3,977 research outputs found
Perturbative Scattering Phase Shifts in One-Dimension: Closed-form Results
A simple closed form expression is obtained for the scattering phase shift
perturbatively to any given order in effective one-dimensional problems. The
result is a hierarchical scheme, expressible in quadratures, requiring only
knowledge of the zeroth order solution and the perturbation potential.Comment: 10 pages in REVTe
Critical densities for the Skyrme type effective interactions
We use the stability conditions of the Landau parameters for the symmetric
nuclear matter and pure neutron matter to calculate the critical densities for
the Skyrme type effective nucleon-nucleon interactions. We find that the
critical density can be maximized by adjusting appropriately the values of the
enhancement factor associated with isovector giant dipole resonance,
the quantity which is directly related to the slope of the symmetry energy
and the Landau parameter . However, restricting , and
to vary within acceptable limits reduces the maximum value for the
critical density by . We also show that among the
various quantities characterizing the symmetric nuclear matter,
depends strongly on the isoscalar effective mass and
surface energy coefficient . For realistic values of and we
get to (fm).Comment: 10 pages, 3 figures. Physicsl Review C (in press
Generalized Supersymmetric Perturbation Theory
Using the basic ingredient of supersymmetry, we develop a simple alternative
approach to perturbation theory in one-dimensional non-relativistic quantum
mechanics. The formulae for the energy shifts and wave functions do not involve
tedious calculations which appear in the available perturbation theories. The
model applicable in the same form to both the ground state and excited bound
states, unlike the recently introduced supersymmetric perturbation technique
which, together with other approaches based on logarithmic perturbation theory,
are involved within the more general framework of the present formalism.Comment: 13 pages article in LaTEX (uses standard article.sty). No Figures.
Sent to Ann. Physics (2004
New Skyrme nucleon-nucleon interaction for the mean-field approximation
The effective Skyrme type interactions have been used in the mean-field models
for several decades, and many different parameterizations of the interaction have
been realized to better reproduce nuclear masses, radii, and various other data. Today,
there are more experimental data of nuclei far from the B stability line. It is time
to improve the prediction power of the Skyrme type effective nucleon-nucleon interactions.
In this dissertation, we present the procedure of the fitting of the mean-field
results to an extensive set of experimental data with some constraints on the Skyrme
parameters and some approximations in the Hartree-Fock mean-field to obtain the
parameters of the new Skyrme type effective interactions, namely, KDE and KDE0.
We investigate the long-standing discrepancy of more than 20% between the values of
the incompressibility coefficient Kn:m: obtained within relativistic and non-relativistic
models. We show that this difference is basically due to the differences in values of
the symmetry energy coefficient J and its slope L associated with the relativistic and
non-relativistic models. We also present the results of fully self-consistent Hartree-Fock based Random Phase Approximation calculations for the centroid energies of
the breathing modes in four nuclei, namely, 90Zr, 116Sn, 144Sm, 208Pb, obtained with
our new Skyrme interaction KDE0. A good agreement with the experimental data is
achieved
Determination of the parameters of a Skyrme type effective interaction using the simulated annealing approach
We implement for the first time the simulated annealing method (SAM) to the
problem of searching for the global minimum in the hyper-surface of the
chi-square function which depends on the values of the parameters of a Skyrme
type effective nucleon-nucleon interaction. We undertake a realistic case of
fitting the values of the Skyrme parameters to an extensive set of experimental
data on the ground state properties of many nuclei ranging from normal to
exotic ones. The set of experimental data used in our fitting procedure
includes the radii for the valence and neutron orbits in
the O and Ca nuclei, respectively, and the breathing mode
energies for several nuclei, in addition to the typically used data on binding
energy, charge radii and spin-orbit splitting. We also include in the fit the
critical density and further constrain the values of the Skyrme
parameters by requiring that (i) the quantity ,
directly related to the slope of the symmetry energy , must be positive for
densities up to (ii) the enhancement factor , associated with
the isovector giant dipole resonance, should lie in the range of
and (iii) the Landau parameter is positive at . We
provide simple but consistent schemes to account for the center of mass
corrections to the binding energy and charge radii.Comment: 33 pages, 4 figures, Phys. Rev. C (in press
Stability and Reversibility of Lithium Borohydrides Doped by Metal Halides and Hydrides
In an effort to develop reversible metal borohydrides with high hydrogen storage capacities and low dehydriding temperature, doping LiBH4 with various metal halides and hydrides has been conducted. Several metal halides such as TiCl3, TiF3, and ZnF2 effectively reduced the dehydriding temperature through a cation exchange interaction. Some of the halide doped LiBH4 are partially reversible. The LiBH4 + 0.1TiF3 desorbed 3.5 wt % and 8.5 wt % hydrogen at 150 and 450 °C, respectively, with subsequent reabsorption of 6 wt % hydrogen at 500 °C and 70 bar observed. XRD and NMR analysis of the rehydrided samples confirmed the reformation of LiBH4. The existence of the (B12H12)â2 species in dehydrided and rehydrided samples gives insight into the resultant partial reversibility. A number of other halides, MgF2, MgCl2, CaCl2, SrCl2, and FeCl3, did not reduce the dehydriding temperature of LiBH4 significantly. XRD and TGA-RGA analyses indicated that an increasing proportion of halides such as TiCl3, TiF3, and ZnCl2 from 0.1 to 0.5 mol makes lithium borohydrides less stable and volatile. Although the less stable borohydrides such as LiBH4 + 0.5TiCl3, LiBH4 + 0.5TiF3, and LiBH4 + 0.5ZnCl2 release hydrogen at room temperature, they are not reversible due to unrecoverable boron loss caused by diborane emission. In most cases, doping that produced less stable borohydrides also reduced the reversible hydrogen uptake. It was also observed that halide doping changed the melting points and reduced air sensitivity of lithium borohydrides
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Notes of Honey Buzzard and Other Birds in Dumai and Rupat Island, Riau Province, Indonesia
Dumai are a town that located coastal area in the Nothern part of Pekan Baru, a capital city of Riau Province (1o 41â 04.1â N, 101o 26â 14,1â E). Dumai is margined directly by Rupat Island and Bengkalis Island in the North and Duri District in the South and East. On February 17, survey is conducted in Dumai harbour which vegetation are dominated rural plant and small scale mangrove. Only few records of bird are reported on 1980 such as storm stork Ciconia stormi (Holmes 1980)
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