695 research outputs found
Backbending in 50Cr
The collective yrast band and the high spin states of the nucleus 50Cr are
studied using the spherical shell model and the HFB method. The two
descriptions lead to nearly the same values for the relevant observables. A
first backbending is predicted at I=10\hbar corresponding to a collective to
non-collective transition. At I=16\hbar a second backbending occurs, associated
to a configuration change that can also be interpreted as an spherical to
triaxial transition.Comment: ReVTeX v 3.0 epsf.sty, 5 pages, 5 figures included. Full Postscript
version available at http://www.ft.uam.es/~gabriel/Cr50art.ps.g
Ground-State Electromagnetic Moments of Calcium Isotopes
High-resolution bunched-beam collinear laser spectroscopy was used to measure
the optical hyperfine spectra of the Ca isotopes. The ground state
magnetic moments of Ca and quadrupole moments of Ca were
measured for the first time, and the Ca ground state spin was
determined in a model-independent way. Our results provide a critical test of
modern nuclear theories based on shell-model calculations using
phenomenological as well as microscopic interactions. The results for the
neutron-rich isotopes are in excellent agreement with predictions using
interactions derived from chiral effective field theory including three-nucleon
forces, while lighter isotopes illustrate the presence of particle-hole
excitations of the Ca core in their ground state.Comment: Accepted as a Rapid Communication in Physical Review
Full shell model calculation of the binding energies of the nuclei
Binding energies and other global properties of nuclei in the middle of the
shell, such as M1, E2 and Gamow-Teller sum rules, have been obtained using
a new Shell Model code (NATHAN) written in quasi-spin formalism and using a
-coupled basis. An extensive comparison is made with the recently
available Shell Model Monte Carlo results using the effective interaction KB3.
The binding energies for -nearly- all the nuclei are compared with
the measured (and extrapolated) results.Comment: 7 page
Resistance and resilience of socialâecological systems to recurrent typhoon disturbance on a subtropical island: Taiwan
Tropical cyclones (TCs) have major effects on ecological and social systems. However, studies integrating the effects of TCs on both social and ecological systems are rare, especially in the northwest Pacific, where the frequency of TCs (locally named typhoons) is the highest in the world. We synthesized studies of effects of recurrent typhoons on social and ecological systems in Taiwan over the last several decades. Many responses to TCs are comparable between social and ecological systems. High forest ecosystem resistance, evident from tree mortality below 2% even following multiple strong typhoons, is comparable with resistance of social systems, including the only 4% destruction of river embankments following a typhoon that brought nearly 3000 mm rainfall in three days. High resilience as reflected by quick returns of leaf area index, mostly in one year, and streamwater chemistry, one to several weeks to preâtyphoon levels of ecosystems, are comparable to quick repair of the power grid within one to several days and returns of vegetable price within several weeks to preâtyphoon levels of the social systems. Landslides associated with intense typhoons have buried mountain villages and transported large quantities of woody debris to the coast, affecting the coastal plains and reefs, illustrating a ridgeâtoâreef link between ecological and societal systems. Metrics of both social and ecological function showed large fluctuations in response to typhoons but quickly returned to preâdisturbance levels, except when multiple intense typhoons occurred within a single season. Our synthesis illustrates that the socialâecological systems in Taiwan are highly dynamic and responsive to frequent typhoon disturbance, with extraordinarily high resistance and resilience. For ecosystems, the efficient responsiveness results from the selective force of TCs on ecosystem structure and processes. For social systems, it is the result of the effects of TCs on planning and decision making by individuals (e.g., farmers), management sectors, and ultimately the government. In regions with frequent TCs, the socialâecological systems are inevitably highly dynamic and rapid responses are fundamental to system resistance and resilience which in turn is key to maintaining structure and function of the socialâecological systems
Energy efficiency parametric design tool in the framework of holistic ship design optimization
Recent International Maritime Organization (IMO) decisions with respect to measures to reduce the emissions from maritime greenhouse gases (GHGs) suggest that the collaboration of all major stakeholders of shipbuilding and ship operations is required to address this complex techno-economical and highly political problem efficiently. This calls eventually for the development of proper design, operational knowledge, and assessment tools for the energy-efficient design and operation of ships, as suggested by the Second IMO GHG Study (2009). This type of coordination of the efforts of many maritime stakeholders, with often conflicting professional interests but ultimately commonly aiming at optimal ship design and operation solutions, has been addressed within a methodology developed in the EU-funded Logistics-Based (LOGBASED) Design Project (2004â2007). Based on the knowledge base developed within this project, a new parametric design software tool (PDT) has been developed by the National Technical University of Athens, Ship Design Laboratory (NTUA-SDL), for implementing an energy efficiency design and management procedure. The PDT is an integral part of an earlier developed holistic ship design optimization approach by NTUA-SDL that addresses the multi-objective ship design optimization problem. It provides Pareto-optimum solutions and a complete mapping of the design space in a comprehensive way for the final assessment and decision by all the involved stakeholders. The application of the tool to the design of a large oil tanker and alternatively to container ships is elaborated in the presented paper
Shell Model Study of the Double Beta Decays of Ge, Se and Xe
The lifetimes for the double beta decays of Ge, Se and
Xe are calculated using very large shell model spaces. The two neutrino
matrix elements obtained are in good agreement with the present experimental
data. For eV we predict the following upper bounds to the
half-lives for the neutrinoless mode: , and . These results are the first from a new generation of Shell
Model calculations reaching O(10) dimensions
Shell Model Study of the Neutron-Rich Nuclei around N=28
We describe the properties of the neutron rich nuclei around N=28 in the
shell mode framework. The valence space comprises the shell for protons an
the shell for neutrons without any restriction. Good agreement is found
with the available experimental data. The N=28 shell closure, even if eroded
due to the large neutron excess, persists. The calculations predict that
S and S are deformed with and
respectively.Comment: 17 pages and 19 figures, LateX, RevTe
Multipolar correlations and deformation effect on nuclear transition matrix elements of double- decay
The two neutrino and neutrinoless double beta decay of Zr,
Mo, Ru, Pd, Te and Nd isotopes
for the transition is studied within the PHFB framework along
with an effective two-body interaction consisting of pairing,
quadrupole-quadrupole and hexadecapole-hexadecapole correlations. It is found
that the effect of hexadecapolar correlations can be assimilated substantially
as a renormalization of the quadrupole-quadrupole interaction. The effect of
deformation on nuclear transition matrix elements is investigated by varying
the strength of quadrupolar correlations in the parent and daughter nuclei
independently. The variation of the nuclear transition matrix elements as a
function of the difference in deformation parameters of parent and daughter
nuclei reveals that in general, the former tend to be maximum for equal
deformation and they decrease as the difference in deformation parameters
increases, exhibiting a very similar trend for the and transition matrix elements.Comment: 6 pages, 2 figure
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