Name
Kovalenko Anna Vladimirovna
Scholastic degree
•
Academic rank
—
Honorary rank
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Organization, job position
Kuban State University
Web site url
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Articles count: 51
The article presents a mathematical model of the effect on ion transport electro convection salt in non-smooth camera channel desalting electro dialysis apparatus in the presence of forced convection. The basic rules of process of electro convection are revealed
In the article we have derived mathematical models of non-stationary transport binary electrolyte in EMS (electromembrane systems: electrodialysis apparatus, electromembrane cell, etc.) for the galvanostatic mode. To be specific, as EMS viewed channel of desalting of EDA (electrodialysis apparatus) and EMS with RMD (rotating membrane disk). We present a formula expressing the intensity of the electric field through the current density and concentration. Also, we have received the differential equation for the current density. The fundamental point here is derived new equation for the unknown vector function of current density of the initial system of equations of Nernst-Planck. In addition, the article shows the output equation for the current density in three dimensions; we have proposed various methods for solving the equation of the current density and the boundary conditions for the current density. The proposed mathematical models of transport binary electrolyte are easy to be generalized to an arbitrary electrolyte. However, the corresponding equations are cumbersome. It should be also noted that the boundary conditions can be varied and depend on the purpose of a particular study in this regard, in this work are just the equation having the general form
The aim of this work is to carry out numerical analysis of time behavior of electroconvection in membrane systems, such as a desalting channel of electrodialysis apparatus. The current-voltage curve and the solution flaw were analyzed theoretically using mathematical models of ions transfer taking into account electroconvection in smooth desalting channel consisting of ideally selective anion- and cation-exchange membranes. The Hurst numbers for different parts of the current-voltage curve were calculated in order to determine whether the parts were persistent. The Fourier-analysis of the oscillating term of the current-voltage curve was carried out for the first time so as to determine predominant frequencies in the signal. Frequencies of passing of complexes of vortexes through the cross-section of the desalting channel were calculated. Frequencies of oscillations of concentration profiles were determined. It was found that the frequencies of oscillations of the concentration profiles coincide with the frequencies of passing of complexes of vortexes through the cross-section of the desalting channel. The oscillations of the current-voltage curve were physically interpreted. Namely, it was shown that the main frequency of oscillations of the current-voltage curve corresponds to the frequency of oscillations of the concentration profiles. The oscillations of the concentration profiles, produced by the passing of complexes of vortexes, cause oscillations of conductivity and, consequently, cause oscillations of resistance and of the current density. It was shown that the main frequency of the signal corresponds to the frequency of passing of complexes of vortexes through the cross-section of the desalting channel
Micro and nanofluidics are the new multidisciplinary
sciences. One of the tasks of which is creation and
management of flow of fluid in the thin channels size
of a few nano- or micrometer which exposed the
external electric field, where the walls are the ion
exchange membrane. Electroosmosis
(electroconvection) plays an important role in these
tasks. A large number of articless were devoted to
electroosmosis. One of the first, Dukhin S.S.,
Mishchuk N.A. and Rubinstein I. gave a theoretical
explanation of the overlimiting current by
electroosmosis. They used two-dimensional Stokes
equation to calculate the flow of the electrolyte, and
one-dimensional equations of Nernst-Planck and
Poisson to calculate the electric power. These
researches have multiple limitations because of the
computational complexity the mathematical
simulation. Thus, there is an actual problem of the
asymptotic solution of boundary value problems for
the two-dimensional systems of equations of NernstPlanck
and Poisson without these restrictions. These
researches we derived in simplified models of
electroosmosis in galvanic dynamical mode using the
decomposition method. We have created a hierarchical
system of two-dimensional mathematical models of
ion transport of salt and electroosmosis in micro- and
nanochannels formed by selective ion-exchange
membranes
For effective management of economic and financial activity of a modern enterprise it is required to have information – software supply for its separate components: branches, divisions, services. Automation of the account allows accelerating significantly the process of granting, processing and the analysis of information necessary for the purposes of management. An important aspect on introduction of a program complex is the concept on its realization, i.e. the head of the company should define the way of development of automation of business - processes, what type of introduction is more preferable to the enterprise, what documents will formalize each of the stages. The article generalizes the data obtained by practical consideration on the basis of the realized projects on introduction of the automated systems in the companies from various fields of activity. The main stages of the design direction in the sphere of automation of business – processes are presented in this work, as well as the features of the subject and the characteristics of each stage, documentary objects for realization of each of them. Also on the basis of the carried-out analysis, the authors described a number of the existing shortcomings on realization of the design direction. In view of the data specified in article, the companies will be able to begin the project on automation of their own business effectively and quickly
This article focuses on the mathematical modeling of
evaluation of financial and economic activities of a
company and on definition (based on this model) of
such balance settings (line F1 and F2) which would
make financial-economic indicators of the activities of
the organization optimal, and the total cumulative
score was the maximum. The knowledge and the use
of the optimal parameters of the balance will allow the
managers to plan strategy for the future development
of the company. The article analyzes the dependencies
of each of the 15 basic indicators (profitability,
turnover, financial stability, liquidity and solvency) of
financial and economic activity of the organization on
the balance parameters. The optimal values of the
parameters of the balance and the main indicators of
financial and economic activities of the organization
have been found. We have also built a mathematical
model of optimal control of financial and economic
indicators in the form of a problem of mathematical
programming. For example, for the company called "Nika" it is shown the possibility of improving
estimation of financial and economic condition of the
organization. Knowledge of the optimal parameters of
the balance will allow the managers to plan strategy
for the future development of the organization. To
solve this problem we have used the method of
generalized reduced gradient implemented in Excel,
with which there was found a maximum of the
objective function for the article restrictions. The
article describes the analysis algorithm of the
optimization problem. A common assessment was
carried out in stages, based on the calculation
algorithm of sequentially improved target functions
There is a 2D mathematical model of ion transport
binary salt with the main conjugate effects of
concentration polarization in the overlimiting current
mode: the bulk charge and the dissociation/
recombination of water, gravity and electroconvection
and Joule heating the solution in the form of a
boundary value problem for systems of differential
equations with partial derivatives in the article. This
system is presented in a form convenient for numerical
solution. We describe the necessary boundary
conditions. This article presents a theoretical study of
the interaction of forced, gravitational and
electroconvection, the dissociation / recombination of
water molecules, and Joule heating of the solution and
heat transport through membranes. We have
constructed a mathematical model of two-dimensional
non-stationary ion transport binary salt in a smooth
rectangular channel desalting electrodialysis device
using equations Nernst-Planck-Poisson, heat
conduction and Navier-Stokes equations and the
natural boundary conditions. For numerical solution
we use the finite element method, with the splitting of
task at each new time layer into three subtasks:
electrochemical, thermal conductivity, hydrodynamic.
Such approach to the development of numerical
methods is the original and can solve arising in
modeling boundary-value problems for a nonlinear system of partial differential equations
This article describes a mathematical model of transport
of salt ions in a cell with a rotating disk cation exchange
membrane at transcendent current regimes, taking into
account electroconvection. Based on this model, we had
a theoretically study of the process of transfer of salt
ions and the dependence of the thickness of the
diffusion layer from the fall of potential. This article is
a continuation of [8] and [9], it conducted a numerical
analysis of boundary value problem for a system of
equations Nernst-Planck-Poisson and Navier-Stokes
equations, modeling the transport of salt ions in a
cylindrical cell with a rotating disc cation exchange
membrane based on electroconvection. It is shown there
is an electroconvection vortex in the center of the
membrane disc. The solution flows around this vortex
and forms a stagnation zone in front of it. With the
increase in the size of the fall of potential, the
electroconvective vortex decreases and at some value,
the electroconvective vortex disappears. The study was
conducted in the 1000 s when the angular velocity of 30 turns in a minute and change of the potential difference
of 0.2V to 1.4V with a step 0.1. As a result, in this
study it is shown that the thickness of the diffusion
layer is practically linearly dependent on the fall of
potential. The linear dependence of the thickness of
diffusion layer from the fall of potential, in the first
approximation, is disturbed by a slight deflection curve,
the causes of which are needed to be found by means of
extra experiments
This article is devoted to the asymptotic analysis of
boundary value problem for a system of equations of
Nernst-Planck and Poisson for a singularly perturbed
system of ordinary differential equations [1], based on
two parameters. This boundary value problem
simulates electrodiffusion of four kinds of ions at the
same time in the diffusion layer in electro-membrane
systems with perfectly selective membrane, taling into
consideration the reaction of recombination of two
ions. Meanwhile the other two ions represent ions of a
binary salt. As a simple example, we consider the
transport of ions sodium, chlorine, hydrogen and
hydroxide, moreover, hydrogen and hydroxyl ions
recombine in the diffusion layer. A more complex case
is the transfer of the products of dissociation of the
dihydrogen phosphate of sodium, namely, ions of
sodium and dihydrogen phosphate, the latter dissociate at the interface, in turn, hydrogen ions and hydrogen
phosphate. Thus, in the solution can simultaneously
store three different types of ions: sodium, hydrogen,
phosphate. During the transfer, hydrogen ions and ions
of hydrogen phosphate recombine to produce
phosphoric acid. The article has revealed the structure
of the Nernst diffusion layer at currents above
Harkatsa current. It is shown, that in the diffusion
layer, there are two types of boundary layers: the inner
(reaction) boundary layer and boundary layer at the
interface solution / membrane
This article is a continuation of the previous works of
the authors [The influence of reaction dissociation /
recombination of molecules of water on transportation
of electrolyte 1:1 in the membrane systems in the
diffusion layer. Part 1. Mathematical model //
Scientific journal of Kuban State Agrarian University,
2016. No. 07(121) and The influence of the reaction of
dissociation / recombination of molecules of water on
transportation of electrolyte 1: 1 in membrane systems
in the diffusion layer. Part 2. Asymptotic analysis //
Scientific journal of Kuban State Agrarian University,
2016. – №08(122)] and devoted to assessing the
possibility of gravitational convection due to the
recombination of hydrogen and hydroxyl ions. The
article presents the solution of a boundary-value
problem, which is a mathematical model of
electrodiffusion for the four types of ions at the same
time (two ions of salts and hydrogen and hydroxyl
ions) in the diffusion layer in electro-membrane
systems with ideal selective membrane, with the heat
transfer equation and the Navier-Stokes equation. The
article shows the possibility of the emergence of
gravitational convection due to the exothermic reaction
of recombination of water molecules in the depth of
the solution. The article considered the reaction of
recombination of hydrogen ions and hydroxyl,
although the main results can be applied, after appropriate modifications, and to amfolit-containing
solutions, such as wine, juices, dairy products,
microbiological processing of biomass (amino acids,
anions of polybasic carboxylic acids), municipal
effluent (anions of phosphoric acid), etc.