Evolution of gas-filled nanocracks in crystalline solids

In this work, the evolution of gas-filled cracks under gas implantation and subsequent annealing is studied on the basis of an elastic continuum approach. The observed growth limitation of He-filled nanocracks in SiC is attributed to their stabilization by the formation of circular dislocation dipoles. The formation and Ostwald ripening of bubble-loop complexes at elevated temperatures is modeled in terms of gas atom exchange between such complexes coupled. with local matrix atom exchange between bubbles and loops of the same complex. The scaling laws derived for the time dependence of bubble and loop sizes are found to be in good agreement with experimental data

Исследование нагрузочной характеристики гибкого вала винтовых забойных двигателей при бурении скважин

Цель работы – проведение расчета гибкого вала винтового забойного двигателя. Область применения: нефтегазовая промышленность.The purpose of the work is to calculate the flexible shaft of the downhole screw motor. Application: oil and gas industry

Point defect dynamics in bcc metals

We present an analysis of the time evolution of self-interstitial atom and vacancy (point defect) populations in pure bcc metals under constant irradiation flux conditions. Mean-field rate equations are developed in parallel to a kinetic Monte Carlo (kMC) model. When only considering the elementary processes of defect production, defect migration, recombination and absorption at sinks, the kMC model and rate equations are shown to be equivalent and the time evolution of the point defect populations is analyzed using simple scaling arguments. We show that the typically large mismatch of the rates of interstitial and vacancy migration in bcc metals can lead to a vacancy population that grows as the square root of time. The vacancy cluster size distribution under both irreversible and reversible attachment can be described by a simple exponential function. We also consider the effect of highly mobile interstitial clusters and apply the model with parameters appropriate for vanadium and $\alpha-$iron.Comment: to appear in Phys. Rev.

Diffusion basis spectrum imaging for identifying pathologies in MS subtypes

Diffusion basis spectrum imaging (DBSI) combines discrete anisotropic diffusion tensors and the spectrum of isotropic diffusion tensors to model the underlying multiple sclerosis (MS) pathologies. We used clinical MS subtypes as a surrogate of underlying pathologies to assess DBSI as a biomarker of pathology in 55 individuals with MS. Restricted isotropic fraction (reflecting cellularity) and fiber fraction (representing apparent axonal density) were the most important DBSI metrics to classify MS using brain white matter lesions. These DBSI metrics outperformed lesion volume. When analyzing the normal-appearing corpus callosum, the most significant DBSI metrics were fiber fraction, radial diffusivity (reflecting myelination), and nonrestricted isotropic fraction (representing edema). This study provides preliminary evidence supporting the ability of DBSI as a potential noninvasive biomarker of MS neuropathology

Non-isothermal nucleation in strongly supercooled liquids

In a strongly supercooled liquid at a temperature below the unit supercooling, a solid nucleus may grow such that the latent heat of freezing stays essentially within the nucleus. The temperature in the nucleus is then higher than in the surrounding liquid. We investigate the possibility that nucleation there may occur nonisothermally. We conclude that this is generally not the case

Асинхронный электропривод неполно-поворотной заслонки

В процессе работы были исследованы переходные процессы модели привода ГУСАР при закрытии заслонки, открытии, повороте на несколько градусов градус, при пониженном напряжении сети. Дипломный проект содержит описание требований предъявляемых к электроприводу заслонки, разработанный алгоритм формирования момента, разработанную модель электропривода заслонки в среде Matlab Simulink. Рассчитаны технико-экономические показатели; рассмотрены основные вопросы экологичности и безопасности проекта.In the process, the transient processes of the GUSAR drive model were studied with the shutter closed, opening, turning several degrees, with a reduced network voltage. The graduation project contains a description of the requirements for an electric drive damper, developed by an algorithm for generating a moment, developed by a model of an electric drive damper in a Matlab Simulink environment. Technical and economic indicators are calculated; The main issues of environmental friendliness and safety of the project are considered