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:284408 During the commissioning phase of Prominent Hill, periods of reduced recovery were experienced with higher-grade ore blends. This was unexpected and as part of the process to identify the cause, surveys were conducted in May 2009, with two different ore blends (copper grades: 1.94per cent Cu (blend 1) and 2.49 per cent Cu (blend 2)). Metallurgical performance was assessed in terms of rougher recovery and grade with consideration of both pulp and froth effects. In addition, hydrodynamic measurements (gas hold up, bubble size, superficial gas velocity) as well as measurements of bubble load and top-of-froth grade were taken during the surveys and full mineralogical assessment of selected streams completed to characterise the nature of the differences. The metallurgical results showed that the lower performance was obtained with blend 2 which contained the higher amount of chalcocite and was higher-grade. Analysis of the survey data showed that for both ore blends more than half of the copper loss occurred in the +38 Jlm size fractions. Almost 30 per cent of the copper in the +38 Jlm fractions that reported to the rougher tails during processing of blend 2 was liberated compared to less than five per cent for blend 1. Additionally almost 60 per cent of the copper in the +38 J.Lm fraction of blend 2 was chalcocite compared with approximately 20 per cent in blend 1. This paper discusses the sensitivity of the chalcocite-to-surface chemistry effects causing marked reductions in recovery either through reduced pulp recovery or froth phase (detachment) effects. The reagent suite and operating conditions were subsequently changed and the recoveries increased substantially and the sensitivity to ore changes eliminated. It should be noted that subsequent optimisation work, which focused on recovery improvement, has led to copper recoveries of over 90 per cent being achieved. 2012-11-05T15:34:33Z Bradshaw, D. J. og Wightman, E. M. og Evans, C. L. og Triffett, B. http://espace.library.uq.edu.au/view/UQ:132508 2008-03-17T00:00:00Z Schwarz, S. E. E. og Alexander, D. og Coleman, R. G. http://espace.library.uq.edu.au/view/UQ:197925 For the application of ultraviolet light emitting diodes, self-organized p–n junctions were formed at the boundaries of facets in cubic boron nitride. The optical and electrical characteristics of these junctions were studied using cathodoluminescence (CL) and electron-beam-induced current (EBIC) in a scanning electron microscope. The p and n regions were clearly distinguished by the variation of CL spectra and monochromatic CL images. A broad band with a peak at 4.0 eV (310 nm) was observed in p-region, but not in n-region. Monochromatic CL image at 4.0 eV showed that the Be impurity distribution in p-region was not uniform. Variation of EBIC profiles indicated the inhomogeneity of diffusion length along p-n junction. The inhomogeneous electroluminescence along the p–n junction under the reverse current condition was clarified by the inhomogeneities revealed by EBIC and CL characterizations. 2010-03-05T00:00:00Z Yuan, X. L. og Niitsuma, J. og Sekiguchi, T. og Takase, M. og Taniguchi, T. http://espace.library.uq.edu.au/view/UQ:272593 2012-04-12T00:00:00Z Resabal, Vannie og Ohtsuka, Toshiaki http://espace.library.uq.edu.au/view/UQ:272595 2012-04-12T00:00:00Z Resabal, Vannie og Ohtsuka, T. og Tanaka, S. http://espace.library.uq.edu.au/view/UQ:161630 2009-01-23T12:07:45Z Mwansa, S. og Condori, P. og Powell, M. S. http://espace.library.uq.edu.au/view/UQ:256424 Considering the difference of drag coefficients of particles moving through areas of varying Reynolds numbers, an extra-mass force acting on particles in the active pulsing air field was introduced. Models of the dynamic motion in which the particles both in Stokes and Newtonian fluids, follow as they move in the pulsing air flow were developed. And a computer numerical simulation was carried out that showed the traces of particles with different densities and diameters, but similar aerodynamic characteristics, as they moved through the turbulent flow, to modify and define the parameters of the models. The motion law of tracing spheres was studied in a laboratory active pulsing air classifier with a high-speed video camera and motion particle analyzer. The mechanism of active pulsing air classification was studied. The results show that simulation can predict the observed results with artificial tracing spheres separated by the laboratory equipment. The comparison of the simulation and laboratory experiment results show that the relative errors of velocities are less than 8% for lighter particles and less than 5% for heavier particles. 2011-10-17T15:39:38Z He, Yaqun og Zhao, Yuemin og Duan, Chenlong og Wang, Haifeng og Zuo, Weiran http://espace.library.uq.edu.au/view/UQ:268614 By applying co-integration analysis, the Granger causality test and an error correction model, the dependency between the energy consumption and the gross domestic product of China was examined. In a further step an analysis was done to establish a correlation between the economic growth of different industries and China's energy consumption. An evidence-based study showed that a co-integration relationship exists between the gross energy consumption and the GDP of China and that the two variables possess bi-directional causality. The energy consumption for the secondary industry has a markedly stimulative effect to the economic growth. This paper also uses an error correction model (ECM) to explain the short-term behavior of energy demands. 2012-02-28T00:00:00Z He, Ya-qun og Lao, Guo-hong og Osuch, Chris E. og Zuo, Weiran og Wen, Ba-feng http://espace.library.uq.edu.au/view/UQ:272591 2012-04-12T00:00:00Z Resabal, Vannie og Jarantilla, A. og Kaibing, A. N. J. http://espace.library.uq.edu.au/view/UQ:193430 2010-01-21T10:19:32Z Gunatilleke, C. V. S. og Gunatilleke, I. A. U. N. og Ethugala, A. U. K. og Weerasekara, N. S. og Esufali, Shameema og Ashton, Peter S. og Ashton, Mark S. og Wijesundara, S. A. http://espace.library.uq.edu.au/view/UQ:261975 2011-11-22T14:00:39Z Jamil, Noorina Hidayu og Palaniandy, Samayamutthirian http://espace.library.uq.edu.au/view/UQ:224071 With increased emphasis on reducing costs and carbon emissions in mineral processing, it is becoming essential to employ the most efficient comminution devices and to use them to maximum effect. High pressure grinding rolls (HPGR) are considered highly efficient compared with other devices, however their relative efficiency in multi-HPGR circuits is less well understood. A series of comminution tests was carried out to evaluate three multi-pass HPGR circuits and a jaw crusher-ball mill circuit. Combinations of HPGR units (1.0 m and 0.25 m diameter), jaw crushers and Bond ball mills were used to grind a 32 mm top size porphyry copper feed (BBWI = 12.1) to a product P80 size of about 150 μm. Up to three passes of HPGR were used in each circuit, with energy measurement and size analysis at each point in the comminution process. The energy efficiencies of individual comminution stages and of the overall circuits were quantified and evaluated using three different approaches. The operating work index method for comparing comminution energy efficiency underestimated HPGR performance due to the large amount of fines generated. The -75 μm efficiency factor and F50/P50 reduction ratio interpolation methods both give a fairer measure because they better take into account the amount of fines generated by HPGR. The results show that the relative comminution efficiencies of the three multi-pass HPGR circuits tested differ by as much as 22%, providing insights as how to best employ HPGR in a comminution circuit. The most energy efficient of the circuits tested was a three-pass HPGR circuit with a 1.0 m diameter roll on the first pass in closed circuit with an 8 mm screen followed by a second and third pass in a 0.25 m roll. 2010-12-09T00:00:00Z Hilden, Marko og Suthers, S. http://espace.library.uq.edu.au/view/UQ:133020 2008-03-27T00:00:00Z Brennan, M. S. og Holtham, P. N. og Khanal, M. og Morrison, R. D. http://espace.library.uq.edu.au/view/UQ:95547 2007-08-23T00:00:00Z Morrison, R. D. og Cleary, P.W. og Valery, W. http://espace.library.uq.edu.au/view/UQ:282988 2012-10-08T13:10:07Z Bbosa, L. og Govender, I. og Mainza, A. og Powell, M. og Plint, N. http://espace.library.uq.edu.au/view/UQ:255645 2011-10-13T00:00:00Z Shi, Fengnian og Kojovic, Toni http://espace.library.uq.edu.au/view/UQ:261957 2011-11-22T11:32:16Z Idrus, Suhaida S. og Ismail, H. og Palaniandy, Samayamutthirian http://espace.library.uq.edu.au/view/UQ:64794 Predictions of flow patterns in a 600-mm scale model SAG mill made using four classes of discrete element method (DEM) models are compared to experimental photographs. The accuracy of the various models is assessed using quantitative data on shoulder, toe and vortex center positions taken from ensembles of both experimental and simulation results. These detailed comparisons reveal the strengths and weaknesses of the various models for simulating mills and allow the effect of different modelling assumptions to be quantitatively evaluated. In particular, very close agreement is demonstrated between the full 3D model (including the end wall effects) and the experiments. It is also demonstrated that the traditional two-dimensional circular particle DEM model under-predicts the shoulder, toe and vortex center positions and the power draw by around 10 degrees. The effect of particle shape and the dimensionality of the model are also assessed, with particle shape predominantly affecting the shoulder position while the dimensionality of the model affects mainly the toe position. Crown Copyright (C) 2003 Published by Elsevier Science B.V. All rights reserved. 2007-08-14T00:00:00Z Cleary, Paul W. og Morrisson, Rob og Morrell, Steve http://espace.library.uq.edu.au/view/UQ:187997 Stirred mills are primarily used for fine and ultra-fine grinding. They dominate these grinding applications because greater stress intensity can be delivered in stirred mills and they can achieve better energy efficiency than ball mills in fine and ultra-fine grinding. Investigations were conducted on whether the greater performance of stirred mills over ball mills in fine grinding can be extended to coarse grinding applications. Four different laboratory ball mills and stirred mills have been tested to grind seven ore samples with feed sizes ranging from 3.35 mm to 150 lm. A case study on full scale operations of a 2.6 MW IsaMill replacing the existing 4 MW regrind ball mill at Kumtor Gold mine in Kyrgyzstan is also included. This paper summarizes the major findings from these investigations. 2009-11-26T13:48:32Z Shi, Fengnian og Morrison, Rob og Cervellin, Andrew og Burns, Fraser og Musa, Fiesal http://espace.library.uq.edu.au/view/UQ:79028 This paper presents and interprets results of experimental measurements of the spatial gas hold-up distribution in a 3 (3) glass rectangular flotation cell at the JKMRC using two different techniques. The gas hold-up device with the capturing technique was developed at the JKMRC and has been used widely in the P9 project(1) while the one with conductivity technique was developed at the CSIRO Thermal and Fluids Engineering laboratory at Highett, Victoria, Australia. Measurements were conducted at more than 64 locations in the cell to determine the local gas hold-up distribution in the cell. Since the measurements using the two techniques were conducted at the same locations, the results may be compared with each other. The results indicate that the gas hold-up varies widely inside the flotation cell. The gas hold-up distributions measured by the two techniques are relatively similar except in some locations which can be reasonably explained. (c) 2006 Elsevier Ltd. All rights reserved. 2007-08-15T00:00:00Z Sanwani, E. og Zhu, Y. og Franzidis, J. P. og Manlapig, E. V. og Wu, J. http://espace.library.uq.edu.au/view/UQ:69522 Cylpebs are slightly tapered cylindrical grinding media with a ratio of length to diameter of unity. The manufactures have made conflicting claims regarding the milling performance of Cylpebs in comparison with balls. One major point of interest is which one grinds finer at the same operating conditions. The difficulty in comparison is due to the shape difference. The two grinding media have different surface area, bulk density and contact mechanisms in grinding action. Comparative tests were conducted using the two types of grinding media in a laboratory Bond ball mill at various conditions of equality such as media mass, size distribution, surface area and input specific energy. The laboratory results indicate that at the same specific energy input level the Cylpebs produce a product with slightly less oversize due to their greater surface area, but essentially the same sizing at the fine end as that produced with the balls. The reason may be that the advantage of greater surface area is balanced by the line contact and area contact grinding actions with the Cylpebs. A new ball mill scale-up procedure [Man, Y.T., 2001. Model-based procedure for scale-up of wet, overflow ball mills, Part 1: outline of the methodology. Minerals Engineering 14 (10), 1237-1246] was employed to predict grinding performance of an industrial mill from the laboratory test results. The predicted full scale operation was compared with the plant survey data. Some problems in the original scale-up procedures were identified. The scale-up procedure was therefore modified to allow the predicted ball mill performance to match the observed one. The calibrated scale-up procedure was used to predict the Cylpebs performance in the full scale industrial mill using the laboratory tests results. (C) 2004 Elsevier Ltd. All rights reserved. 2007-08-15T00:00:00Z Shi, F. http://espace.library.uq.edu.au/view/UQ:256427 The result of the cross-check and empirical study shows that while interpolating coal nature data of a coalfield, the method of geological statistics is superior to ordinary means, including the methods of inverse distance, multinomial interpolation, and radial-base function. Additionally, with using the general and universal Kriging methods, the most accurate results were obtained by applying the Kriging spherical models. 2011-10-17T00:00:00Z He, Yaqun og Zuo, Weiran og Zhang, Shumin og Lao, Guohong og Duan, Chenlong http://espace.library.uq.edu.au/view/UQ:245589 Materials processing using microwave technology have numerous advantages compared to traditional materials processing techniques; however, conventional microwave processing technology suffers from variable product quality due to uneven processing or heating. The variable frequency microwave (VFM) technique is an emerging technology that overcomes the inherent difficulties of uneven heating experienced in conventional microwave facilities and was developed for the purpose of processing many of today's advanced materials including polymers, composites and fibre-reinforced materials and is a rapid and controlled approach to uniform heating. By sweeping through a bandwidth of frequencies, the VFM method creates multiple hot spots within the processing cavity that lead to time-averaged uniform heating. The current work focuses on the sweep-rate regime used in VFMs and the effect of varying this parameter. A “recipe” for a non-linear sweep-rate regime is introduced and compared with the current linear sweep regime and conventional fixed-frequency processing in terms of heating uniformity. Theoretical modelling of the linear and non-linear sweep regimes are presented and are experimentally verified by heat-mapping of a multimode cavity with the aid of thermally sensitive material to quantify improvements in the uniformity of heating. 2011-08-15T14:50:31Z Antonio, C. og Deam, R. T. http://espace.library.uq.edu.au/view/UQ:193039 Although oxidation/passivation of iron in basic solution has been extensively investigated, there is very little information on iron corrosion in weak acidic solutions. In this work, iron surface composition and structure, produced in aerobic aqueous solutions ranging from pH 2 to 5, were determined in detail by the use of infrared external reflection spectroscopy, X-ray photoelectron spectroscopy and scanning electron microscopy. The most striking observation is that at pH 2 and 3 almost all oxidized iron is dissolved in solution, whereas at pH 4 and 5 the product of iron oxidation is deposited on the iron surface in the form of lepidocrocite, γ-FeOOH. Detailed iron surface and solution analyses allow the proposition of the following overall oxidation reactions (equations missing) At pH 2 and 3, only a very thin surface layer consisting of FeO andAt pH 2 and 3, only a very thin surface layer consisting of FeO and Fe(OH)2 with polymeric structure is observed on the iron surface. The amounts of these surface species remain almost constant (2–5 nm) from the first minutes to a few hours of reaction, if pH is kept constant. Nevertheless, with time the akaganeite-like, β-FeOOH structure is also detected. At pH 4 and 5, the amount of lepidocrocite deposited on the iron surface increases with reaction time. Detailed quantitative evaluation of the lepidocrocite produced at pH 5 and its surface distribution on iron was performed based on the comparison of infrared spectroscopic data with spectral simulation results of assumed surface structures. At pH 4 and 5 and a temperature of 40–50 °C, in addition to a very large amount of lepidocrocite other oxy-hydroxide surface species such as goethite (α-FeOOH) and feroxyhite (δ-FeOOH), were identified. Addition of Cl− ions to solution at 10−3 M concentration at pH 5 increases the oxidation rate of iron by about 50%, and lepidocrocite remains the only oxidation product. Similarly, an addition of Fe2+ ions to solution at pH 5 very strongly enhances lepidocrocite formation as well as its conductivity. The latter finding is important for the possible application of metallic iron as a catalyst in redox reactions, for example, for decomposition of difficult-to-biodegrade water pollutants. 2010-01-18T14:55:28Z Montes Atenas, Gonzalo og Mielczarski, Ela og Mielczarski, Jerzy A. http://espace.library.uq.edu.au/view/UQ:282377 2012-09-24T13:23:53Z Bonfils, Benjamin og Julcour-Lebigue, Carine og Guyot, Francois og Bodenan, Francoise og Chiquet, Pierre og Bourgeois, Florent http://espace.library.uq.edu.au/view/UQ:183070 Compression and impact loading experiments have been performed at high velocities to investigate the comminution behaviour of high strength spherical composite particles. Concrete spheres of B35 (compressive strength 35 MPa) strength category have been chosen to represent the composite particles. Breakage mechanism in compression and impact is found to be similar. Crack initiated from the periphery of the contact deformation. Diameter of the contact area depends upon input energy (impact velocity in impacts and loading rate in compressions). Propagation of cracks and formation of meridian and secondary cracks depend upon the input energy. Two cones were observed in compression experiments. It was found that secondary cracks were formed only after forming meridian cracks. Crack initiation and propagation mechanisms under low and high velocity compression loadings were found to be similar. 2009-09-03T00:00:00Z Khanal, Manoj og Schubert, Wolfgang og Tomas, Jürgen http://espace.library.uq.edu.au/view/UQ:96959 2007-08-24T00:00:00Z Brennan, M. S. og Holtham, P. N. og Lyman, G. J. og Rong, R. X. http://espace.library.uq.edu.au/view/UQ:95514 2007-08-23T00:00:00Z Onederra, I. A. og Riihioja, K. J. og Paganini, G. og Roldan, M. http://espace.library.uq.edu.au/view/UQ:95515 2007-08-23T00:00:00Z Onederra, I. A. og Riihioja, K. J. og Chitombo, G. P. http://espace.library.uq.edu.au/view/UQ:103502 2007-08-23T00:00:00Z Runge, K. C. og Harris, C og Franzidis, J. og Manlapig, E. http://espace.library.uq.edu.au/view/UQ:161606 Accurate 3D experimental particle trajectory data, acquired from a laboratory tumbling mill using bi-planar X-ray filming, are used to validate the discrete element method (DEM). Novel numerical characterisation techniques are presented that provide a basis for comparing the experimental and simulated charge behaviour. These techniques are based on fundamental conservation principles, and provide robust, new interpretations of charge behaviour that are free of operator bias. Two- and three-dimensional DEM simulations of the experimental tumbling mill are performed, and the relative merits of each discussed. The results indicate that in its current form DEM can simulate some of the salient features of the tumbling mill charge, however, comparison with the experiment indicate that the technique requires refinement to adequately simulate all aspects of the system 2009-01-23T00:00:00Z McBride, Andrew og Govender, Indresan og Powell, Malcolm og Cloete, Trevor http://espace.library.uq.edu.au/view/UQ:100093 In this paper, a new approach to control Hammerstein processes based on the Passivity Theorem was proposed. A feedforward dynamic passification technique, together with a nonlinear compensator that counteracts the e 2007-08-23T00:00:00Z Chan, K.H. og Bao, J. og Whiten, W. J. http://espace.library.uq.edu.au/view/UQ:95516 2007-08-23T00:00:00Z Pax, R. A. og Gelling, D. http://espace.library.uq.edu.au/view/UQ:268244 2012-02-24T00:00:00Z Maleki-Moghaddam, M. og Yahyaei, M. og Banisi, S. http://espace.library.uq.edu.au/view/UQ:259576 2011-10-25T15:12:20Z Maleji-Moghaddam, M. og Yahyaei, M. og Banisi, S. http://espace.library.uq.edu.au/view/UQ:149913 2008-06-06T00:00:00Z Morrison, R. D. http://espace.library.uq.edu.au/view/UQ:252748 2011-09-21T00:00:00Z McLellan, Benjamin C. og Williams, Ross P. og Lay, Janine og van Riessen, Arie og Corder, Glen D. http://espace.library.uq.edu.au/view/UQ:97029 2007-08-24T00:00:00Z Holtham, P. N. og Rong, R. X. og Subramanian, V. og Sheridan, G. A. og Cameron, P. M. og Gordon, H. http://espace.library.uq.edu.au/view/UQ:284550 2012-11-08T11:22:22Z Schwarz, S. og Alexander, D. http://espace.library.uq.edu.au/view/UQ:261938 2011-11-22T00:00:00Z Palaniandy, Samayamutthirian og Azizli, Khairun Azizi Mohd og Hong, Ee Xun og Hashim, Syed Fuad Saiyid og Hussin, Hashim http://espace.library.uq.edu.au/view/UQ:193219 2010-01-19T00:00:00Z Morrison, Robert http://espace.library.uq.edu.au/view/UQ:193125 2010-01-19T00:00:00Z Morrison, Robert http://espace.library.uq.edu.au/view/UQ:261924 2011-11-21T00:00:00Z McFarlane, A. og Kuhar, L. og Turner, N. og Botsis, N. M. og Ravi, S. http://espace.library.uq.edu.au/view/UQ:163090 The need to provide engineering solutions to full scale blasting problems has driven the development of several empirically based fragmentation models. Arguably, the most popular and successful models have been those applicable to surface blasting such as the Kuz-Ram model; and more recently the KCO model applying the Swebrec function. These models are based on what is generally described as the fragmentation associated with single hole firing conditions, that is, they do not consider the potential interaction of detonating blastholes on the breakage and fragmentation process. The application of precise and short delay timing using electronic detonators has demonstrated the need to incorporate modelling parameters that can adequately show the impact of timing on fragmentation. This paper describes an approach based on the hypothesis that a correction factor can be applied to the uniformity of fragmentation, the expected mean size of fragments and the proportion of fines generated during the blasting process. The correction factor is a function of the ratio between the interhole delay time dt and the minimum response time Tmin, which is defined as the time that elapses between explosive detonation and rock mass movement and is a function of explosive type, rock properties and blast design parameters. The use of this correction factor to predict relative changes in fragmentation from changes in interhole delay timing is demonstrated using a newly proposed two component Swebrec function. Preliminary data analysis demonstrates the practicality of the method. As with any empirical methodology, site specific calibration and further testing is recommended. 2009-02-05T12:06:48Z Onederra, I. http://espace.library.uq.edu.au/view/UQ:240656 2011-05-05T00:00:00Z Powell, Malcolm og Nirmal Weerasekara og Cole, S. og LaRoche, R.D. og Favier, J. http://espace.library.uq.edu.au/view/UQ:161859 2009-01-27T00:00:00Z Cleary, P. W. og Sinnott, M. D. og Morrison, R. D. http://espace.library.uq.edu.au/view/UQ:187983 2009-11-26T12:54:49Z Khanal, Manoj og Morrison, Rob http://espace.library.uq.edu.au/view/UQ:95530 2007-08-23T00:00:00Z Cleary, P. W. og Morrison, R. D. og Morrell, S. http://espace.library.uq.edu.au/view/UQ:166965 2009-03-10T00:00:00Z Holtham, P.N. og Brennan, M.S. og Mangadoddy, N. http://espace.library.uq.edu.au/view/UQ:82217 2007-08-15T00:00:00Z Holtham, P. N.