1,720,977 research outputs found
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
Wetting on a spherical-shell substrate
No full textA density-functional theory for the wetting of an inert spherical-shell substrate by a single-component bulk vapor is developed, on the basis of the usual assumption that the pairwise intermolecular interaction is divided into a repulsive hard sphere and a weak attractive part. The substrate vapor-molecule pairwise interaction is also divided into a hard-wall repulsive interaction and a weak attractive tail. Choosing the attractive interactions properly, a second-order nonlinear functional differential equation results, which is solved numerically with appropriate boundary conditions. It is shown that the wetting layer, formed on the adsorbent, is either a thin or a thick film of finite thickness. Furthermore, in some cases the substrate is not at all wet. The wall-vapor and other interfacial tensions, the associated radii, and the principal tensors (the transverse pT(r) and normal pN(r)) are also calculated. The wall-vapor interface is mainly under tension (pN(r) > pT(r))
The random field Ising model with an asymmetric and anisotropic trimodal probability distribution
No full textThe Ising model in the presence of a random field, drawn from the asymmetric and anisotropic trimodal probability distribution P( hi)=pδ(hi-h0)+qδ( hi+λ*h0)+rδ(hi), is investigated. The partial probabilities p,q,r take on values within the interval [0,1] consistent with the constraint p+q+r=1; asymmetric distribution, hi is the random field variable with basic absolute value h0 (strength); λ is the competition parameter, which is the ratio between the respective strength of the random magnetic field in the two principal directions (+z) and (-z) and is positive so that the random fields are competing, anisotropic distribution. This probability distribution is an extension of the bimodal one allowing for the existence in the lattice of non magnetic particles or vacant sites. The current random field Ising system displays mainly second order phase transitions, which, for some values of p,q and h0, are followed by first order phase transitions joined smoothly by a tricritical point; occasionally, two tricritical points appear implying another second order phase transition. In addition to these points, re-entrant phenomena can be seen for appropriate ranges of the temperature and random field for specific values of λ, p and q. Using the variational principle, we write down the equilibrium equation for the magnetization and solve it for both phase transitions and at the tricritical point in order to determine the magnetization profile with respect to h0, considered as an independent variable in addition to the temperature. © 2012 Elsevier B.V. All rights reserved
Monte Carlo analysis of the critical properties of the two-dimensional randomly bond-diluted Ising model via Wang-Landau algorithm
No full textThe influence of random bond-dilution on the critical properties of the two-dimensional Ising model on a square lattice with periodic boundary conditions is presented using the Monte Carlo process with WangLandau sampling. The lattice linear size is L=20140 and the concentration of the diluted bonds spans a wide range from weak to strong dilution, namely, q=0.05,0.1,0.2,0.3,0.4; the respective percolation limit for the square lattice is qcPERC=0.5. Its pure version (q=0) has a second-order phase transition with vanishing specific heat critical exponent, an example of inapplicability of the Harris criterion. The main effort is focused on the temperature dependence of the specific heat and magnetic susceptibility to estimate the respective maximum values and subsequent pseudocritical temperatures for extracting the relative critical exponents. We have also looked at the probability distribution of the susceptibility, pseudocritical temperature and specific heat for assessing self-averaging. The study is carried out in the appropriately restricted but dominant energy subspaces. By applying the finite-size scaling analysis, the critical exponents are estimated; the specific heat exponent vanishes, the correlation-length exponent ν is equal to one and the critical exponents' ratio (γν) retains its pure-Ising-model value, thus supporting the strong universality hypothesis. © 2010 Elsevier B.V. All rights reserved
Polydispersity effect on the spectrum of light scattered by polymers with nearest- and next-nearest-neighbour interactions
No full textThe effect of polydispersity on the total integrated intensity and spectral density of light scattered by linear polymers in dilute solution is studied. Use is made of the chain model with nearest- and next-nearest-neighbour linear interactions. The length distribution is chosen to be that of Schulz. The analysis proceeds via normal mode decomposition, and the centre of mass contribution to the spectral density—as well as that of the normal modes, with and without mixing—becomes visible. The influence of polydispersity and elastic constants is significantly manifested in the normal mode contributions, and the spectral density curves of the polydisperse system are narrower than those of the monodisperse case. © 1982 Taylor & Francis Ltd
The random field Ising model with an asymmetric trimodal probability distribution
No full textThe Ising model in the presence of a random field is investigated within the mean field approximation based on Landau expansion. The random field is drawn from the trimodal probability distribution P(hi)= pδ(hi-h0)+qδ(hi+h 0)+rδ(hi), where the probabilities p,q,r take on values within the interval [0,1] consistent with the constraint p+q+r=1 (asymmetric distribution), hi is the random field variable and h 0 the respective strength. This probability distribution is an extension of the bimodal one allowing for the existence in the lattice of non magnetic particles or vacant sites. The current random field Ising system displays second order phase transitions, which, for some values of p,q and h0, are followed by first order phase transitions, thus confirming the existence of a tricritical point and in some cases two tricritical points. Also, reentrance can be seen for appropriate ranges of the aforementioned variables. Using the variational principle, we determine the equilibrium equation for magnetization, solve it for both transitions and at the tricritical point in order to determine the magnetization profile with respect to h 0. © 2011 Elsevier B.V. All rights reserved
The Sherrington-Kirkpatrick spin glass model in the presence of a random field with a joint Gaussian probability density function for the exchange interactions and random fields
No full textThe magnetic systems with disorder form an important class of systems, which are under intensive studies, since they reflect real systems. Such a class of systems is the spin glass one, which combines randomness and frustration. The Sherrington-Kirkpatrick Ising spin glass with random couplings in the presence of a random magnetic field is investigated in detail within the framework of the replica method. The two random variables (exchange integral interaction and random magnetic field) are drawn from a joint Gaussian probability density function characterized by a correlation coefficient ρ. The thermodynamic properties and phase diagrams are studied with respect to the natural parameters of both random components of the system contained in the probability density. The de Almeida-Thouless line is explored as a function of temperature, ρ and other system parameters. The entropy for zero temperature as well as for non zero temperatures is partly negative or positive, acquiring positive branches as h0 increases. © 2013 Elsevier B.V. All rights reserved
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