39,166 research outputs found
Surface-slip equations for multicomponent nonequilibrium air flow
Equations are presented for the surface-slip (or jump) values of species concentration, pressure, velocity, and temperature in the low-Reynolds number, high-altitude flight regime of a space vehicle. The equations are obtained from closed form solutions of the mass, momentum, and energy flux equations using the Chapman-Enskog velocity distribution function. This function represents a solution of the Boltzmann equation in the Navier-Stokes approximation. The analysis, obtained for nonequilibrium multicomponent air flow, includes the finite-rate surface catalytic recombination and changes in the internal energy during reflection from the surface. Expressions for the various slip quantities were obtained in a form which can be employed in flowfield computations. A consistent set of equations is provided for multicomponent, binary, and single species mixtures. Expression is also provided for the finite-rate, species-concentration boundary condition for a multicomponent mixture in absence of slip
Heavy Quarkonium Potential Model and the State of Charmonium
A theoretical explanation of the observed splittings among the P~states of
charmonium is given with the use of a nonsingular potential model for heavy
quarkonia. We also show that the recently observed mass difference between the
center of gravity of the states and the state of
does not provide a direct test of the color hyperfine interaction in heavy
quarkonia. Our theoretical value for the mass of the state is in
agreement with the experimental result, and its E1 transition width is
341.8~keV. The mass of the state is predicted to be 3622.3~MeV.Comment: 15 page REVTEX documen
Batch scheduling to minimize maximum lateness
Cataloged from PDF version of article.We address the single-machine batch scheduling problem which arises when there are job families and setup
requirements exist between these families; our objective is to minimize the maximum lateness. As our main result, we give
an improved dynamic program for the solution of the problem. © 1997 Elsevier Science B.V
Chiral Quark Model with Configuration Mixing
The implications of one gluon exchange generated configuration mixing in the
Chiral Quark Model (QM) with SU(3) and axial U(1) symmetry
breakings are discussed in the context of proton flavor and spin structure as
well as the hyperon -decay parameters. We find that QM
with SU(3) symmetry breaking is able to give a satisfactory unified fit for
spin and quark distribution functions, with the symmetry breaking parameters
, and the mixing angle , both for NMC and the
most recent E866 data. In particular, the agreement with data, in the case of
, F, D, and , is quite striking.Comment: 16 pages, LaTex, Table and Appendix adde
Spin dynamics in electrochemically charged CdSe quantum dots
We use time-resolved Faraday rotation to measure coherent spin dynamics in
colloidal CdSe quantum dots charged in an electrochemical cell at room
temperature. Filling of the 1Se electron level is demonstrated by the bleaching
of the 1Se-1S3/2 absorption peak. One of the two Lande g-factors observed in
uncharged quantum dots disappears upon filling of the 1Se electron state. The
transverse spin coherence time, which is over 1 ns and is limited by
inhomogeneous dephasing, also appears to increase with charging voltage. The
amplitude of the spin precession signal peaks near the half-filling potential.
Its evolution at charging potentials without any observable bleaching of the
1Se-1S3/2 transition suggests that the spin dynamics are influenced by
low-energy surface states.Comment: 4 pages, 4 figure
Emission of intermediate mass fragments from hot Ba formed in low-energy Ni+Ni reaction
The complex fragments (or intermediate mass fragments) observed in the
low-energy Ni+NiBa reaction, are studied within
the dynamical cluster decay model for s-wave with the use of the
temperature-dependent liquid drop, Coulomb and proximity energies. The
important result is that, due to the temperature effects in liquid drop energy,
the explicit preference for -like fragments is washed out, though the
C (or the complementary Sn) decay is still predicted to be one
of the most probable -nucleus decay for this reaction. The production
rates for non- like intermediate mass fragments (IMFs) are now higher
and the light particle production is shown to accompany the IMFs at all
incident energies, without involving any statistical evaporation process in the
model. The comparisons between the experimental data and the (s-wave)
calculations for IMFs production cross sections are rather satisfactory and the
contributions from other -waves need to be added for a further
improvement of these comparisons and for calculations of the total kinetic
energies of fragments.Comment: 22 pages, 15 figure
Spectroscopic insensitivity to cold collisions in a two-state mixture of fermions
We have experimentally demonstrated the absence of spectroscopic resonance
shifts in a mixture of two interacting Fermi gases. This result is linked to
observations in an ultracold gas of thermal bosons. There, the measured
resonance shift due to interstate collisions is independent of the coherence in
the system, and twice that expected from the equilibrium energy splitting
between the two states in a fully decohered cloud. We give a simple theoretical
explanation of these observations, which elucidates the effect of coherent
radiation on an incoherent mixture of atoms
Faraday Rotation Spectroscopy of Quantum-Dot Quantum Wells
Time-resolved Faraday rotation studies of CdS/CdSe/CdS quantum-dot quantum
wells have recently shown that the Faraday rotation angle exhibits several
well-defined resonances as a function of probe energy close to the absorption
edge. Here, we calculate the Faraday rotation angle from the eigenstates of the
quantum-dot quantum well obtained with k.p theory. We show that the large
number of narrow resonances with comparable spectral weight observed in
experiment is not reproduced by the level scheme of a quantum-dot quantum well
with perfect spherical symmetry. A simple model for broken spherical symmetry
yields results in better qualitative agreement with experiment.Comment: 9 pages, 4 figure
Double-Occupancy Errors, Adiabaticity, and Entanglement of Spin-Qubits in Quantum Dots
Quantum gates that temporarily increase singlet-triplet splitting in order to
swap electronic spins in coupled quantum dots, lead inevitably to a finite
double-occupancy probability for both dots. By solving the time-dependent
Schr\"odinger equation for a coupled dot model, we demonstrate that this does
not necessarily lead to quantum computation errors. Instead, the coupled dot
ground state evolves quasi-adiabatically for typical system parameters so that
the double-occupancy probability at the completion of swapping is negligibly
small. We introduce a measure of entanglement which explicitly takes into
account the possibilty of double occupancies and provides a necessary and
sufficient criterion for entangled states.Comment: 9 pages, 4 figures include
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