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Model Map and Multistability for a Two Predator-One Prey System
Full text linkThis work contains a review of some important results on a known two predators - one prey system. We also add essential new numerical results on multiple attractors. We consider the case when the predators coexist. We distinguish two possibilities. The first is when the dynamics is well described by the dynamics of a one dimensional map. We discuss the main behaviour of this map. For small parameter regions the map can have two attractors but no more than two. We give a numerical example, when these two attractors exist in the original three-dimensional model. The second case is when this model map is not working and something like spiral chaos often occurs. We give numerical results showing that in this case there can be at least four different attractors and discuss the behaviour of these
Полнота и компактность в нормированных пространствах
No full textДанное пособие предназначено для студентов, изучающих функциональный анализ. Основная цель пособия - научить студентов оперировать понятиями полнота и компактность в метрическом и нормированном пространствах, сложными как в теоретическом, так и в практическом плане. Другая цель пособия состоит в том, чтобы обобщить опыт преподавателей математико-механического факультета СПбГУ и выделить ряд типовых заданий и задач повышенной трудности, традиционно рассматриваемых на практических занятиях по функциональному анализу в СПбГУ. Пособие содержит: формулировки необходимых теоретических сведений, связанных с понятиями полноты и компактности в метрическом и нормированном пространствах, задачи с подробными решениями, а также задачи для самостоятельной работы. Пособие предназначено главным образом в качестве материала для практических занятий, но может быть использовано и при подготовке к экзамену по дисциплине «Функциональный анализ»
Location of zeros of lacunary-type polynomials
No full textAlthough recently proved generalization of Eneström-Kakey theorem by N.A.Rather et al. are applicable to the larger class of polynomials as compared to all other Eneström- Kakeya type results, but are not applicable to the polynomials whose one or two coefficients are zero. For instance, if we consider the polynomial whose one or two coefficients are zero, then one can note that all Eneström-Kakey type results including the recent generalizations by N.A.Rather et al. are not applicable to this polynomial. So it is interesting to look for the results applicable to such class of polynomials. Motivated by this, here we establish the following results applicable to such class of polynomials called the lacunary-type polynomials. In this paper, by relaxing the hypothesis of well-known Eneström-Kakey theorem, we obtain a result which is applicable to the lacunary-type of polynomials and generalizes several well-known results concerning the location of zeros of polynomials. In addition to this, we show by examples that our results presents better information about the bounds of zeros of polynomials than some known results
On ellipticity of static equations of strain gradient elasticity and infinitesimal stability
No full textWithin the framework of strain gradient elasticity under finite deformations we formulate the strong ellipticity conditions of equilibrium equations. Within the model a strain energy density is a function of the first and second deformation gradients. Ellipticity involves certain constraints on the tangent elastic moduli. It is also closely related to infinitesimal stability which is defined as the positive definiteness of the second variation of the potential energy functional. Here we consider the first boundary-value problem, that is with Dirichlettype boundary conditions. For one-dimensional deformations we determine necessary and sufficient conditions of infinitesimal instability. The latter constitute two inequalities for elastic moduli
Экспертное заключение по материалам запроса ГУ МВД России по г. Санкт-Петербургу и Ленинградской области (Отдельные фрагменты исключены из текста опубликованного заключения в целях обеспечения соблюдения требований законодательства)
No full textОтдельные фрагменты исключены из текста опубликованного заключения в целях обеспечения соблюдения требований законодательстваAbstrac
ЭКСПЕРТНОЕ ЗАКЛЮЧЕНИЕ по информационным материалам запроса ГУ МВД России по г. Санкт-Петербургу и Ленинградской области (Отдельные фрагменты исключены из текста опубликованного заключения в целях обеспечения соблюдения требований законодательства)
No full textОтдельные фрагменты исключены из текста опубликованного заключения в целях обеспечения соблюдения требований законодательстваAbstrac
ЭКСПЕРТНОЕ ЗАКЛЮЧЕНИЕ по информационным материалам запроса ГУ МВД России по г. Санкт-Петербургу и Ленинградской области (Отдельные фрагменты исключены из текста опубликованного заключения в целях обеспечения соблюдения требований законодательства)
No full textОтдельные фрагменты исключены из текста опубликованного заключения в целях обеспечения соблюдения требований законодательстваAbstrac
Reflection of the concept of energy transfer in the development strategies of industries and regions of Russia
No full textThe article discusses the reasons and factors that make it necessary to transform the structure
of the energy sector and approaches developed to implement the state policy of energy transition
in modern conditions without creating an additional burden on the environment. The
relevance of the topic is confirmed by the global trend of transition to the use of alternative
energy sources, the development of low-carbon technologies and considerations of the exhaustibility
of sources of fossil raw materials with the objective need to find ways to develop alternative
energy, as well as increased external sanctions pressure. A brief review of approaches
to the development of energy strategies in several foreign countries is presented including relevant
documents of the USA, European Union, Germany and France. The conclusion is made
about the global nature of the energy transition processes and the seriousness of the challenges
facing Russia in the context of current trends in the transformation of the world energy industry
and attempts to use the energy transition factor to increase external pressure. The current
Russian strategic planning documents at the federal, sectoral and regional levels are analyzed
in terms of reflecting the state policy measures for the development of renewable energy and
the decarbonization of the economy. Among the documents of the federal level, the strategies
of national security, economic security, the strategy of socio-economic development with low
greenhouse gas emissions (low-carbon strategy) and the strategy for the development of the
Arctic zone are considered. Industry strategies for the development of metallurgy, energy,
transport, construction, science and technology are analyzed, as well as regional strategies for
some subjects of the Russian Federation. The conclusion is made that it is necessary to develop
a systemic long-term state policy in the field of energy transition and its introduction in the
strategies of industries and regions of Russia.The article was prepared as part of the implementation of the Russian Presidential Academy of
National Economy and Public Administration (RANEPA) program of strategic academic leadership
“Priority-2030”
Problems in Threatened Species Conservation: Differences in National Red Lists Assessments with Global Standards
Full text linkThe solution of transnational environmental problems in the field of the protection of
threatened species and conservation biology directly depends on the level of international communication,
which can significantly decrease due to differences in Red Lists and Red Data Books of
different levels. In order to identify the similarities and differences in approaches to the assessment of
national Red Lists and Books of the Baltic Sea region countries (Russia, Denmark, Germany, Lithuania,
Finland, Poland and Sweden) with the IUCN Red List, a comparative analysis was carried out. It
was determined that the level of discrepancy between Red Data Lists and Books varies considerably,
with differences in the scales of species categories, species lists and categories. Most of the threatened
species at the national level are not listed under the IUCN Red List, while species in a more stringent
category at the national level prevail (37% and 3% on average, respectively). However, national Red
Lists and Red Data Books do not take into account the global trend of the risk of extinction of species.
The percentage of species with insufficient information to define a category at the national or global
level ranges from 6% to 28%. These discrepancies make it difficult to exchange data on threatened
species and create a unified database with information on protected species at different levels and,
therefore, reduce the effectiveness of biodiversity conservation activities at regional and international
levels. The results also demonstrate that countries have an international responsibility to conserve
a species, and the cases identified can provide useful additional information to guide a national
conservation strategyThis research was funded by Saint Petersburg State University, project ID: 101662710
(CZ_MDF-2023-1)
FORMALITY OF SPEECH IN COMMUNICATIVE BEHAVIOR (BASED ON THE FIRST BILINGUAL PHRASEBOOKS)
Full text linkIn the article based on the first Low German-Russian phrasebook (Tönnies Fenne’s Low
German Manual of Spoken Russian. Pskov, 1607), recorded by the merchant from Lubeck
Tony Fenne for the implementation of elementary business and everyday communicative
interaction during the period of trade relations between Russia and the Hanseatic
League, the formulaic statements are considered, i. e. repetitive, standardized replicas
consisting of one or several words, selected and used by native speakers to a large
extent automatically based on their life and communicative experience, depending on the communication situation and on the basis of associative connections developed
by practice. The main attention in the article is focused on formulaic statements that
contribute to the establishment of contact and its maintenance. Contact-establishing
formulas include greeting formulas, also associated with wishes and thanks, dating
formulas and appeals. Among the formulas used to maintain a conversation, the article
highlights requests and wishes characteristic of everyday and business communication.
A special place among the contact-supporting formulas is occupied by metacommunicative
statements that direct the dialogue in the right direction from the speaker’s point of view.
Formulaic utterances with the lexeme God are defined in the article as multifunctional,
which can be used both in situations of establishing contact, and its maintenance and
termination and combine greetings, wishes of health, success, good luck, gratitude,
assurances of God’s help, etc. An important place in the phrasebook is given to paremia —
various maxims, proverbs and sayings that are also multifunctional and are used in
various communicative situations as generalizing instructive statements. Refs 24