188 research outputs found
Long-range thermoelectric effects in mesoscopic superconductor-normal metal structures
We consider a mesoscopic four-terminal superconductor/normal metal (S/N)
structure in the presence of a temperature gradient along the N wire. A
thermoemf arises in this system even in the absence of the thermoelectric
quasiparticle current if the phase difference between the superconductors is
not zero. We show that the thermoemf is not small in the case of a negligible
Josephson coupling between two superconductors. It is also shown that the
thermoelectric voltage has two maxima: one at a low temperature and another at
a temperature close to the critical temperature. The obtained temperature
dependence of the thermoemf describes qualitatively experimental data.Comment: 9 pages, 6 figure
Electron-hole imbalance in superconductor-normal metal mesoscopic structures
We analysed the electron-hole or, in another words, branch imbalance (BI) and
the related electric potential which may arise in a mesoscopic
superconductor/normal metal (S/N) structure under non-equilibrium conditions in
the presence of a supercurrent. Non-equilibrium conditions can be created in
different ways: a) a quasiparticle current flowing between the N reservoirs; b)
a temperature gradient between the N reservoirs and no quasiparticle current.
It is shown that the voltage oscillates with the phase difference
. In a cross-geometry structure the voltage arises in the
vertical branch and affects the conditions for a transition into the
-state.Comment: 6 pages, 5 figures, accepted for publication in Europhysics Letter
Automated control system for a mashing process
The goal of this paper is to describe a system for a mashing process, which is the first part of brewing beer. The mashing is a procedure where the fermentable (and some non-fermentable) sugars are extracted from malts. The program part based on LabVIEW, which is used to control NI CompactRIO. The main target of the project is to reach a predefined levels of the temperatures and maintain it during the pauses. When the necessary break time is ended the system is ready to go to the new value. The precise control of the temperatures during the breaks is one of the critical factors that define the texture and alcohol content of the beer. The system has two tanks with resistors PT100 in both of them, heat exchanger (coil), heater and pump. The first tank has heating element in order to rise the temperature in the other one. This project has practical solution with all explanations and graphs which are proven working ability of this control system
Transport and triplet superconducting condensate in mesoscopic ferromagnet-superconductor structures
We calculate the conductance of a superconductor/ferromagnet (S/F) mesoscopic
structure in the dirty limit. First we assume that the ferromagnet exhibits a
homogeneous magnetization and consider the case that the penetration of the
condensate into the F wire is negligible and the case in which the proximity
effect is taken into account. It is shown that if the exchange field is large
enough, the conductance below the critical temperature , is always smaller
than the conductance in the normal state. At last, we calculate the conductance
for a F/S structure with a local inhomogeneity of the magnetization in the
ferromagnet. We demonstrate that a triplet component of the condensate is
induced in the F wire.This leads to a increase of the conductance below .Comment: 31 pages, 6 figures. to be published in International Journal of
Modern Physics B; references adde
Stimulated emission and lasing in Cu(In,Ga)Se2 thin films
Stimulated emission and lasing in Cu(In,Ga)Se 2 thin films have been demonstrated at a temperature of 20 K using excitation by a nanosecond pulsed N 2 laser with power densities in the range from 2 to 100 kW cm − 2 . Sharp narrowing of the photoluminescence band, superlinear dependence of its intensity on excitation laser power, as well as stabilization of the spectral position and of the full-width at half-maximum of the band were observed in the films at increasing excitation intensity. The stimulated emission threshold was determined to be 20 kW cm − 2 . A gain value of 94 cm − 1 has been estimated using the variable stripe length method. Several sharp laser modes near 1.13 eV were observed above the laser threshold of I thr ~ 50 kW cm −
К вопросу расчетного определения пускового тока электродвигателей забойных машин и тока короткого замыкания в участковых сетях низкого напряжения
Study of porous monolithic sio2 prepeared by sol-gel method
For applications as catalyst supports in flow reactors, porous silica monoliths require a combination of connected pores of micron-scale and nm-scale pores. We have synthesised a range porous silica monoliths, characterised their nm-scale pores and measured their permeability coefficients k. It can be controlled by adjustment of the polymer/silane concentration ratio, whilst maintaining the specific surface area and nm-scale porosity approximately constant
Stimulated emission and optical properties of solid solutions of Cu(In,Ga)Se2 direct band gap semiconductors
Stimulated emission, optical properties, and structural characteristics of non-irradiated and proton-irradiated Cu(In,Ga)Se2 thin films deposited on soda lime glass substrates using co-evaporation of elements in a multistage process were investigated. X-ray diffraction analysis, scanning electron microscopy, X-ray spectral analysis with energy dispersion, low-temperature photoluminescence, optical transmittance and reflectance were used to study the films. Stimulated emission at low temperatures of ~20 K was found in non-irradiated and proton-irradiated Cu(In,Ga)Se2 thin films upon excitation by laser pulses of nanosecond duration with a threshold power density of ~20 kW/cm2. It was shown that the appearance and parameters of the stimulated emission depend strongly on the concentration of ion-induced defects in Cu(In,Ga)Se2 thin films
Nonlinear effects in microwave photoconductivity of two-dimensional electron systems
We present a model for microwave photoconductivity of two-dimensional
electron systems in a magnetic field which describes the effects of strong
microwave and steady-state electric fields. Using this model, we derive an
analytical formula for the photoconductivity associated with photon- and
multi-photon-assisted impurity scattering as a function of the frequency and
power of microwave radiation. According to the developed model, the microwave
conductivity is an oscillatory function of the frequency of microwave radiation
and the cyclotron frequency which turns zero at the cyclotron resonance and its
harmonics. It exhibits maxima and minima (with absolute negative conductivity)
at the microwave frequencies somewhat different from the resonant frequencies.
The calculated power dependence of the amplitude of the microwave
photoconductivity oscillations exhibits pronounced sublinear behavior similar
to a logarithmic function. The height of the microwave photoconductivity maxima
and the depth of its minima are nonmonotonic functions of the electric field.
It is pointed to the possibility of a strong widening of the maxima and minima
due to a strong sensitivity of their parameters on the electric field and the
presence of strong long-range electric-field fluctuations. The obtained
dependences are consistent with the results of the experimental observations.Comment: 9 pages, 6 figures Labeling of the curves in Fig.3 correcte
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