The effect of rotation on the onset of convection in compfessible Walters‘ (model B‘) elastico-viscous fluid heated from below saturating a porous medium is considered. For the porous medium, the Brinkman model is employed and Walters‘ (model B‘) fluid used to characterize the viscoelastic fluid. By applying normal mode analysis method, the dispersion relation has been derived and solved analytically. It is observed that the medium permeability, compressibility, gravity field and vscoelasticity introduce oscillatory modes. For stationary convection, the rotation has stabilizing effect whereas Darcy number and medium permeability have destabilizing/stabilizing effect on the system under certain conditions. and Obsahuje seznam literatury a názvosloví
Measurements of the proper niotlons of young blpolar sunspot groups show that these groups rotate faster than the surroundlng photosphere. The results of the tlme series analysis carrled out on the Irradiance records of the SMM/ACRIM radiometer and on the projected areas of the young, active sunspot groups showed a period near U days In 1980, the year of the solar maximum. The main period in the projected areas of the old sunspot groups was 28 days, which corresponded to the mean photospherlc rotatlon. The faster proper motlon of the young sunspot groups as well as the 24 days periodicity of the young active spot areas might indicate that the young sunspots are connected to the deeper regione of the Sun which rotate faster than the photosphere. Thus, the sunspot groups in the early stage of their life would be an indlcator of rotation of the deeper layers of the Sun.
The dynamics of the mistuned model of the tests bladed disc with double perodicity was experimentally investigated. The mistuning arised due to the implemantation of two bunches of blades with damping heads fixed on opposite ends of the diameter. The dry friction effect in the heads was treated. The scale for measurement of the electromagnetic force acting on the disc was designed. It enables to analyse the real electromagnetic excitation of the disc under rotation and evaluation of the FRF characteristics from measured blade responses under rotation. The identified eigenfrequencies and damping constan ts served as indicators for assessment of stiffening and damping effects of the friction couplings in the heads. and Obsahuje seznam literatury