On statistically stationary homogeneous shear turbulence

A statistically stationary turbulence with a mean shear gradient is realized in a flow driven by suitable body forces. The flow domain is periodic in downstream and spanwise directions and bounded by stress free surfaces in the normal direction. Except for small layers near the surfaces the flow is homogeneous. The fluctuations in turbulent energy are less violent than in the simulations using remeshing, but the anisotropy on small scales as measured by the skewness of derivatives is similar and decays weakly with increasing Reynolds number.Comment: 4 pages, 5 figures (Figs. 3 and 4 as external JPG-Files

Sub-Kolmogorov-Scale Fluctuations in Fluid Turbulence

We relate the intermittent fluctuations of velocity gradients in turbulence to a whole range of local dissipation scales generalizing the picture of a single mean dissipation length. The statistical distribution of these local dissipation scales as a function of Reynolds number is determined in numerical simulations of forced homogeneous isotropic turbulence with a spectral resolution never applied before which exceeds the standard one by at least a factor of eight. The core of the scale distribution agrees well with a theoretical prediction. Increasing Reynolds number causes the generation of ever finer local dissipation scales. This is in line with a less steep decay of the large-wavenumber energy spectra in the dissipation range. The energy spectrum for the highest accessible Taylor microscale Reynolds number R_lambda=107 does not show a bottleneck.Comment: 8 pages, 5 figures (Figs. 1 and 3 in reduced quality

Compensating Wage Differentials and AIDS Risk

We examine the effect of HIV/AIDS infection risks on the earnings of registered nurses (RNs) and other health care workers by combining data on metropolitan statistical area (MSA) AIDS prevalence rates with annual 1987 --2001 Current Population Survey (CPS) and quadrennial 1988 --2000 National Sample Survey of Registered Nurses (SRN) data. Holding constant wages of control groups that are likely not exposed to AIDS risks and group-specific MSA fixed effects, a 10 percent increase in the AIDS rate raises RN earnings by about 0.8 percent in post-1992 samples, when AIDS rates were falling but a more comprehensive categorization of AIDS was used by the CDC. AIDS wage differentials are much larger for RNs and non-nursing health practitioners than for other nursing and health care workers, suggesting that this differential represents compensation paid for job-related exposure to potentially HIV-infected blood.

Electron beam X-Y deflection system Final report

Design and fabrication of electron beam X-Y deflection system for retrofit on welding gun