基于OMNeT++的Ad Hoc网络跨层协议栈仿真

针对OMNeT++的MFW组件中物理层和MAC层模块的错误进行修正和功能改进,实现基于RBAB的IEEE 802.11b协议速率自适应数据传输,建立移动Ad Hoc网络跨层协议栈模型的网络仿真框架,实现将Ad Hoc网络MAC层的速率自适应机制与其路由协议联合优化设计的仿真。结果表明,在移动环境下,采用跨层设计的网络协议栈能大幅提高Ad Hoc网络系统的性能。     

基于改进局部线性特征编码方法的图像分类

特征编码是利用广义视觉词袋模型获得图像稀疏表示的关键步骤。本文研究了两种常用的局部线性特征编码方法即LLC及NSLLC编码方法,并针对其存在的问题,提出了一种利用编码系数非负性约束对其进行改进的方法——NNLLC,并将其应用于图像分类任务中。实验结果表明,该方法能有效改进局部线性特征编码性能,提高图像特征的可区分性,相比于LLC及NSLLC特征编码方法,在图像分类任务中取得了更高的平均分类准确率。     

改进十字链表的存储方法在短路电流计算中的应用

节点导纳矩阵是一个稀疏矩阵,短路电流计算需要对导纳矩阵数据进行查询。为了既能保持快速按行列查询元素数值,又进一步提高按数值查询其所在行列的效率,以便于存储调用及后续矩阵的处理,提出构建高度平衡二叉树的改进十字链表方法,即在十字链表存储的基础上,拓展存储数据结点指针域,形成平衡二叉树,将高度维持在(O(log2n)),平均查找长度也可维持在(O(log2n)),大大降低操作时间复杂度,提高数值查询效率。同时,为保证测试结果的公平性,把构建高度平衡二叉树的时间计入总时间,以进行对比。通过相应算例,验证了该改进方法的高效性。     

一种支持SIMD体系结构的高效分布式堆栈——HEDSSA

随着问题规模的增大和对实时性要求的提高,SIMD向量处理器尤其是带有向量运算单元的处理器在业界得到广泛应用。处理器上程序的运行状态一般由编译器通过堆栈进行管理。已有编译器堆栈设计机制在SIMD体系结构中严重影响了整个应用程序的运行性能。根据SIMD体系结构特点,提出了一种高效分布式堆栈设计方法——HEDSSA。实验结果表明,HEDSSA堆栈使得应用程序在进行局部数据访问、函数调用、发生中断以及动态分配数据时能够以更高的效率访问堆栈数据。     

Automatic camera control in virtual environments augmented using multiple sparse videos

Automated virtual camera control has been widely used in animation and interactive virtual environments. We have developed a multiple sparse camera based free view video system prototype that allows users to control the position and orientation of a virtual camera, enabling the observation of a real scene in three dimensions (3D) from any desired viewpoint. Automatic camera control can be activated to follow selected objects by the user. Our method combines a simple geometric model of the scene composed of planes (virtual environment), augmented with visual information from the cameras and pre-computed tracking information of moving targets to generate novel perspective corrected 3D views of the virtual camera and moving objects. To achieve real-time rendering performance, view-dependent textured mapped billboards are used to render the moving objects at their correct locations and foreground masks are used to remove the moving objects from the projected video streams. The current prototype runs on a PC with a common graphics card and can generate virtual 2D views from three cameras of resolution 768×576 with several moving objects at about 11 fps.     

用OpenGL开发三维交互式虚拟场景

介绍了Ｍｓ Ｗｉｎｄｏｗｓ环境下ＯｐｅｎＧＬ的体系结构和开作原理,深入剖析了用ＶｉｓｕａｌＣ＋＋开发真实感３Ｄ实时虚拟场是时采用的技术特点,并构造了两个可重用和继承的类－纹理贴图和画面输出保存２的设备无磁位图类以及初始化ＯｐｅｎＧＬ工作环境并正确设置调色板的视图类,在此基础上设计了一个模拟３Ｄ射击游戏。     

Source number estimation and separation algorithms of underdetermined blind separation

Recently, sparse component analysis （SCA） has become a hot spot in BSS research. Instead of independent component analysis （ICA）, SCA can be used to solve underdetermined mixture efficiently. Two-step approach （TSA） is one of the typical methods to solve SCA based BSS problems. It estimates the mixing matrix before the separation of the sources. K-means clustering is often used to estimate the mixing matrix. It relies on the prior knowledge of the source number strongly. However, the estimation of the source number is an obstacle. In this paper, a fuzzy clustering method is proposed to estimate the source number and mixing matrix simultaneously. After that, the sources are recovered by the shortest path method （SPM）. Simulations show the availability and robustness of the proposed method.     

Using Wide Table to manage web data: a survey

With the development of World Wide Web (www), storage and utilization of web data has become a big challenge for data management research community. Web data are essentially heterogeneous data, and may change schema frequently, traditional relational data model is inappropriate for web data management. A new data model, called Wide Table (or WT for simplicity), was introduced for this task. There are several characteristics of the WT model. First, WT is usually highly sparsely populated so that most data can be fit into a line or record. Second, queries are composed on only a small subset of the attributes. Thus, existing query processing and optimization techniques for relational database with normalized tables will not work efficiently anymore. Furthermore, WT is usually of extremely large volume. It is thought that only large-scale distributed storage can accommodate themassive data set. In this paper, requirements and challenges to web data management are discussed. Existing techniques for WT, including logical presentation, physical storage, and query processing, are introduced and analyzed in detail.     

基于单点像的光学稀疏孔径图像复原

为了定量评价光学稀疏孔径系统的图像复原效果,提出了一种以稀疏孔径系统单点像作为退化图像进行图像复原的方法.对稀疏孔径系统的单点像进行适当的复原处理,可获得类似爱里斑(即该稀疏孔径等效圆口径系统的单点像)的复原图像.通过比较该复原图像和爱里斑相似程度,即可对该复原算法(或者参数)进行评价.以法国SOLARNET光学稀疏孔径系统为例演示了上述图像复原过程.仿真结果表明,基于单点像的图像复原方法是可行的.     

p范数正则化支持向量机分类算法

L2范数罚支持向量机(Support vector machine,SVM)是目前使用最广泛的分类器算法之一,同时实现特征选择和分类器构造的L1范数和L0范数罚SVM算法也已经提出.但是,这两个方法中,正则化阶次都是事先给定,预设p=2或p=1.而我们的实验研究显示,对于不同的数据,使用不同的正则化阶次,可以改进分类算法的预测准确率.本文提出p范数正则化SVM分类器算法设计新模式,正则化范数的阶次p可取范围为02范数罚SVM,L1范数罚SVM和L0范数罚SVM.