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EN
The main aim of the article is to present the climatology of the peak wind gust frequency in Poland caused by the impact of both atmospheric circulation and the presence of thunderstorm clouds. Nine meteorological stations for the measurement period of 2001-2015 were taken into account. Only SYNOP reports with a peak wind gust higher or equal to 15 m s-1 in thunderstorm and non-thunderstorm days are considered in this study. The results indicate that the highest threat in terms of frequency and strength of peak wind gusts due to convection occurs in July. In winter, thunderstorms are rare, but if they occur, about 80% of them produce wind gusts exceeding a threshold of 15 m s-1. Peak wind gusts in a non-thunderstorm days are the highest and the most frequent in January, and are at a minimum during summer. Comparing both types, peak wind gusts during days with a thunderstorm were on average stronger than those without an involved convection. This indicated that convection was an important factor in enhancing the strength of a wind gust. The highest value in our base was 34 m s-1, recorded in Kraków on 8th July 2015 within the occurrence of a severe thunderstorm, while the highest value in a day without a thunderstorm was 33 m s-1, recorded in Łódź on 31st January 2002.
EN
An unsteady mixed convection flow of a visco-elastic, incompressible and electrically conducting fluid in a hot vertical channel is analyzed. The vertical channel is filled with a porous medium. The temperature of one of the channel plates is considered to be fluctuating span-wise cosinusoidally, i.e., [...]. A magnetic field of uniform strength is applied perpendicular to the planes of the plates. The magnetic Reynolds number is assumed very small so that the induced magnetic field is neglected. It is also assumed that the conducting fluid is gray, absorbing/emitting radiation and non-scattering. Governing equations are solved exactly for the velocity and the temperature fields. The effects of various flow parameters on the velocity, temperature and the skin friction and the Nusselt number in terms of their amplitudes and phase angles are discussed with the help of figures.
EN
There are presented the results of utility trials done on the new models of gloves protecting against the thermal and mechanical factors. Gloves were produced with the use of aluminized basalt fabrics. The construction and composition were designed in the Central InstituteforLabour Protection - National Research Institute [1]. On the basis of prepared questionaries’ the positive assessment of elaborated models of gloves, which underwent the utility trials in the real conditions on the labour stands. It is confirmation of good selection of material packages and construction during the stage of designing the protective gloves with the use of aluminized basalt fabrics.
EN
There were presented in the aspect of construction and material composition existing on the market models of gloves protecting against the thermal factors, and six new glove models produced on the basis of aluminized basalt fabrics, designed in the Central Institute for Labour Protection - National Research Institute. The obtained results of resistance on the mechanical factors (abrasion, tear resistance, puncture and cut resistance as well as thermal factors (resistance on the contact, convective, and radiation heat, flammability, and resistance on the small metal splashes) in each variant confirmed the fulfillment of requirements of appropriate standards.
EN
An analysis of an oscillatory magnetohydrodynamic (MHD) convective flow of a second order (viscoelastic), incompressible, and electrically conducting fluid through a porous medium bounded by two infinite vertical parallel porous plates is presented. The two porous plates with slip-flow condition and the no-slip condition are subjected respectively to a constant injection and suction velocity. The pressure gradient in the channel varies periodically with time. A magnetic field of uniform strength is applied in the direction perpendicular to the planes of the plates. The induced magnetic field is neglected due to the assumption of a small magnetic Reynolds number. The temperature of the plate with no-slip condition is non-uniform and oscillates periodically with time and the temperature difference of the two plates is assumed high enough to induce heat radiation. The entire system rotates in unison about the axis perpendicular to the planes of the plates. Adopting complex variable notations, a closed form solution of the problem is obtained. The analytical results are evaluated numerically and then presented graphically to discuss in detail the effects of different parameters of the problem. The velocity, temperature and the skin-friction in terms of its amplitude and phase angle have been shown graphically to observe the effects of the viscoelastic parameter γ, rotation parameter Ω, suction parameter […], Grashof number Gr, Hartmann number M, the pressure A, Prandtl number Pr, radiation parameter N and the frequency of oscillation […].
EN
A numerical analysis is performed to study the MHD flow of an electrically conducting, incompressible, viscous fluid past a semi-infinite vertical plate with constant heat flux, subjected to a transversely applied magnetic field. The heat due to viscous dissipation and the induced magnetic field are assumed to be negligible. The dimensionless goveming equations are unsteady, two-dimensional, coupled, and non-linear. A most accurate, unconditionally stable and fast converging implicit finite difference scheme is used to solve the non-dimensional goveming equations. Velocity and temperature of the flow have been presented graphically for various parameters. The local and average skin friction and Nusselt number are also presented graphically.
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