Robert Shelby

The low temperature electrical properties of some anisotropic crystals

Abstract The principal complex dielectric constants have been studied at audio frequencies over the temperature range 5.5–380K for α-quartz, sapphire, magnesium fluoride, and calcite. For some samples, the imaginary part of the dielectric constant revealed the presence of dipolar or thermally activated loss mechanisms which are attributed to trace impurities. The effects of these impurities are considered in arriving at values of the real part of the dielectric constants for each of the materials.

Minimally Invasive Tutoring of Complex Physics Problem Solving

Solving complex physics problems requires some kind of knowledge for selecting appropriate applications of physics principles. This knowledge is tacit, in that it is not explicitly taught in textbooks, existing tutoring systems or anywhere else. Experts seem to have acquired it via implicit learning and may not be aware of it. Andes is a coach for physics problem solving that has had good evaluations, but still does not teach complex problem solving as well as we would like. The conventional ITS approach to increasing its effectiveness requires teaching the tacit knowledge explicitly, and yet this would cause Andes to be more invasive. In particular, the textbooks and instructors would have to make space in an already packed curriculum for teaching the tacit knowledge. This paper discusses our attempts to teach the tacit knowledge without making Andes more invasive.

Implicit versus explicit learning of strategies in a non-procedural cognitive skill

University physics is typical of many cognitive skills in that there is no standard procedure for solving problems, and yet a few students still master the skill. This suggests that their learning of problem solving strategies is implicit, and that an effective tutoring system need not teach problem solving strategies as explicitly as model-tracing tutors do. In order to compare implicit vs. explicit learning of problem solving strategies, we developed two physics tutoring systems, Andes and Pyrenees. Pyrenees is a model-tracing tutor that teaches a problem solving strategy explicitly, whereas Andes uses a novel pedagogy, developed over many years of use in the field, that provides virtually no explicit strategic instruction. Preliminary results from an experiment comparing the two systems are reported.

The Andes Physics Tutoring System: An Experiment in Freedom

The Andes physics tutoring system is an experiment in student freedom. It allows students to solve a physics problem in virtually any legal way. This means that Andes must recognize an extremely large number of possible steps occurring in an extraordinarily large number of possible orders. Such freedom raises several research questions. (1) How can Andes solve the technical challenge of understanding student’s behavior in such a wide-open context? (2) How can Andes give pedagogically useful help and guidance? In particular, how can it guide students who are floundering without curtailing the freedom of students who are not floundering? (3) Will Andes be effective in getting students in real classrooms to learn physics? (4) What does it take to scale up Andes and disseminate it widely? The Andes project, which began in the mid 1990’s, has achieved workable solutions to the first three goals: Andes can understand student behavior; It provides pedagogical help similar to that of human experts; Most importantly, Andes causes large, reliable learning gains compared to control classes taught with convention, paper-based instruction. This chapter summarizes the first three results and discusses our progress on the fourth goal, scale-up.