Finite Difference Calculations of InP/InGaAsP Optical Waveguides with Arbitrary Index Profile

A novel realization of non-uniform semivectorial finite difference method for the analysis of semiconductor optical waveguides is presented. By using non-uniform mesh structure computer time is saved while the accuracy is maintained. Also, the accuracy of the results increased by balancing the coefficient matrix without increasing computation time. Calculation of all eigenvalues (real and complex) is enabled by the method. The results of the calculation are compared for uniform and non-uniform methods and for two different optical waveguides. It is indicated that accuracy of the result is mainly dependent on the mesh refinement near the material interfaces. It is also indicated that for small mesh size using non-uniform method is necessary while uniform method is useless due to huge computer time and memory needed.     

The Effect of Radial Nodal Spacing on the Performance of a Mathematical Model of the Human Temperature Regulatory System

A mathematical model of the human temperature regulatory system has been constructed and tested. The number of finite difference nodes used to approximate the radial temperature distribution in each of the major body elements was independently varied. For exposure to warm environments, a four node unequally spaced configuration is adequate, while ten nodes unequally spaced are adequate in cold air environments.     

δ—函数源对有限元计算线天线电流分布的影响

本文以圆柱天线为计算对象,通过数值验证,分析研究δ-函数源对有限元计算线天线电流分布的影响.分析表明,馈点电流虚部随剖分疏密变化很大,特别是当δ-函数源位于计算区域端部时,这种现象更为明显.由此总结出可供借鉴的数值计算经验.     

The Finite Difference Solution of Microwave Circuit Problems

Using finite difference methods this paper shows how solutions may be obtained with the aid of a digital machine to a wide range of microwave circuit problems. These problems include the parameters of TEM-mode transrnission lines, the equivalent circuits of obstacles in these lines, the cutoff frequencies of the fundamental mode in a waveguide of very general cross section, and the equivalent circuits of obstacles in rectangular waveguide. Methods for deriving the appropriate finite difference equations are presented and optimum methods for their solution set out; singularities are also included in the treatment. The paper ends with a resume of some typical results to problems of practical interest which have been obtained by these methods.     

基于地址差额标记的光网络差别服务质量保证

提出了一种适用于哈密顿环保护(HCP)的地址差额标记(ADL)的光节点结构,并在此节点结构基础上实现了差别服务质量(QoS)的光网络保护策略。采用ADL光节点,保护机制可以在光层中直接完成,不需要光电转换。同时可实现对不同业务的QoS保证,进一步减少了对于备用保护波长的要求。分析了ADL光节点下的HCP网络阻塞情况,讨论了不同保护资源下的网络路由阻塞率Blocking—R和预保护资源不足造成的阻塞率Blocking—P以及它们之间的相互关联,并提出当Wp／W=1时基于ADL的HCP网络才能获得有效的服务质量保证。     

圆形槽波导中径向盘对阻抗的影响

应用时域有限差分法(FDTD)计算圆形槽波导中径向盘直径、厚度、位置对输入阻抗的影响。用非均匀网格和三角形网格来近似计算圆形槽波导的圆弧形金属边界附近的场值,用细网格计算径向盘中的场值,用完全匹配层(PML)模拟圆形槽波导的开放边界。最后由电压和电流的离散傅立叶变换的比值得到随径向盘直径、厚度、位置变化的输入阻抗。     

阵元间距对MUSIC算法的影响

本文概述了MUSIC算法,当阵元间距不大于载波半波长时,通过分析得出MUSIC算法空间分辨率随阵元间距增大而提高,并推导阵元间距与MUSIC算法性能的定量关系;当阵元间距大于载波半波长时,讨论空间谱可能出现虚假谱峰的情况,并提出提取真实谱峰的方案.最后通过计算机模拟仿真验证文中结论.     

磁悬浮径向轴承的三维有限元分析

应用ANSYS 10.0软件对磁悬浮径向轴承进行三维有限元仿真与计算分析,得出磁悬浮径向轴承磁力线、磁感应强度和电磁力在轴承中的分布.最后根据磁轴承线圈的两种绕线方式分析其磁场,并据此分析径向磁力轴承的几个特点,为径向磁悬浮轴承的优化和控制系统的设计提供了一定的依据.     

环境辐射对红外辐射温差的影响

根据红外辐射理论,结合实际红外测温原理,通过推导红外测温公式,得到了两种物体间的红外辐射温差计算公式,总结了红外辐射温差随环境温度变化的规律,并完成了相关实验.着重对两种发射率不同的物体在同一热力学温度下的红外辐射温差进行了研究,结果发现辐射温差与物体热力学温度和环境温度有重要关系,物体热力学温度与环境温度相差越大,物体间的辐射温差就越大.另外,在一定情况下发射率低的物体比发射率高的物体辐射温度高.研究结果有利于指导操作员更好地使用红外热像仪和更加灵活、准确地判别目标.     

The Use of Interpolation in Improving Finite Difference Solutions of TEM Mode Structures

A finite difference potential solution to a TEM mode transmission line cross section may be used to define a continuous potential function, leading to an upper bound for the capacitance. The accuracy of the capacitance calculation is shown to depend on the potential function fitted. A method is developed for interpolating a suitable potential function; in the cases considered, the use of this potential function gave capacitance solutions with an error approximately one-fifth that obtained using the usual methods.     

飞秒激光扫描不同温度下的硅片诱导形成微结构的差别

不同温度下利用钛宝石激光器输出的飞秒激光脉冲(脉宽42fs,中心波长800nm,最大单脉冲能量3.6mJ),通过扫描方式在硅表面诱导产生表面微结构。采用光学显微镜和扫描电镜观察飞秒激光诱导硅表面微结构的形貌,发现不同温度下硅片表面形成的微结构区域和形貌出现明显的差异。根据观测结果,分析比较了不同温度条件下硅材料微结构形成的能量阈值。随着温度升高,形成的微结构区域减小,飞秒激光诱导形成硅表面微结构的能量阈值升高。这对于研究飞秒激光与物质的相互作用有一定的参考价值,也能对将来实现硅表面微结构的制作提供参考。     

基于有限元方法的径向肋天线主肋热变形分析

根据径向肋天线主肋的三维实体模型,运用ANSYS参数化设计语言（APDL）建立了径向肋天线主肋的有限元模型。基于ANSYS软件采用有限元分析方法对径向肋天线主肋进行热变形分析,获得了径向肋天线主肋最大变形值与温度梯度的关系,以及径向肋天线主肋两侧面和上、下表面的最大变形值,其结果对径向肋天线主肋的优化设计具有较大的指导...     

基于时域有限差分法的谐振腔分析

用时域有限差分算法处理Cuccia腔圆周边界时,提出了一种圆周边界多边形网格近似处理技巧,与台阶近似相比,提高了计算精度。通过对谐振频率随腔体尺寸变化定性关系的研究,分别得到了谐振频率．f=2．5GHz时的几组Cuccia腔的尺寸,并用微扰法算出了固有品质因数Qo,Cuccia腔在尺寸大小、固有品质因数以及场的均匀性良好。根据优化得到的参数设计制作了Cuccia腔,通过实验测得谐振频率f=2．24GHz,与计算结果基本相符。     

基于有限差分的带间级联结构理论研究

利用前后向有限差分算法,对锑化物带间级联激光器有源区结构InAs/GaSb/AlSb的电子态进行了理论计算与分析。研究了哈密顿量算符序、有效质量参数修正、内界面态对结构能态及波函数的影响。分析表明,导带有效质量参数取正值可以在两种算符序下有效抑制伪解产生,Burt-Foreman算符序下的跃迁能量更为合理。对于内界面采用缓变假设后,其跃迁能量计算值略高于陡变界面下的计算结果,二者的波函数在界面附近差异不明显。     

机载平台径向加速度的无模糊相差检测

在由短基线相差测向严格解给出了相移与频移之间的函数关系之后,导出了一个基于相差和辐射频率测量的信号波长解析公式。随后,通过模拟比较,采用合并等值项的方法对解析公式进行了简化。对简化解的误差分析表明,对于分米波信号,且在实测频率的测量误差大于数兆赫的情况下,由基于短基线相差测量的新方法所得到的波长测量误差可小于 1mm。这可能是至今为止最具有工程应用价值的方法。     

窄相关对伪码测距影响的研究

根据理论分析,相关间隔是影响伪码测距的重要因素。窄相关作为导航接收机研制过程中的主要技术手段,它可以抑制由热噪声带来的测量误差。通过对测量误差建立数学模型分析,得出了窄相关减小测量误差与信号双边前端带宽的关系。通过MATLAB仿真,验证了窄相关对测量误差的贡献是受信号双边前端带宽约束的结论。当信号双边前端带宽固定时,窄相关对测量误差的贡献固定。同时,给出了窄相关的实现条件。为窄相关在工程应用中的应用提供了理论依据。     

不同p电极下InGaN太阳能电池性能研究

利用MOCVD方法在蓝宝石衬底上生长InGaN量子阱结构太阳能电池,并制作出了不同间距和形状的指叉形状p型电极。通过实验对比发现,随着指叉间距的减小,电极面积增加,光吸收面积减小,从而减少了光电流的产生,使得电池效率退化。另据实验发现,由于器件MESA边缘有着更强的电场,相同指叉密度下,将电极制作在器件边缘可取得更好的电池性能。     

A Study on the Finite Difference Approach of the Surface Laplacian

The surface Laplacian of bioelectrical activity was first applied to the Electroencephalogram (EEG) by Hjorth[1]. In the field of ECG, the body surface Laplacian mapping was also developed to provide better spatial resolution than the body surface potential distribution[2]. There are generally two kinds of estimation of surface Laplacian: local methods and global methods. The former calculate the difference of potentials recorded from neighboring electrodes[1]. The latter are based on the…     

排列间距对均匀阵列宽角扫描性能的影响

研究并验证了阵元间距对均匀阵列宽角扫描性能的影响。首先分析并讨论了均匀线阵和面阵阵因 子在宽角扫描区域内的变化规律,研究表明:对于均匀线阵,阵因子对宽角扫描体现“过有利”特性,此时选取宽波束 有源单元方向图单元组阵,便能完成宽角扫描;对于均匀面阵,阵因子对宽角扫描体现“欠有利”特性,此时,阵元间 距的选取对面阵宽角扫描至关重要。据此,提出一款新型磁流元天线验证上述结论,该磁流元天线在xoz 面具有 138°的波束宽度,所组成的16 元线阵和64 元平面阵分别实现了75°和65°的扫描。文中的研究结果可为宽角扫描 相控阵提供理论指导和设计便利。     

The Influence of Finite Bandwidth on the Capture Effect in FM Demodulators

In this paper a formula is derived for the capture ratio of an FM demodulator of which the finite bandwidth has been taken into account. The results obtained in a numerical example are in complete agreement with the measurements made on a physical detector.