Ab Initio Calculations of the Walls Shear Strength of Carbon Nanotubes

The dependence of the energy of interwall interaction in double-walled carbon nanotubes (DWNT) on the relative position of walls has been calculated using the density functional method. This dependence is used to evaluate forces that are necessary for the relative telescopic motion of walls and to calculate the shear strength of DWNT for the relative sliding of walls along the nanotube axis and for their relative rotation about this axis. The possibility of experimental verification of the obtained results is discussed.Comment: 4 pages, 1 figur

Дистанційне навчання як принцип відкритого заняття

Summary. Distance learning is gaining among technologies based on the principles of open learning. This technology widely uses computer curricula for various purposes and modern telecommunications to communicate directly with a student at a distance. The idea of ​​this technology is the interaction of a teacher and a student in a virtual space: both of them are at their computers or gadgets and communicate via the Internet. Distance learning also plays an exceptional role in the modernization of education. In the conditions that have arisen due to the pandemic, students and academic staff should be sensitive to the need to work in forced remote conditions with a more practical and conscious approach to overcoming the existing digital barriers in the education system.Резюме. Среди технологий, основанных на принципах открытого обучения, больших оборотов набирает дистанционное обучение. Эта технология широко использует компьютерные учебные программы различного назначения и современные телекоммуникации для общения непосредственно со студентом на расстоянии. Идеей этой технологии является взаимодействие преподавателя и студента в виртуальном пространстве: оба они находятся у своих компьютеров или гаджетов и общаются с помощью сети «Интернет». Также в модернизации образования исключительную роль занимает дистанционное обучение. В условиях, возникших из-за пандемии, студенты и научно-педагогические работники должны с пониманием относиться к необходимости работать в вынужденных дистанционных условиях с более практичным и осознанным подходом к преодолению существующих цифровых барьеров в системе образования.Резюме. Серед технологій, що базуються на принципах відкритого навчання, великих обертів набирає дистанційне навчання. Ця технологія широко використовує комп᾽ютерні навчальні програми різного призначення та сучасні телекомунікації для спілкування безпосередньо із студентом на відстані. Ідеєю цієї технології є взаємодія викладача і студента у віртуальному просторі: обидва вони знаходяться біля своїх комп᾽ютерів або гаджетів і спілкуються за допомогою мережі «Інтернет». Також у модернізації освіти виключну роль займає дистанційне навчання. В умовах, що виникли через пандемію, студенти і науково-педагогічні працівники повинні з розумінням ставитися до необхідності працювати у вимушених дистанційних умовах із більш практичним та усвідомленим підходом до подолання існуючих цифрових бар᾽єрів у системі освіти

Effect of Thermal Deformation Regimes on the Austenite Growth Kinetics and Recrystallization of Medium Carbon Low-Alloyed Steel for Large-Sized Steam Turbine Rotors

Effect of thermal deformation regimes on the austenite grain growth is studied in the article. The austenite grain growth curve based on the experimental data is constructed. Conclusion about temperature, deformation degree and rate effect is made.The work was carried out using the laboratory equipment ”Structural methods of analysis and properties of materials and nanomaterials” of the Center of Ural Federal University

Simulations of column-averaged CO_2 and CH_4 using the NIES TM with a hybrid sigma-isentropic (σ-θ) vertical coordinate

We have developed an improved version of the National Institute for Environmental Studies (NIES) three-dimensional chemical transport model (TM) designed for accurate tracer transport simulations in the stratosphere, using a hybrid sigma-isentropic (σ-θ) vertical coordinate that employs both terrain-following and isentropic parts switched smoothly around the tropopause. The air-ascending rate was derived from the effective heating rate and was used to simulate vertical motion in the isentropic part of the grid (above level 350 K), which was adjusted to fit to the observed age of the air in the stratosphere. Multi-annual simulations were conducted using the NIES TM to evaluate vertical profiles and dry-air column-averaged mole fractions of CO_2 and CH_4. Comparisons with balloon-borne observations over Sanriku (Japan) in 2000–2007 revealed that the tracer transport simulations in the upper troposphere and lower stratosphere are performed with accuracies of ~5% for CH_4 and SF_6, and ~1% for CO_2 compared with the observed volume-mixing ratios. The simulated column-averaged dry air mole fractions of atmospheric carbon dioxide (XCO_2) and methane (XCH_4) were evaluated against daily ground-based high-resolution Fourier Transform Spectrometer (FTS) observations measured at twelve sites of the Total Carbon Column Observing Network (TCCON) (Bialystok, Bremen, Darwin, Garmisch, Izaña, Lamont, Lauder, Orleans, Park Falls, Sodankylä, Tsukuba, and Wollongong) between January 2009 and January 2011. The comparison shows the model's ability to reproduce the site-dependent seasonal cycles as observed by TCCON, with correlation coefficients typically on the order 0.8–0.9 and 0.4–0.8 for XCO_2 and XCH_4, respectively, and mean model biases of ±0.2% and ±0.5%, excluding Sodankylä, where strong biases are found. The ability of the model to capture the tracer total column mole fractions is strongly dependent on the model's ability to reproduce seasonal variations in tracer concentrations in the planetary boundary layer (PBL). We found a marked difference in the model's ability to reproduce near-surface concentrations at sites located some distance from multiple emission sources and where high emissions play a notable role in the tracer's budget. Comparisons with aircraft observations over Surgut (West Siberia), in an area with high emissions of methane from wetlands, show contrasting model performance in the PBL and in the free troposphere. Thus, the PBL is another critical region for simulating the tracer total column mole fractions

Beam Energy and Centrality Dependence of Direct-Photon Emission from Ultrarelativistic Heavy-Ion Collisions.

The PHENIX collaboration presents first measurements of low-momentum (0.41  GeV/c) direct-photon yield dN_{γ}^{dir}/dη is a smooth function of dN_{ch}/dη and can be well described as proportional to (dN_{ch}/dη)^{α} with α≈1.25. This scaling behavior holds for a wide range of beam energies at the Relativistic Heavy Ion Collider and the Large Hadron Collider, for centrality selected samples, as well as for different A+A collision systems. At a given beam energy, the scaling also holds for high p_{T} (>5  GeV/c), but when results from different collision energies are compared, an additional sqrt[s_{NN}]-dependent multiplicative factor is needed to describe the integrated-direct-photon yield