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Cavitation Scaling Experiments With Headforms: Bubble Acoustics
Recently Ceccio and Brennen [1][2][3] have
examined the interaction between individual traveling
cavitation bubbles and the structure of the boundary layer
and flow field in which the bubble is growing and
collapsing. They were able to show that individual
bubbles are often fissioned by the fluid shear and that this
process can significantly effect the acoustic signal
produced by the collapse. Furthermore they were able to
demonstrate a relationship between the number of
cavitation events and the nuclei number distribution
measured by holographic methods in the upstream flow.
Kumar and Brennen [4][5] have further examined the
statistical properties of the acoustical signals from
individual cavitation bubbles on two different headforms
in order to learn more about the bubble/flow interactions.
All of these experiments were, however, conducted in the
same facility with the same size of headform (5.08cm in
diameter) and over a fairly narrow range of flow
velocities (around 9m/s). Clearly this raises the issue of
how the phenomena identified change with speed, scale
and facility. The present paper will describe further
results from experiments conducted in order to try to
answer some of these important questions regarding the
scaling of the cavitation phenomena. These experiments
(see also Kuhn de Chizelle et al. [6][7]) were conducted
in the Large Cavitation Channel of the David Taylor
Research Center in Memphis Tennessee, on similar
Schiebe headforms which are 5.08, 25.4 and 50.8cm in
diameter for speeds ranging up to 15m/s and for a range
of cavitation numbers
N/P InP homojunction solar cells with an In0.53Ga0.47As contacting layer grown by liquid phase epitaxy
N/P InP homojunction solar cells with an In sub 0.53 Ga sub 0.47 As contacting layer were fabricated by liquid phase epitaxy (LPE). Electron-Beam-Induced-Current (EBIC) measurements were performed on several selected samples. It was found that the background doping level in the base region sometimes results in a deep junction, which greatly affects the cell performance
P/N InP homojunction solar cells by LPE and MOCVD techniques
P/N InP homojunction solar cells have been prepared by using both liquid phase epitaxy (LPE) and metallorganic chemical vapor deposition (MOCVD) growth techniques. A heavily doped p-In sub 0.53Ga sub 0.47As contacting layer was incorporated into the cell structure to improve the fill factor and to eliminate surface spiking at the front surface. The best conversion efficiencies (total area) obtained under AM 1 illumination are 14.2 percent for a LPE cell and 15.4 percent for a MOCVD cell
Effect of dipolar interactions on optical nonlinearity of two-dimensional nanocomposites
In this work, we calculate the contribution of dipole-dipole interactions to
the optical nonlinearity of the two-dimensional random ensemble of
nanoparticles that possess a set of exciton levels, for example, quantum dots.
The analytical expressions for the contributions in the cases of TM and
TE-polarized light waves propagating along the plane are obtained. It is shown
that the optical nonlinearity, caused by the dipole-dipole interactions in the
planar ensemble of the nanoparticles, is several times smaller than the similar
nonlinearity of the bulk nanocomposite. This type of optical nonlinearity is
expected to be observed at timescales much larger than the quantum dot exciton
rise time. The proposed method may be applied to various types of the
nanocomposite shapes.Comment: 8 page
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