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See detailHydrogen-Saturated Silicon Nanowires Heavily Doped with Interstitial and Substitutional Transition Metals
Durgun, E.; Bilc, Daniel ULg; Ciraci, S. et al

in Journal of Physical Chemistry C: Nanomaterials, Interfaces, and Hard Matter (2012), 116

We report a first-principles systematic study of atomic, electronic, and magnetic properties of hydrogen-saturated silicon nanowires (H-SiNW) that are heavily doped by transition metal (TM) atoms placed ... [more ▼]

We report a first-principles systematic study of atomic, electronic, and magnetic properties of hydrogen-saturated silicon nanowires (H-SiNW) that are heavily doped by transition metal (TM) atoms placed at various interstitial and substitutional sites. Our results obtained within the conventional GGA+U approach have been confirmed using a hybrid functional. To reveal the surface effects, we examined three different possible facets of HSiNW along the [001] direction with a diameter of ∼2 nm. The energetics of doping and resulting electronic and magnetic properties are examined for all alternative configurations. We found that except Ti, the resulting systems have a magnetic ground state with a varying magnetic moment. Whereas H-SiNWs are initially nonmagnetic semiconductor, they generally become ferromagnetic metal upon TM doping. They can even exhibit half-metallic behavior for specific cases. Our results suggest that H-SiNWs functionalized by TM impurities form a new type of dilute magnetic semiconductor potentially attractive for new electronic and spintronic devices on the nanoscale. [less ▲]

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See detailHydrogeological assessment of diaphragm walls used to excavate deep shafts associated to tunnels construction
Pujades, Estanislao ULg; Jurado, Anna; Carrera, Jesus et al

Poster (2015, September 17)

Deep shafts are usually required during tunnels construction (for maintenance tasks when tunnel boring machines –TBM- are used) and/or the operation stage of tunnels (emergency exits). Generally, these ... [more ▼]

Deep shafts are usually required during tunnels construction (for maintenance tasks when tunnel boring machines –TBM- are used) and/or the operation stage of tunnels (emergency exits). Generally, these shafts are constructed below the water table and by the cut and cover method. Therefore, impervious diaphragm walls are desired for two main reasons: (1) to reduce risks (stability, inflows, flooding, etc.) and outside impacts (loose of groundwater resource, holes and sinkholes, etc.) during the excavation stage of a shaft and, (2) to avoid leaks and inflows of groundwater during the operation stage once the shaft is finished. Given that defects in diaphragm walls are frequent and can relatively easy be repaired before starting the excavation stage, a useful and new methodology to assess the state of enclosures before excavation is proposed. Its use would allow to reduce impacts on groundwater (construction and operation stages) and costs in case of defects as well as to increase the safety during the construction. The groundwater response regarding different scenarios of diaphragm walls is studied numerically in order to propose a successful procedure to evaluate underground enclosures imperviousness by internal pumping tests. The scenarios consist in circular and square enclosures where the diaphragm walls are assumed as homogeneous (with numerous defects) or heterogeneous (one discrete defect). The homogeneous cases are modeled by considering different effective hydraulic conductivities, while the size and position of the single defect is varied in the simulations of heterogeneous walls. An analysis of diagnostic plots and the comparison between the expected and measured groundwater evolutions inside the enclosure, is proposed to ascertain: (1) if the diaphragm walls can be considered as homogeneous or heterogeneous, (2) the effective hydraulic conductivity of the walls (if they are homogeneous) and, (3) the position of a defect (if they are heterogeneous). [less ▲]

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See detailHydrogeological conditions required for Underground Pumping Storage Hydroelectricity (UPSH) in old mines
Bodeux, Sarah ULg; Pujades, Estanislao ULg; Orban, Philippe ULg et al

in Abstract book (2016, January 26)

Renewable energy sources, because of their intermittence, could not afford a stable production and an adequate variability according to the energy demand. Underground Pumped Storage Hydroelectricity (UPSH ... [more ▼]

Renewable energy sources, because of their intermittence, could not afford a stable production and an adequate variability according to the energy demand. Underground Pumped Storage Hydroelectricity (UPSH) using abandoned mine works is an interesting alternative, in flat regions, to store energy during low demand periods by pumping water from an underground mine to an upper reservoir. From the hydrogeological point of view, two considerations can arise for studying the feasibility before constructing an UPSH plant: 1) the alteration of the natural conditions of surrounding aquifers, and (2) the efficiency of the plant depending on possible leakage in the cavities from the hydrogeological environment. A potential old slate mine was selected through a multi-criterion method and its geometrical and hydrogeological characteristics are used to build a simple but typical model. With the help of the HFEMC approach implemented in the code SUFT3D (HEG-ULg), the groundwater flows are modelled for a representative cavity. Simulations of groundwater flow induced by a UPSH system are performed and the main variables are identified. Piezometric heads around the reservoir oscillate, the magnitude of the oscillations and the time to achieve a pseudo-steady state (magnitude and head reached during oscillations not varying anymore with time) depend on the boundaries, the parameters of the aquifer and the characteristics of the underground reservoir. The required hydrogeological conditions are deduced and a screening methodology can be proposed to assess the main impacts caused in aquifers by UPSH plants. Their efficiency regarding the water level evolution inside the reservoir is also considered accommodating the cyclic pumped storage schemes. [less ▲]

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See detailHydrogeological data requirements for assessment of natural attenuation
Haerens, Bruno; Dassargues, Alain ULg

in Proceedings of the National Colloquium CBGI-BCGI ‘Réhabilitation des zones polluées, inventaire, gestion et assainissement / Herinrichting van verontreinigdde zones, inventaris, beheer en sanering (2002)

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See detailHydrogeological investigations at the Membach station, Belgium, and application to correct long periodic gravity variations
Van Camp, Michel; Vanclooster, Marnik; Crommen, O. et al

in Journal of Geophysical Research (2006), 111(B10),

A comprehensive hydrogeological investigation regarding the influence of variations in local and regional water mass on superconducting gravity measurements is presented for observations taken near the ... [more ▼]

A comprehensive hydrogeological investigation regarding the influence of variations in local and regional water mass on superconducting gravity measurements is presented for observations taken near the geodynamic station of Membach, Belgium. Applying a regional water storage model, the gravity contribution due to the elastic deformation of the Earth was derived. In addition, the Newtonian gravity effect induced by the local water mass variations was calculated, using soil moisture observations taken at the ground surface (about 48 m above the gravimeters). The computation of the gravimetric effect is based on a digital elevation model with spatially discretized rectangular prisms. The obtained results are compared with the observations of a superconducting gravimeter (SG). We find that the seasonal variations can be reasonably well predicted with the regional water storage model and the local Newtonian effects. Shorter-period effects depend on the local changes in hydrology. This result shows the sensitivity of SG observations to very local water storage changes. [less ▲]

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See detailHydrogeological mapping of the Walloon region (Belgium).
Bouezmarni, Mohamed ULg

in Proceedings of the 5th european congress on regional geoscientific cartography and information systems. (2006)

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See detailHydrogeological modeling of radionuclide transport in heterogeneous low-permeability media: a comparison between Boom Clay and Ieper Clay
Huysmans, Marijke; Dassargues, Alain ULg

in Soares, A.; Pereira, M. J.; Dimitrakopoulos, R. (Eds.) GeoENV VI: Geostatistics for Environmental Applications (2006)

Deep low-permeability clay layers are considered as possible suitable environments for disposal of high-level radioactive waste. In Belgium, the Boom Clay is the reference host formation and the Ieper ... [more ▼]

Deep low-permeability clay layers are considered as possible suitable environments for disposal of high-level radioactive waste. In Belgium, the Boom Clay is the reference host formation and the Ieper Clay an alternative host formation for research and safety and feasibility assessment of deep disposal of nuclear waste. In this study, two hydrogeological models are built to calculate the radionuclide fluxes that would migrate from a potential repository through these two clay formations. Transport parameters heterogeneity is incorporated in the models using stochastic sequential simulation of hydraulic conductivity, diffusion coefficient and diffusion accessible porosity, using primary information and several types of secondary information, i.e. resistivity, gamma ray and grain size. The calculated radionuclide fluxes in the two clay formations are compared. Results show that in the Ieper Clay larger differences between the fluxes through the lower and the upper clay boundary occur, larger total output radionuclide amounts are calculated, and a larger effect of parameter heterogeneity on the calculated fluxes is observed, compared to the Boom Clay. [less ▲]

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See detailHydrogeological modeling of radionuclide transport in low permeability media: a comparison between Boom Clay and Ypresian Clay
Huysmans, Marijke; Dassargues, Alain ULg

in Environmental Geology (2006), 50(1), 122-131

Deep low-permeability clay layers are considered as suitable environments for disposal of high-level radioactive waste. In Belgium, the Boom Clay is the reference host formation and the Ypresian Clay an ... [more ▼]

Deep low-permeability clay layers are considered as suitable environments for disposal of high-level radioactive waste. In Belgium, the Boom Clay is the reference host formation and the Ypresian Clay an alternative host formation for research and safety and feasibility assessment of deep disposal of nuclear waste. In this study, two hydrogeological models are built to calculate the radionuclide fluxes that would migrate from a potential repository through these two clay formations. Transport parameter heterogeneity is incorporated in the models using geostatistical co-simulations of hydraulic conductivity, diffusion coefficient and diffusion accessible porosity. The calculated radionuclide fluxes in the two clay formations are compared. The results show that in the Ypresian Clay larger differences between the fluxes through the lower and the upper clay boundary occur, larger total output radionuclide amounts are calculated and a larger effect of parameter heterogeneity on the calculated fluxes is observed, compared to the Boom Clay. [less ▲]

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See detailHydrogeological processes in fractured and porous media: insights from geophysical case studies
Robert, Tanguy ULg; Hermans, Thomas ULg; Nguyen, Frédéric ULg

Conference (2013, January 18)

This presentation focuses on geophysical case studies with the aim to highlight the possibilities to study and monitor hydrogeological processes in the subsurface, including transport processes in ... [more ▼]

This presentation focuses on geophysical case studies with the aim to highlight the possibilities to study and monitor hydrogeological processes in the subsurface, including transport processes in fractured or in porous media. The presentation emphasizes two geoelectrical methods, namely electrical resistivity tomography (ERT) which images the electrical resistivity distribution of the subsurface and self-potential (SP) whose measured signal is directly sensitive to groundwater fluxes. The first case study concerns the geophysical identification and characterization of large hydraulically-active fractured areas in calcareous synclines and in particular the assessment of the joint use of ERT and SP to set up new piezometers in fractured limestone. This assessment shows that piezometers drilled inside less resistive areas and/or in negative SP anomalies presented high hydraulic capacities. Inversely, piezometers drilled inside more resistive zones and/or outside an SP anomaly presented low hydraulic capacities. The SP anomaly related to preferential flow in fractures was thus demonstrated for the first time. All these fractures information, obtained with geophysics, improved the conceptualization and calibration of the groundwater flow model of the calcareous valley. A seasonal monitoring of SP signals proved to be a successful methodology to better understand the hydrodynamics of calcareous aquifers and in particular to follow the seasonal drawdown of the water table in the calcareous valley. Different methodologies to delineate the main groundwater flow direction were also tested. The latter can be achieved for example by drawing an SP map showing the main hydraulic gradients or by monitoring a salt tracer test with ERT to highlight preferential flow in fractures. The second case study concerns the ERT monitoring of a shallow geothermal test conducted in a porous medium (sand). The main objective of this study was to derive temperature from a series of electrical resistivity images since the electrical resistivity is directly sensitive to temperature changes. This field work demonstrates that surface electric resistivity tomography can monitor heat injection and storage experiments in shallow aquifers providing a number of practical applications, such as the monitoring or the design of shallow geothermal systems or the use of heated water to replace salt water in tracer tests. Through these two different case studies, this presentation also emphasizes in a practical way on the importance of data inversion and image appraisal since these issues are crucial to quantitatively study hydrogeological processes. [less ▲]

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See detailHydrogeological study and modelling to implement a groundwater restoration plan near leaking soda industry landfills
Brouyère, Serge ULg; Dassargues, Alain ULg; Michiels, Thierry

in 2nd Int. Symp. on Environmental Contamination, Budapest (1994)

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See detailHydrogeological study by geophysical prospection in Florennes
Dassargues, Alain ULg; Hallet, Vincent; Monjoie, Albéric

Report (1986)

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See detailHydrogeological study of Somes-Szamos transboundary alluvial aquifer
Drobot, Radu; Szucs, Peter; Brouyère, Serge ULg et al

in Ganoulis, Jacques; Aureli, Alice; Fried, Jean (Eds.) Transboundary Water Resources Management: A Multidisciplinary Approach (2011)

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See detailHydrogeological study of Somes-Szamos transboundary alluvial aquifer
Dassargues, Alain ULg; Drobot, Radu; Lenart, Laszlo et al

in Technical/Scientific Issues of Transboudary Water Management: Experience from around the world (2008)

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See detailHydrogeological survey at the Diegem IBM site – First stage and geophysical investigation
Biver, Pierre; Dassargues, Alain ULg; Monjoie, Albéric

Report (1988)

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See detailHydrogeological survey in Diegem (IBM) – Stage II – Drilling and pumping tests
Biver, Pierre; Dassargues, Alain ULg; Monjoie, Albéric

Report (1989)

Detailed reference viewed: 33 (0 ULg)
See detailHydrogéologie du bassin de la Semois. Quelques résultats des études financées par la Région wallonne.
Debbaut, Vincent ULg

in Tribune de l'Eau (La) (1989), 42(538), 32-35

Detailed reference viewed: 31 (1 ULg)