Prolonging thermal barrier coated specimen life by thermal cycle management

Measurements were made of the rate of increase in temperature of a ZrO2-8Y2O3 thermal barrier coated (TBC) specimen for various values of fuel/air (F/A) ratios when the specimen is exposed to a 0.3 Mach burner flame. For rod specimens in a carousel, the heating rates increased with (F/A) ratio and were higher at the inward facing surface for a given (F/A). Plate specimens were more sensitive to burner variations. Calculated results are given for the radial stress in the coated rod specimens for variations in (F/A) ratios from 0.04 to 0.065. Over this range, the radial stress varies from 4.3 to 5.3 MPa. The results indicate that controlling the heating rate of a TBC by controlling the (F/A) ratio offers a potential method to prolong TBC cyclic life; uncontrolled (F/A) ratios will produce scatter in experimental results. Geometric arrangement can have an equivalent effect, but is usually fixed by design

Poisson's ratio in composite elastic media with rigid rods

We study the elastic response of composites of rods embedded in elastic media. We calculate the micro-mechanical response functions, and bulk elastic constants as functions of rod density. We find two fixed points for Poisson's ratio with respect to the addition of rods in 3D composites: there is an unstable fixed point for Poisson's ratio=1/2 (an incompressible system) and a stable fixed point for Poisson's ratio=1/4 (a compressible system). We also derive an approximate expression for the elastic constants for arbitrary rod density that yields exact results for both low and high density. These results may help to explain recent experiments [Physical Review Letters 102, 188303 (2009)] that reported compressibility for composites of microtubules in F-actin networks.Comment: 4 pages, 4 figures, to appear in Phys. Rev. Let

POPULATION-SPECIFIC RECREATION DEMAND MODELS AND THE CONSEQUENCES OF POOLING SAMPLE DATA

This paper considers the implications of different geographical population definitions in analysis of demand for wildlife recreation. Demand functions for fishing, small game hunting, big game hunting, and wildlife enjoyment are estimated for individual Southeastern states and also for a pooled sample of all the states. Statistically significant differences between the state and regional estimates of the variable cost coefficient exist in 18 of the 40 cases. Consumer surplus values derived from state cost coefficients can differ greatly from values derived from pooled coefficients.Resource /Energy Economics and Policy,

GRANGER CAUSALITY AND U.S. CROP AND LIVESTOCK PRICES

Agricultural economists have recently been attracted to procedures suggested by Granger and others which allow observed data to reveal causal relationships. Results of this study indicate that "causality" tests can be ambiguous in identifying behavioral relationships between agricultural price variables. Caution is suggested when using such procedures for model choice.Demand and Price Analysis,

EQUILIBRIUM VERSUS DISEQUILIBRIUM IN THE MARKET FOR NON-FED CATTLE

Beef-cow inventory demand is considered in a disequilibrium model of the U.S. live non-fed cattle market. Statistical results indicated the possible presence of disequilibrium prices. However, post-model evaluation indicated that the market for non-fed cattle has not been characterized by significant disequilibrium price behavior.Demand and Price Analysis, Livestock Production/Industries,

RESEARCH PRODUCTIVITY AND SELECTED CHARACTERISTICS OF AGRICULTURAL ECONOMICS RESEARCH AND TEACHING FACULTY IN THE SOUTHERN REGION

Teaching/Communication/Extension/Profession,

Analytical prediction of friction factors and Nusselt numbers of turbulent forced convection in rod bundles with smooth and rough surfaces

A simple analytical method was developed for the prediction of the friction factor, f, of fully developed turbulent flow and the Nusselt number, Nu, of fully developed turbulent forced convection in rod bundles arranged in square or hexagonal arrays. The friction factor equation for smooth rod bundles was presented in a form similar to the friction factor equation for turbulent flow in a circular pipe. An explicit equation for the Nusselt number of turbulent forced convection in rod bundles with smooth surface was developed. In addition, we extended the analysis to rod bundles with rough surface and provided a method for the prediction of the friction factor and the Nusselt number. The method was based on the law of the wall for velocity and the law of the wall for the temperature, which were integrated over the entire flow area to yield algebraic equations for the prediction of f and Nu. The present method is applicable to infinite rod bundles in square and hexagonal arrays with low pitch to rod diameter ratio, P/D<1.2.Indisponível

ASSESSMENT OF JOURNALS USED BY AGRICULTURAL ECONOMISTS AT LAND-GRANT UNIVERSITIES

Agricultural economists at land-grant universities were surveyed to evaluate the use and assessment of professional journals. Faculty rankings of journals are reported along with faculty perceptions of changes in the quality of selected journals. Of 25 journals used by agricultural economics faculties, the Southern Journal of Agricultural Economics ranked first among regional agricultural economics journals in personal usefulness, subscriptions held, papers submitted, papers published, and participation in the editorial and review processes. The SJAE was also ranked as the second most improved journal among all journals evaluated.Teaching/Communication/Extension/Profession,