A methodology for quadrilateral finite element mesh coarsening

High fidelity finite element modeling of continuum mechanics problems often requires using all quadrilateral or all hexahedral meshes. The efficiency of such models is often dependent upon the ability to adapt a mesh to the physics of the phenomena. Adapting a mesh requires the ability to both refine and/or coarsen the mesh. The algorithms available to refine and coarsen triangular and tetrahedral meshes are very robust and efficient. However, the ability to locally and conformally refine or coarsen all quadrilateral and all hexahedral meshes presents many difficulties. Some research has been done on localized conformal refinement of quadrilateral and hexahedral meshes. However, little work has been done on localized conformal coarsening of quadrilateral and hexahedral meshes. A general method which provides both localized conformal coarsening and refinement for quadrilateral meshes is presented in this paper. This method is based on restructuring the mesh with simplex manipulations to the dual of the mesh. In addition, this method appears to be extensible to hexahedral meshes in three dimensions. Sandia National Laboratories is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy under Contract DE-AC04-94AL85000.     

Contributions of Dichotomic View of plasticity to seamlessly embed accessibility and adaptivity support in user interfaces

Recent legal changes have increased the need for developing accessible user interfaces in computer-based systems. In this sense, previously existing user interfaces are intended to be modified and new user interfaces are intended to be designed taking accessibility guidelines into account. Typically, model-based approaches have been used when developing accessible user interfaces or redefining existing ones. But the use of static models leads to the development of not dynamically adaptable user interfaces. Dynamic adaptation in accessible user interfaces is important due to the fact that interaction difficulties on people with disabilities may change through use. In this paper, we present some contributions that can be obtained from the application of the Dichotomic View of plasticity in the personalization of user interfaces. With the double perspective defined in this approach, it is intended to go further from a mere adaptation to certain user stereotypes, offering also a dynamic support to real limitations or difficulties users can encounter during the use of the UI. This goal is achieved analyzing user logs by an inference engine that dynamically infers modifications in the user interface to adjust it to varying user needs. A case study is presented in order to show how the guidelines and software support defined in the Dichotomic View of plasticity can be applied to develop a component for a particular system aimed at performing dynamic user interface adaptations with accessibility purposes. This approach includes some innovations that make it different from conventional adaptable mechanisms applied to accessibility in some important aspects.     

一类非线性系统基于滑模原理的模糊自适应控制

针对一类非线性系统，设计出了一种自适应控制方案，用模糊逻辑逼近非线性函数，根据滑模原理及李雅普诺夫函数设计出自适应控制器。然后，用模糊推理进行修正，以克服一般滑模控制具有的抖动现象，保证闭环系统的稳定性和跟踪误差收敛于零的某邻域内。     

Timoshenko精确法在悬臂梁适应性分析中的应用

利用有限元、小网格及其他数字技术求解端部加载悬臂梁的挠度及应力,这种方法证明了自适应程序的能力。但是在许多情况下,并没有符合这种精确求解方法的边界条件,因此影响了自适应程序的有效性。事实上,作为一个探索性的问题,这种精确解并不适用于自适应程序,因为完全精确的网格都是相同的。本文对此问题进行了讨论,强调了由于边界条件不匹配精确解而产生的一些错误,用一种更符合实际的悬臂梁模型与之做了对比;同时还讨论了程序的有效性。     

二维自适应有限元网格生成

自适应有限元网格生成是基于误差估计，自动进行有限元网格优化的一种策略。本文提出了一种基于单元误差估计的二维自适应有限元网格生成算法，并讨论了其实现过程。     

A Comparison of Mapping Algorithms for Hierarchical Adaptive FEM in Finite Elasto-Plasticity

The aim of this contribution is a comparison of different mapping techniques usually applied in the field of hierarchical adaptive FE-codes. The calculation of mechanical field variables for the modified mesh is an important but sensitive aspect of adaptation approaches of the spatial discretization. Regarding non-linear boundary value problems procedures of mesh refinement and coarsening imply the determination of strains, stresses and internal variables at the nodes and the Gauss points of new elements based on the transfer of the required data from the former mesh. The kind of mapping of the field variables affects the convergence behaviour as well as the costs of an adaptive FEM-calculation in a non-negligible manner. In order to improve the stability as well as the efficiency of the adaptive process a comparison of different mapping algorithms is presented and evaluated. Within this context, the mapping methods taken into account are

不同品系SPF鸡胚细胞对S191株麻疹病毒的适应性和敏感性比较

目的　了解我国现有SPF鸡蛋对我国S191株麻疹病毒的可利用性。方法　比较S191株麻疹病毒 ,在我国 3个SPF种蛋供应厂商的 5个品系、6种SPF鸡蛋成纤维细胞上的细胞生长、病变特征和病毒效价方面的差异。结果　LOHMAN F、LOHMAN M、SPAFAS品系SPF鸡蛋的细胞生长发育形态和细胞病变较好 ,其中以SPAFAS为最佳 ;病毒效价 ,SPAFAS和LOHMAN M系在大于 5 .0 0LogCCID50 /ml的高滴度区间的样本数分别达 70 %和 71.96 % ,其中LOHMAN M系的样本都在 4.38LogCCID50 /ml以上的较高水平。结论　我国SPF鸡蛋的SPAFAS和LOHMAN M品系均适宜于S191株麻疹病毒的培养及麻疹疫苗生产     

自适应人机界面的评价

1.引言 评价是人机系统设计中的一个重要组成部分。所谓评价是把软件系统按其性能、能、可使用性等方面与某种项定的标准进行比较,验证系统设计是否满足用户需求,检查所开的系统在功能和性能     

基于自适应阈值与基频检测的自发性口语音频分割算法

为了去除自发性口语音频中静音和噪音段的干扰,提高语音识别率和解码识别效率,提出一种音频能量自适应阈值计算方法。针对实时自动口语评测应用,设计了能量阈值自适应系数,该方法将根据能量阈值自适应系数动态地给每个考生的个人单次所有考试音频计算匹配一个能量阈值,以避免阈值选择和硬门限判决造成的误检。在基于自适应能量阀值的音频切分后,加入了基频检测步骤,以判别切分后所得音频段是否为噪声,从而最终分离出纯净的口语音频部分。实验结果表明,该算法能有效准确地切分音频,且鲁棒性较强。