On the enumeration of rectangular (0, 1)-matrices

The construction and enumeration of (0, 1)-matrices with given line-sums is described for the rectangular cases often encountered in applications. Improved approximations are provided for the number of such matrices. Some new enumeration results for semi-regular bipartite graphs are included, and the related category of the quasi-semiregular bipartite graphs is recognized. The range of certain elements of products of a (0, I)-matrix is considered as a function of the line-sums. This, in turn, is related to the range in the numbers of interchanges available. Improvements in statistical practice that come from these constructions and enumerations are described.     

After a Disaster: Lessons in Survey Methodology from Hurricane Katrina

In 2005, the National Science Foundation funded a number of projects to study the impact of Hurricane Katrina. The current article provides an overview of several research approaches used to conduct post-Katrina research. Each method had some advantages and disadvantages. The post-disaster context meant that experience from traditional survey methods often did not apply. Comparisons of advantages and disadvantages associated with each sampling method serve to inform future post-disaster research and illuminate the limits of classical research methods.     

Serial unblocked designs balanced for correlation between neighbours,II

The theory in Part I contained an error that was inferred from the output of a program, written in SAS by Eric P. Smith and David D. Morris. The program produces random BUS designs in accordance with the algorithm of Part I. The theory is here corrected by using a combinatorial argument that involves elementary number theory. The algorithm needs no change but its interpretation is now adjusted.     

一道组合计数问题的讨论

本文指出《组合基础》中一道组合计数题的错解，并给出正确的答案。     

A network algorithm for the exact treatment of the 2×k contingency table

A common statistical problem encountered in biomedical research is to test the hypothesis that the parameters of k binomial populations are all equal. An exact test of significance of this hypothesis is possible in principle, the appropriate null distribution being a normalized product of k binomial coefficients. However, the problem of computing the tail area of this distribution can be formidable since it requires the enumeration of all sets of k binomial coefficients whose product is less than a given constant. Existing algorithms, all of which rely on explicit enumeration to generate feasible binomial coefficients     

Reduced costs propagation in an efficient implicit enumeration for the 01 multidimensional knapsack problem

In a previous work we proposed a variable fixing heuristics for the 0-1 Multidimensional knapsack problem (01MDK). This approach uses fractional optima calculated in hyperplanes which contain the binary optimum. This algorithm obtained best lower bounds on the OR-Library benchmarks. Although it is very attractive in terms of results, this method does not prove the optimality of the solutions found and may fix variables to a non-optimal value. In this paper, we propose an implicit enumeration based on a reduced costs analysis which tends to fix non-basic variables to their exact values. The combination of two specific constraint propagations based on reduced costs and an efficient enumeration framework enable us to fix variables on the one hand and to prune significantly the search tree on the other hand. Experimentally, our work provides two main contributions: (1) we obtain several new optimal solutions on hard instances of the OR-Library and (2) we reduce the bounds of the number of items at the optimum on several harder instances.     

牛磺酸对力竭运动时大鼠脑组织自由基代谢的影响

以大鼠递增负荷力竭性运动为模型 ,观察了牛磺酸 (taurine)对力竭运动时脑组织(皮层运动区和感觉区)自由基代谢的影响 结果显示 :力竭运动后即刻 ,脑组织的MDA显著增加 ,SOD和GSH显著下降 ;补充牛磺酸能使力竭运动脑组织的MDA显著降低 ,阻止SOD下降和维持GSH的水平 ,并使大鼠运动至力竭的时间稍有延长 提示力竭运动使大鼠脑组织自由基代谢加强 ;牛磺酸在大鼠脑组织中具有很强的抗氧化作用 ,其机制可能和牛磺酸与醛基反应有关     

Hard‐to‐Solve Bimatrix Games

The Lemke–Howson algorithm is the classical method for finding one Nash equilibrium of a bimatrix game. This paper presents a class of square bimatrix games for which this algorithm takes, even in the best case, an exponential number of steps in the dimension d of the game. Using polytope theory, the games are constructed using pairs of dual cyclic polytopes with 2d suitably labeled facets in d‐space. The construction is extended to nonsquare games where, in addition to exponentially long Lemke–Howson computations, finding an equilibrium by support enumeration takes on average exponential time.     

A new variant of dual-record population estimation with an application in remote indigenous communities

Dual-record system methods are commonly used as a basis for population estimation. A basic assumption is that the units sampled are drawn only from the population to be estimated. This assumption cannot be met for remote Indigenous communities in Australia. A new variant of dual-record population estimation is presented, which relies on the availability of specific additional information to relax the assumption of perfect frame specification. This variant is applied to two remote Indigenous communities in the Northern Territory of Australia, using locally available data sources. Further theoretical exploration of this method is presented along with possible applications in estimating area-enumerated populations and census coverage.     

Attacking the Market Split Problem with Lattice Point Enumeration

The market split problem was proposed by Cornuéjols and Dawande as benchmark problem for algorithms solving linear systems with 0/1 variables. Here, we present an algorithm for the more general problem A · x = b with arbitrary lower and upper bound on the variables. The algorithm consists of exhaustive enumeration of all points of a suitable lattice which are contained in a given polyhedron. We present results for the feasibility version as well as for the integer programming version of the market split problem which indicate that the algorithm outperforms the previously published approaches to this problems considerably.