24,553 research outputs found
A projection method for statics and dynamics of lattice spin systems
A method based on Monte Carlo sampling of the probability flows projected
onto the subspace of one or more slow variables is proposed for investigation
of dynamic and static properties of lattice spin systems. We illustrate the
method by applying it, with projection onto the order-parameter subspace, to
the three-dimensional 3-state Potts model in equilibrium and to metastable
decay in a three-dimensional 3-state kinetic Potts model.Comment: 4 pages, 3 figures, RevTex, final version to appear in Phys. Rev.
Let
Validation of the New Version PNS3DT Code. G.U. Aero Report 9401.
In this Study, the PNS3DT code developed in the University of Glasgow to solve steady compressible parabolized Navier-Stokes equations with Baldwin-Lomax turbulence model is updated. The choice of primitive variables in the numerical scheme, different wall temperature conditions as well as the effect of different grid stretching strategies are tested in detail. Excellent agreement between the numerical and experimental results is observed. Thus, the code could provide a powerful tool to predict the aerodynamics characteristics on the ogive cylinder surface and to simulate the complicate flow structures around the cylinder
Magnetization switching in nanoscale ferromagnetic grains: simulations with heterogeneous nucleation
We present results obtained with various types of heterogeneous nucleation in
a kinetic Ising model of magnetization switching in single-domain ferromagnetic
nanoparticles. We investigate the effect of the presence of the system boundary
and make comparison with simulations on periodic lattices. We also study
systems with bulk disorder and compare how two different types of disorder
influence the switching behavior.Comment: 3 pages, 4 Postscript figure
An FeLoBAL Binary Quasar
In an ongoing infrared imaging survey of quasars at Keck Observatory, we have
discovered that the z=1.285 quasar SDSS J233646.2-010732.6 comprises two point
sources with a separation of 1.67". Resolved spectra show that one component is
a standard quasar with a blue continuum and broad emission lines; the other is
a broad absorption line (BAL) quasar, specifically, a BAL QSO with prominent
absorption from MgII and metastable FeII, making it a member of the ``FeLoBAL''
class. The number of known FeLoBALs has recently grown dramatically from a
single example to more than a dozen, including a gravitationally lensed example
and the binary member presented here, suggesting that this formerly rare object
may be fairly common. Additionally, the presence of this BAL quasar in a
relatively small separation binary adds to the growing evidence that the BAL
phenomenon is not due to viewing a normal quasar at a specific orientation, but
rather that it is an evolutionary phase in the life of many, if not all,
quasars, and is particularly associated with conditions found in interacting
systems.Comment: AASTEX 13 pp., 4 figs; accepted by ApJ Letter
Extreme Long-time Dynamic Monte Carlo Simulations
We study the extreme long-time behavior of the metastable phase of the
three-dimensional Ising model with Glauber dynamics in an applied magnetic
field and at a temperature below the critical temperature. For these
simulations we use the advanced simulation method of projective dynamics. The
algorithm is described in detail, together with its application to the escape
from the metastable state. Our results for the field dependence of the
metastable lifetime are in good agreement with theoretical expectations and
span more than fifty decades in time.Comment: 13 pages with embedded eps figures. Int. J. Mod. Phys. C, in pres
Long-range electron transfer in structurally engineered pentaammineruthenium (histidine-62) cytochrome c
In many biological processes, long-range electron transfer (ET) plays a key role. When the three-dimensional structures of proteins are accurately known, use of modified proteins and protein-protein complexes provides an experimental approach to study ET rates between two metal centers. For Ru(His)- modified proteins, the introduction of histidine residues at any desired surface location by site-directed mutagenesis opens the way for systematic investigations of ET pathways
Preliminary analysis of performance and loads data from the 2-megawatt mod-1 wind turbine generator
Preliminary test data on output power versus wind speed, rotor blade loads, system dynamic behavior, and start-stop characteristics on the Mod-1 wind turbine generator are presented. These data were analyzed statistically and are compared with design predictions of system performance and loads. To date, the Mod-1 wind turbine generator has produced up to 1.5 MW of power, with a measured power versus wind speed curve which agrees closely with design. Blade loads were measured at wind speeds up to 14 m/s and also during rapid shutdowns. Peak transient loads during the most severe shutdowns are less than the design limit loads. On the inboard blade sections, fatigue loads are approximately equal to the design cyclic loads. On the outboard blade sections, however, measured cyclic loads are significantly larger than design values, but they do not appear to exceed fatigue allowable loads as yet
Charge trapping in polymer transistors probed by terahertz spectroscopy and scanning probe potentiometry
Terahertz time-domain spectroscopy and scanning probe potentiometry were used
to investigate charge trapping in polymer field-effect transistors fabricated
on a silicon gate. The hole density in the transistor channel was determined
from the reduction in the transmitted terahertz radiation under an applied gate
voltage. Prolonged device operation creates an exponential decay in the
differential terahertz transmission, compatible with an increase in the density
of trapped holes in the polymer channel. Taken in combination with scanning
probe potentionmetry measurements, these results indicate that device
degradation is largely a consequence of hole trapping, rather than of changes
to the mobility of free holes in the polymer.Comment: 4 pages, 3 figure
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