基于优化模拟电荷法的直流输电线路电场特性计算

为了提高模拟电荷法计算电场的精度并降低其计算复杂度,采用黄金分割法对模拟电荷法进行优化,提出了一种精度高且易实现的模拟电荷设置方法.应用该模拟电荷法计算了直流输电线路导线表面电场,采用"化曲为直"法绘制了电场线轨迹.在此基础上,基于通量线法对比分析了分裂导线表面最大场强在不同取值方法下求解合成电场和离子流密度时带来的计...     

正定二次最优控制问题的最优值的估计

众多实际应用中,人们常用正定二次规划方法对正定二次最优控制问题的最优值进行逼近估计.为简化计算和加快计算速度,本文设计了一种新的算法,利用线性规划代替二次规划.先用最优控制方法构造一个线性规划,使其最优值与给定二次规划相差一个容易确定的常数.由于线性规划具有形式简单和算法成熟等特点,本文的方法就简化了正定二次最优控制问题的最优值的估计,并加快了计算速度.文中给出一个例子说明这一计算过程,并讨论了计算速度.同时,本文的最后部分,利用参数规划,给出了一个供实际应用的具体算法.     

基于三维混沌系统的图像加密算法

为了改进图像加密算法的安全性和效率,提出了一种基于三维混沌系统和位运算的数字图像加密算法,利用三维混沌序列的坐标分量分别产生置换序列和二值序列,在对待加密图像进行预处理的基础上,先应用混沌置换序列对预处理的结果图像进行基于灰度值位序列的置换操作,然后再应用产生的二值序列对结果图像的灰度值位序列进行位异或加密运算。实验结果表明,该算法具有良好的安全性和加密效果。     

基于XOR Hash的快速IP数据包分类算法研究

文章在哈希算法的基础上,提出了一种基于异或哈希的IP分类算法,该算法的核心有三点:一是将目的/源IP、目的/源端口和协议五域连成比特串,然后分为五块后进行异或,获得分类关键值;二是为了降低冲突率,将异或后的关键值再与一个随机数进行异或,获得最终分类索引值;三是为了保证查找到的规则的正确性,对每一个索引值的源/目的IP地址均匹配一次。通过以上三点改进一般会降低算法的时间复杂度和空间复杂度,通过仿真,当对1万条分类规则进行包分类时,该算法的包分类速度可以达到2Mpps,所消耗的最大内存为6MB。     

适应光照突变的运动目标检测算法

针对光照突然变化条件下的运动目标检测存在的问题,提出一种基于局部二值模式(LBP)的背景建模算法.首先分别计算背景帧和当前帧的LBP纹理特征图,然后将其对应像素进行异或运算,得到的当前像素作为前景的概率,并根据该概率自适应地更新背景,可以使其很快接近真实背景,再用背景减除法得到目标.实验结果表明,文中算法能有效地处理光照的突然变化,背景更新速度快,检测出的目标接近真实目标.     

一种基于BMP图像相邻像素的隐写分析方法

首先介绍BMP文件结构及特点以及相邻像素相关的特性,基于此提出了一种新的隐写分析算法,该算法分别计算每个像素与其八个领域像素的异或值的和,再统计根据计算的值归类,以此扫描完成整个图像。最后统计图像中各个异或值和相同的数目,以此来判断是否含有隐秘信息。实验编程环境为VS2008,通过实验结果表明,此检测算法统计量小、实现简单,在隐秘信息嵌入量较多时具有较高检测率。     

一种基于BMP图像相邻像素的隐写分析方法

首先介绍BMP文件结构及特点以及相邻像素相关的特性,基于此提出了一种新的隐写分析算法,该算法分别计算每个像素与其八个领域像素的异或值的和,再统计根据计算的值归类,以此扫描完成整个图像。最后统计图像中各个异或值和相同的数目,以此来判断是否含有隐秘信息。实验编程环境为VS2008,通过实验结果表明,此检测算法统计量小、实现简单,在隐秘信息嵌入量较多时具有较高检测率。     

高压输电线附近工频电场模型及仿真研究

建立了高压输电线路附近工频电场的数学模型,采用模拟电荷法在时域中计算了高压输电线路附近工频电场的分布,并利用MATLAB编程语言对此分布进行了仿真,得出了高压输电线路附近电场的分布规律及影响因素.与"国际大电网会议第36.01工作组"推荐的方法相比,使用电压瞬时值进行场强计算较易理解,且能适用于更广泛的范围.     

一种双哈希IP数据包分类算法研究

本文在无冲突哈希算法和异或哈希算法的基础上，提出了一种双哈希的IP分类算法，该算法的核心有三点：一是基于目的／源端口和协议域构造无冲突哈希，由于该三域的组合数目非常少，避免了空间爆炸；二是在异或哈希算法的基础上，将目的／源IP连成比特串后分为四块后进行异或，为了降低冲突率，将异或后的关键值再与一个随机数进行异或，获得分类索引值，并用此值生成多比特Trie树，一般情况下减小了空间和时间复杂度；三是在Trie树终点存放最终分类规则的索引值，为了保证查找到的规则的正确性，对每一个索引值的源／目的IP地址均匹配一次。通过以上三点改进一般要降低算法的时间复杂度和空问复杂度，通过仿真，当对1万条分类规则进行包分类时，该算法的包分类速度可以达到2MPps，所消耗的最大内存为4MB。     

异或和取模运算的负载均衡算法

引入信息熵对哈希函数的输入值进行随机度测试,实验证明增加异或字段数并划分字段后进行异或运算能提高运算结果的随机测度值.标识字段有很高的位熵值,函数输入值中加入此值能减少负载迁移次数而运算效率与CRC16接近.采用源IP、目的IP、源端口、目的端口、标识字段作为输入值,并划分为8位的比特串进行异或运算,然后再进行取模运算的双哈希算法运算效率较高而且均衡性好,适合于高速网络环境下的入侵检测.     

The promise of analog computation

Future computing paradigms and technologies will have to be more like the physical processes by which they are realized, and because these processes are primarily continuous, post-Moore’s law computing will involve an increased use of analog computation. Traditionally analog computers have computed ordinary differential equations of time, but analog field computation permits massively parallel temporal integration of partial differential equations. In principle many different physical media – not just electronics – can be exploited to implement the basic operations of analog computing, a small number of which are sufficient to approximate a wide variety of analog computations, thus providing a basis for universal analog computation and general-purpose analog computers. The contentious issue of the computational power of analog computers is addressed best on its own terms, rather by asking it within the context of Church-Turing computation, which distorts the relevant questions and their answers.     

Web platforms for scientific research

This paper considers current trends in creating systems for convenient and secure remote submission (by authorized users) of jobs to computing resources of different types, including supercomputers, clusters, cloud resources, storages, databases, and grid infrastructures. Presently, large computing and storage resources are capable of solving, on their own, the majority of practical problems in the field of science and technology. Therefore, the focus in developing next-generation middleware shifts from global grid systems towards creating convenient and efficient means of access to large individual resources. A web platform for remote access to computing resources is a set of special web services and application-oriented web interfaces. Such web platforms, on a centralized basis, provide users with a number of services interrelated by a specific application area, principle of access, and interface. In this paper, general principles of creating such platforms are considered and some particular implementations of web platforms are briefly described.     

Conquering inseparability: Primary decomposition and multivariate factorization over algebraic function fields of positive characteristic

Algebraic function fields of positive characteristic are non-perfect fields, and many standard algorithms for solving some fundamental problems in commutative algebra simply do not work over these fields. This paper presents practical algorithms for the first time for (1) computing the primary decomposition of ideals of polynomial rings defined over such fields and (2) factoring arbitrary multivariate polynomials over such fields. Difficulties involving inseparability and the situation where the transcendence degree is greater than one are completely overcome, while the algorithms avoid explicit construction of any extension of the input base field. As a corollary, the problem of computing the primary decomposition of a positive-dimensional ideal over a finite field is also solved. The algorithms perform very effectively in an implementation within the Magma Computer Algebra System, and an analysis of their practical performance is given.     

基于LabVIEW的飞机机轮转速模拟装置

针对飞机的地面模拟试验,基于LabVIEW和数据采集卡,开发了飞机机轮转速模拟装置。该装置可同时输出4路正弦信号,模拟飞机机轮转速传感器信号。利用图形界面可以方便地设置信号的幅值和输出方式,输出信号的频率与转速成正比,转速通过读取已知转速-时间曲线或根据当前刹车压力积分计算得到。通过网络可与其它计算机传递数据和指令,实现远程控制。实际应用表明,该装置操作简便,很好地满足了试验需求。     

Neural and Super-Turing Computing

``Neural computing' is a research field based on perceiving the human brain as an information system. This system reads its input continuously via the different senses, encodes data into various biophysical variables such as membrane potentials or neural firing rates, stores information using different kinds of memories (e.g., short-term memory, long-term memory, associative memory), performs some operations called ``computation', and outputs onto various channels, including motor control commands, decisions, thoughts, and feelings. We show a natural model of neural computing that gives rise to hyper-computation. Rigorous mathematical analysis is applied, explicating our model's exact computational power and how it changes with the change of parameters. Our analog neural network allows for supra-Turing power while keeping track of computational constraints, and thus embeds a possible answer to the superiority of the biological intelligence within the framework of classical computer science. We further propose it as standard in the field of analog computation, functioning in a role similar to that of the universal Turing machine in digital computation. In particular an analog of the Church-Turing thesis of digital computation is stated where the neural network takes place of the Turing machine.     

Problem solving techniques in cognitive science

For many years, researchers have tried to discover how humans solve problems. This research has answered many questions, but still many of them remain unanswered. However, knowledge gained in this field has greatly enhanced our understanding and has enabled us to design human-like intelligent systems. In the 1920s the Gestalt psychologists introduced a new field to cognitive science. They discovered that when presented with certain problems we use insight to reach a solution. In the 1950s Newell & Simon then brought the field of problem solving into the information age. They experimented with the idea of problem solving as a search for a solution in a state space. This technique is today utilized in the field of computing and Artificial Intelligence. This paper reviews techniques and looks at how we use previous experience gained by solving problems to solve new similar problems, making analogies between them. Experts’ performance during problem solving is compared to that of novices.     

Parallel mesh-partitioning algorithms for generating shape optimised partitions using evolutionary computing

In this paper, parallel mesh-partitioning algorithms are proposed for generating submeshes with optimal shape using evolutionary computing techniques. It is preferred to employ a formulation for mesh partitioning, which maintains constant number of design variables irrespective of the size of the mesh. Two distinct parallel computing models have been employed. The first model of parallel evolutionary algorithm uses the master–slave concept (single population model) and a new synchronous model is proposed to optimise the performance even on heterogeneous parallel hardware. Alternatively, a multiple population model is also developed which simulates it’s sequential counter part. The advantage of the second model is that it can fit in large size problems with large population even on moderate capacity parallel computing nodes. The performance of the evolutionary computing based mesh-partitioning algorithm is demonstrated first by solving several practical engineering problems and also several benchmark test problems available in the literature and comparing the results with the multilevel algorithms. Later the speedup of the parallel evolutionary algorithms on parallel hardware is evaluated by solving large scale practical engineering problems.     

基于网络的科学问题求解环境研究

科学问题求解环境以一套高效的科学计算工具集为基础,为求解科学问题提供了一个方便易用的平台。把传统的科学问题求解环境同网络的共享与协同特征相结合,为满足科学问题求解过程中普遍存在的知识复用与大规模计算的需求提供了新的机遇。该文介绍了科学问题求解环境的发展历史及存在的问题,在此基础上提出了一种解决方案——基于网络的科学问题求解环境(Grid-PSE)。     

具有实际地形的海洋潮流场云计算环境

针对具有实际地形的海洋潮流场的大规模、复杂的、异构资源共享的计算问题,提出了基于云计算的问题求解环境,建立了具有实际地形的海洋潮流场云计算环境。分析了具有实际地形的海洋潮流场的特点,在此基础上提出了具有实际地形的潮流场的云计算环境的应用服务模式,给出了云计算环境的架构,即XaaS服务架构,建立了云计算资源组织和管理的功能抽象模型,模拟5907号海洋风暴潮的演进过程。     

基于串行DAC8420芯片的模拟量输出卡设计

DAC8420是4路12位DAC芯片,具有功耗低、转换速度快和精度高的特点;同时,其与微处理器的I/O接口采用高速串行连接方式,简化了硬件电路设计.在介绍该芯片内部组成结构的基础上,给出一种多类电信号输出采集卡的软硬件设计,并对系统中的抗干扰措施给予一定的介绍.