机场变频恒压供油过程的实现

恒压供油变频调速技术在机场供油工程中的应用极大地提高了供油作业的安全性与可靠性,并且具有较好的节能效益,是一种先进的控制方式。结合机场自动供油的技术特点和运行方式,对变频恒压供油系统的控制原理进行了分析,对加油控制中多泵并联运行的调压原理和实现方式进行了详细的研究探讨。     

Skewness correction X̄ and R charts for skewed distributions

This paper proposes a skewness correction (SC) method for constructing the and R control charts for skewed process distributions. Their asymmetric control limits (about the central line) are based on the degree of skewness estimated from the subgroups, and no parameter assumptions are made on the form of process distribution. These charts are simply adjustments of the conventional Shewhart control charts. Moreover, the chart is almost the same as the Shewhart chart if the process distribution is known to be symmetrical. The new charts are compared with the Shewhart charts and weighted variance (WV) control charts. When the process distribution is in some neighborhood of Weibull, lognormal, Burr or binomial family, simulation shows that the SC control charts have Type I risk (i.e., probability of a false alarm) closer to 0.27% of the normal case. Even in the case where the process distribution is exponential with known mean, not only the control limits and Type I risk, but also the Type II risk of the SC charts are closer to those of the exact and R charts than those of the WV and Shewhart charts. © 2003 Wiley Periodicals, Inc. Naval Research Logistics 50: 555–573, 2003     

Inventory models with nonlinear shortage costs and stochastic lead times; applications of shape properties of randomly stopped counting processes

In this article, we study generalizations of some of the inventory models with nonlinear costs considered by Rosling in (Oper. Res. 50 (2002) 797–809). In particular, we extend the study of both the periodic review and the compound renewal demand processes from a constant lead time to a random lead time. We find that the quasiconvexity properties of the cost function (and therefore the existence of optimal (s, S) policies), holds true when the lead time has suitable log‐concavity properties. The results are derived by structural properties of renewal delayed processes stopped at an independent random time and by the study of log‐concavity properties of compound distributions. © 2015 Wiley Periodicals, Inc. Naval Research Logistics 62: 345–356, 2015     

Dynamic policy for idling time preservation

This study aims to determine and evaluate dynamic idling policies where an agent can idle while some customers remain waiting. This type of policies can be employed in situations where the flow of urgent customers does not allow the agent to spend sufficient time on back-office tasks. We model the system as a single-agent exponential queue with abandonment. The objective is to minimize the system's congestion while ensuring a certain proportion of idling time for the agent. Using a Markov decision process approach, we prove that the optimal policy is a threshold policy according to which the agent should idle above (below) a certain threshold on the queue length if the congestion-related performance measure is concave (convex) with respect to the number of customers present. We subsequently obtain the stationary probabilities, performance measures, and idling time duration, expressed using complex integrals. We show how these integrals can be numerically computed and provide simpler expressions for fast-agent and heavy-traffic asymptotic cases. In practice, the most common way to regulate congestion is to control access to the service by rejecting some customers upon arrival. Our analysis reveals that idling policies allow high levels of idling probability that such rejection policies cannot reach. Furthermore, the greatest benefit of implementing an optimal idling policy occurs when the objective occupation rate is close to 50% in highly congested situations.     

无人机飞行训练资源配置效率的AHP-Arena综合评价方法

为降低传统层次分析法(analytic hierarchy process,AHP)赋权过程主观片面性影响,提出了一种综合AHP与Arena仿真建模技术的无人机训练资源配置效率评价方法。基于飞行训练流程分析,确定了训练资源配置效率影响因素和效率评价指标,建立了层次型综合评价体系,概括了AHP-Arena综合评价步骤。利用Arena建模软件构建训练流程动态仿真系统并验证有效性,采用单变量数值仿真法、均方差决策法完成了影响因素客观赋权,通过线性加权综合法得出综合评价系数,实现资源配置效率评价与方案优选。实例应用说明了该方法的有效性,同时,该方法可推广至其他类似的训练过程中,亦可为其他多因素、多指标评价决策过程提供借鉴。     

Two novel critical shock models based on Markov renewal processes

In this paper, we investigate systems subject to random shocks that are classified into critical and noncritical categories, and develop two novel critical shock models. Classical extreme shock models and run shock models are special cases of our developed models. The system fails when the total number of critical shocks reaches a predetermined threshold, or when the system stays in an environment that induces critical shocks for a preset threshold time, corresponding to failure mechanisms of the developed two critical shock models respectively. Markov renewal processes are employed to capture the magnitude and interarrival time dependency of environment-induced shocks. Explicit formulas for systems under the two critical shock models are derived, including the reliability function, the mean time to failure and so on. Furthermore, the two critical shock models are extended to the random threshold case and the integrated case where formulas of the reliability indexes of the systems are provided. Finally, a case study of a lithium-ion battery system is conducted to illustrate the proposed models and the obtained results.     

Burning characteristics of high density foamed GAP/CL-20 propellants

The monolithic foamed propellants with high densities were prepared by casting and two-step foaming processes. Glycidyl azide polymer (GAP) and isocyanate were used as the binder system and 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (HNIW, CL-20) was employed as the energetic component. The newly designed formulation containing 60 % CL-20 produced a force constant of 1077 J/g and low flame temperature of 2817 K. Two foamed propellants with densities of 1.32 g/cm³ and 1.53 g/cm³ were fabricated by a confined foaming process and examined by closed bomb tests. The results revealed that porosity significantly affects burning performance. A size effect on combustion behaviors was observed for the foamed propellant with 5.56 % porosity, and a double-hump progressive dynamic vivacity curve was obtained. At last, the 30 mm gun test was carried out to demonstrate the interior ballistic performance, and the muzzle velocity increased by 120 m/s at the same maximum chamber pressure when monolithic propellant was added in the charge.     

气象水文软件测评系统建设研究

介绍了气象水文软件测评系统建设和研究情况,重点分析了测评系统的网络环境、硬件环境、软件环境、测试技术能力、测试流程管理等方面的建设和研究情况.     

基于半马氏决策过程的电容器维修策略优化

针对电容器随机劣化失效的特点,采用半马氏决策过程解决其预防性维修方案设计和维修策略优化问题.在电容器随机劣化的Gaussian-Poisson模型基础上,以检测周期为优化变量,同时考虑预防性维修次数阈值的影响,建立电容器长期运行费用率优化模型.分析表明,对该型号电容器来说,预防性维修相比于事后修理更加有利于节省部件长期运行的费用率.     

基于Multi-Agent技术的大型航天研发项目风险分析方法

大型航天研发项目对于社会经济发展和国防安全有着重要影响,是国家重大工程中一类较为特殊的项目,而风险分析是大型航天研发项目按计划、高质量、低成本完成的重要保障。通过分析大型航天研发项目的特点、风险因素以及管理过程,结合Multi-Agent以及分布式项目管理的理论和技术,研究和提出了一种新的基于Multi-Agent技术的大型航天研发项目风险分析方法,在此基础上针对具体项目进行了实验仿真,获取了项目的风险水平和关键风险因素,为航天研发项目风险管理与控制提供决策支持。