53,293 research outputs found
A Dain Inequality with charge
We prove an upper bound for angular-momentum and charge in terms of the mass
for electro-vacuum asymptotically flat axisymmetric initial data sets with
simply connected orbit space
An Adult with Episodic Abnormal Limb Posturing
info:eu-repo/semantics/publishedVersio
Effective restoration of chiral and axial symmetries at finite temperature and density
The effective restoration of chiral and axial symmetries is investigated
within the framework of the SU(3) Nambu-Jona-Lasinio model. The topological
susceptibility, modeled from lattice data at finite temperature, is used to
extract the temperature dependence of the coupling strength of the anomaly. The
study of the scalar and pseudoscalar mixing angles is performed in order to
discuss the evolution of the flavor combinations of pairs and its
consequences for the degeneracy of chiral partners. A similar study at zero
temperature and finite density is also realized.Comment: 5 pages, 1 figure. Talk given at Strange Quark Matter 2004, Cape
Town, South Africa, 15-20 September, 200
Torque Ripple Minimization in a Switched Reluctance Drive by Neuro-Fuzzy Compensation
Simple power electronic drive circuit and fault tolerance of converter are
specific advantages of SRM drives, but excessive torque ripple has limited its
use to special applications. It is well known that controlling the current
shape adequately can minimize the torque ripple. This paper presents a new
method for shaping the motor currents to minimize the torque ripple, using a
neuro-fuzzy compensator. In the proposed method, a compensating signal is added
to the output of a PI controller, in a current-regulated speed control loop.
Numerical results are presented in this paper, with an analysis of the effects
of changing the form of the membership function of the neuro-fuzzy compensator.Comment: To be published in IEEE Trans. on Magnetics, 200
Slow and fast components in the X-ray light curves of Gamma-Ray Bursts
Gamma-ray burst light curves show quite different patterns: from very simple
to extremely complex. We present a temporal and spectral study of the light
curves in three energy bands (2-5, 5-10, 10-26 keV) of ten GRBs detected by the
Wide Field Cameras on board BeppoSAX. For some events the time profiles are
characterized by peaks superposed on a slowly evolving pedestal, which in some
cases becomes less apparent at higher energies. We describe this behaviour with
the presence of two components (slow and fast) having different variability
time scales. We modelled the time evolution of slow components by means of an
analytical function able to describe asymmetric rising and decaying profiles.
The residual light curves, after the subtraction of the slow components,
generally show structures more similar to the original curves in the highest
energy band. Spectral study of these two components was performed evaluating
their hardness ratios, used also to derive photon indices. Slow components are
found generally softer than the fast ones suggesting that their origin is
likely different. Being typical photon indices lower than those of the
afterglows there is no evidence that the emission processes are similar.
Another interesting possibility is that slow components can be related to the
presence of a hot photosphere having a thermal spectrum with kT around a few
keV superposed to a rapid variable non-thermal emission of the fast component.Comment: 16 pages, 20 figures (18 color, 2 B&W), accepted for publication in
Astronomy and Astrophysic
Two photon decay of and at finite temperature and density
A comparative study of the anomalous decays , at
finite temperature and at finite density, is performed in the framework of the
three--flavor Nambu--Jona-Lasinio. The similarities and differences between
both scenarios are discussed. In both cases the lifetimes of these mesons
decrease significantly at the critical point, although this might not be
sufficient to observe enhancement of these decays in heavy-ion collisions.Comment: 5 pages, 1 figure. Talk given at Strange Quark Matter 2004, Cape
Town, South Africa, 15-20 September, 200
Controlling services in a mobile context-aware infrastructure
Context-aware application behaviors can be described as logic rules following the Event-Control-Action (ECA) pattern. In this pattern, an Event models an occurrence of interest (e.g., a change in context); Control specifies a condition that must hold prior to the execution of the action; and an Action represents the invocation of arbitrary services. We have defined a Controlling service aiming at facilitating the dynamic configuration of ECA rule specifications by means of a mobile rule engine and a mechanism that distributes context reasoning activities to a network of context processing nodes. In this paper we present a novel context modeling approach that provides application developers and users with more appropriate means to define context information and ECA rules. Our approach makes use of ontologies to model context information and has been developed on top of web services technology
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