高考制度改革给大学物理教学带来的新课题

针对部分缺乏高中物理基础的学生在学习大学物理过程中遇到的特殊困难,给大学物理学教学带来的新问题,结合高考“3 X”制度中的“X”,提出了提高大学物理教学质量的对策。     

A domain outlier robust design and smooth estimation approach

Outliers that commonly occur in business sample surveys can have large impacts on domain estimates. The authors consider an outlier‐robust design and smooth estimation approach, which can be related to the so‐called “Surprise stratum” technique [Kish, “Survey Sampling,” Wiley, New York (1965)]. The sampling design utilizes a threshold sample consisting of previously observed outliers that are selected with probability one, together with stratified simple random sampling from the rest of the population. The domain predictor is an extension of the Winsorization‐based estimator proposed by Rivest and Hidiroglou [Rivest and Hidiroglou, “Outlier Treatment for Disaggregated Estimates,” in “Proceedings of the Section on Survey Research Methods,” American Statistical Association (2004), pp. 4248–4256], and is similar to the estimator for skewed populations suggested by Fuller [Fuller, Statistica Sinica 1991;1:137–158]. It makes use of a domain Winsorized sample mean plus a domain‐specific adjustment of the estimated overall mean of the excess values on top of that. The methods are studied in theory from a design‐based perspective and by simulations based on the Norwegian Research and Development Survey data. Guidelines for choosing the threshold values are provided. The Canadian Journal of Statistics 39: 147–164; 2011 © 2010 Statistical Society of Canada     

Berry-Esseen-type bounds for the kernel estimator of conditional distribution and conditional quantiles

Berry-Esseen bounds of order O(n^−1/2) have been obtained for several classes of statistics. In this paper, the rates of convergence in central limit theorem for conditional empirical functions and conditional sample quantiles based on kernel estimators are studied for both conditional and unconditional distributions.     

金融危机之后中国对G20应当持有的基本立场

全球化进程在改变着世界经济与政治治理格局.2008-2009年国际金融危机之后,传统发达国家主导的政治经济格局已日益表现出缺陷与不足,新兴经济体的崛起,以及对全球事务的参与,一方面挑战并改变着传统的全球治理格局,另一方面也弥补了传统格局在解决全球问题上的不足.越来越多的新兴国家参与并决定全球事务是全球化进程的必然趋势,G20在国际事务中日益增强的地位正是这种趋势的主要表现,亦是全球政治格局进一步优化的表现.G20带给中国更多参与国际事务的机会以及与其他国家在各个领域合作共赢的机遇.中国应将G20作为加强国家间在解决全球重大政治经济问题上的协作平台,以替代G8机制,并结合联合国机制及其他区域性合作机制,把国家问的全球性合作推上一个新台阶.     

试论中小零售企业共同物流三维模型的构建

我国中小零售企业进入一个新的发展阶段,迫切需要构建高效合理、运作有序的共同物流体系。中小零售企业共同物流系统应以绩效维度、企业战略维度和时间维度构建共同物流的三维动态模型,形成中小零售企业共同物流的主体模式,并以此提出中小零售企业共同物流运营管理策略。     

基于KIVA3的柴油机碳烟产生机理的数值模拟研究

将Surovikin碳烟生成模型、NSC(Nagle和Strickland-Constable)氧化模型和Neoh等人提出的OH氧化模型编译集成到KIVA3中构建多维计算模型,提出了一个六步化学反应机理模型.针对D6114柴油机进行了数值模拟,得到了这一化学反应机理下的碳烟颗粒数密度曲线及其变化过程图和碳烟产生量曲线.研究结果表明,本文采用的基于部分化学反应的机理模型和现有碳烟计算模型能够较清晰地反映柴油机碳烟生成和氧化的历程,对研究柴油机燃烧和排放具有一定的参考价值.     

Ordering conditional lifetimes of coherent systems

Consider a system of n components that has the property that there exists a number r  (r<n)$(r<n)$, such that if it is known that at most r components have failed, the system is still functioning with probability 1. Suppose that such a system is equipped with a warning light that comes up at the time of the failure of the rth component. The system is still working then, and we are interested in its residual life. In this paper we obtain some results which stochastically compare the residual lives of such systems with the same type, or with different types, of components. Some applications are given. In particular, we derive upper and lower bounds on the expected residual lives of such systems given that the warning light has not come up yet, and given that the component hazard rate functions are bounded from below or from above by a known constant.     

An asymptotically distribution-free test of symmetry

A procedure, based on sample spacings, is proposed for testing whether a univariate distribution is symmetric about some unknown value. The proposed test is a modification of a sign test suggested by Antille and Kersting [1977. Tests for symmetry. Z. Wahrscheinlichkeitstheorie verw. Gebiete 39, 235–255], but unlike Antille and Kersting's test, our modified test is asymptotically distribution-free and is usable in practice. A simulation study indicates that the proposed test maintains the nominal level of significance, α$\alpha$ fairly accurately even for samples of size as small as 20, and a comparison with the classical test based on sample coefficient of skewness, shows that our test has good power for detecting different asymmetric distributions.     

The two-sample -test with a known ratio of variances

We consider the two-sample t-test where error variances are unknown but with known relationships between them. This situation arises, for example, when two measuring instruments average different number of replicates to report the response. In particular we compare our procedure with the usual Satterthwaite approximation in the two sample t-test with variances unequal. Our procedure uses the knowledge of a known ratio of variances while the Satterthwaite approximation assumes only that the two variances are unequal. Simulations show that our procedure has both better size and better power than the Satterthwaite approximation. Finally, we consider an extension of our results to the General Linear Model.