Analytical and experimental investigation of aircraft metal structures reinforced with filamentary composites. Phase 3: Major component development

Analytical and experimental investigations, performed to establish the feasibility of reinforcing metal aircraft structures with advanced filamentary composites, are reported. Aluminum-boron-epoxy and titanium-boron-epoxy were used in the design and manufacture of three major structural components. The components were representative of subsonic aircraft fuselage and window belt panels and supersonic aircraft compression panels. Both unidirectional and multidirectional reinforcement concepts were employed. Blade penetration, axial compression, and inplane shear tests were conducted. Composite reinforced structural components designed to realistic airframe structural criteria demonstrated the potential for significant weight savings while maintaining strength, stability, and damage containment properties of all metal components designed to meet the same criteria

Eddy current inspection of graphite fiber components

The recognition of defects in materials properties still presents a number of problems for nondestructive testing in aerospace systems. This project attempts to utilize current capabilities in eddy current instrumentation, artificial intelligence, and robotics in order to provide insight into defining geometrical aspects of flaws in composite materials which are capable of being evaluated using eddy current inspection techniques. The unique capabilities of E-probes and horseshoe probes for inspecting probes for inspecting graphite fiber materials were evaluated and appear to hold great promise once the technology development matures. The initial results are described of modeling eddy current interactions with certain flaws in graphite fiber samples

Team performance and the optimal spread of talent

Alex Bryson and colleagues use US baseball data to investigate whether performance suffers if there is too wide a gap between the skills of a team's stars and the rest.skill dispersion, baseball, firm performance

Heterogeneous Worker Ability and Team-Based Production: Evidence from Major League Baseball, 1920-2009

A detailed longitudinal dataset is assembled containing annual performance and biographical data for every player over the entire history of professional major league baseball. The data are then aggregated to the team level for the period 1920-2009 in order to test whether teams built on a more even distribution of observed talent perform better than those teams with a mixture of highly able and less able players. The dependent variable used in the regressions is the percentage of games a team wins each season. We find that conditioning on average player ability, dispersion of both batting and pitching talent displays an optimal degree of inequality, in that teams with too high or too low a spread in player ability perform worse than teams with a more balanced distribution of offensive and defensive talent. These findings have potentially important applications both inside and outside of the sporting world.firm performance, skill dispersion, baseball

Heterogeneous Worker Ability and Team-Based Production: Evidence from Major League Baseball, 1920-2009

A detailed longitudinal dataset is assembled containing annual performance and biographical data for every player over the entire history of professional major league baseball. The data are then aggregated to the team level for the period 1920-2009 in order to test whether teams built on a more intermediate distribution of observed talent perform better than those teams with either too high or too low a mixture of highly able and less able players. The key dependent variable used in the regressions is the percentage of games a team wins each season. Our finding is that conditioning on average player ability, dispersion in team pitching and hitting talent prior to the start of a season is related in a non-linear way to subsequent team performance. This suggests that there is an optimum heterogeneity of ability at the team level that maximises joint output. This result is robust to the inclusion of team fixed effects as well as year dummies and after controlling for the potential endogeneity of skill dispersion. These findings have potentially important applications both inside and outside of the sporting world.Baseball, Inequality, Team-based Performance

Estimation using sampled-data containing sequentially correlated noise

Filtering, prediction, and smoothing procedures for multi-stage linear dynamic systems using sampled data with sequentially correlated nois

Heterogeneous Worker Ability and Team-Based Production: Evidence from Major League Baseball, 1920-2009

A detailed longitudinal dataset is assembled containing annual performance and biographical data for every player over the entire history of professional major league baseball. The data are then aggregated to the team level for the period 1920-2009 in order to test whether teams built on a more even distribution of observed talent perform better than those teams with a mixture of highly able and less able players. The dependent variable used in the regressions is the percentage of games a team wins each season. We find that conditioning on average player ability, dispersion of both batting and pitching talent displays an optimal degree of inequality, in that teams with too high or too low a spread in player ability perform worse than teams with a more balanced distribution of offensive and defensive talent. These findings have potentially important applications both inside and outside of the sporting world.skill dispersion, baseball, firm performance

Relationships of preweaning cow-calf characteristics to calf characteristics at selected postweaning points of evaluation

One hundred thirteen Angus cow-calf pairs (62 mature cows and 25 sires) were individually fed ad libitum over a five year period. Variation in cow size and production potential was comparable to that of Tennessee Agricultural Experiment Station herds. Postweaning, calves were individually fed a complete growing and finishing ration. Unit efficiency (UNEFF) was defined as the ratio of cow TON consump-tion to calf weight. Prediction equations (Y = b0 + b1 (AGE) + b2 (AGE)2) for weight, fat, postweaning gain, postweaning TON intake and unit efficiency was determined from biweekly weight, fat and feed consumption records. Instantaneous efficiency (INEFF) was the ratio of the rate of TON intake to the rate of gain at a given point (ratio of slopes of tangent lines to each respective equation). The most efficient point (MEP) was determined as the minimum of the equation for UNEFF. Factor analysis was performed to aid in the description of animals. Regression analysis was performed to determine relation-ships of preweaning cow-calf characteristics to characteristics at selected postweaning endpoints. Preweaning cow-calf character-istics explained appreciable variation in UNEFF, weight, and age, above that explained by year and sex, at MEP, 400 kg weight (WT400), 14 mm fat (FAT14), 207 days postweaning (207DAYS) or at an INEFF of nine kg TDN/kg gain (INEFF9). Cow weight at the previous weaning was negatively related (P\u3c.05) to UNEFF at INEFF9 and to postweaning gain at WT400. Cow weight change from previous to current weaning was positively (P\u3c.05) related to age, postweaning TON and INEFF at MEP. Cow fat positively affected age, fat and postweaning days at MEP (P\u3c.05). Calf weight and postweaning gain, when evaluated at FAT14, were negatively affected (P\u3c.05) by cow fat at previous weaning. Age at all endpoints was positively affected by weaning age (P\u3c.001). Also younger calves at weaning gained more to WT400 (P\u3c.001). Thinner calves at weaning were higher in INEFF at FAT14, but were lower in INEFF at MEP (P\u3c.05). UNEFF at all endpoints was positively related to weaning effi-ciency (P\u3c.001). Weaning efficiency also had a positive effect on gain at WT400 (P\u3c.001) and INEFF at MEP (P\u3c .05). Weaning effi-ciency showed a negative effect (P\u3c.05) on instantaneous rate of gain (INGAIN) when evaluated at MEP, WT400 or 207DAYS. The variables not affected by sex were TON intake at 207DAYS; INEFF and postweaning gain at WT400; INEFF and INGAIN at FAT14; age, postweaning TON intake and days postweaning at MEP; and INGAIN, fat, age and postweaning days at INEFF9. Calf weaning weight had a positive effect on UNEFF, weight, postweaning TON, instantaneous intake and INEFF at MEP (P\u3c.05). Calf weaning weight also had a positive effect on UNEFF, weight, postweaning TON and instantaneous intake at FAT14 (P\u3c.05). Weaning age was a positive effect (P\u3c.001) upon UNEFF, weight, postweaning TDN, fat and instantaneous rate of intake at 207DAYS. AT INEFF9, weaning weight was positively correlated with UNEFF, weight, instan-taneous TDN intake and INGAIN and was negatively correlated with postweaning days (P\u3c .05). At WT400, calf weaning weight had a negative (P \u3c.05) effect on age, postweaning days, postweaning TDN, fat and INEFF and had positive effects on weight, instantaneous rate of intake and INGAIN. Preweaning cow-calf characteristics were relatively unimportant in explaining variation in all calf characteristics studied unless evaluated at 400 kg weight. This is interpreted to be attributed to relationship of these preweaning characteristics to physiological age. Preweaning characteristics of cow-calf pairs were importantly related across all endpoints only to calf age, weight and unit efficiency. These relationships were thought to reflect the part-whole aspects of these variables from weaning to postweaning. These results suggest that little biological antagonism exists between pre- and postweaning factors related to feed efficiency. Increased unit efficiency at weaning is favorably associated with unit efficiency at all endpoints studied and is either favorably associated with calf instantaneous efficiency evaluated at the most efficient point or is independent of that measure of efficiency at other endpoints. Preweaning pair characteristics were related to slaughter age and weight at all endpoints but were largely inde-pendent of level of calf fatness. Variation in preweaning character-isties and relationships between pre- and postweaning characteristics reported in this study provide producers an opportunity to select particular kinds of animals to achieve specific goals in specific production and economic situations

EFFECT OF EXOGENOUS ENZYMES ON APPARENT METABOLIZABLE ENERGY VALUE OF BARLEY IN SWINE AND BROILER CHICKENS

The objective of this thesis was to evaluate the effect of exogenous enzyme supplementation, phytase and xylanase-glucanase, on AME value of barley in poultry and swine. In the first study, 280 broilers were assigned 1 of 8 treatments. Barley inclusion in the diet resulted in decreased (P \u3c 0.05) performance. There was a treatment × phytase × xylanase-glucanase interaction for dry matter retention with birds fed the corn-SBM-barley diet supplemented with phytase and xylanase-glucanase having higher (P \u3c 0.05) DM retention compared to birds fed corn-SBM-based diet with only xylanase-glucanase supplementation. AME and AMEn of corn-SBM-based diets were greater (P \u3c 0.05) than the corn-SBM-barley-based diets. Energy metabolizability and AMEn of barley significantly increased with xylanase-glucanase supplementation. In the second study, 24 pigs (12 pigs/phase) were assigned to 1 of 4 treatments with xylanase-glucanase and phytase. After a 7-d adaption period, urine and feces were quantitatively collected for 5 d. DE of the barley-based diet supplemented with xylanase-glucanase (3,578 kcal/kg) and phytase and xylanase-glucanase in combination (3,617 kcal/kg) were significantly different. Compared to control diets, exogenous enzymes either significantly improved or had a tendency to improve AME and AMEn value of barley in broilers, but not in growing pigs

Do Job Security Guarantees Work?

We investigate the effect of employer job security guarantees on employee perceptions of job security. Using linked employer-employee data from the 1998 British Workplace Employee Relations Survey, we find job security guarantees reduce employee perceptions of job insecurity. This finding is robust to endogenous selection of job security guarantees by employers engaging in organisational change and workforce reductions. Furthermore, there is no evidence that increased job security through job guarantees results in greater work intensification, stress, or lower job satisfaction