References of "Destain, Marie-France"
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See detailOn-the-go georeferenced measurements of soil mechanical strength and differenciation of soil structure.
Destain, Marie-France ULg; Sirjacobs, Damien ULg; Hanquet, Bernard et al

in Geophysical Research Abstracts (2008)

Soil strength is defined as the resistance which as to be overcome to obtain a given soil deformation. Amongst the numerous methods developed to measure soil strength, two are classically used. On one ... [more ▼]

Soil strength is defined as the resistance which as to be overcome to obtain a given soil deformation. Amongst the numerous methods developed to measure soil strength, two are classically used. On one hand, a laboratory method based on triaxial tests of undisturbed soil samples allows the estimation of cohesion and internal friction angle by the Mohr-Coulomb equation. On the other hand, measuring soil penetration resistance by pushing a cone into a soil is a widely used technique. Both techniques deliver discontinuous field information and are not suited to produce digital soil mapping. The objectives of this paper are to present a sensor able to continuously measure soil strength variations. The sensor was constituted of a thin blade pulled in the soil at a constant depth and speed and a beam which transferred the soil-blade forces to a transducer fixed on a vehicle. The transducer measures the draft force Fx, the vertical force Fz and the moment My thanks to an octagonal ring dynamometer. A measurement chain was developed to acquire simultaneously the signals provides by the soil strength sensor and those of a DGPS. Signal processing was notably based on geostatistics and allows soil mapping [1]. Four fields representative of the soils used in silty areas for arable production in Belgium were selected. The measurements were repeated several times during 1999-2003. Targeted test plots were chosen in each field to perform reference measurements, namely granulometry, cohesion, friction angle, pF, water content, dry bulk density, and cone index. The within-field studies revealed high variability caused by texture, history, traffic, etc., and showed a correlation between the sensor signals and physical parameters, such as cone index and soil moisture, as long as no over-consolidation of the soil occurred [2]. To assess the similarity of soil strength between the fields, the data Fx, Fz and My were classified by using canonical variates (CV). The two first CV represented 95.9 % of the variability, which means that two main variables contain the essential part of the information. In a plane (Fz, Fx), three clusters could be distinguished. The first one (trials 1 and 5), characterized by a low draft and a high Fz, corresponded to trials performed in March on soils ploughed during the winter, naked or covered with small vegetation, and characterized by small values of cone index. The second one (trials 2, 3, 4, 7) with high values of Fx and Fz grouped measurements done just after wheat harvest in August. The third cluster (trials 6) corresponded to measurements performed during wheat growth. It may be concluded that the signals from the sensor treated by suited statistical analysis have the potential to differentiate soil structures at a field scale. REFERENCES [1] Sirjacobs D., Hanquet B., Lebeau F., Destain M.-F. (2002). On-line mechanical resistance mapping and correlation with soil physical properties for precision agriculture. Soil and Tillage Research 64, 231-242. [2] Hanquet B., Sirjacobs D., Destain M.-F., Frankinet M., Verbrugge J.-C. (2004). Analysis of soil variability measured with a soil strength sensor. Precision Agriculture, 5, 227-246. [less ▲]

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See detailDetermination of plant height for weed detection in stereoscopic images
Piron, Alexis ULg; Leemans, Vincent ULg; Kleynen, Olivier et al

in AGENG 2008 Conference - Agricultural & Biosystems Engineering for a Sustainable World (2008)

The aim of this study was twofold. The first goal was to acquire high accuracy stereoscopic images of small-scale field scenes, the second to examine the potential of plant height as a discriminant factor ... [more ▼]

The aim of this study was twofold. The first goal was to acquire high accuracy stereoscopic images of small-scale field scenes, the second to examine the potential of plant height as a discriminant factor between crop and weed, within carrot rows. Emphasis was put on how to determine actual plant height taking into account the variable distance from camera to ground and ground irregularities for in-field measurements. Multispectral stereoscopic images were taken over a period of 19 days starting one week after crop emergence and seven weed species were considered. Images were acquired with a mobile vision system consisting in a filter wheel based multispectral camera and a video projector. The stereoscopy technique used belonged to the coded structured light family. The stereoscopic acquisition method yielded good results despite the numerous stereoscopic difficulties exhibited by the scenes. A plant height parameter as opposed to distance from camera to plant pixels gave better results for classification (classification accuracy of up [less ▲]

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See detailImprovements of image processing for wheat ear counting
Cointault, Frédéric; Journaux, Ludovic; Miteran, Joel et al

in Agricultural and biosystems engineering for a sustainable world (2008)

One of the most important activity of agricultural research insititutes concerns the agronomical experiments done under different conditions needing many land observations and valuations to quantify ... [more ▼]

One of the most important activity of agricultural research insititutes concerns the agronomical experiments done under different conditions needing many land observations and valuations to quantify several variables. These observations, although generally accurate, are visually done by the agriculturist technicians and present numerous drawbacks: penibility, weak productivity, numerous labor force, limited sampling … Two feasibility studies lead in our laboratory recently have shown that some of the previous observations, and particularly the counting of the number of wheat ear per m², can be done by color and/or texture image processing for images taken directly in the field with a specific acquisition system. This paper describes the improvements of the previous studies concerning the image acquisition system, and especially the illumination control, and the justification of different hypothesis on the number of classes to detect in an image. The use of a cluster validity index has allowed to prove that 3 classes to determine all the objects in a wheat ear image are not sufficient. A correlation with a study based on the size of the analysis window is currently under investigation to improve the ear detection, which is now of 6%, compared to manual counting done by agriculturist technicians. [less ▲]

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See detailA Computer-Vision Based Precision Seed Drill Guidance Assistance
Leemans, Vincent ULg; Destain, Marie-France ULg

in Computers and Electronics In Agriculture (2007), 59(1-2),

This paper presents a control mechanism aiming to position seed drills relative to the previous lines, while sowing. The position was measured by a machine vision system and used in a feedback control ... [more ▼]

This paper presents a control mechanism aiming to position seed drills relative to the previous lines, while sowing. The position was measured by a machine vision system and used in a feedback control loop. An articulated mechanism was used to ensure the lateral displacement of the drill relative to the tractor. The behaviour of the whole outfit was studied during several field tests. The standard deviation of the error, measured as the difference between the observed inter-row distance and its set value, was 23 mm and its range was less than 100 mm, which was sufficient to fulfil the requirements of the application. Sources of systematic errors were also identified as linked to the geometric considerations. Their correction requires an accurate mounting of the camera, which may be possible for a serial montage. [less ▲]

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See detailÉtude des paramètres opératoires de pressage mécanique des amandes de Vitellaria paradoxa Gaertn C.F. (karité)
Yé, S.; Lebeau, Frédéric ULg; Wathelet, Jean-Paul ULg et al

in Biotechnologie, Agronomie, Société et Environnement = Biotechnology, Agronomy, Society and Environment [=BASE] (2007), 11(4), 267-273

Study of the operational parameters of mechanical pressing of almonds of Vitellaria paradoxa Gaertn C.F. (shea tree). Sheabutter is one of the most diffi cult oleaginous resources to extract by ... [more ▼]

Study of the operational parameters of mechanical pressing of almonds of Vitellaria paradoxa Gaertn C.F. (shea tree). Sheabutter is one of the most diffi cult oleaginous resources to extract by traditional way. In Burkina Faso, where production of sheanuts is estimated at 70 000 tons per year, presses manufactured locally are used to improve the production. In order to optimize the handcraft process of sheabutter production, extraction parameters of Vitellaria paradoxa Gaertn C.F. were studied under laboratory controlled conditions on 3 g samples of ground almonds using a uni-axial compression test machine specifi cally instrumented for this purpose. The studied operational parameters were the grinding (unsieved sample 0.5 mm<Ø<5 mm ; sieved samples 0.5 mm<Ø<1 mm ; 1 mm<Ø<2 mm ; 2 mm<Ø<4 mm ; 4 mm<Ø<5 mm), the heating temperature (30; 50; 70; 90; 110; 130; 150°C) and the extraction pressure (7; 10; 13.4; 15; 16.17; 17.44; 20; 22.43 and 25 MPa). The grinding has favourably infl uenced the extraction rate. The fi nest sieved fraction (0.5 mm<Ø<1 mm) presented the highest extraction rate, 84%. When using unsieved samples, the best results were obtained with a heating temperature of 90°C and an extraction pressure of 20 MPa. In these conditions, the extraction rate reached 78% and the chemical characteristics of the sheabutter were not altered. As a result, a signifi cant increase of the handcrafted presses effi ciency could be reached by simple and inexpensive modifi cations as an increase of the pressure applied to the product, by a decrease of the pressing chamber diameter. [less ▲]

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See detailModelling spray drift using a modified air pollution Gaussian tilting plume model
Stainier, Charles; Destain, Marie-France ULg; Schiffers, Bruno ULg et al

Poster (2007)

The objective of this research is to evaluate a Gaussian tilting plume model that takes into account the spray characteristics of agricultural nozzles to predict drift. The application of this type of ... [more ▼]

The objective of this research is to evaluate a Gaussian tilting plume model that takes into account the spray characteristics of agricultural nozzles to predict drift. The application of this type of model has proved to be effective for aerial pollution applications. To be applied successfully to the spray drift, the model has to give accurate predictions of the deposits regarding the spray and material characteristics as well as the weather parameters. To reach this objective, the model parameters must be correctly set based on appropriate theoretical basis and experimental data. Based on wind tunnel measurements, the effect of the most important characteristics of spray droplets from an agricultural nozzle has been modelled using a Gaussian tilting plume approach by discretizing the different droplet classes. Although the theoretical basis of the model is simple, the predicted drift appeared to be in relatively good agreement with the experimental results. The discrepancies could be explained by poor fitting of the dispersion model parameters. Further work is required to optimise the value of the model parameters. [less ▲]

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See detailAgricultural tools guidance assistance by using machine vision
Leemans, Vincent ULg; Destain, Marie-France ULg

in Proceedings of the NCTAM 2006 7th National Congress on Theoretical and Applied Mechanics (2006, May 30)

This paper presents a regulation mechanism aiming to position agricultural tools relatively to the previous lines, while sowing or harvesting. The sowing rows were revealed by a background correction, the ... [more ▼]

This paper presents a regulation mechanism aiming to position agricultural tools relatively to the previous lines, while sowing or harvesting. The sowing rows were revealed by a background correction, the background being obtained thanks to a median rank filter. The method was found efficient in eliminating the shadows. For the crop rows (chicory rows), a neural network was used to localise the plants. While the petiole and the leaves were easily separated from the soil, the chicory root and the soil having about the same colour and the lighting condition varying widely, it was more difficult to obtain a good contrast between those parts, which leaves place for some improvements. The adapted Hough transform consisted in computing one transform for each line in the cluster with, for reference, the position and direction of the theoretical position of the row. The different transforms were then added. The position was used in a feedback regulation loop. An articulated mechanism was used to ensure the lateral displacement of the tool relatively to the tractor. The behaviour of the whole outfit was studied during several field tests. The standard deviation of the error, measured as the difference between the observed inter-row distance and its theoretica value, was of 23 mm for sowing and 31 mm for harvesting and its amplitude was less than 100 mm for sowing and less than 115 mm during the harvest, which was sufficient to fulfil the requirements of the application. Sources of systematic errors were also identified as linked to the geometric considerations. Their correction requires an accurate mounting of the camera, which may be possible for a serial montage. [less ▲]

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See detailWind tunnel protocol for spray drift assessment
stainier, Charles; Lebeau, Frédéric ULg; Destain, Marie-France ULg et al

Conference (2006, April 11)

The objective of wind tunnel protocol is to measure spray drift in a reproducible way in order to evaluate the relative drift potential

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See detailExperimental evaluation of a spray drift Gaussian tilting plume model.
Stainier, Charles; Robaye, Vincent ULg; Destain, Marie-France ULg et al

in Aspects of Applied Biology (2006), 77(2), 365-370

This paper evaluates the application of a Gaussian tilting plume model to study agricultural spraying drift. The spray drift deposit of each droplet diameter class, measured by a laser particle analyser ... [more ▼]

This paper evaluates the application of a Gaussian tilting plume model to study agricultural spraying drift. The spray drift deposit of each droplet diameter class, measured by a laser particle analyser, is computed independently and summed to give footprint results for different nozzle. The methodology is used to model the drift from a fiat fan nozzle operating in a wind tunnel. Discrepancies with experimental data and the potential for further improvement of this approach are discussed. [less ▲]

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See detailEffect of the entrained air and initial droplet velocity on the release height parameter of a Gaussian spray drift model.
Stainier, C.; Destain, Marie-France ULg; Schiffers, Bruno ULg et al

in Communications in Agricultural and Applied Biological Sciences (2006), 71(2 Pt A),

The increased concern about environmental effect of off-target deposits of pesticides use has resulted in the development of numerous spray drift models. Statistical models based on experimental field ... [more ▼]

The increased concern about environmental effect of off-target deposits of pesticides use has resulted in the development of numerous spray drift models. Statistical models based on experimental field studies are used to estimate off-target deposits for different sprayers in various environmental conditions. Random-walk and computational fluid dynamics (CFD) models have been used to predict the effect of operational parameters and were extensively validated in wind tunnel. A third group, Gaussian dispersion models have been used for several years for the environmental assessment of the pesticide spray drift, mainly for aerial application. When these models were used for the evaluation of boom sprayer spray drift, their predictions were found unreliable in the short range, were the initial release conditions of the droplets have a significant effect on the spray deposits. For longer ranges, the results were found consistent with the field measurements as the characteristics of the source have a reduced influence on the small droplets drift. Three major parameters must be taken into account in order to define realistic initial conditions of the droplets in a spray drift model: the spray pattern of the nozzle, the boom movements and the effect of entrained air and droplet velocities. To take theses parameters into account in a Gaussian model, the nozzle droplet size distribution measured with a Malvern laser particle analyser was used to divide the nozzle output into several size classes. The spray deposits of each diameter class was computed for each successive position of the nozzle combining the nozzle spray distribution with drift computed with a Gaussian tilting plume model. The summation of these footprints resulted in the global drift of the nozzle. For increasing droplet size, the release height used in the Gaussian model was decreased from nozzle height to ground level using an experimental law to take into account the effect of entrained air and droplet initial velocity. The experimental law was adjusted on 2m/s wind tunnel measurements and robustness was evaluated for 1 and 4 m/s. [less ▲]

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See detailDroplet Size Spectra And Drift Effect Of Two Phenmedipham Formulations And Four Adjuvants Mixtures
Stainier, C.; Destain, Marie-France ULg; Schiffers, Bruno ULg et al

in Crop Protection (2006), 25(12),

Relative drift potential was evaluated for three types of hydraulic nozzles (a flat-fan nozzle, a hollow cone nozzle and an air induction nozzle) spraying different liquids: water, emulsifiable ... [more ▼]

Relative drift potential was evaluated for three types of hydraulic nozzles (a flat-fan nozzle, a hollow cone nozzle and an air induction nozzle) spraying different liquids: water, emulsifiable concentrate (EC) and suspension concentrate (SC) formulations of phenmedipham dispersed in water, with or without addition of 4 different tank-mix adjuvants. The droplet size spectra were measured for these 15 spray mixtures using a Malvern Particle Sizer and characterised by the Volume Median Diameter (VMD) and the percentage of liquid contained in droplets less than 100 m (% < 100 m). Horizontal ground drift was measured in a wind tunnel, on glass fibre collectors using a fluorescent tracer dye technique. The relative drift of each spray mixture was characterised by the Drifted Part (DP) which is the part of the sprayed volume drifted between 2 and 6 metres. Although the nozzle type was the predominating parameter regarding to the droplet size spectra and the DP, differences were observed due to the liquids characteristics. The EC formulation produced a smaller droplet size and a greater DP than the SC formulation whatever the tank mix adjuvant used. For the different spray mixtures, the DP was poorly correlated to the VMD or the % < 100 m. However, correlations between the VMD, the % < 100 m and the DP of the flat-fan nozzle and of the hollow cone nozzle were significant. This suggests that a reference nozzle could be used to estimate the drift potential of other nozzle with a similar liquid sheet break-up mechanism. [less ▲]

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See detailApplication Of The Hough Transform For Seed Row Localisation Using Machine Vision
Leemans, Vincent ULg; Destain, Marie-France ULg

in Biosystems Engineering (2006), 94(3),

This paper compares two methods based on machine vision to provide driver assistance in seed drill guidance in order to improve spacing accuracy during contiguous passages. The first case consisted of ... [more ▼]

This paper compares two methods based on machine vision to provide driver assistance in seed drill guidance in order to improve spacing accuracy during contiguous passages. The first case consisted of following the furrow created at the preceding passage by a special marker disc attached to the seed drill. A camera was located on the tractor and detected this furrow. In the second case, the seed rows themselves were detected by the camera without making use of the marker disc. In both cases, several video sequences were acquired in various situations, including different soil textures and various illumination conditions (375 sequences were acquired during three years). A pre-treatment of these sequences was performed and included a background subtraction in order to remove shadows and other wide unevenness. In the first case, the best results were obtained by using an image treatment based on the Hough transform coupled to a recursive filter. The search of the maximum of the Hough transform was performed using a mean shift algorithm. In the second case, where several parallel rows were simultaneously present on the images, an adapted Hough transform was proposed which took into account the a priori knowledge of the rows spacing. The trueness and precision in row detection were superior in the second case. The results are compatible with the application, since the trueness was smaller than 30 mm. This suggested that it can be possible to assist the manual guidance of a seed drill by an automatic system consisting in a camera detecting the seed rows. [less ▲]

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See detailLine Cluster Detection Using A Variant Of The Hough Transform For Culture Row Localisation
Leemans, Vincent ULg; Destain, Marie-France ULg

in Image and Vision Computing (2006), 24(5),

An adaptation of the Hough transform was proposed for the detection of line clusters of known geometry. This method was applied in agriculture for the detection of sowing furrows created by a driller and ... [more ▼]

An adaptation of the Hough transform was proposed for the detection of line clusters of known geometry. This method was applied in agriculture for the detection of sowing furrows created by a driller and of chicory plant rows during harvesting process. The sowing rows were revealed by a background correction, the background being obtained thanks to a median rank filter. The method was found efficient in eliminating the shadows. For the crop rows, a neural network was used to localise the plants. While the petiole and the leaves were easily separated from the soil, the chicory root and the soil having about the same colour and the lighting condition varying widely, it was more difficult to obtain a good contrast between those parts, which leaves place for some improvements. The adapted Hough transform consisted in computing one transform for each line in the cluster with, for reference, the position and direction of the theoretical position of the row. The different transforms were then added. It was found effective for both the sowing rows and the chicory rows. Results remained good even in very noisy conditions, when the rows were incomplete or when artefacts would lead its classical counter part to show several alignments other than the expected ones. The culture rows were localised with a precision of a few centimetres which was compatible with the proposed applications. [less ▲]

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See detailDevelopment of a multi-spectral vision system for the detection of defects on apples
Kleynen, Olivier; Leemans, Vincent ULg; Destain, Marie-France ULg

in Journal of Food Engineering (2005), 69(1), 41-49

A method to sort 'Jonagold' apples based on the presence of defects was proposed. A multi-spectral vision system including four wavelength bands in the visible/NIR range was developed. Multi-spectral ... [more ▼]

A method to sort 'Jonagold' apples based on the presence of defects was proposed. A multi-spectral vision system including four wavelength bands in the visible/NIR range was developed. Multi-spectral images of sound and defective fruits were acquired tending to cover the whole colour variability of this bicolour apple variety. Defects were grouped into four categories: slight defects, more serious defects, defects leading to the rejection of the fruit and recent bruises. Stem-ends/calyxes were detected using a correlation pattern matching algorithm. The efficiency of this method depended on the orientation of the stem-end/calyx according to the optical axis of the camera. Defect segmentation consisted in a pixel classification procedure based on the Bayes' theorem and non-parametric models of the sound and defective tissue. Fruit classification tests were performed in order to evaluate the efficiency of the proposed method. No error was made on rejected fruits and high classification rates were reached for apples presenting serious defects and recent bruises. Fruits with slight defects presented a more important misclassification rate but those errors fitted however the quality tolerances of the European standard. Considering an actual ratio of sound fruits of 90%, less than 2% of defective fruits were classified into the sound ones. (c) 2004 Elsevier Ltd. All rights reserved. [less ▲]

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See detailEffect of tank mixed adjuvants on the drift potential of phenmedipham formulations.
Stainier, Charles; Destain, Marie-France ULg; Schiffers, Bruno ULg et al

in Communications in agricultural and applied biological sciences (2005), 70(4), 979-987

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See detailDetection of defects on fruits by machine vision and unsupervised segmentation
Kleynen, Olivier; Destain, Marie-France ULg

in AgEng 2004 Conference (2004, September)

Defect detection on fruits by machine vision is a complex task. Indeed, the sound tissue colour is not uniform and the defects present a wide variability in colour, shape and texture. Mostly often, images ... [more ▼]

Defect detection on fruits by machine vision is a complex task. Indeed, the sound tissue colour is not uniform and the defects present a wide variability in colour, shape and texture. Mostly often, images are acquired by conventional RGB cameras and defect segmentation is performed by algorithms based on Bayes' rules. The efficiency of these methods can be improved firstly by acquiring images with a dedicated vision system (multi-spectral imager) and secondly by implementing unsupervised segmentation methods (method derived from the 'mean shift' procedure of Camaniciu and Meer, 2002). [less ▲]

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See detailDetection of defects on fruits by machine vision and unsupervised segmentation
Kleynen, Olivier; Destain, Marie-France ULg

in AgEng 2004 Conference - Engineering the fuiture (2004)

Defect detection on fruits by machine vision is a complex task. Indeed, the sound tissue colour is not uniform and the defects present a wide variability in colour, shape and texture. Mostly often, images ... [more ▼]

Defect detection on fruits by machine vision is a complex task. Indeed, the sound tissue colour is not uniform and the defects present a wide variability in colour, shape and texture. Mostly often, images are acquired by conventional RGB cameras and defect segmentation is performed by algorithms based on Bayes'rules. The efficiency of these methods can be improved firstly by acquiring images with a dedicated vision system (multi-spectal imager) and secondly by implementing unsupervised segmentation methods (based on the 'mean shift' procedure; Comaniciu and Meer, 2002). [less ▲]

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See detailA guidance assistance method for precision sugar beet sowing using machine vision.
Leemans, Vincent ULg; Destain, Marie-France ULg

in Pr. Josse De Baerdemaeker (Ed.) AgEng 2004 Conference - Engineering the future - Book of abstracts (2004, September)

This paper presents a method for seed drill guidance by using machine vision

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See detailETUDE PAR IMAGERIE NUMERIQUE ET GRANULOMETRIE LASER DE L'INFLUENCE DE HUIT ADJUVANTS SUR LA FORMATION DU JET DE PULVERISATION POUR TROIS TYPES DE BUSES.
Stainier, Charles; Lebeau, Frédéric ULg; Straet, S. et al

Conference (2004, March 11)

The liquid sheet characteristics as a function of the adjuvant were measured using digital images. The droplet size distribution was measured using a Malvern particle size analyser. It appears that the ... [more ▼]

The liquid sheet characteristics as a function of the adjuvant were measured using digital images. The droplet size distribution was measured using a Malvern particle size analyser. It appears that the dynamical surface tension plays a critical role in the spray formation. Spray formulation containing Li-700, Silwet L-77, Flofix and Actirob are characterised by a lower dynamical surface tension than those containing Tensiofix D03, Trend 90, Frigate and Break-thru S240. For the three agricultural spray nozzles tested and in comparaison with pure water, the first group shortened the length of the liquid sheet before a perforation break-up mode when the second group lengthened it slightly before a wave disintegration break-up mode. The lengthening of the liquid sheet, is followed by a diminution of the VMD. [less ▲]

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See detailSoil variability measured by a soil strenght sensor: within-field variability and similarity between fields
Hanquet, Bernard; Ndao, Tanor; Verbrugge, Jean-Claude et al

in Book of Abstracts (2004)

Many sensing methods for soil physical properties determination are developed to replace time-consuming and expensive soil sampling and analysis. Within this scope, sensors to measure soil strength are ... [more ▼]

Many sensing methods for soil physical properties determination are developed to replace time-consuming and expensive soil sampling and analysis. Within this scope, sensors to measure soil strength are developed in several laboratories. They are generally coupled to DGPS positioning systems to produce maps, showing within-field soil variability. In this study, besides the within-field variability, the sensor was used with another objective: the aim was to appraise the similarity of soil strength between different fields located in silty areas, in Belgium. [less ▲]

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