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随着我国高速铁路的迅速发展,高速铁路电磁干扰对沿线电子设备的影响愈来愈引起人们的关注.目前国内相关高校及科研院所对于该电磁干扰的来源和机理已做了较为深入的研究,得出了一些很有价值的理论成果,但其对雷达的影响程度,尚没有明确的结论.研究通过前期的大量测试数据对列车弓网离线引起的电磁干扰、电磁干扰强度与车速的关系进行统计分析及数学建模,现场测试数据定量分析了此噪声对L波段雷达的影响.通过计算得到了在平原地区条件下(干扰源与受扰雷达之间的电磁波传播路径上无遮挡物,仅存在地面反射),干扰强度与雷达和铁道间距、列车速度之间的关系,得出了雷达的有效防护距离. 相似文献
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为了研究地铁站钢筋混凝土层对地铁弓网离线电弧的屏蔽效能, 基于有限积分法(Finite Integration Technique, FIT)计算并分析了钢筋混凝土对平面波的屏蔽效能; 讨论了不同混凝土结构对屏蔽效能的影响因素; 实测得到了某地铁站的屏蔽效能.研究结果表明:素混凝土对电磁波的屏蔽效能具有一定的周期性, 增加厚度对高频段的屏蔽效能影响不大; 钢筋网的屏蔽效能在0.1~0.8 GHz频带范围内大于30 dB; 双层钢筋混凝土在0.1~1.3 GHz频带范围内的屏蔽效能大于40 dB; 实测屏蔽效能在整体上跟数值计算结果吻合得较好, 验证了本文方法计算钢筋混凝土对地铁弓网离线电弧屏蔽效能的正确性. 相似文献
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作为电力系统、电能应用工程中十分常见的物理现象,低压电器电弧运动与仿真研究越来越受关注.本文结合低压电器电弧运动机理与电弧仿真技术,构建了低压电器电弧仿真模型,就低压电器电弧仿真过程进行了研究. 相似文献
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本文引入Clarke参考模型,采取了一种改进型的瑞利衰落信道模型作为单径瑞利衰落信道的仿真模型,并用MATLAB编程仿真实现.该技术有助于对移动通信系统电磁干扰的研究. 相似文献
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针对高速列车气动噪声越来越大的问题,本文以高速列车某车型为参考建立1:1受电弓区域局部模型,基于宽频带噪声源模型、LES大涡模拟及FW-H声学模型,运用弓头仿生降噪和底部空腔主动射流降噪的整体降噪措施,采用数值模拟法研究高速列车受电弓区域的降噪效果.结果表明:受电弓弓头和底部空腔是气动噪声的主要来源;降噪后,主要噪声源的声功率级都有了较大降幅,其中弓头和空腔部位分别降低了15.28 dB和16.92 dB;中高楼层住宅处的降噪效果更佳,最大声压级降低位置在距地面18 m高处(距受电弓25 m远处),降低了4.94 dBA;远场声压级在低频区域降噪效果更为显著,特别是在800 Hz位置声压级降幅最大,降低了8.21 dBA. 相似文献
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建立了电磁干扰条件下电视指令制导导弹攻击过程中的机弹数据链模型,分析了电磁干扰对导弹攻击过程的主要影响因素,而后基于有限状态机理论,建立了导弹攻击模态转换模型,并引入了状态转换因子以将导弹攻击目标过程中的各种状态联系起来,通过仿真研究了电磁干扰各参数对机弹数据链和导弹攻击过程的影响. 相似文献
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By means of exact conformal mapping method we have defined character of dependence of squares amounts of angular part of film
element on angled part dimension. We propose relations, approximating obtained dependence. Calculation results and experimental
researches of large-scale models are represented. 相似文献
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Moshrefzadeh R.S. Radcliffe M.D. Lee T.C. Mohapatra S.K. 《Lightwave Technology, Journal of》1992,10(4):420-425
The temperature dependence of refractive index of polymer films was determined for a number of slab waveguides by a grating coupling method. This dependence was examined as a function of parameters such as molecular weight and glass transition temperature of the polymer. Temperature-induced changes in N TE-N TM , N being the effective index, were studied systematically for different slab waveguide compositions. It is shown that with proper device design and choice of polymeric materials, thermal effects can be reduced 相似文献
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The article describes a model representation of radar probing data in form of a mixture of background and target samples, which is the sum of two random variables with very different parameters. For model development we research the behavior of the central moments of the distribution mix without assuming the distribution law form. An example it is described the detection of the signal at the output of compression system of chirp ionosonde. 相似文献
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解决IP网QoS问题是目前通信领域的研究热点之一.虽然研究已经取得了一定的进展,但人们对于IP 网QoS本身的含义及相关的问题还有着不同的理解.本文将从IP网QoS的定义入手讨论相关的一些问题以及解决IP网QoS问题所做的各种努力. 相似文献
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《Proceedings of the IEEE. Institute of Electrical and Electronics Engineers》1968,56(6):1024-1032
Assuming that visual responses are due to the action of particles on the membrane of the visual cells, the stochastic variability of the response should be a function of the number of particles producing it. Quantitative predictions can be made with the aid of a model proposed in previous articles. It is found that responses produced in visual cells of Limulus by absorption of a single photon have the stochastic properties which would be expected if the response to one photon were brought about by 25 particles. It is concluded from this that the processes leading to visual responses produce multiplication of particles. The effects of temperature and of metabolic poisons suggest that these processes are of chemical nature. 相似文献
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The approaches to prepare a uniform and unified scientific terminology of chemical carcinogenesis are presented. The main definitions proposed (carcinogen, initiation, promotion, mutagen, multistage carcinogenesis, anti-carcinogen, cocarcinogen, carcinogenic risk, etc.) are based on the current state of comprehending mechanisms of the action of chemical carcinogens. 相似文献
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《半导体学报》2008,29(12):2470-2470