A stochastic network formulation for complex sequential processes

A network model incorporating stochastic features is considered. The model represents a complex sequential process where an object or system moves through a succession of states (nodes) and operating modes (classes) in the course of carrying out its function (fulfilling its purpose). Transitions between states and operating modes occur in a possibly random manner and require (consume) some resource in randomly varying amounts. We discuss the routing behavior and resource requirements of a typical object as it moves through (and eventually out of) the network. We then shift our focus from a single object and its odyssey to the network as a whole, where time is the resource and many objects are entering the network according to a possibly nonhomogeneous Poisson pattern; in this vein, we discuss the evolution of the network over time. Finally, we consider some applications of the formulation, and results.     

Rendezvous search on labeled networks

Two players are independently placed on a commonly labelled network X. They cannot see each other but wish to meet in least expected time. We consider continuous and discrete versions, in which they may move at unit speed or between adjacent distinct nodes, respectively. There are two versions of the problem (asymmetric or symmetric), depending on whether or not we allow the players to use different strategies. After obtaining some optimality conditions for general networks, we specialize to the interval and circle networks. In the first setting, we extend the work of J. V. Howard; in the second we prove a conjecture concerning the optimal symmetric strategy. © 2002 Wiley Periodicals, Inc. Naval Research Logistics 49: 256–274, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/nav.10011     

基于流水线图像处理结构的多层模板相关神经元网络

在自主地面车辆中,视觉系统的重要作用之一是根据路标来定位。本文提出了一种便于流水线图像处理结构实现的多层模板相关神经元网络（ＭＴＣＮＮ）。文中给出了ＭＴＣＮＮ的基本结构及训练算法,并且将其与经典的多层前馈神经元网络（ＭＬＦＮＮ）进行了比较。仿真结果表明,本文提出的算法结构在多层前馈神经元网络的分类能力与采用通用图像处理硬件的可实现性之间,取得了良好的折衷。     

Benders decomposition with alternative multiple cuts for a multi‐product closed‐loop supply chain network design model

In this article, we consider a multi‐product closed‐loop supply chain network design problem where we locate collection centers and remanufacturing facilities while coordinating the forward and reverse flows in the network so as to minimize the processing, transportation, and fixed location costs. The problem of interest is motivated by the practice of an original equipment manufacturer in the automotive industry that provides service parts for vehicle maintenance and repair. We provide an effective problem formulation that is amenable to efficient Benders reformulation and an exact solution approach. More specifically, we develop an efficient dual solution approach to generate strong Benders cuts, and, in addition to the classical single Benders cut approach, we propose three different approaches for adding multiple Benders cuts. These cuts are obtained via dual problem disaggregation based either on the forward and reverse flows, or the products, or both. We present computational results which illustrate the superior performance of the proposed solution methodology with multiple Benders cuts in comparison to the branch‐and‐cut approach as well as the traditional Benders decomposition approach with a single cut. In particular, we observe that the use of multiple Benders cuts generates stronger lower bounds and promotes faster convergence to optimality. We also observe that if the model parameters are such that the different costs are not balanced, but, rather, are biased towards one of the major cost categories (processing, transportation or fixed location costs), the time required to obtain the optimal solution decreases considerably when using the proposed solution methodology as well as the branch‐and‐cut approach. © 2007 Wiley Periodicals, Inc. Naval Research Logistics, 2007     

FROM RIGHTS TO RESPONSIBILITIES

This article aims to explore possible avenues that the international community can use in order to justify forcible intervention in sovereign states in cases where gross and systematic violations of the human rights of the he population take place, but where the legal authority for such intervention is not forthcoming from the Uni ted Nations Security Council. Two possible justifications are identified: the doctrine of humanitarian intervention, which despite being controversial, enjoys a measure of acceptance due to the practice of states in this regard, and the notion of an international responsibility to protect vulnerable populations and individuals. The latter option, despite a vague and uncertain legal basis, offers several advantages: it focuses on the suffering of human beings and not on the rights of states, it enumerates clear and definable thresholds for intervention by the international community and acknowledges that intervention is only one step in the process of achieving peace, to be preceded by preventive action and followed by post-conflict reconstruction. It is submit ted that elements of the notion of an international “responsibility to protect” are to be found in the Constitutive Act of the African Union and especially the Protocol on the Establishment of the Peace and Security Council. Furthermore, the principles underlying this notion, as developed by the International Commission on Intervention and State Sovereignty may serve as guidelines in decisions by the Assembly to authorise interventions in AU members.     

Optimization of steerable sensor network for threat detection

A Markov chain approach to detecting a threat in a given surveillance zone by a network of steerable sensors is presented. The network has a finite number of predetermined states, and transition from one state to another follows a Markov chain. Under the assumption that the threat avoids detection, two game theoretic problems for finding an optimal Markov chain (two surveillance strategies) are formulated: the first maximizes the probability of threat detection for two consecutive detection periods, whereas the second minimizes the average time of detection for the worst‐case threat's trajectory. Both problems are reduced to linear programming, and special techniques are suggested to solve them. For a dynamic environment with moving noise sources, the optimal Markov chain changes at each detection period, and the rate of convergence of the Markov chain to its stationary distribution is analyzed. Both surveillance strategies are tested in numerical experiments and compared one with another. © 2011 Wiley Periodicals, Inc. Naval Research Logistics, 2011     

Equilibrium customer strategies and social–profit maximization in the single‐server constant retrial queue

We consider the single‐server constant retrial queue with a Poisson arrival process and exponential service and retrial times. This system has not waiting space, so the customers that find the server busy are forced to abandon the system, but they can leave their contact details. Hence, after a service completion, the server seeks for a customer among those that have unsuccessfully applied for service but left their contact details, at a constant retrial rate. We assume that the arriving customers that find the server busy decide whether to leave their contact details or to balk based on a natural reward‐cost structure, which incorporates their desire for service as well as their unwillingness to wait. We examine the customers' behavior, and we identify the Nash equilibrium joining strategies. We also study the corresponding social and profit maximization problems. We consider separately the observable case where the customers get informed about the number of customers waiting for service and the unobservable case where they do not receive this information. Several extensions of the model are also discussed. © 2011 Wiley Periodicals, Inc. Naval Research Logistics, 2011     

Lanchester for cyber: The mixed epidemic‐combat model

Future conflict between armed forces will occur both in the physical domain as well as the information domain. The linkage of these domains is not yet fully understood. We study the dynamics of a force subject to kinetic effects as well as a specific network effect–spreading malware. In the course of our study, we unify two well‐studied models: the Lanchester model of armed conflict and deterministic models of epidemiology. We develop basic results, including a rule for determining when explicit modeling of network propagation is required. We then generalize the model to a force subdivided by both physical and network topology, and demonstrate the specific case where the force is divided between front‐ and rear‐echelons. © 2013 Wiley Periodicals, Inc. Naval Research Logistics, 2013     

Rebel movements in the DRC

Despite a generally valiant effort on the part of the United Nations (UN) since 1999 to bring peace and stability to the Democratic Republic of the Congo (DRC), the country continues to be destabilised by rebel forces. These armed movements pose a constant threat to the fragile transition in the DRC, and security in the country is continuously undermined. This article examines rebel forces in the DRC from two perspectives. Firstly, it examines such movements as a manifestation of sub-national terrorism. Secondly, it examines armed movements from the perspective of so-called ‘ungoverned spaces’. The view taken in this article supports the scholarly insight and argument that in countries such as the DRC, armed movements and militias are filling power vacuums that are the result of the inability and lack of military capacity of weak states to fight these movements effectively. Specifically, the eastern and north-eastern parts of the DRC have been major conflict zones where sub-national terrorists employ terror as a strategy. In this context, the DRC is severely affected by terrorism – a phenomenon in the DRC that is intimately linked to the failure to effect sustained development and to consolidate accountable and effective governance.     

Partitioning of biweighted trees

A districting problem is formulated as a network partitioning model where each link has one weight to denote travel time and another weight to denote workload. The objective of the problem is to minimize the maximum diameter of the districts while equalizing the workload among the districts. The case of tree networks is addressed and efficient algorithms are developed when the network is to be partitioned into two or three districts. © 2002 Wiley Periodicals, Inc. Naval Research Logistics 49: 143–158, 2002; DOI 10.1002/nav.10003     

Screening multi-dimensional heterogeneous populations for infectious diseases under scarce testing resources,with application to COVID-19

Testing provides essential information for managing infectious disease outbreaks, such as the COVID-19 pandemic. When testing resources are scarce, an important managerial decision is who to test. This decision is compounded by the fact that potential testing subjects are heterogeneous in multiple dimensions that are important to consider, including their likelihood of being disease-positive, and how much potential harm would be averted through testing and the subsequent interventions. To increase testing coverage, pooled testing can be utilized, but this comes at a cost of increased false-negatives when the test is imperfect. Then, the decision problem is to partition the heterogeneous testing population into three mutually exclusive sets: those to be individually tested, those to be pool tested, and those not to be tested. Additionally, the subjects to be pool tested must be further partitioned into testing pools, potentially containing different numbers of subjects. The objectives include the minimization of harm (through detection and mitigation) or maximization of testing coverage. We develop data-driven optimization models and algorithms to design pooled testing strategies, and show, via a COVID-19 contact tracing case study, that the proposed testing strategies can substantially outperform the current practice used for COVID-19 contact tracing (individually testing those contacts with symptoms). Our results demonstrate the substantial benefits of optimizing the testing design, while considering the multiple dimensions of population heterogeneity and the limited testing capacity.     

Information security: Designing a stochastic‐network for throughput and reliability

Todas information and communication network requires a design that is secure to tampering. Traditional performance measures of reliability and throughput must be supplemented with measures of security. Recognition of an adversary who can inflict damage leads toward a game‐theoretic model. Through such a formulation, guidelines for network designs and improvements are derived. We opt for a design that is most robust to withstand both natural degradation and adversarial attacks. Extensive computational experience with such a model suggests that a Nash‐equilibrium design exists that can withstand the worst possible damage. Most important, the equilibrium is value‐free in that it is stable irrespective of the unit costs associated with reliability vs. capacity improvement and how one wishes to trade between throughput and reliability. This finding helps to pinpoint the most critical components in network design. From a policy standpoint, the model also allows the monetary value of information‐security to be imputed. © 2009 Wiley Periodicals, Inc. Naval Research Logistics, 2009     

构建网络中心战的网络评估模型

为使网络化的部队能在内在的网络性能和外在的决策行动性能之间建立联系,建立了一系列的定量模型,将内在的网络性能和观察-确定-决策-行动(Observe-Orient-Decide-Act:OODA)环之间直接相关,为评估战场上的信息和网络能力建立了合适的模型。该模型也为网络中心战行动的内在和外在关系建立形式化关联迈出了第一步。     

A facility reliability problem: Formulation,properties, and algorithm

Having a robustly designed supply chain network is one of the most effective ways to hedge against network disruptions because contingency plans in the event of a disruption are often significantly limited. In this article, we study the facility reliability problem: how to design a reliable supply chain network in the presence of random facility disruptions with the option of hardening selected facilities. We consider a facility location problem incorporating two types of facilities, one that is unreliable and another that is reliable (which is not subject to disruption, but is more expensive). We formulate this as a mixed integer programming model and develop a Lagrangian Relaxation‐based solution algorithm. We derive structural properties of the problem and show that for some values of the disruption probability, the problem reduces to the classical uncapacitated fixed charge location problem. In addition, we show that the proposed solution algorithm is not only capable of solving large‐scale problems, but is also computationally effective. © 2009 Wiley Periodicals, Inc. Naval Research Logistics, 2010     

航空加权网络抗毁性综合评估方法

根据目前网络抗毁性研究中指标单一、网络无权等不足,针对航空网络的特点,以流量为边权,提出了一种多指标的航空网络抗毁性评估方法。基于网络吞吐量、相似权网络流量、节点相邻边权重分布分别构建了鲁棒性度量、网络效率度量、网络适应性度量。最后通过建立西北地区航空网络进行仿真,结果表明:西北地区航空网络具有与星型网络相似的性能,鲁棒性较差,网络效率较好,咸阳和乌鲁木齐作为中心节点,具有较好的主抗性能。实验结果证明了该评估方法的有效性。     

舰用计算机局部网络通信协议的设计

介绍了舰用计算机局部网络通信协议的设计,重点描述了设计中为提高实时性和可靠性所采用的一些具体技术措施,其中包括:简化ISO/OSI—RM 参考模型,并与IEEE8024标准协议兼容,采用VLSI 技术设计网络接口卡。同时,对其中一些关键技术,如逻辑环的建立与维护、信息的优先级发送与实时响应、数据缓冲区的结构与管理都作了说明。     

Optimal scheduling of objects in circulating systems

A “circulating system” is a finite collection of objects, each of which is oscillaling between two states. The prototype system is that of ships on patrcl,each subject to a quasi-regular “duty-service” cycle. There are various restrictions on the time spent in either state by an object and on the number of objects in a state at any one time. Schedules are sought in which the total number in one state is as large and as constant as possible. The maximal average number in one state is calculated, and a necessary and sufficient condition is given for a schedule to achieve it. Procedures are developed for constructing a schedule which achieves the maximal average in the most constant manner.     

Revisiting inspection game and inspector leadership through reaction networks

The inspection game is a two-player noncooperative game that models a situation where an inspector verifies whether the inspectee complies with the rules (on the assumption that the inspectee has the tendency to violate at least one of the rules). The usual approach in the analysis of this game seeks to find an optimal strategic inspection scheme for each of the two players yielding favorable payoffs. Recently, there have been some developments in the study of such games that use a mathematical structure known as reaction network involving a set of molecular species and the existing reactions among these species. In this paper, we use a reaction network to analyze the inspection game giving an alternative way of modeling the social situation. The molecular species play the role of the players' decision moves and their resulting gain or loss, while the reactions are the encounters of the decisions of the players which, as expected, yield payoffs. We reexamine the dynamics of the inspection game through the lens of reaction network theory and consider various situations that call for more detailed analyses such as equal or unequal reaction rates and inspection leadership. Conditions concerning reaction rates, initial population of decision species, benefits, and costs are determined in order to identify strategies that yield better payoffs both for the inspector and inspectee. These results illustrate practical insights rooted from the formulated simple game models.     

“复杂网络建模与优化学术研讨会”报告摘要

2014年1月20—21日,由国家自然科学基金资助、后勤工程学院基础部组织的"复杂网络建模与优化学术研讨会"在后勤工程学院召开。复杂网络科学是最近10年来新兴的交叉科学,它主要研究复杂物理、生物、社会系统等的网络表示和分析,理解网络结构如何影响系统的功能和行为。近年来,复杂网络研究在生物医学、电子商务、舆论传播、交通优化、恐怖活动预测等方面均有成功应用。在本次学术研讨会上作报告的专家均为国内外复杂网络研究领域的知名专家和优秀青年学者。主要有复杂网络领域国际知名专家、韩国成均馆大学Petter Holme教授,中国科学技术大学汪秉宏教授,电子科技大学周涛教授、荣智海教授,兰州大学吴枝喜教授,杭州师范大学张子柯教授,国防科学技术大学吕欣讲师和后勤工程学院赵静教授。经主办方和报告人同意,本刊汇集了以上专家在此次研讨会上的报告摘要,按时间顺序进行报道。     

浅谈现代远程教育对武警院校教学的深远影响

武警院校拥有丰富的教育资源，依托武警部队日益健全的内部网络系统，大力开展现代远程教育，能够更加紧密院校与部队的联系，及时了解部队的需求，制定出更加符合部队实际的课程体系，更大限度发挥现有教学资源的效益。由于远程教育具有方便快捷，受时间、空间局限小的特性，弥补了由于武警部队点多、线长、面广，分布相对分散，导致部队官兵学习时间不固定、人员难以集中等不便的问题，为武警部队官兵获取文化知识，学习科学技术提供了新的途径。