School of Mechanical & Mining Engineering Publications  UQ eSpace
http://espace.library.uq.edu.au/
The University of Queensland
en
Fez
http://blogs.law.harvard.edu/tech/rss

Analysis of Tshaped equal channel angular pressing using the finite element method
http://espace.library.uq.edu.au/view/UQ:173516
Plastic deformation behavior in Tshaped equal channel pressing, a modified equal channel angular pressing (ECAP) using Tshaped channel instead of conventional Lshaped channel, is analyzed by using the commercial finite element code DEFORM. Simulations were carried out under realistic conditions by considering the strain hardening of material and friction. The deformation behavior is more complicated and the strain induced is highly localized. Severe plastic strain is localized in the bottom region of the workpiece and very small strain is developed in the other region, which is in good agreement with the experimental results reported in the literature showing the nonuniformity in microstructure and hardness distribution. In addition, the load requirements of the TECAP are much higher compared to conventional ECAP.
20090402T14:50:23Z
Anumalasetty, Venkata Nagasekhar; Kim, Hyoung Seop

Analysis of XPS spectra of Fe2+ and Fe3+ ions in oxide materials
http://espace.library.uq.edu.au/view/UQ:163225
Samples of the iron oxides Fe0.94O, Fe3O4, Fe2O3, and Fe2SiO4 were prepared by high temperature equilibration in controlled gas atmospheres. The samples were fractured in vacuum and high resolution XPS spectra of the fractured surfaces were measured. The peak positions and peak shape parameters of Fe 3p for Fe2+ and Fe3+ were derived from the Fe 3p XPS spectra of the standard samples of 2FeO·SiO2 and Fe2O3, respectively. Using these parameters, the Fe 3p peaks of Fe3O4 and Fe1−yO are analysed. The results indicate that high resolution XPS techniques can be used to determine the Fe2+/Fe3+ ratios in metal oxides. The technique has the potential for application to other transition metal oxide systems.
20090205T17:39:01Z
Yamashita, Toru; Hayes, Peter

Analytical and experimental investigation of coolant velocity in high speed grinding
http://espace.library.uq.edu.au/view/UQ:123083
Use of waterbase coolant is a prerequisite in an high speed grinding process to avoid thermal damage and to achieve better surface integrity as well as higher grinding ratio. However, the presence of hazardous chemical additives in the coolant causes environmental problems. As a result, stringent government legislation is being practiced for the coolant use and disposal, which consumes 717% of the total machining cost. This paper reports the coolant flux minimization through controlled jet impingement so as to prolong the coolant replenishment cycle. Control of coolant flux was achieved through development of a "metered quantity coolant" (MQC) nozzle which supplies the required amount of coolant to the grinding zone. Also, this investigation has shown that coolant velocity has a significant influence on the high speed grinding performance. When the coolant velocity is inadequate, coolant could not penetrate into the grinding zone. The increase in coolant velocity was realized with reduction in nozzle opening area and does not use a large quantity of coolant. This is of significance to reduce environmental pollution and machining costs through extended coolant replenishment period. (C) 2004 Elsevier Ltd. All rights reserved.
20080125T16:16:43Z
Ramesh, K; Huang, H; Yin, L

Analytical and experimental study of pressure dynamics in a pulsed water jet device
http://espace.library.uq.edu.au/view/UQ:272544
Pulsed highvelocity water jets are of interest for breaking rocks and other materials. This paper describes a straightforward way of generating single water pulse with a hammer impacting a piston that rests on top of a chamber filled with water. This impacting action pressurises the water, expelling it at high velocity through a nozzle. A theoretical investigation is outlined aimed at gaining a better understanding of this system for generating water pulses. A computational model is developed to simulate the pressure dynamics in the chamber based on continuity and momentum equations for a compressible viscous flow. This model is used to optimise the relative sizes of the hammer and piston as well as the height of the water column to produce the highest velocity water pulse. The model was validated by building an experimental apparatus. In these experiments maximum pressures of about 200 MPa were measured inside the chamber over a time period of about 560 μs. This produced a water pulse with maximum velocity of 600 m/s. Experiments were conducted with nozzle diameters between about 1 mm and 4 mm to study the effect of discharge volume on the pressure history. The results illustrate that although the peak attainable pressure decreases with an increase in nozzle diameter, the duration of the elevated pressure remains similar for all nozzles.
20120411T12:03:16Z
Dehkhoda, Sevda; Hood, Michael; Alehossein, Habib; Buttsworth, David

Analytical and finite element prediction of Lamb wave scattering at delaminations in quasiisotropic composite laminates
http://espace.library.uq.edu.au/view/UQ:281989
20120916T00:07:48Z
Ng, C. T.; Veidt, M.; Rose, L. R. F.; Wang, C. H.

Analytical and numerical verification of a simplified rail corrugation model
http://espace.library.uq.edu.au/view/UQ:84224
20070814T13:34:01Z
Campey, T. J.; Meehan, P. A.

Analytical electron microscopy of proton exchange membrane fuel cells
http://espace.library.uq.edu.au/view/UQ:101819
Microtome sections of proton exchange membrane cells produce a wide range of information ranging from macroscopic distribution of components through specimens in which the detailed distribution of catalyst particles can be observed. Using modern data management practices it is possible to combine information at different scales and correlate processing and performance data. Analytical electron microscopy reveals the compositional variations across used cells at the electrolyte/electrode interface. In particular analytical techniques indicate that sulphur concentrations are likely to diminish at the interface Nafion/anode interface. © 2006 Elsevier B.V. All rights reserved.
20070823T20:26:49Z
Drennan, John; Webb, Rick; Nogita, Kaz; Knibbe, Ruth; Auchterlonie, Graeme; Tatenuma, K.; Hunter, Jane

Analytical maps of aerodynamic damping as a function of operating condition for a compressor profile
http://espace.library.uq.edu.au/view/UQ:104773
20070823T22:36:02Z
PetrieRepar, Paul J.; McGhee, Andrew; Jacobs, Peter A.; Gollan, Rowan

Analytical method of prediction of turbulent boundarylayer separation in hypersonic flows
http://espace.library.uq.edu.au/view/UQ:256265
An analytical method of prediction of turbulent boundarylayer separation in hypersonic flows is presented. The boundary layer is associated with a flat plate for simplicity and is recognized as a fully turbulent boundary layer with a sufficiently high Reynolds number. A separated boundary layer has recirculating flow. The moment of separation can be more easily visualized by looking at velocity profiles within the boundary layer as it is subjected to greater pressure gradients. The velocity gradient at the wall will be zero, and the momentum flux out of the control volume will be approaching zero at the point of incipient separation. The shear stress at the wall cannot be estimated using the seventh power law, since it is not valid in the laminar sublayer. A possible reason for the independence on Reynolds number could be the assumption that the distance over which separation occurs is short and the shear stress can therefore be neglected.
20111016T00:21:41Z
Dann, Andrew G.; Morgan, Richard G.

Analytical methods for better design and repair of mechanical welded structures
http://espace.library.uq.edu.au/view/UQ:101886
20070823T20:30:15Z
Nazari, A.; Guan, Z.; Daniel, W.J.T.; Gurgenci, H.

Analytical model for the design of volumetric solar flow receivers
http://espace.library.uq.edu.au/view/UQ:274448
20120522T09:39:09Z
Veeraragavan, Ananthanarayanan; Lenert, Andrej; Yilbas, Bekir; AlDini, Salem; Wang, Evelyn N.

Analytical prediction and experimental measurement for mode conversion and scattering of plate waves at nonsymmetric circular blind holes in isotropic plates
http://espace.library.uq.edu.au/view/UQ:174459
20090408T08:58:40Z
Cegla, F. B.; Rohde, A.; Veidt, M.

Analytical prediction of strains and forming forces in incremental forming
http://espace.library.uq.edu.au/view/UQ:355938
20150410T16:55:39Z
Daniel, William J. T.; Li, Yanle; Liu, Zhaobing; Meehan, Paul A.

Analytical solution for the flame eigenvalue problem accounting for the effects of conjugate heat transfer in a parallel plate reactor
http://espace.library.uq.edu.au/view/UQ:275206
20120604T11:31:45Z
Veeraragavan, Ananthanarayanan; Cadou, Christopher

Analytical solution of forced convection in a duct of rectangular crosssection saturated by a porous medium
http://espace.library.uq.edu.au/view/UQ:13255
A theoretical analysis is presented to investigate fully developed (both thermally and hydrodynamically) forced convection in a duct of rectangular crosssection filled with a hyperporous medium. The DarcyBrinkman model for flow through porous media was adopted in the present analysis. A Fourier series type solution is applied to obtain the exact velocity and temperature distribution within the duct. The case of uniform heat flux on the walls, i.e. the H boundary condition in the terminology of Kays and Crawford [1], is treated. Values of the Nusselt number and the friction factor as a function of the aspect ratio, the Darcy number, and the viscosity ratio are reported.
20070328T19:29:58Z
Hooman, Kamel; Merrikh, Ali A.

Analyzing the role of “smart” start points in coarse searchgreedy search
http://espace.library.uq.edu.au/view/UQ:221512
An inherent assumption in many search techniques is that information from existing solution(s) can help guide the search process to find better solutions. For example, memetic algorithms can use information from existing local optima to effectively explore a globally convex search space, and genetic algorithms assemble new solution candidates from existing solution components. At the extreme, the quality of a random solution may even be used to identify promising areas of the search space to explore. The best of several random solutions can be viewed as a "smart" start point for a greedy search technique, and the benefits of "smart" start points are demonstrated on several benchmark and realworld optimization problems. Although limitations exist, "smart" start points are most likely to be useful on continuous domain problems that have expensive solution evaluations. © SpringerVerlag Berlin Heidelberg 2007.
20101118T14:33:51Z
Chen, Stephen; Miura, Ken; Razzaqi, Sarah

An analysis of current Australian longwall ventilation methods
http://espace.library.uq.edu.au/view/UQ:96606
20070824T00:40:27Z
Mayes, T. I.; Gillies, A. D. S.

An Analysis Of Fatigue Crack Growth Of A Notched Aircraft Component Under CompressionDominated Spectrum Loading
http://espace.library.uq.edu.au/view/UQ:10093
In engineering structures, fatigue cracks often emanate from geometrical discontinuities such as holes and notches. Experimentally it has been observed that there exists a notchaffected zone, in which the crack growth exhibits a transitional behaviour. Depending on the loading level and the geometry of the notch, the crack growth rate may initially decrease with crack length to reach a minimum. It will then either grow at an accelerated rate, or stop growing. This report details ongoing work in modelling crack growth in the presence of notch plasticity. The local stressstrain distribution ahead of a notch root is determined based on an empirical distribution of the equivalent stress, and the evolution of the notch root stress and strain is calculated using Neuber's rule and an ArmstrongChaboche type nonlinear kinematic hardening model. The stress intensity factor is then calculated using a Green's function approach. A crack growth analysis program has been developed, implementing the above procedures.
20041220T00:00:00Z
Hu, W.; Walker, K. F.

An analysis of the effect of grain refinement on the hot tearing of aluminium alloys
http://espace.library.uq.edu.au/view/UQ:73658
20070815T04:45:55Z
Easton, M.; Wang, H.; Grandfield, J.; St John, D. H.; Sweet, E.

An analysis of the relationship between grain size, solute content, and the potency and number density of nucleant particles
http://espace.library.uq.edu.au/view/UQ:75200
To be able to determine the grain size obtained from the addition of a grain refining master alloy, the relationship between grain size (d), solute content (defined by the growth restriction factor Q), and the potency and number density of nucleant particles needs to be understood. A study was undertaken on aluminium alloys where additions of TiB2 and Ti were made to eight wrought aluminum alloys covering a range of alloying elements and compositions. It was found from analysis of the data that d = a/(3)root pct TiB2 + b/Q. From consideration of the experimental data and from further analysis of previously published data, it is shown that the coefficients a and b relate to characteristics of the nucleant particles added by a grain refiner. The term a is related to the maximum density of active TiB2 nucleant particles within the melt, while b is related to their potency. By using the analysis methodology presented in this article, the performance characteristics of different master alloys were defined and the effects of Zr and Si on the poisoning of grain refinement were illustrated.
20070815T05:42:20Z
Easton, M.; St John, D.

An analysis of the SAFEMine Global Positioning System Collision Avoidance System
http://espace.library.uq.edu.au/view/UQ:297147
In the mining industry, companies are always looking to add value wherever possible through reducing cost, improving production or better use of resources. This paper focuses on the latter. New Hope’s Acland Coal Mine recently installed the SAFEMine Global Positioning System Collision Avoidance System on its fl eet of Caterpillar 785C haul trucks to improve safety at the mine. This system provided a data recording function that was only being used for incident playback. The application of the SAFEMine system was analysed to fi nd a different and benefi cial role for it to be used in. It was found that the data collected could be used in the form of a time and motion study and a test case study was undertaken. The case study provided a number of results including: producing time standards for each segment of a haul cycle, fi nding what effects payloads have on average speeds and loading times, and fi nding the best method for spotting at the coal face and loader. Most importantly the case study showed that the SAFEMine system could perform an effective time and motion study. To review how effective the system was, it was compared to stopwatch studies and fl eet management systems. It was found that the SAFEMine GPS Collision Avoidance System could provide a cheaper, but somewhat less complete alternative to a fl eet management system and would provide a much better alternative, allround, to a stopwatch study.
20130412T12:56:30Z
Knights, B; Kizil, M.S

An analytical model for combustion of hydrogen in the boundary layer with an application to scramjets
http://espace.library.uq.edu.au/view/UQ:84218
20070814T13:33:50Z
Trenker, M.

An analytical model for deformation path design in multistage incremental sheet forming process
http://espace.library.uq.edu.au/view/UQ:324826
Incremental sheet forming (ISF) is a new promising technology due to its flexibility and lowcost tooling properties compared with conventional forming processes. However, a common technical problem encountered in ISF is nonuniform thickness variation of formed parts, particularly excessive thinning on severely sloped regions, which may lead to the part fracture and limit the process formability. Design of multistage deformation paths (intermediate shapes or preforms) before the final part is a desirable and practical way to control the material flow in order to obtain more uniform thickness distribution and avoid forming failure. Based on the shear deformation and the strain compensation idea, an analytical model for designing multistage deformation paths and predicting the thickness strain distribution is proposed. The feasibility of the proposed model is validated by the finite element analysis (FEA) and experimental tests in terms of the comparison of prediction, simulation and experimental results on the thickness strain distribution and the process formability.
20140305T11:56:11Z
Liu, Zhaobing; Li, Yanle; Daniel, Bill; Meehan, Paul

An analytical model for the indentation of rocks by blunt tools
http://espace.library.uq.edu.au/view/UQ:141525
A methodology based on the cavity expansion model is developed to analyze the indentation of rocks by a class of blunt indenters. The analysis covers the particular selfsimilar case of indentation by blunt wedges or cones. As an example, the main results for the indentation of rocks by a spherical tool are presented and the analytical solution is compared with experimental results obtained by indenting a sphere in Harcourt granite.
20080610T12:32:23Z
Alehossein, H.; Detournay, E.; Huang, H.

A nanohybrid of CdTe@CdS nanocrystals and titania nanosheets with pn nanojunctions for improved visible lightdriven hydrogen production
http://espace.library.uq.edu.au/view/UQ:368903
A nanohybrid photocatalyst composed of CdTe@CdS nanocrystals and singlelayered exfoliated titania nanosheets was synthesized through a welldefined restacking approach. The nanohybrid possessed an expanded layered structure, with ultrathin titania nanosheets randomly restacked upon each other and CdTe@CdS nanocrystals sandwiched between the nanosheets. The introduction of CdTe@CdS nanocrystals not only extended the light absorption of the photocatalyst to the visible range, but also formed p–n nanojunctions in the nanohybrid. The resultant materials containing same amount of CdTe@CdS nanocrystals exhibited over 43 times higher activity than pure CdTe@CdS nanocrystals for hydrogen production under visible light irradiation (λ > 420 nm) while titania nanosheets alone were not capable of producing any hydrogen under the same conditions. The superior photocatalytic efficiency of the nanohybrid can be attributed to the effective charge separation, which is achieved by the synergetic effect of proper energy bands alignment and p–n nanojunctions.
20150908T01:45:29Z
Xing, Zheng.; Zong, Xu.; Zhu,Yian.; Chen, ZhiGang.; Bai, Yang.; Wang, Lianzhou.

A nanoscratch method for measuring hardness of thin films
http://espace.library.uq.edu.au/view/UQ:263427
Thin solid films were extensively used in the making of solar cells, cutting tools, magnetic recording devices, etc. As a result, the accurate measurement of mechanical properties of the thin films, such as hardness and elastic modulus, was required. The thickness of thin films normally varies from tens of nanometers to several micrometers. It is thus challenging to measure their mechanical properties. In this study, a nanoscratch method was proposed for hardness measurement. A threedimensional finite element method (3D FEM) model was developed to validate the nanoscratch method and to understand the substrate effect during nanoscratch. Nanoindentation was also used for comparison. The nanoscratch method was demonstrated to be valuable for measuring hardness of thin solid films.
20111213T18:54:30Z
Liu, Sheng; Huang, Han; Gu, Yuantong

An approach to assessing ultrasonic attenuation in molten magnesium alloys
http://espace.library.uq.edu.au/view/UQ:181941
Few experimental data are available on ultrasonic attenuation in molten light alloys due to lack of means of characterization. An approach has been proposed and demonstrated to assessing ultrasonic attenuation in molten magnesium alloys based on the finding that the grain density in ultrasonicated magnesium alloy samples depends linearly on ultrasonic amplitude along the propagation direction. Hence, the attenuation of the ultrasonic amplitude with propagation distance can be effectively assessed according to the variations in the grain density with propagation distance. Metallographic analyses revealed that the dependence of grain density on propagation distance is best described exponentially with respect to different amplitudes. Consequently, the attenuation behavior of the ultrasonic amplitude with propagation distance can be described by the same exponential law. The characteristic ultrasonic attenuation coefficients in three benchmark molten magnesium alloys investigated were determined accordingly. The validation experiments confirmed the validity of the data produced. Ultrasonic attenuation shows dependence on alloy chemistry. ©2009 American Institute of Physics
20090903T09:00:22Z
Qian, Ma; Ramirez, A.

An approach to map geotechnical uncertainty in Longwall Coal Operations
http://espace.library.uq.edu.au/view/UQ:135234
20080414T15:37:49Z
Valenzuela, P.; Li, S.; Knights, P.

An approximate method for solving rarefied and transitional flows using TDEFM with isotropic mesh adaptation
http://espace.library.uq.edu.au/view/UQ:200634
DSMC [1] can become increasingly expensive when extended to the nearcontinuum regime. Because of the statistical nature of the results, long run times are required to build up samples of simulator particles large enough to reduce the statistical scatter to acceptable levels. Here we adapt a kinetic theory based flux method to produce a quick approximate solver for transition and nearcontinuum flows. The results have no statistical scatter. The CPU times are similar to those of traditional continuum (NavierStokes or Euler) solvers. The True Direction Equilibrium Flux Method (TDEFM) [2, 3] is a generalisation of Pullin's kinetic theory based EFM [4]. TDEFM can transfer fluxes of mass, momentum and energy in physically realistic directions from any source cell to any destination cell, even if the cells do not share an interface. TDEFM, as an Euler solver, has been shown to provide good results on a Cartesian grid for flows where standard continuum methods produce unphysical asymmetries apparently because the continuum fluxes are constrained (in one time step) to flow in the grid coordinate directions rather than the correct physical direction. [2, 3] The new method for rarefied flow does not try to produce the correct velocity distribution function, but does ensure that mass, momentum and energy are transported within the flow over the physically correct distances between “pseudocollisions.” To ensure this, (1) the time step is restricted so that mass, momentum and energy are exchanged between contiguous cells only in one time step, and (2) the cells sizes are adapted, as steady state is approached, to be approximately equal to the local mean free path. The results for Mach 5 flow over a flat plate for varying Knudsen numbers show an average difference (compared to DSMC) in the Xvelocity profile near the surface of the plate of less than 6 percent. TDEFM, employing adaptive mesh refinement, required less than 9 percent of the computational time required by DSMC for the same flow. Thus the approximate method could be useful for quick “firstestimate” solutions of otherwise time consuming design problems. ©2009 American Institute of Physics
20100325T11:42:54Z
Smith, M. R.; Cave, H. M.; Wu, J. S.; Macrossan, M. N.

An artificial neural network approach to cooling analysis of electronic components in enclosures filled with nanofluids
http://espace.library.uq.edu.au/view/UQ:235136
Computational fluid dynamics (CFD) and artificial neural network (ANN) are used to examine the cooling performance of two electronic components in an enclosure filled with a Cuwater nanofluid. The heat transfer within the enclosure is due to laminar natural convection between the heated electronic components mounted on the left and right vertical walls with a relatively lower temperature. The results of a CFD simulation are used to train and validate a series of ANN architectures, which are developed to quickly and accurately carry out this analysis. A comparison study between the results from the CFD simulation and the ANN analysis indicates that the ANN accurately predicts the cooling performance of electronic components within the given range of data. ©2011 American Society of Mechanical Engineers
20110312T16:24:31Z
Kargar, A.; Ghasemi, B.; Aminossadati, S. M.

An Asitedeficient perovskite offers high activity and stability for lowtemperature solidoxide fuel cells
http://espace.library.uq.edu.au/view/UQ:320209
Solid oxide fuel cells (SOFCs) directly convert fossil and/or renewable fuels into electricity and/or highquality heat in an environmentally friendly way. However, high operating temperatures result in high cost and material issues, which have limited the commercialization of SOFCs. To lower their operating temperatures, highly active and stable cathodes are required to maintain a reasonable power output. Here, we report a layerstructured Asite deficient perovskite Sr0.95Nb0.1Co0.9O 3δ (SNC0.95) prepared by solidstate reactions that shows not only high activity towards the oxygen reduction reaction (ORR) at operating temperatures below 600 °C, but also offers excellent structural stability and compatibility, and improved CO2 resistivity. An anodesupported fuel cell with SNC0.95 cathode delivers a peak power density as high as 1016mW cm2 with an electrodeareaspecific resistance of 0.052Ω cm2 at 500 °C. A site to be seen: The perovskite Sr 0.95Nb0.1Co0.9O3δ (SNC0.95) with Asite deficiencies shows high activity towards the oxygen reduction reaction (ORR) at low operating temperatures due to its large oxygen vacancy concentration and high electrical conductivity. Moreover, SNC0.95 shows excellent structural stability and chemical compatibilityâ€¥ The CO2 resistivity is also improved. These merits show that SNC0.95 is a promising cathode material for lowtemperature solid oxide fuel cells. Copyright
20131231T00:56:08Z
Zhu, Yinlong; Chen, ZhiGang; Zhou, Wei; Jiang, Shanshan; Zou, Jin; Shao, Zongping

Anatase TiO2 crystal facet growth: Mechanistic role of hydrofluoric acid and photoelectrocatalytic activity
http://espace.library.uq.edu.au/view/UQ:247079
20110904T01:23:53Z
Zhang, Haimin; Wang, Yun; Liu, Porun; Han, Yanhe; Yao, Xiangdong; Zou, Jin; Cheng, Huiming; Zhao, Huijun

Anatase TiO2 single crystals with a large percentage of reactive facets
http://espace.library.uq.edu.au/view/UQ:171039
20090320T12:02:03Z
Yang, Hua Gui; Sun, Cheng Hua; Qiao, Shi Zhang; Zou, Jin; Liu, Gang; Smith, Sean Campbell; Cheng, Hui Ming; Lu, Gao Qing

An atomistic simulation of solid state sintering using Monte Carlo methods
http://espace.library.uq.edu.au/view/UQ:62922
This paper presents results on the simulation of the solid state sintering of copper wires using Monte Carlo techniques based on elements of lattice theory and cellular automata. The initial structure is superimposed onto a triangular, twodimensional lattice, where each lattice site corresponds to either an atom or vacancy. The number of vacancies varies with the simulation temperature, while a cluster of vacancies is a pore. To simulate sintering, lattice sites are picked at random and reoriented in terms of an atomistic model governing mass transport. The probability that an atom has sufficient energy to jump to a vacant lattice site is related to the jump frequency, and hence the diffusion coefficient, while the probability that an atomic jump will be accepted is related to the change in energy of the system as a result of the jump, as determined by the change in the number of nearest neighbours. The jump frequency is also used to relate model time, measured in Monte Carlo Steps, to the actual sintering time. The model incorporates bulk, grain boundary and surface diffusion terms and includes vacancy annihilation on the grain boundaries. The predictions of the model were found to be consistent with experimental data, both in terms of the microstructural evolution and in terms of the sintering time. (C) 2002 Elsevier Science B.V. All rights reserved.
20070814T18:10:57Z
Sutton, RA; Schaffer, GB

Anatomy of a heating and assessment of critical selfheating parameters
http://espace.library.uq.edu.au/view/UQ:101860
Numerical modelling is a valuable tool for simulating the fundamental processes that take place during a heating. The models presented in this paper have enabled a quantitative assessment of the effects of initial pile temperature, pile size and mass and coal particle size on the development of a heating. All of these parameters have a certain criticality in the coal selfheating process.
20070823T20:28:57Z
Humphreys, D. R.

An attitude control strategy using four cold gas thrusters for the SCRAMSPACE 1 experiment
http://espace.library.uq.edu.au/view/UQ:293385
20130311T12:17:45Z
Creagh, Michael; Staden, Paul A.; Tirtey, Sandy

A Natural Feature Representation for Unstructured Environments
http://espace.library.uq.edu.au/view/UQ:174924
This paper addresses the longstanding problem of feature representation in the natural world for autonomous navigation systems. The proposed representation combines Isomap, which is a nonlinear manifold learning algorithm, with expectation maximization, which is a statistical learning scheme. The representation is computed offline and results in a compact, nonlinear, nonGaussian sensor likelihood model. This model can be easily integrated into estimation algorithms for navigation and tracking. The compactness of the model makes it especially attractive for deployment in decentralized sensor networks. Real sensory data from unstructured terrestrial and underwater environments are used to demonstrate the versatility of the computed likelihood model. The experimental results show that this approach can provide consistent models of natural environments to facilitate complex visual tracking and dataassociation problems.
20090409T11:56:07Z
Fabio Tozeto Ramos; Kumar, Suresh; Upcroft, Ben; DurrantWhyte, Hugh

An automated digging control for a wheel loader
http://espace.library.uq.edu.au/view/UQ:114831
An Automated Digging Control System (ADCS) for a wheel loader is developed that utilizes a behaviorbased control structure combined with fuzzy logic. This controller exhibits the realtime reactive responses necessary for executing digging tasks in an uncertain, unstructured and dynamic excavation environment. This paper presents field test results of a prototype ADCS that was developed and implemented on a Caterpillar 980G wheel loader. Test results show that the performance of the automated system is comparable to that of an expert human operator in a wide range of excavation situations.
20071017T11:20:37Z
Lever, Paul J. A.

An automated robotic system for jet engine overhaul. system design and development for honeycomb repair
http://espace.library.uq.edu.au/view/UQ:122308
Jet engines run tender very severe conditions and require periodic overhauling. Owing to the high operating temperature and pressure, most service components become significantly distorted from their original shapes. Therefore, the overhaul of a jet engine has been seen as a difficult subject for process automation. This paper reports R&D activities in Gintic/Singapore to achieve the first automated system worldwide for honeycomb repair.
20080125T15:35:42Z
Zhou, L; Huang, H

An econometrics view of worldwide fossil fuel consumption and the role of US
http://espace.library.uq.edu.au/view/UQ:135267
Crude oil, coal and gas, known as fossil fuels, play a crucial role in the global economy. This paper proposes new econometrics modelling to demonstrate the trend of fossil fuels consumption. The main variables affecting consumption trends are: world reserves, the price of fossil fuels, US production and US net imports. All variables have been analysed individually for more than half a century. The research found that while the consumption of fossil fuels worldwide has increased trends in the US production and net imports have been dependent on the type of fossil fuels. Most of the US coal and gas production has been for domestic use, which is why it does not have a strong influence on worldwide fossil fuel prices. Moreover, the reserves of fossil fuels have not shown any diminution during the last couple of decades and predictions that they were about to run out are not substantiated. The nominal and real price of fossil fuels was found to change depending on the type. Finally, estimates of three econometric models for the consumption of fossil fuels from 1949 to 2006 are presented which identify the effects of significant variables.
20080415T10:30:33Z
Shafiee, Shahriar; Topal, Erkan

An EEGBased technique for operator fatigue determination
http://espace.library.uq.edu.au/view/UQ:101877
20070823T20:29:41Z
Bongers, D. R.

An efficient framework for fluid–structure interaction using the lattice Boltzmann method and immersed moving boundaries
http://espace.library.uq.edu.au/view/UQ:303140
This paper presents a serial computational framework that hydrodynamically couples the lattice Boltzmann method (LBM) and the discrete element method (DEM) for the solution of particle suspension problems in two and three dimensions. The singlerelaxationtime Bhatnagar–Gross–Krook (LBGK) form of the lattice Boltzmann equation is employed with an immersed moving boundary method for the fluid–structure interaction. Similar algorithms have been previously reported in the literature, however, this work deliberately utilizes solution options that minimize the computational overheads of the framework to facilitate simulations of multibody structural fields in large fluid domains. In particular, mixed boundary conditions are employed which combine the simple bounceback technique with the immersed moving boundary method, and the relatively inexpensive D3Q15 lattice is employed for 3D solutions. The fundamentals of the LBM are briefly discussed followed by a review of the coupling techniques available for FSI using the LBM. Options for mapping solid obstacles to the LBM grid are presented and an algorithm for automatic, dynamic subcycling of the two explicit solution schemes is outlined. The LBM–DEM framework is then validated and benchmarked against previously published LBM results, with comments made where appropriate on the comparative accuracy and convergence characteristics. Finally, a multiparticle suspension simulation is presented to qualitatively assess the performance of the framework when a large number of dynamic contacts exist.
20130618T12:10:53Z
Owen, D. R. J.; Leonardi, C. R.; Feng, Y. T.

An efficient measurement strategy for plate wave diffraction tomography
http://espace.library.uq.edu.au/view/UQ:138204
20080512T09:56:40Z
Rohde, A.; Veidt, M.

An efficient stochastic based model for simulating microelectrode recordings of the deep brain
http://espace.library.uq.edu.au/view/UQ:269308
We have developed a computationally efficient stochastic model for simulating microelectrode recordings, including electronic noise and neuronal noise from the local field of 3000 neurons. From this we have shown that for a neuron network model spiking with a stationary Weibull distribution the power spectrum can change from exhibiting periodic behaviour to nonstationary behaviour as the distribution shape is changed. It is shown that the windowed power spectrum of the model follows an analytical result prediction in the range of 1005000 Hz. The analysis of the simulation is compared to the analysis of real patient interoperative subthalamic nucleus microelectrode recordings. The model runs approximately 200 times faster compared to existing models that can reproduce power spectral behaviour. The results indicate that a spectrogram of the real patient recordings can exhibit nonstationary behaviour that can be recreated using this efficient model in real time.
20120308T08:51:04Z
Weegink, K. J.; Varghese, J. J.; Bellette, P. A.; Coyne, T.; Silburn, P. A.; Meehan, P. A.

Anelastic behavior in GaAs semiconductor nanowires
http://espace.library.uq.edu.au/view/UQ:306963
20130818T00:19:19Z
Chen, Bin; Gao, Qiang; Wang, Yanbo; Liao, Xiaozhou; Mai, YiuWing; Tan, Hark Hoe; Zou, Jin; Ringer, Simon P.; Jagadish, Chennupati

Anelastic Phenomena in MgAl Alloys
http://espace.library.uq.edu.au/view/UQ:286627
20121202T00:52:25Z
Nagarajan, D.; Caceres, C. H.; Griffiths, J. R.

An electron diffraction and microscopy investigation of quasiperiodic TaAl superlattices
http://espace.library.uq.edu.au/view/UQ:221848
Quasiperiodic (Fibonacci sequence) TaAl multilayer films were fabricated by magnetron sputtering, and studied by electron and Xray diffraction. Eleven orders of electron diffraction satellite spots were obtained. Their positions and intensities were in good agreement with the data from Xray diffraction, and both were in excellent agreement with the theoretical positions predicted by the projection method, k = 2πD1(n + mτ). Transmission electron microscope studies of the thin film crosssections showed the wellformed layered structures of Fibonacci sequence TaAl superlattices. The films have textures with Ta [110] and Al [111] in the growth direction, and coherent stacking in the quasiperiodic multilayers.
20101121T22:23:00Z
Jiang, S. S.; Zou, J.; Cockayne, D. J. H.; Sikorski, A.; Hu, A; Peng, R. W.

An embeddable data acquisition system: interim report
http://espace.library.uq.edu.au/view/UQ:350484
20150203T09:14:38Z
Jacobs, Peter; Dimitrijevic, Igor

An emerging shale gas play in the Northern Territory
http://espace.library.uq.edu.au/view/UQ:313279
20131031T12:29:43Z
Johnson, R. L.; Dawney, R.; Warner, D.

An empirical analysis of trends in mechanical properties of T6 heat treated AlSiMg casting alloys
http://espace.library.uq.edu.au/view/UQ:141238
The AlSiMg family of alloys is typically used in the T6 heat treated condition for high integrity casting applications, There are several variables that can influence the tensile properties of these alloys besides the actual ageing treatment employed. These are alloy composition, particularly Mg and Fe content, and secondary dendrite arm spacing or SDAS, Tensile data from samples covering a wide range of Mg content (0.30.7%), Fe content (0.050.20%), SDAS (2060 mu m) and two ageing treatments (underand peakaged), have been collected and analysed empirically. Concise relationships have been determined for yield strength, ultimate tensile strength and elongation to fracture in terms of one or more of the experimental variables. The observed trends are explained in terms of basic metallurgical principles and the predictive use of the empiricallydetermined equations is qualified. A comparison of experimentally determined properties and those calculated using the derived relationships highlights some important and clear trends.
20080610T12:13:07Z
Taylor, J. A.; St John, D. H.; Barresi, J.; Couper, M. J.