Convection in a Compressible Rotating Viscoelastic Fluid

Authors : Pardeep Kumar

DOI : doi.org/10.47752/sjsr.62.40.47

Abstract:
The aim of the present work was to study the thermosolutal convection in a compressible rotatory Rivlin-Ericksen viscoelastic fluid in permeable media. Following linear stability theory and normal mode analysis method, the dispersion relation is obtained. For the case of stationary convection, the Rivlin-Ericksen viscoelastic fluid behaves like an ordinary Newtonian fluid. The compressibility, stable solute gradient and rotation are found to postpone the onset of convection, whereas medium permeability hastens or postpones the onset of convection for the case of stationary convection. Also it is found that the system is stable for  and under the condition  , the system becomes unstable. The case of overstability has also been considered wherein sufficient conditions for the non-existence of overstability are obtained. The stable solute gradient and rotation are found to introduce oscillatory modes in the system.

A New CT Construction System Suitable for Micro- and Macro-Focal Beam Guides Using a Multitarget System

Authors : W. Ulmer

DOI : doi.org/10.47752/sjsr.62.33.39

Abstract:
The goal of this study is the improvement of CT constructions by exploiting the Bremsstrahlung created by multitarget systems allowing additional focusing influences by suitable magnetic fields and small-angle scatter of the walls (preferably tungsten). The number of layers of these configurations can be restricted to 10 – 15 layers, if electron voltages are of the order 120 keV – 180 keV, depending on the kind of application (medical CT or CT in the technical/research field). The theoretical results very satisfactorily agree with Monte-Carlo calculations using GEANT4.

Three Predictions of Gravitational Waves, and Black Holes

Authors : Yi-Fang Chang

DOI : doi.org/10.47752/sjsr.6.2.27.32

Abstract:
Gravitational wave forms a focus of physics, astrophysics and cosmology. First, we propose three predictions of gravitational waves: their observations must be nonlinear waves; velocity of gravitational wave should be slightly higher than the velocity of light; gravitational waves in black holes may emit and be observed. Next, we discuss the analogies of the gravitational and electromagnetic fields, and research some relations between black holes and gravitational waves. Finally, we propose the directed gravitational wave observatories of high-energy astrophysics, as such for the huge black holes in the Galactic center.