Discrete Scale Invariance and the "Second Black Monday"

Evidence is offered for log-periodic (in time) fluctuations in the S&P 500 stock index during the three years prior to the October 27, 1997 "correction". These fluctuations were expected on the basis of a discretely scale invariant rupture phenomenology of stock market crashes proposed earlier.Comment: LaTeX file, 4 pages, 2 figure

Testing isomorphism of graded algebras

We present a new algorithm to decide isomorphism between finite graded algebras. For a broad class of nilpotent Lie algebras, we demonstrate that it runs in time polynomial in the order of the input algebras. We introduce heuristics that often dramatically improve the performance of the algorithm and report on an implementation in Magma

Design and evaluation of a cockpit display for hovering flight

A simulator evaluation of a cockpit display format for hovering flight is described. The display format is based on the position-velocity-acceleration representation (PVA) similar to that used in the Pilot Night Vision System in the Army AH-64 helicopter. By only varying the nature of the display law driving the primary indicator in the PVA format, i.e., the acceleration symbol, three candidate displays are created and evaluated. These range from a Status display in which the primary indicator provides true acceleration information to a Command display, in which the primary indicator provides flight director information. Simulation results indicate that two of the three displays offer performance and handling qualities which make them excellent candidates for future helicopter cockpit display systems

Race and Survival Bias in NBA Data

Cross sectional employment data is not random. Workers who survive to a longer level of tenure tend to have a higher level of productivity than those who exit earlier. Wage equations that use cross sectional data could be biased from the over sampling of high productive workers at long levels of tenure. The survival bias that arises in cross sectional data could possibly bias the coefficients in wage equations. This could lead to false positive conclusions concerning the presence of pay discrimination. Using 1989-2008 NBA data we explore the extent of survival bias in wage regressions in a setting in which worker productivity is extremely well documented through a variety of statistical measures. We then examined whether the survival bias affects the conclusions concerning racial pay discrimination. Key Words: NBA, survival bias, pay discrimination