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(2008)Journal ArticleAmorphous Si1-xCx /SiC multilayer films were prepared by alternating deposition of Si-rich Si1-xCx and near-stoichiometric SiC layers by using magnetron sputtering. The as-deposited films were annealed at different temperatures Ta from 800 to 1100 oC. The influence of Ta and Si content in the Si-rich layer on the layered structural stability and on the formation of Si and/or SiC nanocrystals NCs is investigated by a variety of analytical techniques, including x-ray reflectivity XRR, x-ray diffraction XRD, transmission electron microscopy TEM, Raman spectroscopy, and Fourier transform infrared spectrometry FTIR. XRR showed that Si1-xCx /SiC multilayers annealed at temperatures of up to 800 oC retain their layered structure. XRD revealed that Si NCs were formed in samples with a high Si content in the Si-rich layer for Ta 800 oC. At annealing temperatures of 900 oC or greater, the formation of Si NCs was accompanied by the formation of -SiC NCs. Additionally, the formation of Si and SiC NCs was confirmed by TEM imaging and Raman spectroscopy. The Si-NC size obtained from the TEM micrographs is within the range of 3-5 nm. The -SiC NCs are smaller 2-3 nm than Si NCs. Raman analysis identified an 9 cm-1 Raman peak shift in the Si-NC peak to a lower energy with respect to that for bulk Si. FTIR Si-C bond absorption spectra exhibited narrowing of the full width at half maximum and a peak shift toward a higher wave number with increasing Ta. This behavior can be explained by an increase in order as well as an increase in the number of Si-C bonds.
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(2008)Conference PaperIn this article, Life Cycle Assessment (LCA) and Life Cycle Costing (LCC) quantify the performance of variable and fixed speed centrifugal chillers using two refrigerants (HCFC 123 or HFC 134A) in commercial air-conditioning systems. Electricity demand during operation causes the highest environmental and economic burdens for all options. Detailed energy simulation shows that chillers operate most of the time in partial load, therefore energy-optimised variable-speed systems are preferable. We demonstrate the significance of understanding each phase of the life cycle to optimise overall performance. A systems approach, if broadly applied, could reduce the barriers between stakeholders along supply chains.
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(2008)Conference PaperA life cycle assessment (LCA) was used to evaluate the influence of choosing refrigerants R22, R407C or R410A for domestic air conditioners. Other than the chemical characteristics of R22, the other key factor was the operating pressure. Due to high pressure operation, the R410A system experienced the highest leakage rate, energy consumption and global warming potential (GWP). Sensitivity analysis was used to examine the influence of leakage and to show that, compared with the unit’s lifespan, setpoint and efficiency, the climate in different Australian locations and the load profile have significant effects on the energy use and GWP.
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(2008)Conference PaperA model to describe the low frequency dynamic and acoustic responses of a submarine hull subject to an eccentric harmonic propeller shaft excitation is presented. The submarine is modelled as a fluid-loaded, ring stiffened cylindri-cal shell with internal bulkheads and conical end caps. The stiffeners are introduced using a smeared approach. A harmonic axial force is introduced by the propeller and is transmitted to the hull through the shaft. It results in excita-tion of the accordion modes only if the force is symmetrically distributed to the structure. Otherwise the excitation can be modelled as the sum of a distributed load and a moment applied to the edge of the hull. This leads to excitation of the higher order circumferential modes that can result in high noise signature. Structural and acoustic responses are presented in terms of deformation shapes and directivity patterns for the radiated sound pressure. Results for the case of purely axisymmetric excitation and the case in which an eccentricity is introduced are compared.
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(2008)Conference PaperThe paper and pulp industry produces effluent which is high in organic content and salinity, typically making is difficult to treat. For reclamation of this wastewater, the process should be designed such that the water is ‘fit for purpose’. Agricultural reuse of this waste stream is a potential option as the treatment requirements are less intense than for other reuse opportunities. This papers forms part of a larger project for developing an integrated UF-NF-RO system for reclaiming the biologically treated effluent from a thermo-mechanical pulp and paper mill in rural Australia. The current work has characterised the waste water and investigated a suite of commercially available NF membranes as a pre-treatment method for RO. Dead-end stirred cell filtration has been used to evaluate the selective removal of multivalent ions and low molecular weight organics in the NF stage. The result demonstrate the importance of the NF stage to the reclaimed water and show a SAR reduction of between 30-60% is achievable in this system. Of the commercially available membranes tested the membrane which performed the best was the NTR-7450 membrane from Hydranautics.
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(2008)Journal ArticleAbstract This paper demonstrates the application of a new multiaxial creep damage model developed by the authors to predict the failure time of components made of service aged 2.25%Cr-1%Mo, 0.5%Cr-0.5%Mo-0.25%V low alloy steels, titanium and nickel-based superalloys. The model accounts for the tertiary creep behaviour and assumes the creep damage is related to the internal energy absorbed by the material. The authors argue that the model is the most appropriate for characterizing gross creep damage from a macroscopic point of view because it takes into accounts both the multiaxial internal deformation and loading. The verification and application of the model are demonstrated by applying it to the Bridgman notched bars for which the experimental data are available. The predicted failure times by the model are compared with the experimental results and those obtained from the reference stress method. The results show that the proposed model is capable of predicting failure times of the components made of the above-mentioned materials with an accuracy of 2.2% or better. Also, it is shown that the model predicts the creep failure times of the components more accurately than the reference stress method.