椭圆波束对非均匀手征分层粒子的俘获特性研究

非均匀手征分层粒子的俘获特性研究在化学工程、生物医药、光镊、微纳米加工等领域都有着重要的应用.为了有效地俘获及操控手征分层球形粒子,本文对椭圆高斯波束照射下手征分层球形粒子的辐射俘获力展开研究.从广义米理论出发,将入射椭圆高斯波束用矢量球谐函数展开,根据波束散射理论及电磁场动量守恒定理,得出椭圆高斯波束对手征分层球形粒子辐射俘获力的级数表达式,并对椭圆高斯波束入射分层手征细胞时的轴向及横向俘获力进行了数值模拟,讨论了手征参数、极化状态、束腰宽度、损耗以及最外层厚度对俘获情况的影响.研究表明:手征参数的引入会降低非均匀手征粒子的轴向俘获特性,但是选择合适的极化态入射时,可以有效地实现对非均匀手征粒子的稳定俘获.对于内层损耗小的手征多层球形粒子,当内层折射率大于最外层时,最外层厚度大的非均匀手征粒子在光轴上更容易俘获;反之内层折射率小于最外层时,最外层厚度小的粒子在光轴上有更强的束缚;同时与传统圆高斯波束相比,椭圆高斯波束的强会聚性更容易实现对非均匀手征分层细胞的三维俘获,具有良好的应用前景.     

Modified GIT model for predicting wind-speed behavior of low-grazing-angle radar sea clutter

A modified GIT model for describing the variational trend of mean clutter reflectivity as a function of wind speed is proposed. It uses two slope adjustment factors and two critical wind-speed factors to define and adjust the increasing slope of reflectivity with respect to wind speed. In addition, it uses a constant factor to compensate the overall amplitude of clutter reflectivity. The performance of the modified GIT model has been verified on the basis of the L-band low-grazing-angle radar sea clutter data. The results are in good agreement with the experimental data, indicating that the model is more effective in predicting the wind-speed behavior of clutter reflectivity than the conventional GIT model, especially for lower and higher wind speeds. We believe that the proposed model can provide deeper insights into the relationship between radar sea clutter reflectivity and sea state conditions.     

Scattering and propagation of terahertz pulses in random soot aggregate systems

Scattering and propagation of terahertz pulses in random soot aggregate systems are studied by using the generalized multi-particle Mie-solution(GMM) and the pulse propagation theory. Soot aggregates are obtained by the diffusion-limited aggregation(DLA) model. For a soot aggregate in soot aggregate systems, scattering characteristics are analyzed by using the GMM. Scattering intensities versus scattering angles are given. The effects of different positions of the aggregate on the scattering intensities, scattering cross sections, extinction cross sections, and absorption cross sections are computed and compared. Based on pulse propagation in random media, the transmission of terahertz pulses in random soot aggregate systems is determined by the two-frequency mutual coherence function. Numerical simulations and analysis are given for terahertz pulses(0.7956 THz).     

大气信道对星地链路激光通信的影响

星地链路激光通信系统的运行不可避免地要受到湍流大气等随机介质的影响,从而可导致卫星接收信息误码或通信中断。基于Born近似和弱起伏下的Rytov近似,分析推导了激光光束从发射机经湍流大气斜程到达接收机(或目标)时的光场变化。采用McGlamery算法,对Kolmogorov功率谱下的大气湍流随机相位屏进行了数值模拟,进而在模拟的相位屏和惠更斯-菲涅尔原理基础上,将主要适用于模拟平面波相位波前的McGlamery算法推广应用到了高斯光束的光场模拟。研究表明:大气信道段对星地链路激光通信系统有着极为重要的影响,也间接说明了McGlamery算法对准直激光光束相位波前模拟的适用性。     

Relation between Debye series and generalized Lorentz--Mie theory of laser beam scattering by multilayer cylinder

With the recursive relations of Bessel function and applying inductive approach, the consistency between the scattering coefficient formula of Debye series and that of the generalized Lorentz-Mie theory (GLMT) in the scattering of a multilayer cylinder illuminated by a laser beam is proved in detail. As an application example, rainbow phenomenon in the scattering of a two-layer cylinder is discussed by the Debye series components. It can be concluded that the radius and the refractive index of a two-layer cylinder have an effect on the twin-primary rainbow, and the high-order Debye series components which are associated with the high-order rainbows are more complex than those of a homogeneous cylinder.     

原子钟噪声中的混沌现象及其统计特性

原子钟是一个极其精密的振荡源，其内部噪声极大地限制了时间尺度的精确性.通过一种变形Duffing方程模拟原子钟内部的各种周期及混沌现象，给出了过渡混沌、阵发混沌及混沌的统计描述.根据Lyapunov指数的变化，分析了原子钟噪声中的混沌现象及其激发机制.对1994年的6月1日0时至8月20日24时的测量数据进行了分析，给出了相应混沌分量的统计特征. 关键词：     

双尺度动态分形粗糙海面的电磁散射及多普勒谱研究

利用更为符合海面实际散射场计算的双尺度法分析并计算了一维动态分形粗糙海面的后向散射截面，同时与微扰法有关结果进行了比较.研究了动态分形海面后向散射信号的多普勒谱分形特征，分析了不同极化状态下后向散射截面和多普勒谱谱宽随入射角及分维的变化规律，最后详细讨论了多普勒谱中心频率与海面Bragg谐振频率间的关系. 关键词： 双尺度模型 分形海面 电磁散射 多普勒谱     

双折射光纤中非线性耦合Schrdinger方程的小振幅孤波解

采用小振幅孤波近似法，得到非线性耦合Ｓｃｈｒｄｉｎｇｅｒ方程决定的双折射光纤中的小振幅孤波解，它们可以同时存在于正常色散区或者分别处于正常和反常色散区．     

微粗糙面上方球形粒子的光散射及其散射截面的计算

基于互易定理研究了光波入射时微粗糙面与其上方球形粒子复合模型的光散射。根据粗糙表面电流积分方程并利用表面微扰展开，得到了微粗糙面表面极化电流的迭代解，给出了耦合电场的计算方法。结合散射耦合场散射矩阵和已有的微粗糙面及球形粒子的散射矩阵，给出了复合模型散射截面的计算公式，数值计算了复合模型的后向散射截面并进行了详细讨论。     

随机粗糙表面激光散射后向增强效应实验研究

随机粗糙表面激光散射后向增强效应实验研究吴振森（西安电子科技大学物理系西安７１００７１）ＥｘｐｅｒｉｍｅｎｔＲｅｓｅａｒｃｈｏｎＥｎｈａｎｃｅｄＢａｃｋｓｃａｔｅｒｉｎｇｏｆＲａｎｄｏｍＲｏｕｇｈＳｕｒｆａｃｅｓＷｕＺｈｅｎｓｅｎ（Ｄｅｐａｒｔｍｅｎ...