共查询到20条相似文献，搜索用时 312 毫秒
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郑宏兴 《天津工程师范学院学报》2006,16(2):1-4
在广义传播矩阵（CTM）方法分析各向异性分层介质传播特性的基础上，对数值计算进行了研究，克服了有耗介质计算时发散的困难，指出了编程计算时应该注意的问题。在半空间条件下，对分层各向异性有耗介质的反射和透射系数进行了计算，将GTM方法与精确解对比，计算结果一致。 相似文献
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利用数字信号处理技术和电磁场理论,研究了圆柱形导体目标对强电磁脉冲波的散射及目标表面上感应电流;仿真了目标对脉冲散射的同极化衰减随时间的变化以及目标上的脉冲电流的时间变化规律。这不仅适用于研究导体目标的脉冲散射特性,而且适用于形状复杂目标的脉冲散射特性研究介质中的脉冲衰减研究,具有算法简便、准确、高效等特点。 相似文献
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针对广泛关注的左手材料(负折射率媒质),对电磁波穿过左手材料(Left-handedm aterial)构成的平行板时的传播特性做了理论分析;采用FDTD方法对正弦电磁波穿过了LHM的平行板的传播过程进行了数值建模,数值模拟的结果证明了正弦电磁波在穿过平板状的左手材料,会有类似一般凸透镜的聚光效果,以及负折射特性,为LHM的广泛应用提供了理论基础. 相似文献
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本文通过数值计算的结果,具体分析比较了左手介质覆盖导体圆柱与普通介质覆盖导体圆柱对平面波散射的近场和远场的电磁特性,发现这两种介质层在距离中心轴线约1.570λ￣1.80λ范围内的近场分布有明显不同,左手介质层内的场变化较后者缓慢;而二者对平面波的远场分布是完全一致的,几乎没有差别。 相似文献
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李应乐 《咸阳师范学院学报》2006,21(4):20-22
建立了箔条目标模型,得出了箔条目标散射场的解析解,为研究箔条目标的电磁波极化特性奠定了理论基础;研究了电磁波平行投射到箔条上与垂直投射到箔条上的散射特性;结果表明:无论是前向散射还是后向散射,箔条形状的变化对散射特性有着明显的影响,都具有后向散射增强效应,箔条在某一方向上的散射基本上由正对该方向的目标上的电磁源决定。 相似文献
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李应乐 《咸阳师范学院学报》2005,20(2):16-19
研究了高速运动的介质目标对任意频率电磁渡的散射,系统地导出了坐标系相对沿着z轴运动时的坐标变换关系、波矢量变换关系以及电磁场的变换关系。首次给出了两个相对作高速匀速运动的球坐标系中的三角函数的变换关系以及矢量的球坐标分量的变换关系,为研究高速运动目标的电磁波散射奠定了理论基础。利用Mie理论。详细地研究了高速运动介质球的散射特性,得到了散射截面的解析表达式并对其进行了仿真和讨论。结果表明:介质球做高速运动时,前向散射大于后向散射,和其它的观察方位相比,入射波频率对散射的影响不大,多普勒效应起主要作用,目标表面上的二次辐射源以电偶极辐射为主。 相似文献
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不可压各向异性超弹性材料中的空穴生成 总被引：3，自引：0，他引：3
The cavitation problem in a solid sphere composed of an incompressible anisotropic hyper-elastic material under a univroms radial tensile dead load was examined.A new analytical solution was obtained.The stress contruibutions were given and the jumping and concentration of stresses were discussed.The stability of solutions and the effect of the degree of ainsotropy of the material were analyzed. 相似文献
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Calculation of the scattered field of the eccentric scatterers is an old problem with numerous applications. This study considers the interaction of a plane compressional sound wave with a liquid-encapsulated thermoviscous fluid cylinder submerged in an unbounded viscous thermally conducting medium. The translational addition theorem for cylindrical wave functions, the appropriate wave field expansions and the pertinent boundary conditions are employed to develop a closed-form solution in the form of infinite series. The analytical results are illustrated with a numerical example in which the compound cylinder is insonified by a plane sound wave at selected angles of incidence in a wide range of dimensionless frequencies. The backscattered far-field acoustic pressure amplitude and the spatial distribution of the total acoustic pressure in the vicinity of the cylinder are evaluated and discussed for representative values of the parameters characterizing the system. The effects of incident wave frequency, angle of incidence, fluid thermoviscosity, core eccentricity and size are thoroughly examined. Limiting case involving an ideal compressible liquid-coated cylinder is considered and fair agreement with a well-known solution is established. 相似文献
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FINITE ELEMENT-ARTIFICIAL TRANSMITTING BOUNDARY METHOD FOR WAVE SCATTERING FROM IRREGULAR CYLINDER 总被引：1，自引：0，他引：1
用有限元－人工透射边界法求出柱面波在无限长圆柱上的散射近场并与解析解比较，进而对几种不规则目标的散射问题求解．实例说明，该方法过程简单，图象清楚，适应性强，可处理多种复杂的散射问题． 相似文献
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李应乐 《咸阳师范学院学报》2004,19(4):18-22
利用坐标的尺度分析得出了任意椭球粒子散射场的解析解，导出了这种散射场的交叉极化分辨率，并在毫米波段进行了仿真。结果表明：交叉极化分辨率与椭球粒子的尺寸大小、形状及观察方位有关；与后向散射点相比，XPD在前向散射点随形状的变化比较平稳。对于给定形状的椭球目标而言，在大约与入射波相反的方向上，XPD有最大值。 相似文献
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研究了雨介质中导体目标对电磁波的散射特性。当入射波沿垂直方向极化时，得出了毫米波段散射场的表达式，导出了目标的微分散射截面。结果表明：微分散射截面总体上随雨强的增加和频率的升高而减小，具有后向散射增强效应；共极化微分散射截面与交叉极化微分散射截面的比值随降雨率的增大而增大。 相似文献
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Yong-jian Zhi Bin Zhang Kai Li Xiao-yan Huang You-tong Fang Wen-ping Cao 《浙江大学学报(A卷英文版)》2011,12(12):950-956
A switched-mode unit used in electric locomotive generates a strong high frequency conducted electromagnetic interference
(EMI), which radiates electromagnetic energy through railway lines. Evaluation of magnetic field using analytical technique
based on contour integral is presented, in order to assess the electromagnetic environment around a high-speed railway. Actual
railway multiconductor finitely long overhead lines are represented by an infinitely long single line above two-layered earth,
whose characteristic is different from homogeneous earth. Owing to the constraint of the GB/T 24338-2009 and the high frequency
investigated (a few MHz), only the magnetic fields are examined. The magnetic fields consist of four components: the direct
wave, the ideal reflected wave or image wave, the trapped surface wave, and the lateral wave. The calculation results proved
that due to the presence of the trapped surface wave, the magnetic field of the observer point on the interface is strongly
influenced, when the line is on or closed to the interface. 相似文献
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定义了平面波入射柱面透镜的等效菲涅耳数,并基于等效菲涅耳数的含义,利用一种新的简单的方法研究了平面波入射柱面透镜的聚焦光场的聚焦特性。结果显示,聚焦光场的相对焦移可以用一个简单的解析表达式来计算,即表示为等效菲涅耳数的函数。为了说明等效菲涅耳数的定义,将由这种简单的新方法得到的结果与基于衍射积分的数值计算得到的结果进行比较,结果显示,两种方法得到的结果吻合的很好。因此,可以用这种新方法来简单而准确地计算相对焦移。 相似文献
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1Introduction Generalrelativityisthetheoryofstudyinggravita tionandthestructureofspace time.Sinceitsestab lishment,ithasbeenattractinginterestsoftheoreti cians.However,thereislittleobservableandexperi mentalexaminationshowingthefeaturesoflarge scale structureofspace time.Withtechnologicaladvances, severalgravitationaleffectswereinvestigatedsuchas gravitationalwavetest,starkeffect,gravitationallens effect,gravitationalFaraday,etc.Inthispaperwe discussgravitationalFaradayeffect. Itiswellkn… 相似文献
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利用平面电磁波在界面上的反射和折射理论,分析垂直偏振波在芯层介面上的反射,得出沿Z方向传播的TM波在全反射时的相移,利用横向谐振重要条件得到TM模的模式本征方程。 相似文献
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The indirect boundary element method (IBEM) is used to study the surface motion of an alluvial valley in layered half-space for incident plane P-waves based on Wolf’s theory. Firstly, the free field response can be solved by the direct stiffness method, and the scattering wave response is calculated by Green’s functions of distributed loads acting on inclined lines in a layered half-space. The method is verified by comparing its results with literature and numerical analyses are performed by taking the amplification of incident plane P-waves by an alluvial valley in one soil layer resting on bedrock as an example. The results show that there exist distinct differences between the wave amplification by an alluvial valley embedded in layered half-space and that in homogeneous half-space and there is interaction between the valley and the soil layer. The amplitudes are relatively large when incident frequencies are close to the soil layer’s resonant frequencies. 相似文献