3,225 research outputs found
Energy Efficient Engine exhaust mixer model technology report addendum; phase 3 test program
The Phase 3 exhaust mixer test program was conducted to explore the trends established during previous Phases 1 and 2. Combinations of mixer design parameters were tested. Phase 3 testing showed that the best performance achievable within tailpipe length and diameter constraints is 2.55 percent better than an optimized separate flow base line. A reduced penetration design achieved about the same overall performance level at a substantially lower level of excess pressure loss but with a small reduction in mixing. To improve reliability of the data, the hot and cold flow thrust coefficient analysis used in Phases 1 and 2 was augmented by calculating percent mixing from traverse data. Relative change in percent mixing between configurations was determined from thrust and flow coefficient increments. The calculation procedure developed was found to be a useful tool in assessing mixer performance. Detailed flow field data were obtained to facilitate calibration of computer codes
Dipole excitation and geometry of borromean nuclei
We analyze the Coulomb breakup cross sections of Li and He nuclei
using a three-body model with a density-dependent contact interaction. We show
that the concentration of the B(E1) strength near the threshold can be well
reproduced with this model. With the help of the calculated B(E1) value, we
extract the root-mean-square (rms) distance between the core nucleus and the
center of mass of two valence neutrons without resorting to the sum rule, which
may suffer from unphysical Pauli forbidden transitions. Together with the
empirical rms distance between the neutrons obtained from the matter radius
study and also from the three-body correlation study in the break-up reaction,
we convert these rms distances to the mean opening angle between the valence
neutrons from the core nucleus. We find that the obtained mean opening angles
in Li and He agree with the three-body model predictions.Comment: 4 pages, 4 eps figure
A Simple Explanation for the X(3872) Mass Shift Observed for Decay to D^{*0} {D^0}bar
We propose a simple explanation for the increase of approximately
3 MeV/c^2 in the mass value of the X(3872) obtained from
D^{*0} {D^0}bar decay relative to that obtained from decay to J/psi pi+ pi-.
If the total width of the X(3872) is 2-3 MeV, the peak position in the
D^{*0} {D^0}bar invariant mass distribution is sensitive to the final state
orbital angular momentum because of the proximity of the X(3872) to D^{*0}
{D^0}bar threshold. We show that for total width 3 MeV and one unit of orbital
angular momentum, a mass shift ~3 MeV/c^2 is obtained; experimental mass
resolution should slightly increase this value. A consequence is that
spin-parity 2^- is favored for the X(3872).Comment: 3.5 pages, 4 eps figure
Cryogenic zero-gravity prototype vent system
Design, fabrication, and tests of prototype cryogenic zero-gravity heat exchanger vent syste
Low energy bounds on Poincare violation in causal set theory
In the causal set approach to quantum gravity, Poincar\'{e} symmetry is
modified by swerving in spacetime, induced by the random lattice discretization
of the space-time structure. The broken translational symmetry at short
distances is argued to lead to a residual diffusion in momentum space, whereby
a particle can acquire energy and momentum by drift along its mass shell and a
system in equilibrium can spontaneously heat up. We consider bounds on the rate
of momentum space diffusion coming from astrophysical molecular clouds, nuclear
stability and cosmological neutrino background. We find that the strongest
limits come from relic neutrinos, which we estimate to constrain the momentum
space diffusion constant by for neutrinos with
masses , improving the previously quoted bounds by
roughly 17 orders of magnitude.Comment: Additional discussion about behavior of alpha particles in nuclei
added. Version matches that accepted in PR
Experimental proposal for accurate determination of the phase relaxation time and testing a formation of thermalized non-equilibrated matter in highly excited quantum many-body systems
We estimate how accurate the phase relaxation time of quantum many-body
systems can be determined from data on forward peaking of evaporating protons
from a compound nucleus. The angular range and accuracy of the data needed for
a reliable determination of the phase relaxation time are evaluated. The
general method is applied to analyze the inelastic scattering of 18 MeV protons
from Pt for which previously measured double differential cross sections for
two angles in the evaporating domain of the spectra show a strong forward
peaking. A new experiment for an improved determination of the phase relaxation
time is proposed. The experiment is also highly desirable for an accurate test
of a formation of thermalized non-equilibrated matter in quantum many-body
systems.Comment: 5 pages, 3 figure
Extracting CKM phase from and ,
We discuss some aspects of the search for CP asymmetry in the three body B
decays, revealed through the interference among neighbor resonances in the
Dalitz plot. We propose a competitive method to extract the CKM angle
combining Dalitz plot amplitude analysis of
and untagged , . The method also obtains the
ratio and phase difference between the {\it tree} and {\it penguin}
contributions from and decays and the
CP asymmetry between and . From Monte Carlo studies of 100K
events for the neutral mesons, we show the possibility of measuring .Comment: Revised enlarged version to appear at Phys Rev
Symmetry energy and neutron-proton radii studies with a Wigner-Heisenberg monopole-monopole interaction
The symmetry energy in nuclei is studied using a monopole-monopole two boby
interaction which has an isospin dependent term. A Hartree theory is developed
for this interaction which has an oscillator shell model basis with
corresponding shell structure. The role of shell structure on the symmetry
energy is then studied. We also find that the strength of the Heisenberg
interaction is very important for understanding the difference between proton
and neutron radii and features associated with halo nuclei.
PACS numbers: 21.10.Sf, 21.65Cd, 21.65EfComment: 1 table, i figur
Capillary acquisition devices for high-performance vehicles: Executive summary
Technology areas critical to the development of cryogenic capillary devices were studied. Passive cooling of capillary devices was investigated with an analytical and experimental study of wicking flow. Capillary device refilling with settled fluid was studied using an analytical and experimental program that resulted in successful correlation of a versatile computer program with test data. The program was used to predict Centaur D-1S LO2 and LH2 start basket refilling. Comparisons were made between the baseline Centaur D-1S propellant feed system and feed system alternatives including systems using capillary devices. The preferred concepts from the Centaur D-1S study were examined for APOTV and POTV vehicles for delivery and round trip transfer of payloads between LEO and GEO. Mission profiles were determined to provide propellant usage timelines and the payload partials were defined
Hints on the quadrupole deformation of the (1232)
The E2/M1 ratio (EMR) of the (1232) is extracted from the world data
in pion photoproduction by means of an Effective Lagrangian Approach (ELA).This
quantity has been derived within a crossing symmetric, gauge invariant, and
chiral symmetric Lagrangian model which also contains a consistent modern
treatment of the (1232) resonance. The \textit{bare} s-channel
(1232) contribution is well isolated and Final State Interactions (FSI)
are effectively taken into account fulfilling Watson's theorem. The obtained
EMR value, EMR%, is in good agreement with the latest lattice
QCD calculations [Phys. Rev. Lett. 94, 021601 (2005)] and disagrees with
results of current quark model calculations.Comment: Enlarged conclusions and explanations on the E2/M1 ratio. Figure 3
improved. References updated. 5 pages. 3 figures. 2 tables. Accepted for
publication in Physical Review
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