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118 results on '"Levashova, Natalia"'

5. The Use of Contrast Structures Theory for the Mathematical Modelling of the Wind Field in Spatially Heterogeneous Vegetation Cover

Author

Levashova, Natalia, Muhartova, Julia, Davydova, Marina, Hutchison, David, Series editor, Kanade, Takeo, Series editor, Kittler, Josef, Series editor, Kleinberg, Jon M., Series editor, Mattern, Friedemann, Series editor, Mitchell, John C., Series editor, Naor, Moni, Series editor, Pandu Rangan, C., Series editor, Steffen, Bernhard, Series editor, Terzopoulos, Demetri, Series editor, Tygar, Doug, Series editor, Weikum, Gerhard, Series editor, Dimov, Ivan, editor, Faragó, István, editor, and Vulkov, Lubin, editor

Published
2017
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6. Front Dynamics in an Activator-Inhibitor System of Equations

Author

Melnikova, Alina, Levashova, Natalia, Lukyanenko, Dmitry, Hutchison, David, Series editor, Kanade, Takeo, Series editor, Kittler, Josef, Series editor, Kleinberg, Jon M., Series editor, Mattern, Friedemann, Series editor, Mitchell, John C., Series editor, Naor, Moni, Series editor, Pandu Rangan, C., Series editor, Steffen, Bernhard, Series editor, Terzopoulos, Demetri, Series editor, Tygar, Doug, Series editor, Weikum, Gerhard, Series editor, Dimov, Ivan, editor, Faragó, István, editor, and Vulkov, Lubin, editor

Published
2017
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8. Устойчивость стационарного решения с двухмасштабным внутренним переходным слоем системы уравнений типа активатор-ингибитор

Author

Левашова, Наталия Тимуровна, additional, Levashova, Natalia Timurovna, additional, Самсонов, Дмитрий Сергеевич, additional, and Samsonov, Dmitry Sergeevich, additional

Published
2023
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11. An Algorithm for Construction of the Asymptotic Approximation of a Stable Stationary Solution to a Diffusion Equation System with a Discontinuous Source Function.

Author

Nefedov, Nikolay, Tishchenko, Bogdan, and Levashova, Natalia

Subjects
HEAT equation, EXISTENCE theorems, URBAN growth, METROPOLITAN areas, BIOTIC communities
Abstract

An algorithm is presented for the construction of an asymptotic approximation of a stable stationary solution to a diffusion equation system in a two-dimensional domain with a smooth boundary and a source function that is discontinuous along some smooth curve lying entirely inside the domain. Each of the equations contains a small parameter as a factor in front of the Laplace operator, and as a result, the system is singularly perturbed. In the vicinity of the curve, the solution of the system has a large gradient. Such a problem statement is used in the model of urban development in metropolitan areas. The discontinuity curves in this model are the boundaries of urban biocenoses or large water pools, which prevent the spread of urban development. The small parameter is the ratio of the city's outskirts linear size to the whole metropolis linear size. The algorithm includes the construction of an asymptotic approximation to a solution with a large gradient at the media interface as well as the steps for obtaining the existence conditions. To prove the existence and stability theorems, we use the upper and lower solutions, which are constructed as modifications of the asymptotic approximation to the solution. The latter is constructed using the Vasil'yeva algorithm as an expansion of a small parameter exponent. [ABSTRACT FROM AUTHOR]

Published
2023
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12. Существование и устойчивость стационарного решения системы уравнений диффузии в среде с разрывными характеристиками при различных условиях квазимонотонности

Author

Левашова, Наталия Тимуровна, primary, Levashova, Natalia Timurovna, primary, Тищенко, Богдан Викторович, additional, and Tischenko, Bogdan Viktorovich, additional

Published
2022
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17. Paleomagnetism of mid-Paleozoic subduction-related volcanics from the Chingiz Range in NE Kazakhstan: the evolving paleogeography of the amalgamating Eurasian composite continent

Author

Levashova, Natalia M., Van der Voo, Rob, Abrajevitch, Alexandra V., and Bazhenov, Mikhail L.

Subjects
Central Asia -- Natural history, Cratons -- Structure, Paleomagnetism -- Research, Paleogeography -- Research, Earth sciences
Abstract

The tectonic and paleogeographic evolution of the Ural-Mongol belt between the cratons of Baltica, Siberia, and Tarim is key to the formation of the Eurasian composite continent during Paleozoic time, but the views on this complicated process remain disparate and sometimes controversial. A study of three volcanic formations of mid-Silurian, Lower to Middle Devonian, and Middle Devonian age from the southwestern boundary of the Chingiz Range (NE Kazakhstan) yields what are interpreted as primary paleomagnetic directions that help clarify the evolution of the belt. A single-polarity characteristic component in mid-Silurian andesites yields a positive intraformational conglomerate test, whereas dual-polarity prefolding components are isolated from the two Devonian collections. Post-folding, reversed-polarity overprint directions have also been isolated and are likely of Permo-Triassic age. These new data can be evaluated together with previously published paleomagnetic results from Paleozoic rocks in the Chingiz Range, and allow us to establish with confidence the polarity of each result, and hence to determine the hemisphere in which the area was located at a given time. We conclude that NE Kazakhstan was steadily moving northward, albeit with variable velocity, crossing the equator in Silurian time. These new paleomagnetic data from the Chingiz Range also agree with and reinforce the hypothesis that the strongly curved volcanic belts of Kazakhstan underwent oroclinal bending between Middle Devonian and Middle Permian time. A comparison of the Chingiz paleolatitudes with those of Siberia shows, insofar as the sparse data allow, similarities between the northward motion of the Chingiz unit and that of Siberia, which imposes important constraints on the evolving paleogeography of the Ural-Mongol belt. Keywords: paleomagnetism, volcanic arc, orocline, Middle Paleozoic, Central Asia, Siberia, paleogeography.

Published
2009

18. Решение с внутренним переходным слоем двумерной краевой задачи реакция-диффузия-адвекция с разрывными реактивным и адвективным слагаемыми

Author

Левашова, Наталия Тимуровна, primary, Levashova, Natalia Timurovna, primary, Нефедов, Николай Николаевич, additional, Nefedov, Nikolai Nikolaevich, additional, Николаева, Ольга Александровна, additional, and Nikolaeva, Ol'ga Aleksandrovna, additional

Published
2021
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33. Unraveling the early-middle Paleozoic paleogeography of Kazakhstan on the basis of Ordovician and Devonian paleomagnetic results

Author

Bazhenov, Mikhail L, Levashova, Natalia M, Degtyarev, Kirill E, Van der Voo, Rob, Abrajevitch, Alexandra, McCausland, Phil J A, Bazhenov, Mikhail L, Levashova, Natalia M, Degtyarev, Kirill E, Van der Voo, Rob, Abrajevitch, Alexandra, and McCausland, Phil J A

Abstract

It is a common concept that different tectonic units in the western part of the Central Asian Orogenic Belt were united into the landmass of the Kazakhstania continent in the Paleozoic but many important details of its history remain enigmatic and controversial. Recently published paleomagnetic data from this region demonstrate that the ~. 2000. km long horseshoe-shaped Devonian Volcanic Belt was created by oroclinal bending of an originally rectilinear active margin of Kazakhstania. Still, the Silurian and Devonian paleomagnetic results which this interpretation is based upon are limited and unevenly spread along the belt, and additional middle Paleozoic data are highly desirable. Accordingly, we studied three mid-Paleozoic objects from different segments of this volcanic belt. Two of the three new objects yielded paleomagnetic directions that fit perfectly into the oroclinal scenario, whereas the third one provided no interpretable data. The earlier history of Kazakhstania, however, remains misty. We obtained three new Ordovician results in north-central Kazakhstan and found similar inclinations but widely dissimilar declinations. Previously published data show a large scatter of Ordovician declinations in South Kazakhstan and Kyrgyzstan as well. We analyzed all seven Middle-Late Ordovician paleolatitudes and came to the conclusion that a nearly E-W trending active margin of the Kazakhstania landmass had existed at low (~. 10°S) latitudes at that time. We hypothesize that this margin of the Kazakhstania landmass collided with another island arc, called Baydaulet-Akbastau, and with the Aktau-Junggar microcontinent by the Ordovician-Silurian boundary. As a result of this collision, subduction ceased, and regional deformation, magmatism, and rotations of crustal fragments took place in most of Kazakhstania. In Silurian time, Kazakhstania moved northward crossing the equator and rotating clockwise by ~ 45°. This changed the orientation of the Kazakhstania to NW-SE, an

Published
2012

48. Paleomagnetism and geochronology of the Late Cretaceous-Paleogene island arc complex of the Kronotsky Peninsula, Kamchatka, Russia: Kinematic implications

Author

Levashova, Natalia M., Shapiro, Mikhail N., Beniamovsky, Vladimir N., and Bazhenov, Mikhail L.

Subjects
Kamchatka -- Natural history, Geodynamics -- Research, Island arcs -- Research, Plate tectonics -- Research, Earth sciences
Abstract

Research is presented concerning the movement of the Kronotsky island with the continental plate during the Late Cretaceous and with the Pacific plate in the Paleocene. The remnants of ancient island arcs are discussed.

Published
2000

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