1,720,995 research outputs found
Upper mantle anisotropy beneath Peru from SKS splitting: Constraints on flat slab dynamics and interaction with the Nazca Ridge
No full textThe Peruvian flat slab is by far the largest region of flat subduction in the world today, but aspects of its structure and dynamics remain poorly understood. In particular, questions remain over whether the relatively narrow Nazca Ridge subducting beneath southern Peru provides dynamic support for the flat slab or it is just a passive feature. We investigate the dynamics and interaction of the Nazca Ridge and the flat slab system by studying upper mantle seismic anisotropy across southern Peru. We analyze shear wave splitting of SKS , sSKS , and PKS phases at 49 stations distributed across the area, primarily from the PerU Lithosphere and Slab Experiment (PULSE). We observe distinct spatial variations in anisotropic structure along strike, most notably a sharp transition from coherent splitting in the north to pervasive null (non-split) arrivals in the south, with the transition coinciding with the northern limit of the Nazca Ridge. For both anisotropic domains there is evidence for complex and multi-layered anisotropy. To the north of the ridge our View the MathML sourceKS? splitting measurements likely reflect trench-normal mantle flow beneath the flat slab. This signal is then modified by shallower anisotropic layers, most likely in the supra-slab mantle, but also potentially from within the slab. To the south the sub-slab mantle is similarly anisotropic, with a trench-oblique fast direction, but widespread nulls appear to reflect dramatic heterogeneity in anisotropic structure above the flat slab. Overall the regional anisotropic structure, and thus the pattern of deformation, appears to be closely tied to the location of the Nazca Ridge, which further suggests that the ridge plays a key role in the mantle dynamics of the Peruvian flat slab system
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
Determinacion y analisis del factor de calidad de las ondas coda (qc), en el borde suroccidental del peru
No full textEn este presente trabajo de tesis se estudia y se determina el factor de las ondas coda(Qc) para el borde sur occidental del Peru. Estos eventos son de gran utilidad para relizar estudios de investigacion que permitan conocer las caracteristicas fiscas del interior de la tierra.Tesi
Aplicacion de metodos geofisicos y geotecnicos para la evaluacion de riesgos de geodinamica externa en el area urbana de huaycan - lima
No full textEn este presente trabajo de tesis de estudio la diversas oportunidades por eventos sismicos de variedad magnitud que ha generado altos niveles de intensidad, que se se observa como es la dinamica de los suelos las tecnicas q se caracterizan los suelos y la geodinamica externa, las caracterizacion de los suelos,y la zonificacion sismica geotecnica llegando a la conclusion precisas.Tesi
Analisis de residuales de ondas p y propuesta de modelo de equilibrio isostatico para la cordillera andina del peru
No full textEn este presente trabajo de tesis de estudio se propone el modelo de equilibrio isostatico para la Cordillera Andina, a partir de analisis residuales y anomalias de onda P. Estas anomalias pueden ser interpretadas como variaciones en el espesor de la corteza bajo la zon de estudio y permiten comparar los propiedades fisicas de la estructura existente por debajo de ca estacion sismica de manerar regional; por lo cual los resultados permiten proponer que el equilibrio isostatico a nivel de la corteza es suficiente para explicar la variacion espacial de anomalias.Tesi
Aplicacion de metodos geofisicos y geotecnicos para determinar la geometria en 3d del basamento rocoso y la caracterizacion de sitio en la ciudad de huarmey (ancash)
No full textEn este presente trabajo de tesis se estudia y se considera el analisis e interpretacion de la informacion geologica, geomorfologica, geodinamica y geofisica para identificar las caracteristicas locales del suelo a fin de realizar una tipificacion según la norma sismoresistente E-030 y obtener un modelo 3D de la geomotria basamento rocoso. La zona de estudio correspondiente al área del Huarmey de la region de AncashTesi
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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