Loading...
Search for:
subgraphs
0.005 seconds
Total 26 records
Order of the largest sachs subgraphs in graphs
, Article Linear and Multilinear Algebra ; Volume 65, Issue 1 , 2017 , Pages 204-209 ; 03081087 (ISSN) ; Akbari, S ; Tajfirouz, Z ; Sharif University of Technology
Abstract
Let G be a graph. A subgraph H of G is called a Sachs subgraph if each component of H is either a copy of K2 or a 2-regular subgraph of G. The order of the largest Sachs subgraph of G is called the perrank of G. A graph G of order n has full perrank if (G) = n In this article, we characterize the family of all graphs of order n whose permanents of their adjacency matrices are 1. Then we prove that the line graph of G, L(G), has full perrank, unless G is isomorphic to some special trees. © 2016 Informa UK Limited, trading as Taylor & Francis Group
Almost every n -vertex graph is determined by Its 3 log 2 n -vertex subgraphs
, Article International Journal of Foundations of Computer Science ; Volume 31, Issue 5 , 2020 , Pages 611-619 ; Sharif University of Technology
World Scientific
2020
Abstract
This paper proves that almost every n-vertex graph has the property that the multiset of its induced subgraphs on 3log2n vertices is sufficient to determine it up to isomorphism. That is, the probability that there exists two n-vertex graphs with the same multiset of 3log2n-vertex induced subgraphs goes to zero as n goes to infinity. © 2020 World Scientific Publishing Company
The Existence of Subgraphs with Given Properties
, M.Sc. Thesis Sharif University of Technology ; Akbari, Saeed (Supervisor)
Abstract
Let G be a graph. We call G an odd graph if all its vertices have odd degrees. Caro conjectured that for every graph G and every integer k, k > 2, there exists a Zk-coloring for the vertices of G so that for all v 2 V (G), the sum of the colors of all vertices in N[v] is not congruent to 0 modulo k. This thesis is mainly devoted to determining a lower bound for the number of vertices of the largest odd induced subgraph of a given graph with no isolated vertices. Another focus of this thesis is to find an upper bound for the number of odd induced subgraphs, as well as odd induced forests, needed to partition V (G), where G is a given graph with even order. At the end, two variations of Caro’s...
Note: A short proof of a theorem of Tutte
, Article Australasian Journal of Combinatorics ; Volume 42 , 2008 , Pages 299-300 ; 10344942 (ISSN) ; Mahmoodi, A ; Sharif University of Technology
2008
Abstract
Let G be a graph. A spanning subgraph of G is called a {1, 2}-factor if each of its components is a regular graph of degree one or two. In this paper we provide a short proof of a theorem of Tutte which says that a graph G has a {1, 2}-factor if and only if i(GS) ≤ |S| for any S ⊆ V(G), where i(GS) denotes the number of isolated vertices of GS
Circular chromatic index of graphs of maximum degree 3
, Article Journal of Graph Theory ; Volume 49, Issue 4 , 2005 , Pages 325-335 ; 03649024 (ISSN) ; Ghandehari, M ; Ghandehari, M ; Hatami, H ; Tusserkani, R ; Zhu, X ; Sharif University of Technology
Wiley-Liss Inc
2005
Abstract
This paper proves that if G is a graph (parallel edges allowed) of maximum degree 3, then χc′(G) ≤ 11/3 provided that G does not contain H1 or H2 as a subgraph, where H1 and H2 are obtained by subdividing one edge of K23 (the graph with three parallel edges between two vertices) and K4, respectively. As χc′(H1) = χ c′(H2) = 4, our result implies that there is no graph G with 11/3 < χc′(G) < 4. It also implies that if G is a 2-edge connected cubic graph, then χc′(G) ≤ 11/3. © 2005 Wiley Periodicals, inc
On Graph Reconstruction Conjecture
, M.Sc. Thesis Sharif University of Technology ; Mahmoudian, Ebadollah (Supervisor)
Abstract
The reconstruction conjecture is an open and interesting problem that attracts some reserchers. Although some work toward this problem has been done; but no one have been able to solve it comlpetely. In this thesis, some new theorms are developed which extend the domain of reconstructible graphs. Also, a generalization of graph spectrum -called Alpha Spectrum- is introduced that is very effective in recognization of graphs
Protein Function Prediction Using Protein Structure and Computational Methods
, M.Sc. Thesis Sharif University of Technology ; Fatemizadeh, Emad (Supervisor) ; Arab, Shahriar ($item.subfieldsMap.e)
Abstract
Predicting the Amino Acids that have a catalytic effect in the enzymes, is a big step in appointing the activity of the enzymes and classifying them. This is a very challenging job, because an Amino Acid can appear in a variety of active sites.The biological activity of a protein usually depends on the existence of a small number of Amino Acids. Detecting these Amino Acids from the sequence of Amino Acids has many applications. Usually, the Amino Acids that are preserved are known as the Amino Acids that build up the active site, but the algorithms for finding the preserved Amino Acids are much more complex. There are a lot of algorithms for predicting the active sites of Amino Acids, but...
Chromatic number and clique number of subgraphs of regular graph of matrix algebras
, Article Linear Algebra and Its Applications ; Volume 436, Issue 7 , 2012 , Pages 2419-2424 ; 00243795 (ISSN) ; Aryapoor, M ; Jamaali, M ; Sharif University of Technology
Abstract
Let R be a ring and X R be a non-empty set. The regular graph of X, Γ(X), is defined to be the graph with regular elements of X (non-zero divisors of X) as the set of vertices and two vertices are adjacent if their sum is a zero divisor. There is an interesting question posed in BCC22. For a field F, is the chromatic number of Γ( GLn(F)) finite? In this paper, we show that if G is a soluble subgroup of GLn(F), then χ(Γ(G))<∞. Also, we show that for every field F, χ(Γ( Mn(F)))=χ(Γ( Mn(F(x)))), where x is an indeterminate. Finally, for every algebraically closed field F, we determine the maximum value of the clique number of Γ(), where denotes the subgroup generated by A∈ GLn(F)
Decomposing claw-free subcubic graphs and 4-chordal subcubic graphs
, Article Discrete Applied Mathematics ; Volume 296 , 2021 , Pages 52-55 ; 0166218X (ISSN) ; Ahanjideh, M ; Akbari, S ; Sharif University of Technology
Elsevier B.V
2021
Abstract
Hoffmann–Ostenhof's conjecture states that the edge set of every connected cubic graph can be decomposed into a spanning tree, a matching and a 2-regular subgraph. In this paper, we show that the conjecture holds for claw-free subcubic graphs and 4-chordal subcubic graphs. © 2021 Elsevier B.V
Decomposing claw-free subcubic graphs and 4-chordal subcubic graphs
, Article Discrete Applied Mathematics ; Volume 296 , 2021 , Pages 52-55 ; 0166218X (ISSN) ; Ahanjideh, M ; Akbari, S ; Sharif University of Technology
Elsevier B.V
2021
Abstract
Hoffmann–Ostenhof's conjecture states that the edge set of every connected cubic graph can be decomposed into a spanning tree, a matching and a 2-regular subgraph. In this paper, we show that the conjecture holds for claw-free subcubic graphs and 4-chordal subcubic graphs. © 2021 Elsevier B.V
A constant factor approximation for minimum λ-edge-connected k-subgraph with metric costs
, Article SIAM Journal on Discrete Mathematics ; Volume 25, Issue 3 , 2011 , Pages 1089-1102 ; 08954801 (ISSN) ; Salavatipour, M. R ; Sharif University of Technology
Abstract
In the (k, λ)-subgraph problem, we are given an undirected graph G = (V,E) with edge costs and two positive integers k and λ, and the goal is to find a minimum cost simple λ-edge-connected subgraph of G with at least k nodes. This generalizes several classical problems, such as the minimum cost k-spanning tree problem, or k-MST (which is a (k, 1)-subgraph), and the minimum cost λ-edge-connected spanning subgraph (which is a (|V(G)|, λ)-subgraph). The only previously known results on this problem [L. C. Lau, J. S. Naor, M. R. Salavatipour, and M. Singh, SIAM J. Comput., 39 (2009), pp. 1062-1087], [C. Chekuri and N. Korula, in Proceedings of the IARCS Annual Conference on Foundations of...
Application of Constraint Programming in Subgragh Isomorphism Problem
, M.Sc. Thesis Sharif University of Technology ; Eshghi, Kourosh (Supervisor)
Abstract
Subgraph isomorphism problem is an NP-complete problem, which has diverse applications in different fields such as network problems, image processing, text processing, topography, and bioinformatics. Therefore, many researchers from both theoretical and practical viewpoints have considered it. In this research, we try to offer a proper and efficient method to solve this problem by using constraint programming, which is a powerful and efficient method to model and solve complicated combinatorial optimization problems, and criticality and cruciality concepts from a resource planning scope.
In this regard, first one of the most efficient models among existing constraint programming models...
In this regard, first one of the most efficient models among existing constraint programming models...
Persian Abstractive Summarization using Graph-based Abstract Meaning Representation
, M.Sc. Thesis Sharif University of Technology ; Bahrani, Mohammad (Supervisor)
Abstract
This study attempts to introduce a novel approach to abstractive summarization in Persian. According to the methodology the first step is to represent input text sentences into an abstract meaning representation structure. This representation is syntax free thus, it helps the summarization system to represent sentences more semantic based and free of the sentence syntactic structure. In order to select suitable content for the summary output semantic and structural features are extracted from the representation. Data used in this research consists of approximatelty 200 senctences summarized in 30 sentences of a famous story book named: ”The little prince”. An SVM is trained on 80% of...
Bounds for the Energy of Graphs
, Ph.D. Dissertation Sharif University of Technology ; Akbari, Saieed (Supervisor)
Abstract
The energy of a graph G, E(G), is the sum of absolute values of the eigenvalues of its adjacency matrix. Gutman et al. proved that for every cubic graph of order n, E(G) ⩾ n. Here, we improve this result by showing that if G is a connected subcubic graph of order n, n ⩾ 8, then E(G) ⩾ 1.01n. Also, we prove that if G is a traceable subcubic graph of order n,then E(G) ⩾ 1.1n. Let G be a connected cubic graph of order n, it is shown that E(G) > n + 2, for n ⩾ 8 and we introduce an infinite family of connected cubic graphs whose for each element, say G, E(G) ⩾ 1.24n, and some important conjectures will be raised about this. At the end, for a graph G and its vertex induced subgraphs H and K,...
A note on comaximal graph of non-commutative rings
, Article Algebras and Representation Theory ; Volume 16, Issue 2 , 2013 , Pages 303-307 ; 1386923X (ISSN) ; Habibi, M ; Majidinya A ; Manaviyat, R ; Sharif University of Technology
Kluwer Academic Publishers
2013
Abstract
Let R be a ring with unity. The graph (R) is a graph with vertices as elements of R, where two distinct vertices a and b are adjacent if and only if Ra + Rb = R. Let 2(R) be the subgraph of (R) induced by the non-unit elements of R. Let R be a commutative ring with unity and let J(R) denote the Jacobson radical of R. If R is not a local ring, then it was proved that: (a) If 2(R)J(R) is a complete n-partite graph, then n = 2. (b) If there exists a vertex of 2(R)J(R) which is adjacent to every vertex, then R ≅ ℤ2 × F, where F is a field. In this note we generalize the above results to non-commutative rings and characterize all non-local ring R (not necessarily commutative) whose 2(R)J(R) is a...
Finding maximum edge bicliques in convex bipartite graphs
, Article Algorithmica ; Volume 64, Issue 2 , October , 2012 , Pages 311-325 ; 01784617 (ISSN) ; Pu, S ; Sack, J. R ; Uno, T ; Zarrabi Zadeh, H ; Sharif University of Technology
Springer
2012
Abstract
A bipartite graph G = (A,B,E) is convex on B if there exists an ordering of the vertices of B such that for any vertex v ? A, vertices adjacent to v are consecutive in B. A complete bipartite subgraph of a graph G is called a biclique of G. Motivated by an application to analyzing DNA microarray data, we study the problem of finding maximum edge bicliques in convex bipartite graphs. Given a bipartite graph G = (A,B,E) which is convex on B, we present a new algorithm that computes a maximum edge biclique of G in O(nlog3 n log log n) time and O(n) space, where n = |A|. This improves the current O(n 2) time bound available for the problem. We also show that for two special subclasses of convex...
RMAP: A reliability-aware application mapping for network-on-chips
, Article Proceedings - 3rd International Conference on Dependability, DEPEND 2010, 18 July 2010 through 25 July 2010 ; July , 2010 , Pages 112-117 ; 9780769540900 (ISBN) ; Tabkhi, H ; Miremadi, S. G ; IARIA ; Sharif University of Technology
2010
Abstract
This paper proposes a reliability-aware application mapping for mesh-based NoCs. The proposed reliable mapping, called RMAP, adds redundant communications to the application graph in order to improve the reliability of packet delivery in NoCs. The RMAP divides the application graph into two sub-graphs which have the lowest possible communication with each other. One of the sub-graphs is mapped on the upper triangular nodes of the NoC and the other is mapped on the lower triangular nodes. In this way, lower traffic load is imposed on some channels which are efficiently used to route packets of redundant communications. This minimizes the overheads imposed to the NoC due to redundant...
Highly edge-connected factors using given lists on degrees
, Article Journal of Graph Theory ; Volume 90, Issue 2 , 2019 , Pages 150-159 ; 03649024 (ISSN) ; Hasanvand, M ; Ozeki, K ; Sharif University of Technology
Wiley-Liss Inc
2019
Abstract
Let G be a 2k-edge-connected graph with 𝑘 ≥ 0 and let 𝐿(𝑣) ⊆ {𝑘,…, 𝑑𝐺(𝑣)} for every 𝑣 ∈ 𝑉 (𝐺). A spanning subgraph F of G is called an L-factor, if 𝑑𝐹 (𝑣) ∈ 𝐿(𝑣) for every 𝑣 ∈ 𝑉 (𝐺). In this article, we show that if (Formula presented.) for every 𝑣 ∈ 𝑉 (𝐺), then G has a k-edge-connected L-factor. We also show that if 𝑘 ≥ 1 and (Formula presented.) for every 𝑣 ∈ 𝑉 (𝐺), then G has a k-edge-connected L-factor. © 2018 Wiley Periodicals, Inc
QoS network coding
, Article 2008 International Symposium on Information Theory and its Applications, ISITA2008, Auckland, 7 December 2008 through 10 December 2008 ; April , 2008 ; 9781424420698 (ISBN) ; Hossein Khalaj, B ; Crespo, P. M ; Aref, M. R ; Sharif University of Technology
2008
Abstract
In this paper, we present a decentralized algorithm that computes minimum cost QoS flow subgraphs in network coded multicast networks. These subgraphs are minimum cost solutions that also satisfy user-specified QoS constraints, specifically handling elastic rate and delay demands. Although earlier network coding algorithms in this area have only demonstrated QoS improvements, the proposed QoS network coding is clearly different in the sense that it guarantees that given QoS constraints are met over the network
On eigensharp and almost eigensharp graphs
, Article Linear Algebra and Its Applications ; Volume 429, Issue 11-12 , 2008 , Pages 2746-2753 ; 00243795 (ISSN) ; Maimani, H. R ; Sharif University of Technology
2008
Abstract
The minimum number of complete bipartite subgraphs needed to partition the edges of a graph G is denoted by b (G). A known lower bound on b (G) states that b (G) ≥max {p (G), q (G)}, where p (G) and q (G) are the numbers of positive and negative eigenvalues of the adjacency matrix of G, respectively. When equality is attained, G is said to be eigensharp and when b (G) = max {p (G), q (G)} + 1, G is called an almost eigensharp graph. In this paper, we investigate the eigensharpness of graphs with at most one cycle and products of some families of graphs. Among the other results, we show that Pm ∨ Pn, Cm ∨ Pn for m ≡ 2, 3 (mod 4) and Qn when n is odd are eigensharp. We obtain some results on...