320 research outputs found
Data compression for satellite images
An efficient data compression system is presented for satellite pictures and two grey level pictures derived from satellite pictures. The compression techniques take advantages of the correlation between adjacent picture elements. Several source coding methods are investigated. Double delta coding is presented and shown to be the most efficient. Both predictive differential quantizing technique and double delta coding can be significantly improved by applying a background skipping technique. An extension code is constructed. This code requires very little storage space and operates efficiently. Simulation results are presented for various coding schemes and source codes
Bounds on R-parity violating supersymmetric couplings from leptonic and semi-leptonic meson decays
We present a comprehensive update of the bounds on R-Parity violating
supersymmetric couplings from lepton-flavour- and lepton-number-violating decay
processes. We consider tau and mu decays as well as leptonic and semi-leptonic
decays of mesons. We present several new bounds resulting from tau, eta and
Kaon decays and correct some results in the literature concerning B-meson
decays.Comment: 30 pages; changed title, updated some bounds from the literature from
different references, added reference
Extracting the depolarization coefficient D_NN from data measured with a full acceptance detector
The spin transfer from vertically polarized beam protons to Lambda or Sigma
hyperons of the associated strangeness production pp -> pK Lambda (Sigma) is
described with the depolarization coefficient D_NN. As the polarization of the
hyperons is determined by their weak decays, detectors, which have a large
acceptance for the decay particles, are needed. In this paper a formula is
derived, which describes the depolarization coefficient D_NN by count rates of
a 4 pi detector. It is shown, that formulas, which are given in publications
for detectors with restricted acceptance, are specific cases of this formula
for a 4 pi detector.Comment: Accepted for publication by Nuclear Instruments and Methods in
Physics Research Section
Area-Constrained Planar Elastica
We determine the equilibria of a rigid loop in the plane, subject to the
constraints of fixed length and fixed enclosed area. Rigidity is characterized
by an energy functional quadratic in the curvature of the loop. We find that
the area constraint gives rise to equilibria with remarkable geometrical
properties: not only can the Euler-Lagrange equation be integrated to provide a
quadrature for the curvature but, in addition, the embedding itself can be
expressed as a local function of the curvature. The configuration space is
shown to be essentially one-dimensional, with surprisingly rich structure.
Distinct branches of integer-indexed equilibria exhibit self-intersections and
bifurcations -- a gallery of plots is provided to highlight these findings.
Perturbations connecting equilibria are shown to satisfy a first order ODE
which is readily solved. We also obtain analytical expressions for the energy
as a function of the area in some limiting regimes.Comment: 23 pages, several figures. Version 2: New title. Changes in the
introduction, addition of a new section with conclusions. Figure 14 corrected
and one reference added. Version to appear in PR
First Model-Independent Measurement of the Spin Triplet Scattering Length from Final State Interaction in the Reaction
The reaction has been measured with the
COSY-TOF detector at a beam momentum of . The polarized
proton beam enables the measurement of the beam analyzing power by the
asymmetry of the produced kaon (). This observable allows the
spin triplet scattering length to be extracted for the first time
model independently from the final-state interaction in the reaction. The
obtained value is . This value is
compatible with theoretical predictions and results from model-dependent
analyses.Comment: Revised version as accepted for publication in PR
High precision measurement of the associated strangeness production in proton proton interactions
A new high precision measurement of the reaction pp -> pK+Lambda at a beam
momentum of 2.95 GeV/c with more than 200,000 analyzed events allows a detailed
analysis of differential observables and their inter-dependencies. Correlations
of the angular distributions with momenta are examined. The invariant mass
distributions are compared for different regions in the Dalitz plots. The cusp
structure at the N Sigma threshold is described with the Flatt\'e formalism and
its variation in the Dalitz plot is analyzed.Comment: accepted for publication in Eur. Phys. J.
Numerical observation of non-axisymmetric vesicles in fluid membranes
By means of Surface Evolver (Exp. Math,1,141 1992), a software package of
brute-force energy minimization over a triangulated surface developed by the
geometry center of University of Minnesota, we have numerically searched the
non-axisymmetric shapes under the Helfrich spontaneous curvature (SC) energy
model. We show for the first time there are abundant mechanically stable
non-axisymmetric vesicles in SC model, including regular ones with intrinsic
geometric symmetry and complex irregular ones. We report in this paper several
interesting shapes including a corniculate shape with six corns, a
quadri-concave shape, a shape resembling sickle cells, and a shape resembling
acanthocytes. As far as we know, these shapes have not been theoretically
obtained by any curvature model before. In addition, the role of the
spontaneous curvature in the formation of irregular crenated vesicles has been
studied. The results shows a positive spontaneous curvature may be a necessary
condition to keep an irregular crenated shape being mechanically stable.Comment: RevTex, 14 pages. A hard copy of 8 figures is available on reques
Measurement of the Eta Production in Proton Proton Collisions with the COSY Time of Flight Spectrometer
The reaction pp -> pp eta was measured at excess energies of 15 and 41 MeV at
an external target of the Juelich Cooler Synchrotron COSY with the Time of
Flight Spectrometer. About 25000 events were measured for the excess energy of
15 MeV and about 8000 for 41 MeV. Both protons of the process pp eta were
detected with an acceptance of nearly 100% and the eta was reconstructed by the
missing mass technique. For both excess energies the angular distributions are
found to be nearly isotropic. In the invariant mass distributions strong
deviations from the pure phase space distributions are seen.Comment: 15 pages, 14 figures, 4 table
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