Mechanical behavior of thermal barrier coatings for gas turbine blades

Plasma-sprayed thermal barrier coatings (TBCs) will enable turbine components to operate at higher temperatures and lower cooling gas flow rates; thereby improving their efficiency. Future developments are limited by precise knowledge of the material properties and failure mechanisms of the coating system. Details of this nature are needed for realistic modeling of the coating system which will, in turn, promote advancements in coating technology. Complementary experiments and analytical modeling which were undertaken in order to define and measure the important failure processes for plasma-sprayed coatings are presented. The experimental portion includes two different tests which were developed to measure coating properties. These are termed tensile adhesion and acoustic emission tests. The analytical modeling section details a finite element method which was used to calculate the stress distribution in the coating system. Some preliminary results are presented

On the Accuracy of Producer Price Indexes for Pharmaceutical Preparations: An Audit Based on Detailed Firm-Specific Data

This paper reports preliminary results of a detailed audit of one component of the Producer Price Index (PPI), using data from a large muiltproduct company. We compare price indexes constructed in a variety of ways from the universe of products of a large pharmaceutical manufacturer in the US, with price indexes constructed from the particular products of this firm sampled by the BIS, using BIS and alternative index number procedures. A principal finding is that price indexes based on the BIB sample of this firm grew similarly to the published PPI's for SIC 28341, but in contrast, price indexes computed using the universe of products manufactured by the firm grew much more slowly. Although some variations emerge depending on how one undertakes the calculations, our typical finding is that, employing monthly data from January 1984 through December 1989, the BIB sample price index rises at nearly the same rate as the PPI, bet at roughly twice the rate of indexes based on the universe of products shipped by this pharmaceutical firm. We also report results of a preliminary attempt to uncover the source of this disparity, we provide some evidence on the "new goods" problem, and we implement a procedure to mitigate the problem of "drift" associated with the Tornqvist approximation to the Divisia chained index.

Price Indexes for Acute Phase Treatment of Depression

Although broad trends in medical spending in the U.S. over the last decade have received widespread attention from policymakers, very little attention has focused on the components of those changes. For many other industries, economists typically divide nominal expenditures by an official government price index to decompose these expenditures into price and quantity components. In this paper we construct a new price index for the treatment of one illness depression. Making use of results from the published clinical literature and from official treatment guideline standards, we identify therapeutically similar treatment bundles. These bundles can then be linked and weighted to construct price indexes for specific forms of major depression. In doing so, we construct CPI and PPI-like medical price indexes that deal with prices of treatment episodes rather than prices of discrete inputs, that are based on transaction rather than list prices, that take quality changes and expected outcomes into account employ current, time-varying expenditure weights in the aggregation computations. We find that regardless of which index number procedure is employed time period the treatment price index for the acute phase of major depression has hardly changed remaining at 1.00 or falling slightly to around 0.97. This index grows considerably less rapidly than the various official PPIs -- thus the price index for the treatment of the acute phase of major depression has fallen over the 1991-95 time period. A hedonic approach to price index measurement yields broadly similar results. These results imply that given a budget for treatment of depression accomplished in 1995 than in 1991. Our results suggest that at least in the case of acute phase major depression, aggregate spending increases are due to a larger number of effective treatments being provided.

Optical Probe of Quantum Shot Noise Reduction at a Single-Atom Contact

Visible and infra-red light emitted at a Ag-Ag(111) junction has been investigated from tunneling to single atom contact conditions with a scanning tunneling microscope. The light intensity varies in a highly nonlinear fashion with the conductance of the junction and exhibits a minimum at conductances close to the conductance quantum. The data are interpreted in terms of current noise at optical frequencies, which is characteristic of partially open transport channels

Early Retirement and Public Disability Insurance Applications: Exploring the Impact of Depression

This paper investigates the impact of depression on labor force participation among older workers. Empirically, we use two analytic strategies and rely on a sample drawn from the Health and Retirement Survey. Depression directly and indirectly increases individuals%u2019 probability of retiring early and applying for DI benefits, after accounting for other predictors of labor force exit. Accounting for the independent effects of depression, disability associated with physical illness may be smaller than the official statistics suggest. There may be great economic gains in increasing depression treatment awareness and access to treatment for individuals, employers and society.

Estimation of Time-Varying Correlation Functions

The need for estimating the auto- or crosscorrelation functions of nonstationary random processes frequently arises in communication and self-adaptive systems. In most situations only one sample function can he observed over finite time. It is the purpose of this work to establish a firm theoretical basis for such a measurement of time-varying correlation functions, and the emphasis here is on suitable estimation procedures rather than specific measurement techniques. Second order stochastic processes are used as a mathematical model. The minimum mean square error between a weighted time average and the true (ensemble average) correlation function is investigated. This procedure leads to an optimum weighting function which can be obtained numerically under the Gaussian assumption. The results of such an analysis justify the much simpler finite integration-time average as an estimate. By employing a bilinear approximation in time t and delay t to the true correlation function, the mean value and variance of the simple finite-time average are found. A minimum upper bound on the mean square error is used as a criterion for an optimum observation time of such an estimate. Explicit results, however, require again the Gaussian assumption. These approaches are based mainly on a strict error analysis. A more direct approach, that leads to approximants which are random variables with unknown properties, is also outlined. The restrictions and difficulties are discussed. Examples to support the proposed estimation procedures are presented and explicit results appear mostly in graphical form