Microwave-assisted grinding
The use of rapid microwave heating to stress-fracture ore samples is discussed. Iron ores containing hematite, magnetite, and goethite were subjected to microwave energy in batch operations at 3 kW and heated to average maximum temperatures between 840 degrees C and 940 degrees C. Scanning electron microscope (SEM) photomicrographs verified fracturing along grain boundaries and throughout the gangue matrix. Standard Bond grindability tests showed that microwave heating reduced the work index of iron ores by 10 to 24%. Using a continuous-feed belt in a microwave applicator, samples heated more uniformly and quickly than in batch operations. In a microwave chamber designed to simulate a continuous-throughput operation at 3 kW, the grindability of a taconite ore was improved by 13% at a bulk temperature of 197 degrees C. Because stress cracking occurred at a lower temperature, less energy was consumed, thereby improving cost effectiveness. To further improve the economics, preliminary tests were conducted to increase heating rates by using higher microwave powers. The beneficial effects in the grinding circuit and in the extractive operation are discussed.<<ETX>>
Novel comminution process uses electric and ultrasonic energy
Etude experimentale du broyage de differents minerais par decharge electrique et par action d'ultrasons. Mesure du rendement energetique du broyage par decharge electrique et comparaison de celui-ci avec diverses methodes de broyage conventionnelle. Proposition d'un systeme de broyage par decharge electrique suivi d'un broyage par ultrasons
Effects of signaling topic structure on text recall
Two experiments studied effects of signaling devices (headings, overviews, and summaries) on text memory. In Experiment 1, subjects read a text with or without signals, then recalled the topics of the text. Signaling produced better memory for the topics and their organization. In Experiment 2, subjects recalled the content of the text they read, and recalls were scored for the number of accurately recalled ideas. Signals produced recalls that were better organized by text topics. Signals also influenced the distribution of recall of ideas: Subjects remembered more topics but recalled less about each accessed topic if the text they read contained signals than if it did not