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    Wyświetlanie 1-6 z 6
    Tytuł:
    Describing Minor 5-Stars in 3-Polytopes with Minimum Degree 5 and No Vertices of Degree 6 or 7
    Autorzy:
    Batueva, Ts.Ch-D.
    Borodin, O.V.
    Ivanova, A.O.
    Nikiforov, D.V.
    Powiązania:
    https://bibliotekanauki.pl/articles/32361718.pdf
    Data publikacji:
    2022-05-01
    Wydawca:
    Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
    Tematy:
    planar graph
    structural properties
    3-polytope
    5-star
    neighborhood
    Opis:
    In 1940, in attempts to solve the Four Color Problem, Henry Lebesgue gave an approximate description of the neighborhoods of 5-vertices in the class P5 of 3-polytopes with minimum degree 5. This description depends on 32 main parameters. (6, 6, 7, 7, 7), (6, 6, 6, 7, 9), (6, 6, 6, 6, 11), (5, 6, 7, 7, 8), (5, 6, 6, 7, 12), (5, 6, 6, 8, 10), (5, 6, 6, 6, 17), (5, 5, 7, 7, 13), (5, 5, 7, 8, 10), (5, 5, 6, 7, 27), (5, 5, 6, 6, ∞), (5, 5, 6, 8, 15), (5, 5, 6, 9, 11), (5, 5, 5, 7, 41), (5, 5, 5, 8, 23), (5, 5, 5, 9, 17), (5, 5, 5, 10, 14), (5, 5, 5, 11, 13) Not many precise upper bounds on these parameters have been obtained as yet, even for restricted subclasses in P5. In 2018, Borodin, Ivanova, Kazak proved that every forbidding vertices of degree from 7 to 11 results in a tight description (5, 5, 6, 6, ∞), (5, 6, 6, 6, 15), (6, 6, 6, 6, 6). Recently, Borodin, Ivanova, and Kazak proved every 3-polytope in P5 with no vertices of degrees 6, 7, and 8 has a 5-vertex whose neighborhood is majorized by one of the sequences (5, 5, 5, 5, ∞) and (5, 5, 10, 5, 12), which is tight and improves a corresponding description (5, 5, 5, 5, ∞), (5, 5, 9, 5, 17), (5, 5, 10, 5, 14), (5, 5, 11, 5, 13) that follows from the Lebesgue Theorem. The purpose of this paper is to prove that every 3-polytope with minimum degree 5 and no vertices of degree 6 or 7 has a 5-vertex whose neighborhood is majorized by one of the ordered sequences (5, 5, 5, 5, ∞), (5, 5, 8, 5, 14), or (5, 5, 10, 5, 12).
    Źródło:
    Discussiones Mathematicae Graph Theory; 2022, 42, 2; 535-548
    2083-5892
    Pojawia się w:
    Discussiones Mathematicae Graph Theory
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    An Extension of Kotzig’s Theorem
    Autorzy:
    Aksenov, Valerii A.
    Borodin, Oleg V.
    Ivanova, Anna O.
    Powiązania:
    https://bibliotekanauki.pl/articles/31340608.pdf
    Data publikacji:
    2016-11-01
    Wydawca:
    Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
    Tematy:
    plane graph
    normal plane map
    structural property
    weight
    Opis:
    In 1955, Kotzig proved that every 3-connected planar graph has an edge with the degree sum of its end vertices at most 13, which is tight. An edge uv is of type (i, j) if d(u) ≤ i and d(v) ≤ j. Borodin (1991) proved that every normal plane map contains an edge of one of the types (3, 10), (4, 7), or (5, 6), which is tight. Cole, Kowalik, and Škrekovski (2007) deduced from this result by Borodin that Kotzig’s bound of 13 is valid for all planar graphs with minimum degree δ at least 2 in which every d-vertex, d ≥ 12, has at most d − 11 neighbors of degree 2. We give a common extension of the three above results by proving for any integer t ≥ 1 that every plane graph with δ ≥ 2 and no d-vertex, d ≥ 11+t, having more than d − 11 neighbors of degree 2 has an edge of one of the following types: (2, 10+t), (3, 10), (4, 7), or (5, 6), where all parameters are tight.
    Źródło:
    Discussiones Mathematicae Graph Theory; 2016, 36, 4; 889-897
    2083-5892
    Pojawia się w:
    Discussiones Mathematicae Graph Theory
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    More About the Height of Faces in 3-Polytopes
    Autorzy:
    Borodin, Oleg V.
    Bykov, Mikhail A.
    Ivanova, Anna O.
    Powiązania:
    https://bibliotekanauki.pl/articles/31342325.pdf
    Data publikacji:
    2018-05-01
    Wydawca:
    Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
    Tematy:
    plane map
    planar graph
    3-polytope
    structural properties
    height of face
    Opis:
    The height of a face in a 3-polytope is the maximum degree of its incident vertices, and the height of a 3-polytope, h, is the minimum height of its faces. A face is pyramidal if it is either a 4-face incident with three 3-vertices, or a 3-face incident with two vertices of degree at most 4. If pyramidal faces are allowed, then h can be arbitrarily large, so we assume the absence of pyramidal faces in what follows. In 1940, Lebesgue proved that every quadrangulated 3-polytope has h ≤ 11. In 1995, this bound was lowered by Avgustinovich and Borodin to 10. Recently, Borodin and Ivanova improved it to the sharp bound 8. For plane triangulation without 4-vertices, Borodin (1992), confirming the Kotzig conjecture of 1979, proved that h ≤ 20, which bound is sharp. Later, Borodin (1998) proved that h ≤ 20 for all triangulated 3-polytopes. In 1996, Horňák and Jendrol’ proved for arbitrarily polytopes that h ≤ 23. Recently, Borodin and Ivanova obtained the sharp bounds 10 for trianglefree polytopes and 20 for arbitrary polytopes. In this paper we prove that any polytope has a face of degree at most 10 with height at most 20, where 10 and 20 are sharp.
    Źródło:
    Discussiones Mathematicae Graph Theory; 2018, 38, 2; 443-453
    2083-5892
    Pojawia się w:
    Discussiones Mathematicae Graph Theory
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Low 5-Stars at 5-Vertices in 3-Polytopes with Minimum Degree 5 and No Vertices of Degree from 7 to 9
    Autorzy:
    Borodin, Oleg V.
    Bykov, Mikhail A.
    Ivanova, Anna O.
    Powiązania:
    https://bibliotekanauki.pl/articles/31348144.pdf
    Data publikacji:
    2020-11-01
    Wydawca:
    Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
    Tematy:
    planar map
    planar graph
    3-polytope
    structural properties
    5-star
    weight
    height
    Opis:
    In 1940, Lebesgue gave an approximate description of the neighborhoods of 5-vertices in the class $P_5$ of 3-polytopes with minimum degree 5. Given a 3-polytope $P$, by $h_5(P)$ we denote the minimum of the maximum degrees (height) of the neighborhoods of 5-vertices (minor 5-stars) in $P$. Recently, Borodin, Ivanova and Jensen showed that if a polytope $P$ in $P_5$ is allowed to have a 5-vertex adjacent to two 5-vertices and two more vertices of degree at most 6, called a (5, 5, 6, 6, ∞)-vertex, then $h_5(P)$ can be arbitrarily large. Therefore, we consider the subclass \(P_5^\ast\) of 3-polytopes in $P_5$ that avoid (5, 5, 6, 6, ∞)-vertices. For each $P^\ast$ in $P_5^\ast$ without vertices of degree from 7 to 9, it follows from Lebesgue’s Theorem that $h_5(P^\ast) ≤ 17$. Recently, this bound was lowered by Borodin, Ivanova, and Kazak to the sharp bound $h_5(P^\ast) ≤ 15$ assuming the absence of vertices of degree from 7 to 11 in $P^\ast$. In this note, we extend the bound $h_5(P^\ast) ≤ 15$ to all $P^\ast$s without vertices of degree from 7 to 9.
    Źródło:
    Discussiones Mathematicae Graph Theory; 2020, 40, 4; 1025-1033
    2083-5892
    Pojawia się w:
    Discussiones Mathematicae Graph Theory
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Evaluation of stress-strain state of vehicles’ metal structures elements
    Autorzy:
    Hrevtsev, O.
    Selivanova, N.
    Popovych, P.
    Poberezhny, L.
    Rudyak, Yu.
    Shevchuk, O.
    Poberezhna, L.
    Ivanova, A.
    Skyba, O.
    Shashkevych, O.
    Hrytsanchuk, A.
    Powiązania:
    https://bibliotekanauki.pl/articles/2201126.pdf
    Data publikacji:
    2022
    Wydawca:
    Stowarzyszenie Komputerowej Nauki o Materiałach i Inżynierii Powierzchni w Gliwicach
    Tematy:
    thermomechanical stress
    disk brakes durability
    stress and strain state
    vehicle reliability
    braking distance
    naprężenia termomechaniczne
    trwałość hamulców tarczowych
    stan naprężenia i odkształcenia
    niezawodność pojazdu
    droga hamowania
    Opis:
    Purpose: Develop a method for determining and evaluating the stress-strain state, in particular the distribution of thermomechanical stresses in the materials of individual rotating parts of vehicles. Design/methodology/approach: The proposed method is based on the principle of gradual approximations of the solution when the boundary conditions are satisfied on the curvilinear limiting surfaces of the disk body. Findings: The proposed method of determining and estimating the distribution of thermomechanical stresses in the disk material makes it possible to take into account the variable geometry: thickness and presence of a hole in the central part of the disk, also correctly determine stress strain state at any point of unevenly heated rotating axial body. Research limitations/implications: The work uses generally accepted assumptions and limitations for thermomechanical calculations. Originality/value: It is proved that in real disks the stress-strain state is spatial, and the well-known method based on the hypotheses of the plane-stress state does not provide the possibility of calculating the values of stresses in the thickness of the disk. The obtained results can be used as a basis for improving the methodology of auto technical examination of road accidents. In addition, they can be taken into account by design engineers of car brake systems.
    Źródło:
    Archives of Materials Science and Engineering; 2022, 113, 2; 77--85
    1897-2764
    Pojawia się w:
    Archives of Materials Science and Engineering
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    CO2 storage potential of sedimentary basins of Slovakia, the Czech Republic, Poland and the Baltic States
    Autorzy:
    Šliaupa, S.
    Lojka, R.
    Tasáryová, Z.
    Kolejka, V.
    Hladík, V.
    Kotulová, J.
    Kucharič, L.
    Fejdi, V.
    Wójcicki, V.
    Tarkowski, R.
    Uliasz-Misiak, B.
    Šliaupienė, R.
    Nulle, I.
    Pomeranceva, R.
    Ivanova, O.
    Shogenova, A.
    Shogenov, K.
    Powiązania:
    https://bibliotekanauki.pl/articles/2059731.pdf
    Data publikacji:
    2013
    Wydawca:
    Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
    Tematy:
    CO2 geological storage
    saline aquifer
    coal bed
    EOR
    ECBM
    Opis:
    It has been increasingly realised that geological storage of CO2 is a prospective option for reduction of CO2 emissions. The CO2 geological storage potential of sedimentary basins with the territory of Slovakia, the Czech Republic, Poland, and the Baltic States is here assessed, and different storage options have been considered. The most prospective technology is hydrodynamic trapping in the deep saline aquifers. The utilisation of hydrocarbon (HC) fields is considered as a mature technology; however storage capacities are limited in the region and are mainly related to enhanced oil (gas) recovery. Prospective reservoirs and traps have been identified in the Danube, Vienna and East Slovakian Neogene basins, the Neogene Carpathian Foredeep, the Bohemian and Fore-Sudetic Upper Paleozoic basins, the Mesozoic Mid-Polish Basin and the pericratonic Paleozoic Baltic Basin. The total storage capacity of the sedimentary basins is estimated to be as much as 10170 Mt of CO2 in deep saline aquifer structures, and 938 Mt CO2 in the depleted HC fields. The utilisation of coal seams for CO2 storage is related to the Upper Silesian Basin where CO2 storage could be combined with enhanced recovery of coal-bed methane.
    Źródło:
    Geological Quarterly; 2013, 57, 2; 219--232
    1641-7291
    Pojawia się w:
    Geological Quarterly
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-6 z 6

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