1,720,963 research outputs found
Fracture in brittle materials: the atomic-scale viewpoint
No full textWe present the basic formalism, as well as the underlying physical picture of atomistic simulations, as applied to the investigation of materials mechanical behavior. In particular, we discuss brittle fracture in cubic silicon carbide, proving that atomistic simulations are not only consistent with elementary continuum fracture mechanics, but also do provide a better physical insight on atomic-scale features, e.g. lattice trapping. Finally, we show how atomistic simulations could be used as a provider of constitutive relations to be possibly used in continuum modeling
Quantum Confinement by an Order-Disorder Boundary in Nanocrystalline Silicon
No full textWe predict theoretically and show experimentally the occurrence of quantum confinement in hydrogenated nanocrystalline silicon. We prove that only valence states (positively charged carriers) are confined effectively within the nanograins. The emission associated to confined states is verified by photoluminescence experiments on nanocrystalline samples with controlled grain size. According to the present study, we propose nanocrystalline silicon as a promising material for oxygen-free optoelectronics, silicon-based memories and photovoltaics
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
Understanding and tailoring unique electronic and phononic hBN properties
No full textInternational audienceAfter having served for years as a perfect second on the heels of the bright star graphene, hexagonal boron nitride (hBN) has now demonstrated to be able to shine with its own light, offering a unique combination of physical properties that enable its use for a broad range of applications, from quantum technologies to deep UV optoelectronics, mid-infrared nano-photonics and thermal management applications [1]. hBN is indeed a natural hyperbolic material in the mid-IR range. It exhibits strong, thickness-dependent second-order non-linearities. By engineering its defects it can become a room-temperature, single-photon emitter and, finally, even being indirect, its wide bandgap offers very high internal quantum efficiency for deep UV emitters and detectors. All these features stem from its highly anisotropic crystal structure and its polar chemical bond which lead to peculiar electronic band structure, phonon dispersion, strong electron-phonon coupling, and huge excitonic effects [2,3]. Starting then from the description of its constituent elements I will outline the reasons for its exclusive properties and I will highlight recent discoveries and possible routes for further exploiting its huge potential [4,5].[1]B Gil, G Cassabois, R Cusco, G Fugallo, L Artus Nanophotonics 9: 3483–3504 (2020)[2]G. Fugallo, M. Aramini, J. Koskelo, K. Watanabe, T. Taniguchi, M. Hakala, S. Huotari, M. Gatti, and F. Sottile, Phys. Rev. B 92, 165122 (2015).[3]Cepellotti, A., G. Fugallo, L. Paulatto, M. Lazzeri, F. Mauri, and N. Marzari, Nature Comm. 6, 6400. (2015)[4]C. Elias, G. Fugallo, P. Valvin, C. L’Henoret, J. Li, J. H. Edgar, F. Sottile, M. Lazzeri, A. Ouerghi, B. Gil, and G. Cassabois Phys. Rev. Lett. 127, 137401 (2021).[5] G. Cassabois, G. Fugallo, C. Elias, P. Valvin, A. Rousseau, B. Gil, A. Summerfield, C. J. Mellor, T. S. Cheng, L. Eaves, C. T. Foxon, P. H. Beton, M. Lazzeri, A. Segura, and S. Novikov, Phys Rev X 12, 011057 (2022
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
Understanding and tailoring unique electronic and phononic hBN properties
No full textInternational audienceAfter having served for years as a perfect second on the heels of the bright star graphene, hexagonal boron nitride (hBN) has now demonstrated to be able to shine with its own light, offering a unique combination of physical properties that enable its use for a broad range of applications, from quantum technologies to deep UV optoelectronics, mid-infrared nano-photonics and thermal management applications [1]. hBN is indeed a natural hyperbolic material in the mid-IR range. It exhibits strong, thickness-dependent second-order non-linearities. By engineering its defects it can become a room-temperature, single-photon emitter and, finally, even being indirect, its wide bandgap offers very high internal quantum efficiency for deep UV emitters and detectors. All these features stem from its highly anisotropic crystal structure and its polar chemical bond which lead to peculiar electronic band structure, phonon dispersion, strong electron-phonon coupling, and huge excitonic effects [2,3]. Starting then from the description of its constituent elements I will outline the reasons for its exclusive properties and I will highlight recent discoveries and possible routes for further exploiting its huge potential [4,5].[1]B Gil, G Cassabois, R Cusco, G Fugallo, L Artus Nanophotonics 9: 3483–3504 (2020)[2]G. Fugallo, M. Aramini, J. Koskelo, K. Watanabe, T. Taniguchi, M. Hakala, S. Huotari, M. Gatti, and F. Sottile, Phys. Rev. B 92, 165122 (2015).[3]Cepellotti, A., G. Fugallo, L. Paulatto, M. Lazzeri, F. Mauri, and N. Marzari, Nature Comm. 6, 6400. (2015)[4]C. Elias, G. Fugallo, P. Valvin, C. L’Henoret, J. Li, J. H. Edgar, F. Sottile, M. Lazzeri, A. Ouerghi, B. Gil, and G. Cassabois Phys. Rev. Lett. 127, 137401 (2021).[5] G. Cassabois, G. Fugallo, C. Elias, P. Valvin, A. Rousseau, B. Gil, A. Summerfield, C. J. Mellor, T. S. Cheng, L. Eaves, C. T. Foxon, P. H. Beton, M. Lazzeri, A. Segura, and S. Novikov, Phys Rev X 12, 011057 (2022
Understanding and tailoring unique electronic and phononic hBN properties
No full textInternational audienceAfter having served for years as a perfect second on the heels of the bright star graphene, hexagonal boron nitride (hBN) has now demonstrated to be able to shine with its own light, offering a unique combination of physical properties that enable its use for a broad range of applications, from quantum technologies to deep UV optoelectronics, mid-infrared nano-photonics and thermal management applications [1]. hBN is indeed a natural hyperbolic material in the mid-IR range. It exhibits strong, thickness-dependent second-order non-linearities. By engineering its defects it can become a room-temperature, single-photon emitter and, finally, even being indirect, its wide bandgap offers very high internal quantum efficiency for deep UV emitters and detectors. All these features stem from its highly anisotropic crystal structure and its polar chemical bond which lead to peculiar electronic band structure, phonon dispersion, strong electron-phonon coupling, and huge excitonic effects [2,3]. Starting then from the description of its constituent elements I will outline the reasons for its exclusive properties and I will highlight recent discoveries and possible routes for further exploiting its huge potential [4,5].[1]B Gil, G Cassabois, R Cusco, G Fugallo, L Artus Nanophotonics 9: 3483–3504 (2020)[2]G. Fugallo, M. Aramini, J. Koskelo, K. Watanabe, T. Taniguchi, M. Hakala, S. Huotari, M. Gatti, and F. Sottile, Phys. Rev. B 92, 165122 (2015).[3]Cepellotti, A., G. Fugallo, L. Paulatto, M. Lazzeri, F. Mauri, and N. Marzari, Nature Comm. 6, 6400. (2015)[4]C. Elias, G. Fugallo, P. Valvin, C. L’Henoret, J. Li, J. H. Edgar, F. Sottile, M. Lazzeri, A. Ouerghi, B. Gil, and G. Cassabois Phys. Rev. Lett. 127, 137401 (2021).[5] G. Cassabois, G. Fugallo, C. Elias, P. Valvin, A. Rousseau, B. Gil, A. Summerfield, C. J. Mellor, T. S. Cheng, L. Eaves, C. T. Foxon, P. H. Beton, M. Lazzeri, A. Segura, and S. Novikov, Phys Rev X 12, 011057 (2022
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
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