University of Extremadura

About: University of Extremadura is a education organization based out in Badajoz, Spain. It is known for research contribution in the topics: Population & Hyperspectral imaging. The organization has 7856 authors who have published 18299 publications receiving 396126 citations. The organization is also known as: Universidad de Extremadura.

Soil hydrological response under simulated rainfall in the Dehesa land system (Extremadura, SW Spain) under drought conditions

Abstract: Soil hydrology was investigated in the Guadelperalon experimental watershed in order to determine the influence of land use and vegetation cover on runoff and infiltration within the Dehesa land system. Five soil–vegetation units were selected: (1) tree cover, (2) sheep trials, (3) shrub cover, (4) hillslope grass and (5) bottom grass. The results of the simulated rainfall experiments performed at an intensity of 56·6 mm h−1 during one hour on plots of 0·25 m2, and the water drop penetration time test indicate the importance of water repellency in the Dehesa land system under drought conditions. Low infiltration rates (c. 9–44 mm h−1) were found everywhere except at shrub sites and in areas with low grazing pressure. Soil water repellency greatly reduced infiltration, especially beneath Quercus ilex canopies, where fast ponding and greater runoff rates were observed. The low vegetation cover as a consequence of a prolonged drought and grazing pressure, in conjunction with the soil water repellency, induces high runoff rates (15–70 per cent). In spite of this, macropore fluxes were found in different locations, beneath trees, on shrub-covered surfaces, as well as at sites with a dominance of herbaceous cover. Discontinuity of the runoff fluxes due to variations in hydrophobicity causes preferential flows and as a consequence deeper infiltration, especially where macropores are developed. © 1998 John Wiley & Sons, Ltd.

Mathematical modelling of thin-layer infrared drying of wet olive husk

Abstract: The thin-layer infrared drying behaviour of wet olive husk (WOH) was experimentally investigated at the temperature range from 80 °C to 140 °C. The drying rate was found to increase with temperature, hence reducing the total drying time. In particular, as drying temperature was raised from 80 °C up to 140 °C, the time necessary to reduce the moisture content of the sample from 91.97 wt% down to 8.69 wt% (dry basis) changed from 105 min to 35 min. Using a non-linear regression (Marquart's method) and multiple regression analysis, a mathematical model for the thin-layer infrared drying process of WOH was proposed. The values of the diffusivity coefficients at each temperature were obtained using Fick's second law of diffusion. They varied from 5.958 × 10 −9 m 2 /s to 1.589 × 10 −8 m 2 /s over the temperature range. The temperature dependence of the effective diffusivity coefficient was described following an Arrhenius-type relationship. Activation energy for the moisture diffusion was determined as 21.30 kJ/mol.

Ultrasmall Liquid Droplets on Solid Surfaces: Production, Imaging, and Relevance for Current Wetting Research

Abstract: The investigation of micro- and nanoscale droplets on solid surfaces offers a wide range of research opportunities both at a fundamental and an applied level. On the fundamental side, advances in the techniques for production and imaging of such ultrasmall droplets will allow wetting theories to be tested down to the nanometer scale, where they predict the significant influence of phenomena such as the contact line tension or evaporation, which can be neglected in the case of macroscopic droplets. On the applied side, these advances will pave the way for characterizing a diverse set of industrially important materials such as textile or biomedical micro- and nanofibers, powdered solids, and topographically or chemically nanopatterned surfaces, as well as micro-and nanoscale devices, with relevance in diverse industries from biomedical to petroleum engineering. Here, the basic principles of wetting at the micro- and nanoscales are presented, and the essential characteristics of the main experimental techniques available for producing and imaging these droplets are described. In addition, the main fundamental and applied results are reviewed. The most problematic aspects of studying such ultrasmall droplets, and the developments that are in progress that are thought to circumvent them in the coming years, are highlighted.