无标度网络上的队列资源重分配策略

在实际的通信系统中,由于物理条件的限制,每个节点都具有有限长度的队列。研究了在有限队列资源的条件下,队列资源对无标度数据流动力学的影响。提出了一种队列资源重分配策略,策略中节点的队列长度与节点的介数成正比。仿真结果表明,在无标度网络中使用最短路径路由的条件下,所提出的重分配策略可以有效地改进网络的容量。同时对有限队列资源条件下的网络容量进行了理论分析。     

Optimal staffing in nonstationary service centers with constraints

This paper considers optimal staffing in service centers. We construct models for profit and cost centers using dynamic rate queues. To allow for practical optimal controls, we approximate the queueing process using a Gaussian random variable with equal mean and variance. We then appeal to the Pontryagin's maximum principle to derive a closed form square root staffing (SRS) rule for optimal staffing. Unlike most traditional SRS formulas, the main parameter in our formula is not the probability of delay but rather a cost‐to‐benefit ratio that depends on the shadow price. We show that the delay experienced by customers can be interpreted in terms of this ratio. Throughout the article, we provide theoretical support of our analysis and conduct extensive numerical experiments to reinforce our findings. To this end, various scenarios are considered to evaluate the change in the staffing levels as the cost‐to‐benefit ratio changes. We also assess the change in the service grade and the effects of a service‐level agreement constraint. Our analysis indicates that the variation in the ratio of customer abandonment over service rate particularly influences staffing levels and can lead to drastically different policies between profit and cost service centers. Our main contribution is the introduction of new analysis and managerial insights into the nonstationary optimal staffing of service centers, especially when the objective is to maximize profitability. © 2016 Wiley Periodicals, Inc. Naval Research Logistics 63: 615–630, 2017     

Decentralized admission control of a queueing system: A game‐theoretic model

Consider a distributed system where many gatekeepers share a single server. Customers arrive at each gatekeeper according to independent Poisson processes with different rates. Upon arrival of a new customer, the gatekeeper has to decide whether to admit the customer by sending it to the server, or to block it. Blocking costs nothing. The gatekeeper receives a reward after a customer completes the service, and incurs a cost if an admitted customer finds a busy server and therefore has to leave the system. Assuming an exponential service distribution, we formulate the problem as an n‐person non‐zero‐sum game in which each gatekeeper is interested in maximizing its own long‐run average reward. The key result is that each gatekeeper's optimal policy is that of a threshold type regardless what other gatekeepers do. We then derive Nash equilibria and discuss interesting insights. © 2003 Wiley Periodicals, Inc. Naval Research Logistics 50: 702–718, 2003.     

Strategic spectrum occupancy for secondary users in cognitive radio networks with retrials

This article investigates joining strategies and admission control policy for secondary users (SUs) with retrial behavior in a cognitive radio (CR) system where a single primary user (PU) coexists with multiple SUs. Under a certain reward‐cost structure, SUs opportunistically access the PU band when it is not occupied by the PU. If the band is available upon arrival, an SU decides with a probability either to use the band immediately or to balk the system. If the band is occupied, the SU must decide whether to enter the system as a retrial customer or to leave the system. Once the PU requests for service, the service of SU being served, if any, will be interrupted, and the interrupted SU leaves the band and retries for service after a random amount of time. In this article, we study the equilibrium behavior of non‐cooperative SUs who want to maximize their benefit in a selfish, distributed manner with delay‐sensitive utility function. The socially optimal strategies of SUs are also derived. To utilize the PU band more efficiently and rationally, an admission control policy is proposed to regulate SUs who enter the system in order to eliminate the gap between the individually and socially optimal strategies.     

基于排队论的装备维修人员数量需求模型*

确定维修人员需求是对装备维修机构进行科学管理和对维修人员进行有计划培训的需要。在分析装备维修人员构成的随机服务系统特征的基础上,运用排队论理论建立了以平均等待时间为目标的维修人员需求的愿望模型,该模型可更加确切地描述各专业对维修人员的实际需求。通过对模型进行仿真,结果表明了模型的合理性。     

Virtools环境下虚拟装备行为控制方法

为解决当前基于Virtools的装备虚拟训练系统中外观模型与机理模型紧密耦合所导致的模型开发效率低、不可重用的问题,分析了虚拟装备仿真模型结构,提出了一种基于Virtools消息机制的虚拟装备行为控制方法,实现了机理模型与外观模型相互分离、彼此独立的开发和维护,提高了模型的可维护性和可重用性。基于该方法开发的“某高炮虚拟训练系统”,已推广至军事院校的教学、训练,其验证了该方法的可行性。     

MD5的一种新的碰撞攻击

模差分分析是结合整数模减差分和XOR差分而定义的一种新的差分,与单一的模减差分或XOR差分相比,2种差分结合能表达更多的消息,从而可以更有效地分析、破解现有的哈希函数.MD5是哈希函数的一种,对消息的差分分析是对哈希函数实施碰撞攻击的重要手段,从目前已知的基于差分技术的攻击事实看,主要采用的是6比特差分和1比特差分.提...     

基于馈电信息的故障诊断技术研究

综合运用馈电信息基本理论,提出了一个基于馈电信息的故障诊断技术.该技术通过对馈电信息的比较、分析,从而实现对工作状态的监测和故障的检测;通过检测、分析馈电相关的频谱或相关的模式,实现状态分析和故障定位,完成对电子装备的故障诊断.     

THE RESEARCH AND IMPLEMENTATION OF COMBINING LOGIC WITH OBJECT­ORIENTED PARADIGM

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主动队列管理机制中PI算法的一种参数配置方法

研究了主动队列管理机制中PI控制器的参数配置方法。AQM中PI算法默认的参数以及一些文献提出的参数配置方法主要是从稳定性考虑,没有保证系统的动态性能指标。在控制论中,"二阶最优模型"是具有较好的动态性能和稳态性能的二阶系统。提出了一种PI控制器的参数配置方法,可以使TCP/AQM控制模型的开环传递函数具有"二阶最优模型"的形式。NS仿真结果表明采用该方法配置的参数可以提高PI控制器的动态性能并保证系统的稳态性能。最后指出PI控制器参数配置对网络状态的敏感性,以及今后的研究方向。