粉碎机械机构学的形成、研究的内容和发展前景

粉碎机械机构学是与相关粉碎理论相结合,应用于粉碎领域里的一门工程基础学科。随着矿产资源高效节能开发和其它行业里大量的粉碎作业增多,对粉碎机械的使用要求不断发生变化,粉碎机构学的研究越来越成为重要的研究课题,并逐渐形成新的学科分支。随着机构学的现代发展,粉碎机构学理论也将在实践中不断得到丰富、发展和完善。     

“Not Hiding,Not Shouting,Just Me”: Gay Men Negotiate Their Visual Identities

This study explored how British gay men make sense of their appearance and clothing practices and the pressures and concerns they attend to in discursively negotiating their visual identities. A convenience sample of 20 mostly young, White, and middle-class self-identified gay men responded to a qualitative survey on dress and appearance. The participants clearly understood the rules of compulsory heterosexuality and the risks of looking “too gay.” In the data, there was both a strong resistance to the notion of gay as a “master status” and an orientation to the “coming out” imperative in gay communities. The analysis revealed the overriding importance of discourses of authentic individuality for making sense of visual identity and the reported cultivation of appearance and clothing practices that communicate the message that: “I’m not hiding (too closeted), I’m not shouting (too gay), I’m just me (an authentic individual who just happens to be gay).”     

吐鲁番出土文书所见"针氈"考

本文对吐鲁番出土文书中"针氈"一词进行考释,认为"针氈"就是针线荷包,存放针 (线)的生活小用具,也即现代方言中所说的"针扎"、"针插"等。     

基于混合模型的国际原油价格预测研究

由于国际原油价格的剧烈波动,使得准确的原油价格预测极具挑战。为此,提出一种基于变分模态分解、季节性差分自回归滑动平均模型和果蝇优化最小二乘支持向量机的混合模型。利用变分模态分解方法将国际原油价格序列分解成一系列模态分量;针对周期性和非线性特征分量,分别建立季节性差分自回归滑动平均模型和果蝇优化最小二乘支持向量机模型进行预测;将各分量的预测值求和作为最终的预测结果。实证研究结果表明:所提混合模型相较对比模型能够明显提高国际原油价格的预测精度。     

Packing trees in communication networks

Given an undirected edge-capacitated graph and given (possibly) different subsets of vertices, we consider the problem of selecting a maximum (weighted) set of Steiner trees, each tree spanning a subset of vertices, without violating the capacity constraints. This problem is motivated by applications in multicast communication networks. We give an integer linear programming (ILP) formulation for the problem, and observe that its linear programming (LP) relaxation is a fractional packing problem with exponentially many variables and a block (sub-)problem that cannot be solved in polynomial time. To this end, we take an r-approximate block solver (a weak block solver) to develop a (1−ε)/r-approximation algorithm for the LP relaxation. The algorithm has a polynomial coordination complexity for any ε∈(0,1). To the best of our knowledge, this is the first approximation result for fractional packing problems with only weak block solvers (with arbitrarily large approximation ratio) and a coordination complexity that is polynomial in the input size. This leads also to an approximation algorithm for the underlying tree packing problem. Finally, we extend our results to an important multicast routing and wavelength assignment problem in optical networks, where each Steiner tree is to be assigned one of a limited set of given wavelengths, so that trees crossing the same fiber are assigned different wavelengths. A preliminary version of this paper appeared in the Proceedings of the 1st Workshop on Internet and Network Economics (WINE 2005), LNCS, vol. 3828, pp. 688–697. Research supported by a MITACS grant for all the authors, an NSERC post doctoral fellowship for the first author, the NSERC Discovery Grant #5-48923 for the second and fourth author, NSERC Discovery Grant #15296 for the third author, the Canada Research Chair Program for the second author, and an NSERC industrial and development fellowship for the fourth author.     

黄帝时代的物质生活

从历史典籍中搜集相关资料,基于衣、食、住、行4个方面复原黄帝时代的物质生活。研究表明,黄帝时代的衣、食、住、行标志着当时的华夏先民已进入文明时代,且具有一定的社会政治意义;这亦标志着黄帝在中华文明的发源和形成过程中的重大影响。     

教师与机器优劣分析

文章对人类教师与计算机这一现代教学媒体在教学过程中各自的长处和不足进行了对比。指出:教师和计算机在教学过程中都显示了他们的实力,两者既不能互相完全代替,也不能互相排斥,应该运用一种新的方法把他们结合起来,使两者的优势更加有效,都能在教学过程中发挥重要的作用,组成一个高效的教学系统。      

《工程材料》课程教学改革初探

分析了机械类专业《工程材料》课程改革的必要性 ,并从教学目的、教学体系、教学内容与教学方法等方面探讨了该课程教学改革的设想 ,且已在教学实践中加以应用。     

现代机床的色彩设计

在对机床色彩设计的功能、原则和配色规律进行分析的基础上,介绍了机床各部分色彩设计的具体方法.     

清代尚裘之风及其南渐

明清易代,满人尚裘之风流播全国。尚裘之风,不仅表现为裘服用料的多样性,也表现在款式的多样性上,甚至公然破坏了清初制定的服饰制度。这表明,社会风尚的转变,反映了国家权力的变化以及社会流动所带来的冲击。