水下弹性球体对Bessel波束散射的计算及分析

以弹性球体为例,分析Bessel波束入射到水下物体时的声散射。将水下弹性球体声散射场的分波序列计算公式加以推广,应用于Bessel波束入射的情况。借鉴平面波散射的模式,通过几何分析指出了Bessel波束入射下镜反射波和Franz波干涉所形成的反向散射形函数上的峰一峰间隔与波束特征参数β的关系,并首次给出了峰峰间隔的预报公式。同时,采用共振散射理论对每阶分波的弹性散射单独分析,深入研究了β对纯弹性共振的影响,发现通过选取特定的β可以使相应阶分波的弹性散射贡献被消除,从而使在反向散射中对应频率及其附近处的共振得到显著的抑制。

大地主题解算实用算法

针对目前大地主题解算中普遍存在的计算结果奇异、象限判断复杂和适用范围受限等问题,在综合高斯平均引数公式、巴乌曼投影公式、贝塞尔公式和文森特公式等多个解算公式优缺点的基础上,应用球面三角原理和文森特公式嵌套系数思想,兼顾计算机数值计算的应用,重新推算大地主题解算过程,提出正算和反算实用算法。该算法无奇异、适用任意距离,可直接应用于电算化编程实现。实际算例结果表明该算法正确、精度高,检核结果在10-12～10-16之间。

无源测向定位的地球椭球面算法

文章介绍一种不需要解方程组,考虑地球椭球的无源测向定位算法,给出了计算过程和支持软件代码实现的详细描述,并做了算法验证,利用试验测量数据得到了定位结果,与试验设备的定位结果做了比较,同一测量时刻同样的测量数据,本文的定位误差明显小于试验设备的定位误差。

若干重要积分的间接方法

本文(1)将两个复杂而重要的含参无穷积分视为其参变量的函数,运用一致收敛的含参积分对参变量的可导性质,设法将问题转化为关于参变量的简单微分方程,从而间接而巧妙地求出积分结果;(2)对于n维空间的球体体积与表面积的问题,本文介绍一种移花接木的方法,巧妙地推导出n维球体的体积与表面积公式。

Scattering of an unpolarized Bessel beam by spheres

The scattering process of an unpolarized Bessel beam through spherical scatterers is investigated. We derive the analytical solutions of scattered fields of x-and y-polarized Bessel beams using a sphere, after which the dimensionless scattering function for an unpolarized Bessel beam is obtained. The dimensionless scattering function is applicable to spherical scatterers of any size on the beam axis or near it. Through numerical simulations, we demonstrate that extreme points exist in the direction or neighboring direction of the conical angle for spherical scatterers on the beam axis, whereas the existence of extreme points depends on the ratio between the spherical scatterers size and central spot size of the Bessel beam.

Computation and analysis of the Bessel beam scattering by a submerged elastic sphere

Taking an elastic sphere for example, the acoustic scattering of a submerged object illuminated by a Bessel beam is studied. The partial wave series representation for an elastic sphere has been extended to the case of Bessel beam scattering. Referring to the scattering of a plane wave, the peak to peak intervals in backscattering form function caused by the interference of the specular wave and the Franz wave have been analyzed in geometry. The influence of the characteristic parameterβ of a Bessel beam on the peak to peak intervals has been indicated, and a predictive formula of the the first time. Meanwhile the elastic scattering peak to peak intervals has been established for of each partial wave has been separated based on the Resonance Scattering Theory. The influence of β on the pure elastic resonance has been studied further. The results show that selecting specific β can reduce the contribution of a certain partial wave. Therefore the resonance at the corresponding frequency and the nearby region in the backscattering is remarkably suppressed. The work of this paper could be helpful to the applications of Bessel beams on the acoustic detection of submerged objects.

偏心球对贝塞尔波束的散射特性研究

基于广义洛伦兹米理论,研究了偏心球粒子对在轴入射零阶贝塞尔波束的散射。利用球矢量波函数展开,给出了空间各区域电磁场的展开形式以及远场散射场表达式,并利用电磁场的边界条件,给出了各系数关系形式。通过与面积分方程方法的数值结果对比,验证了理论的正确性。数值分析了波束锥型角、偏心球内核介质折射系数、偏心距、内核半径等波束、偏心球参数对远场散射的影响。

高阶矢量贝塞尔涡旋波束的单球形气溶胶粒子散射特性研究

运用广义洛伦兹-米散射理论(GLMT)研究了高阶矢量贝塞尔涡旋波束的单球形气溶胶粒子的散射特性,将直角坐标系下沿z轴方向传播的贝塞尔波束的电磁场强度各分量表达式转化成球坐标系下各个分量的表达式,使用GLMT中的积分局部近似法计算贝塞尔涡旋波束的波束因子,进而计算在轴入射的高阶矢量贝塞尔涡旋波束的单球形气溶胶粒子散射。以硝酸铵球形粒子为例,通过数值计算,讨论了不同拓扑荷数和半圆锥角矢量贝塞尔涡旋波束与气溶胶粒子作用的微分散射截面随散射角变化的分布,以及消光截面、散射截面和吸收截面随均匀球形气溶胶粒子尺寸参数的变化情况。结果表明,随着贝塞尔涡旋波束拓扑荷数的增大,粒子微分散射截面值逐渐减小;拓扑荷数一定的贝塞尔涡旋波束随着光束半圆锥角的增大,消光截面、散射截面和吸收截面各值整体上趋向减小。