9,412 research outputs found
Extended Lie Algebraic Stability Analysis for Switched Systems with Continuous-Time and Discrete-Time Subsystems
Superconducting magnesium diboride films on Silicon with Tc0 about 24K grown via vacuum annealing from stoichiometric precursors
Superconducting magnesium diboride films with Tc0 ~ 24 K and sharp transition
\~ 1 K were successfully prepared on silicon substrates by pulsed laser
deposition from a stoichiometric MgB2 target. Contrary to previous reports,
anneals at 630 degree and a background of 2x10^(-4) torr Ar/4%H2 were performed
without the requirement of Mg vapor or an Mg cap layer. This integration of
superconducting MgB2 films on silicon may thus prove enabling in
superconductor-semiconductor device applications. Images of surface morphology
and cross-section profiles by scanning electron microscopy (SEM) show that the
films have a uniform surface morphology and thickness. Energy dispersive
spectroscopy (EDS) reveals these films were contaminated with oxygen,
originating either from the growth environment or from sample exposure to air.
The oxygen contamination may account for the low Tc for those in-situ annealed
films, while the use of Si as the substrate does not result in a decrease in Tc
as compared to other substrates.Comment: 5 pages, 4 figures, 15 references; due to file size limit, images
were blure
Two-dimensional molecular para-hydrogen and ortho-deuterium at zero temperature
We study molecular para-hydrogen (p-) and ortho-deuterium
(o-) in two dimensions and in the limit of zero temperature by
means of the diffusion Monte Carlo method. We report energetic and structural
properties of both systems like the total and kinetic energy per particle,
radial pair distribution function, and Lindemann's ratio in the low pressure
regime. By comparing the total energy per particle as a function of the density
in liquid and solid p-, we show that molecular para-hydrogen, and
also ortho-deuterium, remain solid at zero temperature. Interestingly, we
assess the quality of three different symmetrized trial wave functions, based
on the Nosanow-Jastrow model, in the p- solid film at the
variational level. In particular, we analyze a new type of symmetrized trial
wave function which has been used very recently to describe solid He and
found that also characterizes hydrogen satisfactorily. With this wave function,
we show that the one-body density matrix of solid p- possesses off-diagonal long range order, with a condensate fraction
that increases sizably in the negative pressure regime.Comment: 11 pages, 9 figure
FUNCTIONALIZATION OF REGIOREGULAR HEAD-TO-TAIL POLY(3-ALKYLTHIOPHENES) SIDE CHAIN
Conjugated polymers possess several intriguing properties including high electrical conductivity, fast and large nonlinear optical responses and visible wavelength chromaticity. Layer by layer conducting polymer structures are even more interesting because they offer many potentia
On the error term in Weyl's law for the Heisenberg manifolds (II)
In this paper we study the mean square of the error term in the Weyl's law of
an irrational -dimensional Heisenberg manifold . An asymptotic formula
is established
Online Forum Thread Retrieval using Pseudo Cluster Selection and Voting Techniques
Online forums facilitate knowledge seeking and sharing on the Web. However,
the shared knowledge is not fully utilized due to information overload. Thread
retrieval is one method to overcome information overload. In this paper, we
propose a model that combines two existing approaches: the Pseudo Cluster
Selection and the Voting Techniques. In both, a retrieval system first scores a
list of messages and then ranks threads by aggregating their scored messages.
They differ on what and how to aggregate. The pseudo cluster selection focuses
on input, while voting techniques focus on the aggregation method. Our combined
models focus on the input and the aggregation methods. The result shows that
some combined models are statistically superior to baseline methods.Comment: The original publication is available at
http://www.springerlink.com/. arXiv admin note: substantial text overlap with
arXiv:1212.533
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