1,721,160 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
Many-body effects in optical spectra of n-doped alloy semiconductor quantum-well structures
No full textRecently observed luminescence spectra in the alloy semiconductor quantum-well system InGaAs/InP show an enhancement of the electron-hole (e-h) recombination oscillator strength at the electron Fermi energy (EFe). This enhancement is explained, using a generalized e-h pair propagator and static screening, as due to multiple e-h scattering and recombination of the electrons at EFe with the small number of optically excited holes which have wave-vector components of the order of kFe (the electron Fermi wave-vector) due to localisation effects. The localisation is taken to rise from alloy disorderRecently observed luminescence spectra in the alloy semiconductor quantum-well system InGaAs/InP show an enhancement of the electron-hole (e-h) recombination oscillator strength at the electron Fermi energy (EFe). This enhancement is explained, using a generalized e-h pair propagator and static screening, as due to multiple e-h scattering and recombination of the electrons at EFe with the small number of optically excited holes which have wave-vector components of the order of kFe (the electron Fermi wave-vector) due to localisation effects. The localisation is taken to rise from alloy disorde
Theoretical model of excitons for type-II quantum-wire systems
No full textA calculation of the exciton binding energy (Ex) and oscillator strength (OS) for quantum wires in type-II semiconductor systems is presented. These structures consist of a cylindrical wire of one semiconductor embedded in a second semiconductor. In the type-II exciton systems in quantum wells the electron is confined in one semiconductor and the hole in the other is due to band lineups in the two materials, which make this arrangement energetically favorable. We use an approach which initially decouples the ρ and z components. We use a variational approach for motion in the ρ direction which allows for correlation of the free particle, and solve for the one-dimensional exciton in the z direction using an effective Coulomb interaction. The solutions are then coupled self-consistently to produce Ex, where Ex(ρ,z)=E(ρ)+E(z), and a product wave function which is used to calculate the OS. We consider the idealized situation of infinite confining barriers and the more realistic case of finite barriers for the system GaAs/AlAs, where the electron is confined in the X state in the AlAs while the hole is confined in the Γ state in the GaAs wire (for a wire diameter of less than 43 Å). For finite barriers Ex peaks at 33 meV for a wire diameter of 16 Å, which represents a large enhancement over the infinite-barrier case due to the strong wave-function correlation possible in two dimensionsA calculation of the exciton binding energy (Ex) and oscillator strength (OS) for quantum wires in type-II semiconductor systems is presented. These structures consist of a cylindrical wire of one semiconductor embedded in a second semiconductor. In the type-II exciton systems in quantum wells the electron is confined in one semiconductor and the hole in the other is due to band lineups in the two materials, which make this arrangement energetically favorable. We use an approach which initially decouples the ρ and z components. We use a variational approach for motion in the ρ direction which allows for correlation of the free particle, and solve for the one-dimensional exciton in the z direction using an effective Coulomb interaction. The solutions are then coupled self-consistently to produce Ex, where Ex(ρ,z)=E(ρ)+E(z), and a product wave function which is used to calculate the OS. We consider the idealized situation of infinite confining barriers and the more realistic case of finite barriers for the system GaAs/AlAs, where the electron is confined in the X state in the AlAs while the hole is confined in the Γ state in the GaAs wire (for a wire diameter of less than 43 Å). For finite barriers Ex peaks at 33 meV for a wire diameter of 16 Å, which represents a large enhancement over the infinite-barrier case due to the strong wave-function correlation possible in two dimension
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
Electron mobility, diffusion and lifetime [in silicon]
No full textDatareviews are given on the following topics: electron mobility in bulk and epitaxial Si; electron mobility in 2D n-type Si; electron mobility at (100) Si surface; minority carrier electron mobility, diffusion length and lifetime, in p-type SiDatareviews are given on the following topics: electron mobility in bulk and epitaxial Si; electron mobility in 2D n-type Si; electron mobility at (100) Si surface; minority carrier electron mobility, diffusion length and lifetime, in p-type S
Excitons in type-II quantum-dot systems: a comparison of the GaAs/AlAs and InAs/GaSb systems
No full textcalculation of the exciton binding energy (Ex) and oscillator strength for quantum dots in type-II semiconductor systems is presented. These structures consist of a spherical dot of one semiconductor embedded in a second semiconductor. As in the type-II exciton systems in quantum wells the electron is confined in one semiconductor and the hole is confined in the other due to band lineups in the two materials which make this arrangement energetically favorable. The authors have considered the systems (i) GaAs/AlAs where the electron is confined in the X state in the AlAs while the hole is confined in the InAs dot while the hole is confined in the GaSb (for a dot radius of less than 56 Å) and (ii) InAs/GaSb where the electron is confined in the InAs dot while the hole is confined in the GaSb (for a dot of radius less than 87 Å). While both of these systems are indirect in real space the GaAs/AlAs system is also indirect in k space. They compare Ex in the type-II dot to Er, the binding energy of a bulk hydrogenic impurity in the bulk barrier. The authors find that for the case of infinite barriers Excalculation of the exciton binding energy (Ex) and oscillator strength for quantum dots in type-II semiconductor systems is presented. These structures consist of a spherical dot of one semiconductor embedded in a second semiconductor. As in the type-II exciton systems in quantum wells the electron is confined in one semiconductor and the hole is confined in the other due to band lineups in the two materials which make this arrangement energetically favorable. The authors have considered the systems (i) GaAs/AlAs where the electron is confined in the X state in the AlAs while the hole is confined in the InAs dot while the hole is confined in the GaSb (for a dot radius of less than 56 Å) and (ii) InAs/GaSb where the electron is confined in the InAs dot while the hole is confined in the GaSb (for a dot of radius less than 87 Å). While both of these systems are indirect in real space the GaAs/AlAs system is also indirect in k space. They compare Ex in the type-II dot to Er, the binding energy of a bulk hydrogenic impurity in the bulk barrier. The authors find that for the case of infinite barriers E
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