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Development and Validation of New Reverberation Chamber for Wireless Devices
Sim, Dong-Uk,Kwak, Sang Il,Kwon, Jong Hwa,Park, Seong-Ook WILEY INTERSCIENCE 2018 WIRELESS COMMUNICATIONS AND MOBILE COMPUTING Vol.2018 No.-
<P>This paper proposes a reverberation chamber structure consisting of new reflectors and mode stirrers for electromagnetic compatibility and wireless terminal measurements. The key design considerations for them are determined through a reasonable approach to analyze the eigenmode for a reverberation chamber and the standard deviation of its working volume based on 3D simulation. The final designs are expected to improve the standard deviation performance of the initial structure of the reverberation chamber and provide a better mode stirring environment. The results measured in the fabricated chamber demonstrate that these predictions are clearly realized. The results satisfy the main requirements of this paper, which are defined in consideration of the specifications of commercial reverberation chamber products. Therefore, the reverberation chamber of this paper is expected to be useful for performance measurement and evaluation of commercial wireless terminals. To verify this logical approach to obtain a good design and its results, the results measured in the actual fabricated reverberation chamber are described along with analytical and computational results.</P>
Sim, Uk,Moon, Joonhee,Lee, Joohee,An, Junghyun,Ahn, Hyo-Yong,Kim, Dong Jin,Jo, Insu,Jeon, Cheolho,Han, Seungwu,Hong, Byung Hee,Nam, Ki Tae American Chemical Society 2017 ACS APPLIED MATERIALS & INTERFACES Vol.9 No.4
<P>Photoelectrochemical cells are used to split hydrogen and oxygen from water molecules to generate chemical fuels to satisfy our ever-increasing energy demands. However, it is a major challenge to design efficient catalysts to use in the photoelectochemical process. Recently, research has focused on carbon-based catalysts, as they are nonprecious and environmentally benign. Interesting advances have also been made in controlling nanostructure interfaces and in introducing new materials as catalysts in the photoelectrochemical cell. However, these catalysts have as yet unresolved issues involving kinetics and light-transmittance. In this work, we introduce high-transmittance graphene onto a planar p-Si photocathode to produce a hydrogen evolution reaction to dramatically enhance photon-to-current efficiency. Interestingly, double-layer graphene/Si exhibits noticeably improved photon-to-current efficiency and modifies the band structure of the graphene/Si photocathode. On the basis of in-depth electrochemical and electrical analyses, the band structure of graphene/Si was shown to result in a much lower work function than Si, accelerating the electron-to-hydrogen production potential. Specifically, plasma-treated double-layer graphene exhibited the best performance and the lowest work function. We electrochemically analyzed the mechanism at work in the graphene-assisted photoelectrode. Atomistic calculations based on the density functional theory were also carried out to more fully understand our experimental observations. We believe that investigation of the underlying mechanism in this high-performance electrode is an important contribution to efforts to develop high-efficiency metal-free carbon-based catalysts for photoelectrochemical cell hydrogen production.</P>