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See detailNon-invasive assessment of tumor hypoxia with the 2-nitroimidazole 18F-EF1 and PET.
HUSTINX, Roland ULg; EVANS, SM.; KACHUR, CY. et al

in Journal of Nuclear Medicine (The) (1999), 40

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See detailNon-invasive imaging of a giant right coronary artery due to a coronary fistula
Gach, Olivier ULg; Davin, Laurent ULg; Legrand, Victor ULg

in Acta Cardiologica (2006), 61(5), 569-571

Coronary artery fistula is a relatively rare finding in patients undergoing diagnostic cardiac catheterization. Incidence, angiographic characteristics and natural history of coronary fistulas of this ... [more ▼]

Coronary artery fistula is a relatively rare finding in patients undergoing diagnostic cardiac catheterization. Incidence, angiographic characteristics and natural history of coronary fistulas of this type have not been well defined in the literature. We report a case of a 54-year-old man in whom such abnormalities have been diagnosed with invasive and non-invasive coronary imaging and review the epidemiology, treatment and prognosis of coronary fistulas. [less ▲]

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See detailNon-Invasive Methods to Predict Breast Muscle Weight in Slow-Growing Chickens
Larivière, Jean-Marc ULg; Michaux, Charles ULg; Verleyen, Vincent ULg et al

in International Journal of Poultry Sciences (2009), 8(7), 689-691

This experiment aims to compare in vivo breast morphometric and ultrasound measurements, as well as live body weight to predict breast meat weight in slow-growing chickens. Traits included Thoracic ... [more ▼]

This experiment aims to compare in vivo breast morphometric and ultrasound measurements, as well as live body weight to predict breast meat weight in slow-growing chickens. Traits included Thoracic Circumference (TC), Chest Width (CW), Keel Length (KL) and angle (KA), Live Weight (LW), thickness of muscle determined by sonography (TM) and Breast Meat Weight (BMW). Birds were then slaughtered and total breast muscles (Pectoralis major and Pectoralis minor) were dissected and weighed. A linear model including sex effect and the different predictor measurements, as covariates, were adjusted to the data. Homogeneity test of slopes between sexes showed no difference. Means of the traits were 115.58g (±19.72) for BMW, 1031 g (±163.44) for LW, 68.65o (±6.89) for KA, 26.81 cm (±1.57) for TC, 10.40 cm (±0.62) for KL, 4.67 cm (±0.47) for CW and 11.52 mm (±1.11) for TM. All traits were highly correlated to BMW: TC (0.85), LW (0.84), KL (0.81) and TM (0.79), except for KA (0.28) and CW (0.19). Finally, TC, LW, KL and TM appear to be valuable indicators for estimating BMW in slow-growing chickens but KA and CW remain poor predictors [less ▲]

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See detailNon-invasive monitoring of mixed cropping systems. A case-study in Ratchaburi province, Thailand
Garré, Sarah ULg; Coteur, Ine; Diels, Jan et al

Poster (2012, July)

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See detailNon-invasive monitoring of soil water dynamics in mixed cropping systems: A case-study in Ratchaburi province, Thailand
Garré, Sarah ULg; Coteur, Ine; Wongleecharoen, Chalemchart et al

in Vadose Zone Journal (2013)

Agriculture on shallow or steep soils in the humid tropics often leads to low resource use efficiency. Contour hedgerow intercropping systems have been proposed to reduce run-off and control soil erosion ... [more ▼]

Agriculture on shallow or steep soils in the humid tropics often leads to low resource use efficiency. Contour hedgerow intercropping systems have been proposed to reduce run-off and control soil erosion. However, competition for water and nutrients between crops and associated hedgerows may reduce the overall performance of contour hedgerow systems. Electrical resistivity tomography (ERT) is a valuable technique used to assess the distribution and dynamics of soil moisture noninvasively. In this study, we demonstrated its potential to measure soil water depletion in the field in distinct cropping patterns in Ratchaburi province, Thailand. The measurements showed that the soils of our experimental plots were very heterogeneous both along the slope as with depth. This observation highlighted some constraints of the ERT method for soil moisture monitoring in the field, such as the difficulty of defining a relationship between electrical conductivity and soil moisture in very heterogeneous soils. Nevertheless, spatial analysis of the data revealed contrasting water depletion patterns under monocropping and intercropping systems. In this way, ERT provides access to information about the vadose zone moisture dynamics that would be unavailable with classical soil moisture measurements. [less ▲]

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See detailNon-invasive monitoring of water and solute fluxes in a cropped soil
Garré, Sarah ULg

Doctoral thesis (2010)

Although the influence of root water uptake on solute transport is commonly recognized as important, it has barely been studied throughout the literature. However, plants take up a big amount of the ... [more ▼]

Although the influence of root water uptake on solute transport is commonly recognized as important, it has barely been studied throughout the literature. However, plants take up a big amount of the infiltrating water and therefore they influence water flow patterns in the soil and concurrently solute transport processes. For this reason, experiments are required to investigate the relationship between plant root water uptake and flow field variability. Within this PhD project, we tried to elucidate the role of root water uptake on soil moisture distribution and solute transport in two undisturbed soil columns. During three consecutive experimental phases, the soil hydraulic and solute transport characteristics were investigated and the influence of growing barley on water content and tracer movement were studied. Soil water concentration and moisture content in the lysimeters were monitored non-invasively using 3-D electrical resistivity tomography (ERT). ERT is a valuable technique to monitor processes in the unsaturated zone. It is suitable to quantify solute concentration or soil moisture content at the decimeter scale in different soils and under varying conditions. In combination with TDR and effluent measurements, different aspects of the solute transport process and manifestations of preferential flow can be investigated. Steady-state step tracer experiments are very suitable for this purpose. Soil moisture measurements with ERT were conducted as well, but an horizon-specific in-situ calibration of the ERT-measurements for water content was a prerequisite for success. We observed that the solute transport in our silty lysimeters was considerably more heterogeneous than in the loamy-sand soil studied by Koestel (2008; 2009a; 2009b). We observed a clear preferential flow path in one of the lysimeters and found that soil layering had a big influence on the leaching process. The measured water depletion rate, being the result of combined effects of root water uptake and soil water redistribution during the barley experiment without irrigation, was compared with the evaporative demand and root length densities. We could observe a gradual downward movement of the maximum water depletion rate together with periods of redistribution when there was less transpiration. However, we were unable to make the distinction between soil water fluxes and root water uptake, since modeling of the soil water flow field using the time series of water content was not satisfying. We observed root growth at rhizotube surfaces and noted an increasing number of roots with depth. Since the minirhizotron measurements were only conducted at four depths and thus represent a small volume of the entire root zone, we estimated a root architecture model for the barley plants using RootTyp. We were able to set up a simple model, but to obtain better results, the effect of soil constraints and the process of re-iteration should be included. Many aspects of water flow and solute transport in the root zone need to be further investigated. The need for high-quality soil moisture data and simultaneous root architecture data remains. ERT is a promising technique to fill part of this gap, however some issues need to be solved before it can be used without difficulties. Next to measurements, the effort to improve our soil water flow models must be continued in order to improve the estimation of soil water fluxes. Only in this way, we will be able to measure root water uptake at the lysimeter and field scale. This is a necessary step towards a better understanding of the interactions in the soil-plant continuum. [less ▲]

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See detailNon-isothermal infiltration in plastic bentonite
François, Bertrand ULg; Laloui, Lyesse

in Alonso, Edouardo; Gens, Antonio (Eds.) Unsaturated Soils (2010)

In deep geological repository involving a multi-barrier system, the engineered materials, generally made of bentonite, constitute an important mechanical, thermal and hydraulic barrier to prevent the ... [more ▼]

In deep geological repository involving a multi-barrier system, the engineered materials, generally made of bentonite, constitute an important mechanical, thermal and hydraulic barrier to prevent the interaction between wastes and biosphere. To better understand the THM (thermo-hydro-mechanical) processes in the clayey confining system, experimental tests must be simulated by the means of advance numerical tools. A unified thermo-mechanical constitutive model for unsaturated soils, ACMEG-TS, has been developed and implemented in the finite element code LAGAMINE. Material is considered as tri-phase non-isothermal thermo-plastic medium. The results of numerical simulations of non-isothermal infiltration tests through FEBEX bentonite are compared with the available sensors measurements and interpreted in the light of elasto-thermo-plasticity of unsaturated soils. Through those simulations, the advancements in the understanding of the involved processes brought by the ACMEG-TS model are discussed. [less ▲]

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See detailNon-isothermal moisture balance equation in porous media: a review of mathematical formulations in Building Physics
Dubois, Samuel ULg; Lebeau, Frédéric ULg; Evrard, Arnaud ULg

in Biotechnologie, Agronomie, Société et Environnement = Biotechnology, Agronomy, Society and Environment [=BASE] (in press)

Understanding heat and mass transfers in porous materials is crucial in many areas of scientific research. Mathematical models have constantly evolved, their differences lying mainly in the choice of the ... [more ▼]

Understanding heat and mass transfers in porous materials is crucial in many areas of scientific research. Mathematical models have constantly evolved, their differences lying mainly in the choice of the driving potentials used to describe moisture flows, as well as in the complexity of characterizing the physical phenomena involved. Models developed in the field of Building Physics (HAM models) are used to describe the behavior of envelope parts and assess their impact on user comfort and energy performance. The water balance equation can be described in many ways; it is a function of the boundary conditions considered and the fact they induce high or low water content in the porous materials used. This paper gives an overview of various formulations for this equation that are found in the Building Physics literature. It focuses first on the physically based formulation of moisture balance, drawing on the Representative Elementary Volume (REV) concept, coupled with thermodynamic flow rates description. This is then reformulated in line with various main moisture state variables offering a wide variety of expressions that are compared with available models. This approach provides access to all secondary transport coefficients associated with the process of mathematical transformation. Particular emphasis is placed on the moisture storage function choice and its impact on the final mathematical formulations. [less ▲]

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See detailNon-isotopic determination of bovine growth hormone levels with a sandwich-immunoassay using detection by electrochemiluminescence (ECL).
Rehfeldt, C.; Deaver, D.; Schneider, F. et al

in Proceedings of the 45th Symposium of the German Society for Endocrinology. (2001, March)

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See detailLe non-lieu de l'exil dans le cinéma de Belgique francophone
Mélon, Marc-Emmanuel ULg

in Bajomée, Danielle; Mabrour, Abdelouahed (Eds.) Exils imaginaires et exils réels dans le domaine francophone. Théorie, histoire, figures, pratiques (2004)

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See detailA non-linear 3D beam finite element for the study of steel frames with tapered members
Boissonnade, N.; Degée, Hervé ULg

in Mota Soares, C. A. (Ed.) Proceedings of the 3rd European Conference on Computational Mechanics, Solids, Structures and Coupled Problems in Engineering (2006)

This paper presents the essentials of an original geometrically and materially nonlinear 3-D tapered beam finite element. The theoretical bases of the element are described, with particular attention paid ... [more ▼]

This paper presents the essentials of an original geometrically and materially nonlinear 3-D tapered beam finite element. The theoretical bases of the element are described, with particular attention paid to the choice of an appropriate displacement field and to the corresponding non-linear axial strains. Specific numerical problems met in the development of the finite element are examined, concerning mainly shear and membrane locking and the handling of rigid body motions. Worked examples on isolated members are presented for various types of analyses: elastic linear, elastic critical and geometrically and materially non-linear analyses. Good accuracy with reference to numerical results is shown, as well as good convergence properties. It is also demonstrated – analytically and numerically – that the use of prismatic beam finite elements for the analysis of tapered beams (segmentation technique) may lead to significant discrepancies when the behaviour is influenced by torsional aspects. Then, the behaviour of two different portal frames with tapered members is proposed, and the results obtained using shell elements, tapered beam elements and prismatic beam elements are compared. This comparison shows that the use of tapered elements leads to results in close agreement with those obtained by shell elements, unlike the prismatic ones. The convenience of the tapered beam element is also highlighted since the total number of degrees of freedom required is significantly reduced compared to a shell modelling, leading to easier meshing, shorter computation time and easier interpretation of results. [less ▲]

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See detailNon-linear aeroelastic prediction for aircraft applications
Henshaw, M.J. de C.; Badcock, Ken J.; Vio, G. A. et al

in Progress in Aerospace Sciences (2007), 434(4-6), 65-137

Current industrial practice for the prediction and analysis of flutter relies heavily on linear methods and this has led to overly conservative design and envelope restrictions for aircraft. Although the ... [more ▼]

Current industrial practice for the prediction and analysis of flutter relies heavily on linear methods and this has led to overly conservative design and envelope restrictions for aircraft. Although the methods have served the industry well, it is clear that for a number of reasons the inclusion of non-linearity in the mathematical and computational aeroelastic prediction tools is highly desirable. The increase in available and affordable computational resources, together with major advances in algorithms, mean that non-linear aeroelastic tools are now viable within the aircraft design and qualification environment. The Partnership for Unsteady Methods in Aerodynamics (PUMA) Defence and Aerospace Research Partnership (DARP) was sponsored in 2002 to conduct research into non-linear aeroelastic prediction methods and an academic, industry, and government consortium collaborated to address the following objectives: (1) To develop useable methodologies to model and predict non-linear aeroelastic behaviour of complete aircraft. (2) To evaluate the methodologies on real aircraft problems. (3) To investigate the effect of non-linearities on aeroelastic behaviour and to determine which have the greatest effect on the flutter qualification process. These aims have been very effectively met during the course of the programme and the research outputs include: (a) New methods available to industry for use in the flutter prediction process, together with the appropriate coaching of industry engineers. (b) Interesting results in both linear and non-linear aeroelastics, with comprehensive comparison of methods and approaches for challenging problems. (c) Additional embryonic techniques that, with further research, will further improve aeroelastics capability. This paper describes the methods that have been developed and how they are deployable within the industrial environment. We present a thorough review of the PUMA aeroelastics programme together with a comprehensive review of the relevant research in this domain. This is set within the context of a generic industrial process and the requirements of UK and US aeroelastic qualification. A range of test cases, from simple small DOF cases to full aircraft, have been used to evaluate and validate the non-linear methods developed and to make comparison with the linear methods in everyday use. These have focused mainly on aerodynamic non-linearity, although some results for structural non-linearity are also presented. The challenges associated with time domain (coupled computational fluid dynamics–computational structural model (CFD–CSM)) methods have been addressed through the development of grid movement, fluid–structure coupling, and control surface movement technologies. Conclusions regarding the accuracy and computational cost of these are presented. The computational cost of time-domain methods, despite substantial improvements in efficiency, remains high. However, significant advances have been made in reduced order methods, that allow non-linear behaviour to be modelled, but at a cost comparable with that of the regular linear methods. Of particular note is a method based on Hopf bifurcation that has reached an appropriate maturity for deployment on real aircraft configurations, though only limited results are presented herein. Results are also presented for dynamically linearised CFD approaches that hold out the possibility of non-linear results at a fraction of the cost of time coupled CFD–CSM methods. Local linearisation approaches (higher order harmonic balance and continuation method) are also presented; these have the advantage that no prior assumption of the nature of the aeroelastic instability is required, but currently these methods are limited to low DOF problems and it is thought that these will not reach a level of maturity appropriate to real aircraft problems for some years to come. Nevertheless, guidance on the most likely approaches has been derived and this forms the basis for ongoing research. It is important to recognise that the aeroelastic design and qualification requires a variety of methods applicable at different stages of the process. The methods reported herein are mapped to the process, so that their applicability and complementarity may be understood. Overall, the programme has provided a suite of methods that allow realistic consideration of non-linearity in the aeroelastic design and qualification of aircraft. Deployment of these methods is underway in the industrial environment, but full realisation of the benefit of these approaches will require appropriate engagement with the standards community so that safety standards may take proper account of the inclusion of non-linearity. [less ▲]

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See detailNon-linear generalization of principal component analysis: From a global to a local approach
Kerschen, Gaëtan ULg; Golinval, Jean-Claude ULg

in Journal of Sound & Vibration (2002), 254(5), 867-876

Principal component analysis (PCA), also known as proper orthogonal decomposition or Karhunen-Loeve transform, is commonly used to reduce the dimensionality of a data set with a large number of ... [more ▼]

Principal component analysis (PCA), also known as proper orthogonal decomposition or Karhunen-Loeve transform, is commonly used to reduce the dimensionality of a data set with a large number of interdependent variables. PCA is the optimal linear transformation with respect to minimizing the mean square reconstruction error but it only considers second-order statistics. If the data have non-linear dependencies, an important issue is to develop a technique which takes higher order statistics into account and which can eliminate dependencies not removed by PCA. Recognizing the shortcomings of PCA, researchers in the field of statistics and neural networks have developed non-linear extensions of PCA. The purpose of this paper is to present a non-linear generalization of PCA, called VQPCA. This algorithm builds local linear models by combining PCA with clustering of the input space. This paper concludes by observing from two illustrative examples that VQPCA is potentially a more effective tool than conventional PCA. (C) 2002 Elsevier Science Ltd. All rights reserved. [less ▲]

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See detailA non-linear homogeneous model for bone-like materials under compressive load.
Mengoni, Marlène ULg; Voide, Romain; Toye, Dominique ULg et al

in Nithiarasu, P.; Löhner, R.; van Loon, R. (Eds.) et al Conference Proceedings - 2nd International Conference on Computational & Mathematical Biomedical Engineering (2011)

Using morphological data provided by computed tomography, finite element (FE) models can be used to compute the mechanical response of bone and bone-like materials without describing the complex local ... [more ▼]

Using morphological data provided by computed tomography, finite element (FE) models can be used to compute the mechanical response of bone and bone-like materials without describing the complex local microarchitecture. A constitutive law is here developed and proposed for this purpose. It captures the non-linear structural behavior of bone-like materials through the use of fabric tensors. It also allows for irreversible strains using a plastic material model, allowing hardening of the yield parameters. These characteristics are expressed in a constitutive law based on the anisotropic continuum damage theory coupled with isotropic elastoplasticity in a finite strains framework. This law is implemented into Metafor, a non-linear FE software. Simulations of cylindrical samples undergoing stepwise compression are presented. [less ▲]

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See detailA non-linear homogeneous model for bone-like materials under compressive load.
Mengoni, Marlène ULg; Voide, Romain; de Bien, Charlotte ULg et al

in International Journal for Numerical Methods in Biomedical Engineering (2012), 28(2), 334-348

Finite element (FE) models accurately compute the mechanical response of bone and bone-like materials when the models include their detailed microstructure. In order to simulate non-linear behavior, which ... [more ▼]

Finite element (FE) models accurately compute the mechanical response of bone and bone-like materials when the models include their detailed microstructure. In order to simulate non-linear behavior, which currently is only feasible at the expense of extremely high computational costs, coarser models can be used if the local morphology has been linked to the apparent mechanical behavior. The aim of this paper is to implement and validate such a constitutive law. This law is able to capture the non-linear structural behavior of bone-like materials through the use of fabric tensors. It also allows for irreversible strains using an elastoplastic material model incorporating hardening. These features are expressed in a constitutive law based on the anisotropic continuum damage theory coupled with isotropic elastoplasticity in a finite strains framework. This material model was implemented into Metafor, a non-linear FE software. The implementation was validated against experimental data of cylindrical samples subjected to compression. Three materials with bone-like microstructure were tested : aluminum foams of variable density (ERG, Oakland, CA), PLA (polylactic acid) foam (CERM, University of Liège) and cancellous bone tissue of a deer antler (Faculty of Veterinary Medicine, University of Liège). [less ▲]

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See detailNon-Linear Identification in Modal Space Using a Genetic Algorithm Approach for Model Selection
Platten, Michael F; Wright, Jan Robert; Worden, Keith et al

in International Journal of Applied Mathematics & Mechanics (2007), 3(1), 72-89

The Non-Linear Resonant Decay Method is an approach for the identification of non-linear systems with large numbers of degrees of freedom. The identified non-linear model is expressed in linear modal ... [more ▼]

The Non-Linear Resonant Decay Method is an approach for the identification of non-linear systems with large numbers of degrees of freedom. The identified non-linear model is expressed in linear modal space and comprises the modal model of the underlying linear system with additional terms representing the non-linear behaviour. Potentially, a large number of these non-linear terms will exist but not all of them will be significant. The problem of deciding which and how many terms are required for an accurate identification has previously been addressed using the Forward Selection and Backward Elimination techniques. In this paper, a Genetic Algorithm optimisation is proposed as an alternative to those methods. A simulated lumped parameter non-linear dynamic system is used to demonstrate the proposed optimisation. The use of separate data sets for the identification and validation of the modal model is also investigated. It is found that the Genetic Algorithm approach yields significantly better results than the Backward Elimination and Forward Selection algorithms in many cases. [less ▲]

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See detailNon-Linear Identification Using a Genetic Algorithm Approach for Model Selection
Platten, Michael F; Wright, Jan Robert; Worden, Keith et al

in Proceedings of the 23rd International Modal Analysis Conference (2005, January)

The Non-Linear Resonant Decay Method is an approach for the identification of non-linear systems with large numbers of degrees of freedom. The identified non-linear model is expressed in linear modal ... [more ▼]

The Non-Linear Resonant Decay Method is an approach for the identification of non-linear systems with large numbers of degrees of freedom. The identified non-linear model is expressed in linear modal space and comprises the modal model of the underlying linear system with additional terms representing the non-linear behaviour. Potentially, a large number of these non-linear terms will exist but not all of them will be significant. The problem of deciding which and how many terms are required for an accurate identification has previously been addressed using the Forward Selection and Backward Elimination techniques. In this paper, a Genetic Algorithm optimisation is proposed as an alternative to those methods. A simulated 5-DOF lumped parameter non-linear system is used to demonstrate the proposed optimisation. The use of separate data sets for the identification and validation of the modal model is also investigated. It is found that the Genetic Algorithm approach yields significantly better results than the Backward Elimination and Forward Selection algorithms in many cases. [less ▲]

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See detailNon-linear loudspeaker simulation. Guitar loudspeaker.
Schmitz, Thomas ULg; Embrechts, Jean-Jacques ULg

Conference (2012, June 06)

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See detailNon-linear magnetic model refinement via a finite element subproblem method
Dular, Patrick ULg; V Sabariego, Ruth ULg; Gyselinck, Johan et al

in Proceedings of the XXI Symposium on Electromagnetic Phenomena in Nonlinear Circuits (EPNC 2010) (2010, June)

Model refinements of non-linear magnetic circuits are performed via a finite element subproblem method. A complete problem is split into subproblems to allow a progression from 1- D to 3-D including ... [more ▼]

Model refinements of non-linear magnetic circuits are performed via a finite element subproblem method. A complete problem is split into subproblems to allow a progression from 1- D to 3-D including linear to non-linear model corrections. Its solution is then expressed as the sum of the subproblem solutions supported by different meshes. A convenient and robust correction procedure is proposed allowing independent overlapping meshes for both source and reaction fields. The procedure simplifies both meshing and solving processes, and quantifies the gain given by each model refinement on both local fields and global quantities. [less ▲]

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See detailNon-linear mechanical solvers for GMSH
Noels, Ludovic ULg; Becker; Nguyen, Van Dung ULg et al

Scientific conference (2012, March)

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