48,023 research outputs found
Reaching large lengths and long times in polymer dynamics simulations
A lattice model is presented for the simulation of dynamics in polymeric
systems. Each polymer is represented as a chain of monomers, residing on a
sequence of nearest-neighbor sites of a face-centered-cubic lattice. The
polymers are self- and mutually avoiding walks: no lattice site is visited by
more than one polymer, nor revisited by the same polymer after leaving it. The
dynamics occurs through single-monomer displacements over one lattice spacing.
To demonstrate the high computational efficiency of the model, we simulate a
dense binary polymer mixture with repelling nearest-neighbor interactions
between the two types of polymers, and observe the phase separation over a long
period of time. The simulations consist of a total of 46,080 polymers, 100
monomers each, on a lattice with 13,824,000 sites, and an interaction strength
of 0.1 kT. In the final two decades of time, the domain-growth is found to be
d(t) ~ t^1/3, as expected for a so-called "Model B" system.Comment: 6 pages, 4 eps figure
Getting a kick out of the stellar disk(s) in the galactic center
Recent observations of the Galactic center revealed a nuclear disk of young
OB stars, in addition to many similar outlying stars with higher eccentricities
and/or high inclinations relative to the disk (some of them possibly belonging
to a second disk). Binaries in such nuclear disks, if they exist in
non-negligible fractions, could have a major role in the evolution of the disks
through binary heating of this stellar system. We suggest that interactions
with/in binaries may explain some (or all) of the observed outlying young stars
in the Galactic center. Such stars could have been formed in a disk, and later
on kicked out from it through binary related interactions, similar to ejection
of high velocity runaway OB stars in young clusters throughout the galaxy.Comment: 2 pages, 2 figs. To be published in the proceedings of the IAU 246
symposium on "Dynamical evolution of dense stellar systems
Machine Learning Chemical Guidelines for Engineering Electronic Structures in Half-Heusler Thermoelectric Materials.
Half-Heusler materials are strong candidates for thermoelectric applications due to their high weighted mobilities and power factors, which is known to be correlated to valley degeneracy in the electronic band structure. However, there are over 50 known semiconducting half-Heusler phases, and it is not clear how the chemical composition affects the electronic structure. While all the n-type electronic structures have their conduction band minimum at either the Γ- or X-point, there is more diversity in the p-type electronic structures, and the valence band maximum can be at either the Γ-, L-, or W-point. Here, we use high throughput computation and machine learning to compare the valence bands of known half-Heusler compounds and discover new chemical guidelines for promoting the highly degenerate W-point to the valence band maximum. We do this by constructing an "orbital phase diagram" to cluster the variety of electronic structures expressed by these phases into groups, based on the atomic orbitals that contribute most to their valence bands. Then, with the aid of machine learning, we develop new chemical rules that predict the location of the valence band maximum in each of the phases. These rules can be used to engineer band structures with band convergence and high valley degeneracy
Improved Limit on theta_{13} and Implications for Neutrino Masses in Neutrino-less Double Beta Decay and Cosmology
We analyze the impact of a measurement, or of an improved bound, on
theta_{13} for the determination of the effective neutrino mass in
neutrino-less double beta decay and cosmology. In particular, we discuss how an
improved limit on (or a specific value of) theta_{13} can influence the
determination of the neutrino mass spectrum via neutrino-less double beta
decay. We also discuss the interplay with improved cosmological neutrino mass
searches.Comment: 22 pages, 5 figures. Minor corrections, matches version in PR
Non-Volatile Magnonic Logic Circuits Engineering
We propose a concept of magnetic logic circuits engineering, which takes an
advantage of magnetization as a computational state variable and exploits spin
waves for information transmission. The circuits consist of magneto-electric
cells connected via spin wave buses. We present the result of numerical
modeling showing the magneto-electric cell switching as a function of the
amplitude as well as the phase of the spin wave. The phase-dependent switching
makes it possible to engineer logic gates by exploiting spin wave buses as
passive logic elements providing a certain phase-shift to the propagating spin
waves. We present a library of logic gates consisting of magneto-electric cells
and spin wave buses providing 0 or p phase shifts. The utilization of phases in
addition to amplitudes is a powerful tool which let us construct logic circuits
with a fewer number of elements than required for CMOS technology. As an
example, we present the design of the magnonic Full Adder Circuit comprising
only 5 magneto-electric cells. The proposed concept may provide a route to more
functional wave-based logic circuitry with capabilities far beyond the limits
of the traditional transistor-based approach
The organization and management of the Virtual Astronomical Observatory
The U.S. Virtual Astronomical Observatory (VAO; http://www.us-vao.org/) has
been in operation since May 2010. Its goal is to enable new science through
efficient integration of distributed multi-wavelength data. This paper
describes the management and organization of the VAO, and emphasizes the
techniques used to ensure efficiency in a distributed organization. Management
methods include using an annual program plan as the basis for establishing
contracts with member organizations, regular communication, and monitoring of
processes.Comment: 9 pages, 3 figures. SPIE Conference 8449: Modeling, Systems
Engineering, and Project Management for Astronomy
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