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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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See detailRTDrift, modèle permettant d’évaluer en temps réel les risques environnementaux liés à la dérive des produits phytosanitaires
Lebeau, Frédéric ULg; Massinon, Mathieu ULg; Verstraete, Arnaud et al

Conference (2011, October 17)

Un modèle, RTDrift, a été développé pour estimer la contamination causée par la dérive pour les pulvérisateurs à rampe en cours de traitement. Un pulvérisateur a été équipé de capteurs pour mesurer les ... [more ▼]

Un modèle, RTDrift, a été développé pour estimer la contamination causée par la dérive pour les pulvérisateurs à rampe en cours de traitement. Un pulvérisateur a été équipé de capteurs pour mesurer les paramètres de la dérive dont la pression de pulvérisation, les mouvements de rampe, la vitesse et direction du vent, la température et l’humidité ainsi que la géo-localisation. Pour chaque position successive des buses, un modèle de diffusionadvection gaussien avec sédimentation est utilisé pour calculer à partir de la buse le transport de chaque classe de gouttes déterminée préalablement par granulométrie laser en prenant en compte l’évaporation. Différents essais de terrain ont été réalisés où la dérive a été mesurée à différentes distances par fluorométrie sur collecteurs. La comparaison avec le modèle montre une estimation satisfaisante de la dérive sur base des mesures embarquées et offre le potentiel d’un estimateur de dérive en temps réel. Les pistes d’améliorations ultérieures sont évoquées. [less ▲]

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See detailA FEASIBILITY STUDY OF DEVELOPING DIRECT INJECTION SPRAYING TECHNOLOGY FOR SMALL SCALE FARMS
El Aissaoui, Abdellah ULg; Lebeau, Frédéric ULg; el bahir, Lhoussein et al

in SZABÓ, Istvan; MAGÓ, László; KURJÁK, Zoltán (Eds.) II. INTERNATIONAL CONFERENCE OF THE CIGR HUNGARIAN NATIONAL COMMITTEE, THE FACULTY OF MECHANICAL ENGINEERING OF THE SZENT ISTVÁN UNIVERSITY, AND THE AGRICULTURAL ENGINEERING BOARD OF THE HUNGARIAN ACADEMY OF SCIENCES (2011, October 12)

The present study focuses on designing hydraulic scheme and process control system for small direct injection sprayer equipped with five meters' boom (10 tip nozzles) based on DC electrical energy supply ... [more ▼]

The present study focuses on designing hydraulic scheme and process control system for small direct injection sprayer equipped with five meters' boom (10 tip nozzles) based on DC electrical energy supply. A numerical model was developed by using finite volume method to study dynamic of concentration change process and to optimize the hydraulic boom design required to overcome lag transport problem related to real time application. The schemes of serial and parallel boom layouts were studied to obtain minimal lag transport for chemical concentration change process. The process control system was modelled in Matlab-SimulinkTM, and a laboratory test bench was implemented with a PID (Proportional Integral Derivative) feedback control for evaluating the performance of the constant carrier flow and the variable total flow strategies. The results of the hydraulic modelling of the serial boom layout showed that 6 mm boom diameter gave a satisfying performance in term of application uniformity (up to 97%) and lag transport along nozzles (from 0.8 to 1.5 s). The prospection of parallel scheme by feeding individually nozzles gave an even reduced lag transport (2 s) along the boom (diameter of 4 mm). The modelling of constant carrier flow control strategy showed a lag time of 2.5 s for the step speed change of 0.6 to 1.2 m/s at constant pressure of 2 bars. The total flow control strategy showed the advantage of reducing lag transport from 4 to 2.3 s when speed varied from 0.6 to 1.2 m/s in accordance with operating pressure (from 1 to 3 bars). The experimental tests showed the importance of varying carrier flow rate to improve the controller dynamic in comparison to the constant carrier flow control. [less ▲]

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See detailRTDrift: a real time model for estimating spray drift from ground applications
Lebeau, Frédéric ULg; Verstraete, Arnaud ULg; Stainier, Charles ULg et al

in Computers & Electronics in Agriculture (2011), 77(2), 161-174

A spray drift model called RTDrift was developed to estimate drift caused by ground sprayer machines. The sprayer was equipped with sensors measuring operational parameters namely spray pressure, boom ... [more ▼]

A spray drift model called RTDrift was developed to estimate drift caused by ground sprayer machines. The sprayer was equipped with sensors measuring operational parameters namely spray pressure, boom height and movements, and geolocalization. Climatic parameters, including wind speed and direction, were measured using a 2-D ultrasonic anemometer mounted on the sprayer. The nozzles spray drop size spectra were characterized using Phase Doppler Interferometer measurements. At every successive boom position, a diffusion-advection Gaussian tilted plume model computed the spray drift deposits for each drop class taking into account evaporation. The contribution of a single nozzle was calculated by integration of the individual puffs with respect to time and summation of the contributions of individual drops classes. The overall drift generated by the sprayer machine was obtained adding the contributions of all the nozzles. Field trials were performed on a fallow field with water and on crops with pesticides in various wind conditions. The ground drift was measured at different drift distances using fluorometric methods. When comparing the results of the model with experimental measurements of deposits, the model produced realistic maps of drift deposits. Some further improvement is needed in the presence of large scale eddies. The model offers potential benefits for the farmer as a real time drift estimator embedded on a sprayer machine [less ▲]

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See detailDevelopment of process control system for potential use of direct injection spraying technology
Aissaoui, Abdellah; Lebeau, Frédéric ULg; el bahir, et al

in Progress in Agricultural Engineering Sciences (2011), 7(1), 33-45

Small-scale farmers face to actual difficulties of applying pesticides accurately and safely on vegetables crops. They mainly use hand operated sprayers. As an issue, a small direct injection system based ... [more ▼]

Small-scale farmers face to actual difficulties of applying pesticides accurately and safely on vegetables crops. They mainly use hand operated sprayers. As an issue, a small direct injection system based on a five meter’s parallel boom layout was designed to improve chemical application. The boom layout was optimized to obtain the same minimal time lag response for the ten nozzles. The dynamic of the system was modeled using Simulink TM as first order model with delay. Two control strategies were implemented using PID (Proportional Integral Derivative) feedback control loops to monitor tracer injection (fluorescing) proportionally to simulated forward speed (from 0.6 to 1.2 m/s) and to control the constant operating pressure (constant carrier flow strategy) or the variable operating pressure proportionally to the injected chemical amount (variable total flow strategy). Different forward speed changes were induced using steps up and down, ramps, sine waves and sweeps excitations to evaluate the control feedback. The system stability was tested for its ability to maintain the expected concentration and application rate. The results show that the time lag remains less than 3 s (dead time < 2 s, time constant < 1 s) and the system keeps stable for the maximal speed variation (ΔV) and acceleration (ā) tested (ΔV = 200%, ā = 0.48 m/s2) which induce less than 10% variation of application rate. [less ▲]

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See detailREAL-TIME MONITORING OF ENVIRONMENTAL FACTORS TO MODEL WHEAT YIELD PRODUCTION
Dumont, Benjamin ULg; Leemans, Vincent ULg; Lebeau, Frédéric ULg et al

Poster (2010, September 07)

This paper presents the results of a one year preliminary study in which a real-time monitoring system was used to feed the STICS soil crop model. The monitoring system was made of a self-organising ... [more ▼]

This paper presents the results of a one year preliminary study in which a real-time monitoring system was used to feed the STICS soil crop model. The monitoring system was made of a self-organising wireless network within which microsensors collected and stored microclimatic and environmental data. As indicated by the statistical criteria (RMSE, normalized deviation and model efficiency), the optimisation of some wheat crop parameters allows the STICS model to predict the yields with good accuracy for three different soil types and seven different nitrogen application rates. [less ▲]

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See detailA MODEL FOR WHEAT YIELD PREDICTION BASED ON REAL-TIME MONITORING OF ENVIRONMENTAL FACTORS
Dumont, Benjamin ULg; Lebeau, Frédéric ULg; Vancutsem, Françoise ULg et al

Poster (2010, July)

This paper presents the results of a one year preliminary study in which a real time monitoring system was used to feed the STICS soil crop model. As indicated by the statistical criteria (RMSE and model ... [more ▼]

This paper presents the results of a one year preliminary study in which a real time monitoring system was used to feed the STICS soil crop model. As indicated by the statistical criteria (RMSE and model efficiency), the optimization of some wheat crop parameters allows the model to predict the yields with good accuracy for different soil type and different nitrogen application rates. [less ▲]

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See detailTEST AND EVALUATION OF TWO PROCESS CONTROL STRATEGIES FOR ADAPTING DIRECT INJECTION PESTICIDE APPLICATION TO SMALL SCALE FARMS
El Aissaoui, Abdellah ULg; Lebeau, Frédéric ULg; Destain, Marie-France ULg et al

Conference (2010, January 13)

Small scale farmers, in developing and in some developed countries, are faced to actual difficulties of applying pesticides accurately and safely on vegetables crops. They mainly use hand operated ... [more ▼]

Small scale farmers, in developing and in some developed countries, are faced to actual difficulties of applying pesticides accurately and safely on vegetables crops. They mainly use hand operated sprayers. As an issue, a small direct injection system based on a five meter's parallel boom layout was designed to improve chemical application. The boom layout was optimised to obtain the same minimal lag time response for the ten nozzles. The dynamic of the system was modelled using SimulinkTM as first order model with delay. Two control strategies were implemented using PID feedback control loops to monitor tracer injection (fluorescing) proportionally to simulated forward speed (from 0.6 to 1.2 m/s) and to control the constant operating pressure (constant carrier flow strategy) or the variable operating pressure proportionally to the injected chemical amount (variable total flow strategy). Different forward speed changes were induced using steps up and down, ramps, sine waves and sweeps solicitations to evaluate the control feedback. The system stability was tested for its ability to maintain the expected concentration and application rate. The results show that the lag time remains less than 3 s (dead time < 2s , time constant < 1s) and the system keeps stable for the maximal speed variation and acceleration tested (∆V=200%, a= 0.48 m/s2) which induce less than 10% variation of application rate. [less ▲]

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See detailDroplet internal flow measurement using micro-PIV
Lebeau, Frédéric ULg; Vetrano, Maria-Rosaria; van Beeck, Jeroen et al

Poster (2009, September 25)

The micro-PIV technique represents a development of the general particle image velocimetry technique to applications in fluid mechanics phenomena at a micrometric scale. It takes advantage from the very ... [more ▼]

The micro-PIV technique represents a development of the general particle image velocimetry technique to applications in fluid mechanics phenomena at a micrometric scale. It takes advantage from the very small depth of field of long distance objectives with high magnification to carry out accurate measurements in the focusing plane. The typical configuration consists of a microscope coupled to a pulsated laser and a double exposure PIV camera. The flow is seeded using sub-micrometric fluorescent particles. The laser light is directed on the investigated flow through the epifluorescent microscope objective. The light re-emitted by the fluorescent particles is detected by the PIV camera equipped of an optical filter to select only the fluorescence wavelength. The micro-PIV technique presents a large interest in the validation of numerical codes developed in different micro-fluidic framework such as biological flows and in industrial application as the ink-jet print-head. To investigate the micro-PIV measurements capabilities for fast moving and deforming droplets, measurement of the flow inside a jet ejected by a piezo-driven capillary up to the droplet formation by Rayleigh instability are studied in combination with PTV in order to distinguish the main liquid movement from the bulk one. Liquids differing from each other for their viscosity and their surface tension as well as piezo-element frequency in the 1 to 8 KHz range are investigated. The flow rate of the jet is adjusted by means of a pushing syringe system. Low concentration of 0.86 microns fluorescent particles is employed as seeding in order to have good signal to noise ratios. The ensemble averaging method is used to increase the height of the correlation peaks. Stroboscopic method is used to achieve several couples of frames taken in the same conditions thanks to high repeatability of piezo-driven instabilities. Moreover changing the delay of stroboscopy all the droplet formation phases can be analyzed in detail. In the experimental configuration, optical aberrations play a role since they affect the position and shape of the particle images and as a consequence the velocity field. The two main optical aberration experienced are astigmatism and measurement plane deformation. Astigmatism cannot be avoided in the experimental configuration, as it is clearly observed on droplet images were particles above and bellow the focalisation plane appear as perpendicular lines (Fig 1a). Nevertheless cross correlation method is not sensitive on particle image shape. As the measurement plane defined by the focal plane of the microscope is located inside a curved transparent object, it deformed as it was passing through a lens. The deformation of the objective plane affects the measurements as a function of the optical configuration, droplet curvature and relative refractive index. However, in the studied configuration, deformed plane differs only from the straight one of about 8 µm. The micro-PIV method is therefore suited to measure the instantaneous vector field inside droplets through cross-correlation methods (Fig 1b). The internal flow recirculation is observed. Measurements can be also performed in different planes inside the droplet depending on focalisation plane. [less ▲]

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See detailApplying control volume finite element for modelling direct injection boom spraying flow
El Aissaoui, Abdellah; Lebeau, Frédéric ULg; Destain, Marie-France ULg et al

Conference (2009, June 23)

Assessment of injection lag transport and uniformity of direct injection boom sprayer is an important issue for successful variable rate spraying technology. To estimate the boom lag transport and ... [more ▼]

Assessment of injection lag transport and uniformity of direct injection boom sprayer is an important issue for successful variable rate spraying technology. To estimate the boom lag transport and pressure loss, a numerical model is formulated on the basis of fluid hydrodynamic conservation equations. The software is implemented in visual basic. To solve the pressure – velocities equations, control volume finite element method (CV) is used to delimit elementary volumes of the boom. Linearization of the conservation laws is ensured by considering discrete form of the equations and calculating velocity and pressure step by step throughout the whole boom. The flow behaviour is simulated into a boom section divided into N elementary volumes, each of them including one nozzle. To test the model, three boom diameters (5, 6 and 8 mm) and two chemical viscosities (10-6 and 10-5 m2/s) were used. Experimental trials are carried out on boom having 2.5 m length (5 nozzles) for measuring pressure gradient and lag transport. Results showed that the model can predict the pressure losses and the lag transport accurately (error within 5%) to optimize boom designs. [less ▲]

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See detailEvaluation of realtime spray drift using RTDrift Gaussian advection-diffusion model
Lebeau, Frédéric ULg; Verstraete, Arnaud ULg; Schiffers, Bruno ULg et al

in Spanoghe, Pieter (Ed.) COMMUNICATIONS IN AGRICULTURAL AND APPLIED BIOLOGICAL SCIENCES (2009, May 19)

A spray drift model was developed to deliver real time information to the pesticide applicator. The sprayer is equipped with sensors to deliver real time measurement of operational parameters as spray ... [more ▼]

A spray drift model was developed to deliver real time information to the pesticide applicator. The sprayer is equipped with sensors to deliver real time measurement of operational parameters as spray pressure, boom height, horizontal boom movements and geolocalization. The spray droplet size spectrum as a function of pressure was characterized using PDI measurements. Wind speed and direction were measured using a sprayer mounted 2-D ultrasonic anemometer. For each successive boom position, a diffusion-advection Gaussian tilting plume model is used to compute the spray drift deposits downwind. Drift is computed independently for each droplet classes and each nozzle based on the operating parameters. Field trials were performed on a test plot in various wind conditions. The ground drift was measured for different drift distances using fluorimetry analysis. Results show that drift deposits are mainly affected by wind speed and direction what was correctly accounted for by the model. Short distance drift deposits values were overestimated by the model while long distance drift was underestimated. It appears that this most probably origins from embarked wind speed measurements and diffusion parameter. It is concluded that a treatment of embarked wind speed and diffusion measurement should be used to minimize these errors. [less ▲]

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See detailImproving in-row weed detection in multispectral stereoscopic images
Piron, Alexis ULg; Leemans, Vincent ULg; Lebeau, Frédéric ULg et al

in Computers & Electronics in Agriculture (2009), 69

Previous research has shown that plant height and spectral reflectance are relevant features to classify crop and weeds in organic carrots: classification based on height gave a classification accuracy ... [more ▼]

Previous research has shown that plant height and spectral reflectance are relevant features to classify crop and weeds in organic carrots: classification based on height gave a classification accuracy (CA) of up to 83% while classification based on a combination of three multispectral bands gave a CA of 72%. The first goal of this study was to examine the simultaneous use of both height and multispectral parameters. It was found that classification rate was only slightly improved when using a feature set comprising both height and multispectral data (2%). The second goal of this study was to improve the detection method based on plant height by setting an automatic threshold between crop and weeds heights, in their early growth stage. This threshold was based on crop row determination and peak detection in plant height probability density function, corresponding to the homogeneous crop population. Using this method, the CA was 82% while the CA obtained with optimal plant height limits is only slightly higher at 86%. [less ▲]

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See detailEffect of surfactants and biomass on the gas/liquid mass transfer in an aqueous-silicone oil two-phase partitioning bioreactor using Rhodococcus erythropolis T902.1 to remove VOCs from gaseous effluents
Aldric, Jean-Marc ULg; Gillet, Sébastien ULg; Delvigne, Frank ULg et al

in Journal of Chemical Technology & Biotechnology (2009), 84

BACKGROUND: The two-phase partitioning bioreactor (TPPB) has become a new strategy in the context of waste gas treatment. However, the impact of biomass and surfactants on gas/liquid (G/L) mass transfer ... [more ▼]

BACKGROUND: The two-phase partitioning bioreactor (TPPB) has become a new strategy in the context of waste gas treatment. However, the impact of biomass and surfactants on gas/liquid (G/L) mass transfer needs to be better evaluated because the impact of these factors on the mass transfer coefficient “ ” and the interfacial area “ ”, respectively, remains misunderstood. RESULTS: Our study showed that, firstly, the surfactant extract produced by Rhodococcus erythropolis reduced the surface hydrophobicity of the biomass. Secondly, an optimal concentration appeared to exist for both of the components, respectively 0.5 g.L-1 and 0.7 g.L-1 for biomass (B) and surfactant extract (SE) when the global mass transfer coefficient ( ) of oxygen was measured in a silicone oil/water TPPB. However, the combination of B and SE was found to induce a negative synergism. In particular, SE improved the interfacial area “ ” by increasing the bubble diameter, while B reduced it as soon as a concentration of 1g.L-1 was exceeded. By contrast, the SE acted negatively on the , while B improved it overall. CONCLUSION: Better consideration is needed of the effect of biotic components in order to understand the phenomenon of G/L mass transfer in a TPPB. The behaviour of biomass growth and surfactants may strongly influence the mathematical models suggested in the literature. [less ▲]

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See detailEfficacité de la technique d’induction florale d’Ananas comosus (L.) Merr. au moyen de charbon actif enrichi à l’éthylène (TIFBio)
Lebeau, Frédéric ULg

in Biotechnologie, Agronomie, Société et Environnement = Biotechnology, Agronomy, Society and Environment [=BASE] (2009), 3

Pineapple is an important export crop for tropical countries. The flower induction treatments are essential to the pineapple production for economical and social reasons. For conventional agriculture ... [more ▼]

Pineapple is an important export crop for tropical countries. The flower induction treatments are essential to the pineapple production for economical and social reasons. For conventional agriculture, many chemicals are available but for organic farming ethylene is the only allowed product. A new flower induction method suited to small organic growers has been developed by the Pesticides Initiative Programme of the Coleacp funded by the European Development Fund. The trials conducted proved that the method reaches more than 80% efficiency at 10 weeks for the different application methods evaluated. The wet application trials show a doses response effect as well as effect of the application replication at 2 days interval. The flowering rate culminates at 100% after 8 weeks for the best results, obtained with the wet treatment at 250 mg per plant applied two times at 2 days interval. The different dry treatments tested gave all 85 – 90% flowering rates at 10 weeks, suggesting the presence of an undetermined limitation factor in the conditions prevailing for the trial. The time of application during the day shows no significant effect. It is concluded that the growers can use the TIFBio technique for production control. It is recommended to evaluate the most suited application technique according to their particular case as environmental effect can affect the efficiency. [less ▲]

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