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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.
411

[pt] ABLAÇÃO POR LASER PULSADO DE ALVOS DE FERRO E NÍQUEL EM ÁGUA E SUAS IMPLICAÇÕES EM ASTROQUÍMICA / [en] PULSED LASER ABLATION OF IRON AND NICKEL TARGETS IN WATER AND ITS IMPLICATIONS IN ASTROCHEMISTRY

JOAO GABRIEL GIESBRECHT F PAIVA 02 December 2021 (has links)
[pt] A pesquisa aponta para a possibilidade de realizar a reação de redução de CO2 (CO2RR) para a formação de nanomateriais de carbono por ablação a laser pulsado(PLA) de alvos magnéticos de Ferro(Fe) e Níquel(Ni) em água pura deionizada. Os materiais coloidais sintetizados foram caracterizados por diferentes técnicas de espectroscopias ópticas (UVVis, ICP-MS, FTIR e Raman) e microscopia eletrônica de transmissão (TEM), revelando a presença de nanopartículas de óxidos e hidróxidos de metais de transição, junto com nanomaterial orgânico. Esse último, é bem visível por TEM, espectroscopia de raio-X por dispersão em energia (EDS), espectroscopia por perda de energia de elétrons (EELS), e espectroscopia Raman, que indica a presença de carbono amorfo grafítico e vibrações CH. No caso do nanomaterial obtido do Níquel, os resultados FTIR confirmam a presença da fase do hidróxido beta-Ni(OH)2, enquanto as medidas Raman e TEM sugerem também a presença de nano-folhas de Ni(HCO3)2. Os resultados experimentais foram enfim discutidos no contexto da origem e da evolução de moléculas simples e complexas de interesse astroquímico, com foco especial nas espécies potencialmente formadas na superfície de pequenos corpos metálicos do Sistema Solar e grãos de poeira cósmica do meio interestelar. / [en] The proposed research points to the possibility to perform CO2 reduction reaction (CO2RR) to solid carbon nanomaterials by the pulsed laser ablation (PLA) of magnetic target of iron (Fe) and nickel (Ni) in pure deionized water. The synthesized colloidal dispersions were characterized by different optical spectroscopies (UV-Vis, ICP-MS, FTIR and Raman) and transmission electron microscopy (TEM), revealing the presence of nanosized transition metal oxide and hydroxide nanoparticles, together with organic nanomaterial. The latter is well visible by TEM, energy-dispersive X-Ray spectroscopy (EDS), electron energy-loss spectroscopy(EELS), and Raman spectroscopy, which indicates the presence of amorphous graphitic carbon and CH vibrations. In the case of Ni derived nanomaterial, FTIR results confirm the presence of a beta-Ni(OH)2 hydroxide phase, while Raman and TEM measurements suggest also the presence of Ni(HCO3)2 nanosheets. The experimental results were finally discussed in the frame of the origin and evolution of simple and complex molecules of astrochemical interest, with special focus on those species potentially formed on the surface of metallic minor bodies in the solar system and cosmic dust grains in the interstellar medium(ISM).
412

Influence of Clay Mineralogy on Soil Dispersion Behavior and Water Quality

Ghezzi, Jessique L 01 May 2010 (has links) (PDF)
Currently, there is very little research available on nonpoint source pollution from rural watersheds. Government regulatory agencies are desperate for information regarding the causes of nonpoint source pollution, which includes the relationship between suspended soil particles and dispersion. Since soil dispersion is dependent on clay mineralogy, knowing the clay mineralogy of the soil in an area can help predict sediment loads entering the surrounding surface waters. This information is necessary to protect the resource value of our rivers, lakes, and estuaries, as well as to protect recreational activities such as fishing or hunting; but most importantly, this information is necessary to ensure the safety of our drinking water supply. Clay mineralogy and its influence on dispersion, as well as dispersion and its relation to water quality are the focus of this study. Soil mineralogy affects water quality in several ways: soil mineralogy determines the dispersivity of the clay portion of the soil and dispersive clays are likely to end up as suspended sediment in surface waters; weathering reactions contribute elements to water as dissolved load, and the sorption properties of clay minerals contribute to soils' ability to filter and carry pollutants. Through the use of X-ray diffraction, dispersivity, atomic absorption spectrometry, cation exchange capacity, and petrographic microscopy, this study shows that the clay mineral fraction of a soil determines the dispersivity, and that dispersed clay minerals contribute excess nutrients and metals as nonpoint source pollutants to surface waters.
413

Shapes of Decay : Narratives and Expressions From the Final Days of a Building

Håkansson Orsvall, August January 2023 (has links)
This thesis project revolves around the last days of an abandoned building in decay, facing demolition. It is situated in Värtahamnen, a harbor area in Stockholm. The area is the subject of a major urban planning project in the upcoming decade. In my project my aim is to contemplate this condition of of a building and how to approach and use the ephemerality of architecture and design in the creative process. By extracting different material behaviors caused by decay and exploring them experimentally, a diverse “buffet” of design concepts and methods are presented. The project also orbits around the subject of preservation, a topic commonly debated during interventions in the built heritage. Instead of taking a stand for or against the demolition of the building, the field of experimental preservation is used as a theoretical and methodological background in the design process, as a way to expand the scope on how to navigate and work artistically with preservation. In conclusion, this project tries to revise our perspective on the concept of decay as something destructive and instead suggest the creative potential in understanding it. It also contributes with reflections and speculations on how we can find new creative strategies for taking the whole lifespan of a design project into account already from the beginning.
414

Typhoon Impacts on the Chemical Weathering Regime and Atmospheric Carbon Consumption of a High Standing Island Watershed, Taiwan

Meyer, Kevin J. January 2016 (has links)
No description available.
415

A chemostratigraphic investigation of the late Ordovician greenhouse to icehouse transition: oceanographic, climatic, and tectonic implications

Young, Seth A. 18 March 2008 (has links)
No description available.
416

Strontium and Carbon Isotope Stratigraphy of the Llandovery (Early Silurian): Implications for Tectonics and Weathering

Gouldey, Jeremy C. 29 September 2008 (has links)
No description available.
417

A mixed method approach to exploring and characterizing ionic chemistry in the surface waters of the glacierized upper Santa River watershed, Ancash, Peru

Eddy, Alex Michelle 17 July 2012 (has links)
No description available.
418

Urban Hospice: A Montage of Expiration and Memory

Finney, Timothy John 23 May 2007 (has links)
Architecture is visuality. Its object is what Norman Bryson has referred to as a screen of signs. "Between subject and the world is inserted the entire sum of discourses which make up visuality, that cultural construct, and make visuality different from vision, the notion of unmediated visual experience. Between retina and the world is inserted a screen of signs, a screen consisting of all the multiple discourses on vision built into the social arena." (Norman Bryson, from Practice; Architecture, Technique, and Representation, by Stan Allen) Architecture and representation are integral to the screen. How do we make architecture? Is the act of making architecture a montage? Can architecture be made through montage? What is the role of montage in an architecture for life and death? The process of making architecture is not a prescribed methodology with a predetermined outcome. Architecture, crafted by the hand of the architect, is a divine act of assemblage of subconscious allegorical thought, image, and tectonics. Through this art of assemblage, an architecture is born capable of instigating a narrative of metaphor and memory. Metaphorical narrative has the innate ability of summoning memory, and is critical in an architecture for life and death. Architecture is the only total sensory means of narrative. / Master of Architecture
419

Erarbeitung einer Methodik zur Reduzierung der Sauerwasserbildung durch gezielte Abraumverkippung unter Beachtung geogener Potentiale / Development of a methodology for reducing acid water formation through specific overburden tilting under consideration of geogenic potentials

Simon, André 05 April 2016 (has links) (PDF)
Mit dem Grundwasserwiederanstieg in Braunkohleabraumkippen werden die aus der Pyritverwitterung resultierenden Stoffausträge an Sulfat-, Eisen-, Schwermetall- und H+-Ionen gelöst. Im Rahmen dieser Dissertation wurde eine Methodik entwickelt, mit deren Hilfe Problembereiche ausgehalten und somit Maßnahmen im aktiven mitteldeutschen Tagebaubetrieb ergriffen werden können, um die zukünftige Beeinflussung der umgebenden Grund- und Oberflächenwasserkörper zu minimieren. An Vorfeldsedimenten konnten in Feld-eluaten, Stoßbeprobungen und Verwitterungsversuchen geochemische Eigenschaften ermittelt werden. In resultierenden Pufferungsversuchen aus karbonathaltigen Geschiebe-mergeln und Hauptaciditätsträgern konnte eine langfristige Minderung der Aciditätswirkung nachgewiesen werden und ein adaptierter Regelkippenaufbau mit laminaren, alterierenden Sichtaufbau begründet werden. In umliegenden Altkippengrundwässern sind Pufferung und Sulfatreduktion als Wiederfestlegungsprozesse der AMD-Problemstoffe belegt worden. / For lignite mining extensive overburden masses have to be moved. Due to the ventilation of the overburden by atmospheric oxygen, there is a weathering of mostly tertiary sulfides. The rebound of groundwater in future tippings dissolves sulfate, iron, heavy metal and H+ ions, resulting from the pyrite weathering. The partial mobilization of overburden sulfides are opposed to hydrogeochemical buffer reactions e.g. the buffering by carbonates as the first step of buffering. Therefore, there are the questions to the mining operators of the measures that can be taken to minimize the geochemical influence of the surrounding ground and surface water bodies. Object of this PhD-thesis is to lead a methodology that helps to characterize the future tilting substrates to find technological and strategic measures for minimizing the acid water formation in the active open pit operation. In Field eluates and weathering tests in the laboratory and in the field, sediments from dry drill holes in the forefront of open pits “Schleenhain” and “Peres” it could be shown that the geological facies formation of sediments has a decisive influence on geochemical characteristics. As the main acidifying sediment the tertiary aquifer number 2 (lying part) and number 3 can be identified with their high sulfur contents. With increasing time of oxygen exposure sulfate, iron, heavy metal and H + ions released massively. Furthermore, it appears that carbonate buffer essentially are available as glacial till only in cohesive Quaternary. With the resulting buffering experiments from glacial till and the most acidic aquifer sediments a long-term retention of iron, heavy metal and H + - ion and a reduction of sulfate release can be shown, if there is a share of at least 40% glacial till to the lying aquifer number 2 sediments or 20% glacial till to the aquifer number 3. The groundwater quality monitoring of unstructured resaturated old dumps near to the active open pits is comparable to a field test. In addition to weathering zones with high levels of pollutants in the presence of carbonates, buffering processes and sulfate reduction with precipitation of problematic substances in secondary mineral phases can be detected. Blending the research results of geological and geochemical data, an important, in principle selectively recoverable, buffer potential already exists. The determined mixing ratio from 80-60 mass-% acidic sediments to 20-40 mass-% buffering sediment from the buffering experiments can be realized in tilting. In the open pit “Schleenhain” the missing buffering material can be compensated by mass offset from the open pit “Peres”. With the use of the already existing equipment, it is possible to establish a laminar, alternately tipping body with good geochemical and geotechnical conditions.
420

Infra-Red Spectrophotometry and X-Ray Diffractometry as Tools in the Study of Nickel Laterites

Azevedo, Luiz Otavio Roffee January 1985 (has links)
Nickel silicate laterite deposits developed on ultra-mafic rocks are similar in many general respects but they vary considerably in detail. The mineralogy of these surficial deposits is very complex and difficult to determine because of the fine grained nature and solid solution characteristics of the hydrous secondary minerals and because many of the phases are actually mineraloids that are poorly ordered or amorphous. To try some new approaches toward clarification of these phases, 24 samples from New Caledonia and Puerto Rico ranging from the ophiolite-ultramafic olivine-pyroxene-chromite-serpentine substrate rocks upward through intermediate phases of weathering to the final oxide -hydroxide iron cap phase were analyzed with the infrared spectrophotometer (IR -10) and with the automated X –ray diffractometer. Four limonite samples were also mineralogically analyzed. Goethite, secondary quartz, cryptomelane, hematite, chromite, talc, thuringite, and garnierite have been identified in various samples as weathering profile products.

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