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Izvestiya Vysshikh Uchebnykh Zavedenii. Matematika最新文献

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Three-webs from circles 由圆组成的三张网
Izvestiya Vysshikh Uchebnykh Zavedenii. Matematika Pub Date : 2023-12-24 DOI: 10.26907/0021-3446-2023-12-71-89
A. M. Shelekhov
{"title":"Three-webs from circles","authors":"A. M. Shelekhov","doi":"10.26907/0021-3446-2023-12-71-89","DOIUrl":"https://doi.org/10.26907/0021-3446-2023-12-71-89","url":null,"abstract":"A new geometric necessary condition for regularity of a curved tree-web is found. A class of tree-webs from circles generalizing the regular tree-web of W. Blaschke from three elliptic bundles of circles with pairwise coinciding vertices is considered, and it is shown that only webs equivalent to the Blaschke web are regular in this class.","PeriodicalId":507800,"journal":{"name":"Izvestiya Vysshikh Uchebnykh Zavedenii. Matematika","volume":"1986 3","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-12-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139160566","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
Generalized integration over non-recifiable flat curves and boundary value problems 不可重复平曲线上的广义积分和边界值问题
Izvestiya Vysshikh Uchebnykh Zavedenii. Matematika Pub Date : 2023-12-23 DOI: 10.26907/0021-3446-2023-12-17-38
D. B. Katz
{"title":"Generalized integration over non-recifiable flat curves and boundary value problems","authors":"D. B. Katz","doi":"10.26907/0021-3446-2023-12-17-38","DOIUrl":"https://doi.org/10.26907/0021-3446-2023-12-17-38","url":null,"abstract":"The review discusses two closely related problems: the solution of the Riemann boundary value problem for analytic functions and some of their generalizations in areas of the complex plane with non-rectifiable boundaries, and the construction of a generalization of the curvilinear integral to non-rectifiable curves that preserves properties important for complex analysis. This work reflects the current state of the issue, and many of the results presented in it were obtained quite recently. At the end of the article, readers are offered a number of unsolved problems, each of which can serve as a starting point for scientific research.","PeriodicalId":507800,"journal":{"name":"Izvestiya Vysshikh Uchebnykh Zavedenii. Matematika","volume":"33 2","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-12-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139162545","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
Convolution kernel determination problem in the third order Moore–Gibson–Thompson equation 三阶摩尔-吉布森-汤普森方程中的卷积核确定问题
Izvestiya Vysshikh Uchebnykh Zavedenii. Matematika Pub Date : 2023-12-23 DOI: 10.26907/0021-3446-2023-12-3-16
D. K. Durdiev, A. A. Boltaev, A. Rahmonov
{"title":"Convolution kernel determination problem in the third order Moore–Gibson–Thompson equation","authors":"D. K. Durdiev, A. A. Boltaev, A. Rahmonov","doi":"10.26907/0021-3446-2023-12-3-16","DOIUrl":"https://doi.org/10.26907/0021-3446-2023-12-3-16","url":null,"abstract":"This article is concerned with the study of the inverse problem of determining the difference kernel in a Volterra type integral term function in the third-order Moore–Gibson–Thompson (MGT) equation. First, the initial-boundary value problem is reduced to an equivalent problem. Using the Fourier spectral method, the equivalent problem is reduced to a system of integral equations. The existence and uniqueness of the solution to the integral equations are proved. The obtained solution to the integral equations of Volterra-type is also the unique solution to the equivalent problem. Based on the equivalence of the problems, the theorem of the existence and uniqueness of the classical solutions of the original inverse problem is proved.","PeriodicalId":507800,"journal":{"name":"Izvestiya Vysshikh Uchebnykh Zavedenii. Matematika","volume":"31 2","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-12-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139161586","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
Method and algorithm for calculating isobaric and non-isobaric three-dimensional turbulent jets of reacting gases 计算反应气体等压和非等压三维湍流射流的方法和算法
Izvestiya Vysshikh Uchebnykh Zavedenii. Matematika Pub Date : 2023-12-09 DOI: 10.26907/0021-3446-2023-11-41-58
S. Khodjiev
{"title":"Method and algorithm for calculating isobaric and non-isobaric three-dimensional turbulent jets of reacting gases","authors":"S. Khodjiev","doi":"10.26907/0021-3446-2023-11-41-58","DOIUrl":"https://doi.org/10.26907/0021-3446-2023-11-41-58","url":null,"abstract":"This paper presents a calculation method and algorithm, as well as numerical results of studying chemically reacting turbulent jets based on three-dimensional parabolic systems of Navier-Stokes equations for multicomponent gas mixtures.Continuity equations are used to calculate the mass imbalance when solving with constant pressure, and with variable pressures, with the equations of motion and continuity.Diffusion combustion of a propane-butane mixture flowing from a square-shaped nozzle in a submerged flow of an air oxidizer has been numerically studied. Pressure variability significantly affects the velocity (temperature) profiles in the initial sections of the jet, and when moving away from the nozzle exit, the pressure effect can be considered imperceptible, but the flame length is longer than at constant pressure, but it does not significantly affect the shape of the flame.The saddle-shaped behavior of the longitudinal velocity in the direction of the major axis is numerically obtained for large initial values of the turbulence kinetic energy of the main jet.Given method allows the study of non-reacting and reactive turbulent jets flowing from a rectangular nozzle.","PeriodicalId":507800,"journal":{"name":"Izvestiya Vysshikh Uchebnykh Zavedenii. Matematika","volume":"25 6","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-12-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139184813","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
Finite element modeling of the eigenvibrations of the square plate with attached oscillator 附带振子的方形板特征振动的有限元建模
Izvestiya Vysshikh Uchebnykh Zavedenii. Matematika Pub Date : 2023-12-09 DOI: 10.26907/0021-3446-2023-11-92-97
D. M. Korosteleva, S. I. Solov’ev
{"title":"Finite element modeling of the eigenvibrations of the square plate with attached oscillator","authors":"D. M. Korosteleva, S. I. Solov’ev","doi":"10.26907/0021-3446-2023-11-92-97","DOIUrl":"https://doi.org/10.26907/0021-3446-2023-11-92-97","url":null,"abstract":"For the problem on eigenvibrations of the plate with an attached oscillator, the new symmetric linear variational statement is proposed. It is established the existence of the sequence of positive eigenvalues of finite multiplicity with limit point at infinity and the corresponding complete orthonormal system of eigenvectors. The new symmetric scheme of the finite element method with Hermite finite elements is formulated. Error estimates consistent with the solution smoothness for the approximate eigenvalues and approximate eigenvectors are proved. The results of numerical experiments illustrating the influence of the solution smoothness on the computation accuracy are presented.","PeriodicalId":507800,"journal":{"name":"Izvestiya Vysshikh Uchebnykh Zavedenii. Matematika","volume":"8 3","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-12-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139184877","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
Approximation of the Lebesgue constant of the Fourier operator by a logarithmic-fractional-rational function 用对数-分数-有理函数逼近傅里叶算子的勒贝格常数
Izvestiya Vysshikh Uchebnykh Zavedenii. Matematika Pub Date : 2023-12-09 DOI: 10.26907/0021-3446-2023-11-75-85
I. A. Shakirov
{"title":"Approximation of the Lebesgue constant of the Fourier operator by a logarithmic-fractional-rational function","authors":"I. A. Shakirov","doi":"10.26907/0021-3446-2023-11-75-85","DOIUrl":"https://doi.org/10.26907/0021-3446-2023-11-75-85","url":null,"abstract":"The Lebesgue constant of the classical Fourier operator is uniformly approximated by a logarithmic-fractional-rational function depending on three parameters; they are defined using the specific properties of logarithmic and rational approximations. A rigorous study of the corresponding residual term having an indefinite (non-monotonic) behavior has been carried out. The obtained approximation results strengthen the known results by more than two orders of magnitude.","PeriodicalId":507800,"journal":{"name":"Izvestiya Vysshikh Uchebnykh Zavedenii. Matematika","volume":"8 4","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-12-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139184764","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
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