Plasmons, the collective electronic oscillations of metallic nanoparticles and nanostructures, are at the forefront of the development of nanoscale optics. Metallic nanostructures with their geometry-dependent optical resonances are a topic of intense current interest due to their ability to manipulate light in ways not possible with conventional optical materials. As optical frequency nanoantennas, reduced-symmetry plasmonic nanoparticles have light-scattering properties that depend strongly on geometry, orientation, and variations in dielectric environment. Particularly fascinating aspect of these systems is the recently realized possibility of creating optical frequency “magnetic plasmon” responses of comparable magnitude to the “electric plasmon” response. It is of our central interest to understand better the plasmonic system so as to manipulate the energy transport mechanism. With the much more advanced numerical calculations, and based on the Finite Element Method (FEM) and Finite-Difference Time-Domain (FDTD) method, we are now able to study various kinds of nanostructures for different interesting optical properties. With the help of FDTD, we show the geometry dependent dissipation rate in different nanosystems. We brought up a new damped harmonic oscillator model to account for the observed difference. We show that our new model better completes the full map of the energy dissipation mechanism, and the predicted outcome agreed very well with the FDTD calculations. Elliptical nanorings were investigated by applying both FEM and FDTD methods. The mulitiple plasmonic resonaces exhibited by elliptical nanorings and the well tunability of the nanosystem make elliptical nanorings very interesting. Different features can be realized by controlling the aspect ratios of the elliptical nanorings. We show another interesting nanostructures, light bending nanocup as well. Due to its unique light scattering properties, nanocup is a very promising candidate in solar cell applications. We studied more about its light redirection properties with the presence of a dielectric substrate and its sensitivity to the subtle geometry differences. Plasmonic heptamer has been shown to possess an intriguing Fano resonance due to the interference of its hybridized subradiant and super-radiant modes. Neighboring fused heptamers can support magnetic plasmons due to the generation of antiphase ring currents in the metallic nanoclusters. We use such artificial plasmonic molecules as basic elements to construct low-loss plasmonic waveguides and devices. The manipulation of magnetic plasmons in heptamer interconnects can further be expanded to more complex systems, for example, by integrating more optical paths to achieve multiple input and output plasmonic networks. With their compact dimensions, outstanding low-loss propagation characteristics, and range of functionalities, magnetic plasmon-based devices based on these structures should be key to the further development of high- performance energy transport components in informa- tion processing and data storage applications.

Micromechanical resonators are used in a variety of sensing and filtering applications. In these applications, the accurate performance of micro resonators depends on the sensitivity of these devices to a particular resonance frequency. This sensitivity is measured using the quality factor Q, which is the ratio of the total input energy into the device to the energy dissipated within a vibration cycle. A higher quality factor indicates a smaller resonance bandwidth, which makes the micro-resonator more effective in identifying a desired signal. Higher Q values result from reductions in dissipation losses. Dissipation losses occur through damping by the ambient fluid, anchor losses, thermoelastic damping, and other sources. The squeeze-film effect is of particular interest in micro-resonators as the fluid enclosed between the resonating components can provide significant dissipation. This work covers investigations into the air damping of oscillating micromachined resonators that operate near a fixed wall, which is parallel to the oscillating surface. The main portion of this work focuses on the theoretical and numerical investigation of the air damping of micromachined resonators when the surrounding gas (air) is in the Free-Molecule regime. Errors and limitations of previous theoretical models have been found and corrected. A molecular dynamics simulation code that is suitable to handle a more general class of resonators has been developed. This code has been used to find the quality factor of a microbeam resonator. The results from the code were compared to existing experimental results, and were found to have very good agreement in the free molecular regime. The simulation was then used to investigate the effects of the oscillation mechanics on the energy dissipation and quality factor. The second part of this work focuses on the region between the bottom surface of a laterally-oscillating disk resonator and the substrate. The compressibility effects of a 1 micron thick film of air on a laterally-oscillating disk resonator were investigated. The pressure perturbation for this case was found to be minimal, which means that the compressibility effects of the fluid film will negligible.

Analytical and experimental laboratory studies were conducted for rapid pressurizing of entrapped gas at the end of a horizontal liquid pipeline. In this paper analytical and experimental model study are presented for pressurizing entrapped gas pocket at the end of a liquid column in a horizontal pipeline. Analytical models are considered such as (1) acoustic effect of both liquid and gas side, (2) variation of liquid length, and (3) thermal damping process. Closed form of solutions were derived for a lumped liquid and lumped gas model if pipeline is a horizontal. Experiments were conducted to verify the analytical models. Comparison of analytical and experimental model results were presented. Analytical model was developed to define the physics behind the gas venting case. Experiments were conducted for a range of orifice sizes from 1/16 to of the pipe diameter with reservoir pressure two, three and four times of ambient pressure for five different pipe configurations. Experimental results confirm the assumption of modified entrapped air model is correct.

This paper is going to emphasize on the air squeeze film damping effect on micro-mechanical resonant beam in MEMS. In general, the low energy density of electrode force will cause high-voltage power supply to drive the electro- micro resonators; reducing the distance between the electrode and resonant beam can be the most efficient way to solve this problem. But bringing different exciting frequency of system and environmental pressure to the air squeeze film effect might cause it changes form similarly to the damping qualities, and this will also change the dynamic characteristics of micro resonator. The dynamic model for double clamped micro-mechanical resonant beam is proposed by using Lagrange¡¦s equation in this study. The corresponding eigenvalue problems of resonant beam are formulated and solved by employing the hypothetical mode method. Under the presumption of viscous damping model, we may obtain a damping factor which includes the parameters of size, temperature and air pressure when energy transfer model is employed to simulate the squeeze film damping effect of two immediate objects. Eventually, the damping ratio and the dynamic characteristics of resonant microbeam are derived by means of exploring the frequency response function of system. Besides, the frequency change of micro-mechanical resonant beam due to an axial force is also considered in the thesis.

In this study, particle impact damping is measured for a cantilever beam with a particle-filled enclosure attached to its free end. Many particle materials are tested: lead spheres, steel spheres, glass spheres, tungsten carbide pellets, lead dust, steel dust, and sand. The effects of particle size are also investigated. Particle diameters are varied from about 0.2 mm to 3 mm. The experimental data collected is offered as a resourceful database for future development of an analytical model of particle impact damping.

Thesis (Ph. D.)--University of Hong Kong, 2001. / Includes bibliographical references (leaves 344-354).

Thesis (Ph. D.)--University of Washington, 2003. / Vita. Includes bibliographical references (leaves 71-80).

Thesis (Ph. D.)--University of Washington, 2002. / Vita. Includes bibliographical references (leaves 72-74).

Thesis (Ph. D.)--University of Hong Kong, 1988.

Thesis (M.S. in Mechanical Engineering)--Naval Postgraduate School, June 2003. / Thesis advisor(s): Young Shin, Ilbae Ham. Includes bibliographical references (p. 63). Also available online.