Littérature scientifique sur le sujet « Cover graph »
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Articles de revues sur le sujet "Cover graph"
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Arumugam, S., Indra Rajasingh, and P. Roushini Leely Pushpam. "Characterization of a class of graphs with unique minimum graphoidal cover." Tamkang Journal of Mathematics 34, no. 4 (2003): 317–26. http://dx.doi.org/10.5556/j.tkjm.34.2003.234.
Texte intégralRésumé :
A graphoidal cover of a graph $ G$ is a collection $ \psi$ of (not necessarily open) paths in $ G$ such that every vertex of $ G$ is an internal vertex of at most one path in $ \psi$ and every edge of $ G$ is in exactly one path in $ \psi$. The minimum cardinality of a graphoidal cover of $ G$ is called the graphoidal covering number of $ G$ and is denoted by $ \eta$ . Two graphoidal covers $ \psi_1$ and $ \psi_2$ of a graph $ G$ are said to be isomorphic if there exists an automorphism $ f$ of $ G$ such that $ \psi_2=\{f(P)/P\in \psi_1\}$. A graph $ G$ is said to have a unique minimum graphoidal cover if any two minimum graphoidal covers of $ G$ are isomorphic. In this paper we characterize the class of all graphs $ G$ with a unique minimum graphoidal cover when $ \delta=2$ and no end block of $ G$ is a cycle.
2
Wang, Shiping, Qingxin Zhu, William Zhu, and Fan Min. "Equivalent Characterizations of Some Graph Problems by Covering-Based Rough Sets." Journal of Applied Mathematics 2013 (2013): 1–7. http://dx.doi.org/10.1155/2013/519173.
Texte intégralRésumé :
Covering is a widely used form of data structures. Covering-based rough set theory provides a systematic approach to this data. In this paper, graphs are connected with covering-based rough sets. Specifically, we convert some important concepts in graph theory including vertex covers, independent sets, edge covers, and matchings to ones in covering-based rough sets. At the same time, corresponding problems in graphs are also transformed into ones in covering-based rough sets. For example, finding a minimal edge cover of a graph is translated into finding a minimal general reduct of a covering. The main contributions of this paper are threefold. First, any graph is converted to a covering. Two graphs induce the same covering if and only if they are isomorphic. Second, some new concepts are defined in covering-based rough sets to correspond with ones in graph theory. The upper approximation number is essential to describe these concepts. Finally, from a new viewpoint of covering-based rough sets, the general reduct is defined, and its equivalent characterization for the edge cover is presented. These results show the potential for the connection between covering-based rough sets and graphs.
3
Tsiovkina, Ludmila Yu. "ON A CLASS OF EDGE-TRANSITIVE DISTANCE-REGULAR ANTIPODAL COVERS OF COMPLETE GRAPHS." Ural Mathematical Journal 7, no. 2 (2021): 136. http://dx.doi.org/10.15826/umj.2021.2.010.
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The paper is devoted to the problem of classification of edge-transitive distance-regular antipodal covers of complete graphs. This extends the classification of those covers that are arc-transitive, which has been settled except for some tricky cases that remain to be considered, including the case of covers satisfying condition \(c_2=1\) (which means that every two vertices at distance 2 have exactly one common neighbour).Here it is shown that an edge-transitive distance-regular antipodal cover of a complete graph with \(c_2=1\) is either the second neighbourhood of a vertex in a Moore graph of valency 3 or 7, or a Mathon graph, or a half-transitive graph whose automorphism group induces an affine \(2\)-homogeneous group on the set of its fibres. Moreover, distance-regular antipodal covers of complete graphs with \(c_2=1\) that admit an automorphism group acting \(2\)-homogeneously on the set of fibres (which turns out to be an approximation of the property of edge-transitivity of such cover), are described. A well-known correspondence between distance-regular antipodal covers of complete graphs with \(c_2=1\) and geodetic graphs of diameter two that can be viewed as underlying graphs of certain Moore geometries, allows us to effectively restrict admissible automorphism groups of covers under consideration by combining Kantor's classification of involutory automorphisms of these geometries together with the classification of finite 2-homogeneous permutation groups.
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Bilar, Vergel, Maria Andrea Bonsocan, Javier Hassan, and Susan Dagondon. "Vertex Cover Hop Dominating Sets in Graphs." European Journal of Pure and Applied Mathematics 17, no. 1 (2024): 93–104. http://dx.doi.org/10.29020/nybg.ejpam.v17i1.4978.
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Let $G$ be a graph. Then a subset $C$ of vertices of $G$ is called a vertex cover hop dominating if $C$ is both a vertex cover and a hop dominating of $G$. The vertex cover hop domination number of $G$, denoted by $\gamma_{vch}(G)$, is the minimum cardinality among all vertex cover hop dominating sets in $G$. In this paper, we initiate the study of vertex cover hop domination in a graph and we determine its relations with other parameters in graph theory. We characterize the vertex cover hop dominating sets in some special graphs, join, and corona of two graphs and we finally obtain the exact values or bounds of the parameters of these graphs.
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Scaria, Deena C., John Joy Mulloor, Liju Alex, and Gopal Indulal. "A note on some graph parameters and graph operations." Open Journal of Discrete Applied Mathematics 8, no. 2 (2025): 32–44. https://doi.org/10.30538/psrp-odam2025.0114.
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This paper introduces the concept of the extended \(H\)-cover of a graph \(G\), denoted as \(G^*_H\) , as a generalization inspired by the extended double cover graphs discussed in Chen [1]. We explore the spectral properties and energy characteristics of \(G^*_H\), deriving formulae for the number of spanning trees in cases where both \(G\) and \(H\) are regular. Our investigation identifies several infinite families of equienergetic graphs and highlights instances of cospectral graphs within \(G^*_H\) . Additionally, we analyze various graph parameters related to the Indu-Bala product of graphs and the partial complement of the subdivision graph (PCSD) of \(G\).
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Priscilla, Paul, and Syed Ali Fathima S. "A Study on Edge Pebbling Number, Covering Cover Edge Pebbling Number of Friendship Graphs, Odd Path and Even Path." Indian Journal of Science and Technology 16, no. 32 (2023): 2480–84. https://doi.org/10.17485/IJST/v16i32.674.
Texte intégralRésumé :
Abstract <strong>Objectives:</strong> To find the edge pebbling number and covering cover edge pebbling number of friendship graphs.<strong> Methods:</strong> The possible minimum edge covering set of the friendship graph is considered and the set with the minimum pebble requirement covering all vertices is selected. <strong>Findings:</strong> Obtained the modified result of edge pebbling number of friendship graph, defined the covering cover edge pebbling number of a graph G, and covering cover edge pebbling number for friendship graphs, odd path and even path is found. Also found that friendship graphs are edge demonic. <strong>Novelty:</strong> Finding the covering cover edge pebbling number of a graph plays a vital role in optimization problems. Since all the vertices are covered, for instance the locations of mobile towers can be considered as edges and residential areas as vertices, and network signals can be modified according to the number of pebbles. <strong>Keywords:</strong> Friendship Graphs; Odd Path; Even Path; Minimum Edge Covering Set; Edge Pebbling Number; Edge Demonic; Covering Cover Edge Pebbling Number
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ZHOU, JIN-XIN, and YAN-QUAN FENG. "TETRAVALENT s-TRANSITIVE GRAPHS OF ORDER TWICE A PRIME POWER." Journal of the Australian Mathematical Society 88, no. 2 (2010): 277–88. http://dx.doi.org/10.1017/s1446788710000066.
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AbstractA graph is s-transitive if its automorphism group acts transitively on s-arcs but not on (s+1)-arcs in the graph. Let X be a connected tetravalent s-transitive graph of order twice a prime power. In this paper it is shown that s=1,2,3 or 4. Furthermore, if s=2, then X is a normal cover of one of the following graphs: the 4-cube, the complete graph of order 5, the complete bipartite graph K5,5 minus a 1-factor, or K7,7 minus a point-hyperplane incidence graph of the three-dimensional projective geometry PG(2,2); if s=3, then X is a normal cover of the complete bipartite graph of order 4; if s=4, then X is a normal cover of the point-hyperplane incidence graph of the three-dimensional projective geometry PG(2,3). As an application, we classify the tetravalent s-transitive graphs of order 2p2 for prime p.
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Alikhani, Saeid. "Graphs Whose Certain Polynomials Have Few Distinct Roots." ISRN Discrete Mathematics 2013 (September 12, 2013): 1–8. http://dx.doi.org/10.1155/2013/195818.
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Let G=(V,E) be a simple graph. Graph polynomials are a well-developed area useful for analyzing properties of graphs. We consider domination polynomial, matching polynomial, and edge cover polynomial of G. Graphs which their polynomials have few roots can sometimes give surprising information about the structure of the graph. This paper is primarily a survey of graphs whose domination polynomial, matching polynomial, and edge cover polynomial have few distinct roots. In addition, some new unpublished results and questions are concluded.
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Liu, Zhi-Qiang, Ping Tang, Weixiong Zhang, and Zheng Zhang. "CNN-Enhanced Heterogeneous Graph Convolutional Network: Inferring Land Use from Land Cover with a Case Study of Park Segmentation." Remote Sensing 14, no. 19 (2022): 5027. http://dx.doi.org/10.3390/rs14195027.
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Land use segmentation is a fundamental yet challenging task in remote sensing. Most current methods mainly take images as input and sometimes cannot achieve satisfactory results due to limited information. Inspired by the inherent relations between land cover and land use, we investigate land use segmentation using additional land cover data. The topological relations among land cover objects are beneficial for bridging the semantic gap between land cover and land use. Specifically, these relations are usually depicted by a geo-object-based graph structure. Deep convolutional neural networks (CNNs) are capable of extracting local patterns but fail to efficiently explore topological relations. In contrast, contextual relations among objects can be easily captured by graph convolutional networks (GCNs). In this study, we integrated CNNs and GCNs and proposed the CNN-enhanced HEterogeneous Graph Convolutional Network (CHeGCN) to incorporate local spectral-spatial features and long-range dependencies. We represent topological relations by heterogeneous graphs which are constructed with images and land cover data. Afterwards, we employed GCNs to build topological relations by graph reasoning. Finally, we fused CNN and GCN features to accomplish the inference from land cover to land use. Compared with other homogeneous graph-based models, the land cover data provide more sufficient information for graph reasoning. The proposed method can achieve the transformation from land cover to land use. Extensive experiments showed the competitive performance of CHeGCN and demonstrated the positive effects of land cover data. On the IoU metric over two datasets, CHeGCN outperforms CNNs and GCNs by nearly 3.5% and 5%, respectively. In contrast to homogeneous graphs, heterogeneous graphs have an IoU improvement of approximately 2.5% in the ablation experiments. Furthermore, the generated visualizations help explore the underlying mechanism of CHeGCN. It is worth noting that CHeGCN can be easily degenerated to scenarios where no land cover information is available and achieves satisfactory performance.
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Domagalski, Rachel, and Sivaram Narayan. "Tree Cover Number and Maximum Semidefinite Nullity of Some Graph Classes." Electronic Journal of Linear Algebra 36, no. 36 (2020): 678–93. http://dx.doi.org/10.13001/ela.2020.5319.
Texte intégralRésumé :
Let $G$ be a graph with a vertex set $V$ and an edge set $E$ consisting of unordered pairs of vertices. The tree cover number of $G$, denoted $\tau(G)$, is the minimum number of vertex disjoint simple trees occurring as induced subgraphs of $G$ that cover all the vertices of $G$. In this paper, the tree cover number of a line graph $\tau(L(G))$ is shown to be equal to the path number $\pi(G)$ of $G$. Also, the tree cover numbers of shadow graphs, corona and Cartesian product of two graphs are found.
 The graph parameter $\tau(G)$ is related to another graph parameter $M_+(G)$, called the maximum semidefinite nullity of $G$. Suppose $S_+(G,\mathbb{R})$ denotes the collection of positive semidefinite real symmetric matrices associated with a given graph $G$. Then $M_+(G)$ is the maximum nullity among all matrices in $S_+(G,\mathbb{R})$. It has been conjectured that $\tau(G)\leq M_+(G)$. The conjecture is shown to be true for graph classes considered in this work.
Thèses sur le sujet "Cover graph"
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Meek, Darrin Leigh. "On graph approximation heuristics : an application to vertex cover on planar graphs." Thesis, Georgia Institute of Technology, 1991. http://hdl.handle.net/1853/24088.
Texte intégral
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Abdullah, Mohammed. "The cover time of random walks on graph." Thesis, King's College London (University of London), 2012. https://kclpure.kcl.ac.uk/portal/en/theses/the-cover-time-of-random-walks-on-graph(c23c303f-a6a2-4489-a059-4ade7c118106).html.
Texte intégralRésumé :
A simple random walk on a graph is a sequence of movements from one vertex to another where at each step an edge is chosen uniformly at random from the set of edges incident on the current vertex, and then transitioned to next vertex. Central to this thesis is the cover time of the walk, that is, the expectation of the number of steps required to visit every vertex, maximised over all starting vertices. In our rst contribution, we establish a relation between the cover times of a pair of graphs, and the cover time of their Cartesian product. This extends previous work on special cases of the Cartesian product, in particular, the square of a graph. We show that when one of the factors is in some sense larger than the other, its cover time dominates, and can become within a logarithmic factor of the cover time of the product as a whole. Our main theorem eectively gives conditions for when this holds. The techniques and lemmas we introduce may be of independent interest. In our second contribution, we determine the precise asymptotic value of the cover time of a random graph with given degree sequence. This is a graph picked uniformly at random from all simple graphs with that degree sequence. We also show that with high probability, a structural property of the graph called conductance, is bounded below by a constant. This is of independent interest. Finally, we explore random walks with weighted random edge choices. We present a weighting scheme that has a smaller worst case cover time than a simple random walk. We give an upper bound for a random graph of given degree sequence weighted according to our scheme. We demonstrate that the speed-up (that is, the ratio of cover times) over a simple random walk can be unbounded.
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Streib, Noah Sametz. "Planar and hamiltonian cover graphs." Diss., Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/43744.
Texte intégralRésumé :
This dissertation has two principal components: the dimension of posets with planar cover graphs, and the cartesian product of posets whose cover graphs have hamiltonian cycles that parse into symmetric chains. Posets of height two can have arbitrarily large dimension. In 1981, Kelly provided an infinite sequence of planar posets that shows that the dimension of planar posets can also be arbitrarily large. However, the height of the posets in this sequence increases with the dimension. In 2009, Felsner, Li, and Trotter conjectured that for each integer h at least 2, there exists a least positive integer c(h) so that if P is a poset with a planar cover graph (the class of posets with planar cover graphs includes the class of planar posets) and the height of P is h, then the dimension of P is at most c(h). In the first principal component of this dissertation we prove this conjecture. We also give the best known lower bound for c(h), noting that this lower bound is far from the upper bound. In the second principal component, we consider posets with the Hamiltonian Cycle--Symmetric Chain Partition (HC-SCP) property. A poset of width w has this property if its cover graph has a hamiltonian cycle which parses into w symmetric chains. This definition is motivated by a proof of Sperner's theorem that uses symmetric chains, and was intended as a possible method of attack on the Middle Two Levels Conjecture. We show that the subset lattices have the HC-SCP property by showing that the class of posets with the strong HC-SCP property, a slight strengthening of the HC-SCP property, is closed under cartesian product with a two-element chain. Furthermore, we show that the cartesian product of any two posets from this strong class has the (weak) HC-SCP property.
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Carney, Nicholas. "Roman Domination Cover Rubbling." Digital Commons @ East Tennessee State University, 2019. https://dc.etsu.edu/etd/3617.
Texte intégralRésumé :
In this thesis, we introduce Roman domination cover rubbling as an extension of domination cover rubbling. We define a parameter on a graph $G$ called the \textit{Roman domination cover rubbling number}, denoted $\rho_{R}(G)$, as the smallest number of pebbles, so that from any initial configuration of those pebbles on $G$, it is possible to obtain a configuration which is Roman dominating after some sequence of pebbling and rubbling moves. We begin by characterizing graphs $G$ having small $\rho_{R}(G)$ value. Among other things, we also obtain the Roman domination cover rubbling number for paths and give an upper bound for the Roman domination cover rubbling number of a tree.
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Sinkovic, John Henry. "The Minimum Rank Problem for Outerplanar Graphs." BYU ScholarsArchive, 2013. https://scholarsarchive.byu.edu/etd/3722.
Texte intégralRésumé :
Given a simple graph G with vertex set V(G)={1,2,...,n} define S(G) to be the set of all real symmetric matrices A such that for all i not equal to j, the ijth entry of A is nonzero if and only if ij is in E(G). The range of the ranks of matrices in S(G) is of interest and can be determined by finding the minimum rank. The minimum rank of a graph, denoted mr(G), is the minimum rank achieved by a matrix in S(G). The maximum nullity of a graph, denoted M(G), is the maximum nullity achieved by a matrix in S(G). Note that mr(G)+M(G)=|V(G)| and so in finding the maximum nullity of a graph, the minimum rank of a graph is also determined. The minimum rank problem for a graph G asks us to determine mr(G) which in general is very difficult. A simple graph is planar if there exists a drawing of G in the plane such that any two line segments representing edges of G intersect only at a point which represents a vertex of G. A planar drawing partitions the rest of the plane into open regions called faces. A graph is outerplanar if there exists a planar drawing of G such that every vertex lies on the outer face. We consider the class of outerplanar graphs and summarize some of the recent results concerning the minimum rank problem for this class. The path cover number of a graph, denoted P(G), is the minimum number of vertex-disjoint paths needed to cover all the vertices of G. We show that for all outerplanar graphs G, P(G)is greater than or equal to M(G). We identify a subclass of outerplanar graphs, called partial 2-paths, for which P(G)=M(G). We give a different characterization for another subset of outerplanar graphs, unicyclic graphs, which determines whether M(G)=P(G) or M(G)=P(G)-1. We give an example of a 2-connected outerplanar graph for which P(G) ≥ M(G).A cover of a graph G is a collection of subgraphs of G such that the union of the edge sets of the subgraphs is equal to the E(G). The rank-sum of a cover C of G is denoted as rs(C) and is equal to the sum of the minimum ranks of the subgraphs in C. We show that for an outerplanar graph G, there exists an edge-disjoint cover of G consisting of cliques, stars, cycles, and double cycles such that the rank-sum of the cover is equal to the minimum rank of G. Using the fact that such a cover exists allows us to show that the minimum rank of a weighted outerplanar graph is equal to the minimum rank of its underlying simple graph.
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Hassan-Shafique, Khurram. "PARTITIONING A GRAPH IN ALLIANCES AND ITS APPLICATION TO DATA CLUSTERING." Doctoral diss., University of Central Florida, 2004. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/4152.
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Any reasonably large group of individuals, families, states, and parties exhibits the phenomenon of subgroup formations within the group such that the members of each group have a strong connection or bonding between each other. The reasons of the formation of these subgroups that we call alliances differ in different situations, such as, kinship and friendship (in the case of individuals), common economic interests (for both individuals and states), common political interests, and geographical proximity. This structure of alliances is not only prevalent in social networks, but it is also an important characteristic of similarity networks of natural and unnatural objects. (A similarity network defines the links between two objects based on their similarities). Discovery of such structure in a data set is called clustering or unsupervised learning and the ability to do it automatically is desirable for many applications in the areas of pattern recognition, computer vision, artificial intelligence, behavioral and social sciences, life sciences, earth sciences, medicine, and information theory. In this dissertation, we study a graph theoretical model of alliances where an alliance of the vertices of a graph is a set of vertices in the graph, such that every vertex in the set is adjacent to equal or more vertices inside the set than the vertices outside it. We study the problem of partitioning a graph into alliances and identify classes of graphs that have such a partition. We present results on the relationship between the existence of such a partition and other well known graph parameters, such as connectivity, subgraph structure, and degrees of vertices. We also present results on the computational complexity of finding such a partition. An alliance cover set is a set of vertices in a graph that contains at least one vertex from every alliance of the graph. The complement of an alliance cover set is an alliance free set, that is, a set that does not contain any alliance as a subset. We study the properties of these sets and present tight bounds on their cardinalities. In addition, we also characterize the graphs that can be partitioned into alliance free and alliance cover sets. Finally, we present an approximate algorithm to discover alliances in a given graph. At each step, the algorithm finds a partition of the vertices into two alliances such that the alliances are strongest among all such partitions. The strength of an alliance is defined as a real number p, such that every vertex in the alliance has at least p times more neighbors in the set than its total number of neighbors in the graph). We evaluate the performance of the proposed algorithm on standard data sets.<br>Ph.D.<br>School of Computer Science<br>Engineering and Computer Science<br>Computer Science
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Cornet, Alexis. "Algorithmes et résultats de complexité pour des problèmes de graphes avec contraintes additionnelles." Thesis, Université Clermont Auvergne (2017-2020), 2018. http://www.theses.fr/2018CLFAC034/document.
Texte intégralRésumé :
Les problèmes de domination (dominant, dominant indépendant, ...) et de couverture (vertex-cover, arbre de Steiner, ...) sont NP-complets. Pour autant, pour la plupart de ces problèmes, il existe toujours une solution constructible en temps polynomial (potentiellement de valeur objective très mauvaise), ou au moins, il est possible de déterminer facilement (en temps polynomial) l'existence ou non d'une solution. Ces problèmes, initialement issus de situations réelles, sont des modélisations simplistes de ces situations. Nous ajoutons donc des contraintes additionnelles modélisant des contraintes pratiques plausibles : les conflits, des paires d'éléments ne pouvant faire simultanément partie d'une solution (modélisant des incompatibilités diverses), la connexité dans un second graphe (les éléments doivent pouvoir communiquer, et le graphe correspondant à ces liens de communication n'est pas forcément le même) et les obligations, des sous-ensembles d'éléments interdépendants devant être ajoutés simultanément à une solution. Notre but ici n'est pas de modéliser un problème réel précis, mais d'étudier la manière dont ces contraintes modifient la complexité des problèmes étudiés. Nous verrons que dans un grand nombre de cas, déterminer l'existence même d'une solution devient difficile, même sans se préoccuper de leur optimisation. Le problème du firefighter modélise des pompiers tentant de contenir un feu se propageant au tour par tour dans un graphe (potentiellement infini). Nous avons étudié ce problème en ajoutant des contraintes sur le déplacement des pompiers (une vitesse de déplacement limitée entre deux tours). Nous verrons que ces contraintes augmentent en général le nombre de pompiers nécessaires mais ne provoquent pas de changements aussi importants que dans les problèmes précédents<br>Domination problems (dominating set, independant dominating set, ...) as well as covering problems (vertex-cover, Steiner tree, ...) are NP-complete. However, for most of these problems, it is always possible to construct a (eventually bad) solution in polynomial time, or at least it is possible to determine whether a solution exists. Those problems originally came from industry, but are simplified modelizations of the real life problems. We add additional constraints modeling plausible practical constraints : conflicts which are pairs of elements that cannot apear simultaneously in a solution (to modelize various incompatibilities), connexity in a second graph (elements of the solution must be able to communicate, and the communication links are a second graph), and obligations which are subsets of interdependant vertices which must be added simultaneously in a solution.We don't aim to model a specific real-world problem, but to study how these plausible constraints affect the complexity of the studied problems. We will see that, in many cases, even determining the existence of a solution (regardless of its size) become hard. The firefighter problem models firefighters aiming to contain a fire spreading turn by turn in a (eventually infinite) graph. We studied this problem with the addition of deplacement constraints for the firefighters (a limited moving speed between turns). We will see that, most of the time, this constraint increase the number of firefighters necessary to contain the fire, but does not trigger such major change as constraints studied in the others problems
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Oosthuizen, Joubert. "Random walks on graphs." Thesis, Stellenbosch : Stellenbosch University, 2014. http://hdl.handle.net/10019.1/86244.
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Thesis (MSc)--Stellenbosch University, 2014.<br>ENGLISH ABSTRACT: We study random walks on nite graphs. The reader is introduced to general
Markov chains before we move on more specifically to random walks on graphs.
A random walk on a graph is just a Markov chain that is time-reversible. The
main parameters we study are the hitting time, commute time and cover time.
We nd novel formulas for the cover time of the subdivided star graph and
broom graph before looking at the trees with extremal cover times.
Lastly we look at a connection between random walks on graphs and electrical
networks, where the hitting time between two vertices of a graph is expressed
in terms of a weighted sum of e ective resistances. This expression in turn
proves useful when we study the cover cost, a parameter related to the cover
time.<br>AFRIKAANSE OPSOMMING: Ons bestudeer toevallige wandelings op eindige gra eke in hierdie tesis. Eers
word algemene Markov kettings beskou voordat ons meer spesi ek aanbeweeg
na toevallige wandelings op gra eke. 'n Toevallige wandeling is net 'n Markov
ketting wat tyd herleibaar is. Die hoof paramaters wat ons bestudeer is die
treftyd, pendeltyd en dektyd. Ons vind oorspronklike formules vir die dektyd
van die verdeelde stergra ek sowel as die besemgra ek en kyk daarna na die
twee bome met uiterste dektye.
Laastens kyk ons na 'n verband tussen toevallige wandelings op gra eke en
elektriese netwerke, waar die treftyd tussen twee punte op 'n gra ek uitgedruk
word in terme van 'n geweegde som van e ektiewe weerstande. Hierdie uitdrukking
is op sy beurt weer nuttig wanneer ons die dekkoste bestudeer, waar
die dekkoste 'n paramater is wat verwant is aan die dektyd.
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Camby, Eglantine. "Connecting hitting sets and hitting paths in graphs." Doctoral thesis, Universite Libre de Bruxelles, 2015. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/209048.
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Dans cette thèse, nous étudions les aspects structurels et algorithmiques de différents problèmes de théorie des graphes. Rappelons qu’un graphe est un ensemble de sommets éventuellement reliés par des arêtes. Deux sommets sont adjacents s’ils sont reliés par une arête.<p>Tout d’abord, nous considérons les deux problèmes suivants :le problème de vertex cover et celui de dominating set, deux cas particuliers du problème de hitting set. Un vertex cover est un ensemble de sommets qui rencontrent toutes les arêtes alors qu’un dominating set est un ensemble X de sommets tel que chaque sommet n’appartenant pas à X est adjacent à un sommet de X. La version connexe de ces problèmes demande que les sommets choisis forment un sous-graphe connexe. Pour les deux problèmes précédents, nous examinons le prix de la connexité, défini comme étant le rapport entre la taille minimum d’un ensemble répondant à la version connexe du problème et celle d’un ensemble du problème originel. Nous prouvons la difficulté du calcul du prix de la connexité d’un graphe. Cependant, lorsqu’on exige que le prix de la connexité d’un graphe ainsi que de tous ses sous-graphes induits soit borné par une constante fixée, la situation change complètement. En effet, pour les problèmes de vertex cover et de dominating set, nous avons pu caractériser ces classes de graphes pour de petites constantes.<p>Ensuite, nous caractérisons en termes de dominating sets connexes les graphes Pk- free, graphes n’ayant pas de sous-graphes induits isomorphes à un chemin sur k sommets. Beaucoup de problèmes sur les graphes sont étudiés lorsqu’ils sont restreints à cette classe de graphes. De plus, nous appliquons cette caractérisation à la 2-coloration dans les hypergraphes. Pour certains hypergraphes, nous prouvons que ce problème peut être résolu en temps polynomial.<p>Finalement, nous travaillons sur le problème de Pk-hitting set. Un Pk-hitting set est un ensemble de sommets qui rencontrent tous les chemins sur k sommets. Nous développons un algorithme d’approximation avec un facteur de performance de 3. Notre algorithme, basé sur la méthode primal-dual, fournit un Pk-hitting set dont la taille est au plus 3 fois la taille minimum d’un Pk-hitting set.<br>Doctorat en Sciences<br>info:eu-repo/semantics/nonPublished
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Levy, Eythan. "Approximation algorithms for covering problems in dense graphs." Doctoral thesis, Universite Libre de Bruxelles, 2009. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/210359.
Texte intégralRésumé :
We present a set of approximation results for several covering problems in dense graphs. These results show that for several problems, classical algorithms with constant approximation ratios can be analyzed in a finer way, and provide better constant approximation ratios under some density constraints. In particular, we show that the maximal matching heuristic approximates VERTEX COVER (VC) and MINIMUM MAXIMAL MATCHING (MMM) with a constant ratio strictly smaller than 2 when the proportion of edges present in the graph (weak density) is at least 3/4, or when the normalized minimum degree (strong density) is at least 1/2. We also show that this result can be improved by a greedy algorithm which provides a constant ratio smaller than 2 when the weak density is at least 1/2. We also provide tight families of graphs for all these approximation ratios. We then looked at several algorithms from the literature for VC and SET COVER (SC). We present a unified and critical approach to the Karpinski/Zelikovsky, Imamura/Iwama and Bar-Yehuda/Kehat algorithms, identifying the general the general scheme underlying these algorithms.<p>Finally, we look at the CONNECTED VERTEX COVER (CVC) problem,for which we proposed new approximation results in dense graphs. We first analyze Carla Savage's algorithm, then a new variant of the Karpinski-Zelikovsky algorithm. Our results show that these algorithms provide the same approximation ratios for CVC as the maximal matching heuristic and the Karpinski-Zelikovsky algorithm did for VC. We provide tight examples for the ratios guaranteed by both algorithms. We also introduce a new invariant, the "price of connectivity of VC", defined as the ratio between the optimal solutions of CVC and VC, and showed a nearly tight upper bound on its value as a function of the weak density. Our last chapter discusses software aspects, and presents the use of the GRAPHEDRON software in the framework of approximation algorithms, as well as our contributions to the development of this system.<p><p>/<p><p>Nous présentons un ensemble de résultats d'approximation pour plusieurs problèmes de couverture dans les graphes denses. Ces résultats montrent que pour plusieurs problèmes, des algorithmes classiques à facteur d'approximation constant peuvent être analysés de manière plus fine, et garantissent de meilleurs facteurs d'aproximation constants sous certaines contraintes de densité. Nous montrons en particulier que l'heuristique du matching maximal approxime les problèmes VERTEX COVER (VC) et MINIMUM MAXIMAL MATCHING (MMM) avec un facteur constant inférieur à 2 quand la proportion d'arêtes présentes dans le graphe (densité faible) est supérieure à 3/4 ou quand le degré minimum normalisé (densité forte) est supérieur à 1/2. Nous montrons également que ce résultat peut être amélioré par un algorithme de type GREEDY, qui fournit un facteur constant inférieur à 2 pour des densités faibles supérieures à 1/2. Nous donnons également des familles de graphes extrémaux pour nos facteurs d'approximation. Nous nous somme ensuite intéressés à plusieurs algorithmes de la littérature pour les problèmes VC et SET COVER (SC). Nous avons présenté une approche unifiée et critique des algorithmes de Karpinski-Zelikovsky, Imamura-Iwama, et Bar-Yehuda-Kehat, identifiant un schéma général dans lequel s'intègrent ces algorithmes.<p>Nous nous sommes finalement intéressés au problème CONNECTED VERTEX COVER (CVC), pour lequel nous avons proposé de nouveaux résultats d'approximation dans les graphes denses, au travers de l'algorithme de Carla Savage d'une part, et d'une nouvelle variante de l'algorithme de Karpinski-Zelikovsky d'autre part. Ces résultats montrent que nous pouvons obtenir pour CVC les mêmes facteurs d'approximation que ceux obtenus pour VC à l'aide de l'heuristique du matching maximal et de l'algorithme de Karpinski-Zelikovsky. Nous montrons également des familles de graphes extrémaux pour les ratios garantis par ces deux algorithmes. Nous avons également étudié un nouvel invariant, le coût de connectivité de VC, défini comme le rapport entre les solutions optimales de CVC et de VC, et montré une borne supérieure sur sa valeur en fonction de la densité faible. Notre dernier chapitre discute d'aspects logiciels, et présente l'utilisation du logiciel GRAPHEDRON dans le cadre des algorithmes d'approximation, ainsi que nos contributions au développement du logiciel.<br>Doctorat en Sciences<br>info:eu-repo/semantics/nonPublished
Livres sur le sujet "Cover graph"
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NoteBooks, Sappuris. Graph Paper, Magenta Cover. Independently Published, 2021.
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Press, Mockup. Graph Notebook: Hardcover Graph Notebook with Retro Style Cover. Independently Published, 2021.
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Publishing, Karabella. Graph Paper: 5x5 Blank Graph Paper with Angel on Cover. Independently Published, 2018.
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Magic, Handwriter. Graph Paper Notebook: Beautiful Soft Cover. Independently Published, 2020.
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NoteBooks, Sappuris. Graph Paper Abstract Halftone Background Cover. Independently Published, 2021.
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Sunny Days Sunny Days School Room. Graph Paper Notepad: 5x5 Graph Ruled Squared Graphing Paper with Coordinate Graph Point Cover. Independently Published, 2019.
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books, touchich. Graph Paper Composition 5x5: Size 6*9,120 Graph Pages ,matte Cover. Independently Published, 2020.
Trouver le texte intégralChapitres de livres sur le sujet "Cover graph"
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Atienza, Nieves, Natalia de Castro, Carmen Cortés, et al. "Cover Contact Graphs." In Graph Drawing. Springer Berlin Heidelberg, 2008. http://dx.doi.org/10.1007/978-3-540-77537-9_18.
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Angel, Eric, Evripidis Bampis, Bruno Escoffier, and Michael Lampis. "Parameterized Power Vertex Cover." In Graph-Theoretic Concepts in Computer Science. Springer Berlin Heidelberg, 2016. http://dx.doi.org/10.1007/978-3-662-53536-3_9.
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Fomin, Fedor V., and Torstein J. F. Strømme. "Vertex Cover Structural Parameterization Revisited." In Graph-Theoretic Concepts in Computer Science. Springer Berlin Heidelberg, 2016. http://dx.doi.org/10.1007/978-3-662-53536-3_15.
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Kourie, Derrick G., and Bruce W. Watson. "Case Study: Lattice Cover Graph Construction." In The Correctness-by-Construction Approach to Programming. Springer Berlin Heidelberg, 2012. http://dx.doi.org/10.1007/978-3-642-27919-5_6.
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Ivković, Zoran, and Errol L. Lloyd. "Fully dynamic maintenance of vertex cover." In Graph-Theoretic Concepts in Computer Science. Springer Berlin Heidelberg, 1994. http://dx.doi.org/10.1007/3-540-57899-4_44.
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Wang, Liang, and Jianxin Zhao. "Computation Graph." In Architecture of Advanced Numerical Analysis Systems. Apress, 2022. http://dx.doi.org/10.1007/978-1-4842-8853-5_6.
Texte intégralRésumé :
AbstractA computation graph is a basic theoretical tool that underlines modern deep learning libraries. It is also an important component in Owl. This chapter first gives a bird’s-eye view on the computation graph in Owl and its importance in computing. We then demonstrate how to use it in Owl with some examples. Then we will continue to cover the design and implementation details of the computation graph module and how it is fitted into Owl’s functor stack.
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Kneis, Joachim, Alexander Langer, and Peter Rossmanith. "Improved Upper Bounds for Partial Vertex Cover." In Graph-Theoretic Concepts in Computer Science. Springer Berlin Heidelberg, 2008. http://dx.doi.org/10.1007/978-3-540-92248-3_22.
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Chen, Jianer, Iyad A. Kanj, and Weijia Jia. "Vertex Cover: Further Observations and Further Improvements." In Graph-Theoretic Concepts in Computer Science. Springer Berlin Heidelberg, 1999. http://dx.doi.org/10.1007/3-540-46784-x_30.
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Kılıç, Baran, Can Özturan, and Alper Şen. "Analyzing Large-Scale Blockchain Transaction Graphs for Fraudulent Activities." In Big Data and Artificial Intelligence in Digital Finance. Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-94590-9_14.
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AbstractEarly public blockchains provided low transaction throughputs in the range of 7–30 transactions per second. With the emergence of permissioned and proof-of-stake-based blockchains, transaction throughputs are expected to rise drastically to thousands per second. Blockchain transactions form directed graphs. With high transaction throughputs and growing blockchain adoption by banks, businesses and customers in general, the number of edges in transaction graphs will dynamically grow to billions. An analysis of large-scale transaction graphs is needed for tracing fraudulent activities on blockchains. This chapter will cover topics such as distributed graph data structures, the use of message passing libraries, and parallel graph algorithms in order to build a scalable transaction graph analysis system. Results from the analysis of the real Ethereum and Bitcoin public blockchain data involving cryptocurrency and ERC20 token transactions will be presented.
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Fellows, Michael R., Daniel Lokshtanov, Neeldhara Misra, Frances A. Rosamond, and Saket Saurabh. "Graph Layout Problems Parameterized by Vertex Cover." In Algorithms and Computation. Springer Berlin Heidelberg, 2008. http://dx.doi.org/10.1007/978-3-540-92182-0_28.
Texte intégralActes de conférences sur le sujet "Cover graph"
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Guan, Renxiang, Zihao Li, Chujia Song, Guo Yu, Xianju Li, and Ruyi Feng. "S2RC-GCN: A Spatial-Spectral Reliable Contrastive Graph Convolutional Network for Complex Land Cover Classification Using Hyperspectral Images." In 2024 International Joint Conference on Neural Networks (IJCNN). IEEE, 2024. http://dx.doi.org/10.1109/ijcnn60899.2024.10650629.
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Krishnan, Sivaram, Jihong Park, Gregory Sherman, Benjamin Campbell, and Jinho Choi. "Graph Koopman Autoencoder for Predictive Covert Communication Against UAV Surveillance." In 2024 IEEE 99th Vehicular Technology Conference (VTC2024-Spring). IEEE, 2024. http://dx.doi.org/10.1109/vtc2024-spring62846.2024.10683140.
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Stephans, Larry C. "The Design of Masonry/Plastic Lining Composite Structures." In CORROSION 1997. NACE International, 1997. https://doi.org/10.5006/c1997-97363.
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Abstract The continued development of plastics with improved corrosion resistance has extended the conditions in which plastics can perform satisfactorily as corrosion resistant linings on steel. The use of a masonry lining over the plastic “membrane” further extends the conditions of service to higher temperatures and more severe mechanical conditions. This type of composite structure consisting of a steel vessel lined with a plastic membrane protected by brick set in resin and/or inorganic mortars presents a number of design challenges. The composite structure must be selected to perform satisfactorily in the chemical environment and be designed to perform satisfactorily in both the steady state and the transient process conditions. The process conditions must be accurately detailed and the lining design must consider the response of several materials with widely differing physical properties to these conditions. Computer software has been developed which will calculate and graph the temperature gradient through the composite lining and calculate and graph the stresses in the lining for both steady state and transient process conditions. This paper covers the process information necessary for the specification and design of a brick and membrane lining in a steel vessel and the use of a computer for die analysis of the lining.
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Werner, Peter, Alexandre Amice, Tobia Marcucci, Daniela Rus, and Russ Tedrake. "Approximating Robot Configuration Spaces with few Convex Sets using Clique Covers of Visibility Graphs." In 2024 IEEE International Conference on Robotics and Automation (ICRA). IEEE, 2024. http://dx.doi.org/10.1109/icra57147.2024.10610005.
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Gusev, Vasily Vasilievich. "Game of vertex cover of a graph." In Academician O.B. Lupanov 14th International Scientific Seminar "Discrete Mathematics and Its Applications". Keldysh Institute of Applied Mathematics, 2022. http://dx.doi.org/10.20948/dms-2022-56.
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The paper considers the problem of finding the significance of vertices in vertex cover of a graph based on its topology. Index computed Shapley-Shubik in a cooperative game of vertex cover for some graph classes.
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Mariano, Matheus Monteiro, Érica Ferreira Souza, André Takeshi Endo, and Nandamudi L. Vijaykumar. "A comparative study of algorithms for generating switch cover test sets." In XV Simpósio Brasileiro de Qualidade de Software. Sociedade Brasileira de Computação - SBC, 2016. http://dx.doi.org/10.5753/sbqs.2016.15122.
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Test case generation based on Finite State Machines (FSMs) has been extensively investigated due to its accuracy and simplicity. Several test criteria have been proposed in the literature to generate test cases based on FSMs. One of the oldest criteria is the Switch Cover. As a main feature, the Switch Cover criterion defines that all transition pairs of an FSM must be covered. The classical Switch Cover algorithm converts the FSM into a graph (known as Dual Graph); this graph is balanced, and, finally, traversed based on an Eulerian Cycle algorithm. In this context, considering the stage where an FSM is converted into a graph, this study investigates other search algorithms on graphs, namely Depth-First Search (DFS) and Breadth-First Search (BFS), for generating test sets from a Dual Graph. We presented an experimental study that compares the DFS, BFS algorithms with the Eulerian Cycle. The study was conducted with a set of random and real-world machines, taking into account the number of test cases, the test suite size, the average length of sequences and generation time.
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Botler, Fábio, and Luiz Hoffmann. "Decomposition of (2k+1)-regular graphs containing special spanning 2k-regular Cayley graphs into paths of length 2k+1." In Encontro de Teoria da Computação. Sociedade Brasileira de Computação - SBC, 2020. http://dx.doi.org/10.5753/etc.2020.11078.
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A Pl-decomposition of a graph G is a set of paths with l edges in G that cover the edge set of G. Favaron, Genest, and Kouider (2010) conjectured that every (2k+1)-regular graph that contains a perfect matching admits a P2k+1-decomposition. They also verified this conjecture for 5-regular graphs without cycles of length 4. In 2015, Botler, Mota, and Wakabayashi extended this result to 5-regular graphs without triangles. In this paper, we verify this conjecture for (2k+1)-regular graphs that contain the k-th power of a spanning cycle; and for 5-regular graphs that contain certain spanning 4-regular Cayley graphs.
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Gangatharan, Venkat Narayanan, Suresh Suseela, and Kala Rukhmoni. "On 2−simple graphoidal cover of a graph." In 1ST INTERNATIONAL CONFERENCE ON MATHEMATICAL TECHNIQUES AND APPLICATIONS: ICMTA2020. AIP Publishing, 2020. http://dx.doi.org/10.1063/5.0025497.
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Divsalar, Dariush, and Lara Dolecek. "Graph cover ensembles of non-binary protograph LDPC codes." In 2012 IEEE International Symposium on Information Theory - ISIT. IEEE, 2012. http://dx.doi.org/10.1109/isit.2012.6283972.
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Skachek, Vitaly. "Characterization of graph-cover pseudocodewords of codes over F3." In 2010 IEEE Information Theory Workshop (ITW 2010). IEEE, 2010. http://dx.doi.org/10.1109/cig.2010.5592884.
Texte intégralRapports d'organisations sur le sujet "Cover graph"
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Lundgren, J. R., and John S. Maybee. Graphs and Matrices: Combinatorial Analysis, Competitions, Covers and Ranks. Defense Technical Information Center, 1993. http://dx.doi.org/10.21236/ada280480.
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Rosenblatt, David, Henry Mooney, Khamal Clayton, et al. Open configuration options Caribbean Economics Quarterly: Volume 11: Issue 1, February 2022: Year in Review in Graphs: Economic Story of 2021 in a Series of Graphs. Inter-American Development Bank, 2022. http://dx.doi.org/10.18235/0004018.
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Last year ended with incipient but fragile economic recoveries in most Caribbean economies. Relatively low vaccination rates remain a concern in the six countries covered by the Caribbean Country Department of the IDB. The sharp rise in commodity prices bolster prospects for commodity exporters in the region, but they also dampen prospects for tourism dependent economies. This edition of the Caribbean Quarterly Bulletin provides a “Year in Review in Graphs” for the overall region and each of the six countries. The graphs cover the evolution of key macroeconomic variable during the course of 2021.
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Nieto-Castanon, Alfonso. CONN functional connectivity toolbox (RRID:SCR_009550), Version 18. Hilbert Press, 2018. http://dx.doi.org/10.56441/hilbertpress.1818.9585.
Texte intégralRésumé :
CONN is a Matlab-based cross-platform software for the computation, display, and analysis of functional connectivity in fMRI (fcMRI). Connectivity measures include seed-to-voxel connectivity maps, ROI-to- ROI connectivity matrices, graph properties of connectivity networks, generalized psychophysiological interaction models (gPPI), intrinsic connectivity, local correlation and other voxel-to-voxel measures, independent component analyses (ICA), and dynamic component analyses (dyn-ICA). CONN is available for resting state data (rsfMRI) as well as task-related designs. It covers the entire pipeline from raw fMRI data to hypothesis testing, including spatial coregistration, ART-based scrubbing, aCompCor strategy for control of physiological and movement confounds, first-level connectivity estimation, and second-level random-effect analyses and hypothesis testing.
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Nieto-Castanon, Alfonso. CONN functional connectivity toolbox (RRID:SCR_009550), Version 20. Hilbert Press, 2020. http://dx.doi.org/10.56441/hilbertpress.2048.3738.
Texte intégralRésumé :
CONN is a Matlab-based cross-platform software for the computation, display, and analysis of functional connectivity in fMRI (fcMRI). Connectivity measures include seed-to-voxel connectivity maps, ROI-to- ROI connectivity matrices, graph properties of connectivity networks, generalized psychophysiological interaction models (gPPI), intrinsic connectivity, local correlation and other voxel-to-voxel measures, independent component analyses (ICA), and dynamic component analyses (dyn-ICA). CONN is available for resting state data (rsfMRI) as well as task-related designs. It covers the entire pipeline from raw fMRI data to hypothesis testing, including spatial coregistration, ART-based scrubbing, aCompCor strategy for control of physiological and movement confounds, first-level connectivity estimation, and second-level random-effect analyses and hypothesis testing.
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Nieto-Castanon, Alfonso. CONN functional connectivity toolbox (RRID:SCR_009550), Version 19. Hilbert Press, 2019. http://dx.doi.org/10.56441/hilbertpress.1927.9364.
Texte intégralRésumé :
CONN is a Matlab-based cross-platform software for the computation, display, and analysis of functional connectivity in fMRI (fcMRI). Connectivity measures include seed-to-voxel connectivity maps, ROI-to- ROI connectivity matrices, graph properties of connectivity networks, generalized psychophysiological interaction models (gPPI), intrinsic connectivity, local correlation and other voxel-to-voxel measures, independent component analyses (ICA), and dynamic component analyses (dyn-ICA). CONN is available for resting state data (rsfMRI) as well as task-related designs. It covers the entire pipeline from raw fMRI data to hypothesis testing, including spatial coregistration, ART-based scrubbing, aCompCor strategy for control of physiological and movement confounds, first-level connectivity estimation, and second-level random-effect analyses and hypothesis testing.
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Turgeon, Mathieu. Causal Modeling with Regression Discontinuity Designs (RDD). Instats Inc., 2023. http://dx.doi.org/10.61700/s3nl5lfnmruqw469.
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This seminar introduces the use of the regression discontinuity design (RDD) to estimate treatment effects from observational data. Day 1 topics include directed acyclic graphs (DAG), potential outcomes framework and associated assumptions, the sharp regression discontinuity design, and tools for visualizing discontinuities. Day 2 topics focus on the estimation of values of interest from a regression discontinuity design, adopting a continuity-based approach to RD analysis. Day 2 will also cover issues related to the validation and falsification of the regression discontinuity design. An official Instats certificate of completion is provided at the conclusion of the seminar. For European PhD students, each seminar offers 2 ECTS Equivalent points.
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Turgeon, Mathieu. Causal Modeling with Regression Discontinuity Designs (RDD). Instats Inc., 2023. http://dx.doi.org/10.61700/o6e22r1sh4h7m469.
Texte intégralRésumé :
This seminar introduces the use of the regression discontinuity design (RDD) to estimate treatment effects from observational data. Sessions 1-3 topics include directed acyclic graphs (DAG), potential outcomes framework and associated assumptions, the sharp regression discontinuity design, and tools for visualizing discontinuities. Sessions 4-6 topics focus on the estimation of values of interest from a regression discontinuity design, adopting a continuity-based approach to RD analysis. Day 2 will also cover issues related to the validation and falsification of the regression discontinuity design. An official Instats certificate of completion is provided at the conclusion of the seminar. For European PhD students, each seminar offers 2 ECTS Equivalent points.
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Heitman, Joshua L., Alon Ben-Gal, Thomas J. Sauer, Nurit Agam, and John Havlin. Separating Components of Evapotranspiration to Improve Efficiency in Vineyard Water Management. United States Department of Agriculture, 2014. http://dx.doi.org/10.32747/2014.7594386.bard.
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Vineyards are found on six of seven continents, producing a crop of high economic value with much historic and cultural significance. Because of the wide range of conditions under which grapes are grown, management approaches are highly varied and must be adapted to local climatic constraints. Research has been conducted in the traditionally prominent grape growing regions of Europe, Australia, and the western USA, but far less information is available to guide production under more extreme growing conditions. The overarching goal of this project was to improve understanding of vineyard water management related to the critical inter-row zone. Experiments were conducted in moist temperate (North Carolina, USA) and arid (Negev, Israel) regions in order to address inter-row water use under high and low water availability conditions. Specific objectives were to: i) calibrate and verify a modeling technique to identify components of evapotranspiration (ET) in temperate and semiarid vineyard systems, ii) evaluate and refine strategies for excess water removal in vineyards for moist temperate regions of the Southeastern USA, and iii) evaluate and refine strategies for water conservation in vineyards for semi-arid regions of Israel. Several new measurement and modeling techniques were adapted and assessed in order to partition ET between favorable transpiration by the grapes and potentially detrimental water use within the vineyard inter-row. A micro Bowen ratio measurement system was developed to quantify ET from inter-rows. The approach was successful at the NC site, providing strong correlation with standard measurement approaches and adding capability for continuous, non-destructive measurement within a relatively small footprint. The environmental conditions in the Negev site were found to limit the applicability of the technique. Technical issues are yet to be solved to make this technique sufficiently robust. The HYDRUS 2D/3D modeling package was also adapted using data obtained in a series of intense field campaigns at the Negev site. The adapted model was able to account for spatial variation in surface boundary conditions, created by diurnal canopy shading, in order to accurately calculate the contribution of interrow evaporation (E) as a component of system ET. Experiments evaluated common practices in the southeastern USA: inter-row cover crops purported to reduce water availability and thereby favorably reduce grapevine vegetative growth; and southern Israel: drip irrigation applied to produce a high value crop with maximum water use efficiency. Results from the NC site indicated that water use by the cover crop contributed a significant portion of vineyard ET (up to 93% in May), but that with ample rainfall typical to the region, cover crop water use did little to limit water availability for the grape vines. A potential consequence, however, was elevated below canopy humidity owing to the increased inter-row evapotranspiration associated with the cover crops. This creates increased potential for fungal disease occurrence, which is a common problem in the region. Analysis from the Negev site reveals that, on average, E accounts for about10% of the total vineyard ET in an isolated dripirrigated vineyard. The proportion of ET contributed by E increased from May until just before harvest in July, which could be explained primarily by changes in weather conditions. While non-productive water loss as E is relatively small, experiments indicate that further improvements in irrigation efficiency may be possible by considering diurnal shading effects on below canopy potential ET. Overall, research provided both scientific and practical outcomes including new measurement and modeling techniques, and new insights for humid and arid vineyard systems. Research techniques developed through the project will be useful for other agricultural systems, and the successful synergistic cooperation amongst the research team offers opportunity for future collaboration.
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Sprague, Joshua, David Kushner, James Grunden, Jamie McClain, Benjamin Grime, and Cullen Molitor. Channel Islands National Park Kelp Forest Monitoring Program: Annual report 2014. National Park Service, 2022. http://dx.doi.org/10.36967/2293855.
Texte intégralRésumé :
Channel Islands National Park (CHIS) has conducted long-term ecological monitoring of the kelp forests around San Miguel, Santa Rosa, Santa Cruz, Anacapa and Santa Barbara Islands since 1982. The original permanent transects were established at 16 sites between 1981 and 1986 with the first sampling beginning in 1982, this being the 33rd year of monitoring. An additional site, Miracle Mile, was established at San Miguel Island in 2001 by a commercial fisherman with assistance from the park. Miracle Mile was partially monitored from 2002 to 2004, and then fully monitored (using all KFM protocols) since 2005. In 2005, 16 additional permanent sites were established to collect baseline data from inside and adjacent to four marine reserves that were established in 2003. Sampling results from all 33 sites mentioned above are included in this report. Funding for the Kelp Forest Monitoring Program (KFM) in 2014 was provided by the National Park Service (NPS). The 2014 monitoring efforts utilized 49 days of vessel time to conduct 1,040 dives for a total of 1,059 hours of bottom time. Population dynamics of a select list of 71 “indicator species” (consisting of taxa or categories of algae, fish, and invertebrates) were measured at the 33 permanent sites. In addition, population dynamics were measured for all additional species of fish observed at the sites during the roving diver fish count. Survey techniques follow the CHIS Kelp Forest Monitoring Protocol Handbook (Davis et al. 1997) and an update to the sampling protocol handbook currently being developed (Kushner and Sprague, in progress). The techniques utilize SCUBA and surface-supplied-air to conduct the following monitoring protocols: 1 m2 quadrats, 5 m2 quadrats, band transects, random point contacts, fish transects, roving diver fish counts, video transects, size frequency measurements, and artificial recruitment modules. Hourly temperature data were collected using remote temperature loggers at 32 sites, the exception being Miracle Mile where there is no temperature logger installed. This annual report contains a brief description of each site including any notable observations or anomalies, a summary of methods used, and monitoring results for 2014. All the data collected during 2014 can be found in the appendices and in an Excel workbook on the NPS Integrated Resource Management Applications (IRMA) portal. In the 2013 annual report (Sprague et al. 2020) several changes were made to the appendices. Previously, annual report density and percent cover data tables only included the current year’s data. Now, density and percent cover data are presented in graphical format and include all years of available monitoring data. Roving diver fish count (RDFC), fish size frequency, natural habitat size frequency, and Artificial Recruitment Module (ARM) size frequency data are now stored on IRMA at https://irma.nps.gov/DataStore/Reference/Profile/2259651. The temperature data graphs in Appendix L include the same graphs that were used in past reports, but include additional violin plot sections that compare monthly means from the current year to past years. In addition to the changes listed above, the layout of the discussion section was reordered by species instead of by site. The status of kelp forests differed among the five park islands. This is a result of a combination of factors including but not limited to, oceanography, biogeography and associated differences in species abundance and composition, as well as sport and commercial fishing pressure. All 33 permanent sites were established in areas that had or were historically known to have had kelp forests in the past. In 2014, 15 of the 33 sites monitored were characterized as developing kelp forest, kelp forest or mature kelp forest. In addition, three sites were in a state of transition. Two sites were part kelp forest and part dominated by Strongylocentrotus purpuratus...
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Saltus, Christina, Molly Reif, and Richard Johansen. waterquality for ArcGIS Pro Toolbox. Engineer Research and Development Center (U.S.), 2021. http://dx.doi.org/10.21079/11681/42240.
Texte intégralRésumé :
Monitoring water quality of small inland lakes and reservoirs is a critical component of USACE water quality management plans. However, limited resources for traditional field-based monitoring of numerous lakes and reservoirs that cover vast geographic areas often leads to reactional responses to harmful algal bloom (HAB) outbreaks. Satellite remote sensing methodologies using HAB indicators is a good low-cost option to traditional methods and has been proven to maximize and complement current field-based approaches while providing a synoptic view of water quality (Beck et al. 2016; Beck et al. 2017; Beck et al. 2019; Johansen et al. 2019; Mishra et al. 2019; Stumpf and Tomlinson 2007; Wang et al. 2020; Xu et al. 2019; Reif 2011). To assist USACE water quality management, we developed an ESRI ArcGIS Pro desktop software toolbox (waterquality for ArcGIS Pro) that was founded on the design and research established in the waterquality R software package (Johansen et al. 2019; Johansen 2020). The toolbox enables the detection, monitoring, and quantification of HAB indicators (chlorophyll-a, phycocyanin, and turbidity) using Sentinel-2 satellite imagery. Four tools are available 1) to automate the download of Sentinel-2 Level-2A imagery, 2) to create stacked image with options for cloud and non-water features masks, 3) to apply water quality algorithms to generate relative estimations of one to three water quality parameters (chlorophyll-a, phycocyanin, and turbidity), and 4) to create linear regression graphs and statistics comparing in situ data (from field-based water sampling) to relative estimation data. This document serves as a user's guide for the waterquality for ArcGIS Pro toolbox and includes instructions on toolbox installation and descriptions of each tool's inputs, outputs, and troubleshooting guidance.