Stochastic lot sizing problem with controllable processing times

In this study, we consider the stochastic capacitated lot sizing problem with controllable processing times where processing times can be reduced in return for extra compression cost. We assume that the compression cost function is a convex function as it may reflect increasing marginal costs of larger reductions and may be more appropriate when the resource life, energy consumption or carbon emission are taken into consideration. We consider this problem under static uncertainty strategy and α service level constraints. We first introduce a nonlinear mixed integer programming formulation of the problem, and use the recent advances in second order cone programming to strengthen it and then solve by a commercial solver. Our computational experiments show that taking the processing times as constant may lead to more costly production plans, and the value of controllable processing times becomes more evident for a stochastic environment with a limited capacity. Moreover, we observe that controllable processing times increase the solution flexibility and provide a better solution in most of the problem instances, although the largest improvements are obtained when setup costs are high and the system has medium sized capacities.     

古希腊悲剧三题

古希腊悲剧光辉灿烂,至今仍洋溢着旺盛的生命力,其理论与创作实践,对我们仍有着参考和借鉴之处。本文主要论述了古希腊悲剧中悲剧主人公的创造,悲剧反映社会生活矛盾的规律,以及悲剧的命运观等三个问题。     

郑和下西洋反思

通过对十五世纪中、西方远航船队的比较 ,昭示世人郑和船队的伟大。通过对郑和下西洋目的的辨析 ,阐明了明成祖朱棣和明宣宗朱瞻基派遣郑和下西洋的真实意图 ,追求“天下共主”的虚名和“贸采琛异”的耗费 ,给明朝社会经济带来了沉重打击。这是“埋葬”伟大郑和船队的根本原因     

基于Supply-hub的2个供应商单制造商批量协调问题研究

考虑一个由2个供应商和单制造商组成的装配型供应链,分析并建立了制造商、Supply-hub和2个供应商的平均成本函数,提出了分别由制造商和2个供应商负责Supply-hub营运及成本时的生产与订货批量模型。研究结果表明:当由制造商负责时,供应商距离Supply-hub越远,制造商的生产批量越大,且Supply-hub中的零部件补货批量相比供应商负责时更大;当由供应商负责时,制造商的生产批量不随供应商的远近而变化,供应商的零部件生产批量也不变。此外,在适用Supply-hub的条件下,相比由制造商负责,由2个供应商负责Supply-hub的运营并分担其成本时,整个供应链的总成本更低,2个供应商与制造商之间可以通过合理分配使2个供应商与制造商的营运成本均有所降低,从而实现整个供应链系统的Pareto优化。     

Assessment of acceptance sampling plans using posterior distribution for a dependent process

In this study, performance of single acceptance sampling plans by attribute is investigated by using the distribution of fraction nonconformance (i.e. lot quality distribution) for a dependent production process. It is the aim of this study to demonstrate that, in order to emphasize consumer risk (i.e. the risk of accepting a bad lot), it is better to evaluate a sampling plan based upon its performance as assessed by the posterior distribution of fractions nonconforming in accepted lots. Similarly, it is the desired posterior distribution that sets the basis for designing a sampling plan. The prior distribution used in this study is derived from a Markovian model of dependence.     

Optimizing lot size and setup time in a JIT environment: a multiple objective application

The just-in-time (JIT) system has been studied extensively and implemented by a number of US firms as an ell'ective production system. The core of JIT involves determination of lot size and setup time reduction so as to increase manufacturing flexibility while minimizing the inventory level. This decision problem usually involves multiple conflicting objectives and mixed-model production. In this paper, goal programming (GP) is applied to a real-world JIT problem involving fabrication of different automotive and industrial rubber composite belts. The model results provide new insights concerning the conflicting nature of several goals, especially between meeting demand and reducing setup or idle time. Also, the GP solution is superior to the current JIT practice of the company.     

A closed-loop supply chain for deteriorating products under stochastic container return times

This paper studies a two-stage supply chain where returnable transport items (RTIs) are used to ship finished products from the supplier to the buyer. Empty RTIs are collected at the buyer and returned to the supplier. The return time of RTIs is considered to be stochastic in this paper, and further finished products are assumed to deteriorate during potential delivery delays. First, the paper develops an analytical model of this supply chain, and then it discusses the properties of the model. Secondly, it presents the results of a simulation study in which the behaviour of the model is analysed. The results of our analysis indicate that the supply chain can influence both the risk of RTI stockouts at the supplier and the deterioration rate by changing the value of the return lot size of RTIs. Further, the results indicate that realising the optimal value for the RTI return lot size is especially important in case the mean return time of RTIs is short, while in case of a long RTI return lead time, an approximation of the optimal RTI return lot size is also acceptable.     

Multi-product lot scheduling with backordering and shelf-life constraints

In this paper, we revisit the economic lot scheduling problem (ELSP), where a family of products is produced on a single machine, or facility, on a continual basis. Our focus is on the determination of a feasible production schedule, including the manufacturing batch size of each item. We assume that total backordering is permissible and that each of the products has a limited post-production shelf life. Several studies examining this problem have suggested a rotational common cycle approach, where each item is produced exactly once every cycle. To ensure schedule feasibility, we resort to the technique of reducing individual production rates and allow the flexibility of producing any item more than once in every cycle, in conjunction with appropriate timing adjustments. In order to solve this more generalized model, which is NP hard, we suggest a two-stage heuristic algorithm. A numerical example demonstrates our solution approach.     

试论韩国巨儒李珥（栗谷）的教育思想

韩国著名学者及教育家李珥具有"立志和诚"的独特教育思想,他系统地提出了立志与确立行动目标的重要性以及"立志和诚"的教育方法、教育目的和教育振兴对策.     

对缓解上海中心城区“停车难”问题的建议

缓解上海中心城区“停车难”问题,应经政府主导、市区联动,全方位整合社会、市场资源,规划设计相配套的资金保障和机制保障。具体做法是：合理规划,增加供给,盘活存量,通过部门协同,依托社区共治推广小区与楼宇错峰停车;通过市场运作,运用科技手段,优化停车市场化管理体制。