A parametric design study of light weight mirror shapes with various support conditions was performed utilizing the finite element program NASTRAN. Improvements in the mirror performance were made based on the following design criteria: (1) minimization of the optical surface wavefront variations, (2) minimization of the self-weight directly related to cost of manufacturing, and (3) optimal location of support points. A pre-processor to automatically generate a finite element model for each mirror geometry was developed in order to obtain the structural deformations systematically. Additionally, a post-processor, which prepares an input data file for FRINGE (an optical computer code) was developed for generating the optical deflections that lead to the surface wavefront variations. Procedures and modeling techniques to achieve the optimum (the lightest and stiffest mirror shape due to self-weight) were addressed. Fundamental natural frequency analyses, for contoured back mirror shapes for a variety of support conditions, were performed and followed by comparisons of the results which were obtained from NASTRAN and a closed-form approximate solution. In addition, element validity and sensitivity studies were conducted to demonstrate the behavior of the element types provided in the NASTRAN program when used for optical applications. Scaling Laws for the evaluations of the optical performances and the fundamental frequencies were established.

Chen, Qiulan. / "November 2010." / Thesis (Ph.D.)--Chinese University of Hong Kong, 2011. / Includes bibliographical references (leaves 140-152). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese.

Since the dawn of the computer age, there has been a push to create miniature devices. These devices were initially integrated circuit (IC) devices to perform calculations for computers. As the technology progressed, the scope of the devices diverged to included microelectromechanical (MEMS) devices, meaning that the devices perform mechanical movements via electrical actuation. More recently, a new generation of devices has evolved called microtechnology-based energy and chemical systems (MECS). MECS may employ MEMS technology, however the systems are not designed to produce only mechanical movement. MECS deal with heat and mass transfer, the basic processes used in energy, chemical and biological systems, in the mesoscale realm. Mesoscale devices range from the size of a sugar cube to the size of a human fist. The possibilities of MECS have not been realized. Heating and cooling systems, chemical mixing/distribution, and locking systems are all potential applications. The devices require: 1) revolutionary design, accounting for the scaling effects on device performance; 2) new fabrication technologies for the creation of these designs; and 3) good material properties for mechanical and chemical interactions. Fabrication requirements for MECS are different than for MEMS in that MECS generally require non-silicon metals. Metal microlamination (MML) has been introduced as a general practice for meeting the fabrication requirements for MECS. Prior MML fabrication methods have emphasized the use of diffusion bonding, soldering, or brazing techniques. This thesis will introduce: 1) a novel microflapper valve design fabricated in mild steel using a novel microprojection welding technique; 2) a novel microfloat valve design fabricated in mild steel using a novel capacitive dissociation process for creating free floating geometries. The devices are characterized by comparing actual flow rates to theoretical flow rates of equivalent orifice sizes. Preliminary results show that the microfloat valve achieved an average diodicity (free flow versus leakage rate) ratio of 11.19, while the microflapper valve achieved an average diodicity ratio of 4.08. The theoretical orifice sizes of the microfloat and microflapper valves are 0.629 mm and 0.611 mm respectively. These results suggest that the float valve is the superior design. / Graduation date: 1999

No description available.

Micro-Electro-Mechanical Systems (MEMS) have played an important role in modern microelectronics, thermal, mechanical and hybrid systems. MEMS technology is a very promising means that might have a great impact on almost every corner of the society. Although many design methodology of MEMS already exists, not as much attention was given to the synthesis and optimization of MEMS devices. This thesis focuses on the optimization of MEMS actuators and MEMS tunable comb drive capacitors. The optimization is based on changing device geometry to achieve desired output parameter profile. For example in the design of MEMS tunable comb drive capacitors, the output parameter is the capacitance tuning range. Numerical experiments were performed to show the successful implementation of the optimization method.

No description available.

Thesis (M.S.)--University of Hawaii at Manoa, 2006. / Includes bibliographical references (leaves 96-99). / xiii, 99 leaves, bound ill. (some col.) 29 cm

Thesis (MTech (Mechanical Engineering))--Cape Peninsula University of Technology, 2005 / Having simple structure and high sensitivity, micro accelerometer is a type of popular transducer used to measure the acceleration in a great variety of conditions. The bridge-type micro accelerometer is a typical micro accelerometer and has many types. As one of research project of Kentron in South Africa, the thesis presented here analyzes the bridge-type capacitive nticro accelerometer (BTCMA) and the bridge-type micro accelerometer with two piezoelectric thin films read-out (BTPMA). In this thesis, the similar structures are used on BTCMA and BTPMA For proving the fundamental mode of the structure can measure acceleration and utilizing the structural and electric characteristic to avoid the effect of higher modes, the program CoventorWare for nticro-electric-mechanical system (MEMS) design and analysis is used here to analyze the modes of these two structures, The two group piezoelectric thin films of BTPMA can be connected in serial or parallel configurations. Integrating piezoelectric effect method, strength method and energy method, the analytical analysis of these two configurations has been done with particular emphasis on the elastic characteristics of the thin films. The analytical formulas of transducer, sensitivity, resonance frequency, noise, quality factor, ntinimum detectable signal and maximum detectable range are obtained. According to the comparison results between these two configurations, the charge output in parallel configuration is a little more than that in serial configuration and the sensitivity in serial configuration is much higher than that in parallel configuration. Finally, a calculation of certain practical nticro accelerometer size is used to prove the above conclusions. On the base of capacitance theory, strength method and energy method, the analytical analysis of the BTCMA has been done in this thesis.

Thesis (MTech (Mechanical Engineering))--Cape Peninsula University of Technology, 2005. / Due to an increasing in industrial micromation need in recent years, the use of micro accelerometers has been highly increased. Consecutively, this has promoted research activities in this field; capacitive accelerometers also have got high concern at large. As a research project of the Kentron in South Africa, this thesis deals with a theoretical model for a one-dimensional micro capacitive accelerometer with U-shape cantilever beam. The properties of the small angle tilted-plate capacitor have been analyzed; the capacitance equation and electrostatic force equation of this kind capacitor have been derived. The sensing element of this accelerometer consists of an inertial mass connected with two cantilever beams. The vibration modes analysis to the sensing element was accomplished by using CoventorWare2004's MemMech module, the result indicates that the main vibration mode can cause the capacitance change observably and the effect of the other modes to the capacitance can be ignored, which satisfied the purpose of the design. In the process of deriving the linearizing acceleration equation, the angle of the inertial mass caused by the deformation of the U-shape cantilever beam was taken into account as well as the electrostatic force between the two electrodes, thus the more precise acceleration linear equation was obtained. The sensitivity equation was derived through the acceleration linear equation, the relationship between the main parameters of the system and the sensitivity has been analyzed. The differential structure of this micro capacitive accelerometer was also analyzed; the linearizing acceleration equation and sensitivity equation of this kind structure were derived, it has been proven that the sensitivity of this structure is twice than the normal structure approximately. The maximum detectable signal was obtained in terms of the fracture strength of the cantilever beam and the maximum displacement of the inertial mass. The minimum detectable signal was obtained in terms of the thermal noise analysis. In the process of the dynamic analysis, the forced vibration produced by the sinusoidal periodic force and sinusoidal periodic moment was analyzed and the transient capacitance equation was derived, this proved the system has good dynamic character in theory. The system was simulated and analyzed by using CoventorWare2004's Saber module. The initial capacitance analysis indicates the relationship between the voltage and the initial capacitance, the result is close to the analytic model. The resonance frequencies analysis indicates that the main dimensions of the sensing element can determine the resonance frequencies and each vibration mode's sequence, the initial dimensions of the sensing element was proved reasonable by analyzing. Sensitivity analysis and Monte Carlo analysis indicate the effect of the sensing element's normal manufacturing tolerance to the system's frequency is small. Impact of plate curvature analysis indicates the effect of the inertial mass's deformation caused by the surface stress to the capacitance is small. Transient analysis obtained the system's transient displacement curve of six directions and transient capacitance curve in normal terms; this proved the system has good dynamic character in the simulating environment.

University of Macau / Faculty of Science and Technology / Department of Electromechanical Engineering