1,720,985 research outputs found
The development of an SPH tree-based algorithm to investigate the evolution of self-gravitating Protoplanetary Disks
Full text linkI Dischi Circumstellari costituiscono un campo di studio molto moderno, per diverse ragioni. Prima di tutto, lo studio dell'evoluzione di tali sistemi mira a spiegare la configurazione delle migliaia di sistemi planetari che sono stati osservati fin ora, e può fornire risposte importanti anche sulla formazione del Sistema Solare.
In secondo luogo, gli sviluppi delle tecnologie interferometriche nella banda Infrarossa e Millimetrica hanno fornito un ampia gamma di possibilità di osservare i dischi con una risoluzione angolare molto piccola. I dischi hanno dunque rappresentato un ampio target osservativo che ha stimolato non in maniera indifferente l'applicazione e il miglioramento delle più avanzate tecniche osservative.
Inoltre, l'evoluzione dei dischi è guidata da diversi processi fisici, sia dinamici sia idrodinamici, e dunque essi figurano tragli oggetti di studio più importanti a cui applciare sofisticate tecniche di modellistica numerica.
In particolare, i dischi Protoplanetari sono diventati, dagli ultimi due decenni, un obbiettivo chiave nel campo dei sistemi stellari multipli. La loro evoluzione in ambienti eterogenei ricchi di stelle e gas rappresenta una nuova frontiera del calcolo numerico applicato all’astronomia, perché implica numerosi problemi ancora irrisolti. Le recenti scoperte di dischi in ammassi aperti ha aperto a nuove prospettive nello studio teorico di sistemi planetari extrasolari nel loro stato primordiale gassoso.
Per queste ragioni, l’attività del mio Dottorato ha come scopo l’implementazione di uno strumento di modellistica numerico, capace di affrontare questi e molti altri problemi legati all’interazione tra gas e stelle. In questo documento, il Sottoscritto presenterà un nuovo algoritmo sviluppato per integrare l’evoluzione temporale di sistemi gassosi (con o senza gravità) e la loro interazione con le stelle. Il codice si basa sul ben noto approccio Smoothed Particles Hydrodynamics (SPH), e contiene un metodo numerico per accoppiare il cas con un limitato numero di punti di massa calcolando, con elevata precisione, la loro mutua interazione gravitazionale. Il calcolo dell’autogravità è fatto approssimando la forza mediante il noto Tree-Scheme.
Dopo aver descritto alcuni test basilari sulla stabilità e sulle prestazioni, il Sottoscritto descriverà il problema astrofisico principale studiato durante il lavoro di dottorato: l’evoluzione di dischi protoplanetari perturbati da stelle che effettuano incontri ravvicinati, che cistituisce uno schema approssimato del più complesso caso di interazione di un disco con l’ambiente stellare in cui esso è immerso.Circumstellar Disks represent a very modern object of investigation, for many reasons. First, the investigation on their evolution aims at explaining the configuration of several thousand of planetary systems detected so far and may give important answers even on the formation of Solar System. Secondly, the early development of the interferometric technique to observe in the infrared and mm wave-length, opened a wide range of possibilities to observe disks with very short angular resolution. Thus, Disks constitute a wide target, stimulating the application and the improvement of the most advanced observational techniques. Moreover, disk evolution is driven by several physical processes, both dynamical and hydrodynamical, they are indeed one of the most important objects of application of several sophisticated numerical techniques.
Protoplanetary disks have become, since the last 20 years, a key target in the field of star clusters. Their evolution in heterogeneous environments rich in stars and gas represents a new frontier for the Numerical Astronomy because it carries several issues still not overcome. The recent discoveries of circumstellar disks in open clusters opened to new perspectives to the theoretical investigations of non-isolated exoplanetary systems in their primordial gaseous state.
For such purposes, my PhD activity aimed at building a suitable numerical investigating instrument, able to face this and many other problems related to the interaction between gaseous systems and stars. In this document, I will present a new Algorithm developed to treat the evolution of gaseous systems (both selfgravitating and non-selfgravitating) and their interaction with Stars. The Code is based on the well-known Lagrangian Smoothed Particle Hydrodynamics approach, and contains a numerical technique to couple a gas distribution with a few amounts of point-mass particles, evaluating,
with high precision, their motion. The calculus of self-gravity is accomplished with a tree-scheme approach.
After describing some basic stability and performance tests, I will focus on the main problem investigated during my work: the evolution of protoplanetary disks perturbed by passing-by stars, which constitute an approximated scheme of the more complex disk-stellar environment interaction
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
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
Author Under Sail The Imagination of Jack London, 1893-1902
No full textIn Author Under Sail, Jay Williams offers the first complete literary biography of Jack London as a professional writer engaged in the labor of writing. It examines the authorial imagination in London's work, the use of imagination in both his fiction and nonfiction, and the ways he defined imagination in the creative process in his business dealings with his publishers, editors, and agents. In this first volume of a two-volume biography, Williams traverses the years 1893 to 1902, from London's "Story of a Typhoon" to The People of the Abyss. The Jack London who emerges in the pages of Author Under Sail is a writer whose partnership with publishers, most notably his productive alliance with George Brett of Macmillan, was one of the most formative in American literary history. London pioneered many author models during the heyday of realism and naturalism, blurring the boundaries of these popular genres by focusing on absorption and theatricality and the representation of the seen and unseen. London created an impassioned, sincere, and extremely personal realism unlike that of other American writers of the time. Author Under Sail is a literary tour de force that reveals the full range of London as writer, creative citizen, and entrepreneur at the same time it sheds light on the maverick side of machine-age literature.Intro -- Title Page -- Copyright Page -- Dedication -- Contents -- Acknowledgments -- Introduction -- 1. Spirit Truth -- 2. From Absorption to Theatricality and Back Again -- 3. "I Will Build a New Present" -- 4. Sons as Authors -- 5. Fathers as Publishers -- 6. The Daughter as Author -- 7. Lovers as Authors -- 8. At Sea with the Family -- 9. Yellow News, Yellow Stories -- 10. The Return Home -- Notes -- Bibliography -- Index -- About Jay WilliamsIn Author Under Sail, Jay Williams offers the first complete literary biography of Jack London as a professional writer engaged in the labor of writing. It examines the authorial imagination in London's work, the use of imagination in both his fiction and nonfiction, and the ways he defined imagination in the creative process in his business dealings with his publishers, editors, and agents. In this first volume of a two-volume biography, Williams traverses the years 1893 to 1902, from London's "Story of a Typhoon" to The People of the Abyss. The Jack London who emerges in the pages of Author Under Sail is a writer whose partnership with publishers, most notably his productive alliance with George Brett of Macmillan, was one of the most formative in American literary history. London pioneered many author models during the heyday of realism and naturalism, blurring the boundaries of these popular genres by focusing on absorption and theatricality and the representation of the seen and unseen. London created an impassioned, sincere, and extremely personal realism unlike that of other American writers of the time. Author Under Sail is a literary tour de force that reveals the full range of London as writer, creative citizen, and entrepreneur at the same time it sheds light on the maverick side of machine-age literature.Description based on publisher supplied metadata and other sources.Electronic reproduction. Ann Arbor, Michigan : ProQuest Ebook Central, YYYY. Available via World Wide Web. Access may be limited to ProQuest Ebook Central affiliated libraries
- …
