共查询到20条相似文献,搜索用时 140 毫秒
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针对微波脉冲激励下复杂屏蔽腔体内部电路耦合电磁量计算的问题,建立了一个微波混沌腔体,通过测试获取了含内部电路的腔体辐射和辐射散射参数,利用随机耦合模型(RCM),对干扰脉冲能量进行了归一化处理,计算分析了微波脉冲宽度、脉冲间隔、脉冲数目以及腔体损耗因子对目标点感应电磁量统计分布的影响。计算结果表明:脉冲干扰下电路目标点耦合电磁量强于功率源激励;在脉冲能量一定的条件下,目标点耦合电磁量与微波脉冲的宽度、间隔和数目的变化均呈现一定的谐振特性,且单脉冲激励对电路的影响明显强于多脉冲。与此同时,实验还研究了电路易受电磁干扰的目标点的确定方法。 相似文献
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为了能够快速有效地求解电大复杂腔体(微波混沌腔)的电磁耦合问题, 文中采用统计电磁学方法研究了该类腔体电磁散射的统计特征. 首先, 根据天线辐射理论, 利用电磁场的本征模展开式建立了腔体耦合输入阻抗表达式. 其次, 利用波动混沌理论和概率统计方法进一步推导出了微波混沌腔的随机耦合模型. 该方法简单并且可以直接推导出三维模型. 最后, 构建了一个三维Sinai微波混沌腔并进行数值仿真实验, 其仿真实验结果与随机耦合模型计算结果的统计特征基本一致. 重要的是, 该模型与复杂腔体的细节特征无关, 能够快速有效地预测微波混沌腔的敏感耦合问题.
关键词:
统计电磁学
微波混沌腔
输入阻抗
随机耦合模型 相似文献
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研究共振声辐射理论(Resonance Radiation Theory:RRT)在水中矩形板的应用。导出了矩形板的共振声辐射公式、并数值验证了其适用性。深入分析了有流体负荷矩形板的复共振频率的物理意义及其与导纳留数、模态辐射率的关系,复共振频率的实部表示实际共振频率,虚部反映模态辐射能力。根据复共振频率容易找到辐射能力相对较强的模态,为有针对性控制声辐射提供了新的思路。鉴于复平面搜根求解模态复共振频率的困难,针对矩形板的特点提出了一种求解复共振频率及留数的快速方法。结合该方法及RRT,提出了一种快速计算辐射声功率的方法,数值验证表明该方法精度高、速度快。 相似文献
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P.R. Stepanishen 《Journal of sound and vibration》1977,55(2):275-288
The radiation impedance of a rectangular piston is expressed as the Fourier transform of its impulse response, which is obtained from the recent work of Lindermann [1]. The analytical evaluation of the transform is performed and new integral expressions are presented for both the radiation resistance and reactance. The integrals are readily evaluated in terms of elementary functions at both the low and high frequency limits. The integrals are also expressed as series of Bessel functions which are valid for all frequencies and aspect ratios. Numerical results are presented to illustrate the behavior of the radiation resistance and reactance as a function of the aspect ratio of the piston and a normalized frequency parameter. Additional numerical results are then presented to illustrate the accuracy of the analytical expressions for the radiation resistance and reactance at low and high frequencies. Finally, numerical results are presented to illustrate the application and accuracy of using standard FFT algorithms to evaluate the radiation resistance and reactance directly from the impulse responses. 相似文献
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Radiation damping effects induced by the dominated solvent in a solution sample can be applied to suppress the solvent signal. The precession pathway and rate back to equilibrium state between solute and solvent spins are different under radiation damping. In this paper, a series of pulse sequences using radiation damping were designed for the solvent suppression in nuclear magnetic resonance (NMR) spectroscopy. Compared to the WATERGATE method, the solute signals adjacent to the solvent would not be influenced by using the radiation damping method. The one-dimensional (1D) 1H NMR, two-dimensional (2D) gCOSY, and J-resolved experimental results show the practicability of solvent suppression via radiation damping effects in 1D and 2D NMR spectroscopy. 相似文献
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By using a new technique developed recently exact closed equations of motion for expectation values for spontaneous emission from two two-level atoms in a detuned damped cavity are derived. These equations are solved numerically for different values of the cavity damping and detuning. It is pointed out that the spontaneous emission is inhibited if the cavity is detuned. Moreover, by comparing the result of the single-atom case with that of the two-atom case it is shown that the collective effects can be suppressed by changing the cavity damping and detuning. 相似文献
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M.R. PFAFFINGERJ. DUAL 《Journal of sound and vibration》2002,253(5):1015-1037
Forced vibrations of a railway track excited at the cut-off frequency of one of its wave modes are examined theoretically, numerically and experimentally in the frequency range from 5 to 50 kHz. The background of this paper is the new idea of using the local vibration zone of the rail close to the excitation to detect passing train wheels. An important parameter which influences this local vibration zone is system damping. The determination of a new quality factor to characterize damping of a system which both resonates and interacts with travelling waves is first studied in the case of a beam on a viscoelastic foundation. Some key differences compared with a single-degree-of-freedom (s.d.o.f.) mechanical oscillator are pointed out and an adopted damping measurement method is suggested. The phenomenological behavior of higher vibration modes is then investigated using a model of several elastically connected beams referred to as the multiple-mode model. Modal damping is introduced and the model is studied both in a continuous and in a discretely supported configuration. Both localized and non-localized modes are observed in the latter case. The cut-off frequencies and mode shapes are also determined experimentally at a real test track using a scanning laser interferometer and show good agreement with numerical calculations. The spatial behavior of the measured system response at the test track corresponds well to the effects predicted by the multiple-mode model. Damping measurements are performed and the quality factors of several modes are determined and discussed. 相似文献
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Felipe A. Asenjo 《Physics letters. A》2009,373(48):4460-4463
The effect of spin of particles is studied using a semi-classical kinetic theory for a magnetized plasma. No other quantum effects are included. We focus in the simple damping effects for the electrostatic wave modes. Besides Landau damping, we show that spin produces two new different effects of damping or instability which are proportional to ?. These corrections depend on the electromagnetic part of the wave that is coupled with the spin vector. 相似文献
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M SAEKI 《Journal of sound and vibration》2002,251(1):153-161
The damping efficiency of an impact damper with granular materials in a horizontally vibrating system is investigated by means of the discrete element method. This method makes it possible to consider effects of granularity such as the particle size, number of particles and friction between two particles. The validity of this numerical method is examined by a comparison of the experimental results. It is shown that the mass ratio, particle size and cavity dimensions influence the damping performance. It is also shown that the cavity dimensions and the particle radius affect the behavior of the granular materials. 相似文献
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C.K.W. Tam 《Journal of sound and vibration》1976,49(3):353-364
A theoretical study of the acoustic modes of a two-dimensional rectangular cavity is presented in this paper. It is found that for cavities with length to depth ratio of unity or larger the natural modes are heavily damped due to acoustic radiation. Numerical results for lower order modes are given. The physical significance of strong radiation damping on the onset of cavity tones induced by outside flow at low Mach number is discussed. 相似文献