Phreatic and hydrothermal eruptions often occur with little or no warning representing a significant hazard within geothermal regions. These violent eruptions occur at a range of temperatures and pressures within varying rock types. A range of mechanisms including heating or decompression, allows hydrothermal/supercritical fluid to rapidly flash to steam, expanding and shattering the surrounding rock to produce an eruption, with no direct magmatic influence. These eruptions are highly variable resulting in the current wide ranging classification schemes, many of which are based on characteristics that are hard to observe and define. This has resulted in confusing nomenclature with many different terms used to describe the same eruptive phenomena. Here a new classification scheme is presented, based on the easily definable features of eruption size, trigger type (natural or anthropogenic) and geological setting (volcanic or hydrothermal). This ultimately produces a classification dividing the eruptions into either phreatic, where magma interacts with cold water but no juvenile material is erupted; or hydrothermal where eruption occurs from an already heated hydrothermal system. Examples are then provided for each classification type. Previous studies have focused exclusively on either physical characteristics of eruptions, small scale experimental modelling of trigger processes or mathematical modelling of various eruption characteristics. Here, a new experimental procedure has been developed to model phreatic fragmentation, based on shock tube experiments for magmatic fragmentation by Alidibirov and Dingwell (1996). Water saturated samples are fragmented from a combination of argon gas overpressure and steam flashing within vesicles. In this thesis, these experimental results have been integrated with the physical characteristics of porosity, permeability and mineralogy to create two new models of phreatic fragmentation. Firstly a generalised model to explain fragmentation processes and secondly a specific model describing the eruption forming Lake Okaro, within the Taupo Volcanic Zone of New Zealand. These models were developed with the overall aim to improve understanding of these eruption types, ultimately improving future hazard modelling. Experiments were performed on Rangitaiki ignimbrite, through which the Okaro eruption occurred. In order to evaluate alteration effects, both unaltered ignimbrite and hydrothermally altered ignimbrite samples were analysed. Experiments were performed at room temperature and 300°C with pressures from 4 to 15 MPa, to reflect likely geothermal conditions while also assessing the effect of liquid water on fragmentation. Results indicate that within these samples 5 to 8 MPa of decompression is required to trigger an eruption, fitting well with the previously identified trend between decompression and porosity for magmatic samples. The fragmentation front propagates through the sample at speeds ranging between 14 m/s to 42 m/s, increasing with higher applied pressures and higher sample porosity. Most importantly, grain size analysis from these experiments show a clear shift to smaller grain sizes when liquid water flashes to steam (independent of pressure or sample type), reflecting the greater energy involved with steam flashing. Previous grain size analysis of the Okaro breccia deposits have indicated that the highest weight percentage of fragments fall between -3.5 and 1.5 phi, with our experimentally produced fragments fitting right within this range at -0.5 to 1.0 phi. Here the first parameterisation of conditions for phreatic and hydrothermal eruptions is presented creating a general fragmentation model along with a case study on Lake Okaro. These models describe how eruptions occur, with stages from initial system priming and overpressure development through to the last stages of eruption and crater formation.

EU har som mål att år 2020 ha minskat utsläppen av växthusgaser med 20 % och ökat andelen förnyelsebar energi till 20 %. I Sverige är andelen fossilt bränsle som förbränns ca 30 %. Denna studie syftar till att utreda om termokemiskt behandlade biobränslen kan ersätta de kommersiella fossila bränslena. Resultatet har nåtts med simulering i programvaran Fuelsim och insamling av experimentella data.  En simulering ska påvisa om syreberikning gynnar bränslena och experimentella data används för att se vilka problem som finns för respektive bränsle. Den biomassa som analyserats kommer från ett vedslag liknande gran eller tall som har genomgått processen mellansnabb pyrolys, torrefiering eller steam explosion. Ingen ekonomisk aspekt har tagits i beaktande vid utvärderandet av bränslena. Pyrolysprocessens produkt pyrolysvätska har flera utmaningar framför sig innan den kan ersätta befintliga oljor. Den är väldigt korrosiv, har en hög fukthalt och en kort lagringstid på sex månader. Pyrolysvätskan tycks gynnas av en syreberikning på 0,5 till 2 %. Pyrolyskoksen har potentialen att ersätta eller samförbrännas med kol i kolpulvereldadepannor. Pyrolysgasen innehåller en stor mängd CO2 vilket ger den ett lågt energiinnehåll. Både pyrolyskoksen och pyrolysgasen bör i första hand förbrännas i en fluidbäddspanna som är integrerad med pyrolysreaktorn eftersom pannanläggningen behöver värmen. Torrefieringsgasen är en biprodukt från framställningen av torrefierad biomassa. Problem med filtrering och kondensering av gasen medför att den bör sameldas med något annat bränsle för att återföra värmen till reaktorn. När den torrefierade biomassan pelleterats förbränns den lämpligast i storskaliga pannor såsom bubblande fluidbädd(BFB)-, eller cirkulerande fluidbädd(CFB)- eller rostpannor men även mindre pelletspannor är möjligt. Intrimning av bl.a. luftflöden är nödvändig vid samförbränning och även vid konvertering från annat bränsle för att uppnå en erforderlig förbränning. Simuleringsresultaten av steam explosion (SE) pellets visar potential som ersättare till både träpelleten och stenkolet. Baserat på simuleringen förbränns SE pellets lämpligast i CFB-, BFB- eller rostpannor. Ett begränsat utbud av experimentella data medför dock att bränslet inte kan utvärderas fullständigt. Studien visar att det inte är helt problemfritt att konvertera från ett kommersiellt bränsle till ett termokemiskt behandlat bränsle och att fler experimentella data behövs för att utvärdera bränslenas förbränningsegenskaper. / A goal set by The European Union is to reduce the emissions from greenhouse gases by 20 % and increase renewable energy with 20 % until year 2020.  Fossil fuels account for about 30 % of Sweden’s combusted fuel. The purpose of this study is to investigate if thermochemically treated biofuels can replace or be co-fired with commercial fuels. The results are gathered from experimental data and from the simulations made with the software Fuelsim.  A simulation will be made to determine whether oxygen-enrichment favors the fuels and experimental data is used to investigate if any combustion problems exist with these fuels. The biomass that have been analyzed comes mainly from pine wood or spruce wood trees which have been processed through either a fast pyrolysis, torrefaction or a steam explosion reactor. No economic aspect has been taken into account in the evaluation of the fuels. One of the pyrolysis process products is pyrolysis liquid which has several challenges ahead before it can replace existing oils. It is very corrosive, has a high moisture content and the storage time is limited to short period of six months. The pyrolysis liquid seems favored by an oxygen-enrichment of 0,5 to 2 % according to the simulation results. The pyrolysis char has the potential to replace or be co-fired with coal in a pulverized coal burner. Pyrolysis gas contains a large amount of CO2, giving it a low energy content. Both char and gas should primarily be combusted in a fluid bed boiler that is integrated with the pyrolysis reactor as boiler plant requires heat. The torrefaction gas is a by-product from the processing of torrefied biomass. Current problems with filtration and condensation of the gas entails that it should be co-fired with another fuel to return the heat to the torrefaction reactor. When the torrefied biomass has been pelletized it is preferably combusted within a large scale boiler such as bubbling fluid bed- (BFB), circulating fluid bed- (CFB) or grate boilers also smaller pellet boilers is possible. Fine adjustments of airflow etc. are required when co-firing or when converting from another fuel to achieve required combustion of the torrefied pellets. The steam explosion pellet simulation results shows that the potential to replace both wood pellets and coal. Based on the results combustion of steam explosion pellets is preferable in either a CFB-, BFB- or grate boiler. This fuel cannot be fully evaluated because of the limited range of experimental data. This study shows that it is problematic to convert from commercial fuels to a thermochemically treated fuel and more experimental data is needed to evaluate the fuels combustion characteristics.

One of the great unsolved evolutionary questions concerns the origin and phylogeny of the major animal phyla that appeared in the fossil record more than 540 million years ago, during the Cambrian explosion. Although new molecular information has been very useful, we still have little understanding about the origin of most of the phyla of bilaterians living today. The richly diverse fossil remains from this critical early Cambrian interval are particularly well exposed in China, where exceptionally-preserved fossil lophotrochozoans including brachiopods are particularly abundant. In particular the exceptionally-preserved Cambrian lophophorates from the Chengjiang and Guanshan Lagerstätten have offered new sources of critical palaeobiological data that have been shown to be important for understanding the early ecology and evolution of lophotrochozoans. This thesis comprises a detailed study of new, abundant, exceptionally-preserved material of five lophotrochozoan species from the Chengjiang and Guanshan Lagerstätten. Kuangshanotreta malungensis from Chengjiang is the earliest known example of an attached acrotretoid brachiopod representing the oldest evidence about the palaeoecology of the diverse yet, enigmatic acrotretoid linguliform stock that comprises an important component of the Cambrian evolutionary fauna. Eoglossa chengjiangensis from Chengjiang is the earliest known representative of the Glossellinae. Diandongia pista occurs abundantly both in the Chengjiang fauna and the younger Guanshan fauna, and it’s exceptionally well-preserved and strongly mineralized shells shows that it belongs within the Botsfordiidae. In contrast, the last two species from Chengjiang examined for this thesis - Yuganotheca elegans and Cotyledion tylodes belong within the stem of the Brachiopoda and the Lophotrochozoan entoprocts.

Zugl.: München, Univ. der Bundeswehr, Diss., 2005

Universiẗat der Bundeswehr, Diss., 2005--München.

Thesis (doctoral)--Technische Universität Darmstadt, 2005.

Made available in DSpace on 2014-06-12T15:53:07Z (GMT). No. of bitstreams: 2 arquivo4927_1.pdf: 1466209 bytes, checksum: 2dd8cd7b46b828a5aa1d2a3f50a6ebef (MD5) license.txt: 1748 bytes, checksum: 8a4605be74aa9ea9d79846c1fba20a33 (MD5) Previous issue date: 2001 / Conselho Nacional de Desenvolvimento Científico e Tecnológico / Cabral Mota, Alexandre; Cezar Alves Sampaio, Augusto. Model checking CSPZ: Techniques to overcome state explosion. 2001. Tese (Doutorado). Programa de Pós-Graduação em Ciência da Computação, Universidade Federal de Pernambuco, Recife, 2001.

This paper examines the history of installation art and explains the concept and themes within my installation component of the studio art major. It details how readymades, site-specificity, and an emphasis on experiential work all contributed to the creation of installation art as a medium. Next, I turn to my own work, exploring the theme of representing time and altering the perceptions of the viewer. Through a web of fishing line and tempered glass, the installation visually imitates a single, frozen moment of an explosion that the viewer can walk into and explore. The paper continues with a discussion of relevant themes in the work by contemporary artists Ori Gerst, Heide Fasnacht, Cornelia Parker, E.V. Day, Lee Bontecou, and James Turrell, and concludes with ideas for the continuation of the project in the spring 2014 semester.

Le Cambrien et l'Ordovicien étaient une période de changements importants dans l'histoire de la vie, lorsque les embranchements animaux actuels ont émergé et des écosystèmes de style moderne se sont développés au cours de l'explosion cambrienne et la radiation ordovicienne. Ces deux événements sont au centre du projet RALI (Rise of Animal Life). Dans le cadre de ce projet, ce travail de thèse se focalise sur trois sujets clés concernant des palynomorphes par rapport aux biodiversifications cambro-ordoviciennes : 1) La biodiversité des acritarches du Cambrien, 2) les palynomorphes de la formation de Fezouata (Ordovicien Inférieur, Maroc), et 3) les palynomorphes inhabituels (« Small Carbonaceous Fossils », SCF) du Lagerstätte de Winneshiek (Ordovicien Moyen, Iowa, Etats-Unis). Pour l'analyse de la biodiversité des acritarches, les données d'apparition des espèces et des genres des acritarches au cours du Cambrien sont assemblées et divers indices de diversité sont calculés. Les résultats montrent un lien possible entre les biodiversités des acritarches et des invertébrés marins pendant l'explosion cambrienne, mais aussi un biais sérieux dans les données des acritarches. Des échantillons provenant du Konservat-Lagerstätte (un site avec des fossiles à conservation exceptionnelle) de Fezouata, qui témoigne des premiers stades de la radiation ordovicienne, et du sous-sol ont délivré des acritarches et chitinozoaires abondants et diversifiés. Leurs implications sont discutées. Les schistes de Winneshiek sont riches en vestiges organiques, y compris d'éventuelles mandibules et plaques filtrantes des crustacés, ainsi que des « algues » filamenteuses avec des cellules géantes. / The Cambrian and Ordovician were times of important changes in the history of life, as the present animal phyla emerged and modern-style ecosystems developed during the so-called Cambrian explosion and the Great Ordovician Biodiversification Event. These two events are the focus of the project RALI “The Rise of Animal Life”. As a part of this project, the present thesis concentrates on three key topics regarding palynomorphs in relation to the Cambro-Ordovician biodiversifications: 1) The biodiversity of Cambrian acritarchs, 2) palynomorphs from the Fezouata Formation (Lower Ordovician, Morocco), and 3) unusual palynomorphs (Small Carbonaceous Fossils, SCFs) from the Winneshiek Lagerstätte (Middle Ordovician, Iowa, USA). For the analysis of acritarch biodiversity, occurrence data of acritarch species and genera during the Cambrian are assembled from the literature and various diversity indices are calculated. The results indicate a possible link between the biodiversities of acritarchs and marine invertebrates during the Cambrian explosion, but also a heavy bias in the acritarch data. The Fezouata Formation bears exceptionally preserved biotas, which document the early stages of the GOBE. Samples from this Konservat-Lagerstätte (site yielding exceptionally preserved fossils) and from the sub-surface of the Fezouata Formation yielded abundant and diverse acritarchs and chitinozoans. Their biostratigraphic, palaeogeographic, taphonomic, and palaeoenvironmental implications are discussed. The Lagerstätten-bearing Winneshiek Shale is rich in organic remains, including possible crustacean mandibles and filter plates, as well as giant-celled filamentous algae.

ABSTRACT A Study on the Violent Interactions of an Immiscible Drop Impacting on a Superheated Pool Mohamad Alchalabi The interactions between two immiscible liquids of different temperatures can be violent to the extent of causing harm to individuals, or damage to equipment, especially when used in the industry. Only a few studies investigated these interactions but they could not produce the violent interactions often reported by the industry, and therefore their results did not help much to develop clear understanding of the dynamics of these interactions. In this work, a high speed imaging system operated at 100,000 frames per second was utilized to record the events and phenomena taking place upon the impact of Perfluorohexane droplet at room temperature onto a hot soybean oil pool at temperatures as high as 300 ºC. The impact velocity was varied by varying the height of the droplet before it pinches off under its own weight. The recorded events identified the occurrence of vortex ring vapor explosions, weak and strong nucleate boiling, and film boiling. An impact velocity vs. oil temperature diagram identifying the regions in which each of these phenomena takes place was generated, and the dynamics driving their occurrences were explored. The vortex ring vapor explosions were found to become less violent as the impact velocity was increased, which was attributed to the existence of a smaller amount of liquid Perfluorohexane within the rings at high speed impacts, which does evaporate but does not expand violently. Weak nucleate boiling occurred at very high impact velocities relatively. As the temperature is increased, however, they start 5 turning into strong nucleate boiling. The strong nucleate boiling usually starts right upon impact, and when the temperature of the oil at one impact velocity is increased, it starts turning into film boiling, in which the liquid Perfluorohexane is covered by a vapor layer of its own vapor.