Vol. 7, No 2, 2003 < Volumes
(ISSN 1428-6394)

Contents:

  • Jarosław Rybicki and Wojciech Sadowski Professor Mieczysław Chybicki 15.01.1936—21.11.2002   abstract | full text
  • Paweł Mo/zejko and Czesław Szmytkowski Electron Elastic Collisions with C3F6 Molecule   abstract | full text
  • Dominik Kawalec, Andrzej Paździerko and Krzysztof Kułakowski Numerical Simulation of the Chaotic Behaviour of a Three-dimensional Pendulum   abstract | full text
  • Siergiej Leble and Andrey Sukhov On Numerical Calculation of Acoustic Field of Plane Source   abstract | full text
  • Eimad E. Elhadi and Wu Keqi Numerical Simulation and Modification of 3D Flow Phenomena in an Axial Flow Fan   abstract | full text
  • Jacek Sokołowski, Romuald Rządkowski and Leszek Kwapisz Frequencies and Modes of Rotating Flexible Shrouded Bladed Discs-Shaft Assemblies   abstract | full text
  • Włodzimierz Przybylski and Stefan Dzionk Modeling of Flow Phenomena Associated with Polymer Injection into a Mold   abstract | full text
  • Jarosław Rybicki, Agnieszka Witkowska, Grzegorz Bergmański, Giorgio Mancini and Sandro Feliziani The Structure of Pb—PbO—SiO2 Glass via Molecular Dynamics Simulation   abstract | full text
  • Dietrich Stauffer and Krzysztof Kułakowski Why Everything Gets Slower?   abstract | full text
  • Mikołaj Sitarz Population Structure in the Penna Model   abstract | full text
  • Robert Krupa, Maria Pociecha, Joanna Szlezynger and Gra/zyna Kruszelnicka A Database on the Tourist Sites of Cracow and its Environs   abstract | full text

Abstracts:

hJarosław Rybicki and Wojciech Sadowski Professor Mieczysław Chybicki 15.01.1936—21.11.2002

 

hPaweł Mo/zejko and Czesław Szmytkowski Electron Elastic Collisions with C3F6 Molecule

We report calculations of differential and integral cross sections for intermediate- and high-energy (50–1000eV) elastic collisions of electrons with hexafluoropropene (C3F6) molecules. The calculations have been carried out using the independent atom model with static-polarization model potential. The present results are compared with elastic cross sections estimated from total and ionization experiments. Agreement between present calculations and the “experiment” is good for energies above 70eV.

 

hDominik Kawalec, Andrzej Paździerko and Krzysztof Kułakowski Numerical Simulation of the Chaotic Behaviour of a Three-dimensional Pendulum

A nonlinear pendulum is designed to demonstrate the chaotic instability of trajectories. Here, we present a simplified theoretical description of its dynamics. Trajectories are found by numerical integration of the Lagrange equations. The results of the simulations agree with the Poincaré-Bendixon theorem. Generic trajectories display chaotic behaviour and are similar to those obtained experimentally.

 

hSiergiej Leble and Andrey Sukhov On Numerical Calculation of Acoustic Field of Plane Source

The harmonics of an acoustic beam have been evaluated numerically by means of an integral representation according to the perturbation theory. A method for evaluation of the integrals of a rapidly oscillating function has been applied. Special attention has been paid to the accuracy of calculations and an algorithm for error estimation has been proposed. A computer program has been realized, and the profiles of the first and the second harmonics have been plotted. The used methods can be applied for the problem with dissipation or dispersion.

 

hEimad E. Elhadi and Wu Keqi Numerical Simulation and Modification of 3D Flow Phenomena in an Axial Flow Fan

This work aims to study and analyze the behavior of flow in an axial flow fan using numerical simulation based on solving Reynolds-averaged Navier-Stokes equations coupled with a modified Spalart-Allaras turbulence model. In the present work, different flow phenomena occuring in an axial flow fan were presented and interpreted at different design conditions and at different regions, with special concern to the rotor exit and stator regions. Large vortices and reverse flow at the stator suction side were observed under high loading conditions. These are mainly due to radial and centrifugal effects in the fluid due to a decreasing flow rate. To avoid this type of flow, the stator flow pattern has been modified using a new stator blade. This blade was designed by changing the stator stagger angle by 10˚in the radial direction. This study indicates that the flow in the modified stator region behaves well and gives better performance than that obtained when using a baseline stator, especially under high loading conditions. This study also indicates that the stator stagger angle has a significant effect on modifying the fan performance.

 

hJacek Sokołowski, Romuald Rządkowski and Leszek Kwapisz Frequencies and Modes of Rotating Flexible Shrouded Bladed Discs-Shaft Assemblies

It is now increasingly necessary to predict accurately, at the design stage and without excessive computing costs, the dynamic behaviour of rotating parts of turbomachines, so that resonant conditions at operating speeds are avoided. In this study, global rotating mode shapes of flexible shrouded bladed disc-shaft assemblies are calculated. The rotating modes have been calculated by using a finite element cyclic symmetry approach. Rotational effects, such as centrifugal stiffening have been accounted for, and all the possible couplings between the flexible parts have been allowed. Gyroscopic effects have been neglected. The numerical results have been compared with the experimental. The calculations show the influence of shaft flexibility on the natural frequencies of shrouded bladed discs up to four nodal diameters for the two first frequencies series.

 

hWłodzimierz Przybylski and Stefan Dzionk Modeling of Flow Phenomena Associated with Polymer Injection into a Mold

The process of plastic injection, although of extensive industrial use, is still relatively poorly researched. In building a finite element model for the injection process, the emphasis was laid on the modeling of phenomena occurring at the polymer-mold interface. With this purpose in mind, the mesh was refined in the vicinity of mold walls. The influence of the air present in the mold during the injection process was also taken into account. As the outcome of solving the problem so formulated, a model of polymer behavior at the mold wall interface has been obtained. Numerical simulations were carried out with the aid of a FIDAP flow-modeling program, and their results were partly verified by experimental means.

 

hJarosław Rybicki, Agnieszka Witkowska, Grzegorz Bergmański, Giorgio Mancini and Sandro Feliziani The Structure of Pb—PbO—SiO2 Glass via Molecular Dynamics Simulation

The paper is dedicated to a molecular dynamics (MD) study of the structure of partially reduced lead-silicate glass of composition 1Pb 1PbO 1SiO2. The simulations have been performed in the constant volume regime, using a two-body potential (Born-Mayer repulsive forces, and Coulomb forces due to full ionic charges). The system was initially prepared as a well equilibrated hot melt, and then slowly cooled down to 300K. The information on short-range correlations were obtained in a conventional way (from pair and angular distribution functions), while the medium-range order was studied via cation-anion ring analysis. In the paper, the short- and medium-range order in the simulated system is discussed and compared with the structure of a glassy completely reduced system, i.e. 2Pb 1SiO2 and unreduced one, i.e. 2PbO 1SiO2 glass.

 

hDietrich Stauffer and Krzysztof Kułakowski Why Everything Gets Slower?

A social system is represented by the Barabási-Albert model. At each node of the graph, an Ising spin is placed, S = ±1, with antiferromagnetic interaction between connected nodes. The time to reach equilibrium via Glauber kinetics does not depend on system size. The average energy associated with the rare spin flips in equilibrium oscillates with the number m of edges of new nodes. The conclusions are illustrated with events from recent European history, where after some strong change a rather immobile society evolved.

 

hMikołaj Sitarz Population Structure in the Penna Model

Numerical simulations of growing population, based on the Penna model, are presented. We consider biological ageing as a result of the accumulation of mutations in the genotype. We present an example of simulated population structure and compare it with that of a real population. We also discuss the role of bad mutations threshold parameter T in the Penna model, to reproduce a smooth transition from the oversimplified logistic model (T → ∞) to the Penna model.

 

hRobert Krupa, Maria Pociecha, Joanna Szlezynger and Gra/zyna Kruszelnicka A Database on the Tourist Sites of Cracow and its Environs

Since the mid-80s, considerable progress has been achieved in relational database technology. The main achievements have been in high performance, high reliability and availability, scalability and development tools. However, the environment for database systems is rapidly changing. There are new challenges that originate from the present hardware technology achievements, as well as from new kinds of data resources that hardly conform to the well-established relational data model (e.g. data from the Web). In the paper, we present the new challenges and research areas, as well as motivations behind them. The article presents a concise report on the experience gained in the last three years in the scope of network provision of bibliographic databases by the Institute for Scientific Information (ISI) and full-text humanities and medical databases by EBSCO Publishing. The authors emphasise the importance and impact of the programme and the databases, co-financed by the State Committee for Scientific Research, on the initiation and continuation of organisational activities and efficient database access management. The paper contains a short review of the information resources presently available, including the titles of bibliographic and full-text databases, the scope of licences, subscription periods, and the volumes of archival resources. It provides statistics illustrating the distribution and extent of the bibliographic database usage by the scientific community, including, active institutional and individual, users and discusses the hardware and software used to provide the network database access services, the availability conditions, as well as the rules of license renewal and co-financing by the interested institutions. The report also deals with the access conditions and access abilities to the electronic versions of humanities, economics and medical databases offered by EBSCO Publishing. It is vital to show the 3 th National Conference “Databases for Science INFOBAZY 2002” structure of the service, the scope of subjects available in the databases, title estimation and the access to html, as well as image source types. Moreover, the report focuses on the modes of access to single database and to several of them simultaneously, as well as on multi-aspect searching with the use of the author and subject indexes and keywords. The article presents the current state of development of INFOCAST – an information decision system supporting technological problems of the foundry industry. Two aspects of the system are related: enrichment of its information and knowledge resources and changes in architecture, both oriented towards improvement of its applicability. The reported stage of development of INFOCAST is characterized by a close integration of its data and knowledge bases by means of the agent-based technology. Due to decentralization, the knowledge and information can be used not only in research and design activities, but also in the exploitation of technological processes. A new database containing 410 cases of nevi pigmentosi, in four categories: benign nevus, blue nevus, suspicious nevus and melanoma malignant, carefully verified by histopathology, is described. The database is entirely different from the base presented previously, and can be readily used for research based on the socalled constructive induction in machine learning. To achieve this, the database features a different set of thirteen descriptive attributes, with a fourteenth additional attribute computed by applying values of the remaining thirteen attributes. In addition, a new program environment for the validation of computer-assisted diagnosis of melanoma, is briefly discussed. Finally, results are presented on determining optimal coefficients for the well-known ABCD formula, useful for melanoma diagnosis. The paper describes a fault-tolerant method of selecting duplicate bibliographic records in catalogues. The method is based on the use of text algorithms; decisions are suggested to librarians who make the final decision. The method was applied to four library catalogues at the Warsaw University of Technology which were compared with the catalogue of the main library. Process of joining catalogues was conducted differently for nonduplicate records and for duplicate ones. Thanks to this method, a significant portion of records in the catalogues of the joining libraries had been found to be duplicate before the catalogues were added. The algorithms proved helpful in assuring high quality of information. The special character of meteorological data, especially various measurement times and standard statistics, makes a programmer solve non-standard problems. The Regional Meteorological Database (RMD) was created in the early nineties of the last century. The RMD uses a data module stored in files, a control module (for data reading and recording) based on indexing by the hashing functions, and a module which makes it possible to display data. The “News on Forest Literature” database contains general reports from journals and serial publications. The database has up to 75 000 records. The database has been created with MICRO CDS/ISIS software. WWW versions of the database contents are made available with EasyInt and ISISWWW software. Experiments in the field of dendrology have been made for many years now. Current researchers, working on these plots, are the forth generation of foresters (two German and two Polish). They have created a large and important database for future forest research. The database of tourist attractions of Cracow and its surrounding area contains categorized data about the tourist infrastructure and attractions of the City and the entire Malopolska region. It includes texts, graphics and numeric data.

 

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