We present a novel new method for modelling magnetized molecular cloud cores using submillimetre linear polarization maps from thermal dust emission. Our PolCat modelling software builds a three-dimensional core model via the use of consecutive parametrized coordinate transformations, and produces simulated polarization maps to fit to observational datasets. We utilize the Ferret evolutionary optimizer to search the parameter space to simultaneously minimize chi-squared for the intensity and polarization position angle maps separately. We have applied PolCat to multiple test problems and several datasets from the SCUPOL Legacy Catalogue. We find that PolCat is able to distinguish between maps of twisted and non-twisted field geometries and identify twist symmetry. Preliminary fits to several datasets show that the best potential field geometries to our sample cores contain field twists. Further research using a larger number of maps is required to determine if twisted fields are commonplace in cores.

In this thesis, the current vs. magnetic field relationships for four magnets, M1, M2, M3, and Hyperon of FNAL Experiment E781 (the charm baryon study) havel,een studied on the basis of algorithms involving sign corrections pertaining to remedying incorrect FNAL EPICURE readout system's current and magnetic field values for E78 I's 4 magnets.After analyzing previous BSU personnel's work involving re-averaging of the current and magnetic field output values for E78 1, further research was carried out in this thesis activity regarding the correction of the algebraic signs of certain current and magnetic field values in the FNAL EPICURE read out values inputted into E781' data bank.Firstly, a code was developed to merge the four files of current and magnetic fields for the four magnets of E78 1, all into one file. Then, an algorithm for a sign correction program was developed in order to both sort the merged data and correct the current and magnetic field signautomatically.In order to obtain a better understanding of the effect of the incorrect sign for a magnet's current and magnetic field on analysis results, a statistical result was summarized. Finally, some conclusions were obtained. / Department of Physics and Astronomy

There are emerging requirements for high accuracy multi-DOF actuators in numerous applications. As one of the novel motors capable of multi-DOF manipulation, permanent magnet spherical motors (PMSMs) that can provide continuous and dexterous motion in one joint have been widely studied for their advantages in structure and energy efficiency. The demands to bring forward the performance of PMSMs for precision applications have motivated this thesis to develop a closed-loop orientation control system with high accuracy and bandwidth. Unlike traditional control methods for PMSMs, which rely on explicit orientation feedback, a new control method (referred to here as direct field-feedback control or in short DFC) directly utilizing the magnetic fields for feedback have been developed in this thesis. Because magnetic field measurements are almost instantaneous and the need for real-time orientation estimation is eliminated in DFC, the system sampling time is greatly reduced. Meanwhile, several field-based methods have been developed for the major components in the DFC system and each component can be processed independently and concurrently with the magnetic field measurements. The parallel computation further improves the system bandwidth and also reduces accumulated error. The DFC system has been experimentally implemented and evaluated. The results show excellent control performances in terms of accuracy and bandwidth. To facilitate the design and analysis of the DFC system, several new algorithms have been developed, which include the modeling and computing of magnetic fields as well as forces and torques, an analysis of bijective relationship between orientation and magnetic fields, and a method for calibration and reconstruction of the rotor magnetic field in 3 dimensional space. These algorithms not only enable the implementation of the DFC system for a PMSM, but also benefit the PMSM studies in design, modeling and field-based sensing. While the immediate outcome of this research is a control system for PMSMs, this new control method can be applied to a broad spectrum of electromagnetic motion systems.

No description available.

Many applications such as automobiles, gyroscopes, machine tools, and transfer systems require orientation control of a rotating shaft. Demands for multi-degree of freedom (DOF) actuators in modern industries have motivated this research to develop a ball-joint-like, brushless, direct-drive spherical wheel motor (SWM) that offers a means to control the orientation of its rotating shaft. This thesis presents a general method for deriving a closed-form magnetic field solution for precise torque calculation. The method, referred here as distributed multi pole (DMP) modeling, inherits many advantages of the dipole model originally conceptualized in the context of physics, but provides an effective means to account for the shape and magnetization of the physical magnet. The DMP modeling method has been validated by comparing simulated fields and calculated forces against data obtained experimentally and numerically; the comparisons show excellent agreement. The DMP models provide a basis to develop a non-contact magnetic sensor for orientation sensing and control of a rotating shaft. Three controllers have been designed and experimentally implemented for the SWM; open-loop and PD with/without an observer. The OL control system, which decouples the spin from the shaft inclination, provides the fundamental design structure for the SWM and serves as a basis for designing feedback controllers with/without an observer. While the observer and controller designs have been developed in the context of a spherical wheel motor, these techniques along with the models and analysis tools developed in this research can be applied to design, analysis and control of most electromagnetic devices. We expect that the analytical method along with the orientation sensor and spherical wheel motor will have broad spectrum of applications.

Thesis (Ph.D.)--McMaster University (Canada), 1993. / Source: Dissertation Abstracts International, Volume: 55-06, Section: B, page: 2189. Adviser: R. Bader.

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

Thesis (Ph. D.)--University of Texas at Austin, 2009. / Title from PDF title page (University of Texas Digital Repository, viewed on Sept. 9, 2009). Vita. Includes bibliographical references.

Thesis (M.S.) -- Worcester Polytechnic Institute. / Keywords: power systems; power transmission; fault location. Includes bibliographical references (leaves 83-84).

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