A delay line phase shifter for the 30-70 GHz range is presented that uses an aluminum micro-ribbon array fabricated in the ground plane of a microstrip transmission line. Phase shift is achieved by changing the propagation velocity of an RF signal in the transmission line by controlling the effective permittivity of the substrate. This is done by actuating the micro-ribbons away from the substrate. This phase shifter has the benefits of analog phase shifts and high Figure of Merit. Simulations were done to model the micro-ribbon deflections, transmission line performance and phase shift. Arrays of 5, 10, and 20 μm wide micro-ribbons were fabricated and tested. At 40.80 GHz, the 20 μm wide micro-ribbons had a measured phase shift of 33º with an actuation voltage of 120 V. The corresponding Figure of Merit was a negative value indicating that there was no line loss due to ribbon deflection. / February 2008

The demand for reduced-size components and devices is pervasive throughout industrial and commerical sectors. This drive to reduce the achievable size of parts and features has furthered the developmen of processes and tools capable of micro scale fabrication. In particular, one of the directions this field has taken is in scaling down traditional machine tools. Being a relatively young area of manufacturing, the area of miniaturized machining is still developing and a significant portion of work remains yet to be done. As a thorough understanding of this area is still developing, experimental tests play a significant role furthering this process. Therefore the direction of this project has been to explore this field using a predominantly experimental approach. The aim of it being to realize a miniaturized machine tool capable of fabricating features and even parts on the micro scale. Additionally the machine should be controlled as a standard milling machine and also be capable of generating free form three dimensional parts. In parallel to developing a machine tool, the project has also been directed at examining the machine's capabilities through a range of tests. For creating such a machine tool, the process was carried out in a two stages. Each stage involved a miniaturized machine tool at a different level. The first machine tool produced primarily served as a proof of concept structure. By performing a range of tests on this machine, it allowed for useful insights be to gained for developing the subsequent stage along with establishing some base performance characteristics which were also used for subsequent comparisons. The primary contributions made in this research include: the development of a miniaturized machine, the completion of experiments that map out the machine's capabilities, and theoretical calculations which further define these limits.

No description available.

Increasing the catalyst utilization is one way to improve the performance of a fuel cell. In this study, the hydrophobic pillared micro structures (HPMS) is used to increase the oxygen/ catalyst layer interface and thereby raise the performance by about 40%. By using the HPMS of a large size, the performance is improved by around 20%, which is just the same as the increment of the contact surface between oxygen and catalyst layer. By halving the loading of the small HPMS and thus increasing the contact surface between oxygen and the catalyst layer by half of the previous amount, the performance increase is also halved. These experimental results indicate that the main reaction zone is near the surface between oxygen and the catalyst layer. Consequently, there is no obvious decrement in the performance when the Pt loading of cathode is halved, just as the experimental results indicated. As a result, the utilization of catalyst is raised substantially.

The machining of materials on micrometer and sub-micrometer scale is considered the technology of the future. The current techniques for micro manufacturing mostly are silicon based. These manufacturing techniques are not suitable for use in demanding applications like aerospace and biomedical industries. Micro electrochemical machining (μECM) removes material while holding micron tolerances and μECM can machine hard metals and alloys. This study aims at developing a novel μECM utilizing high frequency voltage pulses and closed loop control. Stainless steel SS-316L and copper alloy CA-173 were chosen as the workpiece materials. A model was developed for material removal rate. The research studied the effect of various parameters such as voltage, frequency, pulse ON/OFF time, and delay between pulses of the stepper motor on the machined profiles. Experimental data on small drilled holes agreed with theoretical models within 10%. Micro burrs can be effectively removed by optimal μECM. A sacrificial layer helped to improve the hole profile since it reduced 43% of corner rounding.

Abstract This Concept of micro-entrepreneurship deriving from APEC (Asia Pacific Economic Cooperation), it is said that the best method to improve women¡¦s economy is to encourage them by involving into it. Traditionally, Taiwan indigenous peoples had always earned their living by farming, foresting, fishing, and herding as primary industries, which relatively caused tribal society an inferior situation and low income. With recent years of social, industrial, and educational change in structure, the development of knowledge economic gives indigenous peoples an option to start their own enterprise, or chances to serve in all walks of life. On the other hand, our government also makes every effort to popularize to start a enterprise and provides plural entrepreneurship loans. After effective guiding and assisting, a number of entrepreneurships grow by 3000 to 5000 cases per year and have higher portions for women. In 2006, entrepreneurship for women is up to 44.9% and not far from 55.1% for men. From 2002 to 2006, Council of Indigenous People, Executive Yuan had issued 822 loan cases in total from Indigenous People Developing Fund, whiled 346¡]40%¡^ were for women. Therefore, entrepreneurships for indigenous women are growing in market. In Taiwan, about one hundred thousand small and medium-sized enterprises establish every year, but only twenty thousand exist. Low capitalization and less-than-five-people micro enterprises turn over faster. Entrepreneurship is easy, but holding achievements is hard. Council of Indigenous People, Executive Yuan had selected 14 successful indigenous women in 2006. This study, thus, focuses onindigenous women who have their own business by using In-Depth Interviewing and ATLAS.ti software. And we get the result that the key factors for indigenous women in entrepreneurship are keeping practicing and possessing great sense of mission for indigenous culture. We have demonstrated with figures of network. This study finds that when surveying their experiences and progress, responders recalled the major problems were lack of entrepreneurship capitals (mainly), lack of turnover capitals, lack of managing experiences, and lack of adaptable talents. Some would think that government is not a helper but a barrier during entrepreneurship progress. In the future, government should let it as a mirror when driving indigenous policies.

This thesis proposes a multi-parameter implantable micro-stimulator system. By using wireless communication and the muli-parameter control, the infection caused by the wound could be avoided and various stimulation waveforms could be generated for different bio-medical applications. Besides, a graphic user interface (GUI) is implemented for the proposed micro-stimulator for the convenience of usage. Moreover, the in vitro experiments are carried out, where the neurons could be stimulated successfully. To reduce the system area caused by external capacitors required by traditional ASK demodulators, a C-less ASK demodulator is proposed in this thesis. A bias-based envelope detector and a Schmitt trigger are used for demodulation. Moreover, by enlarging the noise margin of the envelope detector, an all-MOS ASK demodulator is carried out such that no passive element is needed and the system area could be further reduced. Besides, two high sensitivity voltage-to-frequency (VFC) are proposed for the full duplex transmission. By using a voltage-to-current converter, a charge and discharge circuit, and an all-MOS voltage window comparator 1 (VWC1), a high sensitivity VFC1 is accomplished. Moreover, a linear VFC2 is also proposed by including a fast all-MOS voltage window comparator, VWC2. Finally, a wide range I/O buffer is proposed for the interface of the implantable micro-stimulator system. With the stacked PMOS and NMOS output stage and the dynamic gate bias generator, high voltage and low voltage signals (VDDH and VDDL) could be transmitted and received without any gate-oxide overstress and leakage currents.

Cutting fluids are mainly used for cooling, lubricating, and chip removing. The use of minimum/minimal quantity lubrication (MQL) in machining processes not only reduces the cost of cutting fluids but also has the potential to alleviate the environmental impact. In addition, the MQL technique could be a viable choice to decrease the damage to the miniature machines due to the near-dry lubrication. Therefore, the objective of this study is aimed at the mechanical performance of MQL for micro-grinding of SK3 steels based on surface finish and tool life. In this study, it is observed that tool breaks in dry grinding or air blow grinding, and it is also found that workpiece surface is burned in dry grinding. However, these phenomena are not observed in MQL grinding. The reason is that the use of MQL reduces the friction between the tool and workpiece and improves the chip removal in micro-grinding. The use of MQL in micro-grinding also leads to better surface roughness and the tool life is more than seven times compared to dry grinding. Experimental results show that the best surface finish is achieved in MQL grinding when the use of cutting fluids is 1.88 ml/hr with the air flow rate of 30 l/min among the lubrication conditions in this study.

Thesis (Ph. D.)--Oregon State University, 2010. / Printout. Includes bibliographical references (leaves 125-134). Also available on the World Wide Web.

Thèse de doctorat : Sciences et ingénierie des matériaux : Paris Est : 2008. / Titre provenant de l'écran-titre.