The stability of graphene band structures against an external periodic perturbation; Na on Graphene

We report that the $\pi$ band of graphene sensitively changes as a function of an external potential induced by Na especially when the potential becomes periodic at low temperature. We have measured the band structures from the graphene layers formed on the 6H-SiC(0001) substrate using angle-resolved photoemission spectroscopy with synchrotron photons. With increasing Na dose, the $\pi$ band appears to be quickly diffused into background at 85 K whereas it becomes significantly enhanced its spectral intensity at room temperature (RT). A new parabolic band centered at $k\sim$1.15 \AA$^{-1}$ also forms near Fermi energy with Na at 85 K while no such a band observed at RT. Such changes in the band structure are found to be reversible with temperature. Analysis based on our first principles calculations suggests that the changes of the $\pi$ band of graphene be mainly driven by the Na-induced potential especially at low temperature where the potential becomes periodic due to the crystallized Na overlayer. The new parabolic band turns to be the $\pi$ band of the underlying buffer layer partially filled by the charge transfer from Na adatoms. The five orders of magnitude increased hopping rate of Na adatoms at RT preventing such a charge transfer explains the absence of the new band at RT.Comment: 6 pages and 6 figure

Use of Microalgae for Advanced Wastewater Treatment and Sustainable Bioenergy Generation

Given that sustainable energy production and advanced wastewater treatment for producing clean water are two major challenges faced by modern society, microalgae make a desirable treatment alternative by providing a renewable biomass feedstock for biofuel production, while treating wastewater as a growth medium. Microalgae have been known to be resilient to the toxic contaminants of highly concentrated organic wastewater (e.g., organic nitrogen, phosphorus, and salinity) and are excellent at sorbing heavy metals and emerging contaminants. Economic and environmental advantages associated with massive algae culturing in wastewater constitute a driving force to promote its utilization as a feedstock for biofuels. However, there are still many challenges to be resolved which have impeded the development of algal biofuel technology at a commercial scale. This review provides an overview of an integrated approach using microalgae for wastewater treatment, CO2 utilization, and biofuel production. The main goal of this article is to promote research in algae technologies by outlining critical needs along the integrated process train, including cultivation, harvesting, and biofuel production. Various aspects associated with design challenges of microalgae production are described and current developments in algae cultivation and pretreatment of algal biomass for biofuel production are also discussed. Furthermore, synergistic coupling of the use of microalgae for advanced wastewater treatment and biofuel production is highlighted in a sustainability context using life cycle analysis.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/140370/1/ees.2016.0132.pd

Paper on a disc: balancing the capillary-driven flow with a centrifugal force

This paper describes the active control of the capillary-driven flow in paper using a centrifugal device.close191

High-Temperature Corrosion Behaviors of Structural Materials for Lead-Alloy-Cooled Fast Reactor Application

The corrosion of nuclear-grade steels in lead-bismuth eutectic (LBE) complicates the realization of high coolant temperatures. Corrosion tests of T91, HT9, and SS316L were performed in static cells at 600 degrees C for 2000 h at an oxygen level of 10(-6) wt.%. The obtained corrosion surfaces of post-processed samples were characterized by several microscopy methods. Up to 1000 h, all the alloys exhibited an evolution of duplex oxide layers, which were spalled until 2000 h due to their increased thickness and decreased integrity. Following the spallation, a thin internal Cr-rich oxide layer was formed above the Cr-depleted zone for T91 and HT9. SS316L was penetrated by LBE down to 300 mu m in severe cases. A comparison on the corrosion depths of the materials with regard to the parabolic oxidation law with abundant literature data suggests that it may lose its validity once the duplex layer is destroyed as it allows LBE to penetrate the metal substrate

Coexistence of WiFi and WiMAX Systems Based on PS-Request Protocols†

We introduce both the coexistence zone within the WiMAX frame structure and a PS-Request protocol for the coexistence of WiFi and WiMAX systems sharing a frequency band. Because we know that the PS-Request protocol has drawbacks, we propose a revised PS-Request protocol to improve the performance. Two PS-Request protocols are based on the time division operation (TDO) of WiFi system and WiMAX system to avoid the mutual interference, and use the vestigial power management (PwrMgt) bit within the Frame Control field of the frames transmitted by a WiFi AP. The performance of the revised PS-Request protocol is evaluated by computer simulation, and compared to those of the cases without a coexistence protocol and to the original PS-Request protocol