References of "Destain, Marie-France"
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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 detailVolatile organic compounds of the roots of barley and their role in the rhizosphere
Fiers, Marie ULg; Barsics, Fanny ULg; Camerman, Marc ULg et al

Poster (2011, May 24)

Volatile organic compounds emitted by plants are known to intervene with various biotic environmental factors. Up to now, most of the studies have been focused on aerial volatiles and root liquid exudates ... [more ▼]

Volatile organic compounds emitted by plants are known to intervene with various biotic environmental factors. Up to now, most of the studies have been focused on aerial volatiles and root liquid exudates. Very few researches have been completed concerning belowground volatiles released into the rhizosphere despite their potential capacity to carry information between organisms. The Rhizovol project, started in autumn 2010, involves 5 different units of Gembloux Agro-Bio Tech collectively studying the production of belowground volatiles by barley roots underlying various biotic interactions in the rhizosphere. Some preliminary results of each partner of the project will be presented. To achieve this goal, analytical methods allowing the sampling, separation, identification and quantification of belowground volatile compounds have to be developed, taking into account their potential modifications in the rhizosphere once released by the roots. They enable the subsequent characterization and study of the interactions between barley and its rhizospheric partners chosen for this study. These interactions imply three types of organisms: beneficial organisms, pathogenic agents and plant and insect pests. Beneficial organisms can promote the growth of barley by the emission of volatiles; on the other hand barley can support their growth and metabolism. These phenomenons will be assessed by the study of 19 strains of plant growth-promoting bacteria (PGPR). Three pathogenic agents - two fungi (Fusarium culmorum and Cochliobolus sativus) and one virus (Barley yellow dwarf virus) - were chosen as they are known to cause various diseases on barley, especially on roots. The attractive or repellent effects of barley root volatiles on the pathogenic agents or their vectors, as well as the effect of volatiles on the diseases evolution will be evaluated. The project also includes several types of pests such as plants and insects. Plants can compete with barley for space and nutrients through volatile interactions. This will be assessed by the study of autotoxicity by barley itself and allelopathy with 8 weeds and a hemiparasitic plant (Rhinanthus minor). The effects of barley volatiles can also impact the severity of the attacks by insects. This part will be conducted with wireworms as they represent worldwide known pests, and aphids, through their viral vector role. Eventually, as soil characteristics can strongly influence the diffusion of volatile compounds, the diffusion behaviour of the identified volatile biomolecules through the soil will be modelled. Tritrophic interactions (e.g. insect-plant-pathogenic fungi) will be studied based on each bitrophic interaction results. Over-all, the Rhizovol project aims at improving the knowledge of interactions mediated by volatile compounds in the rhizosphere and at establishing new biocontrol methods that could contribute to integrated disease and pest management systems. [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 detailAutomatic grading of Bi-colored apples by multispectral machine vision
Unay, Devrim; Gosselin, Bernard; Kleynen, Olivier et al

in Computers & Electronics in Agriculture (2011)

In this paper we present a novel application work for grading of apple fruits by machine vision. Following precise segmentation of defects by minimal confusion with stem/calyx areas on multispectral ... [more ▼]

In this paper we present a novel application work for grading of apple fruits by machine vision. Following precise segmentation of defects by minimal confusion with stem/calyx areas on multispectral images, statistical, textural and geometric features are extracted from the segmented area. Using these features, statistical and syntactical classifiers are trained for two- and multi-category grading of the fruits. Results showed that feature selection provided improved performance by retaining only the important features, and statistical classifiers outperformed their syntactical counterparts. Compared to the state-of-the-art, our two-category grading solution achieved better recognition rates (93.5% overall accuracy). In this work we further provided a more realistic multi-category grading solution, where different classification architectures are evaluated. Our observations showed that the single-classifier architecture is computationally less demanding, while the cascaded one is more accurate. [less ▲]

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See detailWeed detection in 3D images
Piron, Alexis ULg; Van Der Heijden, F.; Destain, Marie-France ULg

in Precision Agriculture (2011), 12(5), 607-622

Machine vision has been successfully used for mechanical destruction of weeds between rows of crops. Knowledge of the position of the rows where crops should be growing and the assumption that plants ... [more ▼]

Machine vision has been successfully used for mechanical destruction of weeds between rows of crops. Knowledge of the position of the rows where crops should be growing and the assumption that plants growing outside such positions are weeds may be used in such systems. However for many horticultural crops, the automatic removal of weeds from inside a row or bands of crops in which the weeds are mixed with plants in a random manner is not solved. The aim of this study was to verify that plant height is a discriminating parameter between crop and weed at early growth stages, as weeds and crops grow at different speeds. Plant height was determined by using an active stereoscopy technique, based on a time multiplexing coded structured light developed to take into account the specificities of the small scale scene, namely occlusion and thin objects, internal reflections and high dynamic range. The study was conducted on two carrot varieties sown at commercial density. Different weed species were present at the time of data acquisition. To accurately represent plant height taking into account the ground irregularities, a new parameter called ‘corrected plant height’ was computed. This parameter was the distance between plant pixels and the actual ground level under them obtained by fitting a surface and seen from a reconstructed point of view corresponding to a camera’s optical axis perpendicular to the ridge plane. The overall classification accuracy without correction was 66% whereas it reached 83% by using the corrected plant height. [less ▲]

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See detailLa vision artificielle: une méthode d'avenir pour la reconnaissance automatisée des plantes adventices?
Piron, Alexis; Dumont, Benjamin ULg; Destain, Marie-France ULg

in Biotechnologie, Agronomie, Société et Environnement = Biotechnology, Agronomy, Society and Environment [=BASE] (2011), 15(4), 597-610

Weeds compete with crop plants for sunlight, moisture and nutrients and can have a detrimental impact on crop yields and quality if uncontrolled. They are destroyed by chemical, non chemical and ... [more ▼]

Weeds compete with crop plants for sunlight, moisture and nutrients and can have a detrimental impact on crop yields and quality if uncontrolled. They are destroyed by chemical, non chemical and integrated methods. To perform a site-specific weeds destruction, combination of these techniques with ground-based machine vision technology has high potential. Several methods exist to differentiate weeds from soil, between the rows. The more complicated problem is encountered when weeds are mixed to crops within the rows. Algorithms based on colorimetric or shape features are widely dependant on the variability of weeds and crops and are difficult to transpose from one situation to another. Measurement of plant height is a promising method, since at low spatial scale, the growthing speed is more uniform for the plants than for the weeds. This growing speed is function of the height and of a characteristic time, such as the number of days after sowing. To implement this method, active stereoscopy combined to an accurate measurement of the soil microrelief is required. [less ▲]

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See detailEvaluation of the performance of infrared thermography for on-line condition monitoring of rotating machines
Leemans, Vincent ULg; Destain, Marie-France ULg; Kilundu, Bovic et al

in Engineering (2011), (3), 1030-1039

This study evaluated the possibility of infrared thermography to measure accurately the temperature of elements of a rotating device, within the scope of condition monitoring. The tested machine was a ... [more ▼]

This study evaluated the possibility of infrared thermography to measure accurately the temperature of elements of a rotating device, within the scope of condition monitoring. The tested machine was a blower coupled to a 500 kW electric motor, that operated in multiples regimes. The thermograms were acquired by a fixed thermographic camera and were processed and recorded every 15 minutes. Because the normal temperature variations could easily mask a drift caused by a failure, a corrected temperature was computed using autorecursive models. It was shown that an efficient temperature correction should compensate for the variations of the process, and for the ambient temperatures variations, either daily or seasonal. The standard deviation of the corrected temperature was of a few tenth of degree, making possible the detection of a drift of less than one degree and the prediction of potential failure. [less ▲]

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See detailPlant leaf roughness analysis by texture classification with generalized Fourier descriptors in a dimensionality reduction context
Journaux, L.; Simon, J.-C.; Destain, Marie-France ULg et al

in Precision Agriculture (2011), 12(3), 345-360

In the context of plant leaf roughness analysis for precision spraying, this study explores the capability and the performance of some combinations of pattern recognition and computer vision techniques to ... [more ▼]

In the context of plant leaf roughness analysis for precision spraying, this study explores the capability and the performance of some combinations of pattern recognition and computer vision techniques to extract the roughness feature. The techniques merge feature extraction, linear and nonlinear dimensionality reduction techniques, and several kinds of methods of classification. The performance of the methods is evaluated and compared in terms of the error of classification. The results for the characterization of leaf roughness by generalized Fourier descriptors for feature extraction, kernel-based methods such as support vector machines for classification and kernel discriminant analysis for dimensionality reduction were encouraging. These results pave the way to a better understanding of the adhesion mechanisms of droplets on leaves that will help to reduce and improve the application of phytosanitary products and lead to possible modifications of sprayer configurations. [less ▲]

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See detailEvaluation of chicory seeds maturity by chlorophyll fluorescence imaging
Ooms, David ULg; Destain, Marie-France ULg

in Biosystems Engineering (2011), 110

Chicory (Cichorium intybus L.) seed production includes sorting to remove foreign materials and non-viable seeds. A machine vision system was developed to monitor the fluorescence in order to detect the ... [more ▼]

Chicory (Cichorium intybus L.) seed production includes sorting to remove foreign materials and non-viable seeds. A machine vision system was developed to monitor the fluorescence in order to detect the immature chicory seeds. It comprised a monochromatic light source, a highpass filter and a monochromatic CCD camera sensitive to red and infrared. With this device, blue light reflected by the seeds was blocked whilst red fluorescence was measured by the camera. A segmentation algorithm was designed to estimate separately the fluorescence intensities of the pappus, a crown of scales, and the main body of the pericarp. Experiments were carried out on five clones of cross-pollinated chicory plants used for seed production. Two hundred flower heads were labelled at flowering and harvested at different times during the maturation process expressed in “days after flowering” (DAF). Germination tests were performed according to the recommendations of the International Seed Testing Association to measure the germination percentage (GP) and the germination rate (GR), an indicator of seed vigour. Seed chlorophyll content diminished during maturation following a different logistic trend for the pappus and the pericarp. The GP increased from 18 DAF to reach its maximum value at 21 DAF, but the GR remained low until 30 DAF and increased afterwards. The potential of chlorophyll fluorescence to be used as an indicator of chicory seed vigour was the greatest between 21 and 36 DAF. [less ▲]

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See detailEvaluation des risques de compaction des sols en Région wallonne
Rosiere, Charlotte ULg; Verbrugge, Jean-Claude; Destain, Marie-France ULg

Poster (2010, November 24)

Le projet de directive européenne COM(2006)232 établit un cadre général pour la protection des sols. Le projet prévoit que les états membres identifient les zones susceptibles d’être touchées par des ... [more ▼]

Le projet de directive européenne COM(2006)232 établit un cadre général pour la protection des sols. Le projet prévoit que les états membres identifient les zones susceptibles d’être touchées par des processus de dégradation (érosion, compaction, salinisation, …) et qu’ils proposent des mesures afin de réduire les risques. La compaction peut affecter la macroporosité, les mouvements de l’eau et de l’air dans le sol, les mécanismes de croissance racinaire, le développement de la faune du sol. De ce fait, elle est donc souvent à l’origine d’une diminution du rendement des cultures. En Région wallonne, les machines destinées à la récolte de betteraves risquent d’engendrer une compaction du sol car elles sont souvent utilisées alors que le sol est humide et que les charges à l’essieu sont importantes. Les machines d’exploitation forestière présentent également des risques pour la compaction du sol. La contrainte de préconsolidation (Pc) est considérée comme la valeur à ne pas dépasser pour éviter que le sol subisse des dégâts difficilement réversibles. Si les contraintes appliquées sont supérieures à Pc, le sol garde un comportement élastique (état réversible) et il n’y a pas de modification dans l’organisation de la porosité du sol. Par contre, si les contraintes appliquées sont supérieures à Pc, le sol entre en plasticité et ses fonctions naturelles sont perturbées. Dans un premier temps, des cartes de sensibilité du sol à la compaction sont élaborées. Elles évaluent la contrainte de préconsolidation des sols de la Région wallonne, au moyen des fonctions de pédotransfert (FPT) de Lebert et Fleige (2003). L’impact des engins sur le sol est étudié au niveau du ‘subsoil’, sous la couche de labour, là où le sol ne peut pas être régénéré par des outils classiques de travail du sol. Les paramètres des FPT sont accessibles au sein de Aardewerk ou sont trouvés dans la littérature. Les valeurs de Pc sont classées selon 6 niveaux de sensibilité, à deux états hydriques différents. Dans un deuxième temps, la distribution des contraintes verticales générées par le passage d’engins ‘types’, caractérisés par les dimensions des pneus, la charge à l’essieu et la pression de gonflage, est calculée à l’aide du logiciel Soilflex. Les Pc du sol sont alors comparées aux contraintes verticales induites par les engins, pour aboutir à des cartes de risque de compaction. Celles-ci simulent 4 scénarios : deux teneurs en eau et deux types d’engins. Afin de valider ces deux types de cartes, des tests oedométriques destinés à mesurer Pc sont réalisés sur des sols agricoles et forestiers. Pour faciliter la démarche et calculer les FPT de Lebert et Fleige avec une plus faible incertitude, il serait utile que la CNSW comporte des données relatives aux fractions granulométriques, à la matière organique des sols, la cohésion, l’angle de frottement interne, la masse volumique apparente sèche de sol, … [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 sorting optimization curve with quality and yield requirements
Ooms, David ULg; Palm, Rodolphe ULg; Leemans, Vincent ULg et al

in Pattern Recognition Letters (2010), 31(9), 983-990

Binary classifiers used for sorting can be compared and optimized using receiver-operating characteristic (ROC) curves which describe the trade-off between the false positive rate and true positive rate ... [more ▼]

Binary classifiers used for sorting can be compared and optimized using receiver-operating characteristic (ROC) curves which describe the trade-off between the false positive rate and true positive rate of the classifiers. This approach is well suited for the diagnosis of human diseases where individual costs of misclassification are of great concern. While it can be applied to the sorting of merchandise or other materials, the variables described by the ROC curve and its existing alternatives are less relevant for that range of applications and another approach is needed. In this paper, quality and yield factors are introduced into a sorting optimization curve (SOC) for the choice of the operating point of the classifier, associated with the prediction of output quantity and quality. Given examples are the sorting of seeds and apples with specific requirements. In both cases the operating point of the classifier is easily chosen on the SOC, while the output characteristics of the sorted product are accurately predicted. [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 detailRisk assessment of soil compaction in Walloon Region (Belgium)
Rosiere, Charlotte ULg; Delvoie, Simon ULg; Charlier, Robert ULg et al

Poster (2010, May 07)

The proposed Soil Framework Directive COM(2006)232 requires Member States to identify areas at risk of erosion, decline in organic matter, salinisation, compaction, sealing and landslides, as well as to ... [more ▼]

The proposed Soil Framework Directive COM(2006)232 requires Member States to identify areas at risk of erosion, decline in organic matter, salinisation, compaction, sealing and landslides, as well as to set up an inventory of contaminated sites. The present project aims to identify the susceptibility to compaction of soils of the Walloon Region (Belgium) and to recommend good farming practices avoiding soil compaction as far as possible. Within this scope, the concept of precompression stress (Pc) (Horn and Fleige, 2003) was used. Pc is defined as the maximum major principal stress that a soil horizon can withstand against any applied external vertical stress. If applied stress is higher than Pc, the soil enters in a plastic state, not easily reversible. For a given soil, the intensity of soil compaction is mainly due to the applied load which depends on vehicle characteristics (axle load, tyre dimensions, tyre inflation pressure, and vehicle velocity). To determine soil precompression stress, pedotransfert functions of Lebert and Horn (1991) defined at two water suctions (pF 1.8 and 2.5) were used. Parameters required by these functions were found within several databases (Aardewerk and Digital Map of Walloon Soils) and literature. The validation of Pc was performed by measuring stress-strain relationships using automatic oedometers. Stresses of 15.6, 31, 3, 62.5, 125, 250, 500 and 1000 kPa were applied for 10 min each. In this study, the compaction due to beet harvesters was considered because the axle load can exceed 10 tons and these machines are often used during wet conditions. The compaction at two depth levels was considered: 30 and 50 cm. Compaction of topsoil was not taken into account because, under conventional tillage, the plough depth is lower than 25 cm. Before and after the passage of the machines, following measurements were performed: granulometry, density, soil moisture, pF curve, Atterberg limits, ... The software Soilflex (Keller et al., 2007) was used to estimate the distribution of the vertical stresses sigma z in the soil. Comparison was performed between sigma z and Pc. The following data simulated the passage of a beet harvester machine (mass: 23 580 kg; load: 18 000 kg) in a silty soil located in Hesbaye and classified as Aba (Sirjacobs et al., 2000). The passage of the machine would create a Pc of around 100 kPa at 30 cm depth, while the stress induced by the machine would reach 240 kPa. In the field borders, where more vehicle traffic was usually observed and where the soil was over consolidated, Pc would reach 180 kPa, while sigma z would be 220 kPa. In both cases, the risk of compaction created by the passage of the machine would be high. [less ▲]

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See detailLa fluorescence chlorophyllienne au service des productions végétales
Eyletters, Muriel; Ooms, David ULg; Destain, Marie-France ULg

in Biofutur (2010), (308), 46-48

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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 detailEtude des potentialités de la vision artificielle pour la reconnaissance optique des semences immatures de chicorée industrielle (Cichorium intybus L.)
Ooms, David ULg; Destain, Marie-France ULg

in Biotechnologie, Agronomie, Société et Environnement = Biotechnology, Agronomy, Society and Environment [=BASE] (2010), 14(1), 253-263

La production commerciale de semences de chicorée industrielle (Cichorium intybus L.) implique l'élimination des semences (cypsèles) non viables de la récolte à l’aide de méthodes non destructives. Dans ... [more ▼]

La production commerciale de semences de chicorée industrielle (Cichorium intybus L.) implique l'élimination des semences (cypsèles) non viables de la récolte à l’aide de méthodes non destructives. Dans ce cadre, deux techniques basées sur la vision artificielle sont étudiées pour reconnaître les semences non viables : la vision couleur et l’imagerie fluorescente. L’analyse de 1500 semences de la variété Nausica en vision en couleur ne permet de détecter que les semences desséchées ou non développées. Ceci est attribué à la très grande variabilité de la couleur, de la forme et de la texture des semences testées. L’imagerie fluorescente est alors envisagée, en vue d’analyser sur les différentes parties des semences (le péricarpe, la zone d’émergence de l’apex radiculaire et les pappi) la répartition de la chlorophylle, qui est un indicateur de la maturité des semences. La faible teneur en chlorophylle et la grande quantité de semences à trier imposent d’utiliser un dispositif de mesure très sensible. Un dispositif d'imagerie de la fluorescence chlorophyllienne de semences est ainsi proposé. Sa particularité consiste à pouvoir modifier le spectre de la source lumineuse (dans le but d’optimiser la sensibilité) et à enregistrer l’évolution de la répartition de la fluorescence en fonction du temps. Le dispositif fournit des images de la répartition de la fluorescence chlorophyllienne sur les cypsèles de chicorée. Il pourrait permettre de réaliser des mesures à plus grande échelle, reliant les attributs de fluorescence avec le pouvoir germinatif et l’état de maturité des semences. [less ▲]

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