Simplified equations of interior ballistics

Subject to the assumptions of zero starting pressure, covolume equal to charge volume, burning rate proportional to pressure, constant burning surface, and no heat loss through gas or projectile friction, the equations of interior ballistics are presented in simple form.It is hoped that these simple equations will be of some aid in making ready approximate evaluations of the effect of variation of any parameter.The general equations are listed in section I. In section II the expressions for the maximum pressure and muzzle velocity are discussed more fully, and the derivatives with respect to various parameters are given.     

Book reviews

Takeshita, Masataka. Ibn ^cArabi's Theory of the Perfect Man and Its Place in the History of Islamic Thought. Tokyo: Institute for the Study of Languages and Cultures of Asia and Africa, 1987 (Studia Culturae Islamicae, 32). iii + 182 pp.

Pryor, John. H. Geography, Technology and War : Studies in the Maritime History of the Mediterranean, 649–1571. Cambridge: Cambridge University Press, 1988. xvii +238pp.;£ 22.50 / US$ 39.50.

Baali, Fuad. Society, State and Urbanism : Ibn Khaldun's Sociological Thought. Albany: State University of New York Press, 1988. 175 pp.; paper US$ 12.95, cloth US$ 34.50

Wilkinson, John (editor) with Hill, Joyce and Ryan, W.F., Jerusalem Pilgrimage 1099–1185. London: The Hakluyt Society,1988. xi + 372pp., 24 maps and plans; £ 16.00.

Heine, Peter. Kulinarische Studien: Vntersuchungen zur Kochkunst im arabisch‐islamischen Mittelalter. Wiesbaden: Otto Harrassowitz,1988. 137pp.; DM 68.     

Learning by viewing versus learning by doing: Evidence‐based guidelines for principled learning environments

A learner‐centered approach is a central feature of instruction based on a constructivist learning model. However, there is some confusion regarding the requirement for behavioral activity as a prerequisite for a learner‐centered environment. We offer evidence in this article that some types of behavioral activity can interfere with cognitive learning processes. We recommend that instructional professionals focus on cognitive activity and summarize evidence‐based methods that support appropriate cognitive activity in behaviorally passive and active learning environments.