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The importance of reduced-scale experiments for the characterization of porous media
No full textIn order to reduce threats to the quality of groundwater resources, prevention and control are the most important activities to carry out. In general, these activities require the ability to model the flow and solute transport phenomena in the aquifer. Thus, it is essential to collect information about potential contamination sources, boundary conditions, hydrological forcing, and the magnitudes and spatial distributions of the hydrodynamic and hydrodispersive parameters of the porous media. Measurements of such parameters, available only at a finite number of locations, are often obtained by means of different techniques and can be representative of various measurement scales. The use of available data, necessarily distributed on different scales, for characterizing porous media at a defined scale is a key question of great interest. With the aim to investigate on the hydraulic conductivity scale effect on a homogeneous porous medium, several experiments were carried out at the Hydrogeosite Laboratory (Marsico Nuovo, Italy). This laboratory is a large scale model sized 10 × 7 × 3 m3, filled with a homogeneous medium made up of quartz-rich sand. The results are described by separating the two important scale-ambits under consideration, obtaining two scale power laws. Moreover, the scale effect of the hydraulic conductivity has been detected by considering the water flow type (uniform or radial) into the porous medium. However, the results, either considering the only scale law or multi-scale laws, confirm what was proved by several authors for heterogeneous porous media, that is the trend of hydraulic conductivity to reach a higher limit when the measurement scale increases and, in our opinion, regardless of the heterogeneity of the porous medium. Finally, a hydrogeophysical approach is described in this chapter, in order to show how a passive geophysical method as self-potential can estimate the hydraulic conductivity. It is an important step when large site should be characterized and few direct borehole data are available. These aspects are important because the hydraulic conductivity estimation is the first step for the characterization of a site
Il miglioramento genetico della patata novella: un obiettivo da perseguire per il rilascio della pataticoltura italiana.
No full textScaling effect of the hydraulic conductivity in a confined aquifer
No full textPrevious studies showed that the values of the representative parameters of an aquifer, such as the hydraulic conductivity (k), increase with the scale, that is, with the aquifer volume involved in the measurement. The main cause of this behavior is commonly ascribed to the heterogeneity of the porous media. Heterogeneity influences the scaling behavior differently for laboratory or field measurement, but the scale dependence of hydraulic conductivity is not dependent on the specific measurement method. In the present study, the scaling law of this parameter was determined on a real confined aquifer, using measurements obtained, both in the laboratory (flow cells) and the field (slug tests and aquifer tests). The corresponding data were statistically analyzed. A scaling law was proposed for both the laboratory and field scale, using the data obtained from flow cells, slug tests, and aquifer tests. Afterward, the scaling law was estimated at just the field scale, first using the slug tests and aquifer tests and then using only the aquifer test data.The scale dependence of the storativity was also investigated for all field measurements and then using only the aquifer test data. In conclusion, for both hydraulic conductivity and storativity, the trend to reach an upper bound increasing the scale parameter was investigated in the scale ranges of 67 and 99 m, respectively, examining only the data set relative to aquifer test measurements. Copyright © 2012 by Lippincott Williams & Wilkins
Estimation of hydraulic conductivity in a large scale laboratory model by means of the self-potential method
No full textEstimation of hydraulic conductivity in a large scale laboratory model by means of the self-potential metho
Hydrogeohysics techniques for the characterization of a heterogeneous aquifer
No full textThe target of this work is the determination of hydraulic conductivity spatial distribution in a real aquifer using a hydrogeophysical approach. This was made possible by analyzing geoelectrical data coming from "cross-hole" electrical resistivity tomography. The geophysical techniques most used in hydrogeological studies are the geoelectrical methods because electrical resistivity is very sensitive to the presence of water. Since the electrical resistivity strongly depends on some hydraulic parameters such as porosity, water content and hydraulic conductivity, several relationships have been developed in order to estimate these hydraulic parameters using the measured electrical resistivity values. In this work, we present an experiment carried out at the Montalto Uffugo test site (Cosenza, Italy) of University of Calabria, where we determined the spatial distribution of hydraulic conductivity using a geoelectrical technique with electrodes located in two boreholes. The cross-hole electrical resistivity tomography (ERT) allowed us to obtain the resistivity distribution in the subsoil and compare it with the geological-stratigraphic information obtained through the analysis of two cores. Then, the data acquisition with the ensuing elaboration led to the characterization of the main aquifer of Montalto Uffugo and the reconstruction of the hydraulic conductivity distribution in the subsoil applying Archie's Law and Purvance and Andricevic's Law. The estimated hydraulic conductivity compares favourably with values previously determined in situ by some hydraulic tests
Resistance to Erwinia in Solanum tuberosum x S. tarijense diploid hybrids and their backcross generations.
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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
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