25,277 research outputs found
Rotation misorientated graphene moire superlattices on Cu(111): classical molecular dynamics simulations and scanning tunneling microscopy studies
Graphene on copper is a system of high technological relevance, as Cu is one
of the most widely used substrates for the CVD growth of graphene. However,
very little is known about the details of their interaction. One approach to
gain such information is studying the superlattices emerging due to the
mismatch of the two crystal lattices. However, graphene on copper is a
low-corrugated system making both their experimental and theoretical study
highly challenging. Here, we report the observation of a new rotational Moire
superlattice of CVD graphene on Cu (111), characterized by a periodicity of
nm and corrugation of , as measured
by Scanning Tunneling Microscopy. To understand the observed superlattice we
have developed a newly parameterized Tersoff-potential for the graphene/Cu
(111) interface fitted to nonlocal van der Waals density functional theory
(DFT) calculations. The interfacial force field with time-lapsed CMD provides
superlattices in good quantitative agreement with the experimental results, for
a misorientation angle of without any further parameter
adjustment. Furthermore, the CMD simulations predict the existence of two
non-equivalent high-symmetry directions of the Moir\'e pattern that could also
be identified in the experimental STM images.Comment: 7 pages, 2 figures, 2 table
Singularities in scalar-tensor gravity
The analysis of certain singularities in scalar-tensor gravity contained in a
recent paper is completed, and situations are pointed out in which these
singularities cannot occur.Comment: 6 pages, LaTe
The Origin of Structures in Generalized Gravity
In a class of generalized gravity theories with general couplings between the
scalar field and the scalar curvature in the Lagrangian, we can describe the
quantum generation and the classical evolution of both the scalar and tensor
structures in a simple and unified manner. An accelerated expansion phase based
on the generalized gravity in the early universe drives microscopic quantum
fluctuations inside a causal domain to expand into macroscopic ripples in the
spacetime metric on scales larger than the local horizon. Following their
generation from quantum fluctuations, the ripples in the metric spend a long
period outside the causal domain. During this phase their evolution is
characterized by their conserved amplitudes. The evolution of these
fluctuations may lead to the observed large scale structures of the universe
and anisotropies in the cosmic microwave background radiation.Comment: 5 pages, latex, no figur
Lines on projective varieties and applications
The first part of this note contains a review of basic properties of the
variety of lines contained in an embedded projective variety and passing
through a general point. In particular we provide a detailed proof that for
varieties defined by quadratic equations the base locus of the projective
second fundamental form at a general point coincides, as a scheme, with the
variety of lines. The second part concerns the problem of extending embedded
projective manifolds, using the geometry of the variety of lines. Some
applications to the case of homogeneous manifolds are included.Comment: 15 pages. One example removed; one remark and some references added;
typos correcte
Cosmological Gravitational Wave in a Gravity with Quadratic Order Curvature Couplings
We present a set of equations describing the cosmological gravitational wave
in a gravity theory with quadratic order gravitational coupling terms which
naturally arise in quantum correction procedures. It is known that the
gravitational wave equation in the gravity theories with a general term
in the action leads to a second order differential equation with the only
correction factor appearing in the damping term. The case for a
term is completely different. The gravitational wave is described by a fourth
order differential equation both in time and space. However, curiously, we find
that the contributions to the background evolution are qualitatively the same
for both terms.Comment: 4 pages, revtex, no figure
A General Phase Matching Condition for Quantum Searching Algorithm
A general consideration on the phase rotations in quantum searching algorithm
is taken in this work. As four phase rotations on the initial state, the marked
states, and the states orthogonal to them are taken account, we deduce a phase
matching condition for a successful search. The optimal options for these phase
are obtained consequently.Comment: 3 pages, 3 figure
Evaluation of a Liquid Amine System for Spacecraft Carbon Dioxide Control
The analytical and experimental studies are described which were directed toward the acquisition of basic information on utilizing a liquid amine sorbent for in use in a CO2 removal system for manned spacecraft. Liquid amine systems are successfully used on submarines for control of CO2 generated by the crew, but liquid amines were not previously considered for spacecraft applications due to lack of development of satisfactory rotary phase separators. Developments in this area now make consideration of liquid amines practical for spacecraft system CO2 removal. The following major tasks were performed to evaluate liquid amine systems for spacecraft: (1) characterization, through testing, of the basic physical and thermodynamic properties of the amine solution; (2) determination of the dynamic characteristics of a cocurrent flow absorber; and (3) evaluation, synthesis, and selection of a liquid amine system concept oriented toward low power requirements. A low weight, low power system concept was developed. Numerical and graphical data are accompanied by pertinent observations
Formation and Propagation of Discontinuity for Boltzmann Equation in Non-Convex Domains
The formation and propagation of singularities for Boltzmann equation in
bounded domains has been an important question in numerical studies as well as
in theoretical studies. Consider the nonlinear Boltzmann solution near
Maxwellians under in-flow, diffuse, or bounce-back boundary conditions. We
demonstrate that discontinuity is created at the non-convex part of the grazing
boundary, then propagates only along the forward characteristics inside the
domain before it hits on the boundary again.Comment: 39 pages, 5 Figure
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