1,720,979 research outputs found
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
Manipulação e mapeamento de correlações quânticas em estados de quatro qudits espaciais
No full textDuring the past thirty years the field of Quantum Information has beenvery successful in proposing protocols and algorithms that involve two-level quantum systems known as qubits. It has been shown that cryptographic keys can be distributed securely using quantum resources and that quantum algorithms can solve tasks such as the factoring of large numbers with an exponential speedup over classical algorithms. Most implementations, however, are restricted to proof-of-concept experiments using few qubits, due to the difficulty of scaling the physical systems utilized. Quantum systems with more than two levels, called qudits, present themselves as an alternative way of obtaining a space with large dimensionality without recurring to a large number of qubits. This reduces the number of particles necessary for implementing protocols in a scale that is relevant for practical applications. Additionally, pairs of entangled qudits are more robust agains noise than their qubit counterparts and are also more adequate for experiments that test the non-local and contextual behavior of nature, as predicted by its description using Quantum Mechanics. In this thesis we present the construction and characterization of a source of states of four qudits. We used a pulsed laser as pump for type-II Spontaneous Parametric Down Conversion (SPDC) to occur on a PPKTP, a KTiOPO4 (KTP) crystal with a periodic ferroelectric domain inversion, a technique called periodic poling. In type-II SPDC a pair of photons, also called biphoton, is generated in which one has horizontal polarization while the other hasvertical polarization. Due to the use of a pulsed pump beam and the highdown-conversion efficiency of our PPKTP, the probability that a single pump pulse will originate two pairs of photons is high. In order to generate qudits we used the multiple-slit implementation, meaning that a multiple slit was placed between the PPKTP and the detectors, encoding discrete qudit states onto the continuous transverse mode of the biphoton. Using double, triple and quadruple slits we produced, respectively, qubit, qutrit and ququart states. A system of lenses placed between the PPKTP and the slits manipulated the amplitude of the transverse biphoton state impinging on the slits and, thus, the quantum correlations between qudits after the slits. By projecting either the near or far field of the crystal onto the slits, the lenses changed the characteristics of the biphoton amplitude function and allowed us to obtain either states with very high entanglement, in the case of the near field, or very low entanglement, in the case of the far field. A lens in the f-f configuration between the plane of the slits and the plane of the detectors projected the far field of the slits, so we could observe conditional interference patterns. We detected the photons in coincidence asa function of the position of two detectors These were used to generate maps of coincidences between two photons with different polarization and for two photons with the same polarization. The first case contains contributions from photons of a single pair and from photons from two different pairs, while the second case contains contributions from different pairs only. In order to isolate the single pair contribution on different-polarization coincidences, we removed the background component from photons of different pairs, given by the same-polarization coincidences. Besides serving to isolate the singlepair signal, same-polarization coincidences confirm the existence two-pair events and give us information about the purity of the reduced state of a single photon, which is related to the degree of entanglement in a biphoton. We conclude that manipulating the biphoton transverse amplitude is a promising technique for generating qudit states while controlling their entanglement and correlation properties, especially if more exotic transverse amplitudes are explored, such as Hermite-Gaussian pump beams or amplitudes engineered with a spatial light modulator. The use of high-efficiency SPDC sources allows for states of more than one biphoton, engineered using transverse amplitude manipulation, to be employed in many different protocolsin Quantum Information, serving as sources of heralded pure or mixedstates, or playing an important role in tests of the non-local and contextual nature of physical systems, as predicted by Quantum Mechanics.Nos seus trinta anos de existência a Informação Quântica teve grande êxito em propor protocolos e algoritmos envolvendo sistemas quânticos de dois níveis, chamados de qubits. Mostrou-se a possibilidade de distribuição segura de chaves criptográficas e algoritmos quânticos capazes de resolver tarefas como a fatoração de grandes números com um ganho exponencial de velocidade em relação aos algoritmos clássicos. A maior parte das implementações, contudo, restringe-se a provas de princípio envolvendo poucos qubits, devido à dificuldade de escalabilidade dos sistemas utilizados. Sistemas quânticos com mais de dois níveis, chamados de qudits, se apresentam como uma possibilidade de obter espaços de maior dimensão sem recorrer a um número muito elevado de qubtis, reduzindo o número de partículas necessário para a implementação de protocolos em escalas relevantes. Além disso, pares emaranhados de qudits são mais resistentes a ruído que aqueles compostos por qubits e também se mostram mais adequados para a realização de experimentos que testem o caráter não-local e contextual da natureza, conforme previsto pela Mecânica Quântica. Nesta tese relatamos a construção e caracterização de uma fonte de estados de quatro qudits. Utilizamos um laser de bombeamento pulsado e um cristal de KTiOPO4 com inversão periódica de domínios (PPKTP) como fonte de pares de fótons, também chamados bifótons, por Conversão Paramétrica Descendente Espontânea (CPDE) tipo II, caso em que o par contém um fóton de polarização horizontal e um fóton de polarização vertical. Devido ao uso do laser pulsado e à alta eficiência de conversão do PPKTP, há grande probabilidade de um mesmo pulso de bombeamento produzir dois bifótons. Codificamos os qudits no modo de momento transversal dos fótons por meio de fendas múltiplas, gerando sistemas com 2, 3 e 4 níveis. Através de elementos ópticos lineares, colocados entre o PPKTP e as fendas, manipulamos a amplitude dos estados transversais dos bifótons incidentes sobre as fendas e, assim, as correlações quânticas entre os qudits após as fendas. Fazendo uso de duas configurações de lentes, projetamos ora o campo próximo e ora o campo distante do PPKTP sobre as fendas, obtendo após i estas estados de qudits com propriedades muito distintas. No caso do campo próximo, observamos alto grau de emaranhamento entre os qudits, enquanto o campo distante produziu estados com baixo emaranhamento, próximo a um estado produto. Caracterizamos o estado dos pares de qudits gerados utilizando mapas de correlação de quarta ordem no campo elétrico dos fótons, obtidos através de medições em coincidência de fotocontagens no campo distante das fendas, projetado sobre o plano dos detectores por uma lente na configuração f-f. Para correlações entre fótons com polarizações diferentes isolamos o sinal devido a fótons pertencentes a um mesmo bifóton via subtração da contribuição de fótons de bifótons distintos, obtida através de medições em coincidência de fótons com a mesma polarização. Estas últimas forneceram ao mesmo tempo comprovação da presença de dois pares de qudits gerados por um mesmo pulso e informação sobre o estado reduzido de um dos fótons do par de qudits, que pode ser utilizada para estimar o emaranhamento no par quando se supõe que o estado global é puro. Concluímos que a manipulação da amplitude do campo dos bifótons antes da fenda é um método muito promissor para a geração controlada de estados de qudits. Acreditamos que amplitudes não-triviais, como a dos modos Hermite-Gaussianos ou ainda mais arbitrárias, geradas por moduladores espaciais de luz, podem ser explorados para obter estados ainda mais gerais do que os obtidos com perfis descritos por funções pares. Combinado ao uso de cristais com alta eficiência de CPDE, pode-se construir uma fonte útil para diversos protocolos de Informação Quântica, como comunicação segura entre muitas partes ou geração de estados de qudits que podem ser utilizados para simular a dinâmica quântica de cavidades, além de servir para testes do caráter não-local e contextual da natureza
Estudo dos efeitos de processamento sobre o comportamento estrutural e magnético do composto intermetálico La(Fe1-xSix)13
No full textIn the present work we conduct an analysis of the relations between the crystal structure, chemical composition and magnetic behavior in intermetallic compounds of the La(Fe1-xSix)13 family in the range 0,11 < x < 0,14 and how they are affected by sintering. We show that the nominal stoichiometry does not correspond to that observed in the intermetallic phase when á-Fe is simultaneously formed . We also correlate theeffects of sintering to the magnetic behavior of the material by altering its transition temperature and possibly its magnetocaloric effect. Possible mechanisms for this are discussed in terms of the present knowledge regarding the origins of the magnetocaloric effect in La(Fe1-xSix)13 compounds.Nesse trabalho é feita uma análise das relações existentes entre a estrutura cristalina, a composição química e o comportamento magnético em compostos magnetocalóricos da família La(Fe1-xSix)13 no intervalo 0,11 < x < 0,14 e como estas são afetadas pela sinterização. Mostramos que a estequiometria nominal não corresponde à que de fato se forma quando ocorre a formação concomitante de a-Fe e que a sinterização influi sobre o comportamento magnético do material, alterando sua temperatura de transição e possivelmente seu efeito magnetocalórico. Justificativas para tal alteração são apresentadas, tendo por base o que se conhece sobre a origem do efeito magnetocalórico no composto estudad
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
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