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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.
141

Geochronologic and Petrologic Context for Deep Crustal Metamorphic Core Complex Development, East Humboldt Range, Nevada

Dilles, Zoe Y G 01 January 2016 (has links)
The Ruby-Humboldt Range in Northeastern Nevada exposes the deepest crust in the western portion of the Sevier Hinterland. The product of unique brittle and ductile accommodations, this block of lower crustal rock is a window into the processes of continental thickening and extension. The structure of the northern tip of the Ruby-Humboldt Range core complex is dominated by a large recumbent fold nappe with a southward closeure cored by Paleoproterozoic-Archean gneissic complexes with complex interdigitated field relationships that record polyphase continental metamorphism. Amphibolite-grade metapelitic rocks within the core and Winchell Lake nappe record a wide range of zircon age dates of metamorphic events the oldest of which at ~2.5 Ga is recorded in adjacent orthogneiss as a crystallization age. At least two younger metamorphic events are recorded within this orthogneiss, most significantly at 1.7-1.8 Ga, an event previously unpublished for this region that links it to Wyoming province activity in addition to inherited component of detrital cores up to 3.7 Ga in age that is among the oldest ages reported in Nevada. The youngest overprint of cretaceous metamorphic overgrowth ranges fro 60-90 Ma in age based on zircon rims in the aforementioned units as well as three garnet amphibolites that intrude the core of the nappe and are interpreted to be metabasic bodies.
142

High fidelity multidisciplinary analyses of flow in weapon bays

Babu, Savio January 2014 (has links)
Modern military aircraft employ weapon bays for carriage and release of stores. The clearance of these stores for release from aircraft may require several flight tests at a range of conditions where the trajectories of released stores are obtained through accelerometers located on the store. Although effective, this is expensive and time consuming and only limited flight tests can be accomplished at critical conditions. Predictions made using store release analysis through wind tunnels and Computational Fluid Dynamics (CFD) have the potential to reduce the number of flight tests required for store clearance. The motivation for the current work, stems from the need to investigate carriage and release of a store from a weapon bay, idealised as a rectangular cavity, through a unique blend of disciplines comprising Computational Fluid Dynamics, Computational Structural Dynamics (CSD), Computational Aero- Aeroacoustics (CAA) and High Performance Computing (HPC). Detached-Eddy Simulations (DES) of flow in clean cavities were carried out to compare two cavities of different aspect ratios for configurations with doors-off and doors-on. Both cavities had similar acoustic signatures and the addition of doors channelled the flow causing acoustic waves to propagate further away from the cavity. DES computations were carried out for a store at different positions relative to a cavity that showed that a store at carriage position pacified the cavity acoustics the most. Fin tip displacements were small for a store at carriage position and exhibited buzzing characteristics. This was similar to the case where a store was positioned at the shear layer of a cavity but with slightly larger displacements. While fin displacements were not large, the results highlighted concerns for fin fatigue life. Comparisons between rigid and elastic fins showed small differences in loads, however, aeroelastic simulations showed that where resonance of structural and cavity modes occurred, large amplitude fin oscillations were predicted. Scale-Adaptive Simulations (SAS) were validated against experimental data for clean cavities and were found to be similar to DES results and could be run at a larger time-step. The cost savings and similarities of SAS to DES encouraged its use for store release computations. Store release computations from a cavity were conducted and the variability of a stores trajectory due to the unsteady cavity flow-field was investigated. Visualisations using Q-criteria highlighted instantaneous structures that were in contact with the store fins causing the trajectory to vary for different release times. Overall, the thesis suggests the use of SAS as an affordable method for analysing store release computations from a cavity and highlights the need for a stochastic evaluation of trajectories from transonic cavities. A study comparing different signal lengths for post-processing unsteady pressure data revealed that, the minimum CFD signal length required to capture all dominant tones was around 0.05s. Different post-processing methods for spectral content were compared and the use of Maximum Entropy Methods (MEMs), based on Burgs Estimator, was suggested as it not only captured dominant tones but also predicted the highest Sound Pressure Levels (SPLs), that could be used to produce the maximum boundary of a given signal.
143

Varmhållning av flygplan - en ny tillämpning av fjärrvärme : Produktutveckling av klimataggregat för flygplan vid markservice. / Heating of airplanes – a new application of district heating : Product development of an air climate unit used for airplanes during ground service.

Sahl, Fredrik January 2015 (has links)
Flygbranschen står idag för 2 % av de globala utsläppen av fossil koldioxid och har som första världsomspännande industri enats om gemensamma globala miljömål för att minska sin klimatpåverkan. Fjärrvärmebranschen står inför tuffa utmaningar då fjärrvärmeunderlaget förutspås minska på sikt. Smart Climate Scandinavian AB:s idé att värma flygplan med fjärrvärme när de står parkerade på backen är världsunik och möter de behov som både fjärrvärme- och flygbranschen har, att hitta nya affärsområden respektive minska sina utsläpp. Syftet med detta examensarbete var att ta fram underlag för utveckling av nästa generations styrsystem för Smart Climates klimataggregat samt undersöka konsekvensen av byte från ett traditionellt aggregat till ett från Smart Climate med hänsyn till energieffektivitet, miljöbelastning och driftkostnad. Mätningar av de termiska egenskaperna hos ett flygplan av typen ATR72-500 genomfördes. Det genomsnittliga U-värdet beräknades till 2,0 W/(m2·K) och värmekapaciteten till 3,421 MJ/kg. Med Excel VBA programmerades en applikation som har använts och kan fortsätta användas som ett verktyg för produktutveckling. Denna applikation beräknar energibehovet för ett flygplan baserat på inställda parametrar, som till exempel utetemperatur och flygplanets termiska egenskaper. Med Excelapplikationen beräknades den potentiella energibesparingen vid införande av nattsänkning, det vill säga tillfälligt sänk temperatur i flygplanet, till ca 30 % av ursprungligt energibehov. En konsekvensanalys av byte från elbaserade aggregat till ett fjärrvärmebaserat aggregat med föreslagen nattsänkning genomfördes. Analysen avgränsar sig till flygplanet som systemgräns och saknar därför en jämförelse av skillnad i förluster som vartdera systemet har. Beräkningarna visar att nattsänkningen innebär en reduktion av det årliga behovet från 25000 kWh till 15500 kWh för en ATR72-500. Traditionella aggregat tillämpar inte denna reglerteknik. Byte av energikälla från el till fjärrvärme innebär en minskning av de globala CO2e-utsläppen med mellan 9000 och 22000 kg per år. Hur stor besparingen i driftkostnad blir beror på rådande energipriser. Vid utveckling av nästa generation styrsystem rekommenderas att nattsänkning införs för Smart Climates aggregat då det visat sig ge stora energibesparingar. Dessutom föreslås styrsystemet vara uppkopplat mot internet för att underlätta framtida reglerjusteringar, datainsamling och produktutveckling. Att styra tillförd effekt på kabintemperaturen har visat sig mer pålitligt än vid styrning med hänsyn endast till utetemperaturen. Framtida studier föreslås fokusera på att utvidga systemgränsen från flygplanet till att ta med energitransportförluster i beräkningarna. Förslagsvis utses en specifik flygplats och systemgränsen sätts vid flygplatsens energimätare för el respektive fjärrvärme. Optimering av glykol/vattenflöde och dimensionering av ledningar, strypventiler och pumpar är intressanta frågeställningar. Frigörande av kapacitet i flygplatsens transformatorstation kan i sig vara en orsak till att välja varmhållning av flygplan med fjärrvärme. Den kanske viktigaste konsekvensen av att ersätta el med fjärrvärme är att högvärdig energi kan användas där den behövs. / The aviation industry today is responsible for 2 % of the fossil carbon dioxide emissions and has, as the first global industry, united around common goals for reducing its effect on climate change. The district heating industry faces tough challenges ahead considering the demand of its primary product is predicted to decrease in the longer run. Smart Climate Scandinavian AB’s idea of heating airplanes parked on ground with district heating unites the needs for both the aviation and district heating industry of reducing emissions and finding new areas of application respectively. The purpose of this thesis is to provide information for development of the next generation Smart Climate air climate unit control system and to study the consequences of changing from a traditional air climate unit to one from Smart Climate, with regard to energy efficiency, environmental impact, and operation cost. The thermal properties of an airplane of the type ATR72-500 where measured. The U-value was calculated to 2,0 W/(m2·K) and the heat capacity to 3,421 MJ/kg. An Excel application was programmed in Excel VBA to be used for product development. The application calculates the energy demand of an airplane based on settings such as outside temperature and the airplane’s thermal properties. The potential energy savings of introducing night time reduction, which is temporarily reducing the temperature in the airplane, is calculated to about 30 % of the initial energy demand. A consequence analysis of changing from a traditional electricity based air climate unit to one based on district heating with the proposed night time reduction was performed. The analysis was limited to the airplane as the system boundary and hence does not include energy losses which both systems have. The night time reduction is not implemented in traditional air climate units and hence the demand in energy is calculated to decrease from 25000 kWh to 15500 kWh per year for an ATR72-500. Changing energy source from electricity to district heating results in a reduced emission of CO2e of somewhere between 9000 and 22000 kg per year. How big the saving in operation cost will be depends on the energy prices for electricity and district heating. An introduction of night time reduction is recommended in the next generation control system of Smart Climate’s air climate unit since it evidently comes with great energy savings. It is also proposed that the next generation is wired up online on the internet. This will facilitate future setting adjustments, data gathering and product development. Also validated during the study is that the technique of regulating the temperature of inlet air by measuring the cabin temperature is more reliable than the traditional technique of using the outside temperature. It is suggested for future studies to include energy transport losses and hence should focus on one airport with well-defined system boundaries. A suggestion is using the same boundary as the energy meters of the airport. Optimizing glycol/water flow and dimensioning of pipes, valves and pumps are interesting issues to investigate. A reduced electricity demand will decrease the needed capacity of the transformer station and could give reason for considering heating airplanes with district heating. Perhaps the most important consequence of replacing electricity with district heating is that primary energy can be used where it is needed.
144

Geocronología y condiciones de cristalización de circones del Plutón Caleu: Evidencias de su prolongada evolución tardimagmática

Molina Cancino, Pablo January 2014 (has links)
Magíster en Ciencias, Mención Geología / Geólogo / El plutón Caleu se ubica en la parte más oriental y joven del Batolito Costero de Chile central (~33ºC), entre las regiones Metropolitana y de Valparaíso, posee un registro único del magmatismo generado a estas latitudes en el clímax del rifting del Cretácico Superior. Corresponde principalmente a un cuerpo compuesto por cuatro franjas de orientación N-S, de composiciones dioríticas a monzograníticas, y con más de ~1000 m de exposiciones verticales en sus partes mediales. Sus zonas litológicas corresponden a: Zona Gabrodiorítica (GDZ), Zona Granodiorítica (GZ), Zona Cuarzo-Monzodiorítica (QMDZ), y Zona Monzogranítica (MGZ). En el presente estudio se utilizó geoquímica y geocronología U-Pb de circones de cada una de las zonas litológicas, junto con determinaciones de geoquímica en roca total para descifrar la etapa tardimagmática del plutón Caleu. Los resultados arrojaron edades 208Pb/235U de 99.7±1.0 (2σ; MSWD = 2.2), 96.8±1.1 (2σ; MSWD = 3.1), 96.8±1.0 (2σ; MSWD = 3.5) y 94.7±0.7 (2σ; MSWD = 0.95) evidenciando un leve decremento de edades de muestras huéspedes básicas a más ácidas, correspondiente a un desarrollo prolongado de la etapa tardimagmática del plutón Caleu. Temperaturas de cristalización de circón (calculadas a partir del termómetro de titanio en circón), muestran dispersiones entre 680 y 850ºC, sin correlaciones claras con su edad. Por otro lado, la geoquímica de circones y de roca total de las partes superiores del plutón (extraídos de QMDZ) evidencian enriquecimiento y dispersión anómalo en sus concentraciones de REE. Basado en un enfoque numérico según modelación termodinámica con el software MELTS, los fundidos que generaron circón (en las unidades GDZ, GZ y QMDZ) fueron altamente cristalinos (66-89% volumétrico de cristales), y se asemejan a MGZ en composiciones, estas ventanas de cristalinidad definen un sistema mush en donde la eficiencia de extracción de líquidos residuales es óptima. Por otro lado se estima que los fundidos que generaron circones en MGZ corresponden a una generación temprana (~32% vol. de cristales), reflejando fraccionamiento de sólidos (posiblemente circón, apatito, hornblenda y/o titanita). Tomando en consideración las evidencias geocronológicas, geotermométricas y composicionales, se propone un mecanismo de advección de líquidos desde su reservorio a través de un sistema magmático altamente cristalino, capaz de dar explicación al desarrollo prolongado y geoquímicamente críptico de la etapa tardimagmática del plutón Caleu.
145

Widespread permafrost thaw during Marine Isotope Stages 11 and 13 recorded by speleothems

Biller, Nicole Brooke January 2017 (has links)
Thesis advisor: Jeremy D. Shakun / Arctic permafrost contains a substantial stock of carbon that could be released to the atmosphere as CH4 and CO2 upon thawing, making it a potentially powerful amplifier of future warming. The sensitivity of permafrost to climate change is uncertain, however, and occurs on time scales longer than those captured by the instrumental record. Speleothems – cave precipitates deposited from flowing or dripping water – in currently frozen regions record past episodes of thaw, which can be used to assess the response of permafrost to long-term warmth. Here, we present 90 uranium-thorium ages on speleothems from across the North American Arctic, sub-Arctic and northern alpine regions to reconstruct a 600-kyr permafrost history. Widespread speleothem growth supports an episode of extensive permafrost thaw during the Marine Isotope Stage 11 interglacial about 400 ka, when global temperature was only slightly warmer than pre-industrial conditions. Additional growth is evident during MIS 13, curiously, a smaller magnitude interglacial. Ice-core records of atmospheric greenhouse gases do not show elevated concentrations at these times, perhaps suggesting that the permafrost carbon pool was smaller than today or released gradually enough to be buffered by other reservoirs. / Thesis (MS) — Boston College, 2017. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Earth and Environmental Sciences.
146

New Constraints on the Age of Deposition and Provenance of the Metasedimentary Rocks in the Nashoba Terrane, SE New England

Loan, MaryEllen Louise January 2011 (has links)
Thesis advisor: J. Christopher Hepburn / The Nashoba terrane of SE New England is one of three peri-Gondwanan tectonic blocks caught between Laurentia and Gondwana during the closure of the Iapetus Ocean in the early to mid- Paleozoic. U-Pb analyses (LA-ICP-MS) were carried out on zircon suites from the meta-sedimentary rocks of the Nashoba terrane. The youngest detrital zircons in the meta-sedimentary rocks of the Nashoba terrane are Ordovician in age. There is no significant difference in age between meta-sedimentary units of the Nashoba terrane across the Assabet River Fault Zone, a major fault zone that bisects the NT in a SE and a NW par. Zircon in meta-sedimentary rocks in the Marlboro Fm., the oldest unit of the Nashoba terrane, is rare, which may reflect the basaltic nature of the source material, and is commonly metamict. The Marlboro Fm. contained the oldest detrital grain of all the analyzed samples, with a core of ~3.3 Ga and rim of ~2.6 Ga indicating that it was sourced from Archaen crustal material. Detrital zircons from the Nashoba terrane show a complete age record between the Paleoproterozoic and Paleozoic that strongly supports a provenance from the Oaxiqua margin of Amazonia. The detrital zircon suite of the Nashoba terrane is distinct from both Avalonia and the Merrimack belt; however, they resemble zircon suites from Ganderia. This study proposes that the Nashoba terrane of Massachusetts correlates with the passive trailing edge of Ganderia. Finally, metamorphic zircon analyses of the terrane show that the Nashoba terrane experienced a peak in hydrothermal fluid infiltration during the Neoacadian orogeny. / Thesis (MS) — Boston College, 2011. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Earth and Environmental Sciences.
147

Civilian control of the military in Portugal and Spain : a policy instruments approach

Olivas Osuna, José Javier January 2012 (has links)
Despite their economic, political and cultural similarities, Portugal and Spain experienced different trajectories of civil-military relations during the twentieth century. After having handed power over to a civilian dictator, Salazar, the Portuguese military eventually caused the downfall of his authoritarian Estado Novo regime and led the transition to democracy. In contrast, in Spain the military, which had helped Franco to defeat the Republic in 1939 remained loyal to the dictatorship’s principles and, after his death, obstructed the democratisation process. This research sheds light on these different patterns by comparing the policy instruments that governments used to control the military throughout Portuguese and Spanish dictatorships and transitions to democracy. First, it applies Christopher Hood’s (1983) ‘NATO’ (nodality, authority, treasure and organisation) framework for the study of tools of government in order to identify trajectories and establish comparisons across time and countries. These tools can be considered as the institutions that structure the relationship between the governments and the military. This thesis documents that the tools used in both counties differed considerably and evolved over time and that only from 1982 onwards a process of convergence can be observed. Second, this thesis contrasts two types of neo-institutional explanations for the evolution of tool choice and civil-military relations. One based on historical junctures and path-dependence (historical causes) and the other on the continuous impact of environmental factors (constant causes). is research demonstrates that both approaches are largely intertwined and to a great extent become complementary and necessary to capture complexity in tool choice. In sum, this thesis shows that dialogue and exchange between different analytical approaches contributes to a deeper understanding of multifaceted social phenomena. The utilisation of public policy analytical frameworks, such as the NATO scheme and neoinstitutionalism, provides a new angle on the evolution of civil-military relations in Portugal and Spain.
148

Design validation of future ballistic neck protection through the development of novel injury models

Breeze, John January 2015 (has links)
The primary aim of this thesis was to develop more acceptable methods of ballistic neck protection that could replace the existing OSPREY ballistic neck collar. Clinical and post mortem injury analysis, computed tomography interpretation and ergonomics assessments were undertaken, resulting in the recommendation of two prototype designs to the Ministry of Defence. These two prototypes have subsequently been renamed the Enhanced Protection Under Body Armour Combat Shirt and the Patrol collar, and are now issued to all UK armed forces personnel deploying on operations overseas. The secondary aim of this thesis was to develop methods to validate the potential medical effectiveness of future body armour designs. Two new novel injury models have been developed using an anthropometrically accurate three- dimensional representation of cervical anatomical structures. Penetration of representative fragment simulating projectiles through skin and muscle was determined experimentally using physical and animal simulants. The Coverage of Armour Tool is being used in the current Ministry of Defence VIRTUS procurement programme to rule out future body armour designs on medical grounds, thereby greatly reducing the number of prototypes requiring ergonomics assessment.
149

Army co-operation command and tactical air power development in Britain, 1940-1943 : the role of army co-operation command in army air support

Powell, Matthew Lee January 2014 (has links)
This thesis examines the impact of the developments made during the First World War and the inter-war period in tactical air support. Further to this, it will analyse how these developments led to the creation of Army Co-operation Command and affected the role it played developing army air support in Britain. Army Co-operation Command has been neglected in the literature on the Royal Air Force during the Second World War and this thesis addresses this neglect by adding to the extant knowledge on the development of tactical air support and fills a larger gap that exists in the literature on Royal Air Force Commands. Army Co-operation Command was created at the behest of the army in the wake of the Battle of France. A key area of development was the communications system to enable troops to request air support in the field. The Command was also involved in developing the Air Observation Post Squadron. Air Observation Post aircraft were used to direct the fire of artillery batteries from the air. In 1943, an operational tactical air force replaced Army Co-operation Command. This study highlights inter-service difficulties over the provision of air support.
150

The military applications of near infrared spectroscopy in trauma

Barker, Tom January 2016 (has links)
This work examines tissue oxygenation (StO2), as measured by near infrared spectroscopy (NIRS), as tool for assessing trauma patients, with particular emphasis on its use in the deployed military environment. Resting StO2 values were examined and found to vary significantly between monitoring sites. Exercise was associated with a significant increase in StO2. Comparing the sensitivities of different NIRS monitoring sites in detecting simulated hypovolaemia, the forearm and deltoid were found be the most sensitive sites. The thenar eminence and brain were not sensitive to mild degrees of hypovolaemia. The administration of morphine was found to attenuate the StO2 response to hypovolaemia at all sites. In a porcine trauma model changes in StO2 recorded from both injured and uninjured muscle sites phase led those of base excess and lactate by 31–37 minutes, and demonstrate that injured monitoring sites can be used to accurately track patients’ response to resuscitation. In the deployed military setting NIRS was found to be a robust, easy to use technique for the initial assessment of patients. Although StO2 was not demonstrable superior to a combination of pulse rate and blood pressure it has several practical advantages that make it a useful adjunct to contemporary trauma care.

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