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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.
1

Stability of Basin-Scale Internal Waves Within the South Arm of the Great Salt Lake

Soelberg, Joshua David 01 May 2009 (has links)
The fluid circulation patterns, temperature distributions, and density gradients of the South Arm of the Great Salt Lake were modeled using the Estuary, Lake, and Coastal Ocean Model (ELCOM) from the Centre for Water Research at the University of Western Australia. The effort is part of a research study in conjunction with the United States Geological Survey (USGS) and the Utah Water Research Lab located at Utah State University. The model was simulated for several different cases of salinity gradients over different time periods, using temperature and wind data from 2006. The model is then used to identify factors which may provide a transport mechanism of heavy metals such as selenium and mercury from the sediment layers to the upper brine layers where it is introduced into the food chain.
2

Development and calibration of “calcite rafts” as a proxy for Holocene aquifer conditions in anchialine settings, Quintana Roo, Yucatán Peninsula, Mexico

Kovacs, Shawn E. January 2017 (has links)
Coastal karst aquifers are important water resources, often providing the only source of freshwater to coastal communities for agriculture, industrial usage and human consumption. In order to implement management strategies and preventative measures for future perseveration of this resource, it is imperative to understand how coastal groundwater conditions are controlled by the interaction of freshwater/seawater on local and regional scales, but also over recent and past time periods. However, there is a limited resource of published hydrological data on recent aquifer conditions. In the Yucatán Peninsula and other anchialine environments, this lack of information inhibits the understanding of the spatial and temporal interaction of the meteoric and marine water masses. Documenting how the aquifer is responding to forcing mechanisms such as large precipitation events, seasonal cycles and short-term sea level rise (e.g. storm surge) will assist in understanding modern aquifer condition but also the interpretation of paleo-records. Utilization of water level and salinity sensors in strategic positions in the aquifer demonstrate that meteoric water mass salinity varies over wet and dry seasons with the movement of the halocline, but also on a short-term basis though large rainfall events. Salinity in the meteoric water mass is influenced by mixing with the marine water mass during intense precipitation events associated with Hurricane Ingrid (2013), Tropical Storm Hanna (2014) and a series of unnamed events in 2015. During wet periods, induced flow from increase precipitation causes turbulent mixing with the marine water mass, increasing salinity in the upper meteoric lens. On the contrary, during dry periods, mixing is reduced, therefore making the meteoric lens less saline. This contemporary understanding of meteoric/marine water mass dynamics can be applied to developing and calibrating the geochemical record of calcite rafts, calcite precipitation at the air-water interface of cave pools, as a hydrological proxy for aquifer conditions. Our monitoring of calcite raft formation, deposition and geochemistry shows that raft accumulations (e.g., raft piles/cones) can offer a good paleoenvironmental archive of changing hydrological conditions. Based on a 2-year observational record, results indicate that calcite raft precipitation/formation occurs continuously but with only minor biases with intense rainfall events altering supersaturation conditions in the surface waters. Testing the use of calcite rafts in sediment cores from Hoyo Negro show that geochemical analyses (87Sr/86Sr, δ18O, δ13C, Sr/Ca and Cl/Ca) show that meteoric water mass salinity varied during the Holocene (~ 8.5 Ka – present) likely due to changing rainfall and or cave passage geomorphology, which is coherent with other independent climate records. Prior to this study, calcite rafts have never been considered a paleo-hydrological archive for aquifer conditions, however, the consistency and cross-validation with independent records demonstrates great potential for future paleohydrological reconstructions. / Thesis / Doctor of Philosophy (PhD)
3

Hydrodynamic capacity study of the wave-energized Baltic aeration pump : General applicability to the Baltic Sea and location study for a pilot project in Kanholmsfjärden

Carstens, Christoffer January 2008 (has links)
To counteract one of the most urgent environmental issues in the Baltic Sea; eutrophication, excessivealgal blooms and hypoxia, a proposal to use wave energy to pump oxygen-rich surface water towardsthe sea bottom is investigated. Proposals have suggested that 100 kg of oxygen per second is needed tooxygenate bottom water and enhance binding of phosphorus to bottom sediments. This corresponds to 10 000 m3/s of oxygen-rich surface water. This thesis investigates a wave-powered device to facilitatethis oxygen ux. Results give expected water flow rates between 0.15 - 0.40 m3/s and meter breakwater.The mean specic wave power for the analyzed wave data is calculated to be between 3 - 4 kW/m wavecrest and the median to 1 kW/m. This study indicate, however, that the energy uxes in the BalticProper are signicantly higher. The study gives that the wave climate of the Baltic Sea is suffciently intense to facilitate vertical pumping with a feasible number of breakwaters. A full-scale implementationin the Baltic Sea would require some 300 to 1 200 oating breakwaters of a length of 50 m each. Thetotal cost is roughly estimated to 170 - 680 million EURO. The study also concludes that the interleavingof surface water should be constrained to a relatively small vertical distance from the outlet depth(20 - 30 m) and not stir up deep water to the surface. Wave modelling for the proposed pilot locationKanholmsfjärden indicate that this bay is not large enough to permanently produce a favorable waveclimate. It is, however, still an interesting location consistently to its vicinity to Stockholm and relativelylong measurement series.
4

La gestion du timbre comme genèse à la création de trois oeuvres musicales originales

Giguère, Patrick 19 April 2018 (has links)
Tableau d’honneur de la Faculté des études supérieures et postdoctorales, 2013-2014. / Mon mémoire de maîtrise porte sur la gestion du timbre comme genèse à la composition de trois œuvres originales : 1) Halocline – 11’45’’ – pour flûte, clarinette, percussions, violon, alto et violoncelle; 2) Le mot juste – 9’30’’ – pour orchestre symphonique; 3) Profondeurs de champ – 16’30’’ – pour orchestre de chambre. Après la présentation de mes préoccupations artistiques, des origines et objectifs de mon travail de création, j’expose l’ensemble de mes recherches préliminaires. Finalement, les œuvres sont sommairement analysées de manière à mettre en lumière des modes de gestion du timbre ayant menés à la composition des œuvres. Ceux-ci tirent leurs origines de réflexions sur des concepts génériques du timbre. 1) Halocline : combinaisons de timbres – l’orchestration traditionnelle; 2) Le mot juste : emprunt de la structure du syntagme « le mot juste » pour la gestion du timbre – la phonétique; 3) Profondeurs de champ : catégorisation de timbres – les techniques instrumentales avancées.
5

Itämeren rehevöitymisen uudistettu diagnoosi ja paradigma

Lappalainen, K. M. (K. Matti) 01 June 2018 (has links)
Abstract The eutrophication of the Baltic Sea continues despite decrease of the external phosphorus load by as much as 80% of the target confirmed by HELCOM. The aim of this thesis is to investigate this paradox, critically evaluate previous explanations for the persistent eutrophication, and to introduce a new diagnosis and paradigm for the causes and processes behind eutrophication of the Baltic Sea. According to the current consensus, anthropogenic nutrient loading is nearly the sole cause of eutrophication and regular cyanobacterial blooms. However, this study shows that the areal phosphorus loading rate, when modeled properly, is surprisingly low, and unlikely to be the primary cause of eutrophication. Instead, the frequency of the salt water pulses has decreased dramatically during the past 40 years. This is the root cause of eutrophication, via the hyper-vicious cycle of the hypoxic and finally anoxic conditions of the deeps causing internal phosphorus loading, denitrification, and nitrogen and carbon fixation. Furthermore, this work confirms that nitrogen fixation increases in low nitrogen conditions, further increasing eutrophication and cyanobacterial blooms. Thus, the most effective way to break the cycle of eutrophication is to improve the oxygen conditions of the deeps, which really is impossible to achieve by decreasing external loading alone. A key result of this work is that natural processes, rather than human activity, plays a decisive role in the eutrophication process – a perspective that typically faces substantial resistance. This thesis discusses how sociological and political views have affected the scientific community and its pursuit to model the mechanisms of eutrophication of the Baltic Sea. In conclusion, this study leads to important novel insights by providing new models for calculating the external and internal phosphorus loads of the Baltic Sea, with results highlighting the importance of natural processes of internal loading from the anoxic deeps. Altogether, this thesis introduces a new a paradigm for eutrophication of the Baltic Sea. / Tiivistelmä Itämeri rehevöityy edelleen, vaikka fosforikuormitusta on vähennetty 80 % tavoitellusta. On siis syytä tutkia miksi Itämeren tila ei ole parantunut. Syntyneen ristiriidan ratkaisemiseksi tarkoituksena on etsiä aiemmista tulkinnoista ristiriitoja, korjata ne ja uudistaa tietopohja uudeksi ja toimivammaksi paradigmaksi. Virhetulkintojen tunnistamiseen sovelletaan Popperin falsifikaatiomenettelyn periaatteita. Konsensuksen mukaan ihmisperäinen kuormitus on lähes yksinomainen syy (sinilevä)rehevyyteen. Kuitenkin Vollenweiderin mallin mukaan tehty, hydrologialla painotettu fosforin pintakuormitus on ollut 1970 - 1980-luvuilla vain lievää rehevyyttä edellyttävällä tasolla. Ulkoinen kuormitus ei siten voi olla suurin rehevyyden aiheuttaja. Sinilevärehevyyttä ylläpitävänä päätekijänä on syvävesiin happea tuovien suolavesipulssien toistuvuuden romahtaminen. Siitä syntyneet syvävesien ja -pohjien hapettomuudet aiheuttavat Gotlanninmeressä sekä sisäistä kuormitusta että lisärehevöittävää typen- ja hiilensidontaa. Yhdessä näitä prosesseja nimitetään nyt supernoidankehäksi. Johtopäätöksiä: • Ihmistieteelliset ja ympäristöpoliittiset näkemykset vaikuttavat luonnontieteellisiin tulkintoihin luultua enemmän. • Suolavesipulssien harventuminen on hapettomuus- ja rehevyyskierteen perussyy. • Syvänteiden hapettomuus on kaikkialle negatiivisesti säteilevä keskeistekijä. • Itämeren supernoidankehä on purettava saattamalla syvänteet hapellisiksi. • Hapellisuutta ei voida saada aikaan ulkoisen kuormituksen vähentämisellä. • Jäljelle jäävät siten teknologiset keinot, joista toteutuskelvollisimmalta näyttää Itämeren hapellisimman ja kylmimmän veden pumppaus 30 metrin syvyydestä syvänteisiin, mikä tehostaa myös pulssivesien virtausta syvänteiden pohjalle. Tämä väitöskirja sisältää viisi vallitsevasta paradigmasta poikkeavaa tulosta: 1. Itämerelle on kehitetty rehevyyden uusi diagnoosi ja paradigma, 2. Luonto dominoi Itämeren tilaa, ei ihminen, 3. Typensidonnalla on lisärehevöittävä mekanismi, 4. Itämerelle on kehitetty uusi fosforin sisäkuormituksen laskentamenetelmä, 5. Virtuaalisen fosforikuormituksen laskenta. Ilman Gotlanninmeren syvänteiden hapellisuutta Itämeri on tuomittu pysymään rehevyyden supernoidankehässä, ’kaksinkertaisessa takalukossa’.

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