823 research outputs found
Antarctic Glacial and Subglacial Topography
1. The data is collected and generalized according to 48,000km of surface traverses in Antarctica during the last 15 years. An evaluation is made of reliability of material and methods of study of the ice cover thickness, evaluation of precision of levelling methods and prospects of aeromagnetic, radar and electrical methods for the study of the ice cover thickness of Antarctica. Methods are suggested which allow to make indirect evaluation of the relief of the subglacial bed of Antarctica according to the relief and inclination of the sufrace, crevassing of the ice cover and geological structures. 2. By application of the material on subglacial bed relief YU.N. AVSYUK, L.I. IVASHUTINA, A.P. KAPITZA and O.G. SOROKHTIN compiled the map of subglacial bed relief of Antarctica. The horizontal contours are drawn every 500m. In the process of Antarctic researches new large forms of sub-ice relief were revealed : Gamburtsev Mts., Vernadsky Mts., Golitsin Mts., Shchukin Mts., Schmidt Plateau, East Plateau, West Plateau. In the process of generalization of materials large faults were found in Antarctica : the Trans-Antarctic trough. 3. The map of the thickness of ice cover in Antarctica has been made by the method of graphical subtraction by using the map of subglacial relief of Antarctica and the map of ice cover surface. The amount of ice in Antarctica was estimated according to that map, which makes 24 million km^3 of ice. 4. On the basis of the analysis of the map of ice cover surface a map has been compiled of the lines of ice flow, and the main ice divides and centers of ice diffluence in Antarctica were determined. 5. Geophysical data testify that the earth\u27s crust in Antarctica is in the state of isostatic equilibrium, while at the same time separate forms of the relief have deviations of mean values of the free air anomaly, which allow to propose a hypothesis about the general reduction of the ice cover of Antarctica in the Holocene. The general retreat of glaciers does not contradict the separate data about shortperiod (within tens or hundreds of years) advances of ice cover edge. 7. The analysis of data about the subglacial relief of Antarctica has been used in calculation of the uprising values of the earth\u27s crust after deglaciation, and a map is compiled predicting contours of the continent in the Post-Glacial Period with compensational uprising. 8. Major trends are suggested of the study of subglacial bed of Antarctica and of the ice cover relief for the solution of the most important glaciological and geomorphological problems of Antarctica
Thermal boundary resistance at Si/Ge interfaces determined by approach-to-equilibrium molecular dynamics simulations
The thermal boundary resistance of Si/Ge interfaces as been determined using
approach-to-equilibrium molecular dynamics simulations. Assuming a reciprocal
linear dependence of the thermal boundary resistance, a length-independent bulk
thermal boundary resistance could be extracted from the calculation resulting
in a value of 3.76x10 m K/W for a sharp Si/Ge interface and thermal
transport from Si to Ge. Introducing an interface with finite thickness of 0.5
nm consisting of a SiGe alloy, the bulk thermal resistance slightly decreases
compared to the sharp Si/Ge interface. Further growth of the boundary leads to
an increase in the bulk thermal boundary resistance. When the heat flow is
inverted (Ge to Si), the thermal boundary resistance is found to be higher.
From the differences in the thermal boundary resistance for different heat flow
direction, the rectification factor of the Si/Ge has been determined and is
found to significantly decrease when the sharp interface is moderated by
introduction of a SiGe alloy in the boundary layer.Comment: 7 pages, 6 figure
Possible field-tuned SIT in high-Tc superconductors: implications for pairing at high magnetic fields
The behavior of some high temperature superconductors (HTSC) such as and , at very high
magnetic field, is similar to that of thin films of amorphous InOx near the
magnetic field-tuned superconductor-insulator transition. Analyzing the InOx
data at high fields in terms of persisting local pairing amplitude, we argue by
analogy that local pairing amplitude also persists well into the dissipative
state of the HTSCs, the regime commonly denoted as the "normal state" in very
high magnetic field experiments.Comment: Revised figures and reference
Recommended from our members
FOREVER: Fault/intrusiOn REmoVal through Evolution & Recovery
The goal of the FOREVER project is to develop a service for Fault/intrusiOn REmoVal through Evolution & Recovery. In order to achieve this goal, our work addresses three main tasks: the definition of the FOREVER service architecture; the analysis of how diversity techniques can improve resilience; and the evaluation of the FOREVER service. The FOREVER service is an important contribution to intrustion-tolerant replication middleware and significantly enhances the resilience
Erosion waves: transverse instabilities and fingering
Two laboratory scale experiments of dry and under-water avalanches of
non-cohesive granular materials are investigated. We trigger solitary waves and
study the conditions under which the front is transversally stable. We show the
existence of a linear instability followed by a coarsening dynamics and finally
the onset of a fingering pattern. Due to the different operating conditions,
both experiments strongly differ by the spatial and time scales involved.
Nevertheless, the quantitative agreement between the stability diagram, the
wavelengths selected and the avalanche morphology reveals a common scenario for
an erosion/deposition process.Comment: 4 pages, 6 figures, submitted to PR
Time-independent approximations for periodically driven systems with friction
The classical dynamics of a particle that is driven by a rapidly oscillating
potential (with frequency ) is studied. The motion is separated into a
slow part and a fast part that oscillates around the slow part. The motion of
the slow part is found to be described by a time-independent equation that is
derived as an expansion in orders of (in this paper terms to the
order are calculated explicitly). This time-independent equation
is used to calculate the attracting fixed points and their basins of
attraction. The results are found to be in excellent agreement with numerical
solutions of the original time-dependent problem.Comment: 5 pages, 4 figures. Revised version. Minor change
Stabilization of unstable steady states by variable delay feedback control
We report on a dramatic improvement of the performance of the classical
time-delayed autosynchronization method (TDAS) to control unstable steady
states, by applying a time-varying delay in the TDAS control scheme in a form
of a deterministic or stochastic delay-modulation in a fixed interval around a
nominal value . The successfulness of this variable delay feedback control
(VDFC) is illustrated by a numerical control simulation of the Lorenz and
R\"{o}ssler systems using three different types of time-delay modulations: a
sawtooth wave, a sine wave, and a uniform random distribution. We perform a
comparative analysis between the VDFC method and the standard TDAS method for a
sawtooth-wave modulation by analytically determining the domains of control for
the generic case of an unstable fixed point of focus type.Comment: 7 pages, 4 figures, RevTe
Characteristics of phonon transmission across epitaxial interfaces: a lattice dynamic study
Phonon transmission across epitaxial interfaces is studied within the lattice
dynamic approach. The transmission shows weak dependence on frequency for the
lattice wave with a fixed angle of incidence. The dependence on azimuth angle
is found to be related to the symmetry of the boundary interface. The
transmission varies smoothly with the change of the incident angle. A critical
angle of incidence exists when the phonon is incident from the side with large
group velocities to the side with low ones. No significant mode conversion is
observed among different acoustic wave branches at the interface, except when
the incident angle is near the critical value. Our theoretical result of the
Kapitza conductance across the Si-Ge (100) interface at temperature
K is 4.6\times10^{8} {\rm WK}^{-1}{\rmm}^{-2}. A scaling law at low temperature is also reported. Based on the features of
transmission obtained within lattice dynamic approach, we propose a simplified
formula for thermal conductanceacross the epitaxial interface. A reasonable
consistency is found between the calculated values and the experimentally
measured ones.Comment: 8 figure
Stability and instability in parametric resonance and quantum Zeno effect
A quantum mechanical version of a classical inverted pendulum is analyzed.
The stabilization of the classical motion is reflected in the bounded evolution
of the quantum mechanical operators in the Heisenberg picture. Interesting
links with the quantum Zeno effect are discussed.Comment: 6 pages, 3 figure
Order from Disorder in Graphene Quantum Hall Ferromagnet
Valley-polarized quantum Hall states in graphene are described by a
Heisenberg O(3) ferromagnet model, with the ordering type controlled by the
strength and sign of valley anisotropy. A mechanism resulting from electron
coupling to strain-induced gauge field, giving leading contribution to the
anisotropy, is described in terms of an effective random magnetic field aligned
with the ferromagnet z axis. We argue that such random field stabilizes the XY
ferromagnet state, which is a coherent equal-weight mixture of the and
valley states. Other implications such as the Berezinskii-Kosterlitz-Thouless
ordering transition and topological defects with half-integer charge are
discussed.Comment: 4 pages, 2 figure
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