A stochastic optimization model for real-time ambulance redeployment

When ambulances are engaged in responding to emergency calls, the ability to respond quickly to future calls is considerably compromised. The available ambulances are typically relocated to reestablish maximal coverage. We present a two-stage stochastic optimization model for the ambulance redeployment problem that minimizes the number of relocations over a planning horizon while maintaining an acceptable service level. We conduct computational testing based on the real historical data from the Region of Waterloo Emergency Medical Services. The results show that the optimal relocation strategies can be computed within 40 s of computational time for a desired service level of 90%.     

Achieving MILP feasibility quickly using general disjunctions

Branch and bound algorithms for Mixed-Integer Linear Programming (MILP) almost universally branch on a single variable to create disjunctions. General linear expressions involving multiple variables are another option for branching disjunctions, but are not used for two main reasons: (i) descendent LPs tend to solve more slowly because of the added constraints, so the overall solution time is increased, and (ii) it is difficult to quickly find an effective general disjunction. We study the use of general disjunctions to reach the first MILP-feasible solution quickly, showing for the first time that general disjunctions can provide speed improvements for hard MILP models. The speed-up is due to new and efficient ways to (i) trigger the inclusion of a general disjunction only when it is likely to be beneficial, and (ii) construct effective general disjunctions very quickly. Our empirical results show performance improvements versus a state of the art commercial MILP solver.     

机会可控的补偿随机规划模型

分析了已有的随机规划处理方法,针对原有方法中存在的不能兼顾补偿和约束机会控制的问题,提出了机会可控的补偿随机规划模型,在补偿随机规划模型的基础上,对允许违背的约束或者相应的补偿增加机会控制.以明确的反应决策者的态度,分析了模型的结构,设计了以遗传算法和单纯形法为基础的分解算法对模型进行求解.实际算例证明了模型和分解算法的有效性.     

A new texture image retrieval way

This paper proposes a new texture image retrieval method for the considering of the population search and random information exchange merits of evolving programming which can be used to optimize image feature vector extraction. The experimental results show that this way can efficiently improve the retrieval accuracy and realize fasttips with the advantage of evolving programming algorithm.     

浅析企业级电子商务

介绍了企业级电子商务的概念,分析了企业发展企业级电子商务的紧迫性和必要性,运用管理学相关理论,阐述了企业级电子商务战略具体实施过程中的8个应用步骤。     

基于PHP的MySQL可视化设计

PHP和MySQL是开发Web数据库的最佳搭档,但MySQL只有命令行实用程序,没有可视化开发环境,这使建立网站时的数据库操作十分困难.采用PHP设计了一个可视的MySQL数据库管理系统,通过浏览器提供MySQL数据库视窗开发环境,使建立网站时的数据库操作变得十分容易.     

一般原方块角形结构的大系统多目标规划有效解的存在性

将具有一般原方块角形结构的大系统多目标规划问题分解为若干个子问题,研究了子问题与大系统问题有效解之间的关系,并讨论了大系统问题有效解的存在性。     

基于线性规划算法的磷生铁最优化成分设计

铝电解槽阳极组装用磷生铁在使用过程中需要的特性与其本体材料的物理性能息息相关。运用材料热力学的方法计算出五大元素(C,Si,P,Mn,S)的含量变化对磷生铁电导率和热膨胀系数的影响,并通过线性回归建立电导率和热膨胀系数与五大元素含量和温度的函数关系,最后利用线性规划最优化算法对某铝厂现行磷生铁成分进行有目的性的优化。通过优化后,磷生铁电导率最大优化率为14.50%,热膨胀系数最大优化率为5.99%。     

复合材料纤维/基体界面失效问题的参变量有限元数值模拟

本文利用参数拟二次规划法和非连续线弹性本构模型,构造了复合材料纤维/基体界面失效问题的细观力学模型并进行了有限元计算分析,得到了与实验相吻合的结果。     

机载多管火箭非满管射击试验方法研究

研究机载多管火箭非满管射击试验方法,为减少机载多管火箭密集度试验用弹量提供新的试验方法。应用发射动力学和多体系统传递矩阵法理论,基于等起始扰动思想,建立了机载多管火箭发射动力学模型、特征方程和动力响应方程,并应用随机整数规划方法,形成了减少机载多管火箭试验用弹量方法。针对某19管机载多管火箭,提出了6发连射的密集度试验方案,试验验证使密集度试验用弹量比常规试验方法减少了68.4%,节省了大量试验费用。