Dynamic inventory and pricing models for competing retailers

We address infinite‐horizon models for oligopolies with competing retailers under demand uncertainty. We characterize the equilibrium behavior which arises under simple wholesale pricing schemes. More specifically, we consider a periodic review, infinite‐horizon model for a two‐echelon system with a single supplier servicing a network of competing retailers. In every period, each retailer faces a random demand volume, the distribution of which depends on his own retail price as well as those charged by possibly all competing retailers. We also derive various comparative statics results regarding the impact several exogenous system parameters (e.g., cost or distributional parameters) have on the equilibrium decisions of the retailers as well as their expected profits. We show that certain monotonicity properties, engrained in folklore as well as in known inventory models for centralized systems, may break down in decentralized chains under retailer competition. Our results can be used to optimize the aggregate profits in the supply chain (i.e., those of the supplier and all retailers) by implementing a specific wholesale pricing scheme. © 2003 Wiley Periodicals, Inc. Naval Research Logistics, 2004.     

电磁发射超高速弹丸气动特性数值分析

采用数值计算方法研究了超高速弹丸的气动流场特性,重点分析了弹丸再入段的气动流场特性.利用风洞试验数据验证了S-A和k-ωSST湍流模型的预测精度,计算结果表明,在法向力预测上,两种湍流模型的预测精度较高,均在2％以内.在轴向力预测上,S-A湍流模型的预测精度较高,误差约为4.6％.当弹丸以大攻角再入时,弹丸横流效应较为...     

影响工科类高职院校高等数学教学质量因素的分析——以新疆高等职业院校为例

通过对工科类高职院校高等数学学生与专业教师的调研,就学生在数学的学习兴趣、学习习惯、学习方法、学习态度、认知水平和基本能力以及专业教师对高等数学的认识等诸多方面影响教学质量的因素进行分析,进一步提出提高高等数学教学质量的策略。     

兵团中学数学教师教育科研现状调查与分析

数学教师是数学教育工作中的主体力量,其教育科研水平直接关系到数学教育专业化的进程。调查发现,兵团中学数学教师的教育科研水平尚处于起步阶段。为提高教师的教育科研水平,应加强以下几个方面的工作:正确认识教学与教育科研的关系;加强教育理论著作、中学数学期刊的阅读;有效利用各级培训,强化对教师的教育科研能力的培养;上级主管部门以及学校应加大对教师从事教育科研的支持力度;建立兵团教育学院和兵团中小学的长期协助、合作关系。最后,兵团教育学院还应考虑创建一份中学数学期刊。     

维吾尔族数学文化调查分析

维吾尔族传统文化中包含着丰富的数学元素。充分挖掘和展示维吾尔族文化中的数学知识,重视课程资源开发,提倡数学学习方式的多样化,深化多元文化视野下的数学教育对于推进少数民族地区数学课程改革具有积极的现实意义。此外,有关民族数学教育学的理论体系的建立及实践探索也是必须涉及的一个重要方面。     

针对高职学生特点巧讲新解部分高数知识

本文先介绍高等职业教育的特点、目前高职学生的情况以及高等数学课在高职教育中的定位,进而说明高职高等数学教学内容整理的必要性,然后给出巧讲新解的部分高数知识,最后进行总结。     

陆军战场机动效果评估

战场机动效果评估是陆军指挥员及指挥机关组织机动过程中的一项重要工作。首先介绍了战场机动效果评估的内容和指标体系,通过对机动时效性、机动到位率、机动隐蔽性和战斗力保持程度等主要内容的定性与定量分析,建立评估指标体系、评估数学模型,分别从机动时刻性、机动到位率、机动隐蔽性和战斗率四个方面评估机动效果,然后得出综合评估模型。以某战场机动场景为例进行仿真分析,得出综合评估结果,证实该方法提高了评估的准确性,为指挥员决策提供重要依据。     

A partial characterization of the optimal ordering/rationing policy for a periodic review system with two demand classes and backordering

We consider a finite horizon periodic review, single product inventory system with a fixed setup cost and two stochastic demand classes that differ in their backordering costs. In each period, one must decide whether and how much to order, and how much demand of the lower class should be satisfied. We show that the optimal ordering policy can be characterized as a state dependent (s,S) policy, and the rationing structure is partially obtained based on the subconvexity of the cost function. We then propose a simple heuristic rationing policy, which is easy to implement and close to optimal for intensive numerical examples. We further study the case when the first demand class is deterministic and must be satisfied immediately. We show the optimality of the state dependent (s,S) ordering policy, and obtain additional rationing structural properties. Based on these properties, the optimal ordering and rationing policy for any state can be generated by finding the optimal policy of only a finite set of states, and for each state in this set, the optimal policy is obtained simply by choosing a policy from at most two alternatives. An efficient algorithm is then proposed. © 2010 Wiley Periodicals, Inc. Naval Research Logistics, 2010     

National security,military spending and the business cycle

This paper develops a Dynamic Stochastic General Equilibrium model where national security is an argument in the agent’s utility function and the government chooses optimally the level of military spending to maximize social welfare. National defense depends on military expenditure and on the strategic environment reflecting a potential hostile external threat. We use aggregate data on consumption, investment, and military spending for the US economy to estimate the parameters of the model. Estimation results suggest that consumption and national defense are complements and that military spending variability is mainly explained by external threat shocks although it also depends on the macroeconomic conditions. We compute impulse response functions of the main macroeconomic variables to several shocks: a total factor productivity shock, a defense technology shock, and a strategic environment shock. Surprisingly, we find that the optimal response to an increase in the external threat (a worsening in the strategic environment) will rise output by reducing consumption and increasing investment.     

工科数学课程创新存在的问题与对策

国内工科数学课程创新能力与机制缺乏，对数学课程体系的创新认识不足，内容过于重视传统数学，数学教师的专业创新能力有待提高等一系列问题严重影响工科院校基础数学课程的创新。应对课程体系、课程内容、课程实施、课程评价进行创新，并提出了相应的对策。