带缝钢板剪力墙抗震性能的有限元分析

本文对带缝钢板剪力墙结构单元在不同地震波、不同地震加速度作用下的抗震性能进行了有限元对比分析。结果表明,对于同一种地震波,随着输入波加速度的提高,顶点位移增大;带缝钢板剪力墙结构单元在不种地震波作用下滞回性能良好,表明带缝钢板剪力墙结构单元具有良好的抗震性能     

Analysis of flow in the plate‐spiral of a reaction turbine using a streamline upwind Petrov–Galerkin method

The prediction of the flow field in a novel spiral casing has been accomplished. Hydraulic turbine manufacturers are considering the potential of using a special type of spiral casing because of the easier manufacturing process involved in its fabrication. These special spiral casings are known as plate‐spirals. Numerical simulation of complex three‐dimensional flow through such spiral casings has been accomplished using a finite element method (FEM). An explicit Eulerian velocity correction scheme has been deployed to solve the Reynolds‐average Navier–Stokes equations. The simulation has been performed to describe the flow in high Reynolds number (10⁶) regimes. For spatial discretization, a streamline upwind Petrov–Galerkin (SUPG) technique has been used. The velocity field and the pressure distribution inside the spiral casing reveal meaningful results. Copyright © 2000 John Wiley & Sons, Ltd.     

自紧密封U型管式换热器管板温度场的ANSYS分析

本文通过有限元分析得出了管板的温度场分布情况,验证了ASME规范中的表皮效应理论。在管板布管区域,管板大部分厚度上的温度都介于管程流体温度和壳程流体温度之间,只有在靠近管板表面处很薄的一层区域内的管板温度接近该侧流体的温度。在管板的不布管区域,管板沿厚度方向的温度由接近于管程流体的温度几乎呈线性降低至接近于壳程流体的温度。管板表层温度与流体温度的接近程度取决于对流传热系数,对流传热系数越小,管板表层温度与流体温度的差值越大。     

等截面纵横弯曲梁的分布传递函数法

建立了等截面纵横弯曲梁的分布传递函数求解模型。这种模型可以适应复杂的边界条件和外力情况,表达公式形式简单规范,便于计算机编程处理。对于复杂系统,根据外力和约束的情况,将其分成多个子系统,并依照分布传递函数方法分别对每个子系统进行处理,借助有限元方法,建立整个系统的平衡方程,最后得出问题的解。     

Theoretical study of sorption-induced bending of polypyrrole films

Polypyrrole films containing perchlorate were electrochemically synthesized and the bending and recovery motion of the films obtained has been investigated. It was found that the thickness of the film and ambient relative humidity (RH) were crucial to the motion of film: An increase of the film thickness decreased the displacement of the bending but increased the bending stress. On the other hand, an increase of the ambient RH decreased both functions. The motion of film was caused by the difference of expansion on both sides of the film owing to anisotropic sorption of water vapor, which could be expressed by the diffusion-limited bending model. The diffusion coefficients calculated from the bending and recovery motion at 25°C, RH 50% were 12.2 × 10⁻⁸ cm² s⁻¹ and 3.5 × 10⁻⁸ cm² s⁻¹, respectively. The maximum expansion of the film surface calculated from the bending curve was about 0.36%. © 1998 John Wiley & Sons, Inc. J. Polym. Sci. B Polym. Phys. 36: 2237–2246, 1998     

应用J积分断裂准则评价应力吸收层抗裂性能

应用弹塑性断裂力学J积分理论,采用半圆弯曲试验评价了3种级配应力吸收层的抗裂性能,发现采用断级配设计的应力吸收层具有良好的抗裂性能,结果表明断裂韧度JC可以用来评价应力吸收层的抗裂性能,由丰富沥青胶浆填充断级配骨架结构的级配设计,可以提高沥青混合料的抗裂能力。     

车牌识别系统中的关键技术研究

针对目前车牌识别系统中的多项关键技术做了改进。车牌识别系统主要包括车牌定位、字符分割和字符识别。首先提出了基于图像转换和数学形态学的车牌定位技术;然后结合垂直投影和连通域算法对车牌进行字符分割;最后采用13点特征法提取字符特征和改进BP网络神经算法对车牌字符进行识别。实验结果表明,本算法能大大提高了车牌识别系统的准确性和鲁棒性,具有较强的实用性。     

Calculation and analysis of low frequency normal modes for DNA

Normal mode calculations for two alternating sequence dodecamers in A, B, and Z conformations have been performed in dihedral angle space extended to endocyclic valence angles to account for sugar ring flexibility. Normal modes are analyzed in terms of helicoidal and backbone parameter variations with special attention being paid to global deformations of the double helix such as bending, twisting, or stretching. Results show that the allomorphic form of DNA has the largest influence on the flexibility of the sugar-phosphate backbone. Amplitudes of these vibrations follow the order: B > Z > A. In contrast, the amplitudes of helicoidal parameter variations are much more dependent on the base sequence. Global deformations of the double helix occur with characteristic times in the range of 1 to 10 ps and can be of mixed character, the strongest bending mode being at the same the time strongest stretching mode. © 1997 by John Wiley & Sons, Inc. J Comput Chem 18: 796–811, 1997     

Development of a new software for the X-ray structural analysis of polymer crystals by utilizing the X-ray imaging plate system

A software and some useful tools have been developed for identifying individual x-ray reflectional peaks recorded with an x-ray imaging plate system. These techniques were applied to analyze the crystal structure of uniaxially oriented polymer samples. Characteristic features of the present method may be summarized as follows. (1) The indexing of the observed reflections and the determination of the unit cell parameters can be made easily on the display of the computer. (2) The integrated intensity of the individual component of the overlapped reflections can be evaluated quantitatively through the curve separation technique. The R_merge's for the equivalent reflections were 5–6%, indicating the exact evaluation of the integrated intensities. (3) The thus obtained reflectional data were successfully utilized for the extraction of the initial structural models by the direct method. The actual applications have been made for orthorhombic polyethylene, trigonal polyoxymethylene, and isotactic polybutene-1, giving the refined crystal structures including even the positions of hydrogen atoms in some cases. The reliability factors were 12, 5, and 15%, respectively, for these three polymer cyrstals. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 1677–1700, 1997     

HF激光脉冲与水柱表面相互作用产生电信号(英文)

研究了脉冲HF激光与水柱表面相互作用下电信号的产生过程。电信号显示了与激光能量线性相关的峰值间有时间间隔的两峰结构,且第二个尖峰在水柱底部的蒸汽腔塌缩后出现。实验还显示电信号的幅值和激光脉冲照射过程中是否存在膨胀和挤压的薄水层密切相关。如果在电池上边缘和石英平板(石英板紧邻电池,并与水柱上表面相接)之间存在一薄水层,电信号强度会增加10倍。