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。     

3-氨基喹啉与常用基体在MALDI-TOFMS测定天然提取植物多糖的比较

采用3-氨基喹啉(3-AQ)、二元基体3-AQ/2,5-二羟基苯甲酸(DHB)及常用于糖类物质测定的DHB和二元基体DHB/1-羟基异喹啉(1-HIQ)对一天然提取植物糖样进行了基体辅助激光解吸/电离飞行时间质谱(MALDI-TOF MS)分析。实验结果表明:此植物糖样由线形和环形聚己糖组成,其最大分子量至少达3000 Da;3-AQ与常用基体DHB及DHB/HIQ相比较,能提供更准确、更全面的样品组成及分子结构信息,且具有优越于常用基体解吸电离环状糖分子的能力。     

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

Low-cycle fatigue strength of 10GN2MFA steel with a single-layer corrosion-resisting coating produced by electroslag strip cladding

The method of testing the uniform single-layer corrosion resisting coating, produced by electroslag strip cladding on 10GN2MFA steel, on the resistance to low-cycle fatigue strength using special specimens is described. Tests were carried out at a temperature of 20 °C with the symmetric axial tension–compression loading cycle (R_e = –1) with the given amplitude of the parent and cladding metal. The tests were carried out in the strain amplitude range ε_a = 0.28–0.8%, the number of cycles to the initiation of a crack was N_i = 340–16,000 cycles, loading frequency f = (0.25–2.0). The area of formation of the cracks was recorded in the experiments. In most cases, the cracks formed in the heat-affected zone in the vicinity of the fusion line and propagated in both the parent and deposited metal. The results show that in the range of low-cycle fatigue for the investigated 10GN2MFA steel with a deposited layer, the calculation coefficient of the decrease of the cyclic strength of the metal with a deposited layer in relation to the fatigue curve for the carbon and alloyed steel with 0.8 ≤ σ_0.2/σ_B ≤ 0.9, the value φ_S = 0.68 should be used in the calculations.     

A comparative analysis of experts’ and consumers’ perceptions of regionality in Australian wine purchase decisions

This study provides insight into consumers’ perception of regionality when purchasing regional wine in terms of regional specialisation for style, volume of production of the wine style, quality of the wine, heritage of the wine region and the distinctiveness of the wine styles produced in the wine regions of Australia. Data were collected from 203 Australian wine consumers through an online survey. The study compares the results of this study with Easingwood et al. [2011. The drivers of wine regionality. Journal of Wine Research, 22(1), 19–33.] study on experts’ opinion of regionality drivers. This paper will expand knowledge on how consumer involvement levels impact decisions relating to purchasing regional wine. This study is of value to academics and wine practitioners alike. It contributes to the wine literature by providing a new perspective on consumers’ perception and draws attention to the risk of drawing conclusions about wine consumption based on experts’ opinions as being reflective of the average consumers’ purchase decision-making.