WiMAX下LDPC编译码器仿真实现的研究

WiMAX下的编码方式是当今通讯技术研究的热门。介绍一种最受关注的纠错编码:低密度奇偶校验码(Low Density Parity Check,LDPC),讨论LDPC码在WiMAX条件下的基本原理和编译码设计;提出运用Visual C++特点构建LDPC码仿真平台,研究仿真设计过程;分析不同实现方法下对LDPC码性能的影响,通过对仿真结果的分析和思考,说明了Visual C++语言应用于LDPC编译码仿真的可行性、实用性和扩展性。     

一种基于最大相似子阵的彩色图像检索算法

颜色是图像的重要特征之一,被广泛用于图像检索。传统的颜色直方图检索算法丢弃了色彩的空间位置信息,影响了算法的检索精度。针对这一问题,提出了一种基于最大相似子阵的彩色图像检索算法,即采用奇数方阵分割图像以捕捉颜色的空间分布特征,从而得到颜色矩阵,通过求解两个颜色矩阵的最大相似子阵实现相似度计算。研究结果表明,所提算法能够准确描述图像的颜色特征,相似度计算非常有效,相比全局直方图有较好的检索精度。     

一种新的工作流频繁闭合模式挖掘算法研究

为了提高工作流环境下频繁模式挖掘的准确性,提出了一种新的频繁闭合模式挖掘算法。首先扩展了依赖 矩阵的定义,即利用工作流日志建立包含直接依赖关系和交叠关系的依赖支持度矩阵。然后扩展了CHARM算法, 以在支持度矩阵的基础上自动挖掘频繁闭合活动集。最后对频繁闭合项集进行处理,以形成最终的工作流频繁闭合 模式。该算法对于并行和选择关系的处理能力优于同类算法。     

基于之型分量码的系统非规则GLDPC码

首先提出了一种新型的编码结构—基于之型分量码的系统非规则GLDPC码;其次在加性高斯白噪声信 道下利用基于高斯近似的密度进化理论设计G}ICI工DPC码的度分布序列;最后对G}IGI_DPC码进行了性能分析。 仿真结果表明,中等码长的ZS-IGLDPC码在误码率性能方面有一定的优势。     

量子纠错码[[7,1,4]]_p(p>3)存在性的图论构造方法

利用由Schingemann和Werner两人提出的构造量子纠错码的图论方法,证明了量子纠错码[[7,1,4]]p(p>3)的存在性。     

时延丢包网络控制系统的分析与控制

针对网络控制系统中同时存在时延和丢包问题,基于零阶保持器的工作机制,将同时受时延和丢包影响的网络控制系统建模为输入带有时延的控制系统,根据李雅普诺夫稳定性理论和时滞系统理论得出控制系统的时滞相关稳定性条件,进一步基于锥补线性化的方法给出控制器的设计方法,有效解决了网络控制系统中同时存在时延和丢包的控制问题。仿真算例表明所提方法的有效性。     

图像重建中的非常稀疏循环矩阵

测量矩阵是压缩传感理论的关键要素之一。针对目前大部分工作中所用的高斯等随机测量矩阵独立随机变元过多,不利于物理实现的问题,引入稀疏带状和稀疏列的概念,形成稀疏带状随机、托普利兹和循环矩阵以及稀疏列随机、循环矩阵,随机变元个数减少约三分之一。采用通用的模拟实验方法,验证此类稀疏矩阵对于真实图像的重建效果及对0-1信号的成功重建概率均与随机高斯矩阵相当。     

一类离散多时滞系统稳定性分析和成本控制

给出一类不确定范数有界离散多时滞系统,采用Lyapunov方法,结合线性矩阵不等式（LMI）技术,论证鲁棒稳定性的一个判据,设计出闲环系统的状态反馈鲁棒控制器,进一步给出可保成本的数学结构。最后利用matlab软件求解LMI,仿真案例验证了该方法的正确性和有效性。     

Transient Thermal Deformations of the Interphase in Polymer Composites

Heterodyne micro-interferometry was utilized to measure out-of-plane transient displacements in the interphase due to thermal cycling. In-situ measurements were made on single carbon fiber/epoxy samples with interphases of varying glass transition temperature. Interphase properties were tailored such that one set of samples had fibers which were coated with a low T_g resin, another set had a higher T_g coating, and in the third set the fibers were uncoated. The interferometric data demonstrated that interphase T_g has a significant effect on the rate and magnitude of the thermal deformations at the fiber/matrix interface. The presence of a low T_g interphase caused an increase in the magnitude of the thermal displacements due to a local softening of the matrix and increase in coefficient of thermal expansion. In addition, the rate at which the displacements increase was also higher due to the reduction in T_g. Samples with untreated fibers (no tailored interphase) behaved as if a low T_g interphase had formed. Experimental displacement profiles were also compared with finite element predictions to assess the behavior of the tailored interphases.     

Influence of Matrix Properties on Fragmentation Test

Physical aging was used to vary the mechanical properties of model single fiber composites without changing the chemistry at the interface in order to study how property changes affect the measurement of interfacial adhesion by the fragmentation test. The properties of epoxy matrix/AS4 single fiber composites driven to full cure (T_g = 166°C) are altered by annealing below T_g. Neat resin samples with identical thermal histories are tested. All aged panels show roughly the same embrittlement with aging characterized by an average 30% decrease in tensile failure strain and 7.3% increase in compressive yield relative to quenched samples. Fragmentation results indicated no change between aged and quenched samples. Results are discussed in terms of micromechanics models for the fragmentation test. Strain at fragmentation increased with aging. This was related to the residual stress state in the model composite and the possibility of the zero stress state of the single fiber composites increasing with thermal annealing.