An economic selective assembly procedure for two mating components with equal variance

An economic procedure of selective assembly is proposed when a product is composed of two mating components. The major quality characteristic of the product is the clearance between the two components. The components are divided into several classes prior to assembly. The component characteristics are assumed to be independently and normally distributed with equal variance. The procedure is designed so that the proportions of both components in their corresponding classes are the same. A cost model is developed based on a quadratic loss function and methods of obtaining the optimal class limits as well as the optimal number of classes are provided. Formulas for obtaining the proportion of rejection and the unavailability of mating components are also provided. The proposed model is compared with the equal width and the equal area partitioning methods using a numerical example. © 1999 John Wiley & Sons, Inc. Naval Research Logistics 46: 809–821, 1999     

基于遗传算法的多目标虚拟装配路径规划

针对以往求解路径规划问题中以路径最短为目标的局限性以及随机选取初始路径的缺陷,引入合适的目标函数和遗传算子,提出了一种基于遗传算法的多目标虚拟装配路径规划方法,利用大范围初始化的方式产生具有代表性的初始群体,设计了具有启发作用、适合路径规划的遗传算子,能够同时得到不同特点的多条路径,优化了装配路径.     

高功率电磁环境下导弹发射阵地近地面电磁脉冲波形仿真*

主要研究在高功率电磁环境下高空核爆到达导弹预设作战阵地近地面时的电磁脉冲环境.首先给出高空核爆电磁脉冲场近地面计算的理论基础,然后分析不同条件下近地面的电磁脉冲环境参数,编程实现了基于时域有限差分算法的电磁脉冲波形数值仿真,完成了多种特定预设战场环境下的电磁脉冲计算,最后给出由于电磁脉冲武器的发展和HEMP波形表述形式变化,给导弹武器系统抗电磁脉冲性能研究带来的影响和新动态趋势.结论认为:应加强对前沿更陡、强度更强电磁脉冲的抵抗能力,防御重点放在机动作战样式方面,提高战地战时抗毁生存能力.     

基于DM642的X264移植及优化

X264算法需要经过移植和优化才能满足实时处理的要求。文中首先分析了如何向DM642平台上移植X264代码,通过存储器优化、线性汇编改写等一系列优化措施实现了摄像头实时采集视频、编码及显示。最后完成了采集、回放独立编码运行于后台的Ping-Pong机制。实验表明,对CIF格式视频编码性能由优化前不足0.5帧/s达到20帧/s以上,此时PSNR下降不足3 dB。     

Influence of multiple structural parameters on interior ballistics based on orthogonal test methods

Influence of multiple structural parameters on the performance of a gun launch system driven by high-pressure reactive gases is important for structural design and performance adjustment. A coupled lumped parameter model was utilized to predict the propellant combustion, and a dynamic finite element method was applied to approximate the mechanical interactions between the projectile and the barrel. The combustion and the mechanical interactions were coupled through a user subroutine interface in ABAQUS. The correctness and the capability of the finite element approximations in capturing small structural changes were validated by comparing predicted resistance with experiments. Based on the coupled model, the influence of structural parameters of a medium-caliber gun on the system performance was investigated. In order to reduce the research costs, orthogonal tests were designed to investigate the comprehensive effects of the parameters. According to statistical analysis, the important order of the structural parameters on the launching process was obtained. The results indicate that the influence of the width of the rotating band stands out among the studied parameters in the gun. The work provides a method to investigate the influence of multiple parameters on system performance and gives guidance for controlling the system performance.     

Chirp信号参数估计算法性能比较

通过数值仿真定量地比较了三种Chirp信号参数估计算法——解线调法、迭代估计法和局部搜索最大似然法的性能,并定性地比较了算法的运算量。仿真结果表明,在三种算法中,局部搜索最大似然法的估计性能最好,而运算量居中;解线调法运算量最大,但估计性能居中;迭代估计法的估计性能最差,但运算量最小。对于实际系统,应根据不同的估计精度和运算量要求,灵活选择不同的算法。综合考虑估计性能和运算量之间的折衷可以得到结论,在三种算法中局部搜索最大似然法是一种相对较好的选择。     

一种实时对中监测装置原理及误差分析研究

设计出了一种可实现实时对中监测的装置。该装置可以在静态和设备运行时进行对中状态监测,还可对设备或轴系引起的对中状态改变量进行测量。介绍了该装置的结构原理,并对其结构误差进行了讨论,结果表明,该装置的误差很小,可以很好满足工程需要。同时,还对该装置的装配误差进行了分析。     

Collaboration in contingent capacities with information asymmetry

We study the optimal contracting problem between two firms collaborating on capacity investment with information asymmetry. Without a contract, system efficiency is lost due to the profit‐margin differentials among the firms, demand uncertainty, and information asymmetry. With information asymmetry, we demonstrate that the optimal capacity level is characterized by a newsvendor formula with an upward‐adjusted capacity investment cost, and no first‐best solution can be achieved. Our analysis shows that system efficiency can always be improved by the optimal contract and the improvement in system efficience is due to two factors. While the optimal contract may bring the system's capacity level closer to the first‐best capacity level, it prevents the higher‐margin firm from overinvesting and aligns the capacity‐investment decisions of the two firms. Our analysis of a special case demonstrates that, under some circumstances, both firms can benefit from the principal having better information about the agent's costs. © 2007 Wiley Periodicals, Inc. Naval Research Logistics 54:, 2007     

结构方程模型参数估计的GME方法

提出应用广义最大熵的方法对结构方程模型的参数进行估计,该方法能够处理有限的或者不完全数据。为了验证广义最大熵方法在估计结构方程模型参数时的性能,采用了一个应用于美国顾客满意指数(ACSI)的结构方程模型生成仿真数据,仿真结果表明,与PLS相比,GME方法具有更高的拟合精度和较低的预测误差,在样本数据较少时,表现更为明显。     

Estimation of the kinetic parameters for thermal decomposition of HNIW and its adiabatic time-to-explosion by Kooij formula

A differential/integral method to estimate the kinetic parameters (apparent activation energy E_a and pre-exponential factor A) for thermal decomposition reaction of energetic materials based on Kooij formula are applied to study the nonisothermal decomposition reaction kinetics of hexanitrohexaazaisowurtzitane (HNIW) by analyzing nonisothermal DSC curve data. The apparent activation energy (E_a) obtained by the integral isoconversional non-isothermal method based on Kooij formula is used to check the constancy and validity of apparent activation energy by the differential/integral method based on Kooij formula. The most probable mechanism function of thermal decomposition reaction of HNIW is determined by a logical choice method. The equations for calculating the critical temperatures of thermal explosion (T_b) and adiabatic time-to-explosion (t_TIad) based on Kooij formula are used to calculate the values of T_b and t_TIad to evaluate the thermal safety and heat-resistant ability of HNIW. All the original data needed for analyzing the kinetic parameters are from nonisothermal DSC curves. The results show that the kinetic model function in differential form and the values of E_a and A of decomposition reaction of HNIW are 3(1 − α)[−ln(1 − α)]^2/3, 152.73 kJ mol⁻¹ and 10^11.97 s⁻¹, respectively, and the values of self-accelerating decomposition temperature (T_SADT), T_b and t_TIad are 486.55 K, 493.11 K and 52.01 s, respectively.