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拟线性双曲组解的奇性形成和特征包络 总被引:1,自引:0,他引:1
一、引言如所知,对一阶拟线性双曲型方程组,即使其初值充分光滑,其柯西问题的解一般说来也要在有限时间内产生奇性,即经典解要发生破裂(Blow up),这在力学上对应于激波的产生等自然现象。通常认为奇性的发生起因于同族特征线产生包络。这一事实在力学上虽已多次应用,但在一般情况下其实还只是一个猜测,有必要在理论上加以分析和讨论。本文对可化约拟线性双曲组的柯西问题肯定地回答了上述的问题,所得的结果对一般情形的讨论也将有一定的启发。 相似文献
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Dispersion characteristics of two-dimensional unmagnetized dielectric plasma photonic crystal 总被引:1,自引:0,他引:1
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This paper studies dispersion characteristics of the
transverse magnetic (TM) mode for two-dimensional unmagnetized
dielectric plasma photonic crystal by a modified plane wave method.
First, the cutoff behaviour is made clear by using the
Maxwell--Garnett effective medium theory, and the influences of
dielectric filling factor and dielectric constant on effective
plasma frequency are analysed. Moreover, the occurence of large gaps in
dielectric plasma photonic crystal is demonstrated by comparing the
skin depth with the lattice constant, and the influence of plasma
frequency on the first three gaps is also studied. Finally, by using
the particle-in-cell simulation method, a transmission curve in the
\Gamma -X direction is obtained in dielectric plasma photonic
crystal, which is in accordance with the dispersion curves
calculated by the modified plane wave method, and the large gap between
the transmission points of 27~GHz and 47~GHz is explained by
comparing the electric field patterns in particle-in-cell
simulation. 相似文献
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本文介绍一种新型毫米波准光学可调辐射源,它采用由面对称三反射镜准光学谐振腔和绕射光栅组成高频互作用系统,利用中等能量级的相对论带状电子注激励,产生频率可调的宽带毫米波、远红外波段的辐射。这种新方案的机理性实验在电子科技大学首次获得成功,其主要实验参数:电子注的能量为400~500kV,电压脉冲宽度70ns,同步脉冲磁场强度1.2T; 磁场脉冲宽度10ms,带状电子注尺寸10nm×1mm;通过热测实验,我们成功地检测到3mm波段的高频信号,其峰值功率达到数十千瓦量级。 相似文献
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以圆柱开槽波导、螺旋摇摆器为模型,考虑了电子初始速度零散、引导磁场等效应对放大器饱和特性的影响,导出了自洽的注波互作用三维非线性方程组.并在此基础上编制了相应的计算软件,通过数值分析的方法研究了圆柱开槽波导自由电子激光放大器的饱和效率、频带宽度等高频特性. 相似文献
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利用根与系数的关系.证明了特征方程没有零实部根的充要条件,给出了矩阵特征值至少具有一个正实部的充分条件,最后通过示例计算验证了该方法的有效性. 相似文献
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Based on an improvement of the Karman-Pohlhausen's method, using nonlinear polynomial fitting and numerical integral, the axial distributions of pressure and its gradient in an axisymmetric rigid vessel with stenosis were obtained, and the distributions related to Reynolds number and the geometry of stenotic vessel were discussed. It shows that with the increasing of stenotic degree or Reynolds number, the fluctuation of pressure and its gradient in stenotic area is intense rapidly, and negative pressure occurs subsequently in the diverging part of stenotic area. Especially when the axial range of stenosis extends, the flow of blood in the diverging part will be more obviously changed. In higher Reynolds number or heavy stenosis, theoretical calculation is mainly in accordance with nast experiments. 相似文献
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