跨国并购与我国企业技术进步的相关性分析

近年来，跨国并购逐渐成为我国企业国际化发展以及构建核心竞争能力的重要途径，而跨国并购能否对我国企业的技术进步起到积极的作用则成为理论研究的热点问题。针对此，采用全要素指标体系，分析了1991~2007年全要素增长率与跨国并购增长率之间的关系，认为:跨国并购的变化对技术进步具有一定的影响关系，但是由于技术并购在对外投资中的比重偏低，过分重视了技术的引进，忽视了技术的吸收消化过程等因素的影响，因此这种影响的效果并不显著。     

An Orthogonality‐Based Estimation of Moments for Linear Mixed Models

Abstract. Estimating higher‐order moments, particularly fourth‐order moments in linear mixed models is an important, but difficult issue. In this article, an orthogonality‐based estimation of moments is proposed. Under only moment conditions, this method can easily be used to estimate the model parameters and moments, particularly those of higher order than the second order, and in the estimators the random effects and errors do not affect each other. The asymptotic normality of all the estimators is provided. Moreover, the method is readily extended to handle non‐linear, semiparametric and non‐linear models. A simulation study is carried out to examine the performance of the new method.     

Studying the dependence between ordinal-nominal categorical variables via orthogonal polynomials

In situations where the structure of one of the variables of a contingency table is ordered recent theory involving the augmentation of singular vectors and orthogonal polynomials has shown to be applicable for performing symmetric and non-symmetric correspondence analysis. Such an approach has the advantage of allowing the user to identify the source of variation between the categories in terms of components that reflect linear, quadratic and higher-order trends. The purpose of this paper is to focus on the study of two asymmetrically related variables cross-classified to form a two-way contingency table where only one of the variables has an ordinal structure.     

Martingale generalizations and preservation of martingale properties

This article investigates circumstances under which seven important martingale properties are preserved by the following six martingale generalizations: quasimartingales, amarts, martingales in the limit, games fairer with time, progressive martingales, and eventual martingales.     

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.     

Decomposition of K m,n into 4-cycles and 2t-cycles

In this paper we show the sufficient conditions for the decomposition of the complete bipartite graphs K _2m,2n and K _2n+1,2n+1−F into cycles of two different lengths 4 and 2t, t>2, where F is a 1-factor of K _2n+1,2n+1. After that we prove that the results are true for t=5 and 6. Dedicated to Frank K. Hwang on the occasion of his 65th birthday. An erratum to this article can be found at     

动静叶相互干涉的三维非定常流场数值模拟

将双时间步法应用于叶栅级的全三维黏性非定常数值求解，讨论了分区算法中内边界条件的给定问题，本算法可保证分区边界上具有与内点相同的精度，具有很好的数值稳定性，且通量基本守恒，将该方法应用于具有弯曲导叶的涡轮级的计算可得到典型的非定常流谱，揭示了动静叶之间的相互干涉对叶片气动性能的影响，数值计算结果表明本文给出的算法是合理有效的。     

Shrinkage and Orthogonal Decomposition

ABSTRACT. The problem of estimating the mean of a multivariate normal distribution when the parameter space allows an orthogonal decomposition is discussed. Risk functions and lower bounds for a class of shrinkage estimators that includes Stein's estimator are derived, and an improvement on Stein's estimator that takes advantage of the orthogonal decomposition is introduced. Uniform asymptotics related to Pinsker's minimax risk is derived and we give conditions for attaining the lower risk bound. Special cases including regression and analysis of variance are discussed.     

On perfect simulation for some mixtures of distributions

This paper studies the implementation of the coupling from the past (CFTP) method of Propp and Wilson (1996) in the set-up of two and three component mixtures with known components and unknown weights. We show that monotonicity structures can be exhibited in both cases, but that CFTP can still be costly for three component mixtures. We conclude with a simulation experiment exhibiting an almost perfect sampling scheme where we only consider a subset of the exhaustive set of starting values.     

一种用于Ad hoc网络的优化拥塞控制算法

从分析Adhoc网络的信息流竞争特点出发,引入了链路干扰集的概念,构建了一个基于链路干扰集的价格框架。在此框架中,某链路的拥塞信息被表示为此链路干扰集的总价格。并提出了相应的分布式平行算法-价格协同法PCA来求解在小时间段内网络状态不变的拥塞控制问题。同时,分析了PCA对网络状态变化的自适应性能。仿真结果表明,PCA能快速收敛到全局优化解,对网络状态的变化有较好的自适应能力,所获得的网络性能比TCP-Reno要优越得多。