Photocopy of typescript. / Digitized by Kansas Correctional Industries

The suppression of turbulent transport is a key requirement for enabling nuclear fusion to become a viable energy source. One possible route to achieving this suppression is through toroidal flow shear. We investigate the effect that flow shear has on the structure of turbulence by analysing data from both measurements of the fluctuating intensity field using the Beam-Emission-Spectroscopy (BES) diagnostic on the spherical tokamak MAST, as well as from numerical simulations of the fluctuating density field in MAST. We develop a procedure to map from the correlation parameters of the intensity field to the correlation parameters of the density field. This procedure is illustrated using the MAST BES system and the validity of the underlying assumptions is tested on fluctuating density fields generated by direct numerical simulations using the gyrokinetic code GS2. By using this procedure, we demonstrate how, in experiment, the flow shear associated with the differential toroidal rotation of tokamak plasmas breaks an underlying symmetry of the turbulent fluctuations imposed by the up-down symmetry of the magnetic equilibrium. Indeed, in both experimental BES measurements and gyrokinetic simulations, this symmetry breaking in ion-scale turbulence in MAST is shown to manifest itself as a tilt of the spatial correlation function and a finite skew in the distribution of the fluctuating intensity (density) field. The tilt is a statistical expression of the "shearing" of the turbulent structures by the mean flow. The skewness of the distribution is related to the emergence of long-lived density structures in sheared, near-marginal plasma turbulence. The extent to which these effects are pronounced is argued (with the aid of the simulations) to depend on the distance from the non- linear stability threshold. Away from the threshold, the symmetry is effectively restored.

Este trabalho buscou estudar os efeitos do nível de Swirl e alteração da massa de combustível injetada nas emissões de poluentes de um motor Diesel. Foram selecionados 15 cabeçotes de uma população de 100 cabeçotes e agrupados pelo nível de Swirl. Como o motor testado utiliza 5 cabeçotes, 15 cabeçotes foram separados e classificados em 3 categorias pelo nível de Swirl. Em seguida, o motor foi montado com as 3 categorias de cabeçotes no dinamômetro com o objetivo de levantar os efeitos nas emissões de gases e parâmetros de desempenho do motor. Foram medidas as emissões de NOx, CO, THC, fuligem, fumaça e consumo de combustível nos 13 pontos do ciclo ESC, complementadas com medições de torque e potência à plena carga. Além disso, nas condições de plena carga foi explorado o efeito da alteração da massa de combustível injetado, pela mudança do ponto final de injeção, nos parâmetros de desempenho e emissões. / This work aimed at the investigation of the effects of the level of Swirl and the amount of fuel mass injected in the emissions of pollutants on a diesel engine. Cylinder heads were selected from a population of 100 cylinder heads and them grouped by Swirl level. As the engine used in the tests have 5 cylinder heads, 15 cylinder heads were separated into 3 categories by the Swirl level. The engine was mounted with the 3 Swirl level cylinder heads categories with the aim to investigate all effects on emissions and performance such as NOx, CO, THC, soot, smoke, fuel consumption, power and torque. The tests were performed following the ESC cycle and exploring the full load curve behavior with changes of the end of injection point, therefore altering the amount of fuel mass injected.

Measurements of the electron-induced electron emission properties of insulators are important to many applications including spacecraft charging, scanning electron microscopy, electron sources, and particle detection technology. However, these measurements are difficult to make since insulators can charge either negatively or positively under charge particle bombardment that in turn alters insulator emissions. In addition, incident electron bombardment can modify the conductivity, internal charge distribution, surface potential, and material structure in ways that are not well understood. A primary goal of this dissertation work has been to make consistent and accurate measurements of the uncharged electron yields for insulator materials using innovative instrumentation and techniques. Furthermore, this dissertation reports on the experimental work undertaken by our group to explore insulator charging rates as a function of incident electron energy and fluence. Specifically, these charging studies include: (i) the study of the effectiveness of charge-neutralization techniques such as low-energy electron flooding and UV light irradiation to dissipate both positive and negative surface potentials induced by incident electron irradiation, (ii) the exploration of several noncontacting methods used to determine insulator surface potentials and the insulator first and second crossover energies that are important in determining both the polarity and magnitude of spacecraft material potentials, (iii) the dynamical evolution of electron emissions and sample displacement current as a function of incident charge fluence and energy with ties to evolving surface potentials as an insulator reaches its current steady state condition, and (iv) the slow evolution of electron yields with continuous incident electron bombardment. These charging data are explained in the context of available insulator charging models. Specific insulator materials tested included chromic acid anodized aluminum, RTVsilicone solar array adhesives, and KaptonTM on aluminum.

No description available.

This thesis reviews in general the topic of electromagnetic compatibility, and electromagnetic interference and their origin and effects in modern electronically controlled motor drives. The measurement techniques for EMI noise are reviewed. The sources of noise of a switching power circuit are described. This thesis investigates the establishment of a procedure for measuring conducted emission produced by motor drives, using a virtual instrument. This procedure is based on the traditional methodology of EMI measurement and the use of simulation techniques. A test bench is designed. The thesis covers the detailed design of a virtual instrument for measuring conducted current produced by motor drives. A line impedance stabilisation network LISN is designed and built. A series of measurements were carried out using the developed instrument. The results show very little difference between the conducted emission produced by induction, permanent magnet and reluctance motor drives. Comparing one of the experimental results with published results from a major test laboratory assesses the validity of the designed instrument. The experimental results refer to drive systems under no load conditions. Useful conclusions are drawn and future research studies recommended. / Master of Engineering (Hons)

Wayne B. Nottingham. / "December 10, 1956." "This report is identical with material published in Handbuch der Physik, Volume XXI, 1956." / Includes bibliographical references. / Army Signal Corps Contract DA35-039-sc-64637 Project 102B Dept. of the Army Projects 3-99-10-022 DA3-99-10-000

R.B. Bien. / "June 29, 1949." / Army Signal Corps Contract No. W36-039-sc-32037 Project No. 102B. Dept. of Army Project No. 3-99-10-022.

Thesis (Ph.D.)--University of Delaware, 2006. / Principal faculty advisor: James Kolodzey, Electrical and Computer Engineering. Includes bibliographical references.

No description available.