130,368 research outputs found
Some remarks on the cyclic response of non-plastic and high-plasticity natural silty soils of the Kathmandu valley (Nepal)
No full textThis note presents the results of constant-volume equivalent-undrained cyclic simple shear tests performed on saturated natural silty soils obtained from two different locations in the Kathmandu valley (Nepal) and characterized by different plasticity. Two simple shear devices were employed: the DSDSS (Double Specimen Cyclic Simple Shear) device and a modified NGI-type DSS device. The above two types of tests complemented each other and jointly covered a wide range of cyclic shear strains amplitudes. Nonlinear soil behavior (i.e. variation of shear stiffness and damping with shear strain level) and liquefaction resistance of the non-plastic silty soil were investigated. The results of the experimental investigation presented in this paper, albeit limited, increase the knowledge on the cyclic response of natural silty soils, especially those of very low plasticity, and provide first geotechnical data on the soft fluvio-lacustrine deposits of the Kathmandu Valley, responsible for site effects and liquefaction phenomena during the 2015 Mw=7.8 Gorkha earthquake
Numerical simulation of site effects in the upper aterno valley array during the aftershock sequence of the 2009 L'Aquila earthquake
No full textOn April 6th, 2009 a Mw=6.3 earthquake jolted the Abruzzo region of Central Italy, very close to the urban center of L'Aquila. Availability of high-quality recordings of the mainshock along with several aftershocks makes the seismic sequence the best recordednear-source events in Italy. In the present study, attention is devoted to the strong motion recordings of the upper Aterno River Valley array, which is part of the Italian Accelerometric Network (Rete Accelerometrica Nazionale, RAN), deployed NW of L'Aquila. These data provide a better understanding of the role played by site effects in the seismic response of the valley in epicentral area. This was accomplished by comparing recordings with the results of 1D and 2D site response analyses. The subsoil model of the Aterno Valley passing through the accelerometric stations was assumed from a previous study and was integrated with the results of dynamic tests carried out on reconstituted samples of coarse materials frequently encountered in the subsoil. First, the ground surface motion computed by assuming linear soil behavior was compared to the small-magnitude (ML=3-3.5) aftershocks recordings. It was found that 2D modeling provides a satisfactory understanding of the amplification phenomena in the array. Moreover, 2D analyses performed slightly better than 1D predictions. Based on this calibration study, further site response analyses were carried out and the computed ground motion was compared with the aftershock recordings of moderate magnitude (MW=4-5.6). In contrast, the results from these events do not show the analogous performance as obtained in the linear range. More specifically, shape of acceleration response spectra is generally satisfactorily simulated whereas discrepancies are observed in terms of PGA as well as maximum spectral amplitude. It is speculated on the possible explanations of these discrepancies
Assessment of site effects in the Kathmandu valley, Nepal, during the 2015 Mw 7.8 Gorkha earthquake sequence using 1D and 2D numerical modelling
No full textThe paper reports on the results of 1D and 2D site response analyses carried out in the Kathmandu Valley, Nepal, in order to investigate how site effects influenced the seismic response during the 2015 Mw 7.8 Gorkha earthquake sequence. The mainshock and a Mw 6.6 aftershock, for which recordings at both rock and soil sites are available, were considered. First, 1D analyses were carried out for the Pulchowk soft soil site, where a borehole was drilled. The shear wave velocity profile was defined using several 2D seismic array surveys carried out in the valley and constrained by noise measurements at Pulchowk site; the nonlinear soil behavior was characterized by means of cyclic simple shear tests carried out on undisturbed soil samples. Both equivalent and nonlinear approaches were adopted in the 1D analyses. Overall, the 1D model was capable to capture some relevant features shown by mainshock recordings such as the de-amplification of medium-to-high frequencies. On the contrary, the unusual high spectral amplification at long periods (3–6 s) recorded during the mainshock was better captured by the 2D finite element analyses carried out on a 20 km-large cross section of the entire valley, thus supporting the hypothesis of the occurrence of basin effects. The paper contributes to the understanding of site effects in Kathmandu Valley for the implementation of seismic risk mitigation strategies in the area
Some remarks on the cyclic response of nonplastic and high-plasticity natural silty soils of the Kathmandu valley (Nepal)
No full textThis note presents the results of constant-volume equivalent-undrained cyclic simple shear tests performed on saturated natural silty soils obtained from two different locations in the Kathmandu valley (Nepal) and characterized by different plasticity. Two simple shear devices were employed: the DSDSS (Double Specimen Cyclic Simple Shear) device and a modified NGI-type DSS device. The above two types of tests complemented each other and jointly covered a wide range of cyclic shear strains amplitudes. Nonlinear soil behavior (i.e. variation of shear stiffness and damping with shear strain level) and liquefaction resistance of the non-plastic silty soil were investigated. The results of the experimental investigation presented in this paper, albeit limited, increase the knowledge on the cyclic response of natural silty soils, especially those of very low plasticity, and provide first geotechnical data on the soft fluvio-lacustrine deposits of the Kathmandu Valley, responsible for site effects and liquefaction phenomena during the 2015 Mw=7.8 Gorkha earthquake
MeSH term explosion and author rank improve expert recommendations
No full textInformation overload is an often-cited phenomenon that reduces the productivity, efficiency and efficacy of scientists. One challenge for scientists is to find appropriate collaborators in their research. The literature describes various solutions to the problem of expertise location, but most current approaches do not appear to be very suitable for expert recommendations in biomedical research. In this study, we present the development and initial evaluation of a vector space model-based algorithm to calculate researcher similarity using four inputs: 1) MeSH terms of publications; 2) MeSH terms and author rank; 3) exploded MeSH terms; and 4) exploded MeSH terms and author rank. We developed and evaluated the algorithm using a data set of 17,525 authors and their 22,542 papers. On average, our algorithms correctly predicted 2.5 of the top 5/10 coauthors of individual scientists. Exploded MeSH and author rank outperformed all other algorithms in accuracy, followed closely by MeSH and author rank. Our results show that the accuracy of MeSH term-based matching can be enhanced with other metadata such as author rank
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe 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
"Closing the R&D Gap, Evaluating the Sources of R&D Spending"
No full textBoth spending and tax policies have been implemented in the United States with the goal of stimulating private sector research and development (R&D). Karier questions whether current R&D policy, especially the research and experimentation tax credit, can contribute to closing the gap between nondefense expenditures on R&D in the United States and such expenditures in other countries, such as Japan and Germany. He also explores possible changes to our current R&D policy to make it more effective.
Dispelling the Myths Behind First-author Citation Counts
No full textWe 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
- …
