Discrete‐time analysis of MAP/PH/1 multiclass general preemptive priority queue

We use the matrix‐geometric method to study the MAP/PH/1 general preemptive priority queue with a multiple class of jobs. A procedure for obtaining the block matrices representing the transition matrix P is presented. We show that the special upper triangular structure of the matrix R obtained by Miller [Computation of steady‐state probabilities for M/M/1 priority queues, Oper Res 29(5) (1981), 945–958] can be extended to an upper triangular block structure. Moreover, the subblock matrices of matrix R also have such a structure. With this special structure, we develop a procedure to compute the matrix R. After obtaining the stationary distribution of the system, we study two primary performance indices, namely, the distributions of the number of jobs of each type in the system and their waiting times. Although most of our analysis is carried out for the case of K = 3, the developed approach is general enough to study the other cases (K ≥ 4). © 2003 Wiley Periodicals, Inc. Naval Research Logistics 50: 662–682, 2003.     

Realignment in the National Football League: Did they do it right?

The National Football League (NFL) in the United States expanded to 32 teams in 2002 with the addition of a team in Houston. At that point, the league was realigned into eight divisions, each containing four teams. We describe a branch‐and‐cut algorithm for minimizing the sum of intradivisional travel distances. We consider first the case where any team can be assigned to any division. We also consider imposing restrictions, such as aligning the AFC (American Football Conference) and the NFC (National Football Conference) separately or maintaining traditional rivalries. We show that the alignment chosen by the NFL does not minimize the sum of intradivisional travel distances, but that it is close to optimal for an alignment that aligns the NFC and AFC separately and imposes some additional restrictions. © 2003 Wiley Periodicals, Inc. Naval Research Logistics 50: 683–701, 2003.     

一种快速有效的循环平稳信号检测方法

TSAE-Z算法把时间切片自相关包络检测和可变步进的Zoom-FFT检测相结合,实现了对循环平稳信号的快速、精确检测,仿真结果表明,在相同数据长度条件下,TSAE-Z算法能够使检测运算时间减少3个数量级;在相同执行时间的条件下,TSAE-Z算法能在提高检测分辨率的同时使检测性能提升6dB以上。     

基于大规模贝叶斯网络的安全性分析算法

贝叶斯网络计算量随着节点数增多呈指数增长,限制了大规模贝叶斯网络在安全性分析中的应用。为此,利用独立性条件分解整个网络,压缩推理时显式表达的项数,给出了计算顶事件发生概率及割集的算法,并分析了算法复杂性。在满足工程需要情况下,将提出算法与基于BDD算法相比,该算法表现出占用内存少、运行速度快的良好性能。     

大型船舶空气尾流场防治新技术的数值模拟

大型船舶空气尾流场对海上飞机安全降落有重要的影响,因此对其进行有效防治技术研究在保障飞机安全、大型船舶海上活动等方面有重要意义。采用计算流体力学方法开展大型船舶空气尾流场特性及其防治技术的数值模拟研究,以带有Spalart-Allmaras湍流模型的Reynolds平均Navier-Stokes方程构建模拟平台开展数值模拟,得到大型船舶空气尾流场规律特性。在此基础上,提出主动补气防治新技术,分别阐述其理论基础、核心方法和技术方案;根据主动补气防治技术思想和理论,进一步开展数值模拟验证研究。结果表明,该技术能显著改善空气尾流场的流场品质,使流场趋于平稳均匀,减小对飞机海上降落的影响。该技术进一步完善了可实现工程应用,并保证飞机海上降落安全,有巨大的应用潜力。     

螺栓法兰连接结构有限元模型参数确定方法

螺栓法兰连接广泛用于各种工业结构中,为准确预测该连接在实际工作中发挥的作用,需要建立准确高效的有限元模型。针对有限元建模过程中模型各种参数的确定问题,综合使用数值仿真手段和试验手段分别对模型网格参数和接触参数的确定开展研究。参数确定后的螺栓法兰连接结构有限元模型在保证计算精度的前提下,计算效率得到显著提高。     

Potential impact of recharging plug‐in hybrid electric vehicles on locational marginal prices

Plug‐in hybrid electric vehicles (PHEVs), upon market penetration, will create additional recharging loads to the electric power systems. This article considers different recharging scenarios and uses game theoretic models to study the potential impact of the recharging loads on locational marginal prices (wholesale electricity prices). Computational results from a Pennsylvania‐New Jersey‐Maryland Interconnection case study show that, under the existing recharging infrastructures, even a small magnitude of load increase caused by PHEV recharging could have a significant undesirable impact on locational marginal prices. The impact could be mitigated to a varying extent by the availability of possible future recharging infrastructures, including realtime pricing recharging meters, battery stations, or vehicle‐to‐grid technology.© 2010 Wiley Periodicals, Inc. Naval Research Logistics, 2010     

Decomposing inventory routing problems with approximate value functions

We present a time decomposition for inventory routing problems. The methodology is based on valuing inventory with a concave piecewise linear function and then combining solutions to single‐period subproblems using dynamic programming techniques. Computational experiments show that the resulting value function accurately captures the inventory's value, and solving the multiperiod problem as a sequence of single‐period subproblems drastically decreases computational time without sacrificing solution quality. © 2010 Wiley Periodicals, Inc. Naval Research Logistics, 2010     

公安边防部队参与涉外联合行动的现状和发展趋势探析

目前公安边防部队参与涉外联合行动主要包括联合执法打击跨国犯罪、承担维和任务维护世界和平、参与涉外联合演习打击恐怖主义等形式。随着国家间联合协作的不断加强,公安边防部队参与涉外联合行动朝着合作范围不断扩大、合作模式更加多样、执法一体化日益明显的趋势发展。     

Scheduling a maintenance activity on parallel identical machines

We study a problem of scheduling a maintenance activity on parallel identical machines, under the assumption that all the machines must be maintained simultaneously. One example for this setting is a situation where the entire system must be stopped for maintenance because of a required electricity shut‐down. The objective is minimum flow‐time. The problem is shown to be NP‐hard, and moreover impossible to approximate unless P = NP. We introduce a pseudo‐polynomial dynamic programming algorithm, and show how to convert it into a bicriteria FPTAS for this problem. We also present an efficient heuristic and a lower bound. Our numerical tests indicate that the heuristic provides in most cases very close‐to‐optimal schedules. © 2008 Wiley Periodicals, Inc. Naval Research Logistics 2009