Observation of Jonscher Law in AC Hopping Conduction of Electron-Doped Nanoporous Crystal 12CaO7Al2O3 in THz Frequency Range

We have performed terahertz time-domain spectroscopy of carrier-doped nanoporous crystal 12CaO7Al2O3 showing the Mott variable range hopping at room temperature. The real part of the dielectric constant clearly demonstrates the nature of localized carriers. The frequency dependence of both the real and imaginary parts of the dielectric constant can be simply explained by assuming two contributions: a dielectric response by the parent compound with no carriers and an AC hopping conduction with the Jonscher law generally reported up to GHz range. The possible obedience to the Jonscher law in the THz range suggests a relaxation time of the hopping carriers much faster than 1ps in the carrier-doped 12CaO7Al2O3.Comment: 4pages 3figures. to be published in Phys. Rev.

Development and validation of new cryogenic cavitation model for rocket turbopump inducer

A rocket propellant is often used cryogenic fluid such as liquid hydrogen or liquid oxygen, and it is known that a suction performance of turbopump inducer (Fig.1) in cryogenic fluid is improved due to Thermodynamic effect . Thermodynamic effect can be explained by temperature decrease inside a cavity region arising from the latent heat absorption. Although this effect is also to be observed in water cavitation, it becomes more accentuated in cryogenic fluid. In order to properly understand the cavitation performance of the inducer, this thermodynamic effect should not be overlooked. In the present study, cryogenic cavitation model without energy equation was established. During the design phase of an inducer, wall clock time of CFD simulation becomes an important point, therefore, equation number should be small. The present model considers that temperature decrease due to latent heat absorption is analytically estimated. Validation calculations were carried out for blunt head form and hydrofoil for water cavitation and two-dimensional blunt body, Laval nozzle and inducer for cryogenic fluids.http://deepblue.lib.umich.edu/bitstream/2027.42/84260/1/CAV2009-final63.pd