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Sensors, Volume 12, Issue 7 (July 2012), Pages 8438-9950

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Open AccessArticle Half-Metallic Properties of Single-Walled Polymeric Manganese Phthalocyanine Nanotubes
Sensors 2012, 12(7), 8438-8446; doi:10.3390/s120708438
Received: 8 May 2012 / Revised: 11 June 2012 / Accepted: 12 June 2012 / Published: 25 June 2012
Cited by 3 | PDF Full-text (831 KB) | HTML Full-text | XML Full-text
Abstract
We present a theoretical study of the electronic and magnetic properties of single-walled manganese phthalocyanine (MnPc) nanotubes which can be thought of as rolled-up ribbons of the two-dimensional (2D) polymeric MnPc sheet. Our density functional theory calculations show that all of the [...] Read more.
We present a theoretical study of the electronic and magnetic properties of single-walled manganese phthalocyanine (MnPc) nanotubes which can be thought of as rolled-up ribbons of the two-dimensional (2D) polymeric MnPc sheet. Our density functional theory calculations show that all of the MnPc nanotubes investigated here are half-metals with 100% spin polarization around the Fermi level. Following the increase of the tube diameter, the number of spin-down energy bands of MnPc nanotubes is always increased while the spin-up band gap of MnPc nanotubes approaches that of the 2D MnPc sheet in an oscillatory manner. Because the half-metallic character of MnPc nanotubes is deeply rooted in the distribution of electrons in the energy bands dominated by the Mn 3d atomic orbitals, adsorption of CO molecules on the Mn ions leads to a redistribution of electrons in the Mn 3d orbitals and thus can tune precisely the spin state and electronic transport properties of MnPc nanotubes, demonstrating promising applications of MnPc nanotubes in future molecular spintronics and single-molecule sensors. Full article
(This article belongs to the Special Issue Molecular Devices and Machines: Cooperativity and Multifunctionality)
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Open AccessArticle Detecting Service Chains and Feature Interactions in Sensor-Driven Home Network Services
Sensors 2012, 12(7), 8447-8464; doi:10.3390/s120708447
Received: 2 May 2012 / Revised: 4 June 2012 / Accepted: 18 June 2012 / Published: 25 June 2012
Cited by 3 | PDF Full-text (136 KB) | HTML Full-text | XML Full-text
Abstract
Sensor-driven services often cause chain reactions, since one service may generate an environmental impact that automatically triggers another service. We first propose a framework that can formalize and detect such service chains based on ECA (event, condition, action) rules. Although the service [...] Read more.
Sensor-driven services often cause chain reactions, since one service may generate an environmental impact that automatically triggers another service. We first propose a framework that can formalize and detect such service chains based on ECA (event, condition, action) rules. Although the service chain can be a major source of feature interactions, not all service chains lead to harmful interactions. Therefore, we then propose a method that identifies feature interactions within the service chains. Specifically, we characterize the degree of deviation of every service chain by evaluating the gap between expected and actual service states. An experimental evaluation demonstrates that the proposed method successfully detects 11 service chains and 6 feature interactions within 7 practical sensor-driven services. Full article
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Open AccessArticle Development of An Automatic Approaching System for Electrochemical Nanofabrication Using Visual and Force-Displacement Sensing
Sensors 2012, 12(7), 8465-8476; doi:10.3390/s120708465
Received: 17 May 2012 / Revised: 12 June 2012 / Accepted: 12 June 2012 / Published: 25 June 2012
Cited by 3 | PDF Full-text (2940 KB) | HTML Full-text | XML Full-text
Abstract
In this paper, a fast automatic precision approaching system is developed for electrochemical nanofabrication using visual and force-displacement sensing. Before the substrate is fabricated, the template should approach the substrate accurately to establish the initial gap between the template and substrate. During [...] Read more.
In this paper, a fast automatic precision approaching system is developed for electrochemical nanofabrication using visual and force-displacement sensing. Before the substrate is fabricated, the template should approach the substrate accurately to establish the initial gap between the template and substrate. During the approaching process, the template is first quickly moved towards the substrate by the stepping motor until a specified gap is detected by the visual feedback. Then, the successive approach using the switch of macro-micro motion with a force-displacement sensing module is triggered to make the template contact with the substrate to nanometre accuracy. The contact force is measured by the force-displacement sensing module which employs the high-resolution capacitive displacement sensor and flexure compliant mechanism. The high sensitivity of this capacitive displacement sensor ensures high accuracy of the template-substrate contact. The experimental results show that the template can reach the substrate accurately and smoothly, which verifies the effectiveness of the proposed approaching system with the visual and the force-displacement sensing modules. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle Development of a Novel Optical Biosensor for Detection of Organophoshorus Pesticides Based on Methyl Parathion Hydrolase Immobilized by Metal-Chelate Affinity
Sensors 2012, 12(7), 8477-8490; doi:10.3390/s120708477
Received: 11 May 2012 / Revised: 11 June 2012 / Accepted: 12 June 2012 / Published: 25 June 2012
Cited by 6 | PDF Full-text (238 KB) | HTML Full-text | XML Full-text
Abstract
We have developed a novel optical biosensor device using recombinant methyl parathion hydrolase (MPH) enzyme immobilized on agarose by metal-chelate affinity to detect organophosphorus (OP) compounds with a nitrophenyl group. The biosensor principle is based on the optical measurement of the product [...] Read more.
We have developed a novel optical biosensor device using recombinant methyl parathion hydrolase (MPH) enzyme immobilized on agarose by metal-chelate affinity to detect organophosphorus (OP) compounds with a nitrophenyl group. The biosensor principle is based on the optical measurement of the product of OP catalysis by MPH (p-nitrophenol). Briefly, MPH containing six sequential histidines (6× His tag) at its N-terminal was bound to nitrilotriacetic acid (NTA) agarose with Ni ions, resulting in the flexible immobilization of the bio-reaction platform. The optical biosensing system consisted of two light-emitting diodes (LEDs) and one photodiode. The LED that emitted light at the wavelength of the maximum absorption for p-nitrophenol served as the signal light, while the other LED that showed no absorbance served as the reference light. The optical sensing system detected absorbance that was linearly correlated to methyl parathion (MP) concentration and the detection limit was estimated to be 4 μM. Sensor hysteresis was investigated and the results showed that at lower concentration range of MP the difference got from the opposite process curves was very small. With its easy immobilization of enzymes and simple design in structure, the system has the potential for development into a practical portable detector for field applications. Full article
(This article belongs to the Section Biosensors)
Open AccessArticle Variable-State-Dimension Kalman-Based Filter for Orientation Determination Using Inertial and Magnetic Sensors
Sensors 2012, 12(7), 8491-8506; doi:10.3390/s120708491
Received: 18 May 2012 / Revised: 8 June 2012 / Accepted: 11 June 2012 / Published: 25 June 2012
Cited by 9 | PDF Full-text (438 KB) | HTML Full-text | XML Full-text
Abstract
In this paper a quaternion-based Variable-State-Dimension Extended Kalman Filter (VSD-EKF) is developed for estimating the three-dimensional orientation of a rigid body using the measurements from an Inertial Measurement Unit (IMU) integrated with a triaxial magnetic sensor. Gyro bias and magnetic disturbances are [...] Read more.
In this paper a quaternion-based Variable-State-Dimension Extended Kalman Filter (VSD-EKF) is developed for estimating the three-dimensional orientation of a rigid body using the measurements from an Inertial Measurement Unit (IMU) integrated with a triaxial magnetic sensor. Gyro bias and magnetic disturbances are modeled and compensated by including them in the filter state vector. The VSD-EKF switches between a quiescent EKF, where the magnetic disturbance is modeled as a first-order Gauss-Markov stochastic process (GM-1), and a higher-order EKF where extra state components are introduced to model the time-rate of change of the magnetic field as a GM-1 stochastic process, namely the magnetic disturbance is modeled as a second-order Gauss-Markov stochastic process (GM-2). Experimental validation tests show the effectiveness of the VSD-EKF, as compared to either the quiescent EKF or the higher-order EKF when they run separately. Full article
(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Italy 2012)
Open AccessArticle Step Length Estimation Using Handheld Inertial Sensors
Sensors 2012, 12(7), 8507-8525; doi:10.3390/s120708507
Received: 2 May 2012 / Revised: 12 June 2012 / Accepted: 13 June 2012 / Published: 25 June 2012
Cited by 42 | PDF Full-text (1294 KB) | HTML Full-text | XML Full-text
Abstract
In this paper a novel step length model using a handheld Micro Electrical Mechanical System (MEMS) is presented. It combines the user’s step frequency and height with a set of three parameters for estimating step length. The model has been developed and [...] Read more.
In this paper a novel step length model using a handheld Micro Electrical Mechanical System (MEMS) is presented. It combines the user’s step frequency and height with a set of three parameters for estimating step length. The model has been developed and trained using 12 different subjects: six men and six women. For reliable estimation of the step frequency with a handheld device, the frequency content of the handheld sensor’s signal is extracted by applying the Short Time Fourier Transform (STFT) independently from the step detection process. The relationship between step and hand frequencies is analyzed for different hand’s motions and sensor carrying modes. For this purpose, the frequency content of synchronized signals collected with two sensors placed in the hand and on the foot of a pedestrian has been extracted. Performance of the proposed step length model is assessed with several field tests involving 10 test subjects different from the above 12. The percentages of error over the travelled distance using universal parameters and a set of parameters calibrated for each subject are compared. The fitted solutions show an error between 2.5 and 5% of the travelled distance, which is comparable with that achieved by models proposed in the literature for body fixed sensors only. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle Analysis and Design of a Speed and Position System for Maglev Vehicles
Sensors 2012, 12(7), 8526-8543; doi:10.3390/s120708526
Received: 3 May 2012 / Revised: 5 June 2012 / Accepted: 6 June 2012 / Published: 25 June 2012
Cited by 2 | PDF Full-text (570 KB) | HTML Full-text | XML Full-text
Abstract
This paper mainly researches one method of speed and location detection for maglev vehicles. As the maglev train doesn’t have any physical contact with the rails, it has to use non-contact measuring methods. The technology based on the inductive loop-cable could fulfill [...] Read more.
This paper mainly researches one method of speed and location detection for maglev vehicles. As the maglev train doesn’t have any physical contact with the rails, it has to use non-contact measuring methods. The technology based on the inductive loop-cable could fulfill the requirement by using an on-board antenna which could detect the alternating magnetic field produced by the loop-cable on rails. This paper introduces the structure of a speed and position system, and analyses the electromagnetic field produced by the loop-cable. The equivalent model of the loop-cable is given and the most suitable component of the magnetic flux density is selected. Then the paper also compares the alternating current (AC) resistance and the quality factor between two kinds of coils which the antenna is composed of. The effect of the rails to the signal receiving is also researched and then the structure of the coils is improved. Finally, considering the common-mode interference, 8-word coils are designed and analyzed. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle Configuring a Context-Aware Middleware for Wireless Sensor Networks
Sensors 2012, 12(7), 8544-8570; doi:10.3390/s120708544
Received: 8 May 2012 / Revised: 11 June 2012 / Accepted: 12 June 2012 / Published: 25 June 2012
Cited by 7 | PDF Full-text (716 KB) | HTML Full-text | XML Full-text
Abstract
In the Future Internet, applications based on Wireless Sensor Networks will have to support reconfiguration with minimum human intervention, depending on dynamic context changes in their environment. These situations create a need for building these applications as adaptive software and including techniques [...] Read more.
In the Future Internet, applications based on Wireless Sensor Networks will have to support reconfiguration with minimum human intervention, depending on dynamic context changes in their environment. These situations create a need for building these applications as adaptive software and including techniques that allow the context acquisition and decisions about adaptation. However, contexts use to be made up of complex information acquired from heterogeneous devices and user characteristics, making them difficult to manage. So, instead of building context-aware applications from scratch, we propose to use FamiWare, a family of middleware for Ambient Intelligence specifically designed to be aware of contexts in sensor and smartphone devices. It provides both, several monitoring services to acquire contexts from devices and users, and a context-awareness service to analyze and detect context changes. However, the current version of FamiWare does not allow the automatic incorporation related to the management of new contexts into the FamiWare family. To overcome this shortcoming, in this work, we first present how to model the context using a metamodel to define the contexts that must to be taken into account in an instantiation of FamiWare for a certain Ambient Intelligence system. Then, to configure a new context-aware version of FamiWare and to generate code ready-to-install within heterogeneous devices, we define a mapping that automatically transforms metamodel elements defining contexts into elements of the FamiWare family, and we also use the FamiWare configuration process to customize the new context-aware variant. Finally, we evaluate the benefits of our process, and we analyze both that the new version of the middleware works as expected and that it manages the contexts in an efficient way. Full article
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Open AccessArticle Supplying the Power Requirements to a Sensor Network Using Radio Frequency Power Transfer
Sensors 2012, 12(7), 8571-8585; doi:10.3390/s120708571
Received: 11 May 2012 / Revised: 12 June 2012 / Accepted: 12 June 2012 / Published: 26 June 2012
Cited by 8 | PDF Full-text (696 KB) | HTML Full-text | XML Full-text
Abstract
Wireless power transmission is a method of supplying power to small electronic devices when there is no wired connection. One way to increase the range of these systems is to use a directional transmitting antenna, the problem with this approach is that [...] Read more.
Wireless power transmission is a method of supplying power to small electronic devices when there is no wired connection. One way to increase the range of these systems is to use a directional transmitting antenna, the problem with this approach is that power can only be transmitted through a narrow beam and directly forward, requiring the transmitter to always be aligned with the sensor node position. The work outlined in this article describes the design and testing of an autonomous radio frequency power transfer system that is capable of rotating the base transmitter to track the position of sensor nodes and transferring power to that sensor node. The system’s base station monitors the node’s energy levels and forms a charge queue to plan charging order and maintain energy levels of the nodes. Results show a radio frequency harvesting circuit with a measured S11 value of −31.5 dB and a conversion efficiency of 39.1%. Simulation and experimentation verified the level of power transfer and efficiency. The results of this work show a small network of three nodes with different storage types powered by a central base node. Full article
(This article belongs to the Section Sensor Networks)
Open AccessArticle Embedded Adaptive Optics for Ubiquitous Lab-on-a-Chip Readout on Intact Cell Phones
Sensors 2012, 12(7), 8586-8600; doi:10.3390/s120708586
Received: 2 May 2012 / Revised: 28 May 2012 / Accepted: 6 June 2012 / Published: 26 June 2012
Cited by 11 | PDF Full-text (1343 KB) | HTML Full-text | XML Full-text
Abstract
The evaluation of disposable lab-on-a-chip (LOC) devices on cell phones is an attractive alternative to migrate the analytical strength of LOC solutions to decentralized sensing applications. Imaging the micrometric detection areas of LOCs in contact with intact phone cameras is central to [...] Read more.
The evaluation of disposable lab-on-a-chip (LOC) devices on cell phones is an attractive alternative to migrate the analytical strength of LOC solutions to decentralized sensing applications. Imaging the micrometric detection areas of LOCs in contact with intact phone cameras is central to provide such capability. This work demonstrates a disposable and morphing liquid lens concept that can be integrated in LOC devices and refocuses micrometric features in the range necessary for LOC evaluation using diverse cell phone cameras. During natural evaporation, the lens focus varies adapting to different type of cameras. Standard software in the phone commands a time-lapse acquisition for best focal selection that is sufficient to capture and resolve, under ambient illumination, 50 μm features in regions larger than 500 × 500 μm2. In this way, the present concept introduces a generic solution compatible with the use of diverse and unmodified cell phone cameras to evaluate disposable LOC devices. Full article
(This article belongs to the Special Issue Ubiquitous Sensing)
Open AccessArticle Spatial Uncertainty Model for Visual Features Using a Kinect™ Sensor
Sensors 2012, 12(7), 8640-8662; doi:10.3390/s120708640
Received: 18 May 2012 / Revised: 12 June 2012 / Accepted: 13 June 2012 / Published: 26 June 2012
Cited by 18 | PDF Full-text (3005 KB) | HTML Full-text | XML Full-text
Abstract
This study proposes a mathematical uncertainty model for the spatial measurement of visual features using Kinect™ sensors. This model can provide qualitative and quantitative analysis for the utilization of Kinect™ sensors as 3D perception sensors. In order to achieve this objective, we [...] Read more.
This study proposes a mathematical uncertainty model for the spatial measurement of visual features using Kinect™ sensors. This model can provide qualitative and quantitative analysis for the utilization of Kinect™ sensors as 3D perception sensors. In order to achieve this objective, we derived the propagation relationship of the uncertainties between the disparity image space and the real Cartesian space with the mapping function between the two spaces. Using this propagation relationship, we obtained the mathematical model for the covariance matrix of the measurement error, which represents the uncertainty for spatial position of visual features from Kinect™ sensors. In order to derive the quantitative model of spatial uncertainty for visual features, we estimated the covariance matrix in the disparity image space using collected visual feature data. Further, we computed the spatial uncertainty information by applying the covariance matrix in the disparity image space and the calibrated sensor parameters to the proposed mathematical model. This spatial uncertainty model was verified by comparing the uncertainty ellipsoids for spatial covariance matrices and the distribution of scattered matching visual features. We expect that this spatial uncertainty model and its analyses will be useful in various Kinect™ sensor applications. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle A Compact Annular Ring Microstrip Antenna for WSN Applications
Sensors 2012, 12(7), 8663-8674; doi:10.3390/s120708663
Received: 28 May 2012 / Revised: 20 June 2012 / Accepted: 20 June 2012 / Published: 26 June 2012
Cited by 3 | PDF Full-text (285 KB) | HTML Full-text | XML Full-text
Abstract
A compact annular ring microstrip antenna was proposed for a wireless sensor network (WSN) application in the 2.4 GHz band. In this paper the major considerations of the conformal antenna design were the compact size and the impact on antenna’s performance of [...] Read more.
A compact annular ring microstrip antenna was proposed for a wireless sensor network (WSN) application in the 2.4 GHz band. In this paper the major considerations of the conformal antenna design were the compact size and the impact on antenna’s performance of a steel installation base. By using a chip resistor of large resistance (120 Ω) the antenna size was reduced to 38% of that a conventional annular ring patch antenna. With the addition of the steel installation base the resonant frequency of the antenna increases about 4.2% and the bandwidth reduces from 17.5% to 11.7% by adjusting the load resistance simultaneously. Several key parameters were discussed and optimized, and the antenna was fabricated and its performance measured. The antenna is well matched at 2.4 GHz with 34.2 dB return loss and –2.5 dBi peak gain. Meanwhile, it exhibits excellent radiation patterns with very low cross-polarization levels. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle WebTag: Web Browsing into Sensor Tags over NFC
Sensors 2012, 12(7), 8675-8690; doi:10.3390/s120708675
Received: 20 March 2012 / Revised: 8 June 2012 / Accepted: 19 June 2012 / Published: 26 June 2012
Cited by 5 | PDF Full-text (422 KB) | HTML Full-text | XML Full-text
Abstract
Information and Communication Technologies (ICTs) continue to overcome many of the challenges related to wireless sensor monitoring, such as for example the design of smarter embedded processors, the improvement of the network architectures, the development of efficient communication protocols or the maximization [...] Read more.
Information and Communication Technologies (ICTs) continue to overcome many of the challenges related to wireless sensor monitoring, such as for example the design of smarter embedded processors, the improvement of the network architectures, the development of efficient communication protocols or the maximization of the life cycle autonomy. This work tries to improve the communication link of the data transmission in wireless sensor monitoring. The upstream communication link is usually based on standard IP technologies, but the downstream side is always masked with the proprietary protocols used for the wireless link (like ZigBee, Bluetooth, RFID, etc.). This work presents a novel solution (WebTag) for a direct IP based access to a sensor tag over the Near Field Communication (NFC) technology for secure applications. WebTag allows a direct web access to the sensor tag by means of a standard web browser, it reads the sensor data, configures the sampling rate and implements IP based security policies. It is, definitely, a new step towards the evolution of the Internet of Things paradigm. Full article
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Open AccessArticle A Study of Hand Back Skin Texture Patterns for Personal Identification and Gender Classification
Sensors 2012, 12(7), 8691-8709; doi:10.3390/s120708691
Received: 17 May 2012 / Revised: 14 June 2012 / Accepted: 18 June 2012 / Published: 26 June 2012
PDF Full-text (1432 KB) | HTML Full-text | XML Full-text
Abstract
Human hand back skin texture (HBST) is often consistent for a person and distinctive from person to person. In this paper, we study the HBST pattern recognition problem with applications to personal identification and gender classification. A specially designed system is developed [...] Read more.
Human hand back skin texture (HBST) is often consistent for a person and distinctive from person to person. In this paper, we study the HBST pattern recognition problem with applications to personal identification and gender classification. A specially designed system is developed to capture HBST images, and an HBST image database was established, which consists of 1,920 images from 80 persons (160 hands). An efficient texton learning based method is then presented to classify the HBST patterns. First, textons are learned in the space of filter bank responses from a set of training images using the -minimization based sparse representation (SR) technique. Then, under the SR framework, we represent the feature vector at each pixel over the learned dictionary to construct a representation coefficient histogram. Finally, the coefficient histogram is used as skin texture feature for classification. Experiments on personal identification and gender classification are performed by using the established HBST database. The results show that HBST can be used to assist human identification and gender classification. Full article
(This article belongs to the Special Issue Hand-Based Biometrics Sensors and Systems)
Open AccessArticle Subtitle Synchronization across Multiple Screens and Devices
Sensors 2012, 12(7), 8710-8731; doi:10.3390/s120708710
Received: 4 June 2012 / Revised: 15 June 2012 / Accepted: 15 June 2012 / Published: 26 June 2012
PDF Full-text (954 KB) | HTML Full-text | XML Full-text
Abstract
Ambient Intelligence is a new paradigm in which environments are sensitive and responsive to the presence of people. This is having an increasing importance in multimedia applications, which frequently rely on sensors to provide useful information to the user. In this context, [...] Read more.
Ambient Intelligence is a new paradigm in which environments are sensitive and responsive to the presence of people. This is having an increasing importance in multimedia applications, which frequently rely on sensors to provide useful information to the user. In this context, multimedia applications must adapt and personalize both content and interfaces in order to reach acceptable levels of context-specific quality of service for the user, and enable the content to be available anywhere and at any time. The next step is to make content available to everybody in order to overcome the existing access barriers to content for users with specific needs, or else to adapt to different platforms, hence making content fully usable and accessible. Appropriate access to video content, for instance, is not always possible due to the technical limitations of traditional video packaging, transmission and presentation. This restricts the flexibility of subtitles and audio-descriptions to be adapted to different devices, contexts and users. New Web standards built around HTML5 enable more featured applications with better adaptation and personalization facilities, and thus would seem more suitable for accessible AmI environments. This work presents a video subtitling system that enables the customization, adaptation and synchronization of subtitles across different devices and multiple screens. The benefits of HTML5 applications for building the solution are analyzed along with their current platform support. Moreover, examples of the use of the application in three different cases are presented. Finally, the user experience of the solution is evaluated. Full article
Open AccessArticle Method for Vibration Response Simulation and Sensor Placement Optimization of a Machine Tool Spindle System with a Bearing Defect
Sensors 2012, 12(7), 8732-8754; doi:10.3390/s120708732
Received: 24 May 2012 / Revised: 13 June 2012 / Accepted: 15 June 2012 / Published: 27 June 2012
Cited by 10 | PDF Full-text (653 KB) | HTML Full-text | XML Full-text
Abstract
Bearing defects are one of the most important mechanical sources for vibration and noise generation in machine tool spindles. In this study, an integrated finite element (FE) model is proposed to predict the vibration responses of a spindle bearing system with localized [...] Read more.
Bearing defects are one of the most important mechanical sources for vibration and noise generation in machine tool spindles. In this study, an integrated finite element (FE) model is proposed to predict the vibration responses of a spindle bearing system with localized bearing defects and then the sensor placement for better detection of bearing faults is optimized. A nonlinear bearing model is developed based on Jones’ bearing theory, while the drawbar, shaft and housing are modeled as Timoshenko’s beam. The bearing model is then integrated into the FE model of drawbar/shaft/housing by assembling equations of motion. The Newmark time integration method is used to solve the vibration responses numerically. The FE model of the spindle-bearing system was verified by conducting dynamic tests. Then, the localized bearing defects were modeled and vibration responses generated by the outer ring defect were simulated as an illustration. The optimization scheme of the sensor placement was carried out on the test spindle. The results proved that, the optimal sensor placement depends on the vibration modes under different boundary conditions and the transfer path between the excitation and the response. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle Using a Genetic Algorithm as an Optimal Band Selector in the Mid and Thermal Infrared (2.5–14 µm) to Discriminate Vegetation Species
Sensors 2012, 12(7), 8755-8769; doi:10.3390/s120708755
Received: 15 May 2012 / Revised: 13 June 2012 / Accepted: 15 June 2012 / Published: 27 June 2012
Cited by 8 | PDF Full-text (822 KB) | HTML Full-text | XML Full-text
Abstract
Genetic variation between various plant species determines differences in their physio-chemical makeup and ultimately in their hyperspectral emissivity signatures. The hyperspectral emissivity signatures, on the one hand, account for the subtle physio-chemical changes in the vegetation, but on the other hand, highlight [...] Read more.
Genetic variation between various plant species determines differences in their physio-chemical makeup and ultimately in their hyperspectral emissivity signatures. The hyperspectral emissivity signatures, on the one hand, account for the subtle physio-chemical changes in the vegetation, but on the other hand, highlight the problem of high dimensionality. The aim of this paper is to investigate the performance of genetic algorithms coupled with the spectral angle mapper (SAM) to identify a meaningful subset of wavebands sensitive enough to discriminate thirteen broadleaved vegetation species from the laboratory measured hyperspectral emissivities. The performance was evaluated using an overall classification accuracy and Jeffries Matusita distance. For the multiple plant species, the targeted bands based on genetic algorithms resulted in a high overall classification accuracy (90%). Concentrating on the pairwise comparison results, the selected wavebands based on genetic algorithms resulted in higher Jeffries Matusita (J-M) distances than randomly selected wavebands did. This study concludes that targeted wavebands from leaf emissivity spectra are able to discriminate vegetation species. Full article
(This article belongs to the Section Remote Sensors)
Open AccessArticle Comparisons between Membrane, Bridge and Cantilever Miniaturized Resistive Vacuum Gauges
Sensors 2012, 12(7), 8770-8781; doi:10.3390/s120708770
Received: 16 May 2012 / Revised: 11 June 2012 / Accepted: 15 June 2012 / Published: 27 June 2012
Cited by 9 | PDF Full-text (319 KB) | HTML Full-text | XML Full-text
Abstract
Using bulk micromachining, meander-shaped resistor elements consisting of 20 nm Cr and 200 nm Au were fabricated on 1 µm thick silicon nitride membranes, bridges, and cantilevers. The resistance change as a function of pressure depends strongly on the thermal resistance of [...] Read more.
Using bulk micromachining, meander-shaped resistor elements consisting of 20 nm Cr and 200 nm Au were fabricated on 1 µm thick silicon nitride membranes, bridges, and cantilevers. The resistance change as a function of pressure depends strongly on the thermal resistance of the two metal lines connecting the heated resistor to the silicon bulk (cold junction) and on the thermal resistance of the silicon nitride. Relative resistance changes ranging from about 3% (small membrane) to 20% (bridge) per mW of input power were obtained when operating the devices in constant voltage mode. The pressure where maximum sensitivity of these gauges occurs depends on the distance ‘d’ between the periphery of the heated resistor element and the silicon cold junction. Devices with ‘d’ ranging from 50 µm to 1,200 µm were fabricated. Assuming that pressures can be reliably measured above the 10% and below the 90% points of the resistance versus pressure curve, the range of these devices is about two orders of magnitude. By integrating two devices, one with d = 65 µm and one with d = 1,200 µm on the same chip and connecting them in series, the range can be increased by about a factor of three. By fabricating the cantilever devices so that they curl upon release, it will be shown that these devices also exhibit larger range due to varying ‘d’. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle An Adaptive OFDMA-Based MAC Protocol for Underwater Acoustic Wireless Sensor Networks
Sensors 2012, 12(7), 8782-8805; doi:10.3390/s120708782
Received: 29 May 2012 / Revised: 20 June 2012 / Accepted: 20 June 2012 / Published: 27 June 2012
Cited by 6 | PDF Full-text (270 KB) | HTML Full-text | XML Full-text
Abstract
Underwater acoustic wireless sensor networks (UAWSNs) have many applications across various civilian and military domains. However, they suffer from the limited available bandwidth of acoustic signals and harsh underwater conditions. In this work, we present an Orthogonal Frequency Division Multiple Access (OFDMA)-based [...] Read more.
Underwater acoustic wireless sensor networks (UAWSNs) have many applications across various civilian and military domains. However, they suffer from the limited available bandwidth of acoustic signals and harsh underwater conditions. In this work, we present an Orthogonal Frequency Division Multiple Access (OFDMA)-based Media Access Control (MAC) protocol that is configurable to suit the operating requirements of the underwater sensor network. The protocol has three modes of operation, namely random, equal opportunity and energy-conscious modes of operation. Our MAC design approach exploits the multi-path characteristics of a fading acoustic channel to convert it into parallel independent acoustic sub-channels that undergo flat fading. Communication between node pairs within the network is done using subsets of these sub-channels, depending on the configurations of the active mode of operation. Thus, the available limited bandwidth gets fully utilized while completely avoiding interference. We derive the mathematical model for optimal power loading and subcarrier selection, which is used as basis for all modes of operation of the protocol. We also conduct many simulation experiments to evaluate and compare our protocol with other Code Division Multiple Access (CDMA)-based MAC protocols. Full article
(This article belongs to the Section Sensor Networks)
Open AccessArticle Immobilization of Ionophore and Surface Characterization Studies of the Titanium(III) Ion in a PVC-Membrane Sensor
Sensors 2012, 12(7), 8806-8814; doi:10.3390/s120708806
Received: 11 May 2012 / Revised: 28 May 2012 / Accepted: 28 May 2012 / Published: 27 June 2012
Cited by 9 | PDF Full-text (481 KB) | HTML Full-text | XML Full-text
Abstract
Novel ionophores comprising various hydroxide and amine structures were immobilized onto poly(vinyl chloride) (PVC) matrices, and these were examined to determine Ti(III) selectivity. To predict the selectivity of Ti(III), a PVC membrane was used to investigate the binding of Ti(III) to c-methylcalix[4]resorcinarene [...] Read more.
Novel ionophores comprising various hydroxide and amine structures were immobilized onto poly(vinyl chloride) (PVC) matrices, and these were examined to determine Ti(III) selectivity. To predict the selectivity of Ti(III), a PVC membrane was used to investigate the binding of Ti(III) to c-methylcalix[4]resorcinarene (CMCR). The study showed that the chelating ligand, CMCR, was coordinated selectively to Ti(III) at eight coordination sites involving the oxygen atoms at the interface of the membrane/solution. The membrane was prepared, based on CMCR as an ionophore, sodium tetrakis(4-fluorophenyl) borate (NaTFPB) as a lipophilic ionic additive, and dioctylphthalate (DOP) as a plasticizer. The immobilization of the ionophore and surface characterization studies revealed that the performance of CMCR-immobilized PVC was equivalent to that of mobile ionophores in supported liquid membranes (SLMs). The strengths of the ion-ionophore (CMCR-Ti(OH)(OH2)52+) interactions and the role of ionophores on membranes were studied via UV-Vis, Fourier transform infrared spectroscopy (FT–IR), scanning electron microscopy (SEM) and and X-ray diffraction (XRD). Full article
(This article belongs to the Section Chemical Sensors)
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Open AccessArticle Searching Dynamic Agents with a Team of Mobile Robots
Sensors 2012, 12(7), 8815-8831; doi:10.3390/s120708815
Received: 9 May 2012 / Revised: 15 June 2012 / Accepted: 20 June 2012 / Published: 27 June 2012
Cited by 1 | PDF Full-text (316 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents a new algorithm that allows a team of robots to cooperatively search for a set of moving targets. An estimation of the areas of the environment that are more likely to hold a target agent is obtained using a [...] Read more.
This paper presents a new algorithm that allows a team of robots to cooperatively search for a set of moving targets. An estimation of the areas of the environment that are more likely to hold a target agent is obtained using a grid-based Bayesian filter. The robot sensor readings and the maximum speed of the moving targets are used in order to update the grid. This representation is used in a search algorithm that commands the robots to those areas that are more likely to present target agents. This algorithm splits the environment in a tree of connected regions using dynamic programming. This tree is used in order to decide the destination for each robot in a coordinated manner. The algorithm has been successfully tested in known and unknown environments showing the validity of the approach. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle Optical Fiber Relative Humidity Sensor Based on a FBG with a Di-Ureasil Coating
Sensors 2012, 12(7), 8847-8860; doi:10.3390/s120708847
Received: 28 May 2012 / Revised: 20 June 2012 / Accepted: 25 June 2012 / Published: 27 June 2012
Cited by 21 | PDF Full-text (599 KB) | HTML Full-text | XML Full-text
Abstract
In this work we proposed a relative humidity (RH) sensor based on a Bragg grating written in an optical fiber, associated with a coating of organo-silica hybrid material prepared by the sol-gel method. The organo-silica-based coating has a strong adhesion to the [...] Read more.
In this work we proposed a relative humidity (RH) sensor based on a Bragg grating written in an optical fiber, associated with a coating of organo-silica hybrid material prepared by the sol-gel method. The organo-silica-based coating has a strong adhesion to the optical fiber and its expansion is reversibly affected by the change in the RH values (15.0–95.0%) of the surrounding environment, allowing an increased sensitivity (22.2 pm/%RH) and durability due to the presence of a siliceous-based inorganic component. The developed sensor was tested in a real structure health monitoring essay, in which the RH inside two concrete blocks with different porosity values was measured over 1 year. The results demonstrated the potential of the proposed optical sensor in the monitoring of civil engineering structures. Full article
(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Portugal)
Open AccessArticle Observability Analysis of a Matrix Kalman Filter-Based Navigation System Using Visual/Inertial/Magnetic Sensors
Sensors 2012, 12(7), 8877-8894; doi:10.3390/s120708877
Received: 14 May 2012 / Revised: 14 June 2012 / Accepted: 18 June 2012 / Published: 27 June 2012
Cited by 7 | PDF Full-text (298 KB) | HTML Full-text | XML Full-text
Abstract
A matrix Kalman filter (MKF) has been implemented for an integrated navigation system using visual/inertial/magnetic sensors. The MKF rearranges the original nonlinear process model in a pseudo-linear process model. We employ the observability rank criterion based on Lie derivatives to verify the [...] Read more.
A matrix Kalman filter (MKF) has been implemented for an integrated navigation system using visual/inertial/magnetic sensors. The MKF rearranges the original nonlinear process model in a pseudo-linear process model. We employ the observability rank criterion based on Lie derivatives to verify the conditions under which the nonlinear system is observable. It has been proved that such observability conditions are: (a) at least one degree of rotational freedom is excited, and (b) at least two linearly independent horizontal lines and one vertical line are observed. Experimental results have validated the correctness of these observability conditions. Full article
(This article belongs to the Special Issue New Trends towards Automatic Vehicle Control and Perception Systems)
Open AccessArticle An ANN-Based Smart Tomographic Reconstructor in a Dynamic Environment
Sensors 2012, 12(7), 8895-8911; doi:10.3390/s120708895
Received: 7 June 2012 / Revised: 18 June 2012 / Accepted: 26 June 2012 / Published: 27 June 2012
Cited by 1 | PDF Full-text (454 KB) | HTML Full-text | XML Full-text
Abstract
In astronomy, the light emitted by an object travels through the vacuum of space and then the turbulent atmosphere before arriving at a ground based telescope. By passing through the atmosphere a series of turbulent layers modify the light’s wave-front in such [...] Read more.
In astronomy, the light emitted by an object travels through the vacuum of space and then the turbulent atmosphere before arriving at a ground based telescope. By passing through the atmosphere a series of turbulent layers modify the light’s wave-front in such a way that Adaptive Optics reconstruction techniques are needed to improve the image quality. A novel reconstruction technique based in Artificial Neural Networks (ANN) is proposed. The network is designed to use the local tilts of the wave-front measured by a Shack Hartmann Wave-front Sensor (SHWFS) as inputs and estimate the turbulence in terms of Zernike coefficients. The ANN used is a Multi-Layer Perceptron (MLP) trained with simulated data with one turbulent layer changing in altitude. The reconstructor was tested using three different atmospheric profiles and compared with two existing reconstruction techniques: Least Squares type Matrix Vector Multiplication (LS) and Learn and Apply (L + A). Full article
(This article belongs to the Section Physical Sensors)
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Open AccessArticle Maximum Likelihood-Based Iterated Divided Difference Filter for Nonlinear Systems from Discrete Noisy Measurements
Sensors 2012, 12(7), 8912-8929; doi:10.3390/s120708912
Received: 28 March 2012 / Revised: 18 June 2012 / Accepted: 21 June 2012 / Published: 27 June 2012
Cited by 7 | PDF Full-text (359 KB) | HTML Full-text | XML Full-text
Abstract
A new filter named the maximum likelihood-based iterated divided difference filter (MLIDDF) is developed to improve the low state estimation accuracy of nonlinear state estimation due to large initial estimation errors and nonlinearity of measurement equations. The MLIDDF algorithm is derivative-free and [...] Read more.
A new filter named the maximum likelihood-based iterated divided difference filter (MLIDDF) is developed to improve the low state estimation accuracy of nonlinear state estimation due to large initial estimation errors and nonlinearity of measurement equations. The MLIDDF algorithm is derivative-free and implemented only by calculating the functional evaluations. The MLIDDF algorithm involves the use of the iteration measurement update and the current measurement, and the iteration termination criterion based on maximum likelihood is introduced in the measurement update step, so the MLIDDF is guaranteed to produce a sequence estimate that moves up the maximum likelihood surface. In a simulation, its performance is compared against that of the unscented Kalman filter (UKF), divided difference filter (DDF), iterated unscented Kalman filter (IUKF) and iterated divided difference filter (IDDF) both using a traditional iteration strategy. Simulation results demonstrate that the accumulated mean-square root error for the MLIDDF algorithm in position is reduced by 63% compared to that of UKF and DDF algorithms, and by 7% compared to that of IUKF and IDDF algorithms. The new algorithm thus has better state estimation accuracy and a fast convergence rate. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle Enabling Flexible and Continuous Capability Invocation in Mobile Prosumer Environments
Sensors 2012, 12(7), 8930-8954; doi:10.3390/s120708930
Received: 22 March 2012 / Revised: 17 June 2012 / Accepted: 19 June 2012 / Published: 28 June 2012
Cited by 10 | PDF Full-text (559 KB) | HTML Full-text | XML Full-text
Abstract
Mobile prosumer environments require the communication with heterogeneous devices during the execution of mobile services. These environments integrate sensors, actuators and smart devices, whose availability continuously changes. The aim of this paper is to design a reference architecture for implementing a model [...] Read more.
Mobile prosumer environments require the communication with heterogeneous devices during the execution of mobile services. These environments integrate sensors, actuators and smart devices, whose availability continuously changes. The aim of this paper is to design a reference architecture for implementing a model for continuous service execution and access to capabilities, i.e., the functionalities provided by these devices. The defined architecture follows a set of software engineering patterns and includes some communication paradigms to cope with the heterogeneity of sensors, actuators, controllers and other devices in the environment. In addition, we stress the importance of the flexibility in capability invocation by allowing the communication middleware to select the access technology and change the communication paradigm when dealing with smart devices, and by describing and evaluating two algorithms for resource access management. Full article
Open AccessArticle An Oxidase-Based Electrochemical Fluidic Sensor with High-Sensitivity and Low-Interference by On-Chip Oxygen Manipulation
Sensors 2012, 12(7), 8955-8965; doi:10.3390/s120708955
Received: 28 May 2012 / Revised: 20 June 2012 / Accepted: 21 June 2012 / Published: 29 June 2012
Cited by 1 | PDF Full-text (1227 KB) | HTML Full-text | XML Full-text
Abstract
Utilizing a simple fluidic structure, we demonstrate the improved performance of oxidase-based enzymatic biosensors. Electrolysis of water is utilized to generate bubbles to manipulate the oxygen microenvironment close to the biosensor in a fluidic channel. For the proper enzyme reactions to occur, [...] Read more.
Utilizing a simple fluidic structure, we demonstrate the improved performance of oxidase-based enzymatic biosensors. Electrolysis of water is utilized to generate bubbles to manipulate the oxygen microenvironment close to the biosensor in a fluidic channel. For the proper enzyme reactions to occur, a simple mechanical procedure of manipulating bubbles was developed to maximize the oxygen level while minimizing the pH change after electrolysis. The sensors show improved sensitivities based on the oxygen dependency of enzyme reaction. In addition, this oxygen-rich operation minimizes the ratio of electrochemical interference signal by ascorbic acid during sensor operation (i.e., amperometric detection of hydrogen peroxide). Although creatinine sensors have been used as the model system in this study, this method is applicable to many other biosensors that can use oxidase enzymes (e.g., glucose, alcohol, phenol, etc.) to implement a viable component for in-line fluidic sensor systems. Full article
(This article belongs to the Special Issue BioMEMS and Advanced Analytical Sensors for Biological Applications)
Open AccessArticle Analysis of Building Envelope Insulation Performance Utilizing Integrated Temperature and Humidity Sensors
Sensors 2012, 12(7), 8987-9005; doi:10.3390/s120708987
Received: 14 May 2012 / Revised: 12 June 2012 / Accepted: 25 June 2012 / Published: 29 June 2012
Cited by 3 | PDF Full-text (847 KB) | HTML Full-text | XML Full-text
Abstract
A major cause of high energy consumption for air conditioning in indoor spaces is the thermal storage characteristics of a building’s envelope concrete material; therefore, the physiological signals (temperature and humidity) within concrete structures are an important reference for building energy management. [...] Read more.
A major cause of high energy consumption for air conditioning in indoor spaces is the thermal storage characteristics of a building’s envelope concrete material; therefore, the physiological signals (temperature and humidity) within concrete structures are an important reference for building energy management. The current approach to measuring temperature and humidity within concrete structures (i.e., thermocouples and fiber optics) is limited by problems of wiring requirements, discontinuous monitoring, and high costs. This study uses radio frequency integrated circuits (RFIC) combined with temperature and humidity sensors (T/H sensors) for the design of a smart temperature and humidity information material (STHIM) that automatically, regularly, and continuously converts temperature and humidity signals within concrete and transmits them by radio frequency (RF) to the Building Physiology Information System (BPIS). This provides a new approach to measurement that incorporates direct measurement, wireless communication, and real-time continuous monitoring to assist building designers and users in making energy management decisions and judgments. Full article
(This article belongs to the Special Issue Ultra-Small Sensor Systems and Components)
Open AccessArticle Improving the Calibration of Image Sensors Based on IOFBs, Using Differential Gray-Code Space Encoding
Sensors 2012, 12(7), 9006-9023; doi:10.3390/s120709006
Received: 15 May 2012 / Revised: 15 June 2012 / Accepted: 28 June 2012 / Published: 2 July 2012
Cited by 2 | PDF Full-text (1184 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents a fast calibration method to determine the transfer function for spatial correspondences in image transmission devices with Incoherent Optical Fiber Bundles (IOFBs), by performing a scan of the input, using differential patterns generated from a Gray code (Differential [...] Read more.
This paper presents a fast calibration method to determine the transfer function for spatial correspondences in image transmission devices with Incoherent Optical Fiber Bundles (IOFBs), by performing a scan of the input, using differential patterns generated from a Gray code (Differential Gray-Code Space Encoding, DGSE). The results demonstrate that this technique provides a noticeable reduction in processing time and better quality of the reconstructed image compared to other, previously employed techniques, such as point or fringe scanning, or even other known space encoding techniques. Full article
(This article belongs to the Section Physical Sensors)
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Open AccessArticle Semi-Blind Signal Extraction for Communication Signals by Combining Independent Component Analysis and Spatial Constraints
Sensors 2012, 12(7), 9024-9045; doi:10.3390/s120709024
Received: 28 April 2012 / Revised: 15 June 2012 / Accepted: 28 June 2012 / Published: 2 July 2012
Cited by 4 | PDF Full-text (343 KB) | HTML Full-text | XML Full-text
Abstract
Signal of interest (SOI) extraction is a vital issue in communication signal processing. In this paper, we propose two novel iterative algorithms for extracting SOIs from instantaneous mixtures, which explores the spatial constraint corresponding to the Directions of Arrival (DOAs) of the [...] Read more.
Signal of interest (SOI) extraction is a vital issue in communication signal processing. In this paper, we propose two novel iterative algorithms for extracting SOIs from instantaneous mixtures, which explores the spatial constraint corresponding to the Directions of Arrival (DOAs) of the SOIs as a priori information into the constrained Independent Component Analysis (cICA) framework. The first algorithm utilizes the spatial constraint to form a new constrained optimization problem under the previous cICA framework which requires various user parameters, i.e., Lagrange parameter and threshold measuring the accuracy degree of the spatial constraint, while the second algorithm incorporates the spatial constraints to select specific initialization of extracting vectors. The major difference between the two novel algorithms is that the former incorporates the prior information into the learning process of the iterative algorithm and the latter utilizes the prior information to select the specific initialization vector. Therefore, no extra parameters are necessary in the learning process, which makes the algorithm simpler and more reliable and helps to improve the speed of extraction. Meanwhile, the convergence condition for the spatial constraints is analyzed. Compared with the conventional techniques, i.e., MVDR, numerical simulation results demonstrate the effectiveness, robustness and higher performance of the proposed algorithms. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle Analysis of Uncertainty and Repeatability of a Low-Cost 3D Laser Scanner
Sensors 2012, 12(7), 9046-9054; doi:10.3390/s120709046
Received: 14 May 2012 / Revised: 26 June 2012 / Accepted: 29 June 2012 / Published: 2 July 2012
Cited by 6 | PDF Full-text (320 KB) | HTML Full-text | XML Full-text
Abstract
Portable 3D laser scanners are a valuable tool for compiling elaborate digital collections of archaeological objects and analysing the shapes and dimensions of pieces. Although low-cost desktop 3D laser scanners have powerful capacities, it is important to know their limitations. This paper [...] Read more.
Portable 3D laser scanners are a valuable tool for compiling elaborate digital collections of archaeological objects and analysing the shapes and dimensions of pieces. Although low-cost desktop 3D laser scanners have powerful capacities, it is important to know their limitations. This paper performs an analysis of the uncertainty and repeatability of the NextEngineTM portable low-cost 3D laser scanner by scanning an object 20 times in two different resolution modes—Macro and Wide. Some dimensions of the object were measured using a digital calliper, and these results were used as the “true” or control data. In comparing the true and the scanned data, we verified that the mean uncertainty in the Macro Mode is approximately half that of the Wide Mode, at ±0.81 mm and ±1.66 mm, respectively. These experimental results are significantly higher than the accuracy specifications provided by the manufacturer. An analysis of repeatability shows that the successive replicates do not match in the same position. The results are better in Macro Mode than in Wide Mode; it is observed that the repeatability factor is slightly larger than the corresponding mode accuracy, with ±0.84 vs. ±0.81 mm in Macro Mode and ±1.82 vs. ±1.66 mm in Wide Mode. We suggest several improvements, such as adding an external reference scale or providing a calibrated object to allow for a self-calibration operation of the scanner. Full article
(This article belongs to the Section Physical Sensors)
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Open AccessArticle Design Parameters of a Miniaturized Piezoelectric Underwater Acoustic Transmitter
Sensors 2012, 12(7), 9098-9109; doi:10.3390/s120709098
Received: 15 May 2012 / Revised: 7 June 2012 / Accepted: 27 June 2012 / Published: 2 July 2012
Cited by 4 | PDF Full-text (685 KB) | HTML Full-text | XML Full-text
Abstract
PZT ceramics have been widely used in underwater acoustic transducers. However, literature available discussing the design parameters of a miniaturized PZT-based low-duty-cycle transmitter is very limited. This paper discusses some of the design parameters—the backing material, driving voltage, PZT material type, power [...] Read more.
PZT ceramics have been widely used in underwater acoustic transducers. However, literature available discussing the design parameters of a miniaturized PZT-based low-duty-cycle transmitter is very limited. This paper discusses some of the design parameters—the backing material, driving voltage, PZT material type, power consumption and the transducer length of a miniaturized acoustic fish tag using a PZT tube. Four different types of PZT were evaluated with respect to the source level, energy consumption and bandwidth of the transducer. The effect of the tube length on the source level is discussed. The results demonstrate that ultralow-density closed-cell foam is the best backing material for the PZT tube. The Navy Type VI PZTs provide the best source level with relatively low energy consumption and that a low transducer capacitance is preferred for high efficiency. A 35% reduction in the transducer length results in 2 dB decrease in source level. Full article
(This article belongs to the Special Issue Ultra-Small Sensor Systems and Components)
Open AccessArticle Laser Scanning on Road Pavements: A New Approach for Characterizing Surface Texture
Sensors 2012, 12(7), 9110-9128; doi:10.3390/s120709110
Received: 2 May 2012 / Revised: 6 June 2012 / Accepted: 26 June 2012 / Published: 3 July 2012
Cited by 15 | PDF Full-text (1755 KB) | HTML Full-text | XML Full-text
Abstract
The surface layer of road pavement has a particular importance in relation to the satisfaction of the primary demands of locomotion, such as security and eco-compatibility. Among those pavement surface characteristics, the “texture” appears to be one of the most interesting with [...] Read more.
The surface layer of road pavement has a particular importance in relation to the satisfaction of the primary demands of locomotion, such as security and eco-compatibility. Among those pavement surface characteristics, the “texture” appears to be one of the most interesting with regard to the attainment of skid resistance. Specifications and regulations, providing a wide range of functional indicators, act as guidelines to satisfy the performance requirements. This paper describes an experiment on the use of laser scanner techniques on various types of asphalt for texture characterization. The use of high precision laser scanners, such as the triangulation types, is proposed to expand the analysis of road pavement from the commonly and currently used two-dimensional method to a three-dimensional one, with the aim of extending the range of the most important parameters for these kinds of applications. Laser scanners can be used in an innovative way to obtain information on areal surface layer through a single measurement, with data homogeneity and representativeness. The described experience highlights how the laser scanner is used for both laboratory experiments and tests in situ, with a particular attention paid to factors that could potentially affect the survey. Full article
(This article belongs to the Section Remote Sensors)
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Open AccessArticle Performance Testing of a Magnetically Suspended Double Gimbal Control Moment Gyro Based on the Single Axis Air Bearing Table
Sensors 2012, 12(7), 9129-9145; doi:10.3390/s120709129
Received: 17 April 2012 / Revised: 18 June 2012 / Accepted: 21 June 2012 / Published: 3 July 2012
Cited by 2 | PDF Full-text (399 KB) | HTML Full-text | XML Full-text
Abstract
Integrating the advantage of magnetic bearings with a double gimble control moment gyroscope (DGCMG), a magnetically suspended DGCMG (MSDGCMG) is an ideal actuator in high-precision, long life, and rapid maneuver attitude control systems. The work presented here mainly focuses on performance testing [...] Read more.
Integrating the advantage of magnetic bearings with a double gimble control moment gyroscope (DGCMG), a magnetically suspended DGCMG (MSDGCMG) is an ideal actuator in high-precision, long life, and rapid maneuver attitude control systems. The work presented here mainly focuses on performance testing of a MSDGCMG independently developed by Beihang University, based on the single axis air bearing table. In this paper, taking into sufficient consideration to the moving-gimbal effects and the response bandwidth limit of the gimbal, a special MSDGCMG steering law is proposed subject to the limits of gimbal angle rate and angle acceleration. Finally, multiple experiments are carried out, with different MSDGCMG angular momenta as well as different desired attitude angles. The experimental results indicate that the MSDGCMG has a good gimbal angle rate and output torque tracking capabilities, and that the attitude stability with MSDGCMG as actuator is superior to 10−3°/s. The MSDGCMG performance testing in this paper, carried out under moving-base condition, will offer a technique base for the future research and application of MSDGCMGs. Full article
(This article belongs to the Section Physical Sensors)
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Open AccessArticle Modelling Carbon Nanotubes-Based Mediatorless Biosensor
Sensors 2012, 12(7), 9146-9160; doi:10.3390/s120709146
Received: 16 April 2012 / Revised: 1 June 2012 / Accepted: 6 June 2012 / Published: 3 July 2012
Cited by 4 | PDF Full-text (348 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents a mathematical model of carbon nanotubes-based mediatorless biosensor. The developed model is based on nonlinear non-stationary reaction-diffusion equations. The model involves four layers (compartments): a layer of enzyme solution entrapped on a terylene membrane, a layer of the single [...] Read more.
This paper presents a mathematical model of carbon nanotubes-based mediatorless biosensor. The developed model is based on nonlinear non-stationary reaction-diffusion equations. The model involves four layers (compartments): a layer of enzyme solution entrapped on a terylene membrane, a layer of the single walled carbon nanotubes deposited on a perforated membrane, and an outer diffusion layer. The biosensor response and sensitivity are investigated by changing the model parameters with a special emphasis on the mediatorless transfer of the electrons in the layer of the enzyme-loaded carbon nanotubes. The numerical simulation at transient and steady state conditions was carried out using the finite difference technique. The mathematical model and the numerical solution were validated by experimental data. The obtained agreement between the simulation results and the experimental data was admissible at different concentrations of the substrate. Full article
(This article belongs to the Section Biosensors)
Open AccessArticle The Development of an UAV Borne Direct Georeferenced Photogrammetric Platform for Ground Control Point Free Applications
Sensors 2012, 12(7), 9161-9180; doi:10.3390/s120709161
Received: 2 May 2012 / Revised: 4 June 2012 / Accepted: 29 June 2012 / Published: 4 July 2012
Cited by 16 | PDF Full-text (1460 KB) | HTML Full-text | XML Full-text
Abstract
To facilitate applications such as environment detection or disaster monitoring, the development of rapid low cost systems for collecting near real time spatial information is very critical. Rapid spatial information collection has become an emerging trend for remote sensing and mapping applications. [...] Read more.
To facilitate applications such as environment detection or disaster monitoring, the development of rapid low cost systems for collecting near real time spatial information is very critical. Rapid spatial information collection has become an emerging trend for remote sensing and mapping applications. In this study, a fixed-wing Unmanned Aerial Vehicle (UAV)-based spatial information acquisition platform that can operate in Ground Control Point (GCP) free environments is developed and evaluated. The proposed UAV based photogrammetric platform has a Direct Georeferencing (DG) module that includes a low cost Micro Electro Mechanical Systems (MEMS) Inertial Navigation System (INS)/ Global Positioning System (GPS) integrated system. The DG module is able to provide GPS single frequency carrier phase measurements for differential processing to obtain sufficient positioning accuracy. All necessary calibration procedures are implemented. Ultimately, a flight test is performed to verify the positioning accuracy in DG mode without using GCPs. The preliminary results of positioning accuracy in DG mode illustrate that horizontal positioning accuracies in the x and y axes are around 5 m at 300 m flight height above the ground. The positioning accuracy of the z axis is below 10 m. Therefore, the proposed platform is relatively safe and inexpensive for collecting critical spatial information for urgent response such as disaster relief and assessment applications where GCPs are not available. Full article
(This article belongs to the Special Issue Ultra-Small Sensor Systems and Components)
Open AccessArticle A Reasoning Hardware Platform for Real-Time Common-Sense Inference
Sensors 2012, 12(7), 9210-9233; doi:10.3390/s120709210
Received: 15 May 2012 / Revised: 13 June 2012 / Accepted: 27 June 2012 / Published: 4 July 2012
Cited by 1 | PDF Full-text (484 KB) | HTML Full-text | XML Full-text
Abstract
Enabling Ambient Intelligence systems to understand the activities that are taking place in a supervised context is a rather complicated task. Moreover, this task cannot be successfully addressed while overlooking the mechanisms (common-sense knowledge and reasoning) that entitle us, as humans beings, [...] Read more.
Enabling Ambient Intelligence systems to understand the activities that are taking place in a supervised context is a rather complicated task. Moreover, this task cannot be successfully addressed while overlooking the mechanisms (common-sense knowledge and reasoning) that entitle us, as humans beings, to successfully undertake it. This work is based on the premise that Ambient Intelligence systems will be able to understand and react to context events if common-sense capabilities are embodied in them. However, there are some difficulties that need to be resolved before common-sense capabilities can be fully deployed to Ambient Intelligence. This work presents a hardware accelerated implementation of a common-sense knowledge-base system intended to improve response time and efficiency. Full article
Open AccessArticle Using a Communication Model to Collect Measurement Data through Mobile Devices
Sensors 2012, 12(7), 9253-9272; doi:10.3390/s120709253
Received: 19 May 2012 / Revised: 21 June 2012 / Accepted: 25 June 2012 / Published: 5 July 2012
Cited by 11 | PDF Full-text (1025 KB) | HTML Full-text | XML Full-text
Abstract
Wireless systems and services have undergone remarkable development since the first mobile phone system was introduced in the early 1980s. The use of sensors in an Ambient Intelligence approach is a great solution in a medical environment. We define a communication architecture [...] Read more.
Wireless systems and services have undergone remarkable development since the first mobile phone system was introduced in the early 1980s. The use of sensors in an Ambient Intelligence approach is a great solution in a medical environment. We define a communication architecture to facilitate the information transfer between all connected devices. This model is based in layers to allow the collection of measurement data to be used in our framework monitoring architecture. An overlay-based solution is built between network elements in order to provide an efficient and highly functional communication platform that allows the connection of a wide variety of devices and technologies, and serves also to perform additional functions such as the possibility to perform some processing in the network that may help to improve overall performance. Full article
Open AccessArticle Laser Scanning Measurements on Trees for Logging Harvesting Operations
Sensors 2012, 12(7), 9273-9285; doi:10.3390/s120709273
Received: 18 May 2012 / Revised: 26 June 2012 / Accepted: 3 July 2012 / Published: 5 July 2012
Cited by 10 | PDF Full-text (494 KB) | HTML Full-text | XML Full-text
Abstract
Logging harvesters represent a set of high-performance modern forestry machinery, which can finish a series of continuous operations such as felling, delimbing, peeling, bucking and so forth with human intervention. It is found by experiment that during the process of the alignment [...] Read more.
Logging harvesters represent a set of high-performance modern forestry machinery, which can finish a series of continuous operations such as felling, delimbing, peeling, bucking and so forth with human intervention. It is found by experiment that during the process of the alignment of the harvesting head to capture the trunk, the operator needs a lot of observation, judgment and repeated operations, which lead to the time and fuel losses. In order to improve the operation efficiency and reduce the operating costs, the point clouds for standing trees are collected with a low-cost 2D laser scanner. A cluster extracting algorithm and filtering algorithm are used to classify each trunk from the point cloud. On the assumption that every cross section of the target trunk is approximate a standard circle and combining the information of an Attitude and Heading Reference System, the radii and center locations of the trunks in the scanning range are calculated by the Fletcher-Reeves conjugate gradient algorithm. The method is validated through experiments in an aspen forest, and the optimized calculation time consumption is compared with the previous work of other researchers. Moreover, the implementation of the calculation result for automotive capturing trunks by the harvesting head during the logging operation is discussed in particular. Full article
(This article belongs to the Special Issue Laser Sensing and Imaging)
Open AccessArticle Model-Driven Methodology for Rapid Deployment of Smart Spaces Based on Resource-Oriented Architectures
Sensors 2012, 12(7), 9286-9335; doi:10.3390/s120709286
Received: 2 May 2012 / Revised: 22 June 2012 / Accepted: 27 June 2012 / Published: 6 July 2012
Cited by 3 | PDF Full-text (1334 KB) | HTML Full-text | XML Full-text
Abstract
Advances in electronics nowadays facilitate the design of smart spaces based on physical mash-ups of sensor and actuator devices. At the same time, software paradigms such as Internet of Things (IoT) and Web of Things (WoT) are motivating the creation of technology [...] Read more.
Advances in electronics nowadays facilitate the design of smart spaces based on physical mash-ups of sensor and actuator devices. At the same time, software paradigms such as Internet of Things (IoT) and Web of Things (WoT) are motivating the creation of technology to support the development and deployment of web-enabled embedded sensor and actuator devices with two major objectives: (i) to integrate sensing and actuating functionalities into everyday objects, and (ii) to easily allow a diversity of devices to plug into the Internet. Currently, developers who are applying this Internet-oriented approach need to have solid understanding about specific platforms and web technologies. In order to alleviate this development process, this research proposes a Resource-Oriented and Ontology-Driven Development (ROOD) methodology based on the Model Driven Architecture (MDA). This methodology aims at enabling the development of smart spaces through a set of modeling tools and semantic technologies that support the definition of the smart space and the automatic generation of code at hardware level. ROOD feasibility is demonstrated by building an adaptive health monitoring service for a Smart Gym. Full article
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Open AccessArticle SGA-WZ: A New Strapdown Airborne Gravimeter
Sensors 2012, 12(7), 9336-9348; doi:10.3390/s120709336
Received: 8 May 2012 / Revised: 25 June 2012 / Accepted: 29 June 2012 / Published: 6 July 2012
Cited by 6 | PDF Full-text (1041 KB) | HTML Full-text | XML Full-text
Abstract
Inertial navigation systems and gravimeters are now routinely used to map the regional gravitational quantities from an aircraft with mGal accuracy and a spatial resolution of a few kilometers. However, airborne gravimeter of this kind is limited by the inaccuracy of the [...] Read more.
Inertial navigation systems and gravimeters are now routinely used to map the regional gravitational quantities from an aircraft with mGal accuracy and a spatial resolution of a few kilometers. However, airborne gravimeter of this kind is limited by the inaccuracy of the inertial sensor performance, the integrated navigation technique and the kinematic acceleration determination. As the GPS technique developed, the vehicle acceleration determination is no longer the limiting factor in airborne gravity due to the cancellation of the common mode acceleration in differential mode. A new airborne gravimeter taking full advantage of the inertial navigation system is described with improved mechanical design, high precision time synchronization, better thermal control and optimized sensor modeling. Apart from the general usage, the Global Positioning System (GPS) after differentiation is integrated to the inertial navigation system which provides not only more precise altitude information along with the navigation aiding, but also an effective way to calculate the vehicle acceleration. Design description and test results on the performance of the gyroscopes and accelerations will be emphasized. Analysis and discussion of the airborne field test results are also given. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle Investigating the Quantitative Structure-Activity Relationships for Antibody Recognition of Two Immunoassays for Polycyclic Aromatic Hydrocarbons by Multiple Regression Methods
Sensors 2012, 12(7), 9363-9374; doi:10.3390/s120709363
Received: 2 May 2012 / Revised: 12 June 2012 / Accepted: 25 June 2012 / Published: 9 July 2012
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Abstract
Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous contaminants found in the environment. Immunoassays represent useful analytical methods to complement traditional analytical procedures for PAHs. Cross-reactivity (CR) is a very useful character to evaluate the extent of cross-reaction of a cross-reactant in immunoreactions and immunoassays. The quantitative relationships between the molecular properties and the CR of PAHs were established by stepwise multiple linear regression, principal component regression and partial least square regression, using the data of two commercial enzyme-linked immunosorbent assay (ELISA) kits. The objective is to find the most important molecular properties that affect the CR, and predict the CR by multiple regression methods. The results show that the physicochemical, electronic and topological properties of the PAH molecules have an integrated effect on the CR properties for the two ELISAs, among which molar solubility (Sm) and valence molecular connectivity index (3χv) are the most important factors. The obtained regression equations for RisC kit are all statistically significant (p < 0.005) and show satisfactory ability for predicting CR values, while equations for RaPID kit are all not significant (p > 0.05) and not suitable for predicting. It is probably because that the RisC immunoassay employs a monoclonal antibody, while the RaPID kit is based on polyclonal antibody. Considering the important effect of solubility on the CR values, cross-reaction potential (CRP) is calculated and used as a complement of CR for evaluation of cross-reactions in immunoassays. Only the compounds with both high CR and high CRP can cause intense cross-reactions in immunoassays. Full article
(This article belongs to the Special Issue Bioassays)
Open AccessArticle Effect of Plasma Treatment on Multi-Walled Carbon Nanotubes for the Detection of H2S and SO2
Sensors 2012, 12(7), 9375-9385; doi:10.3390/s120709375
Received: 6 April 2012 / Revised: 27 June 2012 / Accepted: 28 June 2012 / Published: 9 July 2012
Cited by 15 | PDF Full-text (1296 KB) | HTML Full-text | XML Full-text
Abstract
H2S and SO2 are important characteristic gases of partial discharge (PD) generated by latent insulated defects in gas insulated switchgear (GIS). The detection of H2S and SO2 is of great significance in the diagnosis and assessment [...] Read more.
H2S and SO2 are important characteristic gases of partial discharge (PD) generated by latent insulated defects in gas insulated switchgear (GIS). The detection of H2S and SO2 is of great significance in the diagnosis and assessment of the operating status of GIS. In this paper, we perform experiments on the gas sensitivity of unmodified multi-walled carbon nanotubes (MWNTs) and those modified by atmospheric pressure dielectric barrier discharge (DBD) air plasma at different times (30, 60 and 120 s) for H2S and SO2, respectively. The results show that the sensitivity and response time of modified MWNTs to H2S are both improved, whereas the opposite effects are observed for SO2. The modified MWNTs have almost zero sensitivity to SO2. Thus, the MWNTs modified by atmospheric pressure DBD air plasma present good selectivity to H2S, and have great potential in H2S detection. Full article
(This article belongs to the Section Chemical Sensors)
Open AccessArticle AUV SLAM and Experiments Using a Mechanical Scanning Forward-Looking Sonar
Sensors 2012, 12(7), 9386-9410; doi:10.3390/s120709386
Received: 18 May 2012 / Revised: 27 June 2012 / Accepted: 28 June 2012 / Published: 9 July 2012
Cited by 18 | PDF Full-text (2047 KB) | HTML Full-text | XML Full-text
Abstract
Navigation technology is one of the most important challenges in the applications of autonomous underwater vehicles (AUVs) which navigate in the complex undersea environment. The ability of localizing a robot and accurately mapping its surroundings simultaneously, namely the simultaneous localization and mapping [...] Read more.
Navigation technology is one of the most important challenges in the applications of autonomous underwater vehicles (AUVs) which navigate in the complex undersea environment. The ability of localizing a robot and accurately mapping its surroundings simultaneously, namely the simultaneous localization and mapping (SLAM) problem, is a key prerequisite of truly autonomous robots. In this paper, a modified-FastSLAM algorithm is proposed and used in the navigation for our C-Ranger research platform, an open-frame AUV. A mechanical scanning imaging sonar is chosen as the active sensor for the AUV. The modified-FastSLAM implements the update relying on the on-board sensors of C-Ranger. On the other hand, the algorithm employs the data association which combines the single particle maximum likelihood method with modified negative evidence method, and uses the rank-based resampling to overcome the particle depletion problem. In order to verify the feasibility of the proposed methods, both simulation experiments and sea trials for C-Ranger are conducted. The experimental results show the modified-FastSLAM employed for the navigation of the C-Ranger AUV is much more effective and accurate compared with the traditional methods. Full article
(This article belongs to the Special Issue New Trends towards Automatic Vehicle Control and Perception Systems)
Open AccessArticle Dynamics of Ras Complexes Observed in Living Cells
Sensors 2012, 12(7), 9411-9422; doi:10.3390/s120709411
Received: 12 June 2012 / Revised: 29 June 2012 / Accepted: 4 July 2012 / Published: 9 July 2012
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Abstract
K-Ras works as a switch in many important intracellular signaling pathways and plays important roles in cell growth, proliferation, differentiation and carcinogenesis. For signal transduction from K-Ras to Raf1, the best-characterized effector of K-Ras, the general view is that Ras recruits Raf1 [...] Read more.
K-Ras works as a switch in many important intracellular signaling pathways and plays important roles in cell growth, proliferation, differentiation and carcinogenesis. For signal transduction from K-Ras to Raf1, the best-characterized effector of K-Ras, the general view is that Ras recruits Raf1 from the cytoplasm to the cell membrane. To elucidate this process, we constructed a series of fusion proteins (including Raf1 and K-Ras fused with either fluorescent proteins or fluorescent protein fragments) to compare subcellular localizations of these proteins. Bimolecular fluorescence complementation (BiFC) and a co-transfection system were used. In the BiFC system, the K-Ras/Raf1 complexes were mainly located in the cell membrane, while the Raf1 control was uniformly distributed in the cytoplasm. However, the complexes of Raf1 and K-RasC185S, a K-Ras mutant which loses membrane-localization, were also able to accumulate in the cell membrane. In contrast, an apparent cytosolic distribution pattern was observed in cells co-transfected with mcerulean-Raf1 and EGFP-K-RasC185S, suggesting that the membrane localization of K-Ras/Raf1 complexes is not entirely dependent on K-Ras, and that other factors, such as the irreversible conformation formed between K-Ras and Raf1 may play a role. This study sheds light on the interaction between K-Ras and Raf1 and provides a practical method to elucidate the mechanism underlying K-Ras and Raf1 binding to the cell membrane. Full article
(This article belongs to the Special Issue Live Cell-Based Sensors)
Open AccessArticle A Fully Sensorized Cooperative Robotic System for Surgical Interventions
Sensors 2012, 12(7), 9423-9447; doi:10.3390/s120709423
Received: 18 June 2012 / Revised: 3 July 2012 / Accepted: 3 July 2012 / Published: 9 July 2012
Cited by 4 | PDF Full-text (4047 KB) | HTML Full-text | XML Full-text
Abstract
In this research a fully sensorized cooperative robot system for manipulation of needles is presented. The setup consists of a DLR/KUKA Light Weight Robot III especially designed for safe human/robot interaction, a FD-CT robot-driven angiographic C-arm system, and a navigation camera. Also, [...] Read more.
In this research a fully sensorized cooperative robot system for manipulation of needles is presented. The setup consists of a DLR/KUKA Light Weight Robot III especially designed for safe human/robot interaction, a FD-CT robot-driven angiographic C-arm system, and a navigation camera. Also, new control strategies for robot manipulation in the clinical environment are introduced. A method for fast calibration of the involved components and the preliminary accuracy tests of the whole possible errors chain are presented. Calibration of the robot with the navigation system has a residual error of 0.81 mm (rms) with a standard deviation of ±0.41 mm. The accuracy of the robotic system while targeting fixed points at different positions within the workspace is of 1.2 mm (rms) with a standard deviation of ±0.4 mm. After calibration, and due to close loop control, the absolute positioning accuracy was reduced to the navigation camera accuracy which is of 0.35 mm (rms). The implemented control allows the robot to compensate for small patient movements. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle An Enhanced MEMS Error Modeling Approach Based on Nu-Support Vector Regression
Sensors 2012, 12(7), 9448-9466; doi:10.3390/s120709448
Received: 28 May 2012 / Revised: 25 June 2012 / Accepted: 26 June 2012 / Published: 9 July 2012
Cited by 13 | PDF Full-text (642 KB) | HTML Full-text | XML Full-text
Abstract
Micro Electro Mechanical System (MEMS)-based inertial sensors have made possible the development of a civilian land vehicle navigation system by offering a low-cost solution. However, the accurate modeling of the MEMS sensor errors is one of the most challenging tasks in the [...] Read more.
Micro Electro Mechanical System (MEMS)-based inertial sensors have made possible the development of a civilian land vehicle navigation system by offering a low-cost solution. However, the accurate modeling of the MEMS sensor errors is one of the most challenging tasks in the design of low-cost navigation systems. These sensors exhibit significant errors like biases, drift, noises; which are negligible for higher grade units. Different conventional techniques utilizing the Gauss Markov model and neural network method have been previously utilized to model the errors. However, Gauss Markov model works unsatisfactorily in the case of MEMS units due to the presence of high inherent sensor errors. On the other hand, modeling the random drift utilizing Neural Network (NN) is time consuming, thereby affecting its real-time implementation. We overcome these existing drawbacks by developing an enhanced Support Vector Machine (SVM) based error model. Unlike NN, SVMs do not suffer from local minimisation or over-fitting problems and delivers a reliable global solution. Experimental results proved that the proposed SVM approach reduced the noise standard deviation by 10–35% for gyroscopes and 61–76% for accelerometers. Further, positional error drifts under static conditions improved by 41% and 80% in comparison to NN and GM approaches. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle A Portable and Power-Free Microfluidic Device for Rapid and Sensitive Lead (Pb2+) Detection
Sensors 2012, 12(7), 9467-9475; doi:10.3390/s120709467
Received: 29 May 2012 / Revised: 6 June 2012 / Accepted: 2 July 2012 / Published: 10 July 2012
Cited by 6 | PDF Full-text (312 KB) | HTML Full-text | XML Full-text
Abstract
A portable and power-free microfluidic device was designed for rapid and sensitive detection of lead (Pb2+). 11-mercaptoundecanoic acid (MUA)-functionalized gold nanoparticles (MUA-AuNPs) aggregated in the presence of Pb2+ for the chelation mechanism. When we performed this analysis on a [...] Read more.
A portable and power-free microfluidic device was designed for rapid and sensitive detection of lead (Pb2+). 11-mercaptoundecanoic acid (MUA)-functionalized gold nanoparticles (MUA-AuNPs) aggregated in the presence of Pb2+ for the chelation mechanism. When we performed this analysis on a polydimethylsiloxane (PDMS) microfluidic chip, the aggregations deposited onto the surface of chip and formed dark lines along the laminar flows in the zigzag microchannels. This visual result can be observed by the naked eye through a microscope or just a drop of water as a magnifier. Ten μM Pb2+ was successfully detected. Full article
(This article belongs to the Section Biosensors)
Open AccessArticle A Bayesian Framework for the Automated Online Assessment of Sensor Data Quality
Sensors 2012, 12(7), 9476-9501; doi:10.3390/s120709476
Received: 2 March 2012 / Revised: 3 July 2012 / Accepted: 4 July 2012 / Published: 11 July 2012
Cited by 9 | PDF Full-text (400 KB) | HTML Full-text | XML Full-text
Abstract
Online automated quality assessment is critical to determine a sensor’s fitness for purpose in real-time applications. A Dynamic Bayesian Network (DBN) framework is proposed to produce probabilistic quality assessments and represent the uncertainty of sequentially correlated sensor readings. This is a novel [...] Read more.
Online automated quality assessment is critical to determine a sensor’s fitness for purpose in real-time applications. A Dynamic Bayesian Network (DBN) framework is proposed to produce probabilistic quality assessments and represent the uncertainty of sequentially correlated sensor readings. This is a novel framework to represent the causes, quality state and observed effects of individual sensor errors without imposing any constraints upon the physical deployment or measured phenomenon. It represents the casual relationship between quality tests and combines them in a way to generate uncertainty estimates of samples. The DBN was implemented for a particular marine deployment of temperature and conductivity sensors in Hobart, Australia. The DBN was shown to offer a substantial average improvement (34%) in replicating the error bars that were generated by experts when compared to a fuzzy logic approach. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle Monitoring of Temperature Fatigue Failure Mechanism for Polyvinyl Alcohol Fiber Concrete Using Acoustic Emission Sensors
Sensors 2012, 12(7), 9502-9513; doi:10.3390/s120709502
Received: 7 June 2012 / Revised: 2 July 2012 / Accepted: 3 July 2012 / Published: 11 July 2012
Cited by 4 | PDF Full-text (580 KB) | HTML Full-text | XML Full-text
Abstract
The applicability of acoustic emission (AE) techniques to monitor the mechanism of evolution of polyvinyl alcohol (PVA) fiber concrete damage under temperature fatigue loading is investigated. Using the temperature fatigue test, real-time AE monitoring data of PVA fiber concrete is achieved. Based [...] Read more.
The applicability of acoustic emission (AE) techniques to monitor the mechanism of evolution of polyvinyl alcohol (PVA) fiber concrete damage under temperature fatigue loading is investigated. Using the temperature fatigue test, real-time AE monitoring data of PVA fiber concrete is achieved. Based on the AE signal characteristics of the whole test process and comparison of AE signals of PVA fiber concretes with different fiber contents, the damage evolution process of PVA fiber concrete is analyzed. Finally, a qualitative evaluation of the damage degree is obtained using the kurtosis index and b-value of AE characteristic parameters. The results obtained using both methods are discussed. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle Carriage Error Identification Based on Cross-Correlation Analysis and Wavelet Transformation
Sensors 2012, 12(7), 9551-9565; doi:10.3390/s120709551
Received: 24 May 2012 / Revised: 28 June 2012 / Accepted: 3 July 2012 / Published: 12 July 2012
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Abstract
This paper proposes a novel method for identifying carriage errors. A general mathematical model of a guideway system is developed, based on the multi-body system method. Based on the proposed model, most error sources in the guideway system can be measured. The [...] Read more.
This paper proposes a novel method for identifying carriage errors. A general mathematical model of a guideway system is developed, based on the multi-body system method. Based on the proposed model, most error sources in the guideway system can be measured. The flatness of a workpiece measured by the PGI1240 profilometer is represented by a wavelet. Cross-correlation analysis performed to identify the error source of the carriage. The error model is developed based on experimental results on the low frequency components of the signals. With the use of wavelets, the identification precision of test signals is very high. Full article
(This article belongs to the Section Physical Sensors)
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Open AccessArticle Adaptive UAV Attitude Estimation Employing Unscented Kalman Filter, FOAM and Low-Cost MEMS Sensors
Sensors 2012, 12(7), 9566-9585; doi:10.3390/s120709566
Received: 21 May 2012 / Revised: 2 July 2012 / Accepted: 9 July 2012 / Published: 13 July 2012
Cited by 11 | PDF Full-text (5709 KB) | HTML Full-text | XML Full-text
Abstract
Navigation employing low cost MicroElectroMechanical Systems (MEMS) sensors in Unmanned Aerial Vehicles (UAVs) is an uprising challenge. One important part of this navigation is the right estimation of the attitude angles. Most of the existent algorithms handle the sensor readings in a [...] Read more.
Navigation employing low cost MicroElectroMechanical Systems (MEMS) sensors in Unmanned Aerial Vehicles (UAVs) is an uprising challenge. One important part of this navigation is the right estimation of the attitude angles. Most of the existent algorithms handle the sensor readings in a fixed way, leading to large errors in different mission stages like take-off aerobatic maneuvers. This paper presents an adaptive method to estimate these angles using off-the-shelf components. This paper introduces an Attitude Heading Reference System (AHRS) based on the Unscented Kalman Filter (UKF) using the Fast Optimal Attitude Matrix (FOAM) algorithm as the observation model. The performance of the method is assessed through simulations. Moreover, field experiments are presented using a real fixed-wing UAV. The proposed low cost solution, implemented in a microcontroller, shows a satisfactory real time performance. Full article
(This article belongs to the Special Issue Transducer Systems)
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Open AccessArticle Study on Elastic Helical TDR Sensing Cable for Distributed Deformation Detection
Sensors 2012, 12(7), 9586-9602; doi:10.3390/s120709586
Received: 31 May 2012 / Revised: 30 June 2012 / Accepted: 9 July 2012 / Published: 13 July 2012
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Abstract
In order to detect distributed ground surface deformation, an elastic helical structure Time Domain Reflectometry (TDR) sensing cable is shown in this paper. This special sensing cable consists of three parts: a silicone rubber rope in the center; a couple of parallel [...] Read more.
In order to detect distributed ground surface deformation, an elastic helical structure Time Domain Reflectometry (TDR) sensing cable is shown in this paper. This special sensing cable consists of three parts: a silicone rubber rope in the center; a couple of parallel wires coiling around the rope; a silicone rubber pipe covering the sensing cable. By analyzing the relationship between the impedance and the structure of the sensing cable, the impedance model shows that the sensing cable impedance will increase when the cable is stretched. This specific characteristic is verified in the cable stretching experiment which is the base of TDR sensing technology. The TDR experiment shows that a positive reflected signal is created at the stretching deformation point on the sensing cable. The results show that the deformation section length and the stretching elongation will both affect the amplitude of the reflected signal. Finally, the deformation locating experiments show that the sensing cable can accurately detect the deformation point position on the sensing cable. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle Screening of Stepping Forces in an Arthritic Rat Model Using a Novel Analgesic Meter and Data Acquisition System
Sensors 2012, 12(7), 9603-9612; doi:10.3390/s120709603
Received: 15 June 2012 / Revised: 5 July 2012 / Accepted: 5 July 2012 / Published: 16 July 2012
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Abstract
The stepping forces of normal and Freund Complete Adjuvant (FCA)-induced arthritic rats were studied in vivo using a proposed novel analgesic meter. An infrared charge-coupled device (CCD) camera and a data acquisition system were incorporated into the analgesic meter to determine and [...] Read more.
The stepping forces of normal and Freund Complete Adjuvant (FCA)-induced arthritic rats were studied in vivo using a proposed novel analgesic meter. An infrared charge-coupled device (CCD) camera and a data acquisition system were incorporated into the analgesic meter to determine and measure the weight of loads on the right hind paw before and after induction of arthritis by FCA injection into the paw cavity. FCA injection resulted in a significant reduction in the stepping force of the affected hind paw. The stepping force decreased to the minimum level on day 4 after the injection and then gradually increased up to day 25. Oral administration of prednisolone significantly increased the stepping forces of FCA-induced arthritic rats on days 14 and 21. These results suggest that the novel device is an effective tool for measuring the arthritic pain in in vivo studies even though walking is a dynamic condition. Full article
(This article belongs to the Section Biosensors)
Open AccessArticle A Low-Cost Sensor Buoy System for Monitoring Shallow Marine Environments
Sensors 2012, 12(7), 9613-9634; doi:10.3390/s120709613
Received: 11 May 2012 / Revised: 4 July 2012 / Accepted: 9 July 2012 / Published: 16 July 2012
Cited by 9 | PDF Full-text (2278 KB) | HTML Full-text | XML Full-text
Abstract
Monitoring of marine ecosystems is essential to identify the parameters that determine their condition. The data derived from the sensors used to monitor them are a fundamental source for the development of mathematical models with which to predict the behaviour of conditions [...] Read more.
Monitoring of marine ecosystems is essential to identify the parameters that determine their condition. The data derived from the sensors used to monitor them are a fundamental source for the development of mathematical models with which to predict the behaviour of conditions of the water, the sea bed and the living creatures inhabiting it. This paper is intended to explain and illustrate a design and implementation for a new multisensor monitoring buoy system. The system design is based on a number of fundamental requirements that set it apart from other recent proposals: low cost of implementation, the possibility of application in coastal shallow-water marine environments, suitable dimensions for deployment and stability of the sensor system in a shifting environment like the sea bed, and total autonomy of power supply and data recording. The buoy system has successfully performed remote monitoring of temperature and marine pressure (SBE 39 sensor), temperature (MCP9700 sensor) and atmospheric pressure (YOUNG 61302L sensor). The above requirements have been satisfactorily validated by operational trials in a marine environment. The proposed buoy sensor system thus seems to offer a broad range of applications. Full article
(This article belongs to the Section Remote Sensors)
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Open AccessArticle A Simplified Baseband Prefilter Model with Adaptive Kalman Filter for Ultra-Tight COMPASS/INS Integration
Sensors 2012, 12(7), 9666-9686; doi:10.3390/s120709666
Received: 18 May 2012 / Revised: 19 June 2012 / Accepted: 27 June 2012 / Published: 17 July 2012
Cited by 3 | PDF Full-text (1201 KB) | HTML Full-text | XML Full-text
Abstract
COMPASS is an indigenously developed Chinese global navigation satellite system and will share many features in common with GPS (Global Positioning System). Since the ultra-tight GPS/INS (Inertial Navigation System) integration shows its advantage over independent GPS receivers in many scenarios, the federated [...] Read more.
COMPASS is an indigenously developed Chinese global navigation satellite system and will share many features in common with GPS (Global Positioning System). Since the ultra-tight GPS/INS (Inertial Navigation System) integration shows its advantage over independent GPS receivers in many scenarios, the federated ultra-tight COMPASS/INS integration has been investigated in this paper, particularly, by proposing a simplified prefilter model. Compared with a traditional prefilter model, the state space of this simplified system contains only carrier phase, carrier frequency and carrier frequency rate tracking errors. A two-quadrant arctangent discriminator output is used as a measurement. Since the code tracking error related parameters were excluded from the state space of traditional prefilter models, the code/carrier divergence would destroy the carrier tracking process, and therefore an adaptive Kalman filter algorithm tuning process noise covariance matrix based on state correction sequence was incorporated to compensate for the divergence. The federated ultra-tight COMPASS/INS integration was implemented with a hardware COMPASS intermediate frequency (IF), and INS’s accelerometers and gyroscopes signal sampling system. Field and simulation test results showed almost similar tracking and navigation performances for both the traditional prefilter model and the proposed system; however, the latter largely decreased the computational load. Full article
(This article belongs to the Section Physical Sensors)
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Open AccessArticle A Novel Instrumentation Circuit for Electrochemical Measurements
Sensors 2012, 12(7), 9687-9696; doi:10.3390/s120709687
Received: 27 April 2012 / Revised: 9 June 2012 / Accepted: 9 July 2012 / Published: 17 July 2012
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Abstract
In this paper, a novel signal processing circuit which can be used for the measurement of H+ ion and urea concentration is presented. A potentiometric method is used to detect the concentrations of H+ ions and urea by using H [...] Read more.
In this paper, a novel signal processing circuit which can be used for the measurement of H+ ion and urea concentration is presented. A potentiometric method is used to detect the concentrations of H+ ions and urea by using H+ ion-selective electrodes and urea electrodes, respectively. The experimental data shows that this measuring structure has a linear pH response for the concentration range within pH 2 and 12, and the dynamic range for urea concentration measurement is in the range of 0.25 to 64 mg/dL. The designed instrumentation circuit possesses a calibration function and it can be applied to different sensing electrodes for electrochemical analysis. It possesses the advantageous properties of being multi-purpose, easy calibration and low cost. Full article
(This article belongs to the Section Biosensors)
Open AccessArticle Design and Analysis of a Compact Precision Positioning Platform Integrating Strain Gauges and the Piezoactuator
Sensors 2012, 12(7), 9697-9710; doi:10.3390/s120709697
Received: 14 May 2012 / Revised: 7 June 2012 / Accepted: 10 July 2012 / Published: 17 July 2012
Cited by 3 | PDF Full-text (1201 KB) | HTML Full-text | XML Full-text
Abstract
Miniaturization precision positioning platforms are needed for in situ nanomechanical test applications. This paper proposes a compact precision positioning platform integrating strain gauges and the piezoactuator. Effects of geometric parameters of two parallel plates on Von Mises stress distribution as well as [...] Read more.
Miniaturization precision positioning platforms are needed for in situ nanomechanical test applications. This paper proposes a compact precision positioning platform integrating strain gauges and the piezoactuator. Effects of geometric parameters of two parallel plates on Von Mises stress distribution as well as static and dynamic characteristics of the platform were studied by the finite element method. Results of the calibration experiment indicate that the strain gauge sensor has good linearity and its sensitivity is about 0.0468 mV/μm. A closed-loop control system was established to solve the problem of nonlinearity of the platform. Experimental results demonstrate that for the displacement control process, both the displacement increasing portion and the decreasing portion have good linearity, verifying that the control system is available. The developed platform has a compact structure but can realize displacement measurement with the embedded strain gauges, which is useful for the closed-loop control and structure miniaturization of piezo devices. It has potential applications in nanoindentation and nanoscratch tests, especially in the field of in situ nanomechanical testing which requires compact structures. Full article
(This article belongs to the Special Issue Ultra-Small Sensor Systems and Components)
Open AccessArticle SEMAT — The Next Generation of Inexpensive Marine Environmental Monitoring and Measurement Systems
Sensors 2012, 12(7), 9711-9748; doi:10.3390/s120709711
Received: 23 April 2012 / Revised: 10 May 2012 / Accepted: 2 July 2012 / Published: 18 July 2012
Cited by 8 | PDF Full-text (2807 KB) | HTML Full-text | XML Full-text
Abstract
There is an increasing need for environmental measurement systems to further science and thereby lead to improved policies for sustainable management. Marine environments are particularly hostile and extremely difficult for deploying sensitive measurement systems. As a consequence the need for data is [...] Read more.
There is an increasing need for environmental measurement systems to further science and thereby lead to improved policies for sustainable management. Marine environments are particularly hostile and extremely difficult for deploying sensitive measurement systems. As a consequence the need for data is greatest in marine environments, particularly in the developing economies/regions. Expense is typically the most significant limiting factor in the number of measurement systems that can be deployed, although technical complexity and the consequent high level of technical skill required for deployment and servicing runs a close second. This paper describes the Smart Environmental Monitoring and Analysis Technologies (SEMAT) project and the present development of the SEMAT technology. SEMAT is a “smart” wireless sensor network that uses a commodity-based approach for selecting technologies most appropriate to the scientifically driven marine research and monitoring domain/field. This approach allows for significantly cheaper environmental observation systems that cover a larger geographical area and can therefore collect more representative data. We describe SEMAT’s goals, which include: (1) The ability to adapt and evolve; (2) Underwater wireless communications; (3) Short-range wireless power transmission; (4) Plug and play components; (5) Minimal deployment expertise; (6) Near real-time analysis tools; and (7) Intelligent sensors. This paper illustrates how the capacity of the system has been improved over three iterations towards realising these goals. The result is an inexpensive and flexible system that is ideal for short-term deployments in shallow coastal and other aquatic environments. Full article
(This article belongs to the Section Sensor Networks)
Open AccessArticle Investigation of Interactive Effects on Water Flow and Solute Transport in Sandy Loam Soil Using Time Domain Reflectometry
Sensors 2012, 12(7), 9749-9772; doi:10.3390/s120709749
Received: 5 June 2012 / Revised: 4 July 2012 / Accepted: 16 July 2012 / Published: 18 July 2012
Cited by 2 | PDF Full-text (620 KB) | HTML Full-text | XML Full-text
Abstract
Surface-applied chemicals move through the unsaturated zone with complex flow and transport processes due to soil heterogeneity and reach the saturated zone, resulting in groundwater contamination. Such complex processes need to be studied by advanced measurement and modeling techniques to protect soil [...] Read more.
Surface-applied chemicals move through the unsaturated zone with complex flow and transport processes due to soil heterogeneity and reach the saturated zone, resulting in groundwater contamination. Such complex processes need to be studied by advanced measurement and modeling techniques to protect soil and water resources from contamination. In this study, the interactive effects of factors like soil structure, initial soil water content (SWC), and application rate on preferential flow and transport were studied in a sandy loam field soil using measurement (by time domain reflectometry (TDR)) and modeling (by MACRO and VS2DTI) techniques. In addition, statistical analyses were performed to compare the means of the measured and modeled SWC and EC, and solute transport parameters (pore water velocity and dispersion coefficient) in 12 treatments. Research results showed that even though the effects of soil structural conditions on water and solute transport were not so clear, the applied solution moved lower depths in the profiles of wet versus dry initial SWC and high application rate versus low application rates. The effects of soil structure and initial SWC on water and solute movement could be differentiated under the interactive conditions, but the effects of the application rates were difficult to differentiate under different soil structural and initial SWC conditions. Modeling results showed that MACRO had somewhat better performance than VS2DTI in the estimation of SWC and EC with space and time, but overall both models had relatively low performances. The means of SWC, EC, and solute transport parameters of the 12 treatments were divided into some groups based on the statistical analyses, indicating different flow and transport characteristics or a certain degree nonuniform or preferential flow and transport in the soil. Conducting field experiments with more interactive factors and applying the models with different approaches may allow better understanding of flow and transport processes in addition to the simulations of them in the unsaturated zone. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle Correcting the Temperature Influence on Soil Capacitance Sensors Using Diurnal Temperature and Water Content Cycles
Sensors 2012, 12(7), 9773-9790; doi:10.3390/s120709773
Received: 24 May 2012 / Revised: 6 July 2012 / Accepted: 10 July 2012 / Published: 18 July 2012
Cited by 6 | PDF Full-text (1017 KB) | HTML Full-text | XML Full-text
Abstract
The influence of temperature on the dielectric permittivity of soil is the result of counteracting effect that depends on the soil’s composition and mineralogy. In this paper, laboratory experiments showed that for a given water content, the soil dielectric permittivity was linearly [...] Read more.
The influence of temperature on the dielectric permittivity of soil is the result of counteracting effect that depends on the soil’s composition and mineralogy. In this paper, laboratory experiments showed that for a given water content, the soil dielectric permittivity was linearly related to the temperature, with a slope (α) that varied between samples taken in the same soil. These variations are difficult to predict and therefore, a simple and straightforward algorithm was designed to estimate α based on the diurnal patterns of both the measured dielectric permittivity and the soil temperature. The underlying idea is to assume that soil water content variations can be known with a reasonable accuracy over an appropriate time window within a day. This allows determining the contribution of the soil water content to the dielectric permittivity variations and then, the difference with the observed measurements is attributed to the soil temperature. Implementation of the correction methods in a large number of experiments significantly improved the physical meaning of the temporal evolution of the soil water content as the daily cycles for probes located near the surface or the long-term variations for more deeply installed probes. Full article
(This article belongs to the Section Physical Sensors)
Figures

Open AccessArticle Sensitivity of a Label-Free Guided-Mode Resonant Optical Biosensor with Different Modes
Sensors 2012, 12(7), 9791-9799; doi:10.3390/s120709791
Received: 4 June 2012 / Revised: 26 June 2012 / Accepted: 2 July 2012 / Published: 18 July 2012
Cited by 4 | PDF Full-text (388 KB) | HTML Full-text | XML Full-text
Abstract
Sensitivity is a key factor in the performance of a sensor. To achieve maximum guided-mode resonant optical biosensor sensitivity, a comparison of biosensor sensitivity for Transverse Electric (TE) and Transverse Magnetic (TM) modes based on the distribution of electric fields is presented [...] Read more.
Sensitivity is a key factor in the performance of a sensor. To achieve maximum guided-mode resonant optical biosensor sensitivity, a comparison of biosensor sensitivity for Transverse Electric (TE) and Transverse Magnetic (TM) modes based on the distribution of electric fields is presented in this article. A label-free guided-mode resonant optical biosensor is designed using the quarter-wave anti-reflection method to reflect only a narrow band of wavelengths modulated by the adsorption of a biochemical material on the sensor surface at the reflected frequency. With the distribution of electric fields simulated according to the Rigorous Coupled Wave Analysis (RCWA) theory, it is found that the full width at half maximum of the TM mode is (~4 nm) narrower than that of the TE mode (~20 nm), and the surface sensitivity of the TE mode incident light is three times that of the TM mode. It is proposed in this article that the light mode plays an important role in the sensitivity of guided-mode resonant biosensors. Full article
(This article belongs to the Section Biosensors)
Open AccessArticle Ubiquitous Geo-Sensing for Context-Aware Analysis: Exploring Relationships between Environmental and Human Dynamics
Sensors 2012, 12(7), 9800-9822; doi:10.3390/s120709800
Received: 18 June 2012 / Revised: 12 July 2012 / Accepted: 17 July 2012 / Published: 18 July 2012
Cited by 9 | PDF Full-text (805 KB) | HTML Full-text | XML Full-text
Abstract
Ubiquitous geo-sensing enables context-aware analyses of physical and social phenomena, i.e., analyzing one phenomenon in the context of another. Although such context-aware analysis can potentially enable a more holistic understanding of spatio-temporal processes, it is rarely documented in the scientific literature [...] Read more.
Ubiquitous geo-sensing enables context-aware analyses of physical and social phenomena, i.e., analyzing one phenomenon in the context of another. Although such context-aware analysis can potentially enable a more holistic understanding of spatio-temporal processes, it is rarely documented in the scientific literature yet. In this paper we analyzed the collective human behavior in the context of the weather. We therefore explored the complex relationships between these two spatio-temporal phenomena to provide novel insights into the dynamics of urban systems. Aggregated mobile phone data, which served as a proxy for collective human behavior, was linked with the weather data from climate stations in the case study area, the city of Udine, Northern Italy. To identify and characterize potential patterns within the weather-human relationships, we developed a hybrid approach which integrates several spatio-temporal statistical analysis methods. Thereby we show that explanatory factor analysis, when applied to a number of meteorological variables, can be used to differentiate between normal and adverse weather conditions. Further, we measured the strength of the relationship between the ‘global’ adverse weather conditions and the spatially explicit effective variations in user-generated mobile network traffic for three distinct periods using the Maximal Information Coefficient (MIC). The analyses result in three spatially referenced maps of MICs which reveal interesting insights into collective human dynamics in the context of weather, but also initiate several new scientific challenges. Full article
(This article belongs to the Special Issue Ubiquitous Sensing)
Open AccessCommunication A Micro-Machined Gyroscope for Rotating Aircraft
Sensors 2012, 12(7), 9823-9828; doi:10.3390/s120709823
Received: 1 April 2012 / Revised: 23 May 2012 / Accepted: 1 June 2012 / Published: 23 July 2012
PDF Full-text (633 KB) | HTML Full-text | XML Full-text
Abstract
In this paper we present recent work on the design, fabrication by silicon micromachining, and packaging of a new gyroscope for stabilizing the autopilot of rotating aircraft. It operates based on oscillation of the silicon pendulum between two torsion girders for detecting [...] Read more.
In this paper we present recent work on the design, fabrication by silicon micromachining, and packaging of a new gyroscope for stabilizing the autopilot of rotating aircraft. It operates based on oscillation of the silicon pendulum between two torsion girders for detecting the Coriolis force. The oscillation of the pendulum is initiated by the rolling and deflecting motion of the rotating carrier. Therefore, the frequency and amplitude of the oscillation are proportional to the rolling frequency and deflecting angular rate of the rotating carrier, and are measured by the sensing electrodes. A modulated pulse with constant amplitude and unequal width is obtained by a linearizing process of the gyroscope output signal and used to control the deflection of the rotating aircraft. Experimental results show that the gyroscope has a resolution of 0.008 °/s and a bias of 56.18 °/h. Full article
(This article belongs to the Special Issue Ultra-Small Sensor Systems and Components)
Open AccessArticle Harnessing the Interaction Continuum for Subtle Assisted Living
Sensors 2012, 12(7), 9829-9846; doi:10.3390/s120709829
Received: 19 March 2012 / Revised: 3 July 2012 / Accepted: 11 July 2012 / Published: 23 July 2012
Cited by 5 | PDF Full-text (5124 KB) | HTML Full-text | XML Full-text
Abstract
People interact with each other in many levels of attention, intention and meaning. This Interaction Continuum is used daily to deal with different contexts, adapting the interaction to communication needs and available resources. Nevertheless, computer-supported interaction has mainly focused on the most [...] Read more.
People interact with each other in many levels of attention, intention and meaning. This Interaction Continuum is used daily to deal with different contexts, adapting the interaction to communication needs and available resources. Nevertheless, computer-supported interaction has mainly focused on the most direct, explicit and intrusive types of human to human Interaction such as phone calls, emails, or video conferences. This paper presents the results of exploring and exploiting the potentials of undemanding interaction mechanisms, paying special attention to subtle communication and background interaction. As we argue the benefits of this type of interaction for people with special needs, we present a theoretical framework to define it and propose a proof of concept based on Augmented Objects and a color codification mechanism. Finally, we evaluate and analyze the strengths and limitations of such approach with people with cognitive disabilities. Full article
Open AccessArticle Characterizing the Moisture Content of Tea with Diffuse Reflectance Spectroscopy Using Wavelet Transform and Multivariate Analysis
Sensors 2012, 12(7), 9847-9861; doi:10.3390/s120709847
Received: 2 June 2012 / Revised: 26 June 2012 / Accepted: 9 July 2012 / Published: 23 July 2012
Cited by 13 | PDF Full-text (447 KB) | HTML Full-text | XML Full-text
Abstract
Effects of the moisture content (MC) of tea on diffuse reflectance spectroscopy were investigated by integrated wavelet transform and multivariate analysis. A total of 738 representative samples, including fresh tea leaves, manufactured tea and partially processed tea were collected for spectral measurement [...] Read more.
Effects of the moisture content (MC) of tea on diffuse reflectance spectroscopy were investigated by integrated wavelet transform and multivariate analysis. A total of 738 representative samples, including fresh tea leaves, manufactured tea and partially processed tea were collected for spectral measurement in the 325–1,075 nm range with a field portable spectroradiometer. Then wavelet transform (WT) and multivariate analysis were adopted for quantitative determination of the relationship between MC and spectral data. Three feature extraction methods including WT, principal component analysis (PCA) and kernel principal component analysis (KPCA) were used to explore the internal structure of spectral data. Comparison of those three methods indicated that the variables generated by WT could efficiently discover structural information of spectral data. Calibration involving seeking the relationship between MC and spectral data was executed by using regression analysis, including partial least squares regression, multiple linear regression and least square support vector machine. Results showed that there was a significant correlation between MC and spectral data (r = 0.991, RMSEP = 0.034). Moreover, the effective wavelengths for MC measurement were detected at range of 888–1,007 nm by wavelet transform. The results indicated that the diffuse reflectance spectroscopy of tea is highly correlated with MC. Full article
(This article belongs to the Section Chemical Sensors)
Open AccessArticle Electromagnetic Wave Propagation in Body Area Networks Using the Finite-Difference-Time-Domain Method
Sensors 2012, 12(7), 9862-9883; doi:10.3390/s120709862
Received: 30 May 2012 / Revised: 10 July 2012 / Accepted: 10 July 2012 / Published: 23 July 2012
Cited by 5 | PDF Full-text (2970 KB) | HTML Full-text | XML Full-text
Abstract
A rigorous full-wave solution, via the Finite-Difference-Time-Domain (FDTD) method, is performed in an attempt to obtain realistic communication channel models for on-body wireless transmission in Body-Area-Networks (BANs), which are local data networks using the human body as a propagation medium. The problem [...] Read more.
A rigorous full-wave solution, via the Finite-Difference-Time-Domain (FDTD) method, is performed in an attempt to obtain realistic communication channel models for on-body wireless transmission in Body-Area-Networks (BANs), which are local data networks using the human body as a propagation medium. The problem of modeling the coupling between body mounted antennas is often not amenable to attack by hybrid techniques owing to the complex nature of the human body. For instance, the time-domain Green’s function approach becomes more involved when the antennas are not conformal. Furthermore, the human body is irregular in shape and has dispersion properties that are unique. One consequence of this is that we must resort to modeling the antenna network mounted on the body in its entirety, and the number of degrees of freedom (DoFs) can be on the order of billions. Even so, this type of problem can still be modeled by employing a parallel version of the FDTD algorithm running on a cluster. Lastly, we note that the results of rigorous simulation of BANs can serve as benchmarks for comparison with the abundance of measurement data. Full article
(This article belongs to the Special Issue Body Sensor Networks for Healthcare and Pervasive Applications)
Open AccessArticle User Localization During Human-Robot Interaction
Sensors 2012, 12(7), 9913-9935; doi:10.3390/s120709913
Received: 8 June 2012 / Revised: 6 July 2012 / Accepted: 11 July 2012 / Published: 23 July 2012
Cited by 1 | PDF Full-text (8065 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents a user localization system based on the fusion of visual information and sound source localization, implemented on a social robot called Maggie. One of the main requisites to obtain a natural interaction between human-human and human-robot is an adequate [...] Read more.
This paper presents a user localization system based on the fusion of visual information and sound source localization, implemented on a social robot called Maggie. One of the main requisites to obtain a natural interaction between human-human and human-robot is an adequate spatial situation between the interlocutors, that is, to be orientated and situated at the right distance during the conversation in order to have a satisfactory communicative process. Our social robot uses a complete multimodal dialog system which manages the user-robot interaction during the communicative process. One of its main components is the presented user localization system. To determine the most suitable allocation of the robot in relation to the user, a proxemic study of the human-robot interaction is required, which is described in this paper. The study has been made with two groups of users: children, aged between 8 and 17, and adults. Finally, at the end of the paper, experimental results with the proposed multimodal dialog system are presented. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle A Logistic Regression Model for Predicting Axillary Lymph Node Metastases in Early Breast Carcinoma Patients
Sensors 2012, 12(7), 9936-9950; doi:10.3390/s120709936
Received: 25 May 2012 / Revised: 9 July 2012 / Accepted: 9 July 2012 / Published: 23 July 2012
Cited by 9 | PDF Full-text (263 KB) | HTML Full-text | XML Full-text
Abstract
Nodal staging in breast cancer is a key predictor of prognosis. This paper presents the results of potential clinicopathological predictors of axillary lymph node involvement and develops an efficient prediction model to assist in predicting axillary lymph node metastases. Seventy patients with [...] Read more.
Nodal staging in breast cancer is a key predictor of prognosis. This paper presents the results of potential clinicopathological predictors of axillary lymph node involvement and develops an efficient prediction model to assist in predicting axillary lymph node metastases. Seventy patients with primary early breast cancer who underwent axillary dissection were evaluated. Univariate and multivariate logistic regression were performed to evaluate the association between clinicopathological factors and lymph node metastatic status. A logistic regression predictive model was built from 50 randomly selected patients; the model was also applied to the remaining 20 patients to assess its validity. Univariate analysis showed a significant relationship between lymph node involvement and absence of nm-23 (p = 0.010) and Kiss-1 (p = 0.001) expression. Absence of Kiss-1 remained significantly associated with positive axillary node status in the multivariate analysis (p = 0.018). Seven clinicopathological factors were involved in the multivariate logistic regression model: menopausal status, tumor size, ER, PR, HER2, nm-23 and Kiss-1. The model was accurate and discriminating, with an area under the receiver operating characteristic curve of 0.702 when applied to the validation group. Moreover, there is a need discover more specific candidate proteins and molecular biology tools to select more variables which should improve predictive accuracy. Full article
(This article belongs to the Special Issue Biomarkers and Nanosensors: New Approaches for Biology and Medicine)

Review

Jump to: Research

Open AccessReview Recent Progress in Distributed Fiber Optic Sensors
Sensors 2012, 12(7), 8601-8639; doi:10.3390/s120708601
Received: 1 May 2012 / Revised: 15 June 2012 / Accepted: 19 June 2012 / Published: 26 June 2012
Cited by 116 | PDF Full-text (542 KB) | HTML Full-text | XML Full-text
Abstract
Rayleigh, Brillouin and Raman scatterings in fibers result from the interaction of photons with local material characteristic features like density, temperature and strain. For example an acoustic/mechanical wave generates a dynamic density variation; such a variation may be affected by local temperature, [...] Read more.
Rayleigh, Brillouin and Raman scatterings in fibers result from the interaction of photons with local material characteristic features like density, temperature and strain. For example an acoustic/mechanical wave generates a dynamic density variation; such a variation may be affected by local temperature, strain, vibration and birefringence. By detecting changes in the amplitude, frequency and phase of light scattered along a fiber, one can realize a distributed fiber sensor for measuring localized temperature, strain, vibration and birefringence over lengths ranging from meters to one hundred kilometers. Such a measurement can be made in the time domain or frequency domain to resolve location information. With coherent detection of the scattered light one can observe changes in birefringence and beat length for fibers and devices. The progress on state of the art technology for sensing performance, in terms of spatial resolution and limitations on sensing length is reviewed. These distributed sensors can be used for disaster prevention in the civil structural monitoring of pipelines, bridges, dams and railroads. A sensor with centimeter spatial resolution and high precision measurement of temperature, strain, vibration and birefringence can find applications in aerospace smart structures, material processing, and the characterization of optical materials and devices. Full article
(This article belongs to the Special Issue Optical Fiber Sensors 2012)
Open AccessReview Biomarkers for Use in Monitoring Responses of Nasopharyngeal Carcinoma Cells to Ionizing Radiation
Sensors 2012, 12(7), 8832-8846; doi:10.3390/s120708832
Received: 2 May 2012 / Revised: 6 June 2012 / Accepted: 6 June 2012 / Published: 27 June 2012
Cited by 7 | PDF Full-text (241 KB) | HTML Full-text | XML Full-text
Abstract
Nasopharyngeal carcinoma (NPC) is a common head and neck cancer. The incidence rate is higher in southern China and Southeast Asia in comparison with the Western countries. Radiotherapy is the standard treatment of NPC as the cancer cells are sensitive to ionizing [...] Read more.
Nasopharyngeal carcinoma (NPC) is a common head and neck cancer. The incidence rate is higher in southern China and Southeast Asia in comparison with the Western countries. Radiotherapy is the standard treatment of NPC as the cancer cells are sensitive to ionizing radiation. Radiation treatment has good local control to patients with early NPC. It is essential to monitor the response of the NPC cells to radiation treatment in advance in order to select suitable treatment choice for the patients. This review aims to discuss the potential use of biomarkers in monitoring the responsiveness of NPC cells to radiation treatment. Full article
(This article belongs to the Special Issue Biomarkers and Nanosensors: New Approaches for Biology and Medicine)
Open AccessReview Microfiber-Based Bragg Gratings for Sensing Applications: A Review
Sensors 2012, 12(7), 8861-8876; doi:10.3390/s120708861
Received: 27 April 2012 / Revised: 24 May 2012 / Accepted: 15 June 2012 / Published: 27 June 2012
Cited by 38 | PDF Full-text (1522 KB) | HTML Full-text | XML Full-text
Abstract
Microfiber-based Bragg gratings (MFBGs) are an emerging concept in ultra-small optical fiber sensors. They have attracted great attention among researchers in the fiber sensing area because of their large evanescent field and compactness. In this review, the basic techniques for the fabrication [...] Read more.
Microfiber-based Bragg gratings (MFBGs) are an emerging concept in ultra-small optical fiber sensors. They have attracted great attention among researchers in the fiber sensing area because of their large evanescent field and compactness. In this review, the basic techniques for the fabrication of MFBGs are introduced first. Then, the sensing properties and applications of MFBGs are discussed, including measurement of refractive index (RI), temperature, and strain/force. Finally a summary of selected MFBG sensing elements from previous literature are tabulated. Full article
(This article belongs to the Special Issue Ultra-Small Sensor Systems and Components)
Open AccessReview Study Designs and Statistical Analyses for Biomarker Research
Sensors 2012, 12(7), 8966-8986; doi:10.3390/s120708966
Received: 15 May 2012 / Revised: 21 June 2012 / Accepted: 21 June 2012 / Published: 29 June 2012
Cited by 14 | PDF Full-text (379 KB) | HTML Full-text | XML Full-text
Abstract
Biomarkers are becoming increasingly important for streamlining drug discovery and development. In addition, biomarkers are widely expected to be used as a tool for disease diagnosis, personalized medication, and surrogate endpoints in clinical research. In this paper, we highlight several important aspects [...] Read more.
Biomarkers are becoming increasingly important for streamlining drug discovery and development. In addition, biomarkers are widely expected to be used as a tool for disease diagnosis, personalized medication, and surrogate endpoints in clinical research. In this paper, we highlight several important aspects related to study design and statistical analysis for clinical research incorporating biomarkers. We describe the typical and current study designs for exploring, detecting, and utilizing biomarkers. Furthermore, we introduce statistical issues such as confounding and multiplicity for statistical tests in biomarker research. Full article
(This article belongs to the Special Issue Biomarkers and Nanosensors: New Approaches for Biology and Medicine)
Open AccessReview Game Theory for Wireless Sensor Networks: A Survey
Sensors 2012, 12(7), 9055-9097; doi:10.3390/s120709055
Received: 22 May 2012 / Revised: 21 June 2012 / Accepted: 26 June 2012 / Published: 2 July 2012
Cited by 44 | PDF Full-text (412 KB) | HTML Full-text | XML Full-text
Abstract
Game theory (GT) is a mathematical method that describes the phenomenon of conflict and cooperation between intelligent rational decision-makers. In particular, the theory has been proven very useful in the design of wireless sensor networks (WSNs). This article surveys the recent developments [...] Read more.
Game theory (GT) is a mathematical method that describes the phenomenon of conflict and cooperation between intelligent rational decision-makers. In particular, the theory has been proven very useful in the design of wireless sensor networks (WSNs). This article surveys the recent developments and findings of GT, its applications in WSNs, and provides the community a general view of this vibrant research area. We first introduce the typical formulation of GT in the WSN application domain. The roles of GT are described that include routing protocol design, topology control, power control and energy saving, packet forwarding, data collection, spectrum allocation, bandwidth allocation, quality of service control, coverage optimization, WSN security, and other sensor management tasks. Then, three variations of game theory are described, namely, the cooperative, non-cooperative, and repeated schemes. Finally, existing problems and future trends are identified for researchers and engineers in the field. Full article
(This article belongs to the Section Sensor Networks)
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Open AccessReview A Unifying Review of Bioassay-Guided Fractionation, Effect-Directed Analysis and Related Techniques
Sensors 2012, 12(7), 9181-9209; doi:10.3390/s120709181
Received: 16 May 2012 / Revised: 26 June 2012 / Accepted: 2 July 2012 / Published: 4 July 2012
Cited by 24 | PDF Full-text (548 KB) | HTML Full-text | XML Full-text
Abstract
The success of modern methods in analytical chemistry sometimes obscures the problem that the ever increasing amount of analytical data does not necessarily give more insight of practical relevance. As alternative approaches, toxicity- and bioactivity-based assays can deliver valuable information about biological [...] Read more.
The success of modern methods in analytical chemistry sometimes obscures the problem that the ever increasing amount of analytical data does not necessarily give more insight of practical relevance. As alternative approaches, toxicity- and bioactivity-based assays can deliver valuable information about biological effects of complex materials in humans, other species or even ecosystems. However, the observed effects often cannot be clearly assigned to specific chemical compounds. In these cases, the establishment of an unambiguous cause-effect relationship is not possible. Effect-directed analysis tries to interconnect instrumental analytical techniques with a biological/biochemical entity, which identifies or isolates substances of biological relevance. Successful application has been demonstrated in many fields, either as proof-of-principle studies or even for complex samples. This review discusses the different approaches, advantages and limitations and finally shows some practical examples. The broad emergence of effect-directed analytical concepts might lead to a true paradigm shift in analytical chemistry, away from ever growing lists of chemical compounds. The connection of biological effects with the identification and quantification of molecular entities leads to relevant answers to many real life questions. Full article
(This article belongs to the Special Issue Bioassays)
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Open AccessReview Microarray Technology for Major Chemical Contaminants Analysis in Food: Current Status and Prospects
Sensors 2012, 12(7), 9234-9252; doi:10.3390/s120709234
Received: 8 June 2012 / Revised: 14 June 2012 / Accepted: 15 June 2012 / Published: 5 July 2012
Cited by 11 | PDF Full-text (1202 KB) | HTML Full-text | XML Full-text
Abstract
Chemical contaminants in food have caused serious health issues in both humans and animals. Microarray technology is an advanced technique suitable for the analysis of chemical contaminates. In particular, immuno-microarray approach is one of the most promising methods for chemical contaminants analysis. [...] Read more.
Chemical contaminants in food have caused serious health issues in both humans and animals. Microarray technology is an advanced technique suitable for the analysis of chemical contaminates. In particular, immuno-microarray approach is one of the most promising methods for chemical contaminants analysis. The use of microarrays for the analysis of chemical contaminants is the subject of this review. Fabrication strategies and detection methods for chemical contaminants are discussed in detail. Application to the analysis of mycotoxins, biotoxins, pesticide residues, and pharmaceutical residues is also described. Finally, future challenges and opportunities are discussed. Full article
(This article belongs to the Special Issue Biochips)
Open AccessReview Circulating MicroRNAs: Molecular Microsensors in Gastrointestinal Cancer
Sensors 2012, 12(7), 9349-9362; doi:10.3390/s120709349
Received: 12 May 2012 / Revised: 1 June 2012 / Accepted: 25 June 2012 / Published: 9 July 2012
Cited by 17 | PDF Full-text (212 KB) | HTML Full-text | XML Full-text
Abstract
MicroRNAs (miRNAs) are small molecules of single strand non-coding RNAs, which are able to regulate gene expression. miRNAs have been involved in multiple cellular processes, such as proliferation, apoptosis and differentiation, thus alterations in miRNA expression have been shown to be directly [...] Read more.
MicroRNAs (miRNAs) are small molecules of single strand non-coding RNAs, which are able to regulate gene expression. miRNAs have been involved in multiple cellular processes, such as proliferation, apoptosis and differentiation, thus alterations in miRNA expression have been shown to be directly linked with the pathological origin of multiple diseases, including cancer. In this way, during last few years, an increasing number of exciting advances have contributed to the understanding of miRNA roles in cancer. Moreover, researchers have exploited the special characteristics of miRNAs, such as the tissue and disease specificity or miRNA presence in blood, to explore their use as non-invasive tumour markers. In the present review, we summarize the current data on the potential usefulness of circulating miRNAs as diagnostic and prognostic tools in gastrointestinal tumours. Full article
(This article belongs to the Special Issue Biomarkers and Nanosensors: New Approaches for Biology and Medicine)
Open AccessReview Screening of Aptamers on Microfluidic Systems for Clinical Applications
Sensors 2012, 12(7), 9514-9529; doi:10.3390/s120709514
Received: 30 May 2012 / Revised: 2 July 2012 / Accepted: 6 July 2012 / Published: 11 July 2012
Cited by 19 | PDF Full-text (501 KB) | HTML Full-text | XML Full-text
Abstract
The use of microfluidic systems for screening of aptamers and their biomedical applications are reviewed in this paper. Aptamers with different nucleic acid sequences have been extensively studied and the results demonstrated a strong binding affinity to target molecules such that they [...] Read more.
The use of microfluidic systems for screening of aptamers and their biomedical applications are reviewed in this paper. Aptamers with different nucleic acid sequences have been extensively studied and the results demonstrated a strong binding affinity to target molecules such that they can be used as promising candidate biomarkers for diagnosis and therapeutics. Recently, the aptamer screening protocol has been conducted with microfluidic-based devices. Furthermore, aptamer affinity screening by a microfluidic-based method has demonstrated remarkable advantages over competing traditional methods. In this paper, we first reviewed microfluidic systems which demonstrated efficient and rapid screening of a specific aptamer. Then, the clinical applications of screened aptamers, also performed by microfluidic systems, are further reviewed. These automated microfluidic systems can provide advantages over their conventional counterparts including more compactness, faster analysis, less sample/reagent consumption and automation. An aptamer-based compact microfluidic system for diagnosis may even lead to a point-of-care device. The use of microfluidic systems for aptamer screening and diagnosis is expected to continue growing in the near future and may make a substantial impact on biomedical applications. Full article
(This article belongs to the Special Issue Micro and Nano Technologies for Point-of-Care Diagnosis)
Open AccessReview Synthetic Biomimetic Membranes and Their Sensor Applications
Sensors 2012, 12(7), 9530-9550; doi:10.3390/s120709530
Received: 9 May 2012 / Revised: 5 June 2012 / Accepted: 16 June 2012 / Published: 11 July 2012
Cited by 23 | PDF Full-text (1044 KB) | HTML Full-text | XML Full-text
Abstract
Synthetic biomimetic membranes provide biological environments to membrane proteins. By exploiting the central roles of biological membranes, it is possible to devise biosensors, drug delivery systems, and nanocontainers using a biomimetic membrane system integrated with functional proteins. Biomimetic membranes can be created [...] Read more.
Synthetic biomimetic membranes provide biological environments to membrane proteins. By exploiting the central roles of biological membranes, it is possible to devise biosensors, drug delivery systems, and nanocontainers using a biomimetic membrane system integrated with functional proteins. Biomimetic membranes can be created with synthetic lipids or block copolymers. These amphiphilic lipids and polymers self-assemble in an aqueous solution either into planar membranes or into vesicles. Using various techniques developed to date, both planar membranes and vesicles can provide versatile and robust platforms for a number of applications. In particular, biomimetic membranes with modified lipids or functional proteins are promising platforms for biosensors. We review recent technologies used to create synthetic biomimetic membranes and their engineered sensors applications. Full article
(This article belongs to the Special Issue Biochips)
Open AccessReview A Survey on Gas Sensing Technology
Sensors 2012, 12(7), 9635-9665; doi:10.3390/s120709635
Received: 16 April 2012 / Revised: 18 June 2012 / Accepted: 13 July 2012 / Published: 16 July 2012
Cited by 140 | PDF Full-text (384 KB) | HTML Full-text | XML Full-text
Abstract
Sensing technology has been widely investigated and utilized for gas detection. Due to the different applicability and inherent limitations of different gas sensing technologies, researchers have been working on different scenarios with enhanced gas sensor calibration. This paper reviews the descriptions, evaluation, [...] Read more.
Sensing technology has been widely investigated and utilized for gas detection. Due to the different applicability and inherent limitations of different gas sensing technologies, researchers have been working on different scenarios with enhanced gas sensor calibration. This paper reviews the descriptions, evaluation, comparison and recent developments in existing gas sensing technologies. A classification of sensing technologies is given, based on the variation of electrical and other properties. Detailed introduction to sensing methods based on electrical variation is discussed through further classification according to sensing materials, including metal oxide semiconductors, polymers, carbon nanotubes, and moisture absorbing materials. Methods based on other kinds of variations such as optical, calorimetric, acoustic and gas-chromatographic, are presented in a general way. Several suggestions related to future development are also discussed. Furthermore, this paper focuses on sensitivity and selectivity for performance indicators to compare different sensing technologies, analyzes the factors that influence these two indicators, and lists several corresponding improved approaches. Full article
(This article belongs to the Section Chemical Sensors)
Open AccessReview Foot Plantar Pressure Measurement System: A Review
Sensors 2012, 12(7), 9884-9912; doi:10.3390/s120709884
Received: 15 May 2012 / Revised: 27 June 2012 / Accepted: 3 July 2012 / Published: 23 July 2012
Cited by 71 | PDF Full-text (1051 KB) | HTML Full-text | XML Full-text
Abstract
Foot plantar pressure is the pressure field that acts between the foot and the support surface during everyday locomotor activities. Information derived from such pressure measures is important in gait and posture research for diagnosing lower limb problems, footwear design, sport biomechanics, [...] Read more.
Foot plantar pressure is the pressure field that acts between the foot and the support surface during everyday locomotor activities. Information derived from such pressure measures is important in gait and posture research for diagnosing lower limb problems, footwear design, sport biomechanics, injury prevention and other applications. This paper reviews foot plantar sensors characteristics as reported in the literature in addition to foot plantar pressure measurement systems applied to a variety of research problems. Strengths and limitations of current systems are discussed and a wireless foot plantar pressure system is proposed suitable for measuring high pressure distributions under the foot with high accuracy and reliability. The novel system is based on highly linear pressure sensors with no hysteresis. Full article
(This article belongs to the Section Physical Sensors)

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