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Sensors Journal, IEEE

Issue 8 • Date Aug. 2011

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Displaying Results 1 - 21 of 21
  • [Front cover]

    Page(s): C1
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  • IEEE Sensors Journal publication information

    Page(s): C2
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  • Table of contents

    Page(s): 1633 - 1634
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  • Effects of a Mass Layer With Gradually Varying Thickness on a Quartz Crystal Microbalance

    Page(s): 1635 - 1639
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (485 KB) |  | HTML iconHTML  

    We study the effects of the nonuniform thickness of a thin mass layer on a quartz crystal microbalance. A theoretical analysis is performed on thickness-shear vibration of an AT-cut quartz plate with a nonuniform mass layer. Mindlin's two-dimensional equation for thickness-shear vibration of a quartz plate is used. Free vibration frequencies and modes are obtained. The effects of the mass layer nonuniformity are examined. It is shown that resonant frequencies and energy trapping of thickness-shear modes are sensitive to mass layer nonuniformity. View full abstract»

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  • A Thermal Sensor for Water Using Self-Heated NTC Thick-Film Segmented Thermistors

    Page(s): 1640 - 1645
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (897 KB) |  | HTML iconHTML  

    A simple thermal (heat loss) sensor system was designed in a small plastic tube housing using a negative thermal coefficient (NTC) thick-film thermistor as a self-heating sensor. The voltage power supply [range constant voltage (RCV)-range constant voltage] uses the measured input water temperature to select the applied voltage in steps (up and down) in order to enable operation of the sensor at optimal sensitivity for different water temperatures. The input water temperature was measured using a “cold” NTC thick-film segmented thermistor. The measured calibration curves were modeled. Additional calculated curves were interpolated between the experimental curves in fine steps to cover each temperature of input water and can be used for determining the water volume flow rate or water velocity. The realized prototype flow meter inertia, stability, repeatability, and tolerance were measured and analyzed. The proposed intelligent RCV thermal flow meter system will include a smart power supply with range-constant-voltages (auto-range), a simple acquisition card and custom designed flow meter software. View full abstract»

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  • Inertial Navigation Aided by Vision-Based Simultaneous Localization and Mapping

    Page(s): 1646 - 1656
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1306 KB) |  | HTML iconHTML  

    Inertial and vision sensors are considered essential nowadays in terms of navigation and guidance measurements for autonomous aerial and ground vehicles. In this paper, the concept of aiding Inertial Navigation with Vision-Based Simultaneous Localization and Mapping to compensate for Inertial Navigation divergence is introduced. We describe the changes to the augmented state vector that this sensor fusion algorithm requires and show that repeated measurements of map points during certain maneuvers around or nearby a map point is crucial for constraining the Inertial Navigation position divergence and reducing the covariance of the map point position estimates. In addition, it is shown that such an integrated navigation system requires coordination between the guidance and control measurements and the vehicle task itself to achieve better navigation accuracy. View full abstract»

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  • Modeling and Analysis of a Wavelet Network-Based Optical Sensor for Vibration Monitoring

    Page(s): 1657 - 1668
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    In this paper, we present a wavelet network (WN)-based optical position sensor for vibration monitoring using a quad-cell photodetector array. The proposed system uses a He-Ne laser source whose Gaussian beam impinges on the photodetector array. The optical power distribution from the photodetectors is acquired and fed to a position detection system, which maps the power distribution to the x-y position of the laser beam center. The position detection system uses a WN for function approximation to yield the correct mapping. The advantage of the WN is its generalization property. The network can be trained using a small size lookup table and, when properly trained, can provide a correct estimate of the laser position even if the power readings were not included in the training set. An accurate theoretical model of the system was derived to simulate the optical power variation as the beam scans the photodetector array. An experimental setup was next developed to validate the theoretical model. The results obtained show the effectiveness of WNs to estimate the laser beam position for the purpose of vibration monitoring. View full abstract»

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  • Wireless Magnetic Sensor Node for Vehicle Detection With Optical Wake-Up

    Page(s): 1669 - 1676
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (676 KB) |  | HTML iconHTML  

    Vehicle detectors provide essential information about parking occupancy and traffic flow. To cover large areas that lack a suitable electrical infrastructure, wired sensors networks are impractical because of their high deployment and maintenance costs. Wireless sensor networks (WSNs) with autonomous sensor nodes can be more economical. Vehicle detectors intended for a WSN should be small, sturdy, low power, cost-effective, and easy to install and maintain. Currently available vehicle detectors based on inductive loops, ultrasound, infrared, or magnetic sensors do not fulfill the requirements above, which has led to the search for alternative solutions. This paper presents a vehicle detector which includes a magnetic and an optical sensor and is intended as sensor node for use with a WSN. Magnetic sensors based on magnetoresistors are very sensitive and can detect the magnetic anomaly in the Earth's magnetic field that results from the presence of a car, but their continuous operation would drain more than 1.5 mA at 3 V, hence limiting the autonomy of a battery-supplied sensor node. Passive, low-power optical sensors can detect the shadow cast by car that covers them, but are prone to false detections. The use of optical triggering to wake-up a magnetic sensor, combined with power-efficient event-based software, yields a simple, compact, reliable, low-power sensor node for vehicle detection whose quiescent current drain is 5.5 μA. This approach of using a low-power sensor to trigger a second more specific sensor can be applied to other autonomous sensor nodes. View full abstract»

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  • Design of a Time-Based Micro-g Accelerometer

    Page(s): 1677 - 1683
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    Closed-loop pull-in time operated devices are a good alternative for high sensitivity accelerometers. This paper proposes the use of time measurement as the transduction mechanism for the realization of a high-precision accelerometer. The key feature is the existence of a metastable region that dominates pull-in behavior, thus making pull-in time very sensitive to external accelerations. The main design challenges for a pull-in time parallel-plate capacitive microelectromechanical system (MEMS) accelerometer are related to the damping and the associated tradeoff between sensitivity and noise is discussed. Parallel-plate MEMS structures designed and fabricated in a 25 μm-thick SOI micromachining process (SOIMUMPS) are used to demonstrate the accelerometer time-based approach and experimental results demonstrate a sensitivity of 0.25 μs/μg. View full abstract»

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  • Detection of Bacillus anthracis Spores Using Phage-Immobilized Magnetostrictive Milli/Micro Cantilevers

    Page(s): 1684 - 1691
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (769 KB) |  | HTML iconHTML  

    A type of biosensor based on filamentous phage as bioprobe and magnetostricitve milli/micro-cantilever (MSMC) as a sensor platform is developed for in situ detection of Bacillus anthracis spores in water. The phages are immobilized onto the MSMCs' surface through physical absorption. It is found that the immobilized phages are attached onto the MSMCs' surface through their ends and have a highly packed 2-D configuration. The real-time detection of B. anthracis spores in water with different concentrations was conducted. The experimental results indicate that the smaller the MSMC, the better the detection limit. For example, the detection limit is 104 spores/ml and 105 spores/ml for the MSMCs in size of 1.4 mm × 0.8 mm × 35 μm and 2.8 mm × 1.0 mm × 35 μm, respectively. The SEM observations confirm that the shift in the characteristic frequency of the biosensor is due to the binding of spores on the sensor surface. It is also found that the density of the spores binding at the tip of the cantilever is higher than that in the middle. The specificity of the sensor was studied. It is found that the sensor can detect B. anthracis spores with a much higher binding affinity than the spores of B. cereus and B. megaterium. View full abstract»

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  • Integrated Polarization Analyzing CMOS Image Sensor for Material Classification

    Page(s): 1692 - 1703
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1386 KB) |  | HTML iconHTML  

    Material classification is an important application in computer vision. The inherent property of materials to partially polarize the reflected light can serve as a tool to classify them. In this paper, a real-time polarization sensing CMOS image sensor using a wire grid polarizer is proposed. The image sensor consist of an array of 128 × 128 pixels, occupies an area of 5 × 4 mm2 and it has been designed and fabricated in a 180-nm CMOS process. We show that this image sensor can be used to differentiate between metal and dielectric surfaces in real-time due to the different nature in partially polarizing the specular and diffuse reflection components of the reflected light. This is achieved by calculating the Fresnel reflection coefficients, the degree of polarization and the variations in the maximum and minimum transmitted intensities for varying specular angle of incidence. Differences in the physical parameters for various metal surfaces result in different surface reflection behavior, influencing the Fresnel reflection coefficients. It is also shown that the image sensor can differentiate among various metals by sensing the change in the polarization Fresnel ratio. View full abstract»

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  • Helical Capacitance Sensor-Based Gas Fraction Measurement of Gas–Liquid Two-Phase Flow in Vertical Tube With Small Diameter

    Page(s): 1704 - 1710
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    A helical capacitance sensor for gas fraction including void fraction and volumetric void fraction measurement of gas-liquid two-phase flow in a vertical tube of 5 mm in diameter is presented in this paper. The structure of the helical capacitance sensor is optimized using a finite element method to achieve a homogeneous sensitivity field distribution. A calibration device using the quick closing valve method is designed and used to calibrate the void fraction measurement. Experiment results show that the relative error of gas fraction is less than 10%. The reason for the nonlinearity between the sensor output and gas fraction to be measured is discussed. The linear model describing the relationship between capacitance and gas fraction is obtained by removing the wall capacitance. View full abstract»

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  • Macro-Cell Current Measured by Tower-Type Sensor in Chloride-Contaminated Mortar

    Page(s): 1711 - 1712
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    In this letter, an integrated tower-type sensor (TTS) to be embedded in concrete system for permanent monitoring the service condition of reinforcing steel was developed, such as the macro-cell current, the cover-zone mortar resistance, the open-circuit potential, and the corrosion current density of the build-in sensor electrodes. Sensors have been tested in chloride-contaminated concrete, simulating a kind of marine circumstance. By analyzing the sensor output, a quantitative relationship among the macro-cell current, the cover-zone mortar resistance, the open-circuit potential, and the corrosion current density was established. View full abstract»

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  • Photocatalytic Titanium Dioxide Nanostructures for Self-Regenerating Relative Humidity Sensors

    Page(s): 1713 - 1719
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    Relative humidity sensors with a nanostructured titanium dioxide sensing layer were fabricated using glancing angle deposition. Such sensors exhibit very quick response times and high sensitivity but are prone to aging. In previous work, ultraviolet irradiation has been shown to regenerate and improve the sensor performance. Here, the effect of ultraviolet wavelength and power on sensor performance, aging, and regeneration was studied. In order to quantify the change in sensor response a figure of merit (FOM) was defined as the integrated area between the sensor response curves before and after regeneration or aging. FOM values ranged from 2.1 to 61 for treatment with a mercury vapor lamp. Treated sensors aged at an average rate of -0.43 FOM/day. Regeneration of sensors using commercial ultraviolet light-emitting diodes was demonstrated, resulting in FOMs significantly larger than irradiation with comparable mercury vapor lamp wavelengths. View full abstract»

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  • Mechanical Damage Detection in Polymer Tiles by THz Radiation

    Page(s): 1720 - 1725
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    Today the ultrasonic inspection technique is probably the most popular method for nondestructive evaluation and structural health monitoring. However, ultrasonic waves are not very effective in detecting internal defects in some materials such as ceramic foam tiles used in the thermal protection system (TPS) of the space shuttle, thick polymer composites, and polymer tiles used in various applications. Ultrasonic energy is attenuated very fast in these materials. On the other hand the electromagnetic radiation in THz (1000 GHz) frequency range can penetrate deep inside these materials. Its wavelength is small enough to detect internal defects. To understand the limits of structural damage detection capability of THz electromagnetic radiation or T-ray, mechanical damage in polymer tiles is introduced by drilling holes. Then T-ray is passed through the damaged and defect-free tiles. The received signal strength is found to be affected differently by the internal defect as the frequency changes. Experimental observations are justified from the model predictions. The model takes into account the interaction between the T-ray of finite width and the tile containing the internal defect. View full abstract»

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  • Improved Sensitivity of AlGaN/GaN Field Effect Transistor Biosensors by Optimized Surface Functionalization

    Page(s): 1726 - 1735
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    In this paper, we optimize the AlGaN surface oxidation methods for AlGaN/GaN heterostructure field effect transistor (HFET) biological sensors. Reactive ion etching oxygen plasma, inductively coupled oxygen plasma, and piranha solution are used to oxidize AlGaN surface. After oxidation, X-ray photoelectron spectroscopy and water contact angle measurements are used to check oxidation effectiveness. Labeled streptavidin (SA) molecules are bound to the oxidized surface through linker molecules for comparison of surface modification effectiveness. Schottky diodes are fabricated to investigate the impacts of oxidation processes on electrical properties, such as Schottky barrier heights, sheet carrier concentrations, and interface trap densities. The results show that the inductively coupled plasma oxidation process has a superior behavior compared to the reactive ion etching oxygen plasma and piranha solution oxidation processes. AlGaN/GaN HFET protein sensors fabricated using the inductively coupled plasma oxidation process have exhibited improved sensitivity. An SA solution with the concentration as low as 4.73 pM were successfully detected. View full abstract»

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  • Noncontact Determination of Velocity and Volume of Nanoliter Droplets on the Fly

    Page(s): 1736 - 1742
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (760 KB) |  | HTML iconHTML  

    We present a sensor for measuring volume and velocity of dispensed nanoliter droplets in a noncontact manner on the fly. The sensor-setup has a total thickness of 3.2 mm and can easily be mounted underneath any given nanoliter dispenser for continuous online monitoring of its dispensing performance. The principle is based on the interaction of dispensed single droplets of sample liquid passing the electric field of an open plate capacitor. The effect depends on droplet parameters like volume, velocity, and dielectric constant and is discussed in the paper. The presented data analysis enables a velocity independent volume determination of water droplets in the range from 26 to 82 nl with an accuracy of 3 nl. The sensor signal is sensitive to the alignment of the flight path of the nanoliter droplets within the 1.2-mm wide open capacitor and can lead to systematic volume errors of up to ΔV ~ 12 nl. The impact of different dielectric constants can only be differentiated for very high variations; thus, the sensor needs to be calibrated to the different types of liquids. View full abstract»

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  • IEEE Foundation [advertisement]

    Page(s): 1743
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    Page(s): 1744
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  • IEEE Sensors Council Information

    Page(s): C3
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  • Blank page [back cover]

    Page(s): C4
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Aims & Scope

The IEEE Sensors Journal is a peer-reviewed, monthly online/print  journal devoted to sensors and sensing phenomena

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Meet Our Editors

Editor-in-Chief
Krikor Ozanyan
University of Manchester
Manchester, M13 9PL, U.K.