36,808 research outputs found
The Skyrme Interaction in finite nuclei and nuclear matter
Self-consistent mean-field models are a powerful tool in the investigation of
nuclear structure and low-energy dynamics. They are based on effective
energy-density functionals, often formulated in terms of effective
density-dependent nucleon-nucleon interactions. The free parameters of the
functional are adjusted to empirical data. A proper choice of these parameters
requires a comprehensive set of constraints covering experimental data on
finite nuclei, concerning static as well as dynamical properties, empirical
characteristics of nuclear matter, and observational information on
nucleosynthesis, neutron stars and supernovae. This work aims at a
comprehensive survey of the performance of one of the most successful
non-relativistic self-consistent method, the Skyrme-Hartree-Fock model (SHF),
with respect to these constraints. A full description of the Skyrme functional
is given and its relation to other effective interactions is discussed. The
validity of the application of SHF far from stability and in dense environments
beyond the nuclear saturation density is critically assessed. The use of SHF in
models extended beyond the mean field approximation by including some
correlations is discussed. Finally, future prospects for further development of
SHF towards a more consistent application of the existing and promisingly newly
developing constraints are outlined.Comment: 71 pages, 22 figures. Accepted for publication in Prog.Part.Nucl.Phy
Decorrelation control by the cerebellum achieves oculomotor plant compensation in simulated vestibulo-ocular reflex
We introduce decorrelation control as a candidate algorithm for the cerebellar microcircuit and demonstrate its utility for oculomotor plant compensation in a linear model of the vestibulo-ocular reflex (VOR). Using an adaptive-filter representation of cerebellar cortex and an anti-Hebbian learning rule, the algorithm learnt to compensate for the oculomotor plant by minimizing correlations between a predictor variable (eye-movement command) and a target variable (retinal slip), without requiring a motor-error signal. Because it also provides an estimate of the unpredicted component of the target variable, decorrelation control can simplify both motor coordination and sensory acquisition. It thus unifies motor and sensory cerebellar functions
Ultra-high temperature measuring techniques Final report
Real time technique for measurement of high temperature gases and spectroscopic techniques for temperature measurement of hot cesium seeded hydroge
Finite Nuclei in the Quark-Meson Coupling (QMC) Model
We report the first use of the effective QMC energy density functional (EDF),
derived from a quark model of hadron structure, to study a broad range of
ground state properties of even-even nuclei across the periodic table in the
non-relativistic Hartree-Fock+BCS framework. The novelty of the QMC model is
that the nuclear medium effects are treated through modification of the
internal structure of the nucleon. The density dependence is microscopically
derived and the spin-orbit term arises naturally. The QMC EDF depends on a
single set of four adjustable parameters having clear physical basis. When
applied to diverse ground state data the QMC EDF already produces, in its
present simple form, overall agreement with experiment of a quality comparable
to a representative Skyrme EDF. There exist however multiple Skyrme paramater
sets, frequently tailored to describe selected nuclear phenomena. The QMC EDF
set of fewer parameters, as derived in this work, is not open to such
variation, chosen set being applied, without adjustment, to both the properties
of finite nuclei and nuclear matter.Comment: 9 pages, 1 table, 4 figures; in print in Phys. Rev. Letters. A minor
change in the abstract, a few typos corrected and some small technical
adjustments made to comply with the journal regulation
Self-oscillating control methods for the LCC current-output resonant converter
Abstract—A strategy for self-oscillating control of LCC current-output resonant converters, is presented, based on varying the phase-angle between the fundamental of the input voltage and current. Unlike other commonly employed control methodologies,the proposed technique is shown to provide a convenient, linear system input-output characteristic suitable for the design of regulators.
The method is shown to have a similar effect as controlling
the dc-link supply voltage, in terms of output-voltage/current control. The LCC converter variant is used as an application focus for demonstrating the presented techniques, with simulation and experimental measurements from a prototype converter being used to show the practical benefits. Third-order small and large-signal models are developed, and employed in the formulation of robust output-voltage and output-current control schemes.
However, notably, the presented techniques are ultimately generic and readily applicable to other resonant converter variants
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