99,942 research outputs found
Vectorized Monte Carlo methods for reactor lattice analysis
Some of the new computational methods and equivalent mathematical representations of physics models used in the MCV code, a vectorized continuous-enery Monte Carlo code for use on the CYBER-205 computer are discussed. While the principal application of MCV is the neutronics analysis of repeating reactor lattices, the new methods used in MCV should be generally useful for vectorizing Monte Carlo for other applications. For background, a brief overview of the vector processing features of the CYBER-205 is included, followed by a discussion of the fundamentals of Monte Carlo vectorization. The physics models used in the MCV vectorized Monte Carlo code are then summarized. The new methods used in scattering analysis are presented along with details of several key, highly specialized computational routines. Finally, speedups relative to CDC-7600 scalar Monte Carlo are discussed
Dipole and Quadrupole electroexcitations of the isovector T=1 particle-hole states in C-12
Electroexcitations of the dominantly T=1 particle-hole states of C-12 are
studied in the framework of the harmonic oscillator shell model. All possible
T=1 single-particle-hole states of all allowed angular momenta are considered
in a basis including single-particle states up to the 1f-2p shell. The
Hamiltonian is diagnoalized in this space in the presence of the modified
surface delta interaction. Correlation in the ground state wave functions by
mixing more than one configuration is considered and shows a major contribution
that leads to enhance the calculations of the form factors. A comparison with
the experiment shows that this model is able to fit the location of states and
a simple scaling of the results give a good fit to the experimental form
factors.Comment: 5 pages, 4 figures, 5 tables, Late
New T=1 effective interactions for the f5/2 p3/2 p1/2 g9/2 model space; Implications for valence-mirror symmetry and seniority isomers
New shell model Hamiltonians are derived for the T=1 part of the residual
interaction in the f5/2 p3/2 p1/2 g9/2 model space based on the analysis and
fit of the available experimental data for 57Ni-78Ni isotopes and 77Cu-100Sn
isotones. The fit procedure, properties of the determined effective interaction
as well as new results for valence-mirror symmetry and seniority isomers for
nuclei near 78Ni and 100Sn are discussed.Comment: 4 pages, 5 figure
Women, employment, and child care in Washington State
Thesis (M.C.P.)--Massachusetts Institute of Technology, Dept. of Urban Studies and Planning, 1986.MICROFICHE COPY AVAILABLE IN ARCHIVES AND ROTCHBibliography: leaves 41-52.by Eric B.F. Brown.M.C.P
Macroscopic amplification of electroweak effects in molecular Bose-Einstein condensates
We investigate the possible use of Bose-Einstein condensates of diatomic
molecules to measure nuclear spin-dependent parity violation effects, outlining
a detection method based on the internal Josephson effect between molecular
states of opposite parity. When applied to molecular condensates, the fine
experimental control achieved in atomic bosonic Josephson junctions could
provide data on anapole moments and neutral weak couplings.Comment: 5 pages. To be published Phys. Rev. A (Rapid Communication) (2012
Theoretical and Experimental Studies of Cambered and Twisted Wings Optimized for Flight at Supersonic Speeds
No abstract availabl
Kepler and the Kuiper Belt
The proposed field-of-view of the Kepler mission is at an ecliptic latitude
of ~55 degrees, where the surface density of scattered Kuiper Belt Objects
(KBOs) is a few percent that in the ecliptic plane. The rate of occultations of
Kepler target stars by scattered KBOs with radii r>10km is ~10^-6 to 10^-4 per
star per year, where the uncertainty reflects the current ignorance of the
thickness of the scattered KBO disk and the faint-end slope of their magnitude
distribution. These occultation events will last only ~0.1% of the planned
t_exp=15 minute integration time, and thus will appear as single data points
that deviate by tiny amounts. However, given the target photometric accuracy of
Kepler, these deviations will nevertheless be highly significant, with typical
signal-to-noise ratios of ~10. I estimate that 1-20 of the 10^5 main-sequence
stars in Kepler's field-of-view will exhibit detectable occultations during its
four-year mission. For unresolved events, the signal-to-noise of individual
occultations scales as t_exp^{-1/2}, and the minimum detectable radius could be
decreased by an order of magnitude to ~1 km by searching the individual
3-second readouts for occultations. I propose a number of methods by which
occultation events may be differentiated from systematic effects. Kepler should
measure or significantly constrain the frequency of highly-inclined, ~10
km-sized KBOs.Comment: 5 pages, 1 figure. No changes. Accepted to ApJ, to appear in the
August 1, 2004 issue (v610
Influence of Charge Order on the Ground States of TMTTF Molecular Salts
(TMTTF)2AsF6 and (TMTTF)2SbF6 are both known to undergo a charge ordering
phase transition, though their ground states are different. The ground state of
the first is Spin-Peierls, and the second is an antiferromagnet. We study the
effect of pressure on the ground states and the charge-ordering using 13C NMR
spectroscopy. The experiments demonstrate that the the CO and SP order
parameters are repulsive, and consequently the AF state is stabilized when the
CO order parameter is large, as it is for (TMTTF)2SbF6. An extension of the
well-known temperature/pressure phase diagram is proposed.Comment: 5pages, 5 figures, Proceeding of ISCOM2003, to appear in Journal de
Physique I
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