Vol. 23, No 3, 2019 < Volumes
(ISSN 1428-6394)



hJan Jankowski and Henryk Leszczyński Fourier Image Methods for Evolution Equations of Deep-Water Waves

The velocity potential of the fluid satisfies the Laplace equation with nonlocal boundary conditions on a free surface. This differential problem is transformed to an evolution equation in Fourier variables. The Fourier transform images of boundary functions are approximated by Picard's iterations and the method of lines on meshes related to roots of Hermite polynomials. Due to convolutions of sine and cosine functions the integral terms of Picard's iterations reveal unexpected instabilities for wave numbers in a neighborhood of zero.


hZachary Farrugia and Joseph N. Grima Mechanical and Structural Properties of Poly(Phenylethylene) Systems: a Preliminary Study

The structural and mechanical properties of various types of poly(phenylacetylene) crystalline networked polymers which stack in the third direction in a graphite-like manner have been the subject of extensive research over the past few years. These studies have suggested that depending on the particular manner of substitution of the phenyls, it is possible to achieve some very interesting mechanical properties, which include, in some cases, negative Poisson's ratio (NPR) andór negative linear compressibility (NLC). The current study investigated how alternatives to these systems can be designed, and specifically tailor-made to exhibit desirable anomalous properties, such as NPR and NLC, through the replacement of the acetylene chains with ethylene chains, so as to produce the poly(phenylethylene) equivalents. Using force field-based simulations, via the use of the polymer consistent force-field (PCFF) it was noted that, to a first approximation, these systems mirror some of the analogous properties exhibited by their poly(phenylacetylene) counterparts. In particular, poly(phenylethylene) systems built from 1234- and 1245-substituted phenyls exhibited negative Poisson's ratios, with the latter also exhibiting negative linear compressibility. This anomalous behaviour, mirrors, to some extent, that exhibited by their poly(phenylacetylene) counterparts, albeit some differences were noted, such as a reduction in the degrees of auxeticity. It was also noted that the poly(phenylethylene) systems modelled here tend to stack in the third direction, in a different manner than their poly(phenylacetylene) analogues, which difference is likely to be the factor for such reduction in auxeticity.


hSergey Leble and Anastasiia Chychkalo Heisenberg Analytical-Numerical Model of Nanoparticle with Para- and Ferromagnetism

Two models of two- and three-layers of a magnetic nanoparticle are presented applying the Heisenberg theory with the parameter (exchange integral and closest neighbors) values for surface layers, which differ from the bulk layer values. The difference in the numbers of closest neighbors is taken into account. The corresponding distribution and partition functions are constructed. The magnetization of the particles is calculated by the conventional transition to thermodynamics. The results are illustrated by plots, representing magnetization curves and hysteresis loops for the layer contributions. The magnetization curves for both models are compared.


hLeonardo Pasini and Morena Barboni Queuing Networks to Evaluate Web Applications: Simulation

This work fits into the context of our studies on traffic simulation for computer and telecommunication networks [1–5]. The technique that we use is based on complex queuing network models that allow us to simulate the functioning of network devices, and the traffic flows between them. In a previous work [2] we defined a library of objects for the modeling of the computer network. This library also models the network traffic induced by the execution of web applications run in a distributed fashion on various network devices. In this work we describe the changes applied to the service procedures of some library objects, and we develop a specific study for the evaluation of the execution times of three types of applications: 1. Navigation 2. Download Manager 3. Mobile Agents


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