多层次区域炮兵地面侦察配系效能的评估

为了评估由于侦察区域大、目标机动性强等特点而建立的炮兵地面侦察配系的效能,运用排队论方法,建立了侦察配系效能评估模型.该模型综合考虑了各种因素对侦察配系效能的影响,把侦察区域按照距离的远近划分为不同的范围来进行侦察配系的效能评估.当目标流的速率发生变化时,依然可以灵活运用该模型对侦察配系的效能做出准确的评估.以雷达侦察配系为例,论证了评估模型在侦察效能评估中的可行性,为侦察配系效能评估提供了可靠的分析方法.     

基于FAHP的岸防炮兵雷达作战效能评估分析方法

针对岸防炮兵雷达的特点和作战任务,从探测能力、定位能力、数据处理能力、目标识别能力、抗干扰能力、可用性、可靠性和生存能力8个指标层,建立岸防炮兵雷达作战效能评估的层次结构体系,并确定了指标体系综合指标的随机性和模糊性,运用模糊层次分析法对雷达效能进行综合评估,给出了确立各因素权重的方法.为该雷达作战使用提供了辅助决策的依据.     

层次分析法在反坦克导弹阵地选择中的应用

反坦克导弹是未来高技术战争中不可或缺的反装甲兵种,特别是在渡海登岛作战中,先头抢滩登陆部队能否巩固和扩大登陆场地,很大程度取决于登陆部队反装甲力量的运用.在此过程中,反坦克导弹分队的阵地选择极其重要,运用层次分析法建立反坦克导弹阵地选择的递阶层次模型,通过计算,确定反坦克导弹阵地选择的最佳方案通过组合一致性检验,选择地形单元C_1为反坦克导弹阵地,作为最终的决策依据.     

Consequence of reinforced SiC particles and post process artificial ageing on microstructure and mechanical properties of friction stir processed AA7075

Friction stir processing and post process artificial ageing was successfully carried out on AA7075 with and without reinforcement of SiC particles producing defect free processed zone with uniform distribution of filler material. Effect of SiC particle reinforcement and artificial ageing times on the microstructural modifications was characterized using optical and electron microscopy, electron backscattered diffraction and X-Ray diffraction. Hardness, impact and wear tests were carried out to investigate mechanical behaviour before and after processing. Reinforcement of SiC particles during FSP and subsequent age hardening treatment brought about nearly twofold increase in hardness and impact toughness values by the combined effect of grain refinement, Zener pinning, dispersion strengthening and precipitation hardening. Significant improvement in wear resistance in terms of wear loss was also observed after processing compared to the reference material AA7075-T6. Fractured surface of post FSP age hardened AA7075 alloy exhibited features of ductile fracture during Charpy impact test.     

Optimal production ramp-up in the smartphone manufacturing industry

Motivated by challenges in the smartphone manufacturing industry, we develop a dynamic production ramp-up model that can be applied to economically satisfy nonstationary demand for short-life-cycle products by high-tech companies. Due to shorter life cycles and more rapid evolution of smartphones, production ramp-up has been increasingly critical to the success of a new smartphone. In the production ramp-up, the key challenge is to match the increasing capacity to nonstationary demand. The high-tech smartphone manufacturers are urged to jointly consider the effect of increasing capacity and decreasing demand. We study the production planning problem using a high-dimensional Markov decision process (MDP) model to characterize the production ramp-up. To address the curse of dimensionality, we refine Monte Carlo tree search (MCTS) algorithm and theoretically analyze its convergence and computational complexity. In a real case study, we find that the MDP model achieves revenue improvement by stopping producing the existing product earlier than the benchmark policy. In synthetic instances, we validate that the proposed MCTS algorithm saves computation time without loss of solution quality compared with traditional value iteration algorithm. As part of the Lenovo production solution, our MDP model enables high-tech smartphone manufacturers to better plan the production ramp-up.     

考虑非线性退化与随机失效阈值的剩余寿命预测

针对广泛存在的非线性退化设备,现有方法尚未考虑随机失效阈值对剩余寿命预测结果的影响。因此,通过对设备性能退化过程进行分析,提出了一种综合考虑非线性退化与随机失效阈值的剩余寿命预测方法。基于Wiener过程构建了考虑个体差异与测量误差的非线性退化模型;基于卡尔曼滤波算法建立状态空间模型以实现对退化状态的在线更新;基于极大似然法估计失效阈值分布系数估计方法,得到随机失效阈值的概率分布;基于随机失效阈值推导出剩余寿命的概率分布,实现对剩余寿命的在线预测。算例研究表明,所提方法可以有效地提升剩余寿命预测的准确性,具备一定工程应用价值。     

Revenue maximization in two-station tandem queueing systems

We study optimal pricing for tandem queueing systems with finite buffers. The service provider dynamically quotes prices to incoming price sensitive customers to maximize the long-run average revenue. We present a Markov decision process model for the optimization problem. For systems with two stations, general-sized buffers, and two or more prices, we describe the structure of the optimal dynamic pricing policy and develop tailored policy iteration algorithms to find an optimal pricing policy. For systems with two stations but no intermediate buffer, we characterize conditions under which quoting either a high or a low price to all customers is optimal and provide an easy-to-implement algorithm to solve the problem. Numerical experiments are conducted to compare the developed algorithms with the regular policy iteration algorithm. The work also discusses possible extensions of the obtained results to both three-station systems and two-station systems with price and congestion sensitive customers using numerical analysis.     

电磁发射系统改进FAHP-神经网络健康评估方法

准确定量评估电磁发射系统发射前的健康状态意义重大。针对模糊层次分析方法(Fuzzy Analytic Hierarchy Process, FAHP)在评估电磁发射系统串行结构同级元素健康值时存在较大偏差,且无法适用系统非线性变权重需求的缺陷,提出改进FAHP-神经网络方法。通过在计算同级元素健康指数时构造能够满足串行结构健康评估的非线性函数进行计算,并在数学上证明该方法的有效性;通过引入神经网络系统,在已有的系统先验信息和测量数据的基础上训练模型解决系统健康评估非线性变权重需求。基于电磁发射系统脉冲成形网络系统建立健康评估模型,开展评估试验。结果表明,提出的方法健康评估精度较高,在各种系统健康状态下,评估结果均符合系统实际的健康状况;对比传统的FAHP,提出的改进方法评估精度大幅提升,且在评估试验中没有出现故障误报和漏报的情况,从而验证了提出方法的可行性和工程实用价值。     

On the reduction of total‐cost and average‐cost MDPs to discounted MDPs

This article provides conditions under which total‐cost and average‐cost Markov decision processes (MDPs) can be reduced to discounted ones. Results are given for transient total‐cost MDPs with transition rates whose values may be greater than one, as well as for average‐cost MDPs with transition probabilities satisfying the condition that there is a state such that the expected time to reach it is uniformly bounded for all initial states and stationary policies. In particular, these reductions imply sufficient conditions for the validity of optimality equations and the existence of stationary optimal policies for MDPs with undiscounted total cost and average‐cost criteria. When the state and action sets are finite, these reductions lead to linear programming formulations and complexity estimates for MDPs under the aforementioned criteria.© 2017 Wiley Periodicals, Inc. Naval Research Logistics 66:38–56, 2019     

Planning gamma accelerated degradation tests with two accelerating variables

Gamma accelerated degradation tests (ADT) are widely used to assess timely lifetime information of highly reliable products with degradation paths that follow a gamma process. In the existing literature, there is interest in addressing the problem of deciding how to conduct an efficient, ADT that includes determinations of higher stress‐testing levels and their corresponding sample‐size allocations. The existing results mainly focused on the case of a single accelerating variable. However, this may not be practical when the quality characteristics of the product have slow degradation rates. To overcome this difficulty, we propose an analytical approach to address this decision‐making problem using the case of two accelerating variables. Specifically, based on the criterion of minimizing the asymptotic variance of the estimated q quantile of lifetime distribution of the product, we analytically show that the optimal stress levels and sample‐size allocations can be simultaneously obtained via a general equivalence theorem. In addition, we use a practical example to illustrate the proposed procedure.