80 research outputs found
Metallography of Al-Si Alloys with Alloying By Fe up to 1%
Metallographic analysis of aluminum-silicon alloys with different silicon content from 0 to 12% carried out. All alloys were differed in 2% by silicon amount from each other and all of them were additionally alloyed with iron in an amount of up to 1% in order to improve the technological properties in a die casting process. The paper shows the distribution of structural components of alloys made by electronic microscopy.
Keywords: aluminum-silicon alloys, metallography analysis, eutectic, structure, cast alloy, alloying, electron microscop
Electron transport in a two-terminal Aharonov-Bohm ring with impurities
Electron transport in a two-terminal Aharonov-Bohm ring with a few
short-range scatterers is investigated. An analytical expression for the
conductance as a function of the electron Fermi energy and magnetic flux is
obtained using the zero-range potential theory. The dependence of the
conductance on positions of scatterers is studied. We have found that the
conductance exhibits asymmetric Fano resonances at certain energies. The
dependence of the Fano resonances on magnetic field and positions of impurities
is investigated. It is found that collapse of the Fano resonances occurs and
discrete energy levels in the continuous spectrum appear at certain conditions.
An explicit form for the wave function corresponding to the discrete level is
obtained.Comment: 25 pages (one-column), 8 figure
To the fiftieth anniversary of the KIPT torsatron program
The paper is dedicated to the 50th anniversary of controlled thermonuclear fusion studies performed at the KIPT on the specific stellarator-type experimental installations commonly referred to as “the torsatron”. Detailed data are reported on the operating thermonuclear facility “Uragan-2M”, the research results obtained with it, and also, the prospects for its use as a reactor. The advantages of the torsatron of this type are described, among them being the wide-range parameter variation capability. This is of importance for finding out the regularities related to plasma stability, heating and confinement.Робота присвячена 50-річчю досліджень у ХФТІ з проблеми керованого термоядерного синтезу на експериментальних установах спеціальної конструкції, яку прийнято називати торсатроном. Детально освітлені особливості конструкції діючої термоядерної установки торсатрона “Ураган-2М”, результати досліджень на ній та її реакторні перспективи. Відзначені достоїнства такого типу пристрою, що виражаються в можливостях широкої зміни параметрів, що важливо для встановлення закономірностей, пов’язаних із стійкістю, нагрівом і утриманням плазми.Работа посвящена 50-летию исследований в ХФТИ по проблеме управляемого термоядерного синтеза на экспериментальных установках специальной конструкции, которую принято называть торсатроном. Подробно освещены особенности конструкции действующей термоядерной установки торсатрона “Ураган- 2М”, результаты исследований на ней и ее реакторные перспективы. Отмечены достоинства такого типа устройства, выражающиеся в возможностях широкого изменения параметров, что важно для установления закономерностей, связанных с устойчивостью, нагревом и удержанием плазмы
Linear in-plane magnetoconductance and spin susceptibility of a 2D electron gas on a vicinal silicon surface
In this work we have studied the parallel magnetoresistance of a 2DEG near a
vicinal silicon surface. An unusual, linear magnetoconductance is observed in
the fields up to T, which we explain by the effect of spin olarization
on impurity scattering. This linear magnetoresistance shows strong anomalies
near the boundaries of the minigap in the electron spectrum of the vicinal
system.Comment: (accepted to Phys. Rev. B
Study of BaTiO₃ ceramics doped with Mn and Ce or Nb and Sr
ESR study of BaTiO₃ ferroelectrics doped with cerium or with niobium and
strontium, both types of samples being doped with manganese, was performed
at room temperature. In the samples of the first type the most intensive
line with g-factor 1.9612 was shown to originate from paramagnetic
center Ti³⁺–Ce³⁺. The small intensity line was related to Fe³⁺–Vo center,
which can be unavoidable impurity in BaTiO₃.
In the samples doped with strontium, the six lines intensive spectrum,
which corresponds to hyperfine structure of Mn²⁺, was observed. The intensity
of the spectrum was shown to decrease with strontium concentration
increase. This effect was supposed to be related to the decrease of the
grain sizes that results in migration of manganese and, possibly, niobium
ions. The influence of these impurities, of their charge states and positions
in crystalline lattice of BaTiO₃ on the PTCR effect is discussed.Представлено результати ЕПР досліджень сегнетоелектричної кераміки BaTiO₃ двох серій: легованої церієм та марганцем або ніобієм, стронцієм та марганцем, при кімнатній температурі. Показано,
що у зразках першої серії найбільш інтенсивна лінія з g-фактором
1.9612 належить до парамагнітного центру Ti³⁺–Ce³⁺. Лінії малої інтенсивності належать до центру Fe³⁺–Vo (пов’язаного з неконтрольованою домішкою заліза у зразках) та до іону Mn²⁺.
В другій серії зразків спостерігався спектр, який відповідає надтонкій структурі іону Mn²⁺. Інтенсивність цього спектру зменшувалась
із збільшенням концентрації стронцію. Можливо цей ефект пов’язаний із зменшенням розмірів зерен та міграцією марганцю та, можливо ніобію, у міжзерновий простір. Обговорюється вплив домішок,
їх зарядового стану та позиції у кристалічній ґратці на ефект позитивного температурного коефіцієнту опору
Исследования коллектива кафедры общей фармацевтической и биомедицинской технологии в области биоинженерии растительных продуцентов биологически активных веществ
Article is devoted to the complex researches of various morphological groups of raw materials, a cellular biomass and a productive part of metaboloms of vegetative superproducers of a natural and biotechnological origin. All investigations were carried out according to the Federal special purpose program «Scientific and scientific and pedagogical shots of innovative Russia» for 2009-2013, action item № 1.2.1"Carrying out of scientific researches by scientific groups under the direction of doctors of sciences», Project: «Bioengineering as a basis of mobilization of adaptive potential of bioobjects - superproducers BAS» GK П555/05.08.2009 - НК-97П.Статья посвящена комплексным исследованиям различных морфологических групп сырья, клеточной биомассы и продуктивной части метаболома растительных суперпродуцентов природного и биотехнологического происхождения. Все исследования выполнялись в соответствии с Федеральной целевой программой «Научные и научно-педагогические кадры инновационной России» на 2009-2013 гг., в рамках реализации мероприятия № 1.2.1 «Проведение научных исследований научными группами под руководством докторов наук». Проект: «Биоинженерия как основа мобилизации адаптивного потенциала биообъектов - суперпродуцентов БАВ» ГК П555/05.08.2009 - НК-97П
Particle acceleration mechanisms
We review the possible mechanisms for production of non-thermal electrons
which are responsible for non-thermal radiation in clusters of galaxies. Our
primary focus is on non-thermal Bremsstrahlung and inverse Compton scattering,
that produce hard X-ray emission. We briefly review acceleration mechanisms and
point out that in most astrophysical situations, and in particular for the
intracluster medium, shocks, turbulence and plasma waves play a crucial role.
We consider two scenarios for production of non-thermal radiation. The first is
hard X-ray emission due to non-thermal Bremsstrahlung by nonrelativistic
particles. Non-thermal tails are produced by accelerating electrons from the
background plasma with an initial Maxwellian distribution. However, these tails
are accompanied by significant heating and they are present for a short time of
<10^6 yr, which is also the time that the tail will be thermalised. Such
non-thermal tails, even if possible, can only explain the hard X-ray but not
the radio emission which needs GeV or higher energy electrons. For these and
for production of hard X-rays by the inverse Compton model, we need the second
scenario where there is injection and subsequent acceleration of relativistic
electrons. It is shown that a steady state situation, for example arising from
secondary electrons produced from cosmic ray proton scattering by background
protons, will most likely lead to flatter than required electron spectra or it
requires a short escape time of the electrons from the cluster. An episodic
injection of relativistic electrons, presumably from galaxies or AGN, and/or
episodic generation of turbulence and shocks by mergers can result in an
electron spectrum consistent with observations but for only a short period of
less than one billion years.Comment: 22 pages, 5 figures, accepted for publication in Space Science
Reviews, special issue "Clusters of galaxies: beyond the thermal view",
Editor J.S. Kaastra, Chapter 11; work done by an international team at the
International Space Science Institute (ISSI), Bern, organised by J.S.
Kaastra, A.M. Bykov, S. Schindler & J.A.M. Bleeke
Nonthermal radiation mechanisms
In this paper we review the possible radiation mechanisms for the observed
non-thermal emission in clusters of galaxies, with a primary focus on the radio
and hard X-ray emission. We show that the difficulty with the non-thermal,
non-relativistic Bremsstrahlung model for the hard X-ray emission, first
pointed out by Petrosian (2001) using a cold target approximation, is somewhat
alleviated when one treats the problem more exactly by including the fact that
the background plasma particle energies are on average a factor of 10 below the
energy of the non-thermal particles. This increases the lifetime of the
non-thermal particles, and as a result decreases the extreme energy
requirement, but at most by a factor of three. We then review the synchrotron
and so-called inverse Compton emission by relativistic electrons, which when
compared with observations can constrain the value of the magnetic field and
energy of relativistic electrons. This model requires a low value of the
magnetic field which is far from the equipartition value. We briefly review the
possibilities of gamma-ray emission and prospects for GLAST observations. We
also present a toy model of the non-thermal electron spectra that are produced
by the acceleration mechanisms discussed in an accompanying paper.Comment: 17 pages, 6 figures, accepted for publication in Space Science
Reviews, special issue "Clusters of galaxies: beyond the thermal view",
Editor J.S. Kaastra, Chapter 10; work done by an international team at the
International Space Science Institute (ISSI), Bern, organised by J.S.
Kaastra, A.M. Bykov, S. Schindler & J.A.M. Bleeke
Clusters of galaxies: setting the stage
Clusters of galaxies are self-gravitating systems of mass ~10^14-10^15 Msun.
They consist of dark matter (~80 %), hot diffuse intracluster plasma (< 20 %)
and a small fraction of stars, dust, and cold gas, mostly locked in galaxies.
In most clusters, scaling relations between their properties testify that the
cluster components are in approximate dynamical equilibrium within the cluster
gravitational potential well. However, spatially inhomogeneous thermal and
non-thermal emission of the intracluster medium (ICM), observed in some
clusters in the X-ray and radio bands, and the kinematic and morphological
segregation of galaxies are a signature of non-gravitational processes, ongoing
cluster merging and interactions. In the current bottom-up scenario for the
formation of cosmic structure, clusters are the most massive nodes of the
filamentary large-scale structure of the cosmic web and form by anisotropic and
episodic accretion of mass. In this model of the universe dominated by cold
dark matter, at the present time most baryons are expected to be in a diffuse
component rather than in stars and galaxies; moreover, ~50 % of this diffuse
component has temperature ~0.01-1 keV and permeates the filamentary
distribution of the dark matter. The temperature of this Warm-Hot Intergalactic
Medium (WHIM) increases with the local density and its search in the outer
regions of clusters and lower density regions has been the quest of much recent
observational effort. Over the last thirty years, an impressive coherent
picture of the formation and evolution of cosmic structures has emerged from
the intense interplay between observations, theory and numerical experiments.
Future efforts will continue to test whether this picture keeps being valid,
needs corrections or suffers dramatic failures in its predictive power.Comment: 20 pages, 8 figures, accepted for publication in Space Science
Reviews, special issue "Clusters of galaxies: beyond the thermal view",
Editor J.S. Kaastra, Chapter 2; work done by an international team at the
International Space Science Institute (ISSI), Bern, organised by J.S.
Kaastra, A.M. Bykov, S. Schindler & J.A.M. Bleeke
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