Scientific Journal of KubSAU

Polythematic online scientific journal
of Kuban State Agrarian University
ISSN 1990-4665
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Name

Lebedev Konstantin Andreyevich

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Kuban State University
   

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Articles count: 13

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267 kb

ADAPTIVE TIME SERIES MODELS OF A MOUNTAIN RIVER LEVEL

abstract 1141510109 issue 114 pp. 1517 – 1530 30.12.2015 ru 322
The article presents a technique of short-term forecasting of water level in the river bed of a mountain type using Markov’s chains
151 kb

BEAVER’S TECHNIQUE OF RISK ASSESSMENT IN THE ESTIMATION OF THE FINANCIAL POSITIONS OF COMPANIES USING MATHEMATICAL OPTIMIZATION

abstract 1051501023 issue 105 pp. 425 – 434 30.01.2015 ru 370
In this article we propose a method of determining the share or the significance (weight) of indicators of Beaver and risks R in the portfolio formed by these parameters allowing us to minimize the mean square error evaluating the effectiveness of the portfolio (risk) in the assessment of the financial condition of the companies investigated. The proposed method is the minimization of a quadratic form in variables satisfying lengthy conditions, i.e. the quadratic programming. This technique is implemented using four methods of optimization: analytical method, using built-in function minimization block given, the penalty function method and the gradient method. More so, this technique allows, as shown by the results of the computational experiments, the expert without routine statistical data processing to obtain additional information on the credit worthiness of the investigated enterprise and make a more informed conclusion about its financial condition, which speeds up the decision on granting a loan required by a company. Based on the techniques proposed in this paper, other techniques of assessing the creditworthiness of businesses may be constructed using the results of optimization theory based on well-established applied research methods: Method of evaluating the creditworthiness of Russia, Credit scoring method, the American method, method of Altman and others
135 kb

CONSTRUCTING A THEORETICAL MODEL PREDICTING THE LEVEL OF WATER IN A MOUNTAIN RIVER IS USING MARKOV’S CHAINS

abstract 1141510110 issue 114 pp. 1531 – 1541 30.12.2015 ru 318
The article presents a technique of short-term forecasting of water level in the river bed of a mountain type using Markov’s chains
347 kb

ESTIMATION OF A COMPANY CREDIT STATUS BASED ON THE FIVE-FACTOR “ALTMAN” MODEL USING FUZZY SETS AND SIMULATION

abstract 1081504022 issue 108 pp. 334 – 356 30.04.2015 ru 438
In this article we propose a method that uses the apparatus of the theory of fuzzy sets, together with the five-factor model of Altman in assessing the creditworthiness of an enterprise. Altman's model works in two ways: It applies the root mean square (RMS) integral approximation for the exact calculation of quantitative assessment of creditworthiness (probability of bankruptcy), and using the device of fuzzy sets for ordered sets by the degree of confidence in the resulting probability. In this paper we conducted simulation procedure for the credit assessment and showed the capabilities of the model. The model input parameters , forms system inputs (input variables), allowing you to get the value of the parameter z of Altman. With the help of Altman's model, approximating function L6, the decision function I(p) and the algorithm for calculating preference  we obtain the number of the set i to which belongs a number of ordered sets as fuzzy logic . On the selected simulation parameters, stable statistics can be obtained. Altman's model with the use of computational function allows real values of the input parameters of the enterprise replaced by random values of the simulation model. This technique allows, as shown by the results of computational experiments, the creditor to obtain additional information on the creditworthiness of the investigated enterprise and make a more informed conclusion about its financial condition, which speeds up the decision on the possibility of issuing the required credit. The development of method of estimating fuzzy logic can be applied to other models of assessing the creditworthiness of a company: Davydov's model, Zaitseva's, Saifullina's, Kadykova's and others with appropriate modification
241 kb

ESTIMATION OF A CREDIT STATUS OF THE COMPANY BASED ON THE ALTMAN FIVEFACTOR MODEL USING FUZZY SETS AND INTEGRAL MEAN-SQUARE APPROXIMATION

abstract 1041410039 issue 104 pp. 546 – 561 30.12.2014 ru 529
In this article we have proposed a method using the apparatus of fuzzy sets theory in conjunction with the five-factor model of Altman to assess the creditworthiness of the investigated companies. The Altman model was improved in two ways: by using RMS integral approximation for the exact calculation of the quantitative credit assessment (probability of bankruptcy) and the application of the apparatus of fuzzy sets for ordered sets by the degree of confidence resulting probability
268 kb

FORECASTING THE WATER LEVEL IN A RIVER WITH THE ABRUPT FALLING WATER BASED ON KALMAN-BUSY FILTRATION

abstract 1041410058 issue 104 pp. 775 – 786 30.12.2014 ru 472
The technique of short-term forecasting of the water level in a vein of a mountain type river, based on a method of Kalman-Busy filtration in the make assumption of natural simplifications, characterized for natural objects is offered
1374 kb

MATHEMATICAL MODEL OF ION TRANSPORT THROUGH THE INTERFACE: THE ION EXCHANGE MEMBRANE / STRONG ELECTROLYTE

abstract 1241610011 issue 124 pp. 210 – 242 30.12.2016 ru 169
The article presents a mathematical model of the ion transport across phase boundary exchange membrane / solution. The border is considered as an object in space, endowed with all the physical and chemical properties that are inherent physical and chemical phases. It is regarded as a special physical and chemical environment, having a distributed exchange capacity in which there is space charge dissociation of water molecules. The size of this object is estimated in the range of 1-300 nm. The surface morphology of industrial membrane type MK-40, МA-41 and МA-41P was investigated experimentally by scanning electron microscopy (REM). There was analyzed the amplitude of average surface roughness. In this article, the reaction layer is modeled as a region that forms as a relief morphology of the membrane. Membrane properties are due to the properties of the solution and the properties of the membrane. To determine the dependence of Q(x) is proposed procedure for assessing the proportion of solid phase in the total volume of which can be seen in the vertical cross section microprofile on the membrane surface line. Height multivendors determine the reaction layer zone on frame of model. Influence of surface morphology on the V-A characteristics and the sizes of the convective instability of cation-exchange membrane evaluated numerically simulating the hydrodynamic flow conditions using a solution of the Navier-Stokes equations. The transfer of a strong electrolyte such as NaCl ions through the thin layer of the reaction layer is considered. The place of nanomodel in the structure of a three-layer membrane system is showed. The distribution of the concentration of ions in the system, the charge density distribution and the dependence of the integrate charge with extent nanolayer is present. How to change the shape of the space charge and its integral value with one is investigated
190 kb

MATHEMATICAL MODEL OF THE CORRECTION OF PH SOFTENED WATER IN A LONG CHANNEL OF ELECTRODIALYSIS WITH BIPOLAR MEMBRANE

abstract 1261702002 issue 126 pp. 33 – 49 28.02.2017 ru 199
Theoretically and experimentally, we investigated the process of adjusting the pH of natural water of hydrocarbonate class electrodialyzer with bipolar membranes with channel length of 40 cm. We experimentally measured concentration of components, pH of the solutions in alkaline and acid channels of electrodeposition depending on the current density. The article describes a mathematical model for long channels; to scale the mass transfer characteristics of the process there was applied and verified a method of compartmentalization, which gave the possibility to calculate the dependence of the component along the channel length at different velocities of flow of the solution. Numerical calculations were compared with experimental data on electrodialyser of 10 cm and 40 cm length
203 kb

MATHEMATICAL MODEL OF THE DYNAMICS OF HIV INFECTION WITHOUT TREATMENT

abstract 1101506038 issue 110 pp. 562 – 578 30.06.2015 ru 423
This article discusses the mathematical and numerical modeling of the immune system of the course of HIV infection without treatment. Presently a significant number of scientific papers are devoted to the study of this problem. However, HIV infection is highly volatile and there is no effective drug, in that HIV has the ability to mutate and reproduce itself in the presence of chemical substances that are meant to inhibit or destroy it. The mathematical models used in this paper are conceptual and exploratory in nature. The proposed mathematical model allow us to obtain a complete description of the dynamics of HIV infection, and also an understanding of the progression to AIDS. Thus, the results of the numerical solution of differential equations in this work show that: the disease develops, and at low concentration of the virus, a certain level of stability does not depend on the initial concentration of infestation. In the absence of treatment, for interesting competition between virus and the loss of virus caused by immune response should be strictly greater than the rate of multiplication of the virus in the blood; the reproduction rate of the uninfected cells should be stricly greater than the mortality rate of the uninfected cells
284 kb

MATHEMATICAL MODELING OF ION TRANSPORT THROUGH MEMBRANES IN THE CONDITION OF PREVIOUS SLOW HOMOGENEOUS CHEMICAL REACTION. MATHEMATICAL PROBLEM

abstract 1251701003 issue 125 pp. 85 – 101 31.01.2017 ru 177
In the article we build a mathematical model of elec-tro-diffusion of ions in the diffusion layer of a mem-brane system complicated by the occurrence of the previous slow homogeneous chemical reaction with the condition of electrical neutrality of the solution. We have set a two-point boundary value problem and developed a method to solve it; we have given an algorithm and a numerical method for solving it in Comsol 3.5 environment. The formula for limiting kinetic current was derived. Some of the model’s capabilities to describe the properties of the system are given
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