A bearing is interposed between two surfaces in relative motion to minimize the wear by one surface of the other andl or to reduce the friction between them. A plain bearing is made of, or is lined with, a material that achieves this object under conditions of sliding 'contact between it and one or other (or both) of the surfaces. This review is concerned with the materials of such sliding contact bearings only and does not cover the steel of rolling element bearings, which have their own peculiar property requirements.
77MS paper deals with a central concept in music education, that of 'appraising' music. Through a series of incidents surrounding the development of the Music National Curriculum this concept, new to many, was left undefined. Using research which shows how people cope with change and successfully take on innovations, a need for deeper information on what appraising entails, and the underlying principles involved, was identified -that is, the ' how-to' and 'principles' knowledge of appraising. The paper reports research carried out with a group of teachers to define the activity of appraising music in a way which takes account of real classroom situations and can be used by the 90% of primary teachers who are not music specialists. Because the definition is developed by teachers it is more likely to be understood by other teachers. The paper ends with an example of a programme of work which uses the developed understanding. This includes nine areas of appraising, an explanatory definition and four stages in the process of appraising as well as an understanding of progression in this activity using seven words to indicate progression and identifying a 'putting in' and 'drawing out' stage within this.The children's appraising and progression is discussed and the paper argues that, in choosing this term, the Music Working Group has identified the way in which we come to know and understand the processes involved in music and musical thinking within the three activities of Composing, Performing and Listening.
This article describes the program developed by the authors. This has been successfully given to middle school and high school students as well as to science teachers.2 The activities have even been carried out by a group of students in a presentation for parents and community members. This demonstration program was developed as a part of the Chemistry Supplements Workshop that was given at the Institute of Chemical Education(I.C.E.)at the Uni versity of Wisconsin-Madison, This intensive two-week workshop, which is for elementary through high school instructors, revolves around ways of integrating chemistry demonstrations into the science curriculum. One of the requirements of the workshop for the teachers was to prepare a 20-minute demonstration program on a chemical topic. It is but one of many examples of how to create lesson plans that motivate students. AladdinThe goal of our program was to discuss the factors that affect the rate of chemical reaction. The students who were to participate in our program had, earlier in the week, been introduced to the idea of chemical reactions, ways of predicting if a reaction has occurred, and the general idea of rate. Rather than use a lecture demonstration, we decided to dramatize a set of demonstrations based on a mystical character, an Aladdin lamp genie. The drama was centered around the classic demonstration, "Genie in the Bottle", that produces a large cloud of water vapor. The cloud was reminiscent of a mystical genie and a program was developed to teach the mystical genie and the audience about the factors that affect the rate of chemical reaction. The Chemical GenieThe presentation begins with an excited scientist (wearing goggles) walking into the lab with his "genie bottle". He reports that he had found it on his way to work and sets it on the demonstration table for all to see. He and his fellow scientists decide to open it to examine its contents. But as the cork is removed, the genie appears as a misty cloud.3 The bottle is rigged with a small bag of Mn02 that falls into a 15-20% hydrogen peroxide solution as the cork is removed. As the mist appears, the voice of the genie fills the room via a sound system. A demonstrator dressed as a genie enters the room and grants the scientist three wishes:1. that the students will learn that science can be fun. 2. that students will learn some of the indicators of a chemical reaction: evolution or formation of a gas, color change, heat change, light emission, odor, and precipitate. 3. that students will learn four of the factors that affect reaction rate, which are concentration, temperature, surface area, catalyst.
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