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

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

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 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

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

The separate computation of arcs for optimal flight paths with state variable inequality constraints

Computation of arcs for optimal flight paths with state variable inequality constraint

Are firms paying more for performance?

Purpose – The purpose of this paper is to investigate changes in the economic importance of performance-related-pay (PRP) in Britain through the 2000s using firm-level data. Design/methodology/approach – The authors utilise nationally representative, monthly data on the total wage bill and employment of around 8,500 firms. Using these data, the authors decompose the share of the total economy-wide wage bill accounted for by bonuses into the shares of employment in the PRP and non-PRP sectors, the ratio of base pay between the two sectors, and the gearing of bonus payments to base pay within the PRP sector. Findings – The growth in the economic importance of bonuses in Britain in the mid-2000s – and subsequent fluctuations since the onset of recession in 2008 – can be almost entirely explained by changes in the gearing of bonus to base pay within the PRP sector. There has been no substantial change in the percentage of employment accounted for by PRP firms; if anything it has fallen over time. Furthermore, movements in the gearing of bonuses to base pay in the economy are heavily influenced by changes in Finance: a sector which accounts for a large proportion of all bonus payments in Britain. Research limitations/implications – The paper demonstrates the importance of understanding further how firms decide the size of bonus payments in a given period. Originality/value – This is the first paper to present monthly firm-level data for Britain on the incidence and size of bonus payments in the 2000s