1,978 research outputs found
Latest Jet Results from the Tevatron
Recent QCD jet production measurements in p-pbar collisions at sqrt(s)=1.96
TeV at the Tevatron Collider at Fermilab are presented. Preliminary: inclusive
jet, dijet, isolated photon + jet and Z + jets measurements are compared to
available perturbative QCD models.Comment: 4 pages, 5 figures, to appear in the proceedings of 42nd Recontres de
Moriond on QCD and high energy hadronic interactions, La Thuile, Aosta
Valley, Italy, 17-24 March 200
Development, Characterization, & Implementation of Phase-Change Material Cold Plates for Hybrid-Electric Vehicle Battery Systems
Due to the regulations on internal combustion engine vehicles, there is a large demand of hybrid and electric vehicles with large battery packs as Energy Storage Systems (ESS) capable of long ranges and decreased emissions. These battery packs output large heat loads during charge-depletion mode and currently require active cooling to keep the batteries within operating conditions. The current systems relied onto achieve this are the air and liquid cooled thermal managements systems. A recent alternative approach to current cooling for ESS thermal management is the use of phase-change materials (PCMs). PCMs regulate the temperature of the ESS by leveraging the latent heat of fusion to absorb large amounts of energy at constant temperature while changing phase from solid to liquid. While PCMs have large heat capacities, the downside is their low thermal conductivity which causes them to melt unevenly, which is a main reason PCM is not ideal for cooling systems. The study will involve fully investigating the use of PCM into a hybrid-electric vehicle battery thermal management system. The proposed methodology is to mix thermal conductivity enhancing material, loose carbon fibers, into the PCM to spread the heat absorbed more evenly throughout the entire mass. This material matrix is characterized in order to determine the necessary material and thermal properties to justify its use and implantation in the EcoEagles 2016 Chevrolet Camaro for vehicle testing and validations. Results obtained during multiple vehicle tests have demonstrated that the PCM has successfully kept the battery pack at a safe operating condition of under 45âŠC. This was done passively resulting in a reduced overall vehicle energy consumption and increased vehicle battery pack efficiency. The study continues by investigating the use of a shape-stabilized phase-change material cold plate that is capable of addressing several issues that a represent with the bulk PCM plate in its current state on the vehicle
Quadrupole Deformation of Barium Isotopes
The B(E2:0_1^+ -> 2_1^+) values of the Ba isotopes (Z=56) exhibit a sharp
increase in deformation as the neutron numbers approach the mid-shell value of
N=66. This behavior is anomalous because the 2_1^+ level energies are very
similar to those of the neighboring isotopes. By means of the axially-symmetric
deformed Woods-Saxon (WS) hamiltonian plus the BCS method, we investigated the
systematics of B(E2) of the Ba isotopes. We showed that 15% of the B(E2) values
at N=66 was due to the level crossing, occurring at the deformation with beta
being nearly 0.3, between the proton orbits originating from the orbits
Omega=1/2^-(h11/2) and 9/2^+(g9/2) at zero deformation. The latter of these two
was an intruder orbit originating from below the energy gap at Z=50, rising
higher in energy with the deformation and intruding the Z=50-82 shell. These
two orbits have the largest magnitude of the quadrupole moment with a different
sign among the orbits near and below the Fermi surface. Occupancy and
non-occupancy of these orbits by protons thus affect B(E2:0_1^+ -> 2_1^+)
significantly.Comment: 10 pages, 2 figures, to be published in Phys.Lett.
Single particle calculations for a Woods-Saxon potential with triaxial deformations, and large Cartesian oscillator basis
We present a computer program which solves the Schrodinger equation of the
stationary states for an average nuclear potential of Woods-Saxon type. In this
work, we take specifically into account triaxial (i.e. ellipsoidal) nuclear
surfaces. The deformation is specified by the usual Bohr parameters. The
calculations are carried out in two stages. In the first, one calculates the
representative matrix of the Hamiltonian in the cartesian oscillator basis. In
the second stage one diagonalizes this matrix with the help of subroutines of
the EISPACK library. If it is wished, one can calculate all eigenvalues, or
only the part of the eigenvalues that are contained in a fixed interval defined
in advance. In this latter case the eigenvectors are given conjointly. The
program is very rapid, and the run-time is mainly used for the diagonalization.
Thus, it is possible to use a significant number of the basis states in order
to insure a best convergence of the results.Comment: no figures, but tbles in separate pdf file
Early optical observations of GRBs by the TAROT telescopes: period 2001-2008
The TAROT telescopes (Telescopes a Action Rapide pour les Objets
Transitoires) are two robotic observatories designed to observe the prompt
optical emission counterpart and the early afterglow of gamma ray bursts
(GRBs). We present data acquired between 2001 and 2008 and discuss the
properties of the optical emission of GRBs, noting various interesting results.
The optical emission observed during the prompt GRB phase is rarely very
bright: we estimate that 5% to 20% of GRBs exhibit a bright optical flash
(R<14) during the prompt gamma-ray emission, and that more than 50% of the GRBs
have an optical emission fainter than R=15.5 when the gamma-ray emission is
active. We study the apparent optical brightness distribution of GRBs at 1000 s
showing that our observations confirm the distribution derived by other groups.
The combination of these results with those obtained by other rapid slewing
telescopes allows us to better characterize the early optical emission of GRBs
and to emphasize the importance of very early multi-wavelength GRB studies for
the understanding of the physics of the ejecta.Comment: 13 pages, 2 color figures, 5 b&w figures. Accepted for publication in
Astronomical Journa
Clues from the prompt emission of GRB 080319B
The extremely bright optical flash that accompanied GRB 080319B suggested, at
first glance, that the prompt -rays in this burst were produced by
Synchrotron self Compton (SSC). We analyze here the observed optical and
spectrum. We find that the very strong optical emission poses, due to
self absorption, very strong constraints on the emission processes and put the
origin of the optical emission at a very large radius, almost inconsistent with
internal shock. Alternatively it requires a very large random Lorentz factor
for the electrons. We find that SSC could not have produced the prompt
-rays. We also show that the optical emission and the rays
could not have been produced by synchrotron emission from two populations of
electron within the same emitting region. Thus we must conclude that the
optical and the -rays were produced in different physical regions. A
possible interpretation of the observations is that the -rays arose
from internal shocks but the optical flash resulted from external shock
emission. This would have been consistent with the few seconds delay observed
between the optical and -rays signals
The structure of superheavy elements newly discovered in the reaction of Kr with Pb
The structure of superheavy elements newly discovered in the
Pb(Kr,n) reaction at Berkeley is systematically studied in the
Relativistic Mean Field (RMF) approach. It is shown that various usually
employed RMF forces, which give fair description of normal stable nuclei, give
quite different predictions for superheavy elements. Among the effective forces
we tested, TM1 is found to be the good candidate to describe superheavy
elements. The binding energies of the 118 nucleus and its
decay daughter nuclei obtained using TM1 agree with those of FRDM
within 2 MeV. Similar conclusion that TM1 is the good interaction is also drawn
from the calculated binding energies for Pb isotopes with the Relativistic
Continuum Hartree Bogoliubov (RCHB) theory. Using the pairing gaps obtained
from RCHB, RMF calculations with pairing and deformation are carried out for
the structure of superheavy elements. The binding energy, shape, single
particle levels, and the Q values of the decay are
discussed, and it is shown that both pairing correlation and deformation are
essential to properly understand the structure of superheavy elements. A good
agreement is obtained with experimental data on . %Especially, the
atomic number %dependence of %seems to match with the experimental
observationComment: 19 pages, 5 figure
Skyrme Hartree-Fock Calculations for the Alpha Decay Q Values of Super-Heavy Nuclei
Hartree-Fock calculations with the SKX Skyrme interaction are carried out to
obtain alpha-decay Q values for deformed nuclei above Pb assuming axial
symmetry. The results for even-even nuclei are compared with experiment and
with previous calculations. Predictions are made for alpha-decay Q values and
half-lives of even-even super-heavy nuclei. The results are also compared for
the recently discovered odd-even chain starting at Z=112 and N=165.Comment: 17 pages, 8 figures, 1 tabl
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