1,721,240 research outputs found
Numerical simulations for prediction of seismic ground motion amplification: 2D vs 3D comparison for natural reliefs and earth dams
Full text linkLocal site conditions (i.e., dynamic properties of subsurface and bedrock materials, surface and buried morphology) play an important role on seismic ground motion amplification. Therefore, their effects may become crucial in several geological/geotechnical systems such as earth dams and natural reliefs for selection of ground motion to be used in the analysis of engineering problems. These systems are usually studied based on 2D numerical analyses. However, due to the complexity of geomorphological and geotechnical situations, frequently coupled 3D soil-topography amplification analyses should be conducted to realistically assess the dynamic response.
In this research, large-scale numerical simulations are carried out with the finite difference computer code FLAC3D, that was used for both 2D and 3D analyses. Two case histories have been considered, the Palatino hill, a natural relief in the historical center of Rome, and the Angitola zoned dams in Southern Italy. In both cases visco-elastic linear analyses have been conducted considering models of increasing complexity, from homogeneous to heterogeneous ones with the inclusion of one or more additional layers, in order to distinguish between topographic and stratigraphic/valley amplification. In both cases Chang wavelet was used for input motion for three values of frequency (2Hz, 5Hz and 8Hz).
The comparison between the results of 2D and 3D analyses has been carried out in terms of maximum accelerations and/or displacement in representative points. The numerical analyses have been preceded by a calibration study, comparing the results of 2D and 3D numerical analyses with closed form solutions.
It is shown that 3D behavior can have a pronounced effect on the seismic response of the examined systems in terms of amplitude and shape of the acceleration/displacement profiles. In fact, 3D amplitudes can be much larger than 2D ones depending on the frequency of the input motion. The importance of vertical parasitic component of motion is highlighted, which again is frequency-dependent in that it increases with increasing frequency. For Angitola earth dams, the influence of narrow canyons in which the dams are built significantly contributes to the enhanced amplification of response, which is in agreement with the literature findings
Quaternary mass movements controlled by a structurally complex setting in the central Apennines (Italy)
No full textThe paper discusses the results of an engineering-geology study of an area in central Italy affected by complex gravity induced slope instability. A finite-difference analysis was implemented to demonstrate that stratigraphy and recent tectonics have had a crucial impact on the gravitational processes that have occurred in a built-up area of the central Apennines (Italy). The creation of a reliable geological-evolutionary model proved to be a key tool for subsequent development of a numerical model, capable of elucidating the main factors and parameters controlling slope instabilities. The study area, in the vicinity of the small mountain village of Micigliano (central Apennines), displays extensive outcrops of carbonate platform lithotypes, hemipelagic marly-clayey deposits and arenaceous pelitic turbidites. Its tectonic setting is very complex, with intense faulting (thrusts, normal faults, and complex kinematic faults) and folding. A geological-evolutionary model of the instability processes in the various sectors of the study area was formulated and fine tuned, on the basis of detailed geological and engineering-geology surveys, assumptions on the mechanical and hydraulic characters of the local geological bodies, and observation of the morpho-evolutionary processes. Subsequently, a stress-strain analysis was applied to the model, using the finite-difference method, in order to reconstruct the complex mechanisms governing evolution of the various sectors of the investigated slopes and the effects of gravity-caused instability on the exposed lithotypes. The numerical model also helped to validate the consistency of the stress-strain assumptions with the deformation mechanisms observed in the various investigated sectors of the study area, yielding a kinematic picture of the causal factors of the local gravity-caused instability in space and time. (C) 2003 Elsevier B.V. All rights reserved
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
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
Buffer sizing of a CRMA/ATM InterWorking Unit adopting a loss free access scheme
No full textOne of the main concerns in the interconnection of high speed lANs and ATM based networks is to avoid cell loss in the InterWorking Unit. In fact. in such environment, the retransmissions caused by the higher layers protocols can cause serious congestion problems. As a case study, the interconnection of a Gbit/s CRMA LAN through an ATM-based WAN is here considered. An Integrated Flow and Access Control (IFAC) protocol is proposed which exploiting the characteristics of the CRMA access scheme regulates the emission of cells towards the CRMA/ATM InterWorking Unit so that its buffer resources are not saturated. The emission of the ATM stations is controlled via a backpressure mechanism. The capacity of the InterWorking Unit buffer is virtually increased by utilizing the network latency as well as the station buffers. The protocol effectiveness has been validated through a simulation analysis. On the basis of the obtained results a study on the IWU buffer dimensioning has been carried out. In particular. the minimum buffer needed to can)' a given load has been determined. Moreover, some criteria have been given to properly fix the capacity to be allocated through the ATM interface
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