Yu. V. Mukhartova

Application of a 2D Model for Describing the Turbulent Transfer of CO2 in a Spatially Heterogeneous Vegetation Cover

A numerical 2D model of the turbulent transfer of CO2 in the air between a spatially heterogeneous vegetation cover and the atmospheric surface layer was developed. The model is based on the one-and-a-half closure scheme for averaged equations of hydrodynamics and diffusion of CO2 in the air. The model was applied to assess the possible influence of forest canopy heterogeneity on the turbulent regime and CO2 fluxes in the atmospheric surface layer. CO2 exchange was simulated both at the windward forest edge and around a forest clearing.

Calculation of a parallel-plate waveguide with a chiral insert by the mixed finite element method

A parallel-plate waveguide with metallic boundaries, containing an insert of a chiral substance, is considered. The field distribution inside the insert is studied when the system is excited by the guide’s normal wave incident on the insert. The problem is considered in the full vector formulation. The waveguide is calculated by the mixed finite element method, which makes it possible to avoid spurious modes (so-called spirits).

An urban ecosystem as a superposition of interrelated active media

A space-time model that treats the urban ecosystem as a superposition of active media is expanded to take the heterogeneity of anthropogenic and natural factors into account. The approach is based on representation of urban ecosystems as conjugated active media and is aimed at identifying the threshold values of control parameters. The theoretical basis of the system analysis of the stability of urban ecosystems is provided by synergetic ideas concerning autowave self-organization in active media.

Excitation of electromagnetic oscillations in a domain with chiral filling

The problem of excitation of electromagnetic oscillations by a given distribution of charges and currents in a domain with inhomogeneous chiral filling is examined. The domain in which the problem is considered may either be finite with a perfectly conducting boundary surface or be the complement of a perfectly conducting bounded body. A special functional space is defined on which a generalized initial-boundary value problem is formulated. The Galerkin method is used to prove the existence and uniqueness of a weak solution of this problem.

The electromagnetic initial boundary value problem in a domain with a chiral filling

The problem of the excitation of electromagnetic oscillations by given charge and current distributions in a domain with a nonhomogeneous chiral filling is investigated. The domain where the problem is considered may be both a finite one bounded by an ideally conducting surface and an infinite supplement to an ideally conducting bounded object. The initial boundary value problem is shown to arise, for which the generalized formulation in a special functional space is given. The existence of a unique weak solution to the problem is proven using the Galerkin method.

An impact assessment of forest belts on the SO2 transport within the atmospheric boundary layer using a hydrodynamic model

A numerical two-dimensional hydrodynamic model was used to describe the influence of forest belts of different sizes on turbulent transport of SO2 within the atmospheric surface layer. The results of the model calculations showed that the presence of a forest belt results in an substantial reduction of the horizontal SO2 flux due to the decrease of the wind speed and the absorption of SO2 by tree crowns. The extinction coefficient of SO2 flux increases with an increase in the forest belt size and decrease with the pollution source height.

Calculating the spectral characteristics of a waveguide with homogeneous bi-isotopic filling by using the finite element method

In the present paper, a numerical algorithm is proposed for calculating propagation constants for the vector spectral problem in a rectangular waveguide with perfectly conducting walls and a homogeneous bi-isotropic filling. This algorithm rests on the specific generalized statement of the vector problem and allows using Lagrange finite elements without nonphysical solutions.

Spectral problem in a waveguide with homogeneous bi-isotropic filling

A vector spectral problem in a rectangular waveguide with homogeneous bi-isotropic filling is considered. A generalized statement of this problem is proposed, which is used to develop a finite-element algorithm for calculating propagation constants with spurious solutions eliminated.

Mathematical modeling of bi-isotropic waveguide using the finite elements method

The artificial materials, or metamaterials, that are strongly interacting with electromagnetic field, are currently actively developed and created. They include materials with negative permittivity and permeability, photonic crystals, bi-isotropic media etc. Bi-isotropic medium is the most general case of linear isotropic medium. Its distinctive feature is the existence of the electromagnetic coupling, so the electric or magnetic field acting on such medium produces both polarization and magnetization, unlike the ordinary dielectrics and magnetics Antireflecting coverings, waveguides, antennas, depolarizers etc. can be fabricated on the basis of metamaterials. Thereby the development of effective algorithms for calculating electromagnetic field in such media is a challenging problem. These algorithms can then be used for multiple solving the direct problem, when solving the inverse problem of synthesis of a material with preset features. One of the widely used methods is the finite elements method that permits to consider rather difficult domains. However in the case of electromagnetic problems in the full vector statement the finite elements method can give spurious solutions. There exist two basic ways to struggle against them: a posteriori, when the real solution is separated from spurious ones after calculating, and a priori, when such statements of a problem are used, that nonphysical solutions do not appear. In the second case the method of mixed finite elements is often used. This method effectively suppresses spurious solutions, but it possesses less accuracy than the Lagrangian finite elements method. In this work the numerical algorithm for calculating propagation constants for the spectral electromagnetic problem in the waveguide with perfectly conducting walls and bi-isotropic filling is proposed. This algorithm is based on specific generalized statement of the vector problem, and it permits to use the Lagrangian finite elements without nonphysical solutions.

A resonator with a chiral filling

In this paper the theory of electromagnetic shielded resonators with a uniform chiral filling is considered. An algorithm for determining the parameters of such systems is proposed. As an example, a spherical chiroresonator is investigated, for which the dispersive equation and the eigenfields are obtained. It is shown that only hybrid eigenfields may exist in such a resonator, and pure E- and H-oscillations are not supported.