2,082 research outputs found
Saturation properties and incompressibility of nuclear matter: A consistent determination from nuclear masses
Starting with a two-body effective nucleon-nucleon interaction, it is shown
that the infinite nuclear matter model of atomic nuclei is more appropriate
than the conventional Bethe-Weizsacker like mass formulae to extract saturation
properties of nuclear matter from nuclear masses. In particular, the saturation
density thus obtained agrees with that of electron scattering data and the
Hartree-Fock calculations. For the first time using nuclear mass formula, the
radius constant =1.138 fm and binding energy per nucleon = -16.11
MeV, corresponding to the infinite nuclear matter, are consistently obtained
from the same source. An important offshoot of this study is the determination
of nuclear matter incompressibility to be 288 28 MeV using
the same source of nuclear masses as input.Comment: 14 latex pages, five figures available on request ( to appear in Phy.
Rev. C
Anatomy of neck configuration in fission decay
The anatomy of neck configuration in the fission decay of Uranium and Thorium
isotopes is investigated in a microscopic study using Relativistic mean field
theory. The study includes and in the valley of stability
and exotic neutron rich isotopes , , , ,
, likely to play important role in the r-process
nucleosynthesis in stellar evolution. Following the static fission path, the
neck configurations are generated and their composition in terms of the number
of neutrons and protons are obtained showing the progressive rise in the
neutron component with the increase of mass number. Strong correlation between
the neutron multiplicity in the fission decay and the number of neutrons in the
neck is seen. The maximum neutron-proton ratio is about 5 for U and
Th suggestive of the break down of liquid-drop picture and inhibition
of the fission decay in still heavier isotopes. Neck as precursor of a new mode
of fission decay like multi-fragmentation fission may also be inferred from
this study.Comment: 16 pages, 5 figures (Accepted
Analytical Expression for the RKKY Interaction in Doped Graphene
We obtain an analytical expression for the Ruderman-Kittel-Kasuya-Yosida
(RKKY) interaction in electron or hole doped graphene for linear Dirac
bands. The results agree very well with the numerical calculations for the full
tight-binding band structure in the regime where the linear band structure is
valid. The analytical result, expressed in terms of the Meijer G-function,
consists of a product of two oscillatory terms, one coming from the
interference between the two Dirac cones and the second coming from the finite
size of the Fermi surface. For large distances, the Meijer G-function behaves
as a sinusoidal term, leading to the result for moments located on the same sublattice. The
dependence, which is the same for the standard two-dimensional electron gas, is
universal irrespective of the sublattice location and the distance direction of
the two moments except when (undoped case), where it reverts to the
dependence. These results correct several inconsistencies found in the
literature.Comment: 5 pages, 5 figure
CFD-based process optimization of a dissolved air flotation system for drinking water production
Dissolved air flotation (DAF) has received more attention recently as a separation technique in both drinking water as well as wastewater treatment. However, the process as well as the preceding flocculation step is complex and not completely understood. Given the multiphase nature of the process, fluid dynamics studies are important to understand and optimize the DAF system in terms of operation and design. The present study is intended towards a comprehensive computational analysis for design optimization of the treatment plant in Kluizen, Belgium. Setting up the modelling framework involving the multiphase flow problem is briefly discussed. 3D numerical simulations on a scaled down model of the DAF design were analysed. The flow features give better confidence, but the flocs escape through the outlet still prevails which is averse to the system performance. In order to improve the performance and ease of maintenance, design modifications have been proposed by using a perforated tube for water extraction and are found to be satisfactory. The discussion is further reinforced through validating the numerical model against the experimental findings for stratified flow conditions
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