1,480 research outputs found
S.R. Lewis letter to Z. Eastman, March 5, 1874
No full textBrief letter from S.R. Lewis to Z. Eastman, marking the announcement of an abolitionists' reunion to be held in Chicago in June of 1875. Lewis requests that Eastman, given his close acquaintance with Benjamin Lundy, prepare a public statement of remembrance on Lundy and his contributions to the anti-slavery movement. Benjamin Lundy (1789-1839) was a prominent Quaker abolitionist best known for his development of abolitionist periodicals. His Genius of Universal Emancipation was first published in 1821 from his home in Mt. Pleasant, Ohio, and enjoyed a wide circulation across the antebellum United States. In the 1820s, the young William Lloyd Garrison came to work for The Genius. Benjamin Lundy traveled widely seeking subscriptions to The Genius, giving talks about the anti-slavery movement, and observing and documenting the conditions of enslaved people across the Americas. He was also involved in the establishment of freed slave colonies in Mexico
Modelling and optimization of a permanent-magnet machine in a flywheel
No full textThis thesis describes the derivation of an analytical model for the design and optimization of a permanent-magnet machine for use in an energy storage flywheel. A prototype of this flywheel is to be used as the peak-power unit in a hybrid electric city bus. The thesis starts by showing the feasibility of using a flywheel energy storage system for this application, as opposed to other energy storage technologies. It then continues by describing a prototype flywheel system and the required electrical machine: a radial-flux external-rotor permanent-magnet synchronous machine without slots in the stator iron and with a shielding cylinder. An analytical model for the machine is derived, based on 2D electromagnetic field calculations, including the reaction field of the eddy currents in the shielding cylinder. Torque and losses are calculated by means of the Theorem of Poynting and the Lorentz force. Such a machine was built and the analytical model has been validated by experimental measurements. Lastly, the thesis suggests and implements a machine optimization algorithm.Information Technology and System
Influence of particle size and contact angle on the flotation of chalcopyrite in a laboratory batch flotation cell
No full textAbstract not availableS. Muganda, M. Zanin, S.R. Gran
Design metrics for evaluating the propulsive efficiency of future ships
No full textThere is an increasing need for the ship design process to take account of environmental issues such as the emission of greenhouse gases and the likely extension of a carbon dioxide charging mechanism to international shipping. These issues, together with the need for economic viability, provide further incentives to improve the efficiency of propulsion of ships. The main components of powering are firstly reviewed. Individual components and other power saving devices are identified which should contribute to improvements in the overall efficiency of propulsion. Suitable design metrics and procedures, taking into account economic and environmental factors, are recommended for the design of future ships
Description of S.R. Krom's system and machinery for dry crushing and concentrating ores.
No full textCover title.Mode of access: Internet.MAIN; TN500.K7 1876: Introduction signed by author, S.R. Krom
Regrinding sulphide minerals - Breakage mechanisms in milling and their influence on surface properties and flotation behaviour
No full textChanges in surface properties with grinding and regrinding play a key role in mineral flotation performance. Different particle breakage mechanisms in grinding mills may change the mineral surface properties in different ways, possibly leading to different mineral floatabilities depending upon the predominant breakage mechanism. The Magotteaux Mill® and IsaMill were selected as representations of a tumbling and a stirred mill, respectively. The latter has a greater contribution to particle size reduction from the abrasion mechanism than the former which also has contributions from impact breakage.X. Ye, S. Gredelj, W. Skinner, S.R. Gran
The surface dilational viscosity of polypropylene glycol solutions and its influence on water flow and foam behavior
No full textThe non-equilibrium interfacial properties of a homologous series of aqueous polypropylene glycol solutions (400-2000 g/mol) were investigated as a function of concentration to understand their role in determining foam behavior. The overflowing cylinder technique was used to generate a continually expanding surface. Static and dynamic surface tensions, as well as the surface velocity of the expanding surface, were characterized. The surface dilational viscosity was compared to water flow rate and foam retention time of the polypropylene glycol solutions reported in the literature. This study suggests that the surface dilational viscosity is a key parameter in the Marangoni effect which retards water drainage, resulting in wetter foam and increased water recovery across flowing foams.S.N. Tan, A. Jiang, J.J. Liau, S.R. Grano, R.G. Hor
Quantifying contributions to froth stability in porphyry copper plants
No full textA method to describe froth stability in industrial flotation cells, and its link with froth recovery, is discussed in this paper. The direct measurement of froth stability in industrial flotation cells is still controversial, and different techniques have been developed. In this paper, the froth half-life time and bubble size on the top of the froth are discussed as indicators for froth stability. Experiences at two flotation concentrators treating porphyry copper ore are compared. The relative contributions to froth stability from frother in solution and solids loading in the froth were investigated in both concentrators, and links were found between both the froth half-life and bubble size on the top of the froth and the amount and nature (hydrophobicity) of particles in the concentrate. The comparison also suggests how two significantly different operating strategies for the froth phase may lead to similar outcomes in terms of froth recovery. © 2008 Elsevier B.V. All rights reserved.M. Zanin, E. Wightman, S.R. Grano, J.-P. Franzidi
Detachment of coarse particles from oscillating bubbles-The effect of particle contact angle, shape and medium viscosity
No full textThis paper examines the detachment of coarse particles from oscillating bubbles as a function of particlehydrophobicity and shape, as well as medium viscosity. The detachment experiments were conducted using anovel electro-acoustic technique for both ground quartz particles and spherical glass beads of various diameters and hydrophobicity. The detachment force for both types of particles, calculated from the maximum vibration amplitude at which a particle detaches from a bubble, increased with an increase in the contact angle of particles and viscosity of the suspending medium. At low vibration frequencies, the quasistatic model predicts the experimental detachment force reasonably well. In contrast, at high vibration frequency and, particularly, in high viscosity medium, the quasi-static model does not predict the experimental detachment force. It is hypothesised that the magnitude of the detachment force is determined by the dynamic contact angle, which is governed by the velocity of movement of the three phase contact line. Larger detachment forces were observed for the quartz particles compared to that of the spherical glass beads of the same size range and similar contact angle value. The stability of the bubble-particle aggregates at high viscosity has been related to the dynamic contact angle of particles. At high viscosity, the rate of movement of the three phase contact line, which governs thedynamic contact angle, is reduced thus resulting in more stable bubble-particle aggregates.D. Xu, I. Ametov and S.R. Granohttp://www.journals.elsevier.com/international-journal-of-mineral-processing
Benchmarking the flotation performance of ores
No full textA porphyry copper ore containing chalcopyrite as the principal copper bearing mineral, and pyrite as the only other sulphide mineral, was treated in batch flotation tests under well defined physical conditions. The size-by-size flotation response was benchmarked against established calibration curves to infer an operational contact angle of the sulphide minerals as a function of particle size. The inferred operational contact angle values of the sulphide minerals were validated by independent measurements of contact angle on the concentrates and, in the case of chalcopyrite, by an indirect approach using Time of Flight Secondary Ion Mass Spectrometry (ToF-SIMS). Recovery, flotation rate, and inferred operational contact angle increased with collector addition across all size fractions, with the intermediate and coarse size fractions benefitting the most from increased collector addition. The directly measured and inferred operational contact angles were in reasonable agreement, with an R2 value of 0.7 across all size fractions. There was good agreement between the advancing contact angle values determined using ToF-SIMS and those calculated from direct contact angle measurement on the 53-75 μm size fraction for the case of chalcopyrite. A method for benchmarking flotation response has been developed, which may lead to better flotation process diagnostics and modelling.S. Muganda, M. Zanin, S.R. Gran
- …
