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Jolly, Byami Andrew. "The interaction between deepwater channel systems and growing thrusts and folds, toe-thrust region of the deepwater Niger Delta." Thesis, Imperial College London, 2014. http://hdl.handle.net/10044/1/18409.
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The Niger Delta fold and thrust belt occurs in an area of tectonic shortening – caused by the thin-skinned gravitational collapse of large deltaic sediment wedges above a ductile overpressured shale. Syn-sedimentary processes such as down-slope flowing gravity currents interact with the deforming seafloor topography to produce growth packages that record the deformation history of the folds. The thesis documents the spatial and temporal interaction between Pleistocene to Recent submarine channels, and folds/thrusts that have been growing since 12.8 million years ago (Ma). 3D seismic reflection data and key stratigraphic/horizon ages are used to constrain and analyse the spatial and temporal variation in shortening of major folds having seabed relief. Geomorphic techniques were applied to quantify the geomorphic responses of submarine channels developing coevally with structural deformation. This thesis documents two types of structures (fault-propagation folds and a detachment fold) whose cumulative strain (shortening) varies spatially and through time. The maximum interval shortening rate occurred between 9.5 Ma and 3.7 Ma, and has reduced significantly from that time to present. Channels show a range of interactions with structures, from simple deflection to fold tips to complete diversion. However, channels are capable of crossing the actively growing fault-propagation folds in positions of recent strain minima and at interval strain rates that are generally less than 15 m/Myr. In contrast, channels have been completely diverted by the broad detachment fold albeit growing at comparably lower rates. This thesis emphasizes that careful fold displacement – distance measurements which bracket the time interval of channel system development are very important for predicting sediment pathways in deepwater settings. Detailed geomorphic analysis showed that the bathymetry longitudinal profiles of the active channels are relatively linear with concavity values that range from -0.08 to ̵ 0.34, with an average profile gradient between 0.9[degrees] and 1[degrees]. In contrast, channel systems that have been abandoned and buried for long period of time, have longitudinal profiles that are more convex. The profiles of both the active and buried channels are characterized by knickzones that are apparent near mapped structures – and implicitly record variations in substrate uplift rate. The recently active channels (the modern thalweg) show no systematic width change down-system but they do show an increase in incision depth/erosion of up to 70 % at structural locations. However, the channel system (made of several cut-and-fill sequences), shows clear width narrowing together with time-integrated incision and erosion in response to time-integrated structural uplift. Estimates of the down-system variation in channel bed-shear stress and flow velocity, using the thalweg-geometry of the active channels, suggests that near growing folds and thrusts, the enhanced bed-shear stress-driven incision is up to 200 Pa. and the flow velocity is up to 5 m s-1. In essence, the linear nature of the active channel profiles, in comparison to the convex nature of the buried channel profiles, suggests that the active channels are able to keep pace with the time-integrated uplift of folds and thrusts, and therefore appear to be in topographic steady-state with respect to structural uplift since at least 1.7 Ma. Facies analysis using the seismic data showed that the main seismic facies include: (i) channel axes sands and top-channel sands (ii) sheet-sands or crevasse splays (iii) slump deposits and (iv) pelagic drapes. The growth of structures with seabed relief has affected the location of channel avulsion, the locus and the deposition/distribution of sheet-sands (splays). These splays can spill over the growing fault-propagation folds in areas of lower fold growth rates, and absence of seabed scarps; but are completely blocked, and subsequently incorporated onto the limb of a broad detachment fold in the east of the study area as incoming channels are forced to divert through time. This thesis has contributed to the understanding of: (1) Deformation by thrust-related folds that have been growing since ca. 12 Ma, and attained maximum interval growth rates between 9.5 Ma and 3.7 Ma. These maximum growth rates have reduced significantly in the last 3.7 million years during which submarine channels that are generally less than 1.3 million years old also occurred. (2) How modern seabed channels (i.e., recently active channels) have responded to the time-integrated growth of structures along their paths; and the related effect on the positioning of channels pathways, which in-turn, governs the depositional system – especially the distribution of sands in the toe-thrust area of the deepwater Niger Delta. (3) The time-integrated channel system erosivity, the evolution of the channel system geometry and the channel system fill as these systems interact with active structures through time. (4) How submarine channels in the deepwater Niger Delta achieve, and maintain bathymetric steady-state over periods of approximately 1 – 1.3 million years.
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Nävsjö, Dana. "From Threat to Thrill : A Comparative Study of Bram Stoker's Dracula and Stephenie Meyer's Twilight." Thesis, Linköpings universitet, Institutionen för kultur och kommunikation, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-90929.
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The purpose of this essay was to compare the classic vampire narrative, Bram Stoker's Dracula, to a more contemporary vampire narrative using the first book, Twilight, in Stephenie Meyer's Twilight series as a prime example. By looking at the world of the vampire, the figure of the vampire and the interaction between the vampire and the main female characters in each respective story, the goal was to see how much the vampire narrative has evolved. The argument was that the movement from Dracula to Twilight was from an archetypical, terrifying vampire to a more modern, sexually alluring and romantic vampire, where several aspects of terror have been removed. What has been shown is that there are many aspects that have changed once terror is not the focal point. In addition, this essay also argued that in a classroom setting one could use a modern vampire narrative, such as Twilight, to activate pupils’ interest in vampires which would naturally segue into meaningful discussions, comparisons and analyses of the prototypical vampire narrative found in Dracula. As a result, this activity would also encourage students to read literature and explore new worlds
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Gottschal, Espen Joris. "Dynamic Thrust Allocation." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for marin teknikk, 2014. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-26848.
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The purpose of this Thesis is to research the literature of thrust allocation, thruster modelling and maneuvering design, as well as to design and simulate various dynamic thrust allocation algorithms. Vessels with dynamic positioning (DP) systems are high in demand in multiple industries due to their good abilities to keep position. An important component of the DP system is thrust allocation; algorithms which transform desired forces in surge, sway and yaw into thruster setpoints and rotation angles.Two dynamic thrust allocation algorithms are developed, and a simulation model of a model vessel is developed and used to test the thrust allocation algorithms. Findings indicate that the more complex the algorithms are, the more oscillatory the transients become. In addition, numerical instability is a significant concern because of the sensitivity of the barrier function used. Nonetheless, dynamic thrust allocation represents a powerful way to handle saturations.
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Thrift, Brian Douglas. "Summer diets of sheep grazing spotted knapweed-infested foothill rangeland in Western Montana." Thesis, Montana State University, 2005. http://etd.lib.montana.edu/etd/2005/thrift/ThriftB0505.pdf.
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Thrift, Tanya Marie. "Effects of long-term winter-spring grazing on foothill rangeland." Thesis, Montana State University, 2006. http://etd.lib.montana.edu/etd/2006/thrift/ThriftT0506.pdf.
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Wigginton, Sarah S. "The Influence of Mechanical Stratigraphy on Thrust-Ramp Nucleation and Propagation of Thrust Faults." DigitalCommons@USU, 2018. https://digitalcommons.usu.edu/etd/7344.
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Our current understanding of thrust fault kinematics predicts that thrust faults nucleate on low angle, weak surfaces before they propagate upward and forms a higher angle ramp. While this classic kinematic and geometric model serves well in some settings, it does not fully consider the observations of footwall deformation beneath some thrust faults. We examine an alternative end-member model of thrust fault formation called “ramp-first” fault formation. This model hypothesizes that in mechanically layered rocks, thrust ramps nucleate in the structurally strong units, and that faults can propagate both upward and downward into weaker units forming folds at both fault tips. To explore this model, we integrate traditional structural geology field methods, two dimensional cross section reconstructions, and finite element modeling. Field data and retro-deformable cross sections suggest that thrust faults at the Ketobe Knob, in Utah nucleated in strong layers and propagated upward and downward creating folds in weak layers. These findings support the hypothesis that thrust faults and associated folds at the Ketobe Knob developed in accordance with the ramp-first kinematic model.We can apply this understanding of the mechanics behind thrust fault nucleation and propagation in mechanically layered stratigraphy to a wide range of geological disciplines like structural geology and tectonics, seismology, and petroleum geology. By incorporating our knowledge of lithology into fault models, geologists are more likely to correctly interpret structures with limited data sets.
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Rainey, Joseph Daniel, Andrew Brown, Ondrej Dvorak, Michael T. Dzurak, Francisco Olea, and Timur Suleymanov. "Single Door Thrust Recovery Valve." Thesis, The University of Arizona, 2011. http://hdl.handle.net/10150/144923.
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Surles, Donald Matthew. "INTERACTIONS BETWEEN STRUCTURES IN THE APPALACHIAN AND OUACHITA FORELAND BENEATH THE GULF COASTAL PLAIN." UKnowledge, 2007. http://uknowledge.uky.edu/gradschool_diss/554.
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In Alabama, the Paleozoic Appalachian thrust belt plunges southwest beneath the Mesozoic-Cenozoic Gulf Coastal Plain. In Arkansas, the Paleozoic Ouachita thrust belt plunges southeast beneath the Coastal Plain. The strikes of the exposed thrust belts suggest an intersection beneath the Coastal Plain. Well data and seismic reflection profiles confirm the strike and intersection of the thrust belts, and provide information to determine the structure and general stratigraphy of each thrust belt. In east-central Mississippi, the Appalachian thrust belt curves from the regional northeast trace to westward at the intersection with the southeastern terminus of the Ouachita thrust belt, to northwest where Ouachita thrust sheets are in the Appalachian footwall, and farther west, to a west-southwest orientation. At the intersection, the frontal Appalachian fault truncates the Appalachian thrust sheets. The Appalachian thrust sheets are detached in Lower Cambrian strata and contain a distinctive Cambrian-Ordovician passive-margin carbonate succession. The Ouachita thrust sheets are detached above the carbonate succession and contain a thick Carboniferous clastic succession. The Appalachian thrust sheets east of the intersection rest on an autochthonous footwall with a thin Lower Cambrian sedimentary cover above Precambrian crystalline basement. To the west, the Appalachian thrust sheets rest on an allochthonous footwall of thick Ouachita thrust sheets. The top of Precambrian crystalline basement rocks dips southwestward beneath the Ouachita thrust belt; large-magnitude down-to-southwest basement faults enhance the deepening. Appalachian thrust sheets on the northeast are detached above relatively shallow basement, but to the west, are detached above thick Ouachita thrust sheets, which overlie deeper basement. The structure of the basement reflects the Iapetan rifted margin, where the northwest-striking Alabama-Oklahoma transform bounds the southwest side of the Alabama promontory. The trends of basement structures and subsidence toward the Ouachita thrust belt parallel the Alabama-Oklahoma transform. Shallower basement and synrift basement grabens underlie the northeast-striking Appalachian thrust belt. The curves in strike and along-strike change in footwall structure of the Appalachian thrust belt reflect controls by basement structure and by the structure of the Ouachita thrust belt.
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McEachern, Sally J. (Sally Jane) Carleton University Dissertation Geology. "Structure and U-PB geochronology of the Pembroke thrust stack, central metasedimentary belt boundary thrust zone." Ottawa, 1990.
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Erdem, Erinc. "Thrust Vector Control By Secondary Injection." Master's thesis, METU, 2006. http://etd.lib.metu.edu.tr/upload/12607560/index.pdf.
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A parametric study on Secondary Injection Thrust Vector Control (SITVC) has been accomplished numerically with the help of a commercial Computational Fluid Dynamics (CFD) code called FLUENT®. This study consists of two parts
the first part includes the simulation of three dimensional flowfield inside a test case nozzle for the selection of parameters associated with both computational grid and the CFD solver such as mesh size, turbulence model accompanied with two different wall treatment approaches, and solver type. This part revealed that simulation of internal flowfield by a segregated solver with Realizable k-&
#949
(Rke) turbulence model accompanied by enhanced wall treatment approach is accurate enough to resolve this kind of complex three dimensional fluid flow problems. In the second part a typical rocket nozzle with conical diverging section is picked for the parametric study on injection mass flow rate, injection location and injection angle. A test matrix is constructed
several numerical simulations are run to yield the assessment of performance of SITVC system. The results stated that for a nozzle with a small divergence angle, downstream injections with distances of 2.5-3.5 throat diameters from the nozzle throat lead to higher efficiencies over a certain range of total pressure ratios, i.e., mass flow rate ratios, upstream injections should be aligned more to the nozzle axis, i.e., higher injection angles, to prevent reflection of shock waves from the opposite wall and thus low efficiencies. Injection locations that are too much downstream may result reversed flows on nozzle exit.
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Wold, Henrik Emil. "Thrust allocation for DP in ice." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for teknisk kybernetikk, 2013. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-22354.
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The commercial industry has initiated work on how to make it feasible to enter the Arctic seas. Ice loads affects most aspects of the Arctic operation, and the marine crafts must be able to handle them all. The DP control system, and thus the thrust allocation, is not designed to handle ice loads and will not work properly \cite{Moran}. The main purpose of this master thesis is to enhance the thrust allocation for handling ice loads. This is done by including thruster dynamics and adding thruster ice clearance by thruster wake. When the ice loads are too high for the DP system to handle, a prioritization of the degrees of freedom is included to achieve predictable degradation of performance. To predict possible drift-offs, energy analysis will be used to investigate if the control forces integrated over time contain enough energy to withstand the ice loads.The thrust allocation is based on numerical optimization and implemented in $Matlab$. To make the thrust allocation more realistic, thruster dynamics are added. The first method is to low-pass filter the control forces, and the second is to add restrictions on the change of control forces. To clear the ice away from the hull, thruster ice clearance is implemented. The first solution is to let the algorithm calculate the azimuth angles within predefined sectors, and secondly to force the azimuth thrusters to follow predefined references in control forces and azimuth angles.A case study is done to investigate the performance of the thrust allocation algorithm, where towing tank measurement data from CIV Arctic is used as input. To measure the performance of the thrust allocation, the magnitude of the slack term, $\bm{s}^\top \bm{Q} \bm{s}$, gives a first impression. For further investigation, the error between the forces and moments from the ice loads and the achieved forces and moments from the thrust allocation is used. The results from the case study indicated that when the ice loads were high, the prioritization of degrees of freedom was followed. Both with and without thruster dynamics the error in produced thrust was less than 8 [\%] for small ice conditions, but increased rapidly for 1.2 [m] of ice. The thruster dynamics did not increase the error significantly, except an increase in yaw error for light ice conditions when the low-pass filter was applied. By adding thruster ice clearance, the error in produced thrust increased. Corresponding results were found for the energy considerations. The chosen thrust allocation algorithm gave satisfactory results. By decreasing the ice concentrations, for instance by using ice management, the performance was improved. Adding restrictions on the change of control forces was found to be the best way of including thruster dynamics, because then the restrictions were implicit in the thrust allocation algorithm. Two solutions were also proposed for implementing thruster ice clearance. By letting the thrust allocation find the azimuth angles, the performance of the algorithm was better than by forcing the control forces and azimuth angles to follow predefined references. In spite of this, the second solution was found to be the best in practice because the vessel operator has more control over the thrusters. Some recommendations for future work are to include all the components of the DP control system, do a more advanced implementation of the thruster dynamics and a more detailed energy analysis.
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Orr, Jeb S. "High efficiency thrust vector control allocation." Thesis, The University of Alabama in Huntsville, 2013. http://pqdtopen.proquest.com/#viewpdf?dispub=3561548.
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The design of control mixing algorithms for launch vehicles with multiple vectoring engines yields competing objectives for which no straightforward solution approach exists. The designer seeks to optimally allocate the effector degrees of freedom such that maneuvering capability is maximized subject to constraints on available control authority. In the present application, such algorithms are generally restricted to linear transformations so as to minimize adverse control-structure interaction and maintain compatibility with industry-standard methods for control gain design and stability analysis. Based on the application of the theory of ellipsoids, a complete, scalable, and extensible framework is developed to effect rapid analysis of launch vehicle capability. Furthermore, a control allocation scheme is proposed that simultaneously balances attainment of the maximum maneuvering capability with rejection of internal loads and performance losses resulting from thrust vectoring in the null region of the admissible controls. This novel approach leverages an optimal parametrization of the weighted least squares generalized inverse and exploits the analytic properties of the constraint geometry so as to enable recovery of more than ninety percent of the theoretical capability while maintaining linearity over the majority of the attainable set.
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Стасюк, Роман Миколайович, Роман Николаевич Стасюк, and Roman Mykolaiovych Stasiuk. "Motivational thrust process of physical education." Thesis, Sumy State University, 2015. http://essuir.sumdu.edu.ua/handle/123456789/48663.
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Contents of sports activities specified through motivational sphere that includes motives, interests , values. By driving forces of human behavior are also feelings and emotions. Motivational scope determines not only the important activities carried out, but the prospect of further development activities in the desired direction. In educational research aimed at studying and improving physical education students in higher education institutions tend to analyze some one side of the problem – " teaching" or " student ". Such a one-way analysis of physical education in higher education inevitably leads to conclusions eclectic and cannot be considered and refine it as a dialectical process , where the " subject- object" should be seen as poles self-governing system that self-developing . In theory and practice of physical education insufficiently studied educational conditions of the conscious attitude of students towards physical education, it is impossible to create and implement without the closest personal cooperation between teachers and students.
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Ashley, John. "Aft-deck coflow fluidic thrust vectoring." Thesis, University of Manchester, 2013. https://www.research.manchester.ac.uk/portal/en/theses/aftdeck-coflow-fluidic-thrust-vectoring(7ed7af9a-1970-4126-a9d5-fa33d1b024a9).html.
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Gillis, Robert W. "Low-Thrust Assited Angles-Only Navigation." DigitalCommons@USU, 2011. https://digitalcommons.usu.edu/etd/1001.
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Tradition spacecraft proximity operations require large and expensive on-board sensors and significant ground support. Relative angle measurements can be obtained from small, simple, and inexpensive on-board sensors, but have not traditionally been used for proximity operation because of difficulty generating rang information. In this thesis it is shown that useful relative range data can be generated provided that the spacecraft is experiencing a small continuous thrust such as would be provided by a low-thrust propulsion system.
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Cook, Brian Stephen. "PALINSPASTIC RECONSTRUCTION AROUND A THRUST BELT RECESS: AN EXAMPLE FROM THE APPALACHIAN THRUST BELT IN NORTHWESTERN GEORGIA." UKnowledge, 2010. http://uknowledge.uky.edu/gradschool_diss/5.
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In a well-defined subrecess in the Appalachian thrust belt in northwestern Georgia, two distinct regional strike directions intersect at approximately 50°. Fault intersections and interference folds enable tracing of both structural strikes. Around the subrecess, tectonically thickened weak stratigraphic layers—shales of the Cambrian Conasauga Formation—accommodated ductile deformation associated with the folding and faulting of the overlying Cambrian–Ordovician regional competent layer. The structures in the competent layer are analogous to those over ductile duplexes (mushwads) documented along strike to the southwest in Alabama.
The intersection and fold interference exemplify a long-standing problem in volume balancing of palinspastic reconstructions of sinuous thrust belts. Cross sections generally are constructed perpendicular to structural strike, parallel to the assumed slip direction. An array of cross sections around a structural bend may be restored and balanced individually; however, restorations perpendicular to strike across intersecting thrust faults yield an imbalance in the along-strike lengths of frontal ramps. The restoration leads to a similar imbalance in the surface area of a stratigraphic horizon, reflecting volume imbalance in three dimensions.
The tectonic thickening of the weak-layer shales is evident in palinspastically restored cross sections, which demonstrate as much as 100% increase in volume over the restored-state cross sections. The cause of the surplus shale volume is likely prethrusting deposition of thick shale in a basement graben that was later inverted. The volume balance of the ductile duplex is critical for palinspastic reconstruction of the recess, and for the kinematic history and mechanics of the ductile duplex.
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Overby, Kyle Eugene. "Field based study of thrust faults in the Appalachian Valley and Ridge Province Newport, Virginia." Thesis, Virginia Tech, 2016. http://hdl.handle.net/10919/64983.
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This study focuses on a series of thrust sheets exposed in the Appalachian Valley and
Ridge Province Blacksburg-Pembroke area in southwest Virginia. Structures in the hanging wall of the Saltville thrust (Saltville thrust sheet) and the footwall of the Saltville thrust (Narrows
thrust sheet) are examined. The first part of this study involves the construction of a series of
thrust transport-parallel 1:24,000 scale geologic cross sections to constrain the subsurface
geometry of fault and fold structures within the Saltville and Narrows thrust sheets. The second part of the study involves an outcrop-scale study of geologic structures exposed along a series road cuts in the footwall of the Saltville thrust and the geometric and relative timing relationships between folding, cleavage formation and thrust faulting.
The cross sections show a series of interconnected splay faults branching off of the
Saltville thrust and cutting both its hanging wall and footwall. Angle of dip and magnitude of
dip-slip displacement on thrust and splay faults progressively decrease from hinterland to
foreland within this fault system that is referred to as the Spruce Run Mountain-Newport
(SRMN) fault system. Bedding within this fault system essentially forms a structural transition
zone between the Saltville and Narrows thrust sheets, defining a km-scale fractured synform-antiform fold structure that has many structural attributes usually associated with fault propagation folding.
In the road cut outcrops, early meter-scale faults are folded by later foreland-(NW)
vergent folds. Although cleavage defines convergent cleavage fans about these folds, subtle
obliquities between folds and cleavage indicate that folding post-dates early layer-parallel
shortening and associated foreland-vergent thrusting.Master of Science
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Hackaday, Gary L. "Thrust augmentation for a small turbojet engine." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1999. http://handle.dtic.mil/100.2/ADA362981.
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Thesis (M.S. in Aeronautical Engineering) Naval Postgraduate School, March 1999.Thesis advisor(s): Garth V. Hobson. "March 1999". Includes bibliographical references (p. 75). Also available online.
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Bergsek, Mattias. "THRUST PREDICTION PROGRAM FOR MARINE JET POWER." Thesis, KTH, Marina system, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-77794.
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Marine Jet Power, MJP wishes to investigate the possibility of transforming their current Thrust Prediction Program, TPP written in C++ source code into a more up to date tool for their sales staff. The old TPP, though an accurate and precise tool, is not documented and lacks commentaries in the source code. Therefore the beginning of this master thesis was about documenting and investigates what methods were used to calculate the performance of the water jet system.The next step was splitting the long C++ source code in to smaller functions, this was done using MatLab where several m-files were created with the different functions in. C++ syntax and structure differs from MatLab so the source code must be translated in to MatLab syntax. Once the new TPP was translated and the calculation results were identical with the old TPP a Graphical User Interface, GUI was created and presented to MJP. The current MatLab TPP is not finished, only two of four calculation modes have been translated and MJP wants modifications in the GUI. The additional work needed in order to have the sales tool MJP wishes is currently discussed.
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Barbullushi, Roland. "Tertiary Thrust Belt Evolution Of Southern Albania." Thesis, Imperial College London, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.486276.
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The southern Albania thrust belt comprises Mesozoic - Eocene carbonate sequences incorporated into three major Tertiary thrust sheets verging towards the Apulia foreland in the southwest. The problem of the structural evolution has been previously approached through a hypothesis of orthogonal thin-skinned thrusting controlled by a differential areal extent ofPermo-Triassic evaporites. This thesis uses the interpretation of several seismic profiles to address questions such as those relating to the subsurface geometric patterns ofthe thrust sheets, the kinematic framework the evaporites operated in, the role ofthe pre-existing faults and the timing ofthe evolution. The interpretation demonstrates that significant along - strike changes characterize the subsurface geometry of the thrust sheets. The Permo-Triassic evaporites facilitated their buttressing against a buffer zope in the Apulian foreland primarily within an orthogonal compression regime. Regional clockwise rotation about a pivot point to the north may have provided a transpressional component along the thrusts. Pre-existing normal faults played a significant role on thrusting and accomodation of the strain partitioning. The main structural events included thin-skinned thrusting during Oligocene - Aquitaniane, formation of a buffer zone in the forelarni during Burdigalian and subsequent thrust - buttressing during the Miocene. Post - Pliocene deformation occurs in the foredeep basin.
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Goyal, Gaurav. "Drag and thrust effects of Viscoelastic fluids." Thesis, University of British Columbia, 2016. http://hdl.handle.net/2429/60135.
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Viscoelastic fluids are non-Newtonian fluids exhibiting both viscous and elastic properties. Many fluids of practical importance (polymers, surfactants, mucus, shampoos etc.) display viscoelastic effects to different degrees under a wide range of flow conditions and thus, these fluids present a variety of problems. In this work, we study two problems at very different flow conditions in viscoelastic fluids: a) the effect of swimming gait on bio-locomotion and b) characterizing the drag reducing fluids used for gravel-packing operations in the petroleum industry. For the first problem, we give formulas for the swimming of simplified two-dimensional bodies at low Reynolds numbers in complex fluids using the reciprocal theorem. By way of these formulas, we calculate the swimming velocity due to small-amplitude deformations on the simplest of these bodies, a two-dimensional sheet, to explore general conditions on the swimming gait under which the sheet may move faster, or slower, in a viscoelastic fluid compared to a Newtonian fluid. We show that in general, for small amplitude deformations, a speed increase can only be realized by multiple deformation modes in contrast to slip flows. Additionally, we show that a change in swimming speed is directly due to a change in thrust generated by the swimmer. Later, we work with viscoelastic additives (xanthan and a zwitterionic viscoelastic surfactant, VES), widely used as drag reducers for gravel-packing applications. While the behavior of xanthan is well characterized in the literature, much less is known about the VES characteristics, despite widespread use. We performed a number of rheological tests and flow-loop experiments on VES solutions to understand the structural characteristics to make better process predictions. Unlike xanthan, which displays typical viscoelastic liquid characteristics, VES displays elastic gel-like behaviour. The gel-like behaviour suggests long and relatively unbreakable chain lengths of the wormlike micelles in the VES at room temperature leading to gelation by entanglement. Also, a shear-thickening behaviour of VES samples at higher shear rates is observed, possibly as a result of shear-induced structures. Finally, we present a novel representation scheme to depict the flow-loop results relating the rheological characterization while observing drag reduction.Applied Science, Faculty of
Graduate
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Harl, Nathan Robert. "Low-thrust control of a lunar orbiter." Diss., Rolla, Mo. : University of Missouri-Rolla, 2007. http://scholarsmine.mst.edu/thesis/pdf/Thesis_09007dcc80318673.pdf.
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Thesis (M.S.)--University of Missouri--Rolla, 2007.Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed October 24, 2007) Includes bibliographical references (p. 95-98).
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Bowler, S. "Deformation processes and strain in thrust systems." Thesis, University of Leeds, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.379086.
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Maany, Z. A. "The optimisation of low thrust satellite trajectories." Thesis, University of Hertfordshire, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.375090.
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Riley, Dominic John. "Applications of numerical modelling to thrust tectonics." Thesis, University of Southampton, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.242321.
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Di, Carlo Marilena. "Multi-fidelity global low-thrust trajectory optimisation." Thesis, University of Strathclyde, 2018. http://digitool.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=30754.
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This research work presents methods and techniques for multi-fidelity global optimisation of low-thrust trajectories. In the early stages of the definition of a space mission, tools that can provide a fast and preliminary estimation of the cost of low-thrust transfers are required; a more accurate optimisation process of the trajectories is left for subsequent phases. Therefore, models of different levels of fidelity are needed, based on the current phase of the design and on the desired accuracy. An efficient global optimisation algorithm has then to be used in conjunction with these models, in order to identify the global optimal solution to a given problem. The development of multi-fidelity methods, of an efficient global optimisation algorithm and their application for the solution of low-thrust global optimisation problems, are addressed in this thesis. The lower fidelity models consist of analytical laws for the cost of low-thrust transfers. Higher fidelity innovative laws for transfers between Earth's orbits have been derived. Moreover, a set of analytical equations for the motion of the spacecraft subject to low-thrust acceleration and orbital perturbations is presented. These models are used in conjunction with a novel adaptive multi-population global optimisation algorithm, validated using several test functions and real world problems. To allow for the use of the global solver with higher fidelity, and therefore computationally more expensive models, the use of surrogate model for low-thrust transfer is proposed. Various applications are presented where these tools and methods are successfully applied, and that represent an original scientific contribution. Missions have been designed to deorbit objects from Low Earth Orbit and deploy a constellation in Medium Earth Orbit. The optimisation of a transfer from Geostationary Transfer Orbit to Geosynchronous Orbit is also presented. Interplanetary applications include missions to visit the asteroids of the inner solar system and of the main belt.
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Mirczak, Jareb D. (Jareb Douglas) 1979. "Milli-Newton thrust stand for electric propulsion." Thesis, Massachusetts Institute of Technology, 2003. http://hdl.handle.net/1721.1/82768.
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Block, Philippe (Philippe Camille Vincent). "Thrust Network Analysis : exploring three-dimensional equilibrium." Thesis, Massachusetts Institute of Technology, 2009. http://hdl.handle.net/1721.1/49539.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Architecture, 2009.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Includes bibliographical references (p. 145-153).
This dissertation presents Thrust Network Analysis, a new methodology for generating compression-only vaulted surfaces and networks. The method finds possible funicular solutions under gravitational loading within a defined envelope. Using projective geometry, duality theory and linear optimization, it provides a graphical and intuitive method, adopting the same advantages of techniques such as graphic statics, but offering a viable extension to fully three-dimensional problems. The proposed method is applicable for the analysis of vaulted historical structures, specifically in unreinforced masonry, as well as the design of new vaulted structures. This dissertation introduces the method and shows examples of applications in both fields. Thrust Network Analysis, masonry, historic structures, compression-only structures, limit analysis, equilibrium analysis, funicular design, form-finding, structural optimization, Gothic vaults, reciprocal diagrams.
by Philippe Block.
Ph.D.
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Baig, Shahid. "Non-Keplerian orbits for low-thrust propulsion." Thesis, University of Strathclyde, 2009. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=25745.
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Zuiani, Federico. "Multi-objective optimisation of low-thrust trajectories." Thesis, University of Glasgow, 2015. http://theses.gla.ac.uk/6311/.
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This research work developed an innovative computational approach to the preliminary design of low-thrust trajectories optimising multiple mission criteria. Low-Thrust (LT) propulsion has become the propulsion system of choice for a number of near Earth and interplanetary missions. Consequently, in the last two decades a good wealth of research has been devoted to the development of computational method to design low-thrust trajectories. Most of the techniques, however, minimise or maximise a single figure of merit under a set of design constraints. Less effort has been devoted to the development of efficient methods for the minimisation (or maximisation) of two or more figures of merit. On the other hand, in the preliminary mission design phase, the decision maker is interested in analysing as many design solutions as possible against different trade-off criteria. Therefore, in this PhD work, an innovative Multi-Objective (MO), memetic optimisation algorithm, called Multi-Agent Collaborative Search (MACS2), has been implemented to tackle low-thrust trajectory design problems with multiple figures of merit. Tests on both academic and real-world problems showed that the proposed MACS2 paradigm performs better than or as well as other state-of-the-art Multi-Objective optimisation algorithms. Concurrently, a set of novel approximated, first-order, analytical formulae has been developed, to obtain a fast but reliable estimation of the main trade-off criteria. These formulae allow for a fast propagation of the orbital motion under a constant perturbing acceleration. These formulae have been shown to allow for the fast and relatively accurate propagation of long LT trajectories under the typical acceleration level delivered by current engine technology. Various applications are presented to demonstrate the validity of the combination of the analytical formulae with MACS2. Among them, the preliminary design of the JAXA low-cost DESTINY mission to L2, a novel approach to the optimisation under uncertainty of deflection actions for Near Earth Objects (NEO), and the de-orbiting of space debris with low-thrust and with a combination of low-thrust and solar radiation pressure.
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McCarthy, Martin. "Contra-rotating open rotor reverse thrust aerodynamics." Thesis, Cranfield University, 2011. http://dspace.lib.cranfield.ac.uk/handle/1826/10448.
Full textAbstract:
Reverse thrust operations of a model scale Contra-Rotating Open Rotor design were
numerically modelled to produce individual rotor thrust and torque results comparable
to experimental measurements. The aims of this research were to develop an
understanding of the performance and aerodynamics of open rotors during thrust
reversal operations and to establish whether numerical modelling with a CFD code can
be used as a prediction tool given the highly complex flowfield.
A methodology was developed from single rotor simulations initially before building a
3D‘frozen rotor’ steady-state approach to model contra-rotating blade rows in reverse
thrust settings. Two different blade pitch combinations were investigated (β1,2 =+30°,-
10° and β1,2 =-10°,-20°). Thrust and torque results compared well to the experimental
data and the effects of varying operating parameters, such as rpm and Mach number,
were reproduced and in good agreement with the observed experimental behaviour. The
main flow feature seen in all the reverse thrust cases modelled, both single rotor and
CROR, is a large area of recirculation immediately downstream of the negative pitch
rotor(s).This is a result of a large relative pressure drop region generated by the suction
surfaces of the negative pitch blades.
An initial 3D unsteady sliding-mesh calculation was performed for one CROR reverse
thrust case. The thrust and torque values were in poor agreement with experimental
values and the disadvantages relating to time costs and required computational
resources for this technique were illustrated. However, the results did yield a nominal
unsteady variation of thrust and torque due to rotor phase position.
Overall the work shows that it may be possible to develop a CROR reverse thrust
prediction tool of beneficial quality using CFD models. The research also shows that the
frozen rotor approach can be adopted without undermining the fidelity of the results.
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Greenhalgh, Scott Royal. "Along Strike Variability of Thrust-Fault Vergence." BYU ScholarsArchive, 2014. https://scholarsarchive.byu.edu/etd/4095.
Full textAbstract:
The kinematic evolution and along-strike variation in contractional deformation in overthrust belts are poorly understood, especially in three dimensions. The Sevier-age Cordilleran overthrust belt of southwestern Wyoming, with its abundance of subsurface data, provides an ideal laboratory to study how this deformation varies along the strike of the belt. We have performed a detailed structural interpretation of dual vergent thrusts based on a 3D seismic survey along the Wyoming salient of the Cordilleran overthrust belt (Big Piney-LaBarge field). The complex evolution of the thrust faults that parallel the overthrust belt is demonstrated by the switching of the direction of thrust fault vergence nearly 180° from east to west. The variation in thrust-fault geometry suggests additional complexities in bulk translation, internal strains, and rotations. The thrust zone is composed of two sub-zones, each with an opposing direction of fault vergence, located on the eastern toe of the Hogsback thrust in southwestern Wyoming. The northern west-vergent thrust is a wedge thrust and forms a triangle zone between its upper thrust plane and the lower detachment that has formed in a weak shale layer (the Cretaceous K-Marker bed). Thrusts to the south have a frontal ramp geometry and are consistent with the overall thrust orientation of the Cordilleran overthrust belt located immediately to the west. The two thrust sub-zones are small, relative to the main Hogsback thrust to the west, and adjacent to each other, being separated by a transfer zone measuring in the hundreds of meters along strike. The transfer zone is relatively undisturbed by the faults (at the scale of seismic resolution), but reflections are less coherent with some very small offsets. The thrusts are thin-skinned and located above a shallow-dipping single detachment (or décollement) that is shared by faults in both sub-zones. Lateral growth of the thrust faults link along strike to form an antithetic fault linkage. Structural restoration of thrust faults shows varied amounts of shortening along strike as well as greater shortening in stratigraphic layers of the west-vergent fault to the north. Results from a waveform classification and spectral decomposition attribute analysis support our interpretations of how the variations in the detachment may govern the structural development above it. The kinematic evolution of the dual-verging thrust faults is likely controlled by local pinning within the transfer zone between the thrust-fault sub-zones as well as by changes in the competence of the strata hosting the detachment and in the thickness of the thrust sheet. The analysis and interpretation of dual-vergent thrust structures in the Cordilleran overthrust belt serve as an analog to better understand complex fold, fault, and detachment relations in other thrust belts.
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Case, William Scott. "AEROSPIKE THRUST VECTORING SLOT-TYPE COMPOUND NOZZLE." DigitalCommons@CalPoly, 2010. https://digitalcommons.calpoly.edu/theses/316.
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A study of thrust vectoring techniques of annular aerospike nozzles was conducted. Cold-flow blow-down testing along with solid modeling and rapid prototyping technology were used to investigate the effects of slot size, placement, geometry and orientation. The use of slot-type compound nozzles proved to be a feasible approach to thrust vectoring. Previous methods of thrust vectoring have proved to be difficult to implement in a cost effective manner or have had limited effectiveness or durability.
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Beebe, Stanley Ikuo. "HOLE-TYPE AEROSPIKE COMPOUND NOZZLE THRUST VECTORING." DigitalCommons@CalPoly, 2009. https://digitalcommons.calpoly.edu/theses/164.
Full textAbstract:
Compound aerospike nozzles were designed and tested as part of an ongoing
experimental study to determine the feasibility of thrust vectoring an aerospike
nozzle with the addition of a secondary port. Earlier phases of the study have
indicated that a compound aerospike nozzle could provide sufficient thrust
vectoring. The addition of a hole-type secondary port was found to provide
effective thrust vectoring.
Experiments were carried out to determine the effects of secondary port size,
secondary port inlet geometry and compound aerospike nozzle chamber
pressure. Results show good predictability, axisymmetric flow, and emphasize
the importance of a radius on secondary port inlet geometry.
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Nyberg, Ludwig. "Thrust Allocation for Jet Driven Surface Vessels." Thesis, KTH, Mekatronik, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-271905.
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Dynamic positioning systems have been under development since the first implementation in the early 1960s. The purpose of a dynamic position system is to allow for automatic positioning of a vessel when circumstances do not allow for mooring or anchoring. Historically the development has been driven forward by the offshore industry, while in recent years such systems have been found useful in other parts of the maritime industry as well. However, very few options exist today for jet driven vessels. One of the main parts of a dynamic positioning system is the control allocation. The purpose of this part is to allocate desired actuation to available actuators. It is often desirable to do this while considering a secondary objective, often energy consumption. One allocation algorithm option is direct allocation, which is considered to be quite a basic solution. More advanced options exist in the literature but implementations of them are still uncommon. An example of a more advanced option, allowing for better tuning, is using model-based allocators. Formulating the allocation problem as a linear quadratic problem and using a linear quadratic regulator is one viable option that has been proven to work well for non-jet driven vessels. A general vessel model is developed and used for simulating and testing different allocators. Furthermore, a method for transforming the allocated actuation into parameters that can control the jet engine is also proposed. This is a necessary step in order to be able to implement the allocation onto a vessel. Comparing the allocation options based on step responses with and without disturbances shows that the linear quadratic regulator preforms better than the direct allocator in almost every way. However, the main drawback of model-based controllers is the needed knowledge about the system. This is something that is not required for the direct allocator and is worth taking into account.Dynamiska positioneringssystem har vart under utveckling sedan den första implementeringen i början av 1960-talet. Syftet med ett dynamiskt positioneringssystem är att möjliggöra automatisk positionering av ett fartyg när omständigheterna inte tillåter förtöjning eller förankring. Historiskt har utvecklingen drivits framåt av behovet inom offshoreindustrin, men under senare år har systemen visat sig vara användbara även i andra delar av den marina industrin. Idag finns dock få alternativ anpassade för jetdrivna fartyg. En av huvuddelarna i ett dynamiskt positioneringssystem är kraftallokering. Syftet med denna del är att fördela önskad styrkraft till tillgängliga ställdon. Ofta är det önskvärt att göra detta samtidigt som ett sekundärt mål tas hänsyn till, vanligtvis energiförbrukning. Ett alternativ för kraftallokering är en direkt allokeringsalgoritm, detta är en ganska enkel algoritm. Mer avancerade alternativ finns i litteraturen, men implementerade exempel är fortfarande ovanliga. Ett exempel på ett mer avancerat alternativ, som möjliggör bättre anpassning, är att använda modellbaserade algoritmer. Att formulera allokeringsproblemet som ett linjärt kvadratiskt problem och använda en linjär kvadratisk regulator är ett alternativ som har visat sig fungera bra för icke jetdrivna fartyg. En generell fartygsmodell utvecklas och anvnnds för att simulera och testa de olika allokeringsalgoritmerna. Vidare föreslås en metod för att omvandla den allokerade styrkraften till parametrar som kan styra jetmotorerna. Detta är ett nödvändigt steg för att, i slutändan, kunna implementera styrkrafterna på ett riktigt fartyg. En jämförelse av allokeringsalgoritmer baserade på stegsvar med och utan störningar visar att den linjära kvadratiska regulatorn hanterar de uppsatta testfallen bättre än den direkta allokeraren. Däremot dras den modellbaserade algoritmen med det problemet att omfattande kunskapen krävs angående systemets dynamik. Detta är något som inte krävs för direktallokeraren och är värt att ta hänsyn till.
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Eckert, Christine. "Stereotype Threat." Ruprecht-Karls-Universität, 2014. https://ul.qucosa.de/id/qucosa%3A15350.
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Stereotype Threat wird definiert als ein Gefühl der Bedrohung, das Personen in einer Situation erleben, in der sie befürchten, aufgrund eines negativen Stereotyps über ihre Gruppe beurteilt zu werden bzw. durch ihr Verhalten das Stereotyp unbeabsichtigterweise zu bestätigen. Der Begriff geht auf Claude M. Steele und Joshua Aronson zurück. Stereotype Threat kann als ein situatives Dilemma bezeichnet werden, das bei Mitgliedern stigmatisierter Gruppen in Testsituationen kurzfristig zu signifikanten Leistungseinbußen führen kann. Es kann auch bei anderen Wahlentscheidungen auftreten. Empirisch gesicherte Befunde für die längerfristigen Auswirkungen liegen bisher kaum vor. Auch die auslösenden Bedingungen sind nicht abschließend geklärt.
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Eckert, Christine. "Stereotype Threat." Universitätsbibliothek Leipzig, 2017. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-219437.
Full textAbstract:
Stereotype Threat wird definiert als ein Gefühl der Bedrohung, das Personen in einer Situation erleben, in der sie befürchten, aufgrund eines negativen Stereotyps über ihre Gruppe beurteilt zu werden bzw. durch ihr Verhalten das Stereotyp unbeabsichtigterweise zu bestätigen. Der Begriff geht auf Claude M. Steele und Joshua Aronson zurück. Stereotype Threat kann als ein situatives Dilemma bezeichnet werden, das bei Mitgliedern stigmatisierter Gruppen in Testsituationen kurzfristig zu signifikanten Leistungseinbußen führen kann. Es kann auch bei anderen Wahlentscheidungen auftreten. Empirisch gesicherte Befunde für die längerfristigen Auswirkungen liegen bisher kaum vor. Auch die auslösenden Bedingungen sind nicht abschließend geklärt.
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Pearson, Ofori. "Structural evolution of the central Nepal fold-thrust belt and regional tectonic and structural significance of the Ramgarh thrust." Diss., The University of Arizona, 2002. http://hdl.handle.net/10150/280143.
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Tectonic shortening within the Himalayan fold-thrust belt in Nepal has been accommodated by southward displacement of large thrust sheets. Most workers focus on the impact that the Main Central, Main Boundary, and Main Frontal thrusts have had on the orogen's structural, thermal, and geomorphic evolution. However, mapping across Nepal, has revealed the presence of the Ramgarh thrust, which is another orogen-scale thrust. The Ramgarh thrust, which had previously been recognized in India and far-western Nepal, occurs within Lesser Himalayan zone rocks, and accommodates a magnitude of shortening similar to that of the Main Central thrust. This dissertation focuses on the structural and tectonic significance of the Ramgarh thrust. Minor details notwithstanding, the structural characteristics of the Ramgarh thrust remain consistent along the ∼800 km width of the fold-thrust belt in Nepal. At current levels of erosion, the Ramgarh thrust is always exposed in a hanging-wall flat on footwall flat thrust relationship with other Lesser Himalayan zone rocks, and also with overlying rocks carried by the Main Central thrust. Mapping along a north-south transect in central Nepal has permitted the construction of a balanced cross-section, which shows that the fold-thrust belt has accommodated a minimum of 489 km of tectonic shortening. A large proportion of which was accommodated by slip on the Ramgarh thrust. Integrating structural constraints provided by mapping and the cross-section with existing thermochronologic, thermobarometric, and foreland basin provenance datasets yields a kinematic model for the structural evolution of the fold-thrust belt. Recognition of the structural relationship between the Ramgarh and Main Central thrusts also permits new insight into the nature of the Main Central thrust. Structural mapping combined with Nd isotope studies from the vicinity of the Ramgarh and Main Central thrusts in Langtang National Park suggest that the Main Central thrust can be defined as a relatively narrow tectonostratigraphic contact, and not as a broad, poorly defined, shear zone. Additionally, much of the volume of highly strained rocks in the footwall of the Main Central thrust may be genetically related to deformation on faults (including the Ramgarh thrust) that lie structurally below the Main Central thrust.
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Ruth, Eivind. "Propulsion control and thrust allocation on marine vessels." Doctoral thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for marin teknikk, 2008. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-2335.
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Milton, Johan, and Henrik Johansson. "Development of Trent 700 Thrust Reverser Overhaul Package." Thesis, Mälardalens högskola, Akademin för innovation, design och teknik, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:mdh:diva-12492.
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This report describes a thesis project in aeronautical engineering carried out during April and May 2011 at ST Aerospace Solutions, Arlanda. The company is one of Europe’s leading aviation component maintenance companies. The task for this thesis project has been to develop a baseline overhaul work package for the thrust reverser system of the Rolls-Royce Trent 700 jet engine. An overhaul work package is a collection of maintenance work sheets (MWS) used by the maintenance organization to confirm that a specific maintenance procedure has been carried out correctly. Documenting the maintenance work performed on a component is required in order to comply with the regulations of the European Aviation Safety Agency (EASA). To be able to solve the task, the authors had to study maintenance manuals, learn the functions of the thrust reverser and get an overview of how the maintenance organization works. Much of the work has been conducted in consultation with the company’s engineering department. The result is an overhaul package consisting of approximately 40 MWS’s. These have been designed to promote traceability of actions and to be easily revisable.Denna rapport är resultatet av ett examensarbete i flygteknik som genomförts under våren 2011. Arbetet utfördes hos ST Aerospace Solutions, ett av Europas ledande företag för komponentunderhåll inom flygindustrin. Uppgiften har varit att utveckla ett översynspaket för reverseringssystemet på Rolls-Royce jetmotor Trent 700. Ett översynspaket består av en uppsättning dokument, så kallade ”maintenance work sheets” (MWS), som används för att säkerställa att underhållsorganisationen har utfört det underhåll som krävs. Detta är ett krav enligt den Europeiska luftfartsmyndigheten EASA:s Part 145. Metodiken har främst bestått i att sätta sig in i relaterad dokumentation och underhållsmanualer, samt att skapa sig en förståelse för hur reverseringssystemet och underhållsorganisationen är uppbyggda. Större delen av arbetet har utförts på plats för att kunna samarbeta och diskutera med företagets ingenjörs- och verkstadsavdelningar. Slutresultatet är ett översynspaket som innehåller ca 40 MWS:er, vilka behandlar hela underhållsprocessen. Paketet har utformats med god spårbarhet och reviderbarhet i åtanke.
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Aorpimai, Manop. "Low-thrust orbit control of LEO small satellites." Thesis, University of Surrey, 2000. http://epubs.surrey.ac.uk/843024/.
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In this thesis, we investigate the orbit control strategies of small satellites in Low Earth Orbits (LEO) where the disturbance effects are significant, in particular the nonspherical Earth and atmospheric drag effects. These orbits are not suitable to be controlled by using traditional ground-based control strategies which generally require high-thrust propulsion systems and other expensive resources, both onboard and in the ground segment. In order to react to those disturbances spontaneously and keep a small satellite at a pre-defined station using its limited resources, autonomous orbit control technology needs to be enabled. With the current advances in navigation and propulsion technology, as well as onboard computation systems, the only key issue that needs further investigations for practical implementation of an autonomous orbit operation system is the control algorithm. The orbit control strategies we investigate here are treated separately for each of the orbital control phases, i.e. orbit deployment and acquisition, orbit transfer and orbit maintenance. We present various forms of the solutions of the epicycle motion which allow us to treat each control problem according to the control requirements, nature of perturbations, control time scales and available resources. Although applied in different manners, the optimal low-thrust control scheme is a common aim for all control problems investigated here, as we mainly focus upon applications for low cost small satellites in LEO. The verifications of the strategies proposed in this thesis have been demonstrated not only via computer simulations, but also successfully demonstrated on in-orbit small satellite platforms thanks to an active small satellite programme at Surrey Space Centre. The success of this study is hoped to provide a valuable basis for satellite orbit operations which will involve larger number of satellites with more complex configurations in the future.
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Cotton, James Timothy. "Salt tectonics in compressional fold and thrust belts." Thesis, Imperial College London, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.267734.
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Ashman, D. "High-speed performance of a hydrostatic thrust bearing." Thesis, University of Wolverhampton, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.378961.
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The programme of research reported in this dissertation was undertaken with the aim of improving the high-speed performance of a multi-recessed hydrostatic thrust bearing. A theoretical analysis of the quasi-static behaviour and isothermal frictional power consumption is developed using the basic equations governing viscous fluid flow. The effects of high peripheral speeds are discussed and how recently proposed bearing modifications, in the form of grooved lands and changes in recess geometry, are used to reduce the frictional power consumption, lower operating temperatures, and reduce unwanted hydrodynamic and fluid inertia induced pressure variations. The steady state temperature distribution, frictional power consumption and operating clearance when one bearing member is rotating, and dynamic loading performance are predicted by several specially developed Fortran computer programs. One section concentrates on the design, development and instrumentation of an experimental multi-recessed hydrostatic thrust bearing, which had a facility for changing the pocket geometry using recess inserts. The bearing plate. which had an outside diameter of 200 mm, was operated at rotational speeds between 1000-5000 rpm to give peripheral speeds between 10.5 - 52.5 m/s. A chapter deals with an experimental investigation of the high-speed performance of a multi-recessed hydrostatic thrust bearing, principally the quasi-static loading and flow rate characteristics, temperature and pressure distributions and frictional power consumption. Furthermore, the dynamic response of the test bearing arrangement was investigated experimentally for a range of excitation frequencies between 0- 70 Hz- Finally, the theoretical predictions of characteristics such as quasi-static loading and flow rate, steady state operating conditions and dynamic response are compared with the corresponding experimental results.
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Roberts, Gerald Patrick. "Deformation and diagenetic histories around foreland thrust faults." Thesis, Durham University, 1990. http://etheses.dur.ac.uk/6258/.
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This thesis is concerned with the relationship between deformation and fluid flow along thrust zones. The study was carried out in the Vercors, French Sub-Alpine Chains foreland thrust belt. Study of the thermal alteration of organic matter within the area suggests that prior to west-north-west directed thrusting within the Vercors basin in post middle Miocene times, the rocks now exposed at the surface had not been buried beneath a large thickness of foredeep sediments and remained within the diagenetic realm. Deeper buried levels within the stratigraphy passed into the hydrocarbon generation window prior to thrusting within the Vercors basin. The rocks presently exposed at the surface also remained in the diagenetic realm during and after the thrusting which suggests that thrust sheet loading did not significantly contribute to thermal alteration of organic matter. The structures of the thrust belt may have been possible structural traps for any hydrocarbons which underwent re-migration during the thrusting. The structures have been exhumed by erosion during isostatic uplift. The Rencurel Thrust and overlying Rencurel Thrust Sheet were selected for special study as they are of regional structural importance. The thrust emplaces Urgonian limestones onto Miocene molasse sediments at present erosion levels. The thrust sheet is internally deformed by thrusts and folds. Structural data indicate that the deformation within the thrust sheet and within the Rencurel Thrust Zone occurred during one kinematically linked phase of thrusting. The Rencurel Thrust Zone itself is around 100 metres thick. The higher part of the thrust zone is composed of an array of minor faults developed within the Urgonian. These fault zones are generally less than 10cm wide and are coated in fault gouge. This array of faults is underlain by a gouge zone along the thrust contact between the Urgonian and the Miocene which is several metres thick. The gouge zones were all formed during the action of diffusive mass transfer (DMT) and cataclasis as deformation mechanisms. The wall-rocks to the gouge zones are relatively undeformed by the action of cataclasis. Cataclasis is dilatant and produces fracture porosity which increases the permeability of the fault zones whilst DMT reduces the porosity and permeability of the fault zones due to cement precipitation and pressure dissolution. Cross- cutting relationships between the microstructures indicating the action of cataclasis and DMT, suggest that the porosity and permeability of the fault rocks changed in a complex manner during the incremental deformation. This has important implications for assessing syn-kinematic fluid migration through fault zones. The fault rocks exposed at the surface today are relatively impermeable compared to undeformed wall-rocks away from the fault zone which have permeabilities comparable to those found within hydrocarbon reservoirs. The thrust zone may have been a seal in the sub-surface after the cessation of thrusting but prior to uplift and erosion. Early distributed deformation produced an array of minor faults within the Urgonian. Cataclasis had ceased along these faults before later deformation became localised along the gouge zone which exists along the thrust contact between the Urgonian and the Miocene rocks. Early deformation was accompanied by the migration through fracture porosity of pore waters which were saturated with respect to calcite and had interacted with organic matter which was being thermally altered. This fluid flow system was not connected to fluid flow higher in the stratigraphy which resulted in the precipitation of ferroan calcite within fracture porosity in the Senonian limestones. Late deformation within the thrust zone was accompanied by the migration of hydrocarbons and pore waters saturated with respect to calcite and pyrite. All the pore waters involved in migration through the active thrust zone seem to have migrated up-dip. They migrated from levels in the stratigraphy where organic metamorphism and the maturation of hydrocarbons were occurring to levels in the deformed section which have always remained within the diagenetic realm. Ferroan calcite, pyrite and traces of hydrocarbons have not been found outside the gouge zone along the thrust contact between the Urgonian and Miocene. The fracturing which occurred to open this migration pathway did not re- fracture the inactive minor faults which were impermeable at this time. Fluid migration at this time was confined to beneath the zone of impermeable minor faults in the Urgonian and did not contribute to the diagenesis of the rocks above the thrust zone. Hydrocarbons could not have entered the hanging-wall anticline above the thrust zone from this migration pathway. The fracturing at this time did not produce connected fracture networks pervasively throughout the thrust zone which suggests that the deformation may not have released large amounts of energy in the form of seismic waves.
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Townsend, C. "Thrust tectonics within the Caledonides of northern Norway." Thesis, Bucks New University, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.373605.
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Gilmore, Christopher K. (Christopher Kenneth). "Electro-aerodynamic thrust for fixed-wing aircraft propulsion." Thesis, Massachusetts Institute of Technology, 2017. http://hdl.handle.net/1721.1/112452.
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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Aeronautics and Astronautics, 2017.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 301-314).
Aviation operations negatively impact global climate, degrade surface air quality, and create noise. Towards mitigating these effects, this thesis considers electro-aerodynamic (EAD) propulsion, a form of in-atmosphere electrostatic propulsion, which requires no on-board propellant and has zero primary gaseous emissions. In addition, thrust generation has the potential to be nearly silent and requires no moving parts. Despite these advantages, however, EAD propulsion has yet to be implemented in fixed-wing aircraft, in part due to the limited understanding of EAD thruster performance. The objective of this thesis is to determine the feasibility and viability of EAD propulsion in fixed-wing aircraft applications. This thesis begins with a theoretical assessment of EAD thruster performance. This includes quantification of fundamental thrust density limits and the effect of interacting electric fields on thrust-to-power performance due to closely spaced electrode pairs. Additionally, performance as a function of altitude and vehicle flight speed is quantified, where thrust-to-power ratio is estimated to decrease as both increase. Next, this thesis experimentally assesses the achievable thrust density of EAD propulsion. Current and thrust generated from arrays of electrode pairs are observed to be a function of non-dimensional pair spacings for both parallel and staged operation. A thrust per unit area of 2 - 3 N/m² and per unit volume of 5 - 15 N/m³ are estimated, achieving approximately 50 and 10% of the corresponding one-dimensional space-charge limits, respectively. Results suggest that EAD propulsion is most readily viable at the small unmanned aerial vehicle (UAV) scale. Finally, based on the conclusions of the thrust density assessment, this thesis presents the development of a first-of-its-kind EAD-propelled, small-UAV prototype with the goal of achieving steady-level flight. A design space analysis is performed, determining that designs capable of steady-level flight potentially exist. The prototype development effort concludes with at-scale performance quantification of the primary EAD UAV subsystems. Results indicate that the achievable weight-to-thrust ratio is comparable to the vehicle lift-to-drag ratio. This thesis concludes that at the selected scale of the UAV prototype, EAD propulsion is potentially viable, and steady-level flight is, at worst, "nearly" feasible with the current design.
by Christopher Kenneth Gilmore.
Ph. D.
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Kim, Mischa. "Continuous Low-Thrust Trajectory Optimization: Techniques and Applications." Diss., Virginia Tech, 2005. http://hdl.handle.net/10919/27046.
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Trajectory optimization is a powerful technique to analyze mission feasibility during mission design. High-thrust trajectory optimization problems are typically formulated as discrete optimization problems and are numerically well-behaved. Low-thrust systems, on the other hand, operate for significant periods of the mission time. As a result, the solution approach requires continuous optimization; the associated optimal control
problems are in general numerically ill-conditioned. In addition, case studies comparing the performance of low-thrust technologies for space travel have not received adequate attention in the literature and are in most instances incomplete. The objective of this
dissertation is therefore to design an efficient optimal control algorithm and to apply it to the minimum-time transfer problem of low-thrust spacecraft. We devise a cascaded computational scheme based on numerical and analytical methods. Whereas other conventional optimization packages rely on numerical solution approaches, we employ
analytical and semi-analytical techniques such as symmetry and homotopy methods to assist in the solution-finding process. The first objective is to obtain a single optimized trajectory that satisfies some given boundary conditions. The initialization phase for this first trajectory includes a global, stochastic search based on Adaptive Simulated Annealing; the fine tuning of optimization parameters â the local search â is accomplished by Quasi-Newton and Newton methods. Once an optimized trajectory has been obtained,
we use system symmetry and homotopy techniques to generate additional optimal control solutions efficiently. We obtain optimal trajectories for several interrelated problem families that are described as Multi-Point Boundary Value Problems. We present and prove two theorems describing system symmetries for solar sail spacecraft and discuss symmetry properties and symmetry breaking for electric spacecraft systems models. We demonstrate how these symmetry properties can be used to significantly simplify the solution-finding process.Ph. D.
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Stahl, Brian James. "Thermal Stability and Performance of Foil Thrust Bearings." Case Western Reserve University School of Graduate Studies / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=case1333722754.
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Ito, Eri. "Integrated Earthquake Risk Evaluation for Mega-Thrust Earthquakes." Doctoral thesis, Kyoto University, 2021. http://hdl.handle.net/2433/263356.
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Josselyn, Scott B. "Optimization of low thrust trajectories with terminal aerocapture." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2003. http://library.nps.navy.mil/uhtbin/hyperion-image/03Jun%5FJosselyn.pdf.
Full textAbstract:
Thesis (Aeronautical and Astronautical Engineer)--Naval Postgraduate School, June 2003.Thesis advisor(s): I. Michael Ross, Steve Matousek. Includes bibliographical references (p. 149-150). Also available online.