1,721,032 research outputs found
Advanced time-of-flight diagnostics for real-time characterization of ions accelerated by high energy lasers
No full textTime-Of-Flight (TOF) methods are very effective to detect ions accelerated in laser plasma
interactions, but they show significant limitations when used in experiments
with high energy and intensity lasers, where both high-energy ions and remarkable
levels of Electro Magnetic Pulses (EMPs) in the radiofrequency-microwave range are
generated.
In this joined-doctoral thesis, performed at the La Sapienza University in Rome,
at the institut national de la recherche scientifique (INRS) in Montréal and at ENEA
Centro Ricerche Frascati, an advanced diagnostic technique for the characterization
of protons accelerated by intense laser-matter interactions with high-energy and
high-intensity lasers has been implemented.
The proposed method exploits and improves the advantages given by TOF technique
coupled to Chemical Vapor Deposition diamond detectors and features high sensitivity,
high energy resolution and high radiation hardness. Thanks to the optimization
of the acquisition system and to the careful setup of the TOF line, high signal-to-noise
ratios in environments heavily affected by remarkable EMP fields have been achieved.
In the first part of the work a brief overview of laser-matter interaction is given,
with particular emphasis to processes leading to particle acceleration. Then, the
main diagnostic techniques available for the characterization of secondary sources
produced by laser-matter interaction are presented. Here the TOF technique is
introduced and analyzed when coupled with different kinds of detectors, including
diamonds. The choice of the latter is justified by their physical properties. Various
types of diamond structures and electrode layouts have been tested and their performances
characterized for application as detectors to be employed in TOF lines.
The second part of the work is dedicated to a detailed description of the proposed
advanced technique and to examples of its effectiveness in reducing the EMP noise
and in enhancing the dynamic range, when employed in real experimental scenarios.
A novel procedure to retrieve a calibrated proton spectrum from the performed
measurements is here also proposed and discussed. Eventually, the developed technique
is applied for detecting laser-plasma accelerated particles produced in different
application scenarios and in the most variable laser-matter interaction conditions
and the concept of a new multi-layer detector is also described.Les méthodes de temps de vol (TOF) sont très efficaces pour détecter les ions
accélérés dans les interactions laser-plasma, mais elles présentent des limites importantes
lorsqu’elles sont utilisées dans des expériences avec des lasers à haute
énergie et à haute intensité, où sont générés à la fois des ions à haute énergie et
des niveaux remarquables d’impulsions électromagnétiques (EMP) dans la gamme
radiofréquence-micro-ondes.
Dans cette thèse de doctorat en cotutelle, réalisée à l’Université La Sapienza
de Rome, à l’institut national de la recherche scientifique (INRS) de Montréal et
à l’ENEA Centro Ricerche Frascati, une technique de diagnostic avancée pour la
caractérisation des protons accélérés par des interactions laser-matière intenses avec
des lasers de haute énergie et de haute intensité a été mise en oeuvre.
La méthode proposée exploite et améliore les avantages donnés par la technique
TOF couplée à des détecteurs diamantés à dépôt chimique en phase vapeur et se
caractérise par une grande sensibilité, une résolution énergétique élevée et une grande
dureté de rayonnement. Grâce à l’optimisation du système d’acquisition et à la mise
en place minutieuse de la ligne TOF, des rapports signal/bruit élevés ont été obtenus
dans des environnements fortement affectés par des champs EMP remarquables.
Dans la première partie du travail, un bref aperçu de l’interaction laser-matière
est donné, avec un accent particulier sur les processus conduisant à l’accélération
des particules. Ensuite, les principales techniques de diagnostic disponibles pour la
caractérisation des sources secondaires produites par l’interaction laser-matière sont
présentées. Ici, la technique TOF est introduite et analysée lorsqu’elle est couplée
à différents types de détecteurs, y compris les diamants. Le choix de ces derniers
est justifié par leurs propriétés physiques. Différents types de structures de diamant
et d’agencements d’électrodes ont été testés et leurs performances ont été caractérisées
en vue d’une application en tant que détecteurs à utiliser dans les lignes TOF.
La deuxième partie du travail est consacrée à une description détaillée de la
technique avancée proposée et à des exemples de son efficacité pour réduire le bruit
EMP et améliorer la gamme dynamique, lorsqu’elle est utilisée dans des scénarios
expérimentaux réels. Une nouvelle procédure permettant de récupérer un spectre de
protons calibré à partir des mesures effectuées est également proposée et discutée ici.
Enfin, la technique développée est appliquée pour détecter les particules accélérées par
laser-plasma produites dans différents scénarios d’application et dans les conditions
d’interaction laser-matière les plus variables, et le concept d’un nouveau détecteur
multicouche est également décrit
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
Studio del contatto bronzo-acciaio in condizioni di strisciamento nel settore delle macchine automatiche (Bronze-steel sliding contact in packaging applications)
No full textLo studio condotto è dedicato a componenti di macchine automatiche per la pressatura di polveri ad uso farmaceutico o alimentare, sottoposti ad un contatto tribologico non conforme di strisciamento in condizioni di lubrificazione limite. Il tribosistema studiato comprende due elementi: punzoni in acciaio da utensili X100CrMoV5 e camme in bronzo all’alluminio G-CuAl11Fe4Ni4. Nella fase iniziale dello studio sono stati identificati i meccanismi di usura prevalenti nel tribosistema reale avvalendosi di tecniche standard di failure analysis, mentre nella seconda fase sono state eseguite prove di strisciamento su scala di laboratorio. Nelle prove tribologiche di laboratorio, il coefficiente di attrito è risultato indipendente dalle condizioni di trattamento termico del bronzo, mentre si è rilevata una significativa dipendenza da carico normale e velocità. L’usura del bronzo è risulta principalmente influenzata dalla sua capacità di incrudimento e/o di formare e stabilizzare uno strato protettivo superficiale a base di ossidi di rame, al variare delle condizioni di trattamento termico e dei parametri operativi del moto
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
- …
