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See detailModelling sound diffusion in ray tracing programs
Embrechts, Jean-Jacques ULg

in Proceedings of Acustica 2000-TecniAcustica Congress (2000)

Detailed reference viewed: 22 (8 ULg)
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See detailModelling spray drift using a modified air pollution Gaussian tilting plume model
Stainier, Charles; Destain, Marie-France ULg; Schiffers, Bruno ULg et al

Poster (2007)

The objective of this research is to evaluate a Gaussian tilting plume model that takes into account the spray characteristics of agricultural nozzles to predict drift. The application of this type of ... [more ▼]

The objective of this research is to evaluate a Gaussian tilting plume model that takes into account the spray characteristics of agricultural nozzles to predict drift. The application of this type of model has proved to be effective for aerial pollution applications. To be applied successfully to the spray drift, the model has to give accurate predictions of the deposits regarding the spray and material characteristics as well as the weather parameters. To reach this objective, the model parameters must be correctly set based on appropriate theoretical basis and experimental data. Based on wind tunnel measurements, the effect of the most important characteristics of spray droplets from an agricultural nozzle has been modelled using a Gaussian tilting plume approach by discretizing the different droplet classes. Although the theoretical basis of the model is simple, the predicted drift appeared to be in relatively good agreement with the experimental results. The discrepancies could be explained by poor fitting of the dispersion model parameters. Further work is required to optimise the value of the model parameters. [less ▲]

Detailed reference viewed: 46 (5 ULg)
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See detailModelling squeeze film effects in a MEMS accelerometer with a levitated proof mass
Houlihan, Ruth; Kraft, Michael ULg

in Journal of Micromechanics and Microengineering (2005), 15(5), 893--902

A triaxial accelerometer is presented which employs as its proof mass a mechanically free micromachined disc that is electrostatically levitated. Air damping plays a critical role in the operation of the ... [more ▼]

A triaxial accelerometer is presented which employs as its proof mass a mechanically free micromachined disc that is electrostatically levitated. Air damping plays a critical role in the operation of the accelerometer, providing stability to an inherently unstable system. Systems that operate beyond the cut-off frequency, however, suffer reduced gain due to the spring component of the squeeze film damping, resulting in decreased sensitivity. A finite-element model for extracting squeeze film damping coefficients for transverse and rotational motion of the disc, via an analogy to heat transfer theory, is presented. The use of the analogy enables a reduction of the problem from a complex three-dimensional computational fluid dynamics domain to a two-dimensional heat transfer domain. The model is used to evaluate the effect of including damping holes in the proof mass. The high-frequency oscillation and physical size of the proof mass dictate that the accelerometer is operated well beyond its cut-off frequency and so the inclusion of damping holes in the proof mass can result in an increase rather than decrease in the damping coefficient. The resulting system-level model, implemented in Matlab/Simulink, is then used to evaluate the effect of the squeeze film damping on the device performance. [less ▲]

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See detailModelling strategies for microstructures moving in an electric field
Rochus, Véronique ULg; Andreykiv, Andriy; Rixen, Daniel

in International Conference on Computational Methods for Coupled Problems in Science and Engineering (2007)

Detailed reference viewed: 15 (2 ULg)
Peer Reviewed
See detailModelling surgical cuts, retractions, and resections via Extended Finite Element Method
Vigneron, Lara M.; Verly, Jacques ULg; Warfield, Simon K.

Conference (2004)

Detailed reference viewed: 9 (0 ULg)
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See detailModelling suspended load transport with linear concentration profiles
Khuat Duy, Bruno ULg; Dewals, Benjamin ULg; Archambeau, Pierre ULg et al

in Proceedings of the 8th International Conference on Fluvial Sedimentology (2005)

In numerical simulations, it is always necessary to find an optimum between the simplicity of the model and a good representation of real phenomena. In the field of hydraulic flows simulations, the models ... [more ▼]

In numerical simulations, it is always necessary to find an optimum between the simplicity of the model and a good representation of real phenomena. In the field of hydraulic flows simulations, the models using depth-averaged and moment equations are an interesting compromise between full 3D and simple depth-averaged models. This paper presents the use of a moment equation for suspended load transport. A simple but representative model for the sediment concentration profiles is developed. This original bi-linear concentration profile is compared to the traditional Rouse-profiles and shows a good correspondence despite its great simplicity. Advective and diffusive sediment fluxes are developed analytically and lead to a concise formulation, which is an asset for practical use. A differential equation for the sediment concentration moment is also fully developed, and a special attention is cast to the source term. The finite volume scheme has been chosen to implement the model, because it is particularly well suited for highly advective transport equations, it is conservative and it makes the choice of the upwinding easier. 1D simulations show the capacity of the model to reproduce laboratory experiments described in the literature. [less ▲]

Detailed reference viewed: 43 (5 ULg)
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See detailModelling suspended load with moment equations and linear concentration profiles
Khuat Duy, Bruno ULg; Dewals, Benjamin ULg; Archambeau, Pierre ULg et al

in Raghay, S.; Ouazar, D.; Benkhaldoun, F. (Eds.) Finite volumes for complex applications (2005)

In numerical simulations, it is always necessary to find an optimum between the simplicity of the model and a good representation of real phenomena. In the field of hydraulic flows simulations, the models ... [more ▼]

In numerical simulations, it is always necessary to find an optimum between the simplicity of the model and a good representation of real phenomena. In the field of hydraulic flows simulations, the models using depth-averaged and moment equations are an interesting compromise between full 3D and simple depth-averaged models. This paper presents the use of a moment equation for suspended load transport. A simple but representative model for the sediment concentration profiles is developed. This original bi-linear concentration profile is compared to the traditional Rouse-profiles and shows a good correspondence despite its great simplicity. Advective and diffusive sediment fluxes are developed analytically and lead to a concise formulation, which is an asset for practical use. A differential equation for the sediment concentration moment is also fully developed, and a special attention is cast to the source term. The finite volume scheme has been chosen to implement the model, because it is particularly well suited for highly advective transport equations, it is conservative and it makes the choice of the upwinding easier. 1D simulations show the capacity of the model to reproduce laboratory experiments described in the literature. [less ▲]

Detailed reference viewed: 118 (4 ULg)
See detailModelling system WOLF
Pirotton, Michel ULg; Archambeau, Pierre ULg; Mouzelard, Thibaut et al

Software (2000)

Detailed reference viewed: 63 (11 ULg)
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See detailModelling temporal stability of EPI time series using magnitude images acquired with multi-channel receiver coils.
Hutton, Chloe; Balteau, Evelyne ULg; Lutti, Antoine et al

in PLoS ONE (2012), 7(12), 52075

Detailed reference viewed: 9 (0 ULg)
Peer Reviewed
See detailModelling the Arterial Wall by Finite Elements
Mosora, F.; Harmant, A.; Hallet, Claude ULg et al

in Archives Internationales de Physiologie, de Biochimie et de Biophysique (1993), 101(3, May-Jun), 185-91

The mechanical behaviour of the arterial wall was determined theoretically utilizing some parameters of blood flow measured in vivo. Continuous experimental measurements of pressure and diameter were ... [more ▼]

The mechanical behaviour of the arterial wall was determined theoretically utilizing some parameters of blood flow measured in vivo. Continuous experimental measurements of pressure and diameter were recorded in anesthetized dogs on the thoracic ascending and midabdominal aorta. The pressure was measured by using a catheter, and the diameter firstly, at the same site, by a plethysmograph with mercury gauge and secondly, by a sonomicrometer with ferroelectric ceramic transducers. The unstressed radius and thickness were measured at the end of each experiment in situ. Considering that the viscous component is not important relatively to the nonlinear component of the elasticity and utilizing several equations for Young modulus calculation (thick and thin wall circular cylindrical tube formulas and Bergel's equation) the following values were obtained for this parameter: 0.6 MPa-2 MPa in midabdominal aorta and 2 MPa-6.5 MPa in thoracic ascending aorta. The behaviour of the aorta wall was modelled considering an elastic law and using the finite element program "Lagamine" working in large deformations. The discretized equilibrium equations are non-linear and a unique axi-symmetric, iso-parametric element of 1 cm in length with 8 knots was used for this bi-dimensional problem. The theoretical estimation of radius vessel, utilizing a constant 5 MPa Young modulus and also a variable one, are in good agreement with the experimental results, showing that this finite element model can be applied to study mechanical properties of the arteries in physiological and pathological conditions. [less ▲]

Detailed reference viewed: 28 (5 ULg)
See detailModelling the behaviour of Listeria monocytogenes in cheese
Schvartzman Echenique, Maria Sol ULg

Doctoral thesis (2011)

Cheese is a complex biological system where environmental dynamics take place between pH, moisture, water activity and temperature. Bacteria growing in or on cheese behave differently depending on the ... [more ▼]

Cheese is a complex biological system where environmental dynamics take place between pH, moisture, water activity and temperature. Bacteria growing in or on cheese behave differently depending on the cheese types or in the processing step. In this work, the behaviour of Listeria monocytogenes during cheesemaking and ripening was studied given a milk contamination or surface cross-contamination scenario. When milk was contaminated, L. monocytogenes initiated growth with a different probability during cheesemaking compared to milk or laboratory media, indicating that models built from laboratory media would not accurately predict the behaviour of L. monocytogenes in farmhouse cheese. Lower limits of growth at aw values of 0.94-0.96, depending on contamination level, were identified using an Ordinary Logistic Regression model. In the range tested, the pH showed no effect on growth initiation. Furthermore, L. monocytogenes presented considerable differences in behaviour in pasteurised or raw milk during cheesemaking and ripening. In contrast with the pasteurised milk cheeses, raw milk did not support growth of L. monocytogenes during cheesemaking but during ripening, growth occurred only in raw milk cheeses. The growth observed was modelled with a Logistic Cardinal model. When the contamination was present on the surface only, Listeria was inactivated in cheeses made with pasteurised milk (with pH < 5.4) during ripening and when aw decreased considerably. The inactivation was modelled with a Log-linear response surface model with aw as the factor with higher effect. In contrast, cheese made with raw milk or with pH around neutrality supported the growth of L. monocytogenes and was modelled with the Logistic Cardinal model with pH as the most influencing environmental factor on the growth rate. In summary, the need for food models has been demonstrated and pH and aw were the most significant variables conditioning the behaviour of L. monocytogenes in the various cheese scenarios. [less ▲]

Detailed reference viewed: 27 (0 ULg)
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See detailModelling the behaviour of radionuclides in the aquatic ecosystem
Smitz, Joseph ULg; Everbecq, Etienne ULg

Scientific conference (1986, September)

Radionuclides realeased by nuclear plants in surface waters are not simply transported by the water. Other complex phenomena occur : adsorbtion/desorbtion to sediments, sedimentation and accumulation on ... [more ▼]

Radionuclides realeased by nuclear plants in surface waters are not simply transported by the water. Other complex phenomena occur : adsorbtion/desorbtion to sediments, sedimentation and accumulation on river's bed, interaction with interstitial water, and eventually resuspension in the water column. The aim of this work is the description and modelling of the majors processes which govern the contamination of surface waters and sediments by radionuclides to food chain and to man. The model is applied to the river Meuse. The results shows a good aggreement with available field measurements realized during routine surveys. [less ▲]

Detailed reference viewed: 67 (15 ULg)
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See detailModelling the butterfat crystallisation process
Heyen, Georges ULg; Alleman, Xavier; Kalitventzeff, Boris ULg et al

in Computers & Chemical Engineering (1999), 23(Suppl. S), 819-822

Milk fat exhibits seasonal variations in composition and properties which are undesirable for many subsequent applications. Thus techniques are sought to process dairy products in order to achieve a ... [more ▼]

Milk fat exhibits seasonal variations in composition and properties which are undesirable for many subsequent applications. Thus techniques are sought to process dairy products in order to achieve a consistent quality. A brief introduction to milk fat presents its most important particularities, especially composition, seasonal variations, solid fat content, crystalisation and polymorphism. The differential scanning calorimetry (DSC) analysis allows to estimate the solid fat content. Different methods have been developed to estimate more and more precisely the solid fat content which is certainly an important parameter in the description of the textural properties of butterfat. The industrial crystallisation process is modelled on the basis of pilot plant data. That model allows to approach the particular temperature profile in the scraped surface heat exchangers and to give a first explanation of the involved phenomena. [less ▲]

Detailed reference viewed: 33 (4 ULg)
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See detailModelling the Cape Ghir Upwelling Filament
Troupin, Charles ULg

Scientific conference (2008, December 12)

Detailed reference viewed: 9 (0 ULg)