References of "Ooms, David"
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See detailAmélioration du tri de semences de chicorée industrielle (Cichorium intybus L.) sur base d’attributs mesurés par vision artificielle
Ooms, David ULg

Doctoral thesis (2012)

The commercial production of industrial chicory seeds (cypselae) includes the postharvest elimination of nonviable seeds by non-destructive tools. For this purpose, two machine vision methods were set up ... [more ▼]

The commercial production of industrial chicory seeds (cypselae) includes the postharvest elimination of nonviable seeds by non-destructive tools. For this purpose, two machine vision methods were set up for the detection of nonviable seeds: color vision and fluorescence imaging. In addition, the appropriate criteria to estimate the efficiency of seed sorting were defined using a sorting optimization curve which describe the trade-off between the quality improvement of a seed lot and the loss of material. The analysis of color images of 1,500 seeds of the ‘Nausica’ variety allows only the recognition of desiccated and undeveloped seeds. This is caused by the large natural variability of seed color, shape and texture. Fluorescence imaging was set up in order to analyze the repartition of chlorophyll fluorescence (CF), a marker of seed maturity, on different areas of the seed (pericarp and pappus). 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 and four series of 30 plants from 2 common varieties grown in different weather conditions. The 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. The dry weight (DW), water content (WC), maturation duration, germination percentage (GP), and germination rate (GR) were measured to estimate seed quality. For all experiments, the chlorophyll fluorescence diminished mainly between 16 and 33 DAF during the filling phase of seed development. The correlations between CF and maturity parameters (DW, WC) were comprised between 0.25 and 0.75 in absolute value for seeds that matured 16 to 44 days on the stalk. Sorting simulations were made on the basis of CF alone or in combination with the achene area density (AD) (mg/mm²). The CF was efficient to select seeds produced outdoor or in the greenhouse with the aim of increasing GP or GR but AD was an even better sorting feature. In the greenhouse, where developing seeds were submitted to temperatures higher than 25 °C, the use of CF in combination with AD improved the sorting efficiency. [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 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 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 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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See detailMeasurements Of The Horizontal Sprayer Boom Movements By Sensor Data Fusion
Ooms, David ULg; Lebeau, Frédéric ULg; Ruter, R. et al

in Computers and Electronics In Agriculture (2002), 33(2),

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See detailDevelopment of a multibody model of a sprayer
Ooms, David ULg; Lebeau, Frédéric ULg; Maton, Nicolas et al

in Proceedings of AgEng (2002)

A multibody model of a sprayer boom including the suspension was developed by using ADAMS 11.0 (Mechanical Dynamics). The model was designed with the aim to describe the dynamic behaviour of different ... [more ▼]

A multibody model of a sprayer boom including the suspension was developed by using ADAMS 11.0 (Mechanical Dynamics). The model was designed with the aim to describe the dynamic behaviour of different types of booms and suspensions (double trapezium, trapezium, pendulum, …). This was obtained by creating a general model in which geometrical (dimensions) and mechanical parameters (mass and inertia, friction coefficients, stiffness and damping coefficients of the hinges, …) of the system were easily modified. A graphical interface especially designed authorised this easy modification. The validation of the model was obtained by measuring in real conditions the frame movements as solicitations and the boom movements as responses. The method was applied on a trailed sprayer equipped with a boom of 24 m and a trapezoidal suspension. Good accordance was found between measured and simulated vertical displacements. The model may decrease the development costs of suspension and boom designs. [less ▲]

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