One-facility location with rectilinear tour distances

This article concerns the location of a facility among n points where the points are serviced by “tours” taken from the facility. Tours include m points at a time and each group of m points may become active (may need a tour) with some known probability. Distances are assumed to be rectilinear. For m ≤ 3, it is proved that the objective function is separable in each dimension and an exact solution method is given that involves finding the median of numbers appropriately generated from the problem data. It is shown that the objective function becomes multimodal when some tours pass through four or more points. A bounded heuristic procedure is suggested for this latter case. This heuristic involves solving an auxiliary three-point tour location problem.     

振动非平衡喷管流场的数值研究

从非定常的基本方程出发,采用时间相关法,利用带有平滑项的ＭａｃＣｏｒｍａｃｋ格式对以氮气为实验气体的一维振动非平衡喷管流场进行了数值计算。分析了不同条件下振动非平衡对流场的影响,确定了支配振动非平衡的主要因素。计算结果表明,对于一些实际应用的喷管条件,振动非平衡具有较为显著的影响。     

测量聚合物在高应变率下力学性质的实验系统

本文介绍了一种用于测量材料在高应变率下单轴应力─应变性能的实验测量系统：落重与高速摄影实验系统。该系统在现有的落重装置的基础上,增加了高速摄影和应力过程的同时测量,使得在一次实验中可同时取到应力应变数据。从而避免了这类实验中常用的变形过程中体积不变的假设。通过高速实验提供的实验照片,我们还可以观察到聚合物在高应变率下从变形到断裂的发展过程。     

多状态系统故障树质蕴含集的求取算法

本章首先给出多状态系统状态空间的立方体表示方法,然后建立相应的运算规则。在这些规则的基础上,提出多状态系统故障树质蕴含集的求取算法。通过实例分析,说明了这种方法的可行性。     

关于小高炮射击偏差观测方法之我见

小高炮射击偏差观测的提前时间观测时机法与传统的等距法,两者的观测时机虽不同,精度也不同,但从原理上讲,都是一种近似方法,不能说哪个原理上有问题,哪个原理上无问题。从部队现装备看,在部队日常训练打靶中,前者的观测时机更易于把握,作为现装备的一种革新,有研究必要。     

MPP虚拟多机系统

ＭＰＰ虚拟多机系统是一个特殊的ＰＶＭ系统，本文阐述了ＭＰＰ虚拟多机系统的系统结构和实现技术，并对ＭＰＰ虚拟机的性能进行了初步测试和分析。     

弹道数据处理融合算法的并行计算

针对参考文献[1]中提出的融合多信源信息的融合算法,讨论了其中大计算量的测元遴选问题,并给出了它的并行算法。最后详细地分析了此并行算法的高效性和可扩展性,给出了加速比的仿真结果     

飞船再入舱三维化学非平衡流数值模拟

对飞船再入舱高超声速化学非平衡三维流场进行数值模拟。控制方程为含化学反应源项的全Ｎａｖｉｅｒ－ Ｓｔｏｋｅｓ 方程组, 化学模型为高温空气的七组元模型, 其组元成分为Ｎ２ 、Ｏ２、ＮＯ、Ｎ、Ｏ、ＮＯ＋ 、ｅ－ 。差分格式采用张涵信院士提出的ＮＮＤ激波捕捉格式并用全耦合方法处理流动方程及化学反应方程, 对化学反应源项采用全隐式处理, 运用时间预处理技术以加快收敛。同时, 也对完全气体模型进行计算, 以分析真实气体效应。与实验数据对比, 说明本文结果是可信的。     

GPS仿真器设计

本文详细介绍了在无人机利用ＧＰＳ导航半实物仿真系统中ＧＰＳ仿真器的设计原理。通过分析ＧＰＳ及ＧＰＳ接收机的基本工作方式,ＷＧＳ－８４与各种坐标系的转换关系,研制了ＧＰＳ仿真器。它将由飞行仿真计算机得到的无人机位置信息转换成与之对应的ＧＰＳ信号,输入飞控计算机,以实现ＧＰＳ导航的仿真试验。     

Analysis of decentralized multi‐product pull systems with lost sales

We study a pull‐type, flexible, multi‐product, and multi‐stage production/inventory system with decentralized two‐card kanban control policies. Each stage involves a processor and two buffers with finite target levels. Production stages, arranged in series, can process several product types one at a time. Transportation of semi‐finished parts from one stage to another is performed in fixed lot sizes. The exact analysis is mathematically intractable even for smaller systems. We present a robust approximation algorithm to model two‐card kanban systems with batch transfers under arbitrary complexity. The algorithm uses phase‐type modeling to find effective processing times and busy period analysis to identify delays among product types in resource contention. Our algorithm reduces the effort required for estimating performance measures by a considerable margin and resolves the state–space explosion problem of analytical approaches. Using this analytical tool, we present new findings for a better understanding of some tactical and operational issues. We show that flow of material in small procurement sizes smoothes flow of information within the system, but also necessitates more frequent shipments between stages, raising the risk of late delivery. Balancing the risk of information delays vis‐à‐vis shipment delays is critical for the success of two‐card kanban systems. Although product variety causes time wasted in setup operations, it also facilitates relatively short production cycles enabling processors to switch from one product type to another more rapidly. The latter point is crucial especially in high‐demand environments. Increasing production line size prevents quick response to customer demand, but it may improve system performance if the vendor lead‐time is long or subject to high variation. Finally, variability in transportation and processing times causes the most damage if it arises at stages closer to the customer. © 2007 Wiley Periodicals, Inc. Naval Research Logistics, 2007