591 research outputs found
Extended shell-model calculation for even N=82 isotones with realistic effective interactions
The shell model within the shell is applied to
calculate nuclear structure properties of the even Z=52 - 62, N=82 isotones.
The results are compared with experimental data and with the results of a
quasiparticle random-phase approximation (QRPA) calculation. The interaction
used in these calculations is a realistic two-body G-matrix interaction derived
from modern meson-exchange potential models for the nucleon-nucleon
interaction. For the shell model all the two-body matrix elements are
renormalized by the -box method whereas for the QRPA the effective
interaction is defined by the G-matrix.Comment: 25 pages, Elsevier latex style. Submitted to Nuclear Physics
Study of odd-mass N=82 isotones with realistic effective interactions
The microscopic quasiparticle-phonon model, MQPM, is used to study the energy
spectra of the odd , N=82 isotones. The results are compared with
experimental data, with the extreme quasiparticle-phonon limit and with the
results of an unrestricted shell model (SM)
calculation. The interaction used in these calculations is a realistic two-body
G-matrix interaction derived from modern meson-exchange potential models for
the nucleon-nucleon interaction. For the shell model all the two-body matrix
elements are renormalized by the -box method whereas for the MQPM the
effective interaction is defined by the G-matrix.Comment: Elsevier latex style espart, 26 pages, submitted to Nuclear Physics
Neutrino reactions on La and Ta via charged and neutral currents by the Quasi-particle Random Phase Approximation (QRPA)
Cosmological origins of the two heaviest odd-odd nuclei, La and
Ta, are believed to be closely related to the neutrino-process. We
investigate in detail neutrino-induced reactions on the nuclei. Charged current
(CC) reactions, BaLa and HfTa, are calculated by the standard Quasi-particle Random Phase
Approximation (QRPA) with neutron-proton pairing as well as neutron-neutron,
proton-proton pairing correlations. For neutral current (NC) reactions,
La{La} and TaTa, we generate ground and excited states of odd-even target nuclei,
La and Ta, by operating one quasi-particle to even-even nuclei,
Ba and Hf, which are assumed as the BCS ground state. Numerical
results for CC reactions are shown to be consistent with recent semi-empirical
data deduced from the Gamow-Teller strength distributions measured in the
(He, t) reaction. Results for NC reactions are estimated to be smaller by
a factor about 4 5 rather than those by CC reactions. Finally, cross
sections weighted by the incident neutrino flux in the core collapsing
supernova are presented for further applications to the network calculations
for relevant nuclear abundances
The effect of microstructure on mechanical properties of HVOF sprayed WC-CoCr composite coatings
This study aims for deeper understanding of the composition and phase changes occurring during HVOF spraying of the powder to WC-CoCr coatings. Also, the effect of lamellar microstructure on the mechanical properties is studied. Compositional and microstructural features are studied by means of X-ray diffraction, XRF, FE-SEM and TEM (EDX, EELS). Mechanical properties are mainly studied by different instrumented indentation and nanoindentation techniques. The use of two new fracture parameters, complementing the fracture toughness value of the coating, are proposed and examined. Higher load range indentations are used to measure cross-sectional and surface hardness, elastic modulus and fracture toughness of the coatings. Mechanical properties of individual phases are studied by nanoindentation. To our knowledge this is the first time that the mechanical properties of this amorphous/nanocrystalline matrix are studied. ICP (In-situ Coating Property) sensor, developed for quality control and residual stress evaluation, is also used to measure the elastic modulus and coefficient of thermal expansion (CTE) of the coatings. Abrasion wear resistance of the coatings are studied according to standard ASTM G 65D.
Because of the brittle nature of HVOF coatings, the main focus of this study is in the effects of coating microstructure on fracture toughness, and on crack initiation and propagation resistance. It is shown that even when two similar coatings have equal indentation fracture toughness values, the critical crack initiation loads may be very different. This new parameter is expected to be extremely useful in the evaluation of the coating performance under loading conditions
Shell-Model Effective Operators for Muon Capture in ^{20}Ne
It has been proposed that the discrepancy between the partially-conserved
axial-current prediction and the nuclear shell-model calculations of the ratio
in the muon-capture reactions can be solved in the case of ^{28}Si by
introducing effective transition operators. Recently there has been
experimental interest in measuring the needed angular correlations also in
^{20}Ne. Inspired by this, we have performed a shell-model analysis employing
effective transition operators in the shell-model formalism for the transition
. Comparison of
the calculated capture rates with existing data supports the use of effective
transition operators. Based on our calculations, as soon as the experimental
anisotropy data becomes available, the limits for the ratio can be
extracted.Comment: 9 pages, 3 figures include
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