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

Volume 17, Number 1-2, 2013


Contents:



Abstracts:

  • A.N.Krishnamoorthy, Influence of Antifreeze Proteins on Local Water Structure Dynamics in Presence of Osmolytes

    Antifreeze proteins are synthesized by various organisms to enable their cells to survive subzero environment in the arctic and polar regions. These proteins produce a difference between the melting and freezing points termed as thermal hysteresis. The main objective of this study is to examine the dynamics of water molecules and hydrogen bonds at the protein-water interface of antifreeze protein using atomistic molecular dynamics simulations using GROMACS. For this work a prototype of AFP (antifreeze protein) from antarctic notothenioids (ala-ala-thr repeats) and a mutant which is not antifreeze active were generated using PRODRG server. The hydration dynamics results revealed that the retarded water dynamics in the AFP compared to its mutant was responsible for the antifreeze activity. Furthermore a considerable increase in antifreeze activity were observed for the AFP in presence of osmolytes. The mechanism of action were tested using preferential binding parameter derived from Kirkwood-Buff integerals.

  • O.Szulc, P.Doerffer, J.Zoltak, J.Malecki, Time-accurate Simulation of Flow Past PZL W-3A "Sokol" (Falcon) Helicopter Main Rotor in Forward Flight

    The paper presents the results of numerical simulations based on the URANS approach and the chimera overlapping grids technique of the main PZL W-3A "Sokol" (Falcon) helicopter rotor in forward flight conditions. The low-speed flight case models the helicopter rotor as parallel to the ground keeping forward speed of approximately 99 km/h. Strong Blade-Vortex Interaction (BVI) is responsible for a high level of vibration and noise. The high-speed (266 km/h) case reveals two main problems of modern helicopters: compressibility effects due to strong shock-wave boundary layer interaction on the advancing side and separation leading to a dynamic stall on the retreating side of the rotor. An attempt is made to correlate the results of the simulations with the very limited flight test data.

  • D.C.Gil Montoya, J.Struckmeier, Kinetic-Induced Moment Systems for the Saint-Venant Equations

    Based on the relation between kinetic Boltzmann-like transport equations and nonlinear hyperbolic conservation laws, we derive kinetic-induced moment systems for the spatially one-dimensional shallow water equations (the Saint-Venant equations). Using Chapman-Enskog-like asymptotic expansion techniques in terms of the relaxation parameter of the kinetic equation, the resulting moment systems are asymptotically closed without the need for an additional closure relation. Moreover, the new second order moment equation for the (asymptotically) third order system may act as a monitoring function to detect shock and rarefaction waves, which we confirm by a number of numerical experiments.

  • E.A.Anagnostakis, On a Nanophotonic Response Descriptor

    The photonic response exhibited by typical semiconductor nanodevices is modeled through a notionally universal descriptor by virtue of the Green's function associated with the generic complete, inhomogeneous differential equation. It is derived that the photoresponse evolution is expressible as the sum of saturation-limiting linear nanophotonic behavior and a linear superposition of eigenfunctions of the respective homogeneous Fredholm integral equation.

  • Y.Turel, Survey on Cloud Computing Vulnerability and Cyber Attacks: A Defensive Approach

    Cyber attacks against cloud computing discourage users to migrate to cloud computing. Cloud computing currently has weaknesses in terms of securing data. Unprotected data and weak storage security are potential threats to cloud computing. There are security risks and they should be considered carefully before enterprises migrate to cloud computing. Specifying cloud computing vulnerabilities and defining cyber attacks against infrastructure of the Cloud are the targets of this research. Mitigation of the non-technical problems may decrease the security problems. However, cryptographics, distributed denial of service and flooding attacks damage the servers and services. In this research, my aim is to demonstrate cloud computing vulnerability and the threats against data and storage. Once the cloud security problems are defined, the next step is to look for a solution. Using forensic methods to inspect intrusion attempts, implementing an online forensic workstation monitoring the login details of cloud authentication server, providing evidence of cyber crime are recommended.

  • M.T.Lewandowski, Implementation of the Boundary Element Method to Two-Dimensional Heat Transfer with Thermal Bridge Effects

    The work presents an application of the boundary element method applied to a two-dimensional conductive heat transfer. The algorithm of the method is explained and its advantages are outlined. Green's function as a fundamental solution for Poisson's equation in two dimensions was used and the direct approach was applied. The presented results concern building construction elements as typical cases of thermal bridges. Some properties of the boundary element method which give new possibilities were considered. For instance, forcing selected values of temperature on inner edges of the considered domain or local increasing of the temperature field resolution. The simulations were performed with the author's own algorithm.

  • Z.Mosurska, R.Pajak, PLGrid Plus Supports Polish Science