596 research outputs found
Generation of low-temperature plasma by low-pressure arcs for synthesis of nitride coatings
Experiments were performed to study gas, metal, and mixed metal-gas plasmas. The plasmas were generated with the use of an arc evaporator and a gas-plasma source with a hot filament and hollow cathode that were operated independently or simultaneously. It has been revealed that the arc current of gas-plasma source affects the parameters of the metal-gas plasma and the element concentrations in the coatings. It has been demonstrated that the characteristics of the nitride coatings produced by plasma-assisted vacuum-arc deposition can be controlled by varying the parameters of the arc in the gas-plasma source
Suppression of superconductivity in granular metals
We investigate the suppression of the superconducting transition temperature
due to Coulomb repulsion in granular metallic systems at large tunneling
conductance between the grains, . We find the correction to the
superconducting transition temperature for 3 granular samples and films. We
demonstrate that depending on the parameters of superconducting grains, the
corresponding granular samples can be divided into two groups: (i) the granular
samples that belong to the first group may have only insulating or
superconducting states at zero temperature depending on the bare intergranular
tunneling conductance , while (ii) the granular samples that belong to the
second group in addition have an intermediate metallic phase where
superconductivity is suppressed while the effects of the Coulomb blockade are
not yet strong.Comment: 4 pages, 3 figure
Following the Precepts of I.M. Gubkin
On April 17 2020 National University of Oil and Gas “Gubkin University” celebrates 90th anniversary. The article shows that all these years the University has been strictly following the principles formulated by the founder of the university, academician Ivan Gubkin. The most important of them are the following. The University is the leader of domestic higher oil and gas education, carrying out the advanced training of oil and gas engineering personnel on the basis of innovations in the content and teaching technology. The University is a polytechnic university that combines the entire technological chain of the hydrocarbon industry with its specialties and directions – from finding them to supplying to the market. The University is the driver of the scientific and technological progress of hydrocarbon energy
Effects of fluctuations and Coulomb interaction on the transition temperature of granular superconductors
We investigate the suppression of superconducting transition temperature in
granular metallic systems due to (i) fluctuations of the order parameter
(bosonic mechanism) and (ii) Coulomb repulsion (fermionic mechanism) assuming
large tunneling conductance between the grains . We find the
correction to the superconducting transition temperature for 3 granular
samples and films. We demonstrate that if the critical temperature , where is the mean level spacing in a single grain the bosonic
mechanism is the dominant mechanism of the superconductivity suppression, while
for critical temperatures the suppression of
superconductivity is due to the fermionic mechanism.Comment: 12 pages, 9 figures, several sections clarifying the details of our
calculations are adde
Thermodynamics of the superfluid dilute Bose gas with disorder
We generalize the Beliaev-Popov diagrammatic technique for the problem of
interacting dilute Bose gas with weak disorder. Averaging over disorder is
implemented by the replica method. Low energy asymptotic form of the Green
function confirms that the low energy excitations of the superfluid dirty Boson
system are sound waves with velocity renormalized by the disorder and
additional dissipation due to the impurity scattering. We find the
thermodynamic potential and the superfluid density at any temperature below the
superfluid transition temperature and derive the phase diagram in temperature
vs. disorder plane.Comment: 4 page
Thermal transport in granular metals
We study the electron thermal transport in granular metals at large tunnel
conductance between the grains, and not too low a temperature , where is the mean energy level spacing for a single grain.
Taking into account the electron-electron interaction effects we calculate the
thermal conductivity and show that the Wiedemann-Franz law is violated for
granular metals. We find that interaction effects suppress the thermal
conductivity less than the electrical conductivity.Comment: Replaced with published versio
Measurement of Inverse Pion Photoproduction at Energies Spanning the N(1440) Resonance
Differential cross sections for the process pi^- p -> gamma n have been
measured at Brookhaven National Laboratory's Alternating Gradient Synchrotron
with the Crystal Ball multiphoton spectrometer. Measurements were made at 18
pion momenta from 238 to 748 MeV/c, corresponding to E_gamma for the inverse
reaction from 285 to 769 MeV. The data have been used to evaluate the gamma n
multipoles in the vicinity of the N(1440) resonance. We compare our data and
multipoles to previous determinations. A new three-parameter SAID fit yields 36
+/- 7 (GeV)^-1/2 X 10^-3 for the A^n_1/2 amplitude of the P_11.Comment: 14 pages, 8 figures, submitted to PR
ВЛИЯНИЕ КОМБИНИРОВАННОЙ ПРОКАТКИ НА СТРУКТУРУ И СВОЙСТВА ПРУТКОВ ТИТАНА ВТ1-0
A mathematical model of warm rolling in RSP 14-40 and Trio-180 mills has been constructed using the finite element method with LS-DYNA software. The strain state analysis of rods in the course of rolling at temperatures of 450 °C, 350 °C and room one has been carried out. The evolution of initial coarse-crystalline microstructure in the course of rolling was investigated. The special features of initial microstructure transformation kinetics in rods into nanocrystalline structure and its relation with deformed state and temperature are established.Построена математическая модель теплой прокатки в станах РСП 14-40 и Трио-180 методом конечных элементов в программном продукте LS-DYNA. Проведен анализ деформированного состояния в прутках в процессе прокатки при температурах нагрева 450 и 350 °С и комнатной. Исследована эволюция исходной крупнокристаллической микроструктуры прутков при прокатке. Установлены особенности кинетики трансформации исходной микроструктуры прутков в нанокристаллическую и ее связь с деформированным состоянием и температурой
Superconductivity, phase fluctuations and the c-axis conductivity of bilayer high temperature superconductors
We present a theory of the interplane conductivity of bilayer high
temperature superconductors, focusing on the effect of quantal and thermal
fluctuations on the oscillator strengths of the superfluid stiffness and the
bilayer plasmon. We find that the opening of the superconducting gap and
establishment of superconducting phase coherence each lead to redistribution of
spectral weight over wide energy scales. The factor-of-two relation between the
superfluid stiffness and the change below in the oscillator strength of
the absorptive part of the conductivity previously derived for single-layer
systems, is found to be substantially modified in bilayer systems.Comment: 11 pages, 14 figure
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