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Computational Studies in the Few-Body Problem : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Applied Mathematics at Massey University, Albany, New Zealand
Get PDFIn this research we investigate the gravitational four-body problem which describes the motion in the system of four stars moving under their mutual gravitational forces. It involves studies of the dynamics of few-body systems and finding periodic orbits, and subsequently an analysis of their stability. One of the challenges of the problem is the necessity of using regularisation algorithms in order to avoid singularities when there is a possibility of collision or close encounter between stars.
One of the featured solutions of the problem is the collinear Schubart orbit discovered for systems of three [59] and four [70] bodies. This orbit has been shown to form families of collinear and planar orbits for three bodies by Henon [32]. Sweatman discovered Schubart orbits in the collinear symmetric four-body problem [70, 71].
In this work we generate the families of Schubart orbits starting from the planar orbit obtained by Sweatman [73]. Utilising the symmetries of the four-body Schubart orbits, we solve the Caledonian symmetric four-body problem (CS4BP). Initially we consider the case of equal masses. This is later extended to the case of pairwise symmetric masses.
The family is parametrised by two parameters: the mass of the outer bodies and the distance between the two closest non-symmetric bodies. The collinear orbits are collisional, but there are no collisions when the orbits evolve to planar motion.
The planar family of pairwise symmetric masses is bounded by the line of the collinear Schubart orbits. Within its boundaries, there are four regions separated by two special types of orbits present in the family: the equal-mass orbits and the double choreography orbits. Two of the regions are symmetrical to the other two.
We perform a linear stability analysis of the discovered solutions both in and out of the plane. We also distinguish the influence of symmetrical and non-symmetrical perturbations on the orbits. An algorithm for the orbit search and orbital stability analysis is presented
Computational studies in the planar symmetric six-body problem : this dissertation is submitted for the degree of Doctor of Philosophy, School of Mathematical and Computational Sciences, Massey University
No full textThis thesis presents the study of the gravitational six-body problem which describes the motion of a group of six stars interacting with each other gravitationally. The bodies undergo collisions due to the attractive nature of interactions, which are singular. The singularity is one of the difficulties in exploring the problem. It is necessary to use regularization techniques to avoid singularity when there is a possibility of collisions between the stars.
This study involves finding solutions to the six-body problem, especially periodic ones. One important solution to this problem is the Schubart orbit. Schubart orbits were previously discovered for the three-body [52] and four-body [63] problems. We find the Schubart orbit in a setup of six bodies, where the six bodies are positioned at the vertices of two aligned equilateral triangles. The existence proof of the Schubart orbit is also presented.
Later, we extend our study of the six-body system to the case, where the bodies are placed on the vertices of two non-aligned equilateral triangles. In this case, we generate families of periodic orbits when the bodies have equal masses. One of the featured results of this problem is the Schubart family of periodic orbits. This family starts from the Schubart orbit and when we move along the family the orbits become more complex and unstable.
Another equal-mass family of periodic orbits is generated from the hexagonal orbit. These families of periodic orbits are parametrized by angular momentum. In general, the masses are chosen equal to unity,
and the total energy of the system is fixed as E = −1.
We perform a non-linear stability check of the discovered solutions under the symmetric perturbations. An algorithm for the search of periodic orbits is presented
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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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