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See detailImproving in-row weed detection in multispectral stereoscopic images
Piron, Alexis ULg; Leemans, Vincent ULg; Lebeau, Frédéric ULg et al

in Computers & Electronics in Agriculture (2009), 69

Previous research has shown that plant height and spectral reflectance are relevant features to classify crop and weeds in organic carrots: classification based on height gave a classification accuracy ... [more ▼]

Previous research has shown that plant height and spectral reflectance are relevant features to classify crop and weeds in organic carrots: classification based on height gave a classification accuracy (CA) of up to 83% while classification based on a combination of three multispectral bands gave a CA of 72%. The first goal of this study was to examine the simultaneous use of both height and multispectral parameters. It was found that classification rate was only slightly improved when using a feature set comprising both height and multispectral data (2%). The second goal of this study was to improve the detection method based on plant height by setting an automatic threshold between crop and weeds heights, in their early growth stage. This threshold was based on crop row determination and peak detection in plant height probability density function, corresponding to the homogeneous crop population. Using this method, the CA was 82% while the CA obtained with optimal plant height limits is only slightly higher at 86%. [less ▲]

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See detailImproving Interferometric Null Depth Measurement with statistics : theory and first results with the Palomar Fiber Nuller
Hanot, Charles ULg

Scientific conference (2010, June)

A new "self-calibrated" statistical analysis method has been developed for reducing nulling interferometry data. The idea is to use the statistical distributions of the fluctuating null depths and beam ... [more ▼]

A new "self-calibrated" statistical analysis method has been developed for reducing nulling interferometry data. The idea is to use the statistical distributions of the fluctuating null depths and beam intensities to retrieve the astrophysical null depth (or equivalently the object's visibility) in the presence of fast instrumental fluctuations. The approach yields an accuracy much better (at least ten times) than is presently possible with standard data reduction methods, because the null depth accuracy is no longer limited by the magnitude of the phase and intensity errors but by uncertainties on their probability distributions. This approach was tested on the sky with the two-aperture fiber nulling instrument mounted on the Palomar Hale telescope. Using our new data analysis approach alone - and no observations of calibrators - , we find that astrophysical null depths lower than 0.001 can be reliably measured in the near infrared, with error bars as low as a few 10^-4. This statistical analysis is not specific to our instrument and may be applicable to other interferometers. Therefore I'll also present the application of this method to the measurement of Cepheids angular diameters at the VLTI with a sensitivities down to ~60µas. [less ▲]

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See detailImproving Interferometric null depth measurements using statistical distributions: theory and first results with the Palomar Fiber Nuller
Hanot, Charles ULg; Mennesson, Bertrand; Martin, Stefan et al

in Astrophysical Journal (2011), 729(2), 110

A new "self-calibrated" statistical analysis method has been developed for the reduction of nulling interferometry data. The idea is to use the statistical distributions of the fluctuating null depth and ... [more ▼]

A new "self-calibrated" statistical analysis method has been developed for the reduction of nulling interferometry data. The idea is to use the statistical distributions of the fluctuating null depth and beam intensities to retrieve the astrophysical null depth (or equivalently the object's visibility) in the presence of fast atmospheric fluctuations. The approach yields an accuracy much better (about an order of magnitude) than is presently possible with standard data reduction methods, because the astrophysical null depth accuracy is no longer limited by the magnitude of the instrumental phase and intensity errors but by uncertainties on their probability distributions. This approach was tested on the sky with the two-aperture fiber nulling instrument mounted on the Palomar Hale telescope. Using our new data analysis approach alone—and no observations of calibrators—we find that error bars on the astrophysical null depth as low as a few 10–4 can be obtained in the near-infrared, which means that null depths lower than 10–3 can be reliably measured. This statistical analysis is not specific to our instrument and may be applicable to other interferometers. [less ▲]

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See detailImproving knowledge on Forest elephant’s ecophysiology (Loxodonta africana cyclotis) for better wildlife conservation
Ngama, Steeve ULg; Vermeulen, Cédric ULg; Bindelle, Jérôme ULg

Poster (2015, March 21)

Conservation of large wildlife species is currently a major issue in Africa. Protected areas dedicated for biodiversity conservation unfortunately do not suffice and conservation practices must be ... [more ▼]

Conservation of large wildlife species is currently a major issue in Africa. Protected areas dedicated for biodiversity conservation unfortunately do not suffice and conservation practices must be extended to man-used areas. But in those areas conservation actions are limited because of conflicts between human and wildlife especially due to damages on crops. The worst crop raiders known are elephants because they can destroy the yearly harvest of a field in a single visit. This threatens not only people livelihoods but also elephants themselves when angry farmers retaliate by shooting or trapping them. After decades of investigations crop raiding drivers related to elephants’ ecophysiology remain largely unknown. A pilot study was conducted between July and November 2014 in Monts de Cristal National Park (Gabon, central Africa) to have a first view on environmental drivers to crop raiding. While the presence of some fruiting trees around crop fields lead to more damages, high slopes discouraged elephants. In further experiments, the link between the nutritive value of raided plants and the animal’s physiological requirements and status will be assessed through hormones and parasites measurements; while tracking of individual elephants’ movements using DNA analyses in feces will be done. [less ▲]

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See detailImproving micropropagation of Dioscorea cayenensis – D. rotundata complex by the use of nodal cuttings and microtubers
Ondo Ovono, Paul; Kevers, Claire ULg; Dommes, Jacques ULg

in Acta Agriculturae Scandinavica : Section B - Soil & Plant Science (2013), 63(7), 653-656

Yams (Dioscorea spp) are tuber crops used as staple food in Africa because of their nutritional value. In contrast to the inefficiency of traditional method of planting, micropropagation by nodal cuttings ... [more ▼]

Yams (Dioscorea spp) are tuber crops used as staple food in Africa because of their nutritional value. In contrast to the inefficiency of traditional method of planting, micropropagation by nodal cuttings allows to increase the multiplication and the rapid production of pathogen free plant material. The first aim ofIn this work was to show tha,t micropropagation of yam from both nodal cuttings and microtubers was first possible tested both from nodal cuttings and from microtubersand compared. It appears that microtubers rapidly develop shoots, more rapidly than nodal cuttings. Respectively 16 and 28 weeks are needed to obtain 10 cm high shoots. In a second time, the two techniques of multiplication were used in parallel to improve the multiplication rate. So, one nodal cutting after 28 weeks of culture can be subcultured as nodal cuttings (for 28 other weeks) and as microtuber parts (for 16 weeks). At the end of each subculture of nodes or microtubers, nodal cuttings and microtubers were cut and subcultured. This technique allowed obtaining more rapidly a lot of microtubers. The use of nodal cuttings allowed obtaining about 3 104 cuttings in 2 years. The additional use of the formed microtubers and the division of the microtubers at the subculture in three parts increased this multiplication rate by 15. The importance of this work was to consider microtubers not only as final planting product, but also to include them in the in vitro multiplication protocol to drastically increase the production of cuttings and finally of microtubers. [less ▲]

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See detailImproving model-based cardiac diagnosis with an ECG
Hann, C. E.; Chase, J. G.; Desaive, Thomas ULg et al

in Proceedings (CD) of the 4th European Congress for Medical and Biomedical Engineering (eMBEC 2008), Antwerp, Belgium, Nov 23-27, 2008 (2008)

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See detailImproving Null Depth Measurement with statistics : theory and first results with the Palomar Fiber Nuller
Hanot, Charles ULg

Scientific conference (2010, February)

A unique statistical data analysis method has been developed for reducing nulling interferometry data. The idea is to make use of the statistical distributions of the fluctuating null depths and beam ... [more ▼]

A unique statistical data analysis method has been developed for reducing nulling interferometry data. The idea is to make use of the statistical distributions of the fluctuating null depths and beam intensities to retrieve the astrophysical null depth in the presence of fluctuations. The approach yields an accuracy much better than is possible with standard data reduction methods, because the accuracy of the null depth is not limited by the sizes of the phase and intensity errors but by the uncertainties on these errors. The result is an improvement in the instrumental null depth measurement limit of roughly an order of magnitude. We show in this paper that broadband null depths of 10-4 can be measured in the lab with our infrared Fiber Nuller without achromatic phase shifters. On sky results are also dramatically improved, with measured contrasts up to 5 x 10-4 with our instrument mounted on the Hale telescope at the Palomar Observatory. This statistical analysis is not specific to our instrument and may be applicable to other interferometers. [less ▲]

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See detailImproving our knowledge of rapid geomagnetic field intensity changes observed in Europe between 200 and 1400 AD
Gomez-Paccard, Miriam; Chauvin, Annick; Lanos, Philippe et al

in Earth and Planetary Science Letters (2012), 355-356

vailable archaeomagnetic data indicate that during the past 2500 yr there have been periods of rapid geomagnetic field intensity fluctuations interspersed with periods of almost constant field strength ... [more ▼]

vailable archaeomagnetic data indicate that during the past 2500 yr there have been periods of rapid geomagnetic field intensity fluctuations interspersed with periods of almost constant field strength. Despite Europe being the most widely covered region in terms of archaeomagnetic data the occurrence and the behaviour of these rapid geomagnetic field intensity changes is under discussion and the challenge now is to precisely describe them. The aim of this study is to obtain an improved description of the sharp intensity change that took place in western Europe around 800 AD as well as to investigate if this peak is observed at the continental scale. For this purpose 13 precisely dated early medieval Spanish pottery fragments, four archaeological French kilns and three collections of bricks used for the construction of different French historical buildings with ages ranging between 335 and 1260 AD have been studied. Classical Thellier experiments performed on 164 specimens, and including anisotropy of thermoremanent magnetisation and cooling rate corrections, gave 119 reliable results. The 10 new high-quality mean archaeointensities obtained confirm the existence of an intensity maximum of ∼85 μT (at the latitude of Paris) centred at ∼800 AD and suggest that a previous abrupt intensity change occurred around 600 AD. Together with previously published data from western Europe that we deem to be the most reliable, the new data also suggest the existence of two other abrupt geomagnetic field intensity variations during the 12th century and around the second half of the 13th century AD. High-quality archaeointensities available from eastern Europe indicate that very similar geomagnetic field intensity changes occurred in this region. European data indicate that very rapid intensity changes (of at least 20 μT/century) took place in the recent history of the Earth's magnetic field. The results call for additional high-quality archaeointensities obtained from precisely dated samples and for a selection of the previously published data if a refined description of geomagnetic field intensity changes at regional scales is to be obtained. [less ▲]

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See detailImproving our vision on human cadaveric decomposition chemistry
Stefanuto, Pierre-Hugues ULg; Stadler, S; Perrault, K et al

Conference (2014, April 15)

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See detailImproving Overlay Routing scalability using an Internet Coordinate System
Cantin, François ULg

Doctoral thesis (2012)

Nowadays lots of real time applications are used over the Internet: voice over IP, online video games, etc. For these applications the performance of the path between two communicating nodes is critical ... [more ▼]

Nowadays lots of real time applications are used over the Internet: voice over IP, online video games, etc. For these applications the performance of the path between two communicating nodes is critical. Particularly, most of these applications require small delays between communicating nodes. For these applications, the problem is that the choice of the routes in the Internet is generally not very much guided by performance concerns. It is well known that for lots of node pairs the default Internet path is suboptimal and there exists an alternative path providing a smaller delay between these nodes. In this thesis, we mainly address the problem of finding these alternative paths. Replacing Internet's routing philosophy in order to obtain default paths providing the best performance possible should be a good theoretical solution. However, replacing Internet's routing philosophy by a brand new one is very difficult or even impossible in practice. Another solution is to leave the default routes as they are and to perform indirect routing. Consider a path AB between two nodes A and B. If a path ACB has a smaller delay than AB, then, instead of sending data directly to B, A can send them to C and C can relay them to B. This is called overlay routing because we manage the routing in an overlay network built on top of the Internet (i.e. at the application level). Overlay routing is a promising way to improve the quality of service in the Internet but its main drawback is its poor scalability: measuring the characteristics of the paths, exchanging the measurement results between the nodes and computing the best routes in the full mesh overlay network generally implies a high consumption of resources. In this thesis, our main contribution is the design of a lightweight one-hop overlay routing mechanism improving the latencies: we define criteria that rely on the information provided by an Internet Coordinate System (ICS) in order to provide a small set of potential one-hop shortcuts for any given path in the network with small costs. Our best criterion does not guarantee to find the best shortcut for any given path in a network but, even in networks with hundreds or thousands of nodes, it will restrict the search for potential shortcuts to about one or two percent of the total number of nodes. Even if the estimation-based approach of overlay routing is our main contribution, this thesis also presents general results about routing shortcuts and Internet Coordinate Systems. For an ICS, a routing shortcut is a Triangle Inequality Violation (TIV) and it is often a big problem. Indeed, a TIV will cause estimation errors since, in this particular case, nodes cannot be embedded into any metric space. In this thesis, we study TIVs existing in the Internet and their impact on the Vivaldi ICS. This analysis leads to two contributions. Firstly, we propose criteria to establish, with a high probability of success, if there exists a shortcut or not for a given path AB. Secondly, we propose a Two-Tier architecture for ICSes that mitigates the effect of TIVs on the estimations. Finally, this thesis also discusses the efficiency of two solutions proposed in the literature in order to obtain an ICS that can deal with TIVs. The first one consists in applying non-linear transformations to delays before trying to embed them in a metric space. The second one consists in modelling the estimation problem as a matrix completion problem in order to completely avoid the embedding in a metric space. [less ▲]

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See detailImproving patient positioning accuracy for breast cancer radiation therapy by using the infra red based ExacTrac system
GULYBAN, Akos ULg; Hortobágyi, E.; Sebestyén, Z. et al

in Nowotwory (2008), 58(5), 435-437

We report on a pilot study to investigate for cancer of the breast, the accuracy of patient positioning with the normal standard method (ST) and with the standard method extended with the ExacTrac system ... [more ▼]

We report on a pilot study to investigate for cancer of the breast, the accuracy of patient positioning with the normal standard method (ST) and with the standard method extended with the ExacTrac system (ET). Our work in progress pilot study population consisted of four patients: two positioned using ST and two positioned using ET. The results from the daily electronic portal images showed that with ExacTrac the positional accuracy could be unproved by 50% but with a corresponding increase in overall treatment time of about 2 minutes. [less ▲]

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See detailImproving physical education teachers’ action with overweight students
Cloes, Marc ULg

in Revista Motricidade (2012), 8(S1), 3-4

Nowadays, overweight is one of the most important plagues and many authors believe that the fast increase of this phenomenon during the last decades can be considered as a global epidemic. School has been ... [more ▼]

Nowadays, overweight is one of the most important plagues and many authors believe that the fast increase of this phenomenon during the last decades can be considered as a global epidemic. School has been identified as one of the pillars of the necessary multisectorial approach that must be implemented to fight against this ineworable trend. ... [less ▲]

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See detailImproving Product Quality and Reliability with Customer Experience Data
Brombacher, Aarnout; Hopma, Eva; Ittoo, Ashwin ULg et al

in Quality and Reliability Engineering International (2011), 28(8), 873886

Detailed reference viewed: 36 (2 ULg)
See detailImproving Public Outcomes in Developing Countries. Application of Incentive Theory to Foreign Aid and Public Resource Management
Paul, Elisabeth ULg

Doctoral thesis (2006)

This Ph.D. thesis applies incentive theory – and especially, when relevant, the principal-agent theory – to several aspects of public resource management in developing countries. It uses analytical models ... [more ▼]

This Ph.D. thesis applies incentive theory – and especially, when relevant, the principal-agent theory – to several aspects of public resource management in developing countries. It uses analytical models taking account of realistic constraints of these economies. The first part of the dissertation studies the incentive problems associated with foreign aid management. The second part deals with some “domestic” problems linked with public resource management in those countries. Chapter 2 proposes an analytical framework to guide the design of public expenditure management systems (more precisely, the type of controls a Ministry of Finance could apply to line ministries) according to country-specific parameters. Chapter 3 suggests that, when traditional incentives (sanctions and rewards) fail – which may be the case, at least in the short run, in many developing countries) – increasing public affairs transparency can help improve public outcomes, notably through relying on "informal" accountability systems. Chapter 4 reviews the literature and then draws some important results as to the motivation of public agents. In addition to specific results on the issues targeted in each chapter, this dissertation offers a coherent analytical picture of public resource management in developing countries, and a number of general lessons may be drawn. Improving public outcomes must indeed pass through providing public agents with adequate incentives, so as to align their interests with their principal’s. Different tools may be used, depending on their cost-effectiveness: e.g., controls, incentive premiums, factors acting on non-materialistic motivations or on informal accountability mechanisms. The thesis also proposes some lessons as to the sequencing of reforms dealing with public resource management. [less ▲]

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See detailImproving quality of life in patients with peripheral arterial disease: an important goal.
Kolh, Philippe ULg

in European Journal of Vascular and Endovascular Surgery (2010), 40(5), 626-7

Detailed reference viewed: 8 (1 ULg)