A study is presented of the instability mechanisms of a damped axisymmetric circular disk of uniform thickness rotating about its axis with constant angular velocity and subjected to various transverse space-fixed loading systems. The natural frequencies of spinning floppy disks are obtained for various nodal diameters and nodal circles with a numerical and an approximate method. Exploiting the fact that in most physical applications the thickness of the disk is small compared with its outer radius, we use their ratio to define a small parameter. Because the nonlinearities appearing in the governing partial-differential equations are cubic, we use the Galerkin procedure to reduce the problem into a finite number of coupled weakly nonlinear second-order equations. The coefficients of the nonlinear terms in the reduced equations are calculated for a wide range of the lowest modes and for different rotational speeds. We have studied the primary resonance of a pair of orthogonal modes under a space-fixed constant loading, the principal parametric resonance of a pair of orthogonal modes when the disk is subject to a massive loading system, and the combination parametric resonance of two pairs of orthogonal modes when the excitation is a linear spring. Considering the case of a spring moving periodically along the radius of the disk, we show how its frequency can be coupled to the rotational speed of the disk and lead to a principal parametric resonance. In each of these cases, we have used the method of multiple scales to determine the equations governing the modulation of the amplitudes and phases of the interacting modes. The equilibrium solutions of the modulation equations are determined and their stability is studied. / Master of Science

No description available.

Fong, Kwan Ying. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2010. / Includes bibliographical references (leaves 90-103). / Abstracts in English and Chinese. / Chapter Chapter 1: --- "Introduction, problems and objectives" --- p.1 / Chapter 1.1 --- Introduction --- p.1 / Chapter 1.2 --- Problems --- p.3 / Chapter 1.3 --- Objectives --- p.3 / Chapter Chapter 2: --- Background --- p.4 / Chapter 2.1. --- Head and Neck Cancer --- p.4 / Chapter 2.2 --- Diagnostic Imaging of Head and Neck Cancer --- p.5 / Chapter 2.3. --- Magnetic Resonance Imaging- Physics --- p.8 / Chapter 2.3.1 --- Nuclear Magnetic Resonance Principle --- p.8 / Chapter 2.3.2 --- Proton Magnetic Resonance Imaging --- p.8 / Chapter 2.3.3 --- Relaxation --- p.12 / Chapter 2.3.4 --- Tl- and T2-weighted Imaging --- p.12 / Chapter 2.3.5 --- Diffusion Weighted Imaging (DWI) --- p.13 / Chapter 2.3.6 --- Magnetic Resonance Spectroscopy- Single Voxel Spectroscopy and Chemical Shift Imaging --- p.15 / Chapter Chapter 3: --- Diffusion-weighted imaging in the evaluation head of and neck cancer --- p.21 / Chapter 3.1 --- Introduction - Diffusion-Weighted Imaging in Tumors --- p.21 / Chapter 3.2 --- DWI of Nasopharyngeal Carcinoma --- p.22 / Chapter 3.2.1 --- Introduction and Objectives --- p.22 / Chapter 3.2.2. --- Methods --- p.23 / Chapter 3.2.3. --- Results --- p.27 / Chapter 3.2.4 --- Discussion --- p.31 / Chapter 3.3 --- DWI of Primary Tumors: Comparison of NPC with Squamous Cell Carcinoma and Extra-nodal Non-Hodgkin Lymphoma --- p.33 / Chapter 3.3.1 --- Introduction and Objectives --- p.33 / Chapter 3.3.2. --- Methods --- p.34 / Chapter 3.3.3. --- Results --- p.35 / Chapter 3.3.4 --- Discussion --- p.42 / Chapter 3.3.5 --- Summary of DWI in Head and Neck Cancer --- p.44 / Chapter Chapter 4: --- Chemical shift imaging of head and neck tumors --- p.45 / Chapter 4.1 --- Introduction - Single Voxel Spectroscopy and Chemical Shift Imaging --- p.45 / Chapter 4.2 --- CSI - Methods Used to Reduce Magnetic Field Inhomogeneity --- p.48 / Chapter 4.3 --- Phantom studies - CSI Experiments Using Phantoms --- p.51 / Chapter 4.3.1 --- Introduction and Objectives --- p.51 / Chapter 4.3.2. --- Methods --- p.51 / Chapter 4.3.3 --- Experiment and MR Protocol --- p.54 / Chapter 4.3.4 --- Data Analysis --- p.58 / Chapter 4.3.5 --- Phantom Experimental Results --- p.59 / Chapter 4.3.6 --- Discussion and Conclusion on Phantom Experiments --- p.69 / Chapter 4.4 --- In vivo CSI Study of Human Head and Neck Tumors --- p.72 / Chapter 4.4.1 --- Introduction and Objectives --- p.72 / Chapter 4.4.2 --- Patient Selection --- p.73 / Chapter 4.4.3 --- MRI and CSI Protocol --- p.73 / Chapter 4.4.4 --- Data Analysis --- p.74 / Chapter 4.4.5 --- Results from CSI on Patients --- p.74 / Chapter 4.4.6 --- Discussion and Conclusion of CSI on Patients --- p.81 / Chapter Chapter 5: --- "Summary, conclusion and future studies" --- p.87 / Chapter 5.1 --- Summary --- p.87 / Chapter 5.2 --- Conclusion --- p.89 / Chapter 5.3 --- Future Studies --- p.89 / References --- p.90 / Publications --- p.104

Exterior vehicle noise has a very big impact when it comes to environmental noise pollution. Due to the decrease of the other noise sources of a passenger car, like power-train and air turbulence noise in the last decade, the tyre/road noise has become a more important part in the overall noise generation of a vehicle nowadays. It is considered as the main noise source in nearly all driving conditions, especially with increasing vehicle speed. The easiest idea to tackle this pollution is to introduce rules like speed-limits to control the noise at a certain area or time. More interesting, however, is to approach the problem of unwanted noise directly at the source. This Thesis, carried out at Loughborough University, aims to give a better understanding about the basic noise generation mechanisms at the tyre/road interface. Especially, the air related mechanisms of closed cavities are analysed. With the usage of a solid rubber tyre, unique measurements have been carried out and the results are compared to the theories already existing in the literature. These measurements reveal some of the strengths and weaknesses of the current understanding of air related noise generation.

Lee, Kar Ho Francis. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2011. / Includes bibliographical references (leaves 148-163). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese.

Stroke is the most prevalent neurological disease facing our nation today. Treatments, however, are few and insufficient at reducing the impact of this neurological condition. Experimental animal models are important to improving our understanding of stroke, and for developing new therapies to counter the pathology of stroke. Magnetic Resonance Imaging is the leading tool for the non-invasive investigation of stroke pathophysiology. While most MRI work in animals is conducted under anesthesia, anesthesia has profound effects on cerebral circulation and metabolism, and can affect stroke outcome. Several novel methods were combined with MRI compatible physiologic monitoring equipment to conduct stroke studies in conscious animals. Stress was studied as a factor in these studies and conditioning was utilized to reduce the impact of stress on the animals' physiology. Models of both occlusive and hemorrhagic strokes were successfully implemented within the MRI apparatus. Lastly, experiments using a macrosphere model showed evidence of a pathophysiologic difference between awake and anesthetized animals that undergo stroke.

Abstract not available

Nuclear magnetic resonance force microscopy (NMRFM) is a technique that combines aspects of scanning probe microscopy (SPM) and nuclear magnetic resonance (NMR) to obtain 3 dimensional nanoscale spatial resolution and perform spectroscopy. We describe the components of a helium-3 NMRFM probe and studies of ammonium sulfate ((NH₄)₂SO₄) and magnesium diboride (MgB₂). For our room temperature (NH₄)₂SO₄ studies we were able to perform a 1-D scan and perform nutation and spin echo experiments. In our 77 K MgB₂ we demonstrate a 1-D scan of a 30 micron powder sample. In addition, we describe magnetic measurements of the possible dilute semiconductors Mn[subscript x]Sc[subscript 1-x]N and Fe₀.₁Sc₀.₉N. / text

No description available.

This thesis reports the first indications of the Λ(1520) and ∆(1232)++ decay modes in the Ξc0 → pK−K−π+ decay. The obtained fractions relative the inclusive Ξc0 → pK−K−π+ decay are (6.4±0.6)% and (32.6±1.2)% for the decays through the Λ(1520) and ∆(1232)++ resonances respectively. The estimates were done on a sample of 6449±226 events of the Ξc0 baryon originating in the pure hadron Ξb− → Ξc0π− decay. The fractions presented in this thesis should be seen as an early indication rather than final estimates as more in-depth studies need to be done.