We provide an overview on the underlying physical mechanisms associated with the fluorine plasma ion implantation technology that provides a robust approach to fabricating GaN normally-off transistors. The discussion is based on atomistic modeling and a series of experimental studies including thermal diffusion, positron annihilation spectroscopy, photoconductivity and electroluminescence.
A thermophilic up¯ow anaerobic sludge blanket (UASB) reactor was combined with a mesophilic aerobic uidized bed (AFB) reactor for treatment of a medium strength wastewater with 2,700 mg COD l )1 . The COD removal ef®ciency reached 75% with a removal rate of 0.2 g COD l )1 h )1 at an overall hydraulic retention time 14 hours. The distribution of microbial activity and its change with hydraulic retention time in the two reactors were investigated by measuring ATP concentration in the reactors and speci®c ATP content of the biomass. In the UASB reactor, the difference in speci®c ATP was signi®cant between the sludge bed and blanket solution (0.02 mg ATP g VS )1 versus 0.85 mg ATP g VS )1 ) even though the ATP concentrations in these two zones were similar. A great pH gradient up to 4 was developed along the UASB reactor. Since a high ATP or biological activity in the blanket solution could only be maintained in a narrow pH range from 6.5 to 7.5, the sludge granules showed a high pH tolerance and buffering capacity up to pH 11. The suspended biomass in AFB reactor had a higher speci®c ATP than the biomass ®xed in polyurethane carriers (1.6 mg ATP g VS )1 versus 1.1 mg ATP g VS )1 ), which implies a starvation status of the immobilized cells due to mass transfer limitation. The aerobes had to work under starvation conditions in this polishing reactor. The anaerobic biomass brought into AFB reactor contributed to an increase in suspended solids, but not the COD removal because of its fast deactivation under aerobic conditions. A second order kinetic model was proposed for ATP decline of the anaerobes. The results on distribution of microbial activity in the two reactors as well as its change with hydraulic retention time lead to further performance improvement of the combined anaerobic/aerobic reactor system.
Controllable Self-organization of Polyphenylene Oxide Honeycomb MicrostructurePolymer films with patterned microstructure have been widely applied in various industrial areas such as micro reactors, chemical sensors and micro-molded template etc. In this paper, a self-supporting polymer film with regular honeycomb microstructure is fabricated by self-organization via evaporation of polyphenylene oxide (PPO) solution in which carbon disulfide is used as solvent under humid ambience. Apart from investigation of self-organization mechanism of PPO honeycomb including nucleation, growth of water droplets condensed upon liquid supporting substrate, the quantitative relationship between honeycomb microstructure and ambient conditions is built through tremendous self-organization experiments. The controllable formation of honeycomb microstructure with desirable hydrophobicity was achieved by use of built quantitative relationship. Moreover, hydrophobicity mathematical model of self-organized honeycomb thin film was proposed, and its validation was experimentally verified.
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