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On matrices with the Edmonds-Johnson property
Full text linkThe strong Chvátal rank of a rational matrix A is the smallest number t such that the polyhedron defined by the system b <= A x <= c, l <= x <= u has Chvátal rank at most t for all integral vectors b,c,l,u. Matrices with strong Chvátal rank at most 1 are said to have the Edmonds-Johnson property. There are two main classes of matrices known to have the Edmonds-Johnson property, one was introduced by Edmonds and Johnson, and the other by Gerards and Schrijver.
Characterizing integral matrices with the Edmonds-Johnson property seems complicated. However, Gerards and Schrijver noticed that there are some openings if we restrict ourselves to totally half-modular matrices, and they conjectured a characterization of totally half-modular matrices with the Edmonds-Johnson property. In this thesis we introduce two new classes of totally half-modular matrices with the Edmonds-Johnson property, that prove the validity of the conjecture by Gerards and Schrijver in two particular cases.
In Chapter 3 we study systems of the from b <= Mx <= d, l <= x <= u, where M is obtained from a totally unimodular matrix with two nonzero elements per row by multiplying by 2 some of its columns, and b,d,l,u are integral vectors. We give an explicit description of a totally dual integral system that describes the integer hull of the polyhedron P defined by the above inequalities. Since the inequalities of such totally dual integral system are Chvátal inequalities for P, our result implies that the matrix M has the Edmonds-Johnson property.
In Chapter 4 we consider the class of totally half-modular matrices obtained from matrices 0, ± 1 with at most two nonzero entries per column by multiplying by 2 some of the columns. In this class we characterize, in terms of excluded minors, the matrices that have the Edmonds-Johnson property.Il rango forte di Chvátal di una matrice razionale A è il più piccolo numero t tale che il poliedro definito dal sistema b <= A x <= c, l <= x <= u ha rango di Chvátal al più t per tutti i vettori interi b,c,l,u. Matrici con rango forte di Chvátal al più 1 si dicono avere la proprietà di Edmonds-Johnson. Ci sono due principali classi note di matrici con la proprietà di Edmonds-Johnson, una fu introdotta da Edmonds e Johnson, e l'altra da Gerards e Schrijver.
Caratterizzare le matrici intere con la proprietà di Edmonds-Johnson sembra complicato. Tuttavia, Gerards e Schrijver notarono che ci sono più possibilità se ci restringiamo alle matrici totalmente 1/2-modulari, e congetturarono una caratterizzazione delle matrici totalmente 1/2-modulari con la proprietà di Edmonds-Johnson. In questa tesi introduciamo due nuovi classi di matrici totalmente 1/2-modulari con la proprietà di Edmonds-Johnson, che provano la validità della congettura di Gerards e Schrijver in due casi particolari.
Nel Capitolo 3 studiamo sistemi nella forma b <= Mx <= d, l <= x <= u, dove M è ottenuta da una matrice totalmente unimodulare con due elementi diversi da zero per riga moltiplicando per 2 alcune colonne, e b,d,l,u sono vettori interi. Noi diamo una descrizione esplicita di un sistema totally dual integral che descrive l'inviluppo convesso dei punti interi del poliedro P definito dalle disuguaglianze precedenti. Dato che le disuguaglianze di tale sistema totally dual integral sono disuguaglianze di Chvátal per P, questo implica che la matrice M ha la proprietà di Edmonds-Johnson.
Nel Capitolo 4 consideriamo la classe delle matrici totalmente 1/2-modulari ottenute da matrici 0, ± 1 con al più due elementi non zero per colonna moltiplicando per 2 alcune colonne. In questa classe caratterizziamo, in termini di minori esclusi, le matrici che hanno la proprietà di Edmonds-Johnson
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Integer packing sets form a well-quasi-ordering
No full textAn integer packing set is a set of non-negative integer vectors with the property that, if a vector x is in the set, then every non-negative integer vector y with y≤x is in the set as well. The main result of this paper is that integer packing sets, ordered by inclusion, form a well-quasi-ordering. This result allows us to answer a recently posed question: the k-aggregation closure of any packing polyhedron is again a packing polyhedron.Accepted Author ManuscriptDiscrete Mathematics and Optimizatio
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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