3/2006

Contents:

• R.Ogrodowczyk and K.Murawski, Numerical Simulations of Impulsively Excited Fast Magnetosonic Waves in Two Parallel Slabs - abstract | full text
• A.Ambroziak, Geometrically Non-Linear Analysis of Shells - abstract | full text
• A.Ambroziak, Application of the Murnaghan Model in Analysis of Non-Linear Elastic Material Properties of PVC-coated Fabric - abstract | full text
• A.Ambroziak, Membrane-Hanging Roof Analysis: an Example - abstract | full text
• R.Rzadkowski, M.Drewczynski and L.Kubitz, Natural Frequencies of Tuned and Mistuned Bladed Discs on a Shaft - abstract | full text
• S.Frigio, G.Cosimi, G.Bergmanski, E.Urbanska-Galewska and J.Rybicki, Length Distribution of Fuzzy-end Segments - abstract | full text
• Y.Fu, Y.Cai, Z.Zhang and K.Wu, Energy Consumed by Valves in Conventional Water Systems and the Application of a Power-decentralization System - abstract | full text
• M.Szydlowski and B.Twarog, Numerical Investigation of Flooding of Real-topography Developed Areas Following River Embankment Failure - abstract | full text
• H.A.Jalab, LAN Interconnection Unit Based on an Artificial Neural Network - abstract | full text

Abstracts:

• R.Ogrodowczyk and K.Murawski, Numerical Simulations of Impulsively Excited Fast Magnetosonic Waves in Two Parallel Slabs

  We present numerical results of a temporal evolution of impulsively excited magnetosonic waves in a solar coronal loop that is approximated by a set of two straight plasma slabs of mass density enhancement. Numerical simulations reveal that shapes of wavelet spectra of time signatures of these waves depend on a distance between the strands and on a position of the initial pulse. We find that with a distance growing between these strands short period waves contribute more while long period waves contribute less to the wavelet spectra. We demonstrate that a presence of the second parallel strand affects considerably wave propagation in comparison to one strand alone. We find out that the initial pulse triggers a packet of propagating waves among witch sausage and kink modes are present simultaneously.

• A.Ambroziak, Geometrically Non-Linear Analysis of Shells

  The work's aim has been to verify the suitability of commercial engineering software for geometrically non-linear analysis of shell structures. The paper deals with static, geometrically non-linear analysis of shells made of isotropic materials. The Finite Element Method (FEM) has been chosen to solve the problem. The results of the ROBOBAT Robot Millennium v.19.0 and MSC.Marc v.2005r2 commercial software are compared with the literature results.

• A.Ambroziak, Application of the Murnaghan Model in Analysis of Non-Linear Elastic Material Properties of PVC-coated Fabric

  The aim of the present paper is to propose a method of laboratory tests necessary for identification of non-linear elastic properties of the PVC-coated Panama fabric often used for hanging roofs. Two methods of describing the fabric's non-linear behaviour are investigated: piece-wise linear relations between stress and strain are assumed and the Murnaghan model of solid behaviour is applied. The material parameters are specified on the basis of uniaxial constant strain rate tensile tests in the warp and weft directions. Techniques based on the least squares methods are applied in the identification process.

• A.Ambroziak, Membrane-Hanging Roof Analysis: an Example

  The paper presents an analysis of a membrane-hanging roof subjected to climatic loadings. Discussion of the fundamental equations of the dense net model, used to describe the behaviour of coated woven fabric, and the concept of the climatic loadings is included.

• R.Rzadkowski, M.Drewczynski and L.Kubitz, Natural Frequencies of Tuned and Mistuned Bladed Discs on a Shaft

  The dynamic behaviour of a rotor consisting of two tuned and mistuned bladed discs on a solid shaft is considered. The effect of the shaft's flexibility on the dynamic characteristics of the bladed discs and the coupling effects between the shaft and bladed disc modes are investigated. Results show clearly the coupling effects in a bladed disc-shaft system. Interference diagrams are developed, from which the dynamic behaviour of a bladed disc can be predicted for varying flexibility relationships between solid shafts and bladed discs. The global rotating mode shapes of flexible tuned and mistuned bladed disc-shaft assemblies are calculated. Rotational effects, such as centrifugal stiffening, are accounted for and all the possible couplings between the flexible parts are allowed. Calculated natural frequencies obtained from the blade, the bladed disc and the shaft with two discs are checked to discover resonance conditions and coupling effects. It is shown that blade mistuning strongly affects the interaction between flexible bladed discs and a flexible shaft. This interaction affects the flexible bladed disc modes and is not restricted to the modes with zero, one and two nodal diameters. The torsional frequency of the shaft with two bladed discs is coupled with the zero nodal diameter modes of the single bladed discs. It is shown that including the shaft in the bladed discs model is important from the designer's point of view and may alter the spectrum of frequencies considerably.

• S.Frigio, G.Cosimi, G.Bergmanski, E.Urbanska-Galewska and J.Rybicki, Length Distribution of Fuzzy-end Segments

  We have calculated and discussed the probability density distributions of lengths of fuzzy-end segments, i.e. segments the ends of which assume random positions. We performed our calculations for several simple cases in 1, 2 and 3 dimensions: one end fixed, the other assuming a random position, and both ends at random positions. The obtained statistical data may serve as reference data for calculations of stochastic-geometrical properties of complex systems, such as conformations of complicated bolted constructions with clearances (in structure mechanics) or energy transfer prosesses between molecules in diluted systems (in physics).

• Y.Fu, Y.Cai, Z.Zhang and K.Wu, Energy Consumed by Valves in Conventional Water Systems and the Application of a Power-decentralization System

  The power consumption by valves of a conventional (i.e. power-centralized) water system is analyzed on the example of a water heating system in order to evaluate the extent of energy savings achievable in a power-decentralized system. The configuration and application of a power-decentralized system is briefly discussed.

• M.Szydlowski and B.Twarog, Numerical Investigation of Flooding of Real-topography Developed Areas Following River Embankment Failure

  The paper concerns numerical simulations of flood wave propagation in an urban area resulting from a river embankment failure. Simulations have been performed to predict and analyze the parameters of flash and catastrophic flow in a developed area with the aim of presenting numerical calculations useful for identification of inundation zones. The shallow water equations were assumed as the mathematical model of free-surface unsteady water flow. A numerical scheme of the finite volume method was applied to solve the model equations and the Roe method used to approximate the mass and momentum fluxes. Two test cases of embankment failure are investigated in the paper. The aim of one experiment is to simulate a flood in a model city area, where a group of buildings representing a simplified urban configuration was introduced. In order to verify the calculations, numerical results were examined against experimental data available from laboratory measurements. An experiment of the model city's flooding event was carried out at the hydraulic laboratory of the Gdansk University of Technology. The other test case concerns flash flood simulation on an embanked developed area of real topography.

• H.A.Jalab, LAN Interconnection Unit Based on an Artificial Neural Network

  This paper presents the design of an intelligent interconnection unit based on an artificial neural network (ANN), used when two local area networks (LAN) with different IEEE 802 standard protocols are connected. The proposed ANN is used to activate execution of suitable procedures bridging 802.X LAN and 802.Y LAN.