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1.
Nekateri rezultati o povezanosti in neodvisnih množicah v produktih grafov
Tjaša Paj Erker, 2018, doctoral dissertation

Abstract: Doktorska disertacija obravnava nekatere rezultate na grafovskih produktih. V uvodu bomo na kratko predstavili vsebino doktorske disertacije in ponovili nekatere osnovne pojme teorije grafov, ki jih bomo uporabljali v nadaljevanju. Prva tema, ki jo bomo predstavili so neodvisne množice v direktnem produktu. Govorili bomo o velikosti in strukturi največjih neodvisnih množic v direktnem produktu. Najprej bomo predstavili pomembnejše znane rezultate, nato pa bomo pokazali, da ima direkten produkt lihe poti in poljubnega grafa, ter direkten produkt sodega cikla in poljubnega grafa največjo neodvisno množico, ki je unija dveh pravokotnikov. Ugotovili bomo, da obstajajo v direktnem produktu sode poti in poljubnega grafa največje neodvisne množice, ki so lahko tudi drugačne oblike ter zapisali natančno karakterizacijo teh največjih neodvisnih množic. Zapisali bomo zadostni pogoji za drevesa, da ima direkten produkt drevesa in poljubnega grafa največjo neodvisno množico oblike dveh pravokotnikov. V nadaljevanju bomo raziskali posplošeno 3-povezanost v kartezičnem produktu grafov. Prikazali bomo več naravnih načinov, kako dobiti 3-presečno množico S, pri kateri nam graf razpade na vsaj tri komponente. Nato bomo dokazali, da je eden izmed teh načinov vedno optimalen, če sta G in H 2-povezana grafa na vsaj šestih vozliščih. Tako dobimo natančno vrednost posplošene 3-povezanosti kartezičnega produkta dveh 2-povezanih grafov na vsaj šestih vozliščih. Na koncu se bomo ukvarjali z vprašanjem o zgornji meji najmanjšega diametra krepko orientiranega krepkega produkta. Določili bomo natančno vrednost najmanjšega diametra krepkega produkta dveh poti.
Keywords: direktni produkt, kartezični produkt, krepki produkt, neodvisna množica, povezanost, posplošena povezanost, diameter, krepka orientacija
Published: 11.12.2018; Views: 675; Downloads: 73
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3.
The edge fault-diameter of Cartesian graph bundles
Iztok Banič, Rija Erveš, Janez Žerovnik, 2009, original scientific article

Abstract: Kartezični svežnji so posplošitev krovnih grafov in kartezičnih grafovskih produktov. Naj bo ▫$G$▫ nek s povezavami ▫$k_G$▫-povezan graf in ▫${bar{mathcal{D}}_c(G)}$▫ največji premer podgrafov grafa ▫$G$▫ dobljenih z odstranitvijo $▫c < k_G$▫ povezav. Dokazano je, da je ▫${bar{mathcal{D}}_{a+b+1}(G)} le {bar{mathcal{D}}_a(F)} le {bar{mathcal{D}}_b(B)} + 1$▫, če je ▫$G$▫ grafovski sveženj z vlaknom ▫$F$▫ in bazo ▫$B$▫, ▫$a < k_F$▫, ▫$b < k_B▫$. Dokazano je tudi, da je povezanost s povezavami grafovskega svežnja ▫$G▫$ vsaj ▫$k_F + k_B$▫.
Keywords: matematika, teorija grafov, kartezični grafovski produkti, kartezični grafovski svežnji, povezavni okvarni premer, mathematics, graph theory, Cartesian graph products, Cartesian graph bundles, edge-fault diameter
Published: 10.07.2015; Views: 740; Downloads: 69
URL Link to full text

4.
Edge, vertex and mixed fault diameters
Iztok Banič, Rija Erveš, Janez Žerovnik, 2009, original scientific article

Abstract: Let ▫${mathcal{D}}^E_q(G)$▫ denote the maximum diameter among all subgraphs obtained by deleting ▫$q$▫ edges of ▫$G$▫. Let ▫${mathcal{D}}^V_p(G)$▫ denote the maximum diameter among all subgraphs obtained by deleting ▫$p$▫ vertices of ▫$G$▫. We prove that ▫${mathcal{D}}^E_a(G) leqslant {mathcal{D}}^V_a(G) + 1$▫ a for all meaningful ▫$a$▫. We also define mixed fault diameter ▫${mathcal{D}}^M_{(p,q)}(G)$▫, where ▫$p$▫ vertices and ▫$q$▫ edges are deleted at the same time. We prove that for ▫$0 < l leqslant a$▫, ▫${mathcal{D}}^E_a(G) leqslant {mathcal{D}}^M_{(a-ell,ell)}(G) leqslant {mathcal{D}}^V_a(G) + 1$▫, and give some examples.
Keywords: vertex-connectivity, edge-connectivity, vertex fault diameter, edge fault diameter, mixed fault diameter, interconnection network
Published: 10.07.2015; Views: 601; Downloads: 77
URL Link to full text

5.
Graphʼs theory approach for searching the shortest routing path in RIP protocol
Saša Klampfer, Jože Mohorko, Žarko Čučej, Amor Chowdhury, 2012, original scientific article

Abstract: Routing is a problem domain with an infinite number of final-solutions. One of the possible approaches to solving such problems is using graph theory. This paper presents mathematical analysis methodologies based on circular graphs for solving a shortest path routing problem. The problem is focused on searching for the shortest path within a circular graph. Such a search coincides with the network routing problem domain. In this paper, we introduce in the detail all necessary parts needed to understand such an approach. This includes: definition of the routing problem domain, introduction to circular graphs and their usage, circular graphʼs properties, definition of walks through a circular graph, searching and determining the shortest path within a circular graph, etc. The state of the art routing methods, implemented in contemporary highly sophisticated routers, includes well-known weight-based algorithms and distance-vectors-based algorithms. The proposed solution can be placed between the two abovementioned methods. Each of these known methods strives for optimal results, but each of them also has its own deficiencies, which should be rectified with the proposed new method. This theoretically presented method is argued by a practical example and compared with the RIP (Routing Information Protocol) technique, where we look for the shortest path and possible walks through a specified circular graph.
Keywords: circular graphs, shortest path, graph diameter, walk through, CIGRP, connectivity matrix, network topology, symmetry, fully connected graph
Published: 10.07.2015; Views: 1247; Downloads: 58
URL Link to full text

6.
Edge, vertex and mixed fault-diameters
Iztok Banič, Rija Erveš, Janez Žerovnik, 2008

Abstract: Let ▫${mathcal{D}}^E_q(G)$▫ denote the diameter of a graph ▫$G$▫ after deleting any of its ▫$q$▫ edges, and ▫${mathcal{D}}^V_p(G)$▫ denote the diameter of ▫$G$▫ after deleting any of its ▫$p$▫ vertices. We prove that ▫${mathcal{D}}^E_a(G) le {mathcal{D}}^V_a(G) + 1$▫ a for all meaningful ▫$a$▫. We also define mixed fault diameter ▫${mathcal{D}}^M_{(p,q)}(G)$▫, where ▫$p$▫ vertices and ▫$q$▫ edges are deleted at the same time. We prove that for ▫$0 < l le a$▫, ▫${mathcal{D}}^E_a(G) le {mathcal{D}}^M_{(a-l,l)}(G) le {mathcal{D}}^V_a(G) + 1$▫, and give some examples.
Keywords: matematika, teorija grafov, povezanost, mathematics, (vertex)-connectivity, edge-connectivity, (vertex) fault-diameter, edge-fault diameter, interconnection network
Published: 10.07.2015; Views: 610; Downloads: 69
URL Link to full text

7.
Fault-diameter of Cartesian product of graphs and Cartesian graph bundles
Iztok Banič, Janez Žerovnik, 2006

Abstract: Cartesian graph bundles is a class of graphs that is a generalization of the Cartesian graph products. Let ▫$G$▫ be a ▫$k_G$▫-connected graph and ▫${mathcal{D}}_c(G)$▫ denote the diameter of ▫$G$▫ after deleting any of its ▫$c < k_G$▫ vertices. We prove that if ▫$G_1, G_2, dots, G_q$▫ are ▫$k_1$▫-connected, ▫$k_2$▫-connected,...,▫$k_q$▫-connected graphs and ▫$0 leq a_1 < k_1$▫, ▫$0 leq a_2 < k_2$▫,...,▫$0 leq a_q < k_q$▫ and ▫$a = a_1 + a_2 + dots + a_q + (q-1)$▫, then the fault diameter of ▫$G$▫, a Cartesian product of ▫$G_1$▫, ▫$G_2$▫,...,▫$G_q$▫, with ▫$a$▫ faulty nodes is ▫${mathcal{D}}_{a}(G) leq {mathcal{D}}_{a_1}(G_1)+{mathcal{D}}_{a_2}(G_2) + dots + {mathcal{D}}_{a_q}(G_q) + 1$▫. We also show that ▫${mathcal{D}}_{a+b+1}(G) leq {mathcal{D}}_a(F) + {mathcal{D}}_b(B) + 1$▫ if ▫$G$▫ is a graph bundle with fibre ▫$F$▫ over base ▫$B$▫, ▫$a leq k_F$▫, and ▫$b leq k_B$▫. As an auxiliary result we prove that connectivity of graph bundle ▫$G$▫ is at least ▫$k_F+k_B$▫.
Keywords: mathematics, graph theory, Cartesian graph bundles, Cartesian graph products, fault diameter, interconnection network
Published: 10.07.2015; Views: 525; Downloads: 22
URL Link to full text

8.
The strong isometric dimension of graphs of diameter two
Janja Jerebic, Sandi Klavžar, 2003

Abstract: Krepka izometrična dimenzija ▫$textrm{idim}(G)$▫ grafa ▫$G$▫ je najmanjše število ▫$k$▫, za katero lahko ▫$G$▫ izometrično vložimo v krepki produkt ▫$k$▫ poti. Problem določitve ▫$textrm{idim}(G)$▫ za grafe premera dva je reduciran na problem pokrivanja komplementa grafa ▫$G$▫ s polnimi dvodelnimi grafi. Za primer je pokazano, da je izometrična dimenzija Petersenovega grafa enaka 5.
Keywords: matematika, teorija grafov, izometrični podgraf, krepki produkt grafov, premer grafa, krepka izometrična dimenzija, Petersenov graf, mathematics, graph theory, isometric subgraph, strong product of graphs, graph diameter, strong isometric dimension, Petersen graph
Published: 10.07.2015; Views: 695; Downloads: 28
URL Link to full text

9.
Wide diameter of Cartesian graph bundles
Iztok Banič, Janez Žerovnik, 2010, published scientific conference contribution

Abstract: Fault tolerance and transmission delay of networks are important concepts in network design. The notions are strongly related to connectivity and diameter of a graph, and have been studied by many authors. Wide diameter of a graph combines studying connectivity with the diameter of a graph. Diameter with width ▫$k$▫ of a graph ▫$G$▫, ▫$k$▫-diameter, is defined as the minimum integer ▫$d$▫ for which there exist at least ▫$k$▫ internally disjoint paths of length at most ▫$d$▫ between any two distinct vertices in ▫$G$▫. Denote by ▫${mathscr D}_c(G)$▫ the ▫$c$▫-diameter of ▫$G$▫ and ▫$kappa(G)$▫ the connectivity of ▫$G$▫. In the context of computer networks, wide diameters of Cartesian graph products have been recently studied by many authors. Cartesian graph bundles is a class of graphs that is a generalization of the Cartesian graph products. Let ▫$G$▫ be a Cartesian graph bundle with fiber ▫$F$▫ over base ▫$B$▫, ▫$0 < a le kappa(F)$▫, and ▫$0 < b le kappa(B)$▫. We prove that ▫${mathscr D}_{a+b}(G) le {mathscr D}_a(F) + {mathscr D}_b(B) + 1$▫. Moreover, if ▫$G$▫ is a graph bundle with fiber ▫$F ne K_2$▫ over base ▫$B ne K_2$▫, then ▫${mathscr D}_{a+b}(G) le {mathscr D}_a(F) + {mathscr D}_b(B)$▫. The bounds are tight.
Keywords: mathematics, graph theory, Cartesian graph products, Cartesian graph bundles, wide diameter
Published: 07.06.2012; Views: 1321; Downloads: 71
URL Link to full text

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