Nondestructive assessment of penetration of electron-beam welds

Empirical method correlates penetration of an electron-beam weld with external measurements of the weld. Empirical polygon accurately confirms full-penetration welds while a second, larger polygon provides for penetration of welds near the tip

Education Policy Reform and the Return to Schooling from Instrumental Variabes

We exploit an unusual policy reform which had the effect of reducing the direct cost of schooling in Ireland in the early 1970's. This gave rise to an increased level of schooling but with effects that vary across family background. This interaction generates a set of instrumental variables which we use to estimate the return to schooling allowing for the endogeneity of schooling. We find a large and well determined in the rate of return of the order of 11 or 12% substantially higher than the OLS estimates of around 7%.

Theory of Electron Spin Relaxation in n-Doped Quantum Wells

Recent experiments have demonstrated long spin lifetimes in uniformly n-doped quantum wells. The spin dynamics of exciton, localized, and conduction spins are important for understanding these systems. We explain experimental behavior by invoking spin exchange between all spin species. By doing so we explain quantitatively and qualitatively the striking and unusual temperature dependence in (110)-GaAs quantum wells. We discuss possible future experiments to resolve the pertinent localized spin relaxation mechanisms. In addition, our analysis allows us to propose possible experimental scenarios that will optimize spin relaxation times in GaAs and CdTe quantum wells.Comment: Small corrections made. Accepted to Phys. Rev. B. 8 pages, 5 figure