Double window acceptance sampling

We introduce the concept of a sequential double window procedure and compare the resulting acceptance test with both a fixed sample size method as well as with the Wald sequential probability ratio test. © 2003 Wiley Periodicals, Inc. Naval Research Logistics, 2004     

基于改进核极限学习机和集成学习理论的目标机动轨迹预测

为了提高目标轨迹预测的精度以及预测模型的泛化能力,提出基于改进蝙蝠算法优化的核极限学习机(Kernel Extreme Learning Machine,KELM)和集成学习理论目标机动轨迹预测模型。构建KELM模型,并采用改进的蝙蝠算法对KELM的参数进行优化;以优化后的KELM神经网络为弱预测器,结合集成学习算法生成强预测器,通过训练不断优化强预测的结构和参数,得到一种基于集成学习理论的目标机动轨迹预测模型;基于不同规模的样本,将所得预测模型与逆传播神经网络、支持向量机和极限学习机等模型进行对比分析。仿真结果表明:所提目标机动轨迹预测模型具有较好的预测精度和泛化能力。     

An efficient SPH methodology for modelling mechanical characteristics of particulate composites

Particulate composites are one of the widely used materials in producing numerous state-of-the-art components in biomedical, automobile, aerospace including defence technology. Variety of modelling techniques have been adopted in the past to model mechanical behaviour of particulate composites. Due to their favourable properties, particle-based methods provide a convenient platform to model failure or fracture of these composites. Smooth particle hydrodynamics (SPH) is one of such methods which demonstrate excellent potential for modelling failure or fracture of particulate composites in a Lagrangian setting. One of the major challenges in using SPH method for modelling composite materials depends on accurate and efficient way to treat interface and boundary conditions. In this paper, a master-slave method based multi-freedom constraints is proposed to impose essential boundary conditions and interfacial displacement constraints in modelling mechanical behaviour of composite materials using SPH method. The proposed methodology enforces the above constraints more accurately and requires only smaller condition number for system stiffness matrix than the procedures based on typical penalty function approach. A minimum cut-off value-based error criteria is employed to improve the compu-tational efficiency of the proposed methodology. In addition, the proposed method is further enhanced by adopting a modified numerical interpolation scheme along the boundary to increase the accuracy and computational efficiency. The numerical examples demonstrate that the proposed master-slave approach yields better accuracy in enforcing displacement constraints and requires approximately the same computational time as that of penalty method.     

Survivability assessment of spacecraft impacted by orbit debris

To help optimize the spacecraft design and reduce the risk of spacecraft mission failure, a new approach to assess the survivability of spacecraft in orbit is presented here, including the following three steps:1) Sensitivity Analysis of spacecraft. A new sensitivity analysis method, a ray method based on virtual outer wall, is presented here. Using rays to simulate the debris cloud can effectively address the component shadowing issues. 2) Component Vulnerability analysis of spacecraft. A function"Component functional reduction degree — Component physical damage degree"is provided here to clearly describe the component functional reduction. 3) System-level Survivability Assessment of spacecraft. A new method based on expert knowledge reasoning, instead of traditional artificial failure tree method, is presented here to greatly improve the efficiency and accuracy of calculation.     

Adaptive phasefield modelling of crack propagation in orthotropic functionally graded materials

In this work, we extend the recently proposed adaptive phase field method to model fracture in orthotropic functionally graded materials (FGMs). A recovery type error indicator combined with quadtree decomposition is employed for adaptive mesh refinement. The proposed approach is capable of capturing the fracture process with a localized mesh refinement that provides notable gains in computational efficiency. The implementation is validated against experimental data and other nu-merical experiments on orthotropic materials with different material orientations. The results reveal an increase in the stiffness and the maximum force with increasing material orientation angle. The study is then extended to the analysis of orthotropic FGMs. It is observed that, if the gradation in fracture properties is neglected, the material gradient plays a secondary role, with the fracture behaviour being dominated by the orthotropy of the material. However, when the toughness increases along the crack propagation path, a substantial gain in fracture resistance is observed.     

高炮射弹飞行时间拟合

用插值拟合和最小二乘逼近拟合方法对高炮射弹飞行时间拟合问题进行了研究。通过对插值拟合公式原理及误差规律的分析,提出确定可用区间的"去值检验"方法,说明了插值拟合公式的应用范围。通过对最小二乘拟合公式实际计算结果的分析,得出了"拟合公式阶数取3为最佳"的结论。对其他口径高炮的射弹飞行时间拟合也基本适用。     

部队作战效能综合评估法

高技术条件下局部战争的显著特点是参战单位多、对抗关系复杂、战争不确定因素增加,如何在此情况下客观评估部队的作战效能是作战研究领域一个重点和难点。通过综合运用定性分析法、网络分析法、战斗效能指数法、作战模拟及系统动力学等多种方法和理论,建立了一种可对部队作战效能进行评估的综合评估法。并以高技术条件下岛上进攻作战中装甲团的作战效能评估为例,详细介绍了该方法的实施过程,认为该综合评估法是行之有效的。     

模糊Petri网在空舰导弹武器系统效能分析中的应用

空舰导弹武器系统综合效能分析不但对导弹的定型起着一定作用,而且对装载该导弹的作战飞机的作战效能都具有重要的意义。依据空舰导弹武器系统的战技指标要求,运用模糊Petri网的原理结合层次分析法,对导弹武器的性能采取定性分析与定量分析相结合,以定量分析为主的方法进行评价。仿真实例对某型空舰导弹系统效能进行评价,结果表明它是一种方便、实用、可行的方法。     

管线最大通过能力求解方法研究

长输管线的密闭输送方式采取"泵到泵"接力运行,全线是一个统一的整体, 对管线最大通过能力的计算,要考虑前后泵站间的相互影响,进行迭代计算。针对长输管线 最大通过能力的两种求解方式:迭代法,通过逐步校核,调整计算结果的大小,使其逐步逼近 最终计算结果;分段计算法,分步校核,逐步搜寻全线"瓶颈"段,得到"瓶颈"段的通过能力, 即为全线最大通过能力。分别建立了数学模型,并基于Visual Basic 6.0编程,进行迭代运 算,得到了相应计算结果,对两种方法的理论方法、程序编写、计算结果进行了比较,用于指 导管线计算方法的选择。     

国防科技体系评价

如何科学、合理、有效的评价国防科技体系发展水平,识别国防关键技术,建立健全国防科技体系,是国防建设重中之重。基于未确知测度理论构建国防科技发展水平的评价原则,结合网络分析法确定指标体系权重,有效解决了国防科技体系评价的复杂性、系统性问题。研究表明,国防科技体系评价可以为国防科技发展战略的科学性和可操作性提供参考。