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24 May 1999

Volume 74, Issue 21, pp. 3081-3230

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Ultrasonic characterization of plastic foams via measurements with static pressure variations

Christophe Ayrault, Alexei Moussatov, Bernard Castagnède, and Denis Lafarge

Appl. Phys. Lett. 74, 3224 (1999); http://dx.doi.org/10.1063/1.124112 (3 pages) | Cited 4 times

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A method for ultrasonic characterization of plastic foams by changing the static pressure of air that saturates the foam has been proposed. The method is based on high frequency asymptotic expressions of the standard Johnson–Allard equivalent fluid model. It is shown, both experimentally and theoretically, that the real part of squared acoustical refractive index and logarithm of the transmission coefficient depend linearly on the inverse of the square root of applied static pressure. These linear relations provide a simple and convenient way to determine experimentally the constitutive parameters. The method is illustrated with industrial open-cell foams. Advantages, limitations, and perspectives are discussed. © 1999 American Institute of Physics.
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43.35.-c Ultrasonics, quantum acoustics, and physical effects of sound
43.20.El Reflection, refraction, diffraction of acoustic waves
43.50.-x Noise: its effects and control
62.65.+k Acoustical properties of solids

Instant holography

P. S. Ramanujam, M. Pedersen, and S. Hvilsted

Appl. Phys. Lett. 74, 3227 (1999); http://dx.doi.org/10.1063/1.124113 (3 pages) | Cited 37 times

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Instant photography, epitomized by Polaroid films is characterized by the rapid appearance of an image after exposure. We describe here an instant off-axis holographic process, characterized by exposures as short as 5 ns and an instant display process, not requiring any wet chemical processing. The holograms are made in a side-chain azobenzene polyester and can be erased through a thermal treatment of the film enabling the film to be reused. Significantly, an atomic force microscopic scan of the film shows a strong surface relief after the 5 ns exposure paving the way for a cheap, mass replication of the holograms using a micromolding technique. © 1999 American Institute of Physics.
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42.40.Ht Hologram recording and readout methods
42.70.Ln Holographic recording materials; optical storage media
42.70.Jk Polymers and organics
42.40.Eq Holographic optical elements; holographic gratings
68.35.B- Structure of clean surfaces (and surface reconstruction)
42.79.Vb Optical storage systems, optical disks
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