Introduction

Abstract

Since ancient times it has been the nature of man to build physical structures, ranging from the simple to the very sophisticated and complex. It has also been the nature of man to devise experiments to explain how and why things behave the way as they do in the physical world. As an end goal or as intermediate steps along the way, such activities often involve the design, fabrication, and characterization of test structures of one kind or another from which scientific principles and behavioral patterns are derived, generalized, and applied on a wider scale. An early example of a scientific experiment to prove a hypothesis is attributed to Archimedes, circa 250 BC. In the popular story of the “golden crown,” Archimedes was able to determine the purity of gold in the emperor’s crown by comparing its density, as determined in part by the volume of water displaced, to that of lumps of pure gold and silver [1]. Although there is no known written record by Archimedes of this event, the story serves well to illustrate the concept of non-destructively evaluating the properties of an object by learning derived from test samples.