浅析几类双输入排队系统模型

从矩阵几何解的角度出发,分析了七种类型的Geom/Geom/(Geom/Geom)/H 双输入排队系统.对这几个模型进行了描述,使用拟生灭过程探讨了各类模型的矩阵结构,并给出了其状态转移概率矩阵.     

基于动态自适应t分布变异的人群搜索算法

针对人群搜索算法在进化后期大量个体聚集局部最优时,易陷入局部最优,搜索精度低的缺陷,提出一种基于t分布变异的人群搜索算法.算法使用动态自适应方式确定变异步长,引入t分布变异算子以融合柯西变异和高斯变异的优点,促进算法在进化早期具备良好的全局探索能力,在进化后期收获较强的局部开发能力,增加种群的多样性;采用边界缓冲墙策略处理越界问题,避免越界个体聚集在边界值上的缺陷.实验结果表明,算法比基本人群搜索算法具有更高的寻优精度和收敛速度,是一种有效的算法.     

基于多目标影响图效果作战模型

针对目前基于效果作战评估中没有涉及多目标以及决策者的偏好的情况,将多目标影响图引入到基于效果作战模型.首先分析了基于效果作战中各主要要素之间关系,其次提出了基于效果作战模型构造过程,然后将其与多目标决策理论结合建立了多目标基于效果作战模型,用多目标影响图对其进行建模,并给出了求解方法,最后将基于多目标影响图效果作战模型应用于空战任务分配中.仿真结果表明该模型的有效性.     

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In this paper, we extend the previous Markov-modulated reflected Brownian motion model discussed in [1] to a Markov-modulated reflected jump diffusion process, where the jump component is described as a Markov-modulated compound Poisson process. We compute the joint stationary distribution of the bivariate Markov jump process. An abstract example with two states is given to illustrate how the stationary equation described as a system of ordinary integro-differential equations is solved by choosing appropriate boundary conditions. As a special case, we also give the sationary distribution for this Markov jump process but without Markovian regime-switching.     

小样本定数截尾场合下威布尔和对数正态分布的拟合检验

本文给出了小样本定数截尾场合下两参数威布尔分布和对数正态分布的拟合检验方法,该方法还适用于一般的位置-刻度参数族分布,论文还通过实际算例说明方法的可行性。     

Pattern‐avoiding permutations and Brownian excursion part I: Shapes and fluctuations

Permutations that avoid given patterns are among the most classical objects in combinatorics and have strong connections to many fields of mathematics, computer science and biology. In this paper we study the scaling limits of a random permutation avoiding a pattern of length 3 and their relations to Brownian excursion. Exploring this connection to Brownian excursion allows us to strengthen the recent results of Madras and Pehlivan [25] and Miner and Pak [29] as well as to understand many of the interesting phenomena that had previously gone unexplained. © 2016 Wiley Periodicals, Inc. Random Struct. Alg., 50, 394–419, 2017     

On Moments of Folded and Truncated Multivariate Normal Distributions

Recurrence relations for integrals that involve the density of multivariate normal distributions are developed. These recursions allow fast computation of the moments of folded and truncated multivariate normal distributions. Besides being numerically efficient, the proposed recursions also allow us to obtain explicit expressions of low-order moments of folded and truncated multivariate normal distributions. Supplementary material for this article is available online.     

Effects of Charged Surfactants on Interfacial Water Structure and Macroscopic Properties of the Air-Water Interface

Surfactants are used to control the macroscopic properties of the air-water interface. However, the link between the surfactant molecular structure and the macroscopic properties remains unclear. Using sum-frequency generation spectroscopy and molecular dynamics simulations, two ionic surfactants (dodecyl trimethylammonium bromide, DTAB, and sodium dodecyl sulphate, SDS) with the same carbon chain lengths and charge magnitude (but different signs) of head groups interact and reorient interfacial water molecules differently. DTAB forms a thicker but sparser interfacial layer than SDS. It is due to the deep penetration into the adsorption zone of Br⁻ counterions compared to smaller Na⁺ ones, and also due to the flip-flop orientation of water molecules. SDS alters two distinctive interfacial water layers into a layer where H⁺ points to the air, forming strong hydrogen bonding with the sulphate headgroup. In contrast, only weaker dipole-dipole interactions with the DTAB headgroup are formed as they reorient water molecules with H⁺ point down to the aqueous phase. Hence, with more molecules adsorbed at the interface, SDS builds up a higher interfacial pressure than DTAB, producing lower surface tension and higher foam stability at a similar bulk concentration. Our findings offer improved knowledge for understanding various processes in the industry and nature.     

亚微米电喷雾喷针在非变性质谱分析中的研究进展

非变性质谱技术已成为表征蛋白质结构的重要工具之一。与传统的电喷雾喷针(Electrospray emitter,ESI emitter)相比,亚微米电喷雾喷针具有改变离子电荷态分布和降低盐离子加合等多种特性,可在生理环境下直接解析蛋白质的结构。该文综述了亚微米电喷雾喷针的特性及其在非变性质谱分析中的应用,并对其未来的发展趋势进行了展望。     

ZSM-5分子筛酸位分布及其甲醇制烯烃催化性能的定向管理与调控

ZSM-5分子筛在甲醇制烯烃(MTO)过程中的催化性能和反应机理与其孔道中酸位点分布位置紧密相关. 本文证明在水热合成过程中加入适量的钠离子(Na⁺)可以增加ZSM-5分子筛交叉腔酸位点比例; 从而促进高级甲基苯的生成并加速芳烃循环, 有利于乙烯生成. 相反, 在合成过程中不添加钠离子, 所制备的ZSM-5分子筛直孔道和正弦孔道酸位点比例明显提高, 有利于促进烯烃循环并提高丙烯和C₃₊烯烃选择性.