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See detailEstimation of the turbulent kinetic energy dissipation in a culture cell stirred tank bioreactor
Delafosse, Angélique ULg; Collignon, Marie-Laure ULg; Dossin, Denis et al

in Chemical Engineering Science (2011), 66(8), 1728-1737

The turbulent dissipation rate is a key parameter in stirred tanks and its local values may have a strong influence on the performance of many processes. However, the local dissipation rate estimation is ... [more ▼]

The turbulent dissipation rate is a key parameter in stirred tanks and its local values may have a strong influence on the performance of many processes. However, the local dissipation rate estimation is far from easy in a stirred tank, especially near the impeller discharge where maximum values are encountered. The aim of this work is to estimate the dissipation rate in a vessel used for animal-cell cultures and stirred with a down-pumping axial impeller (Mixel TTP) from velocity fields measured by 2D-PIV. Special attention is paid to the assumptions necessary to estimate the dissipation rate from 2D measurements and to the influence of measurement spatial resolution on the estimated values. The analysis of isotropy ratios measured on vertical, horizontal and tangential planes shows that the turbulence in the impeller discharge is far from isotropic. Isotropy assumptions classically used to estimate the dissipation rate from 2D measurements may thus lead to erroneous values. Based on the measured isotropy ratios, a new relationship is proposed to estimate the dissipation rate in the impeller discharge. This relationship is then used to estimate the dissipation rate on a vertical plane located in the impeller discharge zone. In order to analyze the influence of the measurement spatial resolution on the estimated values of the dissipation, a total of 12 spatial resolutions are tested. Results show that if the spatial resolution is divided by a factor 2, the dissipation rate increases by 220%. For the smallest spatial resolution value used, the maximum dissipation rate estimated is 50 times higher than the mean overall dissipation rate and the corresponding minimum value of the Kolmogorov scale is nearly 3 times smaller than the Kolmogorov scale computed from the mean overall dissipation rate. [less ▲]

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See detailEstimation of tidal boundary conditions and surface winds by assimilation of high-frequency radar surface currents in the German Bight
Barth, Alexander ULg; Alvera Azcarate, Aïda ULg; Gurgel, Klaus-Werner et al

Conference (2010)

Numerical ocean models are affected by errors of various origins: errors in the initial conditions, boundary conditions and atmospheric forcings, uncertainties in the turbulence parametrization and ... [more ▼]

Numerical ocean models are affected by errors of various origins: errors in the initial conditions, boundary conditions and atmospheric forcings, uncertainties in the turbulence parametrization and discretization errors. In data assimilation, observations are used to reduce the uncertainty in the model solution. Ensemble-based assimilation schemes are often implemented such that the expected error of the model solution is minimized. It is shown that the observations can also be used to obtain improved estimates of the, in general, poorly known boundary conditions and atmospheric forcings. An ensemble smoother scheme is presented to assimilate high-frequency (HF) radar surface currents to improve tidal boundary conditions and wind forcings of a circulation model of the German Bight. To create an ensemble of dynamically realistic tidal boundary conditions, a cost function is formulated which is directly related to the probability of each perturbation. This cost function ensures that the perturbations are spatially smooth and that the structure of the perturbations satisfies approximately the harmonic linearized shallow water equations. Based on those perturbations an ensemble simulation is carried out using the full three-dimensional General Estuarine Ocean Model (GETM). Optimized boundary values are obtained using all observations within the assimilation period using the covariances of the ensemble simulation. The approach acts like a smoother scheme since past and future observations are taken into account. The final analysis is obtained by rerunning the model using the optimal perturbation of the boundary conditions. The analyzed model solution satisfies thus the model equations exactly and does not suffer from spurious adjustments often observed with sequential assimilation schemes. Model results are also compared to independent tide gauge data. The assimilation also reduces the model error compared to those sea level observations. The same scheme is also used to correct surface winds. Surface winds are crucial for accurately modeling the marine circulation in coastal waters. The method is validated directly by comparing the analyzed wind speed to in situ measurements and indirectly by assessing the impact of the corrected winds on sea surface temperature (SST) relative to satellite SST. [less ▲]

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See detailAn estimation of total vehicle travel reduction in the case of telecommuting. Detailed analyses using an activity-based modeling approach.
Kochan, Bruno; Bellemans, Tom; Cools, Mario ULg et al

in Proceedings of the 39th European Transport Conference (2011)

Transportation Demand Management (TDM) is often referred to as a strategy adopted by transport planners with the goal to increase transport system efficiency. One of the potential measures that can be ... [more ▼]

Transportation Demand Management (TDM) is often referred to as a strategy adopted by transport planners with the goal to increase transport system efficiency. One of the potential measures that can be adopted in TDM is the implementation of telecommuting. A significant number of studies have been conducted in the past to evaluate the effect of telecommuting on the amount of peak-period trips. However it is less studied whether telecommuting also effectively and significantly reduces total vehicle travel in terms of kilometers traveled throughout the day. For this reason, a conventional modeling approach was adopted in this paper to calculate total kilometers of travel saved in the case telecommuting would materialize in the Flanders area. In a second part, this paper introduces the use of an activity-based modeling approach to evaluate the effect of telecommuting on a more detailed time scale. As the second approach provides a more disaggregate result, both models can be compared on the more aggregate level to validate whether they correspond. [less ▲]

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See detailAn estimation of total vehicle travel reduction in the case of telecommuting. Detailed analysis using an activity-based modeling approach
Kochan, Bruno; Bellemans, Tom; Cools, Mario ULg et al

in Cornelis, Eric (Ed.) Proceedings of the BIVEC-GIBET Transport Research Day 2011 (2011)

ransportation Demand Management (TDM) is often referred to as a strategy adopted by transport planners with the goal to increase transport system efficiency. One of the possible measures that can be ... [more ▼]

ransportation Demand Management (TDM) is often referred to as a strategy adopted by transport planners with the goal to increase transport system efficiency. One of the possible measures that can be adopted in TDM is the implementation of telecommuting. A significant number of studies have been conducted in the past to evaluate the effect of telecommuting on peak-period trips. However it is less studied whether telecommuting also effectively and significantly reduces total vehicle travel. For this reason, a conventional modeling approach was adopted in this paper to calculate total kilometers of travel saved in the case telecommuting would materialize in the Flanders area. In a second part, the paper also introduces the use of an activity-based modeling approach to evaluate the effect of telecommuting. By doing so, an operational activity-based framework is externally validated by means of another completely different model, both calibrated for the same application and study area. [less ▲]

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See detailEstimation of uncertainty from the total error strategy: Application to internal and normative methods
Marini Djang'Eing'A, Roland ULg; Rozet, Eric ULg; Hubert, Cédric ULg et al

in Acta Clinica Belgica (2010), 65

Based on the importance of uncertainty, another approach to estimate this parameter of performance considering the total error (systematic and random) was applied. The data were obtained from the two main ... [more ▼]

Based on the importance of uncertainty, another approach to estimate this parameter of performance considering the total error (systematic and random) was applied. The data were obtained from the two main steps of an analytical method lifecycle: validation and routine for levonorgestrel (LNG) assay and routine for oxygen assay. Results obtained allowed drawing suitable conclusion in terms of prediction of routine and establishment of norms. [less ▲]

Detailed reference viewed: 194 (49 ULg)
See detailEstimation of variance components for cow and parity effects from test-day yields
Bormann, J.; Wiggans, G. R.; Philpot, J. C. et al

in Abstracts from the 2000 ADSA/ASAS joint annual meeting (2000)

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See detailEstimation of Welding Distortions and Straightening Workload Through a Data Mining Analysis
Losseau, Nicolas ULg; Caprace, Jean-David ULg; Archambeau, Dominique et al

in Design, Fabrication and Economy of Welded Structures (DFE) (2008, April)

This paper will present a way to minimize cost in shipbuilding industry by using the results of a data mining analysis aiming to improve the cost knowledge of the straightening process. This statistical ... [more ▼]

This paper will present a way to minimize cost in shipbuilding industry by using the results of a data mining analysis aiming to improve the cost knowledge of the straightening process. This statistical analysis was based on production data from a shipyard and has the scope to establish an assessment formula of the straightening workload. An intermediate step of the analysis was to estimate the welding distortions appearing in stiffened panels. Those generated formulae are useful to improve the research in the following domains: production simulation, cost assessment of ship hull, structure optimization, design for production, etc. [less ▲]

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See detailEstimation par sondage du rendement en grain des cultures de froment
Debouche, Charles ULg; Caussin, R.; Poelaert, J.

in Detroux (Ed.) Fumure et protection phytosanitaire des céréales (1981)

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See detailEstimation préliminaire de l’impact économique induit par l’infection naturelle par le sérotype 8 du virus de la fièvre catarrhale ovine (FCO) en élevage ovin
Saegerman, Claude ULg; Raes, M.; Uyttenhoef, Aude ULg et al

in Epidémiologie et Santé Animale (2008), 54

In Northern Europe, bluetongue caused by the bluetongue virus, serotype 8 (BTV-8), emerged in August 2006 and numerous ruminant herds were found to be affected in 2007. An epidemiological postal survey ... [more ▼]

In Northern Europe, bluetongue caused by the bluetongue virus, serotype 8 (BTV-8), emerged in August 2006 and numerous ruminant herds were found to be affected in 2007. An epidemiological postal survey was sent to 502 sheep holders with the help of the sheep and goats inter-professional federation (called FICOW). A total of 18% of holders responded (mainly meat holders). These holders market their animals on short circuit (direct sales). Despite morbidity and mortality, animal sterility (still not quantified) and lower growth, costs of animal treatment were important (sick animals and/or animals living with sick animals): minimum = 2 €/animal treated; maximum = 135 € / animal treated; mean = 26 €/animal treated and median = 20 €/animal treated. Except for rams, the price of animals (for reproduction and meat) has not varied significantly while the survey was conducted. A second postal survey is programmed after the lambing period to assess reproductive and other economic losses that could not be quantified by the time this surveywas run. [less ▲]

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See detailEstimation préliminaire de l'impact économique induit par l'infection naturelle par le sérotype 8 du virus de la fièvre catarrhale ovine (FCO) en élevage ovin
Saegerman, Claude ULg; Raes, Marianne; Uyttenhoef, Aude et al

in Epidémiologie et Santé Animale (2008), 54

In Northern Europe, bluetongue caused by the bluetongue virus, serotype 8 (BTV-8), emerged in August 2006 and numerous ruminant herds were found to be affected in 2007. An epidemiological postal survey ... [more ▼]

In Northern Europe, bluetongue caused by the bluetongue virus, serotype 8 (BTV-8), emerged in August 2006 and numerous ruminant herds were found to be affected in 2007. An epidemiological postal survey was sent to 502 sheep holders with the help of the sheep and goats inter-professional federation (called FICOW). A total of 18% of holders responded (mainly meat holders). These holders market their animals on short circuit (direct sales). Despite morbidity and mortality, animal sterility (still not quantified) and lower growth, costs of animal treatment were important (sick animals and/or animals living with sick animals): minimum = 2€/animal treated; maximum = 135€/animal treated; mean = 26€/animal treated and median = 20€/animal treated. Except for rams, the price of animals (for reproduction and meat) has not varied significanthly while the survey was conducted. A second postal survey is programmed after the lambing period to assess reproductive and other economic losses that could not be quantified by the time this survey was run. [less ▲]

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See detailEstimation quantitative de la productivité du chêne rouvre en futaies inéquiennes d'Ardenne occidentale.
Otoul, Christian; Rondeux, Jacques ULg

Book published by Faculté des Sciences Agronomiques (1980)

A pilot study has been carried out in order to assess the productivity of various sites for oak (Quercus sessilis) growth in belgian Ardenne. Site quality is evaluated by the measurement of top height at ... [more ▼]

A pilot study has been carried out in order to assess the productivity of various sites for oak (Quercus sessilis) growth in belgian Ardenne. Site quality is evaluated by the measurement of top height at a kay dominant girth of 160 cm. Such a site index seems to be well suited to unevenaged forest structures. Some other calcultations concern relationships between the index and various site factors as aspect, soils and species of plants naturally occuring on the studied areas. Estimations of stands volumes are also made with particular stand volume equations. [less ▲]

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See detailL'estimation rapide des volumes sur pied en taillis sous futaie de chênes
Rondeux, Jacques ULg; Hebert, Jacques ULg; Toussaint, André ULg

in Bulletin des Recherches Agronomiques de Gembloux (1987), 22(3), 199-207

Stand volume equations have been calculated on the basis of data issued from more than 400 sampling plots measured in stands of oaks located in the Sourthern part of Belgium. For using the various ... [more ▼]

Stand volume equations have been calculated on the basis of data issued from more than 400 sampling plots measured in stands of oaks located in the Sourthern part of Belgium. For using the various equations that give the volume per hectare, it is required to assess the basal area per hectare, the top height and according to the type of volume the mean girth. [less ▲]

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See detailEstimation under left parametric truncation and right censoring
Heuchenne, Cédric ULg; Laurent, Géraldine ULg

Scientific conference (2012)

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See detailEstimation under left parametric truncation and right censoring
Heuchenne, Cédric ULg; Laurent, Géraldine ULg

Scientific conference (2012)

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See detailEstimation, prévision et contrôle du gisement solaire en région wallonne
Doutreloup, Sébastien ULg; Fettweis, Xavier ULg; Erpicum, Michel ULg

Poster (2012, April 23)

Présentation des activités et des recherches du Laboratoire de Climatologie et Topoclimatologie de l'Université de Liège dans le domaine du rayonnement solaire

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See detailEstimations du taux de la plus-value en Belgique (1948-1994): méthode et résultats
Geerkens Provin, Eric ULg

in Contradictions (1996), (78-79), 85-98

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See detailEstimations of the Influence of the Non-Linearity of the Aerodynamic Coefficients on the Skewness of the Loading
Denoël, Vincent ULg; Degée, Hervé ULg

in Proceedings of the 6th Asia-Pacific Conference on Wind Engineering (2005)

This paper is devoted to the non linear quasi-steady aerodynamic loading. A linear approximation is often used to compute the response of structures to buffeting forces. Some researchers have however ... [more ▼]

This paper is devoted to the non linear quasi-steady aerodynamic loading. A linear approximation is often used to compute the response of structures to buffeting forces. Some researchers have however shown that it is possible to account for the non linearity of this loading. This non linearity can come (i) from the squared velocity or (ii) from the shape of the aerodynamic coefficients (as functions of the wind angle of attack). In this paper, we show that this second origin can have significant implications on the design of the structure, particularly when the non linearity of the aerodynamic coefficient is important (obvious, isn’t it?) or when the transverse turbulence is important. This paper is devoted to the non linear quasi-steady aerodynamic loading. A linear approximation is often used to compute the response of structures to buffeting forces. Some researchers have however shown that it is possible to account for the non linearity of this loading. This non linearity can come (i) from the squared velocity or (ii) from the shape of the aerodynamic coefficients (as functions of the wind angle of attack). In this paper, we show that this second origin can have significant implications on the design of the structure, particularly when the non linearity of the aerodynamic coefficient is important (obvious, isn’t it?) or when the transverse turbulence is important. [less ▲]

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See detailEstime de soi, comportement à risque et qualité de vie chez des adolescents de 13 à 18 ans
Etienne, Anne-Marie ULg; Riga, Sébastien; Missotten, Pierre ULg et al

Conference (2011, September 08)

L’objectif de l’étude était d’évaluer les capacités de changement d’un adolescent présentant un comportement à risque : être fumeur. Septante adolescents (13 à 18 ans) ont été recrutés : le groupe ... [more ▼]

L’objectif de l’étude était d’évaluer les capacités de changement d’un adolescent présentant un comportement à risque : être fumeur. Septante adolescents (13 à 18 ans) ont été recrutés : le groupe expérimental comprend trente-sept jeunes fumeurs ; le groupe contrôle trente-trois jeunes non -fumeurs. Les fumeurs ont été vus trois fois alors que les sujets du groupe contrôle ont été vus 2 fois sur une période de trois mois. Les principaux questionnaires sont : un questionnaire sociodémographique, l’échelle d’estime de soi de Rosenberg, l’Inventaire Systémique de Qualité de Vie pour Adolescents, trois questions ouvertes qui portent sur le changement, les ressources et la confiance en soi. Les techniques d’intervention sont la balance décisionnelle de l’entretien motivationnel et l’implémentation d’un comportement. Les résultats montrent un effet des entretiens motivationnels chez les fumeurs sur la perception d’être prêt au changement (p = 0,002), sur une meilleure perception de leurs ressources (p<0,001) et sur une augmentation de leur confiance en leur capacité de changement (p = 0,02). L’estime de soi et le score d’écart de qualité de vie restent stables pendant les trois mois à l’exception du score de but des jeunes fumeurs. L’implication clinique de ces résultas sera discutée lors de la présentation orale. [less ▲]

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