MSC Adams用户自定义子程序在卫星姿控系统仿真分析中的应用

利用MSC Adams中用户自定义子程序方法建立卫星姿态控制系统的模型,对卫星附件在轨展开过程进行卫星姿态动力学仿真分析.     

视频虚拟键盘中的按键自定义问题研究

目前,电子数码产品的功能越来越强大,功能的复杂直接导致了操作的繁琐.为此,对视频虚拟键盘中的按键自定义问题进行了细致的研究,提出一种基于视频图像处理技术的用户自定义标示符方法,以求针对不同用户提供不同的操作方式.该方法利用电子数码设备附加的摄像设备,记录用户手指移动轨迹,由此识别出用户标识区域,并为该区域赋予相关信息的功能,即用户对于该区域的点击被识别为指定的按键操作,从而实现用户自定义虚拟键盘的功能.最后对该方法进行了实验验证与分析,证明该方法具有技术可行性,并在操作简单方便和成本控制方面有较好表现.     

基于加密分割的位置隐私保护方法

基于位置的服务(location-based services,LBS)由于存在隐私泄露问题已越来越成为隐私保护领域中的热点.针对用户协作的隐私保护方法无法为参与用户提供自定义匿名度功能,且对协作用户的隐私保护效力不足,提出了一种基于加密分割的位置隐私保护方法.该方法采用分布式结构,通过用户对查询信息进行分割、加密、交换混合,满足了用户自定义匿名度需求,提高了用户间的隐私安全性,同时,采用假名方法抵御长期统计的攻击方式.通过理论分析和实验结果表明所提出的方法具有较好的隐私保护效果.     

LQ—1600K“用户自定义字符”的图形化设计

现在办公自动化中使用最为普遍的打印机，恐怕就要算Epson的LQ－1600K了。LQ－1600K除了具有易操作、高可靠性和高质量等优点外，还具有“用户自定义字符”这一最富有特色的功能。“用户自定义字符”功能的主要目的是能够定义并打印用户自己设计的字符。正如其随机手册上说的——“用户可以设计一套全新的字母表或字样，自制一些适用于数学、物理等多种学科的专用字符，甚至还可以由用户自定义一个图案”。事实上，随机字库的汉字和字符在大多数情况下已经足够了，然而令人遗憾的是LQ－1600K没有提供图形库，在很多需要图形来美化打印效…     

网格用户管理体系结构的研究与设计

在网格系统的研究中，相对于资源(客体)管理而言，对网格用户(主体)管理的研究相对薄弱．网格用户的表示、命名以及网格用户管理的功能及体系结构的确定对实现一个实用的网格用户管理系统非常重要．首先论述了网格用户管理的特点、范围及内容，提出了网格用户的表示及命名方法，描述了网格用户的全生命周期状态图．在此基础上提出了一个网格用户管理体系结构，并实现了一个实用系统VegaGUS．最后给出了该实用系统的性能指标及评价，该系统有效地解决了网格用户管理的关键问题．     

基于NiosⅡ用户自定义指令的AES算法实现

提出一种采用AES算法和RSA算法相结合的混合加解密算法,并采用Altera的NiosII软核用户自定义指令功能实现该混合加解密算法。文中主要对该混合加解密算法中的AES算法进行了设计、论述,通过对AES算法的轮变换和密钥扩展两部分算法的分析,并在NiosII软核上实现其自定义指令,就可以使用简单的几条语句快速地实现AES算法,大大地提高了算法实现的灵活性,最后给出了使用NiosII用户自定义指令实现与使用VerilogHDL实现AES算法效果的对比分析。     

FANUC数控宏程序在编程中的应用

在数控编程中,当刀具反复进行同一切削动作时,虽然使用子程序效果比较好,但若使用用户宏程序的话,就可以使用运算指令、条件转移等功能了.用户宏程序适合于编制更简单、通用性更强的程序,并且与子程序一样,在加工程序中用简单的命令就可以调用.     

基于NiosⅡ用户自定义指令的AES算法实现

提出一种采用AES算法和RSA算法相结合的混合加解密算法,并采用Altera的NiosII软核用户自定义指令功能实现该混合加解密算法。文中主要对该混合加解密算法中的AES算法进行了设计、论述,通过对AES算法的轮变换和密钥扩展两部分算法的分析,并在NiosII软核上实现其自定义指令,就可以使用简单的几条语句快速地实现AES算法,大大地提高了算法实现的灵活性,最后给出了使用NiosII用户自定义指令实现与使用VerilogHDL实现AES算法效果的对比分析。     

基于GPU的加速网格求交算法分析与实现

随着近几年图形硬件的飞速发展,图形处理器(Graphics Processing Unit,简称GPU)的功能越来越强大.现代GPU具备了一定的可编程功能,此功能允许以用户自定义的功能替换原来固定图形流水线中某些模块原有的功能,这使得GPU在功能上更像一个通用处理(General Purpose GPU,GPGPU),针对地质建模软件中频繁使用的三角网格面求交算法进行了研究.通过对三角网格求交问题的具体分析及对图形硬件的分析,利用图形硬件的特殊设计和高浮点运算速度,高内存带宽,实现了高效的基于可视化查询方法计算网格求交的算法.     

功能梯度材料热传导问题的仿真

针对功能梯度材料的热传导问题,提出了一种新的无网格数值算法。首先,从功能梯度材料的二维稳态热传导方程出发,通过引入变量代换,系统地推导了指数型、二次型和三角函数型功能梯度材料热传导方程的基本解。然后基于基本解构造了无网格方法求解功能梯度材料的稳态热传导方程,进而对功能梯度材料的温度分布情况进行仿真。最后,分别以指数型、二次型及三角函数型功能梯度材料板为例,对其温度分布进行仿真。结果表明无网络算法是正确、有效的,且无需网格划分,有理论简单、易于程序实现等优点。     

Dynamic pre-processing software for the hyperviscoelastic modeling of complex anisotropic biological tissue materials

Soft biological tissues are complex structures with intricate microstructure, which is usually highly anisotropic. These tissues are typically composed of multiple fiber bundles, which may have a unique orientation, defined for each single element in a large finite element mesh for modeling complex structures such as the human heart. These complex orientations can be difficult to define in an ABAQUS input deck using existing methods. In general, each change in fiber orientation requires a “new material” to be defined. Using the conventional method of defining material properties in ABAQUS is time consuming and, as a result of the large number of input constants required, is prone to errors. It is therefore deemed desirable to create a new means of material property input. The ⁷CC Cards method presented partitions the material property data for a time-dependent, anisotropic, material response into discrete card images, and thus eliminates much of the redundant data input required by ABAQUS. This strategy is also more efficient, both computationally and from the viewpoint of user time required.     

Contour plotting for function specified at nodal points of a mesh based on a set of irregular profiles

A FORTRAN IV subroutine entitled CMAP is provided for determining the contour lines of a function specified on a mesh made by a set of irregular profiles. The subroutine is independent of the support medium holding the mesh, thus it is possible to work on a large set of data with a small computer.     

基于Abaqus子程序的高分子材料本构关系实现

对于高分子材料的仿真,业界一般使用经典的弹塑性本构模型来描述其应力-应变关系,但其真实的应力-应变关系与经典的弹塑性本构模型存在一定差异,从而导致仿真与实际测试之间的差异.Abaqus提供UMAT/VUMAT子程序接口,让用户可以自己构建新的材料本构模型.通过撰写新的材料本构子程序实现高分子材料应力-应变关系在仿真中的准确描述,减少仿真与测试之间的差异.同时,在卸载段可以通过卸载标志符的选择定义不同的卸载路径,方便用户使用.     

基于SiPESC平台用户材料子程序的UMAT实现

针对复杂环境和加载条件下的材料本构模型,参照Abaqus所提供的用户材料子程序UMAT接口,实现基于SiPESC平台弹塑性分析功能的UMAT本构模型插件封装及调用.采用Ｃ++面向对象程序设计方法编制inp文件读取功能插件,实现Abaqus计算模型向SiPESC平台数据库的导入.将不同UMAT单独编译成动态库,同时利用工厂设计模式,实现不同材料本构模型的动态替换和调用.该设计模式可方便添加本构模型,具有一定的通用性、开放性和可扩展性.数值算例的验证表明基于SiPESC平台的UMAT的有效性.     

Skeleton-driven surface deformation through lattices for real-time character animation

In this paper, an efficient deformation framework is presented for skeleton-driven polygonal characters. Standard solutions, such as linear blend skinning, focus on primary deformations and require intensive user adjustment. We propose constructing a lattice of cubic cells embracing the input surface mesh. Based on the lattice, our system automatically propagates smooth skinning weights from bones to drive the surface primary deformation, and it rectifies the over-compressed regions by volume preservation. The secondary deformation is, in the meanwhile, generated by the lattice shape matching with dynamic particles. The proposed framework can generate both low- and high-frequency surface motions such as muscle deformation and vibrations with few user interventions. Our results demonstrate that the proposed lattice-based method is liable to GPU computation, and it is adequate to real-time character animation.     

Feature‐Preserving Surface Completion Using Four Points

We present a user‐guided, semi‐automatic approach to completing large holes in a mesh. The reconstruction of the missing features in such holes is usually ambiguous. Thus, unsupervised methods may produce unsatisfactory results. To overcome this problem, we let the user indicate constraints by providing merely four points per important feature curve on the mesh. Our algorithm regards this input as an indication of an important broken feature curve. Our completion is formulated as a global energy minimization problem, with user‐defined spatial‐coherence constraints, allows for completion that adheres to the existing features. We demonstrate the method on example problems that are not handled satisfactorily by fully automatic methods.     

Meshing complexity: predicting meshing difficulty for single part CAD models

This paper proposes a method for predicting the complexity of meshing computer aided design (CAD) geometries with unstructured, hexahedral, finite elements. Meshing complexity refers to the relative level of effort required to generate a valid finite element mesh on a given CAD geometry. A function is proposed to approximate the meshing complexity for single part CAD models. The function is dependent on a user defined element size as well as on data extracted from the geometry and topology of the CAD part. Several geometry and topology measures are proposed, which both characterize the shape of the CAD part and detect configurations that complicate mesh generation. Based on a test suite of CAD models, the function is demonstrated to be accurate within a certain range of error. The solution proposed here is intended to provide managers and users of meshing software a method of predicting the difficulty in meshing a CAD model. This will enable them to make decisions about model simplification and analysis approaches prior to mesh generation.     

Elastic mesh technique for 3D BIM simulation with an application to underwater explosion bubble dynamics

The proposed elastic mesh technique (EMT) is a mesh regulation technique, which is based on the assumption that the segments of a mesh are elastic. EMT can be employed in conjunction with the boundary integral method (BIM) for the simulation of three-dimension bubble dynamics in which problems relating to severe mesh distortion as the bubble evolves are a common occurrence. With EMT, the mesh is advanced not by the material velocity, but the optimum shift velocity obtained by minimizing the total elastic energy stored in every segment of the mesh at each time step. In doing so, the prohibitively small time stepping associated with small meshes without EMT in order to maintain numerical stability is mitigated to a large extent. An important feature is that the EMT scheme accords the user the flexibility to implement a non-uniform optimum constitutive relation governing the elastic behavior of mesh segment and which can be further varied with time. Tests were performed for an underwater explosion bubble exhibiting the dynamics of strong jet development with and without EMT for comparison, and the consideration of incorporating EMT as a hybrid system serving as an alternative to the required mesh refinement which is computationally intensive. A full three-dimension simulation of explosion bubble(s) and in the presence of the free surface were further carried out to elucidate the associated flow physics.     

A systematic approach to unstructured mesh generation for ocean modelling using GMT and Terreno

A systematic approach to unstructured mesh generation for ocean modelling is presented. The method optimises unstructured meshes to approximate bathymetry to a user specified accuracy which may be defined as a function of longitude, latitude and bathymetry. GMT (Generic Mapping Tools) is used to perform the initial griding of the bathymetric data. Subsequently, the Terreno meshing package combines automated shoreline approximation, mesh gradation and optimisation methods to generate high-quality bathymetric meshes. The operation of Terreno is based upon clearly defined error measures and this facilitates the automation of unstructured mesh generation while minimising user intervention and the subjectivity that this can introduce.