Papers

Neglecting the effect of overtaking disturbances, the motion of strong plane shock wave in highly viscous medium has been investigated by Chester-Chisnell- Whitham method. The analytical expressions for shock strength decreases as shock advances for low viscous region of a medium to the high viscous region. The dependence of mach number on propagation distance, Pressure and Particle velocity as well as on adiabatic index has also been analyzed for the cases. The results obtained here are also compared Yadav et al. 2 for a freely propagating shock. The obtained expansions are computed and discussed through table

Lanthanide ions doped glasses are studied by researchers for upconversion luminescence. Rare earth doped bismuth tellurite glasses codoped with and without silver nanoparticle were synthesized by melt and quench procedure for the study of enhanced upconversion luminescence. Physical parameters as molar mass, molar volume, and density were evaluated. Amorphous nature of samples was verified by x-ray diffraction. DSC is carried for information of thermal properties. UV-Visible absorption and fluorescence spectra is obtained to get detail information of upconversion luminescence. Upconversion mechanism of rare earth erbium and ytterbium ions discussed. Three prominent upconversion luminescence is observed two in green region  and one is in red.

Present paper is concerned with the oscillatory motion of visco-elastic [Oldroyd  (1958) model] liquid through porous medium and the annular space between two right circular cylinders perpendicular to the flow of liquid when both the cylinders execute simple harmonic motion along the central axis of the cylinders. The amplitudes and frequencies have been taken different for both cylinders. The particular cases have also been discussed in detail. Thevelocity of visco-elastic liquid is effected by porous medium.

The models represent expanding and shearing universe and both models start with Big Bang initially and the expansion stops for large time. The spatial volume increases with time representing inflationary scenario. The shear is zero for large value of time representing isotropization of universe. The Hubble parameter determines the age of the universe. The expression for Hubble parameter matches with FRW model.