Warranty costs: An age‐dependent failure/repair model

An age‐dependent repair model is proposed. The notion of the “calendar age” of the product and the degree of repair are used to define the virtual age of the product. The virtual failure rate function and the virtual hazard function related to the lifetime of the product are discussed. Under a nonhomogeneous Poisson process scenario the expected warranty costs for repairable products associated with linear pro‐rata, nonrenewing free replacement and renewing free replacement warranties are evaluated. Illustration of the results is given by numerical and graphical examples. © 2004 Wiley Periodicals, Inc. Naval Research Logistics, 2004.     

A general approach to the shape of failure rate and MRL functions

Failure rate and mean residual life are two important characteristics for studying reliability of products. In literature, some work studied the shape of failure rate function based on the knowledge of the associated probability density function; some other work investigated the shape of mean residual life function based on the shape of the associated failure rate function separately for continuous case and discrete case. In this article, a general approach is developed which can be applied to the aforementioned studies. © 2004 Wiley Periodicals, Inc. Naval Research Logistics, 2004     

Dynamic inventory and pricing models for competing retailers

We address infinite‐horizon models for oligopolies with competing retailers under demand uncertainty. We characterize the equilibrium behavior which arises under simple wholesale pricing schemes. More specifically, we consider a periodic review, infinite‐horizon model for a two‐echelon system with a single supplier servicing a network of competing retailers. In every period, each retailer faces a random demand volume, the distribution of which depends on his own retail price as well as those charged by possibly all competing retailers. We also derive various comparative statics results regarding the impact several exogenous system parameters (e.g., cost or distributional parameters) have on the equilibrium decisions of the retailers as well as their expected profits. We show that certain monotonicity properties, engrained in folklore as well as in known inventory models for centralized systems, may break down in decentralized chains under retailer competition. Our results can be used to optimize the aggregate profits in the supply chain (i.e., those of the supplier and all retailers) by implementing a specific wholesale pricing scheme. © 2003 Wiley Periodicals, Inc. Naval Research Logistics, 2004.     

R-C系统中由表面散射引起的视场内杂散光分布

推导了R-C系统焦平面上由主镜和次镜表面散射引起的视场内杂散光分布的近似解析表达式.针对典型R-C系统的视场内杂散光分布,由近似表达式得到的计算结果与利用商业光学仿真软件得到的模拟结果具有较好的一致性,说明了近似表达式的正确性.与焦平面上无像差衍射光分布相比较,可以方便地分析强光入射时R-C系统焦平面上不同区域的饱和机制.研究结果表明,对于典型的R-C系统,探测器表面上以几何像点为中心,半径为2.5mm的范围内,衍射光是引起探测器饱和的主要因素;在此范围外,表面散射造成探测器的饱和.该结果为进一步研究强光饱和实验,解释有关现象提供理论分析基础.     

灾害应急反应建模与仿真

为了满足多智能体应急反应仿真的需求,首先对构建多智能体应急反应仿真模拟框架的复杂性进行了分析,在此基础上提出并设计了组件式仿真模拟框架.采用本体(Ontology)建模、语义网模型及产生式规则推理等理论方法构建了仿真模拟框架的场景建模模块、人员Agent建模模块等组件.最后对依照上述研究内容所开发的原型系统进行了测试,对测试结果进行了分析,结果表明该框架能够有效满足多智能体应急反应仿真的建模需求.     

起重机吊重摆角的产生机理与动态仿真研究

针对吊重二自由度摆角非线性动力学模型,研究了起重机吊重摆角的产生机理和摆角的影响因素。起重机小车和大车同时做加（减）速的复合运动时,产生吊重二自由度摆角,摆角的大小受起升绳长度和小车运行加（减）速度大小的影响。动态仿真表明：小车运行加（减）速度对摆角的影响比绳长度显著;小车起动和制动时,吊重做受迫摆动;当小车加（减）速度增大l倍时,吊重摆角约增大0．12rad,摆速约增大0．164rad／s;当绳长度增加2m时,摆角和摆速无明显变化,吊重自由摆动的周期约增加1．3s。     

弹载星敏感器应用方案比较研究

简述了弹载星敏感器几种应用方案的原理,从视场大小、导航星等、观星方式、像元分辨率、三轴姿态精度、动态性能、惯性基准误差分离等方面分析、比较了各种方案的优缺点.除平台方案外,捷联星图方案和单(双)星方案的技术参数相当,动态性能均有待提高.星图方案较单(双)星方案在2个方面占优势:一是星图方案不要求调整星敏感器光轴对准导航星,星跟踪算法等技术能快速识别星图;二是星图方案可同时、连续观测6～8颗星,解算出弹体三轴姿态,可以采用先进的滤波技术准确地分离惯性基准误差.     

论高校中的红色经典教育

红色经典作为中华民族重要的文化积累,对于大学生无疑有着重大的教育意义。本文通过对红色经典的分析来考察红色经典的教育功能,并试图寻找红色经典教育在当代大学生中的实施途径。改变红色经典传播方式,让红色经典成为大学生成长教育中的有效载体。     

舰船维修器材保障点选址决策模型及算法

传统的最大覆盖选址模型没有考虑对服务半径外的需求点的满足和服务时间的响应,而在舰船维修器材保障中,不论需求点到保障点的距离是否大于服务半径,都应对其进行保障服务,且在保障过程中要满足保障时间控制在不影响舰船正常维修任务时间内。针对此问题,运用广义最大覆盖选址模型和时间满意度函数,构建基于时间满意的广义最大覆盖选址模型,并运用一种混合算法———基于遗传模拟退火算法的BP算法对模型进行求解。最后,运用该算法对实例进行了分析计算,计算结果验证了该算法的有效性。     

翼栅绕流流场数值模拟及动力性能研究

基于2D不可压缩定常流动的控制方程,对5个NACA4412非对称翼型组成的平面直列翼栅绕流流场进行了数值模拟,对比分析了同一翼型在翼栅中工作和单独绕流时的升、阻力情况,验证了翼栅装置工作的可行性,反映了翼栅绕流的客观规律性。结果表明:翼栅翼型头部流速和压力急剧变化,尾部出现流涡尾迹,前部是负压区,后部是正压区,内部流速大,压力小;在1/3弦长附近翼栅翼型表面压力出现拐点,拐点之前翼型上下表面压力差较大,拐点之后翼型上下表面压力差较小;翼栅内部流场具有相似、相近性,外部流场差异性较大;翼型的压力差是产生升力的主要原因。