脆性材料轴向压缩破坏型式的理论分析

本文利用混合型裂纹扩展的能量释放率理论对脆性材料受轴向压缩时其内部微观裂纹的扩展规律进行了研究.研究结果表明,沿纵向裂开和沿斜截面剪切断开分别对应于能量释放率的二个极大值的方向.当端面摩擦较小时,由于沿纵向裂开为能量释放率最大值的方向,试件将发生纵向裂开的破坏型式.当端面摩擦较大时,由于端面摩擦将阻碍纵向裂纹的扩展,试件将沿斜截面断裂.利用本理论对于铸铁材料的计算结果与实验结果之间具有很好的一致性.     

非人力资产所有权与企业的边界

产权理论是第一个关于不完全合约和企业合并的正式模型,其核心内涵是说明在不完全合约和潜伏着"敲竹杠"问题的环境中,非人力资产所有权如何影响交易参与人的关系专用性投资。通过考察该理论的基本假设和概念框架发现,它不能对企业边界的决定提供恰当的和充分的解释。企业不仅仅是解决"敲竹杠"问题的机制,合并也不是解决"敲竹杠"问题的惟一途径。     

Improved Approximation for Breakpoint Graph Decomposition and Sorting by Reversals

Sorting by Reversals (SBR) is one of the most widely studied models of genome rearrangements in computational molecular biology. At present, is the best known approximation ratio achievable in polynomial time for SBR. A very closely related problem, called Breakpoint Graph Decomposition (BGD), calls for a largest collection of edge disjoint cycles in a suitably-defined graph. It has been shown that for almost all instances SBR is equivalent to BGD, in the sense that any solution of the latter corresponds to a solution of the former having the same value. In this paper, we show how to improve the approximation ratio achievable in polynomial time for BGD, from the previously known to for any > 0. Combined with the results in (Caprara, Journal of Combinatorial Optimization, vol. 3, pp. 149–182, 1999b), this yields the same approximation guarantee for n! – O((n – 5)!) out of the n! instances of SBR on permutations with n elements. Our result uses the best known approximation algorithms for Stable Set on graphs with maximum degree 4 as well as for Set Packing where the maximum size of a set is 6. Any improvement in the ratio achieved by these approximation algorithms will yield an automatic improvement of our result.     

On influence diagnostic in univariate elliptical linear regression models

We discuss in this paper the assessment of local influence in univariate elliptical linear regression models. This class includes all symmetric continuous distributions, such as normal, Student-t, Pearson VII, exponential power and logistic, among others. We derive the appropriate matrices for assessing the local influence on the parameter estimates and on predictions by considering as influence measures the likelihood displacement and a distance based on the Pearson residual. Two examples with real data are given for illustration.     

空气流化棒助流装置的研究

为了消除料仓内结拱、堵塞等不正常现象,提出了空气流化棒助流装置的设计方案.空气流化棒能够有效地克服料仓内异常料流现象.在流化风作用下的料仓内水泥流动的研究表明当下料口径(D)与料仓直径(D1)之比大于0.08而小于0.13时,物料流量与下料口径呈二次抛物线的关系;当D/D1大于0.13时,物料流量基本不随下料口径的变化而变化;当下料口径一定时,物料流量基本不随物料高度的变化而变化.     

二阶段供应链中提前期压缩的影响与协调

提前期是衡量业务过程绩效一个重要的因素,基于时间竞争的供应链管理战略核心就在于提前期的压缩,提前期压缩是形成供应链战略优势的有力来源.在市场需求预测精度随提前期变化的假设下,采用逻辑证明和数值分析的方法,研究由供应商-零售商构成的两阶段供应链中提前期压缩对供应链及其成员收益的影响以及如何实现供应链的渠道协调.研究结果表明:当供应链的服务水平小于0.5时,提前期的压缩可以获得供应链成员收益的Pareto改进;当供应链的服务水平大于等于0.5,引入线性转移支付补偿机制,可以实现供应链的渠道协调,获得供应链成员收益的Pareto改进.     

全球化视阈中的中国本土电影的叙事

电影一方面是工业文明的产物,同时又是一种特殊的文化产品。在全球化的今天,中国本土电影也日渐向全球化靠拢。虽然全球化使得好莱坞电影在世界范围畅行无阻,但好莱坞电影并不能替代我们对本土文化、本土生活、本土经验的关注与书写。我们的电影首先是本土的,而后才是世界的。     

原版电影听说教学中交际法的渗透

就交际法理论而言,把文化因素和社会因素融会到交际情景中去是外语教学的一个难题.利用真实的视听材料如原版电影安排教学活动,较好地解决了师生教与学中部分教材学习情境的创设问题,丰富了学习情境,为师生教学提供了强有力的支持和服务.由某一话题入手,对影片中出现的语言信息加工处理,用交际性任务来组织课堂教学,使电影、语言素材、教学活动以及涉及到的文化知识、情感态度等有机地融合于教学的整个过程.     

局部环上典型群的非双曲型

引入域上典型群的生成问题所得的成果；对局部环R上典型群生成问题研究，构造度量函数及一平延，为局部环R上典型群向域F上的典型群导入，给出典型群的非双曲型．     

Non-parametric Estimation of the Residual Distribution

Consider a heteroscedastic regression model Y = m ( X ) +σ( X )ε, where the functions m and σ are "smooth", and ε is independent of X . An estimator of the distribution of ε based on non-parametric regression residuals is proposed and its weak convergence is obtained. Applications to prediction intervals and goodness-of-fit tests are discussed.