Thesis. 1976. M.S.--Massachusetts Institute of Technology. Dept. of Electrical Engineering and Computer Science. / Microfiche copy available in Archives and Engineering. / Includes bibliographical references. / M.S.

Advancements in power electronics to higher power levels and faster switching times allow new machine and systems designs, but also create higher stresses on electric machinery insulation. High performance, pulse-width modulated (PWM) inverters are now available for medium voltage drive systems, and are being considered by the U.S. Navy as they move to the "all-electric" ship. If this process is to be successful, a necessary component will be to understand the impact of partial discharge (PD) generation on electric drive systems. Out of the many PD influencing parameters, voltage level, voltage rise-time, switching frequency, and temperature were chosen to be investigated with regards to their influence on PD generation in a comprehensive research project in the Motor Systems Research Facility (MSRF) at Oregon State University (OSU). The tests were performed on representative propulsion coils employing two different 4160 V insulation systems and were evaluated by both an optical and electrical PD detection method. A highly flexible test configuration was developed, capable of adjusting each of the four test parameters independently over a wide range of appropriate values. The developed test program enabled the analysis of the influence of the parameters on the generation of PD, as well as an evaluation of the test coils and PD instrumentation used. It is concluded that, as expected, voltage level is the most significant parameter affecting PD production. However, there is a surprising interdependence of rise-time and pulse-width that requires further investigation. Multiple-cycling tests are seen as appropriate to determine the effect of temperature. Based on the subjective nature of the findings from the test program an improved PD instrument is proposed, which would increase the capabilities and objectivity of the PD detection process. / Graduation date: 2004

Thesis (M.S.)--University of Missouri-Columbia, 2006. / The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file viewed on (February 26, 2007) Includes bibliographical references.

Y company started in 1988 positioned to be the largest and the most advanced coated steel producer. Y company (includes the plant in China)Owned seven continuous hot-dup galvanizing lines , five continuous pre-painting lines¡A6 cold rolling mills and 2 pickling lines .Y company has become not only the biggest coated steel producer in Taiwan ,Mainland China and South East Asia , but also one of the 15th largest producers of coated steel products in the world. Y company is able to offer a wide range of finished products to meet the needs of our customers one-stop shopping need. Y company is a coated ¡V steel producer which produce hot¡Vdip galvanized coils and pre-painted coils by means of the manufacturing process of pickling ,cold rolling ,hot-dip galvanizing and pre-painting .On recent ten years ,the steel market changes sharply, but Y company keep growing continuously , the key factor is to establish the strategic alliance with F company to replace electroplating steel sheet with hot-dip galvanized in computer cases . This research is studying the experience story, which we have overcame a number of difficulties during the period developed the ¡§replacing electroplating steel sheet with hot-dip galvanized in computer cases ¡¨and ¡§developing environmentally- friendly steel ¡¨. it is a story that the strategic alliance strenghthen organization ¡Fand after organization empowerment ¡Ait made the relationship between the members of the strategic alliance more closely. This story is to show the difficulties and challenges what we face by means of the Narrative Inquiry and hope to achieve the next success for the next opportunity on the basis of meanings from this story .

Phased array coils are composed of several surface coils receiving individual element signals simultaneously. Each individual surface coil provides the equivalent of the coil diameter range, and higher SNR. Therefore, combining these non-interactive phased array coils, can achieve a wide range of scan areas, uniform sensitivity and better SNR. Therefore our experiment was performed with two different coils of quadrature coil and phased array coil. Phased array MRS data were compared using various combination approaches. Data acquired by quadrature coil was regarded as a standard to verify the reliability and accuracy of metabolite concentration. The aim of our study is to do eddy current correction before and after the combination of each element coil data with LCModel analysis for quantitative comparison of metabolite concentrations. Our result shows that doing eddy current correction for each phased array coil before signal combination can achieve higher reliability and accuracy of SNR and quantitative concentrations of MR spectra in vivo.

Much of the current research in magnetic resonance engineering focuses on reducing the acquisition time for obtaining an image while simultaneously maximizing the Signal to Noise ratio (SNR) of the image. It is known that improvement in imaging time or resolution is obtained at the cost of SNR. Therefore wherever possible, RF coil engineers design the coil in such a manner so as to maximize SNR for that coil design. In one such design consideration, most coil designers prefer placing low impedance preamplifiers near the coil. The further the pre-amplifiers are from the coil, the greater will be the signal loss due to transmission and higher will be its input impedance as perceived at the coil which would degrade inter-coil isolation. Owing to the current trend of using increasing number of receiver channels (32, 64 or 128) for parallel imaging, placing the preamplifiers near the coil would greatly complicate the coil construction. The primary objective of this research was to find the relation between SNR and referred preamp impedance and whether preamps need to be placed on the coil, or if they can be placed outside the magnet at the end of a transmission line which would simplify the construction of large count array. In addition, SNR was studied as a function of coil design parameters - coil loading, array coil separation, and system frequency. Both theoretical and experimental methods were used to undertake this investigation. A popular electromagnetic modeling technique, finite difference time domain (FDTD), was used to model SNR in arrays of two 3 inch loop coils at 3T and 1.5T. Results were also verified through bench measurement at 3T and 1.5T and by evaluating SNR. To verify the robustness of our results and to assess the possibility of using low cost standard 50 ohm preamps, we carried out additional bench measurements at 4.7T. Results demonstrated that preamplifier placement is critical at low field strength. At higher field strength, SNR degradation due to preamplifier placement was less owing to heavier coil loading.

Proteins have a wide array of essential functions: from serving as enzymatic catalysts to protecting the immune system as antibodies. Proteins spontaneously self-organize into specific, folded structures determined by their amino acid sequences and the interaction between molecular forces. Since the 3-dimensional structure into which they fold often relates to the specific function of the protein, much effort has been directed towards methods to predict the folded structure from a given sequence, with the hope of being able to understand protein functions from sequence information. The protein folding problem can be summarized as the attempt to understand the relationship between a protein sequence and a protein's geometric shape, or fold. Thus, there are two principal problems: given a sequence, what 3-dimensional form will the protein take (forward problem), and given a particular fold, what sequence or sequences code for that form (the inverse problem). In this work, models that represent folds as continuous structures are explored. Models of the two prevalent motifs in protein folds, α helices and β barrels, are developed using axially deformed tubes and surfaces of revolution. These models are then analyzed and used to develop coordinate models of known and unknown structures.

No description available.

No description available.

A fusion-fission (hybrid) reactor is a combination of a fusion device and a subcritical fission reactor, where the fusion device acts as a neutron source and the power is mainly produced in the fission core. Hybrid reactors may be suitable for transmutation of transuranic isotopes in the spent nuclear fuel, due to the safety margin on criticality imposed by the subcritical fission core. The SFLM Hybrid project is a theoretical project that aims to point out the possibilities with steady-state mirror-based hybrid reactors. The quadrupolar magnetic mirror vacuum field is based on the Straight Field Line Mirror field and the central cell is 25 m long. A fission mantle surrounds the mirror cell. The fission to fusion power ratio is about 150 with keff = 0.97, implying that almost all the produced energy comes from fission. Beyond each mirror end magnetic expanders are located, which increase the plasma receiving “divertor” area and provide tolerable heat load on wall materials. The plasma is heated with ion cyclotron radio frequency heating and the fission mantle is cooled using a liquid lead-bismuth eutectic. The device is self-sufficient in tritium, and does not seem to suffer from severe material problems. A remaining issue may be the plasma electron temperature, which need to reach about 500 eV for efficient power production.  In this doctoral thesis, theoretical work has been done with the magnetic coil system of such a device and also with the overall concept. A new coil type, the fishbone coil, suitable for single cell quadrupolar mirrors, has been invented. Two vacuum field coil sets with satisfying properties have been found, where the most recent coil set consists of fishbone coils. Finite ß effects on the magnetic field have been investigated, showing that the flux tube ellipticity increases with ß. The ellipticity of the vacuum field increases slightly with radius, but with finite ß it decreases with radius. The maximum flux surface radial extensions decrease with ß, which is an unexpected and beneficial result. A radial invariant has also been identified, and particle simulations have been made to emphasize that quadrupolar mirrors must be symmetric or confinement may be lost.