57,474 research outputs found
Further application of a semi-microscopic core-particle coupling method to the properties of Gd155,157, and Dy159
In a previous paper a semi-microscopic core-particle coupling method that
includes the conventional strong coupling core-particle model as a limiting
case, was applied to spectra and electromagnetic properties of several
well-deformed odd nuclei. This work, coupled a large single-particle space to
the ground state bands of the neighboring even cores. In this paper, we
generalize the theory to include excited bands of the cores, such as beta and
gamma bands, and thereby show that the resulting theory can account for the
location and structure of all bands up to about 1.5 MeV.Comment: 15 pages including 9 figure(postscript), submitted to Phys.Rev.
Polarization characteristics of the Crab pulsar's giant radio pulses at HFCs phases
We discuss our recent discovery of the giant radio emission from the Crab
pulsar at its high frequency components (HFCs) phases and show the polarization
characteristic of these pulses. This leads us to a suggestion that there is no
difference in the emission mechanism of the main pulse (MP), interpulse (IP)
and HFCs. We briefly review the size distributions of the Crab giant radio
pulses (GRPs) and discuss general characteristics of the GRP phenomenon in the
Crab and other pulsars.Comment: AIP Conference Proceedings "Astrophysical Sources of High Energy
Particles and Radiation", eds. T. Bulik et al. (NY:AIP), Volume 801, 2005,
pp. 324-32
Comparison of giant radio pulses in young pulsars and millisecond pulsars
Pulse-to-pulse intensity variations are a common property of pulsar radio
emission. For some of the objects single pulses are often 10-times stronger
than their average pulse. The most dramatic events are so-called giant radio
pulses (GRPs). They can be thousand times stronger than the regular single
pulses from the pulsar. Giant pulses are a rare phenomenon, occurring in very
few pulsars which split into two groups. The first group contains very young
and energetic pulsars like the Crab pulsar, and its twin (PSR B0540-69) in the
Large Magellanic Cloud (LMC), while the second group is represented by old,
recycled millisecond pulsars like PSR B1937+21, PSR B1821-24, PSR B1957+20 and
PSR J0218+4232 (the only millisecond pulsar detected in gamma-rays). We compare
the characteristics of GRPs for these two pulsar groups. Moreover, our latest
findings of new features in the Crab GRPs are presented. Analysis of our
Effelsberg data at 8.35 GHz shows that GRPs do occur in all phases of its
ordinary radio emission, including the phases of the two high frequency
components (HFCs) visible only between 5 and 9 GHz.Comment: Proceedings of the 363. WE-Heraeus Seminar on: Neutron Stars and
Pulsars (Posters and contributed talks) Physikzentrum Bad Honnef, Germany,
May.14-19, 2006, eds. W.Becker, H.H.Huang, MPE Report 291, pp.64-6
Exploring Human Vision Driven Features for Pedestrian Detection
Motivated by the center-surround mechanism in the human visual attention
system, we propose to use average contrast maps for the challenge of pedestrian
detection in street scenes due to the observation that pedestrians indeed
exhibit discriminative contrast texture. Our main contributions are first to
design a local, statistical multi-channel descriptorin order to incorporate
both color and gradient information. Second, we introduce a multi-direction and
multi-scale contrast scheme based on grid-cells in order to integrate
expressive local variations. Contributing to the issue of selecting most
discriminative features for assessing and classification, we perform extensive
comparisons w.r.t. statistical descriptors, contrast measurements, and scale
structures. This way, we obtain reasonable results under various
configurations. Empirical findings from applying our optimized detector on the
INRIA and Caltech pedestrian datasets show that our features yield
state-of-the-art performance in pedestrian detection.Comment: Accepted for publication in IEEE Transactions on Circuits and Systems
for Video Technology (TCSVT
Possible solution of the Coriolis attenuation problem
The most consistently useful simple model for the study of odd deformed
nuclei, the particle-rotor model (strong coupling limit of the core-particle
coupling model) has nevertheless been beset by a long-standing problem: It is
necessary in many cases to introduce an ad hoc parameter that reduces the size
of the Coriolis interaction coupling the collective and single-particle
motions. Of the numerous suggestions put forward for the origin of this
supplementary interaction, none of those actually tested by calculations has
been accepted as the solution of the problem. In this paper we seek a solution
of the difficulty within the framework of a general formalism that starts from
the spherical shell model and is capable of treating an arbitrary linear
combination of multipole and pairing forces. With the restriction of the
interaction to the familiar sum of a quadrupole multipole force and a monopole
pairing force, we have previously studied a semi-microscopic version of the
formalism whose framework is nevertheless more comprehensive than any
previously applied to the problem. We obtained solutions for low-lying bands of
several strongly deformed odd rare earth nuclei and found good agreement with
experiment, except for an exaggerated staggering of levels for K=1/2 bands,
which can be understood as a manifestation of the Coriolis attenuation problem.
We argue that within the formalism utilized, the only way to improve the
physics is to add interactions to the model Hamiltonian. We verify that by
adding a magnetic dipole interaction of essentially fixed strength, we can fit
the K=1/2 bands without destroying the agreement with other bands. In addition
we show that our solution also fits 163Er, a classic test case of Coriolis
attenuation that we had not previously studied.Comment: revtex, including 7 figures(postscript), submitted to Phys.Rev.
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