Abstract The proposed research of investigating the interaction between high-temperature superconductors and linear motors is introduced. Background on levitated transportation, high-temperature superconductor applications and supercon- ductor theory is given. An analytical model is developed for calculating thrust and levitation forces produced by 3-phase windings on a pair bulk high- temperature superconductors. Results produced by this model for a spacing of 1 pole-pitch and 1 2 pole-pitch are presented. In order to verify the analytical model a prototype system is built from a linear motor primary and vehicles containing 2 rows of superconductors. Two vehicles are built with different spacing between the rows of superconductors in order to investigate the ef- fect of their positioning, with respect to the pole-pitch, on the thrust forces produced. Measured forces on these two vehicles are then compared with pre- dicted values showing that the model predicts the forces with less than 5% error. Problems with the analytical model are also discussed. Finally it is con- cluded that the model developed provides insight to the relationship between high-temperature superconductors and travelling magnetic waves, and that a 1 pole-pitch separation between superconductors produces higher forces. Rec- ommendations for further development of the prototype system are also given.

by Siu Wing Hon. / On t.p. T"c", "2", "3", and "7-x" are subscripts following "superconducting" in the title. / Parallel title in Chinese characters. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1992. / Includes bibliographical references (leaves [79]-[80]). / Acknowledgement --- p.i / Abstract --- p.ii / Table of Content --- p.iii / Chapter Chapter 1 : --- Introduction / Chapter Chapter 2 : --- Growth of YBCO on Spinel / Chapter 2-1. --- Why Spinel --- p.2-1 / Chapter 2-2. --- Film Deposition Technique --- p.2-3 / Chapter 2-2.1 --- Magnetron Sputtering Technique --- p.2-3 / Chapter 2-2.2 --- Pulsed Laser Ablation --- p.2-4 / Chapter Chapter 3 : --- Composition Analysis by XRF / Chapter 3-1. --- Introduction --- p.3-1 / Chapter 3-2. --- Minimum Penetration Depth of EDX for YBCO film --- p.3-5 / Chapter 3-3. --- Thin Film Method and Thin Film Limit --- p.3-9 / Chapter 3-4. --- XRF Setup --- p.3-14 / Chapter 3-5. --- Calibration --- p.3-14 / Chapter 3-5.1 --- Chemical method --- p.3-18 / Chapter 3-5.2 --- Absorption Factor --- p.3-18 / Chapter 3-5.3 --- Diffusion Rate --- p.3-22 / Chapter 3-5.4 --- Justification of Thin Film Method --- p.3-22 / Chapter 3-5.5 --- Result of Calibration by Chemical Method --- p.3-24 / Chapter 3-5.6 --- Calibration by Rutherford Backscattering --- p.3-28 / Chapter 3-6. --- Discussion on XRF --- p.3-31 / Chapter 3-6.1 --- Effect of diffraction line by substrate on X-ray spectrum --- p.3-31 / Chapter 3-6.2 --- Stability of X-ray power supply and its influence on spectrum --- p.3-34 / Chapter Chapter 4 : --- Structural Analysis and Rapid Thermal Annealing / Chapter 4-1. --- XRD Setup --- p.4-1 / Chapter 4-2. --- XRD Analysis --- p.4-2 / Chapter 4-2.1 --- θ-2θ Scan --- p.4-1 / Chapter 4-2.2 --- Phi Scan --- p.4-3 / Chapter 4-2.3 --- Study of Diffraction Peak --- p.4-9 / Chapter 4-3. --- RTA and its influence on structure --- p.4-11 / Chapter 4-3.1 --- RTA Setup --- p.4-13 / Chapter 4-3.2 --- Structural Improvement by RTA --- p.4-13 / Chapter Chapter 5 : --- Conclusion --- p.5-1 / Chapter Appendix : A. --- Mathematical Derivation of Thin Film Limit / Chapter B. --- Powder Diffraction Patterns of YBCO system / Reference

Ling Siu-hing. / Title also in Chinese characters. / Thesis (Ph.D.)--Chinese University of Hong Kong, 1994. / Includes bibliographical references (leaves 220-227). / ACKNOWLEDGEMENT --- p.i / ABSTRACT --- p.ii / Chapter Chapter 1 --- Ceramic thin film --- p.1 / Chapter 1. 1 --- """New stone era""---the importance of ceramics" --- p.1 / Chapter 1.2 --- The importance of epitaxial growth of YBCO films --- p.4 / Chapter 1.3 --- The importance of epitaxial growth of PZT films --- p.9 / Chapter 1.4 --- The similar structures of YBCO and PZT --- p.10 / Chapter Chapter 2 --- Epitaxy --- p.12 / Chapter 2. 1 --- Introduction --- p.12 / Chapter 2.2 --- Basic principle --- p.13 / Chapter Chapter 3 --- Sample preparation Techniques --- p.25 / Chapter 3.1 --- A glimpse at epitaxial film deposition --- p.25 / Chapter 3.2 --- Magnetron sputtering --- p.28 / Chapter 3.2.1 --- Principle --- p.28 / Chapter 3.2.2 --- Set-ups --- p.30 / Chapter 3.2.3 --- High pressure magnetron sputter gun --- p.33 / Chapter 3.2.4 --- Type II unbalanced magnetron gun modification --- p.42 / Chapter 3.3 --- Pulsed Laser Deposition (PLD) --- p.54 / Chapter 3.4 --- Rapid thermal annealing (RTA) --- p.62 / Chapter Chapter 4 --- Characterizations-principles and setups --- p.66 / Chapter 4.1 --- Structure-X-ray diffractometer --- p.66 / Chapter 4.1.1 --- Setup --- p.57 / Chapter 4.1.2 --- Characterization --- p.71 / Chapter 4.1.3 --- High temperature X-ray diffractometer (HTXRD) --- p.83 / Chapter 4.2 --- Surface morphology --- p.86 / Chapter 4.2.1 --- Scanning electron microscopy (SEM) --- p.86 / Chapter 4. 3 --- Composition --- p.89 / Chapter 4.3.1 --- Energy dispersive X-ray spectroscopy --- p.89 / Chapter 4.3.2 --- Rutherford backscattering spectrometry (RBS) --- p.91 / Chapter 4.4 --- Other characterization techniques --- p.93 / Chapter 4.4.1 --- Thickness measurement --- p.93 / Chapter 4.4.2 --- Measurement of Tc in YBCO --- p.93 / Chapter 4.4.3 --- Thermomechanical analysis system (TMS) --- p.95 / Chapter 4.4.4 --- Differential scanning calorimeter (DSC) --- p.98 / Chapter Chapter 5 --- Epitaxial films --- p.99 / Chapter 5. 1 --- YBCO films --- p.99 / Chapter 5.1.1 --- YBCO on sapphire --- p.99 / Chapter 5.1.2 --- YBCO on spinel (MgAl2O4) --- p.115 / Chapter 5.1.3 --- YBC0//SrTi〇3//spinel --- p.130 / Chapter 5.1.4. --- YBCO on Mg〇 --- p.134 / Chapter 5.1.5 --- YBCO on SrTi〇3(110) --- p.143 / Chapter 5.2 --- PZT films --- p.182 / Chapter 5.2.1 --- PZT on MgO --- p.182 / Chapter 5.2.2 --- PZT on spinel --- p.188 / Chapter 5.2.3 --- High temperature structural transition of PZT films --- p.195 / Chapter Chapter 6 --- Conclusion --- p.218 / REFERENCES --- p.220

Aluminum-zirconium alloys exhibit superior strength at elevated temperature in comparison to traditional aluminum casting alloys. These alloys are heat-treatable and their strength depends to a large extent on the quenching and aging steps of the heat treatment process. However, measurements show that the critical cooling rate necessary to retain 0.6 wt. pct. zirconium(the minimum amount necessary for significant strengthening) in a super-saturated solid solution with aluminum is 90ºC/s, which is un-attainable with traditional casting processes. On the other hand, the critical cooling rate necessary to retain 0.4 wt. pct vanadium and 0.1 wt. pct. zirconium in a super- saturated solidsolution with aluminum is only 40ºC/s; which suggests that substituting vanadium for zirconium significantly decreases the critical cooling rate of the alloy. This is an important finding as it means that, unlike the Al-0.6Zr alloy, the Al-0.4V-0.1Zr alloy may be processed into useful components by traditional high pressure die-casting. Moreover, measurements show that the hardness of the Al-0.4V-0.1Zr alloy increases upon aging at 400ºC and does not degrade even after holding the alloy at 300ºC for 100 hours. Also, measurements of the tensile yield strength of the Al-0.4V-0.1Zr alloy at 300ºC show that it is about 3 times higher than that of pure aluminum. This increase in hardness and strength is attributed to precipitation of Al3(Zr,V) particles. Examination of these particles with high resolution transmission electron microscopy (HRTEM) and conventional TEM show that vanadium co-precipitates with zirconium and aluminum and forms spherical particles that have the L12 crystal structure. It also shows that the crystallographic misfit between the precipitate particles and the aluminum matrix is almost eliminated by introducing vanadium into the Al3Zr precipitate and thatthe mean radius of the Al3(Zr,V) particles is in the range from 1nm to 7nm depending on the alloy composition and aging practice. Finally, it is found that adding small amounts of silicon to the Al-0.4V-0.1Zr alloy effectively accelerates formation of the Al3(Zr,V) precipitate.

No description available.

Zhao Kun. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2001. / Includes bibliographical references. / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Mode of access: World Wide Web. / Abstracts in English and Chinese. / Zhao Kun.

No description available.

No description available.

In this thesis, we study the effects of doping in two-dimensional quantum antiferromagnets. We consider cases where the undoped parent compound is a Mott insulator with long-range antiferromagnetic order and focus on the low-doping situations. The limit of localized impurities is studied in a system consisting of a host magnet and two additional weakly coupled spins. We derive the effective Hamiltonian describing the interaction between these impurities as a function of their distance and show that it exhibits xyz anisotropy, leading to NMR and EPR line broadening. We calculate the magnetization disturbance in the host magnet induced by a single impurity and find that it always enhances Neel order. Relaxing the localization constraint, we investigate the single-hole dynamics of the t-J model on the honeycomb lattice. Using exact diagonalizations, series expansion and the self-consistent Born approximation, we calculate the quasi-particle dispersion, bandwidth and residues and compare our findings with the well-established results for the square lattice. Similar to the latter case, we find an almost flat band along the edges of the magnetic Brillouin zone and well-defined hole pockets around the corners. The most important part of this thesis is devoted to the magnetic properties of lightly doped La2-xSrxCuO4, the simplest and by far most studied cuprate superconductor. Starting from the undoped parent compound, we calculate the spin-wave spectrum and the spin-flop transitions in a uniform magnetic field at zero temperature. We then consider the low-doping regime and derive the effective field theory describing the spin dynamics in insulating La2-xSrxCuO4, x ≤ 0.055, at low temperature. The spin structure resulting from the spiral solution of the extended t-J model, obtained by taking into account the Coulomb trapping of holes by Sr ions, is confined in the copper-oxide planes. Our solution explains why the incommensurate structure is directed along the orthorhombic b axis and allows us to calculate the positions and shapes of the neutron scattering peaks numerically. These results are in perfect agreement with experimental data. We also show that topological defects (spin vortex-antivortex pairs) are an intrinsic property of the spin-glass ground state.

Thesis (Ph. D.)--University of Hong Kong, 2006. / Title proper from title frame. Also available in printed format.