A Spectral Coupled-Mode Formulation for Sound Propagation around Axisymmetric Seamounts

A spectral coupled-mode solution of the three-dimensional （319） acoustic field generated by a point source in the presence o[ an axisymmetric seamount is developed. Based on the same theoretical foundation as the for- mulation presented by Taroudakis [3. Comput. Acoust. 4 （1996） 101], the present approach combines a spectral decomposition in azimuth with a coupled-mode theory for two-way range-dependent propagation. However, the earlier formulations are severely limited in terms of frequency, size and geometry o[ the seamount, the seabed composition, and the distance between the source and the seamount, and are there/ore severely limited in regard to realistic seamount problems. Without changing the fundamental theoretical foundation, the present approach applies a number of modifications to the formulation, leading to orders of magnitude improvement in numerical efficiency for realistic problems. Therefore, realistic propagation and scattering scenarios can be modeled, including effects of seamount roughness and realistic sedimentary structure.     

一种小型高稳定电位差计专用电源

本文介绍了一种小型高稳定电位差计专用电源的原理及制作方法．该电源在大学物理实验中具有较广泛的使用价值。     

拟线性系统的概周期解的存在性

<正> 考虑拟线性微分方程系 dX/dt=A(t)X十f(t)十μF(X,t,μ),(1)其中A(t)是t的n阶连续方阵,x是n向量,f(t),F(X,t,μ)是各变量的n连续向量,μ真是小参数. 当A(t)是常数方阵,f(t),F(X,t,μ)是t的一致概周期向量函数,Coddington,Levinson,等人建立了(1)的周期解的存在定理.此可参考[1]和[2].对A(t)为常数方阵,f(t),F(X,t,μ)是t的一致概周期向量函数,更进一步建立了(1)的概周期解的存在定理.     

非线性奇异分数阶边值问题正解的存在性（英文）

本文基于锥上的不动点定理以及正则化和序列化技巧,得到非线性奇异分数阶边值问题正解的存在性.     

第三讲——反射全息图及全息图的复制

<正> 反射全息图在记录时物光和参考光自两侧投射在记录介质上,记录介质必须是厚的。记录介质的厚薄是相对于条纹面间距Λ而言,粗略的说δ>Λ是厚的,δ<Λ是薄的。用厚记录介质记录的全息图,称为体积全息图或厚全息图,用薄记录介质记录的全息图则称为平面全息图或薄全息图。一、体积全息图的几何结构用厚银盐干板记录体积全息图,在线性记录条件下,乳胶中的银粒密度是按余弦规律变化的层状结构。在透射全息图的情形,条纹面的形成如图3-1所示。设xoz面与入射面平行,     

MOCVD法制备BGaN薄膜

利用金属有机物化学气相沉积(MOCVD)技术,在蓝宝石衬底上进行了BGaN薄膜的外延生长,研究了生长厚度、温度、压力和B/Ⅲ比等条件对BGaN薄膜中B组分的影响。X射线衍射测试结果表明,降低生长温度、压力以及增加B/Ⅲ比,更有利于提高BGaN薄膜中B的并入效率。在800℃、30 kPa及B/Ⅲ比为30%的生长条件下,制备的BGaN薄膜中B组分最高,为6.1%。     

(~ρ)-混合误差下回归函数加权核估计的强相合性

设{yi}是固定在点{xi}的观察值,适合模型yi=g(xi) εi.其中g(x)是[0,1]上的未知函数,{εi}是均值为0的随机误差序列.文献中,在{εi}为独立同分布的条件下,通过构造新的函数gn(x),对g(x)进行了估计.论文将{εi}推广至(~ρ)-混合误差序列的情形,通过附加适当的条件和精细的计算,获得了用gn(x)估计g(x)的同样结论.     

深部岩体圆形巷道围岩松动圈形成机理数值试验研究

采用损伤力学和统计理论的单元本构模型,探讨深部岩体巷道围岩破坏规律, 利用岩石破裂过程分析软件RFPA$^{\rm 2D}$, 对深部 岩体中的圆形巷道的变形及非线性渐进破坏特征、巷道周边关键部位的位移和应力变化进行 了分析,研究了圆形巷道围岩松动圈的形成机理. 研究表明：巷道开挖后,其周边形成应力 集中带,随着围岩压力的持续作用,巷道周边产生塑性变形区,并沿径向形成裂纹;随着裂 纹的不断扩展,巷道周边出现松动破裂区,即松动圈. 产生破裂区后,应力集中程度减弱, 应力高峰点向远处转移.     

A geometric factor calculation method based on the isotropic flux assumption

One of the instruments onboard the China Seismic Electromagnetic Satellite （CSES） is the Low Energy Particle Detector （LEPD）. The primary objective of LEPD is to provide measurements of the fluxes, energy spectra and pitch angles of 100 keV to 10 MeV electrons and protons from 2 to 50 MeV in the Earth＇s magnetosphere. The geometric factor is one of the principle parameters of a detector, which converts the physical quantity-count rate to the particle quantity-flux. In this paper, we calculated the geometric factor of LEPD via computer modeling of an isotropic radiation environment. It was first demonstrated that the radiation intensity related should obey a cosine-law, then a general sampling method of generating this distribution via GPS of GEANT4 was explained. Furthermore, combined with flux normalization, a comparison of the geometric factor calculation of a set of 2-layer detectors with different shapes （cylinder, truncated cone and rectangle） was performed. Results show a generally good agreement between simulation and analytical calculations for the cylinder and truncated cone detectors, and the result of the rectangular one, for which there is no accurate analytical formula, is consistent with the previous simulated results by others. As a practical instance of the 2-layer rectangle detector, the geometric factor of LEPD is 10.336±0.036 m cm2·sr for 10 MeV proton and 8.211±0.032 m cm2·sr for 8 MeV electron.