基于广角FD-BPM的PML边界处理方法

本文提出了基于三阶Padé近似广角有限差分光束传输法(FD-BPM)的简单有效的完美匹配层(PML)边界处理方法.分别给出了该方法应用于斜波导和多模干涉(MMI)数值模拟的结果,并与用完全透明边界条件处理的模拟计算结果进行了比较.本文最后对基于广角FD-BPM的PML边界处理方法进行了优化.     

SEM modeling with singular moment matrices Part III: GLS estimation

We discuss generalized least squares (GLS) and maximum likelihood (ML) estimation for structural equations models (SEM), when the sample moment matrices are possibly singular. This occurs in several instances, for example, for panel data when there are more panel waves than independent replications or for time series data where the number of time points is large, but only one unit is observed. In previous articles, it was shown that ML estimation of the SEM is possible by using a correct Gaussian likelihood function. In this article, the usual GLS fit function is modified so that it is also defined for singular sample moment matrices S. In large samples, GLS and ML estimation perform similarly, and the modified GLS approach is a good alternative when S becomes nearly singular. Both GLS approaches do not work for N = 1, since here S = 0 and the modified GLS approach yields biased estimates. In conclusion, ML estimation (and pseudo ML under misspecification) is recommended for all sample sizes including N = 1.     

Numerical analyses of splice losses of photonic crystal fibers

Splice losses between a photonic crystal fiber (PCF) and a single mode fiber (SMF) or a PCF are numerically investigated by using finite element method (FEM) with the circular perfectly matched layer (PML). Results show that the splice loss between a SMF and a PCF with air holes completely collapsed can reach many times of that between a SMF and a PCF without air-hole collapse. We calculate the rotation losses between two identical PCFs of three kinds: large mode area, polarization maintaining and grapefruit. It is shown that for the large mode area PCF and the grapefruit PCF, the rotation losses are sensitive to the wavelength when the rotation angle is larger than zero degree. The non-circular mode field distribution is the main source of the rotation loss.     

Design of a Solid‐State Electrochemiluminescence Biosensor for Detection of PML/RARα Fusion Gene Using Ru(bpy)${{{2+\hfill \atop 3\hfill}}}$‐AuNPs Aggregations on Gold Electrode

A solid‐state electrochemiluminescence (ECL) biosensor based on special ferrocene‐labeled molecular beacon (Fc‐MB) for highly sensitive detection of promyelocytic leukemia/retinoic acid receptor alpha (PML/RARα) fusion gene was developed successfully using Ru(bpy)${{{2+\hfill \atop 3\hfill}}}$ /2‐(dibutylamino)ethanol (DBAE) as detecting pattern. Such a special sensor involves two main parts, an ECL substrate and an ECL intensity switch. The ECL substrate was made by modifying the complex of Ruthenium (II) tris‐(bipyridine) and Au nanoparticles (Ru(bpy)${{{2+\hfill \atop 3\hfill}}}$ ‐AuNPs) onto the Au electrode (AuE) surface. The molecular beacon probe in which the ferrocene tag could effectively quench the ECL of the Ru(bpy)${{{2+\hfill \atop 3\hfill}}}$ acted as ECL intensity switch. The molecular beacon probe was designed with special base sequence, which could hybridize with its complementary target DNA. In the absence of a target, the hairpin structure of the probe forced the ferrocene (Fc) into close proximity with the ECL substrate, thus reducing ECL intensity. Target binding allowed the Fc away from the ECL substrate and resulted in an obvious increment in ECL intensity due to the decreased Fc quenching effect. The effect of the amount of Ru(bpy)${{{2+\hfill \atop 3\hfill}}}$ and the mixing procedure of Ru(bpy)${{{2+\hfill \atop 3\hfill}}}$ and AuNPs solution on the fabrication of ECL film had been investigated. As a result, the change of ECL intensity had a direct relationship with the logarithm of PML/RARα fusion gene concentration in the range of 0.05–500 pM with a detection limit of 7 fM, and the developed biosensor possessed good molecular recognizability in human serum. Thus, the approach holds promise for the early diagnostics and prognosis monitoring of APL and other diseases.     

Complex frequency shifted convolution PML for FDTD modelling of elastic waves

The perfectly matched layer (PML) is nowadays considered as the best optimum absorbing boundary condition available. However, the PML with the classical stretching tensor has certain limitations. Strangely, these limitations have rarely been addressed in elastic wave modelling. For example, substantial reflections occur when strong evanescent waves are propagating parallel to the interface. To circumvent problems like this, the complex frequency shifted stretching tensor has been introduced in electromagnetic modelling. In this paper we show that the convolution PML with this stretching tensor as used in electromagnetic modelling can be adapted for elastic wave modelling. Numerical results of a model where the presence of evanescent waves is predominant show that the PML based on the complex frequency shifted stretching tensor can improve the performance of the absorbing boundary layer considerably.     

Simulation of Millimeter Wave Circulators by FEM with Unifrontal/Multifrontal Technique

The combination of unifrontal and multifrontal techniques is applied for solving a large, sparse, and unsymmetric system of linear equations resulting from the use of edge-based finite element method (FEM) for millimeter wave ferrite devices. The formulation of finite element method combined with the perfectly matched layers (PML) is given and the combined algorithm of unifrontal and multifrontal methods is described. The lower data movement of unifrontal method and the lower fill-in of normal multifrontal methods are combined for an algorithm with their features. The performance of typical waveguide junction circulators is analyzed and the calculated results are compared with those obtained from the literature.     

An optimal 25-point finite difference scheme for the Helmholtz equation with PML

In this paper, we present an optimal 25-point finite difference scheme for solving the Helmholtz equation with perfectly matched layer (PML) in two dimensional domain. Based on minimizing the numerical dispersion, we propose the refined choice strategy for choosing optimal parameters of the 25-point finite difference scheme. Numerical experiments are given to illustrate the improvement of the accuracy and the reduction of the numerical dispersion.     

大型复杂圆柱壳中高频振动噪声仿真计算方法研究

建立大型复杂圆柱壳中高频振动噪声仿真计算方法,对于解决船舶和飞机等大型复杂结构的辐射噪声预报问题具有重要意义。介绍了完美匹配层流固耦合计算方法,并成功应用于大型复杂双层圆柱壳的水下辐射噪声预报,相对于传统的声学流固耦合有限元和边界元计算方法,使外部流场域模型至少缩小了11/15。探讨了环频率和阻尼对圆柱壳结构振动传递的影响,提出了求解中高频声学问题时大型圆柱壳复杂结构仿真建模处理方法。数值算例表明,发展的PML方法和模型简化方法是合理的,可应用工程问题研究。     

基于Z变换的高阶完全匹配层实现

基于拉伸坐标完全匹配层(SC-PML)公式和Z变换方法,提出以非分裂场形式来实现具有多极点的高阶完全匹配层的高效算法,来截断时域有限差分(FDTD)网格.在吸收性能方面,高阶PML同时具有传统PML和复频率偏移完全匹配层(CFS-PML)二者的优点.提供的数值算例是二维TE极化电磁波与无限长且有限宽度的理想电导体(PEC)薄片的相互作用.仿真结果显示,高阶PML公式在衰减低频行波和隐失波及减少后期反射方面效果好,比传统SC-PML和复频率偏移的卷积完全匹配层(CPML)算法有更好的吸收性能.     

手性障碍电磁散射的PML有限元计算

该文建立了手性障碍电磁散射问题的二维模型, 给出问题的有限元分析, 并利用结合PML(perfectly matched layers)技术的有限元法进行数值模拟.