The Effect of Alongshore Protection Structures on Shore Dynamics

A mathematical model of the seashore dynamics is considered. The model describes the seashore protection against destruction by alongshore through structures, underwater trenches, and artificial islands. The results of model calculations are presented and correlated with the data of measurements made on hydraulic models.     

Mathematical modeling of the structure of an accretion disk in a stellar binary system

Numerical simulations of gas-dynamical processes taking place in the accretion disk of a stellar binary system are presented. The initial state of the disk is an equilibrium gaseous configuration. Mechanisms for the development of spiral waves and associated variations in the angular momentum of the gas are considered. The influence of the ratio of the binary-component masses and the initial disk configuration are investigated. It is concluded that the existence of a steady-state disk is impossible without a flow of gas from the donor star.     

FDwave3D: a MATLAB solver for the 3D anisotropic wave equation using the finite-difference method

Seismic modeling plays an important role in geophysics and seismology for estimating the response of seismic sources in a given medium. In this work, we present a MATLAB-based package, FDwave3D, for synthetic wavefield and seismogram modeling in 3D anisotropic media. The seismic simulation is carried out using the finite-difference method over the staggered grid, and it is applicable to both active and passive surveys. The code package allows the incorporation of arbitrary source mechanisms and offers spatial derivative operators of accuracy up to tenth-order along with different types of boundary conditions. First, the methodological aspects of finite-difference method are briefly introduced. Then, the code has been tested and verified against the analytical solutions obtained for the homogeneous model. Further, the numerical examples of layered and overthrust models are presented to demonstrate its reliability.

     

On the role of diffractions in velocity model building: a full-waveform inversion example

Studia Geophysica et Geodaetica - Imaging of small-scale heterogeneities is important for the geological exploration in complex environments. It requires a processing sequence tuned to...     

Comparison between two-and three-dimensional modeling of the structure of an accretion disk in a binary system

We compare two-and three-dimensional modeling of gas-dynamical processes in the accretion disk of a binary system. The origin of spiral waves and the loss of the angular momentum related to them are considered. It is concluded that a steady state of the disk cannot exist without taking into account t he gas inflow from the donor star.     

Method of ecological standardization of the impact on water bodies that cannot be standardized by bioassay: Case study of water bodies in Don basin

The work is focused on studying the possibility to ecologically standardize the characteristics that are not concentrations of chemical substances, i.e., water abundance; water temperature; and pH, which does not belong to standardized characteristics. The initial data include the data of biological (water quality classes by characteristics of plankton, periphyton, and zoobenthos) and physicochemical monitoring in 1975–1991 in water bodies of the Lower Don, as well as data on fish catches and yield in the Lower Don. The values of ecologically tolerable levels are obtained for three factors, such that going above these levels causes the environmental ill-being of the appropriate biological indicator. Nonchemical impacts, represented by water abundance and temperature have almost no effect on the deterioration of ichthyological estimates of the state (the only exception is the correlation between water abundance and sabrefish catches). At the same time, planktonic and benthic estimates appear to be more sensitive indicators of water quality decline in all three factors under consideration. The pH exponent affects all ecological groupings of Don ecosystems. The strictest upper boundaries of ecologically tolerable levels of water abundance were recorded for the sabrefish catches. On the other hand, insufficient water abundance during spring and summer deteriorates the state of planktonic and benthic organisms.     

Mathematical Simulation of Convective Processes in the Liquid Core of the Earth and Implications for the Interpretation of Geomagnetic Field Variations in Polar Latitudes

The flow structure induced by thermal convection in a rotating spherical shell with viscous boundary conditions is considered under the assumption that the differential rotation of the core relative to the mantle is absent. The radial, azimuthal, and meridional components of the flow’s velocity and helicity are studied. With the magnetic field assumed to be frozen into a liquid (frozen-flux hypothesis), it is shown that the numerical results fit the observations of the geomagnetic field variations close to the pole.