嵌入式智能无线接入点系统的设计

该文提出了一种支持蓝牙、IEEE802.11b和GPRS三种不同的无线接入方式的智能无线接入点(AP)系统的实现方案。设计了在嵌入式Linux平台上智能无线AP的软硬件,重点讨论了蓝牙WPAN与Internet/GPRS以及WLAN的互连。     

New preconditioners for systems of linear equations with Toeplitz structure

In this paper, we consider applying the preconditioned conjugate gradient (PCG) method to solve system of linear equations $T x = \mathbf b $ where $T$ is a block Toeplitz matrix with Toeplitz blocks (BTTB). We first consider Level-2 circulant preconditioners based on generalized Jackson kernels. Then, BTTB preconditioners based on a splitting of BTTB matrices are proposed. We show that the BTTB preconditioners based on splitting are special cases of embedding-based BTTB preconditioners, which are also good BTTB preconditioners. As an application, we apply the proposed preconditioners to solve BTTB least squares problems. Our preconditioners work for BTTB systems with nonnegative generating functions. The implementations of the construction of the preconditioners and the relevant matrix-vector multiplications are also presented. Finally, Numerical examples, including image restoration problems, are presented to demonstrate the efficiency of our proposed preconditioners.     

基于串行通信自动配置AP的实现

配置管理AP的方法有很多,如通过网页管理,CIL或SNMP等大型管理软件,如果AP内建CLI模块,对于自动化测试软件来说,利用CLI来自动配置AP成为一种优先考虑的方法,本文主要分析利用串口自动配置AP遇到的问题并提出解决办法。     

基于串行通信自动配置AP的实现

配置管理AP的方法有很多,如通过网页管理,CIL或SNMP等大型管理软件,如果AP内建CLI模块,对于自动化测试软件来说,利用CLI来自动配置AP成为一种优先考虑的方法,本文主要分析利用串口自动配置AP遇到的问题并提出解决办法。     

基于插值A*算法的路径规划

提出一个基于插值的路径规划算法-插值A*.此算法可以在每个栅格路径代价不一致的情况下生成一条平滑路径.由于大多数基于栅格算法规划的路径只能从一个栅格中心到另一栅格中心,也就限制了路径的方向只能是倍数,所以所谓最优路径其实是次优的.插值A*算法在路径规划时,使用线形插值来计算出更精确的路径代价,由此产生更优路径.     

Critical Path Tracing: An Alternative to Fault Simulation

Critical path tracing determines fault detection without explicit. fault simulation. It appears to be a more efficient alternative to conventional methods.     

An estimation problem for linear stochastic equations with memory

We consider optimal estimation of solutions of linear equations with memory. The observation process contains a delay. Expressions are derived for the optimal estimate and the estimation error. Their dependence on the problem parameters is analyzed.Translated from Kibernetika, No. 3, pp. 76–80, May–June 1990.     

Stochastic modelling on the AP120B: An application to water resources planning

The analysis of a hydrologic time series, as used in the assesement of a water supply scheme, is presented to discuss the utility of a pipeline processor (e.g. AP120B) in a stochastic model building exercise. The analysis requires numerical operations on long records which appear particularly suited to a pipeline processor.     

USFKAD: An expert system for partial differential equations

The computation of the solution, by the separation of variables process, of the Poisson, diffusion, and wave equations in rectangular, cylindrical, or spherical coordinate systems, with Dirichlet, Neumann, or Robin boundary conditions, can be carried out in the time, Laplace, or frequency domains by a decision-tree process, using a library of eigenfunctions. We describe an expert system, USFKAD, that has been constructed for this purpose.

Program summary

Title of program:USFKADCatalogue identifier:ADYN_v1_0Program summary URL:http://cpc.cs.qub.ac.uk/summaries/ADYN_v1_0Program obtainable from: CPC Program Library, Queen's University of Belfast, N. IrelandLicensing provisions:noneOperating systems under which the program has been tested: Windows, UNIXProgramming language used:C++, LaTeXNo. of lines in distributed program, including test data, etc.: 11 699No. of bytes in distributed program, including test data, etc.: 537 744Memory required to execute with typical data: 1.3 MegabytesDistribution format: tar.gzNature of mathematical problem: Analytic solution of Poisson, diffusion, and wave equationsMethod of solution: Eigenfunction expansionsRestrictions concerning the complexity of the problem: A few rarely-occurring singular boundary conditions are unavailable, but they can be approximated by regular boundary value problems to arbitrary accuracy.Typical running time:1 secondUnusual features of the program: Solutions are obtained for Poisson, diffusion, or wave PDEs; homogeneous or nonhomogeneous equations and/or boundary conditions; rectangular, cylindrical, or spherical coordinates; time, Laplace, or frequency domains; Dirichlet, Neumann, Robin, singular, periodic, or incoming/outgoing boundary conditions. Output is suitable for pasting into LaTeX documents.     

How to solve linear differential equations: An outline

There are several definitions of closed form solutions to linear differential equations. In this paper, we look for the so-called Liouvillian solutions. Through examples, we give an overview of how the differential Galois theory leads to algorithms to find the Liouvillian solutions. We will outline the general ideas and results, but will give examples instead of proofs. This article was submitted by the author in English.     

Secant methods for sparse systems of nonlinear equations with a special structure

Secant methods for sparse systems of nonlinear equations with a special structure are given, as they arise, e. g., in the solution of boundary value problems for systems of ordinary differential equations by multiple shooting. The presented methods are compared with an adapted Broyden method.     

An explicit Numerov-type method for second-order differential equations with oscillating solutions

In this paper a new explicit Numerov-type method is introduced. The construction is based on a modification of a sixth-order explicit Numerov-type method recently developed by Tsitouras [Ch. Tsitouras, Explicit Numerov type methods with reduced number of stages, Comput. Math. Appl. 45 (2003) 37–42]. Two free parameters are added in order to nullify the phase-lag and the amplification. The method is useful only when a good estimate of the frequency of the problem is known in advance. The parameters depend on the product of the estimated frequency and the stepsize. Numerical results obtained for well-known test problems show the efficiency of the new method.     

An improved FPTAS for Restricted Shortest Path

Given a graph with a cost and a delay on each edge, Restricted Shortest Path (RSP) aims to find a min-cost s-t path subject to an end-to-end delay constraint. The problem is NP-hard. In this note we present an FPTAS with an improved running time of O(mn/ε) for acyclic graphs, where m and n denote the number of edges and nodes in the graph. Our algorithm uses a scaling and rounding technique similar to that of Hassin [Math. Oper. Res. 17 (1) (1992) 36-42]. The novelty of our algorithm lies in its “adaptivity”. During each iteration of our algorithm the approximation parameters are fine-tuned according to the quality of the current solution so that the running time is kept low while progress is guaranteed at each iteration. Our result improves those of Hassin [Math. Oper. Res. 17 (1) (1992) 36-42], Phillips [Proc. 25th Annual ACM Symposium on the Theory of Computing, 1993, pp. 776-785], and Raz and Lorenz [Technical Report, 1999].     

一种简化协议路径测试的方法

在协议测试中,设计测试例是主要工作之一,测试例包括了对状态错和数据错的测试,测试状态错要求对状态图中路径进行遍历。基于向量空间的思想,设计了一个生成基本路径集的算法,使得状态图中任何路径都可由基本路径通过线性组合生成,以达到简化协议路径测试之目的,并对此加以了证明。     

轮廓平移无跳刀连接刀路环树优化算法

提出一个无跳刀的轮廓平移刀路轨迹优化算法．根据刀路环之间父环和子环关系,提出“刀路环树”的概念,将加工刀路的一次环切定义为一个“刀路环向量”,并将刀路环的各个属性定义为刀路环向量的分量．根据无跳刀轨迹的要求,针对刀路环树的各个刀路环向量进行遍历,以获得了一个无跳刀的轮廓平移刀路轨迹算法,并通过与其他算法比较,证明该算法无跳刀、无重复切削,并且可以自动执行．     

An Experimental Study of Internet Path Diversity

Several research studies have been devoted to improving the reliability and performance of the Internet by utilizing redundant communication paths between end points. Multihoming, coupled with intelligent route control, and overlay networks are two main streams in this area of research which attempt to leverage redundant connections of the Internet for increased reliability and performance. However, the effectiveness of these approaches depends on the natural diversity of redundant paths between two endhosts in terms of physical links, routing infrastructure, administrative control, and geographical distribution. Even in the case of redundant paths, if traffic between two hosts is not actually routed along completely disjoint paths, congestion or failure of a single shared link or router can adversely affect the end-to-end performance or availability of all paths. This paper presents an experimental study of path diversity on the Internet, focusing on the impact of path diversity on multihomed and overlay networks. We base our analysis on traceroutes and routing table data collected from several vantage points in the Internet including: looking glasses at 10 major Internet service providers (ISPs), RouteViews servers from 20 ISPs, and more than 50 PlanetLab nodes globally distributed across the Internet. Using this data, we quantify the extent of path diversity in multihoming and overlay networks, highlighting the limitations, and also identifying the source of the limitations in these architectures. From the analysis, we learn that both multihoming route control and current overlay networks are not able to ensure path diversity, which makes it very difficult to provide high-availability services even with the use of these systems. We believe that this work provides the insight into building future systems based on understanding path diversity