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1.
Wiener numbers of pericondensed benzenoid hydrocarbons
Sandi Klavžar, Ivan Gutman, Amal Rajapakse, 1997, izvirni znanstveni članek

Opis: Using a recently developed technique for the calculation of the Wiener number (W) of benzenoid systems, we determine explicit expressions for W for several homologous series of pericondensed benzenoid hydrocarbons. An elementary proof for the correctness of the used method is also included.
Ključne besede: mathematics, chemical graph theory, distance in graphs, Wiener number, benzenoids
Objavljeno: 05.07.2017; Ogledov: 715; Prenosov: 128
.pdf Celotno besedilo (16,93 MB)
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2.
Corroborating a modification of the Wiener index
Ivan Gutman, Janez Žerovnik, 2002, kratki znanstveni prispevek

Opis: 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.
Ključne besede: graph theory, distance, molecular graphs, modified Wiener index, weigted modified Wiener index, branching, chemical graph theory
Objavljeno: 05.07.2017; Ogledov: 554; Prenosov: 57
.pdf Celotno besedilo (85,05 KB)
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3.
A class of modified Wiener indices
Ivan Gutman, Damir Vukičević, Janez Žerovnik, 2004, izvirni znanstveni članek

Opis: 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.
Ključne besede: graph theory, chemical graph theory, modified Wiener index, Nikolić-Trinajstić-Randić index, branching
Objavljeno: 05.07.2017; Ogledov: 626; Prenosov: 80
.pdf Celotno besedilo (125,08 KB)
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4.
A theorem on Wiener-type invariants for isometric subgraphs of hypercubes
Sandi Klavžar, Ivan Gutman, 2006, izvirni znanstveni članek

Opis: Naj bo ▫$d(G,k)$▫ število parov točk grafa ▫$G$▫, ki so na razdalji ▫$k$▫, naj bo ▫$lambda$▫ realno (ali kompleksno) število in naj bo ▫$W_lambda(G) =sum_{k ge 1}d(G,k)k^lambda$▫. Dokazano je, da za delno kocko ▫$G$▫ velja ▫$W_{lambda + 1}(G) = |mathcal{F}| W_lambda(G) - sum_{mathnormal{F} in mathcal{F}} W_lambda(G setminus F)$▫, kjer je ▫$mathcal{F}$▫ particija ▫$E(G)$▫, ki jo inducira Djokovic-Winklerjeva relacija ▫$Theta$▫. Ta rezultat razširja prej znani rezultat za drevesa in implicira različne relacije za topološke indekse, ki temeljijo na razdaljah.
Ključne besede: matematika, teorija grafov, grafovska razdalja, hiperkocka, delna kocka, Wienerjevo število, hiper-Wienerjev indeks, mathematics, graph theory, graph distance, hypercube, partial cube, Wiener number, hyper-Wiener indeks
Objavljeno: 10.07.2015; Ogledov: 775; Prenosov: 76
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5.
On the role of hypercubes in the resonance graphs of benzenoid graphs
Khaled Salem, Sandi Klavžar, Ivan Gutman, 2006, kratki znanstveni prispevek

Opis: Resonančni graf ▫$R(B)$▫ benzenoidnega grafa ▫$B$▫ ima za točke popolna prirejanja v ▫$B$▫, dve popolni prirejanji sta sosednji, če njuna simetrična razlika tvori množico povezav nekega šestkotnika v ▫$B$▫. Družina ▫$mathscr{P}$▫ paroma disjunktnih šestkotnikov benzenoidnega grafa ▫$B$▫ je resonančna v $B$, če ▫$B -- mathscr{P}$▫ vsebuje vsaj eno popolno prirejanje, ali pa je ▫$B -- mathscr{P}$▫ prazno. Dokazano je, da obstaja surjektivna preslikava ▫$f$▫ iz množice hiperkock grafa ▫$R(B)$▫ na resonančne množice v ▫$B$▫, tako da se ▫$k$▫-dimenzionalna kocka preslika na resonančno množico moči ▫$k$▫.
Ključne besede: matematika, teorija grafov, benzenoidni graf, popolno prirejanje, resonančni graf, hiperkocka, mathematics, graph theory, benzenoid graph, perfect matching, resonance graph, hypercube
Objavljeno: 10.07.2015; Ogledov: 884; Prenosov: 59
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