对DES密码的一种新的线性分析

首先推广了变换的线性偏差的概念,然后利用它把密码体制线性偏差的数学描述也进行了推广,给出了DES密码的线性偏差与轮函数F的线性偏差的关系,确定了DES密码16轮以内各轮的线性偏差上界。     

The impact of exponential smoothing forecasts on the bullwhip effect

An important phenomenon often observed in supply chain management, known as the bullwhip effect, implies that demand variability increases as one moves up the supply chain, i.e., as one moves away from customer demand. In this paper we quantify this effect for simple, two‐stage, supply chains consisting of a single retailer and a single manufacturer. We demonstrate that the use of an exponential smoothing forecast by the retailer can cause the bullwhip effect and contrast these results with the increase in variability due to the use of a moving average forecast. We consider two types of demand processes, a correlated demand process and a demand process with a linear trend. We then discuss several important managerial insights that can be drawn from this research. © 2000 John Wiley & Sons, Inc. Naval Research Logistics 47: 269–286, 2000     

Optimizing natural gas pipeline transmission with nonuniform elevation: A new initialization approach

In this paper, we develop an iterative piecewise linear approximation approach with a novel initialization method to solve natural gas pipeline transmission problems with the nonuniform network elevation. Previous approaches, such as energy minimization methods, cannot be applied to solve problems with the nonuniform network elevation because they exclude pressure range constraints, and thus provide solutions far from optimum. We propose a new initialization model that considers pressure range constraints and improves the optimality of the solutions and the computational efficiency. Furthermore, we extend the energy minimization methods and provide the necessary conditions under which the extended methods operate in networks with the nonuniform elevation. We test the performances of the methods with previously reported pipeline networks from the literature, with the open data set GasLib, and with our industrial collaborator. The initialization approach is shown to be more efficient than the method with fixed initial breakpoints. The newly proposed initialization approach generates solutions with a higher accuracy than the extended energy minimization methods, especially in large‐size networks. The proposed method has been applied to natural gas transmission planning by the China National Petroleum Corporation and has brought a direct profit increase of 330 million U.S. dollars in 2015‐2017.     

同轴环缝气流作用下锥形液膜线性稳定性分析

为了分析气液同轴离心式喷嘴的雾化机理,对同轴气体作用下的锥形液膜进行时间稳定性分析,推导同轴气体作用下锥形液膜的色散方程,建立离心式喷嘴出口参数预测模型,用于数值求解色散方程。结果表明：喷嘴出口液膜厚度随着喷注压降的增加而减小,喷雾锥角、液膜速度和轴向速度随着喷注压降的增加而增大。同轴气体作用下液膜由正弦模式的表面波主导,因为正弦模式的表面波增长率远大于曲张模式的表面波增长率。当环缝气体喷注速度较小时,增加气体速度会减小气液相对速度,从而减弱气液相互作用,使得液膜主导表面波增长率和频率减小、破碎时间和破碎长度增加。而当环缝气体速度超过一个临界值后,随着气体速度的增大,液膜主导表面波增长率和频率迅速增大,破碎时间和破碎长度迅速减小。     

【邀请论文】美军未来司令部探析——成立背景、主要职能与未来前景

新一轮科技革命的快速发展正推动战争形态从信息化向智能化演进。美军作为二战后始终位列世界第一的军事力量,正在积极设计未来战争以应对当前的“大国竞争”,2018年刚刚成立的陆军未来司令部正是在这一背景下产生的。未来司令部隶属于美国陆军,主要负责美陆军新型武器装备的研发、未来作战概念创新以及新兴军事科技的测试和应用。成立两年以来,未来司令部已经拥有了一套完善、严密的组织架构,创造了包括C5ISR作战概念在内的一系列理论成果,在空基导弹、远程精确火力系统等新型作战装备上也取得了众多进展。本文基于大量前沿文献研究,廓清了未来司令部的组织架构,总结了其主要职能,并对这一新设司令部的发展前景进行了展望和预测,期望能够为推进军队现代化和未来化建设提供有益启示。     

ISIS’s Warfare Functions: A Systematized Review of a Proto-state’s Conventional Conduct of Combat Operations

This article gives an overall assessment of ISIS’s conventional conduct of combat operations by examining their warfighting functions patterns. In sum, the approach of ISIS comprised fundamental principles: their weapons can be organized into categories, purposeful combination of these forces in keeping with the concept of combined arms combat, and hierarchical command and control executed by experienced commanders. ISIS combat groups combined the elements of formation and firepower as well as movement and mobility. The paper concludes that ISIS obviously had a vast range of conventional capabilities at its disposal and was thus able to conduct major operations.     

定子磁钢轨道拼接错位对动圈式永磁直线电机性能的影响

陆基车载无人机电磁弹射器是一种新型的弹射起飞装置。为了实现高机动性,提出双边动圈式永磁直流直线电机和定子磁钢轨道分段拼接结构方案。为了评估定子磁钢轨道拼接可能对电机性能的影响,建立了永磁直线电机模型。利用有限元分析软件,分析研究了轨道分段拼接上下错位、左右错位以及倾斜错位可能造成的影响,根据分析结果给出了磁钢轨道拼接错位所允许的偏移范围大小。     

永磁无刷直流直线电机齿槽力补偿控制研究

永磁无刷直流直线电机的齿槽定位力对其低速性能影响很大,而单纯的设计方法不可能完全消除齿槽力的影响,为此,必须在控制系统中对齿槽力进行补偿。针对包含齿槽力模型的理想电机控制系统进行了理论分析,指出通过引入位置反馈环节可以消除齿槽力的不良影响。利用有限元分析方法计算了电机的推力和齿槽力波形,验证了低速条件下推力波动主要由齿槽力引起,并说明可以通过位置反馈来补偿推力波动。最后,提出将一个齿槽力周期分为多个区间,然后分段进行线性补偿的简易控制方法。该方法无需高精度的定位装置和复杂的控制算法即可实现对电机齿槽力的补偿,实验结果表明,所提方法能够有效抑制电机的推力波动。     

同时强镇定的一个充分条件

一个稳定的控制器可同时镇定n个对象(同时强镇定)等价于一个控制嚣(不一定稳定)同时镇定n+1个对象(同时镇定).两个以上对象的同时强镇定和三个以上对象的同时镇定是线性系统中一个亟待解决的公开问题.文中所作的基本假定是所有的对象具有相同的简单不稳定零点,在此条件下给出了n个对象同时强镇定的一个充分条件.此条件仅需确定n个对象的不稳定零点并且判定由不稳定零点导出一个相应矩阵是正定的,就能判定n个对象同时强镇定,因此是一个易于检验的充分条件.同时给出了n个对象同时强镇定的算法.丰富了同时强镇定的条件和算法.     

三合一场所火灾中救人行动探讨

通过对近年来“三合一”场所火灾扑救案例的研究,分析了“三合一”场所火灾的特点及其对实施救人行动的影响,提出了“三合一”场所火灾中实施救人行动的指导原则,对火灾发展各阶段救人行动要点进行了探讨。