The nonlinear effects in 2DEG conductivity investigation by an acoustic method

The parameters of two-dimensional electron gas (2DEG) in a GaAs/AlGaAs heterostructure were determined by an acoustical (contactless) method in the delocalized electrons region ($B\le$2.5T). Nonlinear effects in Surface Acoustic Wave (SAW) absorption by 2DEG are determined by the electron heating in the electric field of SAW, which may be described in terms of electron temperature $T_e$. The energy relaxation time $\tau_{\epsilon}$ is determined by the scattering at piezoelectric potential of acoustic phonons with strong screening. At different SAW frequencies the heating depends on the relationship between $\omega\tau_{\epsilon}$ and 1 and is determined either by the instantaneously changing wave field ($\omega\tau_{\epsilon}$$<1$), or by the average wave power ($\omega\tau_{\epsilon}$$>1$).Comment: RevTeX, 5 pages, 3 PS-figures, submitted to Physica Status Sol.(Technical corrections in PS-figs

Single File Diffusion enhancement in a fluctuating modulated 1D channel

We show that the diffusion of a single file of particles moving in a fluctuating modulated 1D channel is enhanced with respect to the one in a bald pipe. This effect, induced by the fluctuations of the modulation, is favored by the incommensurability between the channel potential modulation and the moving file periodicity. This phenomenon could be of importance in order to optimize the critical current in superconductors, in particular in the case where mobile vortices move in 1D channels designed by adapted patterns of pinning sites.Comment: 4 pages, 4 figure

Squeezing as the source of inefficiency in the quantum Otto cycle

The availability of controllable macroscopic devices, which maintain quantum coherence over relatively long time intervals, for the first time allows an experimental realization of many effects previously considered only as Gedankenexperiments, such as the operation of quantum heat engines. The theoretical efficiency \eta of quantum heat engines is restricted by the same Carnot boundary \eta_C as for the classical ones: any deviations from quasistatic evolution suppressing \eta below \eta_C. Here we investigate an implementation of an analog of the Otto cycle in a tunable quantum coherent circuit and show that the specific source of inefficiency is the quantum squeezing of the thermal state due to the finite speed of compression/expansion of the system.Comment: 17 pages, 5 figure

Estimates for parameters and characteristics of the confining SU(3)-gluonic field in an η′\eta^\prime-meson

The confinement mechanism proposed earlier by the author is applied to estimate the possible parameters of the confining SU(3)-gluonic field in an $\eta^\prime$-meson. For this aim the electric form factor of an $\eta^\prime$-meson is nonperturbatively computed in an explicit analytic form. The estimates obtained are also consistent with the width of the electromagnetic decay $\eta^\prime\to2\gamma$. The corresponding estimates of the gluon concentrations, electric and magnetic colour field strengths are also adduced for the mentioned field at the scales of the meson under consideration.Comment: 20 pages, LaTe

Применение ионной теории для расчета сульфидной емкости шлаков

The article considers the issues of sulfur removal in the ladle-furnace unit. The sulfur distribution coefficient depends on sulfide capacity of the slag, sulfur activity coefficient, oxidizing potential of the medium and equilibrium constant. The sulfide capacity CS of slags is one of the most important characteristics of refining capacity of the slags used in extra-furnace steel processing. One of the factors affecting the sulfide capacity is temperature. The formula was proposed showing the dependence of sulfide capacity on the optical basicity and temperature, in the temperature range of 1650 - 1400 °C and when the optical basicity Λ is not more than 0.75; the error of the presented formula does not exceed 6 %. The formula for calculating the optical basicity is proposed, which takes into account the influence of basic, acidic oxides and amphoteric oxide Al2O3 . It is shown that slags, completely consisting of a homogeneous phase, have an increased optical basicity of aluminum oxide. Heterogeneous slags have a reduced optical basicity of Al2O3 in comparison with homogeneous slags. Perhaps, this fact can be explained by the fact that in homogeneous slags there is a deficiency of the basic oxide CaO and in the conditions under consideration Al2O3 compound begins to exhibit more basic properties than acidic ones, thus, in homogeneous slags, the optical basicity of aluminum oxide is increased and approaches optical basicity of CaO oxide. Calculations carried out on the basis of real heats have shown that with an increase in the content of Al2O3 oxide in the slag, its optical basicity decreases. Known value of the optical basicity makes it possible to determine sulfide capacity of the slag, sulfur distribution coefficient between metal and slag, and, accordingly, final sulfur content in the metal. The research results have shown that it is advisable to apply the ionic theory of slags for the sulfide capacity determination. © 2021 National University of Science and Technology MISIS. All rights reserved

Методика коллективной фиксации местоположения наблюдаемых чрезвычайных ситуаций методом прямой засечки на основе мобильного телекомуникационного приложения с картографическим интерфейсом

In modern higher education, it is required not only to prepare students to perform work on finished tasks in the subject area they have studied. It is also necessary to prepare students for independent activities, in which students do not work on ready-made tasks, but, on the contrary, are looking for niches in business, in which they themselves can offer in the subject area they have mastered, business-demanded solutions. This is another area of activity, which also requires development while studying at a university. It can be defined as "entrepreneurial competencies of a student." In recent years, the direction "Startup as a Diploma" has been developing, in which a university graduate protects not conditional academic work, but a real technological project with business prospects, to which the students developing it have ownership rights. The creation and maintenance of such projects changes the relationship between student and teacher, for this activity it is necessary to change the traditional teaching methodology. As a task of teachers, we decided to do the following: Find a subject area related to IT development, in which, due to recent achievements, there are opportunities for fast, technically not very complex technological solutions available to students, with the help of which you can create popular solutions. The work proposes an open source software development project, within which students can, performing tasks that are feasible for themselves, create software applications that are in demand in practice, as well as develop development strategies for related business projects. The project is dedicated to solving the problem of determining the coordinates of observed objects and phenomena based on data entered simultaneously by several users in different places using household mobile devices without using special technological equipment such as theodolites or tacheometers. The authors developed a mobile application, the value of which lies in the fact that in the public field allows you to realize the monitoring potential of the population interested in preventing unwanted or dangerous events and preventing emergency situations; professional allows you to assess the quality of the navigation signal in conditions of possible targeted interference; in the educational aspect organize training in the methods of joint fixation of objects and target designation on educational geopolygons. Currently, the project is being developed by students of the Department of Data Analysis and Machine Learning of the Financial University under the Government of the Russian Federation and the Moscow State University of Geodesy and Cartography. This paper presents a description of the project, the proposed solution architecture. References to source code repositories are given. The results of the pilot versions of the software are given.В современном ВУЗовском обучении требуется не только готовить студентов к выполнению работ по готовым заданиям в изученной ими предметной области. Также нужна подготовка студентов к самостоятельной деятельности, в которой студенты не работают по готовым заданиям, а, наоборот, ищут ниши в бизнесе, в которых они сами могут предложить в освоенной ими предметной области востребованные бизнесом решения. Это – другая сфера деятельности специалистов, которая тоже требует развития во время обучения в ВУЗе. Ее можно определить как «предпринимательские компетенции студента». В последние несколько лет в ВУЗовском обучении даже появилось направление«Стартап как диплом», в рамках которого выпускник университета защищает не условную учебную работу, а реальный технологический проект, имеющий бизнес-перспективы, на который у развивающих его студентов есть права собственности. Создание и ведение таких проектов изменяет отношения студента и преподавателя, для этой деятельности надо изменять традиционную методологию обучения.В качестве задачи преподавателей мы решили сделать следующее:Найти связанную с IT-разработкой предметную область, в которой за счет достижений последнего времени появились возможности быстрых, технически не очень сложных технологических решений, доступных студентам, при помощи которых можно создавать востребованные решения.В работе предложен проект разработки программного обеспечения с открытым исходным кодом, в рамках которого студенты могут, выполняя посильные для себя задачи, создавать востребованные на практике программные приложения, а также разрабатывать стратегии развития связанных с ними бизнес-проектов. Проект посвящен решению задачи нахождения координат различных объектов и явлений, наблюдаемых на открытой местности путем обработки данных, вводимых одновременно несколькими находящимися в разных местах пользователями при помощи бытовых мобильных устройств без использования специального технологического оборудования типа теодолитов или тахеометров.В настоящее время проект разрабатывают студенты Департамента анализа данных и машинного обучения Финансового университета при правительстве РФ и Московского государственного университета геодезии и картографии.В работе представлены описание проекта, кейсы работы с системой, предлагаемая архитектура решения. Даны ссылки на репозитории исходного кода. Приведены результаты работы пилотных версий программного обеспечения

Terahertz Josephson plasma waves in layered superconductors: spectrum, generation, nonlinear, and quantum phenomena

The recent growing interest in terahertz (THz) and sub-THz science and technology is due to its many important applications in physics, astronomy, chemistry, biology, and medicine. We review the problem of linear and non-linear THz and sub-THz Josephson plasma waves in layered superconductors and their excitations produced by moving Josephson vortices. We start by discussing the coupled sine-Gordon equations for the gauge-invariant phase difference of the order parameter in the junctions, taking into account the effect of breaking the charge neutrality, and deriving the spectrum of Josephson plasma waves. We also review surface and waveguide Josephson plasma waves. We review the propagation of weakly nonlinear Josephson plasma waves below the plasma frequency, which is very unusual for plasma-like excitations. In close analogy to nonlinear optics, these waves exhibit numerous remarkable features, including a self-focusing effect, and the pumping of weaker waves by a stronger one. We also present quantum effects in layered superconductors, specifically, the problem of quantum tunnelling of fluxons through stacks of Josephson junctions. We discuss the Cherenkov and transition radiations of the Josephson plasma waves produced by moving Josephson vortices. We also discuss the problem of coherent radiation (superradiance) of the THz waves by exciting uniform Josephson oscillations. The effects reviewed here could be potentially useful for sub-THz and THz emitters, filters, and detectors