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Sensors, Volume 10, Issue 3 (March 2010), Pages 1423-2459

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Open AccessArticle Automatically Augmenting Lifelog Events Using Pervasively Generated Content from Millions of People
Sensors 2010, 10(3), 1423-1446; doi:10.3390/s100301423
Received: 24 December 2009 / Revised: 19 January 2010 / Accepted: 3 February 2010 / Published: 26 February 2010
Cited by 14 | PDF Full-text (4410 KB) | HTML Full-text | XML Full-text
Abstract
In sensor research we take advantage of additional contextual sensor information to disambiguate potentially erroneous sensor readings or to make better informed decisions on a single sensor’s output. This use of additional information reinforces, validates, semantically enriches, and augments sensed data. Lifelog [...] Read more.
In sensor research we take advantage of additional contextual sensor information to disambiguate potentially erroneous sensor readings or to make better informed decisions on a single sensor’s output. This use of additional information reinforces, validates, semantically enriches, and augments sensed data. Lifelog data is challenging to augment, as it tracks one’s life with many images including the places they go, making it non-trivial to find associated sources of information. We investigate realising the goal of pervasive user-generated content based on sensors, by augmenting passive visual lifelogs with “Web 2.0” content collected by millions of other individuals. Full article
(This article belongs to the Section Chemical Sensors)
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Open AccessArticle Achieving Network Level Privacy in Wireless Sensor Networks
Sensors 2010, 10(3), 1447-1472; doi:10.3390/s100301447
Received: 17 December 2009 / Revised: 4 February 2010 / Accepted: 9 February 2010 / Published: 26 February 2010
Cited by 17 | PDF Full-text (477 KB) | HTML Full-text | XML Full-text
Abstract
Full network level privacy has often been categorized into four sub-categories: Identity, Route, Location and Data privacy. Achieving full network level privacy is a critical and challenging problem due to the constraints imposed by the sensor nodes (e.g., energy, memory and computation [...] Read more.
Full network level privacy has often been categorized into four sub-categories: Identity, Route, Location and Data privacy. Achieving full network level privacy is a critical and challenging problem due to the constraints imposed by the sensor nodes (e.g., energy, memory and computation power), sensor networks (e.g., mobility and topology) and QoS issues (e.g., packet reach-ability and timeliness). In this paper, we proposed two new identity, route and location privacy algorithms and data privacy mechanism that addresses this problem. The proposed solutions provide additional trustworthiness and reliability at modest cost of memory and energy. Also, we proved that our proposed solutions provide protection against various privacy disclosure attacks, such as eavesdropping and hop-by-hop trace back attacks. Full article
Open AccessArticle Paper Actuators Made with Cellulose and Hybrid Materials
Sensors 2010, 10(3), 1473-1485; doi:10.3390/s100301473
Received: 25 December 2009 / Revised: 27 January 2010 / Accepted: 20 February 2010 / Published: 26 February 2010
Cited by 18 | PDF Full-text (2742 KB) | HTML Full-text | XML Full-text
Abstract
Recently, cellulose has been re-discovered as a smart material that can be used as sensor and actuator materials, which is termed electro-active paper (EAPap). This paper reports recent advances in paper actuators made with cellulose and hybrid materials such as multi-walled carbon [...] Read more.
Recently, cellulose has been re-discovered as a smart material that can be used as sensor and actuator materials, which is termed electro-active paper (EAPap). This paper reports recent advances in paper actuators made with cellulose and hybrid materials such as multi-walled carbon nanotubes, conducting polymers and ionic liquids. Two distinct actuator principles in EAPap actuators are demonstrated: piezoelectric effect and ion migration effect in cellulose. Piezoelectricity of cellulose EAPap is quite comparable with other piezoelectric polymers. But, it is biodegradable, biocompatible, mechanically strong and thermally stable. To enhance ion migration effect in the cellulose, polypyrrole conducting polymer and ionic liquids were nanocoated on the cellulose film. This hybrid cellulose EAPap nanocomposite exhibits durable bending actuation in an ambient humidity and temperature condition. Fabrication, characteristics and performance of the cellulose EAPap and its hybrid EAPap materials are illustrated. Also, its possibility for remotely microwave-driven paper actuator is demonstrated. Full article
(This article belongs to the Special Issue Advances in Actuators)
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Open AccessArticle Reliable Asynchronous Image Transfer Protocol in Wireless Multimedia Sensor Networks
Sensors 2010, 10(3), 1486-1510; doi:10.3390/s100301487
Received: 5 January 2010 / Revised: 28 January 2010 / Accepted: 5 February 2010 / Published: 26 February 2010
Cited by 6 | PDF Full-text (1091 KB) | HTML Full-text | XML Full-text
Abstract
In the paper, we propose a reliable asynchronous image transfer protocol, RAIT. RAIT applies a double sliding window method to node-to-node transfer, with one sliding window for the receiving queue, which is used to prevent packet loss caused by communication failure between [...] Read more.
In the paper, we propose a reliable asynchronous image transfer protocol, RAIT. RAIT applies a double sliding window method to node-to-node transfer, with one sliding window for the receiving queue, which is used to prevent packet loss caused by communication failure between nodes, and another sliding window for the sending queue, which prevents packet loss caused by network congestion. The routing node prevents packet loss between nodes by preemptive scheduling of multiple packets for a given image. RAIT implements a double sliding window method by means of a cross-layer design between the RAIT layer, routing layer, and queue layer. We demonstrate that RAIT guarantees a higher reliability of image transmission compared to the existing protocols. Full article
Open AccessArticle Concurrent Initialization for Bearing-Only SLAM
Sensors 2010, 10(3), 1511-1534; doi:10.3390/s100301511
Received: 18 December 2009 / Revised: 15 February 2010 / Accepted: 24 February 2010 / Published: 1 March 2010
Cited by 6 | PDF Full-text (477 KB) | HTML Full-text | XML Full-text
Abstract
Simultaneous Localization and Mapping (SLAM) is perhaps the most fundamental problem to solve in robotics in order to build truly autonomous mobile robots. The sensors have a large impact on the algorithm used for SLAM. Early SLAM approaches focused on the use [...] Read more.
Simultaneous Localization and Mapping (SLAM) is perhaps the most fundamental problem to solve in robotics in order to build truly autonomous mobile robots. The sensors have a large impact on the algorithm used for SLAM. Early SLAM approaches focused on the use of range sensors as sonar rings or lasers. However, cameras have become more and more used, because they yield a lot of information and are well adapted for embedded systems: they are light, cheap and power saving. Unlike range sensors which provide range and angular information, a camera is a projective sensor which measures the bearing of images features. Therefore depth information (range) cannot be obtained in a single step. This fact has propitiated the emergence of a new family of SLAM algorithms: the Bearing-Only SLAM methods, which mainly rely in especial techniques for features system-initialization in order to enable the use of bearing sensors (as cameras) in SLAM systems. In this work a novel and robust method, called Concurrent Initialization, is presented which is inspired by having the complementary advantages of the Undelayed and Delayed methods that represent the most common approaches for addressing the problem. The key is to use concurrently two kinds of feature representations for both undelayed and delayed stages of the estimation. The simulations results show that the proposed method surpasses the performance of previous schemes. Full article
(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Spain)
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Open AccessArticle A New Electronic Monitoring Device to Measure Medication Adherence: Usability of the Helping Hand™
Sensors 2010, 10(3), 1535-1552; doi:10.3390/s100301535
Received: 31 December 2009 / Revised: 19 February 2010 / Accepted: 25 February 2010 / Published: 1 March 2010
Cited by 7 | PDF Full-text (142 KB) | HTML Full-text | XML Full-text
Abstract
The aim of this study was to test the user performance, satisfaction and acceptability of the Helping Hand™ (B&O Medicom) electronic medication adherence monitor. Using a mixed-method design, we studied 11 kidney transplant patients and 10 healthy volunteers during three weeks. Although testing showed positive usability aspects, several areas requiring technical improvement were identified: the most important obstacles to usability and acceptability were the weak sound signal, problems loading the medication, and the fact that only one medication could be used at a time. Full article
(This article belongs to the Special Issue Modeling, Testing and Reliability Issues in MEMS Engineering - 2009)
Open AccessArticle Geometric Stability and Lens Decentering in Compact Digital Cameras
Sensors 2010, 10(3), 1553-1572; doi:10.3390/s100301553
Received: 25 December 2009 / Revised: 26 January 2010 / Accepted: 20 February 2010 / Published: 1 March 2010
Cited by 5 | PDF Full-text (1160 KB) | HTML Full-text | XML Full-text
Abstract
A study on the geometric stability and decentering present in sensor-lens systems of six identical compact digital cameras has been conducted. With regard to geometrical stability, the variation of internal geometry parameters (principal distance, principal point position and distortion parameters) was considered. [...] Read more.
A study on the geometric stability and decentering present in sensor-lens systems of six identical compact digital cameras has been conducted. With regard to geometrical stability, the variation of internal geometry parameters (principal distance, principal point position and distortion parameters) was considered. With regard to lens decentering, the amount of radial and tangential displacement resulting from decentering distortion was related with the precision of the camera and with the offset of the principal point from the geometric center of the sensor. The study was conducted with data obtained after 372 calibration processes (62 per camera). The tests were performed for each camera in three situations: during continuous use of the cameras, after camera power off/on and after the full extension and retraction of the zoom-lens. Additionally, 360 new calibrations were performed in order to study the variation of the internal geometry when the camera is rotated. The aim of this study was to relate the level of stability and decentering in a camera with the precision and quality that can be obtained. An additional goal was to provide practical recommendations about photogrammetric use of such cameras. Full article
(This article belongs to the Special Issue Image Sensors)
Open AccessArticle A Z-axis Quartz Cross-fork Micromachined Gyroscope Based on Shear Stress Detection
Sensors 2010, 10(3), 1573-1588; doi:10.3390/s100301573
Received: 22 December 2009 / Revised: 14 January 2010 / Accepted: 30 January 2010 / Published: 1 March 2010
Cited by 13 | PDF Full-text (356 KB) | HTML Full-text | XML Full-text
Abstract
Here we propose a novel quartz micromachined gyroscope. The sensor has a simple cross-fork structure in the x-y plane of quartz crystal. Shear stress rather than normal stress is utilized to sense Coriolis’ force generated by the input angular rate signal. Compared [...] Read more.
Here we propose a novel quartz micromachined gyroscope. The sensor has a simple cross-fork structure in the x-y plane of quartz crystal. Shear stress rather than normal stress is utilized to sense Coriolis’ force generated by the input angular rate signal. Compared to traditional quartz gyroscopes, which have two separate sense electrodes on each sidewall, there is only one electrode on each sidewall of the sense beam. As a result, the fabrication of the electrodes is simplified and the structure can be easily miniaturized. In order to increase sensitivity, a pair of proof masses is attached to the ends of the drive beam, and the sense beam has a tapered design. The structure is etched from a z-cut quartz wafer and the electrodes are realized by direct evaporation using the aperture mask method. The drive mode frequency of the prototype is 13.38 kHz, and the quality factor is approximately 1,000 in air. Therefore, the gyroscope can work properly without a vacuum package. The measurement ability of the shear stress detection design scheme is validated by the Coriolis’ force test. The performance of the sensor is characterized on a precision rate table using a specially designed readout circuit. The experimentally obtained scale factor is 1.45 mV/°/s and the nonlinearity is 3.6% in range of ±200 °/s. Full article
(This article belongs to the Section Chemical Sensors)
Open AccessArticle Conductometric Soot Sensor for Automotive Exhausts: Initial Studies
Sensors 2010, 10(3), 1589-1598; doi:10.3390/s100301589
Received: 14 January 2010 / Revised: 3 February 2010 / Accepted: 22 February 2010 / Published: 1 March 2010
Cited by 24 | PDF Full-text (443 KB) | HTML Full-text | XML Full-text
Abstract
In order to reduce the tailpipe particulate matter emissions of Diesel engines, Diesel particulate filters (DPFs) are commonly used. Initial studies using a conductometric soot sensor to monitor their filtering efficiency, i.e., to detect a malfunction of the DPF, are presented. [...] Read more.
In order to reduce the tailpipe particulate matter emissions of Diesel engines, Diesel particulate filters (DPFs) are commonly used. Initial studies using a conductometric soot sensor to monitor their filtering efficiency, i.e., to detect a malfunction of the DPF, are presented. The sensors consist of a planar substrate equipped with electrodes on one side and with a heater on the other. It is shown that at constant speed-load points, the time until soot percolation occurs or the resistance itself are reproducible means that can be well correlated with the filtering efficiency of a DPF. It is suggested to use such a sensor setup for the detection of a DPF malfunction. Full article
(This article belongs to the Section Chemical Sensors)
Open AccessArticle Mobile Sensor Networks for Inspection Tasks in Harsh Industrial Environments
Sensors 2010, 10(3), 1599-1618; doi:10.3390/s100301599
Received: 4 December 2009 / Revised: 21 January 2010 / Accepted: 20 February 2010 / Published: 1 March 2010
Cited by 1 | PDF Full-text (582 KB) | HTML Full-text | XML Full-text
Abstract
Recent advances in sensor technology have enabled the fast development of mobile sensor networks operating in various unknown and sometimes hazardous environments. In this paper, we introduce one integrative approach to design, analyze and test distributed control algorithms to coordinate a network [...] Read more.
Recent advances in sensor technology have enabled the fast development of mobile sensor networks operating in various unknown and sometimes hazardous environments. In this paper, we introduce one integrative approach to design, analyze and test distributed control algorithms to coordinate a network of autonomous mobile sensors by utilizing both simulation tools and a robotic testbed. The research has been carried out in the context of the mobile sensing project, PicoSmart, in the northern provinces of the Netherlands for the inspection of natural gas pipelines. Full article
(This article belongs to the Special Issue State-of-the-Art Sensors Technology in The Netherlands)
Open AccessArticle An Enhanced Backbone-Assisted Reliable Framework for Wireless Sensor Networks
Sensors 2010, 10(3), 1619-1651; doi:10.3390/s100301619
Received: 10 January 2010 / Revised: 13 February 2010 / Accepted: 22 February 2010 / Published: 1 March 2010
Cited by 11 | PDF Full-text (675 KB) | HTML Full-text | XML Full-text
Abstract
An extremely reliable source to sink communication is required for most of the contemporary WSN applications especially pertaining to military, healthcare and disaster-recovery. However, due to their intrinsic energy, bandwidth and computational constraints, Wireless Sensor Networks (WSNs) encounter several challenges in reliable [...] Read more.
An extremely reliable source to sink communication is required for most of the contemporary WSN applications especially pertaining to military, healthcare and disaster-recovery. However, due to their intrinsic energy, bandwidth and computational constraints, Wireless Sensor Networks (WSNs) encounter several challenges in reliable source to sink communication. In this paper, we present a novel reliable topology that uses reliable hotlines between sensor gateways to boost the reliability of end-to-end transmissions. This reliable and efficient routing alternative reduces the number of average hops from source to the sink. We prove, with the help of analytical evaluation, that communication using hotlines is considerably more reliable than traditional WSN routing. We use reliability theory to analyze the cost and benefit of adding gateway nodes to a backbone-assisted WSN. However, in hotline assisted routing some scenarios where source and the sink are just a couple of hops away might bring more latency, therefore, we present a Signature Based Routing (SBR) scheme. SBR enables the gateways to make intelligent routing decisions, based upon the derived signature, hence providing lesser end-to-end delay between source to the sink communication. Finally, we evaluate our proposed hotline based topology with the help of a simulation tool and show that the proposed topology provides manifold increase in end-to-end reliability. Full article
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Open AccessArticle How Accurate Are Electronic Monitoring Devices? A Laboratory Study Testing Two Devices to Measure Medication Adherence
Sensors 2010, 10(3), 1652-1660; doi:10.3390/s100301652
Received: 31 December 2009 / Revised: 2 February 2010 / Accepted: 25 February 2010 / Published: 2 March 2010
Cited by 5 | PDF Full-text (68 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
In a prospective descriptive laboratory study, 25 Helping Hand™ (HH) (10 without and 15 with reminder system) and 50 Medication Event Monitoring Systems (MEMS) (25 with 18-month and 25 with 2-year battery life) were manipulated twice daily following a predefined protocol during [...] Read more.
In a prospective descriptive laboratory study, 25 Helping Hand™ (HH) (10 without and 15 with reminder system) and 50 Medication Event Monitoring Systems (MEMS) (25 with 18-month and 25 with 2-year battery life) were manipulated twice daily following a predefined protocol during 3 consecutive weeks. Accuracy was determined using the fixed manipulation scheme as the reference. Perfect functioning (i.e., total absence of missing registrations and/or overregistrations) was observed in 70% of the HH without, 87% of the HH with reminder, 20% MEMS with 18 months, and 100% with 2-year battery life respectively. Full article
(This article belongs to the Special Issue Modeling, Testing and Reliability Issues in MEMS Engineering - 2009)
Open AccessArticle Reduced Fluoresceinamine as a Fluorescent Sensor for Nitric Oxide
Sensors 2010, 10(3), 1661-1669; doi:10.3390/s100301661
Received: 28 December 2009 / Revised: 9 February 2010 / Accepted: 22 February 2010 / Published: 2 March 2010
Cited by 8 | PDF Full-text (306 KB) | HTML Full-text | XML Full-text
Abstract
A new fluorescent sensor for nitric oxide (NO) is presented that is based on its reaction with a non fluorescent substance, reduced fluoresceinamine, producing the highly fluorescent fluoresceinamine. Using a portable homemade stabilized light source consisting of 450 nm LED and fiber [...] Read more.
A new fluorescent sensor for nitric oxide (NO) is presented that is based on its reaction with a non fluorescent substance, reduced fluoresceinamine, producing the highly fluorescent fluoresceinamine. Using a portable homemade stabilized light source consisting of 450 nm LED and fiber optics to guide the light, the sensor responds linearly within seconds in the NO concentration range between about 10–750 μM with a limit of detection (LOD) of about 1 μM. The system generated precise intensity readings, with a relative standard deviation of less than 1%. The suitability of the sensor was assessed by monitoring the NO generated by either the nitrous acid decomposition reaction or from a NO-releasing compound. Using relatively high incubation times, the sensor also responds quantitatively to hydrogen peroxide and potassium superoxide, however, using transient signal measurements results in no interfering species. Full article
(This article belongs to the Special Issue Fluorescent Chemosensors)
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Open AccessArticle A Thick-film Sensor as a Novel Device for Determination of Polyphenols and Their Antioxidant Capacity in White Wine
Sensors 2010, 10(3), 1670-1678; doi:10.3390/s100301670
Received: 13 January 2010 / Revised: 28 January 2010 / Accepted: 8 February 2010 / Published: 2 March 2010
Cited by 10 | PDF Full-text (195 KB) | HTML Full-text | XML Full-text
Abstract
A thick-film electrochemical sensor with an iridium-carbon working electrode was used for determining polyphenols and their antioxidant capacity in white wine. Caffeic acid was used as a model species because it has the ability to produce the highest oxidation current. The correlation [...] Read more.
A thick-film electrochemical sensor with an iridium-carbon working electrode was used for determining polyphenols and their antioxidant capacity in white wine. Caffeic acid was used as a model species because it has the ability to produce the highest oxidation current. The correlation coefficient of 0.9975 was obtained between sensor response and caffeic acid content. The total phenolic content (TPC) and scavenging activity on 1,1-diphenyl-2-pycrylhydrazyl (DPPH·) radical were also found to be strongly correlated with the concentration of caffeic acid, with a correlation coefficient of 0.9823 and 0.9958, respectively. The sensor prototype was proven to be a simple, efficient and cost effective device to evaluate the antioxidant capacity of substances. Full article
(This article belongs to the Section Chemical Sensors)
Open AccessArticle Improving the Ability of Image Sensors to Detect Faint Stars and Moving Objects Using Image Deconvolution Techniques
Sensors 2010, 10(3), 1743-1752; doi:10.3390/s100301743
Received: 22 December 2009 / Revised: 25 January 2010 / Accepted: 3 February 2010 / Published: 3 March 2010
Cited by 5 | PDF Full-text (424 KB) | HTML Full-text | XML Full-text
Abstract
In this paper we show how the techniques of image deconvolution can increase the ability of image sensors as, for example, CCD imagers, to detect faint stars or faint orbital objects (small satellites and space debris). In the case of faint stars, [...] Read more.
In this paper we show how the techniques of image deconvolution can increase the ability of image sensors as, for example, CCD imagers, to detect faint stars or faint orbital objects (small satellites and space debris). In the case of faint stars, we show that this benefit is equivalent to double the quantum efficiency of the used image sensor or to increase the effective telescope aperture by more than 30% without decreasing the astrometric precision or introducing artificial bias. In the case of orbital objects, the deconvolution technique can double the signal-to-noise ratio of the image, which helps to discover and control dangerous objects as space debris or lost satellites. The benefits obtained using CCD detectors can be extrapolated to any kind of image sensors. Full article
(This article belongs to the Special Issue Image Sensors)
Open AccessArticle Cobalt Oxide Nanosheet and CNT Micro Carbon Monoxide Sensor Integrated with Readout Circuit on Chip
Sensors 2010, 10(3), 1753-1764; doi:10.3390/s100301753
Received: 31 December 2009 / Revised: 30 January 2010 / Accepted: 4 February 2010 / Published: 3 March 2010
Cited by 16 | PDF Full-text (616 KB) | HTML Full-text | XML Full-text
Abstract
The study presents a micro carbon monoxide (CO) sensor integrated with a readout circuit-on-a-chip manufactured by the commercial 0.35 μm complementary metal oxide semiconductor (CMOS) process and a post-process. The sensing film of the sensor is a composite cobalt oxide nanosheet and [...] Read more.
The study presents a micro carbon monoxide (CO) sensor integrated with a readout circuit-on-a-chip manufactured by the commercial 0.35 μm complementary metal oxide semiconductor (CMOS) process and a post-process. The sensing film of the sensor is a composite cobalt oxide nanosheet and carbon nanotube (CoOOH/CNT) film that is prepared by a precipitation-oxidation method. The structure of the CO sensor is composed of a polysilicon resistor and a sensing film. The sensor, which is of a resistive type, changes its resistance when the sensing film adsorbs or desorbs CO gas. The readout circuit is used to convert the sensor resistance into the voltage output. The post-processing of the sensor includes etching the sacrificial layers and coating the sensing film. The advantages of the sensor include room temperature operation, short response/recovery times and easy post-processing. Experimental results show that the sensitivity of the CO sensor is about 0.19 mV/ppm, and the response and recovery times are 23 s and 34 s for 200 ppm CO, respectively. Full article
(This article belongs to the Special Issue Metal-Oxide Based Nanosensors)
Open AccessArticle Whispering Gallery Modes in Standard Optical Fibres for Fibre Profiling Measurements and Sensing of Unlabelled Chemical Species
Sensors 2010, 10(3), 1765-1781; doi:10.3390/s100301765
Received: 1 January 2010 / Revised: 4 February 2010 / Accepted: 23 February 2010 / Published: 3 March 2010
Cited by 20 | PDF Full-text (4378 KB) | HTML Full-text | XML Full-text
Abstract
Whispering gallery mode resonances in liquid droplets and microspheres have attracted considerable attention due to their potential uses in a range of sensing and technological applications. We describe a whispering gallery mode sensor in which standard optical fibre is used as the [...] Read more.
Whispering gallery mode resonances in liquid droplets and microspheres have attracted considerable attention due to their potential uses in a range of sensing and technological applications. We describe a whispering gallery mode sensor in which standard optical fibre is used as the whispering gallery mode resonator. The sensor is characterised in terms of the response of the whispering gallery mode spectrum to changes in resonator size, refractive index of the surrounding medium, and temperature, and its measurement capabilities are demonstrated through application to high-precision fibre geometry profiling and the detection of unlabelled biochemical species. The prototype sensor is capable of detecting unlabelled biomolecular species in attomole quantities. Full article
(This article belongs to the Special Issue State-of-the-Art Sensors Technology in the UK)
Open AccessArticle Wide Dynamic Range CMOS Potentiostat for Amperometric Chemical Sensor
Sensors 2010, 10(3), 1782-1797; doi:10.3390/s100301782
Received: 1 December 2009 / Revised: 1 February 2010 / Accepted: 2 February 2010 / Published: 4 March 2010
Cited by 12 | PDF Full-text (603 KB) | HTML Full-text | XML Full-text
Abstract
Presented is a single-ended potentiostat topology with a new interface connection between sensor electrodes and potentiostat circuit to avoid deviation of cell voltage and linearly convert the cell current into voltage signal. Additionally, due to the increased harmonic distortion quantity when detecting [...] Read more.
Presented is a single-ended potentiostat topology with a new interface connection between sensor electrodes and potentiostat circuit to avoid deviation of cell voltage and linearly convert the cell current into voltage signal. Additionally, due to the increased harmonic distortion quantity when detecting low-level sensor current, the performance of potentiostat linearity which causes the detectable current and dynamic range to be limited is relatively decreased. Thus, to alleviate these irregularities, a fully-differential potentiostat is designed with a wide output voltage swing compared to single-ended potentiostat. Two proposed potentiostats were implemented using TSMC 0.18-μm CMOS process for biomedical application. Measurement results show that the fully differential potentiostat performs relatively better in terms of linearity when measuring current from 500 ºpA to 10 uA. Besides, the dynamic range value can reach a value of 86 dB. Full article
Open AccessArticle Study of Sodium Ion Selective Electrodes and Differential Structures with Anodized Indium Tin Oxide
Sensors 2010, 10(3), 1798-1809; doi:10.3390/s100301798
Received: 23 December 2009 / Revised: 20 January 2010 / Accepted: 2 February 2010 / Published: 4 March 2010
Cited by 12 | PDF Full-text (230 KB) | HTML Full-text | XML Full-text
Abstract
The objective of this work is the study and characterization of anodized indium tin oxide (anodized-ITO) as a sodium ion selective electrode and differential structures including a sodium-selective-membrane/anodized-ITO as sensor 1, an anodized-ITO membrane as the contrast sensor 2, and an ITO [...] Read more.
The objective of this work is the study and characterization of anodized indium tin oxide (anodized-ITO) as a sodium ion selective electrode and differential structures including a sodium-selective-membrane/anodized-ITO as sensor 1, an anodized-ITO membrane as the contrast sensor 2, and an ITO as the reference electrode. Anodized-ITO was fabricated by anodic oxidation at room temperature, a low cost and simple manufacture process that makes it easy to control the variation in film resistance. The anodized-ITO based on EGFET structure has good linear pH sensitivity, approximately 54.44 mV/pH from pH 2 to pH 12. The proposed sodium electrodes prepared by PVC-COOH, DOS embedding colloid, and complex Na-TFBD and ionophore B12C4, show good sensitivity at 52.48 mV/decade for 10−4 M to 1 M, and 29.96 mV/decade for 107 M to 104 M. The sodium sensitivity of the differential sodium-sensing device is 58.65 mV/decade between 10−4 M and 1 M, with a corresponding linearity of 0.998; and 19.17 mV/decade between 105 M and 104 M. Full article
(This article belongs to the Special Issue ISFET Sensors)
Open AccessArticle Detection of Non-Amplified Mycobacterium tuberculosis Genomic DNA Using Piezoelectric DNA-Based Biosensors
Sensors 2010, 10(3), 1846-1858; doi:10.3390/s100301846
Received: 25 January 2010 / Revised: 11 February 2010 / Accepted: 23 February 2010 / Published: 9 March 2010
Cited by 11 | PDF Full-text (290 KB) | HTML Full-text | XML Full-text
Abstract
Piezoelectric DNA-based biosensor technology was developed as a new method for detection of M. tuberculosis. This method consists of immobilizing a thiol-modified oligonucleotide probe on the gold electrode surface of a quartz crystal, using a self-assembled monolayer method. The advantage of [...] Read more.
Piezoelectric DNA-based biosensor technology was developed as a new method for detection of M. tuberculosis. This method consists of immobilizing a thiol-modified oligonucleotide probe on the gold electrode surface of a quartz crystal, using a self-assembled monolayer method. The advantage of this study is that a non-amplified genomic bacterial DNA target was used. Instead, the genomic DNA was digested by restriction enzyme to obtain DNA fragments containing the target sequence. The fabricated biosensor was evaluated through an examination of 200 samples. No cross hybridization were observed against M. avium complex and other microorganisms. This target DNA preparation, without PCR amplification, will reduce time, costs, and the tedious step of amplification. Full article
(This article belongs to the Special Issue Microbial Sensors and Biosensors)
Open AccessArticle Position Error Compensation via a Variable Reluctance Sensor Applied to a Hybrid Vehicle Electric Machine
Sensors 2010, 10(3), 1918-1934; doi:10.3390/s100301918
Received: 10 December 2009 / Revised: 8 February 2010 / Accepted: 20 February 2010 / Published: 9 March 2010
Cited by 3 | PDF Full-text (207 KB) | HTML Full-text | XML Full-text
Abstract
In the automotive industry, electromagnetic variable reluctance (VR) sensors have been extensively used to measure engine position and speed through a toothed wheel mounted on the crankshaft. In this work, an application that already uses the VR sensing unit for engine and/or [...] Read more.
In the automotive industry, electromagnetic variable reluctance (VR) sensors have been extensively used to measure engine position and speed through a toothed wheel mounted on the crankshaft. In this work, an application that already uses the VR sensing unit for engine and/or transmission has been chosen to infer, this time, the indirect position of the electric machine in a parallel Hybrid Electric Vehicle (HEV) system. A VR sensor has been chosen to correct the position of the electric machine, mainly because it may still become critical in the operation of HEVs to avoid possible vehicle failures during the start-up and on-the-road, especially when the machine is used with an internal combustion engine. The proposed method uses Chi-square test and is adaptive in a sense that it derives the compensation factors during the shaft operation and updates them in a timely fashion. Full article
(This article belongs to the Section Chemical Sensors)
Open AccessArticle A Star Recognition Method Based on the Adaptive Ant Colony Algorithm for Star Sensors
Sensors 2010, 10(3), 1955-1966; doi:10.3390/s100301955
Received: 23 December 2009 / Revised: 13 January 2010 / Accepted: 23 February 2010 / Published: 10 March 2010
Cited by 6 | PDF Full-text (347 KB) | HTML Full-text | XML Full-text
Abstract
A new star recognition method based on the Adaptive Ant Colony (AAC) algorithm has been developed to increase the star recognition speed and success rate for star sensors. This method draws circles, with the center of each one being a bright star [...] Read more.
A new star recognition method based on the Adaptive Ant Colony (AAC) algorithm has been developed to increase the star recognition speed and success rate for star sensors. This method draws circles, with the center of each one being a bright star point and the radius being a special angular distance, and uses the parallel processing ability of the AAC algorithm to calculate the angular distance of any pair of star points in the circle. The angular distance of two star points in the circle is solved as the path of the AAC algorithm, and the path optimization feature of the AAC is employed to search for the optimal (shortest) path in the circle. This optimal path is used to recognize the stellar map and enhance the recognition success rate and speed. The experimental results show that when the position error is about 50″, the identification success rate of this method is 98% while the Delaunay identification method is only 94%. The identification time of this method is up to 50 ms. Full article
(This article belongs to the Section Chemical Sensors)
Open AccessArticle A Comparison of Spectral Angle Mapper and Artificial Neural Network Classifiers Combined with Landsat TM Imagery Analysis for Obtaining Burnt Area Mapping
Sensors 2010, 10(3), 1967-1985; doi:10.3390/s100301967
Received: 18 December 2009 / Revised: 20 January 2010 / Accepted: 4 February 2010 / Published: 11 March 2010
Cited by 28 | PDF Full-text (792 KB) | HTML Full-text | XML Full-text
Abstract
Satellite remote sensing, with its unique synoptic coverage capabilities, can provide accurate and immediately valuable information on fire analysis and post-fire assessment, including estimation of burnt areas. In this study the potential for burnt area mapping of the combined use of Artificial [...] Read more.
Satellite remote sensing, with its unique synoptic coverage capabilities, can provide accurate and immediately valuable information on fire analysis and post-fire assessment, including estimation of burnt areas. In this study the potential for burnt area mapping of the combined use of Artificial Neural Network (ANN) and Spectral Angle Mapper (SAM) classifiers with Landsat TM satellite imagery was evaluated in a Mediterranean setting. As a case study one of the most catastrophic forest fires, which occurred near the capital of Greece during the summer of 2007, was used. The accuracy of the two algorithms in delineating the burnt area from the Landsat TM imagery, acquired shortly after the fire suppression, was determined by the classification accuracy results of the produced thematic maps. In addition, the derived burnt area estimates from the two classifiers were compared with independent estimates available for the study region, obtained from the analysis of higher spatial resolution satellite data. In terms of the overall classification accuracy, ANN outperformed (overall accuracy 90.29%, Kappa coefficient 0.878) the SAM classifier (overall accuracy 83.82%, Kappa coefficient 0.795). Total burnt area estimates from the two classifiers were found also to be in close agreement with the other available estimates for the study region, with a mean absolute percentage difference of ~1% for ANN and ~6.5% for SAM. The study demonstrates the potential of the examined here algorithms in detecting burnt areas in a typical Mediterranean setting. Full article
(This article belongs to the Section Remote Sensors)
Open AccessArticle Quantum Cascade Laser-Based Photoacoustic Spectroscopy for Trace Vapor Detection and Molecular Discrimination
Sensors 2010, 10(3), 1986-2002; doi:10.3390/s100301986
Received: 1 February 2010 / Revised: 12 February 2010 / Accepted: 28 February 2010 / Published: 11 March 2010
Cited by 35 | PDF Full-text (290 KB) | HTML Full-text | XML Full-text
Abstract
We report on the development of a microelectromechanical systems (MEMS)-scale photoacoustic sensor for the detection of trace gases. A mid-infrared quantum cascade laser (QCL) was used to determine detection limits for acetic acid, acetone, 1,4-dioxane, and vinyl acetate. The source was continuously [...] Read more.
We report on the development of a microelectromechanical systems (MEMS)-scale photoacoustic sensor for the detection of trace gases. A mid-infrared quantum cascade laser (QCL) was used to determine detection limits for acetic acid, acetone, 1,4-dioxane, and vinyl acetate. The source was continuously tunable from 1015 cm-1 to 1240 cm-1, allowing for the collection of photoacoustic vibrational spectra for these gases. Exceptional agreement between the measured photoacoustic spectra and the infrared spectra for acetic acid, acetone, 1,4-dioxane, and vinyl acetate was observed. Partial least-squares (PLS) regression was used to develop an algorithm for classification of these compounds based solely on photoacoustic spectra. Full article
(This article belongs to the Special Issue Laser Spectroscopy and Sensing)
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Open AccessArticle Distributed Power Allocation for Sink-Centric Clusters in Multiple Sink Wireless Sensor Networks
Sensors 2010, 10(3), 2003-2026; doi:10.3390/s100302003
Received: 6 January 2010 / Revised: 21 January 2010 / Accepted: 7 February 2010 / Published: 11 March 2010
Cited by 5 | PDF Full-text (420 KB) | HTML Full-text | XML Full-text
Abstract
Due to the battery resource constraints, saving energy is a critical issue in wireless sensor networks, particularly in large sensor networks. One possible solution is to deploy multiple sink nodes simultaneously. Another possible solution is to employ an adaptive clustering hierarchy routing [...] Read more.
Due to the battery resource constraints, saving energy is a critical issue in wireless sensor networks, particularly in large sensor networks. One possible solution is to deploy multiple sink nodes simultaneously. Another possible solution is to employ an adaptive clustering hierarchy routing scheme. In this paper, we propose a multiple sink cluster wireless sensor networks scheme which combines the two solutions, and propose an efficient transmission power control scheme for a sink-centric cluster routing protocol in multiple sink wireless sensor networks, denoted as MSCWSNs-PC. It is a distributed, scalable, self-organizing, adaptive system, and the sensor nodes do not require knowledge of the global network and their location. All sinks effectively work out a representative view of a monitored region, after which power control is employed to optimize network topology. The simulations demonstrate the advantages of our new protocol. Full article
Open AccessArticle Automatic Chessboard Detection for Intrinsic and Extrinsic Camera Parameter Calibration
Sensors 2010, 10(3), 2027-2044; doi:10.3390/s100302027
Received: 6 January 2010 / Revised: 29 January 2010 / Accepted: 2 February 2010 / Published: 15 March 2010
Cited by 38 | PDF Full-text (2539 KB) | HTML Full-text | XML Full-text
Abstract
There are increasing applications that require precise calibration of cameras to perform accurate measurements on objects located within images, and an automatic algorithm would reduce this time consuming calibration procedure. The method proposed in this article uses a pattern similar to that [...] Read more.
There are increasing applications that require precise calibration of cameras to perform accurate measurements on objects located within images, and an automatic algorithm would reduce this time consuming calibration procedure. The method proposed in this article uses a pattern similar to that of a chess board, which is found automatically in each image, when no information regarding the number of rows or columns is supplied to aid its detection. This is carried out by means of a combined analysis of two Hough transforms, image corners and invariant properties of the perspective transformation. Comparative analysis with more commonly used algorithms demonstrate the viability of the algorithm proposed, as a valuable tool for camera calibration. Full article
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Open AccessArticle Signal Amplification by Enzymatic Reaction in an Immunosensor Based on Localized Surface Plasmon Resonance (LSPR)
Sensors 2010, 10(3), 2045-2053; doi:10.3390/s100302045
Received: 20 January 2010 / Revised: 15 February 2010 / Accepted: 4 March 2010 / Published: 12 March 2010
Cited by 16 | PDF Full-text (618 KB) | HTML Full-text | XML Full-text
Abstract
An enzymatic reaction was employed as a means to enhance the sensitivity of an immunosensor based on localized surface plasmon resonance (LSPR). The reaction occurs after intermolecular binding between an antigen and an antibody on gold nano-island (NI) surfaces. For LSPR sensing, [...] Read more.
An enzymatic reaction was employed as a means to enhance the sensitivity of an immunosensor based on localized surface plasmon resonance (LSPR). The reaction occurs after intermolecular binding between an antigen and an antibody on gold nano-island (NI) surfaces. For LSPR sensing, the gold NI surface was fabricated on glass substrates using vacuum evaporation and heat treatment. The interferon-g (IFN-g) capture antibody was immobilized on the gold NIs, followed by binding of IFN-g to the antibody. Subsequently, a biotinylated antibody and a horseradish peroxidase (HRP) conjugated with avidin were simultaneously introduced. A solution of 4-chloro-1-naphthol (4-CN) was then used for precipitation; precipitation was the result of the enzymatic reaction catalyzed the HRP on gold NIs. The LSPR spectra were obtained after each binding process. Using this method, the enzyme-catalyzed precipitation reaction on the gold NI surface was found to effectively amplify the change in the signal of the LSPR immunosensor after intermolecular binding. Full article
(This article belongs to the Special Issue Immunosensors)
Open AccessArticle Response Ant Colony Optimization of End Milling Surface Roughness
Sensors 2010, 10(3), 2054-2063; doi:10.3390/s100302054
Received: 24 January 2009 / Revised: 8 March 2010 / Accepted: 14 March 2010 / Published: 15 March 2010
Cited by 10 | PDF Full-text (366 KB) | HTML Full-text | XML Full-text
Abstract
Metal cutting processes are important due to increased consumer demands for quality metal cutting related products (more precise tolerances and better product surface roughness) that has driven the metal cutting industry to continuously improve quality control of metal cutting processes. This paper [...] Read more.
Metal cutting processes are important due to increased consumer demands for quality metal cutting related products (more precise tolerances and better product surface roughness) that has driven the metal cutting industry to continuously improve quality control of metal cutting processes. This paper presents optimum surface roughness by using milling mould aluminium alloys (AA6061-T6) with Response Ant Colony Optimization (RACO). The approach is based on Response Surface Method (RSM) and Ant Colony Optimization (ACO). The main objectives to find the optimized parameters and the most dominant variables (cutting speed, feedrate, axial depth and radial depth). The first order model indicates that the feedrate is the most significant factor affecting surface roughness. Full article
(This article belongs to the Section Chemical Sensors)
Open AccessArticle Coverage-Guaranteed Sensor Node Deployment Strategies for Wireless Sensor Networks
Sensors 2010, 10(3), 2064-2087; doi:10.3390/s100302064
Received: 30 December 2009 / Revised: 30 January 2010 / Accepted: 3 February 2010 / Published: 15 March 2010
Cited by 31 | PDF Full-text (513 KB) | HTML Full-text | XML Full-text
Abstract
Deployment quality and cost are two conflicting aspects in wireless sensor networks. Random deployment, where the monitored field is covered by randomly and uniformly deployed sensor nodes, is an appropriate approach for large-scale network applications. However, their successful applications depend considerably on [...] Read more.
Deployment quality and cost are two conflicting aspects in wireless sensor networks. Random deployment, where the monitored field is covered by randomly and uniformly deployed sensor nodes, is an appropriate approach for large-scale network applications. However, their successful applications depend considerably on the deployment quality that uses the minimum number of sensors to achieve a desired coverage. Currently, the number of sensors required to meet the desired coverage is based on asymptotic analysis, which cannot meet deployment quality due to coverage overestimation in real applications. In this paper, we first investigate the coverage overestimation and address the challenge of designing coverage-guaranteed deployment strategies. To overcome this problem, we propose two deployment strategies, namely, the Expected-area Coverage Deployment (ECD) and BOundary Assistant Deployment (BOAD). The deployment quality of the two strategies is analyzed mathematically. Under the analysis, a lower bound on the number of deployed sensor nodes is given to satisfy the desired deployment quality. We justify the correctness of our analysis through rigorous proof, and validate the effectiveness of the two strategies through extensive simulation experiments. The simulation results show that both strategies alleviate the coverage overestimation significantly. In addition, we also evaluate two proposed strategies in the context of target detection application. The comparison results demonstrate that if the target appears at the boundary of monitored region in a given random deployment, the average intrusion distance of BOAD is considerably shorter than that of ECD with the same desired deployment quality. In contrast, ECD has better performance in terms of the average intrusion distance when the invasion of intruder is from the inside of monitored region. Full article
(This article belongs to the Section Chemical Sensors)
Open AccessArticle Quantitative Determination of Fibrinogen of Patients with Coronary Heart Diseases through Piezoelectric Agglutination Sensor
Sensors 2010, 10(3), 2107-2118; doi:10.3390/s100302107
Received: 8 January 2010 / Revised: 8 February 2010 / Accepted: 1 March 2010 / Published: 16 March 2010
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Abstract
Fibrinogen can transform fibrin through an agglutination reaction, finally forming fibrin polymer with grid structure. The density and viscosity of the reaction system changes drastically during the course of agglutination. In this research, we apply an independently-developed piezoelectric agglutination sensor to detect the fibrinogen agglutination reaction in patients with coronary heart diseases. The terminal judgment method of determining plasma agglutination reaction through piezoelectric agglutination sensor was established. In addition, the standard curve between plasma agglutination time and fibrinogen concentration was established to determinate fibrinogen content quantitatively. The results indicate the close correlation between the STAGO paramagnetic particle method and the method of piezoelectric agglutination sensor for the detection of Fibrinogen. The correlation coefficient was 0.91 (γ = 0.91). The determination can be completed within 10 minutes. The fibrinogen concentration in the coronary heart disease group was significantly higher than that of the healthy control group (P < 0.05). The results reveal that high fibrinogen concentration is closely correlated to the incurrence, development and prognosis of coronary heart diseases. Compared with other traditional methods, the method of piezoelectric agglutination sensor has some merits such as operation convenience, small size, low cost, quick detecting, good precision and the common reacting agents with paramagnetic particle method. Full article
(This article belongs to the Section Biosensors)
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Open AccessArticle Immobilization of Acetylcholinesterase on Screen-Printed Electrodes. Application to the Determination of Arsenic(III)
Sensors 2010, 10(3), 2119-2128; doi:10.3390/s100302119
Received: 29 December 2009 / Revised: 8 February 2010 / Accepted: 24 February 2010 / Published: 16 March 2010
Cited by 24 | PDF Full-text (212 KB) | HTML Full-text | XML Full-text
Abstract
Enzymatic amperometric procedures for measuring arsenic, based on the inhibitive action of this metal on acetylcholinesterase enzyme activity, have been developed. Screen-printed carbon electrodes (SPCEs) were used with acetylcholinesterase covalently bonded directly to its surface. The amperometric response of acetylcholinesterase was affected [...] Read more.
Enzymatic amperometric procedures for measuring arsenic, based on the inhibitive action of this metal on acetylcholinesterase enzyme activity, have been developed. Screen-printed carbon electrodes (SPCEs) were used with acetylcholinesterase covalently bonded directly to its surface. The amperometric response of acetylcholinesterase was affected by the presence of arsenic ions, which caused a decrease in the current intensity. The experimental optimum working conditions of pH, substrate concentration and potential applied, were established. Under these conditions, repeatability and reproducibility of biosensors were determined, reaching values below 4% in terms of relative standard deviation. The detection limit obtained for arsenic was 1.1 × 10−8 M for Ach/SPCE biosensor. Analysis of the possible effect of the presence of foreign ions in the solution was performed. The method was applied to determine levels of arsenic in spiked tap water samples. Full article
(This article belongs to the Section Biosensors)
Open AccessArticle Real-Time Estimation of Pathological Tremor Parameters from Gyroscope Data
Sensors 2010, 10(3), 2129-2149; doi:10.3390/s100302129
Received: 25 January 2010 / Revised: 26 February 2010 / Accepted: 1 March 2010 / Published: 16 March 2010
Cited by 29 | PDF Full-text (1176 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents a two stage algorithm for real-time estimation of instantaneous tremor parameters from gyroscope recordings. Gyroscopes possess the advantage of providing directly joint rotational speed, overcoming the limitations of traditional tremor recording based on accelerometers. The proposed algorithm first extracts [...] Read more.
This paper presents a two stage algorithm for real-time estimation of instantaneous tremor parameters from gyroscope recordings. Gyroscopes possess the advantage of providing directly joint rotational speed, overcoming the limitations of traditional tremor recording based on accelerometers. The proposed algorithm first extracts tremor patterns from raw angular data, and afterwards estimates its instantaneous amplitude and frequency. Real-time separation of voluntary and tremorous motion relies on their different frequency contents, whereas tremor modelling is based on an adaptive LMS algorithm and a Kalman filter. Tremor parameters will be employed to drive a neuroprosthesis for tremor suppression based on biomechanical loading. Full article
(This article belongs to the Special Issue Motion Detectors)
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Open AccessArticle Data Driven Performance Evaluation of Wireless Sensor Networks
Sensors 2010, 10(3), 2150-2168; doi:10.3390/s100302150
Received: 3 February 2010 / Revised: 22 February 2010 / Accepted: 12 March 2010 / Published: 16 March 2010
Cited by 8 | PDF Full-text (868 KB) | HTML Full-text | XML Full-text
Abstract
Wireless Sensor Networks are presented as devices for signal sampling and reconstruction. Within this framework, the qualitative and quantitative influence of (i) signal granularity, (ii) spatial distribution of sensors, (iii) sensors clustering, and (iv) signal reconstruction procedure are assessed. This is done [...] Read more.
Wireless Sensor Networks are presented as devices for signal sampling and reconstruction. Within this framework, the qualitative and quantitative influence of (i) signal granularity, (ii) spatial distribution of sensors, (iii) sensors clustering, and (iv) signal reconstruction procedure are assessed. This is done by defining an error metric and performing a Monte Carlo experiment. It is shown that all these factors have significant impact on the quality of the reconstructed signal. The extent of such impact is quantitatively assessed. Full article
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Open AccessArticle Trapped Ion Oscillation Frequencies as Sensors for Spectroscopy
Sensors 2010, 10(3), 2169-2187; doi:10.3390/s100302169
Received: 18 January 2010 / Revised: 2 March 2010 / Accepted: 10 March 2010 / Published: 16 March 2010
Cited by 7 | PDF Full-text (338 KB) | HTML Full-text | XML Full-text
Abstract
The oscillation frequencies of charged particles in a Penning trap can serve as sensors for spectroscopy when additional field components are introduced to the magnetic and electric fields used for confinement. The presence of so-called “magnetic bottles” and specific electric anharmonicities creates [...] Read more.
The oscillation frequencies of charged particles in a Penning trap can serve as sensors for spectroscopy when additional field components are introduced to the magnetic and electric fields used for confinement. The presence of so-called “magnetic bottles” and specific electric anharmonicities creates calculable energy-dependences of the oscillation frequencies in the radiofrequency domain which may be used to detect the absorption or emission of photons both in the microwave and optical frequency domains. The precise electronic measurement of these oscillation frequencies therefore represents an optical sensor for spectroscopy. We discuss possible applications for precision laser and microwave spectroscopy and their role in the determination of magnetic moments and excited state lifetimes. Also, the trap-assisted measurement of radiative nuclear de-excitations in the X-ray domain is discussed. This way, the different applications range over more than 12 orders of magnitude in the detectable photon energies, from below μeV in the microwave domain to beyond MeV in the X-ray domain. Full article
(This article belongs to the Special Issue Laser Spectroscopy and Sensing)
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Open AccessArticle Virtual Sensor for Failure Detection, Identification and Recovery in the Transition Phase of a Morphing Aircraft
Sensors 2010, 10(3), 2188-2201; doi:10.3390/s100302188
Received: 7 January 2010 / Revised: 19 February 2010 / Accepted: 21 February 2010 / Published: 17 March 2010
Cited by 13 | PDF Full-text (368 KB) | HTML Full-text | XML Full-text
Abstract
The Helicopter Adaptive Aircraft (HADA) is a morphing aircraft which is able to take-off as a helicopter and, when in forward flight, unfold the wings that are hidden under the fuselage, and transfer the power from the main rotor to a propeller, [...] Read more.
The Helicopter Adaptive Aircraft (HADA) is a morphing aircraft which is able to take-off as a helicopter and, when in forward flight, unfold the wings that are hidden under the fuselage, and transfer the power from the main rotor to a propeller, thus morphing from a helicopter to an airplane. In this process, the reliable folding and unfolding of the wings is critical, since a failure may determine the ability to perform a mission, and may even be catastrophic. This paper proposes a virtual sensor based Fault Detection, Identification and Recovery (FDIR) system to increase the reliability of the HADA aircraft. The virtual sensor is able to capture the nonlinear interaction between the folding/unfolding wings aerodynamics and the HADA airframe using the navigation sensor measurements. The proposed FDIR system has been validated using a simulation model of the HADA aircraft, which includes real phenomena as sensor noise and sampling characteristics and turbulence and wind perturbations. Full article
(This article belongs to the Section Chemical Sensors)
Open AccessArticle Effect of Silver Annealing Conditions on the Performance of Electrolytic Silver/Silver Chloride Electrodes used in Harned Cell Measurements of pH
Sensors 2010, 10(3), 2202-2216; doi:10.3390/s100302202
Received: 22 February 2010 / Revised: 5 March 2010 / Accepted: 16 March 2010 / Published: 17 March 2010
Cited by 6 | PDF Full-text (2646 KB) | HTML Full-text | XML Full-text
Abstract
We have studied the long and short term stability of electrolytic Ag/AgCl electrodes fabricated from Ag wire that has been subjected to a range of different annealing conditions. At elevated temperatures, the presence of oxygen during the annealing process has been shown [...] Read more.
We have studied the long and short term stability of electrolytic Ag/AgCl electrodes fabricated from Ag wire that has been subjected to a range of different annealing conditions. At elevated temperatures, the presence of oxygen during the annealing process has been shown to be detrimental to the performance of electrodes produced. This phenomenon has been attributed to the dissolution of oxygen in the Ag lattice leading to structural changes in the Ag/AgCl electrode material. Electrodes prepared from Ag wire annealed in the absence of oxygen have shown no appreciable change in performance throughout the temperature range employed. This work has resulted in an improved understanding of the optimum annealing conditions required for Ag used in the preparation of electrolytic Ag/AgCl reference electrodes. This work has positive implications for the accuracy of Harned cell measurements of pH. Full article
(This article belongs to the Section Chemical Sensors)
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Open AccessArticle A Deployment of Fine-Grained Sensor Network and Empirical Analysis of Urban Temperature
Sensors 2010, 10(3), 2217-2241; doi:10.3390/s100302217
Received: 15 January 2010 / Revised: 20 February 2010 / Accepted: 15 March 2010 / Published: 18 March 2010
Cited by 8 | PDF Full-text (3008 KB) | HTML Full-text | XML Full-text
Abstract
Temperature in an urban area exhibits a complicated pattern due to complexity of infrastructure. Despite geographical proximity, structures of a group of buildings and streets affect changes in temperature. To investigate the pattern of fine-grained distribution of temperature, we installed a densely [...] Read more.
Temperature in an urban area exhibits a complicated pattern due to complexity of infrastructure. Despite geographical proximity, structures of a group of buildings and streets affect changes in temperature. To investigate the pattern of fine-grained distribution of temperature, we installed a densely distributed sensor network called UScan. In this paper, we describe the system architecture of UScan as well as experience learned from installing 200 sensors in downtown Tokyo. The field experiment of UScan system operated for two months to collect long-term urban temperature data. To analyze the collected data in an efficient manner, we propose a lightweight clustering methodology to study the correlation between the pattern of temperature and various environmental factors including the amount of sunshine, the width of streets, and the existence of trees. The analysis reveals meaningful results and asserts the necessity of fine-grained deployment of sensors in an urban area. Full article
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Open AccessArticle Efficiency of Event-Based Sampling According to Error Energy Criterion
Sensors 2010, 10(3), 2242-2261; doi:10.3390/s100302242
Received: 23 December 2009 / Revised: 5 February 2010 / Accepted: 24 February 2010 / Published: 18 March 2010
Cited by 14 | PDF Full-text (231 KB) | HTML Full-text | XML Full-text
Abstract
The paper belongs to the studies that deal with the effectiveness of the particular event-based sampling scheme compared to the conventional periodic sampling as a reference. In the present study, the event-based sampling according to a constant energy of sampling error is [...] Read more.
The paper belongs to the studies that deal with the effectiveness of the particular event-based sampling scheme compared to the conventional periodic sampling as a reference. In the present study, the event-based sampling according to a constant energy of sampling error is analyzed. This criterion is suitable for applications where the energy of sampling error should be bounded (i.e., in building automation, or in greenhouse climate monitoring and control). Compared to the integral sampling criteria, the error energy criterion gives more weight to extreme sampling error values. The proposed sampling principle extends a range of event-based sampling schemes and makes the choice of particular sampling criterion more flexible to application requirements. In the paper, it is proved analytically that the proposed event-based sampling criterion is more effective than the periodic sampling by a factor defined by the ratio of the maximum to the mean of the cubic root of the signal time-derivative square in the analyzed time interval. Furthermore, it is shown that the sampling according to energy criterion is less effective than the send-on-delta scheme but more effective than the sampling according to integral criterion. On the other hand, it is indicated that higher effectiveness in sampling according to the selected event-based criterion is obtained at the cost of increasing the total sampling error defined as the sum of errors for all the samples taken. Full article
Open AccessArticle Organic ISFET Based on Poly (3-hexylthiophene)
Sensors 2010, 10(3), 2262-2273; doi:10.3390/s100302262
Received: 24 January 2010 / Revised: 13 February 2010 / Accepted: 10 March 2010 / Published: 19 March 2010
Cited by 21 | PDF Full-text (1367 KB) | HTML Full-text | XML Full-text
Abstract
We have fabricated organic field-effect transistors (OFETs) with regioregular poly(3-hexylthiophene) (P3HT) operable at low-voltages in liquid solutions, suitable for in vitro biosensing applications. Measurements in electrolytes have shown that the performance of the transistors did not deteriorate and they can be directly [...] Read more.
We have fabricated organic field-effect transistors (OFETs) with regioregular poly(3-hexylthiophene) (P3HT) operable at low-voltages in liquid solutions, suitable for in vitro biosensing applications. Measurements in electrolytes have shown that the performance of the transistors did not deteriorate and they can be directly used as ionsensitive transducers. Furthermore, more complex media have been tested, with the perspective of cell analysis. Degradation effects acting on the device operating in liquid could be partly compensated by adopting an alternate current measuring mode. Full article
(This article belongs to the Special Issue ISFET Sensors)
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Open AccessArticle Decentralized Sensor Fusion for Ubiquitous Networking Robotics in Urban Areas
Sensors 2010, 10(3), 2274-2314; doi:10.3390/s100302274
Received: 12 January 2010 / Revised: 2 February 2010 / Accepted: 28 February 2010 / Published: 19 March 2010
Cited by 23 | PDF Full-text (2328 KB) | HTML Full-text | XML Full-text
Abstract
In this article we explain the architecture for the environment and sensors that has been built for the European project URUS (Ubiquitous Networking Robotics in Urban Sites), a project whose objective is to develop an adaptable network robot architecture for cooperation between [...] Read more.
In this article we explain the architecture for the environment and sensors that has been built for the European project URUS (Ubiquitous Networking Robotics in Urban Sites), a project whose objective is to develop an adaptable network robot architecture for cooperation between network robots and human beings and/or the environment in urban areas. The project goal is to deploy a team of robots in an urban area to give a set of services to a user community. This paper addresses the sensor architecture devised for URUS and the type of robots and sensors used, including environment sensors and sensors onboard the robots. Furthermore, we also explain how sensor fusion takes place to achieve urban outdoor execution of robotic services. Finally some results of the project related to the sensor network are highlighted. Full article
(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Spain)
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Open AccessArticle Fluorescent Silicate Materials for the Detection of Paraoxon
Sensors 2010, 10(3), 2315-2331; doi:10.3390/s100302315
Received: 4 January 2010 / Revised: 2 March 2010 / Accepted: 8 March 2010 / Published: 19 March 2010
Cited by 21 | PDF Full-text (343 KB) | HTML Full-text | XML Full-text
Abstract
Porphyrins are a family of highly conjugated molecules that strongly absorb visible light and fluoresce intensely. These molecules are sensitive to changes in their immediate environment and have been widely described for optical detection applications. Surfactant-templated organosilicate materials have been described for [...] Read more.
Porphyrins are a family of highly conjugated molecules that strongly absorb visible light and fluoresce intensely. These molecules are sensitive to changes in their immediate environment and have been widely described for optical detection applications. Surfactant-templated organosilicate materials have been described for the semi-selective adsorption of small molecule contaminants. These structures offer high surface areas and large pore volumes within an organized framework. The organic bridging groups in the materials can be altered to provide varied binding characteristics. This effort seeks to utilize the tunable binding selectivity, high surface area, and low materials density of these highly ordered pore networks and to combine them with the unique spectrophotometric properties of porphyrins. In the porphyrin-embedded materials (PEMs), the organosilicate scaffold stabilizes the porphyrin and facilitates optimal orientation of porphyrin and target. The materials can be stored under ambient conditions and offer exceptional shelf-life. Here, we report on the design of PEMs with specificity for organophosphates and compounds of similar structure. Full article
(This article belongs to the Special Issue Fluorescent Chemosensors)
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Open AccessArticle An Adaptive Fault-Tolerant Event Detection Scheme for Wireless Sensor Networks
Sensors 2010, 10(3), 2332-2347; doi:10.3390/s100302332
Received: 20 January 2010 / Revised: 25 February 2010 / Accepted: 10 March 2010 / Published: 19 March 2010
Cited by 23 | PDF Full-text (576 KB) | HTML Full-text | XML Full-text
Abstract
In this paper, we present an adaptive fault-tolerant event detection scheme for wireless sensor networks. Each sensor node detects an event locally in a distributed manner by using the sensor readings of its neighboring nodes. Confidence levels of sensor nodes are used [...] Read more.
In this paper, we present an adaptive fault-tolerant event detection scheme for wireless sensor networks. Each sensor node detects an event locally in a distributed manner by using the sensor readings of its neighboring nodes. Confidence levels of sensor nodes are used to dynamically adjust the threshold for decision making, resulting in consistent performance even with increasing number of faulty nodes. In addition, the scheme employs a moving average filter to tolerate most transient faults in sensor readings, reducing the effective fault probability. Only three bits of data are exchanged to reduce the communication overhead in detecting events. Simulation results show that event detection accuracy and false alarm rate are kept very high and low, respectively, even in the case where 50% of the sensor nodes are faulty. Full article
(This article belongs to the Section Chemical Sensors)
Open AccessArticle Refractive Index Sensor Based on a 1D Photonic Crystal in a Microfluidic Channel
Sensors 2010, 10(3), 2348-2358; doi:10.3390/s100302348
Received: 27 January 2010 / Revised: 10 February 2010 / Accepted: 5 March 2010 / Published: 22 March 2010
Cited by 16 | PDF Full-text (1313 KB) | HTML Full-text | XML Full-text
Abstract
A refractive index sensor has been fabricated in silicon oxynitride by standard UV lithography and dry etching processes. The refractive index sensor consists of a 1D photonic crystal (PhC) embedded in a microfluidic channel addressed by fiber-terminated planar waveguides. Experimental demonstrations performed [...] Read more.
A refractive index sensor has been fabricated in silicon oxynitride by standard UV lithography and dry etching processes. The refractive index sensor consists of a 1D photonic crystal (PhC) embedded in a microfluidic channel addressed by fiber-terminated planar waveguides. Experimental demonstrations performed with several ethanol solutions ranging from a purity of 96.00% (n = 1.36356) to 95.04% (n = 1.36377) yielded a sensitivity (Δλ/Δn) of 836 nm/RIU and a limit of detection (LOD) of 6 x 10-5 RIU, which is, however, still one order of magnitude higher than the theoretical lower limit of the limit of detection 1.3 x 10–6 RIU. Full article
(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Denmark)
Open AccessArticle Ambient Intelligence Systems for Personalized Sport Training
Sensors 2010, 10(3), 2359-2385; doi:10.3390/s100302359
Received: 22 January 2010 / Revised: 3 March 2010 / Accepted: 10 March 2010 / Published: 22 March 2010
Cited by 18 | PDF Full-text (6011 KB) | HTML Full-text | XML Full-text
Abstract
Several research programs are tackling the use of Wireless Sensor Networks (WSN) at specific fields, such as e-Health, e-Inclusion or e-Sport. This is the case of the project “Ambient Intelligence Systems Support for Athletes with Specific Profiles”, which intends to assist athletes [...] Read more.
Several research programs are tackling the use of Wireless Sensor Networks (WSN) at specific fields, such as e-Health, e-Inclusion or e-Sport. This is the case of the project “Ambient Intelligence Systems Support for Athletes with Specific Profiles”, which intends to assist athletes in their training. In this paper, the main developments and outcomes from this project are described. The architecture of the system comprises a WSN deployed in the training area which provides communication with athletes’ mobile equipments, performs location tasks, and harvests environmental data (wind speed, temperature, etc.). Athletes are equipped with a monitoring unit which obtains data from their training (pulse, speed, etc.). Besides, a decision engine combines these real-time data together with static information about the training field, and from the athlete, to direct athletes’ training to fulfill some specific goal. A prototype is presented in this work for a cross country running scenario, where the objective is to maintain the heart rate (HR) of the runner in a target range. For each track, the environmental conditions (temperature of the next track), the current athlete condition (HR), and the intrinsic difficulty of the track (slopes) influence the performance of the athlete. The decision engine, implemented by means of (m; s)-splines interpolation, estimates the future HR and selects the best track in each fork of the circuit. This method achieves a success ratio in the order of 80%. Indeed, results demonstrate that if environmental information is not take into account to derive training orders, the success ratio is reduced notably. Full article
(This article belongs to the Section Chemical Sensors)
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Open AccessArticle Dynamical Jumping Real-Time Fault-Tolerant Routing Protocol for Wireless Sensor Networks
Sensors 2010, 10(3), 2416-2437; doi:10.3390/s100302416
Received: 26 January 2010 / Revised: 3 March 2010 / Accepted: 10 March 2010 / Published: 23 March 2010
Cited by 14 | PDF Full-text (317 KB) | HTML Full-text | XML Full-text
Abstract
In time-critical wireless sensor network (WSN) applications, a high degree of reliability is commonly required. A dynamical jumping real-time fault-tolerant routing protocol (DMRF) is proposed in this paper. Each node utilizes the remaining transmission time of the data packets and the state [...] Read more.
In time-critical wireless sensor network (WSN) applications, a high degree of reliability is commonly required. A dynamical jumping real-time fault-tolerant routing protocol (DMRF) is proposed in this paper. Each node utilizes the remaining transmission time of the data packets and the state of the forwarding candidate node set to dynamically choose the next hop. Once node failure, network congestion or void region occurs, the transmission mode will switch to jumping transmission mode, which can reduce the transmission time delay, guaranteeing the data packets to be sent to the destination node within the specified time limit. By using feedback mechanism, each node dynamically adjusts the jumping probabilities to increase the ratio of successful transmission. Simulation results show that DMRF can not only efficiently reduce the effects of failure nodes, congestion and void region, but also yield higher ratio of successful transmission, smaller transmission delay and reduced number of control packets. Full article
Open AccessArticle Near-Infrared Fluorescence Detection of Acetylcholine in Aqueous Solution Using a Complex of Rhodamine 800 and p-Sulfonato-calix[8]arene
Sensors 2010, 10(3), 2438-2449; doi:10.3390/s100302438
Received: 18 February 2010 / Revised: 4 March 2010 / Accepted: 9 March 2010 / Published: 23 March 2010
Cited by 19 | PDF Full-text (641 KB) | HTML Full-text | XML Full-text
Abstract
The complexing properties of p-sulfonatocalix[n]arenes (n = 4: S[4], n = 6: S[6], and n = 8: S[8]) for rhodamine 800 (Rh800) and indocyanine green (ICG) were examined to develop a near-infrared (NIR) fluorescence detection method for acetylcholine (ACh). We found [...] Read more.
The complexing properties of p-sulfonatocalix[n]arenes (n = 4: S[4], n = 6: S[6], and n = 8: S[8]) for rhodamine 800 (Rh800) and indocyanine green (ICG) were examined to develop a near-infrared (NIR) fluorescence detection method for acetylcholine (ACh). We found that Rh800 (as a cation) forms an inclusion complex with S[n], while ICG (as a twitter ion) have no binding ability for S[n]. The binding ability of Rh800 to S[n] decreased in the order of S[8] > S[6] >> S[4]. By the formation of the complex between Rh800 and S[8], fluorescence intensity of the Rh800 was significantly decreased. From the fluorescence titration of Rh800 by S[8], stoichiometry of the Rh800-S[8] complex was determined to be 1:1 with a dissociation constant of 2.2 mM in PBS. The addition of ACh to the aqueous solution of the Rh800-S[8] complex caused a fluorescence increase of Rh800, resulting from a competitive replacement of Rh800 by ACh in the complex. From the fluorescence change by the competitive fluorophore replacement, stoichiometry of the Rh800-ACh complex was found to be 1:1 with a dissociation constant of 1.7 mM. The effects of other neurotransmitters on the fluorescence spectra of the Rh800-S[8] complex were examined for dopamine, GABA, glycine, and L-asparatic acid. Among the neurotransmitters examined, fluorescence response of the Rh800-S[8] complex was highly specific to ACh. Rh800-S[8] complexes can be used as a NIR fluorescent probe for the detection of ACh (5 × 10-4−10-3 M) in PBS buffer (pH = 7.2). Full article
(This article belongs to the Special Issue Fluorescent Chemosensors)
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Open AccessArticle Cryptanalysis and Security Improvements of ‘Two-Factor User Authentication in Wireless Sensor Networks’
Sensors 2010, 10(3), 2450-2459; doi:10.3390/s100302450
Received: 5 January 2010 / Revised: 4 March 2010 / Accepted: 12 March 2010 / Published: 23 March 2010
Cited by 100 | PDF Full-text (76 KB) | HTML Full-text | XML Full-text
Abstract
User authentication in wireless sensor networks (WSN) is a critical security issue due to their unattended and hostile deployment in the field. Since sensor nodes are equipped with limited computing power, storage, and communication modules; authenticating remote users in such resource-constrained environments [...] Read more.
User authentication in wireless sensor networks (WSN) is a critical security issue due to their unattended and hostile deployment in the field. Since sensor nodes are equipped with limited computing power, storage, and communication modules; authenticating remote users in such resource-constrained environments is a paramount security concern. Recently, M.L. Das proposed a two-factor user authentication scheme in WSNs and claimed that his scheme is secure against different kinds of attack. However, in this paper, we show that the M.L. Das-scheme has some critical security pitfalls and cannot be recommended for real applications. We point out that in his scheme: users cannot change/update their passwords, it does not provide mutual authentication between gateway node and sensor node, and is vulnerable to gateway node bypassing attack and privileged-insider attack. To overcome the inherent security weaknesses of the M.L. Das-scheme, we propose improvements and security patches that attempt to fix the susceptibilities of his scheme. The proposed security improvements can be incorporated in the M.L. Das-scheme for achieving a more secure and robust two-factor user authentication in WSNs. Full article
(This article belongs to the Section Chemical Sensors)

Review

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Open AccessReview Microfabricated Reference Electrodes and their Biosensing Applications
Sensors 2010, 10(3), 1679-1715; doi:10.3390/s100301679
Received: 16 December 2009 / Revised: 28 January 2010 / Accepted: 5 February 2010 / Published: 2 March 2010
Cited by 73 | PDF Full-text (889 KB) | HTML Full-text | XML Full-text
Abstract
Over the past two decades, there has been an increasing trend towards miniaturization of both biological and chemical sensors and their integration with miniaturized sample pre-processing and analysis systems. These miniaturized lab-on-chip devices have several functional advantages including low cost, their ability [...] Read more.
Over the past two decades, there has been an increasing trend towards miniaturization of both biological and chemical sensors and their integration with miniaturized sample pre-processing and analysis systems. These miniaturized lab-on-chip devices have several functional advantages including low cost, their ability to analyze smaller samples, faster analysis time, suitability for automation, and increased reliability and repeatability. Electrical based sensing methods that transduce biological or chemical signals into the electrical domain are a dominant part of the lab-on-chip devices. A vital part of any electrochemical sensing system is the reference electrode, which is a probe that is capable of measuring the potential on the solution side of an electrochemical interface. Research on miniaturization of this crucial component and analysis of the parameters that affect its performance, stability and lifetime, is sparse. In this paper, we present the basic electrochemistry and thermodynamics of these reference electrodes and illustrate the uses of reference electrodes in electrochemical and biological measurements. Different electrochemical systems that are used as reference electrodes will be presented, and an overview of some contemporary advances in electrode miniaturization and their performance will be provided. Full article
(This article belongs to the Special Issue ISFET Sensors)
Open AccessReview Chemical Sensing Using Fiber Cavity Ring-Down Spectroscopy
Sensors 2010, 10(3), 1716-1742; doi:10.3390/s100301716
Received: 15 December 2009 / Revised: 23 January 2010 / Accepted: 6 February 2010 / Published: 2 March 2010
Cited by 48 | PDF Full-text (1705 KB) | HTML Full-text | XML Full-text
Abstract
Waveguide-based cavity ring-down spectroscopy (CRD) can be used for quantitative measurements of chemical concentrations in small amounts of liquid, in gases or in films. The change in ring-down time can be correlated to analyte concentration when using fiber optic sensing elements that [...] Read more.
Waveguide-based cavity ring-down spectroscopy (CRD) can be used for quantitative measurements of chemical concentrations in small amounts of liquid, in gases or in films. The change in ring-down time can be correlated to analyte concentration when using fiber optic sensing elements that change their attenuation in dependence of either sample absorption or refractive index. Two types of fiber cavities, i.e., fiber loops and fiber strands containing reflective elements, are distinguished. Both types of cavities were coupled to a variety of chemical sensor elements, which are discussed and compared. Full article
(This article belongs to the Special Issue Laser Spectroscopy and Sensing)
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Open AccessReview Design of Self-Oscillating Gels and Application to Biomimetic Actuators
Sensors 2010, 10(3), 1810-1822; doi:10.3390/s100301810
Received: 15 January 2010 / Revised: 10 February 2010 / Accepted: 16 February 2010 / Published: 5 March 2010
Cited by 9 | PDF Full-text (752 KB) | HTML Full-text | XML Full-text
Abstract
As a novel biomimetic polymer, we have developed polymer gels with an autonomous self-oscillating function. This was achieved by utilizing oscillating chemical reactions, called the Belousov-Zhabotinsky (BZ) reaction, which is recognized as a chemical model for understanding several autonomous phenomena in biological [...] Read more.
As a novel biomimetic polymer, we have developed polymer gels with an autonomous self-oscillating function. This was achieved by utilizing oscillating chemical reactions, called the Belousov-Zhabotinsky (BZ) reaction, which is recognized as a chemical model for understanding several autonomous phenomena in biological systems. Under the coexistence of the reactants, the polymer gel undergoes spontaneous swelling-deswelling changes without any on-off switching by external stimuli. In this review, our recent studies on the self-oscillating polymer gels and application to biomimetic actuators are summarized. Full article
(This article belongs to the Special Issue Advances in Actuators)
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Open AccessReview Optical Fiber Sensing Based on Reflection Laser Spectroscopy
Sensors 2010, 10(3), 1823-1845; doi:10.3390/s100301823
Received: 5 January 2010 / Revised: 3 February 2010 / Accepted: 5 February 2010 / Published: 5 March 2010
Cited by 20 | PDF Full-text (2387 KB) | HTML Full-text | XML Full-text
Abstract
An overview on high-resolution and fast interrogation of optical-fiber sensors relying on laser reflection spectroscopy is given. Fiber Bragg-gratings (FBGs) and FBG resonators built in fibers of different types are used for strain, temperature and acceleration measurements using heterodyne-detection and optical frequency-locking [...] Read more.
An overview on high-resolution and fast interrogation of optical-fiber sensors relying on laser reflection spectroscopy is given. Fiber Bragg-gratings (FBGs) and FBG resonators built in fibers of different types are used for strain, temperature and acceleration measurements using heterodyne-detection and optical frequency-locking techniques. Silica fiber-ring cavities are used for chemical sensing based on evanescent-wave spectroscopy. Various arrangements for signal recovery and noise reduction, as an extension of most typical spectroscopic techniques, are illustrated and results on detection performances are presented. Full article
(This article belongs to the Special Issue Laser Spectroscopy and Sensing)
Open AccessReview Small Fluxgate Magnetometers: Development and Future Trends in Spain
Sensors 2010, 10(3), 1859-1870; doi:10.3390/s100301859
Received: 22 December 2009 / Revised: 22 January 2010 / Accepted: 5 February 2010 / Published: 9 March 2010
Cited by 7 | PDF Full-text (428 KB) | HTML Full-text | XML Full-text
Abstract
In this paper, we give an overview of the research on fluxgate magnetometers carried out in Spain. In particular we focus in the development of the planar-type instruments. We summarize the fabrication processes and signal processing developments as well as their use [...] Read more.
In this paper, we give an overview of the research on fluxgate magnetometers carried out in Spain. In particular we focus in the development of the planar-type instruments. We summarize the fabrication processes and signal processing developments as well as their use in complex systems and space. Full article
(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Spain)
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Open AccessReview Raman Spectroscopy and Related Techniques in Biomedicine
Sensors 2010, 10(3), 1871-1889; doi:10.3390/s100301871
Received: 27 January 2010 / Revised: 21 February 2010 / Accepted: 1 March 2010 / Published: 9 March 2010
Cited by 42 | PDF Full-text (2920 KB) | HTML Full-text | XML Full-text
Abstract
In this review we describe label-free optical spectroscopy techniques which are able to non-invasively measure the (bio)chemistry in biological systems. Raman spectroscopy uses visible or near-infrared light to measure a spectrum of vibrational bonds in seconds. Coherent anti-Stokes Raman (CARS) microscopy and [...] Read more.
In this review we describe label-free optical spectroscopy techniques which are able to non-invasively measure the (bio)chemistry in biological systems. Raman spectroscopy uses visible or near-infrared light to measure a spectrum of vibrational bonds in seconds. Coherent anti-Stokes Raman (CARS) microscopy and stimulated Raman loss (SRL) microscopy are orders of magnitude more efficient than Raman spectroscopy, and are able to acquire high quality chemically-specific images in seconds. We discuss the benefits and limitations of all techniques, with particular emphasis on applications in biomedicine—both in vivo (using fiber endoscopes) and in vitro (in optical microscopes). Full article
(This article belongs to the Special Issue Laser Spectroscopy and Sensing)
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Open AccessReview Electrical Capacitance Volume Tomography: Design and Applications
Sensors 2010, 10(3), 1890-1917; doi:10.3390/s100301890
Received: 15 January 2010 / Revised: 10 February 2010 / Accepted: 28 February 2010 / Published: 9 March 2010
Cited by 62 | PDF Full-text (1165 KB) | HTML Full-text | XML Full-text
Abstract
This article reports recent advances and progress in the field of electrical capacitance volume tomography (ECVT). ECVT, developed from the two-dimensional electrical capacitance tomography (ECT), is a promising non-intrusive imaging technology that can provide real-time three-dimensional images of the sensing domain. Images [...] Read more.
This article reports recent advances and progress in the field of electrical capacitance volume tomography (ECVT). ECVT, developed from the two-dimensional electrical capacitance tomography (ECT), is a promising non-intrusive imaging technology that can provide real-time three-dimensional images of the sensing domain. Images are reconstructed from capacitance measurements acquired by electrodes placed on the outside boundary of the testing vessel. In this article, a review of progress on capacitance sensor design and applications to multi-phase flows is presented. The sensor shape, electrode configuration, and the number of electrodes that comprise three key elements of three-dimensional capacitance sensors are illustrated. The article also highlights applications of ECVT sensors on vessels of various sizes from 1 to 60 inches with complex geometries. Case studies are used to show the capability and validity of ECVT. The studies provide qualitative and quantitative real-time three-dimensional information of the measuring domain under study. Advantages of ECVT render it a favorable tool to be utilized for industrial applications and fundamental multi-phase flow research. Full article
(This article belongs to the Special Issue Delft Workshop 2008-2009—Sensors and Imagers: a VLSI Perspective)
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Open AccessReview Advances in Lead-Free Piezoelectric Materials for Sensors and Actuators
Sensors 2010, 10(3), 1935-1954; doi:10.3390/s100301935
Received: 6 January 2010 / Revised: 3 February 2010 / Accepted: 12 February 2010 / Published: 10 March 2010
Cited by 103 | PDF Full-text (759 KB) | HTML Full-text | XML Full-text
Abstract
Piezoelectrics have widespread use in today’s sensor and actuator technologies. However, most commercially available piezoelectric materials, e.g., Pb [ZrxTi1-x] O3 (PZT),are comprised of more than 60 weight percent lead (Pb). Dueto its harmful effects, there [...] Read more.
Piezoelectrics have widespread use in today’s sensor and actuator technologies. However, most commercially available piezoelectric materials, e.g., Pb [ZrxTi1-x] O3 (PZT),are comprised of more than 60 weight percent lead (Pb). Dueto its harmful effects, there is a strong impetus to identify new lead-free replacement materials with comparable properties to those of PZT. This review highlights recent developments in several lead-free piezoelectric materials including BaTiO3, Na0.5Bi0.5TiO3, K0.5Bi0.5TiO3, Na0.5K0.5NbO3, and their solid solutions. The factors that contribute to strong piezoelectric behavior are described and a summary of the properties for the various systems is provided. Full article
(This article belongs to the Special Issue Advances in Actuators)
Open AccessReview Metal Oxide Gas Sensors: Sensitivity and Influencing Factors
Sensors 2010, 10(3), 2088-2106; doi:10.3390/s100302088
Received: 17 February 2010 / Revised: 10 March 2010 / Accepted: 14 March 2010 / Published: 15 March 2010
Cited by 402 | PDF Full-text (606 KB) | HTML Full-text | XML Full-text
Abstract
Conductometric semiconducting metal oxide gas sensors have been widely used and investigated in the detection of gases. Investigations have indicated that the gas sensing process is strongly related to surface reactions, so one of the important parameters of gas sensors, the sensitivity [...] Read more.
Conductometric semiconducting metal oxide gas sensors have been widely used and investigated in the detection of gases. Investigations have indicated that the gas sensing process is strongly related to surface reactions, so one of the important parameters of gas sensors, the sensitivity of the metal oxide based materials, will change with the factors influencing the surface reactions, such as chemical components, surface-modification and microstructures of sensing layers, temperature and humidity. In this brief review, attention will be focused on changes of sensitivity of conductometric semiconducting metal oxide gas sensors due to the five factors mentioned above. Full article
(This article belongs to the Special Issue Metal-Oxide Based Nanosensors)
Open AccessReview Stress Sensors and Signal Transducers in Cyanobacteria
Sensors 2010, 10(3), 2386-2415; doi:10.3390/s100302386
Received: 20 January 2010 / Revised: 15 February 2010 / Accepted: 3 March 2010 / Published: 23 March 2010
Cited by 38 | PDF Full-text (403 KB) | HTML Full-text | XML Full-text
Abstract
In living cells, the perception of environmental stress and the subsequent transduction of stress signals are primary events in the acclimation to changes in the environment. Some molecular sensors and transducers of environmental stress cannot be identified by traditional and conventional methods. [...] Read more.
In living cells, the perception of environmental stress and the subsequent transduction of stress signals are primary events in the acclimation to changes in the environment. Some molecular sensors and transducers of environmental stress cannot be identified by traditional and conventional methods. Based on genomic information, a systematic approach has been applied to the solution of this problem in cyanobacteria, involving mutagenesis of potential sensors and signal transducers in combination with DNA microarray analyses for the genome-wide expression of genes. Forty-five genes for the histidine kinases (Hiks), 12 genes for serine-threonine protein kinases (Spks), 42 genes for response regulators (Rres), seven genes for RNA polymerase sigma factors, and nearly 70 genes for transcription factors have been successfully inactivated by targeted mutagenesis in the unicellular cyanobacterium Synechocystis sp. PCC 6803. Screening of mutant libraries by genome-wide DNA microarray analysis under various stress and non-stress conditions has allowed identification of proteins that perceive and transduce signals of environmental stress. Here we summarize recent progress in the identification of sensory and regulatory systems, including Hiks, Rres, Spks, sigma factors, transcription factors, and the role of genomic DNA supercoiling in the regulation of the responses of cyanobacterial cells to various types of stress. Full article
(This article belongs to the Special Issue Advances in Transducers)
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