53,368 research outputs found
The Non-Mesonic Weak Decay of Double-Lambda Hypernuclei: A Microscopic Approach
The non--mesonic weak decay of double-- hypernuclei is studied
within a microscopic diagrammatic approach. Besides the nucleon--induced
mechanism, , widely studied in single-- hypernuclei,
additional hyperon--induced mechanisms, ,
and , are
accessible in double-- hypernuclei and are investigated here. As in
previous works on single-- hypernuclei, we adopt a nuclear matter
formalism extended to finite nuclei via the local density approximation and a
one--meson exchange weak transition potential (including the ground state
pseudoscalar and vector octets mesons) supplemented by correlated and
uncorrelated two--pion--exchange contributions. The weak decay rates are
evaluated for hypernuclei in the region of the experimentally accessible light
hypernuclei Be and B. Our
predictions are compared with a few previous evaluations. The rate for the
decay is dominated by --, -- and
--exchange and turns out to be about 2.5\% of the free decay
rate, , while the total rate for the and decays, dominated by
--exchange, amounts to about 0.25\% of . The
experimental measurement of these decays would be essential for the beginning
of a systematic study of the non--mesonic decay of strangeness
hypernuclei. This field of research could also shed light on the possible
existence and nature of the --dibaryon.Comment: 17 pages, 2 figure
Identifying the lights position in photometric stereo under unknown lighting
Reconstructing the 3D shape of an object from a set of images is a classical
problem in Computer Vision. Photometric stereo is one of the possible
approaches. It stands on the assumption that the object is observed from a
fixed point of view under different lighting conditions. The traditional
approach requires that the position of the light sources is accurately known.
It has been proved that the lights position can be estimated directly from the
data, when at least 6 images of the observed object are available. In this
paper, we give a Matlab implementation of the algorithm for solving the
photometric stereo problem under unknown lighting, and propose a simple
shooting technique to solve the bas-relief ambiguity.Comment: new versio
Integrated Flywheel Technology, 1983
Topics of discussion included: technology assessment of the integrated flywheel systems, potential of system concepts, identification of critical areas needing development and, to scope and define an appropriate program for coordinated activity
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