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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.
81

Seismic and mechanical attributes of lithospheric deformation and subduction in western Canada

Audet, Pascal 11 1900 (has links)
Convergent continental margins are regions of intense deformation caused by the interaction of oceanic plates with continents. The spatial extent of deformation is broadly commensurate with the specific time scale of the causative phenomenon. For example, subduction-related short-term deformation is limited to <200 km from the margin, whereas long-term plate convergence cause deformation over ∼1000 km landward. Deformation is thus manifested in multiple ways, with attributes depending on the scale of measurement. In this thesis we investigate the use of two geophysical approaches in the study of deformation: 1) The analysis of potential-field anomalies to derive estimates of the elastic thickness (Te) of the lithosphere, and 2) The structural study of past and present subduction systems using seismic observations and modelling. Both approaches involve the development of appropriate methodologies for data analysis and modelling, and their application to the western Canadian landmass. Our findings are summarized as follows: 1) We develop a wavelet-based technique to map variations in Te and its anisotropy; 2) We show how a step-wise transition in Te and its anisotropy from the Cordillera to the Craton is a major factor influencing lithospheric deformation; 3) We implement a waveform modelling tool that includes the effects of structural heterogeneity and anisotropy for teleseismic applications, and use it to model the signature of a fossil subduction zone in a Paleoproterozoic terrane; 4) We use teleseismic recordings to map slab edge morphology in northern Cascadia and show how slab window tectonism and slab stretching led to the creation of the oceanic Explorer plate; 5) We use seismic signals from the subducting oceanic crust to calculate elevated Poisson’s ratio and infer high pore-fluid pressures and a low-permeability plate boundary within the forearc region of northern Cascadia. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate
82

Analysis of the gouldsboro pluton and the fehr granite: Understanding the scales of magmatic processes and partial melt generation from the deep to shallow crust

Koteas, George Christopher 01 January 2010 (has links)
The heterogeneity of the continental crust has a first order control on the dynamics of plate tectonic processes and the compositions of the Earth in both time and space. Heterogeneity can be characterized at a variety of scales and in a multitude of tectonic environments, but it is the links between seemingly disparate tectonic settings and crustal levels that are critical in understanding construction of the continents. The focus of this dissertation work is to apply microtextural, microgeochemical, whole rock geochemical and traditional petrographic techniques to study features in both deep and shallow crustal igneous rocks. The goal of these efforts is to better understand the roles that magmatic processes, mafic-felsic magma interaction, and partial melting have on the evolution of continental crust. Two principal field areas were selected, the Gouldsboro pluton in coastal Maine and the Fehr granite in northern Saskatchewan, Canada, because they each represent end-members of the processes involved with the generation, modification, transport, and emplacement of magmas that build continental crust. Evidence for bimodal magmatism preserved in the Silurian age Gouldsboro pluton has led to a refined model for the construction of shallow crustal magma chambers. Research efforts focused on the Neoarchean Fehr granite and Paleoproterozoic Chipman dike swarm have contributed to the current understanding of the links between high temperature metamorphism (migmitization) and the production of new felsic magmas as well as the rheological and chemical influences of mafic-felsic magma interaction in the deep crust. The results of these combined field and laboratory efforts have demonstrated the important role of mafic-felsic magma interaction on the strength and composition of both deep and shallow continental crust and have contributed to the current understanding of the complex links between deep crustal heterogeneity and bimodal magmatism at shallow crustal levels.
83

Geology and Geochemistry of the Western Panamá Canal Basin Volcanic Arc Rocks

Unknown Date (has links)
Panamá arc activity has been divided into three episodes, the Late Cretaceous to Eocene episode, the Miocene episode, and the Pliocene to recent adakite suite. Rocks from the oldest episode are dominantly hornblende bearing, contain a large negative Nb-Ta anomaly, and exhibit enrichment of large-ion lithophile elements (LILEs). These characteristics are all indicators that the Late Cretaceous-Eocene episode rocks formed from a hydrous mantle wedge derived subduction zone magma. Miocene episode rocks are commonly calc-alkaline throughout Panamá. In contrast, Miocene episode rocks from the Panamá Canal (PC) are strongly tholeiitic, lack hydrous minerals, have a decreased Nb-Ta subduction zone signal, and exhibit LILE depletion relative to older PC volcanism as well as the older Panamá arc episodes. New major element, trace element, and radiogenic isotope data has been analyzed for rocks from the Western Canal Basin (WCB) between El Valle volcano and the PC. The rocks contain both calc-alkaline and tholeiitic signatures, and range from basalt to dacite in composition. In terms of trace elements, the rocks exhibit enriched heavy rare earth element concentrations that are among the highest in all of Panamá. The Ba/Yb values for WCB samples are between the depleted PC samples and fluid rich El Valle samples. The WCB Ta/Yb values are similar to PC samples, with both exhibiting a lesser subduction zone signal than the Cretaceous-Eocene arc. On a V versus Ti tectonic discrimination diagram both PC and WCB samples plot in the MORB/BAB/CFB field. Pb and Sr isotope ratios for the Panamá Canal Basin rocks are similar to the Cordilleran arc, whereas Hf and Nd isotope ratios are the highest measured in all of Panamá and are consistent with the contribution of young asthenospheric mantle. Overall, trace element, isotopic and geophysical data indicate that the western Canal basin volcanic rocks formed due to the influx of young juvenile mantle in an extensional tectonic system. One explanation is the existence of an underlying tear in the subducted slab due to the ongoing collision of Panamá and South America. This is consistent with the fracturing of the Isthmus as proposed by Farris et al. (2011), and a tear in the underlying slab would allow for the influx of young mantle material. To place constraints on the crustal structure of the Canal basin, a series of gravity measurements were conducted. Bouguer gravity models exhibit a series of westward deepening half-grabens filled with low-density volcano-sedimentary material. Such horst and graben systems are interpreted to have formed due to extension in both east-west and north-south directions. Sub-orthogonal normal fault systems reflect the extensional nature of the Panamá Canal Basin. The models also indicate that 3 to 5 km thick volcano-sedimentary basins dominate the shallow subsurface, indicating that observed lavas are likely low in volume. Finally, the gravity models show the existence of a continuous sedimentary basin across the isthmus, which allows for the existence of a narrow strait connecting the Caribbean and Pacific during this time as proposed by Collins et al. (1996). / A Thesis submitted to the Department of Earth, Ocean, and Atmospheric Sciences in partial fulfillment of the requirements for the degree of Master of Science. / Fall Semester 2015. / December 7, 2015. / Arc Geochemistry, Bouguer Anomalies, Caribbean Tectonics, El Valle, Isotope Geochemistry, Panama Canal / Includes bibliographical references. / David W. Farris, Professor Directing Thesis; A. Leroy Odom, Committee Member; Vincent J. M. Salters, Committee Member.
84

Design of Liquid Cold Plates for Thermal Management of DC-DC Converters in Aerospace Applications

Vangoolen, Robert January 2022 (has links)
Due to increasing power demands and decreasing component size, thermal management has become the bottleneck for many power electronic applications. The aerospace industry has focused on reducing weight, operating temperature, and pumping power of power converters since these will limit an aircrafts' range and load carrying capacity. This paper outlines a tool created in MATLAB to automate the cold plate design process for DC-DC converters (or similar applications). The tool incorporates a genetic algorithm to fi nd the optimal aligned or staggered pin fi n confi guration that maintains the devices below their critical junction temperature while reducing the system's overall weight and pressure drop. Utilizing this MATLAB design tool, a cold plate was designed, manufactured, and tested. The convection coefficient calculated within MATLAB (via empirical correlations) was veri fed using simplifi ed CFD simulations within 5% of each other. The same CFD setup, boundary condition types, and methodology are then applied for the full-sized prototype cold plate simulations. These simulations were then validated using the experimental results. For all cases, the percentage error between the simulated convection coefficient values (CFD) and the experimental results was less than 12%. The experiments' measured surface temperature and pressure drop errors were less than 8% of the predicted CFD results. Therefore, the MATLAB tool and its correlations/calculations could be veri fied (via CFD) and validated (experimentally) based on good agreement between the CFD and the experimental results. This three-pronged approach (analytical calculations, CFD simulations, and experimental validation) is an effective and robust method to solve heat transfer problems. Overall, with the framework outlined in this thesis, a complete cold plate design can now be completed in weeks instead of months. This streamlined approach will save companies signifi cant time and money in the design and simulation phases, making this tool a valuable addition to the current literature available. / Thesis / Master of Applied Science (MASc)
85

Investigation of Platelet-Surface Interactions Using a Novel Cone and Plate Device / Platelet-Surface Interactions Using a Novel Cone and Plate Device

Skarja, Gary 08 1900 (has links)
Polymers are frequently utilized in blood-contacting biomaterials. Although, these materials exhibit generally favourable mechanical properties, the presence of these artificial surfaces in contact with blood initiates the mechanisms of thrombosis. This occurrence may, in turn, lead to a variety of serious clinical complications. A great deal of work has been done in this laboratory in the past to investigate the interactions of a variety of proteins (particularly coagulation proteins) with artificial surfaces. This interaction is believed to be the initial step in the physiological response to artificial surfaces in contact with blood. A secondary but equally important process is the adhesion and activation of blood platelets to artificial surfaces which may then lead to the formation of thrombi. The work performed here involves the investigation of platelet-surface interactions with a variety of surfaces, primarily a series of sulphonate ion-containing polyurethanes. Similar polymers have been shown by other researchers to exhibit favourable blood-contacting responses while retaining the attractive mechanical properties of polyurethanes in general. To perform the work outlined above, a novel cone and plate device was designed and built which enables the experimenter to investigate platelet-surface interactions under varying shear flow conditions. Collagen and albumin-coated test surfaces were utilized to investigate the platelet adhesion results generated in the device with varying fluid shear rate and time. A typical adhesion time response curve was generated with increasing levels of adhesion noted for increasing shear rate, as expected due to increased platelet transport to the surface. As well, effective platelet diffusion coefficients were calculated from the adhesion data collected using the collagen surface and was found to agree broadly with those found by other researchers. A series of sulphonated polyurethanes were synthesized and both the bulk and surface properties were characterized. A variety of polymer sulphonate concentrations were achieved by use of different constituent molecules (specifically chain extenders and polyols). The polymers, in general, showed high levels of water absorption and increased hydrophilicity in comparison to non-sulphonated analogs. The cone and plate device was used to investigate the platelet adhesion response in a shear flow environment to these surfaces. In general, sulphonate incorporation resulted in a dramatic increase in the level of adhesion to the polyurethane surfaces, indicating that platelets are able to form adhesive interactions with sulphonate functional groups. Platelet adhesion levels to the sulphonated polyurethanes exhibited both time and shear rate dependence. However, differences in adhesion levels between the sulphonated polyurethanes did not appear to be a simple function of the sulphonate concentration. This may indicate that the local environment of the incorporated sulphonate groups in the polyurethane can affect the ability of these groups to interact with the platelet membrane. / Thesis / Master of Engineering (ME)
86

Behavior of Diagonal Knee Moment End-Plate Connections

Italiano, Vincenza M. 14 May 2001 (has links)
An experimental and analytical investigation was conducted to study the behavior of diagonal knee moment end-plate connections and a multiple row extended moment end-plate connection. Diagonal knee moment end-plate connections differ from typical moment end-plate connections because of the large pitch distance required between the top flange and first row of tension bolts. The large pitch distance is outside of the geometric parameters of all previous research. Design solutions are presented for five moment end-plate connections with provisions added to accommodate these parameters. The analytical investigation focused on the limit states of end-plate yielding and bolt rupture. Yield-line analysis was used to predicted end-plate yielding and a simplified Kennedy method proposed by Borgsmiller and Murray (1995) was used to predict bolt rupture including and excluding prying forces. An experimental investigation was conducted to verify the design solutions. Five knee area specimens and one plate girder specimen were tested in this study. The analytical and experimental results are analyzed and compared. For the test specimens that failed in the connection, the predicted results proved to be conservative. Recommendations are presented at the end of the study as well as sample calculations. / Master of Science
87

Using Wavelet for License Plate Detection

Wang, Chung-Shan 30 June 2004 (has links)
Based on digital image processing techniques, the goal of this work is develop a method to automatically detect license plates. To achieve this goal, this thesis uses wavelet transform to first find the position of the license plate. A number of image processing techniques are then developed to identify each character on the license plate. Finally, experimental results are given to demonstrate the effectiveness of the proposed approach, which is the followed by a simple conclusion.
88

Studies From Reactant Supply for Heterogeneous Composite Carbon Fiber Bipolar Plates Applied to a Fuel Cell

chang, chi-an 21 July 2005 (has links)
Via the viewpoint of fuel and oxidant supply in this study, we compare heterogeneous carbon fiber bipolar plates with graphite bipolar plates that apply to fuel cell. In operating condition with different gas inlet pressure and compressing pressure, we study the penetrability of reactant gases that come into the carbon cloth under the rib of a bipolar plate. Eventually the output voltage and power density are measured to prove the advantages of the new bipolar plate. The experimental results show that carbon fiber bipolar bunch in low compressing pressure 2bar already display high gas penetrability. Its dimensionless flow rate is about quadruple of graphite bipolar plates. The reactant gas can enter the carbon cloth either from the side or from the top of the penetrating carbon fiber bipolar bunch. In addition, carbon fiber bipolar plates are affected slightly by compressing pressure. Further, the total electrical resistant of carbon fiber bipolar plates with carbon cloth already decreases to 18.5mΩ*cm&#x00B2; in low compressing pressure 2bar. Therefore, by appling the new bipolar plate, the fuel cell in compressing pressure 2bar and inlet fuel pressure 1.15bar(absolute pressure) can developed a power rate 180mW/cm&#x00B2;. Concerning graphite bipolar plates, we can find that compressing pressure increase from 1bar to 4bar due to the reduction in total resistance so the output voltage and power density can increase to maximum value 113mW/cm2. However, while we augment more compressing pressure, the influence in reducing total resistance is much smaller than that in reducing the porosity of carbon cloth. Therefore, the output power density decreases. Also, output voltage of carbon fiber bipolar plates at 0.5mA/cm2 is 0.38 V and is higher than that of graphite bipolar plate 0.2 V.
89

THREE-DIMENSIONAL VIBRATION ANALYSIS SATISFYING STRESS BOUNDARY CONDITIONS OF CIRCULAR AND ANNULAR

Chuang, Chin- His 30 July 2001 (has links)
In the proposed project¡Athe three - dimensional vibration of circular and annular plates is analyzed by a mixed finite element¡C Stresses¡Aas well as displacements¡A are primary variables in the mixed finite element formulation¡Atherefore¡Aall the stress and displacement boundary conditions can be imposed exactly¡CMeanwhile¡Athe proposed finite element is a modification of axisymmetric finite element which is based on three ¡V dimensional elasticity¡Aso general results of both axisymmetric and unaxisymmetric vibration of circular and annular plates can be obtained¡C Results of the present project will be compared to those by conventional displacement ¡V type finite element¡ARitz method and series method to show the difference among these theories¡CEspecially¡Athe effect of satisfying the stress boundary conditions on the unaxisymmetric vibration analyses can be demonstrated¡Awhich is not available in the literature up to date¡C
90

Analysis of Laminated Anisotropic plates and Shells by Chebyshev Collocation Method

Lin, Chih-Hsun 31 July 2003 (has links)
The purpose of this work is to solve governing differential equations of laminated anisotropic plates and shells by using the Chebyshev collocation method. This method yields these results those can not be accomplished easily by both Navier¡¦s and Levy¡¦s methods in the case of any kind of stacking sequence in composite laminates with the variety of boundary conditions subjected to any type of loading. The Chebyshev polynomials have the characteristics of orthogonality and fast convergence. They and Gauss-Lobatto collocation points can be utilized to approximate the solution of these problems in this paper. Meanwhile, these results obtained by the method are presented as some mathematical functions that they are more applicable than some sets of data obtained by other methods. On the other hand, by simply mathematical transformation, it is easy to modify the range of Chebyshev polynomials from the interval [-1,1] into any intervals. In general, the research on laminated anisotropic plates is almost focused on the case of rectangular plate. It is difficult to handle the laminated anisotropic plate problems with the non-rectangular borders by traditional methods. However, through the merits of Chebyshev polynomials, such problems can be overcome as stated in this paper. Finally, some cases in the chapter of examples are illustrated to highlight the displacements, stress resultants and moment resultants of our proposed work. The preciseness is also found in comparison with numerical results by using finite element method incorporated with the software of NASTRAN.

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