Ontological Analysis For Description Logics Knowledge Base Debugging

International audienceFormal ontology provides axiomatizations of domain independent principles which, among other applications,can be used to identify modeling errors within a knowledge base. The Ontoclean methodology is probably the best-known illustration of this strategy, but its cost in terms of manual work is often considered dissuasive. This article investigates the applicability of such debugging strategies to Description Logics knowledge bases, showing that even a partial and shallow analysis rapidly performed with a top-level ontology can reveal the presence of violations of common sense, and that the bottleneck, if there is one, may instead reside in the resolution of the resulting inconsistency or incoherence

Trimming a consistent OWL knowledge base, relying on linguistic evidence

International audienceIntuitively absurd but logically consistent sets of statements are common in publicly available OWL datasets. This article proposes an original and fully automated method to point at erroneous axioms in a consistent OWL knowledge base, by weakening it in order to improve its compliance with linguistic evidence gathered from natural language texts. A score for evaluating the compliance of subbases of the input knowledge base is proposed, as well as a trimming algorithm to discard potentially erroneous axioms. The whole approach is evaluated on two real datasets, with automatically retrieved web pages as a linguistic input

Prioritized base Debugging in Description Logics

International audienceThe problem investigated is the identification within an input knowledge base of axioms which should be preferably discarded (or amended) in order to restore consistency, coherence, or get rid of undesired consequences. Most existing strategies for this task in Description Logics rely on conflicts, either computing all minimal conflicts beforehand, or generating conflicts on demand, using diagnosis. The article studies how prioritized base revision can be effectively applied in the former case. The first main contribution is the observation that for each axiom appearing in a minimal conflict, two bases can be obtained for a negligible cost, representing what part of the input knowledge must be preserved if this axiom is discarded or retained respectively, and which may serve as a basis to obtain a semantically motivated preference relation over these axioms. The second main contributions is an algorithm which, assuming this preference relation is known, selects some of the maximal consistent/coherent subsets of the input knowledge base accordingly, without the need to compute all of of them

Distributional semantics for ontology verification

International audienceAs they grow in size, OWL ontologies tend to comprise intuitively incompatible statements,even when they remain logically consistent. This is true in particular of lightweight ontologies, especially the ones which aggregate knowledge from different sources. The article investigates how distributional semantics can help detect and repair violation of common sense in consistent ontologies, based on the identification of consequences which are unlikely to hold if the rest of the ontology does. A score evaluating the plausibility for a consequence to hold with regard to distributional evidence is defined, as well as several methods in order to decide which statements should be preferably amended or discarded. A conclusive evaluation is also provided, which consists in extending an input ontology with randomly generated statements, before trying to discard them automatically

Thermal impact on the excavation damage zone around a supported drift using the 2nd gradient model

peer reviewedThe temperature increase induced by radioactive waste decay generates the thermal pressurisation around the excavation damage zone (EDZ), and the excess pore pressure could induce fracture re-opening and propagation. Shear strain localisation in band mode leading to the onset of micro/macro cracks can be always evidenced before the fracturing process from the lab experiments using advanced experimental devices, hence the thermal effects on the rock behaviour around the EDZ could be modelled with the consideration of development of shear bands. A coupled local 2nd gradient model with regularisation technique is implemented, considering the thermo-hydro-mechanical (THM) couplings in order to well reproduce the shear bands. Furthermore, the thermo-poroelasticity framework is summarized to validate the implemented model. The discrepancy of thermal dilation coefficient between solid and fluid phases is proved to be the significant parameter leading to the excess pore pressure. Finally, an application of a heating test based on Eurad Hitec benchmark exercise with a drift supported by a liner is studied. The strain localisation induced by thermal effects is properly reproduced. The plasticity and shear bands evolutions are highlighted during the heating, and the shear bands are preferential to develop in the minor horizontal principal stress direction. Different shear band patterns are obtained with changing gap values between the drift wall and the liner. A smaller gap between the wall and the liner can limit the development of shear bands

Prioritized base debugging in Description Logics

Abstract The problem investigated is the identification within an input knowledge base of axioms which should be preferably discarded (or amended) in order to restore consistency, coherence, or get rid of undesired consequences. Most existing strategies for this task in Description Logics rely on conflicts, either computing all minimal conflicts beforehand, or generating conflicts on demand, using diagnosis. The article studies how prioritized base revision can be effectively applied in the former case. The first main contribution is the observation that for each axiom appearing in a minimal conflict, two bases can be obtained for a negligible cost, representing what part of the input knowledge must be preserved if this axiom is discarded or retained respectively, and which may serve as a basis to obtain a semantically motivated preference relation over these axioms. The second main contributions is an algorithm which, assuming this preference relation is known, selects some of the maximal consistent/coherent subsets of the input knowledge base accordingly, without the need to compute all of of them

Peri-operative red blood cell transfusion in neonates and infants: NEonate and Children audiT of Anaesthesia pRactice IN Europe: A prospective European multicentre observational study

BACKGROUND: Little is known about current clinical practice concerning peri-operative red blood cell transfusion in neonates and small infants. Guidelines suggest transfusions based on haemoglobin thresholds ranging from 8.5 to 12 g dl-1, distinguishing between children from birth to day 7 (week 1), from day 8 to day 14 (week 2) or from day 15 (≥week 3) onwards. OBJECTIVE: To observe peri-operative red blood cell transfusion practice according to guidelines in relation to patient outcome. DESIGN: A multicentre observational study. SETTING: The NEonate-Children sTudy of Anaesthesia pRactice IN Europe (NECTARINE) trial recruited patients up to 60 weeks' postmenstrual age undergoing anaesthesia for surgical or diagnostic procedures from 165 centres in 31 European countries between March 2016 and January 2017. PATIENTS: The data included 5609 patients undergoing 6542 procedures. Inclusion criteria was a peri-operative red blood cell transfusion. MAIN OUTCOME MEASURES: The primary endpoint was the haemoglobin level triggering a transfusion for neonates in week 1, week 2 and week 3. Secondary endpoints were transfusion volumes, 'delta haemoglobin' (preprocedure - transfusion-triggering) and 30-day and 90-day morbidity and mortality. RESULTS: Peri-operative red blood cell transfusions were recorded during 447 procedures (6.9%). The median haemoglobin levels triggering a transfusion were 9.6 [IQR 8.7 to 10.9] g dl-1 for neonates in week 1, 9.6 [7.7 to 10.4] g dl-1 in week 2 and 8.0 [7.3 to 9.0] g dl-1 in week 3. The median transfusion volume was 17.1 [11.1 to 26.4] ml kg-1 with a median delta haemoglobin of 1.8 [0.0 to 3.6] g dl-1. Thirty-day morbidity was 47.8% with an overall mortality of 11.3%. CONCLUSIONS: Results indicate lower transfusion-triggering haemoglobin thresholds in clinical practice than suggested by current guidelines. The high morbidity and mortality of this NECTARINE sub-cohort calls for investigative action and evidence-based guidelines addressing peri-operative red blood cell transfusions strategies. TRIAL REGISTRATION: ClinicalTrials.gov, identifier: NCT02350348

Formulering van een macro-element voor zuigpalen onder trekbelasting

Nowadays, the ongoing electricity demand along with environmental concerns and the search for energy autonomy have been setting the basis for a global development of renewable energies. Among these sources, offshore wind power shows an attractive potential. With the increasing number of wind farms put in place further away from the coastline and in deeper waters, innovative foundation systems are required to guarantee the economic viability of offshore projects. In this context, suction caissons emerge as a suitable and cost-effective solution, and are therefore extensively studied to come up with optimised design strategies. This thesis investigates the behaviour of suction caissons in clay under a vertical tensile load that may arise from specific environmental conditions. The aim is to develop a simplified design method for this specific case. To achieve this target, a 2D numerical study of suction caissons is performed by using the finite element software LAGAMINE (developed at the University of Liège). Different configurations of the soil-foundation model are simulated in order to point out and analyse the key physical factors of the components that are involved in the extraction resistance. The most representative of these parameters are finally assembled to formulate and calibrate a mechanical model of the tensile capacity consisting of rheological elements (springs, sliders, dampers…).Les besoins continus en électricité, couplés aux enjeux environnementaux et aux aspirations d’indépendance énergétique ont posé les jalons de l’expansion mondiale que connait actuellement le domaine des énergies renouvelables. Parmi celles-ci, l’énergie éolienne offshore présente un potentiel de développement énorme. Avec le nombre croissant de turbines installées toujours plus profondément et plus loin des côtes, des systèmes de fondation innovants deviennent indispensables pour assurer la pérennité économique des projets éoliens offshores. Dans ces conditions, les caissons à succion apparaissent comme une solution appropriée et rentable, ce qui accroit l’attrait porté à l’optimisation des méthodes de conception. Ce travail porte spécifiquement sur l’étude du comportement de ce type de fondations dans des sols argileux et sous charges de traction, imposées par les conditions environnementales. L’objectif est de développer une méthode de calcul simplifiée propre à ce cas d’étude. Pour y parvenir, une étude numérique en deux dimensions d’un caisson est réalisée à l’aide du logiciel éléments finis LAGAMINE (développé à l’Université de Liège). Différentes configurations du modèle sol - fondation sont simulées de manière à mettre en évidence et analyser les facteurs physiques des composants intervenant dans la résistance à la traction. Les paramètres les plus représentatifs sont ensuite combinés en vue de formuler et calibrer un modèle mécanique du comportement en traction à partir de divers éléments rhéologiques (ressorts, amortisseurs, dissipateurs...).De behoeften voor elektriciteitsproductie samen met milieu uitdagingen en aspiraties van energie-onafhankelijkheid hebben tegenwoordig de wereldwijde uitbreiding van duurzame energiebronnen uitgestippeld. Onder deze bronnen, offshore windenergie heeft een enorm ontwikkelingspotentieel. Met het toenemende aantal windmolen, die steeds dieper en verder van de kust worden gebouwd, innovatieve funderingssystemen worden nu onmisbaar om de economische levensvatbaarheid van projecten op zee te waarborgen. In deze omstandigheden, maken zuigpalen een geschikte en rendabele optie uit, wat tot optimalisatie van ontwerpmethoden leidt. Dit rapport heeft ten doel deze funderingstechniek in kleigrond onder trekbelasting te onderzoeken. Het oogmerk is een eenvoudige methode te ontwikkelen voor de berekening van deze case studie. Om dit te bereiken, is een numerieke tweedimensionale analyse van een caisson gevoerd door middel van eindige elementen programma LAGAMINE (ontwikkeld aan de Universiteit van Luik). Verschillende configuraties van het grond - fundering model worden dan gesimuleerd om fysische factoren te benadrukken en te analyseren die in de treksterkte worden opgenomen. De meeste vertegenwoordigende parameters worden eindelijk geassembleerd zodat een mechanisch model van het trekgedrag bestaande uit reologische elementen (springveren, energie-verspreiders en dempers) geformuleerd en gekalibreerd kan worden