What you should know about simulation and derivatives

Derivatives (or gradients) are important for both sensitivity analysis and optimization, and in simulation models, these can often be estimated efficiently using various methods other than brute‐force finite differences. This article briefly summarizes the main approaches and discusses areas in which the approaches can most fruitfully be applied: queueing, inventory, and finance. In finance, the focus is on derivatives of another sort. © 2008 Wiley Periodicals, Inc. Naval Research Logistics, 2008     

给定降质约束下一类DCT域图像水印算法的拉伸系数估计

数字水印是数字作品版权保护的重要技术手段。与噪声污染类似,数字水印的嵌入必然会损失原作品的质量。数字图像的质量直接关系其商业价值,在给定降质约束下自适应地调节嵌入深度是符合产业化标准的数字水印关键技术之一。根据DCT交流系数的拉普拉斯分布模型,推导了DCT域典型水印算法中拉伸系数与信噪比和峰值信噪比之间的理论关系。依据该理论关系,得到了在给定降质约束下一类典型图像水印算法的拉伸系数估计方法,实验结果表明该估计方法具有较高的精度。     

基于层次分析法的人为电磁环境复杂程度评估

针对战场电磁环境复杂多变,定性、定量描述难的特点,运用层次分析法(AHP)探索人为电磁环境复杂程度评估问题。建立了评估人为电磁环境的递阶层次结构,细化了评估指标,明确了评价标准,并通过对组合权重的计算,最终将对人为电磁环境复杂程度的评估转换为13个底层参量的检测数据,4个分值标准和5个评定层次。该方法对评估电磁环境的一般复杂性和特定复杂性具有一定的指导意义,较好地满足了战场电磁环境复杂程度评估的需求。     

粘弹性泊松比的各种表述方法

本文讨论线性粘弹泊松比的四种表述法:微分算子法、遗传积分法、复数表示法和经验表示法的实用价值和问题。为固体推进剂力学性态的描述提供了方便。     

火炮身管寿命的分布函数

本文运用可靠性理论和《130mm 加农炮剩余寿命的一种预测模型》一文的结果,证明火炮身管寿命服从 Weibull 分布,并以130mm 加农炮为实例,给出参数的比值估计方法.     

隐蔽锥扫天线方向函数和增益的计算

本文根据隐蔽锥扫天线的工作原理和口径天线理论,分析了该天线方向函数和增益的计算方法。以某雷达天线为例,按所得公式用计算机计算了该天线的技术参数。经实际测量表明,理论值与测量值基本相符,证明了该计算方法的正确性。     

Directional change‐point detection for process control with multivariate categorical data

Most modern processes involve multiple quality characteristics that are all measured on attribute levels, and their overall quality is determined by these characteristics simultaneously. The characteristic factors usually correlate with each other, making multivariate categorical control techniques a must. We study Phase I analysis of multivariate categorical processes (MCPs) to identify the presence of change‐points in the reference dataset. A directional change‐point detection method based on log‐linear models is proposed. The method exploits directional shift information and integrates MCPs into the unified framework of multivariate binomial and multivariate multinomial distributions. A diagnostic scheme for identifying the change‐point location and the shift direction is also suggested. Numerical simulations are conducted to demonstrate the detection effectiveness and the diagnostic accuracy.© 2013 Wiley Periodicals, Inc. Naval Research Logistics, 2013     

Counterinsurgency force ratio: strategic utility or nominal necessity

As a consequence of intervention in Iraq and Afghanistan, force ratio for counterinsurgency (COIN) has come under increased scrutiny. Reduced to its essence, the issue is simply, ‘How many troops does it take to get the job done?’ This answer has been sought by the US military, academia, and think tanks. There have been numerous responses, culminating in several ‘plug-and-play’ equations for minimum force ratios in COIN operations. Due to the impossibility of determining precisely how many insurgent forces there are, it has become common to base force ratios on the population of the country. In the realm of policy, the question above is posed as, ‘How many of our troops does it take to get the job done?’     

装药长径比对EFP成型作用效果影响分析

针对装药长径比对EFP成型的影响,基于一种球缺型药型罩EFP,利用ANSYS／LS-DYNA仿真软件对其成型过程进行建模仿真,研究EFP成型过程及其各项参数．在该基础上,改变装药高度得到不同的装药长径比数据,并对不同长径比EFP形成过程进行仿真,得到不同装药长径比EFP的速度、速度增长率及炸药能量利用率等数据,为选择最佳装药长径比提供依据．     

基于无标度网络的防空反导系统构建

构建高效的防空反导系统是防空反导作战的基础。运用复杂网络理论,建立基于无标度网络防空反导系统模型,并将其统计特征同基于WS小世界网络的模型进行了比较,得出基于无标度网络的防空反导系统有更好鲁棒性和抗毁性,对网络化防空反导系统的构建有一定参考价值。