47 research outputs found
Nonlinear acousto-electric transport in a two-dimensional electron system
We study both theoretically and experimentally the nonlinear interaction
between an intense surface acoustic wave and a two-dimensional electron plasma
in semiconductor-piezocrystal hybrid structures. The experiments on hybrid
systems exhibit strongly nonlinear acousto-electric effects. The plasma turns
into moving electron stripes, the acousto-electric current reaches its maximum,
and the sound absorption strongly decreases. To describe the nonlinear
phenomena, we develop a coupled-amplitude method for a two-dimensional system
in the strongly nonlinear regime of interaction. At low electron densities the
absorption coefficient decreases with increasing sound intensity, whereas at
high electron density the absorption coefficient is not a monotonous function
of the sound intensity. High-harmonic generation coefficients as a function of
the sound intensity have a nontrivial behavior. Theory and experiment are found
to be in a good agreement.Comment: 27 pages, 6 figure
Thermal effects in high density polyethylene and low density polyethylene at high hydrostatic pressures
The temperature changes as a result of rapid hydrostatic pressure applications are reported for high density polyethylene (HDPE) and low density polyethylene (LDPE) in the reference temperature range from 298 to 423 K and in the pressure range from 13.8 to 200 MN m â2 . The adiabatic temperature changes were found to be a function of pressure and temperature. A curve fitting analysis showed that the empirical curve (â/â P ) = ab (Î P ) bâ1 described the experimental thermoelastic coefficients obtained from the experiments. The data were analyzed by determining the predicted thermoelastic coefficients derived from the Thomson equation (â/â P ) Ξ = α T 0 /ϱ C p . The experimental and predicted GrĂŒneisen parameter Îł T were also determined.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/44687/1/10853_2005_Article_BF01132919.pd