Search results for "soil"

Temperature control during Spark Plasma Sintering and application to up-scaling and complex shaping

2013

International audience; The determination and the homogeneity of the sample temperature during consolidation of powders by Spark Plasma Sintering (SPS) are addressed. Densifications were carried out in three different facilities differing by their constructors and their size. A structural transformation activated in a TiAl alloy was used as a marker of the sample temperature and finite element modeling were performed to evaluate the temperature at each point of the set-up. A good agreement between experimental and simulated data is exhibited. Alloys with identical microstructures were sintered and the homogeneity of the microstructure was better in the largest machines or when the sample wa…

Simulating permeability reduction by clay mineral nanopores in a tight sandstone by combining computer X-ray microtomography and focussed ion beam sc…

2021

Solid earth 12(1), 1 - 14 (2021). doi:10.5194/se-12-1-2021

2020

Abstract. Residual pressure can be preserved in mineral inclusions, e.g. quartz-in-garnet, after exhumation due to differential expansion between inclusion and host crystals. Raman spectroscopy has been applied to infer the residual pressure and provides information on the entrapment temperature and pressure conditions. However, the amount of residual pressure relaxation cannot be directly measured. An underestimation or overestimation of residual pressure may lead to significant errors between calculated and actual entrapment pressure. This study focuses on three mechanisms responsible for the residual pressure modification: (1) viscous creep; (2) plastic yield; (3) proximity of inclusion …

Practical Model for Load-Carrying Capacity of Eccentrically Loaded Square Column Footings

2018

In this paper, a practical calculus model based on the strut-and-tie approach for prediction of the load-carrying capacity of eccentrically loaded RC column footings with square cross sections is presented. Existing models based on beam or slab models with flexural and two-way slab punching shear failure are presented and discussed. Several subgrade contact pressure distributions for column footings are considered. A parametric analysis of the effects of footing and column dimensions (depth, width), longitudinal ratio of longitudinal steel, and strength of concrete and steel is made for all models examined. Available experimental data are utilized to verify the model in comparison with exis…

Polyethylene and Biodegradable Starch-Based Mulching Films Positively Affect Winter Melon Production in Sicily

2014

Plastic mulching is widely used in many regions of the world for growing melons. The winter melon is largely grown in the hilly countryside of the Mediterranean island of Sicily (Italy) where mulching plastic films enhance early and total yields. However, removing and disposal of polyethylene plastic mulches after use represent a major disadvantage and an environmental concern. The objective of this trial was to compare the effects of polyethylene (PE) (transparent and black) and biodegradable (black) mulching films on yield, fruit size and quality of melon grown in the open field. The trial was conducted in the north-western coast of Sicily in the province of Trapani, 250-m elevation. Melo…

Evaluation of Subgrade Resilient Modulus Predictive Model for Use in Mechanistic-Empirical Pavement Design Guide

2006

The characterization of unbound materials in the mechanistic–empirical pavement design guide (MEPDG), also known as the 2002 design guide, is reviewed, and this characterization is applied to Minnesota subgrades. The main emphasis is on the collection of k1-, k2-, and k3-parameters for Minnesota fine-grained soils and the procedure for the interpretation of the resilient modulus test to provide an input to the multilayer elastic theory (MLET) analysis (Level 2 input). This is an important aspect of adaptation of the MEPDG, because the guide recommends measurement of resilient moduli from laboratory testing, but the procedure does not specify how to interpret the test data to obtain an input …

Nonmonotone Saturation Profiles for Hydrostatic Equilibrium in Homogeneous Porous Media

2012

Nonmonotonic saturation profiles (saturation overshoot) occur as travelling waves in gravity driven fingering. They seem important for preferential flow mechanisms and have found much attention recently. Here, we predict them even for hydrostatic equilibrium when all velocities vanish. We suggest that hysteresis suffices to explain the effect. Recently, the observation of nonmonotonicity of traveling wave solutions for saturation profiles during constant-flux infiltration experiments has highlighted the shortcomings of the traditional, seventy year old mathematical model for immiscible displacement in porous media. Several recent modifications have been proposed to explain these observation…

Performance assessment of field deployed multi-crystalline PV modules in Nordic conditions

2019

This paper presents an investigation of data monitoring quality and evaluation of performance degradation of four different multi-crystalline silicon (mc-Si) photovoltaic (PV) modules installed in the higher latitude conditions in southern Norway. Degradation of each module has been investigated in terms of degradation of short-circuit current (I SC ), open-circuit voltage (V OC ), fill factor (FF) and maximum power (P MPP ). The analysis for the period of monitoring data from 2014 to 2018 show no considerable module degradation compared to the standard degradation rate of all parameters. The statistical analysis of I SC shows an average degradation of 0.17% for all modules. Spectral correc…

Predicting sediment deposition rate in check-dams using machine learning techniques and high-resolution DEMs

2021

Sediments accumulated in check dams are a valuable measure to estimate soil erosion rates. Here, geographic information systems (GIS) and three machine learning techniques (MARS-multivariate adaptive regression splines, RF-random forest and SVM-support vector machine) were used, for the first time, to predict sediment deposition rate (SR) in check-dams located in six watersheds in SW Spain. There, 160 dry-stone check dams (~ 77.8 check-dams km−2), accumulated sediments during a period that varied from 11 to 23 years. The SR was estimated in former research using a topographical method and a high-resolution Digital Elevation Model (DEM) (average of 0.14 m3 ha−1 year−1). Nine environmental-to…

Bayesian calibration of the nitrous oxide emission module of an agro-ecosystem model

2008

1. NitroEurope Open Science Conference on Reactive Nitrogen and the European Greenhouse Gas Balance ; Ghent (Belgique) - (2008-02-20 - 2008-02-21) / Conférence; Nitrous oxide (N2O) is the main biogenic greenhouse gas contributing to the global warming potential (GWP) of agro-ecosystems. Evaluating the impact of agriculture on climate therefore requires a capacity to predict N2O emissions in relation to environmental conditions and crop management. Biophysical models simulating the dynamics of carbon and nitrogen in agro-ecosystems have a unique potential to explore these relationships, but are fraught with high uncertainties in their parameters due to their variations over time and space. H…