Post-fire mechanical properties of cold-formed steels

Cold-formed steel members have been widely used in residential, industrial and commercial buildings as primary load-bearing and non-load bearing structural elements. These buildings must be properly evaluated after a fire event to assess the nature and extent of structural damage. If the general appearance of the structure is satisfactory after a fire event then the question that has to be answered is how the structural capacity of cold-formed steel members in these buildings has been affected. Elevated temperatures during a fire event affect the structural performance of cold-formed steel members even after cooling down to ambient temperature due to the possible detrimental changes in their mechanical properties. However, the post-fire behaviour of cold-formed steel members has not been investigated in the past and hence there is a need to investigate the post-fire mechanical properties of cold-formed steels. Therefore an experimental study was undertaken at the Queensland University of Technology to understand the residual mechanical properties of cold-formed steels after fire events. Tensile coupon tests were conducted on three different steel grades and thicknesses to obtain their stress-strain curves and relevant mechanical properties after cooling them down from different elevated temperatures. It was found that the post-fire mechanical properties of cold-formed steels are different to the original ambient temperature mechanical properties. Hence a new set of equations is proposed to predict the reduced mechanical properties of cold-formed steels after a fire event.

Characterisation of a cell wall-anchored protein of Staphylococcus saprophyticus associated with linoleic acid resistance

The Gram-positive bacterium Staphylococcus saprophyticus is the second most frequent causative agent of community-acquired urinary tract infections (UTI), accounting for up to 20% of cases. A common feature of staphylococci is colonisation of the human skin. This involves survival against innate immune defenses including antibacterial unsaturated free fatty acids such as linoleic acid which act by disrupting bacterial cell membranes. Indeed, S. saprophyticus UTI is usually preceded by perineal skin colonisation.

Size dependent photodegradation of CdS particles deposited onto TiO2 mesoporous films by SILAR method

The properties of CdS nanoparticles incorporated onto mesoporous TiO2 films by a successive ionic layer adsorption and reaction (SILAR) method were investigated by Raman spectroscopy, UV-visible spectroscopy, transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). High resolution TEM indicated that the synthesized CdS particles were hexagonal phase and the particle sizes were less than 5 nm when SILAR cycles were fewer than 9. Quantum size effect was found with the CdS sensitized TiO2 films prepared with up to 9 SILAR cycles. The band gap of CdS nanoparticles decreased from 2.65 eV to 2.37 eV with the increase of the SILAR cycles from 1 to 11. The investigation of the stability of the CdS/TiO2 films in air under illumination (440.6 µW/cm2) showed that the photodegradation rate was up to 85% per day for the sample prepared with 3 SILAR cycles. XPS analysis indicated that the photodegradation was due to the oxidation of CdS, leading to the transformation from sulphide to sulphate (CdSO4). Furthermore, the degradation rate was strongly dependent upon the particle size of CdS. Smaller particles showed faster degradation rate. The size-dependent photo-induced oxidization was rationalized with the variation of size-dependent distribution of surface atoms of CdS particles. Molecular Dynamics (MD) simulation has indicated that the surface sulphide anion of a large CdS particle such as CdS made with 11 cycles (CdS11, particle size = 5.6 nm) accounts for 9.6% of the material whereas this value is increased to 19.2% for (CdS3) based smaller particles (particle size: 2.7 nm). Nevertheless, CdS nanoparticles coated with ZnS material showed a significantly enhanced stability under illumination in air. A nearly 100% protection of CdS from photon induced oxidation with a ZnS coating layer prepared using four SILAR cycles, suggesting the formation of a nearly complete coating layer on the CdS nanoparticles.

Thermal conductivity of configurable two-dimensional carbon nanotube architecture and strain modulation

We reported the thermal conductivity of the two-dimensional carbon nanotube (CNT)-based architecture, which can be constructed through welding of single-wall CNTs by electron beam. Using large-scale nonequilibrium molecular dynamics simulations, the thermal conductivity is found to vary with different junction types due to their different phonon scatterings at the junction. The strong length and strain dependence of the thermal conductivity suggests an effective avenue to tune the thermal transport properties of the CNT-based architecture, benefiting the design of nanoscale thermal rectifiers or phonon engineering.

“I’m Happy with Who I Am” : A Discursive Analysis of the Self-characterisation Practices of Boys in “Behaviour” Schools

In this chapter, I draw on poststructural theories of language to examine the self-characterisation practices of 33 boys attending special schools for students with disruptive behaviour. During a semi-structured interview, each boy was asked to describe his personality and then to choose from a selection of positive/negative word pairs. The objective was to determine whether these young people would characterise themselves in positive or negative ways. Participants were then asked if there was anything they would change about themselves if they could. Responses were analysed and compared against a discourse model developed from media reports and interviews with their principals. Findings suggest that while discourse may well ‘form the objects of which it speaks’ (Foucault, 1972, p. 49) in the eyes of teachers, principals, psychiatrists and paediatricians, it also offers a means through which the constituted subject can re-author itself in a more positive frame.

Association hierarchy mining and its application for network traffic characterisation

This thesis presents an association rule mining approach, association hierarchy mining (AHM). Different to the traditional two-step bottom-up rule mining, AHM adopts one-step top-down rule mining strategy to improve the efficiency and effectiveness of mining association rules from datasets. The thesis also presents a novel approach to evaluate the quality of knowledge discovered by AHM, which focuses on evaluating information difference between the discovered knowledge and the original datasets. Experiments performed on the real application, characterizing network traffic behaviour, have shown that AHM achieves encouraging performance.

Characterisation of cytokine response to Chlamydia pecorum infection in the koala, Phascolarctos cinereus

This thesis aimed at identifying cytokine markers associated with chlamydial infection and disease in koalas which is facing many threats to its survival, Chlamydia pecorum infections being a major one. To identify immunological markers associated with chlamydial infection and disease in koalas, key cytokines such as TNF alpha, IL10, IFN gamma and IL17A were cloned and sequenced and subsequently developed Quantitative Real Time PCR (qrtPCR) assays. The thesis provides preliminary data on the role of these cytokines in koala chlamydial disease and further longitudinal studies are required to confirm the role played by cytokines in pathology and protection against C. pecorum infection in the koala.

A constitutive model for mechanical response characterization of pumpkin peel and flesh tissues under tensile and compressive loadings

Enhancing quality of food products and reducing volume of waste during mechanical operations of food industry requires a comprehensive knowledge of material response under loadings. While research has focused on mechanical response of food material, the volume of waste after harvesting and during processing stages is still considerably high in both developing and developed countries. This research aims to develop and evaluate a constitutive model of mechanical response of tough skinned vegetables under postharvest and processing operations. The model focuses on both tensile and compressive properties of pumpkin flesh and peel tissues where the behaviours of these tissues vary depending on various factors such as rheological response and cellular structure. Both elastic and plastic response of tissue were considered in the modelling process and finite elasticity combined with pseudo elasticity theory was applied to generate the model. The outcomes were then validated using the published results of experimental work on pumpkin flesh and peel under uniaxial tensile and compression. The constitutive coefficients for peel under tensile test was α = 25.66 and β = −18.48 Mpa and for flesh α = −5.29 and β = 5.27 Mpa. under compression the constitutive coefficients were α = 4.74 and β = −1.71 Mpa for peel and α = 0.76 and β = −1.86 Mpa for flesh samples. Constitutive curves predicted the values of force precisely and close to the experimental values. The curves were fit for whole stress versus strain curve as well as a section of curve up to bio yield point. The modelling outputs had presented good agreement with the empirical values and the constructive curves exhibited a very similar pattern to the experimental curves. The presented constitutive model can be applied next to other agricultural materials under loading in future.

Formation of carbon nanoscrolls from graphene nanoribbons : a molecular dynamics study

Carbon nanoscrolls (CNSs) are one of the carbon-based nanomaterials similar to carbon nanotubes (CNTs) but are not widely studied in spite of their great potential applications. Their practical applications are hindered by the challenging fabrication of the CNSs. A physical approach has been proposed recently to fabricate the CNS by rolling up a monolayer graphene nanoribbon (GNR) around a CNT driven by the interaction energy between them. In this study, we perform extensive molecular dynamics (MD) simulations to investigate the various factors that impact the formation of the CNS from GNR. Our simulation results show that the formation of the CNS is sensitive to the length of the CNT and temperature. When the GNR is functionalized with hydrogen, the formation of the CNS is determined by the density and distribution of the hydrogen atoms. Graphyne, the allotrope of graphene, is inferior to graphene in the formation of the CNS due to the weaker bonds and the associated smaller atom density. The mechanism behind the rolling of GNR into CNS lies in the balance between the GNR–CNT van der Waals (vdW) interactions and the strain energy of GNR. The present work reveals new important insights and provides useful guidelines for the fabrication of the CNS.

Mechanical bending properties of sodium titanate (Na2Ti3O7) nanowires

We report on the mechanical properties of sodium titanate nanowires (Na2Ti3O7 NW) through a combination of bending experiments and theoretical analysis. Na2Ti3O7 NWs with lateral dimensions ranging from 20–700 nm were synthesized by a hydrothermal approach. A focused ion beam (FIB) was used to manipulate the selected Na2Ti3O7 NW over a hole drilled in an indium tin oxide substrate. After welding the nanowire, a series of bending tests was performed. It was observed that the Na2Ti3O7 NW exhibits a brittle behavior, and a nonlinear elastic deformation was observed before failure. By using the modified Euler–Bernoulli beam theory, such nonlinear elastic deformation is found to originate from a combination of surface effects and axial elongation (arising from the bending deformation). The effective Young's modulus of the Na2Ti3O7 NW was found to be independent of the wire length, and ranges from 21.4 GPa to 45.5 GPa, with an average value of 33 ± 7 GPa. The yield strength of the Na2Ti3O7 NW is measured at 2.7 ± 0.7 GPa.

Synthesis of heterocyclic nitroxides with an improved yield by investigating the tetraalkylation of N-benzylphthalimide

The synthesis of a novel class of antioxidants, namely pyridine annulated heterocyclic nitroxides has been investigated. Two analogues were developed that differed in the structure around the free radical nitroxide. The isolation and characterisation of several side products formed in the reactions gave insight into the reaction mechanism. These findings were exploited in order to improve the overall synthetic yield of the reaction.