Dephasing by time-dependent random potentials

Diffusion of electrons in a two-dimensional system with time-dependent random potentials is investigated numerically. The correction to the conductivity due to inelastic scatterings by oscillating potentials is shown to be a universal function of the frequency $\omega$, which is consistent with the weak localization prediction $(e^2)/(3\pi^2 \hbar) log \omega$.Comment: 4 pages, RevTeX, 3 postscript figures, accepted in J. Phys. Soc. Jpn.(1997)Ap

Interface Landau levels in graphene monolayer-bilayer junction

Electronic structure of graphene monolayer-bilayer junction in a magnetic field is studied within an effective-mass approximation. The energy spectrum is characterized by interface Landau levels, i.e., the locally flat bands appearing near the boundary region, resulting in a series of characteristic peaks in the local density of states. Their energies are independent of boundary types such as zigzag or armchair. In the atomic scale, the local density of states shows a Kekul\'{e} pattern due to the valley mixing in the armchair boundary, while does not in the zigzag boundary.Comment: 12 pages, 9 figure

Numerical Study of Inelastic Scatterings by Time-Dependent Random Potentials in Two-Dimensional Systems

Diffusion of electrons in a two-dimensional system with time-dependent random potentials is investigated numerically. In the absence of spin-orbit scattering, the conductivity shows universal weak localization correction. In the presence of it, however, the correction to the conductivity weakly depends on the strength of disorder, and becomes vanishingly small close to the metal-insulator transition point.Comment: 4 pages, 2 figures, Physica B in press, Proceedings for EP2DS-1

Mixing and Microbial Kinetics of Activated Sludge Process

In the activated sludge process, the characteristics of qualitative response observed in the aerator effluent depends largely on the induced microbiological reaction and the pattern of mixing. The latter controls the “age” distribution of mixing liquor. Authors introduced first two kinds of mixing model, one of which is modified complete mixed type and another is to apply for any intermediate mixing condition between complete mixing and plug flow, in order to explain the pattern of flow in the aeration tank. This serves especially for the investigation of microbiological characteristics of conventional and step aeration process. Next, the kinetics of microbial reaction was studied, referring to the previous formulation treating the metabolism of single substrate-organism combination, considering the significance of BOD5 while using it as index of amount of compounded substrates in the sewage ; consequently the over-all effect of miscellaneous sludge organisms was attributed to the term of activity, by which the modified mathematical representation of reaction for such mixed-culture system was proposed. Finally, the authors showed the possibility of calculating exact change in substrate concentration of the effluent by means of computations combining any proposed mixing model with reaction formula. For example, in case of zero- and first-order microbial reaction, the response in effluent substrate concentration was computed and summarized