The probability of the existence of a feasible flow in a stochastic transportation network

Stochastic transportation networks arise in various real world applications, for which the probability of the existence of a feasible flow is regarded as an important performance measure. Although the necessary and sufficient condition for the existence of a feasible flow represented by an exponential number of inequalities is a well‐known result in the literature, the computation of the probability of all such inequalities being satisfied jointly is a daunting challenge. The state‐of‐the‐art approach of Prékopa and Boros, Operat Res 39 (1991) 119–129 approximates this probability by giving its lower and upper bounds using a two‐part procedure. The first part eliminates all redundant inequalities and the second gives the lower and upper bounds of the probability by solving two well‐defined linear programs with the inputs obtained from the first part. Unfortunately, the first part may still leave many non‐redundant inequalities. In this case, it would be very time consuming to compute the inputs for the second part even for small‐sized networks. In this paper, we first present a model that can be used to eliminate all redundant inequalities and give the corresponding computational results for the same numerical examples used in Prékopa and Boros, Operat Res 39 (1991) 119–129. We also show how to improve the lower and upper bounds of the probability using the multitree and hypermultitree, respectively. Furthermore, we propose an exact solution approach based on the state space decomposition to compute the probability. We derive a feasible state from a state space and then decompose the space into several disjoint subspaces iteratively. The probability is equal to the sum of the probabilities in these subspaces. We use the 8‐node and 15‐node network examples in Prékopa and Boros, Operat Res 39 (1991) 119–129 and the Sioux‐Falls network with 24 nodes to show that the space decomposition algorithm can obtain the exact probability of these classical examples efficiently. © 2016 Wiley Periodicals, Inc. Naval Research Logistics 63: 479–491, 2016     

On the hierarchy of γ‐valid cuts in global optimization

Concavity Cuts play an important role in concave minimization. In Porembski, J Global Optim 15 ( 17 ), 371–404 we extended the concept underlying concavity cuts which led to the development of decomposition cuts. In numerical experiments with pure cutting plane algorithms for concave minimization, decomposition cuts have been shown to be superior to concavity cuts. However, three points remained open. First, how to derive decomposition cuts in the degenerate case. Second, how to ensure dominance of decomposition cuts over concavity cuts. Third, how to ensure the finite convergence of a pure cutting plane algorithm solely by decomposition cuts. These points will be addressed in this paper. © 2007 Wiley Periodicals, Inc. Naval Research Logistics, 2008     

捷联惯导大失准角误差模型在快速传递对准中的应用

针对快速传递对准中主子惯导相对姿态存在大角度的情况,推导了捷联惯导大失准角误差模型.该模型采用欧拉角表示姿态误差,并用欧拉运动方程准确描述其传播规律.鉴于该模型中的姿态观测方程是复杂的非线性函数,采用无需求导的UKF算法,并采用奇异值分解(SVD)解决方差阵的病态问题.仿真结果表明,该算法在小角度误差条件下滤波精度优于线性模型,并且适用于大角度误差条件.     

四元数长方矩阵的同时复对角化

利用四元数矩阵的奇异值分解(SVD),对两个四元数长矩阵给出了其同时复对角化的充要条件,进一步对一个四元数长矩阵集合,针对其同时复对角化问题,给出了一系列充分必要条件.     

Liquid phase in-situ synthesis of LiF coated boron powder composite and performance study

Among practical metal additives, boron (B) has a high volumetric heating value, making it a promising choice as a fuel additive. Although B can theoretically yield a large amount of energy upon complete combustion, its combustion is retarded by the initial presence of B oxide, which coats the surfaces of B particle. To improve the ignition and combustion properties of B powder, LiOH and NH₄F were used as precursors to synthesize uniformly LiF-coated B composites (LiF-B) in situ. The LiF-B mixture was also prepared for comparison using a physical method. X-ray diffraction (XRD), Fourier-transform infrared (FTIR), scanning electron microscope (SEM), and energy-dispersive X-ray spectroscopy (EDS) were used to characterize the morphologies and compositions of the products. The thermal and combustion properties of the samples were characterized by thermal gravity-differential thermal gravity (TG-DTG), differential scanning calorimetry (DSC) and closed bomb experiment. The XRD, FTIR, SEM and EDS results demonstrated the successful preparation of the coated LiF-B sample. The TG-DTG and closed bomb experiment results indicated that the addition of LiF decreased the ignition temperature of B powder, and increasing its reaction efficiency. DSC results show that when LiF-B was added, the released heat of underwater explosive increased by 6727.2, 7280.4 and 3109.6 J/g at heating rates of 5, 10, and 15 °C/min, respectively. Moreover, LiF-B decreased the activation energy of secondary combustion reaction of explosive system as calculated through Kissinger's method by 28.9%, which indicated an excellent catalytic effect for the thermal decomposition of underwater explosive. The results reveal that LiF can improve the combustion efficiency of B powder, thereby increasing the total energy of explosives. The mechanical sensitivity increased slightly after adding LiF-B to the underwater explosive. Compared to the underwater explosive with added B, the mechanical sensitivity of the explosive with added LiF-B was significantly lower.     

希尔伯特-黄变换在脉冲涡流信号消噪与识别中的应用

针对传统方法无法有效识别不同尺寸细小裂纹所产生的脉冲涡流信号,提出一种基于希尔伯特-黄变换的脉冲涡流信号消噪与识别算法。对脉冲涡流信号进行集成经验模态分解并通过归一化自相关函数及其方差特性分选出含有噪声的本征模态函数;对含噪声的本征模态函数进行阈值消噪并与未做处理的本征模态函数重构成无噪声信号;对无噪声信号进行希尔伯特-黄变换并计算出希尔伯特边际谱;根据希尔伯特边际谱的差异识别出不同细小尺寸的表面与下表面裂纹。实验结果表明了所提方法的有效性,经过集成经验模态分解消噪,消除了噪声对脉冲涡流信号的干扰;而基于希尔伯特-黄变换的方法则能够有效识别出不同尺寸的裂纹。     

基于投影分解与k最近邻距离的异常证据检测算法

为降低异常证据对合成结果的影响,提出了基于投影分解与k最近邻距离的异常证据检测算法。该算法在对证据集中所有证据进行焦元单一元素投影分解的基础上,重新构造证据的基本概率赋值,然后利用证据之间形成的欧式距离,采用k最近邻距离算法对异常证据进行检测。无线传感器网络应用实验分析表明:该算法可有效地对异常证据进行检测。对检测前后的证据利用证据合成规则进行融合对比结果发现,剔除了异常证据的合成结果并具有良好的峰值性和可分辨性,合成结果有利于融合决策。     

合成双射流冲击平板流场结构与模态分解分析

为揭示合成双射流冲击平板流场结构特征,通过大涡模拟方法对合成双射流冲击平板流动进行了仿真,采用有限时间Lyapunov指数方法对流场的拉格朗日涡结构进行了识别,并与欧拉框架下的速度矢量和涡量结果进行了对比分析。结果表明,在合成双射流两股射流交替作用下,射流核心区涡系结构较为复杂且涡量丰富,远离核心区存在一对稳定的涡结构,且拉格朗日涡结构与涡量对应较好,为合成双射流冲击冷却的布局设计提供了指导。另外,流场本征正交分解表明,第一阶模态关于激励器出口中心轴线大致对称,其能量占总体能量的35%,前6阶模态的能量占80%;根据前6阶模态所反映的流场特性,合成双射流冲击平板流场具有高度的对称性。     

含噪混合盲扰信分离中联合降噪技术研究

针对盲扰信分离技术在含噪混合条件下分离效果差的问题,文章采用经验模态分解和小波变换联合的降噪技术进行分离前的消噪预处理,研究了联合降噪的三种模式,分别对其降噪效果进行了仿真分析,得到了一种较好的联合降噪模式。将该模式与无噪环境下的盲分离算法相结合,弥补了经典盲源分离算法处理含噪混合盲扰信分离的不足。仿真结果表明该算法在一定范围的低信噪比条件下,能够从含噪的混合信号中恢复出通信信号源。     

基于agent的多传感器管理原型系统研究

近年来,基于agent的分布式智能系统已成功应用于众多领域。将多agent技术应用于多传感器管理领域研究,以开发多传感器智能管理的多agent系统,提出了其原型系统的基本框架和系统实现途径及方法,其中着重研究了融合agent与传感器agent的原型系统结构、基于多a-gent理论的传感器管理问题分布式任务分解与控制问题以及agent之间的协调合作问题。原型系统的研究,为实际应用系统的研制开发提供了理论指导和方法依据。