1111 |
Simulation d'évènements rares par Monte Carlo dans les réseaux hautement fiables / Rare event simulation using Monte Carlo in highly reliable networksSaggadi, Samira 08 July 2013 (has links)
Le calcul de la fiabilité des réseaux est en général un problème NP-difficile. On peut par exemple s’intéresser à la fiabilité des systèmes de télécommunications où l'on veut évaluer la probabilité qu’un groupe sélectionné de nœuds peuvent communiquer. Dans ce cas, un ensemble de nœuds déconnectés peut avoir des conséquences critiques, que ce soit financières ou au niveau de la sécurité. Une estimation précise de la fiabilité est ainsi nécessaire. Dans le cadre de ce travail, on s'intéresse à l’étude et au calcul de la fiabilité des réseaux hautement fiables. Dans ce cas la défiabilité est très petite, ce qui rend l’approche standard de Monte Carlo inutile, car elle nécessite un grand nombre d’itérations. Pour une bonne estimation de la fiabilité des réseaux au moindre coût, nous avons développé de nouvelles techniques de simulation basées sur la réduction de variance par échantillonnage préférentiel. / Network reliability determination, is an NP-hard problem. For instance, in telecommunications, it is desired to evaluate the probability that a selected group of nodes communicate or not. In this case, a set of disconnected nodes can lead to critical financials security consequences. A precise estimation of the reliability is, therefore, needed. In this work, we are interested in the study and the calculation of the reliability of highly reliable networks. In this case the unreliability is very small, which makes the standard Monte Carlo approach useless, because it requires a large number of iterations. For a good estimation of system reliability with minimum cost, we have developed new simulation techniques based on variance reduction using importance sampling.
|
1112 |
Modélisation et paramétrisation hydrologique de la ville, résilience aux inondations / Hydrological modelling and parameterization of cities, flood resilienceGiangola-Murzyn, Agathe 30 December 2013 (has links)
L'évolution constante des villes passe par l'urbanisation des zones encore disponibles induisant des effets sur les bilans hydriques des celles-ci. De plus, le changement climatique susceptible d'exacerber les extrêmes (dont les inondations) influence lui aussi ces bilans. La ville est donc un objet hydrologique spécifique qu'il faut replacer dans son contexte évolutif, ce qui élargit considérablement la gamme d'échelles spatio-temporelles à prendre en compte pour son analyse et sa simulation. L'Union Européenne considère que la gestion du risque d'inondation doit remplacer la défense classique contre celle-ci. Cette nouvelle approche est plus holistique : elle prend en compte toutes les composantes du risque et cherche a réduire la vulnérabilité des récepteurs (habitants, bâtiments et infrastructures). Elle débouche sur la question de la résilience des systèmes urbains où les technologies correspondantes doivent être intégrées en des systèmes résilients aux inondations. Il est donc indispensable de développer des outils permettant l'évaluation de la performance de ces derniers, et ce à différentes échelles. Ces préoccupations ont défini l'axe de développement de Multi-Hydro : faire interagir des modèles déjà éprouvés représentant une composante du cycle de l'eau, permettre d'effectuer ainsi des progrès substantiels dans la modélisation de l'eau en ville avec une facilité d'utilisation. Multi-Hydro est ainsi basé sur des équations physiques supportées par des modèles distribués couplés. Grâce à un outil SIG dédié, MH-AssimTool, les informations géographiques et physiques nécessaires à la modélisation sont facilement assimilés pour chaque zone et résolution. En effet, une attention particulière été portée sur les observables ayant le moins de dépendance en échelle. L'emploi d'outils d'analyse multi-échelles permet de représenter leur variabilité et de définir des paramétrisations robustes du fonctionnement hydrologique à différentes échelles. L'ensemble de ces développements a été utilisé pour aborder la question de la résilience face aux inondations à différentes échelles d'un système urbain, dans le cadre de différents projets européens (SMARTeST, RainGain, BlueGreenDream) ou nationaux (Ville Numérique), à l'aide d'une approche systémique sur des scénarios pour plusieurs cas d'étude :- un petit bassin versant de Villecresnes (Val-de-Marne) qui a servi a l'évaluation des impacts de chaque modification apportée au modèle au cours de son développement.- la partie Est de la commune de Saint-Maur-des-Fossés (Val-de-Marne) qui a subi un audit de l'état du réseau d'assainissement (cartographie précise des canalisations et campagnes de mesures) et dont les résultats préliminaires ont permis de poser la problématique de la modélisation des rivières.- un quartier d'Heywood (grande banlieue de Manchester, Royaume Uni), qui a subi plusieurs inondations durant la dernière décennie et demande une modélisation assez fine pour permettre l'évaluation de l'impact de quatre scénarios de protection.- le bassin versant de la Loup, dont l'exutoire est occupé par un bassin de stockage des eaux de pluie, a été modélisé pour quatre évènements d'intensités et de durées variables et a permis de débuter la validation du modèle.- la zone de Spaanse Polder (Rotterdam, Pays Bas), pose la problématique de la modélisation des zones très planes au système de drainage complexes (pompes, exutoires multiples). Cette zone permet de guider les développements futurs de Multi-Hydro. Dans le contexte de l'amélioration de la résilience des villes face aux inondations, Multi-Hydro se place comme étant un outil qui offre la possibilité de simuler des scénarios permettant l'évaluation des impacts à l'échelle globale de modifications à plus petites échelles. Grâce a sa facilité de mise en place que lui confère MH-AssimTool, ainsi que sa structure modulaire et sa liberté de licence, Multi-Hydro est en train de devenir un outil d'aide à la décision / The constant evolution of cities can be seen as the urbanisation of the still available areas. This introduces complex effects with respect to the balance of water. In addition, the highly variable nature of the climate and weather can easily exacerbate the extremes (including floods) thus influencing the water balance. The European Union considers that the management of flood risk is an appropriate strategy to replace conventional defense strategies against floods. This new strategy is a more holistic approach: it takes into account all the components at risk and seeks to reduce the vulnerability of receptors (people, buildings and infrastructures).Thus, resilience measures not only consist of individual technical solutions but they need to be integrated to a ‘safety chain', which requires the development of resilience systems and tools. It is therefore essential to develop tools for assessing the performance of the latter, and at different scales. These concerns have help define the development of Multi-Hydro: interacting models already proven to represent different components of the water cycle to allow substantial progress in the modelling of urban water combined with ease use. Multi-Hydro is based on physical equations supported by distributed and coupled models. With a dedicated GIS MH-AssimTool, the geographical and physical information required for modelling are easily assimilated for each zone and at each resolution. Indeed, special attention was paid to the observables with the least scale dependence. Tools for multi-scale analysis are used to represent their variability at smaller scales than their own scales, thus allowing a more robust definition of hydrological parameterisations at different scales. All of these developments have been used to address the issues involved in flooding resilience at different urban system levels, within the framework of the European (Smartest, RainGain and BlueGreenDream) and national (Ville Numérique) projects, using a systemic approach on the scenarios of several case studies:- A small watershed Villecresnes (Val-de-Marne), used to assess the impacts of each change made in the model during its development.- The eastern part of the municipality of Saint-Maur-des-Fossés (Val-de-Marne ), has undergone a state audit of the drainage network (precise mapping of pipes and measurement campaigns). The preliminary results helped raise the issue of modelling rivers.- A district at Heywood (suburbs of Manchester, UK), has suffered several floods over the last decade and requires more detailed modelling in order to allow for the assessment of impact of four protection scenarios.- The catchment area of the Loup, whose outlet is connected to a runoff water storage tank, was modelled over four events of varying durations and intensities and helped start the validation of the model.- The Spaanse Polder area (Rotterdam , Netherlands), poses the problem of modelling very flat terrain with a complex drainage system (pumps and multiple outlets). This area will help to guide the future development of Multi-Hydro. In the context of improving the resilience of cities to flooding, Multi-Hydro is therefore placed as a tool that provides the ability to simulate scenarios for impact assessment at the basin scale of changes to smaller scales. Due to its ease of implementation at various scales conferred by MH-AssimTool and its modular structure and its free access property, Multi-Hydro is becoming a support decision tool
|
1113 |
Campus BuddyChoudhary, Anamika Nupur January 1900 (has links)
Master of Science / Department of Computer Science / Daniel A. Andresen / New to K-State??? No worries!!! This app will be your first friend and help you with everything you may need. Every new incoming student to K-State has to do a set of mandatory activities before they start their classes. Many times they use a pamphlet or word of mouth by students or faculty around, on what to do and whom to visit. But, this information may not be reliable or could have been expired/updated, and students miss on certain crucial things which delays their work. The same follows with various events organized by the college to welcome new students.
This app will be a solution for all these problems. It will provide students with all the details they need before they actually become familiar with the school and even after that. Each student gets to see the To-Do's which are a set of mandatory activities, he/she has to do before they enroll for the classes and also, he can know about various events happening around the university. Students can also suggest new events if they are not already updated in the events list. All these activities are monitored and controlled by the Admin.
|
1114 |
"Cut and Break"-beskrivningar i svenskt teckenspråk : Barns och vuxnas avbildande verbkonstruktioner / "Cut and Break"-descriptions in Swedish Sign Language : Children's and adults' depicting verb constructionsSimper-Allen, Pia January 2016 (has links)
Previous studies on children’s acquisition of depicting verbs in signed languages have chiefly studied the use of classifiers in verbs of motion and location, particularly the order in which the different classes of handshape are acquired. The age of the children in these studies have ranged from age three to thirteen, and an important finding has been that classifier constructions are not fully acquired until early adolescence. Most of these studies have used an elicitation tool to investigate the production and comprehension of classifiers, but have not provided any adult target norms of the test items when scoring children’s achievement. The present dissertation provides a detailed description of both adults’ and children’s verb constructions in descriptions of cutting and breaking events in Swedish Sign Language (SSL), specifically focusing on the number of hands used in signing, handshape category and hand activity, which has not been previously described for any sign language. As part of this study, 14 deaf adults (ages 20–72) and 11 deaf children (2;1–6;6) of deaf parents, all native-users of SSL, performed a task that involved describing 53 video clips of cutting and breaking events. The clips show an event in which an actor separates material, either with the aid of a tool or without. Additionally, some clips show an entity separating by itself without an actor being involved. The adults described the events with depicting verb constructions that are produced with two hands. The analysis of the handshapes produced three categories: substitutor, manipulator and descriptor. The most frequent construction in the description of events without a tool was two acting manipulators (depicting a hand handling an object), whereas in descriptions of events with a tool the combinations were acting substitutor or manipulator with a non-acting manipulator. The acting hand referred to the tool and the non-acting manipulator to the affected entity. In descriptions of events without an actor, either two substitutors or two manipulators were used. In addition to depicting verb constructions, the descriptions also contained resultative complements, i.e. signs carrying information about the result of the activity being carried out. The complements were either lexical signs or some form of depicting verb construction. Similar observations have not been noted for any other signed language. In the manner of the adults, the children used depicting verb constructions in descriptions of cutting and breaking events (681 tokens), but they also used pointing and lexical signs (64 tokens). Nearly half of the verb constructions that were used by the children corresponded to the adult target forms. The majority of the constructions describing events without a tool corresponded to the adult target forms using two acting manipulators, even among the youngest informants. In events with a tool, only a third of the constructions corresponded to the adult target forms (emerging at 4;8 – 5;0); the remaining two-thirds were deviating constructions in terms of number of hands, handshape category and hand activity. Resultative complement are sparsely used by children (57 tokens), the most chosen type of complement being lexical signs. Pervasive features of children’s constructions were the addition of contact between the hands and a preference for substitutors, something not found in adults’ constructions. These features were elucidated within the framework of Real Space blending theory, with the study showing that children first use visible blended entities and that invisible blended entities do not emerge until 4;8–5;0. / <p>Disputationen teckenspråkstolkas</p>
|
1115 |
Krizová připravenost Nemocnice ve Frýdku-Místku na vybrané mimořádné události / Crisis readiness of the hospital in Frydek - Mistek relating to selected extraordinary events.ŠMÍDOVÁ, Monika January 2019 (has links)
The diploma thesis "Crisis readiness of the hospital in Frydek - Mistek relating to selected extraordinary events" deals with issues concerning current state of readiness of the Hospital in Frydek-Mistek for selected extraordinary events and the tries to create methods and approaches to improve the hospital's emergency preparedness. I chose mainly qualitative research with quantitative elements for answering research question. First step was random choice from hospitals in Moravian-Silesian Region, so I visited the hospital in Frydek-Mistek and I made data retrieval dealing with extraordinary events. Based on my own observations and the provided documents I detected an incorrect crisis preparedness plan and because it is important to have such an operative plan, which deals with extraordinary events and the inaccurate plan could place hospital to risk, I decided to revise the plan by using special methology, which is set up for this issue. Since the risks involved in the crisis preparedness plan were insufficient in my opinion, I conducted my own risk analysis of the external and internal environment focusing on hospital operation in risk. Then I used the "KARS" method, which is a qualitative risk analysis within its correlation. I determined the risks that should be resolved primarily and after that I revised the plan by using new knowledge. The result of the diploma thesis is a draft plan for crisis readiness of the hospital in Frydek - Mistek, which could be used and refilled by hospital managment alternatively. The plan will be handed over to the hospital management.
|
1116 |
Radiologické události na vybraných radiodiagnostických pracovištích - analýza opakování snímků v důsledku chybného ozáření pacienta / Radiation incidents at selected radiologic workplaces - the analysis of repeated images due to wrong irradiation of pacient.ZÁKOUTSKÁ, Eliška January 2019 (has links)
The thesis derives from the needs of institutions using sources of ionizing radiation to implement a new legislative regarding nuclear law, effective since 1st January 2017. The thesis is focused on radiological events at radiological institutions of chosen healthcare facilities. The theoretical part makes the reader familiar with the term "radiological event", generally elaborates on the field of diagnostic radiography and radiation protection. The practical part of the thesis deals with evaluation of the most occurring causes and the frequency of radiological events, obtained from the records of medical irradiation, even of wrongly carried out exposures in chosen diagnostic radiography institutions and wrongly sorted radiological events to a relevant category. To fulfil all the goals of the master thesis and to apply the results of the work in practice, also the contents of following document were evaluated - "Evaluation of the means of radiation protection", which every holder of permission to work with ionizing radiation has to submit to the SŮJB yearly, till 30th April, with the data from the previous year. This rule is valid since the new nuclear law was adopted. The results of this thesis served the chosen institution to create such report till 30th April 2019, with a broader extent of the analysis and evaluation than last year. The maximal detail of the report about causes and frequency of radiological events and mapping the real situation at the facilities serves also to the State Office for Nuclear Safety (SONS) to create a Recommendation of the SONS regarding the radiological events. Equally, the thesis was beneficial to the observed facilities, to realise the causes and frequency of radiological events in individual years. It is then up to an individual institution and to the employee supervising the radiation protection, to evaluate the consequences of the found causes, for example to point them out within a yearly training of radiation employees, and to consistently see to the compliance of all preventive measures, which proposal and implementation also belongs to the main tasks of the supervisor.
|
1117 |
SM-veckans arv : En studie om hur idrottsföreningar påverkats av att arrangera idrottsevenemanget SM-veckan i Sundsvall 2015 / The legacy of SM-veckan : A study on how sports club were impacted by hosting the sports event SM-veckan in Sundsvall 2015Edin, Mattias, Hedström, Gustaf January 2019 (has links)
SM-veckan is a Swedish sports event that gathers minor sports to host their national championships during the same week at the same place. In focus during this study was six Swedish sports clubs in three different sports who were hosts of their respective sports national championship at the event SM-veckan in Sundsvall during the summer of 2015. The aim with this study was to add knowledge about how a sports event impact the hosting sports clubs by investigating the legacy SM-veckan left for the hosting clubs. Qualitative data was gathered through interviews with the six hosting sports clubs, a project leader and a competition leader for one of the sports. The sports clubs got to answer questions about how they were impacted by the event, but also about their goals and expectations of hosting the event. The results show that the sports clubs had very few goals and very low expectations to get something out of hosting the event. The clubs had experienced a small economic impact but did also believe that they had made a statement proving themselves as good hosts. In general the result showed that the event have had very little impact on the hosting sports clubs. One of the clubs had a clear objective to achieve a timing equipment through the event which they also managed to do. This study’s conclusion is that hosts must set up clear goals for why they host an event to be able to leverage and get something out of the event
|
1118 |
Estimation de la disponibilité par simulation, pour des systèmes incluant des contraintes logistiques / Availability estimation by simulations for systems including logisticsRai, Ajit 09 July 2018 (has links)
L'analyse des FDM (Reliability, Availability and Maintainability en anglais) fait partie intégrante de l'estimation du coût du cycle de vie des systèmes ferroviaires. Ces systèmes sont hautement fiables et présentent une logistique complexe. Les simulations Monte Carlo dans leur forme standard sont inutiles dans l'estimation efficace des paramètres des FDM à cause de la problématique des événements rares. C'est ici que l'échantillonnage préférentiel joue son rôle. C'est une technique de réduction de la variance et d'accélération de simulations. Cependant, l'échantillonnage préférentiel inclut un changement de lois de probabilité (changement de mesure) du modèle mathématique. Le changement de mesure optimal est inconnu même si théoriquement il existe et fournit un estimateur avec une variance zéro. Dans cette thèse, l'objectif principal est d'estimer deux paramètres pour l'analyse des FDM: la fiabilité des réseaux statiques et l'indisponibilité asymptotique pour les systèmes dynamiques. Pour ce faire, la thèse propose des méthodes pour l'estimation et l'approximation du changement de mesure optimal et l'estimateur final. Les contributions se présentent en deux parties: la première partie étend la méthode de l'approximation du changement de mesure de l'estimateur à variance zéro pour l'échantillonnage préférentiel. La méthode estime la fiabilité des réseaux statiques et montre l'application à de réels systèmes ferroviaires. La seconde partie propose un algorithme en plusieurs étapes pour l'estimation de la distance de l'entropie croisée. Cela permet d'estimer l'indisponibilité asymptotique pour les systèmes markoviens hautement fiables avec des contraintes logistiques. Les résultats montrent une importante réduction de la variance et un gain par rapport aux simulations Monte Carlo. / RAM (Reliability, Availability and Maintainability) analysis forms an integral part in estimation of Life Cycle Costs (LCC) of passenger rail systems. These systems are highly reliable and include complex logistics. Standard Monte-Carlo simulations are rendered useless in efficient estimation of RAM metrics due to the issue of rare events. Systems failures of these complex passenger rail systems can include rare events and thus need efficient simulation techniques. Importance Sampling (IS) are an advanced class of variance reduction techniques that can overcome the limitations of standard simulations. IS techniques can provide acceleration of simulations, meaning, less variance in estimation of RAM metrics in same computational budget as a standard simulation. However, IS includes changing the probability laws (change of measure) that drive the mathematical models of the systems during simulations and the optimal IS change of measure is usually unknown, even though theroretically there exist a perfect one (zero-variance IS change of measure). In this thesis, we focus on the use of IS techniques and its application to estimate two RAM metrics : reliability (for static networks) and steady state availability (for dynamic systems). The thesis focuses on finding and/or approximating the optimal IS change of measure to efficiently estimate RAM metrics in rare events context. The contribution of the thesis is broadly divided into two main axis : first, we propose an adaptation of the approximate zero-variance IS method to estimate reliability of static networks and show the application on real passenger rail systems ; second, we propose a multi-level Cross-Entropy optimization scheme that can be used during pre-simulation to obtain CE optimized IS rates of Markovian Stochastic Petri Nets (SPNs) transitions and use them in main simulations to estimate steady state unavailability of highly reliably Markovian systems with complex logistics involved. Results from the methods show huge variance reduction and gain compared to MC simulations.
|
1119 |
Valeurs et choix vocationnel chez les jeunes : déterminants de l’évolution des valeurs chez des élèves du collège et lycée / Values and vocational choice among young people : determinants of the evolution of values in high school and high school studentsMpouki, Bernard 13 December 2018 (has links)
Malgré une abondante littérature scientifique consacrée aux valeurs en tant que croyances et préférences partagées, les valeurs des adolescent.e.s sont peu étudiées. Ainsi, l’objectif de cette thèse consiste à contribuer à une meilleure compréhension des valeurs, à travers l’analyse des déterminants du changement des valeurs à l’adolescence. Nous avons réalisé trois études auprès des élèves à l’aide du questionnaire des valeurs de Schwartz. La première étude porte sur l’analyse du lien entre le facteur âge et l’évolution des valeurs chez les adolescent.e.s. La deuxième étude analyse le rôle des variables personnelles et sociodémographiques sur le changement des valeurs. La dernière étude porte sur l’impact des événements de vie inopinés sur l’évolution des valeurs. A partir de l’examen de la littérature proposée à ce sujet et des résultats de ces trois études, un modèle théorique de l’évolution des valeurs est proposé. De même, l’implication pratique de cette recherche préconise une approche holistique et dynamique d’aide à l’élaboration des projets des adolescent.e.s. / Despite a wealth of scientific literature on values as shared beliefs and preferences, adolescent values are poorly studied. Thus, the aim of this thesis is to contribute to a better understanding of values, through the analysis of the determinants of change in values in adolescence. We conducted three student studies using the Schwartz Values Questionnaire. The first study deals with the analysis of the link between the age factor and the evolution of values in adolescents. The second study analyzes the role of personal and sociodemographic variables in changing values. The last study focuses on the impact of unplanned life events on the evolution of values. From the review of the literature proposed on this subject and the results of these three studies, a theoretical model of the evolution of values is proposed. Similarly, the practical implication of this research advocates a holistic and dynamic approach to assist in the development of adolescent projects.
|
1120 |
Evènements météo-océaniques extrêmes / Extreme meteo-oceanic eventsMazas, Franck 17 November 2017 (has links)
Cette thèse sur travaux vise à rassembler et unifier les travaux réalisés sur le sujet des évènements météo-océaniques extrêmes depuis 2009, dans le cadre de mon travail à SOGREAH, devenu depuis ARTELIA. À mesure que progressaient ces travaux, un thème central a progressivement apparu : la notion d'évènement, tel qu'une tempête. Ce concept fournit un cadre robuste et pertinent, en particulier dans le cas des extrêmes multivariés (par exemple, la probabilité d'occurrence conjointe des vagues et des niveaux marins), ainsi qu'une meilleure compréhension de la notion de période de retour, très utilisée dans le domaine de l'ingénierie.Les principaux résultats des travaux réalisés au cours de la décennie écoulée sont les suivants :- mise à jour de la méthodologie de détermination des houles ou vents extrêmes :- développement et justification d'un cadre en deux étapes pour la modélisation sup-seuil des extrêmes univariés (méthode du renouvellement), introduisant la notion d'évènement et la séparation des seuils physique et statistique,- proposition d'outils pratiques pour le choix du seuil statistique,- introduction de la méthode du bootstrap paramétrique pour le calcul des intervalles de confiance,- identification d'un comportement problématique de l'Estimateur du Maximum de Vraisemblance et proposition d'une solution : utilisation de distributions à trois paramètres avec l'estimateur des L-moments,- application du cadre POT (Peaks-Over-Threshold) à la Méthode des Probabilités Jointes (JPM) pour la détermination des niveaux marins extrêmes :- distinction entre les valeurs séquentielles et les pics des évènements à l'aide d'indices extrémaux pour les surcotes et les niveaux marins,- construction d'un modèle mixte pour la distribution des surcotes,- raffinements pour le traitement de la dépendance marée-surcote,- application du cadre POT-JPM pour l'analyse conjointe des hauteurs de vagues et des niveaux marins :- proposition d'une procédure alternative d'échantillonnage,- analyse séparée de la marée et de la surcote dans le but de modéliser la dépendance entre la hauteur de vagues et la surcote ; avec incorporation dans la distribution conjointe de la hauteur de vagues et du niveau marin à l'aide d'une opération de convolution 2D1D,- utilisation de copules des valeurs extrêmes,- présentation améliorée du chi-plot,- introduction d'une nouvelle classification pour les analyses multivariées :- Type A : un phénomène unique décrit par différentes grandeurs physiques qui ne sont pas du même type,- Type B : un phénomène fait de différentes composantes, décrits par des grandeurs physiques du même type d'un composant à l'autre,- Type C : plusieurs phénomènes décrits par des grandeurs physiques qui ne sont pas du même type,- interprétation de la signification des évènements multivariés :- lien avec l'échantillonnage,- lien avec les différentes définitions de la période de retour,- dans le cas bivarié : transformation d'une distribution conjointe de variables descriptives de l'évènement vers la distribution des couples de variables séquentielles,- génération de graphes de srotie alternatifs tels que les contours d'iso-densité pour les couples de variables séquentielles,- un package R dédié, artextreme, pour l'implémentation des méthodes ci-dessus / This PhD on published works aims at unifying the works carried out on the topic of extreme metocean events since 2009, while working for SOGREAH then ARTELIA.As these works went along, a leading theme progressively appeared: the notion of event, such as a storm. This concept provides a sound and relevant framework in particular in the case of multivariate extremes (such as joint probabilities of waves and sea levels), as well as a better understanding of the notion of return period, much used for design in the field of engineering.The main results of the works carried out in the last decade are as follows:- updating of the methodology for determining extreme wave heights or wind speeds:- development and justification of a two-step framework for extreme univariate over-threshold modelling introducing the concept of event and the separation of the physical and statistical thresholds,- proposal of practical tools for choosing the statistical threshold,- introduction of the parametric bootstrap approach for computing confidence intervals,- identification of a problematic issue in the behaviour of the Maximum Likelihood Estimator and proposal of a solution: use of 3-parameter distributions along with the L-moments estimator,- application of the POT framework to the Joint Probability Method for determining extreme sea levels:- distinction between sequential values and event peaks through extremal indexes for surge and sea level,- construction of a mixture model for the surge distribution,- refinements for handling tide-surge dependence,- application of the POT-JPM framework for the joint analysis of wave height and sea level:- proposal of an alternative sampling procedure,- separate analysis of tide and surge in order to model the dependence between wave height and surge to be incorporated in the joint distribution of wave height and sea level thanks to a 2D1D convolution operation,- use of extreme-value copulas,- improved presentation of the chi-plot,- introduction of a new classification for multivariate analyses:- Type A: a single phenomenon described by different physical quantities that are not of the same kind,- Type B: a phenomenon made of different components, described by physical quantities of the same kind between one component and another,- Type C: several phenomena described by physical quantities that are not of the same kind,- interpretation of the meaning of multivariate events:- link with the sampling procedure,- link with the different definitions of the return period,- in the bivariate case: transformation of the joint distribution of event-describing variables into the joint distribution of sequential pairs,- generation of alternative output plots such as contours of density for sequential pairs;- a dedicated R package, artextreme, for implementing the methodologies presented above
|
Page generated in 0.1371 seconds