基于排队论的飞行器协同突防效能分析

介绍了防空导弹作战有效性分析的排队论模型的原理，分析了其在实际应用中的处理方法；利用排队论模型，结合无人飞行器协同突防和防空体系作战过程，估算了排队论的参数，初步对飞行器协同作战的突防效能进行了评估；最后探讨了提高飞行器协同突防效能的途径．     

Modelling and design for a shuttle-based storage and retrieval system

The shuttle-based storage and retrieval system (SBS/RS) is a relatively new part-to-picker order picking system. We have developed a performance estimation and design algorithm for the SBS/RS. The performance estimation is based on a queuing model. The design algorithm aims to find the minimum cost configurations in terms of number of tiers, aisles, lifts and workstations with given throughput, tote capacity and order cycle time requirements. We used simulation driven by parameters abstracted from an actual SBS/RS to verify the performance estimation, and applied the design algorithm in the case study. The results indicate that: (1) compared to simulation results, the throughput of the performance estimation is nearly identical when the arrival rate is below the maximum capacity; (2) the design algorithm yields a configuration with 28.1% cost reduction in the current system. In addition, we also compared the shuttle system with the competing robotic order fulfilment system (robotic system in short) in terms of facility cost, building cost and order cycle time. We found that the shuttle system is a better choice if large storage capacity and high throughput are required whereas the robotic order fulfilment system performs better if small storage capacity and low throughput are required.     

System performance analysis of flexible flow shop with match processing constraint

Blocking makes the analytical modelling of open queuing networks with finite buffers intractable because the product-form solutions are unavailable. In this paper, about mould manufacturing, a four-stage flexible flow shop with match processing constraint is first modelled as an open queuing network with finite buffers. According to the characteristics of the matching node, the inter-arrival time distributions of parts arriving at the nodes are assumed to be exponential or general. Next, based on approximation of queuing theory, the Decomposition of State Space Method and the Generalized Expansion Method are developed for system performance evaluation. Then, experiments to assess the accuracy of the proposed methods are reported by comparing the analytical results with simulations. Finally, a case of a real-life production system of mould manufacturing is studied to show the application of the proposed methods. The results of experiments reveal that the proposed methods are feasible and effective for system performance evaluation and they can even solve large-size practical problems in a reasonable time. The results in this paper can provide a basis for system design or resource planning, to solve buffer allocation problems and capacity configuration problems.     

基于马尔科夫的医疗转诊策略研究

基于马尔科夫理论对医院之间转诊合作问题进行建模,将其转化为排队问题进行研究.首先采用分解思想结合矩阵几何的方法求解系统中病人平均等待时间、资源利用率等主要系统评价指标,然后使用Arena仿真验证近似解的准确性,最后从经济收益的角度探究了不同规模医院合作时的最优转诊策略,为医院之间进行转诊合作提供了决策参考和理论依据.     

Solving the response time variability problem by means of the electromagnetism-like mechanism

The response time variability problem (RTVP) is an NP-hard combinatorial scheduling problem that has been recently formalised in the literature. The RTVP has a wide range of real-life applications such as in the automobile industry, when models to be produced on a mixed-model assembly line have to be sequenced under a just-in-time production. The RTVP occurs whenever products, clients or jobs need to be sequenced so as to minimise variability in the time between the instants at which they receive the necessary resources. In two previous studies, three metaheuristic algorithms (a multi-start, a GRASP and a PSO algorithm) were proposed to solve the RTVP. We propose solving the RTVP by means of the electromagnetism-like mechanism (EM) metaheuristic algorithm. The EM algorithm is based on an analogy with the attraction-repulsion mechanism of the electromagnetism theory, where solutions are moved according to their associated charges. In this paper we compare the proposed EM metaheuristic procedure with the three metaheuristic algorithms aforementioned and it is shown that, on average, the EM procedure improves strongly on the obtained results.     

Model to determine the capacity of wafer fabrications for batch-serial processes with time constraints

Time constraints related issues are unavoidable in wafer fabrications. However, when the lots released from a batch workstation overload the downstream serial workstation the consequences are more serious. Under a time constraints environment, peak workload is a critical problem that seriously hurts the overall performance of the downstream workstation. This work applies a GI/G/m queuing network to develop a capacity planning model for batch-serial processes. By applying this queuing network model, the expected waiting time between batch-serial processes can be estimated. Managers can also determine the capacity through the setting of expected rate of exceeding time constraints. The arrival smoothing of the upstream batch workstation and its effect on the downstream workstation is also analysed. The results show that arrival smoothing can effectively decrease the waiting time on the downstream serial workstation through increasing the upstream number of batch machines and decreasing the batch size. The results also conclude that increasing the number of downstream serial machines is not the only option under the batch-serial process in a time constraint environment. Therefore, an investment function of batch-serial process equipment with time constraints is established in this work that can support managers when making investment decisions.     

基于WLAN与蜂窝网协同的终端选择算法

为保证基于无线局域网络(WLAN)组网的多网络协同分流传输中的业务服务质量,提出一种基于WLAN与蜂窝网协同的终端选择算法。利用排队论对协同传输系统进行建模,在最优化流量分配方案下,通过遍历比较不同终端集合对应的系统各链路总时延以确定最佳从终端集合。仿真结果表明,该算法可有效选出若干终端使得系统各链路总时延最小,并且系统性能较优。     

互联网流采样技术综述

网络流量测量对网络管理、网络监控、网络设计和网络规划具有重要的意义.由于网络带宽以摩尔速率增长,流采样作为一种以有限资源实时获取网络运行状况的方式引起了广泛的关注.文章在分析早期流采样技术现状及不足的基础上,详细综述了大流采样算法、流公平采样算法、全流采样算法及异常检测流采样算法四种互联网流采样技术,对四种技术的性能指标给出了理论分析及证明,最后展望了互联网流采样技术可能发展的四个方向.     

基于反馈优先服务策略的产品研发管理模型研究

为了研究产品开发排队系统的平稳分布和稳态性能,运用排队理论对产品开发过程进行建模和分析,在改进传统反馈服务笨略基础上,构建产品开发反馈优先排队模型;通过构建拟生灭过程求解反馈优先服务策略下排队系统稳态性能指标,并对传统反馈服务策略和反馈优先服务策略下的性能指标进行比较.结果表明,反馈优先的存在对产品开发任务的时延产生较大影响,通过算例对反馈优先服务策略下产品开发排队系统稳态性能指标进行验证,数值模拟表明产品开发排队系统中的反馈优先服务策略优于传统的反馈服务策略.     

WMN中基于循环补偿的公平调度算法

针对无线Mesh网络(WMN)中数据包调度方案公平性欠缺的问题,提出一种基于循环补偿的公平调度算法。该算法将Mesh节点中需要发送的数据包缓存在各自的数据流队列中,轮询处理队列的调度请求。利用信道状态监测机制确定队列的信道特征,通过循环补偿模型将队列调度过程划分为发送、补偿、休眠3个时期,各时期循环执行实现通信数据流间的平衡调度。仿真结果表明,该算法在公平性和吞吐量方面的有效性。