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Off-Axis monitoring of the laser beam directed energy deposition process of metals (DED-LB/M)
No full textLa Fabbricazione Additiva (AM) ha rivoluzionato la progettazione e la produzione di componenti metallici
complessi, offrendo flessibilità e personalizzazione senza pari. Tra i vari processi di AM, il processo di
Deposizione Diretta di Metalli mediante Fascio Laser (DED-LB) eccelle nella costruzione, riparazione e
miglioramento di parti metalliche, apportando vantaggi in particolare ai settori ad alte prestazioni come
quello aerospaziale. Tuttavia, la sua complessità e variabilità portano spesso a difetti che compromettono
la qualità finale delle parti, sottolineando la necessità di strategie avanzate di monitoraggio e controllo.
Questa tesi indaga le tecniche di monitoraggio fuori-asse per il processo DED-LB/M focalizzandosi sul
miglioramento della rilevazione dei difetti e sull'ottimizzazione della qualità, efficienza e affidabilità del
processo attraverso nuove soluzioni. Il monitoraggio off-axis ha il vantaggio significativo di catturare dati
spaziali relativi al bagno di fusione e alla dinamica della deposizione che spesso non sono visibili dalle
prospettive dei dispositivi in asse, ed è anche relativamente più facile da implementare. La ricerca esplora
metodi di monitoraggio termico e ottico, insieme ad approcci guidati dall'intelligenza artificiale (IA), per
sviluppare un quadro completo di monitoraggio in-process per il processo DED-LB/M.
Lo studio esamina l'evoluzione, i vantaggi e le applicazioni della AM in vari settori, con un focus specifico
sul DED-LB/M. Vengono analizzati i componenti chiave del processo, come il sistema laser, il meccanismo
di alimentazione della polvere e i sistemi di controllo, evidenziandone le applicazioni, come la produzione
di parti 3D complesse e la riparazione di componenti meccanici, mediante l’uso di materiali comuni nel
settore aerospaziale, come acciai, superleghe a base di nichel e leghe di titanio.
Vengono esaminate le tecnologie di monitoraggio all'avanguardia esistenti, seguite dalla presentazione di
diversi casi studio sul monitoraggio termico e ottico utilizzando telecamere CCD/CMOS. Questi sistemi
analizzano l'evoluzione della pozza fusa, consentendo di rilevare, durante il processo di deposizione,
distorsioni geometriche e anomalie come spegnimenti del laser e interruzioni del flusso di polvere. Viene
inoltre introdotto un sistema di monitoraggio multi-vista, che offre soluzioni flessibili adatte a varie
configurazioni di DED-LB/M, in grado di catturare con maggior accuratezza l'evoluzione spaziale della pozza
fusa.
Viene presentato uno studio comparativo tra nuovi metodi di monitoraggio mediante scansione laser e
quelli basati sull’uso di telecamere CMOS ad alta risoluzione che mette in evidenza i rispettivi punti di forza
e ne suggerisce le relative applicazioni ottimali. Sono stati sviluppati indicatori chiave di prestazione (KPIs)
per la rilevazione di difetti geometrici e sub-superficiali attraverso algoritmi personalizzati di elaborazione
delle immagini, validati da analisi metallografiche. Viene proposto un approccio innovativo per la
valutazione in-process dell'efficienza di deposizione, utilizzando i dati di uno scanner laser prototipale per
identificare deviazioni del volume delle tracce depositate rispetto a quello previsto.
Sono state applicate tecniche di IA, per la prima volta nella letteratura scientifica, per monitorare in modo
innovativo la distanza di standoff e rilevare l'eventuale otturazione dell'ugello. In particolare, un modello
di rilevamento degli oggetti, appositamente addestrato, migliora la sicurezza e il controllo del processo
avvisando gli utenti su condizioni critiche come l'otturazione dell'ugello o la diminuzione della distanza di
standoff. D’altro canto, un modello di machine learning (ML) getta le basi per poter prevedere le modifiche
ottimali da apportare a parametri di processo chiave, come la distanza di standoff o la potenza laser, per
migliorare la precisione dimensionale dei prodotti attraverso un approccio “feed forward”.
Attraverso questi casi studio, questa tesi fornisce preziose informazioni sulle tecniche di monitoraggio
fuori-asse, contribuendo a nuove soluzioni di controllo qualità nella fabbricazione additiva dei metalli e al
progresso del processo DED-LB/M.Additive Manufacturing (AM) has revolutionized the design and production of complex metal components,
offering unparalleled flexibility and customization. Among the various AM processes, the Laser Beam
Directed Energy Deposition (DED-LB) process excels in the construction, repair, and enhancement of metal
parts, particularly benefiting high-performance industries such as aerospace. However, its complexity and
variability often result in defects that compromise the quality of the final parts, underscoring the need for
advanced monitoring and control strategies.
This thesis investigates off-axis monitoring techniques for DED-LB/M, focusing on improving defect
detection and optimizing process efficiency and reliability through new solutions. Off-axis monitoring has
the significant advantage of capturing spatial data related to the melt pool and deposition dynamics, which
are often not visible from on-axis perspectives, and is also relatively easier to implement. The research
explores thermal and optical monitoring methods, along with artificial intelligence (AI) driven approaches,
to develop a comprehensive in-process monitoring framework for DED-LB/M.
The study examines the evolution, benefits, and applications of AM across various industries, with a
specific focus on DED-LB/M. Key process components, such as the laser system, powder feeding
mechanism, and control systems, are analyzed, highlighting applications like the production of complex
3D parts and the repair of mechanical components using materials crucial in the aerospace sector, such as
steels, nickel-based superalloys, and titanium alloys.
Existing state-of-the-art monitoring technologies are reviewed, followed by the presentation of several
case studies on thermal and optical monitoring using CCD/CMOS cameras. These systems analyze the
evolution of the melt pool, allowing for in-process detection of geometric distortions and anomalies such
as laser shutdowns and powder flow interruptions. A multi-view monitoring system is also introduced,
offering flexible solutions suitable for various DED-LB/M configurations, capable of more accurately
capturing the spatial evolution of the melt pool.
A comparative study between new laser scanning monitoring methods and those based on high-resolution
CMOS cameras is presented, highlighting their respective strengths and suggesting optimal applications.
Key performance indicators (KPIs) for detecting geometric and subsurface defects were developed through
custom image processing algorithms, validated against metallographic analyses. An innovative approach
for in-process evaluation of deposition efficiency is proposed, utilizing prototype laser scanner data to
identify deviations in the deposited track volume.
AI techniques have been applied for the first time in the scientific literature to monitor standoff distance
and detect potential nozzle clogging. Specifically, a custom-trained object detection model enhances
process safety and control by alerting users to critical conditions such as nozzle clogging or reduced
standoff distance. On the other hand, a machine learning (ML) model lays the groundwork for predicting
optimal adjustments to key process parameters, such as standoff distance or laser power, to improve the
dimensional accuracy of the products through a feed forward approach.
Through these case studies, this thesis provides valuable insights into off-axis monitoring techniques,
contributing to new quality control solutions in metal additive manufacturing and advancing the DED
LB/M process
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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