Journal of Numerical and Applied Mathematics最新文献_第5页

MODELING OF A VENTILATED CAVITY BEHIND A STREAMLINED BODY 流线型车身后通风腔的建模

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Journal of Numerical and Applied Mathematics Pub Date : 2021-01-01 DOI: 10.17721/2706-9699.2021.1.09

G. Voropaiev, V. I. Korobov, N. Dimitrieva

引用次数: 0

HYDRAULIC MODELS IN THE PROBLEMS OF THERMAL POWER PLANT AUXILIARY ENERGY EFFICIENCY IMPROVEMENT 水工模型在火电厂辅助能源效率提高中的问题

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Journal of Numerical and Applied Mathematics Pub Date : 2021-01-01 DOI: 10.17721/2706-9699.2021.1.04

V. Vanin, M. Kruhol

{"title":"HYDRAULIC MODELS IN THE PROBLEMS OF THERMAL POWER PLANT AUXILIARY ENERGY EFFICIENCY IMPROVEMENT","authors":"V. Vanin, M. Kruhol","doi":"10.17721/2706-9699.2021.1.04","DOIUrl":"https://doi.org/10.17721/2706-9699.2021.1.04","url":null,"abstract":"The work is devoted to the study of thermal power plants auxiliary energy efficiency. The main mechanisms in the auxiliary systems are centrifugal mechanisms that work in complex hydraulic networks with variable productivity. The main ways to adjust the parameters of the centrifugal mechanisms are to change the speed of rotor rotation, change the guide vane angle and throttle. The operation mode of a complex hydraulic network which includes a group of centrifugal mechanisms with a mixed connection scheme is analyzed. The system of equations which characterize the hydraulic system has been obtained on the basis of Kirchhoff's laws. The centrifugal mechanisms' operating characteristics are given by approximation dependences obtained with the method of least squares and similarity laws. To analyze efficiency of different methods of centrifugal mechanisms parameters regulation, optimal control problems were set and solved. The constraints for the problems are a system of equations that describe the hydraulic system operation and technical constraints that depend on the control method. Through solving the problems, values of the optimal parameters and weighted average efficiency of the group mechanisms were obtained. Studies have shown that the most effective way to regulate the centrifugal mechanisms parameters is to use an individual frequency drive, the least effective is to use only changing angle of centrifugal mechanism's guide vane. Utilization of group control is highly efficient and not inferior to individual frequency drive. However, this statement is correct under condition of the operating characteristics agreement with the centrifugal mechanisms’ operating modes similarity.","PeriodicalId":40347,"journal":{"name":"Journal of Numerical and Applied Mathematics","volume":"1 1","pages":""},"PeriodicalIF":0.1,"publicationDate":"2021-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85094124","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

PARTICULARS OF A WAVE FIELD IN A SEMI-INFINITE WAVEGUIDE WITH MIXED BOUNDARY CONDITIONS AT ITS EDGE 边缘有混合边界条件的半无限波导中波场的特性

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Journal of Numerical and Applied Mathematics Pub Date : 2021-01-01 DOI: 10.17721/2706-9699.2021.1.13

N. Gorodetskaya, I. Starovoit, T. Shcherbak

{"title":"PARTICULARS OF A WAVE FIELD IN A SEMI-INFINITE WAVEGUIDE WITH MIXED BOUNDARY CONDITIONS AT ITS EDGE","authors":"N. Gorodetskaya, I. Starovoit, T. Shcherbak","doi":"10.17721/2706-9699.2021.1.13","DOIUrl":"https://doi.org/10.17721/2706-9699.2021.1.13","url":null,"abstract":"The work is devoted to the analysis of the wave field, which is excited by the reflection of the first normal propagation Rayleigh-Lamb wave from the edge of an elastic semi-infinite strip, part of which is rigidly clamped, and part is free from stresses. The boundary value problem belongs to the class of mixed boundary value problems, the characteristic feature of which is the presence of a local feature of stresses at the point of change of the type of boundary conditions. To solve this boundary value problem, the paper proposes a method of superposition, which allows to take into account the feature of stresses due to the asymptotic properties of the unknown coefficients. Asymptotic dependences for coefficients are determined by the nature of the feature, which is known from the solution of the static problem. The criterion for the correctness of the obtained results was the control of the accuracy of the law of conservation of energy, the error of which did not exceed 2% of the energy of the incident wave for the entire considered frequency range. The paper evaluates the accuracy of the boundary conditions. It is shown that the boundary conditions are fulfilled with graphical accuracy along the entire end of the semi-infinite strip, except around a special point ($epsilon$). In this case, along the clamped end of the semi-infinite strip in the vicinity of a special point of stress remain limited. The presence of the region $epsilon$ and the limited stresses are due to the fact that the calculations took into account the $N$ members of the series that describe the wave field, and starting from the $N+1$ member of the series moved to asymptotic values of unknown coefficients, the number of which was also limited to $2N$. As the value $N$ increased, the accuracy of the boundary conditions increased, the region $epsilon$ decreased, and the magnitude of the stresses near the singular point increased.","PeriodicalId":40347,"journal":{"name":"Journal of Numerical and Applied Mathematics","volume":"135 1","pages":""},"PeriodicalIF":0.1,"publicationDate":"2021-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86825720","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

GAUSS APPROXIMATION FOR NUMBER DISTRIBUTION IN OF A PASCAL’S TRIANGLE 帕斯卡三角形中数字分布的高斯近似

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Journal of Numerical and Applied Mathematics Pub Date : 2021-01-01 DOI: 10.17721/2706-9699.2021.1.01

Technical University, Kherson State, академия, Украина

引用次数: 0

METHODS OF OPTIMIZATION OF PARAMETRIC SYSTEMS 参数系统的优化方法

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Journal of Numerical and Applied Mathematics Pub Date : 2021-01-01 DOI: 10.17721/2706-9699.2021.1.20

V. Matvienko, V. V. Pichkur, D. Cherniy

引用次数: 0

THE DIFFUSION-DRIFT PROCESS WITH ACCOUNT HEATING AND RECOMBINATION IN THE p-i-n DIODES ACTIVE REGION MATHEMATICAL MODELING BY THE PERTURBATION THEORY METHODS 用微扰理论方法建立了p-i-n二极管有源区中考虑加热和复合的扩散漂移过程的数学模型

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Journal of Numerical and Applied Mathematics Pub Date : 2021-01-01 DOI: 10.17721/2706-9699.2021.1.03

A. Bomba, I. P. Moroz

{"title":"THE DIFFUSION-DRIFT PROCESS WITH ACCOUNT HEATING AND RECOMBINATION IN THE p-i-n DIODES ACTIVE REGION MATHEMATICAL MODELING BY THE PERTURBATION THEORY METHODS","authors":"A. Bomba, I. P. Moroz","doi":"10.17721/2706-9699.2021.1.03","DOIUrl":"https://doi.org/10.17721/2706-9699.2021.1.03","url":null,"abstract":"With prolonged transmission of an electric current through the semiconductor devices, in a particular p-i-n diodes, an electron-hole plasma of their active region is heated. This paper presents the theoretical studies results of the plasma heating effect by the Joule heat release in the p-i-n diode volume and the charge carriers recombination energy release on the plasma concentration distribution in the p-i-n diodes active region. The mathematical model is proposed for predicting the electron-hole plasma stationary concentration distribution and the temperature field in the i-region of the bulk p-i-n diodes in the form of a nonlinear boundary value problem in a given area for the equations system, which consist of the charge carrier current continuity equations, the Poisson and the thermal conductivity. It is shown that the differential equations of the model contain a small parameter in such a way that the Poisson equation is singularly perturbed and the heat conduction equation is regularly perturbed. An approximate solution of the problem posed is obtained in the form of the corresponding asymptotic series in powers of the small parameter. The asymptotic serieses, which describes the behavior of the plasma concentration and potential in the investigated region, containing near-boundary corrections to ensure the fulfillment of the boundary conditions. The terms of these series are found as a result of solving a sequence of boundary value problems, obtained as a result of splitting the original problem, for systems of linear differential equations. The boundary value problem for a nonlinear heat equation is reduced to a sequence of problems for the corresponding linear inhomogeneous equations. The process of refining solutions is iterative. The stabilization of the process is ensured by the existence of negative feedback in the system (as the temperature rises, the mobility of charge carriers decreases).","PeriodicalId":40347,"journal":{"name":"Journal of Numerical and Applied Mathematics","volume":"25 1","pages":""},"PeriodicalIF":0.1,"publicationDate":"2021-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84708659","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 3

THE CHEBYSHEV PROJECTIONS ON POLYHEDRON 多面体上的切比雪夫投影

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Journal of Numerical and Applied Mathematics Pub Date : 2021-01-01 DOI: 10.17721/2706-9699.2021.2.02

V. Zorkaltsev

{"title":"THE CHEBYSHEV PROJECTIONS ON POLYHEDRON","authors":"V. Zorkaltsev","doi":"10.17721/2706-9699.2021.2.02","DOIUrl":"https://doi.org/10.17721/2706-9699.2021.2.02","url":null,"abstract":"The problem of minimizing weighted Chebyshev norm on a convex polyhedron defined as the set of solutions to a system of linear inequalities may have a non-unique solution. Moreover, among the solutions to this problem, there may be clearly not suitable points of the polyhedron for the role of the closest points to the zero vector. It complicates, in particular, the Chebyshev approximation. In order to overcome the problems arising from this, the Haar condition is used, which means the requirement for the uniqueness of the solution of the indicated problem. This requirement is not always easy to verify and it is not clear what to do if it is not true. An algorithm is presented that always generates a unique solution to the indicated problem, based on the search with respect to interior points for optimal solutions of a finite sequence of linear programming problems. The solution developed is called the Chebyshev projection of the origin onto the polyhedron. It is proved that this solution is a vector of a polyhedron with Pareto-minimal absolute values of the components. It is proved that the sets of Chebyshev (according to the introduced algorithm) and Euclidean projections of the origin of coordinates onto the polyhedron, formed by varying the positive weight coefficients in the minimized Euclidean and Chebyshev norms, coincide.","PeriodicalId":40347,"journal":{"name":"Journal of Numerical and Applied Mathematics","volume":"9 1","pages":""},"PeriodicalIF":0.1,"publicationDate":"2021-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87777114","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

PHYSICAL AND MATHEMATICAL MODELING OF THE WAVE QUENCHING CHAMBER WITH THE UPPER PART IN THE FORM OF A PERMEABLE WATERFRONT 对上部为透水滨水形式的消波室进行了物理和数学建模

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Journal of Numerical and Applied Mathematics Pub Date : 2021-01-01 DOI: 10.17721/2706-9699.2021.1.26

A. G. Kharchenko, L. P. Abramova, I. A. K. I.B, Kudybyn, Institute of Hydromechanics, Academy of, Sciences of, Kyiv Ukraine

引用次数: 0

CONTROLLABILITY OF A LINEAR DISCRETE SYSTEM WITH CHANGE OF THE STATE VECTOR DIMENSION 随状态向量维数变化的线性离散系统的可控性

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Journal of Numerical and Applied Mathematics Pub Date : 2021-01-01 DOI: 10.17721/2706-9699.2021.1.23

V. V. Pichkur, D. A. Mazur, V. Sobchuk

引用次数: 0

TWO-LEVEL PROBLEMS AND TWO-STAGE PROXIMAL ALGORITHM 两级问题与两阶段近端算法

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Journal of Numerical and Applied Mathematics Pub Date : 2021-01-01 DOI: 10.17721/2706-9699.2021.2.07

V. Semenov, Yana Vedel, S. Denisov

引用次数: 0