What is a crystal to the new chemical crystallographer,after that first,automated structure analysis?

This educational review postulates the importance of maintaining an adequate level of crystallographic education among structure-dependent scientists whose interests are not primarily in crystallography, at a time when automation and validation have made it possible to obtain high-quality structure analyses in many cases with a minimum of crystallographic background. The topics addressed are intended to form a second round of crystallographic education for a novice user whose first round involved hands-on experience with structure solution and an introduction to elementary concepts. The specific topics, chosen for their relevance as basic knowledge and their lack of emphasis in many formal treatments, are (1) crystallographic reference frames and the utility of the reciprocal cell in geometrical calculations; (2) the relationship between the two concepts that constitute our model of the crystal, namely the unit cell and the lattice; (3) the manner in which an atom is represented in concept and in practice; (4) the importance of interleaved symmetry elements required by the presence of additional symmetry on a lattice; (5) the harnessing of the natural properties of the crystalline state for the potential manipulation of properties of synthetic crystals; and (6) useful terminology for navigating a crystal structure.     

On the equilibrium of funicular polyhedral frames and convex polyhedral force diagrams

This paper presents a three-dimensional extension of graphic statics using polyhedral form and force diagrams for the design of compression-only and tension-only spatial structures with externally applied loads. It explains the concept of 3D structural reciprocity based on Rankine’s original proposition for the equilibrium of spatial frames. It provides a definition for polyhedral reciprocal form and force diagrams that allows including external forces and discusses their geometrical and topological characteristics. This paper furthermore provides a geometrical procedure for constructing a pair of reciprocal polyhedral diagrams from a given polyhedron representing either the form or force diagram of a structural system. Using this method, this paper furthermore suggests a design strategy for finding complex funicular spatial forms in pure compression (or tension), based on the construction of force diagrams through the aggregation of convex polyhedral cells. Finally, it discusses the effect of changes in the geometry of the force diagram on the geometry of the form diagram and the distribution of forces in it.     

模糊数学在零件分组中的应用研究

在充分研究减法聚类法、模糊C均值聚类法和最大隶属度原则的基础上,针对机械零件分组中的模糊性,将以上的方法或者原则应用到其中,并结合工程实际情况作适当修改,使其更符合工程实际。通过实例验证了此方法的正确性和实用性,并分析了这种方法的优缺点。     

基于谱减法及频谱方差的语音端点检测方法

为提高在强背景噪声条件下语音端点检测的性能,提出一种将改进的谱减法和频谱方差相结合的方法。先利用谱减法对带噪语音信号进行增强处理,然后使用基于频谱方差的方法进行检测,并以一男一女对10个数字和26个英文字母各发音2次的录音作为样本进行仿真验证。实验结果表明:该方法计算简单,可靠性高,能有效减少背景噪声,提高语音信号的信噪比,在较低的信噪比下仍能比较准确地检测到语言信号的端点。     

地震作用下钢管混凝土柱框支剪力墙结构受力性能研究

采用通用有限元程序MIDAS—Gem对15层的钢管混凝土柱框支剪力墙结构和普通框支剪力墙结构进行了4种工况下的计算，对2种框支剪力墙结构的受力性能进行了对比分析，并推导了适用于框支柱为钢管混凝土的框支剪力墙结构的转换层上、下层结构等效剪切刚度比γ计算公式，同时提出一些合理化建议，以指导工程设计。     

高层框架在基础随机位移下的随机振动反应分析

本文采用连续化方法 ,将高层框架化为剪切型竖向悬臂杆件 ,研究了高层框架在地面随机位移干扰作用下的随机响应。这个方法简单实用 ,易于在工程结构设计中推广应用     

钢筋混凝土框架抗震节点统一设计方法探讨

在过去３０年里，很多国家进行了大量的地震荷载作用下钢筋混凝土框架梁柱节点及连接方面的研究工作。在试验研究的基础上，设计方法不断产生并被编入到规范中。然而关于节点的性能和设计方法却存在着不同的意见和争论，因此很难对所有问题达成共识和建立统一的设计方法。根据作者对钢筋混凝土框架节点的研究成果和对国内外资料掌握的基础上，对框架抗震节点的统一设计方法进行了初步探讨。     

Pushdown resistance as a measure of robustness in progressive collapse analysis

This paper presents a technique termed ‘pushdown analysis’ that can be used to investigate the robustness of building systems by computing residual capacity and establishing collapse modes of a damaged structure. The proposed method is inspired by the pushover method commonly used in earthquake engineering. Three variants of the technique, termed uniform pushdown, bay pushdown and incremental dynamic pushdown, are suggested and exercised using nonlinear analysis on 10-story steel moment frames designed for moderate and high levels of seismic risk. Simulation results show that the frame designed for high seismic risk is more robust than the corresponding one designed for moderate seismic risk. The improved performance is attributed to the influence of seismic detailing, specifically, the presence of reduced beam sections and stronger columns. It is shown that the dynamic impact factors associated with column removal are significantly lower than the commonly used value of 2.0 and are in line with lower values in the guidelines recently proposed by the US Department of Defense. The study suggests that seismic ‘fuses’ can play a role in the design for robustness and a discussion of the implications of this observation is provided.     

钢结构在仿古建筑中的应用

北京菖蒲河公园服务设施工程为钢结构仿古建筑 ,是钢结构在新领域的探索和尝试。较详细地阐述了在钢结构方案设计阶段铰接柱脚与刚接柱脚、门式刚架模型与普钢模型的计算结果比较、梁柱接头特殊节点的处理方法等 ,可供类似工程设计参考。     

Buckling lengths of irregular frame columns

In several design codes and specifications, simplified formulae and diagrams are given for determining the buckling lengths of frame columns. It is shown that these formulae may yield rather erroneous results, especially for irregular frames. This is due to the fact that the code formulae utilise only local stiffness distributions. In this paper, a simplified procedure for determining approximate values for the buckling loads of both regular and irregular frames is developed. The procedure utilises lateral load analysis of frames and yields errors on the order of 5%, which may be considered suitable for design purposes. The proposed procedure is applied to several numerical examples and it is shown that all the errors are in the acceptable range and on the safe side.