Browsing
     by title


0-9 A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

or enter first few letters:   
OK
Full Text
Peer Reviewed
See detailEstimating crop-specific evapotranspiration using remote-sensing imagery at various spatial resolutions for improving crop growth modelling
Sepulcre-Cantó, Guadalupe; Gellens-Meulenberghs, Françoise; Arboleda, Alirio et al

in International Journal of Remote Sensing (2013)

By governing water transfer between vegetation and atmosphere, evapotranspiration (ET) can have a strong influence on crop yields. An estimation of ET from remote sensing is proposed by the EUMETSAT ... [more ▼]

By governing water transfer between vegetation and atmosphere, evapotranspiration (ET) can have a strong influence on crop yields. An estimation of ET from remote sensing is proposed by the EUMETSAT ‘Satellite Application Facility’ (SAF) on Land Surface Analysis (LSA). This ET product is obtained operationally every 30 min using a simplified SVAT scheme that uses, as input, a combination of remotely sensed data and atmospheric model outputs. The standard operational mode uses other LSA-SAF products coming from SEVIRI imagery (the albedo, the downwelling surface shortwave flux, and the downwelling surface longwave flux), meteorological data, and the ECOCLIMAP database to identify and characterize the land cover. With the overall objective of adapting this ET product to crop growth monitoring necessities, this study focused first on improving the ET product by integrating crop-specific information from high and medium spatial resolution remote-sensing data. A Landsat (30 m)-based crop type classification is used to identify areas where the target crop, winter wheat, is located and where crop-specific Moderate Resolution Imaging Spectroradiometer (MODIS) (250 m) time series of green area index (GAI) can be extracted. The SVAT model was run for 1 year (2007) over a study area covering Belgium and part of France using this supplementary information. Results were compared to those obtained using the standard operational mode. ET results were also compared with ground truth data measured in an eddy covariance station. Furthermore, transpiration and potential transpiration maps were retrieved and compared with those produced using the Crop Growth Monitoring System (CGMS), which is run operationally by the European Commission’s Joint Research Centre to produce in-season forecast of major European crops. The potential of using ET obtained from remote sensing to improve crop growth modelling in such a framework is studied and discussed. Finally, the use of the ET product is also explored by integrating it in a simpler modelling approach based on light-use efficiency. The Carnegie–Ames–Stanford Approach (CASA) agroecosystem model was therefore applied to obtain net primary production, dry matter productivity, and crop yield using only LSA-SAF products. The values of yield were compared with those obtained using CGMS, and the dry matter productivity values with those produced at the Flemish Institute for Technological Research (VITO). Results showed the potential of using this simplified remote-sensing method for crop monitoring. [less ▲]

Detailed reference viewed: 65 (10 ULg)
Full Text
Peer Reviewed
See detailEstimating daily yield and content of major fatty acids from single milking
Arnould, Valérie ULg; Reding, Romain; Delvaux, Charles et al

Poster (2014, February 07)

Reducing the frequency of milk recording and the number of recorded samples per test-day could be a solution in order to reduce costs of official milk recording. However, fewer samples lead to a decrease ... [more ▼]

Reducing the frequency of milk recording and the number of recorded samples per test-day could be a solution in order to reduce costs of official milk recording. However, fewer samples lead to a decrease in the accuracy of predicted daily yields. Unfortunately, the current published equations use the milking interval that is often not available and/or reliable in practice. The first objective of this study was to propose models using easily available traits. Therefore the milking interval was replaced by a combination of data easily recorded by milk recording. The second objective of this study was to enlarge the previous investigations to milk fatty acids (FA) in order to propose a practical method for estimating accurate daily milk, fat and major FA yields from single milking. The fit goodness of proposed models was evaluated based on the correlation values between the estimated and observed daily yields in addition to the calculation of the mean square error. Obtained results are promising. Correlation values were comprised between 96.4% and 97.6% when daily yield were estimated from morning milking, and from 96.9% to 98.3% when daily yield were estimated from evening milking. The combination of records related to lactation stage, month of test, milk yield, and fat could replace the milking interval effect. Because of their simplicity, proposed models would be easy to implement. [less ▲]

Detailed reference viewed: 30 (8 ULg)
Full Text
Peer Reviewed
See detailEstimating daily yield and content of major fatty acids from single milking: First approach
Arnould, Valérie ULg; Froidmont, Eric; Nguyen, Nam et al

Poster (2011, July 11)

Detailed reference viewed: 33 (17 ULg)
Full Text
Peer Reviewed
See detailEstimating daily yield of major fatty acids from single milking: first approach.
Arnould, Valérie ULg; NGuyen, N. H.; Froidmont et al

in Journal of Dairy Science (2011, July), 94(E-Suppl. 1), 29

Reducing the frequency of milk recording and the number of recorded samples per test-day could be a solution in order to reduce costs of milk recording. However, this solution leads to decrease also the ... [more ▼]

Reducing the frequency of milk recording and the number of recorded samples per test-day could be a solution in order to reduce costs of milk recording. However, this solution leads to decrease also the accuracy of predicting daily yield. According to the literature, several authors have already worked on this problematic. Unfortunately, some effects used in previous studies are not often available or reliable in used databases. This study was aimed to enlarge these investigations to milk fatty acids (FA) production: saturated FA, mono-unsaturated FA, unsaturated FA, medium-chain FA, and long chain FA and to propose a simple, robust and practical method for estimating accurate daily major FA yield from single milking. To do this, five dairy cows were followed between January 2007 and December 2010. FA contents were predicted by mid-infrared spectrometry. The final database contained 1,440 records. The first step was to ensure that used effects were available in most used databases. According to the availability of data, height models were tested to estimate daily yields from both morning and evening milking. These models were compared on the basis of the coefficient of determination values between estimated and observed daily yields and the mean square error. The proposed models included progressively several effects such as the milk yield, the fat and protein content, some classes of stage in lactation, of month of test or of month of calving. As expected, R² values were higher when these effects are introduced in the model and were comprised between 0.87 and 0.88 when daily yield were estimated from morning milking, and from 0.75 and 0.86 when daily yield were estimated from evening milking. It was concluded that the introduction of these effects did highly improve the daily predictability of all trait yield and can partially replace the milking interval effect. It was also observed that daily yields estimated from evening milkings are less accurate than those estimated from morning milkings. Finally, the applied model will depend on the availability of the data and to the convenience of the applied model to the studied population. Keywords: Milk recording, Fatty acids, prediction [less ▲]

Detailed reference viewed: 43 (13 ULg)
Full Text
Peer Reviewed
See detailEstimating dead wood during national forest inventories: a review of inventory methodologies and suggestions for harmonization
Woodall, Christopher W.; Rondeux, Jacques ULg; Verkerk, Pieter J. et al

in Environmental Management (2009), 44(4), 624-631

Efforts to assess forest ecosystem carbon stocks, biodiversity, and fire hazards have spurred the need for comprehensive assessments of forest ecosystem dead wood (DW) components around the world ... [more ▼]

Efforts to assess forest ecosystem carbon stocks, biodiversity, and fire hazards have spurred the need for comprehensive assessments of forest ecosystem dead wood (DW) components around the world. Currently, information regarding the prevalence, status, and methods of DW inventories occurring in the world’s forested landscapes is scattered. The goal of this study is to describe the status, DW components measured, sample methods employed, and DW component thresholds used by national forest inventories that currently inventory DW around the world. Study results indicate that most countries do not inventory forest DW. Globally, we estimate that about 13% of countries inventory DW using a diversity of sample methods and DW component definitions. A common feature among DW inventories was that most countries had only just begun DW inventories and employ very low sample intensities. There are major hurdles to harmonizing national forest inventories of DW: differences in population definitions, lack of clarity on sample protocols/estimation procedures, and sparse availability of inventory data/reports. Increasing database/ estimation flexibility, developing common dimensional thresholds of DW components, publishing inventory procedures/protocols, releasing inventiory data/reports to international peer review, and increasing communication (e.g.,workshops) among countries inventorying DW are suggestions forwarded by this study to increase DW inventory harmonization. [less ▲]

Detailed reference viewed: 11 (8 ULg)
Full Text
See detailEstimating diagonal second order terms in structural approximations with quasi-Cauchy techniques
Duysinx, Pierre ULg; Nguyen, Van Hien; Bruyneel, Michaël ULg et al

in CHENG, Gen Dong (Ed.) Proceedings of the 4th World Congress of Structural and Multidisciplinary Optimization WCSMO4 (2001, June)

This paper reports preliminary results obtained when estimating diagonal second order terms to be used in structural approximations with the quasi-Cauchy updates which was recently proposed by Zhu ... [more ▼]

This paper reports preliminary results obtained when estimating diagonal second order terms to be used in structural approximations with the quasi-Cauchy updates which was recently proposed by Zhu, Nazareth, and Wolkowicz (SIAM J. of Optimization, 9 (4), 1192-1204, 1999). At first, the theory of quasi-Cauchy updates is presented. Main characteristics of the developments that were necessary to use quasi-Cauchy updates in the context of structural optimization are drawn. The available numerical results allow comparing quasi-Cauchy second order term estimations with other estimation procedures. [less ▲]

Detailed reference viewed: 36 (0 ULg)
Full Text
Peer Reviewed
See detailEstimating effects of permanent environment, lactation stage, age, and pregnancy on test-day yield.
Bormann, J.; Wiggans, G. R.; Philpot, J. C. et al

in Journal of Dairy Science (2002), 85(1), 2631-26321

Detailed reference viewed: 10 (2 ULg)
Full Text
Peer Reviewed
See detailEstimating fatty acid content in cow milk using mid-infrared spectrometry
Soyeurt, Hélène ULg; Dardenne, Pierre; Dehareng, Frédéric et al

in Journal of Dairy Science (2006), 89(9), 3690-3695

Detailed reference viewed: 53 (13 ULg)
Full Text
Peer Reviewed
See detailEstimating Glomerular Filtration Rate in 2012 - Does the New Chronic Kidney Disease Epidemiology Equation Fare Better than Older Equations?
DELANAYE, Pierre ULg; Krzesinski, Jean-Marie ULg

in European Nephrology (2012), 6(1), 15-20

Measuring or estimating glomerular filtration rate (GFR) is still considered the best way to apprehend global renal function. In 2009, the Chronic Kidney Disease Epidemiology (CKD-EPI) equation was ... [more ▼]

Measuring or estimating glomerular filtration rate (GFR) is still considered the best way to apprehend global renal function. In 2009, the Chronic Kidney Disease Epidemiology (CKD-EPI) equation was proposed as a better estimator of GFR than the Modification of Diet in Renal Disease (MDRD) study equation. It is supposed to underestimate GFR to a lesser degree in higher GFR levels. In this article, we present and discuss the performances of this new equation. Based on articles published between 2009 and 2012, we underline its advantages, notably better knowledge of chronic kidney disease prevalence, but also its limitations, especially in some specific populations. Our conclusion is that all equations are estimations and that nephrologists should always remain cautions in their interpretation. [less ▲]

Detailed reference viewed: 21 (4 ULg)
Full Text
Peer Reviewed
See detailEstimating glomerular filtration rate in Asian subjects: where do we stand?
DELANAYE, Pierre ULg; CAVALIER, Etienne ULg; Mariat, Christophe et al

in Kidney International (2011), 80(5), 439-440

Detailed reference viewed: 15 (2 ULg)
See detailEstimating Inter-Sensor Sea Surface Temperature Biases using DINEOF analysis
Tomazic, Igor ULg; Alvera Azcarate, Aïda ULg; Troupin, Charles ULg et al

Poster (2013)

Climate studies need long-term data sets of homogeneous quality, in order to discern trends from other physical signals present in the data and to minimise the contamination of these trends by errors in ... [more ▼]

Climate studies need long-term data sets of homogeneous quality, in order to discern trends from other physical signals present in the data and to minimise the contamination of these trends by errors in the source data. Sea surface temperature (SST), defined as one of essential climatology variables, has been increasingly used in both oceanographical and meteorological operational context where there is a constant need for more accurate measurements. Satellite-derived SST provides an indispensable dataset, with both spatially and temporally high resolutions. However, these data have errors of 0.5 K on a global scale and present inter-sensor and inter-regional differences due to their technical characteristics, algorithm limitations and the changing physical properties of the measured environments. These inter-sensor differences should be taken into account in any research involving more than one sensor (SST analysis, long term climate research . . . ). The error correction for each SST sensor is usually calculated as a difference between the SST data derived from referent sensor (e.g. ENVISAT/AATSR) and from the other sensors (SEVIRI, AVHRR, MODIS). However, these empirical difference (bias) fields show gaps due to the satellite characteristics (e.g. narrow swath in case of AATSR) and to the presence of clouds or other atmospheric contaminations. We present a methodology based on DINEOF (Data INterpolation Empirical Orthogonal Functions) to reconstruct and analyse SST biases with the aim of studying temporal and spatial variability of the SST bias fields both at a large scale (European seas) and at a regional scale (Mediterranean Sea) and to perform the necessary corrections to the original SST fields. Two different approaches were taken: by analysing SST biases based on reconstructed SST differences and based on differences of reconstructed SST fields. Corrected SST fields based on both approaches were validated against independent in situ buoy SST data or with ENVISAT/AATSR SST data for areas without in situ data (e.g. eastern Mediterranean). [less ▲]

Detailed reference viewed: 7 (0 ULg)
Full Text
Peer Reviewed
See detailEstimating internal pelvic sizes using external body measurements in the double-muscled Belgian Blue beef breed
Coopman, F.; de Smet, S.; Gengler, Nicolas ULg et al

in Animal Science (2003), 76(Part 2), 229-235

In the double-muscled (DM) Belgian Blue beef (BBB) breed, caesarean section (CS) is being applied systematically as a management tool to prevent dystocia. As a matter of fact, CS is the only possible way ... [more ▼]

In the double-muscled (DM) Belgian Blue beef (BBB) breed, caesarean section (CS) is being applied systematically as a management tool to prevent dystocia. As a matter of fact, CS is the only possible way of calving in the breed. High birth weight and a relatively small pelvic area are the main causes of dystocia and, in the DM-BBB breed, the reasons for the systematically applied CS. Selection for lower birth weight and larger pelvic sizes might reduce dystocia and routine CS. Few data on inner pelvic sizes of pedigree animals are available. Using external measurements to estimate the inner pelvic sizes might be an option to resolve this problem. In this study, animals of the DM-BBB breed were measured and weighed on farms and in abattoirs. External and internal pelvic sizes increased with live weight and age of the animals. Gender had a significant influence on inner pelvic traits. Increased muscular conformation was associated with decreased inner pelvic dimensions. Models with weight, gender, age, withers height and outer pelvic width (TcTc) can be used to estimate inner pelvic sizes (R-2 between 0.35 and 0.77). The estimated inner pelvic sizes can then be used to genetically evaluate pelvic traits in the DM-BBB breed. Improving weight, withers height and TcTc width in combination with lowering muscular conformation may help to decrease the high rate of caesarean section in the DM-BBB. [less ▲]

Detailed reference viewed: 74 (2 ULg)
Full Text
Peer Reviewed
See detailEstimating marine biogeochemical rates of the carbonate pH system—A Kalman filter tested
Soetaert; Grégoire, Marilaure ULg

in Ecological Modelling (2011), 222

Oxygen (O2), nitrate (NO3), dissolved inorganic carbon (DIC) or pCO2, and pH or total alkalinity (TA), are useful indices of marine chemical, physical and biological processes operating on varying ... [more ▼]

Oxygen (O2), nitrate (NO3), dissolved inorganic carbon (DIC) or pCO2, and pH or total alkalinity (TA), are useful indices of marine chemical, physical and biological processes operating on varying timescales. Although these properties are increasingly being monitored at high frequency, they have not been extensively used for studying ecosystem dynamics. We test whether we can estimate time-evolving biogeochemical rates (e.g. primary production, respiration, calcification and carbonate dissolution, and nitrification) from synthetic high frequency time-series of O2, NO3, DIC, pCO2, TA or pH. More specifically, a Kalman filter has been implemented in a very simplified biogeochemical model describing the dynamics of O2, NO3, DIC and TA and linking the concentration data to biogeochemical fluxes. Different sets of concentration data are assimilated and biogeochemical rates are estimated. The frequency of assimilation required to get acceptable results is investigated and is compared with the frequency of sampling in the field or in controlled experimental settings. Smoothing of the data to remove data noise before assimilation improves the estimation of the biogeochemical rates. The best estimated rates are obtained when assimilating O2, NO3 and TA although the assimilation of DIC instead of TA also gives satisfactory results. In case pH or pCO2 is assimilated rather than DIC or TA, the linearization of the (now nonlinear) observation equation introduces perturbations and the Kalman filter behaves suboptimal. We conclude that, given the resolution of data required, the tool has potential to estimate biogeochemical rates of the carbonate system under controlled settings. [less ▲]

Detailed reference viewed: 29 (1 ULg)
Full Text
See detailEstimating myostatin gene effect on milk performance traits using estimated gene content for a large number of non-genotyped cows
Buske, Bernd; Vanrobays, Marie-Laure ULg; Szydlowski, Maciej et al

Conference (2011, August 29)

Detailed reference viewed: 31 (18 ULg)
Full Text
Peer Reviewed
See detailEstimating myostatin gene effect on milk performance traits using estimated gene content for a large number of non-genotyped cows
Buske, Bernd ULg; Szydlowski, Maciej; Verkenne, Catherine et al

in Animal (2011), 5(1), 43-47

Detailed reference viewed: 51 (22 ULg)
Full Text
Peer Reviewed
See detailEstimating nocturnal ecosystem respiration from the vertical turbulent flux and change in storage of CO2
van Gorsel, Eva; Delpierre, Nicolas; Leuning, Ray et al

in Agricultural and Forest Meteorology (2009), 149(11), 1919-1930

Micrometeorological measurements of night time ecosystem respiration can be systematically biased when stable atmospheric conditions lead to drainage flows associated with decoupling of air flow above and ... [more ▼]

Micrometeorological measurements of night time ecosystem respiration can be systematically biased when stable atmospheric conditions lead to drainage flows associated with decoupling of air flow above and within plant canopies. The associated horizontal and vertical advective fluxes cannot be measured using instrumentation on the single towers typically used at micrometeorological sites. A common approach to minimize bias is to use a threshold in friction velocity, u*, to exclude periods when advection is assumed to be important, but this is problematic in situations when in-canopy flows are decoupled from the flow above. Using data from 25 flux stations in a wide variety of forest ecosystems globally, we examine the generality of a novel approach to estimating nocturnal respiration developed by van Gorsel et al. (van Gorsel, E., Leuning, R., Cleugh, H.A., Keith, H., Suni, T., 2007. Nocturnal carbon efflux: reconciliation of eddy covariance and chamber measurements using an alternative to the u*-threshold filtering technique. Tellus 59B, 397-403, Tellus, 59B, 307-403). The approach is based on the assumption that advection is small relative to the vertical turbulent flux (F-C) and change in storage (F-S) of CO2 in the few hours after sundown. The sum of F-C and F-S reach a maximum during this period which is used to derive a temperature response function for ecosystem respiration. Measured hourly soil temperatures are then used with this function to estimate respiration R-Rmax. The new approach yielded excellent agreement with (1) independent measurements using respiration chambers, (2) with estimates using ecosystem light-response curves of F-c + F-s extrapolated to zero light, R-LRC, and (3) with a detailed process-based forest ecosystem model, R-cast. At most sites respiration rates estimated using the u*-filter, R-ust, were smaller than R-Rmax, and R-LRC. Agreement of our approach with independent measurements indicates that R-Rmax, provides an excellent estimate of nighttime ecosystem respiration. (C) 2009 Elsevier B.V. All rights reserved. [less ▲]

Detailed reference viewed: 81 (17 ULg)
Full Text
See detailEstimating pCO2 from remote sensing in the Belgian Coastal Zone
Borges, Alberto ULg; Ruddick, K.; Harlay, Jérôme ULg

Conference (2012, May 09)

Detailed reference viewed: 25 (1 ULg)
Full Text
See detailEstimating pCO2 from remote sensing in the Belgian Coastal Zone
Borges, Alberto ULg; Ruddick, Kevin; Harlay, Jérôme ULg

Poster (2012, April 22)

Detailed reference viewed: 18 (2 ULg)
Full Text
See detailEstimating pCO2 from remote sensing in the Belgian coastal zone
Borges, Alberto; Ruddick, Kevin; Lacroix, Geneviève et al

in ESA Special Publication SP-686 (2010)

In coastal waters, a purely field observation based approach will probably be insufficient to better constrain estimates of air-sea CO2 fluxes, to study their inter-annual variability and their long-term ... [more ▼]

In coastal waters, a purely field observation based approach will probably be insufficient to better constrain estimates of air-sea CO2 fluxes, to study their inter-annual variability and their long-term changes. One approach to achieve these goals is to use remotely sensed fields of relevant biogeochemical variables to extrapolate available data, and produce maps of the partial pressure of CO2 (pCO2) and air-sea CO2 fluxes. In the open ocean this approach has to some extent been successfully used based on fields of chlorophyll-a (Chla) and sea surface temperature (SST). This approach remains challenging in coastal waters that have complex optical properties (Case-II waters) and that exhibit highly dynamic pCO2 temporal and spatial variations. In the frame of the Belgian funded BELCOLOUR-II project (Optical remote sensing of marine, coastal and inland waters; http://www.mumm.ac.be/BELCOLOUR/), three field cruises per year (April, July and September) for optical measurements were carried in 2007, 2008, 2009 in the Southern Bight of the North Sea (SBNS). Based on these data-sets, we derived algorithms to compute pCO2 from Chl-a and sea surface salinity (SSS) using multipolynomial regressions (MPR). Here we report the first application of the MPR algorithms to derive pCO2 fields in the Belgian coastal zone based on data gathered in 2007, using remote sensed Chl-a (MERIS) and SSS computed with a 3-D hydrodynamical model of SBNS (COHERENS). [less ▲]

Detailed reference viewed: 29 (0 ULg)
Full Text
See detailEstimating pCO2 from remote sensing in the Belgian Coastal Zone
Borges, Alberto ULg; Ruddick, K.; Lacroix, G. et al

in ESA Living Planet Symposium : 28 June - 2 July 2010, Bergen, Norway (2010)

Detailed reference viewed: 16 (3 ULg)