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See detailComparison of soil porosity structure under conventional and reduced tillage
Destain, Marie-France ULg; Roisin, Christian; Marmi, Abdeljalil ULg et al

Conference (2015, July)

The soil porosity structures under conventional (CT) and reduced tillage (RT) were compared on a Luvisol (Belgium) on a field experiment initiated in 2003. The total porosity n was computed from the bulk ... [more ▼]

The soil porosity structures under conventional (CT) and reduced tillage (RT) were compared on a Luvisol (Belgium) on a field experiment initiated in 2003. The total porosity n was computed from the bulk density (BD) and the microporosity structure was analysed by mercury intrusion porosimetry (MIP) in the range 0.003 to 73μm. It was presented in two forms: (i) cumulative pore volume vs equivalent pore radius r, from which four classes of porosity were defined: r < 0.2μm (microporosity); 0.2 ≤ r < 9µm (mesoporosity); 9 ≤ r < 73µm (MIP macroporosity); r ≥ 73μm (macroporosity); (ii) pore-size distribution (PSD). Besides the MIP measurements, the intrinsic behaviour of soil samples was investigated in one-dimensional compression tests. At 0.10m depth, n was 7% lower under RT than CT and corresponded mainly to a reduction of macroporosity r ≥ 73 μm which corresponds to pores in which water movement is important (P<0.05). The plough pan structure under CT was clearly different from other layers. It presented a higher precompression stress (Pc>160kPa) related to an increased proportion of small voids. When converting CT to RT, this compacted layer was still persistent after 10 years at 0.30m depth. With BD reaching 1.7Mgm-3, this layer could restrict the gas/water fluxes with negative environmental consequences. In the subsoil, n was similar under CT and RT (44%) but the porosity structure of RT was more favourable than under CT. Indeed, the macroporosity r ≥ 73 μm was 10% higher under RT than CT and the radius of the more represented pores was increased (3.2μm in RT versus 2.7μm in CT). This suggested that process of recovering the textural porosity due to long-term climatic and biological processes had begun in the subsoil of RT. [less ▲]

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See detailA comparison of soil properties under four vegetation units from six metalliferous hills in Katanga
Kaya Muyumba, Donato ULg; Mahy, Grégory ULg; Ngongo Luhembwe, Michel et al

Conference (2013, April 12)

In Katanga (Democratic Republic of Congo), numerous metalliferous hills are distributed along what is called the copperhill belt from Kolwezi to Lubumbashi. Very specific vegetation developed on these ... [more ▼]

In Katanga (Democratic Republic of Congo), numerous metalliferous hills are distributed along what is called the copperhill belt from Kolwezi to Lubumbashi. Very specific vegetation developed on these hills within the miombo forest in response to very specific soil conditions, among which the copper content. Previous studies have already shown the existence of gradients of copper from the mineralized rocks outcropping at the top of the hills to the foot slopes on colluviums. After a characterization of the vertical variability of soil properties in pits distributed along the main slopes, we investigated the soil-vegetation relationships in six hills located between the towns of Tenke and Fungurume. Observation 1-square meter plots were installed in four vegetation units and sixty of them were selected according to their relative importance on the six hills. The soil from the top 10cm was sampled and analyzed for pH, Total Organic Carbon, available P, K, Mg, Ca, Cu, Co and Mn and soluble Cu and Co. Analysis of variance was performed in order to assess whether the effects of the “Hill” and of the “Vegetation Unit” were significant to explain soil chemical variability. Additionally, short transects were sampled at the boundaries from adjacent vegetation units in order to evaluate the gradual or rough nature of change in soil properties under these units. [less ▲]

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See detailComparison of soil water potential sensors
Degré, Aurore ULg; Cadwell, Todd; van der Ploeg, Martine

in Geophysical Research Abstracts (2015)

Temporal and spatial monitoring of soil water potential and soil water content are necessary for quantifying water flow in the domains of hydrology, soil science and crop production as knowledge of the ... [more ▼]

Temporal and spatial monitoring of soil water potential and soil water content are necessary for quantifying water flow in the domains of hydrology, soil science and crop production as knowledge of the soil water retention curve is important for solving Richards’ equation. Numerous measurement techniques exist nowadays that use various physical properties of the soil-water complex to record changes in soil water content or soil water potential. Laboratory techniques are very useful to determine static properties of the soil water retention curve, and have been used to show the impacts of hysteresis. Yet, other spatiotemporal dynamics resulting from for example growing root systems, biological activity, periodic tillage and their impact on the soil structure cannot satisfactory be quantified in static setups in the laboratory. ). To be able to quantify the influence of soil heterogeneity, and spatiotemporal dynamics on the soil water retention curve, an in situ approach combining soil moisture and soil water potential measurements could provide useful data. Such an in situ approach would require sensors that can measure a representative part of the soil water retention curve. The volumetric soil water content is often measured using time domain reflectometry, and has gained widespread acceptance as a standard electronic means of volumetric water content measurement. To measure the soil water potential, water filled tensiometers are used in most studies. Unfortunately, their range remains limited due to cavitation. Recently, several new sensors for use under in situ conditions have been proposed to cover a wider range of pressure head: Polymer tensiometers, MPS (Decagon) and pF-meter (ecoTech). In this study, we present the principles behind each measurement technique. Then we present the results of a fully controlled experiment where we compared two MPS sensors, two pF-meter sensors and two POT sensors in the same repacked soil. It allows us to discuss advantages and disadvantages of each method. A CS616 volumetric water content probe was installed to compare in situ measured retention curves with laboratory measured retention curves for each method. [less ▲]

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See detailComparison of soil water potential sensors: a drying experiment
Degré, Aurore ULg; van der Ploeg, Martine; Caldwell, Todd et al

in Vadose Zone Journal (in press)

The soil water retention curve (WRC) plays a major role in soil’s hydrodynamic behaviour. Many measurement techniques are currently available for determining WRC in the laboratory. Direct in situ WRC can ... [more ▼]

The soil water retention curve (WRC) plays a major role in soil’s hydrodynamic behaviour. Many measurement techniques are currently available for determining WRC in the laboratory. Direct in situ WRC can be obtained from simultaneous soil moisture and water potential readings covering a wide tension range, from saturation to wilting point. There are many widely used soil moisture probes. Whereas near-saturation tension can be measured using water-filled tensiometers, wider ranges of water potential require new, more expensive and less widely used probes. This paper reports on a comparison of three types of soil water potential sensors that could allow us to measure water potential in the field, with a range relevant to water uptake by plants. Polymer tensiometers (POTs), MPS-2 probes and pF-meters were compared, in a controlled drying experiment. The study showed that the POTs and MPS-2 probes had good reliability in their respective range. Combined with a soil moisture probe, these two sensors can provide observed WRCs. The pF-meters below -30 kPa were inaccurate and their response was sensitive to measurement interval, with greater estimated suction at shorter measurement intervals. Recommendations are provided for future tests. In situ-WRC can provide supplementary information, particularly with regard to its spatial and temporal variability. It could also improve the results of other measurement techniques, such as geophysical observations. [less ▲]

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See detailComparison of some modules of the Lie algebra of vector fields
Lecomte, Pierre ULg; Mathonet, Pierre ULg; Tousset, E.

in Indagationes Mathematicae (1996), 7(4), 461-471

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See detailComparison of Spectral Colorimetric Measurements vs. Color Pictures in Dermatology
Blain, Pascal ULg; Michel, Fabrice; Moreau, Vincent et al

Poster (2010, April 13)

We studied scars and wounds depths and surfaces thanks to our interferometric fringes projector 3D scanner1, 2. Color information of a wound indicates its deterioration level. That’s why the visual color ... [more ▼]

We studied scars and wounds depths and surfaces thanks to our interferometric fringes projector 3D scanner1, 2. Color information of a wound indicates its deterioration level. That’s why the visual color restitution, as realistic as possible, is a highly important parameter. Firstly our acquired 3D pictures were color mapped with an image recorded by a RGB camera. The results were not efficient enough. In order to improve our technique and provide more precise information, we add a spectral characterization to the set-up. Before adding the spectral information and a realistic color mapping to the 3D measurements, we evaluate the performances of colorimetric measurements. The tests have been made on mice with scars on their back. [less ▲]

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See detailComparison of spin echo (SE), gradient echo ( GE ) and Fat Saturation MRI sequences for imaging the canine elbow
Snaps, Frédéric ULg; Saunders, J.; Park, R. D. et al

in Veterinary Radiology & Ultrasound (1998), 39(6), 518-523

Two comparison studies were performed. In the first conventional spin-echo (T1- and T2-weighted) sequences and a three-dimensional (3-D Fourier transform [3DFT]) echo gradient fast-imaging sequence were ... [more ▼]

Two comparison studies were performed. In the first conventional spin-echo (T1- and T2-weighted) sequences and a three-dimensional (3-D Fourier transform [3DFT]) echo gradient fast-imaging sequence were compared for imaging the canine normal elbow joint. In all three sequences, there was an isointense signal of the articular cartilage and a hyposignal of the subchondral bone, as compared with the muscles. The medial coronoid process of the ulna was clearly seen on the dorsal plane images, it appeared with a homogenous low-intensity signal. Its articulation with the radius was clearly outlined. In a second study, the 3DFT echo gradient fast-imaging sequence was compared to a fat saturation sequence on normal shoulder and elbow joints. Elbows were imaged with and without injection of saline, in an attempt to show the opposing cartilaginous articular surfaces. This distinction was possible in the shoulder joint but not in the elbow because of insufficient spatial resolution. On the three MRI sequences compared, gradient echo fast imaging with steady-state precession (GE FISP) sequence was found to be the most suitable for imaging the canine elbow joint. [less ▲]

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See detailComparison of spin echo, gradient echo and fat saturation magnetic resonance imaging sequences for imaging the canine elbow
Snaps, Frédéric ULg; Saunders, Jimmy H.; Park, Richard D. et al

in Veterinary Radiology & Ultrasound (1998), 39(6), 518-523

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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 detailComparison of Staphylococcus aureus strains isolated from bovine mastitis
Bardiau, Marjorie ULg; Duprez, Jean-Noel; Mainil, Jacques et al

Poster (2012, July)

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See detailComparison of steam and nitrogen in the physical deacidification of soybean oil
Decap, Philippe; Danthine, Sabine ULg; Vanbrabant, Béatrice et al

in Journal of the American Oil Chemists' Society (2004), 81(6), 611-617

Deacidification in physical refining is one of the most sensitive steps in refining edible vegetable oils because of its large impact on the quality of the oil. The removal of volatile compounds such as ... [more ▼]

Deacidification in physical refining is one of the most sensitive steps in refining edible vegetable oils because of its large impact on the quality of the oil. The removal of volatile compounds such as FFA is accomplished at elevated temperatures and a high vacuum with a stripping gas, usually steam. The aim of this work was to verify, at the laboratory level, the advantages of using an alternative stripping gas, nitrogen, instead of steam. An ideal vapor-liquid equilibrium model (lVLE) was used to compare the stripping capacities of steam and nitrogen and to analyze the effects of various operational parameters (temperature, pressure, amount of stripping gas) on the residual acidity of the oil. There was no clear evidence that nitrogen showed a higher capacity to strip FFA than steam. The IVLE model seemed suitable to describe FFA laboratory distillation by using steam or nitrogen, provided the final residual content of FFA was not too low. [less ▲]

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See detailComparison of structural features of spin-coated and USP-deposited templated α-Fe2O3films
Toussaint, Caroline ULg; Chatzikyriakou, Daphne; Cloots, Rudi ULg et al

Poster (2015)

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See detailComparison of supervised learning techniques for atmospheric pollutant monitoring in a Kraft pulp mill
Sainlez, Matthieu ULg; Heyen, Georges ULg

in Journal of Computational & Applied Mathematics (2012)

In this paper, supervised learning techniques are compared to predict nitro- gen oxide (NOx) pollutant emission from the recovery boiler of a Kraft pulp mill. Starting from a large database of raw process ... [more ▼]

In this paper, supervised learning techniques are compared to predict nitro- gen oxide (NOx) pollutant emission from the recovery boiler of a Kraft pulp mill. Starting from a large database of raw process data related to a Kraft recovery boiler, we consider a regression problem in which we are trying to predict the value of a continuous variable. Generalization is done on the worst case configuration possible to make sure the model is adequate: the training period concerns stationary operations while test periods mainly fo- cus on NOx emissions during transient operations. This comparison involves neural network techniques (i.e., multilayer perceptron and NARX network), tree-based methods and multiple linear regression. We illustrate the potential of a dynamic neural approach compared to the others in this task. [less ▲]

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See detailA comparison of supraglacial lake observations derived from MODIS imagery at the western margin of the Greenland ice sheet
Leeson, A.; Shepherd, A.; Sundal, A. et al

in Journal of Glaciology (2013), 59(208), 1179-1188

Supraglacial lakes (SGLs) affect the dynamics of the Greenland ice sheet by storing runoff and draining episodically. We investigate the evolution of SGLs as reported in three datasets, each based on ... [more ▼]

Supraglacial lakes (SGLs) affect the dynamics of the Greenland ice sheet by storing runoff and draining episodically. We investigate the evolution of SGLs as reported in three datasets, each based on automated classification of satellite imagery. Although the datasets span the period 2001–10, there are differences in temporal sampling, and only the years 2005–07 are common. By subsampling the most populous dataset, we recommend a sampling frequency of one image per 6.5 days in order to minimize uncertainty associated with poor temporal sampling. When compared with manual classification of satellite imagery, all three datasets are found to omit a sizeable (29, 48 and 41%) fraction of lakes and are estimated to document the average size of SGLs to within 0.78, 0.48 and 0.95 km2 . We combine the datasets using a hierarchical scheme, producing a single, optimized, dataset. This combined record reports up to 67% more lakes than a single dataset. During 2005–07, the rate of SGL growth tends to follow the rate at which runoff increases in each year. In 2007, lakes drain earlier than in 2005 and 2006 and remain absent despite continued runoff. This suggests that lakes continue to act as open surface–bed conduits following drainage. [less ▲]

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See detailComparison of surface and column carbon monoxide at a high altitude, a megacity and a southern hemisphere site
Té, Yao; Jeseck, Pascal; Franco, Bruno ULg et al

Conference (2016, June 02)

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See detailComparison of T1 and T2 - weighted and Blade MRI sequences for examination of canine normal abdomen
Hoffmann; Buttin; Haye et al

Poster (2008)

Detailed reference viewed: 58 (1 ULg)
See detailA Comparison of TEC Values Derived by Using GPS, Ionosonde and NNSS Data
Warnant, René ULg; Jodogne, Jean-Claude; Van Camp, Michel

in Kersley, Len (Ed.) Proceedings of Beacon Satellite Symposium '94 (1994)

Detailed reference viewed: 21 (0 ULg)