需求演化过程建模

对需求任务、需求活动、需求工程过程以及需求工程过程系统进行形式化定义.用信息熵对需求任务演化进行度量,用联合熵对需求活动、需求工程过程以及需求工程过程系统演化进行度量.从需求工程过程的角度,用条件-事件网对需求工程过程的迭代、反馈进行微观演化建模.从系统工程的角度,用耗散结构理论对整个软件需求工程过程系统进行宏观演化建模.     

非线性J-C模型中场的熵压缩

运用量子信息熵理论研究了非线性Jaynes—Cummings模型中场的熵压缩特性，讨论了克尔介质与原子初态对场熵压缩的影响。结果表明强克尔介质相互作用可以产生深度压缩光，原子相干性也影响场熵压缩效应的存在和压缩深度。     

一类2次多项式混沌系统的均匀化方法研究

该文给出了一般的2次多项式混沌系统与Tent映射拓扑共轭的充分条件,并依据该条件,给出了一类2次多项式混沌系统及其概率密度函数;进一步得到了能够将这类系统均匀化的变换函数;给出了一个新的2次多项式混沌系统并进行均匀化处理,对其产生的序列进行了信息熵、Kolmogorov熵和离散熵分析,结果显示该均匀化方法的均匀化效果显著且不改变序列混沌程度。     

一类牛顿迭代法求解绝对值方程

绝对值方程Ax-|x|=b,A∈R^n×n,b∈Rⁿ是一类特殊的非线性方程,而且是NP-Hard问题。文中通过引入极大熵函数的概念,将原绝对值方程转化成一个非线性光滑方程组行进求解,并给出了求解的牛顿迭代法及其收敛性分析。实验结果证明了该方法的正确性和有效性。     

网络流量模型的非线性特征量的提取及分析

本文基于相空间重构理论,在高维相空间中对网络流量的宏观和微观特性进行研究分析.首先,提取网络流量的宏观非线性特征量,如关联维数、Kolmogorov熵和最大Lyapunov指数,实现了网络流量时序非线性动力学特性的定量分析.然后,通过对四种典型突发性流量模型的多重分形谱的计算,揭示了流量模型不同层次的行为特征,并给出了刻画突发性流量的有效微观参数.为进一步利用混沌动力学理论对网络行为的控制和建模奠定了基础.     

基于涌现视角的类BitTorrent性能分析模型

BitTorrent作为一种典型的实际P2P系统,在理论和实践中引起了广泛关注.给出一个有效的类BitTorrent系统分析模型一直是人们努力的一个方向.本文基于系统科学中的涌现概念,从微观到宏观来研究BitTorrent系统,给出了BitTorrent系统的微-宏观分析模型.首先从相对清晰的系统微观(结点)状态和行为入手,选取表征BitTorrent结点的参数,称为微观参数;根据BitTorrent的结点行为,基于这些微观参数,给出系统的微观行为描述;选取表征BitTorrent宏观态的变量,称为宏观变量;然后依据宏观变量与微观变量的关系,基于微观行为描述,建立系统的宏观演化方程;进而研究系统的宏观特性.实验表明该模型能够有效刻画BitTorrent系统的行为.     

Raman跃迁中原子的熵压缩

运用量子信息熵理论研究了Raman跃迁中原子的熵压缩特性.讨论了系统初态参数对原子信息熵压缩的影响.结果表明:信息熵压缩的分量数、压缩方向、压缩深度可以由原子的分布角、双模相干场相对位相和平均光子数的选取来控制.结果证明了信息熵能实现对原子压缩效应的高灵敏量度.     

基于运动模型的一类传感器管理方法

利用目标检测前后信息熵的变化以及卡尔曼滤波方程中协方差的预测与更新阵,可以计算出传感器对目标进行检测或跟踪所产生的信息增量,并给出了一类基于信息增量最大化传感器管理方法.仿真结果表明:与顺序跟踪方法相比,该方法能够更合理分配有限的传感器资源,提高跟踪系统的整体性能;与随机检测与跟踪方法相比,该方法在保证一定跟踪精度的前提下,能最大限度地发现并跟踪新目标.     

一种新的定量评估电磁环境复杂度方法

针对跳频信号分选提出了采用“复合信息熵”定量评估电磁环境复杂度的方法。“复合信息熵”分三个部分：类型熵、密度熵、分布熵，综合考虑了电磁环境中包含的信号类型数、跳频跳速、跳频电台数目和信道使用是否均匀等因素，合理反映了电磁环境的复杂度。在固定的观测时段内，熵值随着信号种类数增加、跳频跳速加快、跳频电台数目增多、信道使用不均匀度增加而增加。仿真结果表明方法有效。     

基于最大熵准则的多视角SAR目标分类方法

针对合成孔径雷达（Synthetic aperture radar,SAR）目标分类问题,提出基于最大熵准则的多视角方法。采用经典的图像相似度测度构建不同视角SAR图像之间的相关性矩阵,在此基础上分别计算不同视角组合条件下的非线性相关信息熵值。非线性相关信息熵值可分析多个变量之间的统计特性,熵值的大小即可反映不同变量之间的内在关联。根据最大熵的原则选择最优的视角子集,其中SAR图像具有最大的内在相关性。分类过程以联合稀疏表示为基础,对具有最大熵值的多个视角进行联合表示。联合稀疏表示模型同时处理若干稀疏表示问题,在它们具有关联的条件下具有提升重构精度的优势。根据不同视角求解得到的表示系数,按照类别分别计算对于选取多视角的重构误差,并根据误差最小的准则进行最终决策。文中方法可有效对多视角SAR图像样本进行相关性分析,并利用联合稀疏表示利用这种相关性,能够更好提高分类精度。采用MSTAR数据集对方法进行分析测试,通过与几类其他方法在多种测试条件下进行对比,结果显示了最大熵准则在多视角选取中的有效性和文中方法对SAR目标分类性能的优越性。     

Composite Macroscopic and Microscopic Diversity of Sectorized Macrocellular and Microcellular Mobile Radio Systems Employing RAKE Receiver over Nakagami Fading Plus Lognormal Shadowing Channel

This paper presents a generalized model of binary phase shift keying (BPSK) direct sequence code division multiple access (DS/CDMA) macrocellular and microcellular sectorized mobile radio systems over Nakagami fading plus lognormal shadowing channels. RAKE receiver, perfect and imperfect sectorization, voice activity monitoring, microscopic and composite microscopic plus macroscopic diversity are considered. The interrelationships among the number of interfering cells, sectorization degree, sectorization imperfection, voice activity factor, fading parameter, microscopic diversity degree, microscopic plus macroscopic diversity degree and the number of users are considered. Numerical results show that voice activity monitoring and sectorization can reduce multiple access interference (MAI). Furthermore, composite microscopic plus macroscopic diversity system can counteract the fast and slow fading components simultaneously.     

Band discontinuities as heterojunction device design parameters

A simple model that incorporates macroscopic and microscopic effects is proposed to predict the band discontinuities that govern the electrical and optical properties of heterojunction transistors and optoelectronic devices. It is found that the band discontinuities are determined by the short-range interface dipole and the bulk effects for nondegenerate systems and the agreement with the recent experiments is good. Furthermore, the recently observed failure of common anion rule for heterojunctions is correctly predicted.     

Model of electrostatic actuated deformable mirror using strongly coupled electro-mechanical finite element

The aim of this paper is to deal with multi-physics simulation of micro-electro-mechanical systems (MEMS) based on an advanced numerical methodology. MEMS are very small devices in which electric as well as mechanical and fluid phenomena appear and interact. Because of their microscopic scale, strong coupling effects arise between the different physical fields, and some forces, which were negligible at macroscopic scale, have to be taken into account. In order to accurately design such micro-electro-mechanical systems, it is of primary importance to be able to handle the strong coupling between the electric and the mechanical fields. In this paper, the finite element method (FEM) is used to model the strong coupled electro-mechanical interactions and to perform static and transient analyses taking into account large mesh displacements. These analyses will be used to study the behaviour of electrostatically actuated micro-mirrors.     

微小零件显微检测图像的清晰度评价

根据微小零件显微检测图像纹理相似、边缘信息太少和灰度分布范围有限等特点,从算法的基本原理出发,对传统清晰度评价函数进行了分析。针对传统清晰度评价函数无法兼具高灵敏度和抗噪性的缺陷,提出了一种基于局域方差信息熵的清晰度评价算法。该算法利用局域方差对各灰度级的自信息量进行加权,一方面弥补了信息熵函数缺失的空间信息,避免清晰度误判;另一方面增加清晰区域像素参与计算信息量时的权重,同时减少背景区域和噪声区域像素计算的权重,从而提高函数灵敏度。实验结果表明,与传统清晰度评价函数相比,局域方差信息熵函数不仅灵敏度很高,而且具有较好的抗噪性,可用于实际的自动对焦系统中。     

Influence of chemical etching on metal contacts to II-VI compounds: CdTe and ZnSe

The chemical nature of CdTe and ZnSe surfaces prepared by various chemical treatments has been studied by X-ray photoelectron spectroscopy. It has been found that the stoichiometry of the surfaces is very sensitive to the chemical treatments and each surface shows a similar pattern. In general bromine-containing or acid-based solutions preferentially remove the semiconductor cation, leaving a semiconductor anion-rich surface. In contrast, alkaline-based systems preferentially remove the semiconductor anion to produce a semiconductor cation-rich surface. Metal contacts fabricated on these surfaces show considerable differences in current-transport properties. The stability of these metal-semiconductor contacts has also been investigated and the microscopic interactions at these interfaces studied with Auger depth profiling and secondary-ion mass spectroscopy surface imaging techniques. The influence of microscopic interactions on the macroscopic electrical properties is presented and discussed in detail     

A maximum entropy method for lightwave system performance evaluation

A constrained maximum entropy criterion is used to approximate the cumulative distribution function of the photocurrent generated by an avalanche photodiode in response to an incident information-bearing optical signal. The approximate distribution, derived from known moments of the photocurrent, is used to evaluate the probability of error in direct detection lightwave systems. In this application, the results of the maximum entropy method are equivalent to those of a Gauss quadrature rule method. However the maximum entropy method exhibits a relative efficiency in terms of the required number of moments of the photocurrent.     

激光等离子体烧蚀推力的机理研究

随着航天空航空天技术的发展,激光等离子体推进受到了人们的普遍关注。基于激光与物质相互作用产生等离子体的空间分布,本文从微观、宏观和简化模型推导了碳靶的烧蚀压与激光强度的幂函数关系,幂指数分别是0.60493、2/3和2/3。实验测得碳靶的最大偏移量与激光能量的幂函数关系,幂指数为0.61936。实验与微观模型的幂指数相对相差大约仅有约2.32,而与宏观或简化模型的幂指数相对相差大约达到了约7.64,这表明了微介模型的合理性。然而,在误差允许的范围内,宏观或简化模型也是适用的。激光等离子体烧蚀推力的机理分析对开展工程研究具有一定的指导意义。