The motion of a plate in a rotating fluid at an arbitrary angle of attack

Slow motion of a thin plate at a finite angle of attack in a rotating container filled with a viscous incompressible fluid is analysed. The Rossby and Ekman numbers are assumed to be small. The solution method is developed by studying horizontal translation of an elliptical plate. The plate is shown to carry a stagnant Taylor column with it as it moves. Detailed analysis of the structure of the vertical shear column bounding the Taylor column is circumvented by integrating the equations of motion across the shear column. A jump condition based upon mass conservation in the shear column which relates the geostrophic regions inside and outside the Taylor column results. This jump condition and its method of derivation can be used to analyse arbitrary (slow) motion of any thin plate at any angle of attack. The fluid motion resulting when a disk moves using all six degrees of freedom at an infinitesimal angle of attack is discussed. The forces and moments on the disk are calculated and the streamlines of the geostrophic flow are displayed

Reforming the Defined-Benefit Pension System

Defined-benefit pensions typically expose workers to a form of financial risk that they are ill positioned to bear and unable to hedge. If workers understand that risk, they will offer employers a lower “price” (in the form of salary concessions) than the capital markets would offer for the same cash flow. The resulting financial inefficiency reduces the value of the firm sponsoring the pension plan. The paper identifies reforms that would essentially eliminate the financial risk borne by workers and hence the financial inefficiency inherent in risky pensions. It would also essentially eliminate the substantial financial exposure currently borne by taxpayers. The key reform elements are tighter rules governing funding and portfolio investment, market-oriented pricing of the insurance offered by the Pension Benefit Guaranty Corporation, and improved disclosure of information related to pension plans in firms’ public financial statements, in the federal budget, and in statements provided to workers.macroeconomics, defined-benefit pension, pension system, financial risk

Turbulence and transition modeling for high-speed flows

Research conducted during the past three and a half years aimed at developing and testing a turbulence/transition model applicable to high-speed turbulent flows is summarized. The first two years of the project focused on fully turbulent flows, while emphasis shifted to boundary-layer development in the transition region during the final year and a half. A brief summary of research accomplished during the first three years is included and publications that describe research results in greater detail are cited. Research conducted during the final six months of the period of performance is summarized. The primary results of the last six months of the project are elimination of the k-omega model's sensitivity to the freestream value of omega and development of a method for triggering transition at a specified location, independent of the freestream turbulence level

Why Do Firms Offer Risky Defined Benefit Pension Plans?

Even risky pension sponsors could offer essentially riskless pension promises by contributing a sufficient level of resources to their pension trust funds and by investing those resources in fixed-income securities designed to deliver their payoffs just as pension obligations are coming due. However, almost no firm has chosen to fund its plan in this manner. We study the optimal funding choice for plan sponsors by developing a simple model of pension financing in which the total compensation offered to workers must clear the labor market. We find that if workers understand the implications of pension risk, they will demand greater compensation for riskier pension promises than for safer ones, all else equal. Indeed, in our model, pension sponsors maximize their value by making their pension promises free of risk. We close by positing some explanations for why no real-world firm follows the prescription of our model.

Why Do Firms Offer Risky Defined Benefit Pension Plans?

Even risky pension sponsors could offer essentially riskless pension promises by contributing a sufficient level of resources to their pension trust funds and by investing those resources in fixed-income securities designed to deliver their payoffs just as pension obligations are coming due. However, almost no firm has chosen to fund its plan in this manner. We study the optimal funding choice for plan sponsors by developing a simple model of pension financing in which the total compensation offered to workers must clear the labor market. We find that if workers understand the implications of pension risk, they will demand greater compensation for riskier pension promises than for safer ones, all else equal. Indeed, in our model, pension sponsors maximize their value by making their pension promises free of risk. We close by positing some explanations for why no real-world firm follows the prescription of our model.

Some Evidence on Finite Sample Behavior of an Instrumental Variables Estimator of the Linear Quadtratic Inventory Model

We evaluate some aspects of the finite sample distribution of an instrumental variables estimator of a first order condition of the Holt et al. (1960) linear quadratic inventory model. We find that for some but not all empirically relevant data generating processes and sample sizes, asymptotic theory predicts a wide dispersion of parameter estimates, with a substantial finite sample probability of estimates with incorrect signs. For such data generating processes, simulation evidence suggests that different choices of left hand side variables often produce parameter estimates of an opposite sign. More generally, while the asymptotic theory often provides a good approximation to the finite sample distribution, sometimes it does not