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1

Length distribution of fuzzy-end segments

Frigio S., Cosimi G., Bergmański G., Urbańska-Galewska E., Rybicki J.

TASK Quarterly : scientific bulletin of Academic Computer Centre in Gdansk

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2006

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Vol. 10, No 3

291-309

EN

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 per-formed 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 construc-tions with clearances (in structure mechanics) or energy transfer processes between molecules in diluted systems (in physics).

2

The structure of rarefied and densified PbSiO3 glass: a molecular dynamics study

Bergmański G., Białoskórski M., Rychcik-Leyk M., Witkowska A., Rybicki J., Mancini G., Frigio S., Feliziani S.

TASK Quarterly : scientific bulletin of Academic Computer Centre in Gdansk

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2004

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Vol. 8, No 3

393-412

EN

The paper is a molecular dynamics (MD) study of the structure of rarefied and densified lead-silicate glass of the PbSiO3 composition. Simulations have been performed in the constant volume regime for systems with densities of 3000, 4000, 5000, 5970 (normal density), 7000 and 8000kg/m3, using a two-body potential (Born-Mayer repulsive forces and Coulomb forces due to full ionic charges). All the systems were initially prepared as well equilibrated hot melts, and then slowly cooled down to 300K. The information on short-range correlations was obtained in a conventional way (from radial and angular distribution functions), while the middle-range order was studied via cation-anion ring analysis, using our new programme for basal ring determination. The structure of rarefied and densified glasses is compared with the structure of the same glasses under normal conditions. Moreover, the present results on PbSiO3 glass are compared with the corresponding data previously obtained for rarefied and densified PbGeO3 glass (Rybicki et al. 2001 Comput. Met. Sci. Technol. 7 91-112).

3

The structure of porous and spontaneously densified amorphous PbSiO3 : a molecular dynamics study

Chomenko K., Bergmański G., Białoskórski M., Rychcik-Leyk M., Feliziani S., Frigio S., Witkowska A., Rybicki J.

Computational Methods in Science and Technology

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2004

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Vol. 10, nr 1

21-38

EN

In the paper we propose and test a "gel-drying" method of obtaining porous oxide glasses in Molecular Dynamics (MD) simulations. The simulation is started with low (screened) values of ionic charges. Then, the charges are gradually increased (to mimic the gradual elimination of a polar solvent) up to full ionic charges (a completely dry gel). This computational trick is applied to produce a porous PbSiO3 system. The structure of the resulting low-density samples is analysed in detail. Then, the porous structures are submitted to spontaneous densification, and the structure of the obtained dense bulk glasses is analysed. Finally, the structures of bulk glass obtained via spontaneous densification (density p - 8250 kg/m3) and bulk glass of the same density obtained via isotropic compression are compared.

4

Molecular dynamics study of short and medium range order in modified BGO glasses

Walentynowicz A., Witkowska A., Białoskórski M., Rybicki J., Feliziani S., Frigio S., Cosimi G.

Computational Methods in Science and Technology

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2004

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Vol. 10, nr 2

203-218

EN

In the paper we present our recent Molecular Dynamics (MD) simulations of the structure of bismuth-germanate (BGO) glasses of x[pBi2 (1-p)Bi2O3](1-x)GeO2 composition, where x denotes the content of the bismuth oxide in unmodified glasses, and p - the fraction of neutral bismuth that can appear in the surface modification process (e.g, annealing in hydrogen atmosphere). We consider glasses of compositions x = 0.1, 0.2, 0.3 and reduction degrees = O, 0.25, 0.5, 0.75, 1. The simulation results are analysed in detail and compared with the structural data provided by other authors.

5

Computer simulations of one-dimensional coupled map lattices

Boldrighini C., Cosimi G., Frigio S., Pellegrinotti A.

TASK Quarterly : scientific bulletin of Academic Computer Centre in Gdansk

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1998

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Vol. 2, No 1

5-17

EN

We perform computer simulations of some one-dimensional models of coupled map lattices (CML) with symmetry and diffusive nearest neighbour coupling, to study Ising-type transitions. Such transitions appear to be related to the presence of a dip (minimum) in the plot of the Lyapunov dimension versus coupling parameter.