Bandwidth Allocation and Reservation - End-to-End Specification

The Bandwidth Allocation and Reservation (BAR) activity within JRA4 of the EGEE project specified and implemented the necessary components and interfaces to enable the EGEE Grid middleware to request and use guaranteed bandwidth services. This report describes the components and interfaces required for an end-to-end BAR service and how they interact

Accuracy of a domain decomposition method for the recovering of discontinuous heat sources in metal sheet cutting

This paper describes a method for the retrieval of discontinuous heat sources involved in a metal cutting process. Two smoothing techniques were used in the present study in order to smooth noisy sensor data recorded by temperature sensors. The two smoothing techniques are a least squares polynomial fit and a Lagrangian smoothing. These data are then used to recover the heat source. It is found that the least squares polynomial provides over-smoothed results and the Lagrangian smoothing produces phyically acceptable results of the retrieved heat source

Simulation of 2-D metal cutting by means of a distributed algorithm

Temperature distributions involved in some metal-cutting or surface-milling processes may be obtained by solving a non-linear inverse problem. A two-level concept on parallelism is introduced to compute such temperature distribution. The primary level is based on a problem-partitioning concept driven by the nature and properties of the non-linear inverse problem. Such partitioning results to a coarse-grained parallel algorithm. A simplified 2-D metal-cutting process is used as an example to illustrate the concept. A secondary level exploitation of further parallel properties based on the concept of domain-data parallelism is explained and implemented using MPI. Some experiments were performed on a network of loosely coupled machines consist of SUN Sparc Classic workstations and a network of tightly coupled processors, namely the Origin 2000

A domain decomposition algorithm for inverse welding problems

A mathematical model and a numerical scheme for the inverse determination of heat sources generated by means of a welding process is presented in this paper. The accuracy of the heat source retrieval is discussed

Performance evaluation of a distributed algorithm for an inverse heat conduction problem

Numerical solutions of realistic 2-D and 3-D inverse problems may require a very large amount of computation. A two-level concept on parallelism is often used to solve such problems. The primary level uses the problem partitioning concept which is a decomposition based on the mathematical/physical problem. The secondary level utilizes the widely used data partitioning concept. A theoretical performance model is built based on the two-level parallelism. The observed performance results obtained from a network of general purpose Sun Sparc stations are compared with the theoretical values. Restrictions of the theoretical model are also discussed

Domain decomposition methods for welding problems

This paper, a 2-D non-linear electric arc-welding problem is considered. It is assumed that the moving arc generates an unknown quantity of energy which makes the problem an inverse problem with an unknown source. Robust algorithms to solve such problems e#ciently, and in certain circumstances in real-time, are of great technological and industrial interest. There are other types of inverse problems which involve inverse determination of heat conductivity or material properties [CDJ63][TE98], inverse problems in material cutting [ILPP98], and retrieval of parameters containing discontinuities [IK90]. As in the metal cutting problem, the temperature of a very hot surface is required and it relies on the use of thermocouples. Here, the solution scheme requires temperature measurements lied in the neighbourhood of the weld line in order to retrieve the unknown heat source. The size of this neighbourhood is not considered in this paper, but rather a domain decomposition concept is presented and an examination of the accuracy of the retrieved source are presented. This paper is organised as follows. The inverse problem is formulated and a method for the source retrieval is presented in the second section. The source retrieval method is based on an extension of the 1-D source retrieval method as proposed in [ILP]

Time domain decomposition for European options in financial modelling

This paper is organised as follows. First, a description of the mathematical model for the dimensionless 2D non-linear metal cutting problem is given. Second, the description of the problem partitioning is given. Different numerical schemes are used in different sub-domains in order to solve different sub-problems. Numerical results are shown for a metal cutting application. Third, the exploitation of the parallel properties of the numerical schemes are explained. The resulting parallel implementation uses MPI (Message Passing Interface) directives [4] and is suitable for network-cluster (distributed) computing as well as for traditional tightly-coupled multi-processor systems. Finally, some conclusions are drawn. 2. Dimensionless 2D Non-linear Metal Cutting Problems The metal cutting problem considered here is a 2D thin sheet of metal defined in the domain D = f(x; y) : 0 ! x ! 1 and 0 ! y ! 1g. The material property is assumed to be homogeneous across the domain of interest and the following assumptions are made for an idealised cutting :- (1) the application of a cutting tool at the cutter points is equivalent to the application of a source at these points, (2) no phase changes occur during cutting and (3) the thickness of the cutter is negligible. The cutting is considered to be applied along the y-axis at x = x c . Assumption (1) introduces an unknown source of strength Q c (y; t) at x c and together with assumption (2), the cutting problem can be described by the dimensionless 2D non-linear, unsteady, parabolic, heat conduction equation, @u @t = @ @x (k(u) @u @x ) + @ @y (k(u) @u @y ) + Q c (y; t)ffi(x \Gamma x c ) 2 D; (1) subject to initial condition u(x; y; 0) = U i (x; y), boundary conditions u(0; y; t) = B 0 (y; t), u(1; y; t) = B 1 (y; t), u(x; 0..

Comparison of three algorithms for nonlinear metal cutting problems

This paper compares three alternative numerical algorithms applied to a nonlinear metal cutting problem. One algorithm is based on an explicit method and the other two are implicit. Domain decomposition (DD) is used to break the original domain into subdomains, each containing a properly connected, well-formulated and continuous subproblem. The serial version of the explicit algorithm is implemented in FORTRAN and its parallel version uses MPI (Message Passing Interface) calls. One implicit algorithm is implemented by coupling the state-of-the-art PETSc (Portable, Extensible Toolkit for Scientific Computation) software with in-house software in order to solve the subproblems. The second implicit algorithm is implemented completely within PETSc. PETSc uses MPI as the underlying communication library. Finally, a 2D example is used to test the algorithms and various comparisons are made

Simulation of 2-D metal cutting by means of a distributed algorithm

Temperature distributions involved in some metal cutting or surface milling processes may be obtained by solving a nonlinear inverse problem. A two-level concept on parallelism is introduced to compute such temperature distribution. The primary level is based on a problem partitioning concept driven by the nature and properties of the nonlinear inverse problem. Such partitioning results to a coarsegrained parallel algorithm. A simplified 2-D metal cutting process is used as an example to illustrate the concept. A secondary level exploitation of futher parallel properties based on the concept of domain-data parallelism is explained and implemented using MPI. Some experiments were performed on a network of loosely coupled machines consist of SUN Sparc Classic workstations and a network of tightly coupled processors namely the Origin 2000