Thesis (Ph. D.)--Virginia Polytechnic Institute and State University, 1991. / Vita. Abstract. Includes bibliographical references (leaves 163-170). Also available via the Internet.

Vibration isolation is a procedure through which the transmission of oscillating disturbances or forces is reduced. The ideal isolator is one that will support the equipment being isolated without transmitting any dynamic forces. An isolator with infinite static stiffness and zero dynamic stiffness will achieve this goal. Although this ideal isolation cannot be obtained in practice, it can be approximated through a wide range of devices. This approximation occurs over a limited frequency band and methods of increasing this band were investigated. The goal of this thesis was to further our understanding of mechanical systems that can approximate the ideal isolator behaviour. To compare the various devices the blocked transfer dynamic stiffness was defined. This value was found to represent the isolator properties without the additional complication of the equipment being isolated as happens in traditional transmissibility methods. Three classes of devices were distinguished namely isolators, vibration-absorbing isolators (VAl) and amplified vibration-absorbing isolators (AVAI). The last two types exploit nodalisation to reduce the dynamic stiffness over a limited frequency range. The focus of this work is the broadening of the effective low stiffness bandwidth of amplified vibration-absorbing isolators by adapting system characteristics. If the excitation is tonal time-varying these devices can be used successfully. Two novel adaptive amplified vibration-absorbing isolators were introduced and studied in the time and frequency domains. The type I AVAI uses flexible reservoir walls to vary the isolation frequency. The type II device incorporates a heavy metal slug. Both devices use variable pressure air springs to change their stiffness. The use of air springs are convenient, offers low damping and can be used in an application such as a pneumatic rock drill handle to eliminate the need for a control system. Conceptual design methodologies for both damped and un-damped fixed and adaptive isolation frequency AVAls are presented. To determine the effects of tuning the equations were transformed in terms of constant frequency ratios and the variable stiffness ratio. The devices can be controlled using an optimisation approach, but care should be taken since the method could be unsuccessful in some cases. The design was then applied to a pneumatic rock drill. This application was particularly demanding because the stiffness had to be large enough for the operator to remain in control of the drill, yet low enough to offer isolation. Extensive measurements of drill vibration at a test facility found that the maximum acceleration values were 18.72 m/s2. The maximum allowed under the proposed European Union legislation is 10 m/s2 for short durations. The excitation consisted of a large tonal component and wide-band noise. The tonal component contributed ~50% of the total weighted equivalent acceleration experienced by the operator and a vibration absorbing isolator should therefore be an ideal solution. The measurements also showed that the excitation frequency is a function of the supply air pressure. By using the supply air pressure to feed the air spring the device could be made self-¬tuning. Numerical simulation showed that there is only a slight difference between using the supply pressure and forcing coincidence of the excitation and isolation frequencies. It was also found that the vibration levels could be reduced to below 10 m/s2<./sup> in some cases. / Thesis (PhD (Mechanical Engineering))--University of Pretoria, 2006. / Mechanical and Aeronautical Engineering / unrestricted

Current and future space exploration operations rely heavily on space-borne telescopes, of which mirrors are an integral component. However, traditional solid mirrors are heavy and require a big storage space. Deploying membrane mirrors can alleviate many of these obstacles. Membrane mirrors are light and can be compactly stowed resulting in cheap launching costs. It was also demonstrated that membrane mirror would provide quality optical imaging capabilities. However, membrane mirrors exhibit undesirable vibrations that can be caused by thermal gradients or internally-induced excitations. The undesirable vibration degrades the performance of these mirrors. Hence, it is proposed to augment membrane mirrors with smart actuators around their outer rim. Smart actuators can be used to suppress the undesirable vibration. More importantly, such a system provide the capability to form appropriate surfaces to correct for aberrations in an incoming wavefront. In this spirit, this work aims at modeling and control a membrane mirror augmented with smart actuators. The approach here to consider a membrane strip augmented with smart actuators as a prelude for studying circular membranes. We consider strips of membrane material, and treat two such structures: a membrane strip augmented with a single piezoceramic bimorph acting in bending, and a membrane strip augmented with multiple macro-fiber composite bimorphs. The later structure is studied under two actuation configurations. In the first configuration, both actuators act in bending. In the other configuration, one actuator acts in bending and the second acts in tension. The developed models of both structures were validated experimentally. Then, control laws were derived for both structures. An optimal proportional-integral controller is used for the membrane strip augmented with a single piezoceramic bimorph. For the membrane strip augmented with two macro-fiber composite bimorphs, a sliding mode controller with a switching command is used. Simulation results are presented to demonstrate the efficacy of the proposed control laws. Then, a circular membrane augmented with macro-fiber composite bimorph actuators is considered. We derive the governing equation of the structure for the general configuration, where actuators are producing bending moments and radial loading. Then, we seek a reduced order model of the structure. We work on obtaining a Galerkin expansion of the model where the test functions used are the mode shapes of the structure as obtained from a finite element analysis conducted in a commercial software package. Then the control problem is considered. The objective is to correct for optical aberrations, so the Zernike polynomial basis functions are used. A transformation from the optical modes to the mechanical modes is presented and an augmented adaptive controller is used to correct for image aberrations. The results presented show the efficacy of the controller. / Ph. D.

by Lai Chun Yu. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2000. / Includes bibliographical references (leaves 75-79). / Abstracts in English and Chinese. / LIST OF FIGURES --- p.vi / LIST OF TABLES --- p.ix / Chapter 1 --- INTRODUCTION --- p.1 / Chapter 1.1 --- Background --- p.1 / Chapter 1.1.1 --- Vibration Control of Suspension Systems --- p.1 / Chapter 1.1.2 --- Semi-active Devices --- p.3 / Chapter 1.2 --- Literature Review --- p.5 / Chapter 1.2.1 --- MR Fluid and Damper --- p.5 / Chapter 1.2.2 --- Vibration Control --- p.6 / Chapter 1.2.3 --- Robust Control --- p.8 / Chapter 1.3 --- Research Objective --- p.9 / Chapter 1.4 --- Organization of the Thesis --- p.9 / Chapter 2 --- MR DAMPER BEHAVIOR AND MODELING --- p.11 / Chapter 2.1 --- MR Damper --- p.12 / Chapter 2.2 --- Mathematical Model --- p.13 / Chapter 2.3 --- Experimental Setup --- p.15 / Chapter 2.4 --- Damper Characteristics --- p.18 / Chapter 2.5 --- Comparison Between Model with Experimental Data --- p.25 / Chapter 2.5.1 --- Graphical Study --- p.26 / Chapter 2.5.2 --- Quantitative Study --- p.26 / Chapter 2.5.3 --- Other Input Tests --- p.27 / Chapter 3 --- SEMI-ACTIVE VIBRATION CONTROL --- p.33 / Chapter 3.1 --- Dynamic Modelling of Suspension Systems --- p.33 / Chapter 3.2 --- Single-degree-of-freedom (SDOF) Passive Suspension System --- p.34 / Chapter 3.2.1 --- Viscous Damper --- p.34 / Chapter 3.2.2 --- MR Damper --- p.37 / Chapter 3.3 --- Single-degree-of-freedom (SDOF) Semi-active Suspension System --- p.41 / Chapter 3.3.1 --- Ideal Skyhook Control --- p.41 / Chapter 3.3.2 --- Semi-active Skyhook Control --- p.44 / Chapter 3.4 --- Semi-active Robust Control Development --- p.46 / Chapter 3.5 --- Sliding Mode Control --- p.47 / Chapter 3.6 --- Semi-active Damper Control --- p.51 / Chapter 3.6.1 --- On-off Control --- p.52 / Chapter 3.6.2 --- Continuous-state Control --- p.53 / Chapter 3.6.3 --- Comparison Between On-off and Continuous-state Controller --- p.54 / Chapter 4 --- SIMULATION STUDIES --- p.57 / Chapter 4.1 --- Transmissibility --- p.57 / Chapter 4.2 --- Different Base Excitations --- p.59 / Chapter 4.2.1 --- Bump Input --- p.60 / Chapter 4.2.2 --- Random Input --- p.62 / Chapter 5 --- CONCLUSION --- p.67 / Chapter 5.1 --- Summary --- p.67 / Chapter 5.2 --- Future Work --- p.68 / APPENDIX --- p.69 / Chapter A.1 --- Semi-active Control with MR Damper ´ؤ Main Program Listing --- p.69 / Chapter A.2 --- Sub-program Listing (Dynamic System) --- p.70 / Chapter A.3 --- Sub-program Listing (Sliding Mode Controller) --- p.73 / Chapter A.4 --- Sub-program Listing (MR Damper Model) --- p.73 / BIBLIOGRAPHY --- p.75

Lam Hiu Fung. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2001. / Includes bibliographical references (leaves 106-111). / Abstracts in English and Chinese. / abstract --- p.i / 摘要 --- p.iii / acknowledgements --- p.v / table of contents --- p.vi / list of figures --- p.viii / list of tables --- p.xi / Chapter 1 --- introduction --- p.1 / Chapter 1.1 --- Controllable Suspension System --- p.1 / Chapter 1.1.1 --- Automotive Suspension System --- p.2 / Chapter 1.1.2 --- Controllable Devices --- p.4 / Chapter 1.1.3 --- MR Fluid and Damper --- p.5 / Chapter 1.2 --- Vibration Control --- p.5 / Chapter 1.2.1 --- Active Control --- p.5 / Chapter 1.2.2 --- Semi-active Control --- p.6 / Chapter 1.2.3 --- Robust Control --- p.7 / Chapter 1.3 --- Research Objective --- p.7 / Chapter 1.4 --- Thesis Outline --- p.8 / Chapter 2 --- PARAMETRIC STUDY OF SUSPENSION SYSTEMS --- p.9 / Chapter 2.1 --- System Models and Transmissibility --- p.9 / Chapter 2.1.1 --- Passive Suspension System --- p.10 / Chapter 2.1.2 --- Skyhook Suspension System --- p.15 / Chapter 2.1.3 --- Groundhook Suspension System --- p.24 / Chapter 2.1.4 --- Hybrid Suspension System --- p.32 / Chapter 2.1.5 --- Comparison among four suspension systems --- p.41 / Chapter 2.2 --- Characteristics analysis --- p.45 / Chapter 2.2.1 --- Passive Suspension System --- p.45 / Chapter 2.2.2 --- Skyhook Suspension System --- p.47 / Chapter 2.2.3 --- Groundhook Suspension System --- p.50 / Chapter 2.2.4 --- Hybrid Suspension System --- p.52 / Chapter 2.3 --- Stability --- p.54 / Chapter 2.3.1 --- Stability in the Sense of Lyapunov for Suspension Systems --- p.54 / Chapter 2.3.2 --- Stability for four Suspension Systems --- p.57 / Chapter 2.4 --- Optimization --- p.63 / Chapter 2.4.1 --- Single-Degree-of-Freedom Passive System --- p.63 / Chapter 2.4.2 --- Two-Degree-of-Freedom Passive System --- p.65 / Chapter 2.4.3 --- Hybrid Suspension System --- p.67 / Chapter 3 --- SUSPENSION SYSTEM WITH VIBRATION CONTROLLER --- p.71 / Chapter 3.1 --- Two-Degree-of-Freedom Quarter Car Model --- p.71 / Chapter 3.2 --- MR Damper --- p.73 / Chapter 3.3 --- Vibration Controller --- p.75 / Chapter 3.3.1 --- System Controller: Sliding Mode Control --- p.76 / Chapter 3.3.2 --- Damper Controller: Continuous-state Control --- p.83 / Chapter 4 --- SIMULATION RESULTS --- p.85 / Chapter 4.1 --- Transmissibility analysis --- p.86 / Chapter 4.2 --- Simulation --- p.89 / Chapter 4.2.1 --- Test by Bump Excitation --- p.89 / Chapter 4.2.2 --- Test by Random Excitation (White noise) --- p.91 / Chapter 4.2.3 --- Test by Road Elevation Profile --- p.95 / Chapter 5 --- CONCLUSIONS AND FUTURE WORK --- p.99 / Chapter 5.1 --- Summary --- p.99 / Chapter 5.2 --- Future Work and Further Development --- p.100 / Chapter 5.2.1 --- Parametric study of the MR suspension system --- p.100 / Chapter 5.2.2 --- Systematic method for selecting control gains --- p.101 / Chapter 5.2.3 --- New control algorithm --- p.101 / Chapter 5.2.4 --- Extension to half and full car models --- p.102 / Chapter 5.2.5 --- System implementation --- p.102 / appendix / Chapter A.1 --- Additional information of the transmissibility of unsprung mass.… --- p.103 / Chapter A.2 --- Additional figures of the random excitation test: --- p.104 / BIBLIOGRAPHY --- p.106

Graduation date: 1995

This dissertation is focused on synthesis, characterization and formation mechanism of anionic-surfactant-templated mesoporous silica (AMS). Structural control mechanisms of AMS are investigated. First, different ionization degree of anionic surfactant affected by the acidity or alkalinity of the synthesis system gives rise to different charging density of micelles and therefore determines the organic/inorganic interface curvature, producing mesophases from cage-type to cylindrical, bicontinuous and lamellar. Second, mesocage/mesocage electrostatic repulsive interaction affects the formation of cage-type mesostructure, which is derived from a full-scaled synthesis-field diagram of AMS. The mesocage/mesocage interaction changes with charge density of mesocages and gives rise to their different packing manners. Third, the structural properties of AMS materials could be tuned by molecular features of surfactant and co-structure-directing agent (CSDA). The pore size of AMS is found to be controlled by alkyl chain length, ionization degree of surfactant and the CSDA/surfactant ratio. Alkyl chain length of surfactant determines size of micelles and thus mesopores. Larger ionization degrees of anionic surfactant give rise to smaller pore sizes due to thermodynamic coiling of alkyl chains of surfactant. The hydrophobic interactions between the pendant organic groups of CSDA on the silica wall and the hydrophobic core of the micelles drive a contraction of the mesopores. A mesoporous silica with novel bicontinuous cubic Pn-3m structure has been prepared using a diprotic anionic surfactant. 3d-reconstruction of the structure shows that it is bicontinuous composed of an enantiomeric pair of 3d mesoporous networks that are interwoven with each other, divided by a D surface. Inverse replication suggests the possible presence of ordered complimentary micropores in the material.

Shape memory alloys (SMAs) have recently attracted much attention as a smart material that can be used in passive protection systems such as energy dissipating devices and base isolation systems. For the purpose of investigating the potential use of SMAs in seismic engineering applications a soft computing approach, namely a neurofuzzy technique is used to model dynamic behavior of CuAlBe shape memory alloy wires. Experimental data are collected from two test programs that have been performed at the University of Chile. First, in order to evaluate the effect of temperature changes on the behavior of superelastic SMA wires, a large number of cyclic, sinusoidal, tensile tests are conducted at various temperatures. Second, to assess dynamic effects of the material, a series of laboratory experiments are conducted on a scale model of a three story model of a building that is stiffened with SMA wires and given excitation by a shake table. Two fuzzy inference systems (FISes) that can predict hysteretic behavior of CuAlBe wire have been created using these experimental data. Both fuzzy models employ a total of three input variables (strain, strain-rate, and temperature or prestress) and one output variable (predicted stress). Values of the initially assigned membership functions for each input are adjusted using a neural-fuzzy procedure to accurately predict the correct stress level in the wires. Results of the trained FISes are validated using test results from experimental records that had not been previously used in the training procedure. Finally, numerical simulations are conducted to illustrate practical use of these wires in a civil engineering application. In particular, dynamic analysis of a single story frame and a three story benchmark building that are equipped with SMA damping elements are conducted. Then, an isolated bridge that utilizes a linear rubber bearing together with SMA elements is analyzed. Next, in order to show recentering ability of SMAs, nonlinear time history analysis of a chevron like braced frame is implemented. The results reveal the applicability for structural vibration control of CuAlBe wire whose highly nonlinear behavior is modeled by a simple, accurate, and computational efficient FIS.

Uranium deposits associated with Paleoproterozoic successor basins were investigated using structural, petrographic, geochronological and geochemical relationships to understand the character and timing of ore-forming fluids and the structural control on uranium mineralization. The work focused on two successor basins that share similar geological characteristics: the Martin Lake Basin in the Beaverlodge area in Canada, and the El Sherana Basin in the South Alligator River area in Australia. The Beaverlodge area records six temporally distinct stages of U mineralization spatially associated with the Martin Lake successor basin. Early minor stages are hosted in cataclasite and veins at ca. 2.29 Ga and in albitized granite in the Gunnar deposit between ca. 2.3 Ga and 1.9 Ga, which predates the main stage of U mineralization of hydrothermal breccias that formed at ca. 1.85 Ga. Later stages of mineralization are related to minor veins at ca. 1.82 Ga linked to alkaline mafic dikes associated with the Martin Lake Basin and to minor veins at ca. 1.62 Ga corresponding to the timing of unconformity-type U mineralization in the overlying Athabasca Basin. The main breccia-type U mineralizing event that affected all deposits in the Beaverlodge area formed at ca. 1.85 Ma from metamorphic fluids at ca. 330oC linked to metasomatism during regional metamorphism of the Trans-Hudson Orogen. The ore-forming fluids were likely derived from metamorphic remobilization of pre-existing U-rich basement rocks, and ascended upward along deep fracture systems that resulted from brittle reactivation of early ductile shear zones. The main event of U mineralization in the South Alligator River area formed at ca. 1.82 Ma, subsequent to deposition of the El Sherana Group at 1.84-1.83 Ma. The formation of these deposits is related to fluids derived from diagenetic processes in sandstone of the El Sherana Group. Mineralization formed when a 250oC, low latitude, oxidizing, U-bearing basinal brine from diagenetic aquifers in the Coronation sandstone descended downward into the unconformity along fracture systems created by brittle reactivation of the El Sherana-Palette fault system. Uranium deposits associated with successor basins in the Beaverlodge and South Alligator River area are older than those in the U-rich Athabasca and Kombolgie basins. Rocks that host these deposits have been folded, and then exhumed during subsequent tectonic events. These older U deposits can be considered as a potential source for detrital uraninite that fed sediments of the Athabasca and Kombolgie basins and therefore contributed to the inventory of uranium that formed unconformity-related U mineralization in the younger basins. Therefore, the occurrence of older U mineralization associated with successor basins can be considered as positive criterion for exploration of unconformity-related U mineralization in younger Paleoproterozoic basins. / Thesis (Ph.D, Geological Sciences & Geological Engineering) -- Queen's University, 2012-08-13 18:54:41.141

Thesis (Ph.D.) - James Cook University, 2004. / Typescript (photocopy) Appendices: leaves 135-137. Bibliography: leaves 126-134.