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41.
Results of simulations, designed to illustrate the influence of power system stabilizers (PSS) on inter-area and local oscillations in interconnected power systems, are reported. It is shown that the PSS location and the voltage characteristics of the system loads are significant factors in the ability of a PSS to increase the damping of interarea oscillations. It is also shown that an interaction between modes in two distinct parts of a power system is possible, due to resonance, and that this might cause distortions in mode shape and participation factors  相似文献   
42.
43.
We investigate the transverse modal properties of cylindrical subwavelength metal-clad nanowire and micropost lasers via rigorous theoretical waveguide analysis, including the effects of finite thickness metal cladding and gain in the core. The results of this analysis show that air-metal surface guided TM01 and some hybrid surface guided modes suffer less loss but are less confined to the core, while core-metal surface guided modes are better confined to the core but suffer greater loss. An increase in the thickness of the metal cladding reduces the loss of the core-metal surface guided modes. The modal gain and confinement of the metal-clad cavity are compared to an unclad cavity.  相似文献   
44.
The complexity of many chemical and refining reaction systems and the thus-derived tedious and time-consuming process of building the associated kinetic models have been major obstacles in the use of fundamental kinetics in the solution of chemical engineering problems. This review summarizes work aimed at removing theses obstacles. Our recent work that has led to the enhancement of the Kinetic Modeler's Toolbox (KMT) and the development of the Kinetic Model Editor (KME) presents an end-to-end solution to the kinetic modeling process, including automated feedstock modeling, reaction network construction, kinetic rate estimation, model programming, process system configurations, model customizations, compilations, model execution and results analysis.  相似文献   
45.
Molecular electrostatic potential (MEP) maps of certain 3-methoxy flavone derivatives having different anti-picornavirus activities have been studied. Geometries of the molecules were optimised and charge distributions computed using the AM1 molecular orbital method. Hybridization displacement charges (HDC) were combined with the L?wdin charge distributions to compute the MEP maps. Reliability of the method of computing MEP maps was tested by studying certain other molecules for which ab initio MEP results are available. The anti-picornavirus activities of the flavones have been shown to be related with negative MEP values in two regions, one near the 3-methoxy group and another in a diagonally opposite region near the substituent attached to the C7 atom of the molecules.  相似文献   
46.
Ross.  AH Gilh.  KS 《电信科学》1996,12(3):6-17
本文主要讨论数字移动通信中扩频码分多址技术,阐明了CDMA体制的优越之外,分析了CDMA的关键技术,全面介绍了CDMA系统设计的基本原则和IS-95-A空中接口标准的含义。  相似文献   
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48.
A new self-tuning regulator for control of mean arterial blood pressure using sodium nitroprusside is presented. In addition to adapting to various patient response gains and time constants, the controller can accommodate variations in pure time delays, a problem that has not been addressed fully in previously proposed controllers. The control algorithm derivation is based on incorporating a self-turning controller with an adaptive discrete time delay compensator. The derivation, however, is general and can potentially be applied to other pharmacological agents in addition to sodium nitroprusside. The a priori information required for implementation of the controller is the estimate of the order of the patient response transfer function and the range of the pure time delay. An attractive feature of the controller is its capability to optimize the level of the infused drug during the transient phase of the control without creating an output offset. This feature tends to reduce the overall level of the infused drug. Hence, it may be useful when the cost of a drug or its long-term administration side effects is of concern, such as in the case of sodium nitroprusside  相似文献   
49.
Vascular wall fibrinolytic system proteins are believed to play a pivotal role in atherogenesis. Tissue-type plasminogen activator (t-PA) and urokinase plasminogen activator (u-PA) influence persistence of luminal thrombi and proteolysis of extracellular matrix, respectively. The major physiologic inhibitor of t-PA and u-PA is plasminogen activator inhibitor type 1 (PAI-1). All three of these fibrinolytic system proteins have been detected in vascular endothelial cells, smooth muscle cells, and macrophages by light microscopic immunohistochemistry. This study was undertaken to delineate, by immunoelectron microscopy, the loci of PAI-1 in smooth muscle cells from intact morphologically normal and atherosclerotic human arteries as well as in isolated and cultured smooth muscle cells from arteries. In intact vessels, PAI-1 immunoreactivity was associated with contractile filaments in cells in both normal and atherosclerotic tissues. Lipid-laden smooth muscle cells in atherosclerotic vessels were mainly of the synthetic phenotype and displayed lesser amounts of PAI-1 associated with rough endoplasmic reticulum and contractile filaments. Isolated smooth muscle cells exhibited either a contractile or synthetic phenotype. In the cells with a contractile phenotype, PAI-1 was associated with the contractile elements, whereas in the cells with a synthetic phenotype, the PAI-1 was associated predominantly with elements of the endoplasmic reticulum. Because PAI-1 is associated predominantly with contractile filaments in smooth muscle cells, the net amount of immunodetectable PAI-1 appears to be greater in contractile compared with synthetic phenotype cells.  相似文献   
50.
Cognitive accounts of panic predict that panic disorder patients will be particularly prone to misinterpret autonomic sensations. Several studies have produced results consistent with this prediction, but each is open to alternative interpretation. To clarify matters, 2 studies administered the Body Sensations Interpretation Questionnaire (BSIQ) to panic patients and controls. Panic patients were more likely to interpret ambiguous autonomic sensations as signs of immediately impending physical or mental disaster and were more likely than other anxiety disorder patients and nonpatients to believe these interpretations. In a 3rd study, a brief version of the BSIQ was shown to have satisfactory test-retest reliability, to change with treatment, and to discriminate treatments that varied in their effects on panic.  相似文献   
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