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In this paper, unitary symmetrizers are considered. It is well known that using Newton operatoralgorithm, similar to the usual Newton algorithm, for extracting the square root, one can provethat for every Hermitian operator T 0, there exists a unique Hermitian operator S 0 suchthat T = S2. Moreover, S commutes with every bounded operator R with which commutes T. Theoperator S is called a square root of the operator T and is denoted by T1=2. The existence of thesquare root allows one to determine the absolute value jTj = (TT)1=2 of the bounded operator T.For every bounded linear operator T : H ! H there exists a unique partially isometric operatorU : H ! H such that T = UjTj, KerU = KerT. Such an equality is called a polar expansionof the operator T. The Schmidt operator is understood as the unitary multiplier of the polarexpansion of a compact inverse operator, with the help of which E. Schmidt was the rst to obtainthe expansion of a compact and not-self-adjoint operator and introduced so-called s-numbers.This paper shows that the unitary symmetrizer of an operator diers only in sign from the adjointSchmidt operator. The main result of the paper: if A is an invertible and compact operator, andS is a unitary operator such that the operator SA is self-adjoint, then the operator AS is alsoself-adjoint and the formula S = U holds, where U is the Schmidt operator.

Mixed partial differential equation of parabolic type with involution is considered. The sufficient conditions of the existence and uniqueness of the solution for the parabolic type equations with involution is obtained. The Fourier method is used to find a classical solution of the mixed problem for the transformed parabolic type equation with involution.

N.E. Erzhanov, Institute of Mathematics and Mathematical Modelling, Almaty, Kazakhstan, imanbaevnur@mail.ru, I. Orazov, Institute of Mathematics and Mathematical Modelling, Almaty, Kazakhstan, i_orazov@mail.ru Нуржан Ермешевич Ержанов, кандидат физико-математических наук, доцент, ведущий научный сотрудник, Институт математики и математического моделирования (г. Алматы, Республика Казахстан), imanbaevnur@mail.ru. Исабек Оразов, кандидат физико-математических наук, профессор, ведущий научный сотрудник, Институт математики и математического моделирования (г. Алматы, Республика Казахстан), i_orazov@mail.ru. We consider a mathematical model which represents the extraction process of a target component from the polydispersed porous material. The suggested model is demonstrated by the example of a flat solid material with bidispersed pores of different size in the form of a system of channels of macropores with micropores facing their walls. The macropores and the micropores in the material have homogeneous size. We model a case when micropores of the solid material (dispersed medium) are initially filled with an oil (dispersion phase), which is our target component. The macropores are filled in with a pure solvent. In the process of extraction the oil diffuses from the micropore to the macropore, and then from the micropores to the external solvent volume, wherein the ratio of concentrations in the macropore and the micropore is taken in accordance with the linear law of adsorption. The well-posedness of the formulated mathematical model has been justified. Рассматривается математическая модель, моделирующая процесс экстракции целевого компонента из пористого полидисперсного материала. Предлагаемая модель демонстрируется на примере плоского твердого материала с бидисперсными порами разного размера, в виде системы каналов макропор, на стенки которых выходят микропоры. Макропоры и микропоры в материале имеют однородный размер. Моделируется случай, когда микропоры твердого материала (дисперсионной среды) первоначально заполнены маслом (дисперсная фаза), являющимся нашей целевой компонентой. А макропоры заполнены чистым растворителем. В процессе экстракции масло диффундирует из микропоры в макропору, а затем из макропоры во внешний объем растворителя, при этом соотношение концентраций в макропоре и микропоре принимается подчиненным линейному закону адсорбции. Обоснована корректность сформулированной математической модели.

We consider one family of problems simulating the determination of the temperature and density of heat sources from given values of the initial and final temperature. The mathematical statement of these problems leads to the inverse problem for the heat equation, where it is required to find not only a solution of the problem, but also its right-hand side that depends only on a spatial variable. A specific feature of the considered problems is that the system of eigenfunctions of the multiple differentiation operator subject to boundary conditions of the initial problem does not have the basis property.We prove the unique existence of a generalized solution to thementioned problem.

We consider a class of problems modeling the process of determining the temperature and density of heat sources given initial and finite temperature. Their mathematical statements involve inverse problems for the heat equation in which, solving the equation, we have to find the unknown right-hand side depending only on the space variable. We prove the existence and uniqueness of classical solutions to the problem, solving the problem independently of whether the corresponding spectral problem (for the operator of multiple differentiation with not strongly regular boundary conditions) has a basis of generalized eigenfunctions.

In this paper we consider one family of problems simulating the determination of target components and density of sources from given values of the initial and final states. The mathematical statement of these problems leads to the inverse problem for the diffusion equation, where it is required to find not only a solution of the problem, but also its right-hand side that depends only on a spatial variable. One of specific features of the considered problems is that the system of eigenfunctions of the multiple differentiation operator subject to boundary conditions does not have the basis property.We prove the existence and uniqueness of classical solutions of the problem, solving the problem independently of whether the corresponding spectral problem (for the operator of multiple differentiation with not strengthened regular boundary conditions) has a basis of generalized eigenfunctions.

We study the nature of the spectrum of the periodic problem for the heat equation with a lower-order term and with a deviating argument. A significant influence of the lower-order term on the correct solvability of this problem is found. We obtain a criterion for the strong solvability of the above-mentioned problem.