1,721,683 research outputs found
A theoretical investigation of the wave height and level-crossing distributions
No full textIn the general theory off stochastic processes, among the most challenging and still mainly unsolved problems are those concerning the zero- and level-crossing behaviour and extreme distribution of sample functions of stochastic processes. In this work, we investigate these properties for a class of stationary Gaussian ergodic random processes, with special reference to the ocean wave process. The motivation for this research was provided by the desire to find a useful distribution of wave heights for the broad-band ocean wave process. It was found that the most meaningful definition of wave heights is the so called zero-up-crossing wave heights. We show that the distribution of zero-up-crossing wave heights is closely related to the distributions of absolute maxima (or minima), of the first passage time, and of the adjacent zero-crossings. Thus, these distributions are the main concern of this thesis. A dynamical model for the ocean wave process is first constructed. With a Gaussian white noise input, the output process of this dynamic system is a vector Markov process. Although many statistical properties of one dimensional Markov processes are known and reviewed in Chapter 2, there has been little similar progress for vector Markov processes. In the case of random initial velocities for the one-dimensional Markov processes, an approximate formula for the probability density function of absolute maxima between adjacent zero crossings is derived. We use a simple example to show how this formula can be used. We then study second order (two-dimensional) vector Markov processes in order to find a more accurate expression and better results for the absolute maxima distribution. The only existing analytical formula for two dimensional vector Markov process is the joint probability density function of adjacent zero crossing intervals and crossing velocities for a second order oscillator given McKean (1963). Wong (1966, 1970) extended McKean's result to a wider class of random processes (Wong's processes) which includes the ocean wave process as a special case. In this thesis, we establish formal relationships between the level-crossing and absolute maxima distribution of McKean's process and those of Wong's process. In fact, we show that these relationships are applicable to a class of random processes (i.e. generalised Wong's processes), slightly wider than Wong's process. We then proceed to find the joint probability density function of the first passage time and crossing velocities for the McKean's process. From this joint probability density, we can find the probability density function of absolute maxima for both McKean's process and generalised Wong's processes. A simulation study via digital filtering is performed to confirm the analytical results. Finally, an optimal weighting function is proposed for the estimation of directional ocean wave spectrum.</p
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
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe 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
Locality-preserving dynamic load balancing for data-parallel applications on distributed-memory multiprocessors
No full textAuthor-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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