Search results for " earth"
showing 10 items of 8811 documents
Determinants of the interannual relationships between remote sensed photosynthetic activity and rainfall in tropical Africa
2007
International audience; The response of photosynthetic activity to interannual rainfall variations in Africa South of the Sahara is examined using 20 years (1981-2000) of Normalised Difference Vegetation Index (NDVI) AVHRR data. Linear correlations and regressions were computed between annual NDVI and annual rainfall at a 0.5° latitude/longitude resolution, based on two gridded precipitation datasets (Climate Prediction Center Merged Analysis of Precipitation [CMAP] and Climatic Research Unit [CRU]). The spatial patterns were then examined to detect how they relate to the mean annual rainfall amounts, land-cover types as from the Global Land Cover 2000 data set, soil properties and soil typ…
Earth Bricks with Halloysite Nanoclay: Research and Experimentation for the Sustainability of Materials
2021
The paper illustrates the experimentation activities on rammed earth and nanotechnologies conducted by the authors. The experimental research was carried out with the aim of improving the performance of rammed earth bricks with clay nanotubes, creating a ‘new material’ with reduced embodied energy and low CO2 emissions into the atmosphere. Specifically, the analysed performances are related to the compressive strength that expand their area of use as a building material.
Global Estimation of Biophysical Variables from Google Earth Engine Platform
2018
This paper proposes a processing chain for the derivation of global Leaf Area Index (LAI), Fraction of Absorbed Photosynthetically Active Radiation (FAPAR), Fraction Vegetation Cover (FVC), and Canopy water content (CWC) maps from 15-years of MODIS data exploiting the capabilities of the Google Earth Engine (GEE) cloud platform. The retrieval chain is based on a hybrid method inverting the PROSAIL radiative transfer model (RTM) with Random forests (RF) regression. A major feature of this work is the implementation of a retrieval chain exploiting the GEE capabilities using global and climate data records (CDR) of both MODIS surface reflectance and LAI/FAPAR datasets allowing the global estim…
Current Social and Rangeland Access Trends among Pastoralists in the Western Algerian Steppe
2021
International audience; In the western Algerian steppe, the public authorities have carried out actions aimed at rural development (agricultural development programs) and combating desertification (grazing reserves) to counter the significant and rapid loss of vegetation cover of pastures by overgrazing, and the consequent impacts on local livelihoods. In the Rogassa area, these actions have impacted land tenure and the ancestral and collective way of land use and access. These changes have caused transformations in lifestyle and pasture management. This research aims to characterize how such changes are affecting local pastoralists and what their perceptions are about them. A selective sam…
Més enllà de Kohlberg: l'aprenentatge ètic per a la coherència entre judici, sentiments i accions morals
2017
espanolPara la comunidad educativa el desarrollo moral sigue siendo un asunto de preocupacion. Varios agentes educativos dedican tiempo y esfuerzo a un tema que, actualmente, evidencia una clara separacion entre lo teorico y lo practico, un sesgo entre lo que uno piensa y lo que uno hace, entre el razonamiento y las acciones morales. Las finalidades y las intenciones de los agentes educativos son respetables; pero contrariamente a estas, ninos y adolescentes actuan de manera demasiado reactiva y les cuesta generalizar ciertos comportamientos. En esta linea, el planteamiento de Kohlberg, centrado en el desarrollo del juicio y el razonamiento moral, parece proporcionarles principalmente eleme…
Crystal field and magnetism with Wannier functions: Rare-earth doped aluminum garnets
2015
Using the recently developed method we calculate the crystal field parameters in yttrium and lutetium aluminum garnets doped with seven trivalent Kramers rare-earth ions. We then insert calculated parameters into the atomic-like Hamiltonian taking into account the electron-electron, spin-orbit and Zeeman interactions and determine the multiplet splitting by the crystal field as well as magnetic $\hat{g}$ tensors. We compare calculated results with available experimental data.
The crater lake of Ilamatepec (Santa Ana) volcano, El Salvador: insights into lake gas composition and implications for monitoring
2019
We here present the first chemical characterization of the volcanic gas plume issuing from the Santa Ana crater lake, a hyper-acidic crater lake (pH of − 0.2 to 2.5) in north-western El Salvador. Our results, obtained during regular surveys in 2017 and 2018 using a Multi-GAS instrument, demonstrate a hydrous gas composition (H2O/SO2 ratios from 32 to 205) and SO2 as the main sulfur species (H2S/SO2 = 0.03–0.1). We also find that gas composition evolved during our investigated period, with the CO2/SO2 ratio decreasing by one order of magnitude from March 2017 (37.2 ± 9.7) to November 2018 (< 3). This compositional evolution toward more magmatic (SO2-rich) compositions is interpreted in the c…
TISSBERT: A benchmark for the validation and comparison of NDVI time series reconstruction methods
2018
[EN] This paper introduces the Time Series Simulation for Benchmarking of Reconstruction Techniques (TISSBERT) dataset, intended to provide a benchmark for the validation and comparison of time series reconstruction methods. Such methods are routinely used to estimate vegetation characteristics from optical remotely sensed data, where the presence of clouds decreases the usefulness of the data. As for their validation, these methods have been compared with previously published ones, although with different approaches, which sometimes lead to contradictory results. We designed the TISSBERT dataset to be generic so that it could simulate realistic reference and cloud-contaminated time series …
Straw uses trade-off only after soil organic carbon steady-state
2018
Soil organic matter (SOM) is the key for a healthy soil and a relevant property to achieve the sustainability on soil management. However, soils are still net exporters of organic matter. One example is the use of wheat straw residue for industrial and energy applications, which has gained attention in the last years. The offfarm use of this abundant and low cost resource should follow sustainability criteria to avoid soil degradation and SOM losses. Straw residue incorporation is recognized as a recommended management practice to control erosion and mitigate CO2 emissions by increasing SOM. The goal of this work was: i) to evaluate the steady-state carbon (C) level in relation to C input a…
Acoustic wave guides as infinite-dimensional dynamical systems
2015
We prove the unique solvability, passivity/conservativity and some regularity results of two mathematical models for acoustic wave propagation in curved, variable diameter tubular structures of finite length. The first of the models is the generalised Webster's model that includes dissipation and curvature of the 1D waveguide. The second model is the scattering passive, boundary controlled wave equation on 3D waveguides. The two models are treated in an unified fashion so that the results on the wave equation reduce to the corresponding results of approximating Webster's model at the limit of vanishing waveguide intersection.