207 research outputs found
Remote sensing upscaling of interception loss from isolated oaks: Sardon catchment case study, Spain
Towards an improved assessment of the water balance at the catchment scale : a coupled model approach
Measurement and modelling of rainfall interception by two differently aged secondary forests in upland Eastern Madagascar
Hydrogeophysics and remote sensing for the design of hydrogeological conceptual models in hard rocks - Sardón catchment (Spain)
Hard rock aquifers are highly heterogeneous and hydrogeologically complex. To contribute to the design of hydrogeological conceptual models of hard rock
aquifers, we propose a multi-techniques methodology based on a downward approach that combines remote sensing (RS), non-invasive hydrogeophysics and
hydrogeological field data acquisition. The proposed methodology is particularly suitable for data scarce areas. It was applied in the pilot research area of
Sardón catchment (80 km2) located west of Salamanca (Spain). The area was selected because of hard-rock hydrogeology, semi-arid climate and scarcity of
groundwater resources.
The proposed methodology consisted of three main steps. First, we detected the main hydrogeological features at the catchment scale by processing: (i) a
high resolution digital terrain model to map lineaments and to outline fault zones; and (ii) high-resolution, multispectral satellite QuickBird and WorldView-2
images to map the outcropping granite. Second, we characterized at the local scale the hydrogeological features identified at step one with: i) ground
penetrating radar (GPR) to assess groundwater table depth complementing the available monitoring network data; ii) 2D electric resistivity tomography (ERT)
and frequency domain electromagnetic (FDEM) to retrieve the hydrostratigraphy along selected survey transects; iii) magnetic resonance soundings (MRS) to
retrieve the hydrostratigraphy and aquifer parameters at the selected survey sites. In the third step, we drilled 5 boreholes (25 to 48 m deep) and performed
slug tests to verify the hydrogeophysical interpretation and to calibrate the MRS parameters. Finally, we compiled and integrated all acquired data to define
the geometry and parameters of the Sardón aquifer at the catchment scale.
In line with a general conceptual model of hard rock aquifers, we identified two main hydrostratigraphic layers: a saprolite layer and a fissured layer. Both
layers were intersected and drained by fault zones that control the hydrogeology of the catchment. The spatial discontinuities of the saprolite layer were well
defined by RS techniques while subsurface geometry and aquifer parameters by hydrogeophysics. The GPR method was able to detect shallow water table at
depth between 1 and 3 m b.g.s. The hydrostratigraphy and parameterization of the fissured layer remained uncertain because ERT and FDEM geophysical
methods were quantitatively not conclusive while MRS detectability was restricted by low volumetric water content. The proposed multi-technique methodology
integrating cost efficient RS, hydrogeophysics and hydrogeological field investigations allowed us to characterize geometrically and parametrically the Sardón
hard rock aquifer system, facilitating the design of hydrogeological conceptual model of the area
Thermal activation between Landau levels in the organic superconductor -(BEDT-TTF)SFCHCFSO
We show that Shubnikov-de Haas oscillations in the interlayer resistivity of
the organic superconductor -(BEDT-TTF)SF
CHCFSO become very pronounced in magnetic fields ~60~T.
The conductivity minima exhibit thermally-activated behaviour that can be
explained simply by the presence of a Landau gap, with the
quasi-one-dimensional Fermi surface sheets contributing negligibly to the
conductivity. This observation, together with complete suppression of chemical
potential oscillations, is consistent with an incommensurate nesting
instability of the quasi-one-dimensional sheets.Comment: 6 pages, 4 figure
Generating fuzzy rules by learning from olive tree transpiration measurement - An algorithm to automatize Granier sap flow data analysis
The present study aims at developing an intelligent system of automating data analysis and prediction
embedded in a fuzzy logic algorithm (FAUSY) to capture the relationship between environmental variables
and sap flow measurements (Granier method). Environmental thermal gradients often interfere
with Granier sap flow measurements since this method uses heat as a tracer, thus introducing a bias in
transpiration flux calculation. The FAUSY algorithm is applied to solve measurement problems and provides
an approximate and yet effective way of finding the relationship between the environmental variables
and the natural temperature gradient (NTG), which is too complex or too ill-defined for precise
mathematical analysis. In the process, FAUSY extracts the relationships from a set of input–output environmental
observations, thus general directions for algorithm-based machine learning in fuzzy systems
are outlined. Through an iterative procedure, the algorithm plays with the learning or forecasting via a
simulated model. After a series of error control iterations, the outcome of the algorithm may become
highly refined and be able to evolve into a more formal structure of rules, facilitating the automation
of Granier sap flow data analysis. The system presented herein simulates the occurrence of NTG with reasonable
accuracy, with an average residual error of 2.53% for sap flux rate, when compared to data processing
performed in the usual way. For practical applications, this is an acceptable margin of error given
that FAUSY could correct NTG errors up to an average of 76% of the normal manual correction process. In
this sense, FAUSY provides a powerful and flexible way of establishing the relationships between the
environment and NTG occurrencesinfo:eu-repo/semantics/publishedVersio
Superconductivity mediated by charge fluctuations in layered molecular crystals
We consider the competition between superconducting, charge ordered, and metallic phases in layered molecular crystals with the theta and beta" structures. Applying slave-boson theory to the relevant extended Hubbard model, we show that the superconductivity is mediated by charge fluctuations and the Cooper pairs have d(xy) symmetry. This is in contrast to the kappa-(BEDT-TTF)(2)X family, for which theoretical calculations give superconductivity mediated by spin fluctuations and with d(x)2(-y)2 symmetry. We predict several materials that should become superconducting under pressure
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