1,721,010 research outputs found
Political Loyalties and the Economy: the U.S. case Gianluigi Galeotti (con A.Forcina) The Review of Economics and Statistics
No full textOn non-blocking properties of Parallel Delta Networks
No full textThis paper deals with the definition of a class of NxN interconnection networks called Parallel Delta Network (PDN). For this class of networks the non-blocking conditions are given. In particular, by means of the graph colouring technique, it has been proved that the minimum number of Delta subnetworks (L) necessary to provide the non-blocking property is L=nfS/21-1 where n is the size of the basic switching element and S the number of stages required by an NxN Delta network. A routing algorithm for the establishment of any permutation has been defined.
It operates for any value of n and shows a polynomial time
complexity equal to O(N3/2). Moreover, in case of the setup
of a single connection request, this algorithm assures a
time complexity equal to O(VN). This property makes it
well suitable to an asynchronous telecommunication
environment
Marginal models and pruning of association rules
No full textAssociation rules are a well established tool in data mining software which are nowadays used to describe statistical associations in many fields. Classical association rules (also called boolean rules), which have been introduced in the context of market basket analysis by Agrawal, Imielinski and Swami, are statements about the fact that the presence of a subset of items called "antecedent" is likely to imply the presence of another set of items called "consequent". In market basket analysis, for instances, there will be a transaction (that is, a nonempty set of items) for each customer (actually for each single bill), each of which consisting of a selection from the set of the K products (items) present in the store.
To reduce the mass of discovered rules to a manageable number of patterns, a number of selection and pruning methods have been proposed. The use of statistical measures and statistical tests have also been advanced to asses the "interestingness" of an association rule. Here, to test the "interestingness" of a rules, or of a set of rules, we outline how recent developments in the analysis of frequency data, in particular on the theory of marginal models, can be applied to this context.
Marginal models are a rather recent extension of log-linear models intended to analyze simultaneously several marginal distributions of interest. As such, this is an approach particularly suitable for investigating association rules where we are mostly interested in low dimensional marginal distributions in view of the fact that they provide a simple way of summarizing the most tangible and easily accessible structures in the data. In the following we outline this general approach and indicate how it could be applied to solve a few specific problems related to pruning of association rules
Marginal models and pruning of association rules
No full textAssociation rules are a well established tool in data mining techniques which are nowadays used to detect empirical associations in large data sets. To reduce the mass of discovered rules to a manageable number of patterns, a number of selection and pruning methods have been proposed. The use of statistical tests have also been advocated to asses the "interestingness" of an association rule. Along these lines, here we outline how recent developments in the analysis of frequency data, in particular the theory of marginal models, can be applied to this context
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
Non-compliance in surgical patients with herniated lumbar discs: an application of a latent class model as selection model
No full textIn a recent prospective observational study carried out on a sample of patients with herniated lumbar discs who underwent physiotherapy, the recovery rate of those who had been recommended surgical treatment, but did not comply and chose physiotherapy instead, was not appreciably different from that of the other patients, although their prognosis was worse. In order to investigate whether this finding may be due to a confounding effect induced by unobserved features of the patients, we have fitted to the data a latent class model which considers the joint probability of recovery and two other response variables presumably affected by individual choice (participation rate and compliance) as dependent on a latent variable and a set of covariates. Thus the assumption of conditional independence is relaxed and conditional association is modelled by regressing the outcomes one on the other.
The results of our study indicate that the latent classes may be interpreted as dividing the patients according to whether they are highly versus moderately motivated towards therapy. More precisely, conditionally on the rest of the covariates, the more motivated subjects attend a larger number of therapy sessions and seem to benefit much more from the therapy. In addition, the fact that the proportion of less motivated patients among non-compliers is tiny may be due to a selection mechanism, which may explain the surprisingly good performance of physiotherapy for these patients
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
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