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Remote sensing analysis of small scale dynamic phenomena in the atmospheric boundary layer / Kostas Cheliotis (2021)  

Public Titre : Remote sensing analysis of small scale dynamic phenomena in the atmospheric boundary layer Type de document : Thèse/HDR Auteurs : Kostas Cheliotis, Auteur ; Hervé Delbarre, Auteur Editeur : Dunkerque : Université du Littoral-Côte-d'Opale Année de publication : 2021 Importance : 139 p. Format : 21 x 30 cm Note générale : bibliographie Thèse présentée pour obtenir le grade de Docteur de l’Université du Littoral Côte d’Opale, Mention : Physique, Spécialité : Milieux dilués et optiques fondamentales Langues : Français (fre) Descripteur : [Vedettes matières IGN] Atmosphère [Termes IGN] analyse discriminante [Termes IGN] analyse texturale [Termes IGN] balayage laser [Termes IGN] classification dirigée [Termes IGN] données lidar [Termes IGN] données localisées 3D [Termes IGN] effet atmosphérique [Termes IGN] lidar à effet Doppler [Termes IGN] lidar atmosphérique [Termes IGN] météorologie [Termes IGN] vent Index. décimale : THESE Thèses et HDR Résumé : (auteur) The aim of this thesis project was to study the coherent turbulent structures (convective rolls & streaks) and more generally the medium to large fluctuations in the atmospheric boundary layer using the observations recorded by a single Doppler (wind) lidar during a 2-month campaign in Paris, France. An innovative method was developed in order to classify automatically the radial wind speed patterns visible on the quasi-horizontal lidar scans, based on texture analysis parameters and supervised machine learning algorithms. A 150-case training ensemble was built using ancillary data (satellite pictures and weather observations) to ascertain the manual classification into four types: rolls, thermals, streaks and “others”. The performance of the classification process was assessed on the training ensemble using the 10-fold cross-validation method. A very satisfying 9% error was obtained for the Quadratic Discriminant Analysis algorithm, using only 5 texture analysis parameters classifiers. This process was then applied to classify the whole dataset (4577 lidar scans) and the results showed that the classified structures respected a plausible diurnal cycle and were associated with the meteorological parameters as expected by the theoretical knowledge. The size of the coherent structures in the direction transverse to the mean wind were estimated from the wind spectrums on a four-day case study. They ranged from 400 to 800 m for the cases classified as streaks, and from 1.3 to 2.0 km for the cases classified as rolls. These results pave the way for future long-term studies providing statistical insight on the frequency of occurrence of the different structure types, their physical properties, and their impact on pollutants’ concentrations. Numéro de notice : 28616 Affiliation des auteurs : non IGN Nature : Thèse française Note de thèse : Thèse de Doctorat : Milieux dilués et optiques fondamentales : Côte d'Opale : France : 2021 Organisme de stage : Laboratoire de Physico-Chimie de l'Atmosphère DOI : sans En ligne : https://hal.science/tel-03259369/ Format de la ressource électronique : URL Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=99504

An agent-based model of public space use / Kostas Cheliotis in Computers, Environment and Urban Systems, Vol 81 (May 2020)  

Public [article]  inComputers, Environment and Urban Systems > Vol 81 (May 2020) . - n° 101476 Titre : An agent-based model of public space use Type de document : Article/Communication Auteurs : Kostas Cheliotis, Auteur Année de publication : 2020 Article en page(s) : n° 101476 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Analyse spatiale [Termes IGN] architecture urbaine [Termes IGN] comportement [Termes IGN] espace public [Termes IGN] espace urbain [Termes IGN] modèle orienté agent [Termes IGN] modélisation spatiale [Termes IGN] piéton [Termes IGN] urbanisme Résumé : (auteur) Computational models have been described as exceptionally adept at examining the complex relationships of human and crowd behaviour, with a significant portion dedicated to investigating spatial behaviour in defined environments. Within this context, this paper presents an agent-based model (ABM) for simulating activity in public spaces at the level of the individual user. Although other ABMs of individuals' spatial activity exist, they are often found to simulate specific building-related activities, and fewer still are found to examine activity in public spaces, in a systematic manner. This research provides a generalized formalization of human spatial behaviour incorporating stationary activities and social interaction within a 3D environment, and is presented using a widely accepted framework for describing ABM, the Overview, Design Concepts, and Details (ODD) protocol. A sample study using a synthetic environment is used to demonstrate applicability, and the model is tested extensively to establish robustness. Furthermore, model output is compared to observed activity patterns in other studies of similar spaces, and simulated spatial patterns of activity are found to match those observed in real-world scenarios, providing insight into the dynamics of the processes, and highlighting the potential of this approach for studying the complexities of human spatial behaviour. Numéro de notice : A2020-696 Affiliation des auteurs : non IGN Thématique : GEOMATIQUE Nature : Article DOI : 10.1016/j.compenvurbsys.2020.101476 Date de publication en ligne : 19/02/2020 En ligne : https://doi.org/10.1016/j.compenvurbsys.2020.101476 Format de la ressource électronique : url article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=96249 [article]