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Wyświetlanie 1-6 z 6
Tytuł:
About (k, l)-Kernels, Semikernels and Grundy Functions in Partial Line Digraphs
Autorzy:
Balbuena, C.
Galeana-Sánchez, H.
Guevara, M.
Powiązania:
https://bibliotekanauki.pl/articles/31343207.pdf
Data publikacji:
2019-11-01
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
digraphs
in-domination
kernel
Grundy function
Opis:
Let D be a digraph of minimum in-degree at least 1. We prove that for any two natural numbers k, l such that 1 ≤ l ≤ k, the number of (k, l)-kernels of D is less than or equal to the number of (k, l)-kernels of any partial line digraph ℒD. Moreover, if l < k and the girth of D is at least l +1, then these two numbers are equal. We also prove that the number of semikernels of D is equal to the number of semikernels of ℒD. Furthermore, we introduce the concept of (k, l)-Grundy function as a generalization of the concept of Grundy function and we prove that the number of (k, l)-Grundy functions of D is equal to the number of (k, l)-Grundy functions of any partial line digraph ℒD.
Źródło:
Discussiones Mathematicae Graph Theory; 2019, 39, 4; 855-856
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Parallel Digraphs-building Computer Algorithm for Finding a Set of Characteristic Polynomial Realisations of Dynamic System
Autorzy:
Hryniów, K.
Markowski, K. A.
Powiązania:
https://bibliotekanauki.pl/articles/384585.pdf
Data publikacji:
2016
Wydawca:
Sieć Badawcza Łukasiewicz - Przemysłowy Instytut Automatyki i Pomiarów
Tematy:
dynamic system
GPGPU
characteristic polynomial
digraphs
algorithm
Opis:
This paper presents in-depth the parallel computer algorithm for the determination of characteristic polynomial realisations of dynamic system. The main differences between the depicted method and other state of- the-art solutions include finding not few realisations, but a whole set, and the fact that the found realisations are always minimal among all possible. As digraphsbuilding methods used in the algorithm are NP-complete or NP-hard problems, the algorithm is paralleled and GPGPU (General-Purpose computing on Graphics Processor Units) computation is proposed as the only feasible solution. The article describes in detail the proposed method, discusses it’s complexity, presents optimisation solutions and still open problems. The working algorithm is illustrated with a numerical example and compared to results of other known methods.
Źródło:
Journal of Automation Mobile Robotics and Intelligent Systems; 2016, 10, 3; 38-51
1897-8649
2080-2145
Pojawia się w:
Journal of Automation Mobile Robotics and Intelligent Systems
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Cancellation of direct products of digraphs
Autorzy:
Hammack, Richard
Toman, Katherine
Powiązania:
https://bibliotekanauki.pl/articles/744073.pdf
Data publikacji:
2010
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
graph direct product
graph product cancellation
digraphs
Opis:
We investigate expressions of form A×C ≅ B×C involving direct products of digraphs. Lovász gave exact conditions on C for which it necessarily follows that A ≅ B. We are here concerned with a different aspect of cancellation. We describe exact conditions on A for which it necessarily follows that A ≅ B. In the process, we do the following: Given an arbitrary digraph A and a digraph C that admits a homomorphism onto an arc, we classify all digraphs B for which A×C ≅ B×C.
Źródło:
Discussiones Mathematicae Graph Theory; 2010, 30, 4; 575-590
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Frucht’s Theorem for the Digraph Factorial
Autorzy:
Hammack, Richard H.
Powiązania:
https://bibliotekanauki.pl/articles/30146632.pdf
Data publikacji:
2013-05-01
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
Frucht’s theorem
digraphs
graph automorphisms
digraph factorial
Opis:
To every graph (or digraph) A, there is an associated automorphism group Aut(A). Frucht’s theorem asserts the converse association; that for any finite group G there is a graph (or digraph) A for which Aut(A) ≅ G. A new operation on digraphs was introduced recently as an aid in solving certain questions regarding cancellation over the direct product of digraphs. Given a digraph A, its factorial A! is certain digraph whose vertex set is the permutations of V (A). The arc set E(A!) forms a group, and the loops form a subgroup that is isomorphic to Aut(A). (So E(A!) can be regarded as an extension of Aut(A).) This note proves an analogue of Frucht’s theorem in which Aut(A) is replaced by the group E(A!). Given any finite group G, we show that there is a graph A for which E(A!) ≅ G.
Źródło:
Discussiones Mathematicae Graph Theory; 2013, 33, 2; 329-336
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
New classes of critical kernel-imperfect digraphs
Autorzy:
Galeana-Sánchez, Hortensia
Neumann-Lara, V.
Powiązania:
https://bibliotekanauki.pl/articles/744203.pdf
Data publikacji:
1998
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
digraphs
kernel
kernel-perfect
critical kernel-imperfect
block-cutpoint tree
Opis:
A kernel of a digraph D is a subset N ⊆ V(D) which is both independent and absorbing. When every induced subdigraph of D has a kernel, the digraph D is said to be kernel-perfect. We say that D is a critical kernel-imperfect digraph if D does not have a kernel but every proper induced subdigraph of D does have at least one. Although many classes of critical kernel-imperfect-digraphs have been constructed, all of them are digraphs such that the block-cutpoint tree of its asymmetrical part is a path. The aim of the paper is to construct critical kernel-imperfect digraphs of a special structure, a general method is developed which permits to build critical kernel-imperfect-digraphs whose asymmetrical part has a prescribed block-cutpoint tree. Specially, any directed cactus (an asymmetrical digraph all of whose blocks are directed cycles) whose blocks are directed cycles of length at least 5 is the asymmetrical part of some critical kernel-imperfect-digraph.
Źródło:
Discussiones Mathematicae Graph Theory; 1998, 18, 1; 85-89
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Dichromatic number, circulant tournaments and Zykov sums of digraphs
Autorzy:
Neumann-Lara, Víctor
Powiązania:
https://bibliotekanauki.pl/articles/743771.pdf
Data publikacji:
2000
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
digraphs
dichromatic number
vertex-critical
Zykov sums
tournaments
circulant
covering numbers in hypergraphs
Opis:
The dichromatic number dc(D) of a digraph D is the smallest number of colours needed to colour the vertices of D so that no monochromatic directed cycle is created. In this paper the problem of computing the dichromatic number of a Zykov-sum of digraphs over a digraph D is reduced to that of computing a multicovering number of an hypergraph H₁(D) associated to D in a natural way. This result allows us to construct an infinite family of pairwise non isomorphic vertex-critical k-dichromatic circulant tournaments for every k ≥ 3, k ≠ 7.
Źródło:
Discussiones Mathematicae Graph Theory; 2000, 20, 2; 197-207
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-6 z 6

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