Magnetic bearings are increasingly being used in a wide variety of applications in the industry such as compressors, turbines, motors, generators etc. Also, there are different types available depending upon their construction. The research presented here investigates a high temperature permanent magnet biased magnetic bearing system which is jointly being researched by National Aeronautics and Space Administration (NASA) and Electron Energy Corporation (EEC). The purpose of this research was to develop a permanent magnet biased magnetic bearing system using high temperature (HT) permanent magnets (PM) developed by EEC. This system was designed for high performance, high temperature (1000F) and high speed applications. The entire system consisted of two radial bearings, two catcher bearings, one axial thrust bearing and a motor. The central rotor shaft is powered by a high temperature permanent magnet motor to be able to run at the designed conditions of 20,000 rpm. This thesis documents the design of a feedback control law that stabilizes this HTPM biased AMB levitated system and summarizes efforts to build a test rig for the HT tests of the machine. A decentralized PD control law is used to achieve successful levitation. An existing PD analog controller with single input single output (SISO) control law for each axis (previously used for a flywheel test rig) is used as a feedback controller for this HTPM magnetic bearing system. Modeling and simulation of the resulting closed loop system is done in Matlab to test for stability and an iterative approach leads to optimum values of proportional and derivative gain pairs. The notch filter locations are also determined through this closed loop iterative simulation.

The purpose of this study is to understand the composition of the secondary forest of Nanjenshan area. A 5-ha plot was established at altitudes 200-264m on the north ridge of Nanjenshan. All free-standing woody plantsin the plot with DBH¡Ù1cm were identified, measured, tagged and mapped. A total of 108 tree species belonging to 40 families and 77 genera was recorded. The dominant species are Acacia confusa, Lagerstroemia subcostata, Psychotria rubra, Ficus septica¤ÎDendrocnide meyeniana. The dominant families are Fabaceae, Moraceae, Euphorbiaceae, Rubiaceae¤ÎLythraceae. TWINSPAN analysis reveales four groups. Group 1 is dominanted by Acacia confusa, Glochidion philippicum and Psychotria rubra. Group 2 is dominanted by Acacia confusa, Psychotria rubra and Lagerstroemia subcostata. Group 3 is dominanted by Acacia confusa, Psychotria rubra and Glochidion rubrum. Group 4 is dominanted by Acacia confusa, Lagerstroemia subcostata and Dendrocnide meyeniana. There are four kind of distribution pattern in this plot. Machilus obovatifolia and Osmanthus marginatus occurred on the hilltop; Dendrocnide meyeniana and Ficus virgata occurred on the middle-woody site; Zanthoxylum ailanthoides and Wendlandia uvariifolia only occurred along the steamside; Acacia confusa and Psychotria rubra were commonly distributed over the plot.

The design, analysis, and control of Disc-type Linear Permanent Magnet Synchronous Machines are presented in this dissertation. The machine is designed in order to have the features of high power density, high efficiency, direct drive without extra transmission device, simple mechanical structure, and wide operating speed range for the electric vehicle applications. The Feasible Triangle Technique for permanent magnet synchronous machine design is employed to increase torque density and reduce torque ripple. Magnetic theory and the finite element method are involved to establish machine mathematical model to simulate and analyze the proposed machine. The coupling field between rotor and stator can be analyzed from flux distribution by using three-dimensional finite element method. The numerical simulation and experimental results are used to verify the machine model and the operational characteristics of machine. The dissertation provides the procedures for design, analysis, and control of the proposed machine.

The objective of this thesis is to provide the modeling procedure for a tubular permanent magnet generator with Halbach array. The cylindrical-coordinated magnetic flux distributions generated by the stator winding currents and permanent magnets can be realized by deriving the magnetic vector potential in Bessel form from the Maxwell's equations. Then, the functional expressions of inductance matrix and magnetic flux linkage can be obtained. The detailed mathematic model of the proposed system combined with the actual operational properties can be further established and implemented by using the Matlab/Simulink software. The applicability of such mathematic model is also confirmed with experimental results.

Thesis (M.S.) in Electrical Engineering--University of Maine, 2009. / Includes vita. Includes bibliographical references (leaf 49).

No description available.

This thesis is devoted to investigation of some properties of the permanent function over the set Omega_n of n-by-n doubly stochastic matrices. It contains some basic properties as well as some partial progress on Foregger's conjecture. CONJECTURE[Foregger] For every n\in N, there exists k=k(n)>1 such that, for every matrix A\in Omega_n, per(A^k)<=per(A). In this thesis the author proves the following result. THEOREM For every c>0, n\in N, for all sufficiently large k=k(n,c), for all A\in\Omega_n which minimum nonzero entry exceeds c, per(A^k)<=per(A). This theorem implies that for every A\in\Omega_n, there exists k=k(n,A)>1 such that per(A^k)<=per(A).

No description available.

This thesis is devoted to investigation of some properties of the permanent function over the set Omega_n of n-by-n doubly stochastic matrices. It contains some basic properties as well as some partial progress on Foregger's conjecture. CONJECTURE[Foregger] For every n\in N, there exists k=k(n)>1 such that, for every matrix A\in Omega_n, per(A^k)<=per(A). In this thesis the author proves the following result. THEOREM For every c>0, n\in N, for all sufficiently large k=k(n,c), for all A\in\Omega_n which minimum nonzero entry exceeds c, per(A^k)<=per(A). This theorem implies that for every A\in\Omega_n, there exists k=k(n,A)>1 such that per(A^k)<=per(A).

Thesis (M.S.)--University of Michigan, 1981.