Product fineness during grinding in stirred media mills is mainly influenced by the specific energy input, the stress energy transferred by the colliding grinding media and the stress frequency. The stress energy from grinding media collisions is heterogeneously distributed in stirred media mills. Herein, in order to characterize the stress energy distribution and the local grinding media collision frequencies, the grinding media motion was calculated using discrete element method (DEM) simulations coupled with computational fluid dynamics (CFD). The local grinding media concentration, velocity profiles, grinding media collisions and stress energies were compared for varied total grinding media fillings and stirrer speeds. It was confirmed that the normalized grinding media velocity profile can be used to divide the grinding chamber into four types of zones that allow the modeling of the stress energy distribution. However, the collision frequency showed very different distributions for varied stirrer velocities and grinding media fillings.

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ritic eruptions they had nothing to object; but the I Dougal Brisbane gold medal of the Royal Society of volcanic facies appeared to them a privilege restricted Edinburgh has been conferred on him, in recognition to recent geological times. To this the present writer of the zeal aud skill displayed in explaining the geo might b?ar personal testimony, as he found his" way logical peculiarities of his mother-land. He is now at of Damas "onlywhen he was fortunate enough to ram-the summit of his career, and not so heavily laden ble over North Wales, and gather with his own hands with years but that we may express for him the wish pieces of vesicular lava embedded in the tuffs of the ad multos annos. Let us hope that he will long re Snowdon, or bowlders of true felsite, lying at the base main at the head of the distinguished staff to which of the Cambrian series at Llanberis. he has given so profitable an impulse, and continue Not only has Sir Archibald, in common with his to serve as a comforting example for those who refuse countrymen, always escaped that kind of misconcep-to acknowledge any other means of genuine success tion, but he will have contributed more effectively than constant labor and faithfulness to duty. than any other to place the matter in the true light.A. DE LAPPARENT. Thanks to the cliffs of Scotland, he has been able to trace the roots of old volcanoes, to show true volcanic bombs entombed in sediments, and to mark the site round which vast piles of lavas and tutTs, 5,000 or 6,000 feet in thickness, had been heaped up. Likewise, in HEAT AN D CHEMICAL ENERGY.

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