Aeroelastic forced response analysis of turbomachinery

An introduction is given to the research activity that is underway to enable the prediction of turbomachinery aeroelastic forced response. An effort is being made to assemble a computer program (FREPS) which incorporates the aeroelastic structural models, unsteady aerodynamic models, and forcing function models. The structural and aerodynamic models are currently well developed. The forcing function models are at a primitive level. A significant activity has begun to identify the forcing functions due to stator-rotor aerodynamic interaction

Greenback-Gold Returns and Expectations of Resumption, 1862-1879

We propose a unified framework for studying the greenback-gold price during the U.S. suspension of convertibility from 1862 to 1879. The gold price is viewed as a floating exchange rate, with a fixed destination given by gold standard parity because of the prospect of resumption. We test this perspective using daily data for the entire period, and measure the effect of news during and after the Civil War. New evidence of a decline in the volatility of gold returns after the Resumption Act of 1875 provides statistical support for the importance of expectations of resumption.greenbacks, gold standard, regime switching

Temporary controls on capital inflows

During the past decade a number of countries imposed capital controls that had two distinguishing features: they were asymmetric, in that they were designed principally to discourage capital inflows, and they were temporary. This paper studies formally the consequences of these policies, calibrates their potential effectiveness, and assesses their welfare implications in an environment in which the level of capital inflows can be suboptimal. In addition, motivated by the fact that these types of controls have often been left in place after the dissipation of the shock that lead to the controls being implemented, the paper evaluates the welfare cost of procrastination in removing these types of controls.capital flows controls international interest rates inflation reserve requirements

Risk, Managerial Skill and Closed-End Fund Discounts

Empirical evidence from the UK market is brought to bear on recent theories of closed-end fund discounts. Market pricing of skill, relative to the fees charged for it, accounts for a significant portion of discount variation, but cannot explain the rarity of index funds or why they trade at a discount. Index funds have lower discount volatility. Discount risk is much more systematic on international than on domestic funds. It is argued that even idiosyncratic risk is priced in closed-end funds, because they are likely to represent a significant proportion of investors’ risky portfolios.Closed-end fund; fund management; systematic risk

Too much of a good thing: The macroeconomic effects of taxing capital inflows

In addition to altering fiscal, monetary, and exchange rate policies in response to the surge in international capital inflows in the early 1990s,policy makers in many countries in ASIa, Eastern Europe, and Latin America have resorted to measures to control capital inflows.We provide a preliminary assessment of the effects of some of the macroeconomic effects of these policies.capital controls capital inflows reserve requirements taxes

Portfolio Diversification, Leverage, and Financial Contagion

This paper studies the extent to which basic principles of portfolio diversification explain "contagious selling" of financial assets when there are purely local shocks (e.g., a financial crisis in one country). The paper demonstrates that elementary portfolio theory offers key insights into "contagion." Most important, portfolio diversification and leverage are sufficient to explain why an investor will find it optimal to significantly reduce all risky asset positions when an adverse shock impacts just one asset. This result does not depend on margin calls: it applies to portfolios and institutions that rely on borrowed funds. The paper also shows that Value-at-Risk portfolio management rules do not have significantly different consequences for portfolio rebalancing than a variety of other rules. Copyright 2000, International Monetary Fund

SSME single crystal turbine blade dynamics

A study was performed to determine the dynamic characteristics of the Space Shuttle main engine high pressure fuel turbopump (HPFTP) blades made of single crystal (SC) material. The first and second stage drive turbine blades of HPFTP were examined. The nonrotating natural frequencies were determined experimentally and analytically. The experimental results of the SC second stage blade were used to verify the analytical procedures. The analytical study examined the SC first stage blade natural frequencies with respect to crystal orientation at typical operating conditions. The SC blade dynamic response was predicted to be less than the directionally solidified blade. Crystal axis orientation optimization indicated the third mode interference will exist in any SC orientation

The effect of steady aerodynamic loading on the flutter stability of turbomachinery blading

An aeroelastic analysis is presented which accounts for the effect of steady aerodynamic loading on the aeroelastic stability of a cascade of compressor blades. The aeroelastic model is a two degree of freedom model having bending and torsional displacements. A linearized unsteady potential flow theory is used to determine the unsteady aerodynamic response coefficients for the aeroelastic analysis. The steady aerodynamic loading was caused by the addition of airfoil thickness and camber and steady flow incidence. The importance of steady loading on the airfoil unsteady pressure distribution is demonstrated. Additionally, the effect of steady loading on the tuned flutter behavior and flutter boundaries indicates that neglecting either airfoil thickness, camber or incidence could result in nonconservative estimates of flutter behavior

Targeting foreclosure interventions: an analysis of neighborhood characteristics associated with high foreclosure rates in two Minnesota counties

This study examines the statistical association of foreclosure sales with social, economic and housing variables measured at the Census tract level for two purposes of interest to foreclosure mitigation practitioners —- to assess whether it is feasible to identify in advance neighborhoods likely to have high rates of foreclosure, and to explore the socioeconomic traits of high-foreclosure neighborhoods so as to design appropriate mitigation programs. We collected data on foreclosure sales in 2002 from the sheriff’s departments of Hennepin and Ramsey counties, the two core counties that comprise the Minneapolis-St. Paul MSA. We find that several factors commonly associated with high foreclosure sale rates could have correctly identified, in advance, most neighborhoods with high rates of mortgage foreclosure. To guide the design of foreclosure mitigation programs, we also present evidence that foreclosure risks in our two counties were highest in neighborhoods with elevated credit risk indicators and a high proportion of homeowners who are recent minority buyers or young. We show that an accurate credit risk variable is among the best predictors of foreclosure and also critically affects our multivariate analysis of factors associated with foreclosure. To limit social losses associated with foreclosures, we conclude that consideration should be given to enhancing public access to data on mortgages, foreclosures, and foreclosure risk factors, especially the neighborhood distribution of credit scores.