The Local Artificial Boundary Conditions for Numerical Simulations of the Flow Around a Submerged Body

We consider in this work the numerical approximations of the two-dimensional steady potential flow around a body moving in a liquid of finite constant depth at constant speed and distance below a free surface. Several vertical segments are introduced as the upstream and the downstream artificial boundaries, where a sequence of high-order local artificial boundary conditions are proposed. Then the original problem is solved in a finite computational domain, which is equivalent to a variational problem. The numerical approximations for the original problem are obtained by solving the variational problem with the finite element method. The numerical examples show that the artificial boundary conditions given in this work are very effective.     

Local Encoding Transformations for Optimizing OBDD-Representations of Finite State Machines

Ordered binary decision diagrams are the state-of-the-art representation of switching functions. In order to keep the sizes of OBDDs tractable, heuristics and dynamic reordering algorithms are applied to optimize the underlying variable order. When finite state machines are represented by OBDDs the state encoding can be used as an additional optimization parameter. In this paper, we analyze local encoding transformations which can be applied dynamically. First, we investigate the potential of re-encoding techniques. We then propose the use of an XOR-transformation and show why this transformation is most suitable among the set of all encoding transformations. The presented theoretical framework establishes a new optimization technique for OBDDs.     

A Timed Verification of the IEEE 1394 Leader Election Protocol

The IEEE 1394 architecture standard defines a high performance serial multimedia bus that allows several components in a network to communicate with each other at high speed. In the physical layer of the architecture, a leader election protocol is used to find a spanning tree with a unique root in the network topology. If there is a cycle in the network, the protocol treats this as an error situation. This paper presents a formal model of the leader election protocol in the language IOA and a correctness proof. Hereby, it is shown that under certain timing restrictions the protocol behaves correctly. The timing parameters in the IEEE 1394 standard documentation obey the restrictions found in this proof.     

动态系统的常微分方程组建模—基于不同搜索技术的实验研究

以人口模型和化学反应模型为例,通过大量实验研究比较了分别采用基于两种传统的搜索方法即局部搜索算法和模拟退火算法、遗传算法（简称GA）四者相结合的14种不同算法建立动态系统的常微分方程组模型的实验结果,得到了有关各算法性能比较的一些新的结论。两个实例的实验结果表明：在14种算法中,GP＋GA＋LS－MU算法（即在采用GP的模型结构的优化过程中嵌入采用GA的模型参数的优化过程,并且在每一演化代对种群中的部分个体进行基于GP的标准变异算子产生邻域解的局域搜索过程）是目前解决常微分方程组建模问题的最好算法。     

解Hamilton-Jacobi方程的无振荡局部加密方法

０．引 言 近年来,Ｈａｍｉｌｔｏｎ－Ｊａｃｏｂｉ方程（简称Ｈ－Ｊ方程）的数学理论与数值逼近已引起人们越来越多的关注．Ｈ－Ｊ方程不仅在原有的领域例如控制论、微分几何等有非常重要的应用［８］,而且不断开拓新的应用领域,例如用于网格生成［５］以及流体界面的水平集方法计算 ［９,１２,１３,１５］等．由于 Ｈ－Ｊ方程解的导数会出现间断,导致解曲面（线）出现尖点或纽结等现象［７］,故如何做到既节省计算时间,又能在光滑区域高精度数值求解和较好地分辨间断是一个十分重要的问题．文卜］通过在每个坐标方向构造单变量的…     

Asymptotic Fourier Coefficients for a C∞ Bell (Smoothed-“Top-Hat”) & the Fourier Extension Problem

In constructing local Fourier bases and in solving differential equations with nonperiodic solutions through Fourier spectral algorithms, it is necessary to solve the Fourier Extension Problem. This is the task of extending a nonperiodic function, defined on an interval , to a function which is periodic on the larger interval . We derive the asymptotic Fourier coefficients for an infinitely differentiable function which is one on an interval , identically zero for , and varies smoothly in between. Such smoothed “top-hat” functions are “bells” in wavelet theory. Our bell is (for x ≥ 0) where where . By applying steepest descents to approximate the coefficient integrals in the limit of large degree j, we show that when the width L is fixed, the Fourier cosine coefficients a _j of on are proportional to where Λ(j) is an oscillatory factor of degree given in the text. We also show that to minimize error in a Fourier series truncated after the Nth term, the width should be chosen to increase with N as . We derive similar asymptotics for the function f(x)=x as extended by a more sophisticated scheme with overlapping bells; this gives an even faster rate of Fourier convergence     

区域车辆信息管理系统建设设想

充分利用计算机技术和Internet技术,开展车辆管理和网上服务已成为一种发展趋势,重点介绍了区域车辆信息管理系统的建设设想及软件体系构架。     

网络存储技术的探讨

本文介绍了传统的依赖服务器存储的缺陷以及网络存储的现状,对附网存储及存储局域网技术进行了论述,把二者进行了比较,并总结出了二者优势和缺点,最后介绍存储局域网和附网存储的应用。     

A Novel Self-Creating Neural Network for Learning Vector Quantization

This paper presents a novel self-creating neural network scheme which employs two resource counters to record network learning activity. The proposed scheme not only achieves the biologically plausible learning property, but it also harmonizes equi-error and equi-probable criteria. The training process is smooth and incremental: it not only avoids the stability-and-plasticity dilemma, but also overcomes the dead-node problem and the deficiency of local minimum. Comparison studies on learning vector quantization involving stationary and non-stationary, structured and non-structured inputs demonstrate that the proposed scheme outperforms other competitive networks in terms of quantization error, learning speed, and codeword search efficiency.     

RTK测量技术中的坐标转换方法研究

介绍了全球卫星定位系统（GNSS）在测绘工作中的应用发展历程,讲述了采用RTK技术获取的WGS84坐标转换到地方坐标的方法,结合工程数据进行了坐标转换研究,得出了三参数、四参数及七参数坐标转换方法的应用范围及使用条件。