Numerical modeling of the InAs quantum dot with application of coordinate transformation and the finite difference method

In order to resolve the three dimensional Schrödinger equation, we report in this paper a method providing sufficient accuracy, stability and flexibility with respect to the size and shape of the quantum dot. This numerical method, already used in the two-dimensional case, is based on a suitable combination of coordinate transformation and the finite difference method. It provides an efficient and simple approach for the energy and wavefunction calculations of quantum nanostructures. The proposed method is used to investigate the electron and hole energy levels as well as their wave functions in InAs/GaAs strained and unstrained quantum dots with the aim to attain the 1.55 μm wavelength with realistic dot size. The optical transition energies and the oscillator strengths are also studied. The obtained results are in agreement with several previous works.     

Calculating modes of quantum wire and dot systems using a finite differencing technique

In this paper the Schrödinger equation of both a quantum wire and a quantum dot are solved using a finite difference approach. It is demonstrated that the method is valid for the simple case of an infinitely deep quantum wire, where the solutions obtained are within 0.25 meV of the analytical solutions. The method is then used to calculate the eigenenergies of a triangular wire with finite barriers. The eigenenergies of the more complex case of a pyramidal quantum dot were then calculated using this method. The method is compared to an eigenvalue method in terms of memory usage, time requirements and the numerical solutions. It is shown that this method has the advantages of being relatively fast, usable with any wire geometry and any potential profile. In addition, the demand on computer memory varies linearly with the size of the system under investigation.     

A robust numerical method for self-polarization energy of spherical quantum dots with finite confinement barriers

By utilizing a novel three-layer dielectric model for the interface between a spherical quantum dot and the surrounding matrix, a robust numerical method for calculating the self-polarization energy of a spherical quantum dot with a finite confinement barrier is presented in this paper. The proposed numerical method can not only overcome the inherent mathematical divergence in the self-polarization energy which arises for the simplest and most widely used step-like model of the dielectric interface, but also completely eliminate the potential numerical divergence which may occur in the Bolcatto-Proetto's formula [P.G. Bolcatto, C.R. Proetto, Partially confined excitons in semiconductor nanocrystals with a finite size dielectric interface, J. Phys. Condens. Matter 13 (2001) 319-334], an approximation method commonly employed for more realistic three-layer dielectric models such as the linear and the cosine-like models frequently mentioned in the literature. Numerical experiments have demonstrated the convergence of the proposed numerical method as the number of the steps used to discretize the translation layer in a three-layer model goes to infinity, an important property that the Bolcatto-Proetto's formula appears not necessarily to possess.     

Effect of band structure discretization on the performance of full-band Monte Carlo simulation

Full-band Monte Carlo simulation offers a very accurate simulation technique, but is often limited by its high demand on computation time. The advantage of a numerical representation of the band structure over an analytical approximation is the accurate representation of the energy bands in the high energy regime. This allows accurate treatment of hot carrier effects in semiconductors. In this work we outline an efficient full-band Monte Carlo (FBMC) simulator and investigate the accuracy of simulation results for different meshing approaches for the Brillouin zone.     

基于向量模的坐标变换不变性的碎片匹配方法

根据向量模在平移、旋转等坐标变换中具有不变性的特征,给出了一种新的碎片匹配算法。先对碎片图像进行预处理得到图像边界,然后计算每条边界曲线上任意两点构成的向量的模（欧式距离）,并按边界点顺序排列向量模值,比较向量模值,找出最长的匹配段就是两个碎片的匹配边。在拼接时,同样根据模的这一特征,已知点坐标和模值,解方程组即可求得其余边界点在目标坐标系的坐标。该方法原理简明,编程容易,计算速度快。最后通过实验验证了该方法的有效性。     

On numerical stabilization in the solution of Saint-Venant equations using the finite element method

Solving the Saint-Venant equations by using numerical schemes like finite difference and finite element methods leads to some unwanted oscillations in the water surface elevation. The reason for these oscillations lies in the method used for the approximation of the nonlinear terms. One of the ways of smoothing these oscillations is by adding artificial viscosity into the scheme. In this paper, by using a suitable discretization, we first solve the one-dimensional Saint-Venant equations by a finite element method and eliminate the unwanted oscillations without using an artificial viscosity. Second, our main discussion is concentrated on numerical stabilization of the solution in detail. In fact, we first convert the systems resulting from the discretization to systems relating to just water surface elevation. Then, by using M-matrix properties, the stability of the solution is shown. Finally, two numerical examples of critical and subcritical flows are given to support our results.     

Characteristic modeling and the control of flexible structure

Appropriate modeling for a controlled plant has been a remarkable problem in the control field. A new modeling theory, i.e. characteristic modeling, is roundly demonstrated. It is deduced in detail that a general linear constant high-order system can be equivalently described with a two-order time-varying difference equation. The application of the characteristic modeling method to the control of flexible structure is also introduced. Especially, as an example, the Hubble Space Telescope is used to illustrate the application of the characteristic modeling and adaptive control method proposed in this paper.     

径向加强肋-薄膜伞状天线结构动力学建模与数值仿真

大型空间可展开抛物面天线由于其特殊的应用价值,近年来广受人们关注.本文研究的径向加强肋-薄膜伞状天线是其中一种典型的非线性结构系统,为了掌握其在轨动力学特性,合理精确地建立径向加强肋-薄膜伞状天线的结构动力学模型至关重要.为描述径向加强肋-薄膜伞状天线物理模型中的预紧力问题,引入温度预应力等效方法解决天线结构模态的初始条件施加问题,通过有限元求解获得了其动力学特性,为径向加强肋-薄膜伞状天线的结构设计与力学研究提供了依据,并为其工程化实施奠定了理论研究基础.     

三维分子结构的制作、显示和格式转换

本文总结了各种三维分子结构在计算机和网络上显示与制作的方法,包括三维动画如3D Studio MAX、VRML、化学结构插件如MDL Chime Plugin、CS ChemOffice Plugin和HyperChem Plugin等、CML、Flash 3D动画、JAVA动画等,比较了他们制作和显示三维分子的优缺点,同时总结了各种三维分子结构格式的相互关系及转换方法,认为以通用的“mol”格式可以作中介可以较好地实现格式转换。     

Comparative investigation of reflection and band gap properties of finite periodic wideband artificial magnetic conductor surfaces for microwave circuits applications in X‐band

In this study, novel designs of artificial magnetic conductors (AMCs) for wideband operation are introduced. By using two techniques of the planar parasitic patches and stacked elements, AMC unit cells are achieved. The first design of the AMC unit cell is composed of four symmetric patches with two arms, which are coupled to a rhombic patch at the center. The second AMC design is configured of two stacked patches, which are connected together through the air spacing. The first and second AMC designs operate at the frequencies of 10.15 and 10.65 GHz with ±90° reflection phase bandwidths of 8 to 12.38 GHz (43.15%) and 8 to 12.90 GHz (46%), respectively, for X‐band operation. The proposed AMC unit cells present prominent features such as symmetric structures and wide bandwidths with distinct capabilities. To achieve an accurate evaluation of AMC performance, the reflection and band gap properties of the finite periodic AMC surfaces are investigated. The finite periodic arrays of the AMC reflectors are implemented and tested. The measured results show that they can be applied for wideband applications in microwave circuits and low profile antennas. The 15 × 15 AMC planar and stacked arrays under normal incidence operate at the frequencies of 9.89 and 10.25 GHz with the measured bandwidths of 7.85 to 12.02 GHz and 7.77 to 12.58 GHz, respectively. In addition, to identify the band gap properties of the finite periodic planar and stacked AMC arrays, the method of the suspended microstrip line is applied. For this purpose, the measured band gaps of the planar and stacked arrays include the ranges of 8.12 to 12.63 GHz and 7.81 to 12.10 GHz below ?20 dB, respectively.     

Lagrange子流形理论在约束力学系统正则变换和勒让德变换中的应用

Lagrange方程与Hamilton方程之间的勒让德变换理论和Hamilton方程的正则变换理论在分析力学中具有重要的地位,从局域坐标的角度很难找到勒让德变换和正则变换之间的相关性. 本文主要基于辛流形的Lagrange子流形理论从全局上给出正则变换理论和勒让德变换理论的统一几何解释,进而在几何力学的角度清晰的描述Hamilton系统的正则变换和Lagrange方程与Hamilton方程之间的勒让德变换的几何结构.     

Damage analysis and numerical simulation for failure process of a reinforced concrete arch structure

This work focuses on the implementation of damage mechanics model to explain and understand failure mechanisms of the concrete structures. A tensorial damage theory and an isotropic application to the arch ribs of a real bridge are presented. Two reinforced concrete arch ribs of a 28 year old bridge has been removed from the field to the laboratory. They were loaded up to failure in order to study the remaining strength of the structure. The damage model involves three independent parameters for simulating the damage behaviors of the concrete material. The damage theory—additional load—finite element method is developed to simulate numerically the failure process of the RC structures based on the proposed damage model. The predicted displacements, strains and failure mode of the RC arch are good agreement with the experimental results. The values of the three material parameters that describe the damage characteristics of concrete were obtained. The numerical calculations revealed the interested behaviors of concrete in a damaging process. The proposed damage model can be used effectively to describe the damage and fracture behaviors of concrete.     

最小二乘有限元法和有限体积法在CFD中的应用比较

为比较最小二乘有限元法（Least Square Finite Element Method,LSFEM）和有限体积法在CFD应用中的优劣,采用最小二乘法离散不可压N-S方程的有限元模型,得到正定对称线性系统,采用高效的预处理共轭梯度法求解方程组;利用LSFEM和基于有限体积法的FLUENT分别计算Kovasznay流动、定常二维和三维后台阶流动以及非定常圆柱绕流等4个实例并比较计算结果.结果表明,LSFEM比有限体积法的收敛性和精确性更好,在CFD领域的应用价值很高.     

An ontology-based analysis and semantics for organizational structure modeling in the ARIS method

This paper focuses on the issue of ontological analysis for organizational structure modeling in the ARIS method with the following contributions: (i) an interpretation of the language in terms of real-world entities in the UFO foundational ontology; (ii) the identification of inappropriate elements of the language, using a systematic ontology-based analysis approach; and (iii) recommendations for improvements of the language to resolve the issues identified.     

图结构在航空遥感图像特征点匹配中的应用

为了解决海上航空遥感图像拍摄目标及相机视角变化快,相似特征多导致的匹配不一致问题,并提高匹配算法的效率,提出了一种基于图结构的航空遥感图像特征点匹配算法。该特征匹配过程分为初始匹配和精确匹配两步,首先采用快速特征提取算法SURF进行特征提取并进行初始匹配,然后在精确匹配过程中充分考虑图像的局部空间结构及全局信息,建立[K]近邻图结构,用[K]近邻结构差异与点集的变换误差作为匹配的收敛条件,以解决图像目标发生变化而导致的[K]近邻结构不一致及[K]近邻结构相同时仍然存在干扰点两个问题,最终实现快速精确的特征匹配。     

A complete development process of finite element software for body-in-white structure with semi-rigid beams in .NET framework

At the conceptual design stage, simplified finite element (FE) model of body-in-white (BIW) structure focuses on its specific merit to provide early-stage predictions for detailed FE model of that. This paper exploits a semi-rigid beam element (SRBE) that consists of a beam element with two semi-rigid connections at the ends to simulate the flexibility of joint. Guyan reduction method condenses the SRBE as a super element. A special finite element software for structural modeling and analysis of BIW (SMAB) is developed in .NET framework. The Unified Modeling Language is employed to depict the classes and their relationship. The design patterns are identified and applied in the framework design to facilitate communication and system expansion. Microsoft DirectX and GDI+ implement graphics display of spatial BIW frame and planar thin-walled cross section. Based on multi-threaded technology in .NET, subspace iteration method is paralleled to speed up the mode analysis. As a result, the efficiency of the SRBE is demonstrated by a benchmarking automotive body. Multi-threaded parallel is effective and useful, especially for frequency optimization.     

A dissipative exponentially-fitted method for the numerical solution of the Schrödinger equation and related problems

In this paper a dissipative exponentially-fitted method for the numerical integration of the Schrödinger equation and related problems is developed. The method is called dissipative since is a nonsymmetric multistep method. An application to the the resonance problem of the radial Schrödinger equation and to other well known related problems indicates that the new method is more efficient than the corresponding classical dissipative method and other well known methods. Based on the new method and the method of Raptis and Cash a new variable-step method is obtained. The application of the new variable-step method to the coupled differential equations arising from the Schrödinger equation indicates the power of the new approach.     

A comparison of neural network and multiple regression analysis in modeling capital structure

Empirical studies of the variation in debt ratios across firms have used statistical models singularly to analyze the important determinants of capital structure. Researchers, however, rarely employ non-linear models to examine the determinants and make little effort to identify a superior prediction model. This study adopts multiple linear regressions and artificial neural networks (ANN) models with seven explanatory variables of corporation’s feature and three external macro-economic control variables to analyze the important determinants of capital structures of the high-tech and traditional industries in Taiwan, respectively. Results of this study show that the determinants of capital structure are different in both industries. The major different determinants are business-risk and growth opportunities. Based on the values of RMSE, the ANN models achieve a better fit and forecast than the regression models for debt ratio, and ANNs are cable of catching sophisticated non-linear integrating effects in both industries. It seems that the relationships between debt ratio and independent variables are not linear. Managers can apply these results for their dynamic adjustment of capital structure in achieving optimality and maximizing firm’s value.     

VRML和JAVA融合机制用于晶体结构建模

论述如何将JAVA和VRML技术结合起来模拟晶体结构,从融合机制和实现方法入手,重点探讨晶体结构数据在JAVA和VRML之间的传输过程,并以镁橄榄石(Mg2SiO4)三维晶体结构模拟为例,证明这种融合机制的可行性和优越性。