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<article article-type="research-article" dtd-version="1.3" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xml:lang="ru"><front><journal-meta><journal-id journal-id-type="publisher-id">vestifm</journal-id><journal-title-group><journal-title xml:lang="ru">Известия Национальной академии наук Беларуси. Серия физико-математических наук</journal-title><trans-title-group xml:lang="en"><trans-title>Proceedings of the National Academy of Sciences of Belarus. Physics and Mathematics Series</trans-title></trans-title-group></journal-title-group><issn pub-type="ppub">1561-2430</issn><issn pub-type="epub">2524-2415</issn><publisher><publisher-name>The Republican Unitary Enterprise Publishing House "Belaruskaya Navuka"</publisher-name></publisher></journal-meta><article-meta><article-id pub-id-type="doi">10.29235/1561-2430-2022-58-2-135-143</article-id><article-id custom-type="elpub" pub-id-type="custom">vestifm-638</article-id><article-categories><subj-group subj-group-type="heading"><subject>Research Article</subject></subj-group><subj-group subj-group-type="section-heading" xml:lang="ru"><subject>МАТЕМАТИКА</subject></subj-group><subj-group subj-group-type="section-heading" xml:lang="en"><subject>MATHEMATICS</subject></subj-group></article-categories><title-group><article-title>Вещественная автономная квадратичная система трех дифференциальных уравнений с бесконечным числом предельных циклов</article-title><trans-title-group xml:lang="en"><trans-title>A real autonomous quadratic system of three differential equations with an infinite number of limit cycles</trans-title></trans-title-group></title-group><contrib-group><contrib contrib-type="author" corresp="yes"><name-alternatives><name name-style="eastern" xml:lang="ru"><surname>Гринь</surname><given-names>А. А.</given-names></name><name name-style="western" xml:lang="en"><surname>Hryn</surname><given-names>A. A.</given-names></name></name-alternatives><bio xml:lang="ru"><p>Гринь Александр Александрович – доктор физико-математических наук, профессор, заведующий кафедрой математического анализа, дифференциальных уравнений и алгебры</p><p>ул. Ожешко, 22, 230023, Гродно</p></bio><bio xml:lang="en"><p>Aliaksandr A. Hryn – Dr. Sc. (Physics and Mathematics), Professor, Head of the Department of Mathematical Analysis, Differential Equations and Algebra</p><p>22, Ozheshko Str., 230023, Grodno</p></bio><email xlink:type="simple">grin@grsu.by</email><xref ref-type="aff" rid="aff-1"/></contrib><contrib contrib-type="author" corresp="yes"><name-alternatives><name name-style="eastern" xml:lang="ru"><surname>Мусафиров</surname><given-names>Э. В.</given-names></name><name name-style="western" xml:lang="en"><surname>Musafirov</surname><given-names>E. V.</given-names></name></name-alternatives><bio xml:lang="ru"><p>Мусафиров Эдуард Владимирович – кандидат физико-математических наук, доцент, доцент кафедры технической механики</p><p>ул. Курчатова, 1а, 230005</p></bio><bio xml:lang="en"><p>Eduard V. Musafirov – Ph. D. (Physics and Mathe matics), Associate Professor of the Department of Technical Mechanics</p><p>1а, Kurchatov Str., 230005, Grodno</p></bio><email xlink:type="simple">Musafirov_ev@grsu.by</email><xref ref-type="aff" rid="aff-1"/></contrib><contrib contrib-type="author" corresp="yes"><name-alternatives><name name-style="eastern" xml:lang="ru"><surname>Проневич</surname><given-names>А. Ф.</given-names></name><name name-style="western" xml:lang="en"><surname>Pranevich</surname><given-names>A. F.</given-names></name></name-alternatives><bio xml:lang="ru"><p>Проневич Андрей Францевич – кандидат физико-математических наук, доцент, проректор по научной работе</p><p>ул. Гаспадарчая, 23, 230005, Гродно</p></bio><bio xml:lang="en"><p>Andrei F. Pranevich – Ph. D. (Physics and Mathematics), Associate Professor, Vice-Rector for Research</p><p>23, Gaspadarchaya Str., 230005, Grodno</p></bio><email xlink:type="simple">pranevich@grsu.by</email><xref ref-type="aff" rid="aff-1"/></contrib></contrib-group><aff-alternatives id="aff-1"><aff xml:lang="ru"><institution>Гродненский государственный университет имени Янки Купалы</institution></aff><aff xml:lang="en"><institution>Yanka Kupala State University of Grodno</institution></aff></aff-alternatives><pub-date pub-type="collection"><year>2022</year></pub-date><pub-date pub-type="epub"><day>05</day><month>07</month><year>2022</year></pub-date><volume>58</volume><issue>2</issue><fpage>135</fpage><lpage>143</lpage><permissions><copyright-statement>Copyright &amp;#x00A9; Гринь А.А., Мусафиров Э.В., Проневич А.Ф., 2022</copyright-statement><copyright-year>2022</copyright-year><copyright-holder xml:lang="ru">Гринь А.А., Мусафиров Э.В., Проневич А.Ф.</copyright-holder><copyright-holder xml:lang="en">Hryn A.A., Musafirov E.V., Pranevich A.F.</copyright-holder><license xml:lang="ru" license-type="creative-commons-attribution" xlink:href="https://creativecommons.org/licenses/by/4.0/" xlink:type="simple"><license-p>Данная работа распространяется под лицензией Creative Commons Attribution 4.0.</license-p></license><license xml:lang="en" license-type="creative-commons-attribution" xlink:href="https://creativecommons.org/licenses/by/4.0/" xlink:type="simple"><license-p>This work is licensed under a Creative Commons Attribution 4.0 License.</license-p></license></permissions><self-uri xlink:href="https://vestifm.belnauka.by/jour/article/view/638">https://vestifm.belnauka.by/jour/article/view/638</self-uri><abstract><p>Рассматривается задача построения вещественных автономных квадратичных систем трех дифференциальных уравнений с нелокальным существованием бесконечного числа предельных циклов. Имеется в виду, что бесконечное число предельных циклов, появившись из фокуса за счет бифуркации Андронова – Хопфа, может существовать в фазовом пространстве не только в окрестности фокуса и не только для значений параметра, близких к бифуркационному значению. Для решения поставленной задачи применяется способ нахождения предельных циклов как линий пересечения инвариантной плоскости с семейством инвариантных эллиптических параболоидов. Затем исследование предельных циклов построенной системы третьего порядка сводится к исследованию соответствующей системы второго порядка на каждом из инвариантных эллиптических параболоидов. Доказательство нелокального существования предельного цикла и установление характера его устойчивости для такой системы второго порядка проводится с помощью построения топографической системы Пуанкаре или перехода к полярным координатам.</p></abstract><trans-abstract xml:lang="en"><p>In this paper, we consider the problem of construction of real autonomous quadratic systems of three differential equations with the nonlocal existence of an infinite number of limit cycles. This means that an infinite number of limit cycles, emerging from the focus due to the Andronov – Hopf bifurcation, can exist in the phase space not only in the vicinity of the focus and not only for parameter values close to the bifurcation value. To solve this problem we use the method of determination of limit cycles as the curves of intersection of an invariant plane with a family of invariant elliptic paraboloids. Then the study of the limit cycles of the constructed system of the third order is reduced to the study of the corresponding system of the second order on each of the invariant elliptic paraboloids. The proof of the nonlocal existence of the limit cycle and the investigation of its stability for such a second-order system is carried out by constructing a topographic system of Poincaré functions or by transforming to polar coordinates.</p></trans-abstract><kwd-group xml:lang="ru"><kwd>автономная квадратичная система третьего порядка</kwd><kwd>предельный цикл</kwd><kwd>инвариантная поверхность</kwd><kwd>точка покоя</kwd><kwd>бифуркация Андронова – Хопфа</kwd></kwd-group><kwd-group xml:lang="en"><kwd>autonomous quadratic system of the third order</kwd><kwd>limit cycle</kwd><kwd>invariant surface</kwd><kwd>stationary point</kwd><kwd>Andronov –  Hopf bifurcation</kwd></kwd-group><funding-group><funding-statement xml:lang="ru">Исследование поддержано проектом Horizon 2020-2017-RISE-777911.</funding-statement><funding-statement xml:lang="en">The research is supported by the project Horizon 2020-2017-RISE-777911.</funding-statement></funding-group></article-meta></front><back><ref-list><title>References</title><ref id="cit1"><label>1</label><citation-alternatives><mixed-citation xml:lang="ru">Методы качественной теории в нелинейной динамике / Л. 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