Variational method to study vortex matter in mesoscopic superconductors

A simple variational model is proposed to analyze the superconducting state in long cylindrical type-II superconductor placed in the external magnetic field. In the framework of this model, it is possible to solve the Ginzburg-Landau equations for the states with axially symmetric distributions of the order parameter. Phase transitions between different superconducting states are studied in the presence of external magnetic field and an equilibrium phase diagram of thin cylinder is obtained. The lower critical field of the cylindrical type-II superconductor with arbitrary values of radius and Ginzburg-Landau parameter is found. The field dependence of the magnetization of thin cylinder, which can carry several magnetic flux quanta, is calculated.Comment: 10 pages, 5 figures, submitted to Physica

Vortex phases in mesoscopic cylinders with suppressed surface superconductivity

Vortex structures in mesoscopic cylinder placed in external magnetic field are studied under the general de Gennes boundary condition for the order parameter corresponding to the suppression of surface superconductivity. The Ginzburg-Landau equations are solved based on trial functions for the order parameter for vortex-free, single-vortex, multivortex, and giant vortex phases. The equilibrium vortex diagrams in the plane of external field and cylinder radius and magnetization curves are calculated at different values of de Gennes "extrapolation length" characterizing the boundary condition for the order parameter. The comparison of the obtained variational results with some available exact solutions shows good accuracy of our approach.Comment: RevTex, 11 pages, 10 figure

Обеспечение работоспособности главного электродвигателя и пирамидальной прочности пропульсивного комплекса судов ледового класса

Новые проектируемые современные ледоколы и ледокольные суда, включая суда двойного действия (DAS), значительно выходят за рамки предыдущего опыта эксплуатации, что обуславливает необходимость разработки уточненных методов обеспечения работоспособности и надежности пропульсивного комплекса (ПК). На ПК (винто-рулевые колонки судов DAS) воздействуют интенсивные ледовые нагрузки, обусловленные использованием режимов движения задним ходом в ледовых условиях, ростом ледовой ходкости и операционных скоростей. Обеспечение прочности гребного винта (ГВ) и работоспособности главного электродвигателя (ГЭД) ПК являются одними из главных задач современного ледоколостроения, решение которых определяет операционную эффективность ледокольного судна во льдах. Авторами статьи разработана усовершенствованная методика, позволяющая спроектировать эффективный ГВ с высокими прочностными характеристиками, на основе имеющихся экспериментальных данных современных ледокольных судов. В статье представлены основные подходы методологии, разработанной авторами на базе лаборатории пропульсивных комплексов судов АО ЦНИИМФ, для определения и регулирования ледовых нагрузок в системе ГВ валопровод ГЭД, расчета и снижения силы поломки лопасти ГВ и обеспечения принципа пирамидальной прочности.Nowadays an intensification of interest, and use, of arctic waters for shipping as well as a high demand for ice ships is widely observed. Modern ice ships projects (e.g. double-acting ships) go beyond previous operational and design experience significantly. Therefore, the improvement of calculation methods needs to be developed. Azimuth thruster propellers on DAS have to meet the demanding operating environments. Propeller strength and operability of the propulsion complex mainly influence the operational effectiveness of the modern icebreakers and ice ships. Deep analysis of past investigations devoted to propeller/ice interaction was fulfilled. It gives an opportunity to highlight the main factors determining the efficiency of ice propellers and to develop the advanced methods of propeller strength calculation. Modern operating experience as well as the refined methodologies are used to develop efficient ice propellers with high strength characteristics. The refined methods have been developed to assign and regulate ice loads for propulsion complexes design to calculate and reduce the damage force of the propeller blade and to ensure pyramid strength.</jats:p

Formation of Porous Silicon Layers on Insulating Substrate for Microbridge – Type Sensor Applications

ABSTRACTFormation processes of porous silicon on insulating substrate were studied. It was demonstrated that both electrochemical and chemical formation methods allow to transform heavily doped p-type polycrystalline silicon into homogeneous porous silicon. Porous silicon was successfully used as sacrificial layer in the fabrication process of microbridge structures.</jats:p