Thesis (M.Phil.)--Chinese University of Hong Kong. / Bibliography: leaves 78-79.

by Ho Hing Wa. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1999. / Includes bibliographical references. / Abstracts in English and Chinese. / Abstract --- p.i / 摘要 --- p.iii / Acknowledgment --- p.iv / Table of Contents --- p.v / Chapter 1 --- Introduction / Chapter 1.1 --- Background of optical generation of millimeter-waves --- p.1 -1 / Chapter 1.2 --- Application of the two-section DFB laser on optical generation of millimeter-waves --- p.1 -4 / Chapter 1.3 --- Analysis --- p.1-4 / Chapter 1.4 --- Organization of Thesis --- p.1 -5 / References --- p.1-6 / Chapter 2 --- Techniques of Optical Generation of Millimeter-waves / Chapter 2.1 --- Direct modulation and mode-locking of lasers --- p.2-1 / Chapter 2.2 --- Beating of two optical waves --- p.2-3 / References --- p.2-11 / Chapter 3 --- Experimental Results and Discussions / Chapter 3.1 --- Device structure and experimental setup --- p.3-1 / Chapter 3.2 --- Light-Current Characteristics of the two-section laser --- p.3-3 / Chapter 3.3 --- Spectral behaviours of the two-section DFB laser --- p.3-5 / Chapter 3.3.1 --- Linewidth of the two-section DFB laser --- p.3-5 / Chapter 3.3.2 --- Wavelength tuning of the two-section DFB laser --- p.3-5 / Chapter 3.3.3 --- Biasing conditions for the dual-mode oscillations --- p.3-16 / Chapter 3.4 --- Optical generation of millimeter-waves --- p.3-17 / Chapter 3.4.1 --- Mechanism of beating --- p.3-17 / Chapter 3.4.2 --- Generation of millimeter-waves by optical beating --- p.3-20 / Chapter 3.5 --- Optical Transmission of the millimeter-waves --- p.3-22 / References --- p.3-24 / Chapter 4 --- Theory of DFB Laser / Chapter 4.1 --- Development of DFB laser --- p.4-1 / Chapter 4.2 --- Structure of DFB laser --- p.4-2 / Chapter 4.3 --- Model of one-section DFB laser --- p.4-4 / Chapter 4.4 --- Analysis of two-section DFB laser --- p.4-10 / Chapter 4.4.1 --- Introduction of transfer matrix method --- p.4-11 / Chapter 4.4.2 --- Formulation of transfer matrix --- p.4-12 / Chapter 4.4.3 --- Application of the transfer matrix --- p.4-13 / References --- p.4-17 / Chapter 5 --- Numerical Analysis of the Spectral Behaviours of the Two-Section DFB Laser / Chapter 5.1 --- Solving the Transcendental Equation --- p.5-1 / Chapter 5.2 --- Simulation of the spectral behaviour of the two-section DFB laser --- p.5-4 / Chapter 5.2.1 --- Assumptions and Approximations --- p.5-4 / Chapter 5.2.2 --- Parameters --- p.5-5 / Chapter 5.2.3 --- Computer Implementation --- p.5-6 / Chapter 5.2.4 --- Results and Discussion --- p.5-7 / References --- p.5-14 / Chapter 6 --- Conclusion / Chapter 6.1 --- Summary --- p.6-1 / Chapter 6.2 --- Future works --- p.6-2 / Appendices / Appendix A Source code for simulation of spectral behaviours of the two-section DFB laser --- p.A-1

Mak Hon-lung. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2000. / Includes bibliographical references (leaves [105]-107). / Abstracts in English and Chinese. / Abstract --- p.ii / Acknowledgements --- p.iii / Contents --- p.iv / List of Figures --- p.vii / List of Tables --- p.x / Chapter Chapter 1. --- Introduction --- p.1 / Chapter 1.1 --- The origin of Heisenberg model --- p.1 / Chapter 1.2 --- High temperature superconductivity --- p.3 / Chapter 1.3 --- This project --- p.6 / Chapter Chapter 2. --- Studies of spin wave theory --- p.7 / Chapter 2.1 --- Introduction --- p.7 / Chapter 2.2 --- The uniform antiferromagnetic Heisenberg Model --- p.9 / Chapter 2.2.1 --- Linearization --- p.11 / Chapter 2.2.2 --- Quadratic equation --- p.15 / Chapter 2.2.3 --- Quadratic equation with Constraint --- p.20 / Chapter 2.2.4 --- Other results --- p.24 / Chapter 2.3 --- The anisotropic Heisenberg model --- p.29 / Chapter 2.3.1 --- The uniaxial model --- p.29 / Chapter 2.3.2 --- The XY Ferromagnetic model --- p.31 / Chapter Chapter 3. --- Theoretical approach --- p.35 / Chapter 3.1 --- Classical ground state --- p.35 / Chapter 3.2 --- Quantum fluctuation --- p.37 / Chapter 3.2.1 --- Linear combination of operators --- p.42 / Chapter 3.3 --- Calculation of physical quantities --- p.44 / Chapter 3.3.1 --- Zero mode problem --- p.48 / Chapter Chapter 4. --- Results of unfrustrated systems --- p.52 / Chapter 4.1 --- Introduction --- p.52 / Chapter 4.2 --- Uniform system --- p.52 / Chapter 4.3 --- Missing bond case --- p.55 / Chapter 4.4 --- Vacancy case --- p.58 / Chapter 4.5 --- Ferromagnetic impurity case --- p.61 / Chapter 4.6 --- Antiferromagnetic impurity case --- p.65 / Chapter 4.7 --- Abnormal antiferromagnetic bond case --- p.68 / Chapter Chapter 5. --- Ferromagnetic bond case --- p.71 / Chapter 5.1 --- Origin of ferromagnetic bond --- p.71 / Chapter 5.2 --- Numerical results --- p.72 / Chapter 5.2.1 --- The classical results --- p.72 / Chapter 5.2.2 --- Quantum corrections --- p.75 / Chapter 5.3 --- Results of other schemes --- p.76 / Chapter 5.3.1 --- Spin wave approach --- p.76 / Chapter 5.3.2 --- Other approaches --- p.77 / Chapter Chapter 6. --- The transmittance pattern in a necklace like system --- p.80 / Chapter 6.1 --- Introduction --- p.80 / Chapter 6.2 --- The model --- p.81 / Chapter 6.3 --- Ring configuration --- p.82 / Chapter 6.4 --- Chain configuration --- p.86 / Chapter 6.5 --- The transmittance pattern --- p.87 / Chapter 6.5.1 --- Constant and varying flux --- p.89 / Chapter 6.5.2 --- Random flux --- p.91 / Chapter 6.5.3 --- Constant impurity --- p.93 / Chapter 6.5.4 --- Some random effects --- p.96 / Chapter 6.6 --- Summary --- p.98 / Chapter 6.7 --- "Appendix, Derivation of basic equations " --- p.100 / Chapter Chapter 7. --- Conclusion --- p.103 / Bibliography --- p.105

by Chen Tian Wen. / Thesis submitted in: December 1998. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1999. / Includes bibliographical references (leaves 84-87). / Text in English; abstract also in Chinese. / by Chen Tian Wen. / Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Motivation of the Studies --- p.1 / Chapter 1.2 --- Structure of this Thesis --- p.2 / Chapter 2 --- A Brief Review on Sonoluminescence --- p.3 / Chapter 2.1 --- History of SL --- p.3 / Chapter 2.2 --- Experimental conditions and observations --- p.3 / Chapter 2.3 --- Theoretical results --- p.6 / Chapter 3 --- Normal Modes of EM Fields in Spherical Geometry --- p.12 / Chapter 3.1 --- Maxwell's Equations in Vacuum --- p.12 / Chapter 3.2 --- Normal Modes in Spherical Geometry --- p.13 / Chapter 3.2.1 --- Normal Modes in Homogeneous Dielectric Medium --- p.14 / Chapter 3.2.2 --- A Dielectric Sphere Embedded in an Ambient Dielelctric Medium --- p.17 / Chapter 3.2.3 --- Generalization to Layered Spheres --- p.18 / Chapter 4 --- Quantization of EM field and Field-atom Interaction --- p.21 / Chapter 4.1 --- Introduction --- p.21 / Chapter 4.2 --- Quantization of the EM fields --- p.22 / Chapter 4.3 --- Physical Interpretations --- p.24 / Chapter 4.4 --- Dipole Transition Rate in a Dielectric Medium --- p.26 / Chapter 4.5 --- Radiation rate of a dipole inside and outside a homogeneous sphere --- p.28 / Chapter 4.6 --- Summary --- p.45 / Chapter 5 --- SL Models as Layered Spheres --- p.49 / Chapter 5.1 --- Motivation of the Layered Sphere Model --- p.49 / Chapter 5.2 --- A small core and a thick outer layer --- p.50 / Chapter 5.3 --- A large core and a thin outer layer --- p.62 / Chapter 5.4 --- Summary --- p.68 / Chapter 6 --- Realistic Model from Numerical Hydro dynamic simulations --- p.70 / Chapter 6.1 --- The Model --- p.70 / Chapter 6.2 --- Results from Numerical Simulations --- p.73 / Chapter 6.3 --- Summary --- p.79 / Chapter 7 --- Conclusion --- p.81

The aim of this work is to improve the practice of multicomponent data processing in the time domain. I present a detailed study carried out on a 2D multicomponent dataset acquired over the Lomond Field, North Sea. I show that this area is seismically anisotropic and that failure to account for the anisotropy leads to poor converted wave imaging results. Anisotropy is included in a complex model-building scheme prior to Pre-Stack Time Migration (PSTM). The basic parameters required in converted wave processing are the converted-wave stacking velocity based on non-hyperbolic moveout and different P-wave to S-wave velocity ratios. These parameters are extracted from analysis on asymptotically binned gathers, that is, gathers binned with a constant value of the velocity ratio vp/vs. I present results of a sensitivity analysis and I show that in areas affected by dip the stacking velocity is sensitive to changes in the initial vp/vs ratio. These small velocity errors are propagated as the square in the re-calculation of the depth-variant velocity ratio and cannot be ignored. I show that using imaging criteria to define the binning velocity ratio provides a valid and velocity-independent estimate in zones of complex geology. The vertical velocity ratio is derived conventionally by event matching in the P-wave and converted wave stacks. I present an attempt to use well-log derived velocity ratios to avoid this interpretative step. The velocity ratio derived from 4C seismic data is about 30% higher than that derived from well logs. I analyse three possible causes for this discrepancy: the effects of gas, polar anisotropy and frequency-dependent dispersion. Gas has little effect in the Lomond Field logs, while polar anisotropy lowers the well-log derived vp/vs ratio by about 15%. Frequency-dependent dispersion also lowers the well-log derived velocity ratio, but it is difficult to quantify. Residual errors in the seismic interpretation have also to be considered. Importantly, I prove that the ratio leading to the best image is the one derived from seismic data, which suggests that the use of the raw well-log derived velocity ratio in multicomponent processing should be avoided. I quantify anisotropy using an effective parameter, representing converted-wave anisotropy, ceff, which is a combination of P- and S-wave anisotropy. This parameter can be estimated from converted wave seismic data alone and I illustrate two different ways of extracting it. I present imaging results from a full anisotropic PSTM processing sequence. This flow requires careful model building and allows updating in the time-migrated domain. Comparing the values of the anisotropic parameter and of the binning velocity ratio before and after PSTM highlights the difference between the initial model and the updated model. Both parameters are in fact sensitive to the presence of dip. I show that the values of the anisotropic parameter change after PSTM, suggesting that part of the residual moveout attributed to anisotropy prior to PSTM was caused by dip. This consideration confirms the importance of defining the model in the time-migrated domain. The PSTM image matches with a high degree of accuracy the geological interpretation carried out by BG Group. PSTM tests show that the inclusion of anisotropy allows the use of the full range of offsets, which is important to produce the correct image of the target area. I compare this result with the image obtained from a flow based on isotropic Dip Moveout (DMO) and post stack migration. Differences in the position of the steep-dipping events and geological misties are evident in the post-stack migrated image. This mis-positioning is due to the isotropic approximation and to the limitation of the DMO and post-stack migration flow. I also present results of an integrated analysis of local geology, well logs and seismic data to confirm the presence of polar anisotropy in the Lomond Field. The sediments forming the overburden are mainly composed of finely laminated shales. The image I obtained from the full Pre-Stack Depth Migration on P-P data reveals a depth mismatch with the well markers. Since the pre-stack gathers show that the correct velocities are applied, this depth mismatch has to be attributed to the presence of anisotropy. Other clear evidences of anisotropy come from well logs. P-velocity angular dependency is evident in sonic logs. I show that a similar angular dependency also exists when comparing interval velocities and average velocities from seismic data and from vertical well logs and check shots. These considerations leave little doubt that the Lomond Field is seismically anisotropic.

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The research programme has investigated methods for assessing the seakeeping performance of high speed vessels. This has included a review and assessment of seakeeping attributes, the development of a suitable database of motion characteristics using experimental and numerical techniques and proposals for assessing the seakeeping characteristics of alternative vessels. An experimental test programme was carried out in regular head and oblique waves as well as irregular open seas on two different hull forms of fast displacement catamarans. The results of the experiments in oblique waves are extended to beam and foUowing headings using the transfer functions &om a 3D pulsating source code at headings from head to following seaa in regular waves. This effectively provides a meajis of generating 3D transfer functions. The methodology used to compare and assess the seakeeping performance of vessels at an early design stage is discussed. The use of short crested seas as opposed to long crested is assessed and the differences compared. This leads to the use of spreading relationships to generate 3D transfer functions from the database of transfer functions in regular head waves. This allows the motion prediction method to be greatly enhanced by ciHowing any heading to be assessed. The proposed attributes and criteria suitable for assessing the seakeeping performance of high speed vessels are summarised.

by Tsang, Yuk-fai. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1996. / Includes bibliographical references (leaves 67-68). / by Tsang, Yuk-fai. / Chapter 1 --- Introduction --- p.4 / Chapter 2 --- Uniform accelerated charge radiation --- p.7 / Chapter 2.1 --- An old paradox: Radiate or not? --- p.7 / Chapter 2.2 --- Uniform Accelerating Charge(UAC) --- p.8 / Chapter 2.3 --- EM fields of UAC --- p.9 / Chapter 2.4 --- Radiation of UAC --- p.13 / Chapter 2.5 --- Energy conservation: acceleration energy --- p.14 / Chapter 3 --- Numerical calculation of EM field energy --- p.18 / Chapter 3.1 --- EM fields of UAC --- p.19 / Chapter 3.2 --- Comparison of total EM field energy --- p.23 / Chapter 3.3 --- Results --- p.28 / Chapter 4 --- Modification of the paradox --- p.30 / Chapter 4.1 --- Uniformly accelerated frame (UAF) --- p.30 / Chapter 4.2 --- Radiation in UAF --- p.32 / Chapter 4.3 --- The paradox in another situation --- p.34 / Chapter 5 --- The rotating frame --- p.37 / Chapter 5.1 --- The reference frames --- p.37 / Chapter 5.2 --- Geometric properties of co-rotating frame --- p.38 / Chapter 5.3 --- Maxwell equations in non-inertial frame --- p.41 / Chapter 6 --- Transformation of radiation fields to rotating frame --- p.42 / Chapter 6.1 --- EM fields of a moving charge --- p.43 / Chapter 6.2 --- Dipole radiation --- p.44 / Chapter 6.3 --- Dipole radiation of a rotating charge --- p.45 / Chapter 7 --- Tr ansformation of the complete fields to rotating frame --- p.49 / Chapter 7.1 --- Lienard-Wiechert Fields --- p.49 / Chapter 7.2 --- Determination of R --- p.54 / Chapter 7.3 --- Radiation is a frame-dependent phenomenon --- p.58 / Chapter 7.4 --- Transformation of static field --- p.59 / Chapter 8 --- Conclusions --- p.62 / Chapter 8.1 --- Comparison of the transformation of EM fields / Chapter 8.2 --- Radiation is a frame-dependent phenomenon --- p.64 / Chapter 8.3 --- The concept of photon --- p.65 / Chapter 8.4 --- Problems left --- p.65 / Reference --- p.67

The dynamics of the atmosphere and ocean are dominated by slowly evolving, large-scale motions. However, fast, small-scale motions in the form of inertia-gravity waves are ubiquitous. These waves are of great importance for the circulation of the atmosphere and oceans, mainly because of the momentum and energy they transport and because of the mixing they create upon breaking. So far the study of inertia-gravity waves has answered a number of questions about their propagation and dissipation, but many aspects of their generation remain poorly understood. The interactions that take place between the slow motion, termed balanced or vortical motion, and the fast inertia-gravity wave modes provide mechanisms for inertia-gravity wave generation. One of these is the instability of balanced flows to gravity-wave-like perturbations; another is the so-called spontaneous generation in which a slowly evolving solution has a small gravity-wave component intrinsically coupled to it. In this thesis, we derive and study a simple model of inertia-gravity wave generation which considers the evolution of a small-scale, small amplitude perturbation superimposed on a large-scale, possibly time-dependent °ow. The assumed spatial-scale separation makes it possible to apply a WKB approach which models the perturbation to the flow as a wavepacket. The evolution of this wavepacket is governed by a set of ordinary differential equations for its position, wavevector and its three amplitudes. In the case of a uniform flow (and only in this case) the three amplitudes can be identifed with the amplitudes of the vortical mode and the two inertia-gravity wave modes. The approach makes no assumption on the Rossby number, which measures the time-scale separation between the balanced motion and the inertia-gravity waves. The model that we derive is first used to examine simple time-independent flows, then flows that are generated by point vortices, including a point-vortex dipole and more complicated flows generated by several point vortices. Particular attention is also paid to a flow with uniform vorticity and elliptical streamlines which is the standard model of elliptic instability. In this case, the amplitude of the perturbation obeys a Hill equation. We solve the corresponding Floquet problem asymptotically in the limit of small Rossby number and conclude that the inertia-gravity wave perturbation grows with a growth rate that is exponentially small in the Rossby number. Finally, we apply the WKB approach to a flow obtained in a baroclinic lifecycle simulation. The analysis highlights the importance of the Lagrangian time dependence for inertia-gravity wave generation: rapid changes in the strain field experienced along wavepacket trajectories (which coincide with fluid-particle trajectories in our model) are shown to lead to substantial wave generation.

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