55 research outputs found
Microscopic calculation of proton capture reactions in mass 60-80 region and its astrophysical implications
Microscopic optical potentials obtained by folding the DDM3Y interaction with
the densities from Relativistic Mean Field approach have been utilized to
evaluate S-factors of low-energy reactions in mass 60-80 region
and to compare with experiments. The Lagrangian density FSU Gold has been
employed. Astrophysical rates for important proton capture reactions have been
calculated to study the behaviour of rapid proton nucleosynthesis for waiting
point nuclei with mass less than A=80
Environment-induced dynamical chaos
We examine the interplay of nonlinearity of a dynamical system and thermal
fluctuation of its environment in the ``physical limit'' of small damping and
slow diffusion in a semiclassical context and show that the trajectories of
c-number variables exhibit dynamical chaos due to the thermal fluctuations of
the bath.Comment: Revtex, 4 pages and 4 figure
A study of the efficiency of the class of -states as a quantum channel
Recently, a new class of -states has been defined by Agarwal and Pati
\cite{agarwal} and it has been shown that they can be used as a quantum channel
for teleportation and superdense coding. In this work, we identify those
three-qubit states from the set of the new class of -states which are most
efficient or suitable for quantum teleportation. We show that with some
probability is best suited for
teleportation channel in the sense that it does not depend on the input state.Comment: 7 pages, Late
Detailed electronic structure studies on superconducting MgB and related compounds
In order to understand the unexpected superconducting behavior of MgB
compound we have made electronic structure calculations for MgB and closely
related systems. Our calculated Debye temperature from the elastic properties
indicate that the average phonon frequency is very large in MgB compared
with other superconducting intermetallics and the exceptionally high in
this material can be explained through BCS mechanism only if phonon softening
occurs or the phonon modes are highly anisotropic. We identified a
doubly-degenerate quasi-two dimensional key-energy band in the vicinity of
along -A direction of BZ which play an important role in
deciding the superconducting behavior of this material. Based on this result,
we have searched for similar kinds of electronic feature in a series of
isoelectronic compounds such as BeB, CaB, SrB, LiBC and
MgBC and found that MgBC is one potential material from the
superconductivity point of view. There are contradictory experimental results
regarding the anisotropy in the elastic properties of MgB ranging from
isotropic, moderately anisotropic to highly anisotropic. In order to settle
this issue we have calculated the single crystal elastic constants for MgB
by the accurate full-potential method and derived the directional dependent
linear compressibility, Young's modulus, shear modulus and relevant elastic
properties. We have observed large anisotropy in the elastic properties. Our
calculated polarized optical dielectric tensor shows highly anisotropic
behavior even though it possesses isotropic transport property. MgB
possesses a mixed bonding character and this has been verified from density of
states, charge density and crystal orbital Hamiltonian population analyses
Generalized quantum Fokker-Planck, diffusion and Smoluchowski equations with true probability distribution functions
Traditionally, the quantum Brownian motion is described by Fokker-Planck or
diffusion equations in terms of quasi-probability distribution functions, e.g.,
Wigner functions. These often become singular or negative in the full quantum
regime. In this paper a simple approach to non-Markovian theory of quantum
Brownian motion using {\it true probability distribution functions} is
presented. Based on an initial coherent state representation of the bath
oscillators and an equilibrium canonical distribution of the quantum mechanical
mean values of their co-ordinates and momenta we derive a generalized quantum
Langevin equation in -numbers and show that the latter is amenable to a
theoretical analysis in terms of the classical theory of non-Markovian
dynamics. The corresponding Fokker-Planck, diffusion and the Smoluchowski
equations are the {\it exact} quantum analogues of their classical
counterparts. The present work is {\it independent} of path integral
techniques. The theory as developed here is a natural extension of its
classical version and is valid for arbitrary temperature and friction
(Smoluchowski equation being considered in the overdamped limit).Comment: RevTex, 16 pages, 7 figures, To appear in Physical Review E (minor
revision
Use of an Alternative Probe for Improving Flue Gas Collection for Estimation of Hg
Combustion of coal in thermal power stations is one of the major sources of anthropogenic emission of mercury. In view of increased consumption of various fossil fuels such as coal, oil and gas, there is a growing concern in India on environmental degradation brought about by fuel combustion. Proper collection and estimation of mercury in flue gas is essential for assessing and monitoring the level of mercury emissions into the environment. Conventional method of drawing samples from flue gas for mercury estimation generally uses ss-probe (stainless steel probe). This can lead to the problem of sticking of mercury vapour on alloy steel surface, thereby introducing error in estimation. A new technique of using suitably designed glass probe is proposed which can minimize the problems associated with steel probe. A suitable glass probe has been designed and constructed which is provided with easily assembled and demountable parts. The newly constructed glass probe has been tested and verified by drawing Hg vapour samples from simulated Hg-laden gas stream as obtained from simple laboratory arrangements in a nebulised flame system of AAS equipment.
A comparative assessment for collection of flue gas has been carried out by inserting the probe inside the sample port of the stack, at the position of the mean velocity point. The flue gas samples are drawn maintaining an iso-kinetic condition. The collection of the gas samples had been done side by side by using a glass probe and a stainless steel probe in a 500MW-boiler unit of a coal based power plant situated at Singrauli region of India. The comparative study shows a slightly improved mercury sample, collected through glass probe as compared to the ss- probe (stainless steel probe)
Application of Instrumental Techniques for Determining the Physico-chemical Properties of Airborne Particulate Matter
Coal mining and other coal utilization technologies need crushing of coal which are usually carried out in dry condition therefore a considerable amount of dust is generated. The characterization of the dust particles for size distribution analysis, important trace metal composition, nature of organic aerosol have been carried out by laser based particle size analyzer, atomic absorption spectroscopy (AAS) and Fourier transform infrared (FT-IR) spectroscopy, the data reveal that more than 50% of suspended particulate matter are in the size range of 6.38 to 9.63µm in the morning area. Further the suspended particulate matters obtained from main roadside contains 10-18% benzene soluble fraction and lead is present in higher concentration in comparison with other areas. The data further revealed that suspended particulate matter of Jharia coalfield contain coal particles, quartz and clay minerals encapsulated with different hydrocarbons compounds probably originated from vehicular exhausts and trace metals, like pb, etc
- …