The mechanism of hypervortex pinning in a granular superconductor at intergranular contacts and intragranular defects is proposed for describing the field dependence of the critical current density and pinning potential. The results are in good agreement with those obtained experimentally. The proposed model describes the peak effect and the percolation mechanism of conductivity in ceramic superconductors.

This paper deals with experimental verification of reciprocity relations for nonlinear quadripole, such as Hall transducer. It is shown that the matrix of quadripole resistances can be decomposed into the sum of matrices. The classical reciprocity relations will be valid for linear part of matrix of resistances.

UDC 519.216We propose an algorithm for estimating the parameters of a signal from its quasiharmonic representation and a method for estimation of slowly varying coefficients of a second-order differential equation. The considered approach uses Tikhonov's regularization for the class of slowly varying functions. The results of statistical modeling for the Mathieu equation are presented. Solution of the frequency comparison problem on the example of estimation of the frequency instability of a quartz resonator setting a signal sampling rate is considered. Relations for determining the sampling rate are obtained and the results of numerical simulation are reported.

Abstract-This paper deals with reciprocity relations derivation for a nonlinear, stationary, homogeneous and isotropic plasma-like medium in an external homogeneous magnetic field. A special case of such a medium is the charge carriers collective in semiconductors. It is shown that the classical reciprocity relations will be valid even in the presence of nonlinearity, and they can be used for Hall magnetometer bias compensation.

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