第三代短波自动链路建立系统特性分析及仿真实现

分析了第三代短波自动链路建立系统的工作特性及技术特点，并对系统仿真实现的原则及一些细节问题进行了较深入的探讨，同时对仿真实现中涉及的链路质量分析（LQA）算法进行了研究。     

Efficient and accurate approach for powder compaction problems

 In this paper, a new approach for powder cold compaction simulations is presented. A density-dependent plastic model within the framework of finite strain multiplicative hyperelastoplasticity is used to describe the highly nonlinear material behaviour; the Coulomb dry friction model is used to capture friction effects at die-powder contact; and an Arbitrary Lagrangian–Eulerian (ALE) formulation is used to avoid the (usual) excessive distortion of Lagrangian meshes caused by large mass fluxes. Several representative examples, involving structured and unstructured meshes are simulated. The results obtained agree with the experimental data and other numerical results reported in the literature. It is shown that, contrary to other Lagrangian and adaptive h-remeshing approaches recently reported for this type of problems, the present approach verifies the mass conservation principle with very low relative errors (less than 1% in all ALE examples and exactly in the pure Lagrangian examples). Moreover, thanks to the use of an ALE formulation and in contrast with other simulations, the presented density distributions do not present spurious oscillations. Received: 20 March 2002 / Accepted: 15 October 2002 The partial financial support of the Ministerio de Ciencia y Tecnología (grant number DPI 2001-2204) is gratefully acknowledged.     

Monitoring of CdTe atomic layer epitaxy using in-situ spectroscopic ellipsometry

Atomic layer epitaxy or ALE has proven to be useful for the growth of epitaxial layers of high uniformity, good quality, and well-controlled thickness. In this study, we have carried out in-situ monitoring during the atmospheric pressure ALE of CdTe on GaAs (100) substrates using spectroscopic ellipsometry (SE). The susceptor temperature, reactant partial pressures, as well as the flow and flush duration for each precursor are crucial process variables for ALE growth. Growth was carried out for 20–25 cycles under different sets of these process conditions during the experiment and in-situ SE was used to verify the presence of layer-by-layer growth, which enabled the quick determination of the process window. We observed ALE growth of CdTe at 300°C, supporting the explanation that the growth of CdTe occurs via a surface catalyzed decomposition of the Te precursor di-isopropyltelluride (DIPTe). Investigation of ALE mode growth behavior for different susceptor temperatures and DIPTe flush times indicated that the growth was limited by competition between desorption and reaction of the adsorbed DIPTe species on the Cd terminated surface.     

大型水陆两栖飞机入水压力测试技术研究

针对我国自主研制的大型水陆两栖飞机入水压力测试需求,首先分析了船底结构压力场及测试环境,通过 ALE 算法对 船底压力进行数值仿真,得出船底入水时刻压力分布;并结合基于改进 Wanger 模型的理论计算,确定入水压力最优测点,设计 基于非线性振动模型的信号传感方案;其次,分析机上改装实际工程难题,确定传感器改装工艺;最终通过飞行试验,验证了方 案的可行性及仿真模型的可靠性,测试结果与仿真结果最大偏差为 3. 4%,并为下一阶段测试方案的优化与完善提供依据。     

Multiple levels of cell by cell Adaptive Mesh Refinement in the Lagrangian step of the ALE code CORVUS

A multi-level cell by cell Adaptive Mesh Refinement (AMR) hydrodynamics capability has been developed for the Lagrangian step of the 2D Arbitrary Lagrangian Eulerian (ALE) code CORVUS. Connectivity arrays are used rather than a hierarchical data structure. We solve only on the dynamic unstructured mesh rather than on every level of a refinement hierarchy. The strength, artificial viscosity, slide and programmed burn methods have been generalised to work with AMR. Results are presented for a range of Lagrangian test problems.     

A Multiscale/stabilized Formulation of the Incompressible Navier–Stokes Equations for Moving Boundary Flows and Fluid–structure Interaction

This paper presents a multiscale/stabilized finite element formulation for the incompressible Navier–Stokes equations written in an Arbitrary Lagrangian–Eulerian (ALE) frame to model flow problems that involve moving and deforming meshes. The new formulation is derived based on the variational multiscale method proposed by Hughes (Comput Methods Appl Mech Eng 127:387–401, 1995) and employed in Masud and Khurram in (Comput Methods Appl Mech Eng 193:1997–2018, 2006); Masud and Khurram in (Comput Methods Appl Mech Eng 195:1750–1777, 2006) to study advection dominated transport phenomena. A significant feature of the formulation is that the structure of the stabilization terms and the definition of the stabilization tensor appear naturally via the solution of the sub-grid scale problem. A mesh moving technique is integrated in this formulation to accommodate the motion and deformation of the computational grid, and to map the moving boundaries in a rational way. Some benchmark problems are shown, and simulations of an elastic beam undergoing large amplitude periodic oscillations in a viscous fluid domain are presented.     

基于四阶混合累积量的自适应线谱增强器

将四阶累积量的递推算法推广到求正弦信号的混合四阶累积量，并提出了一种计算正弦信号四阶混合累积量的自适应线谱增强递推算法。该线谱增强器的结构为自适应FIR滤波器，当输入为含有高斯噪声的正弦信号且处于稳态时，滤波器的权系数与输入信号的四阶混合累积量的一维切片成正比，而与高斯噪声无关，从而使信号的线谱成份得到增强。仿真结果表明，该算法从高斯色噪声中提取正弦信号的能力优于二阶自适应短时相关增强器。     

下游圆柱涡致振动的升阻力特性及涡脱落模态分析

采用分块耦合方法结合任意拉格朗日欧拉法数值求解非定常二维不可压缩NS方程和Poisson
方程，分析了下游圆柱涡致振动的涡脱落模态以及升阻力特性。圆柱振荡频率比值为0.30～1.49。分析了
各种模态之间相互转化的跃迁点、升力与振幅间相位和模态间转化的关系，以及初始涡量形成的差异与模
态间转化的关系，研究了当涡脱落向下游移动时的演化和重组现象。研究发现，涡的横向和流向间距以及
涡街的大小随频率比的变化而变化；存在3种典型的涡脱落模态，即2P、2S 和 P+S模态，各种模态之间相
互竞争从而促进了流体与结构间相互作用的发展。