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

The objective of this thesis is to establish an electromagnetic energy conversion mechanism that is suitable for electric power generation from solar thermal energy. Based on the generator design and thorough electromagnetic path design, a tubular linear generator system design will be proposed. The stator armature with three-phase concentrated windings mounted on a slotless structure is targeted to be implemented for this structure of the generator design, and a special designed of two-segmental Halbach permanent magnet array will be installed on the mover to fulfill the desired tubular linear generator construction. From detailed magnetic equivalent circuit (MEC) analysis and three-dimensional finite element analyses, the feasibility and applicability of the proposed machine system concepts will be verified. Finally, the steady-state operational characteristic of this generator have been estimated cinfirm the design objectives.

The main purpose of this research is to design a thermal energy conversion device, which is aimed to collect unused heat produced by nature. In order to achieve high-efficiency conversion, some novel devices will be studied to convert heat energy into mechanical power. A simple heat exchanger as well as heat engine device is proposed in this study. Dichloromethane is used as an important factor due to its physical properties. Finally, the concept of a tubular linear generator will be adopted to generate electric power. The feature of the proposed simple thermal energy conversion device is that we can use unused heat sources as input, such as solar energy and waste heat from car engines. Besides, the system is capable to work under the condition of low-temperature difference

Strengthening of aluminium and stainless steel structural tubular sections using adhesive bonded fibre-reinforced polymer (FRP) subjected to web crippling has been investigated. Aluminium and stainless steel tubular sections may experience web crippling failure due to local concentrated loads or reactions. The web crippling strength can be enhanced by strengthening the webs of the sections in localized regions. The current international specifications of aluminium and stainless steel structures do not provide web crippling design rules for strengthening of tubular sections. Therefore, there is a need to develop safe and reliable web crippling design rules for FRP strengthened aluminium and stainless steel structures. An extensive test program was performed on FRP strengthening of aluminium and cold-formed stainless steel tubular sections subjected to web crippling. The test specimens consisted of 6061-T6 heat-treated aluminium alloy, ferritic stainless steel type EN 1.4003 and lean duplex type EN 1.4162 square and rectangular hollow sections. A total of 254 web crippling tests was conducted in this study. The tests were performed on eighteen different sizes of tubular sections which covered a wide range of web slenderness (flat portion of web depth-to-thickness) ratio from 6.2 to 62.2. The web crippling tests were conducted under the four loading conditions according to the American Specification and Australian/New Zealand Standard for cold-formed steel structures, namely End-Two-Flange, Interior-Two-Flange, End-One-Flange and Interior-One-Flange loading conditions. The investigation was mainly focused on the effects of different adhesive, FRP, surface treatment, widths of FRP plate and web slenderness of tubular sections for strengthening against web crippling. Six different adhesives, six different FRPs, two different surface treatments, three different widths of FRP plate were considered. It was found that the web crippling capacity of aluminium tubular sections are significantly increased due to FRP strengthening, especially for those sections with large value of web slenderness. The web crippling strength can be increased up to nearly 3 times using the appropriate adhesive and FRP for aluminium tubular sections, whereas the web crippling strength can be increased up to 51% and 76% for ferritic and lean duplex stainless steel tubular sections, respectively. The finite element models for FRP strengthened aluminium and stainless steel tubular structural members subjected to web crippling were developed and calibrated against the experimental results. The debonding between FRP plate and aluminium or stainless steel tubes was carefully modelled using cohesive element. It is shown that the calibrated model closely predicted the web crippling strengths and failure modes of the tested specimens. An extensive parametric study included 212 web crippling specimens was carried out using the verified finite element models to examine the behaviour of strengthened aluminium and stainless steel tubular sections subjected to web crippling. Design equations are proposed to predict the web crippling strengths of FRP strengthened aluminium and stainless steel tubular sections based on the experimental and numerical results. The web crippling strengths obtained from the tests and numerical analysis were compared with the design strengths calculated using the proposed equations. The reliability of the proposed design rules was evaluated using reliability analysis. / published_or_final_version / Civil Engineering / Doctoral / Doctor of Philosophy

This thesis proposes two forms of external confinement for concrete filled steel tubular (CFST) columns. The confinement efficiency is studied by examining the axial strength enhancement and ductility improvement of the CFST columns with external confinement. Due to the heavy demand of confining steel to restore the column ductility in seismic regions, it is more efficient to confine these columns by hollow steel tube to form CFST column. Compared with transverse reinforcing steel, steel tube provides a stronger and more uniform confining pressure to the concrete core, and reduces the steel congestion problem for better concrete placing quality. The CFST columns are therefore characterised by higher strength, ductility and large energy absorption before failure. However, a major shortcoming of CFST columns is the imperfect steelconcrete interface bonding occurred at the elastic stage as steel dilates more than concrete in compression. This adversely affects the confining effect and decreases the elastic modulus. To resolve the problem, it is proposed in this thesis to use external steel confinement in the forms of rings and ties to restrict the dilation of steel tube. For verification, a series of uni-axial compression test was performed on some CFST columns with external steel rings and ties. From the results, it was found that the external steel rings could improve both the axial strength and stiffness of the CFST columns significantly. However, the steel ties could not improve either the axial strength or elastic stiffness significantly. The confining efficiency was then investigated by comparing the strength of these confined-CFST columns with the reinforced concrete (RC) columns counterparts with the same concrete and steel volume. It is evident that the axial strength of CFST columns is much higher than the RC columns, which suggests that the application of CFST columns can utilise less construction materials and reduce the demolition waste. A theoretical model is also proposed for predicting the axial strength of ring-confined CFST columns. Comparison between the predicted results and the test results obtained by the author and other researchers shows that the proposed model gives good estimation for both unconfined and confined CFST columns. / published_or_final_version / Civil Engineering / Master / Master of Philosophy

My research has focused on the precipitation of iron minerals, mostly oxides and hydroxides, in aqueous systems across steep pH and Eh gradients. Unlike most work in this area, which involves loose precipitates filtered out of solutions, I have focused on precipitated aggregates and, more specifically, on those that are self-organized into dis-crete structures or patterns. This topic is actually quite narrow because such types of natu-ral material organization are rare within the geochemical realm compared with the mor-phological richness of crystals, not to mention the phantasmagoria of life.My investigation of iron-based examples has included three types of physical sys-tems: 1) growth of tubular structures around bubbles coming off a charged cathode in a free solution where convection dominates; 2) development of Liesegang patterns within gelled solutions due to reactions dominated by diffusion; and 3) formation of a cement-ing matrix within the aqueous interface between particles of silica. The third case in-volves physical characteristics of the first two in that it is primarily a tightly packed, dif-fusion-limited process, but at least initially the generation of gases can create mechani-cally driven flows through the interstitial spaces.All three systems and studies are inextricably related for both tubular ('vermi-form') structures and Liesegang patterns are commonly found in natural iron-cemented sediments such as massive laterite, ironstone deposits, and banded iron formations. They are also found on a much smaller scale within discrete 'concretions' and represent the two poles of the gradient between convection-based and diffusion-based systems. As Seilacher (2001) states concerning concretions, "the distribution and precipitation of dis-solved constituents, such iron and manganese, proceeds in two radically different mor-phospaces, which are typified by dendrites [and I would include tubes and other linear growth] on the one hand and Liesegang rings on the other." Both have been observed in my lab creations with surprising frequency and tenacity even in systems thought to be in-hibitory.

Despite the prominent role played by open tubular columns in gas chromatography, they have enjoyed comparatively little success as supports for open tubular liquid chromatography (OTLC), owing to impractical channel diameters (3-5 μm) required to facilitate retention in the liquid phase. In an effort to circumvent the technical issues associated with such narrow diameters, columns with multiple parallel channels have been suggested as alternatives – to this end, micro-structured fibres (MSFs) have been proposed as supports for OTLC. Much research has been conducted using MSFs for chromatography in the Oleschuk group, and although some success has been achieved, performance has been continuously hindered by flow velocity variation among the channels stemming from differences in channel sizes (or channel variance) as well as differences in stationary phase coverage, which serve to degrade column efficiency. Recent efforts have focused on devising a novel method for assessing the channel variance of MSFs. This method seeks to determine hole tolerance through evaluation of the extent of band broadening that occurs when performing chromatography in the absence of a retentive mechanism. Using this method, a linear correlation between the relative standard deviation of the channel diameters and the amount of broadening was revealed. To supplement the results, computational fluid dynamics was employed to simulate fluid flow through multi-channel columns. The results of these simulations again provided a linear correlation between the RSD of the channel diameters and the extent of flow velocity variation among the channels. / Thesis (Master, Chemistry) -- Queen's University, 2012-08-15 11:57:28.915

Thesis (Ph. D.)--University of Hong Kong, 2009. / Includes bibliographical references (leaves 269-283) Also available in print.

Thesis (M. Phil.)--Hong Kong University of Science and Technology, 2004. / Includes bibliographical references (leaves 149-154). Also available in electronic version. Access restricted to campus users.

Thesis (Ph. D.)--University of Hong Kong, 1996. / Includes bibliographical references (leaf 180-212).