An Introduction to Advanced Hot-Formed Steel for Automobile

A recently developed advanced hot-formed （AHF） steel for automobile is introduced and three physical metallurgy concepts based on which the AHF steel was designed are reviewed, they are dynamic carbon partitioning （DCP）, flash copper precipitation and bake toughening. AHF steel is an upgrade of the existing hot-formed steel especially suitable for making components with superior crashworthiness; it can be processed by regular hot stamping equipment and process. A kinetics model for DCP is expressed in detail, which can be used to calculate the volume fraction of retained austenite based on four materials and processing parameters. The flash copper precipitation used as an additional strengthening mechanism for AHF steel is also discussed and its ultrafast kinetics can be attributed to the enhancement of quenched-in vacancies on copper diffusion. Also, the bake toughening of AHF steel is addressed; the mechanism of which may be related to the elimination of the less stable block-like retained austenite.     

低碳钢淬火等温碳配分中粒状贝氏体组织演变及性能

利用彩色金相、扫描电镜及拉伸实验等方法,研究了IQPB热处理工艺下低碳硅锰钢在450℃时不同等温时间淬火碳配分工艺对其组织及力学性能影响。结果表明,经不同时间等温碳配分工艺处理,实验钢显微组织基本由粒状贝氏体及粒状组织构成。当配分时间在200~600s时,晶界边缘大块状M/A岛数量逐渐减少,但细小颗粒状M/A岛数量逐渐增多并趋于有序化排列,导致抗拉强度升高,伸长率降低。随碳配分时间延长,细小颗粒状M/A岛又趋于弥散化排列,并且当碳配分时间大于1 200s时出现无碳化物板条贝氏体,其贝氏体板条间的薄膜状残余奥氏体更加稳定,同时受弥散排列的细小颗粒状M/A岛影响,伸长率得到提高,抗拉强度减少。     

基于Ncut准则的图分割的新算法

针对有权图分割时不能很好解决子图内部耦合度不高的问题,使用可以同时优化子图内部顶点耦合度和子图之间顶点耦合度的Ncut准则,提出了一种新的基于迭代改善策略的RNK分割算法。算法通过不断交换可以改善Ncut值的顶点对优化现有分割。与传统分割算法相比,可以同时保证子图内最大耦合度和子图间最小的耦合度。并提出一种散列技术,提高查找最优交换顶点对的效率。当图为稠密矩阵时,改善效果尤为明显。通过对随机图分割的实验结果表明,该算法较传统的KL算法可以得到更理想的分割结果。     

防火分区模式对商业设计的影响:商业调研总结之一

在国内建成的大型商业综合体建筑中,多采用以下两种防火分区模式——常规的防火分区模式和亚安全区模式。本篇文章将结合杭州万象城和北京石景山万达广场两个实例,分析这两种防火分区模式的设计要点和它们对整个商业的业态布局、交通组织、店铺划分、空间效果等一系列问题产生的影响。     

On some parallel banded system solvers

This paper describes algorithms for solving narrow banded systems and the Helmholtz difference equations that are suitable for multiprocessing systems. The organization of the algorithms highlight the large grain parallelism inherent in the problems.     

A procedure for the unsupervised abdunction of linguistic distributional classes in probabilistic languages

A probabilistic version of word distributional equivalence, which includes the usual notion of syntactic distributional classes as a special case, is formulated. A computational procedure for the unsupervised discovery of probabilistic distributional classes, using random text presentation, is shown to converge stochastically to the correct classification. The results of a simulation experiment are presented. A geometrical interpretation of the procedure, in which words are represented as vectors in an infinite-dimensional inner product space, is discussed.     

一种改进的计算机网络k-划分优化遗传算法

本文运用无向图多划分优化的方法研究计算机网络k-划分优化问题，结合问题本身的特点，设计了一种启发式遗传算法，从适应度函数设计，遗传操作算子以及参数选取等方面对经典遗传算法进行了改进，实验研究验证了算法的正确性和高效性。     

抗误码的小波图像编码

提出了一种改进的SPIHT算法，可以把错误的影响控制在局部范围内，极大地提高了小波压缩图像传输的抗误码性能。实验证明该算法是有效并且可行的。     

基于神经网络的动态成本分析

建立了一个神经网络成本分析模型,采用模糊聚类算法自动确定网络隐含层节点数,并将成本因素分析算法编制成软件,用于分析影响成本的技术经济指标变动趋势.在对影响某钢铁公司选矿厂综合铁精矿成本因素分析的应用中,取得了较好的效果.