Advanced propeller research

Recent results of aerodynamic and acoustic research on both single rotation and counterrotation propellers are reviewed. Data and analytical results are presented for three propellers: SR-7A, the single rotation design used in the NASA Propfan Test Assessment (PTA) flight program; CRP-X1, the initial 5+5 Hamilton Standard counterrotating design; and F7-A7, the 8+8 counterrotating G.E. design used in the proof of concept Unducted Fan (UDF) engine. In addition to propeller efficiencies, cruise and takeoff noise, and blade pressure data, off-design phenomena involving formation of leading edge vortexes are described. Aerodynamic and acoustic computational results derived from 3-D Euler and acoustic radiation codes are presented. Research on unsteady flows which are particularly important for understanding counterrotation interaction noise, unsteady loading effects on acoustics, and flutter or forced response is described. The first results of 3-D unsteady Euler solutions are illustrated for a single rotation propeller at angle of attack and for a counterrotation propeller. Basic experimental and theoretical results from studies on the unsteady aerodynamics of oscillating cascades are outlined

Borders, Common Currencies, Trade, and Welfare: What Can We Learn from the Evidence?

Recent evidence indicates that the intensity of economic exchange within and across borders is significantly different: linkages are much tighter within, than among, nation-states. These findings, however, do not necessarily imply that borders and separate national currencies represent significant barriers to trade that should be removed, since the evidence is also consistent with the alternative hypothesis, that domestic exchange is more efficient because domestic producers are better able to satisfy the requirements of local consumers, owing to common tastes and institutions and the existence of local information and social networks. Focusing primarily on trade linkages within and between Canada and the United States, the authors review the evidence on the extent to which national borders lessen the intensity of international economic linkages, primarily trade in goods and services, and the effects on domestic welfare. They also examine the evidence on the impact of common currencies on trade and welfare. They determine that, since the empirical models employed to date in this research cannot distinguish between alternative explanations of the evidence, it is not yet possible to draw firm conclusions for policy-making.

Computer program for parameterization of nucleus-nucleus electromagnetic dissociation cross sections

A computer subroutine parameterization of electromagnetic dissociation cross sections for nucleus-nucleus collisions is presented that is suitable for implementation in a heavy ion transport code. The only inputs required are the projectile kinetic energy and the projectile and target charge and mass numbers