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排序方式: 共有185条查询结果,搜索用时 296 毫秒
21.
文章提出了一种将非结构化数据集中存储,同时支持事务的存储方案,并依据此方案实现了一个高效、易用的数据存储系统GSL。GSL的数据存储接口与文件系统的接口风格一致,同时支持事务处理。文章将GSL与文件系统和Oracle数据库的BLOB存储效率进行了测试和比较,结果表明GSL的存储效率与文件系统相当,并优于BLOB。 相似文献
22.
对等网络(P2P)成为近年来的研究热点,如何进行高效准确的资源搜索是实现对等网络应用的关键问题。本文在分析Gnutella网络的基本泛洪算法存在问题的基础之上,介绍了现有的资源搜索改进方法,包括优化网络拓扑结构方法、改进转发机制方法、基于路由信息方法和基于缓存的方法。 相似文献
23.
In this work, a new vertex-based finite volume method (FVM) using unstructured grids and cell-based data structure is proposed
for computational analysis of two-and three-dimensional (2D/3D) general structural dynamic problems. The governing equations
are spatially discretized by the FVM and an implicit dual time stepping scheme is employed to integrate the equations in time.
The proposed method is applied to calculate deformations and dynamics of 2D and 3D cantilevers, as well as simply supported
and clamped square plates. Computational results obtained are found to agree well with analytical solutions. It can be a viable
alternative to the traditional finite element method (FEM) for structural dynamic calculations. And it can be seamlessly integrated
into FVM-based Computational Fluid Dynamics (CFD) solver for simulating fluid-structure interaction (FSI). 相似文献
24.
S. Pimpalnerkar 《International Journal of Heat and Mass Transfer》2005,48(6):1128-1136
This paper describes applications of the discretization procedure presented in the companion paper [A.W. Date, Solution of transport equations on unstructured meshes with cell-centered colocated variables. Part I. Discretization, Companion Paper, this volume]. Six problems having different domain complexities, presence of body and surface forces and, boundary conditions are solved. Where possible, the solutions are compared with published experimental or numerical data. 相似文献
25.
点对点(Peer-to-Peer)网络已发展成为当今最为流行的资源共享系统之一.其中的资源搜索是一个关键性问题.但其常用的基于简单flooding机制的信息资源搜索方法造成了严重的通信消耗,本文借鉴人际传播中谣言传播机制,结合节点吸引因子(在真实系统中,新增节点不仅与网络中已有的度数较高的节点连接,而且与吸引因子较大的... 相似文献
26.
We consider a multiobjective robust controller synthesis problem for an LTI system subject to unstructured perturbations. Our design specifications include robust stability, robust performance (H2-norm) bounds and time-domain bounds (output and command input peak). We derive sufficient conditions, based on a single quadratic Lyapunov function, for the existence of an LTI controller such that the closed-loop system satisfies all specifications simultaneously. These conditions can be numerically checked using finite-dimensional, convex optimization over LMIs, associated with a two-dimensional search. When considering only a subset of the specifications, we recover previous results from the literature, such as those obtained in mixed H2/H∞ control. 相似文献
27.
A mesh-vertex finite volume scheme for solving the Euler equations on triangular unstructured meshes is implemented on a MIMD (multiple instruction/multiple data stream) parallel computer. Three partitioning strategies for distributing the work load onto the processors are discussed. Issues pertaining to the communication costs are also addressed. We find that the spectral bisection strategy yields the best performance. The performance of this unstructured computation on the Intel iPSC/860 compares very favorably with that on a one-processor CRAY Y-MP/1 and an earlier implementation on the Connection Machine.The authors are employees of Computer Sciences Corporation. This work was funded under contract NAS 2-12961 相似文献
28.
Ana Costa e Silva Alípio M. Jorge Luís Torgo 《International Journal on Document Analysis and Recognition》2006,8(2-3):144-171
This paper plans an end-to-end method for extracting information from tables embedded in documents; input format is ASCII, to which any richer format can be converted, preserving all textual and much of the layout information. We start by defining table. Then we describe the steps involved in extracting information from tables and analyse table-related research to place the contribution of different authors, find the paths research is following, and identify issues that are still unsolved. We then analyse current approaches to evaluating table processing algorithms and propose two new metrics for the task of segmenting cells/columns/rows. We proceed to design our own end-to-end method, where there is a higher interaction between different steps; we indicate how back loops in the usual order of the steps can reduce the possibility of errors and contribute to solving previously unsolved problems. Finally, we explore how the actual interpretation of the table not only allows inferring the accuracy of the overall extraction process but also contributes to actually improving its quality. In order to do so, we believe interpretation has to consider context-specific knowledge; we explore how the addition of this knowledge can be made in a plug-in/out manner, such that the overall method will maintain its operability in different contexts.The opinions expressed in this article are the responsibility of the authors and do not necessarily reflect those of Banco de Portugal. 相似文献
29.
Local refinement of three-dimensional finite element meshes 总被引:6,自引:0,他引:6
Mesh refinement is an important tool for editing finite element meshes in order to increase the accuracy of the solution. Refinement is performed in an iterative procedure in which a solution is found, error estimates are calculated, and elements in regions of high error are refined. This process is repeated until the desired accuracy is obtained.Much research has been done on mesh refinement. Research has been focused on two-dimensional meshes and three-dimensional tetrahedral meshes ([1] Ning et al. (1993) Finite Elements in Analysis and Design, 13, 299–318; [2] Rivara, M. (1991) Journal of Computational and Applied Mathematics 36, 79–89; [3] Kallinderis; Vijayar (1993) AIAA Journal,31, 8, 1440–1447; [4] Finite Element Meshes in Analysis and Design,20, 47–70). Some research has been done on three-dimensional hexahedral meshes ([5] Schneiders; Debye (1995) Proceedings IMA Workshop on Modelling, Mesh Generation and Adaptive Numerical Methods for Partial Differential Equations). However, little if any research has been conducted on a refinement algorithm that is general enough to be used with a mesh composed of any three-dimensional element (hexahedra, wedges, pyramids, and/or retrahedra) or any combination of three-dimensional elements (for example, a mesh composed of part hexahedra and part wedges). This paper presents an algorithm for refinement of three-dimensional finite element meshes that is general enough to refine a mesh composed of any combination of the standard three-dimensional element types. 相似文献
30.
The technology of replication is often used in the unstructured Peer-to-peer (P2P) systems to allocate more replicas for the hot spots in order for a higher search performance. But the questions that what is the optimal number of copies for each file and what is the practicable approach to the optimal number are seldom answered in the related works. In terms of success rate, this paper firstly investigates the optimal allocation of copies for each file according to query rate with the routing algorithm of random walks. Then a practicable method is proposed to approach the optimal allocation in the unstructured P2P systems. Our results offer a new understanding of replication and our work contributes much to the content distribution in the Internet environment. 相似文献