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961.
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964.
Indian Remote Sensing Satellite-P3 (IRS-P3: 1996-017A) was launched into a near-Earth, polar, Sun-synchronous orbit by India's Polar Satellite Launch Vehicle (PSLV-D3) on March 21, 1996. The Indian X-ray Astronomy Experiment (IXAE) is one of the prime payloads onboard IRS-P3. IXAE has two sets of detectors: three pointed-mode proportional counters (PPCs) and one X-ray Sky Monitor (XSM). IRS-P3 is configured to operate in two modes, namely, Earth-pointing mode and stellar-pointing mode. In Earth-pointing mode the remote sensing payloads are in operation; in addition, XSM maps the sky for bright X-ray sources and X-ray transients. In stellar mode, the PPCs observe several Galactic, bright X-ray, and extragalactic sources. The microprocessor-based processing electronics system was designed and developed for PPC data-handling and telemetering the stored data to the ground station. The system has been working well from the day the IXAE was commissioned. The processing electronics system for the PPCs, its interfaces, and the in-orbit instrument performance are described. Some results of the pointed mode observations are also presented  相似文献   
965.
The authors report here experimental results relating X-ray interaction location and event splitting. The X-ray interaction location can be localized at subpixel scale using the mesh technique. The authors found that the center of gravity of the split event is well-correlated with the X-ray interaction location. They analyzed the data using two models for the charge cloud shape: one is the rectangular model and the other is the Gaussian model. Although the authors could not distinguish between these models, they measured a root mean square charge cloud size of 1 to 2 μm for X-rays of Y-L (1.9 keV), Ag-L (3.0 keV), and Ti-K (4.5 keV). When the X-rays enter near the pixel boundary, the charge splits into adjacent pixels, allowing determination of the X-ray interaction location with an accuracy of 1.5 to 2.2 μm. The authors, therefore, expect that the X-ray CCD can function as an X-ray imager with subpixel resolution, which will be especially useful in applications involving very high spatial resolution optics  相似文献   
966.
A device simulator is used to analyze the heavy ion induced failure mechanism in insulated gate bipolar transistors (IGBTs) and to investigate hardening solutions. Single event latchup was already identified as the failure mechanism. Lateral and vertical modifications of the P+ plug are proposed to reduce the efficiency of the parasitic thyristor, responsible for the latchup, and validated by 2D-simulations on a N-channel IGBT cell structure  相似文献   
967.
Single-event effects (SEEs) in two resolver-to-digital converters (RDCs) have been studied using heavy ions and pulsed laser light. The important role of the pulsed laser in establishing single-event upset (SEU) and single-event latchup (SEL) levels prior to accelerator testing is described, as is its role in evaluating the test software and hardware and in gaining a better understanding of the origins of the SEEs. Results from pulsed-laser testing are in quantitative agreement with those from heavy-ion testing: the RDC-19220 is sensitive to both SEUs and SELs whereas the AD2S80 is less sensitive to SEUs and immune to SEL  相似文献   
968.
There are a number of factors that affect the intensity of the apical region in cardiac SPECT images, which sometime lead to apparent defects in this region. In some patient studies, images reconstructed with non-uniform attenuation correction appear to have a significant decrease of apical intensity, whereas images reconstructed without such correction have only a slight decrease. This phenomenon has been evaluated using a series of simulations, phantom experiments, and a patient study. The effects of a number of factors upon the severity of the apparent apical defects were studied, including: partial volume effect, non-uniform attenuation, and depth-dependent detector response. Simulation and phantom results indicate that (1) since the apex is generally less attenuated than the rest of the heart wall, attenuation correction boosts the intensity of non-apical regions more than that of the apex (by as much as 20%); and (2) partial volume effects due to discretization inadequacies and finite spatial resolution may cause as much as a 26% decrease in reconstructed intensity in the apical region. These two effects, in combination, may partially explain the presence of apparent apical defects when attenuation correction is performed. In addition, detector response compensation consistently reduced the severity of apparent apical defects. These results agree with and help to explain the occurrence of apparent apical defects observed in patient data  相似文献   
969.
An experimental study of the effect of flow geometry (circular, rectangular, triangular, and dumb-bell shaped) on the critical heat flux (CHF) was performed using R-134a as a coolant. The CHF is affected by the following geometric parameters: hydraulic-equivalent diameter, heated length, gap size, channel shape, and curvature. It may also be affected by the thermal conductivity of the wall material and wall thickness. The effect of flow geometry on CHF is influenced by flow parameters. The effect of these parameters on CHF was examined, and recommendations for predicting the CHF in non-circular geometries have been made.  相似文献   
970.
In this paper an automated system to generate fuel reload patterns for a boiling water reactor (BWR), based on heuristic search methods using engineers expertise is presented. The main components of the system are the knowledge base, the inference engine, the 3D BWR simulator PRESTO-B and the user interface. The knowledge base includes a generation knowledge base and a modification knowledge base, which are concerned with the way human experts generate reload patterns. The system has been developed and applied to the Laguna Verde Nuclear Power Plant, achieving similar patterns to those used in the operation. No optimization algorithm has been incorporated in this system, therefore the generated reload patterns are the best estimate according the knowledge and experience of the nuclear engineers. Future works are being developed in this area using evolutionary optimization techniques as a complement of this system.  相似文献   
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