53,421 research outputs found
Strain engineered graphene using a nanostructured substrate: II Pseudo-magnetic fields
The strain induced pseudo-magnetic field in supported graphene deposited on
top of a nanostructured substrate is investigated by using atomistic
simulations. Step, elongated trench, one dimensional barrier, spherical
bubbles, Gaussian bump and Gaussian depression are considered as support
structures for graphene. From the obtained optimum configurations we found very
strong induced pseudo-magnetic fields which can reach up to 1000\,T due
to the strain-induced deformations in the supported graphene. Different
magnetic confinements with controllable geometries are found by tuning the
pattern of the substrate. The resulting induced magnetic fields for graphene on
top of a step, barrier and trench are calculated. In contrast to the step and
trench the middle part of graphene on top of a barrier has zero pseudo-magnetic
field. This study provides a theoretical background for designing magnetic
structures in graphene by nanostructuring substrates. We found that altering
the radial symmetry of the deformation, changes the six-fold symmetry of the
induced pseudo-magnetic field.Comment: 7 pages, 9 figures, To appear in Phys. Rev.
Self-diffusion in a monatomic glassforming liquid embedded in the hyperbolic plane
We study by Molecular Dynamics simulation the slowing down of particle motion
in a two-dimensional monatomic model: a Lennard-Jones liquid on the hyperbolic
plane. The negative curvature of the embedding space frustrates the long-range
extension of the local hexagonal order. As a result, the liquid avoids
crystallization and forms a glass. We show that, as temperature decreases, the
single particle motion displays the canonical features seen in real
glassforming liquids: the emergence of a "plateau" at intermediate times in the
mean square displacement and a decoupling between the local relaxation time and
the (hyperbolic) diffusion constant.Comment: Article for the "11th International Workshop on Complex Systems
An experimental investigation of vortex breakdown on a delta wing
An experimental investigation of vortex breakdown on delta wings at high angles is presented. Thin delta wings having sweep angles of 70, 75, 80 and 85 degrees are being studied. Smoke flow visualization and the laser light sheet technique are being used to obtain cross-sectional views of the leading edge vortices as they break down. At low tunnel speeds (as low as 3 m/s) details of the flow, which are usually imperceptible or blurred at higher speeds, can be clearly seen. A combination of lateral and longitudinal cross-sectional views provides information on the three dimensional nature of the vortex structure before, during and after breakdown. Whereas details of the flow are identified in still photographs, the dynamic characteristics of the breakdown process were recorded using high speed movies. Velocity measurements were obtained using a laser Doppler anemometer with the 70 degree delta wing at 30 degrees angle of attack. The measurements show that when breakdown occurs the core flow transforms from a jet-like flow to a wake-like flow
Computer-aided processing of LANDSAT MSS data for classification of forestlands
There are no author-identified significant results in this report
The generalized Fenyes-Nelson model for free scalar field theory
The generalized Fenyes--Nelson model of quantum mechanics is applied to the
free scalar field. The resulting Markov field is equivalent to the Euclidean
Markov field with the times scaled by a common factor which depends on the
diffusion parameter. This result is consistent between Guerra's earlier work on
stochastic quantization of scalar fields. It suggests a deep connection between
Euclidean field theory and the stochastic interpretation of quantum mechanics.
The question of Lorentz covariance is also discussed.Comment: 6 page
New shield for gamma-ray spectrometry
Gamma-ray shield that can be evacuated, refilled with a clean gas, and pressurized for exclusion of airborne radioactive contaminants effectively lowers background noise. Under working conditions, repeated evacuation and filling procedures have not adversely affected the sensitivity and resolution of the crystal detector
Evaluation of an advanced directionally solidified gamma/gamma'-alpha Mo eutectic alloy
An attempt was made to improve on the properties of the candidate jet engine turbine blade material AG-60, a gamma/gamma prime-alpha Mo eutectic composite. Alloy 38 (AG-170) was evaluated in the greatest detail. This alloy, Ni-5.88 A1-29.74 Mo-1.65 V-1.2C Re (weight percent), represents an improvement beyond AG-60, based on mechanical testing of the transverse and/or longitudinal orientations over a range of temperatures in tension, shear, rupture, and rupture after thermal exposure. It is likely that other alloys in the study represent a similar improvement
Strain engineered graphene using a nanostructured substrate: I Deformations
Using atomistic simulations we investigate the morphological properties of
graphene deposited on top of a nanostructured substrate. Sinusoidally
corrugated surfaces, steps, elongated trenches, one dimensional and cubic
barriers, spherical bubbles, Gaussian bump and Gaussian depression are
considered as support structures for graphene. The graphene-substrate
interaction is governed by van der Waals forces and the profile of the graphene
layer is determined by minimizing the energy using molecular dynamics
simulations. Based on the obtained optimum configurations, we found that: (i)
for graphene placed over sinusoidally corrugated substrates with corrugation
wave lengths longer than 2\,nm, the graphene sheet follows the substrate
pattern while for supported graphene it is always suspended across the peaks of
the substrate, (ii) the conformation of graphene to the substrate topography is
enhanced when increasing the energy parameter in the van der Waals model, (iii)
the adhesion of graphene into the trenches depends on the width of the trench
and on graphene's orientation, i.e. in contrast to a small width (3 nm)
nanoribbon with armchair edges, the one with zig-zag edges follows the
substrate profile, (iv) atomic scale graphene follows a Gaussian bump substrate
but not the substrate with a Gaussian depression, and (v) the adhesion energy
due to van der Waals interaction varies in the range [0.1-0.4] J/m^2.Comment: 12 pages and 16 figures, To appear in Phys. Rev.
Superspace Formulation for the BRST Quantization of the Chiral Schwinger Model
It has recently been shown that the Field Antifield quantization of anomalous
irreducible gauge theories with closed algebra can be represented in a BRST
superspace where the quantum action at one loop order, including the Wess
Zumino term, and the anomalies show up as components of the same superfield. We
show here how the Chiral Schwinger model can be represented in this
formulation.Comment: 11 pages, Late
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