Comparative study of two biggest mineral wastes in South Africa for mine reclamation: A geotechnical study

Abstract : Laboratory investigations were conducted on two mineral wastes to assess their geotechnical properties for mine backfilling. Composite Coal Fly Ash (CFA) sludge recovered from CFA and acid mine drainage (AMD) reaction (ratios 1:2 and 1:3) and gold mine tailings (GMT) with 3 % cement were evaluated at varying curing ages. Both samples showed favourable characteristics for use in mine reclamation. However, solid/liquid ratios should be maintained to ensure maximum strength. The results show that CFA can be recommended for mine reclamation due to it geotechnical properties. The use of GMT is possible, however blending with higher percentages of cement should be considered

Evaluation of South African gold tailings as a mine backfilling material

Abstract : This paper presents the results of laboratory investigations conducted on gold mine tailings (GMT) to assess their chemical, mineralogical, leaching and geotechnical characteristics as well their acid generating potential in view of assessing its suitability as an alternative backfilling solution in mine reclamation. Chemical characterisation revealed that GMT is dominated by Si, Al and Fe with notable amounts of Cr, Zr, Zn, Pb, Ce, As, Ba, Ni, V, Sr, Nd, Cu, U and Co. Mineralogical characterisation revealed a composition of silicate minerals with secondary minerals such as jarosite, goethite and hematite. Acid base accounting (ABA) results showed that GMT are acid generating. During column leach experiments, leaching of elements and SO42- was significant at initial stages and became negligible thereafter. GMT composites exhibited moderate strength parameters. The effect of curing age and addition of cement contributed to the shear strength of the material. Furthermore, GMT showed favourable characteristics for use in mine backfilling; however, solid/liquid ratios should be maintained to ensure maximum strength. The use of GMT for backfilling is therefore possible; however, blending with higher percentages of cement and alkaline materials such as coal fly ash should be considered to chemically stabilise the material

Activation of Aromatic C‐F Bonds by a N‐Heterocyclic Olefin (NHO)

A N-heterocyclic olefin (NHO), a terminal alkeneselectively activates aromatic C-F bonds without the need of anyadditional catalyst. As a result, a straightforward methodology wasdeveloped for the formation of different fluoroaryl substituted alkenesin which the central carbon-carbon double bond is in a twistedgeometry.Fil: Mandal, Debdeep. International Centre Of Theoretical Science. Tata Institute Of Fundamental Research; EspañaFil: Chandra, Shubhadeep. Freie Universität Berlin.; AlemaniaFil: Neuman, Nicolás Ignacio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; ArgentinaFil: Mahata, Alok. International Centre Of Theoretical Science. Tata Institute Of Fundamental Research; EspañaFil: Sarkar, Arighna. International Centre Of Theoretical Science. Tata Institute Of Fundamental Research; EspañaFil: Kundu, Abhinanda. International Centre Of Theoretical Science. Tata Institute Of Fundamental Research; EspañaFil: Anga, Srinivas. International Centre Of Theoretical Science. Tata Institute Of Fundamental Research; EspañaFil: Rawat, Hemant. International Centre Of Theoretical Science. Tata Institute Of Fundamental Research; EspañaFil: Schulzke, Carola. ERNST MORITZ ARNDT UNIVERSITÄT GREIFSWALD (UG);Fil: Sarkar, Biprajit. Freie Universität Berlin.; AlemaniaFil: Mote, Kaustubh R.. International Centre Of Theoretical Science. Tata Institute Of Fundamental Research; EspañaFil: Chandrasekhar, Vadapalli. International Centre Of Theoretical Science. Tata Institute Of Fundamental Research; EspañaFil: Jana, Anukul. International Centre Of Theoretical Science. Tata Institute Of Fundamental Research; Españ

Experimental study and analysis of lubricants dispersed with nano Cu and TiO2 in a four-stroke two wheeler

The present investigation summarizes detailed experimental studies with standard lubricants of commercial quality known as Racer-4 of Hindustan Petroleum Corporation (India) dispersed with different mass concentrations of nanoparticles of Cu and TiO2. The test bench is fabricated with a four-stroke Hero-Honda motorbike hydraulically loaded at the rear wheel with proper instrumentation to record the fuel consumption, the load on the rear wheel, and the linear velocity. The whole range of data obtained on a stationery bike is subjected to regression analysis to arrive at various relationships between fuel consumption as a function of brake power, linear velocity, and percentage mass concentration of nanoparticles in the lubricant. The empirical relation correlates with the observed data with reasonable accuracy. Further, extension of the analysis by developing a mathematical model has revealed a definite improvement in brake thermal efficiency which ultimately affects the fuel economy by diminishing frictional power in the system with the introduction of nanoparticles into the lubricant. The performance of the engine seems to be better with nano Cu-Racer-4 combination than the one with nano TiO2

A GPU implementation of a track-repeating algorithm for proton radiotherapy dose calculations

An essential component in proton radiotherapy is the algorithm to calculate the radiation dose to be delivered to the patient. The most common dose algorithms are fast but they are approximate analytical approaches. However their level of accuracy is not always satisfactory, especially for heterogeneous anatomic areas, like the thorax. Monte Carlo techniques provide superior accuracy, however, they often require large computation resources, which render them impractical for routine clinical use. Track-repeating algorithms, for example the Fast Dose Calculator, have shown promise for achieving the accuracy of Monte Carlo simulations for proton radiotherapy dose calculations in a fraction of the computation time. We report on the implementation of the Fast Dose Calculator for proton radiotherapy on a card equipped with graphics processor units (GPU) rather than a central processing unit architecture. This implementation reproduces the full Monte Carlo and CPU-based track-repeating dose calculations within 2%, while achieving a statistical uncertainty of 2% in less than one minute utilizing one single GPU card, which should allow real-time accurate dose calculations