Characteristic length for pinning force density in Nb3SnNb{_3}Sn

The pinning force density $F{_p}(J{_c},B)=J{_c} \times B$ (where $J_c$ is the critical current density, $B$ is applied magnetic field) is one of main quantities which characterizes the resilience of a superconductor to carry dissipative-free transport current in applied magnetic field. Kramer (1973 J. Appl. Phys. 44 1360) and Dew-Hughes (1974 Phil. Mag. 30 293) proposed a widely used scaling law for the pinning force density amplitude: $F{_p}(B)=F{_{p,max}}((p+q){^{(p+q)}}/({p^p}{q^q}))(B/B_{c2}){^p}(1-B/B{_{c2}})^q$, where $F{_{p,max}}$, $B{_{c2}}$, $p$, and $q$ are free-fitting parameters. Since late 1970-s till now, several research groups reported experimental data for the dependence of $F_{p,max}$ on the average grain size, $d$, in $Nb{_3}Sn$-based conductors. Godeke (2006 Supercond. Sci. Techn. 19 R68) proposed that the dependence obeys the law $|F{_{p,max}}(d)|=A \times log(1/d)+B$. However, this scaling law has several problems, for instance, the logarithm is taken from a non-dimensionless variable, and $|F{_{p,max}}(d)|< 0$ for large grain sizes and $|F{_{p,max}}(d)|\rightarrow \infty$ for $d \rightarrow 0$. Here we reanalysed full inventory of publicly available $|F{_{p,max}}(d)|$ data for $Nb{_3}Sn$ conductors and found that the dependence can be described by $F_{p,max}(d)= F_{p,max}(0)exp(-d/{\delta})$ law, where the characteristic length, ${\delta}$, is varying within a remarkably narrow range, i.e. ${\delta}=(175 \pm 13) nm$, for samples fabricated by different technologies. The interpretation of the result is based on an idea that the in-field supercurrent is flowing within a thin surface layer (the thickness of ${\delta}$) near the grain boundary surfaces. Alternative interpretation is that ${\delta}$ represents characteristic length for the exponentially decay flux pinning potential from dominant defects in $Nb{_3}Sn$ superconductors, which are grain boundaries.Comment: 22 pages, 8 figure

Role of the individual lateral profile in language mastering

Findings of the sensory-motor asymmetry investigation are presented in the paper. Four groups of students differentiated on the basis of the dominant hemispheric activation and dominance of the acoustic, visual and motor analyzers are studied, psychophysiological and electrophysiological peculiarities in the examined groups being determined. The individual lateral profile is established to influence the successful language mastering. Results obtained during the investigation point to the close correlations between functional hemispheric asymmetry, types of the higher nervous activity and students' academic achievement

Psychophysiological mechanisms of speech perception and their role in methods of listening comprehension teaching

The article deals with the investigation findings of the listening comprehension mechanisms in left and right - hemisphere dominant students, factors contributing to effective language mastering being analyzed

Intra and interhermispheric coherence peculiarities in foreign language perception

Findings of the EEG investigation of students studying English, German, French and Latin are presented in the paper. Cortical activity peculiarities in frequency ranges between 4 and 30 Hz are revealed, EEG determinants of language abilities being estimated. Theta and beta bands are established to be more involved in the process of language perception. English and German cause greater left-hemisphere activity that is particularly marked in parietal, temporal and central regions. Perception of Latin and French is accompanied by the brain activity displacement to the right hemisphere. Results obtained during the investigation point to the close correlations between EEG peculiarities, short-term memory and successful language mastering

Psychophysiological mechanisms of speech perception and their role in training of students to audition

The article deals with the investigation findings of the listening comprehension mechanisms in left and right - hemisphere dominant students, factors contributing to effective language mastering being analyzed

DIATOMITES AND OPOKA FROM WESTERN KAZAKHSTAN DEPOSITS: LITHOGEOCHEMISTRY, STRUCTURAL AND TEXTURAL PARAMETERS, POTENTIAL OF USE

Link for citation: Smirnov P.V., Zhakipbayev B.E., Staroselets D.A., Deryagina O.I., Batalin G.A., Gareev B.I., Vergunov A.V. Diatomites and opoka from Western Kazakhstan deposits: lithogeochemistry, structural and textural parameters, potential of use. Bulletin of the Tomsk Polytechnic University. Geo Аssets Engineering, 2023, vol. 334, no. 7, рр. 187-201. In Rus. The relevance. In recent decades, individual studies in the Republic of Kazakhstan have been aimed at expanding the potential of using rocks of large and industrial exploitation of silicite deposits for revising their physicochemical, mineralogical parameters, and assessing the prospects for expanding their use in new industries and technologies in the construction and technical industries, materials science based on deep chemical processing of mineral raw materials. The article presents new data on the chemical-mineralogical and structural parameters of diatomites from the Utesai deposit and opoka from the Taskala deposit of the Republic of Kazakhstan. The main aim: comprehensive analysis of the chemical-mineral composition and structural and textural features of rocks from two largest deposits of silicon raw materials in the Western part of Kazakhstan – the Utesai diatomite deposit and the Taskala opoka deposit. Objects: diatomites of the Utesai deposit and opoka of the Taskala deposits in the western part of the Republic of Kazakhstan. Methods: field research, lithological and petrographic analysis of thin sections, X-ray diffraction analysis, differential thermal analysis, scanning electron microscopy, X-ray fluorescence analysis. Results. The studied diatomites and opoka are characterized by a high degree of homogeneity; they are represented by typical phases for silicic rocks of the region – opal-CT, clay minerals with an admixture of quartz and feldspars. From the mineralogical point of view, the most obvious difference between the studied diatomites and the Trans-Urals is the significant content of kaolinite – over 10 %, while in the diatomites of the Trans-Urals, the main clay component is smectite and mixed-layer illite-smectite formations. The rocks under consideration are clayey diatomites and clayey flasks, the total content of basic oxides allows us to characterize raw materials as medium quality, most suitable for the production of foam glass materials, and, in particular, glass fiber, in the production of which alumina is an important functional component. At the same time, the significant content of clay and other impurities does not allow us to recommend such raw materials for the production of filter and sorbing materials