基于改进ESO的交流伺服系统FOPID定位控制

针对高炮炮控交流伺服系统高精度定位控制存在的外界干扰及诸多非线性因素,提出了基于连续光滑函数fan()的改进扩张状态观测器(ESO),并将其应用于分数阶PID控制器,即CS-ESO-FOPID。该控制器将所有外界干扰因素作为"总干扰"获取干扰实时量,并通过改进扩张状态观测器实现非线性因素的实时动态补偿。数字仿真证明,CS-ESO观测优于传统ESO观测,CS-ESO-FOPID的动态控制精度及对外部扰动的鲁棒性均优于FOPID控制,避免了基于传统ESO的分数阶PID易出现的高频颤振现象,从而验证了该控制策略的可行性和有效性。     

Maritime security and capacity building in the Gulf of Guinea: On comprehensiveness,gaps, and security priorities

It is widely acknowledged that maritime security in the Gulf of Guinea is a highly complex phenomenon involving a variety of issues (legal deficiencies, inadequate military equipment, and challenges like corruption, political unrest and youth unemployment) as well as a multiplicity of external responders. To make sense of the impact that external actors have when they address this complex problem through various maritime capacity building endeavours, this article argues that there is a need to understand the attractiveness of capacity building vis-à-vis the widely acknowledged need for a comprehensive approach, as well as the difficulties of translating the potential for comprehensiveness into practice (as important aspects of the problem remain largely unaddressed). Further, it is argued that it is important to appreciate that even if these gaps – i.e. the aspects that maritime capacity building currently leaves unaddressed – represent a ‘failure’ to deliver a comprehensive response, they are at the same time illustrative of how the maritime capacity building activities of various external actors also ‘succeed’ in having an impact on this regional security landscape – for instance, by influencing how certain aspects of this multifaceted problem are prioritised, whilst others are only marginally addressed, if at all.     

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。     

管道在线检测技术及检测机器人研究

概述了管道检测技术发展现状,介绍了最新检测技术的原理,分析了管道内检测机器人的技术要点,概括介绍了课题组在差压式管内检测机器人周围流场建模与仿真、腐蚀环境下管道钢裂纹群演化的混沌动力学、差压式管内检测机器人的通过性能、管内检测机器人运行速度和姿态分析及运动状态控制、管内检测机器人小型化、小型化管内检测机器人检测精度、小型化管内检测机器人定位精度及管道剩余寿命的预测方法等方面的研究进展,为今后的研究打下了坚实的基础。     

多目标跟踪系统测量结果识别算法分析

首先针对多目标自动跟踪问题,对测量结果的两种识别方法和判定规则进行了讨论,给出了目标状态模型、参数模型和探测模型,并对这些模型进行了评估,在此基础上重点分析了多目标自动跟踪状态下基于状态模型参数识别测量结果的算法。最后指出了这种算法的优缺点。     

Workload distribution of discrete‐time parallel queues with two servers

We study discrete‐time, parallel queues with two identical servers. Customers arrive randomly at the system and join the queue with the shortest workload that is defined as the total service time required for the server to complete all the customers in the queue. The arrivals are assumed to follow a geometric distribution and the service times are assumed to have a general distribution. It is a no‐jockeying queue. The two‐dimensional state space is truncated into a banded array. The resulting modified queue is studied using the method of probability generating function (pgf) The workload distribution in steady state is obtained in form of pgf. A special case where the service time is a deterministic constant is further investigated. Numerical examples are illustrated. © 2000 John Wiley & Sons, Inc. Naval Research Logistics 47: 440–454, 2000     

Discrete equal‐capacity p‐median problem

This paper examines the discrete equal‐capacity p‐median problem that seeks to locate p new facilities (medians) on a network, each having a given uniform capacity, in order to minimize the sum of distribution costs while satisfying the demand on the network. Such problems arise, for example, in local access and transport area telecommunication network design problems where any number of a set of p facility units can be constructed at the specified candidate sites (hence, the net capacity is an integer multiple of a given unit capacity). We develop various valid inequalities, a separation routine for generating cutting planes that are specific members of such inequalities, as well as an enhanced reformulation that constructs a partial convex hull representation that subsumes an entire class of valid inequalities via its linear programming relaxation. We also propose suitable heuristic schemes for this problem, based on sequentially rounding the continuous relaxation solutions obtained for the various equivalent formulations of the problem. Extensive computational results are provided to demonstrate the effectiveness of the proposed valid inequalities, enhanced formulations, and heuristic schemes. The results indicate that the proposed schemes for tightening the underlying relaxations play a significant role in enhancing the performance of both exact and heuristic solution methods for this class of problems. © 2000 John & Sons, Inc. Naval Research Logistics 47: 166–183, 2000.     

基于Floyd算法的常规导弹连续波次作战运输规划

为提高常规导弹连续波次作战效能,对常规导弹连续波次作战运输规划问题进行研究。以Floyd算法为基础,首先生成了作战机动区域的交通网络最短路径、距离矩阵;其次将常规导弹连续波次作战运输过程分解为不同阶段,以运输过程中的整体暴露时间最短为目标,构建了初始规划方案0-1整数规划模型;然后考虑道路通行量及地域容量限制,对初始规划方案中存在的地域容量超过限制及单行道路中会车、超车情况进行逐步循环优化,以得到最佳运输规划方案;最后选择了一个作战案例想定,通过Matlab编程对案例进行了求解,得到了针对此案例的最佳运输规划方案,验证了模型的正确性和算法的有效性。     

Humanitarian response to hurricane disasters: Coordinating flood‐risk mitigation with fundraising and relief operations

To alleviate flooding, caused by hurricanes, governments build structural barriers called levees. In addition, relief providers such as the nongovernmental organizations and charities raise funds, and procure and deliver supplies (food, water, and medicines) for humanitarian relief. The strategy for managing disasters must, therefore, weigh the costs and benefits of building levees as well as procuring and delivering supplies. We use a three‐stage decision making framework to study how the investment in levee capacity can be integrated with supply procurements, fundraising, and rapid response. One of our major findings is that a large fundraising cost discourages postdisaster funding, implying relatively large investments in levee and prepositioned supplies. That notwithstanding, a large social value (of saving life) can tilt the balance in favor of postdisaster funding. If the levee capacity increases, funding for predisaster procurement is reduced without affecting postdisaster funding. For a sufficiently large increase in capacity, however, postdisaster response becomes superfluous. We also find that hurricane uncertainty motivates levees with large capacity. In contrast, levee‐failures motivate levees with small capacity.     

Drone usage by militant groups: exploring variation in adoption

Judging by recent media reporting and pronouncements by senior US military and security officials, the use of drones by militant groups is both reshaping conflict between armed non-state actors and state parties and now presents a grave and direct threat to nations in the West and elsewhere. But does this threat warrant the attention it is currently receiving? To answer this question, this article surveys how various militant groups have used drones both tactically on the battlefield and for wider strategic purposes. Closely examining how drones have been employed and by whom provides a basis for understanding variation in adoption. The article shows how drone usage or non-usage is highly contingent on the setting of the conflict, the aims of different groups, and the capacity of groups to adopt the technology. Though advances in drone technology could make the use-case more appealing for militant groups, drones will be subject to the same back-and-forth, techno-tactical adaptation dynamic between adversaries that have accompanied prior military innovations.