A 3D Finite Element Method for Flexible Multibody Systems

An efficient finite element (FE) formulation for the simulation of multibody systems is derived from Hamilton's principle. According to the classical assumptions of multibody systems, a large rotation formulation has been chosen, where large rotations and large displacements, but only small deformations of the single bodies are taken into account. The strain tensor is linearized with respect to a co-rotated frame. The present approach uses absolute coordinates for the degrees of freedom and forms an alternative to the floating frame of reference formulation that is based on relative coordinates and describes deformation with respect to a co-rotated frame. Due to the modified strain tensor, the present formulation distinguishes significantly from standard nodal based nonlinear FE methods. Constraints are defined in integral form for every pair of surfaces of two bodies. This leads to a small number of constraint equations and avoids artificial stress singularities. The resulting mass and stiffness matrices are constant apart from a transformation based on a single rotation matrix for each body. The particular structure of this transformation allows to prevent from the usually expensive factorization of the system Jacobian within implicit time--integration methods. The present method has been implemented and tested with the FE-package NGSolve and specific 3D examples are verified with a standard beam formulation.     

Impurity effects on photoluminescence in lateral epitaxially overgrown GaN

Using a two-photon laser-scanning microscope (LSM), the spectral and intensity variations of photoluminescence (PL) in a lateral epitaxially overgrown GaN film were mapped with submicron resolution. The PL results are correlated with the carrier-density variation obtained by confocal-Raman microscopy and the surface Fermi-level positions measured by scanning Kelvin-force microscopy. Near-bandgap emission spectra taken in the wing regions provide support for the previously proposed, compensated-impurity band, which arises from the incorporation of a high concentration of impurities, resulting in a carrier density of ∼10²⁰ cm⁻³.     

光干涉法测量微机械零件变形的研究

介绍了用光干涉法测量微加速度计零件变形的研究。将准直单色光投射入由一玻璃片和被测件之间形成的空气楔中，被测件表面和玻璃片底面反射的光发生干涉，由面阵CCD接收。用快速傅立叶变换（FFT）图像处理方法得到被测微悬臂梁的三维形变图。该方法可对微小器件的微位移作分辨办为10nm的测量，并直观的显示测量结果。     

用P507-磺化煤油溶液从硝酸溶液中萃取分离镅(锔)与稀土元素

测定了镅(锔)和轻稀土元素(La、Ce、Pr、Nd、Sm)在P507-磺化煤油和硝酸溶液中的分配比,确定了它们被萃取能力的顺序为:La相似文献   

高纯Eu_2O_3痕量元素的火花源质谱法测定

本文介绍了采用相对灵敏度因子法和同位素稀释法直接定量分析５Ｎ～６Ｎ的高纯Ｅｕ２Ｏ３，中２０多种痕量元素，大多数元素检测限为０．００ｘμｇ／ｇ，相对标准偏差在３０％以内。其中Ｃｕ、Ｚｎ采用同位素稀释法进行测定，相对标准偏差优于１０％。     

VLSI circuit reconstruction from mask topology

This paper discusses whether and how parasitic circuit elements must be included in the circuit simulator source file to obtain reliable simulation results. In particular, attention is paid to fabrication tolerances, wire capacitance (including fringing effects), wire resistance (dispersive line effects), coupling capacitances and capacitances associated with contacts and the aspect ratio of (non-rectangular) transistors.     

内蒙古红花沟金矿元素地化特征统计研究

用聚类分析、因子分析等数学地质方法对红花沟金矿莲花山矿区地表出露石英脉的元素地化特征进行了统计研究，确定了该区元素组合特征和找矿指示元素．提出了“组合元素预测法”，并用该方法对矿区石英脉含矿性进行了评价，取得了较好的地质效果．     

解Fuzzy关系方程的首列消元法

提出的首列消元法,方法简单,解题有序,消除了冗余运算,求解含有相同值的判别方程容易。     

稀土硬质合金刀具的切削性能与机理研究

稀土硬质合金材料是国家重点科研专题之一。本文通过系统的切削试验，研究该材料用作金属切削刀具的性能特点；并通过扫描电镜和能谱分析等先进手段，揭示其切削机理。还对其潜在的技术、经济效益进行了分析。