用蒙特卡罗方法计算快中子屏蔽体的厚度

文中使用蒙特卡罗方法,模拟了３００ｋｅＶ氘束流Ｔ（ｄ,ｎ）４Ｈｅ中子源发出的中子在球壳屏蔽体介质铁中的输运规律;对计算结果进行解释和分析,得出将中子能量从１４ＭｅＶ慢化到１ＭｅＶ以下所需的最佳屏蔽厚度。所得结果与国际上同类屏蔽体所取参数相一致,具有一定的应用参考价值。     

UNIX 网络性能管理的流量监测技术研究

网络性能管理的主要目标是高性能和高吞吐量。标准UNIX系统缺乏对网络的流量的有效管理。本文研究了在标准UNIX网络实现性能管理中的网络流量监测、主机网络／系统状况动态检测等技术，依据检测结果用户可以进行网络动态配置或重新分配网络资源，从而改善UNIX系统的网络性能及吞吐量等技术。结果表明所提供的技术手段是有效的。     

具有电介质衬套的多波切仑柯夫振荡器

提出了具有电介质衬套的多波切仑柯夫振荡器的概念，并采用粒子模拟方法对之进行了研究。结果表明：电介质衬套能使器件在较低二极管电压下正常工作，同时，在低电压区的辐射效率明显提高。这对开发多波切仑柯夫振荡器在爆磁压缩产生高功率微波等领域的应用具有参考价值。研究还发现：微波频率随电介质的介电常数增大而单调下移，电介质的介电常数及导引磁场的强度均具有最佳值。     

碳纤维增强聚合物基复合材料频率选择表面的电磁传输特性

为了避免采用金属频率选择表面制备的天线罩中存在的热残余应力和弱黏接界面等问题,采用与聚合物基复合材料罩壁结构相容性好的碳纤维增强聚合物基复合材料制备频率选择表面,利用自由空间法对试样的电磁传输性能进行测试,并采用数值分析模型对碳纤维复合材料频率选择表面的电磁传输机制和电磁传输影响因子进行分析。结果表明:碳纤维复合材料频率选择表面具有频率选择功能,但谐振频率处的电磁传输损耗较大;通过改变复合材料频率选择表面的单元缝隙率、厚度、电导率以及介电常数可以实现对其电磁传输性能的调节。     

靶场转型对标准化的需求与对策

围绕靶场转型建设的指导思想和目标，阐述了标准化在靶场转型建设中的地位和作用，分析了靶场转型对标准化的需求及靶场标准化与靶场转型的差距，给出了在靶场转型建设过程中开展标准化的几点建议。     

Nonperiodic preventive maintenance for repairable systems

As a complex system with multiple components usually deteriorates with age, preventive maintenance (PM) is often performed to keep the system functioning in a good state to prolong its effective age. In this study, a nonhomogeneous Poisson process with a power law failure intensity is used to describe the deterioration of a repairable system, and the optimal nonperiodic PM schedule can be determined to minimize the expected total cost per unit time. However, since the determination of such optimal PM policies may involve numerous uncertainties, which typically make the analyses difficult to perform because of the scarcity of data, a Bayesian decision model, which utilizes all available information effectively, is also proposed for determining the optimal PM strategies. A numerical example with a real failure data set is used to illustrate the effectiveness of the proposed approach. The results show that the optimal schedules derived by Bayesian approach are relatively more conservative than that for non‐Bayesian approach because of the uncertainty of the intensity function, and if the intensity function are updated using the collected data set, which indicates more severe deterioration than the prior belief, replacing the entire system instead of frequent PM activities before serious deterioration is suggested. © 2010 Wiley Periodicals, Inc. Naval Research Logistics, 2010     

Dynamic server assignment policies for assembly‐type queues with flexible servers

We seek dynamic server assignment policies in finite‐capacity queueing systems with flexible and collaborative servers, which involve an assembly and/or a disassembly operation. The objective is to maximize the steady‐state throughput. We completely characterize the optimal policy for a Markovian system with two servers, two feeder stations, and instantaneous assembly and disassembly operations. This optimal policy allocates one server per station unless one of the stations is blocked, in which case both servers work at the unblocked station. For Markovian systems with three stations and instantaneous assembly and/or disassembly operations, we consider similar policies that move a server away from his/her “primary” station only when that station is blocked or starving. We determine the optimal assignment of each server whose primary station is blocked or starving in systems with three stations and zero buffers, by formulating the problem as a Markov decision process. Using this optimal assignment, we develop heuristic policies for systems with three or more stations and positive buffers, and show by means of a numerical study that these policies provide near‐optimal throughput. Furthermore, our numerical study shows that these policies developed for assembly‐type systems also work well in tandem systems. © 2008 Wiley Periodicals, Inc. Naval Research Logistics, 2008     

A dual criteria sequencing problem with earliness and tardiness penalties

We consider the problem of sequencing n jobs on a single machine, with each job having a processing time and a common due date. The common due date is assumed to be so large that all jobs can complete by the due date. It is known that there is an O(n log n)‐time algorithm for finding a schedule with minimum total earliness and tardiness. In this article, we consider finding a schedule with dual criteria. The primary goal is to minimize the total earliness and tardiness. The secondary goals are to minimize: (1) the maximum earliness and tardiness; (2) the sum of the maximum of the squares of earliness and tardiness; (3) the sum of the squares of earliness and tardiness. For the first two criteria, we show that the problems are NP‐hard and we give a fully polynomial time approximation scheme for both of them. For the last two criteria, we show that the ratio of the worst schedule versus the best schedule is no more than . © 2002 Wiley Periodicals, Inc. Naval Research Logistics 49: 422–431, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/nav.10020     

燃气轮机仿真软件构造方法综述

从方法论的角度综述了燃气轮机仿真软件的研究现状,分析了过程式方法和过程式模块化方法的不足,阐明采用面向对象方法的必要性,并对未来的发展方向作了初步探讨.     

试论我国高校就业指导体系的建构问题

从二十世纪八十年代开始,我国对普通高校教育体制进行改革,并取得很大成绩,使高等教育的规模有了跨越式的发展,质量与效益也同时大幅度提高。1999年开始的连续几年高校扩招使我国的高等教育从"精英化高等教育"快速步入"大众化高等教育"时代,但同时也使扩招后毕业生的就业成为亟待解决的问题。高校毕业生就业率成为对高校培养人才质量的检验指标,以及对高校社会适应性的检验指标,与学校的生存与发展紧密相连。面对产业结构的调整和高校毕业生大幅度增加的双重压力,高校就业指导工作日显重要,建立一支高水准,高效率的就业指导队伍成为高校建设中应优先解决的问题之一。