The West Iberia (WIM) and Newfoundland (NFM) continental margins formed over a succession of rift events related to the opening of the North Atlantic between the Late Triassic and the Early Cretaceous. They are characterized by a variable width Ocean- Continent Transition (Zone) where exhumed and serpentinized mantle has been cored. Results from 1-D well backstripping along the Portuguese shelf suggest 40-45% greater extension factors (β) than previous estimates. In addition, the age and duration of both the Late Triassic-earliest Jurassic and the Late Jurassic rifting episodes have been better constrained. It appears, for example, that the Late Jurassic rift propagates northwards along the margin, as inferred for the continental break-up during the Early Cretaceous. Combined backstripping and gravity modelling techniques (POGM), together with new bathymetry and sediment thickness grids, have been used to estimate the effective elastic thickness, T_e, of the lithosphere. Results along closely space profiles in the WIM reveal that T_e decreases from 15-40 km over unthinned Variscan basement to ≤ 15 km over stretched continental and transitional crust. Along strike, a good correlation is found between the modelled mechanical structure and the segmentation of the Variscan basement onshore. Discrepancies between observed and calculated anomalies are discussed in terms of other processes that affected the margin, such as serpentinization and inversion. Thermo-mechanical rheological modelling techniques have also been tested. The compiled software inputs the β's constrained from POGM to determine the thermal structure of the margin, which, in turn, has been used to construct models of rheology and, hence, T_e. The models predict an increase in the T_e of thinned continental lithosphere with age since rifting, between < 20 and > 35 km, and suggest that processes such as ductile shearing and mantle serpentinization might have permanently weakened the lithosphere. Results from POGM along conjugate profiles off WI and NF reveal a greater longterm strength of extended continental and transitional basement in the NFM (T_e's of 10-40 km). This analysis further supports the hypothesis that the low T_e's modelled in the WIM might be related to its complex structural framework. In order to explain the large asymmetries observed in the amount of basement subsidence (500-1300 in) between the WI and NF margins a lithospheric-scale "simple shear" rift model is proposed for the latest stages of rifting and continental break-up.

Orientador: Marco Antonio Bottino / Banca: Luiz Felipe Valandro Soares / Banca: Eduardo Miyashita / Banca: Paulo Francisco Cesar / Banca: Carlos Augusto Pavanelli / Resumo: Este estudo avaliou o efeito de diferentes protocolos de jateamento na resistência à flexão biaxial e na estabilidade estrutural de uma cerâmica de Y-TZP. Para tanto, duzentos e dezesseis discos sinterizados de Y-TZP (Lava, 3M ESPE) (ISO 6872, diâmetro: 15 mm, espessura: 2 mm) foram confeccionados pelo fabricante. Para o ensaio de resistência à flexão, 180 discos (n=10) foram divididos entre 18 grupos de acordo com os fatores "tipo de partícula (Al2O3- 50 e 110μm; SiO2- 30 e 110 μm)", "pressão (2,5 e 3,5 bar)" e "ciclagem mecânica (CM) (com e sem)". O jateamento foi realizado a uma distância de 10 mm e com duração de 20 s: Gr1- Controle - (sem tratamento de superfície); Gr2- Al2O3 50 μm/2,5 bar; Gr3- Al2O3 50 μm/3,5 bar; Gr4- Al2O3 110 μm/2,5 bar; Gr5- Al2O3 110 μm/3,5 bar; Gr6- SiO2 30 μm/2,5 bar; Gr7- SiO2 30 μm/3,5 bar; Gr8- SiO2 110 μm/2,5 bar; Gr9- SiO2 110 μm /3,5 bar. Os grupos Gr10 a Gr18 são respectivamente os grupos anteriores submetidos à CM (100.000 ciclos, 50 N, 4 Hz, água 370C. Em seguida todas as amostras foram submetidas ao ensaio de resistência à flexão biaxial (ISO 6872) em máquina de ensaio universal (EMIC, 1 mm/min). Após ensaio de flexão, os dados obtidos (MPa) foram submetidos ao teste de Dunnett (5%) e à Análise de Variância (3 fatores). Para determinar a quantidade e profundidade de possíveis transformações de fase da zircônia (t→m) induzida pelo jateamento e/ou pela ciclagem mecânica, foi realizada a análise de difração de Raios-X em vinte amostras (n=2) dos grupos Gr1 ao Gr9 e Gr18, antes e após tratamento térmico (ciclo de queima da VM9/Vita). Os resultados demonstraram que todos os protocolos de jateamento promoveram um aumento significativo da resistência à flexão da cerâmica de Y-TZP em relação... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: This study evaluated the effect of different air-particle-abrasion protocols on the biaxial flexural strength and on the structural stability of Y-TZP ceramic. Disc shaped (ISO 6872, Ø: 15 mm, thick: 2 mm) sintered zirconia specimens (N=216) were obtained from the manufacturer (Lava, 3M ESPE). To the flexure test 180 discs (n=10) were divided among the groups according to the factors "particle (Al2O3 50 and 110μm; SiO2 30 and 110 μm)", "pressure (2.5 and 3.5 bar)" and "mechanical cycling (MC)(with and without)". The air-particle-abrasion protocols were performed with 10 mm of distance and duration of 20 s: Gr1- Control - (without air-particle-abrasion); Gr2- Al2O3 50 μm/2,5 bar; Gr3- Al2O3 50 μm/3,5 bar; Gr4- Al2O3 110 μm/2,5 bar; Gr5- Al2O3 110 μm/3,5 bar; Gr6- SiO2 30 μm/2,5 bar; Gr7- SiO2 30 μm/3,5 bar; Gr8- SiO2 110 μm/2,5 bar; Gr9- SiO2 110 μm /3,5 bar. The groups Gr10 to Gr18 are those groups before submitted to MC, respectively (100.000 cycles; 50 N, 4 Hz, water 370C). After, all specimens were tested for biaxial flexural strength (ISO 6872) in a universal testing machine (EMIC). After, all specimens were tested for biaxial flexural strength (ISO 6872) in a universal testing machine (EMIC). The data were submitted to statistical tests ANOVA and Dunnett (5%). To determine the percentage and deep of possible zirconia transformations (te mo) after the air-particle-abrasion protocols and/or MC, the X-Ray diffraction was performed on 20 samples (n=2) from the groups Gr1 to Gr9 and Gr18, before and after thermal treatment (VM9/Vita firing cycle). The results showed that all air-particle-abrasion protocols increased significantly the flexure strength of the Y-TZP ceramic compared to the negative Control... (Complete abstract click electronic access below) / Doutor

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1979. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND AERONAUTICS. / Includes bibliographical references. / by Michael Derryck Turner. / M.S.

This thesis presents a) a scheme for selecting the most suitable flexure hinge compliance equations, and b) a simple methodology of deriving kinetostatic models of micro-motion stages by incorporating the scheme mentioned above. There were various flexure hinge equations previously derived using different methods to predict the compliances of circular flexure hinges. However, some of the analytical/empirical compliance equations provide better accuracies than others depending on the t/R ratios of circular flexure hinges. Flexure hinge compliance equations derived previously using any particular method may not be accurate for a large range of t/R ratios. There was no proper scheme developed on how to select the most suitable and accurate hinge equation from the previously derived formulations. Therefore, the accuracies and limitations of the previously derived compliance equations of circular flexure hinges were investigated, and a scheme to guide designers for selecting the most suitable hinge equation based on the t/R ratios of circular flexure hinges is presented in this thesis. This thesis also presents the derivation of kinetostatic models of planar micromotion stages. Kinetostatic models allow the fulfillment of both the kinematics and the statics design criteria of micro-motion stages. A precise kinetostatic model of compliant micro-motion stages will benefit researchers in at least the design and optimisation phases where a good estimation of kinematics, workspace or stiffness of micro-motion stages could be realised. The kinetostatic model is also an alternative method to the finite-element approach which uses commercially available software. The modelling and meshing procedures using finite-element software could be time consuming. The kinetostatic model of micro-motion stages wasdeveloped based on the theory of the connection of serial and parallel springs. developed based on the theory of the connection of serial and parallel springs. The derivation of the kinetostatic model is simple and the model is expressed in closed-form equations. Material properties and link parameters are variables in this model. Compliances of flexure hinges are also one of the variables in the model. Therefore the most suitable flexure hinge equation can be selected based on the scheme aforementioned in order to calculate the kinetostatics of micro-motion stages accurately. Planar micro-motion stages with topologies of a four-bar linkage and a 3-RRR (revolute-revolute-revolute) structure were studied in this thesis. These micromotion stages are monolithic compliant mechanisms which consist of circular flexure hinges. Circular flexure hinges are used in most of the micro-motion stages which require high positioning accuracies. This is because circular flexure hinges provide predominantly rotational motions about one axis and they have small parasitic motions about the other axes. The 3-RRR micro-motion stage studied in this thesis has three-degrees-of-freedom (DOF). The 3-RRR stage consists of three RRR linkages and each RRR linkage has three circular flexure hinges. A Pseudo-Rigid-Body-Model (PRBM), a kinetostatic model and a two-dimensional finite-elementanalysis (FEA) model generated using ANSYS of micro-motion stages are presented and the results of these models were compared. Advantages of the kinetostatic model was highlighted through this comparison. Finally, experiments are presented to verify the accuracy of the kinetostatic model of the 3-RRR micromotion stage. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1289361 / Thesis (Ph.D.) -- University of Adelaide, School of Mechanical Engineering, 2007

Thesis (Ph. D.)--University of Hong Kong, 2007. / Title proper from title frame. Also available in printed format.

The position control has played an important role in high-tech industries. For example, we hope the control performance fast and precisely in the biomedical industry or high-speed precision machinery. However, the high-precision positioning platform will encounter backlash, friction, hysteresis ... and so on. Therefore, this paper will use the linear voice coil motor to drive single-axis flexure mechanism, to solve the nonlinear problem unnecessarily. Then, the quantized current regulator has been reached by high efficiency robust frequency control and to design with a low-pass filter of the interference within the system parameter estimation to reduce the impact of changes in items, and then by the simulation test analysis showed that the proposed hybrid control method has simultaneous control of voice coil motor current and the flexure mechanism targeting the advantages of location, and the use of traditional pulse-width modulation of the PI current controller with integral type of smooth position control mode, respectively quantized current regulator and the disturbance estimator to do a comparative analysis of simulation . Finally the use analogies full the bridge electric circuit, several logic and the operational amplifier realizes the quantification current regulator.

Thesis (Ph. D.)--University of Hong Kong, 2009. / Includes bibliographical references (p. 237-242). Also available in print.

Thesis (Ph. D.)--University of Missouri-Columbia, 2001. / Typescript. Vita. Includes bibliographical references (leaves 162-168). Also available on the Internet.

Thesis (Ph. D.)--University of Missouri-Columbia, 2001. / Typescript. Vita. Includes bibliographical references (leaves 162-168). Also available on the Internet.

Thesis (Ph. D.) in Civil Engineering--University of Maine, 2000. / Includes vita. Includes bibliographical references (leaves 206-219).