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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
131

Variabilité spatio-temporelle des flux sédimentaires dans le Golfe de Gascogne : contributions relatives des forçages climatiques et des activités de chalutage / Spatio-temporal variability of sediment fluxes in the Bay of Biscay : relative contributions of climate forcings and trawling activities

Mengual, Baptiste 12 December 2016 (has links)
L'étude de la variabilité spatio-temporelle des flux sédimentaires sous l'influence des forçages naturels et des activités de chalutage a été entreprise à l'échelle du plateau continental du Golfe de Gascogne, en associant des données in situ et une modélisation numérique 3D déterministe. Deux campagnes en mer spécifiques ont été menées pour quantifier les impacts physiques induits par un chalut professionnel au niveau de la Grande-Vasière, en termes de remise en suspension (panache turbide), et de perturbation de la structure et de la nature du sédiment superficiel. Ces données ont permis d'estimer à 0.13 kg.m-2 le taux d'érosion moyen. Leur croisement avec des données d'effort de pêche a conduit à une cartographie mensuelle du flux d'érosion par chalutage. D'autre part, un modèle hydro-sédimentaire 3D réaliste a été mis en place et calibré à partir de mesures au point fixe. Une attention particulière a été accordée au paramétrage de l'érosion naturelle sous l'influence combinée des vagues et des courants. Une nouvelle formulation de la loi d'érosion adaptée aux mélanges de sable fin et de vase classiquement rencontrés sur les plateaux continentaux a été proposée et a permis d'optimiser significativement la réponse du modèle en termes de turbidité. Deux simulations de 5 ans ont été réalisées en incluant ou non l'influence du chalutage de fond, dans le but de quantifier et comparer les contributions relatives des forçages naturels et anthropique sur les flux verticaux (érosion) et horizontaux (transport solide) de sédiments. La variabilité temporelle des flux est décrite en une succession de régimes caractéristiques répondant à divers forçages (e.g. marée, vent, vagues, chalutage), et les flux résiduels saisonniers et annuels sont commentés : sans tenir compte des apports fluviaux, le flux de matériel vaseux a été estimé à 1.6 Mt/an sortant par le nord (au droit de La Pointe du Raz) et à 0.62 Mt/an vers le talus continental (au niveau de l'isobathe 180 m). / The spatio-temporal variability of sediment fluxes under the influence of natural forcings and trawling activities was assessed at the scale of the Bay of Biscay shelf, from in situ data and a 3D process-based numerical modelling. Two sea trials were carried out to quantify physical impacts induced by a professional trawling gear over an intensively trawled area of the shelf, the "Grande-Vasière", in terms of resuspension (turbid plume) and alteration of the surficial sediment nature and structure. These data enabled to estimate an average trawling-induced erosion rate of 0.13 kg.m-2. Their combination with fishing effort data led to monthly spatial distributions of trawling-induced erosion fluxes.Besides, a 3D realistic hydro-sedimentary model has been set up and calibrated from measurements acquired at a mooring station. The calibration task mainly consisted in assessing the natural erosion law setting under the influence of waves and currents. A new formulation of the erosion law has been proposed to describe the erosion of any mixture of mud and fine sand (sediment facies classically encountered on continental shelves) and led to a noteworthy improvement of the model response in terms of turbidity. Two 5-year simulations were performed accounting for natural forcings only or both natural and anthropogenic forcings in order to quantify and compare their respective contributions to sediment fluxes (vertical and horizontal sediment dynamics). The temporal variability of sediment fluxes is described in a succession of typical regimes occurring in response to various conditions of forcings (e.g. tide, wind, wave, trawling), and residual fluxes are assessed at seasonal and annual scales: without accounting for riverine sediment inputs, the mud flux is estimated to 1.6 Mt/yr outflowing northward (at the latitude of the Pointe du Raz) and to 0.62 Mt/yr toward the continental slope (through the 180 m isobath).
132

Barnskrik i Hades? : Attityder till döda spädbarn i antika Grekland. / Screaming babies in Hades? : Attitudes to dead infants in ancient Greece.

Svedlund, Sofie January 2020 (has links)
In Homer’s work Iliad, Achilles is harassed in the sleep by the ghost of his friend Patroclus who demands a burial by him to be able to find peace. From this we get an understanding of how important it was for the ancient Greeks that their dead were given a proper burial for the soul to enter Hades and be able to find peace. If the deceased body was not buried, the soul became restless that harassed and had the power to harm the living. Infants belong to the group of individuals that do not appear to have had any consistent way of how to deal with them after they died. Some of them did not receive anything even close to a burial that a deceased adult would have received. Why infants were handled differently in certain contexts and locations is a mystery and begs the question of whether they were not considered to be people when they died and what was required to be considered worthy of a funeral when being dead. The purpose of this study was to investigate whether infants ended up in Hades or not, with the ancient Greeks' view of death and dead bodies as a theoretical starting point. To fulfill the purpose, the following questions were asked; how were dead infants handled? Were they considered to be 'real' individuals? How do the dead infants relate to the notions of becoming restless dead? To be able to answer these questions, I researched material from three different categories of evidence. The discussion has been divided into archaeological, iconographical, and literary sources. There are many different answers to the questions of this thesis as the different sorts of source material indicate diverse answers and attitudes to infants. It all probably depends on the different geographical places, economy, and status in society. These different answers also generate different attitudes to infants and whether they in fact were a real person. But through this thesis I have displayed factors that can support my theory about infants in Hades and that they – in worst case scenario – could end up like restless dead.

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