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

Technological progress in operation of multiservice sport centers viewed as management issue

Objective of the study was to consider benefits of social technologies in application to the modern multiservice sport center (MSC) management systems. To analyze the factors and conditions of effect on the MSC service progress, we performed a questionnaire survey of the MSC clientele and service personnel in July-October 2015 in the Belgorod regio

Development and research of the stamp for cutting of a rolled stock with a differentiated clamp

The work aims to develop and research a stamp with a differentiated clamp of a rolled stock for cutting by shear. A new stamp design with a differentiated clamp of the rolled stock has been developed. In terms of their technical and economic indicators, these stamps meet or exceed the modern samples of similar punch tools. At the same time, in the process of vertical cutting, a constant position of the rolled stock axis is ensured. The transmission of force to the clamp through the rolled stock is excluded. The stamp design ensures its sufficiently high rigidity and relatively small overall dimensions. Based on the analysis of the mathematical model of a stamp with a differentiated clamp, the effective angles of force transmission to the clamp and the cutting of the rolled stock between the stamp parts have been established. The resulting model was used to optimize the angles of force transfer to the clamp, and the cutting rolled stock, respecting the force from the side of a buffer and the minimum required press force. At the same time, the vertical stroke of the moving parts is reduced, the overall dimensions of the stamp are decreased, and the buffer also has a minimum size. To reduce the required force of the press, it is necessary to reduce the value of a frictional slipping coefficient by using antifriction materials on contact surfaces and ensuring good lubrication conditions. The results of the conducted experiments confirm the adequacy of the mathematical model. The value of the required force on the press slide available from experiments is slightly higher than the values obtained by the developed analytical model. The results of the stamp implementation show that: the stamps are efficient and reliable in exploitation; the quality of the cutoff workpieces corresponds to the quality indicators of the workpieces cut on similar modern equipment

Комплексне лікування синдрому діабетичної стопи з позицій фізичної та реабілітаційної медицини

Комплексне лікування синдрому діабетичної стопи з позицій фізичної та реабілітаційної медицин

Approximate Ginzburg-Landau solution for the regular flux-line lattice. Circular cell method

A variational model is proposed to describe the magnetic properties of type-II superconductors in the entire field range between $H_{c1}$ and $H_{c2}$ for any values of the Ginzburg-Landau parameter $\kappa>1/\sqrt{2}$. The hexagonal unit cell of the triangular flux-line lattice is replaced by a circle of the same area, and the periodic solutions to the Ginzburg-Landau equations within this cell are approximated by rotationally symmetric solutions. The Ginzburg-Landau equations are solved by a trial function for the order parameter. The calculated spatial distributions of the order parameter and the magnetic field are compared with the corresponding distributions obtained by numerical solution of the Ginzburg-Landau equations. The comparison reveals good agreement with an accuracy of a few percent for all $\kappa$ values exceeding $\kappa \approx 1$. The model can be extended to anisotropic superconductors when the vortices are directed along one of the principal axes. The reversible magnetization curve is calculated and an analytical formula for the magnetization is proposed. At low fields, the theory reduces to the London approach at $\kappa \gg 1$, provided that the exact value of $H_{c1}$ is used. At high fields, our model reproduces the main features of the well-known Abrikosov theory. The magnetic field dependences of the reversible magnetization found numerically and by our variational method practically coincide. The model also refines the limits of some approximations which have been widely used. The calculated magnetization curves are in a good agreement with experimental data on high-T$_c$ superconductors.Comment: 8 pages, RevTex, 6 figures, submitted to Phys. Rev.

On the low temperature properties and specific anisotropy of pure anisotropically paired superconductors

Dependences of low temperature behavior and anisotropy of various physical quantities for pure unconventional superconductors upon a particular form of momentum direction dependence for the superconducting order parameter (within the framework of the same symmetry type of superconducting pairing) are considered. A special attention is drawn to the possibility of different multiplicities of the nodes of the order parameter under their fixed positions on the Fermi surface, which are governed by symmetry. The problem of an unambiguous identification of a type of superconducting pairing on the basis of corresponding experimental results is discussed. Quasiparticle density of states at low energy for both homogeneous and mixed states, the low temperature dependences of the specific heat, penetration depth and thermal conductivity, the I-V curves of SS and NS tunnel junctions at low voltages are examined. A specific anisotropy of the boundary conditions for unconventional superconducting order parameter near $T_c$ for the case of specular reflection from the boundary is also investigated.Comment: 20 page

The Rotating Gliding Discharge in Quartz Tube and Open Half-Space at Atmospheric Pressure

Rotating sliding discharge (RGD) was investigated into limited volume and open half-space. The cur-rent-voltage characteristics of the discharge and its specifications are described. The results of optical research: photos and emission spectra of the discharge are presented

Finite Temperature Perturbation Theory for a Spatially Inhomogeneous Bose-condensed Gas

We develop a finite temperature perturbation theory (beyond the mean field) for a Bose-condensed gas and calculate temperature-dependent damping rates and energy shifts for Bogolyubov excitations of any energy. The theory is generalized for the case of excitations in a spatially inhomogeneous (trapped) Bose-condensed gas, where we emphasize the principal importance of inhomogeneouty of the condensate density profile and develop the method of calculating the self-energy functions. The use of the theory is demonstrated by calculating the damping rates and energy shifts of low-energy quasiclassical excitations, i.e. the quasiclassical excitations with energies much smaller than the mean field interaction between particles. In this case the boundary region of the condensate plays a crucial role, and the result for the damping rates and energy shifts is completely different from that in spatially homogeneous gases. We also analyze the frequency shifts and damping of sound waves in cylindrical Bose condensates and discuss the role of damping in the recent MIT experiment on the sound propagation.Comment: 16 pages, 3 figures, Revtex, uses epsfi