A generalised finite difference scheme based on compact integrated radial basis function for flow in heterogeneous soils

In the present paper, we develop a generalised finite difference approach based on compact integrated radial basis function (CIRBF) stencils for solving highly nonlinear Richards equation governing fluid movement in heterogeneous soils. The proposed CIRBF scheme enjoys a high level of accuracy and a fast convergence rate with grid refinement owing to the combination of the integrated RBF approximation and compact approximation where the spatial derivatives are discretised in terms of the information of neighbouring nodes in a stencil. The CIRBF method is first verified through the solution of ordinary differential equations, 2-D Poisson equations and a Taylor-Green vortex. Numerical comparisons show that the CIRBF method outperforms some other methods in the literature. The CIRBF method in conjunction with a rational function transformation method and an adaptive time-stepping scheme is then applied to simulate 1-D and 2-D soil infiltrations effectively. The proposed solutions are more accurate and converge faster than those of the finite different method employed with a second-order central difference scheme. Additionally, the present scheme also takes less time to achieve target accuracy in comparison with the 1D-IRBF and HOC schemes

Improved numerical methods for modeling flow and transport processes in partially saturated porous media

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Civil Engineering, 1989.M.I.T. copy lacks leaf 258.Includes bibliographical references (leaves 264-275).by Efthimios T. Bouloutas.Ph.D

Centralized vs Distributed Fault Localization

In this paper we compare the performance of fault localization schemes for communication networks. Our model assumes a number of management centers, each responsible for a logically autonomous part of the whole telecommunication network. We briefly present three different fault localization schemes: namely, "Centralized", "Decentralized" and "Distributed" fault localization, and, we compare their performance with respect to the computational effort each requires and the accuracy of the solution that each provides. 1 INTRODUCTION Usually, a single fault in a large network results in a number of alarms, and it is not always easy to identify the primary source(s) of failure. The problem of fault management becomes even worse when several faults occur coincidentally in the telecommunication network. The fault management process can be divided into three stages: alarm correlation, fault identification, and testing. The first two stages, usually referred to as the fault localization process..

An Alarm Filtering Algorithm for Optical Communication Networks

A single failure in a communication network can trigger many alarms. We propose an alarm filtering algorithm for the management of an optical network using Wavelength Division Multiplexing (WDM). The algorithm supports: (i) multiple failures and (ii) passive network elements that do not generate alarms but may fail. This algorithm will be applied to the network of the ACTS COBNET project. Keywords Alarm Filtering, Fault Recognition, WDM Networks, Failure Diagnosis 1 INTRODUCTION In the last few years, there has been a rapid development of communication networks. Some time ago, each communication link was transmitting a single channel. By using optical fiber, several information channels can be multiplexed in one link. As a consequence, the transmitted information as well as the data rate have increased. The drawback of this evolution is that the information lost when a failure occurs has also increased. Fault Recognition identifies the failure from the occasioned alarms and its sp..

Distributed Fault Identification in Telecommunication Networks

Telecommunications networks are often managed by a large number of management centers, each responsible for a logically autonomous part of the network. This could be a small subnetwork such as an Ethernet, a Token Ring or an FDDI ring, or a large subnetwork comprised of many smaller networks. In response to a single fault, in a telecommunications network, many network elements may raise alarms, which are typically reported only to the subarea management center that contains the network element raising the alarm. As a result, a particular management center has a partial view of the status of the network. Management Centers must therefore cooperate in order to correctly infer the real cause of the failure. The algorithms proposed in this paper, outline the way these management centers could collaborate in correlating alarms and identifying faults. Key Words: Distributed Fault Identification, Management Domain, Alarms. 1 First Bank of Boston, Boston MA 0216, USA. Work done while the aut..