Rotary-wing aircraft terrain-following/terrain-avoidance system development

Work being accomplished to develop a real-time, piloted simulation of a helicopter using the vertical motion simulator at NASA Ames is discussed. The trajectory generation algorithm and the flight path controller are described, and the software integration of the entire terrain following/terrain avoidance (TF/TA) system is discussed. Real-time simulation requirements and the unique features of applying TF/TA system to helicopter flight are summarized. Initial results indicate that the system is satisfactory for automatic, low level TF/TA helicopter flight

Accounting for peak shifting in traditional cost-benefit analysis

When cost-benefit analysis fails to account for peak-shifting the benefits of road improvement options are miscalculated. Using theory from transportation economics, we derive a simple model that disaggregates the average daily equilibrium into peak, counter-peak, and off-peak equilibria. This paper demonstrates how accounting for peak-shifting improves the performance of cost-benefit analysis.Transportation Demand, Transportation Supply, Congestion, Cost/Benefit Analysis, Planning Policy

Why Are Stocks So Risky?

With the decline in privately and publicly guaranteed benefits for pensions and health care, people increasingly must finance a greater share of their retirement expenses through their own savings. The relatively high long-term return on equity makes investments in stocks seem both an attractive and suitable means of accumulating the substantial wealth that savers will require. Yet, the 50 percent drop in the Standard & Poor’s 500 Index from May 2008 to March 2009 is only the latest reminder that stocks pose considerable risk for investors. In the past, equity returns over periods as long as 10 or 20 years have diverged substantially from their long-term averages, tarnishing the appeal of stocks even as investments for the long run...

Factorization and the Soft-Collinear Effective Theory: Color-Suppressed Decays

We discuss the soft-collinear effective theory (SCET) and kinematic expansions in B-decays, focusing on recent results for color suppressed B -> D^(*) X decays. In particular we discuss model independent predictions for B^0 -> D^0 pi^0 and B^0 -> D^*0 pi^0, and update the comparison using new experimental data. We show why HQET alone is insufficient to give these results. SCET predictions are also reviewed for other B and Lambda_b decay channels that are not yet tested by data.Comment: 5 pages, plenary talk given by I.S. at Beauty 200

Teacher Labor Markets and the Perils of Using Hedonics to Estimate Compensating Differentials in the Public Sector

Assesses the difficulties of using hedonic modeling -- which assigns dollar weights to teacher- and location-specific factors to set salaries -- in determining pay differentials for public school teachers, including the lack of wage flexibility