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No full textPoznańAn analytical solution of the flow of a hydromagnetic fluid through a porous medium between permeable beds is obtained and studied. The fluid is under an exponential decaying pressure gradient and the uniform magnetic field in a direction normal to the flow saturated porous medium is considered. Two governing equations, namely Navier-Stokes equations and Darcy’s law, are employed for the flow between and through the permeable beds, respectively. Injection and suction of the fluid through lower and upper permeable beds, respectively, with same velocity are allowed in the presence of porous medium and the uniform magnetic field. The velocity field and the volume flux are calculated analytically and presented graphically for different choices of the parameters exhibiting their phenomenal nature. Additionally if we replace the exponentially decaying pressure gradient by the pulsatile one and porousity of medium tends to zero, the results match excellently with those of Malathy and Srinivas [T. Malathy and S. Srinivas, Pulsatile flow of a hydromagnetic fluid between permeable beds, Int. Comm. In Heat and Mass Transfer 35, 681-688 (2008)]
No full textPoznańWe consider the elastic scattering in deformed space with minimal length. We give the basic relation for the elastic scattering in deformed space. We also investigate the partial wave method in deformed space. It is shown that the relations for the scattering amplitude and cross-section formally coincides with ordinary ones
No full textPoznańThis paper shows how the renewal process in which the sums of independent random variables of the modified Makeham distribution appear can be approximated by the surrogate distribution
No full textPoznańWe study the two dimensional quantum system governed by the Schrödinger operator with delta type potential. The interaction is supported by line Γ which coincides with a straight at infinity and which admits two widely separated deformations. The aim of this paper is to express the number of bound states of our system by the number of bound states of the system with single deformation
No full textPoznańTwo configurational temperature expressions are investigated from the point of view of their utility as a diagnostic tool for Monte Carlo (MC) simulations. The MC calculations were performed for systems of spherically symmetric particles in the bulk and in a channel. Different density and system size conditions are considered. It is shown that the configurational temperature based on the ratio of two averages of the force functions can serve as a suitable method for calculating the temperature for the MC simulation. This configurational temperature can signal the presence of random number correlations and can serve as a cross-check formula in MC studies of strongly confined systems
No full textPoznańThe “Defence in depth” strategy for securing computer systems claims that technologies used to protect a network should fulfill the “Protect, Detect and React” paradigm. “This means that in addition to incorporating protection mechanisms, organizations need to expect attacks and include attack detection tools” [1]. This paper presents MetaIDS – the Intrusion Detection System developed in Poznań Supercomputing and Networking Center. It detects both attack attempts and successful attacks to the system. The paper highlights typical problems with intrusions detection, principle of the MetaIDS work and real attack example seen from the perspective of MetaIDS
No full textPoznańThe paper analyses Grid networking resource virtualization technologies and requirements in the context of computational mobility. The mechanisms of network virtualization supported by Xen and xVM/Crossbow are presented and compared. A network virtualization model, consisting of three layers, is presented. Changes in virtual network infrastructures resulting from VM or zone mobility are investigated in detail. Typical migration process scenarios are presented, in addition to system commands used prior to and following migration in order to restore network communication. The concept of automating this process is also described
No full textPoznańPrinciples of laser cooling and trapping of atoms with regard to the magneto-optical trap (MOT) are described. Some details of the MOT and the accompanying measuring system, both constructed at the Institute of Physics, PAS in Warsaw, are given. Two examples of experimental results are shown
