1,721,116 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
Polarimetric imaging and light depolarization physics : ultra-resolved speckle field polarimetry and opto-microwaves approaches.
No full textLa polarisation est une des propriétés physiques de la lumière, modifiée lors d’une interaction entre celle-ci et la matière, mais indétectable à l’œil nu et aux capteurs d’image standards. Des imageurs polarimétriques ont été conçus de longue date pour permettre d’analyser cette information et mettre en évidence des contrastes invisibles aux imageurs standard. L’Institut Foton développe depuis plusieurs années une technique d’imagerie polarimétrique, inspirée d’approches optique-hyperfréquence, dite par « brisure d’orthogonalité ». La première partie de ce travail de thèse détaille un protocole de calibration rigoureux de la chaîne d’acquisition/démodulation cohérente, et valide une imagerie sélective de propriétés polarimétriques des échantillons imagés dite brisure d’orthogonalité « induite ». Par ailleurs, en imagerie cohérente, un des phénomènes physiques macroscopiques bien connu est celui de la dépolarisation spatiale (volumique et/ou surfacique) qui demeure un sujet d’investigation à l’échelle « locale », c’est-à-dire à l’échelle des grains de speckle (tavelures) formés lors de la diffusion lumineuse cohérente par un objet complexe et désordonné. Ainsi, pour mieux comprendre ce mécanisme, nous présentons les améliorations (instrumentales, méthodologiques et en termes de traitement de données) que nous avons apportées à un banc d’imagerie polarimétrique de Stokes de champ de speckle hautement résolu existant au sein de l’Institut FOTON. Nous démontrons que l’optimisation du protocole d’acquisition portant sur le choix des états d’analyse et de la méthode d’estimation permet une détermination précise et rapide de l’information polarimétrique, plus robuste notamment aux imperfections expérimentales (erreurs systématiques). Des expériences similaires ont démontré l’existence d’un phénomène dit de « repolarisation », où la lumière résultante d’une source cohérente dépolarisée avec un milieu dépolarisant/diffusant se retrouve localement partiellement polarisée. En combinant le banc d’imagerie et l’approche d’imagerie optique-hyperfréquences par brisure d’orthogonalité, nous sommes parvenus à mesurer des contrastes polarimétriques dit de brisure d’orthogonalité, inédits à l’échelle du champ de speckle. Ces nouveaux contrastes couplés à l’imagerie de Stokes classiques nous permettent d’apporter une interprétation expérimentale nouvelle et éclairante du phénomène de « repolarisation ».Polarization is one of the physical properties of light, which is modified when light interacts with matter, but is undetectable to the naked eye and to standard image sensors. Polarimetric imagers have been designed for a long time to analyze this information and to highlight contrasts invisible to standard imagers. The Foton Institute has been developing for several years a polarimetric imaging technique, inspired by optical-hyperfrequency approaches, called "orthogonality breaking". The first part of this thesis details a rigorous calibration protocol of the coherent acquisition/demodulation chain, and validates a selective imaging of polarimetric properties of the imaged samples, called "induced" orthogonality breaking. In addition, in coherent imaging, one of the well-known macroscopic physical phenomena is spatial depolarization (volumetric and/or surface), which remains a subject of investigation at the "local" scale, i.e. at the scale of speckle grains formed during coherent light scattering by a complex and disordered object. Thus, to better understand this mechanism, we present the improvements (instrumental, methodological and in terms of data processing) that we have made to a highly resolved speckle field Stokes polarimetric imaging bench existing within the FOTON Institute. We demonstrate that the optimization of the acquisition protocol concerning the choice of the analysis states and the estimation method allows an accurate and fast determination of the polarimetric information, more robust in particular to experimental imperfections (systematic errors). Similar experiments have demonstrated the existence of a so-called "empolarization" phenomenon, where the resulting light from a depolarized coherent source with a depolarizing/diffusing medium becomes locally partially polarized. By combining the imaging bench and the optical-hyperfrequency imaging approach by orthogonality breaking, we succeeded in measuring polarimetric contrasts called orthogonality breaking, new at the speckle field scale. These new contrasts coupled to classical Stokes imaging allow us to bring a new and enlightening experimental interpretation of the "empolarization" phenomenon
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
Imagerie temps-réel à longues distance à travers le brouillard
No full textL'imagerie à travers les milieux turbides comme le brouillard, les tissus, les colloïdes, etc. répond à plusieurs besoins de la vie courante. L'imagerie à travers de tels milieux diffusants est un défi auquel peuvent répondre les nouveaux systèmes d'imagerie, la théorie de l'information et l'étude des lois de transport de la lumière dans les milieux aléatoires. La thèse est divisée en deux parties adressant deux modalités d'imagerie différentes, à savoir : l'imagerie de contraste polarimétrique et l'imagerie modulée en intensité. Dans les deux cas, des systèmes d'imagerie en temps réel sont proposés et mis au point. Leurs performances sont évaluées à la fois théoriquement et expérimentalement. Dans la première partie de la thèse, une caméra polarimétrique à deux canaux instantanés conçue autour d'un prisme de Wollaston est utilisée pour imager de manière optimale une source de lumière polarisée noyée dans un brouillard. Une expérience en situation réelle a été mise en place à proximité du campus de Beaulieu à Rennes. La source est placée sur une tour de télécommunication située à plus d'un kilomètre du système imageant. Les données acquises dans diverses conditions météorologiques montrent que l'efficacité de cette caméra polarimétrique dépend de la corrélation du bruit de fond dans les deux images initiales. Ceci a été confirmé grâce à une analyse fondée sur la théorie de l'information qui montre que le contraste polarimétriques maximal est obtenu par une combinaison linéaire des deux canaux polarimétriques dont la pondération dépendant de la corrélation du bruit de fond dans les deux canaux. Un système de détection, intégrant cette représentation polarimétrique optimale, a été développé pour explorer de bout en bout les capacités offertes par l'imagerie polarimétrique à deux canaux à travers le brouillard. Ces études trouvent des applications directes dans le transport par temps dégradé, y compris pour l'aide à l'atterrissage d'aéronefs. Dans la même logique, la deuxième partie de la thèse porte sur l'apport de la modulation d'intensité plein champ pour imager les photons balistiques dans les milieux diffusants. En utilisant de concert la théorie de la diffusion et la théorie de l'information, nous avons pu montrer que, pour un budget de photons donné, il existait une fréquence de modulation minimale pour laquelle le filtrage de photons balistique devient efficace. Cette fréquence dépend des propriétés de diffusion du milieu intermédiaire et se trouve être dans la gamme du MHz en situation réelle. L'imagerie en temps réel à de telles fréquences étant un vrai défi, nous avons proposé un système de démodulation plein champ inédit basé sur l'utilisation d'un cristal électro-optique. Ce système d'imagerie, dont nous avons breveté le principe, est en mesure de démoduler avec une caméra standard une scène en temps réel et en plein champ à des fréquences de plusieurs MHz (voire GHz) sans synchronisation de phase. Un prototype de ce système a été développé permettant de confirmer qu'il était robuste, portable et rentable. Le travail présenté dans cette thèse ouvre la voie à la mise en œuvre de systèmes d'imagerie de pointe fonctionnant dans des situations réelles, allant de l'imagerie biomédicale, à la sécurité.Imaging through turbid media like fog, tissues, colloids etc. has various applications in real-life situations. The problem of imaging through such scattering media presents a challenge that can be addressed by using novel imaging schemes, information theory and laws of light transport through random scattering media. The thesis is divided into two parts corresponding to two different imaging modalities, namely, polarimetric contrast imaging and intensity modulated light imaging. In both the cases, advanced imaging systems, capable of imaging in real-time are used and their performances are evaluated both theoretically and experimentally. In the first part of the thesis, a two-channel, snapshot polarimetric camera, based on a Wollaston prism is used to attain optimal imaging of polarized light source through fog. An original outdoor experiment is setup in the vicinity of the campus Beaulieu in Rennes, France, where a source is placed on a telecommunication tower more than a kilometer away from the imaging system. Data acquired in various weather conditions show that the efficiency of the two-channel polarimetric camera depends on the background noise correlation in the two images. Further, this was confirmed using an information theoretical analysis, which showed that a polarimetric contrast maximizing image representation is a linear combination of the two polarimetric images whose weights depend on the background noise correlation. Based on the derived optimal polarimetric representation, a detection scheme was presented, leading to an end-to-end study of two-channel polarimetric imaging through fog that may be useful in transport applications like aircraft landing/taxiing in degraded weather. The second part of the thesis deals with intensity modulated light and its potential for ballistic photon imaging through scattering media. First, using the diffusion theory of photon transport and information theory, it was shown that for a given photon budget, ballistic imaging can be achieved for a minimum modulation frequency that depends on the scattering properties of the intervening medium. In real-life situation, the minimum frequency can be in the range of MHz. Real-time imaging at these frequencies is a challenge. Hence, a novel demodulation camera system based on electro-optics was proposed and patented. The imaging system is capable of real-time, full-field demodulation at frequencies of several MHz (potentially, in GHz as well), without requiring a phase synchronized source. A prototype of the imaging system was developed and shown that a demodulation camera based on the proposed design is robust, portable and cost-effective. Finally, the work presented in this thesis pave way for implementation of advanced imaging systems in real-life situations, varying from biomedical imaging to transport safety
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
Stochastic Complexity-Based Model Selection With False Alarm Rate Control in Optical Spectroscopy
No full textInternational audienceStochastic complexity-based penalization criteria can prove efficient and robust in spectroscopy applications for unsupervised identification and concentration estimation of spectrally interfering chemical components. It is shown here how the so-called Normalized Maximized Likelihood (nMDL) introduced in Rissanen (1996) can be tailored to provide control of the detection performances in terms of probability of false alarm. Numerical experiments conducted on realistic simulated optical spectroscopy signals evidence that the nMDL approach outperforms standard information criteria in terms of model selection performances. Moreover, the ability to control false alarm rates with the proposed modified nMDL criterion is demonstrated on simulations
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