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See detailContribution to the Inverse Dynamics of Flexible Manipulators
Guimaraes Bastos Junior, Guaraci ULg

Doctoral thesis (2013)

This thesis studies innovative, stable but non-causal inverse dynamics algorithms for flexible manipulators. Robust direct optimal control methods are proposed. The nonlinear finite element method is used ... [more ▼]

This thesis studies innovative, stable but non-causal inverse dynamics algorithms for flexible manipulators. Robust direct optimal control methods are proposed. The nonlinear finite element method is used to derive the mechanical model of the multibody system and the time discretization is performed using the generalized-alpha method. The sparse gradients of the optimization constraints are computed using a semi-analytical method. The inverse dynamics of both serial and parallel kinematic manipulators with flexible links and joints is successfully studied using the proposed method. Finally, the possible extension of the method for the integrated control/structure optimization of mechatronic systems is investigated. [less ▲]

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See detailContribution to the knowledge of lichens in northern France
Diederich, Paul; Van Den Broeck, Dries; Ertz, Damien et al

in Bulletin de la Société des Naturalistes Luxembourgeois (2006), 106

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See detailContribution to the Macrophytic Typology of Belgian Reference Watercourses
Galoux, Daniel; Cherot, Frédéric; Rosillon, Francis ULg et al

in Advances in Botany (2015), Volume 2015, Article ID 651369

The objective of the study is to create a typology of macrophytes for the reference watercourses of the Meuse River catchment ... [more ▼]

The objective of the study is to create a typology of macrophytes for the reference watercourses of the Meuse River catchment basininWalloniaasasteptowardstheimplementationoftheEuropeanWaterFrameworkDirective.The50sitesstudiedarethe objectofaphysicochemicalandenvironmentalcharacterizationfollowedbyafloristicsurvey(phanerogams,mosses,liverworts, andmacroalgae).Sixclustersofwatercourseswiththeircharacteristicspeciesarehighlightedbytwo-wayclusteringandindicator species. The abundance of phanerogams in some watercourses of the Arden region is not only linked to light intensity but also dependsonthedegreeofslopeandthenatureofthegeologicalsubstrate [less ▲]

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See detailContribution to the management of inherited disorders in Belgian Blue Cattle Breed
Sartelet, Arnaud ULg

Conference (2013, April 23)

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See detailContribution to the modeling of shellfish zooplankton production in wastewater stabilization ponds (WSP)
Liady, Mouhamadou Nourou Dine ULg; Fiogbé, Emile-Didier; Vasel, Jean-Luc ULg

Conference (2011, May 13)

This bibliographical study falls under the context of researching financial autonomy for durable management of South countries’ wastewater ponds (WSP), and growing interest on shellfish zooplanktons that ... [more ▼]

This bibliographical study falls under the context of researching financial autonomy for durable management of South countries’ wastewater ponds (WSP), and growing interest on shellfish zooplanktons that contribute to water treatment and can be recovered in aquaculture and many industrial applications. Our project w ill start by gathering available data aiming at the development of a mathematical model of the contribution of zooplankton in pond ecosystems. This model would include the effect of most driving factors on the growth of shellfish zooplankton in WSP combined with water treatment effi ciency and biomass productivities. After a description of various types of WSP and their corresponding zooplanktons, emphasis is put on the shellfish cladocerans, especially Daphnia. The range of growth rates in various conditions is provided and expressions of growth kinetic, merging the effect of most important factors identified. These expressions of kinetic and the corresponding stoichiometry will serve as a first approach in our model. We hope that this type of research will help in the development of sustainable sanitation systems in developing countries. [less ▲]

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See detailContribution to the modeling of wastewater sludge drying kinetics: study of the operating conditions effect
Bennamoun, Lyes; Belhamri, A.; Léonard, Angélique ULg

in Tsotsas, E.; Metzger, T.; Peglow, M. (Eds.) Proceedings of IDS 2010 - Drying 2010 (2010, October)

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See detailA contribution to the moss flora of southern South Africa
Vanderpoorten, Alain ULg; Barker, N. P.

in Journal of Bryology (2004), 26(Part 3), 230-232

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See detailContribution to the optimization of closed-loop multibody systems : application to parallel manipulators
Collard, Jean-François; Fisette, Paul; Duysinx, Pierre ULg

in Proceedings of the 5th World Congress of Structural and Multidisciplinary Optimization WCSMO5 (2003, May)

This paper describes an original and robust method to optimize the design of closed-loop mechanisms, especially parallel manipulators. In other words, these mechanisms include assembling constraints we ... [more ▼]

This paper describes an original and robust method to optimize the design of closed-loop mechanisms, especially parallel manipulators. In other words, these mechanisms include assembling constraints we solved using a Newton-Raphson algorithm which may fail when the Jacobian matrix of the constraints is ill-conditioned. Therefore, the technique we propose takes advantage of that conditioning to penalize properly the objective function. Applications are shown: on the one hand, a simple example about the design of a planar ejector and, on the other hand, more realistic examples about the kinematical properties of parallel robots, in particular Delta-type and HexaSlide-type manipulators. [less ▲]

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See detailContribution to the optimization of closed-loop multibody systems: Application to parallel manipulators
Collard, Jean-François; Fisette, Paul; Duysinx, Pierre ULg

in Multibody System Dynamics (2005), 13(1), 69-84

This paper describes an original and robust method to optimize the design of closed-loop mechanisms, especially parallel manipulators. These mechanisms involve non linear assembling constraints. During ... [more ▼]

This paper describes an original and robust method to optimize the design of closed-loop mechanisms, especially parallel manipulators. These mechanisms involve non linear assembling constraints. During optimization, the Newton-Raphson algorithm we use to solve these constraints may fail when the Jacobian matrix of the constraints is ill-conditioned and stops the redesign process. To circumvent the difficulty, the technique we propose takes advantage of numerical conditioning to penalize the objective function. Applications to an academic example and parallel robots demonstrate the capabilities of the methodology. [less ▲]

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See detailContribution to the phylogeography of the garden dormouse (Eliomys quercinus)
Libois, Roland ULg; Michaux, J; Ramalhinho, Maria da Graça et al

in Macholan, Milos; Bryja, Josef; Zima, Jan (Eds.) European Mammalogy 2003 (2003, July)

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See detailContribution to the phytochemical study of indolomonoterpenic alkaloids isolated from Strychnos usambarensis and investigation of their activity on Plasmodium falciparum
Cao, Martine ULg

Doctoral thesis (2012)

Our research focuses on the extended study of antimalarial and anticancer alkaloids isolated from Strychnos usambarensis (leaves and fruits), and is subdivided into two main axes: - The development of a ... [more ▼]

Our research focuses on the extended study of antimalarial and anticancer alkaloids isolated from Strychnos usambarensis (leaves and fruits), and is subdivided into two main axes: - The development of a purification method for natural compounds such as tertiary indolomonoterpenic alkaloids (in particular for isostrychnopentamine or ISP) to improve the isolation process and to get significant quantities of purified compounds. - The investigation of the pharmacological properties of ISP, especially on Plasmodium falciparum. The first part of the thesis is devoted to the phytochemical study of S. usambarensis leaves. It includes the development and the optimization of a simple and rapid HPLC method in order to perform a one-step-transposition in preparative scale (J Pharm Biomed Anal, 2011). In parallel to this work, a brand new alkaloid was isolated from the crude alkaloid extract of S. usambarensis leaves, 17-O-acetyl, 10-hydroxycorynantheol. The compound, assessed for its antiplasmodial activity on the 3D7 and W2 strains of P. falciparum, represents one of the most active monoindolic alkaloid known to date with a remarkable selectivity for the parasite (Planta Medica, 2011). Fruits were also investigated in order to identify the main components and maybe the presence of ISP. Two major alkaloids were characterized by analytical HPLC and were therefore studied in LC-NMR and mass spectrometry (MS) after solid phase extraction (SPE): palicoside and akagerine (Phytochem Letters, 2012). In addition, we also carried out hemisynthesis of isostrychnopentamine during the PhD mandate. The concept was to hemisynthetize ISP from 11-OH usambarine, a tertiary alkaloid more abundant in the leaves. Unfortunately, the first experiments were not as conclusive as expected. The second part of the thesis concerns the investigation of the mode of action of ISP on P. falciparum. A metabolomic approach displaying the metabolomic differences induced in the parasites was combined to a transcriptomic study evaluating genes expression via a microarray analysis, in order to better understand the biological processes involved in P. falciparum in response to ISP. For this purpose we performed a study in 1H NMR metabolomics on culture media of P. falciparum under ISP treatment. In addition, we investigated gene activation using microarrays and analyzed the alterations of the P. falciparum 3D7 transciptome in synchronous cultures after exposure to ISP. Differences in gene expression were highlighted: out of the 4700 genes analyzed, 84 were differentially expressed, 40 over-expressed and 44 under-expressed and some of them were related to specific metabolic pathways. [less ▲]

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See detailContribution to the problem of the reproducibility of dual photon absorptiometry
Reginster, Jean-Yves ULg; Urbin-Choffray, D; Denis, D et al

in Journal of Bone and Mineral Research (1986), 1(S1), 280

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See detailContribution to the simulation of nitrates transport in a double-porosity aquifer
Biver, Pierre; Hallet, Vincent; Dassargues, Alain ULg

in Solutions'95, XXVI International Congress of the International Aassociation of Hydrogeologists (IAH) (1995)

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See detailContribution to the specialist committee V.3 entitled "Fabrication Technology" of the 16th International Ship and Offshore Structure Congress
Caprace, Jean-David ULg

in Borzecki, T.; Bruce, G.; Han, Y. S. (Eds.) et al Specialist committee V.3 - Fabrication technology (2008, August)

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See detailContribution to the statistical evaluation of data obtained in External Quality Assessment programmes
Coucke, Wim ULg

Doctoral thesis (2012)

Laboratory medicine has undergone a spectacular evolution in the last decades and has become today of crucial importance for supporting diagnostic and therapeutic decisions. The increase of the volume of ... [more ▼]

Laboratory medicine has undergone a spectacular evolution in the last decades and has become today of crucial importance for supporting diagnostic and therapeutic decisions. The increase of the volume of laboratory analyses has not gone without an emerging risk of measurement errors that may have far-reaching consequences, even on the patient’s life. External Quality Assessment (EQA), already established since several decades in various countries and often running on an international level, aim at going further than the "internal quality control" procedures of every laboratory and at improving laboratory quality by inter-laboratory comparisons. An EQA round generally consists of sending aliquots of the same sample to various laboratories for assaying selected tests. After finishing the assays, results are reported back to the EQA organizer. Subsequently these results are subject to a statistical analysis, which is performed globally, for all the participants, or for each analytical technique separately. Finally, a report is sent to every participant that informs about the acceptability of the individual results, with respect to predefined limits, and with respect to the group of peers. This thesis, structured in five chapters, focuses on the External Quality Control of clinical laboratories by a critical analysis of existing methods and by creating new approaches that permit to improve the current procedures. The first chapter of this work emphasizes the evolution of the role of the clinical laboratory and EQA in the quality improvement. After the report ’To Err is Human: Building a Safer Health System’, numerous scientists became interested in investigating the frequency, source and impact of laboratory errors. The Total Testing Process (TTP) became recognized as the best framework to investigate laboratory errors. The three different phases of the TTP - respectively, the pre-analytical, analytical and post-analytical phases - are described in detail and the nature and frequency of errors in each phase explained. For each phase, possible improvements are described and the role of EQA is suggested. Today, EQA principally focuses on the assessment and improvement of the analytical phase. Proposals are made to improve the role of EQA for assessing and improving pre- and post-analytical error as well, by using specific sample material and by automating the reporting of data and laboratory reports to the EQA participants. The principle of the comparison of results of a laboratory with those obtained by the other laboratories is traditionally based on the calculation of "z-scores". An indepth study comparing different techniques has been made, shedding new light on the shortcomings and strong points of the different approaches. We concluded that robust techniques may exhibit weak performance for smaller sample size, while techniques that eliminate outliers before calculating zscores should be recommended. The second Chapter discusses the role of EQA as a tool to assess harmonization between methods. The role of EQA is described, together with the pitfalls and current shortcomings for assessing harmonization. A major problem in assessing standardization between methods is the possible presence of matrix effects in control samples, in which a method-specific bias may appear. Several explanations for matrix effects are mentioned and statistical techniques are described that assist EQA organizers to split up the data in homogeneous peer groups using multivariate statistics. The chapter also reviews several techniques to be used in method comparison studies, and the preference for the use of orthogonal regression is expressed. In addition, an example is given of a method-comparison study for Estradiol and Progesterone, with a novel technique of assessing standardization between various methods, in the presence of matrix effects for a small number of samples. The study also reveals that standardization between various methods is not attained, and that the striving for standardization with standards of higher order may not be satisfactory. Chapter 3 introduces different evaluation techniques that combine information from different samples or parameters: Variance and bias index scores, Mean ranking scores, counts of z- and u-scores, and a long-term analytical Coefficient of Variation. Also, a new and original method is introduced that uses 3 steps to identify outliers in a first step, to find laboratories with exceeding variability in a second, and to identify laboratories with high bias in a third step. Each of the techniques are evaluated and discussed by means of a data set in which accidental outliers, high variability and high bias were induced. In addition, the comparison between the different evaluation methods reveals that distinguishing between variability and bias is a tedious task, and that some long-term analysis methods lack robustness against outliers. Also, it is proven that evaluation techniques summarizing results of different parameters may hide useful information. In addition, the 3-step method is proposed as a method for discerning between errors produced in the pre- or post-analytical phase, and errors that arise from the analytical phase. Chapter 4 applies the 3-step method to data obtained from the Belgian EQA. Data sets from alcohol, flow cytometry, lithium and semen analysis surveys are examined. The method is extended for applicability to heteroscedastic, i.e. unequal residual variability, regression models and demonstrates that it is able to be used in a wide range of surveys. For each of the surveys under consideration, a follow-up is made of the occurrence of accidental mistakes, and the evolution of within-laboratory variability and bias for selected methods. It highlights several conclusions that show a striking similarity for various EQA surveys: an improvement of laboratory performance has been attained over time. The major improvement was a reduction of accidental mistakes. The analytical performance of selected methods, however, did not show an improvement over time. In Chapter 5, some graphical representations of EQA data are explored and a graphical representation of the 3-step method is described. The histogram, normal quantile plot and box plot are described in detail and suggested for providing a quick visual overview of EQA data. Other graphical representations that respond to specific questions are given and discussed as well, like Shewhart charts, Cusum charts and graphical representations to combine variability and bias in one graph. In addition, the 3-step method is graphically explored by means of three distinct graphs. The chapter finishes by suggesting the use of interactive graphs for improving feedback from the EQA organizers to the EQA participants by means of Scalable Vector Graphics. The latter is illustrated with web-accessible examples of long-term evaluation of z-scores and the results of the 3-step method for the data obtained in the Belgian EQA for alcohol determination in blood. In brief, this work describes in a critical and constructive way current statistical methods used in EQA and proposes novel statistical and graphical techniques to help alleviating the future needs of External Quality Assessment programmes. [less ▲]

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See detailContribution to the study of acoustic communication in two Belgian river bullheads (Cottus rhenanus and C. perifretum) with further insight into the sound-producing mechanism
Colleye, Orphal ULg; Ovidio, Michaël ULg; Salmon, André et al

in Frontiers in Zoology (2013), 10(71),

Background: The freshwater sculpins (genus Cottus) are small, bottom-living fishes widely distributed in North America and Europe. The taxonomy of European species has remained unresolved for a long time ... [more ▼]

Background: The freshwater sculpins (genus Cottus) are small, bottom-living fishes widely distributed in North America and Europe. The taxonomy of European species has remained unresolved for a long time due to the overlap of morphological characters. Sound production has already been documented in some cottid representatives, with sounds being involved in courtship and agonistic interactions. Although the movements associated with sound production have been observed, the underlying mechanism remains incomplete. Here, we focus on two closely related species from Belgium: C. rhenanus and C. perifretum. This study aims 1) to record and to compare acoustic communication in both species, 2) to give further insight into the sound-producing mechanism and 3) to look for new morphological traits allowing species differentiation. Results: Both Cottus species produce multiple-pulsed agonistic sounds using a similar acoustic pattern: the first interpulse duration is always longer, making the first pulse unit distinct from the others. Recording sound production and hearing abilities showed a clear relationship between the sound spectra and auditory thresholds in both species: the peak frequencies of calls are around 150 Hz, which corresponds to their best hearing sensitivity. However, it appears that these fishes could not hear acoustic signals produced by conspecifics in their noisy habitat considering their hearing threshold expressed as sound pressure (~ 125 dB re 1 ␣Pa). High-speed video recordings highlighted that each sound is produced during a complete back and forth movement of the pectoral girdle. Conclusions: Both Cottus species use an acoustic pattern that remained conserved during species diversification. Surprisingly, calls do not seem to have a communicative function. On the other hand, fish could detect substrate vibrations resulting from movements carried out during sound production. Similarities in temporal and spectral characteristics also suggest that both species share a common sound-producing mechanism, likely based on pectoral girdle vibrations. From a morphological point of view, only the shape of the spinelike scales covering the body allows species differentiation. [less ▲]

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