An integrated production and inventory model for a whole manufacturing supply chain involving reverse logistics with finite horizon period

This paper proposes a model and solution method for coordinating integrated production and inventory cycles in a whole manufacturing supply chain involving reverse logistics for multiple items with finite horizon period. A whole manufacturing supply chain involving reverse logistic consists of tier-2 suppliers supplying raw materials to tier-1 suppliers, tier-1 suppliers producing parts, a manufacturer which manufactures and assembles parts from tier-1 suppliers into finished products, distributors distributing finished products to retailers, retailers selling products to end customers and a third party which collects the used finished products from end customers, dissembles collected products into parts, and feed the parts back to the supply chain. In this system, we consider a finite horizon period. A mathematical model for representing the behaviors of the system is developed. Solution methods based on decentralized and a combination of decentralized and centralized decision making process, referred to as the semi-centralized decision making process, are proposed to solve the model while the centralized decision making process is solved by a mixed integer nonlinear programming method. A numerical example is used to demonstrate the model and the solutions based on the three types of the coordination.     

A mathematical model and genetic algorithm-based approach for parallel two-sided assembly line balancing problem

Assembly lines are usually constructed as the last stage of the entire production system and efficiency of an assembly line is one of the most important factors which affect the performance of a complex production system. The main purpose of this paper is to mathematically formulate and to provide an insight for modelling the parallel two-sided assembly line balancing problem, where two or more two-sided assembly lines are constructed in parallel to each other. We also propose a new genetic algorithm (GA)-based approach in alternatively to the existing only solution approach in the literature, which is a tabu search algorithm. To the best of our knowledge, this is the first formal presentation of the problem as well as the proposed algorithm is the first attempt to solve the problem with a GA-based approach in the literature. The proposed approach is illustrated with an example to explain the procedures of the algorithm. Test problems are solved and promising results are obtained. Statistical tests are designed to analyse the advantage of line parallelisation in two-sided assembly lines through obtained test results. The response of the overall system to the changes in the cycle times of the parallel lines is also analysed through test problems for the first time in the literature.     

环状区域的车辆路径方案生成系统及优化模型

针对顾客满足环状区域分布的车辆路径问题(VRP),以大幅度地缩减问题求解的状态空间为突破口,引入人工智能和运筹学理论,提出求解这类特殊车辆路径问题的两阶段方法.第1阶段考虑行车时间和车载容量,提出带有控制策略的深度优先搜索算法自动生成备选的车辆路径方案集合.第2阶段将此备选方案集合归结为整数规划模型.采用VB6.0编程语言构建了车辆路径方案生成系统,并实现该系统与运筹学求解软件lindo的集成.通过案例验证了上述方法及自动求解系统的有效性.该项研究为解决环状配送区域的车辆路径问题这一难题提供了新方法.     

THE DYNAMICS OF A STABLE CARTEL: THE RAILROAD EXPRESS 1851–1913

The railroad express was probably the most successful cartel in U.S. business history. The key to its stability lay in the fact that collusion was largely an effort to create a cost-reducing distribution network. Because cost was dependent on collusion, the five cartel members could both underprice entrants and punish defectors. It is shown that in a Bertrand-type price war, colluding firms could effectively drive a defector into bankruptcy. As a result, the express controlled its market and remained a stable organization for more than half a century.     

The evolution in China's fertility and an analysis of population development]

There have been numerous projections on China's population at the end of century. Their differences are due to different estimations on the effects of fertility determinants. 2 simulation models have been developed, both from micro and macro levels, to estimate the population at the end of the century on the basis of 6 different fertility patterns. 3 possible options for fertility patterns are discussed. 1.) The 1 child per family option means that every couple has 1 child by the year 1989, the population of China will be 1.2 billion in the year 2000. Even if this is a ideal situation, it would not be a feasible policy, as the pressure from the rural population to have more than 1 child has been increasing in recent years. Nevertheless, it is still possible for urban couples to accept having only 1 child. Therefore, encouraging more people to have 1 child should be held as a basic policy. 2.) Under the option of 2 children per family with 2 or 3 years of spacing, the total population in the year 2000 would be 1.2 - 1.4 billion, which is unacceptable in terms of the development situation. 3.) Following a differential fertility policy towards urban, rural, and minority populations would mean that urban couples would have 1 child, rural couples whose first child is a girl or those who are in special circumstance would have 2 children. Minorities would have 2 or 3 children. AMong the above options, number 3 is more likely to be achieved in view of current socioeconomic, cultural, and demographic factors.     

Is the world threatened with overpopulation?

Global population trends are reviewed. The author concludes that a level of overpopulation is inevitable, not primarily because of problems of food supply but because of the environmental degradation that will result from population increases. The author suggests that these environmental changes will lead to increases in mortality and declines in fertility.     

水稻生产环节外包决策实证研究——基于江西省稻农水稻种植数据的研究

基于江西省2011年325户稻农和2007年307户同一稻农两年各水稻种植季节内水稻种植8个生产环节的要素投入和要素来源微观数据,实证分析水稻生产环节外包决策,研究发现:不同特征的水稻生产环节间的外包程度有很大差别;不同种植规模的稻农在水稻生产外包的环节上也存在差别;分析稻农水稻生产环节外包决策问题,应在季节层面而非加总的农户层面进行探索。Mvprobit模型的回归结果表明,稻农水稻生产各个环节的外包决策是相关的;对于不同特征的水稻生产环节,影响其外包的因素存在差别。总体而言,增加非农就业机会、提高非农收入水平,以及降低外包价格,均有助于外包比例的提高。     

Implementation of China's population policy

On July 1, 1982 China's 3rd national population census reported the population of the 29 provinces, municipalities, and autonomous regions on the mainland at 1,008,175,288, showing a net increase of 460,000,000 or 84% over the 548,000,000 recorded at the end of 1949. At this time China's population is about 1/4 of the world. Its population policy must conform to her national conditions and will be successful only to the extent that it does so. Discussion focuses on the main features of China's population policy. In 1953 the State Council instructed the Ministry of Health to support birth control by providing contraceptives. It also ratified provisions concerning contraception and induced abortions. In 1962 the State Council issued "Instructions on Conscientious Advocacy of Family Planning." China not only advocates and publicized family planning but also takes specific measures. Special administrative organizations were established in 1964 to oversee scientific research, production, and supply of contraceptives and to provide couples of childbearing age with free contraceptives. An all round attack on family planning work in 1966 led to unchecked childbirth resulting in rapid population growth. In 1971 Premier Zhou Enlai reiterated the importance of population control in 1971 and asked that it be incorporated into the 4th Five Year Plan for the development of the national economy. Family planning was incorporated into the Constitution in 1978. China's 20 years of experiences with family planning suggest that a country's population policy becomes effective only with repeated efforts. The 10-year period of turmoil undermined the enforcement of the population policy. Recently the State Family Planning Commission organized a nationwide fertility survey which indicated tremendous successes for China's population control drive. The total fertility rate dropped from 5.29 in the 1950s to 2.63 in the 1980s. The population census shows that the momentum of China's population growth cannot be checked without strict measures because the population is characterized by a huge base figure, a young age composition, and a fertility rate much higher than a population replacement level. China's population policy is formulated in line with her national conditions. Specific provisions for family planning reflect different ways to deal with different people.