10,900 research outputs found
Cosmic Evolution in Generalised Brans-Dicke Theory
We have studied the Generalised Brans-Dicke theory and obtained exact
solutions of a(t),phi(t),and omega(t) for different epochs of the cosmic
evolution .We discuss how inflation,decceleration,cosmic acceleration can
result from this solution.The time variation of G(t) is also examined.Comment: 12 pages, no figure
CFD analysis of heat transfer in a helical coil heat exchanger with constant wall heat transfer coefficient
There is a wide application of coiled heat exchanger in the field of cryogenics and other industrial applications for its enhanced heat transfer characteristics and compact structure. Lots of researches are going on to improve the heat transfer rate of the helical coil heat exchanger. Here, in this work, an analysis has been done for a tube-in-tube helical heat exchanger with constant heat transfer coefficient with turbulent flow. There are various factors present that may affect the heat transfer characteristics of the heat exchanger. Here, the experiment has been done by varying the curvature ratio i.e. ratio of coil diameter to inner tube diameter and inlet velocity of the hot fluid in the inner tube. The curvature ratio is varied from 8 to 25 and inlet velocity is varied from 1m/s to 2m/s step wise. The analysis has done using ANSYS 13 CFD methodology. Different parameters are calculated from the results obtained and graphs are plotted between various parameters such as Nusselt number, friction factor, pressure drop and pumping power versus Reynolds number. These graphs have been analyzed and discussed to find out the optimal result for which the heat exchanger would give the best performance
Application of Relativistic Coupled-cluster Theory to Electron Impact Excitations of Mg in the Plasma Environment
A relativistic coupled-cluster (RCC) theory is implemented to study electron
impact excitations of atomic species. As a test case, the electron impact
excitations of the resonance transitions
are investigated in the singly charged magnesium (Mg) ion using this
theory. Accuracies of wave functions of Mg are justified by evaluating its
attachment energies of the relevant states and compared with the experimental
values. The continuum wave function of the projectile electron are obtained by
solving Dirac equations assuming distortion potential as static potential of
the ground state of Mg. Comparison of the calculated electron impact
excitation differential and total cross-sections with the available
measurements are found to be in very good agreements at various incident
electron energies. Further, calculations are carried out in the plasma
environment in the Debye H\"uckel model framework, which could be useful in the
astrophysics. Influence of plasma strength on the cross-sections as well as
linear polarization of the photon emission in the transition is investigated for different incident electron energies.Comment: 9 pages, 1 table and 3 figure
Effect of both Z and Z'-mediated flavor-changing neutral currents on the baryonic rare decay decays into
We study the effect of both Z and Z'-mediated flavor-changing neutral
currents (FCNCs) on the rare
decay. We find the branching ratio is reasonably enhanced from its standard
model value due to the effect of both Z and Z'-mediated FCNCs, and gives the
possibility of new physics beyond the standard model. The contribution of
Z'-boson depends upon the precise value of the mass of Z' boson.Comment: 14 page
On some strategies using auxiliary information for estimating finite population mean
This paper presents an empirical investigation of the performance of five strategies for estimating the finite population mean using parameters such as mean or variance or both of an auxiliary variable. The criteria used for the choices of these strategies are bias, efficiency and approach to normality (asymmetry)
- …