Thesis (M.S.)--University of Missouri-Columbia, 2004. / Typescript. Includes bibliographical references (leaves 111-114). Also available on the Internet.

Thesis (M.S.)--University of Missouri-Columbia, 2004. / Typescript. Includes bibliographical references (leaves 76-80). Also available on the Internet.

Thesis (M.S.)--University of Missouri-Columbia, 2004. / Typescript. Includes bibliographical references (leaves 111-114). Also available on the Internet.

No description available.

Electrical, forming and switching characteristics of metal-semiconductor-metal (MSM) memory switches of ion bombarded hydrogenated amorphous silicon (a-Si:H) and its alloys are presented. MSM devices for memory switching applications are known to be characterised by instabilities as well as non-uniformity and irreproducibility of the forming and switching characteristics. It is believed that the presence of defect states in the semiconductor layer plays a significant role in the observation of memory switching in these MSM devices. Gas-phase doping and current stressing of the semiconductor are some of the techniques that have been used in the past to introduce mid-gap defect states. In this work, we use for the first time, ion bombardment as a novel tool for defect introduction into the semiconductor material of the MSM devices and we compare the electrical, forming and switching characteristics of these devices to those fabricated using the previous techniques mentioned above. A significant observation is that as the density of defects is increased in the semiconductor film with increasing implantation dose, conduction in the devices changes from barrier-controlled thermionic emission to bulk controlled where carriers hop through the defect states in a Poole-Frenkel manner. This transformation eliminates problems associated with Schottky barriers such as quality of contacts, oxidation, etc. In the forming characteristics, not only do we report enhanced uniformity of the forming voltages (VF) but also the magnitude of VF is observed to vary systematically with the implantation dose used. The ON states and switching characteristics in the bombarded devices are also observed to be much more stable presumably as a result of the uniformity of the defects introduced by ion bombardment. We report also an enhanced switching ratio in the ion bombarded devices, especially after partial annealing of the bombardment induced Si dangling bond defects.

This thesis presents the development of a Hybrid Multilevel Switching Converter (HMSC) for Ring-Magnet Power Supplies (RMPS). The thesis includes the analysis, design and control of the proposed converter. It introduces multilevel switching converters to the field of ring-magnet power supplies. RMPS feed the electromagnets that produce the magnetic field required to energize and guide subatomic particles in a synchrotron. The accuracy and extreme precision of this magnetic field imposes stringent restrictions on the design and performance of the RMPS used. Study of conventional power supplies highlights the need for modern power supply solutions which can meet the specifications of RMPS. The complete frequency-domain analysis of the conventional resonant-type RMPS along with the Energy Make-up Unit (EMU) is presented. The resonant frequency drift is identified as the main factor in the design of the EMU. The analysis of the input filter network is presented for development of design criteria for input filter components. The principle advantages and disadvantages of the resonant-type RMPS are summarized before identifying multilevel converters as a viable option among switching converters for a non-resonant type of RMPS. The Hybrid Multilevel Switching Converter (HMSC) is proposed as a non-resonant type RMPS to overcome the disadvantages of the resonant-type RMPS. The operational features of the HMSC are explained and the simplification of the general HMSC configuration for positive output currents is identified. The steady-state analysis of the HMSC develops comprehensive design criteria for the device ratings and component stresses, including the methods for reducing the switching losses in the HMSC. Multilevel converters encounter voltage balancing problem among the DC-link capacitors. It is shown that the HMSC configuration is versatile in minimizing this problem. Harmonic spectrum of the output voltage of the HMSC is derived and the effect of number of output voltage levels in reducing the harmonic contents is established. A detailed survey of different current control techniques is presented to form the background for developing an effective current control algorithm for multilevel converters. A dead-beat current control strategy is chosen as an appropriate control technique to suit the needs of RMPS. The control scheme is extended to the control of multilevel converters in general. The control algorithm is developed to track a given arbitrary current reference signal for both single-variable and multi-variable systems. It is also shown that the output dead-beat control is a special case of the pole placement technique. The transient behaviour of the system has been studied and stability considerations of the system are examined. Extensive computer simulation studies have been performed using SABER to study the reference tracking nature of the proposed control scheme. The output current of the HMSC using the modified dead-beat control scheme is shown to follow a given arbitrary-reference with very small tracking error. The reference tracking nature has been simulated for a simple RL magnet load and a magnet load with LCR filter. Experimental results obtained from a laboratory prototype of the HMSC with an RL load, have been presented to substantiate the analytical results. Criteria for improvement in the reference tracking properties of the proposed system have been identified. / Graduate

In this work, MEMS inertial switches intended to be triggered at multiple acceleration thresholds in two directions were implemented and proven effective. The switches consume virtually no power in their open switching state. Multiple acceleration thresholds can be beneficial in triggering different actions for different acceleration events. Low power consumption can aid in their use for portable applications such as in cycling helmets. The developed designs rely mainly on a suspended shuttle mass, which is used to implement one of two methods of actuation. The first relies on simple contact between the moving shuttle mass and a flexible electrode. In the second, the pull-in instability is induced by applying a voltage between a cantilever and an electrode, and then having the shuttle mass force the cantilever moving towards the electrode as it moves under the applied acceleration. Ten designs varying in their actuation method, suspension design, intended acceleration thresholds, and dimensions were modeled using a finite element model, fabricated, through the SOIMUMPs process, and then electrically and mechanically tested. Mechanical testing has been conducted using Drop-table tests and mechanical shakers. The simple contact devices were proven effective through shock test results showing triggering at two acceleration thresholds in two directions. Initial results also were promising for the pull-in based devices showing switching by moving their shuttle mass with a probe while applying appropriate voltage and observing under a microscope.

<p>High pressure surface discharge switches have become the subject of applied research in recent years due to their important application in pulse power systems. The purpose of this study is to gain a better understanding of the subject so that an optimum design of the switch may be achieved. The surface discharge phenomena is examined under single channel static breakdown condition to attempt to isolate individual processes involved. The multichannel switch developed by the NRC is tested with a resistive load assembly to determine the optimum operating conditions. The lifetime characteristic is also studied using a small experimental device. Finally, two models for the switch are developed to fit the observed data. </p> / Thesis / Master of Engineering (MEngr)

No description available.

International Telemetering Conference Proceedings / October 25-28, 1999 / Riviera Hotel and Convention Center, Las Vegas, Nevada / This paper presents the future of optical networking via photonic switches as a potential replacement for the existing electronic cross-connects. Although optical amplifiers are now mainstream and wave division multiplexing (WDM) systems are a commercial reality, the industry’s long-term vision is one of the all-optical network. This will require optical switching equipment such as all-optical or “photonic” cross-connect switches that will provide packet switching at an optical layer. Currently, as voice calls or data traffic are routed throughout Range and commercial networks, the information can travel through many fiber-optic segments which are linked together using electronic cross-connects. However, this electronic portion of the network is the bottleneck that is preventing the ideal network from achieving optimal speeds. Information is converted from light into an electronic signal, routed to the next circuit pathway, then converted back into light as it travels to the next network destination. In an all-optical network, the electronics are removed from the equation, eliminating the need to convert the signals and thereby significantly improving network performance and throughput. Removing the electronics improves network reliability and restoration speeds in the event of an outage, provides greater flexibility in network provisioning, and provides a smooth transition when migrating to future optical transmission technologies. Despite the fact that photonic switching remains uncommercialized, it now seems apparent that the core switches in both the public networks and DoD Range networks of the early 21st century will probably carry ATM cells over a photonic switching fabric.