2,763 research outputs found
A unified 'bang-bang' principle with respect to R-invariant performance benchmarks
published_or_final_versio
Proper motions with Subaru I. Methods and a first sample in the Subaru Deep Field
We search for stars with proper motions in a set of twenty deep Subaru
images, covering about 0.28 square degrees to a depth of i ~ 25, taken over a
span of six years. In this paper, we describe in detail our reduction and
techniques to identify moving objects. We present a first sample of 99 stars
with motions of high significance, and discuss briefly the populations from
which they are likely drawn. Based on photometry and motions alone, we expect
that 9 of the candidates may be white dwarfs. We also find a group of stars
which may be extremely metal-poor subdwarfs in the halo.Comment: 12 pages, 8 figures, submitted to PAS
The Growth Of Highly Doped p-GaN On Sapphire By RF Plasma-Assisted Molecular Beam Epitaxy.
In this paper, we present the study of the electrical, structural and optical properties of p-type GaN grown on sapphire by RF plasma-assisted molecular beam epitaxy
(RF-MBE)
Effects Of Thermal Annealing Of Pt Schottky Contacts On n-GaN.
In this paper, the Schottky behavior of Pt contact on n- GaN grown by RF-plasma assisted molecular beam epitaxy was investigated under different annealing temperatures
Time-dependent density-functional theory for open systems
By introducing the self-energy density functionals for the dissipative
interactions between the reduced system and its environment, we develop a
time-dependent density-functional theory formalism based on an equation of
motion for the Kohn-Sham reduced single-electron density matrix of the reduced
system. Two approximate schemes are proposed for the self-energy density
functionals, the complete second order approximation and the wide-band limit
approximation. A numerical method based on the wide-band limit approximation is
subsequently developed and implemented to simulate the steady and transient
current through various realistic molecular devices. Simulation results are
presented and discussed.Comment: 16 pages, 12 figure
Intracluster supernovae in the Multi-epoch Nearby Cluster Survey
The Multi-Epoch Nearby Cluster Survey (MENeaCS) has discovered twenty-three
cluster Type Ia supernovae (SNe) in the 58 X-ray selected galaxy clusters (0.05
< z < 0.15) surveyed. Four of our SN Ia events have no host galaxy on close
inspection, and are likely intracluster SNe. Deep image stacks at the location
of the candidate intracluster SNe put upper limits on the luminosities of faint
hosts, with M_{r} > -13.0 mag and M_{g} > -12.5 mag in all cases. For such
limits, the fraction of the cluster luminosity in faint dwarfs below our
detection limit is <0.1%, assuming a standard cluster luminosity function. All
four events occurred within ~600 kpc of the cluster center (projected), as
defined by the position of the brightest cluster galaxy, and are more centrally
concentrated than the cluster SN Ia population as a whole. After accounting for
several observational biases that make intracluster SNe easier to discover and
spectroscopically confirm, we calculate an intracluster stellar mass fraction
of 0.16^{+0.13}_{-0.09} (68% CL) for all objects within R_{200}. If we assume
that the intracluster stellar population is exclusively old, and the cluster
galaxies themselves have a mix of stellar ages, we derive an upper limit on the
intracluster stellar mass fraction of <0.47 (84% one-sided CL). When combined
with the intragroup SNe results of McGee & Balogh, we confirm the declining
intracluster stellar mass fraction as a function of halo mass reported by
Gonzalez and collaborators. (Abridged)Comment: 24 pages, 8 figures, ApJ publishe
Phase ordering and roughening on growing films
We study the interplay between surface roughening and phase separation during
the growth of binary films. Already in 1+1 dimension, we find a variety of
different scaling behaviors depending on how the two phenomena are coupled. In
the most interesting case, related to the advection of a passive scalar in a
velocity field, nontrivial scaling exponents are obtained in simulations.Comment: 4 pages latex, 6 figure
3D oceanographic data compression using 3D-ODETLAP
This paper describes a 3D environmental data compression technique for oceanographic datasets. With proper point selection, our method approximates uncompressed marine data using an over-determined system of linear equations based on, but essentially different from, the Laplacian partial differential equation. Then this approximation is refined via an error metric. These two steps work alternatively until a predefined satisfying approximation is found. Using several different datasets and metrics, we demonstrate that our method has an excellent compression ratio. To further evaluate our method, we compare it with 3D-SPIHT. 3D-ODETLAP averages 20% better compression than 3D-SPIHT on our eight test datasets, from World Ocean Atlas 2005. Our method provides up to approximately six times better compression on datasets with relatively small variance. Meanwhile, with the same approximate mean error, we demonstrate a significantly smaller maximum error compared to 3D-SPIHT and provide a feature to keep the maximum error under a user-defined limit
Helium Shell Detonations on Low Mass White Dwarfs as a Possible Explanation for SN 2005E
Recently several type Ib supernovae (SNe; with the prototypical SN 2005E)
have been shown to have atypical properties. These SNe are faint (absolute peak
magnitude of ~ -15) and fast SNe that show unique composition. They are
inferred to have low ejecta mass (a few tenths of a solar mass) and to be
highly enriched in calcium, but poor in silicon elements and nickel. These SNe
were therefore suggested to belong to a new class of calcium-rich faint SNe
explosions. Their properties were proposed to be the result of helium
detonations that may occur on helium accreting white dwarfs. In this paper we
theoretically study the scenario of helium detonations, and focus on the
results of detonations in accreted helium layers on low mass carbon-oxygen (CO)
cores. We present new results from one dimensional simulations of such
explosions, including their light curves and spectra. We find that when the
density of the helium layer is low enough the helium detonation produces large
amounts of intermediate elements, such as calcium and titanium, together with a
large amount of unburnt helium. Our results suggest that the properties of
calcium-rich faint SNe could indeed be consistent with the helium-detonation
scenario on small CO cores. Above a certain density (larger CO cores) the
detonation leaves mainly 56Ni and unburnt helium, and the predicted spectrum
will unlikely fit the unique features of this class of SNe. Finally, none of
our studied models reproduces the bright, fast evolving light curves of another
type of peculiar SNe suggested to originate in helium detonations (SNe 1885A,
1939B and 2002bj).Comment: 15 pages, 8 figure
Dynamic scaffold of chiral binaphthol derivatives with the alkynylplatinum(II) terpyridine moiety
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