1,721,177 research outputs found
A sandbox experiment of self-potential signals associated with a pumping test
No full textThe flow of water in a charged porous material is the source of in the relaxation phase following the shutdown of the an electrical field called the streaming potential. The origin of this pump. Despite the fact that the problem is treated here coupling is associated with the drag of the excess of charge contained for a thin tank (two-dimensional approximation), all the in the vicinity of the pore–water interface by the pore fluid flow. In this results obtained in this paper can easily be transposed paper, we present a sandbox experiment to study this “hydroelectric” to the three-dimensional case corresponding to the apcoupling in the case of a pumping test. A relatively thin Plexiglas plication of the method in the field. tank was filled with homogeneous sand and then infiltrated with tapwater. A pumping test experiment was performed in the middle THEORY of the tank with a peristaltic pump. The resulting electrical potential distribution was measured passively at the top of the tank with a net- In this section, we present a model that will be used later work of 27 nonpolarizable electrodes related to a digital multichan- to interpret the sandbox experiment. The porous material is nel multimeter plus an additional electrode used as a reference. A assumed to be isotropic with respect to all the material properdetectable electrical field was produced at the ground surface and ties introduced below. The total electrical density J (A m2) analyzed with analytical solutions of the coupled hydroelectric prob- is the sum of a conductive current given by Ohm’s Law and lem. After the shutdown of the pump, the electrical potential and the a driving current density JS. The latest is associated with the piezometric level exhibit similar relaxation times in the vicinity of the pore fluid pressure field (e.g., Titov et al., 2000, 2002; Revil pumping well. This means that the electrical potential measured at et al., 2003, and references therein). This yields the following the ground surface can be used to track the flow of the groundwater constitutive equation: and possibly to invert the distribution of the hydraulic transmissivity of the ground
High resolution ERT applied in sand-bed channel mouth infilling. The test site of Pégoulier channel in the Rhône Delta, France
No full textElectrical Resistivity Tomography (ERT) was applied in a sand-infilled paleo-channel located in the Rhoˆ ne Delta, in Southern France. The detailed pattern and sedimentological evolution of the channel fill deposits – know from both historical and geological sources – made it the ideal site to test the ERT method. A geoelectrical survey was performed, using the ABEM SAS-4000 multi-electrode array system in March 2003. Very low electrical resistivity values were obtained, ranging from 0.3 to 10 Ohm m, consistent with the high salinity measured in situ (the pore water conductivity was found to range from 0.9 to 1.2 S/m at 25 C). The electrical resistivity profiles reflect mainly salinity variations. Indeed, in this case, salinity is so high that surface conductivity associated with clay minerals can be safely neglected. ERT provided valuable high-resolution information that complemented other exiting data such as historical information, bathymetric, geological, and lithostratigraphic data, which allowed the architecture of the channel to be defined. The ERT was used to determine the infilling dynamics of the Pe ́ goulier Channel, which opens new perspectives in terms of paleoenvironmental reconstruction and paleodynamic studies
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
Electrical conductivity, ground displacement, gravity changes, and gas flow at Solfatara crater (Campi Flegrei caldera, Italy): Results from numerical modeling
No full textHydrothermal fluid circulation may cause measurable gravity changes and ground deformation. We extend
our previous studies and increase the number of observable parameters to include gas temperature, the rate of
diffuse degassing, the extent of the degassing area, and electrical conductivity. We have carried out
simulations using TOUGH2/EOS2 of a large scale hydrothermal system, then we have calculated observables
arising from changes in hydrothermal fluid circulation. Our results show that fluids affect many observable
parameters generating detectable signals. However, a more detailed description of the shallow subsurface is
necessary to properly calculate electrical conductivity. Studies at Solfatara volcano (Campi Flegrei caldera,
Italy) highlight the presence of an unsaturated layer at depth and allow to determine the position of the water
table. Then, we present results from a new, small scale simulation, focused on the crater, and carried out with
a new, refined meshgrid taking into account the real topography. Aim of the work is to calculate a detailed
electrical conductivity map and reproduce the main features of the Solfatara crater
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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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