http://espace.library.uq.edu.au/ The University of Queensland en Fez http://blogs.law.harvard.edu/tech/rss http://espace.library.uq.edu.au/view/UQ:270721 2012-03-20T00:00:00Z Tiedje, N. S. og Hattel, J. og Taylor, J. A. og Easton, M. A. http://espace.library.uq.edu.au/view/UQ:181285 A sparse-Lagrangian multiple mapping conditioning (MMC) model for turbulent diffusion flames is presented and tested against experimental data for a piloted methane/air jet diffusion flame (Sandia Flame D). The model incorporates a large eddy simulation for the flow field and a stochastic multiple mapping conditioning (MMC) approach for the reactive scalars. The stochastic MMC models the filtered density function of the scalar composition field. The numerical implementation involves a sparse-Lagrangian particle scheme in which there are fewer particles than there are LES grid cells. Predictions of similar accuracy to previously published Flame D simulations are achieved using only 35,000 particles (of these only 10,000 are chemically active). Sub-filter conditional dissipation is modelled by interactions between pairs of particles which are closely located in a reference mixture fraction space interpolated from the underlying Eulerian filtered field. A model is developed for the mixing time-scale which is proportional to the distance between mixing particles. It is shown that the time-scale can be adjusted to achieve good predictions for time-averaged mean and fluctuating statistics of passive and reactive scalars. © 2009 Elsevier Inc. All rights reserved. 2009-09-03T00:00:00Z Cleary, M. J. og Klimenko, A. Y. og Janicka, J. og Pfitzner, M. http://espace.library.uq.edu.au/view/UQ:199885 2010-03-19T00:00:00Z Ge, Yipeng og Cleary, M.J. og Klimenko, A.Y. http://espace.library.uq.edu.au/view/UQ:96654 2007-08-24T00:00:00Z Grandfield, J. F. og Nguyen, T. T. og Redden, G og Taylor, J. A. http://espace.library.uq.edu.au/view/UQ:202038 2010-04-08T00:00:00Z Meehan, P.A. og Daniel, W.J.T. og Ding, S. http://espace.library.uq.edu.au/view/UQ:123449 A number of economists have argued that a property tax with a lower rate applied to improvement values than to land values is superior to a property tax with a uniform tax rate that yields the same total revenue. This paper explores the statutory incidence of shifting to two-rate property taxation from single-rate property taxation. The authors recommend a tax credit provision to mitigate the regressive tendencies of this type of tax reform. 2008-01-25T00:00:00Z England, R. W. og Zhao, M. C. http://espace.library.uq.edu.au/view/UQ:63191 A 2-m, adiabatic column has been successfully refurbished and recommissioned for coal self-heating research at The University of Queensland. Subbituminous coal from the Callide Coalfields reached thermal runaway in just under 19 days from a starting temperature of 20-22 degreesC. The coal was loaded as two layers, with an R-70 index of 2.73 degreesC h(-1) and 5.90 degreesC h(-1) for the upper layer and lower layer respectively. Initially, a hotspot developed in the upper layer between 120 and 140 cm from the air inlet due to moisture adsorption. After 7 days, self-heating in the lower half of the column began to take over, consistent with the higher R-70 index of this coal. The location of the final hotspot was approximately 60 cm from the air inlet. Further tests on Australian coals, with the column, will enable a better understanding of coal self-heating under conditions closely resembling mining, transport and storage of coal. The results from the column will also provide industry with the information needed to manage the coal self-heating hazard. (C) 2002 Elsevier Science Ltd. All rights reserved. 2007-08-14T00:00:00Z Beamish, B. B. og Lau, A. G. og Moodie, A. L. og Vallance, T. A. http://espace.library.uq.edu.au/view/UQ:101880 2007-08-23T00:00:00Z Knights, P. og Jullian, F. og Jofre, L. http://espace.library.uq.edu.au/view/UQ:201299 Two experimental approaches were employed to assess the fibre/matrix adhesion between polymer threads and epoxy resin by transverse fibre bundle (TFB) tests. The first approach was to measure interfacial bonding strength of the fibre/matrix interface in dog-bone-shaped tensile specimens by applying normal stress until failure, simulating the Mode I failure mode. The second approach was to determine the fibre/epoxy interfacial bonding strength in shear (simulating the Mode II failure mode) by means of a V-notched beam shear testing method, i.e. a modified Iosipescu test. In both methods, polymer threads were transversely incorporated in the middle section of the specimens. It was found that both methods were simple, reliable, and sensitive to changes in the fibre/matrix adhesion conditions, though interpretation of the test results was somewhat complex. The two experimental approaches were able to produce consistent results and can thus be adopted as alternative methods for determining the interfacial bonding properties between fibres and matrix in composite systems where conventional micro-mechanical or macro-mechanical testing methods cannot be used. 2010-03-30T00:00:00Z Deng, S. og Qi, B. og Hou, M. og Ye, L. og Magniez, K. http://espace.library.uq.edu.au/view/UQ:10064 A vibration-based technique is employed to evaluate the structural integrity using mode coupling property. The methodology is first demonstrated on a single hollow section beam by analytical simulation and experimental validation. A welded test rig with a fatigue crack is then investigated by applying this technique. The test rig consists of chord members cross-connected by smaller branches. The fatigue crack is generated by a reciprocating mechanism. The proposed approach discriminates the cracked member through the emergence of coupled mode that is observable on FRF plots. The test results of the structure under intact and cracked states are presented. It is suggested that this method has the potential to detect cracks in welded structures. 2004-12-20T00:00:00Z Liu, D. og Gurgenci, H. og Veidt, M. http://espace.library.uq.edu.au/view/UQ:241779 2011-06-08T00:00:00Z Erten, O. og Kizil, Mehmet S. og Beamish, Bevan B. og McAndrew, L. http://espace.library.uq.edu.au/view/UQ:68883 Commercial explosives behave non-ideally in rock blasting. A direct and convenient measure of non-ideality is the detonation velocity. In this study, an alternative model fitted to experimental unconfined detonation velocity data is proposed and the effect of confinement on the detonation velocity is modelled. Unconfined data of several explosives showing various levels of nonideality were successfully modelled. The effect of confinement on detonation velocity was modelled empirically based on field detonation velocity measurements. Confined detonation velocity is a function of the ideal detonation velocity, unconfined detonation velocity at a given blasthole diameter and rock stiffness. For a given explosive and charge diameter, as confinement increases detonation velocity increases. The confinement model is implemented in a simple engineering based non-ideal detonation model. A number of simulations are carried out and analysed to predict the explosive performance parameters for the adopted blasting conditions. 2007-08-15T00:00:00Z Esen, S. http://espace.library.uq.edu.au/view/UQ:192273 This paper presents a robust stochastic framework for the incorporation of visual observations into conventional estimation, data fusion, navigation and control algorithms. The representation combines Isomap, a non-linear dimensionality reduction algorithm, with expectation maximization, a statistical learning scheme. The joint probability distribution of this representation is computed offline based on existing training data. The training phase of the algorithm results in a nonlinear and non-Gaussian likelihood model of natural features conditioned on the underlying visual states. This generative model can be used online to instantiate likelihoods corresponding to observed visual features in real-time. The instantiated likelihoods are expressed as a Gaussian mixture model and are conveniently integrated within existing non-linear filtering algorithms. Example applications based on real visual data from heterogenous, unstructured environments demonstrate the versatility of the generative models. 2010-01-12T00:00:00Z Kumar, S. og Ramos, F. og Upcroft, B. og Durrant-Whyte. H. http://espace.library.uq.edu.au/view/UQ:193081 This paper presents a robust stochastic model for the incorporation of natural features within data fusion algorithms. The representation combines Isomap, a non-linear manifold learning algorithm, with Expectation Maximization, a statistical learning scheme. The representation is computed offline and results in a non-linear, non-Gaussian likelihood model relating visual observations such as color and texture to the underlying visual states. The likelihood model can be used online to instantiate likelihoods corresponding to observed visual features in real-time. The likelihoods are expressed as a Gaussian Mixture Model so as to permit convenient integration within existing nonlinear filtering algorithms. The resulting compactness of the representation is especially suitable to decentralized sensor networks. Real visual data consisting of natural imagery acquired from an Unmanned Aerial Vehicle is used to demonstrate the versatility of the feature representation. 2010-01-18T00:00:00Z Kumar, S. og Ramos, F. og Upcroft, B. og Ridley, M. og Ong, L. og Sakkarieh, S. og Durrant-Whyte, H. http://espace.library.uq.edu.au/view/UQ:189156 Nano-sized domains have been widely observed in rare-earth-doped ceria, but their structure model remains unclear. In this work, based on the study of high resolution transmission electron microscopy (HRTEM) and selected area electron diffraction (SAED) of Gd-doped ceria, the structure model of the domains was constructed by a combination of defect clusters with oxygen vacancy chains. Then, the SAED patterns were simulated using this structure model. The simulated results are consistent with the observed SAED patterns. 2009-12-06T00:00:00Z Ye, Fei og Mori, Toshiyuki og Ou, Ding Rong og Zou, Jin og Drennan, John http://espace.library.uq.edu.au/view/UQ:41283 High-speed milling (HSM) has many advantages over conventional machining. Among these advantages, the lower cutting force associated with the machining process is of particular significance for Nitinol alloys because their machined surfaces show less strain hardening. In this article, a systematic study has been carried out to investigate the machining characteristics of a Ni50.6Ti49.4 alloy in HSM. The effects of cutting speed, feed rate, and depth of cut on machined surface characteristics and tool wear are studied. It is found that an increase in cutting speed has resulted in a better surface finish and less work hardening. This is attributed to the reduction of chip cross-sectional area or chip thickness, which thus leads to a lower cutting force or load. 2007-08-13T00:00:00Z Huang, H http://espace.library.uq.edu.au/view/UQ:95321 2007-08-23T00:00:00Z Ruzic, V. og Nesic, S. http://espace.library.uq.edu.au/view/UQ:220742 Human bone fracture associated with osteoporosis was hypothesized to be related to the alteration of mechanical properties in bones. In this work, cortical and trabecular bones from human femoral heads were studied. Bone samples of eight female and four male patients, with ages varying from 37 to 93 years, were collected from total hip replacement surgery. Reduced modulus (Er) and hardness (H) of osteons, interstitial lamellae and trabeculae were characterized by nanoindentation. The results showed both the reduced modulus and hardness of the interstitial lamellae were significant higher than those of osteons and trabeculae. Though there was no significant difference in microstructures in the Group A (age < 60 years) and B (age > 60 years), the Group B bones demonstrated to be stiffer. 2010-11-17T00:00:00Z Lin, Chih Ling og Huang, Han og Cribb, Bronwen W. og Russell, Anthony http://espace.library.uq.edu.au/view/UQ:189055 Normal grain sized metals of aluminium, copper and 70:30 brass were extruded by the equal channel angular extrusion (ECAE) process to a total strain of similar to17. It was found that grain structures of submicron- and nano- sizes developed in all the extruded metals. Electron backscatter diffraction analysis confirmed that a high volume of high angle boundaries existed in the extruded metals, showing development of a well established grain structure. The extruded structures were found to remain stable without significant grain growth in subsequent annealings at temperatures up to 200degreesC. Nanoindentation measurements were performed to examine the mechanical properties of the materials. It was found that the hardness of the metals was much higher than the initial materials of normal grain sizes. The hardness enhancement was most significant in the copper-zinc alloy. Nanoindentation measurements revealed the mechanical characteristics of the metals, showing variations of the stiffness and elastic modulus in these materials. 2009-12-04T00:00:00Z Short, K. og Wuhrer, Richard og Collins, G. og Yeung, Wing Yiu http://espace.library.uq.edu.au/view/UQ:193651 In a comparative study, N2+, Ar+ and Ca+ ion implantation was used to modify subcutaneous augmentation material (SAM), a micro-porous form of polytetrafluoroethylene (PTFE) and nonporous PTFE, with a view to assessing the effect of ion implantation on the chemical and physical structure of these materials as well as the effect of porosity on the response to ion implantation. SAM is used as an implant material for reconstructive surgery, and this study is part of a larger investigation into methods of modifying SAM to improve its tissue integration potential. Ion implantation was carried out at an energy of 30 keV, with doses of 1×1015 and 1×1016 ions/cm2. SRIM.2000.39 was used to simulate N2+, Ar+ and Ca+ implantation of PTFE. X-ray photoelectron spectroscopy (XPS) was used for the characterisation of chemical structural changes in the ion-implanted samples, while scanning electron microscopy (SEM) was used for the characterisation of physical structural changes. Rutherford backscattering spectroscopy (RBS) was used to determine the elemental surface composition of Ca+ and Ar+ implanted samples. Advancing and receding water contact angles were measured using the sessile drop method. XPS analysis showed that all ion-implanted samples had undergone chemical structural changes. Some variation was noted between samples implanted with different ions and at different doses. SEM analysis showed that physical structural changes were independent of ion mass with some variation between doses. Water contact angle measurements showed some variation between samples, with nonporous samples showing dose dependent behaviour. 2010-01-22T00:00:00Z Colwell, J. M. og Wentrup-Byrne, E. og Bell, J. M. og Wielunski, L. S. http://espace.library.uq.edu.au/view/UQ:140413 2008-06-10T00:00:00Z Kanchibotla, S. S. og Scott, A. http://espace.library.uq.edu.au/view/UQ:55525 This paper presents a case study that explores how operator digging style juxtaposes with mechanical capability for a class of hydraulic mining excavators. The relationships between actuator and digging forces are developed and these are used to identify the excavator's capability to apply forces in various directions. Two distinct modes of operation are examined to see how they relate to the mechanical capabilities of the linkage and to establish if one has merit over the other. It is found that one of these styles results in lower loading of the machine. 2007-08-13T00:00:00Z Hall, A. S. og McAree, P. R. http://espace.library.uq.edu.au/view/UQ:34830 Algorithms for explicit integration of structural dynamics problems with multiple time steps (subcycling) are investigated. Only one such algorithm, due to Smolinski and Sleith has proved to be stable in a classical sense. A simplified version of this algorithm that retains its stability is presented. However, as with the original version, it can be shown to sacrifice accuracy to achieve stability. Another algorithm in use is shown to be only statistically stable, in that a probability of stability can be assigned if appropriate time step limits are observed. This probability improves rapidly with the number of degrees of freedom in a finite element model. The stability problems are shown to be a property of the central difference method itself, which is modified to give the subcycling algorithm. A related problem is shown to arise when a constraint equation in time is introduced into a time-continuous space-time finite element model. (C) 1998 Elsevier Science S.A. 2007-08-13T00:00:00Z Daniel, WJT http://espace.library.uq.edu.au/view/UQ:196921 2010-02-26T00:00:00Z Halley, P. J. og Khemani, K. og Krummel, E. og Nicholson, T. og Russo, M. A. L. og Strounina, E. og Truss, R. http://espace.library.uq.edu.au/view/UQ:127705 The effect of moisture content and temperature on water diffusion into a modified high amylose (<= 90%) maize thermoplastic starch blend was investigated. Gravimetric and magnetic resonance imaging (MRI) studies were conducted to elucidate the diffusion mechanism and diffusion coefficients for this system. The diffusion coefficient data demonstrated that the rate of water diffusion into this blend was significantly dependent upon temperature and moisture content. Water diffusion was faster at higher temperatures and generally for samples stored at higher relative humidity environments. It was revealed from the gravimetric data that water diffusion into this starch blend was Fickian; however, further analysis of the MRI images found that the water diffusion mechanism was exponentially dependent on the concentration. This result was determined by comparing experimental water concentration profiles to a theoretical model calculated using the implicit Crank-Nicolson finite difference method. 2008-02-18T00:00:00Z Russo, Melissa A. L. og Strounina, Ekaterina og Waret, Muriel og Nicholson, Timothy og Truss, Rowan og Halley, Peter J. http://espace.library.uq.edu.au/view/UQ:264234 The two-parameter Weibull distribution has been widely used for modelling the lifetime of products and components. In this paper we study the effect of the shape parameter on the failure rate and three variables of importance in the context of maintenance and reliability improvement. These variables are (i) time to failure, (ii) age at replacement based on risk and (iii) residual life. We propose a classification scheme for the distribution based on the shape parameter and discuss the application of the results. 2012-01-01T00:00:00Z Jiang, R. og Murthy, D. N. P. http://espace.library.uq.edu.au/view/UQ:138220 2008-05-12T00:00:00Z Huang, H. og Irwan, R. og Kurriyagawa, T. http://espace.library.uq.edu.au/view/UQ:55538 The stress corrosion cracking (SCC) behavior and pre-exposure embrittlement of AZ31 magnesium alloy have been studied by slow strain rate tensile (SSRT) tests in this paper. It is showed that AZ31 sheet material is susceptible to SCC in distilled water, ASTM D1.387 solution, 0.01 M NaCl and 0.1 M NaCl solution. The AZ31 magnesium alloy also becomes embrittled if pre-exposed to 0.01 M NaCl solution prior to tensile testing. The degree of embrittlement increased with increasing the pre-exposure time, It is proposed that both the pre-exposure embrittlement and SCC were due to hydrogen which reduces the cohesive strength. i,e,. hydrogen embrittlement, (c) 2005 Elsevier B.V. All rights reserved. 2007-08-13T00:00:00Z Song, R.G. og Blawert, C og Dietzel, W. og Atrens, A. http://espace.library.uq.edu.au/view/UQ:268410 The demand for ultra-thin silicon wafers has escalated in recent years with the rapid development of miniaturized electronic devices. In this work, diamond grinding for thinning silicon wafers was carried out on an ultra-precision grinding machine. The thinning performance and the minimum wafer thickness were investigated under different grinding conditions. It was found that the grain depth of cut that was used to characterize the overall grinding conditions played an important role in the determination of the final grinding performance. The relationship between the subsurface damage of the ground wafer and the minimum wafer thickness achieved was also revealed. 2012-02-26T00:00:00Z Zhou, L. og Tian, Y. B. og Huang, H. og Sato, H. og Shimizu, J. http://espace.library.uq.edu.au/view/UQ:76286 An investigation was carried out on the transition of an iron electrode from active to passive state in a sulphuric acid solution. It was found that the active-passive transition was an auto-catalytic process in which a pre-passive film grew on the electrode surface. The growing pre-passive film had a fractal edge whose dimension was affected by the applied passivating potential and the presence of chlorides in the solution. Applying a more positive passivating potential led to a faster active-passive transition and resulted in a more irregular pre-passive film. If chlorides were introduced into the sulphuric acid solution, the active-passive transition became more rapid and the pre-passive film more irregular. Apart from the influence on the growth of the pre-passive film, the presence of chlorides in the passivating solution was found to deteriorate the stability of the final passive film. All these phenomena can be understood if the passivating iron electrode is regarded as a dissipative system. To explain these results, a fractal pre-film model is proposed in this paper. (C) 2004 Elsevier Ltd. All rights reserved. 2007-08-15T00:00:00Z Song, Guangling og Cao, Chu-Nan og Chen, Sheng-Hao http://espace.library.uq.edu.au/view/UQ:197459 2010-03-03T00:00:00Z Palanisamy, S. og Nagarajah, C.R. og Iovenitti, P. http://espace.library.uq.edu.au/view/UQ:151483 This work presents a superposition approach to investigate forced convection in microducts of arbitrary cross-section, subject to H1 and H2 boundary condition, in the slip-flow regime with further complication of a temperature jump condition assumption. It is shown that applying an average slip velocity and temperature jump definition, one can still use the no-slip/no-jump results with some minor modifications. Present results for slip flow in microchannels of parallel plate, circular, and rectangular cross-sections are found to be in complete agreement with those in the literature. Application of this methodology to microchannels of triangular cross-section is also verified by comparing the present results with those obtained numerically by undertaking the commercially available software CFD-ACE. 2008-06-19T00:00:00Z Hooman, K. http://espace.library.uq.edu.au/view/UQ:95520 2007-08-23T00:00:00Z Segui, J. http://espace.library.uq.edu.au/view/UQ:95316 2007-08-23T00:00:00Z Klimenko, A. Y. og Class, A.G. http://espace.library.uq.edu.au/view/UQ:122823 Precipitations that exhibit irrational transformation crystallography can often be explained in terms of the O-lines in the habit plane. The present work developed an analytical O-line method, which is more useful than the numerical O-line method to study the variation in the habit plane and its structure in a systematic manner. This method has an advantage that the orientation relationship (OR) is the output from the calculation, while in many other models interpreting precipitation crystallography the OR is either an input or is constrained by a prerequisite condition. This paper described the derivation of this method and its application to the study of the precipitation crystallography in fcc-bcc systems. Examples were given for three alloy systems, namely Cu-0.33 wt% Cr and Ni-45 wt% Cr alloys and a duplex-phase alpha-gamma stainless steel. The solutions include the OR between the precipitates and their matrix, the habit plane, the invariant line and the dislocation structure in the habit plane. The calculated results are in good agreement with the experimental observations reported in the literatures. Furthermore, the variation in the optimum O-line features with the lattice parameter ratio has also been studied systematically, providing some guidelines for estimating and understanding possible transformation crystallography from different fcc-bcc systems. 2008-01-25T00:00:00Z Qiu, D. og Zhang, W. Z. http://espace.library.uq.edu.au/view/UQ:114750 A set of extrusion samples of Al-Si-Mg alloys (0.5 wt%Mg and 0.3-0.8 wt%Si) were, respectively, T1- and T4-heat-treated. Differential scanning calorimetry (DSC) was used to heat the samples to particular temperatures to promote the formation of precipitates for study by transmission electron microscopy (TEM). It was found that, apart from beta ", beta', and B', there were many precipitates showing rectangular lattices when viewed along the long axes of the precipitates. It is considered that the residual stresses (or dislocations) in the extrusion after the TI-treatment facilitated the nucleation and growth of the precipitates during the heating in the DSC. (C) 2001 Elsevier Science Ltd. All rights reserved. 2007-10-17T00:00:00Z Yao, J. Y. og Graham, D. A. og Rinderer, B. og Couper, M. J. http://espace.library.uq.edu.au/view/UQ:183495 2009-09-03T00:00:00Z Qiu, D. og Zhang, W. -Z. http://espace.library.uq.edu.au/view/UQ:123028 The crystallography and the structure of the habit plane of proeutectoid alpha precipitates in beta matrix in a Ti-7.26 wt%Cl were studied using TEM. The orientation relationship was found to deviate slightly from the ideal Burgers orientation relationship. The habit plane of precipitates was found to be normal to a particular set of Deltag's. A set of dislocations, about 11 nm apart, were observed on the habit plane of the precipitates. The Burgers vector of the dislocations, as determined by g (.) b contrast analyses, is [1 -11](beta)/2([2-1-13](alpha)/6). This Burgers vector is different from those determined by previous investigations. The observations are discussed in terms of an analytical O-line model and tend to Support the prediction of the O-line model. (C) 2004 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved. 2008-01-25T00:00:00Z Ye, F. og Zhang, W.Z. og Qiu, D. http://espace.library.uq.edu.au/view/UQ:129204 Transmission electron microscopy (TEM) is used to conduct the systematic study of the annealing induced crystallization, both continuously and isothermally, of a Zr-based metallic glass. Through detailed microstructure analysis, it is found that the crystallization of this metallic glass is initialized by a nano-scaled primary crystallization process with a tetragonal structured crystal (a = 0.96 nm and c = 2.82 nm) as the primary phase. A eutectic crystallization is followed afterwards with two types of crystalline phases as the crystallization products, one of which is determined to be a metastable orthorhombic phase (a = 0.69 nm, b = 0.75 nm and c = 0.74 nm). Upon annealing at a raised temperature or isothermal treatments, a solid state phase transformation takes place and the orthorhombic metastable phase transforms into two types of tetragonal crystalline phases. The whole crystallization process of this metallic glass is in turn realized, and the thermal stability and nano-crystallization mechanism are discussed based on the microstructure and thermal analyses. (C) 2007 Elsevier Ltd. All rights reserved. 2008-02-18T00:00:00Z Yan, M og Zou, Jin og Shen, J http://espace.library.uq.edu.au/view/UQ:9906 This paper describes a rarefied hypervelocity test facility producing gas speeds greater than 7 km/s. The X1 expansion tube at the University of Queensland has been used to produce nitrogen flows at 8.9 and 9.5 km/s with test flow durations of 50 and 40 microsecond­s respectively. Rarefied flow is indicated by values of the freestream breakdown parameter > 0.1 (Cheng's rarefaction parameter < 10) and freestream Knudsen numbers up to 0.038, based on a model size of 9 mm. To achieve this, the test gas is expanded from the end of the acceleration tube into a dump tank. Nominal conditions in the expansion are derived from CFD predictions. Measured bar gauge (Pitot) pressures show that the flow is radially uniform when the Pitot pressure has decreased by a factor ten. The measured bar gauge pressures are an increasing fraction of the expected Pitot pressure as the rarefaction parameters increase. 2005-02-23T00:00:00Z Macrossan, Michael N. og Chiu, H.- H. og Mee, David J. http://espace.library.uq.edu.au/view/UQ:129570 Fully developed forced convection inside a circular tube filled with saturated porous medium and with uniform heat flux at the wall is investigated on the basis of a Brinkman-Forchheimer model. The matched asymptotic expansion method is applied at small Darcy numbers. For large Darcy numbers, the solution for the Brinkman-Forchheimer momentum equation is found in terms of an asymptotic expansion. Once the velocity distribution is determined, the energy equation is solved using the same asymptotic technique. The results for the two limiting cases of clear fluid and Darcy flow conditions show good agreement with those available in the literature. 2008-02-18T00:00:00Z Hooman, K. og Gurgenci, H. http://espace.library.uq.edu.au/view/UQ:8948 The distribution functions for the linear and angular momentum of N particles selected from an equilibrium gas are derived. The most probable momentum (per unit mass) increases with N. If the particles of an astronomical system are assumed to come from an original 'cosmic gas', universal mass-versus-momentum relations can be derived. The derived mass-versus-angular momentum relation is similar but not identical to that which has been reported, and which may hold for the angular momentum of the mass of the entire universe. The derived relationship applied ot the initial conditions and evolutionary effects may account for the difference between this prediction and the observed relationship 2005-11-22T00:00:00Z Macrossan, M. N. http://espace.library.uq.edu.au/view/UQ:294483 2013-03-22T13:46:59Z Lee, Joseph og Feng, Bo http://espace.library.uq.edu.au/view/UQ:144602 A coupled thermomechanical model to simulate light alloy solidification problems in permanent composite moulds is presented. This model is based on a general isotropic thermoelasto-plasticity theory and considers the different thermomechanical behaviours of each component of the mould as well as those of the solidifying material during its evolution from liquid to solid. To this end, plastic evolution equations, a phase-change variable and a specific free energy function are proposed in order to derive temperature-dependent material constitutive laws. The corresponding finite element formulation and the staggered scheme used to solve the coupled nonlinear system of equations are also presented. Finally, the temperature and displacement predictions of the model are validated with laboratory measurements obtained during an experimental trial. (C) 1999 Elsevier Science Ltd. All rights reserved. 2008-06-10T00:00:00Z Celentano, Diego og Gunasegaram, Dayalan og Nguyen, Thang http://espace.library.uq.edu.au/view/UQ:83032 This paper describes the results of atmospheric corrosion testing and of an examination of patina samples from Brisbane, Denmark, Sweden, France, USA and Austria. The aim was threefold: (1) to determine the structure of natural patinas and to relate their structure to their appearance in service and to the atmospheric corrosion of copper; (2) to understand why a brown rust coloured layer forms on the surface of some copper patinas; (3) to understand why some patinas are still black in colour despite being of significant age. During the atmospheric corrosion of copper, a two-layer patina forms on the copper surface. Cuprite is the initial corrosion product and cuprite is always the patina layer in contact with the copper. The growth laws describing patina formation indicate that the decreasing corrosion rate with increasing exposure time is due to the protective nature of the cuprite layer. The green patinas were typically characterised by an outer layer of brochantite, which forms as individual crystals on the surface of the cuprite layer, probably by a precipitation reaction from an aqueous surface layer on the cuprite layer. Natural patinas come in a variety of colours. The colour is controlled by the amount of the patina and its chemical composition. Thin patinas containing predominantly cuprite were black. If the patina was sufficiently thick, and the [Fe]/[Cu] ratio was low, then the patina was green, whereas if the [Fe]/[Cu] ratio was approximately 10 at%, then the patina is rust brown in colour. The iron was in solid solution in the brochantite, which might be designated as a (copper/iron) hydroxysulphate. In the brown patinas examined, the iron was distributed predominately in the outermost part of the patina. (c) 2005 Elsevier Ltd. All rights reserved. 2007-08-15T00:00:00Z FitzGerald, K. P. og Nairn, J. og Skennerton, G. og Atrens, A. http://espace.library.uq.edu.au/view/UQ:57493 Atmospheric corrosion tests have been conducted at Heron Island, Queensland, a low SO2 marine environment. The corrosion rates for copper followed the linear bi-logarithmic law. X-ray diffraction identified atacamite (basic copper chloride) and cuprite (cuprous oxide) as the predominant corrosion products. Biogenic and anthropogenic sources of pollution did not have a measurable influence. 2007-08-13T00:00:00Z Skennerton, G og Nairn, J og Atrens, A http://espace.library.uq.edu.au/view/UQ:128982 The defects in 3C-SiC film grown on (001) plane of Si substrate were studied using a 200 kV high-resolution electron microscope with point resolution of 0.2 nm. A posterior image processing technique, the image deconvolution, was utilized in combination with the image contrast analysis to distinguish atoms of Si from C distant from each other by 0.109 nm in the [110] projected image. The principle of the image processing technique utilized and the related image contrast theory is briefly presented. The procedures of transforming an experimental image that does not reflect the crystal structure intuitively into the structure map and of identifying Si and C atoms from the map are described. The atomic configurations for a 30 degrees partial dislocation and a microtwin have been derived at atomic level. It has been determined that the 30 degrees partial dislocation terminates in C atom and the segment of microtwin is sandwiched between two 180 degrees rotation twins. The corresponding stacking sequences are derived and atomic models are constructed according to the restored structure maps for both the 30 degrees partial dislocation and microtwin. Images were simulated based on the two models to affirm the above-mentioned results. 2008-02-18T00:00:00Z Tang, C.Y. og Li, F.H. og Wang, R. og Zou, J. og Zheng, X.H. og Liang, J.W. http://espace.library.uq.edu.au/view/UQ:77402 This work reports on a critical measurement to understand the intergranular stress corrosion cracking (IGSCC) of pipeline steels: the atom probe field ion microscope (APFIM) measurement of the carbon concentration at a grain boundary (GB). The APFIM measurement was related to the microstructure and to IGSCC observations. The APFIM indicated that the GB carbon concentration of X70 was similar to 10 at% or less, which correlated with a high resistance to IGSCC for X70. (C) 2005 Elsevier Ltd. All rights reserved. 2007-08-15T00:00:00Z Atrens, A. og Wang, J. Q. og Stiller, K. og Andren, H. O. http://espace.library.uq.edu.au/view/UQ:57515 An experimental white cast iron with the unprecedented fracture tough ness of 40 MPa m(1/2) is currently being studied to determine the mechanisms of toughening. This paper reports the investigation of the role of strain-induced martensitic (SIM) transformation. The dendritic microconstituent in the toughened alloy consists primarily of retained austenite, with precipitated M(7)C(3) carbides and some martensite. Refrigeration experiments and differential scanning calorimetry (DSC) were used to demonstrate, firstly, that this retained austenite has an ''effective'' sub-ambient M(S) temperature and, secondly, that SIM transformation can occur at ambient temperatures. Comparison between room temperature and elevated temperature K-Ic tests showed that the observed SIM produces a transformation toughening response in the alloy, contributing to, but not fully accounting for, its high tough ness. SIM as a mechanism for transformation toughening has not previously been reported for white cast irons. Microhardness traverses on crack paths and X-ray diffraction (XRD) on fracture surfaces confirmed the interpretation of the K-Ic experiments. Further DSC and quantitative XRD showed that, as heat-treatment temperature is varied, there is a correlation between fracture toughness and the volume fraction of unstable retained austenite. 2007-08-13T00:00:00Z Hann, SK og Gates, JD http://espace.library.uq.edu.au/view/UQ:221844 2010-11-21T00:00:00Z Zou, J. og Li, F.H. og Yang, D.Y. og Jiang, Y.D. og Kuo, K.H.