1,372 research outputs found
Measurements of Nanoscale Domain Wall Flexing in a Ferromagnetic Thin Film
We use the high spatial sensitivity of the anomalous Hall effect in the
ferromagnetic semiconductor Ga1-xMnxAs, combined with the magneto-optical Kerr
effect, to probe the nanoscale elastic flexing behavior of a single magnetic
domain wall in a ferromagnetic thin film. Our technique allows position
sensitive characterization of the pinning site density, which we estimate to be
around 10^14 cm^{-3}. Analysis of single site depinning events and their
temperature dependence yields estimates of pinning site forces (10 pN range) as
well as the thermal deactivation energy. Finally, our data hints at a much
higher intrinsic domain wall mobility for flexing than previously observed in
optically-probed micron scale measurements
Equilibrium solutions of the shallow water equations
A statistical method for calculating equilibrium solutions of the shallow
water equations, a model of essentially 2-d fluid flow with a free surface, is
described. The model contains a competing acoustic turbulent {\it direct}
energy cascade, and a 2-d turbulent {\it inverse} energy cascade. It is shown,
nonetheless that, just as in the corresponding theory of the inviscid Euler
equation, the infinite number of conserved quantities constrain the flow
sufficiently to produce nontrivial large-scale vortex structures which are
solutions to a set of explicitly derived coupled nonlinear partial differential
equations.Comment: 4 pages, no figures. Submitted to Physical Review Letter
Correlation Between Microstructure and Thermionic Electron Emission from Os-Ru Thin Films on Dispenser Cathodes
Osmium-ruthenium films with different microstructures were deposited onto dispenser cathodes and subjected to 1000 h of close-spaced diode testing. Tailored microstructures were achieved by applying substrate biasing during deposition, and these were evaluated with scanning electron microscopy, x-ray diffraction, and energy dispersive x-ray spectroscopy before and after close-spaced diode testing. Knee temperatures determined from the close-spaced diode test data were used to evaluate cathode performance. Cathodes with a large {10-11} Os-Ru film texture possessed comparatively low knee temperatures. Furthermore, a low knee temperature correlated with a low effective work function as calculated from the close-spaced diode data. It is proposed that the formation of strong {10-11} texture is responsible for the superior performance of the cathode with a multilayered Os-Ru coating
Composition and Work Function Relationship in Os–Ru–W Ternary Alloys
Os–Ru thin films with varying concentrations of W were sputter deposited in order to investigate their structure–property relationships. The films were analyzed with x-ray diffraction to investigate their crystal structures, and a Kelvin probe to investigate their work functions. An Os–Ru–W film with ∼30 at. % W yielded a work function maximum of approximately 5.38 eV. These results align well with other studies that found work function minima from thermionic emission data on M-type cathodes with varying amounts of W in the coatings. Furthermore, the results are consistent with other work explaining energy-level alignment and charge transfer of molecules on metal oxides. This may shed light on the mechanism behind the “anomalous effect” first reported by Zalm et al., whereby a high work function coating results in a low work function for emitting cathode surfaces. An important implication of this work is the potential for the Kelvin probe to evaluate the effectiveness of dispenser cathode coatings
Теплогидравлический расчёт ТВС ИРТ-3М в реакторе ИРТ-Т с различными поверхностями теплообмена
The master’s thesis has attempted to model thermal-hydraulic behavior of the fuel assembly of IRT-3M type of IRT-T reactor with various heat-conductivity surfaces.В магистерской диссертации приведено теплогидравлическое моделирование ТВС типа ИРТ-3М реактора ИРТ-Т с различными поверхностями теплообмена
Scanning electron‐acoustic microscopy of MgO crystals
The capability of scanning electron‐acoustic microscopy in the characterization of MgO crystals has been studied. The conditions for the observation of different surface and subsurface features in as‐grown and deformed crystals are described and the results are discussed on the basis of thermal and nonthermal mechanisms of acoustic signalgeneration
Clustering of matter in waves and currents
The growth rate of small-scale density inhomogeneities (the entropy
production rate) is given by the sum of the Lyapunov exponents in a random
flow. We derive an analytic formula for the rate in a flow of weakly
interacting waves and show that in most cases it is zero up to the fourth order
in the wave amplitude. We then derive an analytic formula for the rate in a
flow of potential waves and solenoidal currents. Estimates of the rate and the
fractal dimension of the density distribution show that the interplay between
waves and currents is a realistic mechanism for providing patchiness of
pollutant distribution on the ocean surface.Comment: 4 pages, 1 figur
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