Mathematics in Industrial Problems

This is the fourth volume in the series "Mathematics in Industrial Prob­ lems." The motivation for these volumes is to foster interaction between Industry and Mathematics at the "grass roots"; that is, at the level of spe­ cific problems. These problems come from Industry: they arise from models developed by the industrial scientists in ventures directed at the manufac­ ture of new or improved products. At the same time, these problems have the potential for mathematical challenge and novelty