Publish in OALib Journal

ISSN: 2333-9721

APC: Only $99


Any time

2019 ( 13 )

2018 ( 10 )

2017 ( 11 )

2016 ( 13 )

Custom range...

Search Results: 1 - 10 of 2898 matches for " Thierry Winiarski "
All listed articles are free for downloading (OA Articles)
Page 1 /2898
Display every page Item
Modeling Water Infiltration and Solute Transfer in a Heterogeneous Vadose Zone as a Function of Entering Flow Rates  [PDF]
Erij Ben Slimene, Laurent Lassabatere, Thierry Winiarski, Remy Gourdon
Journal of Water Resource and Protection (JWARP) , 2015, DOI: 10.4236/jwarp.2015.713083
Abstract: Due to its rapid movement, preferential flow (PF) in the vadose zone allows much faster contaminant transport, which may have a significant impact on ground-water quality. PF can occur in heterogeneous vadose zones and it strongly depends on hydric and hydraulic conditions like entering flow rates at surface. This study deals with the modeling of the establishment of PF, and related solute transfer during the infiltration phase in a strongly heterogeneous glaciofluvial deposit. This deposit is made of four contrasting lithofacies (sand, gravel, bimodal gravel and matrix-free gravel) and lies underneath an urban infiltration basin (Lyon, France). Previous studies have been carried out on this site and linked the regionalization of soil pollution with the lithological heterogeneity. But none of them clearly demonstrated how heterogeneity could impact flow and solute transfer and may explain such a regionalization. In this study, we model flow and solute transfer at the trench scale for both uniform and heterogeneous profiles in order to characterize the effect of lithological heterogeneity. In addition, such a modeling was performed for two different entering flow rates to depict the influence of condition at surface on PF. A key result is that heterogeneity clearly impacts unsaturated flow and solute transfer. Numerical modeling permitted pointing out the existence of PF paths associated with the sedimentary heterogeneity of the glaciofluvial deposit. For lower surface fluxes, the sand lens and matrix-free gravel were the sources of capillary barrier effects, leading to a funneled flow and a groundwater recharge characterized by earlier and more dispersed wetting fronts. Such a flow pattern enhances solutes transfer and reduces solute retention by soil. Thus, the effect of heterogeneity on solute transfer is significant, especially for the most reactive solutes.
Combined Effect of Infiltration, Capillary Barrier and Sloping Layered Soil on Flow and Solute Transfer in a Heterogeneous Lysimeter  [PDF]
Le Binh Bien, Dieuseul Predelus, Laurent Lassabatere, Thierry Winiarski, Rafael Angulo-Jaramillo
Open Journal of Modern Hydrology (OJMH) , 2013, DOI: 10.4236/ojmh.2013.33018
Abstract: This aim of this paper is to describe a study of the combined effect of infiltration, capillary barrier and sloping layered soil on both flow and solute transport processes in a large, physical model (1 × 1 × 1.6 m3) called LUGH (Lysimeter for Urban Groundwater Hydrology) and a 3D numerical flow model. Sand and a soil composed of a bimodal sand-gravel mixture were placed in the lysimeter to simulate one of the basic structural and textural elements of the heterogeneity observed in the vadose zone under an infiltration basin of Lyon (France). Water and an inert tracer (KBr) were injected from the top of the lysimeter using a specific water sprinkler system and collected at 15 different outlets at the bottom. The outlet flows and the 15 breakthrough curves obtained presented high heterogeneity, emphasising the establishment of preferential flows resulting from both capillary barrier and soil layer dip effects. Numerical modelling led to better understanding of the mechanisms responsible for these heterogeneous transfers and it was also used to perform a sensitivity analysis of the effects of water velocity (water and solute flux fed by the sprinkler) and the slope interface. The results show that decreasing velocity and increasing the slope of the interface can lead to the development of preferential flows. In addition, the offset of the centre of gravity of the flow distribution at the output increases linearly as a function of the slope angle of the layered soil. This paper provides relevant information on the coupling between hydrodynamic processes and pollutant transfer in unsaturated heterogeneous soil and emphasizes the role of the geometry of the interfaces between materials and boundary conditions as key factors for preferential flow.

Assessing the Mobility of Lead, Copper and Cadmium in a Calcareous Soil of Port-au-Prince, Haiti
Urbain Fifi,Thierry Winiarski,Evens Emmanuel
International Journal of Environmental Research and Public Health , 2013, DOI: 10.3390/ijerph10115830
Abstract: The presence of heavy metals in the environment constitutes a potential source of both soil and groundwater pollution. This study has focused on the reactivity of lead (Pb), copper (Cu) and Cadmium (Cd) during their transfer in a calcareous soil of Port-au-Prince (Haiti). Kinetic, monometal and competitive batch tests were carried out at pH 6.0. Two simplified models including pseudo-first-order and pseudo-second-order were used to fit the experimental data from kinetics adsorption batch tests. A good fit of these data was found with pseudo-second-order kinetic model which indicates the applicability of this model to describe the adsorption rates of these metals on the soil. Monometal batch tests indicated that both Langmuir and Freundlich models allowed a good fit for experimental data. On the basis of the maximum adsorption capacity ( q max), the order affinity of Pb, Cu and Cd for the studied soil was Pb 2+ > Cu 2+ > Cd 2+. Competitive sorption has proved that the competition between two or several cations on soils for the same active sites can decrease their q max. These results show that, at high metal concentrations, Cd may pose more threat in soils and groundwater of Port-au-Prince than Pb and Cu.
Tracing Water Flow and Colloidal Particles Transfer in an Unsaturated Soil  [PDF]
Dieuseul Prédélus, Laurent Lassabatere, Artur Paiva Coutinho, Cédric Louis, Thomas Brichart, Erij Ben Slimène, Thierry Winiarski, Rafael Angulo-Jaramillo
Journal of Water Resource and Protection (JWARP) , 2014, DOI: 10.4236/jwarp.2014.67067

In recent years, many studies have been carried out on colloidal particle transfer in the unsaturated zone because they can be a risk to the environment either directly or as a vector of pollutants. A study was conducted on the influence of porous media structure in unsaturated conditions on colloidal particle transport. Three granular materials were set up in columns to replicate a fluvio-glacial soil from the unsaturated zone in the Lyon area (France). It is a sand, a bimodal mixture in equal proportion by weight of sand and gravel, and a fraction of bimodal mixture. Nanoparticles of silica (SiO2-Au-FluoNPs), having a hydrodynamic diameter between 50 and 60 nm, labeled by organic fluorescent molecules were used to simulate the transport of colloidal particles. A nonreactive tracer, bromide ion (Br-) at a concentration of C0,s = 10-2 M was used to determine the hydrodispersive properties of porous media. The tests were carried out first, with a solution of nanoparticles (C0,p = 0.2 g/L) and secondly, with a solution of nanoparticles and bromine. The transfer model based on fractionation of water into two phases, mobile and immobile, MIM, correctly fits the elution curves. The retention of colloidal particles is greater in the two media of bimodal particle size than that in the sand, which clearly demonstrates the role of textural heterogeneity in the retention mechanism. The increase in ionic strength produced by alimenting the columns with colloidal particle suspension in the presence of bromide, increases retention up to 25% in the sand. The total concentration profile of nanoparticles collected at the end of the experiment shows that the colloidal particles are retained primarily at the entrance of the columns. Hydrodispersive calculated parameters indicate

Vadose Zone Heterogeneity Effect on Unsaturated Water Flow Modeling at Meso-Scale  [PDF]
Artur Paiva Coutinho, Laurent Lassabatere, Thierry Winiarski, Jaime Joaquim da Silva Pereira Cabral, Antonio Celso Dantas Antonino, Rafael Angulo-Jaramillo
Journal of Water Resource and Protection (JWARP) , 2015, DOI: 10.4236/jwarp.2015.74028
Abstract: The understanding of unsaturated flow in heterogeneous formations is a prerequisite to the understanding of pollutant transfer in the vadose zone and the proper management of infiltration basins settled over such heterogeneous formations. This study addresses the effect of lithological heterogeneity of a glaciofluvial deposit on flow in the vadose zone underneath an infiltration basin settled in the Lyon suburbs. The basin had already been the subject of several previous studies, some of which demonstrated the impact of soil heterogeneity. But all of them were only based on the sedimentological study of a trench and no study addressed the potential spatial variability of results due to the spatial variability of soil heterogeneity. In this study, we model flow in the vadose zone for several case studies, including drainage, water infiltration during a rainfall event, and a complete meteorological chronic. These calculations were conducted for several sections, previously characterized in the basin using GPR and sedimentological study and compared with a blank (homogeneous section). The results clearly show that heterogeneity impacts unsaturated flow and that these impacts depend upon the section considered. Some geometrical architectural and textural parameters were proposed to explain the spatial variability and effect of the soil heterogeneity on unsaturated flow, thus establishing the first step towards modeling unsaturated flow in the basin at the meso-scale.
The risk in IT projects – statistical evaluation tools
Jacek Winiarski
Contemporary Economy , 2012,
Abstract: The purpose of this article is to present the possibility of using statistical tools to assess the magnitude of the threat of projects. The text presents the author’s interpretation of the phenomenon of the risk inherent in the process of implementing IT projects and assesses the usefulness of selected statistical tools that can be used in the analysis of the risks that could cause derogation to the planned size of the resources of the project.
On weights which admit the reproducing kernel of Bergman type
Zbigniew Pasternak-Winiarski
International Journal of Mathematics and Mathematical Sciences , 1992, DOI: 10.1155/s0161171292000012
Abstract: In this paper we consider (1) the weights of integration for which the reproducing kernel of the Bergman type can be defined, i.e., the admissible weights, and (2) the kernels defined by such weights. It is verified that the weighted Bergman kernel has the analogous properties as the classical one. We prove several sufficient conditions and necessary and sufficient conditions for a weight to be an admissible weight. We give also an example of a weight which is not of this class. As a positive example we consider the weight (z)=(Imz)2 defined on the unit disk in ¢ .
The band-gap of Tl-doped gallium nitride alloys
M. J. Winiarski
Physics , 2015, DOI: 10.1016/j.commatsci.2015.06.013
Abstract: Structural and electronic properties of hypothetical zinc blende Tl(x)Ga(1-x)N alloys have been investigated from first principles. The structural relaxation, preformed within the LDA approach, leads to a linear dependence of the lattice parameter a on the Tl content x. In turn, band structures obtained by MBJLDA calculations are significantly different from the corresponding LDA results. The decrease of the band-gap in Tl-doped GaN materials (for x<0.25) is predicted to be a linear function of x, i.e. 0.08 eV per atomic % of thallium. The semimetallic character is expected for materials with x>0.5. The obtained spin-orbit coupling driven splitting between the heavy-hole and split-off band at the Gamma point of the Brillouin zone in Tl(x)Ga(1-x)N systems is significantly weaker when compared to that of Tl-doped InN materials.
Electronic structure of non-centrosymmetric superconductors Re24(Nb;Ti)5 by ab initio calculations
M. J. Winiarski
Physics , 2014, DOI: 10.1016/j.jallcom.2014.07.081
Abstract: Electronic structures of superconducting Re24Nb5 and Re24Ti5 have been calculated employing the full-potential local-orbital method within the density functional theory. The investigations were focused on the influence of the antisymmetric spin-orbit coupling on band structures and Fermi surfaces of these non-centrosymmetric systems. The predicted here density of states at the Fermi level for Re24Ti5 is abnormally low with respect to that deduced from previous heat capacity measurements. This discrepancy suggests an intermediate coupled superconducting state in Re24Ti5. The differences between electronic properties of both compounds could explain more robust superconductivity in the Nb-based material.
Rzadsze ro liny naczyniowe z obszaru Lublina
Anna Rysiak , Florian wi s , Piotr winiarski
Annales UMCS, Agricultura , 2008, DOI: 10.2478/v10081-008-0005-6
Abstract: In the territory of Lublin the abudance of the synanthropic flora, both native (apophytes) and foreign or brought in (anthropophytes) is worth noting. There is a serious fear that most of these synanthropic plants, which previously made their home exclusively or most often in Lublin as compared with the neighboring areas, may spread beyond the boundaries of the city, threatening the local plants to a differing degree. The paper lists the stations of more rare vascular plants on a regional and national scale, discovered within the city of Lublin. While describing the plant stations, all kinds of information collected about them were taken into consideration. Unpublished herbarium materials and those published from strictly defined stations as well as those without specified locations were taken into account. With the latter type of stations, only source information was given. With new plant stations, their detailed descriptions were presented: their location in the ATPOL grid squares, sites of their occurrence in specific parts of Lublin, main habitat conditions and the approximate number of plant specimens.
Page 1 /2898
Display every page Item

Copyright © 2008-2017 Open Access Library. All rights reserved.