1,721,163 research outputs found
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
Design of microlaser in medium infrared wavelength range for biomedicine and environmental monitoring
No full textI micro-risonatori ottici svolgono un ruolo importantissimo nella fotonica moderna. In particolare negli ultimi anni l’attenzione si è concentrata sui micro-risonatori a simmetria circolare, come ad esempio micro-sfere, micro-anelli, micro-dischi e micro-toroidi. Essi sono caratterizzati da dimensioni particolarmente ridotte, fattori di qualità eccezionalmente alti e volumi modali bassissimi diventando così una valida alternativa ai tradizionali micro-risonatori ottici come le cavità Fabry-Pérot. Questi dispositivi trovano applicazione in numerosi ambiti, come la sensoristica, il filtraggio ottico e l’ottica non lineare. Numerose ed interessanti sono le applicazioni di tali strutture nel medio infrarosso in ambiti come la biologia e la medicina, la spettroscopia molecolare, il monitoraggio ambientale, l’astronomia e l’astrofisica. Ad esempio, nel medio infrarosso si trovano numerose transizioni vibrazionali che agiscono come ‘impronte digitali’ di bio-molecole e specie organiche consentendo così lo sviluppo di innovative applicazioni spettroscopiche e di nuovi sensori. Inoltre, l’atmosfera terrestre presenta due finestre di trasparenza a 3 – 5 μm e 8 – 13 μm rendendo così possibili applicazioni come il rilevamento remoto di esplosivi, ad esempio in aeroporti e ai controlli di confine, e sistemi di telecomunicazioni protetti. Per sfruttare tali potenzialità, è necessario utilizzare vetri che siano trasparenti nel medio infrarosso, come ad esempio i vetri calcolgenuri. I vetri calcolgenuri sono caratterizzati da una buona resistenza meccanica e chimica in acqua e atmosfera. Inoltre presentano alto indice di rifrazione, alta efficienza quantica, bassa phonon energy e alta solubilità alle terre rare consentendo l’emissione di luce alle alte lunghezze d’onda.
Obiettivo di questa tesi è stato la progettazione di innovativi dispositivi in vetro calcogenuro per applicazioni nel medio infrarosso utilizzando codice home-made scritto appositamente. L’attenzione si è concentrata su tre tipologie di dispositivi: micro-sfere, micro-dischi e micro-bolle. Per eccitare il campo elettromagnetico all’interno di queste strutture si possono utilizzare differenti metodi, ma i più efficienti fanno uso del campo evanescente di fibre ottiche rastremate (taper) o di guide d’onda opportunamente progettate.
Un primo ambito di ricerca ha riguardato lo sviluppo di una nuova procedura di progettazione di amplificatori a micro-risonatore utilizzando l’algoritmo particle swarm optimization (PSO). Tale approccio ha consentito di massimizzare il guadagno di un amplificatore realizzato da una micro-sfera drogata con Erbio che emette luce a 2.7 μm.
Una diversa attività di ricerca ha consentito di definire un innovativo approccio alla caratterizzazione spettroscopica delle terre rare integrando lo studio elettromagnetico dei WGM eccitati in una micro-sfera con l’algoritmo PSO. Il metodo è basato su due passaggi successivi: nel primo vengono recuperati i parametri geometrici della struttura, nel secondo i parametri spettroscopici. Il tool complessivo consente di ricavare i parametri spettroscopici con un errore minore di quello generalmente ottenuto utilizzando strumentazione di misura estremamente costosa. Inoltre la procedura sviluppata è estremamente versatile e potrebbe essere applicata per progettare innovativi sistemi per la sensoristica.
Un’ulteriore attività ha riguardato le interessanti applicazioni che possono essere ottenute eccitando un micro-risonatore per mezzo di una fibra ottica rastremata avente due identici LPG (Long Period Grating) ai lati. Infatti gli LPG possono essere utilizzati per selezionare quale modo di core della fibra deve essere accoppiato con il risonatore WGM. Facendo uso di diverse coppie di LPG che lavorano a differenti lunghezze d’onda, è possibile accoppiare selettivamente differenti micro-risonatori utilizzando una stessa fibra ottica ed ottenendo così un sistema di sensing distribuito. Un codice ad-hoc è stato sviluppato e validato. Inoltre, sono stati condotti studi preliminari su sensori a micro-bolla che hanno dimostrato la fattibilità di un sensore sensibile alla concentrazione di glucosio.
Ultimo ambito di ricerca ha riguardato i sistemi laser basati su micro-dischi drogati con terre-rare. L’industria fotonica tende a privilegiare strutture planari perché più compatte, più facilmente integrabili e più economiche da realizzare. Anche in questo caso è stato sviluppato un codice numerico con lo scopo di simulare un micro-disco drogato con terre-rare e accoppiato a due guide d’onda di tipo ridge, una per il segnale utile ed una per il segnale di pompa. Il modello è stato validato utilizzando un micro-disco drogato con Erbio e che emette luce a 4.5 μm. Successivamente il modello è stato utilizzato per progettare un innovativo e promettente micro-disco drogato con Praseodimio e che emette a 4.7 μm.Optical micro-resonators represent one of the most important devices in photonics. A special kind is constituted by the WGM resonators, i.e. devices with circular symmetry such as spheres, rings, disks and toroids. They are characterized by very small dimensions, exceptionally quality factor and very low modal volume becoming a valuable alternative to the traditional optical micro-resonators, such as Fabry-Pérot cavities. These devices allow applications in several fields, such as sensing, optical filtering and nonlinear optics. In particular, different applications in biology and medicine, molecular spectroscopy, environmental monitoring, astronomy and astrophysics are feasible in Mid-Infrared wavelength range. For example, it includes a lot of strong vibrational transitions that act as “fingerprints” of many bio-molecules and organic species allowing the develop of innovative spectroscopic applications and novel sensors. In addition, the earth's atmosphere is transparent in two atmospheric transmission windows at 3–5 μm and 8–13 μm and then applications such as remote explosive detection, e.g. in airports and for border control, and covert communication systems are feasible. The wide transparency window of chalcogenide glasses in Mid-Infrared makes possible the development of several devices. Chalcogenide glasses are characterized by good mechanical strength and chemically durability in water and atmosphere. Furthermore, the high refractive index, high quantum efficiency, the low phonon energy and high rare-earth solubility enables the emissions at long wavelengths.
In this thesis, the design of innovative chalcogenide devices for applications in Mid-Infrared is investigated using an ad-hoc home-made computer code. The devices are based on three kinds of micro-resonators: microspheres, micro-disks and microbubbles. The WGM resonators are efficiently excited by using tapered fiber and ridge waveguides.
A novel design procedure is developed using the particle swarm optimization approach (PSO). It allows to maximize the gain of an amplifier based on an erbium-doped microsphere lasing at 2.7 μm.
An innovative technique in order to characterize the spectroscopic properties of rare-earth is developed integrating the WGM electromagnetic investigation with PSO algorithm. The method is based on two subsequent steps: in the first one, the geometrical parameters are recovered, in the second one, the spectroscopic parameters. The recovered values are affected by an error less than that provided by high-cost measurement instruments. Furthermore, the procedure is very versatile and could be applied to develop innovative sensing systems.
Interesting applications could be obtained exciting the micro-resonator by a tapered fiber with two identical LPGs on the sides. Indeed the LPGs can select the fiber modes coupling with the WGM resonator. Using different pairs of identical LPGs operating in different wavelength bands, it is possible to selective couple different micro-resonators by using the same optical fiber. An ad-hoc computer code is developed and validated and it demonstrated the feasibility of a microbubble glucose sensor.
In order to obtain a compact and cost-saving light source in Mid-Infrared, rare-earth doped micro-disk are investigated. A computer code is developed in order to simulate a rare-earth doped micro-disk coupled to two ridge waveguide, one at signal wavelength and the other one at pump wavelength. The model is validated using an erbium-doped micro-disk emitting at 4.5 μm. A very promising device for application in Mid-Infrared is obtained using a praseodymium-doped micro-disk emitting at 4.7 μm.Les micro-résonateurs optiques comptent parmi les dispositifs les plus importants en photonique. Les résonateurs WGM sont assez particuliers. Il s'agit de composant présentant une symétrie circulaire comme c'est le cas des sphères, des anneaux, des disques et des tores. Les résonateurs WGM sont de très petites dimensions. Ils présentent un facteur de qualité exceptionnel et un volume modal très faible et constituent une alternative intéressante aux micro-résonateurs optiques traditionnels, tels que les cavités Fabry-Pérot. Ces appareils peuvent être utilisés dans plusieurs domaines, notamment la télédétection, le filtrage optique et l'optique non linéaire. D'autres applications sont possibles en biologie, médecine, spectroscopie moléculaire, surveillance environnementale, astronomie et astrophysique grâce à l'exploitation du rayonnement moyen infrarouge. Les micro-résonateurs optiques comportent un grand nombre de transitions vibrationnelles qui agissent comme des «empreintes» pour de nombreuses molécules organiques permettant le développement d'applications spectroscopiques innovantes et de nouveaux capteurs. Il convient de noter que l'atmosphère de la terre est transparente au niveau des deux fenêtres de transmission atmosphérique. La première est comprise entre 3 et 5 μm et la seconde entre 8 et 13 μm, ce qui rend possible des applications telles que la détection d'explosifs à distance dans les aéroports ou dans le cadre du contrôle aux frontières ainsi que le brouillage de communication confidentielles. La large fenêtre de transparence en verres de chalcogénures dans le domaine spectral infrarouge rend envisageable le développement de nombreuses applications. Les verres de chalcogénure sont caractérisés par une bonne résistance mécanique et une durabilité chimique suffisante dans l'eau et l'atmosphère. Par ailleurs, l'indice de réfraction élevé, le rendement quantique élevé, l'énergie de phonon faible et la solubilité importante des terres rares permettent des émissions dans le domaine spectral du moyen IR.
Dans cette thèse, la conception de dispositifs innovants en chalcogénure pour des applications utilisant le moyen infrarouge est étudiée en utilisant un code d'ordinateur personnel formé de façon aléatoire. Les appareils reposent sur des trois types de micro-résonateurs : les microsphères, les micro-disques et les microbulles. Les résonateurs WGM sont efficacement excités à l'aide de fibres nervurées et de guides d'ondes optiques de forme conique.
Le nouveau procédé de conception est développé en utilisant la méthode d'optimisation par essaims particulaires (PSO). Elle permet de maximiser le gain d'un amplificateur reposant sur une microsphère d'émission laser dopée à l'erbium à 4,5 μm.
Une technique innovante permettant de caractériser les propriétés spectroscopiques de la terre rare intégrant la recherche électromagnétique en mode WGM grâce à l'algorithme PSO a été développée. La méthode est basée sur deux étapes successives : dans la première, les paramètres géométriques sont récupérés tandis que les paramètres spectroscopiques le sont dans la seconde. Les valeurs récupérées sont entachées d’une erreur inférieure à celle prévue par les instruments de mesure ayant un coût élevé. La procédure est très polyvalente. Elle peut être appliquée à la conception de systèmes de détection innovants.
Des applications intéressantes peuvent être obtenues en excitant le micro-résonateur avec une fibre conique présentant deux LPG identiques sur les côtés. En effet, les FLP peuvent sélectionner le couplage de modes de fibre avec le résonateur WGM. En utilisant différentes paires de FLP identiques, opérant dans différentes bandes de longueurs d'onde, il est possible de coupler de façon sélective différents résonateurs à l'aide de la même fibre optique. Un code informatique aléatoire a été développé et validé. Il a démontré la faisabilité d'un capteur de microbulles de glucose.
Un microdisque en terre rare dopé est étudié pour obtenir une source de lumière compacte et économique dans l'infrarouge moyen. Un code informatique est développé afin de simuler un micro-disque de terre rare dopé et associé à deux guides d'ondes nervurés, un pour le signal et l'autre pour la pompe. Le modèle est validé à l'aide d'un micro-disque dopée à l'erbium émettant à 4,5 μm. Ce dispositif très prometteur pour des applications dans le moyen infrarouge est obtenu en utilisant un micro-disque de praséodyme dopé émettant à 4,7 μm
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
A close look at the hydration layer and at the premelting layer of K-feldspar
No full textIn this work, we perform molecular dynamics simulations to investigate the structural properties of water at the interface with K-feldspar. We aim at understanding the modifications induced on water structure by the presence of this mineral. We analysed both the hydration layer of K-feldspar in supercooled water and the premelting layer at the interface between K-feldspar and hexagonal ice. We studied the density profile, the orientational tetrahedral order parameter, the distribution of the cos(gamma) function, the hydrogen bond distribution, the number of water molecules belonging to different phases close to the surface of the feldspar. We focused on the interplay between high-density water and low-density water to inquire on local modifications of water structure with respect to the bulk phase. We investigated four different pressures where the structure of bulk water spans from high-density liquid (locally more disordered) to low-density liquid (locally more ordered). The investigation showed that both the hydration and the premelting layers present a low-density liquid water component and similarities as a function of pressure with the corresponding bulk. We also find that the premelting layer shows structural features intermediate between the liquid and the crystalline state acting as a matching layer
Dynamical crossover and its connection to the Widom line in supercooled TIP4P/Ice water
No full textWe perform molecular dynamics simulations with the TIP4P/Ice water model to characterize the relationship between dynamics and thermodynamics of liquid water in the supercooled region. We calculate the relevant properties of the phase diagram, and we find that TIP4P/Ice presents a retracing line of density maxima, similar to what was previously found for atomistic water models and models of other tetrahedral liquids. For this model, a liquid-liquid critical point between a high-density liquid and a low-density liquid was recently found. We compute the lines of the maxima of isothermal compressibility and the minima of the coefficient of thermal expansion in the one phase region, and we show that these lines point to the liquid-liquid critical point while collapsing on the Widom line. This line is the line of the maxima of correlation length that emanates from a second order critical point in the one phase region. Supercooled water was found to follow mode coupling theory and to undergo a transition from a fragile to a strong behavior right at the crossing of the Widom line. We find here that this phenomenology also happens for TIP4P/Ice. Our results appear, therefore, to be a general characteristic of supercooled water, which does not depend on the interaction potential used, and they reinforce the idea that the dynamical crossover from a region where the relaxation mechanism is dominated by cage relaxation to a region where cages are frozen and hopping dominates is correlated in water to a phase transition between a high-density liquid and a low-density liquid
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