Experimental investigation of the radial structure of energetic particle driven modes

Alfv\'en eigenmodes (AEs) and energetic particle modes (EPMs) are often excited by energetic particles (EPs) in tokamak plasmas. One of the main open questions concerning EP driven instabilities is the non-linear evolution of the mode structure. The aim of the present paper is to investigate the properties of beta-induced AEs (BAEs) and EP driven geodesic acoustic modes (EGAMs) observed in the ramp-up phase of off-axis NBI heated ASDEX Upgrade (AUG) discharges. This paper focuses on the changes in the mode structure of BAEs/EGAMs during the non-linear chirping phase. Our investigation has shown that in case of the observed down-chirping BAEs the changes in the radial structure are smaller than the uncertainty of our measurement. This behaviour is most probably the consequence of that BAEs are normal modes, thus their radial structure strongly depends on the background plasma parameters rather than on the EP distribution. In the case of rapidly upward chirping EGAMs the analysis consistently shows shrinkage of the mode structure. The proposed explanation is that the resonance in the velocity space moves towards more passing particles which have narrower orbit widths.Comment: submitted to Nuclear Fusio

Thermoelectric prospects of nanomaterials with spin-orbit surface bands

Nanostructured composites and nanowire arrays of traditional thermoelectrics like Bi, Bi(1-x)Sb(x) and Bi(2)Te(3) have metallic Rashba surface spin-orbit bands featuring high mobilities rivaling that of the bulk for which topological insulator behavior has been proposed. Nearly pure surface electronic transport has been observed at low temperatures in Bi nanowires with diameter around the critical diameter, 50 nm, for the semimetal-to semiconductor transition. The surface contributes strongly to the thermopower, actually dominating for temperatures T < 100 K in these nanowires. The surface thermopower was found to be -1 T microvolt/(K^2), a value that is consistent with theory. We show that surface electronic transport together with boundary phonon scattering leads to enhanced thermoelectric performance at low temperatures of Bi nanowire arrays. We compare with bulk n-BiSb alloys, optimized CsBi(4)Te(6) and optimized Bi(2)Te(3). Surface dominated electronic transport can be expected in nanomaterials of the other traditional thermoelectrics.Comment: 18 pages, 3 figure

Estimating the First-year Corrosion Losses of Structural Metals for Continental Regions of the World

The knowledge of the first-year corrosion losses of metals (K1) in various regions of the world is of great importance in engineering applications. The K1 values are used to determine the categories of atmospheric corrosivity, and K1 is also the main parameter in models for the prediction of long-term corrosion losses of metals. In the absence of experimental values of K1, their values can be predicted on the basis of meteorological and aerochemical parameters of the atmosphere using the dose-response functions (DRF). Currently, the DRFs presented in ISO 9223:2012(E) /1/ standard are used for predicting K1 in any region of the world, along with the unified DRFs /2/ and the new DRFs /3/. The predicted values of corrosion losses (K1pr) of carbon steel, zinc, copper and aluminum obtained by various DRFs for various continental regions of the world are presented. In this work we used the atmosphere corrosivity parameters and experimental data on the corrosion losses of metals for the first year of exposure (K1exp) for the locations of the tests performed under the international UN/ECE program, the MICAT project, and the Russian program. For the first time, a comparative assessment of the reliability of various DRFs is given by comparing the values of K1pr and K1ex using graphical and statistical methods. The statistical indicators of reliability of predicting the corrosion losses of metals are calculated for various categories of atmosphere corrosivity. It is shown that the new dose-response functions offer the highest reliability for all categories of atmosphere corrosivity

Observation of three-dimensional behavior in surface states of bismuth nanowires and the evidence for bulk Bi charge fractionalization

Whereas bulk bismuth supports very-high mobility, light, Dirac electrons and holes in its interior, its boundaries support a layer of heavy electrons in surface states formed by spin orbit interaction in the presence of the surface electric field. Small diameter d trigonal Bi nanowires (30 nm < d < 200 nm) were studied via magnetotransport at low temperatures and for fields up to 14 T in order to investigate the role of surfaces in electronic transport. A two-dimensional behavior was expected for surface charges; however we found instead a three-dimensional behavior, with a rich spectrum of Landau levels in a nearly spherical Fermi surface. This is associated with the long penetration length of surface states of trigonal wires. The prospect of the participation of surface transport and surface-induced relaxation of bulk carriers in the electronic properties of macroscopic samples is evaluated. We show that recent observations of magnetoquantum peaks in the Nernst thermopower coefficient, attributed to two-dimensional electron gas charge fractionalization, can be more plausibly interpreted in terms of these surface states.Comment: 14 pages, 3 figure

Activation of learning and creative activity of the vocational pedagogical university students

The relevance of the problem under study is based on the society’s demand for training students - future professional training teachers ready to solve in a creative manner a wide range of professional and pedagogical tasks, as well as to develop professionally-oriented creative work in the process of training; it is also caused by the insufficient extent of the prior research within the vocational training theory of scientific and methodological mechanisms required for implementing this process. The purpose of the article is to develop a conceptual structural model of professionally-oriented learning and creative activity of the vocational pedagogical university students. Leading method for studying this problem is modelling which allows to consider this problem as the process of goaloriented and deliberate acquiring by future professionals the creative approaches to implementation of professional activity. The article presents a structural model of learning and creative activity of vocational pedagogical university students, justifies the necessity to single out in the structure of the students’ learning and creative activity three interconnected components (creative, professional-pedagogical and personal-acmeological), proves the productivity of activating the learning and creative activity of the vocational pedagogical university students by organizing it as quasi-professional process of searching and solving professional tasks which are subjectively and objectively new, on the basis of using synectics including association methods of activating creative thinking integrated into the its structure. The article can be useful for teachers within the vocational and pedagogical education system, as well as for professionals who develop creative abilities of students based on the heuristic creativity methods. © 2016 Krayukhina et al

Surface state band mobility and thermopower in semiconducting bismuth nanowires

Many thermoelectrics like Bi exhibit Rashba spin-orbit surface bands for which topological insulator behavior consisting of ultrahigh mobilities and enhanced thermopower has been predicted. Bi nanowires realize surface-only electronic transport since they become bulk insulators when they undergo the bulk semimetal-semiconductor transition as a result of quantum confinement for diameters close to 50 nm. We studied 20-, 30-, 50- and 200-nm trigonal Bi wires. Shubnikov-de Haas magnetoresistance oscillations caused by surface electrons and bulklike holes enable the determination of their densities and mobilities. Surface electrons have high mobilities exceeding 2(m^2)/(Vsec) and contribute strongly to the thermopower, dominating for temperatures T< 100 K. The surface thermopower is - 1.2 T microvolt/(K^2), a value that is consistent with theory, raising the prospect of developing nanoscale thermoelectrics based on surface bands.Comment: 19 pages. 3 figure

TUTORING AS A FORM OF PEDAGOGICAL SUPPORT OF STUDENTS’ INDIVIDUAL EDUCATIONAL TRAJECTORIES

Purpose: The key provisions on which the tutor relies on the context of his work are the principles underlying open education: transparency; flexibility; continuity; variability; individual approach; individualization. Methodology: The relevance of the study is associated with the processes characteristic of the school system in modern Russia (modernization, optimization, change in the structural foundations), as well as the objective need of society in the search for fundamentally new approaches to the content and construction of the educational process in the educational institution. Result: Tutoring should be considered as a resource of individual evolution of personality, as a form of productive exploitation of open education opportunities for the development of individual educational programs, taking into account the specifics of a particular student. As pedagogical conditions for the implementation of the model of tutor support of the formation of basic school students’ research skills should be considered: innovative educational environment; scientific and methodological provision of tutor support of the process of building basic school students’ research skills; professional skills of the tutor. Applications: This research can be used for universities, teachers, and students. Novelty/Originality: In this research, the model of Tutoring as a Form of Pedagogical Support of Students’ Individual Educational Trajectories is presented in a comprehensive and complete manner

The floor in the interplanetary magnetic field: Estimation on the basis of relative duration of ICME observations in solar wind during 1976-2000

To measure the floor in interplanetary magnetic field and estimate the time- invariant open magnetic flux of Sun, it is necessary to know a part of magnetic field of Sun carried away by CMEs. In contrast with previous papers, we did not use global solar parameters: we identified different large-scale types of solar wind for 1976-2000 interval, obtained a fraction of interplanetary CMEs (ICMEs) and calculated magnitude of interplanetary magnetic field B averaged over 2 Carrington rotations. The floor of magnetic field is estimated as B value at solar cycle minimum when the ICMEs were not observed and it was calculated to be 4,65 \pm 6,0 nT. Obtained value is in a good agreement with previous results.Comment: 10 pages, 2 figures, submitted in GR