1,720,965 research outputs found
EOS: un nuovo modello di trasporto radiativo per atmosfere di pianeti abitabili basato su HELIOS
No full textLa prossima generazione di strumenti astronomici permetterà di ottenere spettri di atmosfere esoplanetarie in qualità e quantità crescenti. La modellizzazione del trasporto radiativo in queste atmosfere è essenziale sia per la loro interpretazione, sia per collegarle allo stato fisico alla superficie planetaria tramite modelli climatici dedicati.
In questa tesi presento EOS, un nuovo modello di trasporto radiativo specializzato nel trattamento delle atmosfere di pianeti rocciosi. Questo modello è basato sui moderni codici open-source HELIOS e HELIOS-K sviluppati presso l'Università di Berna e pubblicati sulla Exoclime Simulation Platform (ESP). I codici in questione fanno uso della potenza di calcolo offerta dai processori grafici (conosciuti in inglese come GPU) e sono ben integrati con una varietà di dtabase di dati spettrali (HITRAN, HITEMP, Kurucz...). Finora HELIOS e HELIOS-K sono stati applicati perlopiù allo studio di pianeti giganti gassosi. Il mio lavoro è consistito principalmente nell'adattare questi codici allo studio delle atmosfere dei pianeti di tipo terrestre, che risultano essere i più interessanti per la ricerca futura di biofirme.
L'obiettivo a breve termine della mia attività è stato quello di fornire un nuovo trattamento del trasporto radiativo al modello climatico latitudinale-verticale ESTM (Earth-like planets Surface Temperature Model), sviluppato a Trieste. L'obiettivo a lungo termine è invece quello di fornire uno strumento multidisciplinare alla comunità astrofisica, che permetta di collegare i risultati dei modelli climatici ai dati osservativi.
Nel primo capitolo introduco brevemente le proprietà di popolazione note degli esopianeti e i molti limiti che persistono nella caratterizzazione dettagliata di singoli casi.
Nel secondo capitolo mi focalizzo sul presentare il funzionamento dei modelli climatici, la modellizzazione dei profili atmosferici verticali e i principali feedback climatici.
Nel terzo capitolo affronto più in dettaglio la descrizione di EOS. Dopo aver introdotto le equazioni che regolano il trasporto radiativo in condizioni "clear sky" (ovvero senza considerare nubi, foschie o altri particolati atmosferici) descrivo in dettaglio i parametri adottati per il calcolo delle sezioni d'urto molecolari di scattering e assorbimento, con particolare riguardo per i continui di assorbimento della CO2 e dell'H2O.
Nel quarto capitolo mostro i risultati del processo di caratterizzazione e intercomparazione di EOS.
Nel quinto capitolo descrivo il mio contributo alla revisione del modello climatico ESTM e in special modo alle formulazioni per il trattamento di nubi e ghiacci. Questa attività mi ha permesso di validare indirettamente EOS rispetto ai dati osservativi della Terra.
Nel sesto capitolo presento il mio lavoro di analisi statistica sull'abitabilità di pianeti in sistemi binari. Questo lavoro, parallelo al resto descritto in questa tesi, mi ha permesso di indentificare dei casi per un successivo approfondimento con l'uso di EOS e ESTM.
Nel settimo capitolo presento tre applicazioni di EOS e ESTM: lo studio dell'abitabilità di pianeti circumsecondari, l'analisi del clima della Terra Archeana in funzione di diverse possibili composizioni atmosferiche e l'uso degli spettri sintetici generati da EOS per collegare i risultati delle simulazioni climatiche ale future osservazioni.
Nel capitolo finale riassumo i principali risultati del lavoro di dottorato e tratteggio i possibili sviluppi futuri.The next generation of ground- and space-based astronomical facilities will be able to retrieve exoplanetary atmospheric spectra in increasing quantity and of increasing quality. Radiative transfer (RT) models of these atmospheres are essential both for interpreting observational data and for linking these data to the planetary physical state with the aid of dedicated climate models.
Here I present EOS, a new RT model tailored for terrestrial-type planets. This model is based on HELIOS and HELIOS-K, which are novel and publicly available codes developed by the University of Bern as a part of the Exoclime Simulation Platform (ESP) repository. These codes make full use of the computing power of Graphics Processing Units and are integrated with a variety of molecular and atomic line repositories such as HITRAN, HITEMP and Kurucz. Until now, HELIOS and HELIOS-K have been mostly applied to study Jupiter-like planets. My work consisted in adapting these codes for the studying of rocky planet atmospheres, which are the most interesting for future searches of atmospheric bisognatures.
The immediate goal is to provide a state-of-the-art RT for the Earth-like planets Surface Temperature Model (ESTM), an energy balance climate model with upgraded treatment of the vertical and horizontal energy transport developed in Trieste. The long term purpose is to provide the astrophysical community with an interdisciplinary tool able to provide a link between climate model results and observational data.
In the First Chapter I make a brief introduction on the known properties of the exoplanet population and the many existing limitations to its study.
In the Second Chapter I focus on the topic of climate and atmospheric modeling and I outline the main climate feedback processes, specifically concerning their role in defining the Circumstellar Habitable Zone (CHZ).
In the Third Chapter I detail the structure of the EOS procedure. After introducing the equations of radiative transfer for clear sky conditions and the approximations adopted by HELIOS, I describe the molecular cross section parameters adopted in this study, especially those concerning the treatment of continuum absorption features of CO2 and H2O.
In the Fourth Chapter I show the testing and intercomparison work done on EOS. Concerning the former, I studied how the procedure responded to variatios of both model parameters and physical inputs. Concerning the latter, I observed how EOS predictions compared to those of other published RT codes.
In the Fifth Chapter I describe the work done to update the ESTM model by enhancing the prescriptions for the treatment of the main properties of clouds and ice. This activity allowed me to indirectly test EOS predictions against observational data of Earth.
In the Sixth Chapter I present my statistical analysis of planetary habitability in binary star systems (published in 2020 in ApJ). This parallel analysis yielded a set of cases that I then investingated using the coupled EOS-ESTM model.
In the Seventh Chapter I present three applications of EOS and ESTM: a preliminary study of the habitability of two circumsecondary planets in a binary system, motivated by the statistical results presented in the previous Chapter; the study of the effects on the Archean Earth climate of different atmospheric chemical makeups; and how the EOS-generated synthetic emission/reflectance spectra can help the data analysis of future space missions.
Finally, in the Conclusions I wrap up the content of this work and present some future perspectives
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
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