一类具有时滞和常数收获率的比率型功能性反应的捕食-被捕食模型的稳定性与Hopf分支

研究一类具有时滞和常数收获率的比率型功能性反应的捕食—被捕食模型。首先,分析了模型奇点的类型,研究了正平衡点的局部稳定性以及Hopf分支的存在性;然后应用中心流形和规范型理论,得到了关于确定Hopf分支方向和分支周期解稳定性的计算公式;最后,应用Matlab软件对所得理论结果进行了数值模拟。     

Simultaneous determination of production and maintenance schedules using in‐line equipment condition and yield information

In many manufacturing environments, equipment condition has a significant impact on product quality, or yield. This paper presents a semi‐Markov decision process model of a single‐stage production system with multiple products and multiple maintenance actions. The model simultaneously determines maintenance and production schedules, accounting for the fact that equipment condition affects the yield of each product differently. It extends earlier work by allowing the expected time between decision epochs to vary by both action and machine state, by allowing multiple maintenance actions, and by treating the outcome of maintenance as less than certain. Sufficient conditions are developed that ensure the monotonicity of both the optimal production and maintenance actions. While the maintenance conditions closely resemble previously studied conditions for this type of problem, the production conditions represent a significant departure from earlier results. The simultaneous solution method is compared to an approach commonly used in industry, where the maintenance and production problems are treated independently. Solving more than one thousand test problems confirms that the combination of both features of the model—accounting for product differences and solving the problems simultaneously—has a significant impact on performance. © 2007 Wiley Periodicals, Inc. Naval Research Logistics, 2008     

Dynamic evacuation routes for personnel on a naval ship

We propose a dynamic escape route system for emergency evacuation of a naval ship. The system employs signals that adapt to the causative contingency and the crew's physical distribution about the ship. A mixed‐integer nonlinear programming model, with underlying network structure, optimizes the evacuation process. The network's nodes represent compartments, closures (e.g., doors and hatches) and intersections, while arcs represent various types of passageways. The objective function integrates two potentially conflicting factors: average evacuation time and the watertight and airtight integrity of the ship after evacuation. A heuristic solves the model approximately using a sequence of mixed‐integer linear approximating problems. Using data for a Spanish frigate, with standard static routes specified by the ship's designers, computational tests show that the dynamic system can reduce average evacuation times, nearly 23%, and can improve a combined measure of ship integrity by up to 50%. In addition, plausible design changes to the frigate yield further, substantial improvements. Published 2008 Wiley Periodicals, Inc. Naval Research Logistics 2008     

Delivery‐date and capacity management in a decentralized internal market

We study competitive due‐date and capacity management between the marketing and engineering divisions within an engineer‐to‐order (ETO) firm. Marketing interacts directly with the customers and quotes due‐dates for their orders. Engineering is primarily concerned with the efficient utilization of resources and is willing to increase capacity if the cost is compensated. The two divisions share the responsibility for timely delivery of the jobs. We model the interaction between marketing and engineering as a Nash game and investigate the effect of internal competition on the equilibrium decisions. We observe that the internal competition not only degrades the firm's overall profitability but also the serviceability. Finally, we extend our analysis to multiple‐job settings that consider both flexible and inflexible capacity. © 2008 Wiley Periodicals, Inc. Naval Research Logistics, 2008     

基于重要性采样的空时分组码快速仿真系统设计

高效的仿真技术对研究提高军事通信的性能具有重要意义。针对传统的蒙特卡罗仿真时间长的问题,提出了基于重要性采样的空时分组码高效仿真方法,给出了仿真模型和实现流程。仿真和分析结果表明本方法在运行较少的时间内能够获得较好的误码性能。采用该高效仿真方法可以加快军事通信技术研究的进程。     

双阵被动测距方法仿真

利用有一定间距的两部声纳基阵提供的目标方位和时延差的信息,实现对目标的被动测距。建立了测距物理模型,给出了后置距离滤波算法。通过仿真实验验证了模型的有效性,并通过分析两阵间距及时延差均方误差对测距的影响,表明了由于声场环境及特性的影响,选择适当的阵间距和时延差均方误差在实际测距试验中是非常重要的。     

防空导弹引战配合效率评估仿真方法与应用

某型防空导弹引信采用分组分档延时控制方式,延时参数根据典型目标设置。针对在实战中可能出现的对非典型目标的攻击问题,给出了评价射击效果的定量指标,建立了数学模型,利用Matlab/Simulink搭建了仿真模块。在该防空导弹飞行过程动态仿真系统的基础上,对非典型目标的射击进行了仿真,得出了最佳延迟时间,实际仿真结果表明极大地提高了射击效率。     

某住宅地下室结构方案分析及比较

地下室设计是高层建筑结构设计中重要的组成部分。地下室顶板及底板的结构方案有多种,在保证安全的前提下,应满足经济性要求。以深圳某住宅地下室结构设计为例,对地下室顶板及底板进行了几种常见方案的比较,地下室顶板采用单向梁造价比井字梁约低10%,比十字梁约低11%(柱网8000×8000)。地下室底板采用无梁板式造价比梁板式约低22%(柱网为7800×7800)。     

FDTD分析时域平面TEM喇叭天线阵

运用FDTD对时域天线阵进行仿真分析,并在外场进行测量研究。结果表明:阵列可以提高增益,增强方向性,该阵列天线适合于用作实际的超宽带雷达天线阵。     

基于扩张观测器的三维有限时间收敛导引律

为了保证视线角速率在弹目碰撞前收敛到零附近的较小邻域内从而达到准平行接近的状态,本文基于自抗扰控制的不确定性估计补偿思想,应用反演控制方法设计了一种考虑导弹自动驾驶仪二阶动态特性和目标机动的三维有限时间收敛导引律。根据有限时间收敛控制理论,严格证明了系统的有限时间收敛特性;为抑制量测噪声,将传统跟踪微分器进行改进并应用于扩张状态观测器与反演控制的设计中。仿真结果表明:在自动驾驶仪响应延迟情况下,所设计的导引律能够导引导弹在有限时间内精确地拦截高速机动目标;改进的跟踪微分器精度高、响应快;基于改进跟踪微分器的扩张观测器估计效果理想。