Optimal policies for M/M/m queue with two different kinds of (N,T)‐policies

In this paper, two different kinds of (N, T)‐policies for an M/M/m queueing system are studied. The system operates only intermittently and is shut down when no customers are present any more. A fixed setup cost of K > 0 is incurred each time the system is reopened. Also, a holding cost of h > 0 per unit time is incurred for each customer present. The two (N, T)‐policies studied for this queueing system with cost structures are as follows: (1) The system is reactivated as soon as N customers are present or the waiting time of the leading customer reaches a predefined time T, and (2) the system is reactivated as soon as N customers are present or the time units after the end of the last busy period reaches a predefined time T. The equations satisfied by the optimal policy (N*, T*) for minimizing the long‐run average cost per unit time in both cases are obtained. Particularly, we obtain the explicit optimal joint policy (N*, T*) and optimal objective value for the case of a single server, the explicit optimal policy N* and optimal objective value for the case of multiple servers when only predefined customers number N is measured, and the explicit optimal policy T* and optimal objective value for the case of multiple servers when only predefined time units T is measured, respectively. These results partly extend (1) the classic N or T policy to a more practical (N, T)‐policy and (2) the conclusions obtained for single server system to a system consisting of m (m ≥ 1) servers. © 2000 John Wiley & Sons, Inc. Naval Research Logistics 47: 240–258, 2000     

酸性条件下几种锅炉炉管钢腐蚀性能分析

研究了几种锅炉炉管钢在 p H=3的 H2 SO4 溶液中腐蚀速率的差异 .电化学测试结果表明 :炉管钢的腐蚀速率与钢中合金元素的种类和含量有一定关系 ;含铬、钼量较高的钢种腐蚀速率较低 .由此可见 ,铬元素是抑制炉管钢在酸性介质中发生腐蚀的最主要的合金元素 ,其他元素如钼、镍等对炉管钢的腐蚀性能也有重要影响     

基于PC机对多总线导航计算机软件开发方法的研究

对基于多总线结构的计算机传统软件开发方式的局限性进行了分析 ,对一种基于IBM PC机为开发平台 ,采用 C语言开发的软件开发方法进行了研究和探讨 .文章对这一方法在使用中所存在的主要问题和解决的主要技术手段作了介绍 .在实际开发过程中 ,该方法已被证明简便、可行、有效 ,这对于类似基于多总线结构的导航计算机的许多计算机的软件开发均有一定的借鉴作用     

灭火力量部署的计算机图形标识

灭火兵力部署的计算机图形标识旨在用计算机图形标识的方法模拟消防力量部署。本文通过程序设计对图标进行选择、移动、删除、位置记录等操作 ,将灭火力量标识到火场的适当位置 ,从而实现对消防力量决策、消防兵力实时部署的计算机模拟 ,可应用于计算机灭火指挥模拟训练系统中。     

化学危险品运输车辆应防火灾爆炸事故

本文通过具体案例分析了化学危险品运输车辆可能发生火灾爆炸事故的原因,并提出了应采取的安全措施。     

Scheduling to minimize the total compression and late costs

We consider a single-machine scheduling model in which the job processing times are controllable variables with linear costs. The objective is to minimize the sum of the cost incurred in compressing job processing times and the cost associated with the number of late jobs. The problem is shown to be NP-hard even when the due dates of all jobs are identical. We present a dynamic programming solution algorithm and a fully polynomial approximation scheme for the problem. Several efficient heuristics are proposed for solving the problem. Computational experiments demonstrate that the heuristics are capable of producing near-optimal solutions quickly. © 1998 John Wiley & Sons, Inc. Naval Research Logistics 45: 67–82, 1998     

气体化学反应速率的 DSMC 方法

为预报化学反应过程,应用ＤＳＭＣ方法研究了双原子分子的离解反应,讨论了高温情况下（Ｔ～Ｅａ／ｋ）采用由实验测定得到的反应速率与气体温度间Ａｒｒｈｅｎｉｕｓ经验关系式的可靠性问题,分析了振动热非平衡效应对于离解反应速率的影响,给出了由ＤＳＭＣ方法得到的离解反应速率与气体温度的关系曲线。     

大型柔性空间结构的多级分散化振动控制

文中直接以结构的动力学变量作为系统状态,从理论上推导出了反馈和状态变量的解析表达式。基于该表达式,对一空间站模型进行了仿真。结果表明,该方法具有计算量小、稳定性好的优点,便于在线控制。     

扭轮摩擦驱动系统研究

扭轮摩擦驱动是集摩擦传动和螺旋传动为一体的传动系统,它既具有摩擦传动动态特性好,同时又有螺旋传动导程小的特点。本文介绍一种扭轮摩擦驱动系统,它的导程小于０．２ｍｍ,行程为２５０ｍｍ,运动分辨率可达纳米级水平。它由扭轮摩擦传动机构、气体静压导轨及相关部件组成,是一种大行程高分辨率的新型驱动系统。     

Estimating the point availability with right‐censored data

The point availability of a one‐unit system at a specified time is defined as the probability that the component is operating at that time. When both operating time and repair time are subject to random (right) censorship, we propose an asymptotic nonparametric approach for constructing confidence intervals for the point availability of the system. The technique is based on the fact that a product limit estimator converges to a Gaussian process. The method is also extended to finding confidence intervals for the point availability of a complex system using the δ‐Method. © 1999 John Wiley & Sons, Inc. Naval Research Logistics 46: 119–127, 1999