667 research outputs found
Piezoelectric mechanism of orientation of stripe structures in two-dimensional electron systems
A piezoelectric mechanism of orientation of stripes in two-dimensional
quantum Hall systems in GaAs heterostructures is considered. The anisotropy of
the elastic moduli and the boundary of the sample are taken into account. It is
found that in the average the stripes line up with the [110] axis. In double
layer systems the wave vector of the stripe structure rotates from the [110] to
[100] axis if the period of density modulation becomes large than the
interlayer distance. From the experimental point of view it means that in
double layer systems anisotropic part of resistivity changes its sign under
variation of the external magnetic field.Comment: 8 page
Novel inferences of ionisation & recombination for particle/power balance during detached discharges using deuterium Balmer line spectroscopy
The physics of divertor detachment is determined by divertor power, particle
and momentum balance. This work provides a novel analysis technique of the
Balmer line series to obtain a full particle/power balance measurement of the
divertor. This supplies new information to understand what controls the
divertor target ion flux during detachment.
Atomic deuterium excitation emission is separated from recombination
quantitatively using Balmer series line ratios. This enables analysing those
two components individually, providing ionisation/recombination source/sinks
and hydrogenic power loss measurements. Probabilistic Monte Carlo techniques
were employed to obtain full error propagation - eventually resulting in
probability density functions for each output variable. Both local and overall
particle and power balance in the divertor are then obtained. These techniques
and their assumptions have been verified by comparing the analysed synthetic
diagnostic 'measurements' obtained from SOLPS simulation results for the same
discharge. Power/particle balance measurements have been obtained during
attached and detached conditions on the TCV tokamak.Comment: The analysis results of this paper were formerly in arXiv:1810.0496
Critical velocities in two-component superfluid Bose gases
On the ground of the Landau criterion we study the behavior of critical
velocities in a superfluid two-component Bose gas. It is found that under
motion of the components with different velocities the velocity of each
component should not be lower than a minimum phase velocity of elementary
excitations (s_). The Landau criterion yields a relation between the critical
velocities of the components (v_{c1}, v_{c2}). The velocity of one or even both
components may exceed s_. The maximum value of the critical velocity of a given
component can be reached when the other component does not move. The approach
is generalized for a two-component condensate confined in a cylindrical
harmonic potential.
PACS numbers: 03.75.Kk,03.75.MnComment: 6 pages, 1 figure
Low-temperature phonon thermal conductivity of cuprate single crystals
The effect of sample size and surface roughness on the phonon thermal
conductivity of NdCuO single crystals was studied down to 50
mK. At 0.5 K, is proportional to , where is the
cross-sectional area of the sample. This demonstrates that is
dominated by boundary scattering below 0.5 K or so. However, the expected
dependence of is not observed down to 50 mK. Upon roughing the
surfaces, the dependence is restored, showing that departures from
are due to specular reflection of phonons off the mirror-like sample surfaces.
We propose an empirical power law fit, to (where
) in cuprate single crystals. Using this method, we show that
recent thermal conductivity studies of Zn doping in YBaCuO
re-affirm the universal heat conductivity of d-wave quasiparticles at .Comment: 4 pages, 4 figure
Non-linear Simulations of MHD Instabilities in Tokamaks Including Eddy Current Effects and Perspectives for the Extension to Halo Currents
The dynamics of large scale plasma instabilities can strongly be influenced
by the mutual interaction with currents flowing in conducting vessel
structures. Especially eddy currents caused by time-varying magnetic
perturbations and halo currents flowing directly from the plasma into the walls
are important. The relevance of a resistive wall model is directly evident for
Resistive Wall Modes (RWMs) or Vertical Displacement Events (VDEs). However,
also the linear and non-linear properties of most other large-scale
instabilities may be influenced significantly by the interaction with currents
in conducting structures near the plasma. The understanding of halo currents
arising during disruptions and VDEs, which are a serious concern for ITER as
they may lead to strong asymmetric forces on vessel structures, could also
benefit strongly from these non-linear modeling capabilities. Modeling the
plasma dynamics and its interaction with wall currents requires solving the
magneto-hydrodynamic (MHD) equations in realistic toroidal X-point geometry
consistently coupled with a model for the vacuum region and the resistive
conducting structures. With this in mind, the non-linear finite element MHD
code JOREK has been coupled with the resistive wall code STARWALL, which allows
to include the effects of eddy currents in 3D conducting structures in
non-linear MHD simulations. This article summarizes the capabilities of the
coupled JOREK-STARWALL system and presents benchmark results as well as first
applications to non-linear simulations of RWMs, VDEs, disruptions triggered by
massive gas injection, and Quiescent H-Mode. As an outlook, the perspectives
for extending the model to halo currents are described.Comment: Proceeding paper for Theory of Fusion Plasmas (Joint Varenna-Lausanne
International Workshop), Varenna, Italy (September 1-5, 2014); accepted for
publication in: to Journal of Physics: Conference Serie
Nonlinear absorption of surface acoustic waves by composite fermions
Absorption of surface acoustic waves by a two-dimensional electron gas in a
perpendicular magnetic field is considered. The structure of such system at the
filling factor close to 1/2 can be understood as a gas of {\em composite
fermions}. It is shown that the absorption at can be strongly
nonlinear, while small deviation form 1/2 will restore the linear absorption.
Study of nonlinear absorption allows one to determine the force acting upon the
composite fermions from the acoustic wave at turning points of their
trajectories.Comment: 7 pages, 1 figure, submitted to Europhysics letter
Вплив параметрів технологічного процесу на якісні показники кулінарної продукції
Operating enterprises in the restaurant industry must apply various methods, methods, and means of process control, which will ensure the proper quality and safety of culinary products and dishes. One of the most critical tasks for a restaurant business manager is producing high-quality culinary products. The quality of food products is the essence of its consumer properties, determined by the satisfaction of the population's need for complete nutrition. The set of properties of culinary products is characterized by nutritional value and organoleptic indicators. However, control services periodically detect violations of sanitary, technological, and other regulatory requirements by enterprises of the restaurant industry, which indicates a possible danger to the health of consumers of culinary products. Under these circumstances, controlling the technological processes of the production of culinary products is relevant for industry institutions, requiring a constant search for the most effective methods and means of quality control. The quality and safety of dishes are the primary criteria for food, so restaurant establishments must daily practice continuous control of the processes of manufacturing products and providing services. This will help ensure the appropriate level of food quality with the analysis of the results of control operations, which can determine ways to improve the quality of products. The technical control system (control objects, control operations, their sequence, technical equipment, modes, methods, means of mechanization, and automation) is developed simultaneously with the design of the manufacturing technology of technical devices by the service of the chief technologist of the enterprise or relevant design and technological organizations with the participation of the technical control department (VTK). All technological processes of making dishes and culinary products in restaurants can be divided into two stages – mechanical culinary and thermal culinary processing. Within the framework of the study of the safety indicators of new products, an essential component is the analytical and experimental examination of minced meat products of the emulsion structure with EAGP regarding the determination of the type and content of food additives for compliance with legislative and regulatory documents on the regulation of food additives in the composition of food products. Analytical studies have established that the EAHP food additive based on sunflower oil – mono- and diacylglycerol fatty acids is a safe additive E471 of GRAS (Generally Regarded As Safe) status, which is used in the composition of food products according to technological necessity without restrictions and quantitatively not are regulated. Therefore, the minced meat semi-finished product of the emulsion structure fully meets the requirements of the current legislation of Ukraine in terms of EAHP content. Thus, studies of the general chemical composition, quality indicators, and safety of chopped meat semi-finished product of emulsion structure, made using the EAHP food additive based on sunflower oil, confirm the compliance of this product with the requirements of the state food control system.Діючі підприємства ресторанного господарства повинні застосовувати різні методи, способи і засоби контролю процесів, що забезпечить належну якість і безпечність кулінарної продукції та страв. Одним із найважливіших завдань для керівника підприємства ресторанного господарства є випуск кулінарної продукції високої якості. Якість продукції харчування – сутність її споживчих властивостей, обумовлених задоволенням потреби населення в повноцінному харчуванні. Сукупність властивостей кулінарної продукції характеризується харчовою цінністю та органолептичними показниками. Однак служби контролю періодично виявляють порушення санітарних, технологічних та інших нормативних вимог підприємствами ресторанного господарства, що вказує на ймовірну небезпеку для здоров’я споживачів кулінарної продукції. За цих обставин питання контролю технологічних процесів виготовлення кулінарної продукції є актуальним для закладів галузі, потребує постійного пошуку найефективніших методів та засобів контролю якості. Якість і безпека страв є першочерговими критеріями харчування, тому заклади ресторанного господарства повинні щоденно практикувати безперервний контроль виконуваних процесів з виготовлення продукції та надання послуг. Це допоможе забезпечити належний рівень якості страв з аналізом результатів операцій контролю, який може визначати шляхи підвищення якості продукції. Система технічного контролю (об’єкти контролю, контрольні операції, їхня послідовність, технічне оснащення, режими, методи, засоби механізації та автоматизації) розробляється одночасно з проектуванням технології виготовлення технічних пристроїв службою головного технолога підприємства або відповідними проектно-технологічними організаціями за участю відділу технічного контролю (ВТК). Усі технологічні процеси виготовлення страв та кулінарних виробів у закладах ресторанного господарства можна поділити на два етапи – механічна кулінарна і теплова кулінарна обробка. У межах дослідження показників безпечності нової продукції важливою складовою є аналітична та експериментальна експертиза м’ясних посічених виробів емульсійної структури з ЕАГП щодо визначення виду і вмісту харчових добавок на відповідність законодавчим і нормативним документам з регламентування харчових добавок у складі харчових продуктів. Аналітичними дослідженнями встановлено, що харчова добавка ЕАГП на основі соняшникової олії – моно- і діацилгліцерини жирних кислот, є безпечною добавкою Е471 статусу GRAS (Generally Regarded As Safe – абсолютно безпечно), яка використовується у складі харчових продуктів за технологічною необхідністю без обмежень і кількісно не регламентуються. Тому м’ясний посічений напівфабрикат емульсійної структури за вмістом ЕАГП повністю відповідає вимогам чинного законодавства України. Таким чином, дослідження загального хімічного складу, показників якості та безпечності м’ясного посіченого напівфабрикату емульсійної структури, виготовленого з використанням харчової добавки ЕАГП на основі соняшникової олії, підтверджують відповідність даного продукту вимогам державної системи контролю харчових продуктів
Investigating the impact of the molecular charge-exchange rate on detached SOLPS-ITER simulations
Plasma-molecular interactions generate molecular ions which react with the
plasma and contribute to detachment through molecular activated recombination
(MAR), reducing the ion target flux, and molecular activated dissociation
(MAD), both of which create excited atoms. Hydrogenic emission from these atoms
have been detected experimentally in detached TCV, JET and MAST-U deuterium
plasmas. The TCV findings, however, were in disagreement with SOLPS-ITER
simulations for deuterium indicating a molecular ion density () that was
insufficient to lead to significant hydrogenic emission, which was attributed
to underestimates of the molecular charge exchange rate () for deuterium (obtained by rescaling the hydrogen rates by their
isotope mass).
In this work, we have performed new SOLPS-ITER simulations with the default
rate setup and a modified rate setup where ion isotope mass rescaling was
disabled. This increased the content by . By disabling
ion isotope mass rescaling: 1) the total ion sinks are more than doubled due to
the inclusion of MAR; 2) the additional MAR causes the ion target flux to
roll-over during detachment; 3) the total emission in the divertor
increases during deep detachment by roughly a factor four; 4) the neutral atom
density in the divertor is doubled due to MAD, leading to a 50\% increase in
neutral pressure; 5) total hydrogenic power loss is increased by up to 60\% due
to MAD. These differences result in an improved agreement between the
experiment and the simulations in terms of spectroscopic measurements, ion
source/sink inferences and the occurrence of an ion target flux roll-over
Density Induced Interchange of Anisotropy Axes at Half-Filled High Landau Levels
We observe density induced 90 rotations of the anisotropy axes in
transport measurements at half-filled high Landau levels in the two dimensional
electron system, where stripe states are proposed (=9/2, 11/2, etc). Using
a field effect transistor, we find the transition density to be
cm at =9/2. Hysteresis is observed in the
vicinity of the transition. We construct a phase boundary in the filling
factor-magnetic field plane in the regime . An in-plane magnetic
field applied along either anisotropy axis always stabilizes the low density
orientation of the stripes.Comment: 1 revtex file, 3 eps figure
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