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

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Light manipulation is an important method to enhance the light-matter interactions in micro and nano photonic materials and structures by generating usefulelectric field components and increasing time and pathways of light propagationthrough the micro and nano materials and structures. For example, quantum wellinfrared photodetector (QWIP) cannot absorb normal incident radiation so thatthe generation of an electric field component which is parallel to the original incident direction is a necessity for the function of QWIP. Furthermore, the increaseof time and pathways of light propagation in the light-absorbing quantum wellregion will increase the chance of absorbing the photons.The thesis presents the theoretical studies of light manipulation and light-matter interaction in micro and nano photonic materials and structures, aiming atimproving the performance of optical communication devices, photonic integrateddevices and photovoltaic devices.To design efficient micro and nano photonic devices, it is essential to knowthe time evolution of the electromagnetic (EM) field. Two-dimensional and three-dimensional finite-difference time-domain (FDTD) methods have been adopted inthe thesis to numerically solve the Maxwell equations in micro and nano photonicmaterials and structures.Light manipulation in micro and nano material and structures studied in thisthesis includes: (1) light transport in the photonic crystal (PhC) waveguide, (2)light diffraction by the micro-scale dielectric PhC and metallic PhC structures(gratings); and (3) exciton-polaritons of semiconductor quantum dots, (4) surfaceplasmon polaritons at semiconductor-metallic material interface for subwavelengthlight control. All these aspects are found to be useful in optical devices of multiplebeam splitter, quantum well/dot infrared photodetectors, and solar cells. / QC 20120507

Rates of car ownership in the United States exceed that of all other large nations in the world. This high rate contributes to the unexpressed demand for road space that renders highway expansion useless as a strategy for decreasing traffic congestion. It also necessitates the provision of on-site parking in residential buildings, decreasing the affordability of housing in urban areas. Furthermore, the curb-side parking needed to make room for the high number of cars in the country takes away space that could be used for bike lanes, transit lanes, or widened sidewalks. Therefore, the United States could benefit from a reduction in rates of household car ownership. In this paper, I use cross-sectional data from the National Highway Transportation Survey to determine the impact on heavy and light rail on car ownership in American cities. I find that the presence of heavy rail is associated with a lower rate of car ownership, while the presence of light rail is not.

: In our designed culture, every environment, object and picture is analyzed from the viewpoint of colour and light. Colour and light play an important role in social life and culture. This paper springs from an epistemological project about concept formation in the field of colour and light. Based on own observations and scientific and scholarly references it presents a graphic model describing possible constituent relations between colour and light experiences. Design is the art of using knowledge – implicit or explicit – about how humans perceive, experience, and relate to the world around. In design all senses are involved, but when dealing with colour and light we can confine ourselves to vision; designers must understand the conditions of visual perception. Human experience of colour and light has many sources; the given cultural context (conventional meanings of colour and light), the direct experience of the world around (colour and light expressions) and the basic perceptual functions (formal aspects of colour and light). There is need for distinct concepts and concise approaches to understand coherence of aesthetic and functional expressions. Design education calls for coherent and well defined structures that can be used to describe connections and distinctions between experiences of different kinds. / Human Colour and Light Synthesis.Towards a coherent field of knowledge

Coplanar microstrip structures placed on dielectric substrates are used as high frequency electro-optic modulators. The method of lines, a mathematical technique for solving partial differential equations, has been applied to solve for the propagation characteristics of such a configuration. It has been determined that simple transmission line models are adequate to describe this system. The propagation characteristics are expressed in terms of the equivalent impedance and the phase velocity of the signal on the microstrip. In order to maximize the effective bandwidth of the modulator, the impedance is matched to that of the surrounding dielectric substrate, and the difference in the phase velocities of the two signals is minimized. The numerical technique developed here allows for the analysis of inhomogeneous dielectric substrates, so that trench structures for tuning the propagation characteristics to their desired values can be modelled. The numerical results for typical structures are presented, and suggest that the method of lines is a viable one for analyzing these modulator structures. / Graduation date: 1991

Low cost, light weight, recyclability, and high specific strength of natural fibres make them a good replacement for synthetic fibre such as glass in fibre reinforced plastics (FRP). Green and ecofriendly source of these fibres offer less reliance on oil sources. However, their moisture uptake ability, low thermal stability and quality variations are some disadvantages that restrict their use. Biodegradable polymers or biopolymers such as polylactic acid polymers (PLA) are polyesters of lactic acid, and originally made from renewable agricultural raw materials e.g. corn starch. Development of new composite products from the existing renewable resources has a strong potential to bring a new biodegradable composite material suitable for the automotive and packaging industry to replace non-renewable petroleum based plastics. These biodegradable composites could degrade completely in soil or by composting process and do not emit any toxic or harmful components. The purpose of this work is to investigate the effects of increasing natural fibre content, and also adding Biomax modifier on the mechanical properties of poly lactic acid. PLA was reinforced with two different kinds of sustainable natural fibres, cotton, and jute fibres respectively. Biomax strong 120 was used as modifier for PLA/natural fibre composites in order to improve the impact strength and toughness properties. Mixtures of different fibre mass proportions as reinforcement, and PLA as a base resin with modifier additive were compounded in a twin-screw extruder. The extruded materials were processed in a novel compression moulding system to produce test samples. Composites without any modifier content were also produced under the same conditions and used as reference materials. iv Addition of plant fibres to the PLA reduces the composites flexural strength, while improves the elastic modulus significantly, compared to neat PLA. PLA 3001D based composites containing 40% jute fibre exhibited the highest stiffness (5.9 GPa) amongst the composites. Investigation of the impact properties of the composites showed that increasing fibre mass proportion leads to an increase in the impact strength of the composites. The impact strength of the PLA/cotton composite is more promising than PLA/Jute composites. The most significant result is that addition of even 3% Biomax Strong 120 had a positive effect on the impact properties of the specimens. Analysis of the rheological properties of the composites demonstrates that the cotton fibre reinforced PLA has higher complex viscosity than Jute fibre reinforced PLA composites. The DSC results explain that the crystallization temperature increases with increasing the jute fibre content. Furthermore composite‟s microstructure was monitored using Scanning Electron Microscope (SEM). A better adhesion between the cotton fibres and the PLA matrix than jute fibres and PLA was observed in the SEM images. / UOIT

Organic light emitting diodes (OLEDs) are being commercialized in display applications, and will be potentially in lighting applications in the near future. This thesis is about the design of high performance OLEDs, which includes both the electrical and optical design of OLEDs. In particular, the following work is included in this thesis: i) Energy level alignment and charge injection at metal/organic interfaces have been systematically studied. ii) Transition metal oxide anodes have been developed to inject sufficient holes into the OLEDs due to their high work function. The oxide anodes have also been used to systematically study the transport properties in organic semiconductors. iii) Highly simplified OLED devices with unprecedentedly high efficiency have been realized using both fluorescent and phosphorescent emitters. The high performance was enabled by using a high work function metal oxide anode and a hole transport material with very a deep highest occupied molecular orbital (HOMO). iv) An optical model has been developed to describe the optical electric field across the OLED device. By using the model, a high performance flexible OLED using metal anode was designed and realized.

Ett examensarbete på högskolenivå som går igenom framtagningen av en ny produkt åt friluftsföretaget light my fire.

In temperate climate with pronounced seasonality, ice and snow cover reduces light conditions during winter which in turn reduce search efficiency for visual feeding consumers like fish. Furthermore, a suggested major effect of future climate change is an increased input of allochtonous DOC to aquatic systems which causes an increased brownification and hence reduced overall light conditions. In this study, I sampled YOY three-spined sticklebacks (Gasterosteus aculeatus) of different sizes overwintering in clear and brown water model ecosystems to examine if consumption were dependent on light conditions (natural light variability over winter) and if consumption were reduced in brown water. Three-spined sticklebacks were able to feed at different winter conditions and the prey biomass in stomachs was higher in clear- than in brown water despite higher resource levels in brown water treatments. Moreover when light intensity increased in late winter compared to midwinter conditions prey biomass in stomachs increased in both clear and brown water systems. Dominated prey taxa in the diet were chironomids and copepods. Results from this study suggest that when fish species are able to feed at low temperature and resource availability are sufficient light conditions during winter can be an important factor affecting overwinter survival in YOY fish because visual prey encounters and hence consumption rates are affected by light conditions. Future climate change scenarios with predicted increased brownification may therefore affect over winter survival in fish because of the negative effect of low light intensity (brownification) on prey consumption in fish in turn potentially changing recruitment success and densities of fish.