共查询到18条相似文献,搜索用时 140 毫秒
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以西安地铁2号线南门到钟楼的隧道某区段为研究对象,运用理论计算和采用FDS软件进行火灾模拟仿真,找出了火源热释放率与纵向通风临界风速的关系,从而可以根据火源热释放率快速计算出临界风速,达到快速救援的目的。 相似文献
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基于全微分和统计理论推导了星载相干测风激光雷达合成水平风速和风向误差的解析表达式,利用克拉默-拉奥误差下界代替Frehlich经验公式对风场的随机风速误差进行评估,建立了通用型的星载相干测风激光雷达合成水平风速和风向误差计算模型.在NASA/NOAA提出的星载测风激光雷达系统设计指标框架下,对风速及风向误差模型进行可行性分析,得到了总的径向随机误差随着探测距离的变化关系及水平风速区间的选取对随机误差的影响.同时,为了计算合成采样误差,改变不同的垂直分辨率和方向角取值,对水平分量的采样误差进行对比分析.仿真结果表明,合成的水平风速和风向的误差范围为0.8~3.2 m/s和2.38°~3.49°,基本符合星载测风激光雷达的相关指标要求. 相似文献
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采用IFA-300热线风速仪对由成都光电研究所研制的压缩气体驱动的标准型风刀在不同压强下刀口处的风速进行了标定,并对风刀刀口处的流场特性进行了研究.实验结果表明,风刀刀口处的风速与压缩气体的压强成线性关系,压强越大,刀口处的风速也越大;风刀刀口处流场的稳定性和均匀性与流场的具体位置有关,风刀风道中心位置的流场流速最大,不稳定度最低,大约为2%;在风刀风道的边缘位置,流场流速最小,不稳定度最高,不稳定度接近28%左右. 相似文献
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Influence of a Constant Magnetic Field on Nervous Tissues: I. Nerve Conduction Velocity Studies 总被引:1,自引:0,他引:1
A study of the biomagnetic response of the circumesophageal connective of the lobster has been undertaken in order to investigate the influence of a constant magnetic field upon (i) the nerve impulse conduction velocity of the entire trunk, and (ii) the membrane potentials and the transmembrane currents of the giant axon of this nerve, under voltage-clamp conditions using the double sucrose gap technique. In this first paper, the results of the conduction velocity experiments are reported. They show that there is no significant effect of a 1.2 T magnetic field upon conduction velocity of the isolated nerve of the lobster, in either parallel or perpendicular configurations with respect to the field. The results of the biomagnetic experiments on the giant axon of the lobster under current-clamp and voltage-clamp conditions will be reported later. 相似文献
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浅海环境中运动目标可以生成稳定的干涉声场,干涉声场结构中蕴含目标的距离、速度等信息。该文提出一种利用运动目标干涉声场进行被动距离速度估计的方法——匹配干涉场处理方法。首先对浅海波导环境中的干涉现象和结构特性进行理论分析,推导了匹配干涉场方法聚焦原理。然后将运动目标的时间-频率干涉场转换成与目标距离速度相关的距离-频率干涉场,与拷贝声场进行相关处理实现目标距离速度同时估计。进一步分析了算法估距性能以及海深、声速剖面、海底海面等环境对估距性能的影响,给出了算法宽容性的仿真结论。最后通过实际运动目标的海上试验数据处理验证了所提方法的有效性。 相似文献
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Empirical evidence from submicrometer technology in GaAs- and InGaAs-based field-effect transistors (FETs) has led to an expectation that velocities exceeding the steady state values would be observed in III-V nitride devices. However, scaling of devices down to 0.7 and 0.25 /spl mu/m has so far not yielded any performance enhancement that may suggest an overshoot. In this paper, we examine transport in AlGaN-GaN heterojunction FETs (HFETs) to examine whether velocity overshoot effects occur. Our findings show that very high scattering rates when combined with unusual field profiles, result in a change in the local transport mechanism, and, in the source-gate region, combine to reduce/ify velocity overshoot effects. We also find that the effect of nonequilibrium phonons on transport in the channel is minimal, with the peak nonequilibrium phonon occupation being smaller than the equilibrium phonon occupation. 相似文献
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根据热平衡状态下的麦克斯韦速度分布函数,得到了三维空间中两原子间相对运动速度的分布函数。以四能级理论模型为基础,将此分布函数考虑到激光感生碰撞截面的计算之中,直接积分态振幅的运动方程,对弱场和强场两种情况下Eu-Sr系统中的一个激光感生碰撞过程进行了数值计算,得到了特定温度下系统的激光感生碰撞截面的谱线线型。将该数值计算的结果与以前的理论工作进行了比较,分析了两原子间相对运动速度分布对激光感生碰撞过程的影响。分析表明,两原子之间相对运动速度的统计分布虽然不影响激光感生碰撞截面的谱线线型,但对碰撞截面的峰值大小有一定的影响。结论与前人的理论预言相吻合,证明了数值计算的正确性。 相似文献
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Contactless measurement of wind flow has been utilized in many fields,such as weather forecasting,hurricane tracking,and aeronautic alarm.In this paper,a novel multi-laser beams measuring system(MLBM) for high precision detection of wind field based on optical scintillations and small perturbation theory was proposed and verified.According to the fluctuation intensity of laser backscatter received by two detectors,peak delay technique was adopted to determine the velocity of wind flow.Detailed procedure to ... 相似文献