This paper discussed a way of applied stress to control the photonic crystal fiber dispersion curve, so that it can act on the anomalous dispersion or normal dispersion region area. By this way, we can design the pulse compressor and pulse stretcher for higher peak power laser system. Recently, high-power shortpulse laser has become an indispensable tool in many field, using short-pulse laser oscillator, combined with chirped-frequency amplification technology to produce high-power short-pulse laser system can be used for industrial or medical applications. The all-fiber laser system not only provide better pulse quality and also increased pulse laser system on the stability of the environment.

This study investigates analytically and experimentally extrusion processes of magnesium hollow tubes by a single-cylinder extrusion machine and double-cylinder extrusion machine. The first part of this study is to conduct analysis and experiment of hollow helical tube extrusion by single-cylinder extrusion machine. Firstly, a design criterion is proposed to determine the forming parameters and discuss the effects of product size, extrusion ratio, billet length, etc. on the mandrel surface stress. The effects of the die bearing part length, angle of rotation, extrusion speed, initial temperature, petal number, etc. on the radial filling ratio are also investigated. Better parameters are chosen from analytical results to conduct hot extrusion experiments for obtaining sound products. Microstructure observation and hardness test are conducted at the cross-section of the product. The experimental values of extrusion load and product¡¦s dimensions are compared with the analytical values to verify the validity of the analytical models. The second part of this study is to conduct analysis and experiment of hollow tubes extrusion by a double-cylinder extrusion machine. The effects of extrusion ratio, billet length, mandrel diameter, etc. on the drawing force on the mandrel and critical conditions without mandrel fracture are discussed.

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Today many saproxylic species are threatened because of habitat decline in Europe. Hollow trees represent a great part of the habitats that saproxylic species use. Since hollows takes a long time to develop, management actions are needed to prevent the extinction of saproxylic species. The aim of this study was to investigate the succession of saproxylic beetle species in artificial habitats in the form of wooden boxes. Wooden boxes were filled with a potential substrate and placed at different distances (0-1800 m) from oak hollow hot spots. In addition to the start mixture, four different additional substrates were added. In total, 4510 specimens of 114 saproxylic beetle species were sampled in 43 boxes over ten years. The specimens of tree-hollow species, wood rot species and nest species increased with 38% from the fourth to the final year but species richness decline from 47 to 29, respectively. A dead hen had a tendency for attracting more species but the small effect of different added substrates diminished over the years and had no significant effect on species richness after ten years. There was a higher similarity in species richness after ten years between the boxes and real hollow oaks. In conclusion, the artificial habitat developed into a more hollow like environment, with fewer but more abundant wood mould specialists, during ten years. This study clearly shows that the wooden boxes are used as habitats for saproxylic species as the boxes seems to develop into a more hollow-like habitat with time.

The advancement of the structural steel manufacturing industry has led to the recent emergence of steel members with Elliptical Hollow Sections (EHS) and Semi Elliptical Hollow Sections (SEHS). Although these sections are gaining popularity among architects, the lack of design guidelines specifically tailored towards these sections inhibits their efficient structural use. Within this context, this thesis provides several steps towards the development of such guidelines. A review of the manufacturing process of hot-rolled steel sections is conducted with emphasis on hollow structural sections. The main factors affecting the formation of residual stresses during cooling of the sections are discussed. Lower bound plastic interaction relations for EHS subjected to combinations of axial force, bi-axial bending moments and torsion are then derived. The formulation is based on the lower bound theorem of plasticity and the maximum distortional energy density yield criterion. Its applicability for conducting the cross-sectional interaction check in structural steel design problems is illustrated through a practical example. A simplified and conservative interaction equation is then proposed based on curve fitting of the results of the lower bound solution. Upper bound interaction relations are next developed for EHS subjected to combinations of axial force, bi-axial bending moments, torsion and bimoments. The formulation is based on kinematically admissible strain fields within the context of the upper bound theorem of plasticity. The interaction relations derived successfully capture the effect of confining radial strains present at welded end sections, as well as sections that are free to deform in the radial direction away from end welded sections. An iterative solution technique is developed to solve the resulting highly non-linear system of interaction relations. The effects of residual stresses and initial imperfections on axial compressive resistance of hot-rolled EHS are then incorporated into the lower bound interaction relations. Towards that goal, the thermo-mechanical properties of steel were extracted from the literature. A thermo-mechanical finite element model was developed for prediction of residual stresses in rolled sections. The validity of the model was assessed by comparison against residual stress measurements available in the literature. The model is then applied to predict the residual stresses in hot-rolled EHS. A series of geometric and material nonlinear finite element analyses is conducted on columns of EHS sections. The analyses include predicted residual stresses and initial out-of-straightness imperfections in order to determine the inelastic buckling capacity of EHS members and generate column curves for EHS sections. The column curves are subsequently compared to those based on Canadian, American and European design codes. Two column curve equations are proposed in a format similar to that of the Canadian Standards for buckling about major and minor axes. The column curves were subsequently combined with the interaction relations developed to provide design rules for EHS members under combined loads. The last contribution of the thesis provides a formulation of lower bound interaction relations for SEHS subject to combinations of axial force, bi-axial bending moments and torsion. An iterative scheme for solving the parametric form of the interaction relations is developed and a grid of admissible stress resultant combinations is generated. A series of trial functions are fitted to the grid of internal force combinations and two simplified and conservative interaction equations are proposed.

The glassy copolyimide 6FDA-DAM:DABA was investigated as a polymer backbone for membranes used in aggressive sour gas separation applications. An esterification crosslinking mechanism enabled the synthesis of materials with augmented H₂S/CH₄ selectivity and plasticization resistance. These materials make use of polyethylene glycol (PEG) crosslinking agents and are referred to as PEGMC polymers. Rigorous dense film characterization of the novel crosslinkable materials indicates that excellent H₂S/CH₄ selectivity (24) is achievable while still maintaining high CO₂/CH₄ selectivity (29) under high pressure ternary mixed gas (CO₂/H₂S/CH₄) feeds. Defect-free asymmetric hollow fiber membranes were formed and appropriate crosslinking conditions were determined, allowing for the characterization of these fibers under realistic sour gas feed conditions. Also, a PDMS post-treatment was used to give ultra-high permselectivity for aggressive feeds. Using several mixed gas feeds containing high concentrations of CO₂ and H₂S at feed pressures up to 700 psig, it is shown that the crosslinked asymmetric hollow fiber membranes developed and manufactured through this work are capable of maintaining excellent separation performance even under exceedingly taxing operating conditions. For example, CO₂/CH₄ and H₂S/CH₄ permselectivity values of 47 and 29, respectively, were obtained for a 5% H₂S, 45% CO₂, 50% CH₄ feed at 35°C with 700 psig feed pressure. An extremely aggressive 20% H₂S, 20% CO₂, 60% CH₄ mixed gas feed with 500 psig feed pressure was also used; the maximum CO₂/CH4 and H₂S/CH₄ permselectivity values were found to be 38 and 22, respectively.

Synthesis and Applications of Novel Periodic Mesoporous Organosilicas by Chun Xiang (Cynthia) LIN Abstract This dissertation is concerned with the synthesis, functionalization, and applications of periodic mesoporous organosilica (PMO) with a unique hollow spherical morphology, with the main objectives as follows: • Developing new techniques to synthesize mesoporous silica and organosilica materials • Designing different approaches to modify PMO and silica materials to meet various applications • Developing innovative applications of novel PMO materials in biological fields. The key features that have been achieved in this work are highlighted as follows: • A series of studies has been carried out and resulted in a new strategy for the synthesis of PMO material with a novel hollow morphology. This new approach employs both hydrocarbon and fluorocarbon surfactants as mixed structure-directing-agents in alkaline medium. Moreover, a vesicle and liquid crystal "dual-templating" mechanism has been proposed. • Detailed observation on the formation mechanism of hollow PMO has revealed that the demixing temperature (Td) plays an important role on the formation of highly ordered mesostructure of PMO hollow spheres. Beside that, dissimilarity on the hydrophobic nature of silica - organic silica precursors has brought differences in the resulted materials. • Different approaches in the modification of PMO hollow spheres with several functional groups and commercial magnetic ferrite nanoparticles have shown some unique features of this material. It was found that different reactive sites of each functional group bring different disruptive effect on the mesopore geometry of hollow PMO. Furthermore, hollow PMO material show different behavior on encapsulating the commercial magnetic ferrite nanoparticles compared to superparamagnetic particles, where different techniques should be applied, which involved several factors that need to be carefully adjusted. • Applications of hollow PMO in biological field were performed on drug and DNA delivery. A comparison between periodic mesoporous silica (PMS) and PMO as drug carriers showed the differences in wall composition between pure silica and hybrid organic silica, also the morphology (hollow and solid spheres) play important roles in controlling adsorption capacity and drug release rate. In addition, different pH value of release medium also brings significant effect on release profile. As a carrier of DNA, magnetic modified hollow PMO material showed biocompatibility towards sugarcane callus. Moreover, this study has introduced a new innovative technique on delivering DNA into plant cell through the application of modified hollow PMO with barium magnetic core and enzyme digestion approach.

Hot-dip galvanizing is widely used for corrosion protection of steel structures. However, there has been a plethora of recent reports on premature cracking in galvanized steel structures, which have resulted in some early decommissions or even hazardous collapses. This research focuses on cold-formed Rectangular Hollow Sections (RHS). A total of 108 tensile coupons were tested to investigate the effects of galvanizing as well as different pre-galvanizing treatments on the material properties around the cross sections of the specimens. For the first time, this thesis reports a comprehensive measurement of residual stresses in different directions at the member ends which are directly relevant to the cracking issue. The results were also compared to the residual stresses far away from the member ends, which are relevant to structural stability research. In all, the research provides a better understanding of the characteristics and structural performance of galvanized RHS to facilitate its application. The recommendations can help engineers, fabricators, and galvanizers mitigate the risk of cracking in RHS during galvanizing. / Graduate

>Magister Scientiae - MSc / Inorganic based membranes which have a symmetric/asymmetric structure have been produced using an immersion induced phase inversion and sintering method. An organic binder solution (dope) containing yttria-stabilised zirconium (YSZ) particles is spun through a triple orifice spinneret to form a hollow fibre precursor, which is then sintered at elevated temperatures to form a ceramic support. The phase inversion process for the formation of hollow fibre membranes was studied in order to produce the best morphological structure/support for palladium based membranes. The spinning parameters, particle size, non-solvent concentration, internal coagulant as well as the calcination temperature were investigated in order to determine the optimum values. Sintering temperature was also investigated, which would yield a sponge-like structure with an optimized permeability, while retaining a smooth outer surface. The supports produced by phase inversion were characterized in terms of dimension by mercury porosimetry, compressed air permeability, Surface Electron Microscopy (SEM) and Atomic Force Microscopy (AFM). The morphology of the produced ceramic support showed either dense or porous characteristics governed by the dynamics of the phase inversion process. The particle size of YSZ was examined in order to decrease the amount of agglomerates in the spinning suspension. Zetasizer tests indicated that at 15 minutes, the ultrasonic bath effectively homogenised the YSZ particles and prohibited soft agglomerates from reforming in the spinning suspension. In this study, an increase in air gap had no noticeable effect on the finger like voids but it had a considerable effect on both the inner diameter (ID) and outer diameter (OD) of the green fibres, while an increase in bore liquid flow rate and extrusion pressure promoted viscous fingering and significant effect on the ID and OD of the fibres, respectively. There was a decrease in porosity and permeability with increasing sintering temperature, addition of water concentration in the spinning suspension and varying N-methylpyrrolidone (NMP) aqueous solution of the internal coagulant. The amount of YSZ added to the starting suspension influenced the properties of the support structure. Viscous deformation was observed for dope with lower particle loading thus resulted in the formation of cracks and defects during sintering.

This thesis present a study of thermo-gelling polycaprolactone (PCL) dispersion which consist of a mixture of PCL microspheres (MSs) and thermo-responsive, graft cationic copolymer. The PCL microspheres are solid or colloidosomes (hollow). This study aims toward an injectable colloidal cell delivery system. The thermo-responsive copolymer used in this study is a new family of cationic graft copolymer. The cationic graft copolymer consisted of cationic poly(N,N-dimethylaminoethyl methacrylate) backbone and poly 2-(2-methoxyethoxy) ethyl methacrylate (PMA) side chains. A series of new cationic graft copolymers were synthesized with different PMA arm length and grafting density. A representative copolymer showed good cell viabililty. The solid PCL MSs were prepared using solvent evaporation method. The MSs were mixed with the thermo-responsive graft copolymer. At room temperature the mixture were liquid-like and gelled at body temperature (37 ˚C). This indicates that the mixture systems were injectable. The injectable route offers a minimal invasive route to fill defect void inside the body. Furthermore, a porous morphology was evident for the mixed gels at 37 ˚C and the porosity could be altered using different composition of the mixed components. The mixed system showed self-healing properties for low volume fraction of PMA. The mixed system particle gel was more ductile in electrolyte but showed similar morphology to the mixed system particle gels prepared in water. This part of the study was carried out using PCL MSs prepared by cetyltrimethylammonium bromide (CTAB) as surfactant. A brief study using polyvinyl alcohol (PVA) as the surfactant showed that the PCL MSs had similar diameter and gel morphology which suggests that the model systems studied using CTAB may be applicable to the PVA system. Microencapsulation attracts interest due to its ability to deliver and control release actives and also its application in many fields. Colloidosomes are one of the microcapsules/microspheres used for microencapsulation. In this study a two step, facile and scaleable colloidosome preparation method was introduced. The PCL colloidosome shell consisted of partially fused small nanoparticles. The PCL colloidosomes were birefringence under cross polarised light due to the stress applied during solvent evaporation. A brief study showed that the mixture system of colloidosomes and thermo-responsive graft copolymer are able to gel at 37 ˚C.