No description available.

The object of this thesis is to investigate the performance in detail and to improve the efficiency of an exterior-rotor burshless DC motor provided by a motor manufacturing company. The finite element software package FLUX3D will be adopted to conduct all the analyzing works. At first, the three-dimensional static magnetic model of the machine will be formulated by FLUX3D. After confirming the preliminary analyzing results with practical measurements, static magnetic circuit of the machine system will be established to seek the possible flux leakage paths. By adjusting the thickness of permanent magnets and the shapes of stator poles, the effectiveness of machine operational efficiency improvements as well as induced torque changes will be obtained. Finally, from these investigations, adequate suggestions for design and construct the associate machine will be provided.

Thesis (Ph.D.) - University of St Andrews, February 2008.

A study was conducted to investigate the effect of magnetic devices on the precipitates in a condenser’s tubes when seawater is used as cooling water. This test was necessary to evaluate these devices as possible replacements for conventional methods of water treatment. In the test program, a small condenser was operated with conditions similar to utility condensers. This condenser was modified to include twelve tubes. The inlet water box was divided to provide for two parallel magnetic water treatment streams, and one control untreated water stream for comparison purposes. With and without the use of a magnetic device, the chemical analysis and the thickness of the deposits showed no significant difference. The only difference that was observed in these deposits was their crystallogical structure. When the magnetic device was in place, deposits were flaky (powder-like), chipped, and showed no strong adhesion to the inner surface of the condenser’s tubes. Without the use of a magnetic device, deposits were flocculated, hard, and crusty. This thesis proposes a theory which may help explain the differences in the deposits. The theory will include homogenous nucleation to explain the physical changes of the deposits. The discussion will also postulate how well the magnetic energy improved the homogenous nucleation process. A method of analysis is proposed which demonstrates how the critical radius of a nucleus is affected by a magnetic field.

No description available.

Title from PDF of title page (University of Missouri--Columbia, viewed on Feb. 19, 2010). The entire thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file; a non-technical public abstract appears in the public.pdf file. Dr. Randy Curry, Thesis Supervisor Includes bibliographical references.

No description available.

A Finite Element model was built to analyze and examine a 2-D axisymmetric MR damper. This model has been validated with the experimental data. The results obtained in this thesis will help designers to create more efficient and reliable MR dampers. We can create some design analysis to change the shape of the piston in the damper or other parameters in the model. The main benefit of this research is to show a 2-D MR damper and generate the magnetic flux density along the MR Fluid gap. We can detect saturation by looking at the nodal solution for the magnetic flux density. Increasing the current in the model, results in an increase in magnetic induction. We studied four different configurations of an MR damper piston in order to determine how changing the shape of the piston affects the maximum force that the damper can provide. In designing MR dampers, the designer always faces the challenge of providing the largest forces in the most compact and efficient envelope. Therefore, it is important to identify the configuration that gives more force in less space. In chapter 4, shows the magnetic flux density contour before and after reaching the rheological saturation. By increasing the current, the color spectrum of the magnetic flux density will shift from the MR fluid gap to the piston centerline. In chapter 5, we provided a reasonably good amount of force in model 4 at 1.4 Amps, but it reaches saturation before the other models. For cases with power constraint or heat build up limitations, this model could work the best among the four designs that we considered. For cases where higher electrical currents can be tolerated, model 3 would be the most advantageous design, since it provides the largest force among the four models. / Master of Science

The surface (photosphere) of the Sun is threaded throughout by magnetic fields. Groups of magnetic fields form magnetic features (of a wide range of sizes in flux and area) on the surface where the fields are directed into or out of the Sun. The aim of this thesis is to examine in detail the four key processes, emergence, cancellation, fragmentation and coalescence, which determine the behaviour of small-scale magnetic features, in the Sun's photosphere. I identify features in both Hinode/NFI and SOHO/MDI full-disk to enable these processes to be examined at the currently smallest observable scales and over an entire solar cycle. The emerging event frequency versus flux distribution, for intranetwork emerging regions to active regions, is found to follow a power-law distribution with index -2.50, which spans nearly 7 orders of magnitude in flux (10¹⁶ - 10²³ Mx) and 18 orders of magnitude in frequency. The global rate of flux emergence is found to be 3.9 x 10²⁴ Mx day⁻¹. Since the slope of all emerged fluxes is less than -2 this implies that most of the new flux that is fed into the solar atmosphere is from small-scale emerging events. This single power-law distribution over all emerged fluxes suggest a scale-free dynamo, therefore indicating that in addition to dynamo actions in the tachocline producing sunspots, a turbulent dynamo may act throughout the convection zone. Similarly for cancellations I find a power-law relationship between the frequency of cancellation and the peak flux lost per cancelling event (for events detected in both Hinode/NFI and SOHO/MDI full-disk), with slope -2.10. Again, the process of cancellation appears to be scale free and the slope is less than -2 indicating that numerous small-scale features are cancelling the majority of flux on the Sun. I also estimate the frequency of all surface processes at solar maximum and find, 1.3 x 10⁸, 4.5 x 10⁷, 4.0 x 10⁷ and 3.6 x 10⁶ events per day over the whole surface for emergence, cancellation, fragmentation and coalescence events, respectively. All the surface processes are found to behave in a similar manner over all flux scales. The majority of events for all processes occur in features with flux below 10²º Mx, which highlights the dynamic nature of the magnetic carpet. Using SOHO/MDI full-disk data I investigate the cyclic variation of the 4 key processes throughout cycle 23. It is found that the rate of emerging events, cancellations, fragmentations and coalescences varied in anti-phase with the solar cycle by factors of 3.4, 3.1, 2.4 and 2.2, respectively over the cycle. Not surprisingly, therefore, the number of network features detected throughout the cycle also exhibits an anti-phase variation over the solar cycle by a factor of 1.9. The mean peak flux of tracked small-scale network, fragmenting, coalescing and cancelling features showed in-phase relationships with the solar cycle by factors of 1.4, 1.7, 2.4 and 1.2, respectively. The total flux which is emerged and cancelled by small-scale events, varied in anti-phase with the solar cycle, by factors of 1.9 and 3.2. This is clearly due to the variation in the number of emerging and cancelling events and the fact that the flux of individual emerging events showed no cyclic variation. The results in this thesis show that the large-scale solar cycle plays a complex role in the surface processes features undergo. The fact that the number of ephemeral regions emerging has an anti-phase variation to the solar cycle has a knock-on effect in the number of features which are available to undergo surface processes. Also decaying active regions, during more active periods, contribute more small-scale features, with high flux density, into the network which has an effect on the surface processes. This work has revealed the significant importance of small-scale features in the flux budget through continual emergence and cancellation, plus highlighted how through dynamic surface motions, small-scale features form the fundamental components with which the network is developed.

This work is an investigation into the curvature related potential for flux to flow in the radial direction in the back-iron of laminated axial flux machine cores. Analytical and numerical models are presented. Analysis based on these models has shown that, in practical axial flux machines, the radial component of the flux density can be neglected with respect to the flux density distribution in the core back-iron. It has also been found that if the core permeability, core conductivity and number of poles are sufficiently high then power loss due to curvature related cross-lamination flux is negligible compared to normal eddy current losses. A closed form expression to predict losses due to curvature related radial flux is also presented. This expression allows axial flux machine designers to make quick assessment of the need to consider these losses when designing axial flux machines.