67,548 research outputs found
Homogeneous SPC/E water nucleation in large molecular dynamics simulations
We perform direct large molecular dynamics simulations of homogeneous SPC/E
water nucleation, using up to molecules. Our large system
sizes allow us to measure extremely low and accurate nucleation rates, down to
, helping close the gap between
experimentally measured rates .
We are also able to precisely measure size distributions, sticking
efficiencies, cluster temperatures, and cluster internal densities. We
introduce a new functional form to implement the Yasuoka-Matsumoto nucleation
rate measurement technique (threshold method). Comparison to nucleation models
shows that classical nucleation theory over-estimates nucleation rates by a few
orders of magnitude. The semi-phenomenological nucleation model does better,
under-predicting rates by at worst, a factor of 24. Unlike what has been
observed in Lennard-Jones simulations, post-critical clusters have temperatures
consistent with the run average temperature. Also, we observe that
post-critical clusters have densities very slightly higher, , than
bulk liquid. We re-calibrate a Hale-type vs. scaling relation using
both experimental and simulation data, finding remarkable consistency in over
orders of magnitude in the nucleation rate range, and K in the
temperature range.Comment: Accepted for publication in the Journal of Chemical Physic
Dynamic Tax Competition under Asymmetric Productivity of Public Capital
We here expand the static tax competition models in symmetric small regions, which were indicated by Zodrow and Mieszkowski (1986) and Wilson (1986), to a dynamic tax competition model in large regions, taking consideration of the regional asymmetry of productivity of public capital and the existence of capital accumulation. The aim of this paper is to verify how the taxation policy affects asymmetric equilibrium based on a simulation analysis using an overlapping generations model in two regions. It is assumed that the public capital as a public input is formed on the basis of the capital tax of local governments and the lump-sum tax of the central government. As demonstrated in related literature, the optimal capital tax rate should become zero when the lump-sum tax is imposed only on older generations, however, the optimal tax rate may become positive when it is imposed proportionally on younger and older generations. In the asymmetric equilibrium, several cooperative solutions can possibly exist which can achieve a higher welfare standard than the actualized cooperative solution either in Region1 or 2
The flares of August 1972
Analysis is made of observations of the August, 1972 flares at Big Bear and Tel Aviv, involving monochromatic movies, magnetograms, and spectra. In each flare the observations fit a model of particle acceleration in the chromosphere with emission produced by impart and by heating by the energetic electrons and protons. The region showed twisted flux and high gradients from birth, and flares appear due to strong magnetic shears and gradients across the neutral line produced by sunspot motions. Post flare loops show a strong change from sheared, force-free fields parallel to potential-field-like loops, perpendicular to the neutral line above the surface
Three-dimensional eddy current analysis by the boundary element method using vector potential
A boundary-element method using a magnetic vector potential for eddy-current analysis is described. For three-dimensional (3-D) problems, the tangential and normal components of the vector potential, tangential components of the magnetic flux density, and an electric scalar potential on conductor surfaces are chosen as unknown variables. When the approximation is introduced so that the conductivity of the conductor is very large in comparison with the conductivity of air, the number of unknowns can be reduced; also, for axisymmetric models the scalar potential can be eliminated from the unknown variables. The formulation of the boundary-element method using the vector potential, and computation results by the proposed method, are presented </p
Stability of ferromagnetism in the Hubbard model on the kagom\'e lattice
The Hubbard model on the kagom\'e lattice has highly degenerate ground states
(the flat lowest band) in the corresponding single-electron problem and
exhibits the so-called flat-band ferromagnetism in the many-electron ground
states as was found by Mielke. Here we study the model obtained by adding extra
hopping terms to the above model. The lowest single-electron band becomes
dispersive, and there is no band gap between the lowest band and the other
band. We prove that, at half-filling of the lowest band, the ground states of
this perturbed model remain saturated ferromagnetic if the lowest band is
nearly flat.Comment: 4 pages, 1 figur
Theory of AC Anomalous Hall Conductivity in d-electron systems
To elucidate the intrinsic nature of anomalous Hall effect (AHE) in
-electron systems, we study the AC anomalous Hall conductivity (AHC) in a
tight-binding model with ()-orbitals. We drive a general
expression for the AC AHC , which is valid for finite
quasiparticle damping rate =, and find that the AC AHC is
strongly dependent on . When , the AC AHC shows a spiky peak
at finite energy that originates from the interband particle-hole
excitation, where represents the minimum band-splitting measured from
the Fermi level. In contrast, we find that this spiky peak is quickly
suppressed when is finite. By using a realistic value of
at in -electron systems, the spiky peak
is considerably suppressed. In the present model, the obtained results also
represents the AC spin Hall conductivity in a paramagnetic state.Comment: 13pages, 9 figure
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