A forward network simplex algorithm for solving multiperiod network flow problems

An optimization model which is frequently used to assist decision makers in the areas of resource scheduling, planning, and distribution is the minimum cost multiperiod network flow problem. This model describes network structure decision-making problems over time. Such problems arise in the areas of production/distribution systems, economic planning, communication systems, material handling systems, traffic systems, railway systems, building evacuation systems, energy systems, as well as in many others. Although existing network solution techniques are efficient, there are still limitations to the size of problems that can be solved. To date, only a few researchers have taken the multiperiod structure into consideration in devising efficient solution methods. Standard network codes are usually used because of their availability and perceived efficiency. In this paper we discuss the development, implementation, and computational testing of a new technique, the forward network simplex method, for solving linear, minimum cost, multiperiod network flow problems. The forward network simplex method is a forward algorithm which exploits the natural decomposition of multiperiod network problems by limiting its pivoting activity. A forward algorithm is an approach to solving dynamic problems by solving successively longer finite subproblems, terminating when a stopping rule can be invoked or a decision horizon found. Such procedures are available for a large number of special structure models. Here we describe the specialization of the forward simplex method of Aronson, Morton, and Thompson to solving multiperiod network network flow problems. Computational results indicate that both the solution time and pivot count are linear in the number of periods. For standard network optimization codes, which do not exploit the multiperiod structure, the pivot count is linear in the number of periods; however, the solution time is quadratic.     

A note on a modified primal-dual algorithm to speed convergence in solving linear programs

The primal-dual algorithm is modified in a two part procedure. In the first part, the pivot row is selected so that an artificial variable is always dropped. The end of the first part usually produces some basic variables with negative values. The second part consists of selecting the most negative basic variable. The equation, represented by the selected basic variable, is multiplied through by minus one and then added to all equations with negative basic variables; it is then augmented by an artificial variable. This procedure produces feasibility for all basic variables and maintains canonical form. The standard primal-dual method is then used to complete the solution. Computational results are presented.     

贯彻科技兴军战略,提高军事职业教育质量水平

发展军事职业教育是健全新型军事人才培养体系的重大举措。贯彻科技兴军战略,必须深刻认识提高军事职业教育质量水平的重大意义,清晰把握提高军事职业教育质量水平的内在要求,切实找准提高军事职业教育质量水平的重要抓手。     

零彗差自由点条件下的失调光学系统波像差特性分析

基于矢量像差理论,对反射式光学系统的一类特殊失调状态——满足零彗差自由点条件展开研究,分析了该特殊失调下三阶彗差和三阶像散的全视场波像差特性,建立了三阶像散双节点位置的解析计算公式,研究发现该类失调不会引入三阶彗差,并且会导致三阶像散的一个节点位于中心视场附近,揭示了当前传统装调方法中仅采用轴上彗差为零作为系统完善装调的弊端,并基于像差特性分析提出了一种仅根据轴上视场引入定量失调误差前后的像差变化来评估系统完善装调的方法。利用CODE V(Version 10.2)对两反式光学系统进行了仿真分析,结果表明文中建立的模型和方法可定量分析三阶像散双节点的位置及该类失调对系统波像差的影响规律,并验证了所提出系统完善装调方法的有效性。     

车载机载稳瞄系统FSM补偿技术

提出并采用一种粗／精／组合二级稳定的新方案,用于对车、机载多传感器光电综合系统瞄准线（ＬＯＳ）及图象进行高精度稳定与跟踪。本技术的重要特征是采用挠性支承精稳反射镜（ＦＳＭ）组件以及粗／精多回路复合控制技术以获得高回路带宽和对扰动的大幅度衰减。用一个双自由度陀螺进行稳定及跟踪,有效地解决了粗／精通道的匹配与耦合。与传统的ＬＯＳ稳定系统相比较,稳定精度提高近一个数量级     

一种新的多属性决策方法

针对模糊多属性决策问题,提出了一种新的属性值以三角模糊数形式给出的模糊多属性决策方法。首先定义了两三角模糊数的中心决策矩阵;其次通过引入方案间优势度和优势度比较矩阵概念及其计算公式,从而给出了方案的排序,实例分析说明了所提出的决策方法的合理性及其算法的有效性。     

基于混合判断矩阵优选大区域防空作战方案

对混合判断矩阵和完全一致性混合判断矩阵这2个概念进行了新的应用。针对大区域防空作战决策中指挥员可能给出的混合判断信息情形,构建混合判断矩阵,并基于互反判断信息和互补判断信息的转换公式,利用文献中给出的求解混合判断矩阵排序向量的简便方法,将其应用于大区域防空作战方案的排序和择优,辅助防空作战指挥员提高决策能力和质量,同时对于防空作战辅助决策系统设计也具有较好的参考价值。     

综合火控系统对地轰炸精度分析仿真

针对航空轰炸武器火控系统精度分析问题,分别建立了数值微分算法和蒙特卡洛算法模型,并开发了仿真分析软件.给出了两种模型的推导过程,以及微分步长的优化方法.利用本算法软件对某型火控系统进行精度分析仿真,并对多组典型投弹条件的仿真结果进行分析.结果表明,两种算法优势互补,能有效地对火控系统进行精度分析,对改进系统设计、提高系...     

针对舰船目标高分辨距离像的特征选择方法

为了提高基于高分辨距离像(HRRP)的舰船目标识别率,首先通过目标区域提取来解决HRRP的幅度敏感性和平移敏感性的问题;然后根据传统的特征提取方法,提取出15个较好的特征进行多特征综合识别;最后在基于Fisher准则的特征选择方法上进行改进,提出了一种基于特征互补性的特征选择方法,选择一个最优特征子集。通过仿真实验验证了提出的特征选择方法,同时选择出一个最佳分类器。     

Why provoke? the Sino-US competition in East Asia and North Korea’s strategic choice

This article seeks to make sense of North Korean provocations in light of the Sino-US strategic competition in post-Cold War East Asia, where such variables as China’s rise, US’s pivot to Asia, and growing Sino-ROK economic ties are driving the strategic choices of major states in the region. The article examines the main motivations behind Pyongyang’s provocations since the end of the Cold War, discusses their implications for the Sino-US strategic competition in East Asia, and offers predictions about the future of North Korean provocations. The central thesis of the article is that Pyongyang has exploited the Sino-US strategic competition in East Asia for its regime survival. By raising North Korea’s strategic value to China, the intensifying Sino-US competition allows Pyongyang to continue provocations, regardless of Beijing’s explicit opposition.     

基于粗集和证据推理的海外基地保障点选址评估

针对海外基地保障点选址问题,结合专家组给出的影响选址评估意见,建立海外基地保障点选址评估指标体系。在此基础上,引用粗集和证据推理方法对评估指标因素进行信息处理优化,利用历史数据得到的客观信息与主观判断进行互补,实现主观判断与客观信息相结合,并用粗集进行属性约简,简化指标体系。该方法能提高评价结果的准确度和可信度,弥补海外基地保障点选址因素复杂,计算可操作性差的缺陷,为海外基地保障点选址决策提供理论依据。     

基于完全互补码的DS-UWB无线通信系统性能

基于完全互补码极好的相关特性,采用其作为扩频码,提出了基于完全互补码的DS-UWB系统模型.为了多个用户使用该系统,其中发射端采用码片移位方式实现.接收端则采用相关接收机解调用户信息.N路接收信号分别相关运算后叠加并进行判决,对前后码元的关联性使得系统性能有很大提高.在AWGN环境下和802.15.3a推出的UWB信道模型(CM2)下,对单用户和4用户情况下该模型的误比特率性能与采用Gold码和Walsh码时的性能进行了仿真分析.从仿真结果可以看出,采用完全互补码的DS-UWB系统性能有显著提高.     

A hybrid method for simulation factor screening

Factor screening is performed to eliminate unimportant factors so that the remaining important factors can be more thoroughly studied in later experiments. Controlled sequential bifurcation (CSB) and controlled sequential factorial design (CSFD) are two new screening methods for discrete‐event simulations. Both methods use hypothesis testing procedures to control the Type I Error and power of the screening results. The scenarios for which each method is most efficient are complementary. This study proposes a two‐stage hybrid approach that combines CSFD and an improved CSB called CSB‐X. In Phase 1, a prescreening procedure will estimate each effect and determine whether CSB‐X or CSFD will be used for further screening. In Phase 2, CSB‐X and CSFD are performed separately based on the assignment of Phase 1. The new method usually has the same error control as CSB‐X and CSFD. The efficiency, on the other hand, is usually much better than either component method. © 2009 Wiley Periodicals, Inc. Naval Research Logistics, 2010     

低成本微小型无人机航姿测量系统设计

根据微小型无人机航姿测量需求,利用MEMS传感器设计了一种低成本的航姿测量系统．针对低成本MEMS陀螺仪本身漂移较大、容易发散、无法完成较长时间较高精度测量的特点,提出一种实时性强、计算量小的信息融合方法．利用地球重力场、地磁场2个参考向量,采用互补滤波对不同传感器的数据进行融合,实现提高该航姿测量系统测量精度的目的．实验结果表明,该航姿测量系统的更新速率达到450Hz,姿态角测量误差〈1°,航向角测量误差〈2°,能够满足微小型无人机航向和姿态测量需求．     

复杂系统脆弱性综合分析方法

为全面识别复杂系统中的脆弱点,科学评价其脆弱性,针对纯拓扑脆弱性分析方法的不足,在考虑非拓扑因素条件下,提出一种结合复杂网络技术和效能评估技术的复杂系统脆弱性综合分析方法,从拓扑结构和非拓扑因素两方面全面分析复杂系统的脆弱性。以复杂网络的中心性指标为基础,通过广义指标法进行拓扑脆弱性分析;借鉴概率风险评价理论,从易攻性和易坏性两个方面对非拓扑脆弱性进行评价;通过对两者结果的综合得到总的脆弱性分析结果。示例结果表明:拓扑和非拓扑分析的结果有交集但又有所区别,两者密切相关且互为补充,并能共同筛选出复杂系统中的关键环节。较之纯粹的拓扑结构分析,综合分析得到的结果更为全面。     

一种新的动态信道化接收机设计方法

针对复杂电磁环境中存在多个非均匀分布的、不同带宽的信号的情况,提出一种新的动态信道化接收机设计方法。设计一个半带滤波器,并通过内插运算压缩它的频率响应,形成周期频谱;对输入信号进行滤波,同时使原信号经过一定延迟后减去滤波后的信号,形成两路在频谱上互补的信号;用均匀分析滤波器组对得到的两路信号分别进行滤波分解处理,实现监视频段的均匀信道化;根据能量检测结果将属于同一信号的相邻子信道信号作为下一步重构处理的输入,并设计出相应的综合滤波器组提取信号。理论分析和仿真结果验证了新方法的有效性。     

The practice of strategy: South African defence in stasis

The article concerns the strategy development processes of the South African Department of Defence in South Africa. It intends to identify the probable causes of the observed failure of the South African National Defence Force to develop appropriate departmental policy and military strategy. Military strategy comprises force development, force employment, force deployment and the coordination of these elements in pursuit of national, grand-strategic objectives. (See Dennis M. Drew and Donald M. Snow, Making Twenty-first Century Strategy: An Introduction to Modern National Security Processes and Problems Montgomery, AL: Air University Press, Maxwell Air Force Base, November 2006, 103). Of these four constructs, the article concerns itself only with the first two. The article analyses two complementary approaches to strategy formation: a resource-driven, inside-out model and an interests-driven, outside-in method. The article concludes that the Department is preoccupied with the inside-out method to the lasting detriment of the declared strategic intent of the defence policy.     

Optimal retail assortments for substitutable items purchased in sets

We consider the problem of optimizing assortments in a multi‐item retail inventory system. In addition to the usual holding and stockout costs, there is a fixed cost for including any item in the assortment. Customers' preferences for items include both probabilistic substitution patterns and the desire to purchase sets of complementary items. We develop a demand model to capture this behavior, and derive tractable approximations that allow us to formulate the optimization problem as a 0–1 mixed integer linear program. Numerical examples are solved to illustrate key insights into how both complementary and substitute items affect the optimal assortment and the expected profit. © 2003 Wiley Periodicals, Inc. Naval Research Logistics 50: 793–822, 2003.     

A method for quadratic programming

A solution to the quadratic programming is presented with the constraint of the form Ax ≥ b using the linear complementary problem approach.     

Anti-follower jamming wide gap multi-pattern frequency hopping communication method

This paper deals with the follower jamming (FJ) resistance for the frequency hopping (FH) communication system over additive white Gaussian noise (AWGN) channel. Conventional FH systems are susceptible to be jammed by FJ, and multi-pattern frequency hopping (MPFH) has good resistance to FJ. To further improve the FJ rejection capability of MPFH, we propose a wide gap multi-pattern frequency hopping (WGMPFH) scheme. WGMPFH uses channels to represent messages, and the data channel and complementary channel are hopping on orthogonal frequency slots according to wide gap FH patterns. The transmitted signal lures FJ to aim at the data channel and the complementary channel is away from FJ by adopting wide gap frequency patterns. FJ does not affect the complementary channel but increases the signal energy in the data channel, thus the effect of FJ is reduced. Its bit error rate (BER) is derived under FJ and the effects of three FJ parameters (tracking success probability, jamming duration ratio and jamming bandwidth ratio) on the BER performance of WGMPFH are investigated versus the conventional FH/BFSK and MPFH system. Numerical and simulation results show that when under the worst-case FJ, the proposed WGMPFH outperforms the MPFH by about 1–3 dB and outperforms the conventional FH/BFSK by more than 4 dB. The proposed WGMPFH shows superior jamming rejection performance under FJ especially in severe signal-to-jamming ratio (SJR).