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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)

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See detailElectrical resistivity and magnetic susceptibility of NpNi2Al3 and NpPd2Al3
Seret, Alain ULg; Wastin, Frank; Bednarczyk, Eugène et al

Poster (1994, April)

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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 resistivyt tomography as tool to image preferential flow pathways in soils
Kasteel, Roy; Garré, Sarah ULg; Koestel, Johannes et al

Conference (2009)

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See detailElectrical stimulation as a modality to improve performance of the neuromuscular system
Vanderthommen, Marc ULg; Duchateau, Jacques

in Exercise and Sport Sciences Reviews (2007), 35(4), 180-185

Transcutaneous neuromuscular electrical stimulation (NMES) can modify the order of motor unit recruitment and has a profound influence on the metabolic demand associated with producing a given muscle ... [more ▼]

Transcutaneous neuromuscular electrical stimulation (NMES) can modify the order of motor unit recruitment and has a profound influence on the metabolic demand associated with producing a given muscle force. Because of these differences, interventions that combine NMES with voluntary contractions can provide beneficial outcomes for some individuals. The adaptations evoked by NMES are not confined to the activated muscle but also involve neural adaptations through reflex inputs to the spinal cord and supraspinal centers. [less ▲]

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See detailElectrical tomography investigation in bubble columns
Toye, Dominique ULg; Fransolet, Emmanuelle; Léonard, Angélique ULg et al

Scientific conference (2004, August)

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See detailElectrical transport and magnetic properties of Mn3O4-La0.7Ca0.3MnO3 ceramic composites prepared by a one-step spray-drying technique
Vertruyen, Bénédicte ULg; Fagnard, Jean-François ULg; Vanderbemden, Philippe ULg et al

in Journal of the European Ceramic Society (2007), 27(13-15), 3923-3926

La0.7Ca0.3MnO3/Mn3O4 composites can be synthesized in one step by thermal treatment of a spray-dried precursor, instead of mixing pre-synthesized powders. Another advantage of this composite system is ... [more ▼]

La0.7Ca0.3MnO3/Mn3O4 composites can be synthesized in one step by thermal treatment of a spray-dried precursor, instead of mixing pre-synthesized powders. Another advantage of this composite system is that a long sintering step can be used without leading to significant modification of the manganite composition. The percolation threshold is reached at ~ 20 vol% of manganite phase. The 77 K low field magnetoresistance is enhanced to ~ 11 % at 0.15 T when the composition is close to the percolation threshold. (c) 2007 Elsevier Ltd. All rights reserved. [less ▲]

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See detailElectrical transport and percolation in magnetoresistive manganite/insulating oxide composites: Case of La0.7Ca0.3MnO3/Mn3O4
Vertruyen, Bénédicte ULg; Cloots, Rudi ULg; Ausloos, Marcel ULg et al

in Physical Review. B (2007), 75(16), 165112

We report the results of electrical resistivity measurements carried out on well-sintered La0.7Ca0.3MnO3/Mn3O4 composite samples with almost constant composition of the magnetoresistive manganite phase ... [more ▼]

We report the results of electrical resistivity measurements carried out on well-sintered La0.7Ca0.3MnO3/Mn3O4 composite samples with almost constant composition of the magnetoresistive manganite phase (La0.7Ca0.3MnO3). A percolation threshold (phi c) occurs when the La0.7Ca0.3MnO3 volume fraction is ~ 0.19. The dependence of the electrical resistivity rho as a function of La0.7Ca0.3MnO3 volume fraction fLCMO can be described by percolationlike phenomenological equations. Fitting the conducting regime (fLCMO > phic) by the percolation power law rho # (fLCMO - phic)^(-t) returns a critical exponent value of 2.0±0.2 at room temperature and 2.6±0.2 at 5 K. The increase of t is ascribed to the influence of the grain boundaries on the electrical conduction process at low temperature. (C) 2007 The American Physical Society. [less ▲]

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See detailElectrical transport in saturated and conjugated molecular wires
Remacle, Françoise ULg; Levine, R. D.

in Faraday Discussions (2006), 131

The mechanism for charge transport in dithio molecular wires tethered between two gold electrodes is investigated, using both a steady state and a time-dependent quantum mechanical approach. The interface ... [more ▼]

The mechanism for charge transport in dithio molecular wires tethered between two gold electrodes is investigated, using both a steady state and a time-dependent quantum mechanical approach. The interface with the electrodes is modeled by two gold clusters and the electronic structure of the entire Au-n-S-bridge-S-Au-n system is computed ab initio at the DFT level and semi-empirically, with the extended Huckel theory. Current vs. applied bias, I-V, curves are computed using a scattering Landauer-type formalism in a steady state picture. The applied source-drain and gate voltages are included at the ab initio level in the electronic Hamiltonian and found to influence strongly the I-V characteristics. The time evolution of a non stationary electronic wave packet initially localized on a gold atom at one end of the extended system shows that charge transfer proceeds sequentially, by a hopping mechanism, to the opposite end. Analysis of the effective one electron Hamiltonian matrix shows that the sulfur atom endows a resistive character to the Au-C-S junctions. The S atoms are however rather well coupled to both the gold and carbon atoms so that typically the super exchange limit for electron transfer is not reached unless the molecular bridge is saturated and the Fermi window function is narrow. [less ▲]

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See detailElectrically addressing a molecule-like donor pair in silicon: An atomic scale cyclable full adder logic
YAN, Yonghong; Mol, J. A.; Verduijn, J. et al

in Journal of Physical Chemistry C: Nanomaterials, Interfaces, and Hard Matter (2010), 114

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See detailElectrification Rurale. Vers une technique innovatrice pour l'Afrique.
Lilien, Jean-Louis ULg; omboua, Alphonse

in Revue d'electricité et d'électronique industrielle (2006), N°1-2006

In many developing countries , there are a lot of high voltage lines which cross many regions to supply electricity to the main towns or connect to networks the distanced electric substations . These ... [more ▼]

In many developing countries , there are a lot of high voltage lines which cross many regions to supply electricity to the main towns or connect to networks the distanced electric substations . These lines, used for supplying electricity to big towns, cross a lot of villages whose people broadly poor hope to be supplied with electricity without a suitable solution. However it seems very deplorable that the power conducted by these lines doesn’t profit to surrounding population. Unfortunately , for these villages , the use of classical substations is too expensive to the power distributors because of high cost of investment and production for these potential scattered consumers with the low demand of electricity. This paper presents the original solution settled in 2002 in one of the village located in Congo Brazzaville and continue to operate correctly in 2006. It is a new power transformer, based on the technique of SF6 measuring transformer, which is connected on one phase of the high voltage line 220kV and which produces the low voltage 230 V directly useful by the rural population. This prototype sample for the rural electrification has been designed to deliver a power of 50kVA. A cheap and robust system ! It requires a large popularization, mainly in sub saharian Africa that has got many such opportunities. Outside the role of bulk power transmission, the high voltage line is now also able to distribute a part of it. [less ▲]

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See detailElectro-assisted assembly of aliphatic thiol, dithiol and dithiocarboxylic acid monolayers on copper
Maho, Anthony ULg; Denayer, Jessica ULg; Delhalle, J. et al

in Electrochimica Acta (2011), 56(11), 3954-3962

Molecular assemblies of organothiol molecules on polycrystalline copper surfaces are a well known process to confer them specific organizational and protective properties. In this paper, an original and ... [more ▼]

Molecular assemblies of organothiol molecules on polycrystalline copper surfaces are a well known process to confer them specific organizational and protective properties. In this paper, an original and promising approach is considered through an electro-assisted adsorption process via a cathodic polarization of the copper substrate. Spectroscopic characterizations (PM-IRRAS, XPS) and electrochemical studies (CV, LSV, cathodic desorption, SECM) highlight and confirm the benefits brought by this methodology in terms of resulting SAMs features and considerable savings of preparation time. In addition to normal alkylthiols with a monopod anchoring group, alkyldithiocarboxylic acid and alkyldithiol monolayers - both bipodal - are characterized with the prospect of forming either easier to remove or more adherent films, respectively. © 2011 Elsevier Ltd. All rights reserved. [less ▲]

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See detailElectro-mechanical Coupling in MEMS: Modeling and Experimental Validation
Rochus, Véronique ULg; Golinval, Jean-Claude ULg

Scientific conference (2007)

This paper presents the advantages of a strong coupled formulation to model the electro-mechanical coupling appearing in MEMS. The classical modeling approach is to use a staggered methodology iterating ... [more ▼]

This paper presents the advantages of a strong coupled formulation to model the electro-mechanical coupling appearing in MEMS. The classical modeling approach is to use a staggered methodology iterating between two different programs to obtain the solution of the coupled problem. In this research a strong coupled formulation is proposed and a tangent stiffness matrix of the whole problem is computed. Using this matrix, nonlinear algorithms such as the Riks-Crisfield algorithm may be applied to solve the static nonlinear problem and accurately determine the static pull-in voltage. Moreover, the natural frequencies may be computed around each equilibrium positions. The dynamic behavior of the structure may also be studied and two new parameters are defined: the dynamic pull-in voltage and the dynamic pull-in time. This strong coupled methodology deriving from variational principle may also be used for topology optimization and extended finite elements. [less ▲]

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