1,720,957 research outputs found
Sviluppo di nuovi strumenti, approcci e sistemi basati sulle nanotecnologie per la termoelettricità e la raccolta di energia
No full textIl successo globale dipende dalla generazione, raccolta e gestione del budget energetico. L'elettricità è l'energia moderna più influente, con utilizzi di mercato in rapida crescita, generati principalmente da tecnologie basate sulla combustione. Tali tecnologie e l'elettronica di consumo diffusa generano molto calore sprecato e "calore di bassa qualità", calore che è troppo basso, disomogeneo, discontinuo o impossibile da recuperare con metodi convenzionali.
I nanomateriali e la nanotecnologia stanno rendendo i generatori termoelettrici (TEG), che convertono il calore in elettricità senza parti in movimento, più attraenti. Inoltre, c'è un forte impegno politico per il recupero energetico e una rinnovata attenzione all'esplorazione spaziale, un settore correlato ai TEG. Questo studio esamina la risposta termoelettrica a temperatura intermedia e alta dei materiali nanostrutturati innovativi. I risultati hanno fatto conoscere i meccanismi di drogaggio, la nanostrutturazione e le prestazioni termoelettriche e hanno fatto progredire lo sviluppo di materiali di conversione energetica ad alta efficienza.
Per quanto riguarda i materiali, gli studi riportati in questa tesi includono ZnO drogato con Al, ZnSe drogato con Fe, ZnSe drogato con Cu, Bi2Te3 drogato con Se e SnO drogato con Mg, e si concentrano sull'impatto del drogaggio e della nanostrutturazione sulle proprietà termoelettriche. Viene condotta un'analisi sistematica dell'influenza di diverse condizioni di temperatura sulle proprietà termoelettriche. Sono stati utilizzati due approcci per la preparazione sia di nanoparticelle che di film sottili dei materiali: sintesi idrotermica e sputtering magnetron. Per quanto riguarda le metodologie e le tecniche di caratterizzazione, è stata utilizzata la XRD per eseguire la caratterizzazione strutturale. La topografia superficiale è stata studiata utilizzando AFM. La morfologia dei nanocristalli è stata esaminata tramite SEM e l'analisi della composizione elementare è stata condotta tramite EDX. Le proprietà di trasporto sono state misurate con il metodo a 4 sonde nell'intervallo di temperatura 25–350°C.
La tesi è organizzata come segue. I capitoli da 1 a 3 coprono gli argomenti sopra menzionati, vale a dire l'introduzione alla termoelettricità su scala nanometrica, materiali e metodi e tecniche per nanostrutture termoelettriche. Il capitolo 4 studia le proprietà TE dei film sottili di ZnO (AZO) drogato con Al, sottolineando l'influenza di diverse concentrazioni di drogaggio di Al (2–8 at.%) sulle caratteristiche di trasporto elettrico e termoelettrico. I film sottili di AZO, con uno spessore di 300 nm, sono stati depositati tramite sputtering magnetron RF. Le caratterizzazioni strutturali e morfologiche indicano che livelli di drogaggio aumentati determinano una migliore conduttività elettrica, con resistività che scende al di sotto di 2 × 10–3 Ohm˖cm al 3 at.% di Al. Il coefficiente di Seebeck è stato visto variare tra 22 e 33 μV/K, raggiungendo un picco all'8 at.% di drogaggio. Nel capitolo 5, studiamo l'impatto del drogaggio di Fe2+ sulle caratteristiche TE delle nanoparticelle di ZnSe prodotte dalla tecnica idrotermale. L'indagine SEM ha dimostrato agglomerati di nanocristalliti di dimensioni variabili a tutti i livelli di drogaggio, mentre la spettroscopia XRD e Raman ha convalidato la struttura cubica dei campioni. Le caratteristiche di trasporto elettrico sono state migliorate con concentrazioni di drogaggio Fe potenziate e il fattore di potenza è stato aumentato da 13 μWm–1K–2 a 120 μWm–1K–2, con un fattore di potenza massimo di 9 × 10–3 Wm–1K–2 a 150°C.Global success depends on energy budget generation, harvesting, and management. Electricity is the most influential modern energy, with rapidly rising market uses, mostly generated by combustion-based technologies. Such technologies and pervasive consumer electronics generate a lot of wasted heat and 'low grade heat'—heat that is too low, inhomogeneous, discontinuous, or impossible to recover by conventional methods.
Nanomaterials and nanotechnology are making thermoelectric generators (TEGs), which convert heat-to-electricity without moving parts, more appealing. In addition, there is strong political commitment to energy recovery and renewed attention on space exploration, a TEG-related industry. This study examines innovative nanostructured materials' intermediate and high-temperature thermoelectric response. The findings shed knowledge on doping mechanisms, nanostructuring, and thermoelectric performance and advance the development of high-efficiency energy conversion materials.
On the material side, the studies reported in this thesis include Al doped ZnO, Fe doped ZnSe, Cu doped ZnSe, Se doped Bi2Te3 and Mg doped SnO, and focus on the impact of doping and nanostructuring on the thermoelectric properties. Systematic analysis of the influence of different temperature conditions on thermoelectric properties is conducted. Two approaches for the preparation of both nanoparticles and thin films of the materials were used: hydrothermal synthesis and magnetron sputtering. On the side of characterization methodologies and techniques, XRD was used to perform structural characterisation. Surface topography was investigated using AFM. Morphology of the nanocrystals was examined by SEM and elemental composition analysis was conducted by EDX. The transport properties were measured by the 4-probe method in the temperature range 25–350°C.
The thesis is organized as follows. Chapters 1 to 3 covers the topics mentioned above, namely the introduction to nanoscale thermoelectricity, thermoelectric nanostructures materials and methods and techniques. Chapter 4 studies the TE properties of Al-doped ZnO (AZO) thin films, emphasising the influence of different Al doping concentrations (2–8 at.%) on electrical and thermoelectric transport characteristics. The AZO thin films, measuring 300 nm in thickness, were deposited via RF magnetron sputtering. Structural and morphological characterisations indicate that increased doping levels result in improved electrical conductivity, with resistivity falling below 2 × 10–3 Ohm˖cm at 3 at.% Al. The Seebeck coefficient was seen to vary between 22 and 33 μV/K, reaching a peak at 8 at.% doping. In chapter 5, we study the impact of Fe2+ doping on the TE characteristics of ZnSe nanoparticles produced by the hydrothermal technique. SEM investigation demonstrated agglomerates of nanocrystallites of varying sizes at all doping levels, whereas XRD and Raman spectroscopy validated the cubic structure of the samples. Electrical transport characteristics were improved with enhanced Fe doping concentrations and the power factor was increased from 13 μWm–1K–2 to 120 μWm–1K–2, with a maximum power factor of 9 × 10–3 Wm–1K–2 at 150°C. Chapter 6 focus on the details study of the influence of copper doping on the TE characteristics of ZnSe nanoparticles produced by the hydrothermal technique. Our research indicates that Cu doping markedly increases electrical conductivity and the Seebeck coefficient, resulting in enhanced power factors. The Cu-doped ZnSe nanostructures showed various phases with a nanocrystalline shape, characterised by an average grain size of less than 5 nm
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
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
- …
