2,521 research outputs found
Laser ranging ground station development
The employment of ground to conduct radar range measurements of the lunar distance is discussed. The advantages of additional ground stations for this purpose are analyzed. The goals which are desirable for any new type of ranging station are: (1) full time availability of the station for laser ranging, (2) optimization for signal strength, (3) automation to the greatest extent possible, (4) the capability for blind pointing, (5) reasonable initial and modest operational costs, and (6) transportability to enhance the value of the station for geophysical purposes
Density of states of a binary Lennard-Jones Glass
We calculate the density of states of a binary Lennard-Jones glass using a
recently proposed Monte Carlo algorithm. Unlike traditional molecular
simulation approaches, the algorithm samples distinct configurations according
to self-consistent estimates of the density of states, thereby giving rise to
uniform internal-energy histograms. The method is applied to simulate the
equilibrium, low-temperature thermodynamic properties of a widely studied glass
former consisting of a binary mixture of Lennard-Jones particles. We show how a
density-of-states algorithm can be combined with particle identity swaps and
configurational bias techniques to study that system. Results are presented for
the energy and entropy below the mode coupling temperature.Comment: 6 pages, 3 figures, accepted by J Chem Phy
Constant Pressure Hybrid Molecular Dynamics-Monte Carlo Simulations
New hybrid Molecular Dynamics-Monte Carlo methods are proposed to increase
the efficiency of constant-pressure simulations. Two variations of the isobaric
Molecular Dynamics component of the algorithms are considered. In the first, we
use the extended-ensemble method of Andersen [H. C. Andersen J. Chem. Phys.
{\bf 72},2384 (1980)]. In the second, we arrive at a new constant-pressure
Monte Carlo technique based on the reversible generalization of the
weak-coupling barostat [H. J. C. Berendsen et. al J. Chem. Phys. {\bf 81},
3684(1984)]. This latter technique turns out to be highly effective in
equilibrating and maintaining a target pressure. It is superior to the
extended-ensemble method, which in turn is superior to simple volume-rescaling
algorithms. The efficiency of the proposed methods is demonstrated by studying
two systems. The first is a simple Lennard-Jones fluid. The second is a mixture
of polyethylene chains of 200 monomers.Comment: 10 pages, 4 figure
Instability of the Ekman Spiral with Applications to the Planetary Boundary Layers
Spiral boundary layer instability applied to planetary boundary layer
Density of States Monte Carlo Method for Simulation of Fluids
A Monte Carlo method based on a density-of-states sampling is proposed for
study of arbitrary statistical mechanical ensembles in a continuum. A random
walk in the two-dimensional space of particle number and energy is used to
estimate the density of states of the system; this density of states is
continuously updated as the random walk visits individual states. The validity
and usefulness of the method are demonstrated by applying it to the simulation
of a Lennard-Jones fluid. Results for its thermodynamic properties, including
the vapor-liquid phase coexistence curve, are shown to be in good agreement
with high-accuracy literature data.Comment: 5 pages, 3 figures, accepted by J Chem Phy
LANDSAT menhaden and thread herring resources investigation
The author has identified the following significant results. The most significant achievement is the successful charting of high probability fishing areas from LANDSAT MSS data
LANDSAT follow-on experiment: Gulf of Mexico menhaden and thread herring resources investigation
The author has identified the following significant results. The most significant achievement realized is the successful mapping of high probability fishing areas from LANDSAT MSS data for two Mississippi Sound missions
Laser ranging retro-reflector experiment
This report focuses on the Apollo 14 and 15 arrays, and discusses the experiments status.NAS9-11025prepared by J.E. Faller
Multicanonical Parallel Tempering
We present a novel implementation of the parallel tempering Monte Carlo
method in a multicanonical ensemble. Multicanonical weights are derived by a
self-consistent iterative process using a Boltzmann inversion of global energy
histograms. This procedure gives rise to a much broader overlap of
thermodynamic-property histograms; fewer replicas are necessary in parallel
tempering simulations, and the acceptance of trial swap moves can be made
arbitrarily high. We demonstrate the usefulness of the method in the context of
a grand-multicanonical ensemble, where we use multicanonical simulations in
energy space with the addition of an unmodified chemical potential term in
particle-number space. Several possible implementations are discussed, and the
best choice is presented in the context of the liquid-gas phase transition of
the Lennard-Jones fluid. A substantial decrease in the necessary number of
replicas can be achieved through the proposed method, thereby providing a
higher efficiency and the possibility of parallelization.Comment: 8 pages, 3 figure, accepted by J Chem Phy
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