TASK Quarterly   Scientific Bulletin of the Centre of Informatics - Tricity Academic Supercomputer & networK   ISSN 1428-6394

4/2005


Contents:



Abstracts:

  • L.Pasini and S.Feliziani, Construction of Queue-Based Simulators for Web Applications Distributed on Computer Networks

    Modern Internet and web applications involve interactions among remote host computers connected by communication networks. Simulation modelling is an important technique to evaluate performance in the implementation of a web-distributed application over given networks formed by computer hosts connected by heterogeneous networks. In this paper we extend a previous work concerning the construction of a queue-based simulator of communication networks. We define a set of new queue-based object types which permit us to specify the behaviour of a web-distributed application whose software components run over different hosts in a given communication network. We apply this technique to show how to build a simulator to evaluate the performance of various software architectures for a web-distributed application run over a given computer network.

  • L.Pasini, S.Feliziani and M.Giorgi, Simulation of Road Systems and Queuing Network Models

    The purpose of this paper is to describe the versatility of queuing network systems for modelling vehicular traffic flows in road systems. These techniques are applicable in a simulation context because of the complexity of the resulting models, which can not be solved by mathematical analytical solvers. Moreover, these techniques can be used to model and simulate the behaviour of an automatic control system of vehicular flow in the same frame.

  • K.M.G.Noaman and H.A.Jalab, Data Security Based on Neural Networks

    The paper is concerned with the study and design of a data security system based on neural networks. Data with different keys were taken as test data, encrypted, decrypted and compared with the original data. The results have confirmed its advantages over other techniques.

  • E.Zieniuk and A.Boltuc, Identification of Polygonal Domains Using PIES in Inverse Boundary Problems Modeled by 2D Laplace's Equation

    The paper presents an original method to identify polygonal boundary geometry in 2D boundary problems defined by Laplace's equation using a parametric integral equation system (PIES). In the PIES, the polygonal boundary shape is defined mathematically by means of parametric linear segments, with a small number of corner points being posed. Identification of the polygonal boundary is reduced to identification of the corner points. Finally, the solution of the problem is reduced to the solution of a non-linear system of algebraic equations. Coordinates of identified corner points are obtained after solving the system of equations.

  • L.Zashkova, N.Penkova and R.Karamfilowa, Heat Transfer Processes in a Biogas-Reactor

    Visualizations and numerical values are presented of some fluid flow and heat transfer parameters in a biogas reactor with and without a stirring frame. Results obtained through mathematical modeling and computer simulation with ANSYS 8.0/Flotran are used for a heat transfer calculation method for the investigated bioreactor type.

  • B.Dobrowolski, K.Krecisz and A.Spyra, Usability of Selected Turbulence Models for Simulation Flow Through a Pipe Orifice

    A modern CFD code was used to simulate fluid flow through a pipeline with an orifice. A two-dimensional flow was assumed. The influence of the turbulence model and the size of the numerical grid on the quality of the obtained results was tested. It appears from the performed calculations that the standard Launder-Spalding k-ε model yields the best results for two-dimensional flows through pipeline-orifice systems.

  • L.Misici and M.Felici, Mixing in a Stirred Vessel. A parallel Implementation with Lattice Boltzmann Coloured Particles Model

    The main purpose of this paper is to present a new method for the study of single fluid mixing in a stirred vessel. The simulation has been realized with a parallel implementation of the Lattice Boltzmann coloured particles model. The mixing phenomenon is compared with the one derived with a Lagrangian approach.

  • A.Ambroziak, Numerical Modelling of Elasto-Viscoplastic Bodner-Partom Constitutive Equations

    The aim of the paper is to propose an FE procedure for static and dynamic non-linear analysis including elasto-viscoplastic constitutive equations of the Bodner-Partom model. Basic equations of the constitutive model are given with the flow graph used in the FE procedure. The proposed procedure has been applied in the MSCM commercial system with a user-defined UVSCPL subroutine that enables application to a wide range of varied finite elements. A number of simple problems of static and dynamic analysis are presented to show the accuracy of this approach. The numerical simulations are compared with experiments to validate the proposed FE procedure.

  • K.Malarz, M.Zborek and B.Wrobel, Curie Temperatures for the Ising Model on Archimedean Lattices

    Critical temperatures for the ferro-paramagnetic transition in the Ising model are evaluated for five Archimedean lattices, basing on Monte Carlo simulations. The obtained Curie temperatures are 1.25, 1.40, 1.45, 2.15 and 2.80 [J/kB] for (3,122), (4,6,12), (4,82), (3,4,6,4) and (34,6) lattices, respectively.