387; doi:10.3390/s111110372
Received: 27 September 2011 / Revised: 21 October 2011 / Accepted: 24 October 2011 / Published: 31 October 2011
Cited by 8 | PDF Full-text (1151 KB) | HTML Full-text | XML Full-text
Abstract
Fluorescent composite fibrous assembles of nanoparticle-polyelectrolyte fibers are useful multifunctional materials, utilized in filtration, sensing and tissue engineering applications, with the added benefits of improved mechanical, electrical or structural characteristics over the individual components. Composite fibrous mats were prepared by electrospinning aqueous [...] Read more.
Fluorescent composite fibrous assembles of nanoparticle-polyelectrolyte fibers are useful multifunctional materials, utilized in filtration, sensing and tissue engineering applications, with the added benefits of improved mechanical, electrical or structural characteristics over the individual components. Composite fibrous mats were prepared by electrospinning aqueous solutions of 6 wt% poly(acrylic acid) (PAA) loaded with 0.15 and 0.20% v/v, carboxyl functionalized CdSe/ZnS nanoparticles (SNPs). The resulting fluorescent composite fibrous mats exhibits recoverable quenching when exposed to high humidity. The sensor response is sensitive to water concentration and is attributed to the change in the local charges around the SNPs due to deprotonation of the carboxylic acids on the SNPs and the surrounding polymer matrix. Full article
(This article belongs to the Special Issue Sensing with Quantum Dots)
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Open AccessCommunication Following Glucose Oxidase Activity by Chemiluminescence and Chemiluminescence Resonance Energy Transfer (CRET) Processes Involving Enzyme-DNAzyme Conjugates
Sensors 2011, 11(11), 10388-10397; doi:10.3390/s111110388
Received: 26 September 2011 / Revised: 24 October 2011 / Accepted: 25 October 2011 / Published: 31 October 2011
Cited by 18 | PDF Full-text (705 KB) | HTML Full-text | XML Full-text
Abstract
A hybrid consisting of glucose oxidase-functionalized with hemin/G-quadruplex units is used for the chemiluminescence detection of glucose. The glucose oxidase-mediated oxidation of glucose yields gluconic acid and H2O2. The latter in the presence of luminol acts as substrate [...] Read more.
A hybrid consisting of glucose oxidase-functionalized with hemin/G-quadruplex units is used for the chemiluminescence detection of glucose. The glucose oxidase-mediated oxidation of glucose yields gluconic acid and H2O2. The latter in the presence of luminol acts as substrate for the hemin/G-quadruplex-catalyzed generation of chemiluminescence. The glucose oxidase/hemin G-quadruplex hybrid was immobilized on CdSe/ZnS quantum dots (QDs). The light generated by the hybrid, in the presence of glucose, activated a chemiluminescence resonance energy transfer process to the QDs, resulting in the luminescence of the QDs. The intensities of the luminescence of the QDs at different concentrations of glucose provided an optical means to detect glucose. Full article
(This article belongs to the Special Issue Sensing with Quantum Dots)
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Open AccessArticle LPS Auto-Calibration Algorithm with Predetermination of Optimal Zones
Sensors 2011, 11(11), 10398-10414; doi:10.3390/s111110398
Received: 30 September 2011 / Revised: 26 October 2011 / Accepted: 26 October 2011 / Published: 31 October 2011
Cited by 4 | PDF Full-text (892 KB) | HTML Full-text | XML Full-text
Abstract
Accurate coordinates for active beacons placed in the environment are required in Local Positioning Systems (LPS). These coordinates and the distances (or differences of distances) measured between the beacons and the mobile node to be localized are inputs to most trilateration algorithms. [...] Read more.
Accurate coordinates for active beacons placed in the environment are required in Local Positioning Systems (LPS). These coordinates and the distances (or differences of distances) measured between the beacons and the mobile node to be localized are inputs to most trilateration algorithms. As a first approximation, such coordinates are obtained by means of manual measurements (a time-consuming and non-flexible method), or by using a calibration algorithm (i.e., automatic determination of beacon coordinates from ad hoc measurements). This paper presents a method to calibrate the beacons’ positions in a LPS using a mobile receiver. The method has been developed for both, spherical and hyperbolic trilateration. The location of only three test points must be known a priori, while the position of the other test points can be unknown. Furthermore, the paper describes a procedure to estimate the optimal positions, or approximate areas in the coverage zone, where the test-points necessary to calibrate the ultrasonic LPS should be placed. Simulation and experimental results show the improvement achieved when these optimal test-points are used instead of randomly selected ones. Full article
(This article belongs to the Special Issue Sensorial Systems Applied to Intelligent Spaces)
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Open AccessArticle Collective Odor Source Estimation and Search in Time-Variant Airflow Environments Using Mobile Robots
Sensors 2011, 11(11), 10415-10443; doi:10.3390/s111110415
Received: 22 September 2011 / Revised: 20 October 2011 / Accepted: 25 October 2011 / Published: 2 November 2011
Cited by 12 | PDF Full-text (929 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
This paper addresses the collective odor source localization (OSL) problem in a time-varying airflow environment using mobile robots. A novel OSL methodology which combines odor-source probability estimation and multiple robots’ search is proposed. The estimation phase consists of two steps: firstly, the separate [...] Read more.
This paper addresses the collective odor source localization (OSL) problem in a time-varying airflow environment using mobile robots. A novel OSL methodology which combines odor-source probability estimation and multiple robots’ search is proposed. The estimation phase consists of two steps: firstly, the separate probability-distribution map of odor source is estimated via Bayesian rules and fuzzy inference based on a single robot’s detection events; secondly, the separate maps estimated by different robots at different times are fused into a combined map by way of distance based superposition. The multi-robot search behaviors are coordinated via a particle swarm optimization algorithm, where the estimated odor-source probability distribution is used to express the fitness functions. In the process of OSL, the estimation phase provides the prior knowledge for the searching while the searching verifies the estimation results, and both phases are implemented iteratively. The results of simulations for large-scale advection–diffusion plume environments and experiments using real robots in an indoor airflow environment validate the feasibility and robustness of the proposed OSL method. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle Angular Rate Estimation Using a Distributed Set of Accelerometers
Sensors 2011, 11(11), 10444-10457; doi:10.3390/s111110444
Received: 26 September 2011 / Revised: 25 October 2011 / Accepted: 31 October 2011 / Published: 2 November 2011
Cited by 9 | PDF Full-text (494 KB) | HTML Full-text | XML Full-text
Abstract
A distributed set of accelerometers based on the minimum number of 12 accelerometers allows for computation of the magnitude of angular rate without using the integration operation. However, it is not easy to extract the magnitude of angular rate in the presence [...] Read more.
A distributed set of accelerometers based on the minimum number of 12 accelerometers allows for computation of the magnitude of angular rate without using the integration operation. However, it is not easy to extract the magnitude of angular rate in the presence of the accelerometer noises, and even worse, it is difficult to determine the direction of a rotation because the angular rate is present in its quadratic form within the inertial measurement system equations. In this paper, an extended Kalman filter scheme to correctly estimate both the direction and magnitude of the angular rate through fusion of the angular acceleration and quadratic form of the angular rate is proposed. We also provide observability analysis for the general distributed accelerometers-based inertial measurement unit, and show that the angular rate can be correctly estimated by general nonlinear state estimators such as an extended Kalman filter, except under certain extreme conditions. Full article
(This article belongs to the Special Issue Collaborative Sensors)
Open AccessArticle Temperature Field Analysis for PZT Pyroelectric Cells for Thermal Energy Harvesting
Sensors 2011, 11(11), 10458-10473; doi:10.3390/s111110458
Received: 22 September 2011 / Revised: 26 October 2011 / Accepted: 31 October 2011 / Published: 2 November 2011
Cited by 13 | PDF Full-text (1183 KB) | HTML Full-text | XML Full-text
Abstract
This paper proposes the idea of etching PZT to improve the temperature variation rate of a thicker PZT sheet in order to enhance the energy conversion efficiency when used as pyroelectric cells. A partially covered electrode was proven to display a higher [...] Read more.
This paper proposes the idea of etching PZT to improve the temperature variation rate of a thicker PZT sheet in order to enhance the energy conversion efficiency when used as pyroelectric cells. A partially covered electrode was proven to display a higher output response than a fully covered electrode did. A mesh top electrode monitored the temperature variation rate and the electrode area. The mesh electrode width affected the distribution of the temperature variation rate in a thinner pyroelectric material. However, a pyroelectric cell with a thicker pyroelectric material was beneficial in generating electricity pyroelectrically. The PZT sheet was further etched to produce deeper cavities and a smaller electrode width to induce lateral temperature gradients on the sidewalls of cavities under homogeneous heat irradiation, enhancing the temperature variation rate. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle A Mobile Ferromagnetic Shape Detection Sensor Using a Hall Sensor Array and Magnetic Imaging
Sensors 2011, 11(11), 10474-10489; doi:10.3390/s111110474
Received: 5 September 2011 / Revised: 14 October 2011 / Accepted: 1 November 2011 / Published: 3 November 2011
Cited by 8 | PDF Full-text (374 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents a Mobile Hall Sensor Array system for the shape detection of ferromagnetic materials that are embedded in walls or floors. The operation of the Mobile Hall Sensor Array system is based on the principle of magnetic flux leakage to [...] Read more.
This paper presents a Mobile Hall Sensor Array system for the shape detection of ferromagnetic materials that are embedded in walls or floors. The operation of the Mobile Hall Sensor Array system is based on the principle of magnetic flux leakage to describe the shape of the ferromagnetic material. Two permanent magnets are used to generate the magnetic flux flow. The distribution of magnetic flux is perturbed as the ferromagnetic material is brought near the permanent magnets and the changes in magnetic flux distribution are detected by the 1-D array of the Hall sensor array setup. The process for magnetic imaging of the magnetic flux distribution is done by a signal processing unit before it displays the real time images using a netbook. A signal processing application software is developed for the 1-D Hall sensor array signal acquisition and processing to construct a 2-D array matrix. The processed 1-D Hall sensor array signals are later used to construct the magnetic image of ferromagnetic material based on the voltage signal and the magnetic flux distribution. The experimental results illustrate how the shape of specimens such as square, round and triangle shapes is determined through magnetic images based on the voltage signal and magnetic flux distribution of the specimen. In addition, the magnetic images of actual ferromagnetic objects are also illustrated to prove the functionality of Mobile Hall Sensor Array system for actual shape detection. The results prove that the Mobile Hall Sensor Array system is able to perform magnetic imaging in identifying various ferromagnetic materials. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle A Conjugated Aptamer-Gold Nanoparticle Fluorescent Probe for Highly Sensitive Detection of rHuEPO-α
Sensors 2011, 11(11), 10490-10501; doi:10.3390/s111110490
Received: 24 August 2011 / Revised: 11 October 2011 / Accepted: 1 November 2011 / Published: 3 November 2011
Cited by 13 | PDF Full-text (709 KB) | HTML Full-text | XML Full-text
Abstract
We present here a novel conjugated aptamer-gold nanoparticle (Apt-AuNPs) fluorescent probe and its application for specific detection of recombinant human erythropoietin-α (rHuEPO-α). In this nanobiosensor, 12 nm AuNPs function as both a nano-scaffold and a nano-quencher (fluorescent energy acceptor), on the surface [...] Read more.
We present here a novel conjugated aptamer-gold nanoparticle (Apt-AuNPs) fluorescent probe and its application for specific detection of recombinant human erythropoietin-α (rHuEPO-α). In this nanobiosensor, 12 nm AuNPs function as both a nano-scaffold and a nano-quencher (fluorescent energy acceptor), on the surface of which the complementary sequences are linked (as cODN-AuNPs) and pre-hybridized with carboxymethylfluorescein (FAM)-labeled anti-rHuEPO-α aptamers. Upon target protein binding, the aptamers can be released from the AuNP surface and the fluorescence signal is restored. Key variables such as the length of linker, the hybridization site and length have been designed and optimized. Full performance evaluation including sensitivity, linear range and interference substances are also described. This nanobiosensor provides a promising approach for a simple and direct quantification of rHuEPO-α concentrations as low as 0.92 nM within a few hours. Full article
(This article belongs to the Special Issue Aptamer-Based Sensors)
Open AccessArticle The Effect of Composition of Different Ecotoxicological Test Media on Free and Bioavailable Copper from CuSO4 and CuO Nanoparticles: Comparative Evidence from a Cu-Selective Electrode and a Cu-Biosensor
Sensors 2011, 11(11), 10502-10521; doi:10.3390/s111110502
Received: 20 September 2011 / Revised: 20 October 2011 / Accepted: 31 October 2011 / Published: 3 November 2011
Cited by 18 | PDF Full-text (895 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
The analysis of (bio)available copper in complex environmental settings, including biological test media, is a challenging task. In this study, we demonstrated the potential of a recombinant Pseudomonas fluorescens-based biosensor for bioavailability analysis of CuSO4 and CuO nanoparticles (nano-CuO) in seventeen different ecotoxicological and microbiologial test media. In parallel, free Cu in these test media was analysed using Cu-ion selective electrode (Cu-ISE). In the case of CuSO4, both free and bioavailable Cu decreased greatly with increasing concentration of organics and phosphates in the tested media. A good correlation between free and bioavailable Cu was observed (r = 0.854, p < 0.01) indicating that the free Cu content in biological test media may be a reasonably good predictor for the toxicity of CuSO4. As a proof, it was demonstrated that when eleven EC50 values for CuSO4 from different organisms in different test media were normalized for the free Cu in these media, the difference in these EC50 values was decreased from 4 to 1.8 orders of magnitude. Thus, toxicity of CuSO4 to these organisms was attributed to the properties of the test media rather than to inherent differences in sensitivity between the test organisms. Differently from CuSO4, the amount of free and bioavailable Cu in nano-CuO spiked media was not significantly correlated with the concentration of organics in the test media. Thus, the speciation of nano-CuO in toxicological test systems was not only determined by the complexation of Cu ions but also by differential dissolution of nano-CuO in different test conditions leading to a new speciation equilibrium. In addition, a substantial fraction of nano-CuO that was not detectable by Cu-ISE (i.e., not present as free Cu-ions) was bioavailable to Cu-biosensor bacteria. Thus, in environmental hazard analysis of (nano) particulate materials, biosensor analysis may be more informative than other analytical techniques. Our results demonstrate that bacterial Cu-biosensors either in combination with other analytical/speciation techniques or on their own, may serve as a rapid (eco)toxicological screening method. Full article
(This article belongs to the Special Issue Sensing of Toxic and Hazardous Metals in Various Environmental Media)
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Open AccessArticle Effect of Inductive Coil Shape on Sensing Performance of Linear Displacement Sensor Using Thin Inductive Coil and Pattern Guide
Sensors 2011, 11(11), 10522-10533; doi:10.3390/s111110522
Received: 27 September 2011 / Revised: 25 October 2011 / Accepted: 25 October 2011 / Published: 3 November 2011
Cited by 9 | PDF Full-text (596 KB) | HTML Full-text | XML Full-text
Abstract
This paper discusses the effect of inductive coil shape on the sensing performance of a linear displacement sensor. The linear displacement sensor consists of a thin type inductive coil with a thin pattern guide, thus being suitable for tiny space applications. The [...] Read more.
This paper discusses the effect of inductive coil shape on the sensing performance of a linear displacement sensor. The linear displacement sensor consists of a thin type inductive coil with a thin pattern guide, thus being suitable for tiny space applications. The position can be detected by measuring the inductance of the inductive coil. At each position due to the change in inductive coil area facing the pattern guide the value of inductance is different. Therefore, the objective of this research is to study various inductive coil pattern shapes and to propose the pattern that can achieve good sensing performance. Various shapes of meander, triangular type meander, square and circle shape with different turn number of inductive coils are examined in this study. The inductance is measured with the sensor sensitivity and linearity as a performance evaluation parameter of the sensor. In conclusion, each inductive coil shape has its own advantages and disadvantages. For instance, the circle shape inductive coil produces high sensitivity with a low linearity response. Meanwhile, the square shape inductive coil has a medium sensitivity with higher linearity. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle Automated Image Analysis for the Detection of Benthic Crustaceans and Bacterial Mat Coverage Using the VENUS Undersea Cabled Network
Sensors 2011, 11(11), 10534-10556; doi:10.3390/s111110534
Received: 4 July 2011 / Revised: 8 October 2011 / Accepted: 1 November 2011 / Published: 4 November 2011
Cited by 10 | PDF Full-text (1985 KB) | HTML Full-text | XML Full-text
Abstract
The development and deployment of sensors for undersea cabled observatories is presently biased toward the measurement of habitat variables, while sensor technologies for biological community characterization through species identification and individual counting are less common. The VENUS cabled multisensory network (Vancouver Island, [...] Read more.
The development and deployment of sensors for undersea cabled observatories is presently biased toward the measurement of habitat variables, while sensor technologies for biological community characterization through species identification and individual counting are less common. The VENUS cabled multisensory network (Vancouver Island, Canada) deploys seafloor camera systems at several sites. Our objective in this study was to implement new automated image analysis protocols for the recognition and counting of benthic decapods (i.e., the galatheid squat lobster, Munida quadrispina), as well as for the evaluation of changes in bacterial mat coverage (i.e., Beggiatoa spp.), using a camera deployed in Saanich Inlet (103 m depth). For the counting of Munida we remotely acquired 100 digital photos at hourly intervals from 2 to 6 December 2009. In the case of bacterial mat coverage estimation, images were taken from 2 to 8 December 2009 at the same time frequency. The automated image analysis protocols for both study cases were created in MatLab 7.1. Automation for Munida counting incorporated the combination of both filtering and background correction (Median- and Top-Hat Filters) with Euclidean Distances (ED) on Red-Green-Blue (RGB) channels. The Scale-Invariant Feature Transform (SIFT) features and Fourier Descriptors (FD) of tracked objects were then extracted. Animal classifications were carried out with the tools of morphometric multivariate statistic (i.e., Partial Least Square Discriminant Analysis; PLSDA) on Mean RGB (RGBv) value for each object and Fourier Descriptors (RGBv+FD) matrices plus SIFT and ED. The SIFT approach returned the better results. Higher percentages of images were correctly classified and lower misclassification errors (an animal is present but not detected) occurred. In contrast, RGBv+FD and ED resulted in a high incidence of records being generated for non-present animals. Bacterial mat coverage was estimated in terms of Percent Coverage and Fractal Dimension. A constant Region of Interest (ROI) was defined and background extraction by a Gaussian Blurring Filter was performed. Image subtraction within ROI was followed by the sum of the RGB channels matrices. Percent Coverage was calculated on the resulting image. Fractal Dimension was estimated using the box-counting method. The images were then resized to a dimension in pixels equal to a power of 2, allowing subdivision into sub-multiple quadrants. In comparisons of manual and automated Percent Coverage and Fractal Dimension estimates, the former showed an overestimation tendency for both parameters. The primary limitations on the automatic analysis of benthic images were habitat variations in sediment texture and water column turbidity. The application of filters for background corrections is a required preliminary step for the efficient recognition of animals and bacterial mat patches. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle Simplistic Attachment and Multispectral Imaging with Semiconductor Nanocrystals
Sensors 2011, 11(11), 10557-10570; doi:10.3390/s111110557
Received: 14 September 2011 / Revised: 26 October 2011 / Accepted: 26 October 2011 / Published: 7 November 2011
Cited by 5 | PDF Full-text (4356 KB) | HTML Full-text | XML Full-text
Abstract
Advances in spectral deconvolution technologies are rapidly enabling researchers to replace or enhance traditional epifluorescence microscopes with instruments capable of detecting numerous markers simultaneously in a multiplexed fashion. While significantly expediting sample throughput and elucidating sample information, this technology is limited by [...] Read more.
Advances in spectral deconvolution technologies are rapidly enabling researchers to replace or enhance traditional epifluorescence microscopes with instruments capable of detecting numerous markers simultaneously in a multiplexed fashion. While significantly expediting sample throughput and elucidating sample information, this technology is limited by the spectral width of common fluorescence reporters. Semiconductor nanocrystals (NC’s) are very bright, narrow band fluorescence emitters with great potential for multiplexed fluorescence detection, however the availability of NC’s with facile attachment chemistries to targeting molecules has been a severe limitation to the advancement of NC technology in applications such as immunocytochemistry and immunohistochemistry. Here we report the development of simple, yet novel attachment chemistries for antibodies onto NC’s and demonstrate how spectral deconvolution technology enables the multiplexed detection of 5 distinct NC-antibody conjugates with fluorescence emission wavelengths separated by as little as 20 nm. Full article
(This article belongs to the Special Issue Sensing with Quantum Dots)
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Open AccessArticle Kinematics of Gait: New Method for Angle Estimation Based on Accelerometers
Sensors 2011, 11(11), 10571-10585; doi:10.3390/s111110571
Received: 1 October 2011 / Revised: 24 October 2011 / Accepted: 25 October 2011 / Published: 7 November 2011
Cited by 21 | PDF Full-text (1165 KB) | HTML Full-text | XML Full-text
Abstract
A new method for estimation of angles of leg segments and joints, which uses accelerometer arrays attached to body segments, is described. An array consists of two accelerometers mounted on a rigid rod. The absolute angle of each body segment was determined [...] Read more.
A new method for estimation of angles of leg segments and joints, which uses accelerometer arrays attached to body segments, is described. An array consists of two accelerometers mounted on a rigid rod. The absolute angle of each body segment was determined by band pass filtering of the differences between signals from parallel axes from two accelerometers mounted on the same rod. Joint angles were evaluated by subtracting absolute angles of the neighboring segments. This method eliminates the need for double integration as well as the drift typical for double integration. The efficiency of the algorithm is illustrated by experimental results involving healthy subjects who walked on a treadmill at various speeds, ranging between 0.15 m/s and 2.0 m/s. The validation was performed by comparing the estimated joint angles with the joint angles measured with flexible goniometers. The discrepancies were assessed by the differences between the two sets of data (obtained to be below 6 degrees) and by the Pearson correlation coefficient (greater than 0.97 for the knee angle and greater than 0.85 for the ankle angle). Full article
(This article belongs to the Section Physical Sensors)
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Open AccessArticle Absolute Radiometric Calibration of ALS Intensity Data: Effects on Accuracy and Target Classification
Sensors 2011, 11(11), 10586-10602; doi:10.3390/s111110586
Received: 15 September 2011 / Revised: 31 October 2011 / Accepted: 4 November 2011 / Published: 7 November 2011
Cited by 16 | PDF Full-text (741 KB) | HTML Full-text | XML Full-text
Abstract
Radiometric calibration of airborne laser scanning (ALS) intensity data aims at retrieving a value related to the target scattering properties, which is independent on the instrument or flight parameters. The aim of a calibration procedure is also to be able to compare [...] Read more.
Radiometric calibration of airborne laser scanning (ALS) intensity data aims at retrieving a value related to the target scattering properties, which is independent on the instrument or flight parameters. The aim of a calibration procedure is also to be able to compare results from different flights and instruments, but practical applications are sparsely available, and the performance of calibration methods for this purpose needs to be further assessed. We have studied the radiometric calibration with data from three separate flights and two different instruments using external calibration targets. We find that the intensity data from different flights and instruments can be compared to each other only after a radiometric calibration process using separate calibration targets carefully selected for each flight. The calibration is also necessary for target classification purposes, such as separating vegetation from sand using intensity data from different flights. The classification results are meaningful only for calibrated intensity data. Full article
(This article belongs to the Section Remote Sensors)
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Open AccessArticle Design of Selective Gas Sensors Using Additive-Loaded In2O3 Hollow Spheres Prepared by Combinatorial Hydrothermal Reactions
Sensors 2011, 11(11), 10603-10614; doi:10.3390/s111110603
Received: 16 September 2011 / Revised: 31 October 2011 / Accepted: 4 November 2011 / Published: 7 November 2011
Cited by 12 | PDF Full-text (1248 KB) | HTML Full-text | XML Full-text
Abstract
A combinatorial hydrothermal reaction has been used to prepare pure and additive (Sb, Cu, Nb, Pd, and Ni)-loaded In2O3 hollow spheres for gas sensor applications. The operation of Pd- and Cu-loaded In2O3 sensors at 371 °C [...] Read more.
A combinatorial hydrothermal reaction has been used to prepare pure and additive (Sb, Cu, Nb, Pd, and Ni)-loaded In2O3 hollow spheres for gas sensor applications. The operation of Pd- and Cu-loaded In2O3 sensors at 371 °C leads to selective H2S detection. Selective detection of CO and NH3 was achieved by the Ni-In2O3 sensor at sensing temperatures of 371 and 440 °C, respectively. The gas responses of six different sensors to NH3, H2S, H2, CO and CH4 produced unique gas sensing patterns that can be used for the artificial recognition of these gases. Full article
(This article belongs to the Special Issue Sensing at the Nano-Scale: Chemical and Bio-Sensing)
Open AccessArticle All-Optical Frequency Modulated High Pressure MEMS Sensor for Remote and Distributed Sensing
Sensors 2011, 11(11), 10615-10623; doi:10.3390/s111110615
Received: 26 September 2011 / Revised: 27 October 2011 / Accepted: 4 November 2011 / Published: 8 November 2011
Cited by 1 | PDF Full-text (326 KB) | HTML Full-text | XML Full-text
Abstract
We present the design, fabrication and characterization of a new all-optical frequency modulated pressure sensor. Using the tangential strain in a circular membrane, a waveguide with an integrated nanoscale Bragg grating is strained longitudinally proportional to the applied pressure causing a shift [...] Read more.
We present the design, fabrication and characterization of a new all-optical frequency modulated pressure sensor. Using the tangential strain in a circular membrane, a waveguide with an integrated nanoscale Bragg grating is strained longitudinally proportional to the applied pressure causing a shift in the Bragg wavelength. The simple and robust design combined with the small chip area of 1 × 1.8 mm2 makes the sensor ideally suited for remote and distributed sensing in harsh environments and where miniaturized sensors are required. The sensor is designed for high pressure applications up to 350 bar and with a sensitivity of 4.8 pm/bar (i.e., 350 ×105 Pa and 4.8 × 10−5 pm/Pa, respectively). Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle Bio-Sensing of Cadmium(II) Ions Using Staphylococcus aureus
Sensors 2011, 11(11), 10638-10663; doi:10.3390/s111110638
Received: 16 September 2011 / Revised: 31 October 2011 / Accepted: 7 November 2011 / Published: 8 November 2011
Cited by 20 | PDF Full-text (1053 KB) | HTML Full-text | XML Full-text
Abstract
Cadmium, as a hazardous pollutant commonly present in the living environment, represents an important risk to human health due to its undesirable effects (oxidative stress, changes in activities of many enzymes, interactions with biomolecules including DNA and RNA) and consequent potential risk, [...] Read more.
Cadmium, as a hazardous pollutant commonly present in the living environment, represents an important risk to human health due to its undesirable effects (oxidative stress, changes in activities of many enzymes, interactions with biomolecules including DNA and RNA) and consequent potential risk, making its detection very important. New and unique technological and biotechnological approaches for solving this problems are intensely sought. In this study, we used the commonly occurring potential pathogenic microorganism Staphylococcus aureus for the determination of markers which could be used for sensing of cadmium(II) ions. We were focused on monitoring the effects of different cadmium(II) ion concentrations (0, 1.25, 2.5, 5, 10, 15, 25 and 50 µg mL−1) on the growth and energetic metabolism of Staphylococcus aureus. Highly significant changes have been detected in the metabolism of thiol compounds—specifically the protein metallothionein (0.79–26.82 mmol/mg of protein), the enzyme glutathione S-transferase (190–5,827 µmol/min/mg of protein), and sulfhydryl groups (9.6–274.3 µmol cysteine/mg of protein). The ratio of reduced and oxidized glutathione indicated marked oxidative stress. In addition, dramatic changes in urease activity, which is connected with resistance of bacteria, were determined. Further, the effects of cadmium(II) ions on the metabolic pathways of arginine, β-glucosidase, phosphatase, N-acetyl β-D-glucosamine, sucrose, trehalose, mannitol, maltose, lactose, fructose and total proteins were demonstrated. A metabolomic profile of Staphylococcus aureus under cadmium(II) ion treatment conditions was completed seeking data about the possibility of cadmium(II) ion accumulation in cells. The results demonstrate potential in the application of microorganisms as modern biosensor systems based on biological components. Full article
(This article belongs to the Special Issue Sensing of Toxic and Hazardous Metals in Various Environmental Media)
Open AccessArticle Interoperation of an UHF RFID Reader and a TCP/IP Device via Wired and Wireless Links
Sensors 2011, 11(11), 10664-10674; doi:10.3390/s111110664
Received: 28 June 2011 / Revised: 3 October 2011 / Accepted: 27 October 2011 / Published: 8 November 2011
Cited by 2 | PDF Full-text (853 KB) | HTML Full-text | XML Full-text
Abstract
A main application in radio frequency identification (RFID) sensor networks is the function that processes real-time tag information after gathering the required data from multiple RFID tags. The component technologies that contain an RFID reader, called the interrogator, which has a tag [...] Read more.
A main application in radio frequency identification (RFID) sensor networks is the function that processes real-time tag information after gathering the required data from multiple RFID tags. The component technologies that contain an RFID reader, called the interrogator, which has a tag chip, processors, coupling antenna, and a power management system have advanced significantly over the last decade. This paper presents a system implementation for interoperation between an UHF RFID reader and a TCP/IP device that is used as a gateway. The proposed system consists of an UHF RFID tag, an UHF RFID reader, an RF end-device, an RF coordinator, and a TCP/IP I/F. The UHF RFID reader, operating at 915 MHz, is compatible with EPC Class-0/Gen1, Class-1/Gen1 and 2, and ISO18000-6B. In particular, the UHF RFID reader can be combined with the RF end-device/coordinator for a ZigBee (IEEE 802.15.4) interface, which is a low-power wireless standard. The TCP/IP device communicates with the RFID reader via wired links. On the other hand, it is connected to the ZigBee end-device via wireless links. The web based test results show that the developed system can remotely recognize information of multiple tags through the interoperation between the RFID reader and the TCP/IP device. Full article
(This article belongs to the Special Issue Selected Papers from FGIT 2010)
Open AccessArticle Low-Cost Oil Quality Sensor Based on Changes in Complex Permittivity
Sensors 2011, 11(11), 10675-10690; doi:10.3390/s111110675
Received: 10 October 2011 / Revised: 31 October 2011 / Accepted: 4 November 2011 / Published: 10 November 2011
Cited by 5 | PDF Full-text (874 KB) | HTML Full-text | XML Full-text
Abstract
Real time oil quality monitoring techniques help to protect important industry assets, minimize downtime and reduce maintenance costs. The measurement of a lubricant’s complex permittivity is an effective indicator of the oil degradation process and it can be useful in condition based [...] Read more.
Real time oil quality monitoring techniques help to protect important industry assets, minimize downtime and reduce maintenance costs. The measurement of a lubricant’s complex permittivity is an effective indicator of the oil degradation process and it can be useful in condition based maintenance (CBM) to select the most adequate oil replacement maintenance schedules. A discussion of the working principles of an oil quality sensor based on a marginal oscillator to monitor the losses of the dielectric at high frequencies (>1 MHz) is presented. An electronic design procedure is covered which results in a low cost, effective and ruggedized sensor implementation suitable for use in harsh environments. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle A Configurable Sensor Network Applied to Ambient Assisted Living
Sensors 2011, 11(11), 10724-10737; doi:10.3390/s111110724
Received: 4 October 2011 / Revised: 21 October 2011 / Accepted: 27 October 2011 / Published: 15 November 2011
Cited by 7 | PDF Full-text (245 KB) | HTML Full-text | XML Full-text
Abstract
The rising older people population has increased the interest in Ambient Assisted Living systems. This article presents a system for monitoring the disabled or older persons developed from an existing surveillance system. The modularity and adaptability characteristics of the system allow an [...] Read more.
The rising older people population has increased the interest in Ambient Assisted Living systems. This article presents a system for monitoring the disabled or older persons developed from an existing surveillance system. The modularity and adaptability characteristics of the system allow an easy adaptation for a different purpose. The proposed system uses a network of sensors capable of motion detection that includes fall warning, identification of persons and a configurable control system which allows its use in different scenarios. Full article
(This article belongs to the Special Issue Smart Spaces and Ubiquitous Solutions)
Open AccessArticle Sensor Network Architectures for Monitoring Underwater Pipelines
Sensors 2011, 11(11), 10738-10764; doi:10.3390/s111110738
Received: 29 September 2011 / Revised: 31 October 2011 / Accepted: 4 November 2011 / Published: 15 November 2011
Cited by 28 | PDF Full-text (316 KB) | HTML Full-text | XML Full-text
Abstract
This paper develops and compares different sensor network architecture designs that can be used for monitoring underwater pipeline infrastructures. These architectures are underwater wired sensor networks, underwater acoustic wireless sensor networks, RF (Radio Frequency) wireless sensor networks, integrated wired/acoustic wireless sensor networks, [...] Read more.
This paper develops and compares different sensor network architecture designs that can be used for monitoring underwater pipeline infrastructures. These architectures are underwater wired sensor networks, underwater acoustic wireless sensor networks, RF (Radio Frequency) wireless sensor networks, integrated wired/acoustic wireless sensor networks, and integrated wired/RF wireless sensor networks. The paper also discusses the reliability challenges and enhancement approaches for these network architectures. The reliability evaluation, characteristics, advantages, and disadvantages among these architectures are discussed and compared. Three reliability factors are used for the discussion and comparison: the network connectivity, the continuity of power supply for the network, and the physical network security. In addition, the paper also develops and evaluates a hierarchical sensor network framework for underwater pipeline monitoring. Full article
(This article belongs to the Special Issue Underwater Sensor Nodes and Underwater Sensor Networks)
Open AccessArticle Analysis of Doppler Effect on the Pulse Compression of Different Codes Emitted by an Ultrasonic LPS
Sensors 2011, 11(11), 10765-10784; doi:10.3390/s111110765
Received: 11 October 2011 / Revised: 8 November 2011 / Accepted: 9 November 2011 / Published: 15 November 2011
Cited by 5 | PDF Full-text (5238 KB) | HTML Full-text | XML Full-text
Abstract
This work analyses the effect of the receiver movement on the detection by pulse compression of different families of codes characterizing the emissions of an Ultrasonic Local Positioning System. Three families of codes have been compared: Kasami, Complementary Sets of Sequences and [...] Read more.
This work analyses the effect of the receiver movement on the detection by pulse compression of different families of codes characterizing the emissions of an Ultrasonic Local Positioning System. Three families of codes have been compared: Kasami, Complementary Sets of Sequences and Loosely Synchronous, considering in all cases three different lengths close to 64, 256 and 1,024 bits. This comparison is first carried out by using a system model in order to obtain a set of results that are then experimentally validated with the help of an electric slider that provides radial speeds up to 2 m/s. The performance of the codes under analysis has been characterized by means of the auto-correlation and cross-correlation bounds. The results derived from this study should be of interest to anyone performing matched filtering of ultrasonic signals with a moving emitter/receiver. Full article
(This article belongs to the Special Issue Sensorial Systems Applied to Intelligent Spaces)
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Open AccessArticle A Nanostructured Piezoelectric Immunosensor for Detection of Human Cardiac Troponin T
Sensors 2011, 11(11), 10785-10797; doi:10.3390/s111110785
Received: 10 October 2011 / Revised: 2 November 2011 / Accepted: 9 November 2011 / Published: 16 November 2011
Cited by 9 | PDF Full-text (263 KB) | HTML Full-text | XML Full-text
Abstract
A piezoelectric immunosensor based on gold nanoparticles (AuNPs) co-immobilized on a dithiol-modified surface is proposed for detection of human cardiac troponin T (TnT). Anti-human troponin T (anti-TnT) antibodies were covalently immobilized on the nanostructured electrode surface by thiol-aldehyde linkages. In a homogeneous bulk solution, TnT was captured by anti-TnT immobilized on the QCM electrode. Cyclic voltammetry studies were used to characterize the AuNPs layer on the electrode surface and the anti-TnT immobilization steps. The QCM-flow immunosensor exhibited good reliability, measuring concentrations of TnT from 0.003 to 0.5 ng mL−1 in human serum with high linearity (r = 0.989; p < 0.01). The immunosensor exhibited a 7% coefficient of variation and 0.0015 ng mL−1 limit of detection, indicating a high reproducibility and sensitivity. The proposed QCM nanostructured immunosensor is easy to use and has promising potential in the diagnosis of acute myocardial infarction due to its speed and high sensitivity. Full article
(This article belongs to the Special Issue Nano-Biosensors)
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Open AccessArticle Brillouin Corrosion Expansion Sensors for Steel Reinforced Concrete Structures Using a Fiber Optic Coil Winding Method
Sensors 2011, 11(11), 10798-10819; doi:10.3390/s111110798
Received: 8 October 2011 / Revised: 10 November 2011 / Accepted: 12 November 2011 / Published: 16 November 2011
Cited by 18 | PDF Full-text (2127 KB) | HTML Full-text | XML Full-text
Abstract
In this paper, a novel kind of method to monitor corrosion expansion of steel rebars in steel reinforced concrete structures named fiber optic coil winding method is proposed, discussed and tested. It is based on the fiber optical Brillouin sensing technique. Firstly, [...] Read more.
In this paper, a novel kind of method to monitor corrosion expansion of steel rebars in steel reinforced concrete structures named fiber optic coil winding method is proposed, discussed and tested. It is based on the fiber optical Brillouin sensing technique. Firstly, a strain calibration experiment is designed and conducted to obtain the strain coefficient of single mode fiber optics. Results have shown that there is a good linear relationship between Brillouin frequency and applied strain. Then, three kinds of novel fiber optical Brillouin corrosion expansion sensors with different fiber optic coil winding packaging schemes are designed. Sensors were embedded into concrete specimens to monitor expansion strain caused by steel rebar corrosion, and their performance was studied in a designed electrochemical corrosion acceleration experiment. Experimental results have shown that expansion strain along the fiber optic coil winding area can be detected and measured by the three kinds of sensors with different measurement range during development the corrosion. With the assumption of uniform corrosion, diameters of corrosion steel rebars were obtained using calculated average strains. A maximum expansion strain of 6,738 με was monitored. Furthermore, the uniform corrosion analysis model was established and the evaluation formula to evaluate mass loss rate of steel rebar under a given corrosion rust expansion rate was derived. The research has shown that three kinds of Brillouin sensors can be used to monitor the steel rebar corrosion expansion of reinforced concrete structures with good sensitivity, accuracy and monitoring range, and can be applied to monitor different levels of corrosion. By means of this kind of monitoring technique, quantitative corrosion expansion monitoring can be carried out, with the virtues of long durability, real-time monitoring and quasi-distribution monitoring. Full article
(This article belongs to the Special Issue Optical Fiber Sensors 2012)
Open AccessArticle Fuzzy Mobile-Robot Positioning in Intelligent Spaces Using Wireless Sensor Networks
Sensors 2011, 11(11), 10820-10839; doi:10.3390/s111110820
Received: 18 September 2011 / Revised: 1 November 2011 / Accepted: 14 November 2011 / Published: 17 November 2011
Cited by 9 | PDF Full-text (2284 KB) | HTML Full-text | XML Full-text
Abstract
This work presents the development and experimental evaluation of a method based on fuzzy logic to locate mobile robots in an Intelligent Space using Wireless Sensor Networks (WSNs). The problem consists of locating a mobile node using only inter-node range measurements, which [...] Read more.
This work presents the development and experimental evaluation of a method based on fuzzy logic to locate mobile robots in an Intelligent Space using Wireless Sensor Networks (WSNs). The problem consists of locating a mobile node using only inter-node range measurements, which are estimated by radio frequency signal strength attenuation. The sensor model of these measurements is very noisy and unreliable. The proposed method makes use of fuzzy logic for modeling and dealing with such uncertain information. Besides, the proposed approach is compared with a probabilistic technique showing that the fuzzy approach is able to handle highly uncertain situations that are difficult to manage by well-known localization methods. Full article
(This article belongs to the Special Issue Sensorial Systems Applied to Intelligent Spaces)
Open AccessCommunication Electrochemical Characterization of Riboflavin-Enhanced Reduction of Trinitrotoluene
Sensors 2011, 11(11), 10840-10850; doi:10.3390/s111110840
Received: 21 September 2011 / Revised: 1 November 2011 / Accepted: 17 November 2011 / Published: 18 November 2011
Cited by 2 | PDF Full-text (194 KB) | HTML Full-text | XML Full-text
Abstract
There is great interest in understanding trinitrotoluene (TNT) and dinitrotoluene (DNT) contamination, detection and remediation in the environment due to TNT’s negative health effects and security implications. Numerous publications have focused on detecting TNT in groundwater using multiple techniques, including electrochemistry. The [...] Read more.
There is great interest in understanding trinitrotoluene (TNT) and dinitrotoluene (DNT) contamination, detection and remediation in the environment due to TNT’s negative health effects and security implications. Numerous publications have focused on detecting TNT in groundwater using multiple techniques, including electrochemistry. The main degradation pathway of nitrotoluenes in the environment is reduction, frequently with biological and/or photolytic assistance. Riboflavin has also been noted to aid in TNT remediation in soils and groundwater when exposed to light. This report indicates that adding riboflavin to a TNT or DNT solution enhances redox currents in electrochemical experiments. Here AC voltammetry was performed and peak currents compared with and without riboflavin present. Results indicated that TNT, DNT and riboflavin could be detected using AC voltammetry on modified gold electrodes and the addition of riboflavin affected redox peaks of TNT and DNT. Poised potential experiments indicated that it is possible to enhance reduction of TNT in the presence of riboflavin and light. These results were dramatic enough to explain long term enhancement of bioremediation in environments containing high levels of riboflavin and enhance the limit of detection in electrochemically-based nitrotoluene sensing. Full article
(This article belongs to the Section Chemical Sensors)
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Open AccessArticle Rapid Detection of Polychlorinated Biphenyls at Trace Levels in Real Environmental Samples by Surface-Enhanced Raman Scattering
Sensors 2011, 11(11), 10851-10858; doi:10.3390/s111110851
Received: 1 October 2011 / Revised: 8 November 2011 / Accepted: 9 November 2011 / Published: 18 November 2011
Cited by 7 | PDF Full-text (951 KB) | HTML Full-text | XML Full-text
Abstract
Detection of trace levels of persistent pollutants in the environment is difficult but significant. Organic pollutant homologues, due to their similar physical and chemical properties, are even more difficult to distinguish, especially in trace amounts. We report here a simple method to [...] Read more.
Detection of trace levels of persistent pollutants in the environment is difficult but significant. Organic pollutant homologues, due to their similar physical and chemical properties, are even more difficult to distinguish, especially in trace amounts. We report here a simple method to detect polychlorinated biphenyls (PCBs) in soil and distilled spirit samples by the surface-enhanced Raman scattering technique using Ag nanorod arrays as substrates. By this method, polychlorinated biphenyls can be detected to a concentration of 5 μg/g in dry soil samples within 1 minute. Furthermore, based on simulation and understanding of the Raman characteristics of PCBs, we recognized homologues of tetrachlorobiphenyl by using the surface-enhance Raman scattering method even in trace amounts in acetone solutions, and their characteristic Raman peaks still can be distinguished at a concentration of 10-6 mol/L. This study provides a fast, simple and sensitive method for the detection and recognition of organic pollutants such as polychlorinated biphenyls. Full article
(This article belongs to the Special Issue Sensing of Organic Pollution in Soil, Air, Water and Food)
Open AccessArticle Calibrating Single-Ended Fiber-Optic Raman Spectra Distributed Temperature Sensing Data
Sensors 2011, 11(11), 10859-10879; doi:10.3390/s111110859
Received: 19 October 2011 / Revised: 15 November 2011 / Accepted: 16 November 2011 / Published: 21 November 2011
Cited by 46 | PDF Full-text (499 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Hydrologic research is a very demanding application of fiber-optic distributed temperature sensing (DTS) in terms of precision, accuracy and calibration. The physics behind the most frequently used DTS instruments are considered as they apply to four calibration methods for single-ended DTS installations. [...] Read more.
Hydrologic research is a very demanding application of fiber-optic distributed temperature sensing (DTS) in terms of precision, accuracy and calibration. The physics behind the most frequently used DTS instruments are considered as they apply to four calibration methods for single-ended DTS installations. The new methods presented are more accurate than the instrument-calibrated data, achieving accuracies on the order of tenths of a degree root mean square error (RMSE) and mean bias. Effects of localized non-uniformities that violate the assumptions of single-ended calibration data are explored and quantified. Experimental design considerations such as selection of integration times or selection of the length of the reference sections are discussed, and the impacts of these considerations on calibrated temperatures are explored in two case studies. Full article
(This article belongs to the Special Issue Optical Fiber Sensors 2012)
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Open AccessArticle Distributed Bees Algorithm Parameters Optimization for a Cost Efficient Target Allocation in Swarms of Robots
Sensors 2011, 11(11), 10880-10893; doi:10.3390/s111110880
Received: 10 October 2011 / Revised: 15 November 2011 / Accepted: 15 November 2011 / Published: 21 November 2011
Cited by 5 | PDF Full-text (378 KB) | HTML Full-text | XML Full-text
Abstract
Swarms of robots can use their sensing abilities to explore unknown environments and deploy on sites of interest. In this task, a large number of robots is more effective than a single unit because of their ability to quickly cover the area. [...] Read more.
Swarms of robots can use their sensing abilities to explore unknown environments and deploy on sites of interest. In this task, a large number of robots is more effective than a single unit because of their ability to quickly cover the area. However, the coordination of large teams of robots is not an easy problem, especially when the resources for the deployment are limited. In this paper, the Distributed Bees Algorithm (DBA), previously proposed by the authors, is optimized and applied to distributed target allocation in swarms of robots. Improved target allocation in terms of deployment cost efficiency is achieved through optimization of the DBA’s control parameters by means of a Genetic Algorithm. Experimental results show that with the optimized set of parameters, the deployment cost measured as the average distance traveled by the robots is reduced. The cost-efficient deployment is in some cases achieved at the expense of increased robots’ distribution error. Nevertheless, the proposed approach allows the swarm to adapt to the operating conditions when available resources are scarce. Full article
(This article belongs to the Special Issue Collaborative Sensors)
Open AccessArticle Development of a New Surface Acoustic Wave Based Gyroscope on a X-112°Y LiTaO3 Substrate
Sensors 2011, 11(11), 10894-10906; doi:10.3390/s111110894
Received: 12 October 2011 / Revised: 11 November 2011 / Accepted: 11 November 2011 / Published: 21 November 2011
Cited by 7 | PDF Full-text (948 KB) | HTML Full-text | XML Full-text
Abstract
A new micro gyroscope based on the surface acoustic wave (SAW) gyroscopic effect was developed. The SAW gyroscopic effect is investigated by applying the surface effective permittivity method in the regime of small ratios of the rotation velocity and the frequency of [...] Read more.
A new micro gyroscope based on the surface acoustic wave (SAW) gyroscopic effect was developed. The SAW gyroscopic effect is investigated by applying the surface effective permittivity method in the regime of small ratios of the rotation velocity and the frequency of the SAW. The theoretical analysis indicates that the larger velocity shift was observed from the rotated X-112°Y LiTaO3 substrate. Then, two SAW delay lines with reverse direction and an operation frequency of 160 MHz are fabricated on a same X-112°Y LiTaO3 chip as the feedback of two SAW oscillators, which act as the sensor element. The single-phase unidirectional transducer (SPUDT) and combed transducers were used to structure the delay lines to improve the frequency stability of the oscillator. The rotation of a piezoelectric medium gives rise to a shift of the propagation velocity of SAW due to the Coriolis force, resulting in the frequency shift of the SAW device, and hence, the evaluation of the sensor performance. Meanwhile, the differential structure was performed to double the sensitivity and compensate for the temperature effects. Using a precise rate table, the performance of the fabricated SAW gyroscope was evaluated experimentally. A sensitivity of 1.332 Hz deg−1 s at angular rates of up to 1,000 deg s−1 and good linearity are observed. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle Dynamic Control of Adsorption Sensitivity for Photo-EMF-Based Ammonia Gas Sensors Using a Wireless Network
Sensors 2011, 11(11), 10930-10939; doi:10.3390/s111110930
Received: 13 October 2011 / Revised: 11 November 2011 / Accepted: 18 November 2011 / Published: 22 November 2011
Cited by 1 | PDF Full-text (1354 KB) | HTML Full-text | XML Full-text
Abstract
This paper proposes an adsorption sensitivity control method that uses a wireless network and illumination light intensity in a photo-electromagnetic field (EMF)-based gas sensor for measurements in real time of a wide range of ammonia concentrations. The minimum measurement error for a [...] Read more.
This paper proposes an adsorption sensitivity control method that uses a wireless network and illumination light intensity in a photo-electromagnetic field (EMF)-based gas sensor for measurements in real time of a wide range of ammonia concentrations. The minimum measurement error for a range of ammonia concentration from 3 to 800 ppm occurs when the gas concentration magnitude corresponds with the optimal intensity of the illumination light. A simulation with LabView-engineered modules for automatic control of a new intelligent computer system was conducted to improve measurement precision over a wide range of gas concentrations. This gas sensor computer system with wireless network technology could be useful in the chemical industry for automatic detection and measurement of hazardous ammonia gas levels in real time. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle Alternative Post-Processing on a CMOS Chip to Fabricate a Planar Microelectrode Array
Sensors 2011, 11(11), 10940-10957; doi:10.3390/s111110940
Received: 24 October 2011 / Revised: 9 November 2011 / Accepted: 18 November 2011 / Published: 22 November 2011
Cited by 5 | PDF Full-text (3834 KB) | HTML Full-text | XML Full-text
Abstract
We present an alternative post-processing on a CMOS chip to release a planar microelectrode array (pMEA) integrated with its signal readout circuit, which can be used for monitoring the neuronal activity of vestibular ganglion neurons in newborn Wistar strain rats. This chip [...] Read more.
We present an alternative post-processing on a CMOS chip to release a planar microelectrode array (pMEA) integrated with its signal readout circuit, which can be used for monitoring the neuronal activity of vestibular ganglion neurons in newborn Wistar strain rats. This chip is fabricated through a 0.6 µm CMOS standard process and it has 12 pMEA through a 4  ´ 3 electrodes matrix. The alternative CMOS post-process includes the development of masks to protect the readout circuit and the power supply pads. A wet etching process eliminates the aluminum located on the surface of the p+-type silicon. This silicon is used as transducer for recording the neuronal activity and as interface between the readout circuit and neurons. The readout circuit is composed of an amplifier and tunable bandpass filter, which is placed on a 0.015 mm2 silicon area. The tunable bandpass filter has a bandwidth of 98 kHz and a common mode rejection ratio (CMRR) of 87 dB. These characteristics of the readout circuit are appropriate for neuronal recording applications. Full article
(This article belongs to the Special Issue Biochips)
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Open AccessArticle Autonomous Navigation for Autonomous Underwater Vehicles Based on Information Filters and Active Sensing
Sensors 2011, 11(11), 10958-10980; doi:10.3390/s111110958
Received: 8 October 2011 / Revised: 11 November 2011 / Accepted: 18 November 2011 / Published: 22 November 2011
Cited by 16 | PDF Full-text (1109 KB) | HTML Full-text | XML Full-text
Abstract
This paper addresses an autonomous navigation method for the autonomous underwater vehicle (AUV) C-Ranger applying information-filter-based simultaneous localization and mapping (SLAM), and its sea trial experiments in Tuandao Bay (Shangdong Province, P.R. China). Weak links in the information matrix in an extended [...] Read more.
This paper addresses an autonomous navigation method for the autonomous underwater vehicle (AUV) C-Ranger applying information-filter-based simultaneous localization and mapping (SLAM), and its sea trial experiments in Tuandao Bay (Shangdong Province, P.R. China). Weak links in the information matrix in an extended information filter (EIF) can be pruned to achieve an efficient approach-sparse EIF algorithm (SEIF-SLAM). All the basic update formulae can be implemented in constant time irrespective of the size of the map; hence the computational complexity is significantly reduced. The mechanical scanning imaging sonar is chosen as the active sensing device for the underwater vehicle, and a compensation method based on feedback of the AUV pose is presented to overcome distortion of the acoustic images due to the vehicle motion. In order to verify the feasibility of the navigation methods proposed for the C-Ranger, a sea trial was conducted in Tuandao Bay. Experimental results and analysis show that the proposed navigation approach based on SEIF-SLAM improves the accuracy of the navigation compared with conventional method; moreover the algorithm has a low computational cost when compared with EKF-SLAM. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle Thermal Infrared Spectrometer for Earth Science Remote Sensing Applications—Instrument Modifications and Measurement Procedures
Sensors 2011, 11(11), 10981-10999; doi:10.3390/s111110981
Received: 18 October 2011 / Revised: 16 November 2011 / Accepted: 16 November 2011 / Published: 23 November 2011
Cited by 17 | PDF Full-text (1469 KB) | HTML Full-text | XML Full-text
Abstract
In this article we describe a new instrumental setup at the University of Twente Faculty ITC with an optimized processing chain to measure absolute directional-hemispherical reflectance values of typical earth science samples in the 2.5 to 16 µm range. A Bruker Vertex [...] Read more.
In this article we describe a new instrumental setup at the University of Twente Faculty ITC with an optimized processing chain to measure absolute directional-hemispherical reflectance values of typical earth science samples in the 2.5 to 16 µm range. A Bruker Vertex 70 FTIR spectrometer was chosen as the base instrument. It was modified with an external integrating sphere with a 30 mm sampling port to allow measuring large, inhomogeneous samples and quantitatively compare the laboratory results to airborne and spaceborne remote sensing data. During the processing to directional-hemispherical reflectance values, a background radiation subtraction is performed, removing the effect of radiance not reflected from the sample itself on the detector. This provides more accurate reflectance values for low-reflecting samples. Repeat measurements taken over a 20 month period on a quartz sand standard show that the repeatability of the system is very high, with a standard deviation ranging between 0.001 and 0.006 reflectance units depending on wavelength. This high level of repeatability is achieved even after replacing optical components, re-aligning mirrors and placement of sample port reducers. Absolute reflectance values of measurements taken by the instrument here presented compare very favorably to measurements of other leading laboratories taken on identical sample standards. Full article
(This article belongs to the Section Remote Sensors)
Open AccessArticle Selective Change Driven Imaging: A Biomimetic Visual Sensing Strategy
Sensors 2011, 11(11), 11000-11020; doi:10.3390/s111111000
Received: 15 October 2011 / Revised: 15 November 2011 / Accepted: 18 November 2011 / Published: 23 November 2011
Cited by 3 | PDF Full-text (2383 KB) | HTML Full-text | XML Full-text
Abstract
Selective Change Driven (SCD) Vision is a biologically inspired strategy for acquiring, transmitting and processing images that significantly speeds up image sensing. SCD vision is based on a new CMOS image sensor which delivers, ordered by the absolute magnitude of its change, [...] Read more.
Selective Change Driven (SCD) Vision is a biologically inspired strategy for acquiring, transmitting and processing images that significantly speeds up image sensing. SCD vision is based on a new CMOS image sensor which delivers, ordered by the absolute magnitude of its change, the pixels that have changed after the last time they were read out. Moreover, the traditional full frame processing hardware and programming methodology has to be changed, as a part of this biomimetic approach, to a new processing paradigm based on pixel processing in a data flow manner, instead of full frame image processing. Full article
(This article belongs to the Special Issue Biomimetic Sensors, Actuators and Integrated Systems)
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Open AccessArticle System-Level Biochip for Impedance Sensing and Programmable Manipulation of Bladder Cancer Cells
Sensors 2011, 11(11), 11021-11035; doi:10.3390/s111111021
Received: 8 October 2011 / Revised: 17 November 2011 / Accepted: 17 November 2011 / Published: 23 November 2011
Cited by 14 | PDF Full-text (2036 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
This paper develops a dielectrophoretic (DEP) chip with multi-layer electrodes and a micro-cavity array for programmable manipulations of cells and impedance measurement. The DEP chip consists of an ITO top electrode, flow chamber, middle electrode on an SU-8 surface, micro-cavity arrays of [...] Read more.
This paper develops a dielectrophoretic (DEP) chip with multi-layer electrodes and a micro-cavity array for programmable manipulations of cells and impedance measurement. The DEP chip consists of an ITO top electrode, flow chamber, middle electrode on an SU-8 surface, micro-cavity arrays of SU-8 and distributed electrodes at the bottom of the micro-cavity. Impedance sensing of single cells could be performed as follows: firstly, cells were trapped in a micro-cavity array by negative DEP force provided by top and middle electrodes; then, the impedance measurement for discrimination of different stage of bladder cancer cells was accomplished by the middle and bottom electrodes. After impedance sensing, the individual releasing of trapped cells was achieved by negative DEP force using the top and bottom electrodes in order to collect the identified cells once more. Both cell manipulations and impedance measurement had been integrated within a system controlled by a PC-based LabVIEW program. In the experiments, two different stages of bladder cancer cell lines (grade III: T24 and grade II: TSGH8301) were utilized for the demonstration of programmable manipulation and impedance sensing; as the results show, the lower-grade bladder cancer cells (TSGH8301) possess higher impedance than the higher-grade ones (T24). In general, the multi-step manipulations of cells can be easily programmed by controlling the electrical signal in our design, which provides an excellent platform technology for lab-on-a-chip (LOC) or a micro-total-analysis-system (Micro TAS). Full article
(This article belongs to the Special Issue Biochips)

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Open AccessReview A Comprehensive Approach to WSN-Based ITS Applications: A Survey
Sensors 2011, 11(11), 10220-10265; doi:10.3390/s111110220
Received: 4 October 2011 / Revised: 20 October 2011 / Accepted: 24 October 2011 / Published: 28 October 2011
Cited by 24 | PDF Full-text (1270 KB) | HTML Full-text | XML Full-text
Abstract
In order to perform sensing tasks, most current Intelligent Transportation Systems (ITS) rely on expensive sensors, which offer only limited functionality. A more recent trend consists of using Wireless Sensor Networks (WSN) for such purpose, which reduces the required investment and enables [...] Read more.
In order to perform sensing tasks, most current Intelligent Transportation Systems (ITS) rely on expensive sensors, which offer only limited functionality. A more recent trend consists of using Wireless Sensor Networks (WSN) for such purpose, which reduces the required investment and enables the development of new collaborative and intelligent applications that further contribute to improve both driving safety and traffic efficiency. This paper surveys the application of WSNs to such ITS scenarios, tackling the main issues that may arise when developing these systems. The paper is divided into sections which address different matters including vehicle detection and classification as well as the selection of appropriate communication protocols, network architecture, topology and some important design parameters. In addition, in line with the multiplicity of different technologies that take part in ITS, it does not consider WSNs just as stand-alone systems, but also as key components of heterogeneous systems cooperating along with other technologies employed in vehicular scenarios. Full article
(This article belongs to the Special Issue Collaborative Sensors)
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Open AccessReview Surface X-Ray Diffraction Results on the III-V Droplet Heteroepitaxy Growth Process for Quantum Dots: Recent Understanding and Open Questions
Sensors 2011, 11(11), 10624-10637; doi:10.3390/s111110624
Received: 16 September 2011 / Revised: 25 October 2011 / Accepted: 2 November 2011 / Published: 8 November 2011
Cited by 3 | PDF Full-text (2009 KB) | HTML Full-text | XML Full-text
Abstract
In recent years, epitaxial growth of self-assembled quantum dots has offered a way to incorporate new properties into existing solid state devices. Although the droplet heteroepitaxy method is relatively complex, it is quite relaxed with respect to the material combinations that can [...] Read more.
In recent years, epitaxial growth of self-assembled quantum dots has offered a way to incorporate new properties into existing solid state devices. Although the droplet heteroepitaxy method is relatively complex, it is quite relaxed with respect to the material combinations that can be used. This offers great flexibility in the systems that can be achieved. In this paper we review the structure and composition of a number of quantum dot systems grown by the droplet heteroepitaxy method, emphasizing the insights that these experiments provide with respect to the growth process. Detailed structural and composition information has been obtained using surface X-ray diffraction analyzed by the COBRA phase retrieval method. A number of interesting phenomena have been observed: penetration of the dots into the substrate (“nano-drilling”) is often encountered; interdiffusion and intermixing already start when the group III droplets are deposited, and structure and composition may be very different from the one initially intended. Full article
(This article belongs to the Special Issue Sensing with Quantum Dots)
Open AccessReview Piezoresistive Strain Sensors Made from Carbon Nanotubes Based Polymer Nanocomposites
Sensors 2011, 11(11), 10691-10723; doi:10.3390/s111110691
Received: 9 October 2011 / Revised: 5 November 2011 / Accepted: 7 November 2011 / Published: 11 November 2011
Cited by 88 | PDF Full-text (3700 KB) | HTML Full-text | XML Full-text
Abstract
In recent years, nanocomposites based on various nano-scale carbon fillers, such as carbon nanotubes (CNTs), are increasingly being thought of as a realistic alternative to conventional smart materials, largely due to their superior electrical properties. Great interest has been generated in building [...] Read more.
In recent years, nanocomposites based on various nano-scale carbon fillers, such as carbon nanotubes (CNTs), are increasingly being thought of as a realistic alternative to conventional smart materials, largely due to their superior electrical properties. Great interest has been generated in building highly sensitive strain sensors with these new nanocomposites. This article reviews the recent significant developments in the field of highly sensitive strain sensors made from CNT/polymer nanocomposites. We focus on the following two topics: electrical conductivity and piezoresistivity of CNT/polymer nanocomposites, and the relationship between them by considering the internal conductive network formed by CNTs, tunneling effect, aspect ratio and piezoresistivity of CNTs themselves, etc. Many recent experimental, theoretical and numerical studies in this field are described in detail to uncover the working mechanisms of this new type of strain sensors and to demonstrate some possible key factors for improving the sensor sensitivity. Full article
(This article belongs to the Section Physical Sensors)
Open AccessReview Plasmonic Nanostructures for Nano-Scale Bio-Sensing
Sensors 2011, 11(11), 10907-10929; doi:10.3390/s111110907
Received: 8 October 2011 / Revised: 13 November 2011 / Accepted: 14 November 2011 / Published: 21 November 2011
Cited by 77 | PDF Full-text (1413 KB) | HTML Full-text | XML Full-text
Abstract
The optical properties of various nanostructures have been widely adopted for biological detection, from DNA sequencing to nano-scale single molecule biological function measurements. In particular, by employing localized surface plasmon resonance (LSPR), we can expect distinguished sensing performance with high sensitivity and [...] Read more.
The optical properties of various nanostructures have been widely adopted for biological detection, from DNA sequencing to nano-scale single molecule biological function measurements. In particular, by employing localized surface plasmon resonance (LSPR), we can expect distinguished sensing performance with high sensitivity and resolution. This indicates that nano-scale detections can be realized by using the shift of resonance wavelength of LSPR in response to the refractive index change. In this paper, we overview various plasmonic nanostructures as potential sensing components. The qualitative descriptions of plasmonic nanostructures are supported by the physical phenomena such as plasmonic hybridization and Fano resonance. We present guidelines for designing specific nanostructures with regard to wavelength range and target sensing materials. Full article
(This article belongs to the Special Issue Nano-Biosensors)
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Open AccessCorrection Correction: Ngo, T.D. LinkMind: Link Optimization in Swarming Mobile Sensor Networks. Sensors 2011, 11, 8180-8202
Sensors 2011, 11(11), 10165; doi:10.3390/s111110165
Received: 25 October 2011 / Accepted: 26 October 2011 / Published: 26 October 2011
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Abstract The author’s affiliation was wrong in [1]. The “National University of Brunei” should be “University of Brunei Darussalam”. [...] Full article
(This article belongs to the Section Biosensors)

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