Application of piece‐wise linear weight functions for 2D 8‐node quadrilateral element in contact problems

The present study is a continuation of our previous work with the aim to reduce problems caused by standard higher order elements in contact problems. The difficulties can be attributed to the inherent property of the Galerkin method which gives uneven distributions of nodal forces resulting in oscillating contact pressures. The proposed remedy is use of piece‐wise linear weight functions. The methods to establish stiffness and/or mass matrix for 8‐node quadrilateral element in 2D are presented, i.e. the condensing and direct procedures. The energy and nodal displacement error norms are also checked to establish the convergence ratio. Interpretation of calculated contact pressures is discussed. Two new 2D 8‐node quadrilateral elements, QUAD8C and QUAD8D, are derived and tested in many examples, which show their good performance in contact problems. Copyright © 2004 John Wiley & Sons, Ltd.     

A simple approximation algorithm for the weighted matching problem

We present a linear time approximation algorithm with a performance ratio of 1/2 for finding a maximum weight matching in an arbitrary graph. Such a result is already known and is due to Preis [STACS'99, Lecture Notes in Comput. Sci., Vol. 1563, 1999, pp. 259-269]. Our algorithm uses a new approach which is much simpler than the one given by Preis and needs no amortized analysis for its running time.     

高分子量丙烯酰胺-DAC共聚物的研制

采用复合引发体系 ,以丙烯酰胺 (AM)和阳离子单体丙烯酰氧乙基三甲基氯化铵(DAC)为共聚体 ,进行水溶液绝热聚合 ,研制了一种DAC单体含量为 4 0 %～ 5 0 %、相对分子质量大于 1× 10 7的阳离子型聚丙烯酰胺。     

聚乙烯丙纶复合防水卷材的特点及其应用

介绍了聚乙烯丙纶复合防水卷材的产品结构特点和性能特点、防水系统结构特点和配套材料、应用拼接技术以及产品应用范围。     

特低渗油藏渗流特征及增产技术研究

从特低渗储层渗流机理研究出发，分析了其渗流规律——非达西渗流特征；根据储层中上覆岩石围压变化，通过室内试验表述了其对渗透率伤害。研究提出了改善渗流特征的注水条件、井网优化和压裂对策，可以有效提高这类油藏的开发效果。     

What do we learn from binding features? Evidence for multilevel feature integration.

Four experiments were conducted to investigate the relationship between the binding of visual features (as measured by their aftereffects on subsequent binding) and the learning of feature-conjunction probabilities. Both binding and learning effects were obtained, but they did not interact. Interestingly, (shape-color) binding effects disappeared with increasing practice, presumably because of the fact that only 1 of the features involved was relevant to the task. However, this instability was only observed for arbitrary, not highly overlearned combinations of simple geometric features and not for real objects (colored pictures of a banana and strawberry), where binding effects were strong and resistant to practice. These findings suggest that learning has no direct impact on the strength or resistance of bindings or on speed with which features are bound; however, learning does affect the amount of attention particular feature dimensions attract, which again can influence which features are considered in binding. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

最优特征子集选择问题

机器学习和模式识别面临的一个重要问题，就是特征子集的选择问题，即从一个大的已生征特集合，选择一个子集合来一致地描述已知例。特别，最优特征子集选择问题，即最小的特征子集问题的 计算杂性至今学不清楚。     

新型无灰分散剂的结构分析研究

通过薄膜渗析、红外光谱、凝胶渗透色谱、皂化反应等一系列手段建立了一套对无灰分散剂的系统分析方法，并利用该方法得到了一种新型无灰分散剂及其衍生物的平均结构、相对分子质量分布、分散度等重要结构信息，得出该新型无灰分散剂的结构与传统无灰分散剂的结构不同。     

眼球的自动定位

提出了一种由粗到细自动定位人脸的一个重要特征即眼球圆心的方法，该方法综合运用局部二值化，霍夫变换，像纱聚类，边缘提取等技术，对均匀或非均匀光照下拍摄或戴眼镜的照片都能获得很高的定位精度，适用于处理证件照。     

基于运动矢量的视频图象数字水印算法

数字水印技术是近年发展起来的一种用于数字产品版权保护和真伪性论证的新兴技术。与静止图象相比，视频水印技术要满足盲检的要求。本文根据运动矢量的特征值ρl，提出了一种视频图象水印新算法。实验结果表明，所提出的水印算法简单、快速，能满足视频编码的实时性要求；算法与现有的视频压缩标准有很好的兼容性；水印的提取具有盲检功能，无需原图象；水印的嵌入不影响I帧的图象质量，与嵌入水印前的原压缩图象相比，嵌入水印后的视频图象信噪比损失很小。