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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.
51

Comparative geomorphology of two active tectonic structures, near Oxford, North Canterbury

May, Bryce Derrick January 2004 (has links)
The North Canterbury tectonic setting involves the southward propagating margin of easterly strike-slip activity intersecting earlier thrust activity propagating east from the Alpine Fault. The resulting tectonics contain a variety of structures caused by the way these patterns overlap, creating complexities on the regional and individual feature scale. An unpublished map by Jongens et al. (1999) shows the Ashley-Loburn Fault System crossing the plains from the east connected with the Springfield Thrust Fault in the western margins, possibly the southern limit of the east-west trending strikeslip activity. Of note are two hill structures inferred to be affected by this fault system. View Hill to the west, is on the south side of this fault junction, and Starvation Hill further east, was shown lying on the north side of a left stepover restraining bend. During thrust uplift and simple tilting of the View Hill structure, at least two uplift events post date last Pleistocene aggradation accounting for variations in scarp morphology. Broad constraints on fault dip and the age of the displacement surface suggest that slip-rates are in the order of 0.5 mm/year. East from View Hill, the strike-slip fault was originally thought to curve northeast, around the southeast of Starvation Hill. But there is neither evidence of a scarp, nor other clear evidence of surface faulting at Starvation Hill, which poses the question of the extent to which folding may reflect both fault geometry and fault activity. Starvation Hill is a triangular shape, with a series of distinctive smooth, semi-planar surfaces, lapping across both sides of the hill at a range of elevations and gradients. These surfaces are thought to be remnants of old river channels, and are indicative of tilting and upwarping of the hill structure. 3D computer modelling of these surfaces, combined with studies of the cover sequence on the hill, resulted in inferences being drawn as to the location of hinge lines of a dual-hinged anticline and an overview of the tectonic history of the hill. This illustrates the potential to apply topographical and geomorphic studies to the evolution of geometrically complex structures Starvation Hill is interpreted to be the result of two fault-generated folds, one fault trending north, the other, more recent fault, trending east. These two faults are thought to be sequentially developed segments of the original fault zone inferred by Jongens et al. (1999) but with reinterpreted location and mechanism detail. The presence of two faults has resulted in overprinted differential uplift of the structure, which has been significantly degraded, especially in the southwest corner of the hill. The majority of the formation of the northerly trending structure of Starvation Hill is inferred to be pre-Otiran, with uplift of the later east trending structure continuing into the late Pleistocene and Holocene.
52

Kinematic History of the Northwestern Argentine Thrust Belt and Late Cretaceous Tectonic Underplating Beneath the Canadian Cordillera

Pearson, David Malcolm January 2012 (has links)
The American Cordillera, a major mountain belt spanning>15000 km along the western margins of North and South America, formed as a result of crustal shortening and magmatism during ocean-continent convergence. These mountains were the loci of addition and redistribution of continental crust. The contributions presented here address the style, timing, and kinematics of underthrusting of continental crust in the retroarc of the central Andes as well as the rapid burial and metamorphism of forearc rocks that contributed to magmatism in the Canadian Cordillera. This work involved geological mapping and structural analysis coupled with geo- and thermochronological analysis. In the central Andes, results confirm a southward transition in structural style and magnitude of Cenozoic shortening that coincides with the disappearance of a thick Paleozoic basin that accommodated major Cenozoic shortening. U-Pb and (U-Th)/He results also demonstrate that thrust belt kinematics in northwestern Argentina were greatly influenced by pre-orogenic heterogeneities in Cretaceous rift architecture. Results from western Canada reveal that rapid underthrusting of forearc rocks occurred during Late Cretaceous time, likely associated with an episode of shallow subduction. This event did not result in basement-involved foreland uplifts thought to be a signature of shallow subduction in the western United States and central Argentina. Taken together, this work has the major implication that variations in the pre-orogenic upper crustal architecture strongly influence the behavior of the continental lithosphere during orogenesis, a result that challenges geodynamic models that largely neglect upper plate heterogeneities.
53

Thermal history and fluid circulation in deformational structures associated with the Bambuí Group at the fold-and-thrust zone, western margin of the São Francisco Craton / not available

Esteves, Melina Cristina Borges 11 May 2018 (has links)
As condições de pressão e temperatura existentes no evento tectônico que atuou na zona de fold-and-thrust da margem oeste do Cráton do São Francisco foram estimadas com base em estudos estruturais, microestruturais, petrográficos e de inclusões fluidas de veios sintectônicos. A presença de veios de diferentes gerações na zona de fold-and-thrust é evidenciada por fluidos atuando em diferentes cenários de paleoestresse ao longo da história deformacional da área. A área é composta por rochas do Grupo Bambuí fracamente deformadas que registram condições de metamorfismo que variam de diagênese a fácies subxisto verde. Dois eventos tectônicos foram identificados através da disposição geométrica dos veios e da superfície dobrada: (i) uma compressão principal NE-SW (D1) com \'sigma\'1 subhorizontal de orientação SW e \'sigma\'3 sub-vertical, relacionado à formação de veios sintectônicos sub-horizontais de orientação NW formados em condições que atingiram pelo menos 140- 160°C e pressões em torno de 200-363 MPa; (ii) uma compressão posterior NW-SE (D2) com \'sigma\'1 sub-horizontal de orientação NW e \'sigma\'3 também sub-horizontal de orientação NE. Estão relacionados à D2 a formação de veios sintectônicos sub-verticais paralelos à clivagem, formados nas mesmas condições mínimas de temperatura de 140-160°C e pressões entre 181- 295 MPa. A indicação de flutuações na pressão durante esses eventos desempenhou um papel crucial, pois os fluidos influenciam significativamente os processos mecânicos, os mecanismos de deformação e as reações químicas que operam em cinturões de fold-andthrust. Os fluidos apresentam composição formada por H2O-NaCl-CaCl2, onde o processo de mistura de diferentes fontes de fluidos (metamórficas e meteóricas) é evidenciado pela tendência evolutiva de temperaturas de homogeneização e salinidades, resultando em alguma variação na salinidade (12 contra 4% em peso equivalente de NaCl para os veios subhorizontais e para os paralelos à clivagem, respectivamente). Este trabalho confirma que a combinação entre a reconstrução do paleoestresse e o estudo de inclusões fluidas podem fornecer informações fundamentais sobre a relação entre o fluxo de fluidos e a tectônica de terrenos orogênicos, contribuindo para o conhecimento científico sobre a evolução deformacional/metamórfica do Grupo Bambuí e, consequentemente, da zona de fold-andthrust da margem ocidental do Cráton do São Francisco. / P-T conditions existing at the tectonic event that acted at the fold-and-thrust zone of the western margin of the São Francisco Craton were estimated on the basis of structural, microstructural, petrographic and fluid inclusion study of syntectonic veins. The presence of veins of different generations in the fold-and-thrust zone is evidenced by fluids operating at different scenarios of paleostress throughout the deformation history. The area are composed of weakly deformed rocks of the Bambuí Group recording a metamorphism with conditions ranging from diagenetic to sub-greenschist facies. Two tectonic events were identified by vein geometric arrangement and folded surface, a major early NE-SW compression (D1 - \'sigma\'1 subhorizontal SW-trending and \'sigma\'3 subvertical), related with subhorizontal NW-trending syntectonic veins formed at conditions that have reached at least 140°C and pressures around 200-363 MPa; and later NW-SE compression (D2 - \'sigma\'1 subhorizontal NW-trending and \'sigma\'3 subhorizontal NE-trending), related with subvertical syntectonic cleavage-parallel veins formed at the same range of temperature and pressures between 181-295 MPa. Indication of fluctuations in pressure during these events played a crucial role as fluids significantly influence the mechanical processes, deformation mechanisms and chemical reactions that operate in fold-thrust belts. Fluids show H2O-NaCl-CaCl2 composition where mixing process of different fluids sources (metamorphic and meteoric) are evidenced by evolutive trending of homogenization temperatures and salinities resulting in some variation in salinity (12 against 4 wt.% NaCl eq. for subhorizontal and cleavage-parallel veins respectively). This research confirms that combine the reconstruction of the paleostress states and fluid inclusion studies can provide fundamental information of relationship between fluid flow and tectonic of orogenic terrains contributing to the scientific knowledge about the deformational/metamorphic evolution of the Bambuí Group and the fold-and-thrust zone of the western margin of the São Francisco Craton.
54

Thermal history and fluid circulation in deformational structures associated with the Bambuí Group at the fold-and-thrust zone, western margin of the São Francisco Craton / not available

Melina Cristina Borges Esteves 11 May 2018 (has links)
As condições de pressão e temperatura existentes no evento tectônico que atuou na zona de fold-and-thrust da margem oeste do Cráton do São Francisco foram estimadas com base em estudos estruturais, microestruturais, petrográficos e de inclusões fluidas de veios sintectônicos. A presença de veios de diferentes gerações na zona de fold-and-thrust é evidenciada por fluidos atuando em diferentes cenários de paleoestresse ao longo da história deformacional da área. A área é composta por rochas do Grupo Bambuí fracamente deformadas que registram condições de metamorfismo que variam de diagênese a fácies subxisto verde. Dois eventos tectônicos foram identificados através da disposição geométrica dos veios e da superfície dobrada: (i) uma compressão principal NE-SW (D1) com \'sigma\'1 subhorizontal de orientação SW e \'sigma\'3 sub-vertical, relacionado à formação de veios sintectônicos sub-horizontais de orientação NW formados em condições que atingiram pelo menos 140- 160°C e pressões em torno de 200-363 MPa; (ii) uma compressão posterior NW-SE (D2) com \'sigma\'1 sub-horizontal de orientação NW e \'sigma\'3 também sub-horizontal de orientação NE. Estão relacionados à D2 a formação de veios sintectônicos sub-verticais paralelos à clivagem, formados nas mesmas condições mínimas de temperatura de 140-160°C e pressões entre 181- 295 MPa. A indicação de flutuações na pressão durante esses eventos desempenhou um papel crucial, pois os fluidos influenciam significativamente os processos mecânicos, os mecanismos de deformação e as reações químicas que operam em cinturões de fold-andthrust. Os fluidos apresentam composição formada por H2O-NaCl-CaCl2, onde o processo de mistura de diferentes fontes de fluidos (metamórficas e meteóricas) é evidenciado pela tendência evolutiva de temperaturas de homogeneização e salinidades, resultando em alguma variação na salinidade (12 contra 4% em peso equivalente de NaCl para os veios subhorizontais e para os paralelos à clivagem, respectivamente). Este trabalho confirma que a combinação entre a reconstrução do paleoestresse e o estudo de inclusões fluidas podem fornecer informações fundamentais sobre a relação entre o fluxo de fluidos e a tectônica de terrenos orogênicos, contribuindo para o conhecimento científico sobre a evolução deformacional/metamórfica do Grupo Bambuí e, consequentemente, da zona de fold-andthrust da margem ocidental do Cráton do São Francisco. / P-T conditions existing at the tectonic event that acted at the fold-and-thrust zone of the western margin of the São Francisco Craton were estimated on the basis of structural, microstructural, petrographic and fluid inclusion study of syntectonic veins. The presence of veins of different generations in the fold-and-thrust zone is evidenced by fluids operating at different scenarios of paleostress throughout the deformation history. The area are composed of weakly deformed rocks of the Bambuí Group recording a metamorphism with conditions ranging from diagenetic to sub-greenschist facies. Two tectonic events were identified by vein geometric arrangement and folded surface, a major early NE-SW compression (D1 - \'sigma\'1 subhorizontal SW-trending and \'sigma\'3 subvertical), related with subhorizontal NW-trending syntectonic veins formed at conditions that have reached at least 140°C and pressures around 200-363 MPa; and later NW-SE compression (D2 - \'sigma\'1 subhorizontal NW-trending and \'sigma\'3 subhorizontal NE-trending), related with subvertical syntectonic cleavage-parallel veins formed at the same range of temperature and pressures between 181-295 MPa. Indication of fluctuations in pressure during these events played a crucial role as fluids significantly influence the mechanical processes, deformation mechanisms and chemical reactions that operate in fold-thrust belts. Fluids show H2O-NaCl-CaCl2 composition where mixing process of different fluids sources (metamorphic and meteoric) are evidenced by evolutive trending of homogenization temperatures and salinities resulting in some variation in salinity (12 against 4 wt.% NaCl eq. for subhorizontal and cleavage-parallel veins respectively). This research confirms that combine the reconstruction of the paleostress states and fluid inclusion studies can provide fundamental information of relationship between fluid flow and tectonic of orogenic terrains contributing to the scientific knowledge about the deformational/metamorphic evolution of the Bambuí Group and the fold-and-thrust zone of the western margin of the São Francisco Craton.
55

Aerodynamic Thrust Vectoring For Attitude Control Of A Vertically Thrusting Jet Engine

Schaefermeyer, M. Ryan 01 May 2011 (has links)
NASA’s long range vision for space exploration includes human and robotic missions to extraterrestrial bodies including the moon, asteroids and the martian surface. All feasible extraterrestrial landing sites in the solar system are smaller and have gravitational fields of lesser strength than Earth’s gravity field. Thus, a need exists for evaluating autonomous and human-piloted landing techniques in these reduced-gravity situations. A small-scale, free-flying, reduced-gravity simulation vehicle was designed by a group of senior mechanical engineering students with the help of faculty and graduate student advisors at Utah State University during the 2009-2010 academic year. The design reproduces many of the capabilities of NASA’s 1960s era lunar landing research vehicle using small, inexpensive modern digital avionics instead of the large, expensive analog technology available at that time. The final vehicle design consists of an outer maneuvering platform and an inner gravity offset platform. The two platforms are connected through a set of concentric gimbals which allow them to move in tandem through lateral, vertical, and yawing motions, while remaining independent of each other in rolling and pitching motions. A small radio-controlled jet engine was used on the inner platform to offset a fraction of Earth’s gravity (5/6th for lunar simulations), allowing the outer platform to act as though it is flying in a reduced-gravity environment. Imperative to the stability of the vehicle and fidelity of the simulation, the jet engine must remain in a vertical orientation to not contribute to lateral motions. To this end, a thrust vectoring mechanism was designed and built that, together with a suite of sensors and a closed loop control algorithm, enables precise orientation control of the jet engine. Detailed designs for the thrust vectoring mechanisms and control avionics are presented. The thrust vectoring mechanism uses thin airfoils, mounted directly behind the nozzle, to deflect the engine’s exhaust plume. Both pitch and yaw control can be generated. The thrust vectoring airfoil sections were sized using the two-dimensional airfoil section compressible-flow CFD code, XFOIL, developed at the Massachusetts Institute of Technology. Because of the high exhaust temperatures of the nozzle plume, viscous calculations derived from XFOIL were considered to be inaccurate. XFOIL was run in inviscid flow mode and viscosity adjustments were calculated using a Utah State University-developed compressible skin friction code. A series of ground tests were conducted to demonstrate the thrust vectoring system’s ability to control the orientation of the jet engine. Detailed test results are presented.
56

Magnitude of Displacement and Styles of Deformation on the Paris and Laketown Thrust Faults, Northern Utah

Kendrick, Richard D. 01 May 1994 (has links)
Surface geology is combined with abundant industry seismic-reflection and drill­-hole data in the central Bear River Range and Bear Lake Plateau to depict the forms and interactions of the Paris-Woodruff-Willard, Laketown-Meade-Home Canyon, and Crawford thrust faults. Displacement on the Paris thrust diminished to the south, and died out in splays where displacement was transferred to the Willard thrust. West of Woodruff, Utah, splays of the Laketown thrust deformed a complex footwall imbricate of the Willard thrust. To the east, a major northeast-striking Crawford thrust splay exhibits a change in slip vectors from east to southeast. Reorientation of these slip vectors is recorded by an imbricate stack of thrusts in the Willard thrust footwall to the west. The sharp bend in the surface trace of the Crawford normal fault southeast of Randolph, Utah, reflects the separation of the south-southeast-trending surface traces of the Crawford thrust and this northeast-trending splay. Cross sections indicate that the Sheep Creek thrust, a major splay off the basal decollement at the base of the Crawford thrust sheet, accommodated displacement during the transition from thrusting on the western thrust system (Paris-Woodruff-Willard, and Laketown-Meade-Home Canyon) to the structurally lower eastern thrust system (Crawford, Absaroka, and younger thrusts). The Sheep Creek thrust trends northeast and folded the Laketown thrust in the central Bear River Range. Shortening in the northeast part of the study area was accommodated by the Home Canyon thrust along a detachment in the Jurassic Twin Creek Limestone. Several splays from this thrust extensively folded the footwall of the Meade thrust and rocks of the Bear Lake Plateau, and thereby formed a series of hanging-wall anticlines that have been extensively drilled for hydrocarbons.
57

Development of the Multiple Use Plug Hybrid for Nanosats (Muphyn) Miniature Thruster

Eilers, Shannon Dean 01 May 2013 (has links)
The Multiple Use Plug Hybrid for Nanosats (MUPHyN) prototype thruster incorporates solutions to several major challenges that have traditionally limited the deployment of chemical propulsion systems on small spacecraft. The MUPHyN thruster offers several features that are uniquely suited for small satellite applications. These features include 1) a non-explosive ignition system, 2) non-mechanical thrust vectoring using secondary fluid injection on an aerospike nozzle cooled with the oxidizer flow, 3) a non-toxic, chemically-stable combination of liquid and inert solid propellants, 4) a compact form factor enabled by the direct digital manufacture of the inert solid fuel grain. Hybrid rocket motors provide significant safety and reliability advantages over both solid composite and liquid propulsion systems; however, hybrid motors have found only limited use on operational vehicles due to 1) difficulty in modeling the fuel flow rate 2) poor volumetric efficiency and/or form factor 3) significantly lower fuel flow rates than solid rocket motors 4) difficulty in obtaining high combustion efficiencies. The features of the MUPHyN thruster are designed to offset and/or overcome these shortcomings. The MUPHyN motor design represents a convergence of technologies, including hybrid rocket regression rate modeling, aerospike secondary injection thrust vectoring, multiphase injector modeling, non-pyrotechnic ignition, and nitrous oxide regenerative cooling that address the traditional challenges that limit the use of hybrid rocket motors and aerospike nozzles. This synthesis of technologies is unique to the MUPHyN thruster design and no comparable work has been published in the open literature.
58

Internal Deformation, Evolution, and Fluid Flow in Basement-Involved Thrust Faults, Northwestern Wyoming

Goddard, James V. 01 May 1993 (has links)
An integrated field , microstructure, fracture statistic , geochemistry , and laboratory permeability study of the East Fork and White Rock fault zones , of similar age and tectonic regime but different structural level and hydrogeologic history , provides detailed information about the internal deformation and fluid flow processes in fault zones . The primary conclusions of this research are: 1) Fault zones can be separated into subzones of protolith, damaged zone , and gouge /cataclasite , based on physical morphology and permeability structure . At deep structural levels, gouge/cataclasite zones are more evolved (thicker with increased grain size reduction) due to strain localization , higher pressure and temperature, and fluid/rock interaction ; 2) Deformation mechanisms evolved from primarily brittle fracturing and faulting in the damaged zone to extreme, fluid-enhanced chemical breakdown and cataclasis which localized strain in the fault core. Deformation in the deep-level-fault core may be a combination of frictional and quasiplastic mechanisms, and is largely controlled by extremely fine-grained clays, zeolites , and other phyllosilicates that may have acted as a thermally pressurized, fluid-saturated lubricant; 3) Permeability in fault zones was temporally heterogeneous and anisotropic (permeability of damaged zone>protolith>gouge /cataclasite, permeability along fault> permeability across fault); 4) Volume loss was concentrated in the fault cores and was negligible at intermediate structural levels and high at deep structural levels in the semi-brittle to brittle regime ; 5) Fluid flow and solute transport were concentrated upwards and subparallel to the fault in the damaged zone ; 6) Faults at both the local and regional scale acted as fluid flow conduit/barrier systems depending upon the evolutionary stage and interval in the seismic cycle ; 7) Fluid/rock volume ratios , fluid flux , and fluid/rock volume ratios over time ranged from ⋍ 103 to 104, 10-6 ms-1 to 10-9 ms-1, and 0.05 L/m3 rock•yr to 0.50 L/m3 rock•yr, respectively, suggesting that enormous quantities of fluids passed through the fault zones; 8) Box counting fractal analyses of fault zone fractures showed that fracture spatial and density distribution is scale-invariant at the separate scales of outcrop , hand-sample , and thin section, but self-affine from outcrop to thin-section scale; 9) Linear fractal analysis depicts clustering and density distribution as a function of orientation, and may be a quick, robust method of estimating two-dimensional fracture permeability; and 10) Fractal analysis of fractures is not a comprehensive statistical method, but can be used as another supplemental statistical parameter.
59

A Theoretical and Experimental Comparison of Aluminum as an Energetic Additive in Solid Rocket Motors with Thrust Stand Design

Farrow, Derek Damon 01 August 2011 (has links)
The use of aluminum as an energetic additive in solid rocket propellants has been around since the 1950’s. Since then, much research has been done both on the aluminum material itself and on chemical techniques to properly prepare aluminum particles for injection into a solid propellant. Although initial interests in additives were centered on space limited applications, performance increases opened the door for higher performance systems without the need to remake current systems. This thesis aims to compare the performance for aluminized solid rocket motors and non-aluminized motors, as well as focuses on design considerations for a thrust stand that can be created easily at low cost for initial testing. A theoretical model is created for predicting propellant performance and the results are compared with experimental data taken from the thrust stand as well as existing data. What is seen at the end of testing is the non-aluminized grains follow the same trends as previously conducted tests and firings. The aluminized grains follow their expected trend but at a lower performance level due to grain degradation. However, the aluminized grains still show a specific impulse increase of 6%-23% over the non-aluminized grains.
60

Optimal dimensionless design and analysis of jet ejectors as compressors and thrust augmenters

Mohan, Ganesh 16 August 2006 (has links)
A jet ejector may be used as a compressor or to enhance thrust of watercraft or aircraft. Optimization of jet ejectors as compressors and thrust augmenters was conducted using the software GAMBIT (Computer Aided Engineering (CAE) tool for geometry and mesh generation) and FLUENT (Computational Fluid Dynamics (CFD) solver kit). Scripting languages PYTHON and SCHEME were used to automate this process. The CFD model employed 2D axis symmetric, steady-state flow using the ε−k method (including wall functions) to model turbulence. Initially, non-dimensionalization of the jet ejector as a gas compressor was performed with respect to scale, fluid, and operating pressure. Surprisingly, rather than the conventional parameters like Mach or Re number, the results showed a completely new parameter (christenedGM- Gauge Mach) that when kept constant will result in non-dimensionalization. Non-dimensionalization of a jet ejector for watercraft propulsion was conducted using 2D axis symmetric, steady-state flow modeling using the ε−kmethod (including wall functions). It showed consistent results for the same velocity ratio (r) of nozzle velocity to free-stream velocity for different scales, fluids, and ambient pressures.

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