992 research outputs found
The turbulent dissipation rate from PIV measurements
No full textThe result of a particle-image velocimetry (PIV) measurement is a velocity field averaged over interrogation windows. This severely affects the measurement of small-scale turbulence quantities when the interrogation window size is much larger than the smallest length scale in turbulence. A direct measurement of the dissipation rate demands the measurement of gradients of the velocity field, which are now underestimated because the small-scale motion is not resolved. A popular procedure is to relate the statistical properties of the measured, but underresolved gradients to those of the true ones, invoking a large-eddy argument [3]. We show that the used proportionality constant, the Smagorinsky constant, should depend on the window overlap, on the used elements of the strain tensor, and on the way in which derivatives are approximate
How the dispersion of a droplet cloud depends on its initial size
No full textA cloud of droplets evolves under the influence of strong turbulence. The droplets are made from a phosphorescent fluid. From this cloud we select at t = 0 a narrow line by exciting the droplets with a UV laser, which causes them to glow for a few milliseconds. The dispersion of this line is followed in time using a fast intensified camera. A large range of droplet sizes (Stokes number St) was measured. It appears that lines with St \approx 1 disperse faster than a line of fluid tracers. Lines of droplets which are narrowest initially, spread fastest
Experimental allergic encephalomyelitis in Lewis rats bearing avian sarcoma virus-induced brain tumors
No full textReverend William M. Paden, D.D.
No full textThis photograph is a portrait, featured in a publication, of Reverend William M. Paden, D.D. He is wearing a dark suit, light shirt, and a dark tie with polka dots. His hair is parted in the middle and he wears a mustache. He is also wearing wire-rimmed glasses. The background is a medium gray shade.The photograph is in good condition, except for a slight wrinkle in the bottom right corner. On the back the paper appears torn because of glue and there is a small pink spot in the bottom half of the photograph. The following text is printed at the bottom of the photograph: "Reverend William M. Paden D.D. Beloved, purposeful, Missioner of Good Cheer. Leader of Presbyterianism in Utah for thirty-four years, as Pastor, Executive, Author and Counselor. Together by the grace of God, we enter the forward-looking years, growing ever richer in Christian faith and service." The Archives, Giovale Library, Westminster College, has a collection of materials authored by William Paden and also materials about him. Additional biographic information about Dr Paden is available in: Brackenridge, R. Douglas. Westminster College of Salt Lake City. Logan, Utah: Utah State University Press, 1998, pp. 118, 121, 124, 140
On fully nonlinear CR invariant equations on the Heisenberg group
No full textAbstractIn this paper we provide a characterization of second order fully nonlinear CR invariant equations on the Heisenberg group, which is the analogue in the CR setting of the result proved in the Euclidean setting by A. Li and the first author in Li and Li (2003) [21]. We also prove a comparison principle for solutions of second order fully nonlinear CR invariant equations defined on bounded domains of the Heisenberg group and a comparison principle for solutions of a family of second order fully nonlinear equations on a punctured ball
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