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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
11

Mechanical and superconducting properties of bulk bismuth superconductors at various processing stages. / 鉍系超導體在各製備階段之機械及超導特性 / Mechanical and superconducting properties of bulk bismuth superconductors at various processing stages. / Bi xi chao dao ti zai ge zhi bei jie duan zhi ji xie ji chao dao te xing

January 2000 (has links)
by Yu-Kit Lam =鉍系超導體在各製備階段之機械及超導特性 / 林宇傑. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2000. / Includes bibliographical references. / Text in English; abstracts in English and Chinese. / by Yu-Kit Lam = Bi xi chao dao ti zai ge zhi bei jie duan zhi ji xie ji chao dao te xing / Lin Yujie. / Table of Contents --- p.i / Acknowledgments --- p.iv / Abstract --- p.v / Chapter Chapter 1 --- Related Work on Bulk Bi-based High Tc Superconductor --- p.1 / Chapter 1.1 --- Historical Background of Superconductivity --- p.1 / Chapter 1.2 --- Basic Properties of Superconductivity --- p.4 / Chapter 1.3 --- Basic Properties of Bi-based Superconductor --- p.7 / Chapter 1.4 --- Fabrication Methods of Bi-based Superconductor --- p.12 / Chapter 1.4.1 --- Precursor Preparation --- p.12 / Chapter 1.4.1.1 --- Solid State Reaction Method --- p.12 / Chapter 1.4.1.2 --- Sol-gel Method --- p.15 / Chapter 1.4.1.3 --- Co-decomposition Method --- p.17 / Chapter 1.4.1.4 --- Freeze-drying and Spray-drying Methods --- p.17 / Chapter 1.4.1.5 --- Comparison for precursor preparation methods --- p.18 / Chapter 1.4.2 --- Pelletization and Sintering --- p.20 / Chapter 1.5 --- Potential applications of Bi-based superconductors --- p.22 / Chapter 1.5.1 --- Criteria for practical applications --- p.22 / Chapter 1.5.2 --- Superconducting tapes --- p.23 / Chapter 1.5.3 --- Current leads --- p.26 / Chapter 1.6 --- Objectives of the Project --- p.27 / Chapter 1.7 --- References --- p.28 / Chapter Chapter 2 --- Fabrication of Bulk Bi(Pb)-2223 Superconductor --- p.33 / Chapter 2.1 --- Introduction --- p.33 / Chapter 2.2 --- Precursor Preparation --- p.33 / Chapter 2.3 --- Grinding Process --- p.34 / Chapter 2.4 --- Pelletization Process --- p.35 / Chapter 2.5 --- The Sintering --- p.37 / Chapter 2.6 --- Characterizations --- p.38 / Chapter 2.7 --- References --- p.40 / Chapter Chapter 3 --- Principles and Instruments of Characterizations --- p.41 / Chapter 3.1 --- Scanning Electron Microscopy and Energy Dispersive X-ray Spectroscopy --- p.41 / Chapter 3.1.1 --- Basic Principle --- p.41 / Chapter 3.1.2 --- Sample Preparation --- p.42 / Chapter 3.2 --- Crystal Structure Determination Using X-ray Diffraction Spectroscopy --- p.44 / Chapter 3.3 --- Vibrating Sample Magnetometer --- p.48 / Chapter 3.3.1 --- Basic Principle --- p.48 / Chapter 3.3.2 --- Sample Preparation --- p.49 / Chapter 3.4 --- Standard Four-Probe Method for Electrical Measurement --- p.51 / Chapter 3.5 --- Density Measurement of Sintered Samples --- p.52 / Chapter 3.6 --- Hardness Tests --- p.54 / Chapter 3.7 --- Determination of Flexural Strength of Sintered Samples --- p.56 / Chapter 3.8 --- References --- p.57 / Chapter Chapter 4 --- Results and Discussions / Chapter 4.1 --- Results from X-Ray Diffraction Spectroscopy --- p.58 / Chapter 4.1.1 --- Green Pellet --- p.58 / Chapter 4.1.2 --- 50-Hour Sintered Pellet --- p.58 / Chapter 4.1.3 --- "100-Hour, 150-Hour, and 200-Hour Sintered Pellets" --- p.59 / Chapter 4.1.4 --- Volume Fraction of the High Tc Phase --- p.59 / Chapter 4.2 --- Microstructure Observed by Scanning Electron Microscopy --- p.63 / Chapter 4.2.1 --- Green Pellet --- p.63 / Chapter 4.2.2 --- 50-Hour Sintered Pellet --- p.64 / Chapter 4.2.3 --- "100-Hour, 150-Hour, and 200-Hour Sintered Pellets" --- p.64 / Chapter 4.3 --- Chemical Composition Using Energy Dispersive X-ray Spectroscopy --- p.68 / Chapter 4.4 --- Results from Vibrating Sample Magnetometer --- p.71 / Chapter 4.5 --- Densification of Sintered Samples --- p.75 / Chapter 4.6 --- Hardness at Various Stages of Processing --- p.77 / Chapter 4.7 --- Flexural Strength at Various Stages of Processing --- p.79 / Chapter 4.8 --- I-V Characterization Using Standard Four-Probe Method --- p.82 / Chapter 4.9 --- Weibull Modulii of Sintered Samples --- p.85 / Chapter 4.10 --- Future Oultlook --- p.86 / Chapter 4.11 --- References --- p.87 / Chapter Chapter 5 --- Summary --- p.89 / Appendix A Polishing of Pelletizing Mold / Chapter A.1 --- Introduction --- p.92 / Chapter A.2 --- Grinding Process --- p.92 / Chapter A.3 --- Final Polishing Process --- p.93
12

Study of Ferromagnetism and superconductivity in layered YBCO/LCMO thin films: (YBCO/LCMO 薄膜的鐵磁與超導特性研究). / YBCO/LCMO 薄膜的鐵磁與超導特性研究 / CUHK electronic theses & dissertations collection / Study of Ferromagnetism and superconductivity in layered YBCO/LCMO thin films: (YBCO/LCMO bo mo de tie ci yu chao dao te xing yan jiu). / YBCO/LCMO bo mo de tie ci yu chao dao te xing yan jiu

January 2001 (has links)
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.
13

Doped quantum antiferromagnets

L??scher, Andreas, Physics, Faculty of Science, UNSW January 2007 (has links)
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.
14

Probing the physics of high temperature superconductivity : spin dynamics and pair-breaking effects /

Kao, Ying-Jer. January 2001 (has links)
Thesis (Ph. D.)--University of Chicago, Dept. of Physics, 2001. / Includes bibliographical references. Also available on the Internet.
15

Interfacial studies of high temperature superconducting Bi₂Sr₂Can-₁Cun 0₂n+₄ and Ag

Fang, Yue 05 1900 (has links)
No description available.
16

High temperature superconducting microwave devices

Kale, K. S. January 1996 (has links)
This thesis describes investigations into the application of high temperature superconductoR<sub>s</sub>(HTS) for microwave devices. The ultimate aim of this research was to produce HTS components that would demonstrate the commercial potential of their use in spacecraft such as satellites or in base stations for terrestrial cellular communication systems. During the course of this research the surface resistance (R<sub>s</sub>) of HTS thick and thin films deposited onto different substrates has been measured by a variety of techniques. These have been compared and contrasted with each other. There has been a particular emphasis upon the use of dielectric resonators as characterization tools and this thesis describes their use to measure the R<sub>s</sub>of films and the loss tangents of the materials used in them. Consideration has been given to losses in the walls of the enclosures that surround dielectric resonators which is an area that has been neglected in previous work. Many of the films characterized had R<sub>s</sub> values lower than normal conductoR<sub>s</sub>at the same temperature and frequency including a thick film which had an R<sub>s</sub>of 2.7mΩ±8.0% at 77K and scaled to 10 GHz which represents the second lowest result achieved in a thick film to date. Using such high quality films a number of devices have been made including microstrip resonatoR<sub>s</sub>operating at 1.7-8.4 GHz, 5.58 GHz, 23 GHz and 24.75 GHz dielectric resonatoR<sub>s</sub>and filteR<sub>s</sub>with centre frequencies from 5.58-13 GHz. Such devices have shown performance enhancements of up to 700% over their normal conductor equivalents. Benefits have been delivered in light, low volume packages which is of particular advantage to the satellite communications industry. Finally, there has been a demonstration, for the first time, of a tunable HTS thin film filter.
17

Doped quantum antiferromagnets

L??scher, Andreas, Physics, Faculty of Science, UNSW January 2007 (has links)
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.
18

Quantum phenomena in strongly correlated electron systems /

Shevchenko, Pavel V. January 1999 (has links)
Thesis (Ph. D.)--University of New South Wales, 1999. / Also available online.
19

Non-extensive statistics and high temperature superconductivity /

Uys, Hermann. January 2001 (has links)
Thesis (M.Sc.(Physics))--University of Pretoria, 2001. / Summaries in Afrikaans and English. Includes bibliographical references (p. 41-46). Also available online.
20

Theoretical investigation of high-Tc cuprate superconductors using t-J model : transport properties /

Xia, Xiangjun. January 2005 (has links)
Thesis (Ph.D.)--Hong Kong University of Science and Technology, 2005. / On t.p. "c" of Tc is subscript. Includes bibliographical references (leaves 80-90). Also available in electronic version.

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