1,720,978 research outputs found
Development of an advanced geostatistical model for shear wave velocity profiles to manage uncertainties and variabilities in Ground Response Analyses
Full text linkL'abstract è presente nell'allegato / the abstract is in the attachmen
RELIABILITY OF SOIL POROSITY ESTIMATION FROM SEISMIC WAVE VELOCITIES
Full text linkSoil porosity is a state parameter of fundamental importance for several geotechnical problems. Geophysical testing provide appealing strategies for the determination of soil porosity, as several geophysical parameters are directly related to soil porosity. In particular the theory of wave propagation in saturated porous media, developed by Biot in the 1950s, allows the determination of soil porosity from the measured velocity of propagation of compressional and shear waves. A formal assessment of the reliability of the estimated porosity values is of primary importance to evaluate the applicability of this approach to solve practical geotechnical problems. In this paper the propagation of measurement uncertainties on the estimated values of soil porosity is theoretically evaluated. Moreover, experimental data of multiple acquisitions of cross-hole tests are considered. Data collected by different operators are also used to assess the confidence interval associated to different equipment, acquisition practices and testing methodology
INFLUENZA DELLE INCERTEZZE NELLA VALUTAZIONE DEI PROFILI DI Vs SULLE ANALISI DI RSL: IL CASO STUDIO DI FONTE DEL CAMPO (RI)
Full text linkLa valutazione delle incertezze nei parametri e la loro propagazione all'interno degli studi di risposta sismica locale rappresentano un carattere fondamentale nella valutazione del rischio sismico e nella microzonazione del territorio. Il profilo delle velocità delle onde di taglio (Vs), in particolare, rappresenta il parametro chiave per descrivere il comportamento del deposito sia per bassi, che per alti livelli deformativi. La valutazione della pericolosità di un sito specifico, pertanto, deve tenere in conto di tali incertezze a livello probabilistico, in modo da fornire un risultato consistente con lo studio probabilistico di base, e che tenga conto di diversi livelli di nonlinearità
MODELLI GEOSTATISTICI PER LA VALUTAZIONE DELLE INCERTEZZE E DELLE VARIABILITA’ NEI PROFILI DI Vs
Full text linkIl parametro meccanico fondamentale per la valutazione della risposta sismica locale è il profilo di velocità delle onde di taglio (VS). Esso è valutabile attraverso tecniche geofisiche sperimentali in situ, le quali presentano caratteristiche tecniche ed assunzioni teoriche differenti.
Nell’ambito di queste tecniche di indagine sperimentali, una valutazione delle incertezze e delle variabilità associate al processo di misura rappresenta una necessità indispensabile, soprattutto alla luce dei moderni approcci di valutazione non ergodica della risposta sismica locale. Per rispondere a tale esigenza, si utilizzano modelli geostatistici, i quali hanno la potenzialità di fornire un “quadro” delle incertezze epistemiche e variabilità aleatorie in gioco, tramite una randomizzazione.
L’unico modello geostatistico disponibile per tali applicazioni fu sviluppato da Gabriel Toro nel 1995. Esso rappresenta un tentativo di fornire uno strumento valido per la randomizzazione dei profili di VS ed è utilizzato in tutto il mondo per studi di pericolosità sismica, anche di edifici strategici. Il modello è stato implementato nel software STRATA e, più recentemente, nell’ultima versione del software DEEPSOIL.
La presente nota vuole inizialmente presentare le nozioni generali alla base del modello di Toro, valutando criticamente i vari elementi che lo compongono. Successivamente, verrà proposta una nuova implementazione rigorosa ed innovativa del modello, dotata di potenzialità maggiori rispetto alle versioni ad oggi disponibili. In particolare, il modello implementato è caratterizzato da un cambiamento radicale riguardante le ipotesi e l’idea alla base del processo di randomizzazione. Infatti, la novità principale riguarda il superamento dell’assunzione della velocità intervallare come variabile aleatoria principale, scomponendo il problema nelle due variabili aleatorie indipendenti alla base del processo di misura: la distanza ed il tempo
Geostatistical models for the assessment of the influence of shear wave velocity uncertainty and variability on ground response analyses
No full textA robust assessment of the influence of epistemic uncertainties and aleatory
variabilities on ground response analyses is a fundamental requirement for modern probabilistic
seismic hazard analyses. The study of epistemic uncertainties and aleatory variabilities should
follow three sequential steps: identification, quantification, and management (IQM procedure).
A fundamental input for ground response analyses is the shear-wave velocity (VS) profile. The
VS profile can be obtained via various types of geophysical tests. Each test has specific characteristics.
For these reasons, a consistent IQM procedure must be established to assess the type
and amount of uncertainties involved in the measurements, also addressing the peculiarities of
the investigated site. We propose a geostatistical model for the management of the uncertainties
included in the VS profiles obtained with surface wave tests. The model is based on the separate
randomization of travel times and layer thicknesses. It generates profiles that are consistent with
the measured “site signatures” such as the Rayleigh wave dispersion curve and the predominant
site period. The model can be easily generalized for other geophysical tests
The Polito Surface Wave flat-file Database (PSWD): statistical properties of test results and some inter-method comparisons
Full text linkThe compilation and maintenance of experimental databases are of crucial importance in all research fields, allowing for researchers to develop and test new methodologies. In this work, we present a flat-file database of experimental dispersion curves and shear wave velocity profiles, mainly from active surface wave testing, but including also data from passive surface wave testing and invasive methods. The Polito Surface Wave flat-file Database (PSWD) is a gathering of experimental measurements collected within the past 25 years at different Italian sites. Discussion on the database content is reported in this paper to evaluate some statistical properties of surface wave test results. Comparisons with other methods for shear wave velocity measurements are also considered. The main novelty of this work is the homogeneity of the PSWD in terms of processing and interpretation methods. A common processing strategy and a new inversion approach were applied to all the data in the PSWD to guarantee consistency. The PSWD can be useful for further correlation studies and is made available as a reference benchmark for the validation and verification of novel interpretation procedures by other researchers
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
- …
