18,148 research outputs found
Improving America's competitiveness
Go metric and remove barriers to nationwide branch banking: these are the best ways to improve U.S. export performance in world markets.Balance of trade ; Competition ; Dollar
Dynamical Effects of Nuclear Rings in Disk Galaxies
We investigate the dynamical response of stellar orbits in a rotating barred
galaxy potential to the perturbation by a nuclear gaseous ring. The change in
3D periodic orbit families is examined as the gas accumulates between the inner
Lindblad resonances. It is found that the phase space allowable to the x2
family of orbits is substantially increased and a vertical instability strip
appears with the growing mass of the ring. A significant distortion of the x1
orbits is observed in the vicinity of the ring, which leads to the intersection
between orbits with different values of the Jacobi integral. We also examine
the dependence of the orbital response to the eccentricity and alignment of the
ring with the bar. Misalignment between an oval ring and a bar can leave
observational footprints in the form of twisted near-infrared isophotes in the
vicinity of the ring. It is inferred that a massive nuclear ring acts to weaken
and dissolve the stellar bar exterior to the ring, whereas only weakly
affecting the orbits interior to the inner Lindblad resonances. Consequences
for gas evolution in the circumnuclear regions of barred galaxies are discussed
as well.Comment: 27 pages, 11 postscript figures included, latex using aastex 4.0,
uuencoded compressed tar file, to appear in Ap
Wilson chiral perturbation theory, Wilson-Dirac operator eigenvalues and clover improvement
Chiral perturbation theory for eigenvalue distributions, and equivalently
random matrix theory, has recently been extended to include lattice effects for
Wilson fermions. We test the predictions by comparison to eigenvalue
distributions of the Hermitian Wilson-Dirac operator from pure gauge (quenched)
ensembles. We show that the lattice effects are diminished when using clover
improvement for the Dirac operator. We demonstrate that the leading Wilson
low-energy constants associated with Wilson (clover) fermions can be determined
using spectral information of the respective Dirac operator at finite volume.Comment: Presented at "Xth Quark Confinement and the Hadron Spectrum," October
2012, Garching, Germany. To appear as PoS (Confinement X) 07
Measurements of farfield sound generation from a flow-excited cavity
Results of 1/3-octave-band spectral measurements of internal pressures and the external acoustic field of a tangentially blown rectangular cavity are compared. Proposed mechanisms for sound generation are reviewed, and spectra and directivity plots of cavity noise are presented. Directivity plots show a slightly modified monopole pattern. Frequencies of cavity response are calculated using existing predictions and are compared with those obtained experimentally. The effect of modifying the upstream boundary layer on the noise was investigated, and its effectiveness was found to be a function of cavity geometry and flow velocity
Impact of a process improvement program in a production software environment: Are we any better?
For the past 15 years, Computer Sciences Corporation (CSC) has participated in a process improvement program as a member of the Software Engineering Laboratory (SEL), which is sponsored by GSFC. The benefits CSC has derived from involvement in this program are analyzed. In the environment studied, it shows that improvements were indeed achieved, as evidenced by a decrease in error rates and costs over a period in which both the size and the complexity of the developed systems increased substantially. The principles and mechanics of the process improvement program, the lessons CSC has learned, and how CSC has capitalized on these lessons are also discussed
Framework for non-perturbative analysis of a Z(3)-symmetric effective theory of finite temperature QCD
We study a three dimensional Z(3)-symmetric effective theory of high
temperature QCD. The exact lattice-continuum relations, needed in order to
perform lattice simulations with physical parameters, are computed to order
O(a^0) in lattice perturbation theory. Lattice simulations are performed to
determine the phase structure of a subset of the parameter space.Comment: 28 pages, 11 figures; v3: references rearranged, typos corrected,
figs changed, published versio
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