Influence of vehicle source directivity in Japanese and European outdoor sound prediction models under a semi-finite thick barrier configuration

The Japanese ASJ RTN-Model 2018, European Harmonoise and CNOSSOS-EU outdoor sound prediction models are respectively known to have symmetric, asymmetric and omnidirectional sound emission directivities along front-back direction of the source vehicle. However, the influence of such difference in directivities to final predicted sound levels has not been investigated much. In this study, the influence is investigated using the ASJ Model and the Harmonoise under a configuration of semi-finite thick barrier along a source road. The configuration is an idealization of Japanese roadside buildings that have gaps in between, unlike European buildings that continuously extend over a whole urban block. Under the configuration, distribution of A-weighted sound levels around the end face of the barrier are computed with and without source directivity taken into account by each model. It is found from the results that the source directivity of the ASJ model makes little difference in the noise level distribution. In contrast, the source directivity of Harmonoise is found to make differences of 0.5-0.8 dB at right behind the barrier depending on vehicle running direction. However, a combined effect of source directivity and reflection at the end face is found to be negligible.

Tuning electron correlation in magic-angle twisted bilayer graphene using Coulomb screening

Controlling the strength of interactions is essential for studying quantum phenomena emerging in systems of correlated fermions. We introduce a device geometry whereby magic-angle twisted bilayer graphene is placed in close proximity to a Bernal bilayer graphene, separated by a 3-nanometer-thick barrier. By using charge screening from the Bernal bilayer, the strength of electron-electron Coulomb interaction within the twisted bilayer can be continuously tuned. Transport measurements show that tuning Coulomb screening has opposite effects on the insulating and superconducting states: As Coulomb interaction is weakened by screening, the insulating states become less robust, whereas the stability of superconductivity at the optimal doping is enhanced. The results provide important constraints on theoretical models for understanding the mechanism of superconductivity in magic-angle twisted bilayer graphene.

Characterization of Ba-Introduced Thin Gate Oxide on 4H-SiC

A thickness of Ba-introduced gate oxide was controlled with the oxygen concentration and a barrier layer thickness at a post-deposition annealing. The oxidation rate becomes slower with the low oxygen concentration and the thick barrier layer, and the thin oxide of 12 nm was realized with O2 5% and 9 nm of the barrier layer. This Ba-introduced thin gate oxide resulted in the field effect mobility of 13 cm2/Vs and the interface state density of 2×1011 cm-2eV-1 at 0.25 eV below the conduction band edge of 4H-SiC.

Role of barrier layer in the developing phase of “Category 6” super typhoon Haiyan

With the remarkable intensity of 170 knots, Typhoon Haiyan starts as a tropical depression on November 3 and develops to the peak as super tropical cyclone (TC) on November 7 in 2013. This intensity makes Haiyan one of the strongest TCs record ever observed and 35 knots higher than the maximum of the existing highest category. Haiyan originated from the eastern part of the Northwest Pacific Warm Pool and moved westward over warm water with a thick barrier layer (BL). The BL reduced the vertical mixing and entrainment caused by Haiyan and prevented the cold thermocline water into the mixed layer (ML). As a result, sea temperature cooling associated with wind stirring was suppressed. Relative high sea surface temperature (SST) kept fueling Haiyan via latent heat flux release, which favored the rapid development of a “Category 6” super typhoon.