1,721,025 research outputs found
Logistic regression model for evaluating soil liquefaction probability using CPT data
No full text[[abstract]]A simple model for evaluating liquefaction probability using cone penetration test (CPT) data is developed based on logistic regression analyses of 396 case histories. The proposed model uses the normalized cone penetration resistance and soil behavior type index as input parameters; therefore, only CPT testing is necessary for evaluating the liquefaction probability of a site. The selection of the model parameters and the expression of equations are based on results of probability examinations and rigorous statistical analyses. Moreover, the derivation of the logistic regression model is presented in a system of equations. The incorporation of these procedures in developing the model not only fully satisfies the statistic requirements but also highlights the physical meanings of the model parameters. Comparisons of the proposed probability model with previously proposed deterministic and probabilistic approaches are performed to demonstrate the improvements. For practical purposes, the developed model is implemented to establish the relationship between the factor of safety against liquefaction and the probability of liquefaction.[[note]]SC
Development of an in situ dynamic liquefaction test
No full text[[abstract]]A new field-testing technique has been developed in which liquefaction and pore pressure generation characteristics of soil are measured in situ. The in situ dynamic liquefaction test utilizes a large, hydraulic shaker to load dynamically a soil deposit. The soil response is measured with embedded instrumentation. The embedded instrumentation includes newly developed liquefaction test sensors that incorporate velocity transducers (geophones) and pore pressure transducers in a single case. The recorded data are used to describe pore pressure generation and liquefaction characteristics in terms of the relationship between shear strain and induced pore pressure ratio. The analytical techniques used to compute shear strain from particle velocity measurements are discussed and compared. The results from testing a 1.2-m by 1.2-m by 1.2-m reconstituted field test specimen are presented. The shear strain-pore pressure relationships at selected numbers of loading cycles that were determined from the in situ dynamic liquefaction test are compared with those measured by other investigators in the laboratory. The field-measured relationships show the same shape as the lab-measured relationships, but the field data indicate a smaller threshold strain for pore pressure generation (similar to0.005%). This difference is attributed to the low effective stresses in the reconstituted field specimen.[[note]]SC
Characterization of liquefaction resistance in gravelly soil: large hammer penetration test and shear wave velocity approach
No full text[[abstract]]Gravelly soil is generally recognized to have no liquefaction potential. However, liquefaction cases were reported in central Taiwan in the 1999 Chi-Chi Taiwan earthquake and in the 1988 Armenia earthquake. Thus, further studies on the liquefaction potential of gravelly soil are warranted. Because large particles can impede the penetration of both standard penetration test and cone penetration test, shear wave velocity-based correlations and large hammer penetration tests (LPT) are employed to evaluate the liquefaction resistance of gravelly soils. A liquefied gravelly deposit site during the Chi-Chi earthquake was selected for this research. In situ physical properties of soil deposits were collected from exploratory trenches. Instrumented LPT and shear wave. velocity (V(s)) measurements were performed to evaluate the liquefaction resistance. In addition, large-scale cyclic triaxial tests on remolded gravelly soil samples (15 cm in diameter, 30 cm in height) were conducted to verify and improve LPT-based and V(s)-based correlations. The results show that the LPT and shear wave velocity methods are reasonably suitable for liquefaction assessment of gravelly soils. (C) 2004 Elsevier Ltd. All rights reserved.[[note]]SC
Direct evaluation of effectiveness of prefabricated vertical drains in liquefiable sand
No full text[[abstract]]A dynamic full scale testing program was performed to quantitatively assess the effectiveness of prefabricated vertical drains as a liquefaction countermeasure. The testing program involved a new in situ liquefaction testing technique, which uses a large hydraulic vibrator to generate waves propagating through an embedded instrumentation area to measure the coupled soil-pore water response. The effectiveness of prefabricated vertical drains is assessed experimentally by comparing the pore pressure generation, pore pressure dissipation, and settlement from two reconstituted soil specimens; one without a drain in place and the other with a single drain installed. Because the prefabricated drain was installed during the specimen preparation process, no accompanying densification during installation occurred. Therefore, the effect of drainage alone was evaluated. The testing results show that the drainage provided by prefabricated drains can significantly reduce pore pressure generation, accelerate post-shaking pore pressure dissipation, and limit associated settlement. The outcome also shows that the Dew developed in situ liquefaction testing technique can be an alternative to quantitatively evaluate the effects of various liquefaction remediation techniques. (C) 2004 Elsevier Ltd. All rights reserved.[[note]]SC
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
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