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See detailElectrical conduction by interface states in semiconductor heterojunctions
El Yacoubi, Mohamed; Evrard, Roger ULg; Nguyen, Ngoc Duy ULg et al

in Semiconductor Science & Technology (2000), 15

Electrical conduction in semiconductor heterojunctions containing defect states in the interface region is studied. As the classical drift-diffusion mechanism cannot in any case explain electrical ... [more ▼]

Electrical conduction in semiconductor heterojunctions containing defect states in the interface region is studied. As the classical drift-diffusion mechanism cannot in any case explain electrical conduction in semiconductor heterojunctions, tunnelling involving interface states is often considered as a possible conduction path. A theoretical treatment is made where defect states in the interface region with a continuous energy distribution are included. Electrical conduction through this defect band then allows the transit of electrons from the conduction band of one semiconductor to the valence band of the second component. The analysis is initiated by electrical measurements on n-CdS/p-CdTe heterojunctions obtained by chemical vapour deposition of CdS on (111) oriented CdTe single crystals, for which current--voltage and capacitance--frequency results are shown. The theoretical analysis is based on the numerical resolution of Poisson's equation and the continuity equations of electrons, holes and defect states, where a current component corresponding to the defect band conduction is explicitly included. Comparison with the experimental curves shows that this formalism yields an efficient tool to model the conduction process through the interface region. It also allows us to determine critical values of the physical parameters when a particular step in the conduction mechanism becomes dominant. [less ▲]

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See detailElectrical conductivity in carbon black-loaded polystyrene-polyisoprene blends. Selective localization of carbon black at the interface
Soares, Bluma G; Gubbels, Frédéric; Jérôme, Robert ULg et al

in Polymer Bulletin (1995), 35(1-2), 223-228

The electrical conductivity of carbon-black loaded polystyrene-polyisoprene blends has been studied. In this ternary system, the filler is at the interface of co-continuous polyblends as confirmed by the ... [more ▼]

The electrical conductivity of carbon-black loaded polystyrene-polyisoprene blends has been studied. In this ternary system, the filler is at the interface of co-continuous polyblends as confirmed by the very low value of the filler percolation threshold (0.2 vol % for blends compression molded at 250 degrees C) and by optical microscopy. As a result of the selective localization of carbon black at the interface, the percolation threshold is very sensitive to the compression molding temperature. [less ▲]

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See detailElectrical conductivity of polystyrene-rubber blends loaded with carbon black
Soares, Bluma G.; Gubbels, Frédéric; Jérôme, Robert ULg et al

in Rubber Chemistry and Technology (1997), 70(1), 60-70

Detailed reference viewed: 23 (2 ULg)
See detailElectrical imaging in hydrogeophysics
Nguyen, Frédéric ULg

Scientific conference (2010, February 26)

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See detailElectrical investigation of TCMs: role of structural defects and external stress
Langley, Daniel ULg; Giusti, Gael; Consonni, Vincent et al

Conference (2012, October 24)

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See detailElectrical investigations of granular arches
Dorbolo, Stéphane ULg; Vandewalle, Nicolas ULg

in Physica A: Statistical Mechanics and its Applications (2002), 311(3-4), 307-312

Compaction dynamics and granular arches have been studied using the electrical resistance of a packing. An exponential decay of the resistance is found whatever the electrical current is. A fluctuation ... [more ▼]

Compaction dynamics and granular arches have been studied using the electrical resistance of a packing. An exponential decay of the resistance is found whatever the electrical current is. A fluctuation regime is then encountered. A characteristic relaxation time has been pointed out and is linked to the arch formation in the system. (C) 2002 Elsevier Science B.V. All rights reserved. [less ▲]

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See detailElectrical machine analysis considering field-circuit-movement and skewing effects
de Oliveira, Ana Margarida; Antunes, R.; Kuo-Peng, Patrick et al

in Compel-the International Journal for Computation and Mathematics in Electrical and Electronic Engineering (2004), 23(4), 1080-1091

This paper presents a method to analyse electrical machines considering simultaneously the electromagnetic field, electric circuit, control loop, movement and skewing effects. The major contribution of ... [more ▼]

This paper presents a method to analyse electrical machines considering simultaneously the electromagnetic field, electric circuit, control loop, movement and skewing effects. The major contribution of this work leans on its generality, i.e. it can be applied to electrical machines connected to static converters submitted to any control laws, avoiding an a priori analysis. Simulation results of a three-phase Brushless AC (BLAC) motor fed by a PWM converter is presented as well as a comparison of simulation and experimental results obtained using a two-phase-on converter were also presented. [less ▲]

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See detailElectrical mapping of spontaneous ventricular fibrillation in acutely ischemic pigs.
Desaive, Thomas ULg; Janssen, Nathalie; Péters, Fabrise et al

in Proceedings of the 5th Belgian Day on Biomedical Engineering, 2005, Brussels (2005)

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See detailElectrical microenvironment influence on the hydrolytic activity of free and immobilised Yarrowia lipolytica lipase
Paquot, Michel ULg; Deleu, Magali ULg; Beaufils, C. et al

in Biotechnology Letters (1996), 18(1), 73-78

The role of electrical properties of interfaces upon the activity of free and immobilised Yarrowia lipolytica lipase has been investigated. Sodium taurocholate and Sedipur 400, an anionic polyacrylamide ... [more ▼]

The role of electrical properties of interfaces upon the activity of free and immobilised Yarrowia lipolytica lipase has been investigated. Sodium taurocholate and Sedipur 400, an anionic polyacrylamide, enhance the negative character of the fatty droplets of substrate and tend to improve the lipolytic activity while the cationic polyacrylamide (Sedipur 900) has opposite effects. Ca+ which reduces the fatty droplets charge as Sedipur 900, is however a good activator of the enzyme. The role of electrical properties on the optimum pH of the immobilised enzyme is clearer. Immobilisation of the lipase on a positively charged support shifts its optimum pH to acidic pH by repulsion towards H+ ions around the support. [less ▲]

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See detailElectrical modelling of interface traps in GeSn MOS structures
Baert, Bruno ULg; Cerica, Delphine ULg; Schmeits, Marcel ULg et al

Conference (2014, November 13)

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See detailElectrical properties of improper ferroelectrics from first principles
Stengel, Massimiliano; Fennie, Craig J.; Ghosez, Philippe ULg

in Physical Review. B, Condensed Matter and Materials Physics (2012), 86

We study the interplay of structural and polar distortions in hexagonalYMnO3 and short-period PbTiO3/SrTiO3 (PTO/STO) superlattices by means of first-principles calculations at constrained electric ... [more ▼]

We study the interplay of structural and polar distortions in hexagonalYMnO3 and short-period PbTiO3/SrTiO3 (PTO/STO) superlattices by means of first-principles calculations at constrained electric displacement field D. We find that in YMnO3 the tilts of the oxygen polyhedra produce a robustly polar ground state, which persists at any choice of the electrical boundary conditions. Conversely, in PTO/STO the antiferrodistortive instabilities alone do not break inversion symmetry, and open-circuit boundary conditions restore a nonpolar state.We suggest that this qualitative difference naturally provides a route to rationalizing the concept of “improper ferroelectricity” from the point of view of first-principles theory. We discuss the implications of our arguments for the design of novel multiferroic materials with enhanced functionalities and for the symmetry analysis of the phase transitions. [less ▲]

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See detailElectrical resistance tomography sensor simulations: comparison with experiments
Fransolet, E.; Crine, Michel ULg; L'Homme, Guy ULg et al

in Measurement Science & Technology (2002), 13(8), 1239-1247

This paper compares experimental results (differences of potential), obtained with a 16-electrode electrical resistance tomography (ERT) device using the adjacent-electrode pair measurement strategy, with ... [more ▼]

This paper compares experimental results (differences of potential), obtained with a 16-electrode electrical resistance tomography (ERT) device using the adjacent-electrode pair measurement strategy, with finite-element method (FEM) simulations in two and three dimensions. In the first part of the paper, ERT measurements made on a homogeneous medium are compared with two- and three-dimensional FEM simulations. It is shown that the dependence of the electrical field on the axial coordinate cannot be neglected. Consequently, only the three-dimensional FEM simulations are able to fit the experimental results. In the second part of the paper, ERT measurements on static physical phantoms immersed in water evidence that ERT is significantly more sensitive to non-symmetrical distributions than to symmetrical ones. This observation is confirmed by three-dimensional FEM simulations performed on numerical phantoms that mimic the physical ones. In the last part of the paper, an attempt to use three-dimensional simulations to determine the characteristics (diameter and gas content) of a gas core created by injecting a gas flow from a single-orifice gas sparger leads to promising results. [less ▲]

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See detailElectrical resistivity and magnetic susceptibility measurements on Np2T2X compounds
Pereira, Laura C.J.; Seret, Alain ULg; Wastin, Frank et al

Poster (1995, April)

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See detailElectrical resistivity and magnetic susceptibility of AnT2Al3 (An = Np, Pu; T = Ni, Pd)
Seret, Alain ULg; Wastin, Franck; Warenborgh, Joan-Carlos et al

Poster (1994, August)

Detailed reference viewed: 5 (0 ULg)
See detailElectrical resistivity and magnetic susceptibility of NpNi2Al3 and NpPd2Al3
Seret, Alain ULg; Wastin, Frank; Bednarczyk, Eugène et al

Poster (1994, April)

Detailed reference viewed: 20 (1 ULg)
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See detailElectrical Resistivity Monitoring of Heat Tracer to Characterize Lab-Scale Hydraulic Conductivity Distributions
Adetokunbo, Peter; Hermans, Thomas ULg; Oware, Erasmus

Poster (2016, December 14)

Knowledge of the spatial variations of hydraulic conductivity (K) is crucial to almost every hydrogeological investigation. The representative scale of K estimates from traditional slug and pumping tests ... [more ▼]

Knowledge of the spatial variations of hydraulic conductivity (K) is crucial to almost every hydrogeological investigation. The representative scale of K estimates from traditional slug and pumping tests are, however, inadequate to accurately predict hydrogeological processes. There is increasing interest in the application of electrical resistivity tomography (ERT) to quantify spatially continuous K variations. ERT estimation of high-resolution K distributions, however, requires continuous injection of saline tracer (ST) into an aquifer over an extended period, which is feasible but impractical. Here, we present electrical resistivity thermography (ERTh) to evaluate the potential application of time-lapse ER monitoring of heat tracer (HT) to characterize high-resolution K architectures. Unlike ST, long term HT experiments are comparatively easier to manage and repeatable with minimal environmental impact. We estimate K variations via petrophysical coupling of flow and heat transport with joint time-lapse ER and discrete multi-level temperature breakthrough curves. We illustrate the strategy with a 2-D lab-scale sandbox experiment. To construct the heterogeneous field, three lenses with high-K properties with each consisting of gravel, coarse sand, and a mixture of coarse and fine sand, were created within a background of comparatively low-K fine sand. The experiment involved continuous injection and extraction of heat, respectively, at the left and right boundaries of the lab-scale aquifer. We simultaneously performed time lapse ER monitoring of the heat transport and temperature measurements at four discrete multi-levels near the heat extraction well. Results of the coupled inversions demonstrate that ER monitoring of heat tracer provides a unique opportunity to characterize high-resolution spatially continuous K variations, which seems more practical for field applications in contrast to that of the traditional ST. [less ▲]

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See detailElectrical resistivity of AnT2Al3 (An = Np, Pu; T = Ni, Pd)
Seret, Alain ULg; Wastin, Franck; Waerenborgh, Joan-Carlos et al

in Physica B: Condensed Matter (1995), 206 & 207

Structural data and resistivity studies of NpNi2Al3, NpxU1−xPd2Al3 (x = 1, 0.5, 0.3, 0.1) and PuPd2Al3 are reported. The resistivity curves display Kondo features and clear anomalies at the magnetic ... [more ▼]

Structural data and resistivity studies of NpNi2Al3, NpxU1−xPd2Al3 (x = 1, 0.5, 0.3, 0.1) and PuPd2Al3 are reported. The resistivity curves display Kondo features and clear anomalies at the magnetic transition. Moreover, at least two kinds of magnetic structure exist in these compounds, one favouring the electrical conductivity and the other decreasing it. [less ▲]

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See detailElectrical resistivity tomography and self-potential case studies for fractured aquifer characterization and monitoring
Robert, Tanguy ULg; Dassargues, Alain ULg; Nguyen, Frédéric ULg

in Geophysical Research Abstracts (2010), 12

Electrical resistivity tomography (ERT) and self-potential (SP) investigations have been conducted in complex carboniferous limestones aquifers in Belgium (synclinorium structures). The aims of this study ... [more ▼]

Electrical resistivity tomography (ERT) and self-potential (SP) investigations have been conducted in complex carboniferous limestones aquifers in Belgium (synclinorium structures). The aims of this study were (1) to detect and characterize fractured zones in hard rock aquifers, (2) to monitor groundwater flow/water content in these fractured or karstic areas and (3) to use geophysical data to support groundwater flow model set-up and calibration. The investigated areas lie in calcareous synclines. Electrical images allowed us to detect and characterize (in terms of direction, width and depth) several less resistive anomalies, which are interpreted in terms of fractured and/or karstic zones. To interpret the ERT images, data errors as well as image appraisal indicators (resolution matrix, sensitivity matrix and DOI index) were analysed and compared. This allowed us to determine the depth of investigation of ERT and to avoid the misinterpretation of the resulting images. Inversions based on focusing scheme are tested against smoothness-constraint inversion on these field data to provide more realistic images on the basis of prior geological knowledge. Self-potential measurements were performed along the electrical profiles and allowed us to find negative anomalies possibly related with groundwater preferential flow pathways. By taking the assumption that only the electrokinetic effect plays a role in the SP signals, we were able to estimate a first distribution of the water table along our profiles. The SP data showed that in this particular tectonic structure, two perpendicular hydraulic gradients are present. The first gradient is related with the main fold axis direction and is the major drainage system. The second hydraulic gradient is related with the flanks of the calcareous valley. Geophysical data concurrently with ‘ground truth’ geological and hydrogeological data allowed us to better understand the groundwater flow in these calcareous synclines and to verify the conceptual groundwater flow model. [less ▲]

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See detailElectrical resistivity tomography and self-potential methods as a tool for fractured aquifer characterization and monitoring
Robert, Tanguy ULg; Nguyen, Frédéric ULg

Poster (2010, January 12)

Electrical resistivity tomography (ERT) and self-potential (SP) investigations are currently conducted in carboniferous limestones in Belgium. The aims of this study are (1) to characterize and (2) to ... [more ▼]

Electrical resistivity tomography (ERT) and self-potential (SP) investigations are currently conducted in carboniferous limestones in Belgium. The aims of this study are (1) to characterize and (2) to monitor the groundwater flow in fractured or karstic area and (3) to use these geophysical data as a help for groundwater flow model conceptualisation and inverse calibration. Large ERT profiles (320 meters) allow us to image the electrical resistivity distribution of the first 60 meters of the subsurface and to detect and characterize (in terms of direction, width and depth) some fractured and/or karstic zones expected to be less resistive. Data errors as well as indicators of resolution (resolution matrix, sensitivity matrix and DOI index) are analysed in order to calculate the depth of investigation of ERT and to avoid the misinterpretation of the resulting images. Self-potential measurements are performed along the electrical profiles and permit us to find some negative anomalies possibly related with groundwater preferential flow pathways. Since SP signals are related with the groundwater flow when taking into account the electrokinetic effect, we are able to estimate a first distribution of the water table along our profiles. These geophysical data concurrently with ‘ground truth’ geological and hydrogeological data give us a way to better understand the groundwater flow in limestone synclines of the Dinant Synclinorium geological structure. Still, further efforts are needed (1) to fully cover the syncline area and (2) to couple the SP, ERT and hydrogeological data through a more complex forward model of the electrokinetic effect of the self-potential method. [less ▲]

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See detailElectrical resistivity tomography to monitor enhanced biodegradation of hydrocarbons with Rhodococcus erythropolis T902.1 at a pilot scale
Masy, Thibaut ULg; Caterina, David; Tromme, Oliver et al

in Journal of Contaminant Hydrology (2016), 184

Petroleum hydrocarbons (HC) represent the most widespread contaminants and in-situ bioremediation remains a competitive treatment in terms of cost and environmental concerns. However, the efficiency of ... [more ▼]

Petroleum hydrocarbons (HC) represent the most widespread contaminants and in-situ bioremediation remains a competitive treatment in terms of cost and environmental concerns. However, the efficiency of such a technique (by biostimulation or bioaugmentation) strongly depends on the environment affected and is still difficult to predict a priori. In order to overcome these uncertainties, Electrical Resistivity Tomography (ERT) appears as a valuable non-invasive tool to detect soil heterogeneities and to monitor biodegradation. The main objective of this study was to isolate an electrical signal linked to an enhanced bacterial activity with ERT, in an aged HC-contaminated clayey loam soil. To achieve this, a pilot tank was built to mimic field conditions. Compared to a first insufficient biostimulation phase, bioaugmentation with Rhodococcus erythropolis T902.1 led to a HC depletion of almost 80% (6900 to 1600 ppm) in 3 months in the center of the contaminated zone, where pollutants were less bioavailable. In the meantime, lithological heterogeneities and microbial activities (growth and biosurfactant production) were successively discriminated by ERT images. In the future, this cost-effective technique should be more and more transferred to the field in order to monitor biodegradation processes and assist in selecting the most appropriate remediation technique. [less ▲]

Detailed reference viewed: 123 (37 ULg)