极大代数及其在离散事件动态系统中的应用

在人类社会活动中,有许多活动属于离散事件或离散事件动态系统。在极大代数意义下,这类系统可用线性系统的理论和方法建立数学模型、求解状态方程,讨论可控性、可观性,以及实现系统运行的优化设计。     

三角形线元的渐近展开与外推

本文通过正则坐标变换,把光滑域上的有限元解的误差估计转化为正六边形域上6PC剖分下的误差估计。在适当的条件下给出了三角形线元解的渐近展开式(u—u_h)(z)=c(u)h~2+o(h~3|lnh|)及外推估计式‖u-u_h‖_(0,2,M~h)=o(h~3|lnh|)。     

The continuing resonance of the war as risk management perspective for understanding military interventions

In the late 1990s and 2000s, a slew of books and journal articles proposed that a nexus between risk management and warfare was emerging. This article argues that risk management ideas continue to shape recent campaigns against Libya, Islamic State, Syria, and the war on terror from Niger, Yemen to Somalia. It uses existing literature on risk and warfare to examine four key aspects of contemporary interventions. First, the article evaluates the overall strategic context as security concerns shift from terrorism toward renewed great power competition. Second, it re-assesses the risk calculus for military action through the language and grammar of risk invoked by politicians. Third and fourth, it addresses the continuing reliance on air power and the managerial ethos of military operations as important features of war as risk management.     

Damage accumulation and probability of kill for gun and target engagements

Determination of the gunfire probability of kill against a target requires two parameters to be taken into consideration: the likelihood of hitting the target (susceptibility) and the conditional probability of kill given a hit (vulnerability). Two commonly used methods for calculating the latter probability are (1) treating each hit upon the target independently, and (2) setting an exact number of hits to obtain a target kill. Each of these methods contains an implicit assumption about the probability distribution of the number of hits‐to‐kill. Method (1) assumes that the most likely kill scenario occurs with exactly one hit, whereas (2) implies that achieving a precise number of hits always results in a kill. These methods can produce significant differences in the predicted gun effectiveness, even if the mean number of hits‐to‐kill for each distribution is the same. We therefore introduce a new modeling approach with a more general distribution for the number of hits‐to‐kill. The approach is configurable to various classes of damage mechanism and is able to match both methods (1) and (2) with a suitable choice of parameter. We use this new approach to explore the influence of various damage accumulation models on the predicted effectiveness of weapon‐target engagements.     

“电机统一理论”在电机控制中的作用

直流电机在恒速时其电压方程为常系数的线性微分方程,在电机控制中能进行快速的转矩和磁通控制。而异步电机是一个多变量、强耦合、非线性的时变参数系统,很难直接通过外加信号准确控制电磁转矩。但若以转子磁通这一旋转的空间矢量为参考坐标,应用"电机统一理论",利用从静止坐标系到旋转坐标系之间的变换,则可以把定子电流中的励磁电流分量与转矩电流分量变成标量独立开来,进行分别控制。这样,通过坐标变换重建的电机模型就可等效为一台直流电机,从而可像直流电机那样进行快速的转矩和磁通控制,给电机控制系统带来新的契机。     

一种改进的多相码信号参数估计法

目前,对由频率导出的一类多相码脉压雷达信号(Frank码和P1 ～ P4码)进行参数估计是电子对抗侦察技术中的难点之一.针对此问题,提出一种基于改进的分数阶傅里叶变换(FrFT)的多相码信号参数估计方法.该法利用积分二次相位函数将FrFT的二维搜索转换为2次一维搜索,较大减少了计算量.仿真表明,该法能在较小的计算量下达到与RWT和RAT法相当的估计精度.     

道德教育的社会支持系统探析

在社会转型时期的学校教育受到许多挑战,加上一直以来对学校在道德教育中的作用被过分放大,使学校面临巨大的压力。实际上,真正的、有效的道德教育需要一个广泛的支持系统。我国需要结合学校、家庭、社区及社会的综合力量,营造"大德育"的环境,建立起道德教育的社会支持系统。     

一种高效的通信电台测试点优化故障诊断策略

针对通信电台的测试诊断问题,通过建立“故障一测试”相关性矩阵,提出了一种GADPSO算法与最大诊断信息量准则结合进行通信电台故障诊断的方法．GADPSO算法收敛速度快、计算精度高,既避免了陷入局部最优和早熟收敛,又提高了优化效率;最大诊断信息量准则能全面评判测试点,快速有效地获得测试顺序．该方法为通信电台故障诊断提供了一种高效诊断策略．     

Revenue management under randomly evolving economic conditions

We consider a dynamic pricing model in which the instantaneous rate of the demand arrival process is dependent on not only the current price charged by the concerned firm, but also the present state of the world. While reflecting the current economic condition, the state evolves in a Markovian fashion. This model represents the real‐life situation in which the sales season is relatively long compared to the fast pace at which the outside environment changes. We establish the value of being better informed on the state of the world. When reasonable monotonicity conditions are met, we show that better present economic conditions will lead to higher prices. Our computational study is partially calibrated with real data. It demonstrates that the benefit of heeding varying economic conditions is on par with the value of embracing randomness in the demand process. © 2015 Wiley Periodicals, Inc. Naval Research Logistics 66:73–89,2019     

Exact analysis of (R,s, S) inventory control systems with lost sales and zero lead time

We study an (R, s, S) inventory control policy with stochastic demand, lost sales, zero lead‐time and a target service level to be satisfied. The system is modeled as a discrete time Markov chain for which we present a novel approach to derive exact closed‐form solutions for the limiting distribution of the on‐hand inventory level at the end of a review period, given the reorder level (s) and order‐up‐to level (S). We then establish a relationship between the limiting distributions for adjacent values of the reorder point that is used in an efficient recursive algorithm to determine the optimal parameter values of the (R, s, S) replenishment policy. The algorithm is easy to implement and entails less effort than solving the steady‐state equations for the corresponding Markov model. Point‐of‐use hospital inventory systems share the essential characteristics of the inventory system we model, and a case study using real data from such a system shows that with our approach, optimal policies with significant savings in inventory management effort are easily obtained for a large family of items.