1. The Graovac-Pisanski index of connected bipartite graphs with applications to hydrocarbon moleculesMatevž Črepnjak, Martin Knor, Niko Tratnik, Petra Žigert Pleteršek, 2021, original scientific article Abstract: The Graovac-Pisanski index, also called the modified Wiener index, was introduced in 1991 and represents an extension of the original Wiener index, because it considers beside the distances in a graph also its symmetries. Similarly as Wiener in 1947 showed the correlation of the Wiener indices of the alkane series with the boiling points, in 2018 the connection between the GraovacPisanski index and the melting points of some hydrocarbon molecules was established. In this paper, we prove that the Graovac-Pisanski index of any connected bipartite graph as well as of any connected graph on an even number of vertices is an integer number. These results are applied to some important families of hydrocarbon molecules. By using a computer programme, the graphs with a non-integer Graovac-Pisanski index on at most nine vertices are counted. Finally, an infinite class of unicyclic graphs with a non-integer Graovac-Pisanski index is described.
Keywords: modified Wiener index, Graovac-Pisanski index, graph distance, automorphism group, hydrocarbons, carbon nanostructures
Published in DKUM: 14.02.2025; Views: 0; Downloads: 8
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2. An asymptotic relation between the wirelength of an embedding and the Wiener indexK. Jagadeesh Kumar, Sandi Klavžar, R. Sundara Rajan, Indra Rajasingh, T. M. Rajalaxmi, 2021, original scientific article Abstract: Wirelength is an important criterion to validate the quality of an embedding of a graph into a host graph and is used in particular in VLSI (Very-Large-Scale Integration) layout designs. Wiener index plays a significant role in mathematical chemistry, cheminformatics, and elsewhere. In this note these two concepts are related by proving that the Wiener index of a host graph is an upper bound for the wirelength of a given embedding. The wirelength of embedding complete ▫$2^p$▫-partite graphs into Cartesian products of paths and/or cycles as the function of the Wiener index is determined. The result is an asymptotic approximation of the general upper bound.
Keywords: Wiener index, embedding, wirelength, complete 2p-partite graph, Cartesian product of graphs, integer labeling
Published in DKUM: 23.09.2024; Views: 0; Downloads: 5
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3. Weighted wiener indices of molecular graphs with application to alkenes and alkadienesSimon Brezovnik, Niko Tratnik, Petra Žigert Pleteršek, 2021, original scientific article Abstract: There exist many topological indices that are calculated on saturated hydrocarbons since they can be easily modelled by simple graphs. On the other hand, it is more challenging to investigate topological indices for hydrocarbons with multiple bonds. The purpose of this paper is to introduce a simple model that gives good results for predicting physico-chemical properties of alkenes and alkadienes. In particular, we are interested in predicting boiling points of these molecules by using the well known Wiener index and its weighted versions. By performing the non-linear regression analysis we predict boiling points of alkenes and alkadienes.
Keywords: weighted Wiener index, alkenes, alkadienes, boiling point
Published in DKUM: 30.05.2024; Views: 115; Downloads: 16
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4. The cut method on hypergraphs for the Wiener indexSandi Klavžar, Gašper Domen Romih, 2023, original scientific article Abstract: The cut method has been proved to be extremely useful in chemical graph theory. In this paper the cut method is extended to hypergraphs. More precisely, the method is developed for the Wiener index of ▫$k$▫-uniform partial cube-hypergraphs. The method is applied to cube-hypergraphs and hypertrees. Extensions of the method to hypergraphs arising in chemistry which are not necessary ▫$k$▫-uniform and/or not necessary linear are also developed.
Keywords: hypergraphs, Wiener index, cut method, partial cube-hypergraphs, hypertrees, phenylene, Clar structures
Published in DKUM: 11.04.2024; Views: 230; Downloads: 10
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5. Wiener index of strong product of graphsIztok Peterin, Petra Žigert Pleteršek, 2018, original scientific article Abstract: The Wiener index of a connected graph ▫$G$▫ is the sum of distances between all pairs of vertices of ▫$G$▫. The strong product is one of the four most investigated graph products. In this paper the general formula for the Wiener index of the strong product of connected graphs is given. The formula can be simplified if both factors are graphs with the constant eccentricity. Consequently, closed formulas for the Wiener index of the strong product of a connected graph ▫$G$▫ with a cycle are derived.
Keywords: Wiener index, graph product, strong product
Published in DKUM: 30.11.2017; Views: 1479; Downloads: 446
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6. Altered Wiener indicesDamir Vukičević, Janez Žerovnik, 2005, original scientific article Abstract: Recently Nikolić, Trinajstić and Randić put forward a novel modification ▫$^mW(G)$▫ of the Wiener number ▫$W(G)$▫, called modified Wiener index, which definition was generalized later by Gutman and the present authors. Here we study another class of modified indices defined as ▫$W_{min,λ}(G) = ∑(V(G)^λm_G(u,ν)^λ−m_G(u,ν)^{2λ})$▫ and show that some of the important properties of ▫$W(G)$▫, ▫$^mW(G)$▫ and ▫$^λW(G)$▫ are also properties of ▫$W_{min,λ}(G)$▫, valid for most values of the parameter λ. In particular, if ▫$T_n$▫ is any n-vertex tree, different from the n-vertex path ▫$P_n$▫ and the n-vertex star ▫$S_n$▫, then for any λ ≥ 1 or λ < 0, ▫$^W_{min,λ}(P_n) > W_{min,λ}(T_n)>W_{min,λ}(S_n)$▫. Thus for these values of the parameter λ, ▫$W_{min,λ}(G)$▫ provides a novel class of structure-descriptors, suitable for modeling branching-dependent properties of organic compounds, applicable in QSPR and QSAR studies. We also demonstrate that if trees are ordered with regard to ▫$W_{min,λ}(G)$▫ then, in the general case, this ordering is different for different λ.
Keywords: mathematics, chemical graph theory, Wiener index, modified Wiener index
Published in DKUM: 17.08.2017; Views: 1227; Downloads: 129
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7. Corroborating a modification of the Wiener indexIvan Gutman, Janez Žerovnik, 2002, other scientific articles Abstract: In a recent work [Chem. Phys. Lett. 333 (2001) 319-321] Nikolić, Trinajstić, and Randie put forward a novel modification ▫$^m$▫W of the Wiener index. We now show that ▫$^m$▫W possesses the basic properties required by a topological index to be acceptable as a measure of the extent of branching of the carbon-atom skeleton of the respective molecule (and therefore to be a structure-descriptor, potentially applicable in QSPR and QSAR studies). In particular, if ▫$T_n$▫ is any n-vertex tree, different from the n-vertex path ▫$P_n$▫ and the n-vertex star ▫$S_n$▫, then mw(Pn) < mW(Tn) < mW(Sn). We also show how the concept of the modified Wiener index can be extended to weighted molecular graphs.
Keywords: graph theory, distance, molecular graphs, modified Wiener index, weigted modified Wiener index, branching, chemical graph theory
Published in DKUM: 05.07.2017; Views: 1146; Downloads: 90
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8. A class of modified Wiener indicesIvan Gutman, Damir Vukičević, Janez Žerovnik, 2004, original scientific article Abstract: The Wiener index of a tree T obeys the relation W(T) = Σen1(e) • n2(e) where n1(e) and n2(e) are the number of vertices on the two sides of the edge e, and where the summation goes over all edges of T. Recently Nikolić, Trinajstić and Randić put forward a novel modification mW of the Wiener index, defined as mW(T) = Σe[n1(e) • n2(e)]–1. We now extend their definition as mWλ(T) = Σe[n1(e) • n2(e)]λ, and show that some of the main properties of both W and mW are, in fact, properties of mWλ, valid for all values of the parameter λ≠0. In particular, if Tn is any n-vertex tree, different from the n-vertex path Pn and the n-vertex star Sn, then for any positive λ, mWλ(Pn) > mWλ(Tn) > mWλ(Sn), whereas for any negative λ, mWλ(Pn) < mWλ(Tn) < mWλ(Sn). Thus mWλ provides a novel class of structure-descriptors, suitable for modeling branching-dependent properties of organic compounds, applicable in QSPR and QSAR studies. We also demonstrate that if trees are ordered with regard to mWλ then, in the general case, this ordering is different for different λ.
Keywords: graph theory, chemical graph theory, modified Wiener index, Nikolić-Trinajstić-Randić index, branching
Published in DKUM: 05.07.2017; Views: 1196; Downloads: 107
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9. Vukičević, Damir(CT-SPL): Distinction between modifications of Wiener indices. (English summary). - MATCH Commun. Math. Comput. Chem. No. 47 (2003), 87--105.Sandi Klavžar, 2004, review, book review, critique Keywords: matematika, teorija grafov, razdalja, Wienerjev indeks, mathematics, graph theory, distance, Wiener index
Published in DKUM: 10.07.2015; Views: 1013; Downloads: 34
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10. On the canonical metric representation, average distance, and partial Hamming graphsSandi Klavžar, 2006, original scientific article Abstract: Average distance of a graph is expressed in terms of its canonical metric representation. The equality can be modified to an inequality in such a way that it characterizes isometric subgraphs of Hamming graphs. This approach simplifies recognition of these graphs and computation of their average distance.
Povprečna razdalja grafa je izražena s pomočjo kanonične metrične reprezentacije. Enakost lahko preoblikujemo v neenakost tako, da karakterizira izometrične podgrafe Hammingovih grafov. Ta pristop poenostavlja prepoznavanje teh grafov ter izračun povprečne razdalje.
Keywords: matematika, teorija grafov, kanonična metrična reprezentacija, Hammingovi grafi, delni Hammingovi grafi, Wienerjev indeks, algoritem prepoznavanja, mathematics, graph theory, cononical metric representation, Hamming graphs, partial Hamming graphs, Wiener index, recognition algorithm
Published in DKUM: 10.07.2015; Views: 1357; Downloads: 138
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