Influence of high frequency pulse on electrode wear in micro-EDM

An electromagnetic coupling mathematical model is established by finite element method and is verified by the contrastive experiments of copper matrix Ni–TiN cylindrical coating electrode, copper electrode and Cu50W electrode. The wear mechanism of Ni–TiN/Cu composite electrode in the case of high-frequency pulse current is studied, and the influence of the fluctuation frequency of discharge current on electrode wear in micro-EDM is found out. Compared with the electrode made from homogeneous material, the high frequency electromagnetic properties of Ni–TiN composite layer can be used effectively to inhibit the effect of high frequency pulse on the electrode and improve the distribution trend of current density.     

一种北斗／CDMA导航系统数据融合的联邦卡尔曼滤波算法

北斗卫星与CDMA无线网络定位相结合的组合导航系统可以广泛应用于军事和民用领域,而有效进行数据融合是提高北斗/CDMA组合导航系统定位精度的关键.针对北斗/CDMA组合导航系统的特点,提出了一种基于联邦卡尔曼滤波的北斗/CDMA导航数据融合算法.算法采用机动目标的"当前"统计模型,分别建立了北斗定位系统和CDMA定位系统的状态方程,通过对相应定位参数进行滤波处理,提高了北斗/CDMA导航系统的定位精度.     

面向信息化战争的广义兰切斯特作战模型

由于经典兰切斯特方程不能描述信息对于信息化战争的影响,因此在分析兰切斯特线性律和平方律的基础上,通过引入战场感知系数和信息优势系数,并利用信息优势系数对线性律和平方律中毁伤系数进行修正,提出了能够描述信息对战争影响的广义兰切斯特作战模型,仿真实验结果说明其能够有效地描述信息优势对于改变战争进程所发挥的重要作用。该模型为研究信息化战争的交战过程提供理论参考。     

机动输油管线泵机组仿真模型构建

受经费、人力、装备等因素的制约，机动型输油管线的实装训练往往难以开展，而开展仿真训练则是提高训练水平和效益的重要手段。构建机动输油管线泵机组仿真模型是模拟器研制和管线系统仿真的基础。建立了机动输油管线泵机组柴油机、增速器、离心泵的数学模型，给出了泵机组仿真计算的基本流程，建立了基于统一建模语言（UML）的泵机组仿真模型类图。所提出的建模方法同样适用于滑片泵泵机组。     

Assortment optimization with position effects under the nested logit model

We study the assortment optimization problem with position effects under the nested logit model, whose goal is to find the revenue-maximizing subset of products as well as their corresponding display positions. In this joint assortment-position optimization problem, the choices of products are affected by not only their qualities and prices but also the positions where they are displayed. Despite determining the assortment and their corresponding display positions sequentially, we propose to solve this problem in an integrated way to obtain the optimal solution. We formulate this problem as a nonlinear binary integer programming model and develop a dynamic programming based solution approach to obtain the optimal assortment-position assignments. We carry out extensive numerical experiments to evaluate the benefit of our integrated approach. The most important insight we discover is that it is not necessarily better to put the most attractive products in the best position. Moreover, we show that compared to the sequential approaches, our approach can improve revenue by 10.38% on average, which suggests that firms should take into consideration position effects when making assortment decisions. Finally, we discuss results related to two extensions of this problem, that is, the special case when positions are preassigned to nests, and the joint assortment-position-price optimization problem.     

基于多视点的武器装备体系需求建模

简要分析了国内外武器装备体系需求研究的现状,总结了武器装备体系需求特点,基于视点的需求开发方法,给出了武器装备体系需求的需求视点,建立了武器装备体系需求建模的过程模型,提出了基于UML元语言的一致性检验方法,为构建我军一体化联合作战的武器装备体系做出了探索性的研究.     

高中数学研究性学习的实践与研究

在中学开设研究性学习课程，是基础教育课程改革的具体目标之一。针对现有课程体系的弊端，重知识传授而轻过程和技能训练，重学科知识体系而不关心社会实践活动。重间接经验的传授而忽视学生的直接体验积累。为培养学生乐于探究勤于动手的学习精神，分析和解决的能力，本人在几年的教学实践中，不断探究，积累了一些经验。本文就此问题谈谈高中数学研究性学习的实践与体会。     

惯导速度信息辅助的被动雷达导引头量测误差抑制方法

针对被动雷达导引头由于受空间限制测角精度不高的问题,提出了一种基于弹目信息状态变量的扩展卡尔曼滤波方法。通过弹目信息状态变量(弹目距离、弹目视线方位角、弹目视线俯仰角)描述弹目相对位置信息,利用惯导速度信息构建基于弹目信息状态变量变化率的弹目相对运动模型。所提方法充分利用信息资源,抑制导引头量测随机误差,对于提高导弹的打击精度和攻击效果,具有重要的实际应用价值,仿真试验证明该算法的有效性。     

An approximate dynamic programing approach to the development of heuristics for the scheduling of impatient jobs in a clearing system

A single server is faced with a collection of jobs of varying duration and urgency. Each job has a random lifetime during which it is available for nonpreemptive service. Should a job's lifetime expire before its service begins then it is lost from the system unserved. The goal is to schedule the jobs for service to maximize the expected number served to completion. Two heuristics have been proposed in the literature. One (labeled π^S) operates a static priority among the job classes and works well in a “no premature job loss” limit, whereas the second (π^M) is a myopic heuristic which works well when lifetimes are short. Both can exhibit poor performance for problems at some distance from the regimes for which they were designed. We develop a robustly good heuristic by an approximative approach to the application of a policy improvement step to the asymptotically optimal heuristic π^S, in which we use a fluid model to obtain an approximation for the value function of π^S. The performance of the proposed heuristic is investigated in an extensive numerical study. © 2010 Wiley Periodicals, Inc. Naval Research Logistics 2010     

Scheduling parallel machines with inclusive processing set restrictions

We consider the problem of assigning a set of jobs to different parallel machines of the same processing speed, where each job is compatible to only a subset of those machines. The machines can be linearly ordered such that a higher‐indexed machine can process all those jobs that a lower‐indexed machine can process. The objective is to minimize the makespan of the schedule. This problem is motivated by industrial applications such as cargo handling by cranes with nonidentical weight capacities, computer processor scheduling with memory constraints, and grades of service provision by parallel servers. We develop an efficient algorithm for this problem with a worst‐case performance ratio of + ε, where ε is a positive constant which may be set arbitrarily close to zero. We also present a polynomial time approximation scheme for this problem, which answers an open question in the literature. © 2008 Wiley Periodicals, Inc. Naval Research Logistics, 2008