References of "Lebeau, Frédéric"
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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 detailOn-line flow cytometry profiling of Escherichia coli stress response
Brognaux, Alison ULg; Han, Shanshan; Sorensen, Soren et al

Conference (2013, February 08)

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See detailSTUDY OF THE EFFECT OF TWO SURFACTANTS ON SPRAY RETENTION BY BARLEY LEAVES
Boukhalfa, Hassina dite Hafida ULg; Massinon, Mathieu ULg; Lebeau, Frédéric ULg

Poster (2013, February 08)

Surfactants are nowadays very useful additives to improve the effectiveness of phytosanitary treatments. They contribute to change the types of impact and thus the amount of spray retained by the leaves ... [more ▼]

Surfactants are nowadays very useful additives to improve the effectiveness of phytosanitary treatments. They contribute to change the types of impact and thus the amount of spray retained by the leaves of the treated plant. We performed tests of retention on whole 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 surfactant, 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 surfactant and doubled by the second. By cons on small pieces of barley leaves, the amount was increased by the use of surfactants but not to the same scale. This study concluded that the use of surfactants in spray pesticides may increase the amount of retention as a function of leaf area and the surfactant used. [less ▲]

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See detailCHARACTERIZATION OF AGRICULTURAL SPRAY BY DIGITAL ANALYSIS OF SHADOWGRAPHY IMAGES
De Cock, Nicolas; 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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See detailOn-line profiling of Escherichia coli stress response
Brognaux, Alison ULg; Shanshan, Han; Sorensen, Soren et al

in Communications in Agricultural and Applied Biological Sciences (2013)

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See detailA low-cost, multiplexable, automated flow cytometry procedure for the characterization of microbial stress dynamics in bioreactors
Brognaux, Alison ULg; Han, Shanshan; Sorensen, Soren J et al

in Microbial Cell Factories (2013), 12(100), 1-14

Background Microbial cell population heterogeneity is now recognized as a major source of issues in the development and optimization of bioprocesses. Even if single cell technologies are available for the ... [more ▼]

Background Microbial cell population heterogeneity is now recognized as a major source of issues in the development and optimization of bioprocesses. Even if single cell technologies are available for the study of microbial population heterogeneity, only a few of these methods are available in order to study the dynamics of segregation directly in bioreactors. In this context, specific interfaces have been developed in order to connect a flow cytometer directly to a bioreactor for automated analyses. In this work, we propose a simplified version of such an interface and demonstrate its usefulness for multiplexed experiments.Results A low-cost automated flow cytometer has been used in order to monitor the synthesis of a destabilized Green Fluorescent Protein (GFP) under the regulation of the fis promoter and propidium iodide (PI) uptake. The results obtained showed that the dynamics of GFP synthesis are complex and can be attributed to a complex set of biological parameters, i.e. on the one hand the release of protein into the extracellular medium and its uptake modifying the activity of the fis promoter, and on the other hand the stability of the GFP molecule itself, which can be attributed to the protease content and energy status of the cells. In this respect, multiplexed experiments have shown a correlation between heat shock and ATP content and the stability of the reporter molecule. Conclusion This work demonstrates that a simplified version of on-line FC can be used at the process level or in a multiplexed version to investigate the dynamics of complex physiological mechanisms. In this respect, the determination of new on-line parameters derived from automated FC is of primary importance in order to fully integrate the power of FC in dedicated feedback control loops. [less ▲]

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See detailReview of physicochemical processes involved in agrochemical spray retention
Massinon, Mathieu ULg; Lebeau, Frédéric ULg

in Biotechnologie, Agronomie, Société et Environnement = Biotechnology, Agronomy, Society and Environment [=BASE] (2013)

This review provides a broad view of the processes and parameters involved in applying agrochemicals to the leaves of field crops. Treatment efficiency is assessed using macroscopic and microscopic ... [more ▼]

This review provides a broad view of the processes and parameters involved in applying agrochemicals to the leaves of field crops. Treatment efficiency is assessed using macroscopic and microscopic approaches to investigate spray retention. With the macroscopic approach, aspects related to spray coarseness, carrier volume, leaf wettability, plant architecture, crop density and additives are addressed. Comparative studies have highlighted the wide variability in spray retention as a function of these parameters. They have failed, however, to describe the underlying physical relationships clearly enough to generalize the results. These relationships are better investigated using a microscopic approach, where drop impact behavior is established in relation to target surface and fluid properties. The wetting regime (either Wenzel or Cassie-Baxter) depends on the leaf surface microscopic roughness ratio (r) and chemical nature, fluid dynamic surface tension and drop impact energy. Adhesion, rebound and disintegration have been observed successively with increasing drop impact energy. Transitions between impact outcomes are influenced by fluid rheology and the dynamic surface tension of the fluid. The effect of surface orientation remains poorly explored, but it seems to have a limited influence on retention. Recent fundamental studies on superhydrophobicity and wetting should help practitioners in their search for an ever more rational application of agrochemicals. They could also drive the development of new systematic retention testing methods. [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)

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 detailAssessment of pesticide application method efficiency by high-speed image analysis
Massinon, Mathieu ULg; Denis, Thierry; Perriot, Benjamin et al

Conference (2012, July 08)

This paper investigates if increased blackgrass weeding efficiency by reduced volume per hectare observed during 2010 Arvalis field trials may be related to increased pesticide application method ... [more ▼]

This paper investigates if increased blackgrass weeding efficiency by reduced volume per hectare observed during 2010 Arvalis field trials may be related to increased pesticide application method efficiency. Retention on blackgrass leaves was assessed by an image analysis method. The setup consists of a high-speed camera shooting drop impact on horizontal leaf target. An herbicide (Archipel® [125 g/ha] + Actirob® [1 l/ha]) was sprayed at the usual volume of 150 l/ha and at a reduced volume of 65 l/ha. Adjuvants use (Epsotop® [1%] + Heliosol® [0.5%]) was also evaluated at 65 l/ha to highlight the effect of mixture surface tension modification. Drop properties before impact were extracted by image analysis and a phase diagram derived. Volumetric proportions of impact types are determined inside 11 energy classes to assess the effect of formulation and application method. The volume median diameter (VMD) before impact was slightly decreased by the reduction to 65 l/ha because of nozzle and pressure changes and also by the use of the adjuvants leading to the reduction of surface tension. Without adjuvants the reduction to 65l/ha increased the proportion of adhesion while rebound remained unchanged and fragmentation decreased. With adjuvants, drop fragmentation occurs for a lower energy class but the proportion of fragmentation also decreases with because of reduced VMD. A slight effect on the transitions between impact classes was observed because of formulation concentration change at reduced volume/hectare. A major effect of adjuvants on retention was highlighted as bouncing disappeared. [less ▲]

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See detailTHE EFFECT OF LEAF ORIENTATION ON SPRAY RETENTION ON BLACKGRASS
Massinon, Mathieu ULg; Boukhalfa, Hassina dite Hafida ULg; MARECHAL, Pierre- et al

Conference (2012, July)

Spray application efficiency depends on the pesticide application method as well as target properties. A wide range of drop impact angles exists during the spray application process because of drop ... [more ▼]

Spray application efficiency depends on the pesticide application method as well as target properties. A wide range of drop impact angles exists during the spray application process because of drop trajectory and the variability of the leaf orientation. As the effect of impact angle on retention is still poorly documented, laboratory studies were conducted to highlight the effect of leaf orientation on drop impact outcomes. 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. Excised blackgrass [Alopecurus myosuroides HUDS. (ALOMY)] leaves were stretched between two parts of a U-shaped support. A surfactant (Break-Thru® S240) was sprayed to highlight the effect of mixture surface tension. The whole device was tilted from 0 to 90°. Relative volume proportions were computed within of an energy scale divided into 11 classes. These proportions have been weighted by an average volume distribution and the results were summed for all energy classes to obtain the total volume proportions for each impact outcomes and for all leaf angles. For distilled water (high surface tension) the increase of rebound proportion with the increase of drop impact angle is highlighted. For surfactant (lower surface tension), it results in an increase of drop fragmentation in Cassie-Baxter wetting regime. To be statistically representative, bigger drop samples should be used. [less ▲]

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See detailImagerie par ombroscopieavec eclairage LED
De Cock, Nicolas ULg; Lebeau, Frédéric ULg

Scientific conference (2012, June 07)

Imagerie par ombroscopie avec LEDs pulsées L’imagerie par ombroscopie est une technique adaptée à la visualisation des gouttes, particules, bulles,.. Cette méthode se base sur une imagerie de haute ... [more ▼]

Imagerie par ombroscopie avec LEDs pulsées L’imagerie par ombroscopie est une technique adaptée à la visualisation des gouttes, particules, bulles,.. Cette méthode se base sur une imagerie de haute résolution et un éclairage de fond pulsé. Dans une variante de la méthode, la lumière est émise au moyen de sources LEDs de haute puissance focalisées par des optiques en vue d'obtenir une haute illumination de la scène. Le plan focal et la profondeur de champ des composants de l’optique définissent le volume de mesure en combinaison avec le filtrage de l'image réalisé en post-traitement. Ce post-traitement s'impose pour régler les problèmes d'uniformité de l'arrière plan provenant tant des différences entre LEDs que des particules non focalisées ainsi que de différences d’atténuation en fonction de la taille des particules. La source lumineuse est une lampe composée de LEDs pulsées à un intervalle fonction de la vitesse des particules. En utilisant une impulsion courte pour l’éclairage et un overdrive du courant nominal des LEDs, il est possible de figer le mouvement jusqu’à des vitesses élevées par des temps d'exposition de quelques microsecondes. Un contrôleur à deux voies permet de réaliser une double impulsion, ce qui combiné à une caméra double exposition permet la détermination des vitesses de particules en fonction de leur taille. Des travaux sur la mesure de granulométrie et vitesse de jet en pulvérisation agricole ainsi que d'impact de gouttes sur des surfaces superhydrophobes illustent le propos. Une technique de calibrage des algorithmes au moyen de gouttes monodisperses est présentée. [less ▲]

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See detailExperimental method for the assessment of agricultural spray retention based on high-speed imaging of drop impact on a synthetic superhydrophobic surface
Massinon, Mathieu ULg; Lebeau, Frédéric ULg

in Biosystems Engineering (2012), 112(1), 56-64

Spray retention is a critical stage in pesticide application since non-retained drops can result in reduced efficacy, economic loss and environmental contamination. Current methods of retention assessment ... [more ▼]

Spray retention is a critical stage in pesticide application since non-retained drops can result in reduced efficacy, economic loss and environmental contamination. Current methods of retention assessment are based either on field experiments or laboratory studies. The former are usually performed on whole plants under realistic spray application conditions but offer no insight into the physics behind the process whilst the latter mainly focus on drop impact physics but are usually restricted to unrealistically low drop speeds. The aim of the paper is to devise an experimental method to investigate retention at drop scale level as a function of operational parameters but under controlled realistic conditions. A device based on highspeed video was developed to study retention on a synthetic superhydrophobic surface for a moving agricultural nozzle. The sizes and velocities of the drops generated were measured immediately before impact using image analysis. Impact class proportions were established and transition boundaries between impact outcomes were quantified using Weber number. Two contrasting experiments were performed to investigate the ability of method to detect small parametric changes. The insignificant changes in spray pattern that occur from pressure changes, did not significantly affect impact class boundaries, but changed the proportion of drops in each class because of size and velocity variations. The use of a surfactant reduced the volume median diameter of the spray, increased impact speed and changed the impact class boundaries. The method should allow a precise parametric investigation of spray retention in laboratory and close to field conditions. [less ▲]

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See detailStudy of pesticide retention on leaves using high-speed imaging
Massinon, Mathieu ULg; Lebeau, Frédéric ULg

Poster (2012, February 08)

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See detailComparison of spray retention on synthetic superhydrophobic surface with retention on outdoor grown wheat leaves
Massinon, Mathieu ULg; Lebeau, Frédéric ULg

in International Advances in Pesticide Application: Aspects of Applied Biology 114, 2012 (2012, January)

A method has been designed to test the retention of drops generated by a moving agricultural nozzle using high speed imaging both on synthetic and leaf surfaces. The method allows a precise investigation ... [more ▼]

A method has been designed to test the retention of drops generated by a moving agricultural nozzle using high speed imaging both on synthetic and leaf surfaces. The method allows a precise investigation of spray retention by a characterisation of impact speed, drop diameter and impact behaviour. The paper presents a comparison of the spray behaviour on the synthetic surface with the behaviour on outdoor grown wheat leaves fixed on a microscope slide. Target surfaces were horizontal. A range of surface tension was tested using the tank-mix adjuvant Break-Thru S240 at different concentrations in distilled water. Results show the relevance of a synthetic surface for use as reference for the assessment of spray application efficiency. The drop behaviour on the superhydrophobic slide was representative of difficult-to-wet leaves surfaces. The reference surface avoids the natural variability of leaves and is therefore more suited to conduct comparative assessment of formulation retention performance. [less ▲]

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See detailÉvaporation d’une gouttelette en chute libre dans l’air
Massinon, Mathieu ULg; Lebeau, Frédéric ULg

Software (2012)

Simple model taking into account the movement and transfer of heat and mass at the droplet in free fall in the air.

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See detailHygrothermal modelling of Lime-Hemp concrete used as building material and indoor climate buffering characterization
Dubois, Samuel ULg; Evrard, Arnaud; Lebeau, Frédéric ULg

Poster (2012)

Hygroscopic building materials can affect the indoor air by exchanging moisture with it and buffering the ambient humidity variations. The Nordtest protocol and the concomitant Moisture Buffer Value (MBV ... [more ▼]

Hygroscopic building materials can affect the indoor air by exchanging moisture with it and buffering the ambient humidity variations. The Nordtest protocol and the concomitant Moisture Buffer Value (MBV) parameter definition has been one of the first attempt to characterize this moisture regulation performance. This paper present an attempt to confront this well-established experimental protocol with a mathematical model implemented in the Comsol multiphysics solver. The power of the simulation will be showed with a good correlation between the modelling and the experimental phase for the MBV determination of a lime-hemp concrete bloc. [less ▲]

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See detailÉtude de la distribution granulométrique de particules de chanvre: Méthodes par tamisage et analyse d'image
Dubois, Samuel ULg; Lebeau, Frédéric ULg

Report (2011)

Ce document présente une analyse de la répartition granulométrique d'une chènevotte commerciale. Deux techniques différentes sont étudiées. La première consiste à séparer les particules mécaniquement par ... [more ▼]

Ce document présente une analyse de la répartition granulométrique d'une chènevotte commerciale. Deux techniques différentes sont étudiées. La première consiste à séparer les particules mécaniquement par tamisage. La diversité morphologique des particules de chanvre entraîne cependant des questions quant à l'interprétation des résultats obtenus, et plus particulièrement sur les paramètres physiques réellement discriminatoires dans cette séparation en classes granulométriques. Il est montré ici que l'analyse d'image permet de répondre à cette question et d'apporter des informations précieuses dans la description des particules. A cette fin, la performance de descripteurs issus d'algorithmes de calcul en analyse d'image est étudiée. Enfin, une représentation multi-classes de la distribution granulométrique de la chènevotte est proposée, regroupant les descriptions dimensionnelle et morphologique des particules. [less ▲]

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