Doubly-Salient Reluctance Machines (DSRMs) sidestep many of the issues with permanent magnet and induction machines and embody the lowest cost and simplest manufacturing of the motor technologies. Major drawbacks to RMs have been (1) the need for failure-prone electrolytic capacitors, (2) large torque ripple, and (3) acoustic noise. Conventionally, these drawbacks have been addressed independently either through (1) excitation control or (2) machine design, but not as a holistic system or solution. This disseratation presents a design for high-efficiency low-cost RM while producing smooth output torque and avoiding pulsating inverter input current and the associated electrolytic capacitor. We propose a method for shaping the machine reluctance profile to reduce machine torque ripple to a desired level (here, <5%) without compromising on machine efficiency or power density, a Shaped Reluctance Machine (ShRM). Furthermore, a comprehensive approach which combines both phase excitation control and machine design to cooperatively address the excursions of input and output powers from their average values which results in less than 5% ripple for both electrical and mechanical net power — essentially a DC Reluctance Machine (DCRM). Compared to conventional practice in DSRMs, electrical power ripple is reduced by 85 times and torque ripple is reduced by almost 20 times, while overall efficiency, torque density, and power density are maintained. / Ph. D.

ITC/USA 2007 Conference Proceedings / The Forty-Third Annual International Telemetering Conference and Technical Exhibition / October 22-25, 2007 / Riviera Hotel & Convention Center, Las Vegas, Nevada / Modern telemetry systems using state of the art field programmable gate arrays (FPGAs) and signal processing components require lower voltage supplies to support various CMOS core geometries while still needing multiple higher voltage rails to support legacy interfaces. Addressing these power supply requirements efficiently requires switching power supply topologies that if left unchecked can generate high input surge currents and high levels of detrimental noise for both the sensitive analog signal processing circuitry and the power supply input source. This paper focuses on the design considerations and tradeoffs associated with implementing an efficient telemetry encoder power supply while mitigating the resulting noise effects typically associated with switching power supplies. This noise can negatively affect the power supply input source and the linear signal processing circuitry within the telemetry encoder.

<p>ABSTRACT</p><p>The fauna of the Lower Cambrian is far from fully understood, as is the environment of that epoch. Some of the most crucial moments in the history of evolution takes place during this epoch; the Cambrian explosion and the appearance of ecosystems as we know them. That makes it an important period to investigate. Doing so, the Lower Cambrian offers a lot of problems, one of which is that body fossils are seldom preserved. That has often left us with trace fossils to create an image of the Lower Cambrian life, but also some bedrock features such as ripple marks.</p><p>The main purpose of this work has been to investigate the possibilities of relating the wave lengths and forms of recent wave-generated ripples to fossil ones, and also to evaluate the methods for that kind of comparison. In this case the ripple marks belong to about 520 million year old sandstone formations at the shore of Trolmens strand (Kinnekulle area) and the mine Centralgruvan (Kvarntorp, Kumla). In total eighteen ripple trains from the Lower Cambrian were compared to the recent ripples in the shallow waters of Persbols strand and a somewhat steeper offshore area of Herrängen, northern and southern lake Skagern respectively.</p><p>After measuring the ripples several methods were used to find a practical and accurate procedure for the Persbols strand area. The conclusion is that, depending on depth and water transparency, a combination of methods should be used. Closest to the shore it was possible to take photos along the entire section from above water level, but because of the water depth further from the shore the aim of measuring the entire distance had to be abandoned. Instead, measurements should be taken with an adequate frequency, in this case every other meter up to one hundred meter from the shore line.</p><p>As a result of the measured recent ripples three different zones have been distinguished. One is situated 0-3 m from the shore line, or also a water depth down to 20 cm. The ripples in this area have wavelengths between one and four cm. and are asymmetrical, in some cases transforming to symmetrical in the outer part of the zone. It is only in this area, and some very shallow parts outside this zone, catenary ripples can be found. They are built up in the meter closest to the shore.</p><p>The second zone is situated approximately 3-80 m from the shore, or in areas of 20-80 cm water depth. The wave lengths grow from some 4 to 8 cm as the water depth increases. The ripple form is symmetrical, with the exception of some areas on the lake side of sand banks. Also, ripples with short crests and long throughs seems to dominate this zone.</p><p>Further out from the shore, more than 80 m, or in waters deeper than 80-100 cm, a third zone appears. The wave lengths are about 10 cm and, without any exceptions, the ripples are, symmetrical. None of the largescale fossil ripple marks were located due to the fact that no measurements further than 100 m from the shore were made.</p><p>The methods used here will make it possible to determine the environment of formation of the ripple marks, at least within 100 m from the shore, to the degree considered necessary for investigations in Earth science. Furthermore, the depth of water has appeared to be just as an important factor as the distance to the shore.</p>

Ion beam erosion of solid surfaces is known to produce a variety of surface morpholo- gies, such as pits, mounds or crests. Very often self-organized patterns composed of highly correlated arrays of dots or ripples at sub-micrometer and nanometer length scale could be obtained. Ion beam erosion patterning have demonstrated the poten- tial to tailor related surface properties for optoelectronic and spintronic applications, such as modulated photoemission induced by quantum con¯nement of nanodots and magnetic anisotropy induced by nanoripples. On the other hand, one considerable practical importance and e®ect of ion beam erosion is that of surface smoothing of nanometer features, during etching or ¯lm deposition coincident with energetic species. In my dissertation, systematic investigations of ripple formation and smooth- ing during low energy Ar+ ion erosion of sapphire surfaces using synchrotron grazing incidence small angle x-ray scattering and atomic force microscopy are performed. It is found in the pattern formation that the wavelength of ripples can be varied over a remarkably wide range by changing the ion incidence angle. The ion induced viscous °ow smoothing mechanism explains the general trends of the ripple wavelength at low temperature and incidence angles larger than 30±. The behavior at high temper- atures suggests relaxation by surface di®usion. However, strong smoothing is inferred from the observed ripple wavelength near normal incidence, which is not consistent with either surface di®usion or viscous °ow relaxation. Furthermore, a real-time x- ray scattering experiment is presented showing that ion smoothing of a pre-patterned surface near normal incidence is consistent with the e®ect of a collision-induced lat- eral current. Quantitative agreement is obtained using ion-collision simulations to compute the magnitude of the surface current. The results lead to predictions for the surface morphology phase diagram as a function of ion beam energy and incidence angle that substantially agree with experimental observations. The ion-induced lat- eral current smoothing model is applicable to many surfaces that become amorphous but maintain the stoichiometry of bulk materials during ion bombardment.

Tantalum capacitors are electronic components that are widely used in many types of devices. They are particularly valued for their exceptionally high capacitance and volumetric efficiency. One of the most vital performance parameters for this type of capacitor is the ability to handle unwanted AC ripple, since high levels of ripple can lead to overheating and capacitor failure. Yet the actual ripple limit for a capacitor has been historically difficult to quantify, and has been previously provided to customers only in the form of heavily padded estimates. Throughout the capacitor industry there has been significant demand for more realistic ripple ratings. The discussion here describes a new test system that has been designed to meet this demand for ripple characterization of wet tantalum capacitors.

No description available.

ABSTRACT The fauna of the Lower Cambrian is far from fully understood, as is the environment of that epoch. Some of the most crucial moments in the history of evolution takes place during this epoch; the Cambrian explosion and the appearance of ecosystems as we know them. That makes it an important period to investigate. Doing so, the Lower Cambrian offers a lot of problems, one of which is that body fossils are seldom preserved. That has often left us with trace fossils to create an image of the Lower Cambrian life, but also some bedrock features such as ripple marks. The main purpose of this work has been to investigate the possibilities of relating the wave lengths and forms of recent wave-generated ripples to fossil ones, and also to evaluate the methods for that kind of comparison. In this case the ripple marks belong to about 520 million year old sandstone formations at the shore of Trolmens strand (Kinnekulle area) and the mine Centralgruvan (Kvarntorp, Kumla). In total eighteen ripple trains from the Lower Cambrian were compared to the recent ripples in the shallow waters of Persbols strand and a somewhat steeper offshore area of Herrängen, northern and southern lake Skagern respectively. After measuring the ripples several methods were used to find a practical and accurate procedure for the Persbols strand area. The conclusion is that, depending on depth and water transparency, a combination of methods should be used. Closest to the shore it was possible to take photos along the entire section from above water level, but because of the water depth further from the shore the aim of measuring the entire distance had to be abandoned. Instead, measurements should be taken with an adequate frequency, in this case every other meter up to one hundred meter from the shore line. As a result of the measured recent ripples three different zones have been distinguished. One is situated 0-3 m from the shore line, or also a water depth down to 20 cm. The ripples in this area have wavelengths between one and four cm. and are asymmetrical, in some cases transforming to symmetrical in the outer part of the zone. It is only in this area, and some very shallow parts outside this zone, catenary ripples can be found. They are built up in the meter closest to the shore. The second zone is situated approximately 3-80 m from the shore, or in areas of 20-80 cm water depth. The wave lengths grow from some 4 to 8 cm as the water depth increases. The ripple form is symmetrical, with the exception of some areas on the lake side of sand banks. Also, ripples with short crests and long throughs seems to dominate this zone. Further out from the shore, more than 80 m, or in waters deeper than 80-100 cm, a third zone appears. The wave lengths are about 10 cm and, without any exceptions, the ripples are, symmetrical. None of the largescale fossil ripple marks were located due to the fact that no measurements further than 100 m from the shore were made. The methods used here will make it possible to determine the environment of formation of the ripple marks, at least within 100 m from the shore, to the degree considered necessary for investigations in Earth science. Furthermore, the depth of water has appeared to be just as an important factor as the distance to the shore.

For gravity wave trains propagating over an arbitrary wavy bottom, a perturbation expansion is developed to the third-order by employing three small perturbation parameters. Both the resonant and non-resonant cases are treated and the singular behavior at resonance is treated separately. All the theoretical results are presented in explicit forms and easy to apply. The bottom effects of different mean water depths and different degrees of undulation, as well as the steepness of incident waves, are clearly described by the theoretical results. In general non-resonant cases, the surface fluctuations deduced from undulated bottom topography decrease as the relative water depth increases and vice versa. The theory can be applied to the cases for wave trains propagating over wavy bottom topography with any arbitrary incident angles which are closer to natural phenomenon in coastal zone. Not only the well-known Bragg resonance but also the higher-order Bragg resonances are included in resonant cases. Unlike previous studies that analyze specific bottom topographies based on prescribed resonant conditions, both Bragg and higher-order Bragg resonances are revealed through the perturbation procedure step by step. For the resonant wave field, the amplification with propagating distance and time is revealed with the aid of the growth of energy flux. This theory is successfully verified by reducing to simpler situations. Also, the analytical results for the special case of two-dimensional wavy bottom are compared with experimental data for validation.

Thesis (B.S.)--University of Missouri, School of Mines and Metallurgy, 1913. / The entire thesis text is included in file. Typescript. Some illustrations by author. Title from title screen of thesis/dissertation PDF file (viewed April 30, 2009) Includes bibliographical references.

Thesis (Ph.D.)--Memorial University of Newfoundland, 1997. / Bibliography: leaves 109-114. Also available online.