References of "Lebeau, Frédéric"
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See detailSpray retention assment combining high-speed shadow imagery and fluorescence techniques
Massinon, Mathieu ULg; Boukhalfa, Hassina dite Hafida ULg; Lebeau, Frédéric ULg

in International Advances in Pesticide Application: Aspects of Applied Biology 122, 2014 (2014, January 08)

Droplet behaviour during impact affects retention by leaves. The increase of droplet adhesion to plant leaves is the objective when applying crop protection products, while droplet bouncing and ... [more ▼]

Droplet behaviour during impact affects retention by leaves. The increase of droplet adhesion to plant leaves is the objective when applying crop protection products, while droplet bouncing and fragmentation are usually seen as detrimental to spray retention. However, observation of droplet impacts on barley using high speed imaging showed that fragmentation impact outcome can occur in two different wetting regimes: Cassie-Baxter or Wenzel’s regime. In the latter, a fraction of the droplet is anchored in the surface roughness, what contributes to retention. Three mixtures were sprayed on excised barley leaves with an 11003 flat-fan nozzle operating at 0.2 MPa. Simultaneous measurements were performed using high speed imaging for droplet impact characterisation. A fluorescent tracer was added to the spray mixture for retention assessment. Retention was related to impact type considering the fraction of the droplet remaining on the leaf surface after a droplet splashing occurring in Wenzel’s wetting regime. This fraction varied from 28‒46% depending on the spray mixture and was correlated to the Volume Median Diameter DV0.5 of the impacting droplets. [less ▲]

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See detailThe effect of surface orientation on spray retention
Massinon, Mathieu ULg; Boukhalfa, Hassina dite Hafida ULg; Lebeau, Frédéric ULg

in Precision Agriculture (2014)

Research in precision spraying investigates the means to reduce the amount of herbicide applied by directing droplets more accurately towards the weeds. The trend in the development of spot spraying ... [more ▼]

Research in precision spraying investigates the means to reduce the amount of herbicide applied by directing droplets more accurately towards the weeds. The trend in the development of spot spraying equipment is an increase of the spatial resolution and new actuators that are able to target very small areas. However, there is a lack of methods for assigning rates of herbicides relating target to optimal droplet features. A wide range of droplet impact angles occurs during the spray application process because of droplet trajectories and the variability of leaf orientation. In this study, laboratory experiments were conducted to highlight the effect of surface orientation on droplet impact outcomes (adhesion, rebound or splashing) on two very difficult-to-wet surfaces: an artificial surface with a regular roughness pattern and an excised black-grass leaf with an anisotropic roughness pattern. Measurements were performed for different surface orientations with a high-speed camera coupled with backlighting LED. Droplets of two formulations (distilled water and distilled water + a surfactant) were produced with a moving flat-fan hydraulic nozzle to obtain a wide range of droplet sizes and velocities, which were measured by image analysis. Increasing surface angle reduces surface area available for droplet capture. Droplet impact behaviors are then modified since surface tilt induces a tangential velocity component at impact and, consequently, a reduction of the normal component. Impact modifications have also been observed due to the anisotropic roughness pattern of a black-grass leaf. The integration of droplet-surface interaction information offers a significant way to further improve the precision spraying efficiency by considering the optimal droplet size, speed and ejection angle depending on the target surface and architecture. [less ▲]

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See detailUse of rotary atomiser to optimize retention on barley leaves while reducing driftable droplets
Ouled Taleb Salah, Sofiene ULg; Massinon, Mathieu ULg; Boukhalfa, Hassina dite Hafida ULg et al

in International Advances in Pesticide Application, Aspects of Applied Biology 122 (2014, January)

Controlled Droplet Application using rotary atomiser is based on an improved control of droplet size and trajectory comparatively to hydraulic nozzles. On the basis of literature, it was stated that the ... [more ▼]

Controlled Droplet Application using rotary atomiser is based on an improved control of droplet size and trajectory comparatively to hydraulic nozzles. On the basis of literature, it was stated that the use of 60° forward angled spray combined with the narrow drop size distribution of a rotary atomiser could lead to low drift and high retention on monocotyledonous and superhydrophobic weeds at early stage. A Micromax120 atomiser was tuned to emit 270 µm VMD, 60° angled forward, to increase interception by the canopy structure. A spray mixture containing a superspreader adjuvant was used to avoid drop bouncing. An increase of spray retention comparatively to a Teejet 11002 at 1.4 bars was observed, although not proved statistically significant by these preliminary trials. On the drift side, the tilted spinning disc seemed to be advantageous since droplet spectra contains a low percentage of droplets under 100 µm and presents an ejection velocity of 25 m.s-1 at 5000 RPM. The spray drift was reduced about 50%. However, these setting were not found as efficient as expected. Indeed, angled spray proved to be more sensitive to advection and turbulence, as the spray was more exposed to the airflow than for the vertical position. It appears that angling the spray and choosing a drop size spectrum with a Volume Median Diameter as big as 270 µm is not sufficient to reduce significantly this issue. Some alternatives as decreasing the emission height are possible with angled sprays but require height control that seems difficult to reach in practical situations. [less ▲]

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See detailDe l’expérimentation à la modélisation des propriétés hygrothermiques de parois isolées en paille
Louis, Arnaud ULg; Evrard, Arnaud; Courard, Luc ULg et al

in Annales du Bâtiment et des Travaux Publics (2013)

Some results of aPROpaille project are presented. The goal of this project is to improve the knowledge about hygrothermal performances of walls in which thermal insulation is mainly provided by straw ... [more ▼]

Some results of aPROpaille project are presented. The goal of this project is to improve the knowledge about hygrothermal performances of walls in which thermal insulation is mainly provided by straw. Besides an overall characterization of straw properties and two types of earth plaster, a series of tests was performed to determine the hygrothermal properties of these materials: porosity, sorption curve, water vapour diffusion, capillary absorption, total water absorption, specific heat and thermal conductivity. The determination of these parameters required sometimes the implementation of unusual protocols or unreleased materials. Numerical simulations based on the properties defined in the test campaign are also presented. Results clearly point out the influence of the type of plaster and the orientation of fibres into straw bale. [less ▲]

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See detailUse of on-line flow cytometry for the characterization of physiological behavior in stress conditions during the bioprocess
Brognaux, Alison ULg; Han, Shanshan; Soren, Sorensen et al

Poster (2013, November 15)

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See detailÉlaboration du référentiel de compétences du master bioingénieur en Sciences et Technologies de l'Environnement
Colaux-Castillo-Bocanegra, Catherine ULg; Colinet, Gilles ULg; Debouche, Charles ULg et al

in Poulin, Richard (Ed.) Séminaire CITEF 2013 La liaison formation-emploi : l'approche compétences et la formation tout au long de la vie (2013, October 18)

Le département des Sciences et Technologies de l’Environnement (STE) de Gembloux Agro-Bio Tech faculté de l’Université de Liège a profité d’un changement d’intitulé de son diplôme de bioingénieur pour ... [more ▼]

Le département des Sciences et Technologies de l’Environnement (STE) de Gembloux Agro-Bio Tech faculté de l’Université de Liège a profité d’un changement d’intitulé de son diplôme de bioingénieur pour réviser son programme des études. Pour ce faire, il a adopté l’approche compétence. Afin de préparer au mieux ses futurs diplômés aux attentes du monde professionnel actuel et à venir, des anciens diplômés et des employeurs potentiels ont participé à la validation du référentiel de compétences associé à cette formation. Cette publication reprend les étapes clés de la création du référentiel de compétences et son exploitation dans la conception d’un programme des études cohérent. [less ▲]

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See detailUse of on-line flow cytometry to detect segregation in the microbial population
Brognaux, Alison ULg; Zune, Quentin ULg; Han, Shanshan et al

Poster (2013, October 08)

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See detailDesign, Construction and Validation of a Guarded Hot Plate Apparatus for Thermal Conductivity Measurement of High Thickness Crop-Based Specimens
Dubois, Samuel ULg; Lebeau, Frédéric ULg

in Materials and Structures (2013)

The search for sustainability achievement in the building sector led to the use of crop-based insulation materials. Among these, raw products like plant straws bales can present elementary representative ... [more ▼]

The search for sustainability achievement in the building sector led to the use of crop-based insulation materials. Among these, raw products like plant straws bales can present elementary representative volumes (REVs) in the size order of several square centimeters. Fibers orientation may play an important role on material thermal behavior. Measuring their thermal conductivities with standard steady-state equipment can thus lead to some inaccuracies due to the necessity of resetting lower thickness samples. This paper presents a Guarded Hot Plate (GHP) apparatus designed to test high thickness samples, up to 40cm, with an accuracy of 2%. The different parts of the machine are described in details along with design process and challenges encountered. Temperature and heat flux measurements in the device represent critical design stages where optimal accuracy is needed in order to optimize the resulting global error. Regarding this, necessary numerical and experimental analyzes were conducted emphasizing on intrinsic systematic error assessment. To complete the study, some validations tests are performed on a reference material and other widely-spread polystyrene slabs. These tests take into account the optimal computation parameters resulting from the numerical analysis and the apparatus proved to be in accordance with accuracy requirements. [less ▲]

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See detailModeling the hygrothermal behavior of biobased construction materials
Dubois, Samuel ULg; Evrard, Arnaud; Lebeau, Frédéric ULg

in Journal of Building Physics (2013)

Materials with high moisture exchange capacity may have a strong impact on indoor climate conditions as well as building energy performance. Crop-based materials, characterized by their high porosity and ... [more ▼]

Materials with high moisture exchange capacity may have a strong impact on indoor climate conditions as well as building energy performance. Crop-based materials, characterized by their high porosity and hygroscopicity, belong to this category. Modeling their hygrothermal behavior accurately is thus particularly relevant for appropriate building design. A COMSOL Multiphysics transient heat air and moisture model is developed in this article to simulate moisture exchange between a lime–hemp concrete block and surrounding air during a Moisture Buffer Value evaluation test. Results are then compared with the validated heat air and moisture software using performance criteria showing a slight preference for both moisture exchanges and latent heat effect characterization. It offers yet additional advantages in terms of flexibility and transparency as well as further evolution potential. [less ▲]

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See detailDe l’expérimentation à la modélisation des propriétés hygrothermiques de parois isolées en paille
Louis, Arnaud ULg; Evrard, Arnaud; Biot, Benjamin et al

Conference (2013, May 31)

First results of aPROpaille project are presented. The goal of this project is to improve the knowledge about hygrothermal performances of walls in which thermal insulation is mainly provided by straw ... [more ▼]

First results of aPROpaille project are presented. The goal of this project is to improve the knowledge about hygrothermal performances of walls in which thermal insulation is mainly provided by straw. Besides an overall properties characterization of straw and two types of earth plaster, a series of tests was performed to determine the hygrothermal properties of these materials: porosity, sorption curve, water vapour diffusion, capillary absorption, total water absorption, specific heat and thermal conductivity. The determination of these parameters required sometimes the implementation of unusual protocols or unreleased materials. Numerical simulations based on the properties defined in the test campaign are also presented. Results clearly point out the influence of the type of plaster and the orientation of fibres into straw bale. [less ▲]

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See detailHygrothermal behavior modeling of different Lime-Hemp Concrete mixes
Dubois, Samuel ULg; Lebeau, Frédéric ULg

Conference (2013, May 28)

This paper studies the specific hygrothermal behavior of Lime-Hemp concretes through analysis of non-linear coupled heat and moisture transfer using a research model. Three compositions were studied ... [more ▼]

This paper studies the specific hygrothermal behavior of Lime-Hemp concretes through analysis of non-linear coupled heat and moisture transfer using a research model. Three compositions were studied, varying the type of binder. First Moisture Buffer Value determination tests are lead experimentally using the NORDTEST protocol. These dynamic experiments, which reveal the moisture storage and exchange capacity together with latent heat effects, are then modeled using a set of partial differential equations. The reduction of humidity buffering capacity induced by hydraulic binder incorporation is properly evaluated and the hygrothermal parameters can be assessed by inverse modeling. [less ▲]

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See detailAssessment of a 3S rotary atomizer
Ouled Taleb Salah, Sofiene ULg; Massinon, Mathieu ULg; Lebeau, Frédéric ULg

Poster (2013, May 23)

Spinning disc sprayers were first introduced to control cotton pests and diseases. These atomizers were recognized for their production of a uniform droplet size spectrum than conventional nozzles. They ... [more ▼]

Spinning disc sprayers were first introduced to control cotton pests and diseases. These atomizers were recognized for their production of a uniform droplet size spectrum than conventional nozzles. They have proved to be the most successful way of delivering pesticides in the form of Controlled Droplet Application (CDA) at very low volume application. But they were almost abandoned since the years of 1990 for high and medium volume application. Their use was found inefficient in arable crops such as cereals due to the use of inappropriate application rate and problem of penetration of spray in cereal canopies. However, these spray generators may be the best solution when the spray was to be targeted to a small weed with hydrophobic leaf surface where adhesion in the impact is essential for treatment efficiency while minimizing drift and splash thanks to reduced droplet span. In this study, aiming to maximize the control of black grass in cereals, characterization of the droplet size spectra was performed to predict the trajectory droplet and estimate the number that will hit the targeted surface. So, a CDA Micromax Ltd rotary atomizer 3S was operated at different rotation speeds (2000, 3500 and 5000 rpm), flow rates and pressures. A camera X stream -3S which allows the acquisition images in PIV mode, connected to a led lightening set at double mode exposure, were placed in front of the edge of the disc on a spray bench. Images were treated through a laboratory developed Matlab code for Particle Tracking Velocimetry Sizing. Droplets speeds according to diameters were extracted. Droplets cumulative volume according to diameters was also obtained. As the flow rate rose, the volume median diameter (VMD) increased. On the other hand, the VMD decreased as the rotation speed increased. Satellites droplets were observed when the atomizer was operating at a disc speed of 2000 rpm. For each flow rate corresponding to a drop size VMD, the number of droplets/cm2 that will affect pesticide coverage was calculated. Thus, the number of droplets that will effectively adhere depend on their impact at the moment of their arrival to the surface target. [less ▲]

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See detailHigh-speed imaging use to predict spray retention on barley leaves
Boukhalfa, Hassina dite Hafida ULg; Massinon, Mathieu ULg; Lebeau, Frédéric ULg

in Communications in Agricultural and Applied Biological Sciences (2013, May 21), Vol 78(2)(1-386 (2013)), 31-36

Laboratory studies were conducted to validate the effectiveness of the use of high-speed imaging method to replace chemical nalysis by fluoremetrie. Measurements were performed with a high-speed camera ... [more ▼]

Laboratory studies were conducted to validate the effectiveness of the use of high-speed imaging method to replace chemical nalysis by fluoremetrie. Measurements were performed with a high-speed camera coupled with a retro-LED lighting. Size and velocity of the drop were extracted by image analysis. Drop impact types were determined by the operator. Drops were produced with a flat-fan nozzle mounted on a movable ramp. Two surfactants (Break-Thru® S240 and Li700 ®) were sprayed on BBCH 12 barley leaves to highlight the effect of the reduction of surface tension. Relative volume proportions were computed within of an energy scale divided into 11 classes based on the Weber number. results are compared to the results of the chemical analysis by spectrofluerometry. [less ▲]

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See detailZoom sur la rétention par les plantes
Lebeau, Frédéric ULg; Massinon, Mathieu ULg; Destain, Marie-France ULg

Conference given outside the academic context (2013)

This video aims to get an insight on the mechanisms involved in retention of pesticides on plants. Using high magnification lenses, high speed camera and led back-light, the elaboration of retention on ... [more ▼]

This video aims to get an insight on the mechanisms involved in retention of pesticides on plants. Using high magnification lenses, high speed camera and led back-light, the elaboration of retention on plant leaves is better understood. The behavior of different drops diameters and speed is observed and linked to the physics behind. The video is dedicated to plant protection products users and should give them a clear understanding of the relevant parameters to be mastered to avoid losses and reduce polution. [less ▲]

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See detailImprovement of spray retention on barley leaves by adjuvants
Boukhalfa, Hassina dite Hafida ULg; Massinon, Mathieu ULg; Lebeau, Frédéric ULg

Poster (2013, April 18)

Adjuvants contribute to change the types of impact and thus the amount of spray retained by the leaves of the treated plant. We have performed tests of retention on barley plants on BBCH 12 stage and ... [more ▼]

Adjuvants contribute to change the types of impact and thus the amount of spray retained by the leaves of the treated plant. We have performed tests of retention on barley plants on BBCH 12 stage and small pieces of barley leaves at the same stage of growth. Spraying was done in three ways: water without adjuvant, water with Break-Thru® S240 and water with Li700®. The three slurries of fluorescein contained in an amount of 0.2 g / l. Fluorescein retained by the leaves in both cases is then measured by a spectrofluoremeter. The retention tests on whole plants show that it is tripled by the first adjuvant and doubled by the second. On the other side, on small pieces of barley leaves, the amount was increased by the use of surfactants but not to the same extend. This study concluded that the use of adjuvants in spray pesticides increases the amount of retention as a function of leaf area and the type of adjuvant. [less ▲]

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See detailCHARACTERIZATION OF AGRICULTURAL SPRAY BY DIGITAL ANALYSIS OF SHADOWGRAPHY IMAGES
De Cock, Nicolas ULg; Massinon, Mathieu ULg; Lebeau, Frédéric ULg

Poster (2013, February 08)

Agricultural sprays are among the most common two-phase flows studied because their characteristics determine the efficiency of treatment as well as environmental contamination. At present, the relevance ... [more ▼]

Agricultural sprays are among the most common two-phase flows studied because their characteristics determine the efficiency of treatment as well as environmental contamination. At present, the relevance of different characterization techniques of the highly polydispersed sprays used in this application remains controversial. Digital analysis of shadowgraphy images presents an attractive option for the characterization of both velocity and size of droplets present in the spray. This study presents an overview of the contrast problems inherent in the use of backlighted images and propose appropriate solution to ensure the quality of measurements. Generally, background light presents heterogeneities associated with light sources and optical arrangement. These can be solved by substracting from each images a composite background. An other particular focus is given to one major drawback of volumetric lighting, the presence of out focus droplets. These droplets have to be removed during the image analysis process because the measurement of their diameters can't be done accuratly. The rejection of these out of focus objects is based on a quantitative parameter which was calibrated with a obliquely shot monodispersed spray. The final step of the image processing is determining velocity of the droplet by tracking a same droplet on two successive images. The tracking algorithm is based on the size of the droplet, its more probable displacement and its direction. [less ▲]

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