An upper bound on the minimal total cost of the transportation problem with varying demands and supplies

In general cases, to find the exact upper bound on the minimal total cost of the transportation problem with varying demands and supplies is an NP-hard problem. In literature, there are only two approaches with several shortcomings to solve the problem. In this paper, the problem is formulated as a bi-level programming model, and proven to be solvable in a polynomial time if the sum of the lower bounds for all the supplies is no less than the sum of the upper bounds for all the demands; and a heuristic algorithm named TPVDS-A based on genetic algorithm is developed as an efficient and robust solution method of the model. Computational experiments on benchmark and new randomly generated instances show that the TPVDS-A algorithm outperforms the two existing approaches.     

Another Remark on the Alternative Expectation Formula

Students in a calculus-based probability course will often see the expectation formula for nonnegative continuous random variables in terms of the survival function. This alternative expectation formula has a wide spectrum of applications. It is natural to ask whether there is a multivariate version of this formula. This note gives an affirmative answer by establishing such a formula using two different approaches. The two approaches employed in this note correspond to the two approaches for the univariate case. Supplementary materials for this article are available online.     

Editorial collaborators

A simulation study of the binomial-logit model with correlated random effects is carried out based on the generalized linear mixed model (GLMM) methodology. Simulated data with various numbers of regression parameters and different values of the variance component are considered. The performance of approximate maximum likelihood (ML) and residual maximum likelihood (REML) estimators is evaluated. For a range of true parameter values, we report the average biases of estimators, the standard error of the average bias and the standard error of estimates over the simulations. In general, in terms of bias, the two methods do not show significant differences in estimating regression parameters. The REML estimation method is slightly better in reducing the bias of variance component estimates.     

Univariate and multivariate models of positive and negative networks: Liking,disliking, and bully–victim relationships

Three relations between elementary school children were investigated: networks of general dislike and bullying were related to networks of general like. These were modeled using multivariate cross-sectional (statistical) network models. Exponential random graph models for a sample of 18 classrooms, numbering 393 students, were summarized using meta-analyses. Results showed (balanced) network structures with positive ties between those who were structurally equivalent in the negative network. Moreover, essential structural parameters for the univariate network structure of positive (general like) and negative (general dislike and bullying) tie networks were identified. Different structures emerged in positive and negative networks. The results provide a starting point for further theoretical and (multiplex) empirical research about negative ties and their interplay with positive ties.     

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.     

凉山彝族地区主要林业资源开发史述论

探讨了凉山彝族地区主要林业资源开发的历史过程,对林业资源开发对象、开发方式、开发效果、开发的组织管理、开发力度等问题进行了讨论。认为历史时期凉山彝族地区获开发的林业资源种类偏少;林业资源开发方式单一,开发的产品多为初级产品;只注重开发而忽略了资源保护;林业资源的开发呈现出有序性和无序性并存的特点;林业资源开发的力度呈上升趋势,但进程相对缓慢。     

国家木材供给安全保障对策的研究

通过对我国森林资源现状、全国木材总体供需情况、木材及木质产品进口情况的调查与分析,提出了建立我国木材供给安全保障的对策。在现阶段我国需以科学发展观为指导,统筹发展生态林业和用材林基地建设,编制并实施＂全国人工用材林发展专项规划＂,合理配置森林资源,进一步完善国家信贷扶持政策和投入机制,科学开展森林经营工作,提高林分质量和生长量,增加木材资源储备和供给能力,最终达到保障国家木材供给安全的目标。     

我国林业产业链整合研究

以迈克尔·波特的价值链和宏基创始人施振荣的“微笑曲线”为理论基础,指出中国的林业产业长期处于价值链的低端,即“两头在外,大进大出”（原料来自国外、产品销往国外）,分析了中国林业产业链的特点和各个环节中所存在的问题,并以跨国集团美国国际纸业公司的产业链为参照,指出了我国林业产业链应该努力的方向。最后给出了整合我国林业产业链的建议。     

论国有林场改革的法律模式选择

法人组织的不同经营目的使得其采用不同的组织形式。国有林场法律模式的选择首先要区分生态公益型和商品经营型两种不同性质的林场。生态公益型国有林场采取事业单位法律模式可以保障其实现提供生态公共物品的职能;商品经营型国有林场采用公司法律模式能够相对清晰地界定国家与林场间的权利义务关系、减弱所有者缺位问题。国有林场改革中对法律制度的局限性也应有清醒的认识。     

P2P应用层数据流量优化

为减少对主干网络带宽的消耗,提出了一套数据流量优化方法。首先通过把Peer间的邻居关系明确划分为物理邻居关系和逻辑邻居关系,并用探路者算法来发现Peer的物理邻居,实现拓扑匹配;然后在数据调度算法中,引入通报/退避机制,把大部分数据传输控制在城域网络内部。通过建立模拟仿真环境进行实验分析,证实了该方法可以减少90%以上的网络数据流量。