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Evaluation of Fiber Optic Strain Measurement System for Monitoring FRP Bridge Decks

AIP Conference Proceedings 2005年第1期760卷 1485-1492页

作者： P. Klinkhachorn G. M. Lonkar Udaya B. Halabe H. V. S. GangaRao 1Lane Department of Computer Science and Electrical Engineering West Virginia University Morgantown WV 26505‐6109 2Department of Civil and Environmental Engineering Constructed Facilities Center West Virginia University Morgantown WV 26505‐6103

The use of Fiber Optic sensors for structural monitoring applications has attained popularity among researchers and practitioners recently due to their immense advantages. This paper discusses a continuous structural monitoring technique using surface mounted and embedded fiber optic strain sensors to measure the strain in FRP bridge decks. An Extrinsic Fabry‐Perot Interferometric (EFPI) strain sensor was selected for evaluation as it offers a good compromise between accuracy and cost considerations. This EFPI strain sensor, along with a conventional strain gauge, was surface mounted on a FRP bridge decks. The decks were then subjected to an accelerated aging test in an environmental chamber and the performance of both the strain sensors was recorded for a performance comparison. The results from the seven months of accelerated aging that is equivalent to 10 years of actual life show that the strain gauge sensor and the EFPI Fiber Optic sensor are still in working condition. The EFPI fiber optic sensor detects minute and sudden changes in strain more effectively than the strain gauge sensor. Placement in the environmental chamber did not affect the EFPI sensor’s performance and is an indication of its applicability to field structural monitoring for lengthy periods of time. The second part is a preliminary work where a fiber optic sensor was embedded inside a FRP plate during the pultrusion process. This shows the feasibility of manufacturing FRP bridge decks with embedded fiber optic sensors.

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Automatic Detection of Subsurface Defects Using Infrared Thermography

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AIP Conference Proceedings 2005年第1期760卷 1469-1476页

作者： G. M. Lonkar P. Klinkhachorn Udaya B. Halabe H. V. S. GangaRao 1Lane Department of Computer Science and Electrical Engineering West Virginia University Morgantown WV 26505‐6109 2Department of Civil and Environmental Engineering Constructed Facilities Center West Virginia University Morgantown WV 26505‐6103

The popularity of FRP bridge decks has increased in recent times because of their high strength to weight ratio, fatigue resistance etc. Defects due to degradation of the bridge deck malign their properties and adversely affect the structural integrity. These defects need to be detected and continuously monitored using field techniques such as infrared thermography. The process of manually analyzing the infrared images is tedious and ambiguous. Instead, using software algorithms on the infrared images of FRP decks can increase the defect detection speed and accuracy. This paper proposes a software automated defect detection technique to detect subsurface anomalies in fiber reinforced polymer (FRP) bridge decks. Thermal images of the FRP decks were captured using a radiometric infrared camera. Software algorithms using morphological image processing and fuzzy clustering techniques were developed to analyze the images for detecting the defects automatically. They were tested on infrared images of FRP bridge decks prepared in the laboratory. In the tests conducted, simulated subsurface defects of varying size, thickness and wearing surfaces were fabricated in the laboratory. The tests include a performance analysis of detecting delaminations and debonds, and the effect of distance on the detecting ability of the algorithm. The algorithms were also tested with FRP deck specimens under solar radiation, to test the response under a passive heat source. The study showed that Infrared Thermography can be effectively used to detect subsurface defects and the process can be automated with substantial accuracy.

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Empirical Modeling of Surface Crack Detection in Concrete Using an Open‐Ended Rectangular Waveguide

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AIP Conference Proceedings 2005年第1期760卷 539-546页

作者： J. Nadakuduti R. Zoughi G. Chen 1Applied Microwave Nondestructive Testing Laboratory (amntl) Electrical and Computer Engineering Department University of Missouri‐Rolla Rolla MO 65409 2Department of Civil Architectural and Environmental Engineering University of Missouri‐Rolla Rolla MO 65409

Microwave nondestructive testing and evaluation of surface‐breaking and internal cracks in cement‐based materials, employing open‐ended rectangular waveguide probes, has the potential to be a viable approach for the purpose of structural health monitoring. This paper presents an empirical model for simulating crack characteristic signal (signal reflected by a cracked sample under test as a function of scanning distance) given the dielectric property of the material, crack dimensions, probe aperture dimensions, operating frequency and the standoff distance.

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A Novel Rotating Magnetic Field Eddy Current Transducer for the Examination of Fuel Channels in PHWR Nuclear Power Plants

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AIP Conference Proceedings 2005年第1期760卷 471-478页

作者： R. Grimberg L. Udpa S. Udpa A. Savin 1Nondestructive Testing Department National Institute of Research and Development for Technical Physics 47 D. Mangeron Blvd. lasi 700050Romania 2Department of Electrical and Computer Engineering Michigan State University 2120 Engineering Building East Lansing MI 48824‐1226

For the control of fuel channels of PHWR CANDU type, a novel type of rotating magnetic field eddy current transducer was developed, as well as the afferent electronic equipment. So, the position and the tilt of garter springs using neuro‐fuzzy network could be determined, and the presence of the discontinuities on external and internal surface of the tubes can be emphasized. A numerical code for the solving of the forward problem was developed.

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Microwave Resonant Transfer Plasma Propulsion

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AIP Conference Proceedings 2004年第1期699卷 553-566页

作者： Anthony J. Marchese Peter M. Jansson John L. Schmalzel 1Department of Mechanical Engineering Rowan University Glassboro NJ 08028 2Department of Electrical and Computer Engineering Rowan University Glassboro NJ 08028

During the past decade, several research groups have begun to report unique spectroscopic results for mixed gas plasma systems in which one of the species present is hydrogen gas. In these experiments, researchers have reported excessive line broadening of H emission lines and peculiar non‐Boltzmann population of excited hydrogen states. The hydrogen line broadening in these studies has been attributed to Doppler broadening associated with anomalously high random translational velocity of H atoms (i.e. fast hydrogen). The spectroscopic data suggest the presence of a newly identified regime of energetic mixed gas hydrogen plasma systems, called resonant transfer (RT) plasmas. The data also suggest that these RT plasma systems have unique characteristics that warrant further exploration for propulsion applications. Preliminary calculations suggest that a microwave RT plasma thruster could achieve performance several orders of magnitude greater than chemical rocket propulsion. Accordingly, the NASA Institute for Advanced Concepts (NIAC) has funded a study aimed at assessing the potential of RT plasmas for propulsion applications. This paper will discuss the results of the NIAC Phase I study including spectroscopic characterization of the RT plasma, development of RT plasma thruster hardware and preliminary test firing of two separate RT plasma thrusters.

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Hall‐Effect Measurements Under AC Excitation for the Reconstruction of Obliterated Serial Numbers in Magnetic Steels

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AIP Conference Proceedings 2004年第1期700卷 1445-1451页

作者： M. J. Johnson C. C. H. Lo L. B. Naidu 1Center for Nondestructive Evaluation Iowa State University Ames IA 50011 2Department of Electrical and Computer Engineering Iowa State University Ames IA 50011

Existing forensic techniques employed to recover obliterated serial numbers fall mainly into one of two categories, those requiring extensive sample preparation including the use of acid etchants, and those utilizing magnetic particles to image irregularities in surface magnetic properties. The former is time consuming and utilizes potentially harmful chemicals while the latter messy and potentially low in sensitivity. A new approach is being investigated whereby the stray magnetic field is measured using a Hall effect sensor. The sample is magnetized using an electromagnetic c‐core yoke. For increased sensitivity, an AC approach is being utilized that benefits from the use of a lock‐in amplifier. The approach has been tested on some artificial specimens and part of a real gun with the serial numbers removed by surface grinding.

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The MEMS Loop Heat Pipe Based on Coherent Porous Silicon — The Modified System Test Structure

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AIP Conference Proceedings 2004年第1期699卷 164-173页

作者： Debra Cytrynowicz Praveen Medis Srinivas Parimi Ahmed Shuja H. Thurman Henderson Frank M. Gerner 1Center for Microelectronic Sensors and MEMS Department of Electrical and Computer Engineering and Computer Science University of Cincinnati Post Office Box 210030 Cincinnati Ohio 45221‐0030 2Department of Mechanical Industrial and Nuclear Engineering University of Cincinnati Post Office Box 210030 Cincinnati Ohio 45221‐0030

The previous papers presented at STAIF 2002 and STAIF 2003 discussed the design, fabrication and characterization of the evaporator section and the initial test cell of a planar MEMS loop heat pipe based upon coherent porous silicon or “CPS” technology. The potentially revolutionary advantage of CPS technology is that it is planar and allows for pores or capillaries of absolutely uniform diameter. Coherent porous silicon can be mass‐produced by various MEMS fabrication techniques. The preliminary experiments made with the original test structure exhibited the desired temperature and pressure differences, but these differences were extremely small and oscillatory. This paper describes modifications made to the initial test cell design, which were intended to improve its evacuated, closed loop performance. Included among these changes were the redesign of the compensation chamber and condenser, an increase in the porosity of the coherent porous silicon wick, the fabrication of silicon top “hot” plates with an increased depth of the vapor reservoir and the integration of metal resistive heater elements onto the backside of the top plates to simulate the input heat. Some changes were made in the test sequence to produce more discernable differences in temperatures and pressures. The most recent results of the tests made with the modified system will be presented.

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Coherent Soft X‐ray Branchline at the Advanced Light Source

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AIP Conference Proceedings 2004年第1期705卷 448-449页

作者： Kristine Rosfjord Charles Kemp Paul Denham Eric Gullikson Phillip Batson Senajith Rekawa David Attwood 1Center for X‐Ray Optics Lawrence Berkeley National Laboratory Berkeley CA 94720 2Department of Electrical Engineering and Computer Sciences University of California Berkeley CA 94720

A new coherent soft X‐ray branchline at the advanced light source has begun operation. Using the third harmonic from an 8 cm period undulator, this branch delivers coherent soft x‐rays ranging from 200eV to 1000eV. Here the beamline layout and Airy patterns generated by single pinhole diffraction at 500 eV and 600 eV are presented.

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Pulse Laser Ignition of Preheated PETN

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AIP Conference Proceedings 2004年第1期706卷 1005-1008页

作者： K. Nagayama H. Ebisuzaki S. Kubota M. Nakahara 1Department of Aeronautics and Astronautics Faculty of Engineering Kyushu University Fukuoka 812‐8581 Japan 2Department of Earth Resources Engineering Faculty of Engineering Kyushu University Fukuoka 812‐8581 Japan 3Department of Computer and Communication Faculty of Engineering Fukuoka Institute of Technology Fukuoka811‐0295 Japan

Nd:YAG pulse laser was used to ignite powdered and preheated PETN. To enhance efficiency of laser absorption by PETN, it was mixed with a small amount of carbon black powder. In this study, we will propose two‐pulse laser ignition method, the first pulse is a long pulse to heat up PETN up to melting point, then second laser to ignite the heated PETN. By adopting this procedure, second short pulse laser energy can be reduced to ensure that the energy can be transferred by relatively slender plastic optical fiber. To simulate the slow laser heating process by long pulse laser, high‐power cw YAG laser up to 30W was used. While two ns‐YAG laser of about 200 mJ/pulse with 4 ns and 12 ns were used for ignition. Higher peak power with donut‐like profile laser beam of 4 ns duration gives damage to fibers, while lower peak power with relatively flat profile laser beam of 12 ns duration can safely pass through optical fiber of 1 mm diameter. We performed a series of melting experiments of PETN under normal optical microscope. From these experiments, the experimental conditions and time to the onset of PETN melting was determined. Then the ignition experiments were performed by choosing a delay time between two laser irradiation timing as a parameter. Shortest detonation delay was evidenced at the delay time close to the time that the PETN specimen is almost starting to melt.

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Johnson Noise Thermometry For Space Reactor Temperature Measurement

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AIP Conference Proceedings 2004年第1期699卷 567-573页

作者： David E. Holcomb Roger A. Kisner Michael J. Roberts 1aNuclear Science and Technology Division Oak Ridge National Laboratory Oak Ridge TN 37831 1bEngineering Science and Technology Division Oak Ridge National Laboratory Oak Ridge TN 37831 2Department of Electrical and Computer Engineering University of Tennessee Knoxville TN 37996

A primary difference between terrestrial and remotely located reactors is the ability to periodically recalibrate and replace the instrumentation. Because of this, space reactors place a premium on self‐calibrating, long‐term reliable instrumentation. The primary temperature measurements for the SP‐100 reactor were to be made using W/W‐Re thermocouples. However, the large gamma and neutron dose expected at the coolant outlet (>1 MGy γ; 3×1015 fast neutron fluence) combined with the high temperature (1375 K nominal; 1650 K maximum) meant that the thermocouples would drift significantly over the lifetime of the reactor. A combined Johnson noise resistance thermometer capable of performing under these extreme conditions was developed by ORNL (Carroll, 1994). Johnson noise is a fundamental representation of temperature—it is the vibration of the electronic field surrounding atoms as they thermally vibrate. Johnson noise, however, is fundamentally a small signal (∼4×10−7 Vrms for a 100 Ω resistor at 300 K, using a 100 kHz bandwidth) spread throughout the frequency spectrum. Creating the electronics and signal processing required to effectively measure and interpret the noise signal remains challenging. ORNL has recently developed closely related Johnson Noise Thermometry (JNT) electronics and signal processing capabilities under a DOE International Nuclear Energy Research Initiative Project with the Korean Atomic Energy Research Institute (U.S. DOE, 2002). An overview of the application of JNT to space nuclear power and the current status of the ORNL JNT capabilities is the subject of this paper.

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