In this paper, We has been studied the lifetime degradation of LED lighting system compared to MH lighting. Especially the effect of temperature level on the lifetime degradation has been investigated. The results show that temperature plays a role in the lifetime degradation and slope of degradation line represent as temperature level differently. However, It is possible to estimate the lifetime of LED lighting system using equation induced the slope of degradation line.

Degradation

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Electronic-dimensionality reduction of bulk MoS₂ by hydrogen treatment

Physical Chemistry Chemical Physics (2018)

Soohyun Cho Beom Seo Kim Beomyoung Kim Wonshik Kyung Jeongjin Seo

A reduction in the electronic-dimensionality of materials is one method for achieving improvements in material properties. Here, a reduction in electronic-dimensionality is demonstrated using a simple hydrogen treatment technique. Quantum well states from hydrogen-treated bulk 2H-MoS2 are observed using angle resolved photoemission spectroscopy (ARPES). The electronic states are confined within a few MoS2 layers after the hydrogen treatment. A significant reduction in the band-gap can also be achieved after the hydrogen treatment, and both phenomena can be explained by the formation of sulfur vacancies generated by the chemical reaction between sulfur and hydrogen.

10.1039/c8cp02365d

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Electronic structure of LiFe 1 - x Mn x As (x = 0, 0.04)

APS (2015)

Jeongjin Seo Bumsung Lee Kee Hoon Kim Changyoung Kim

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Possible electric field induced indirect to direct band gap transition in MoSe$_{\mathrm{2}}$

Bulletin of the American Physical Society (2017)

Beom Seo Kim Wonshik Kyung Jeongjin Seo Junyoung Kwon Changyoung Kim

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Electron Number-Based Phase Diagram of Pr1−xLaCexCuO4−δ…

Physical Review Letters (2017)

Dongjoon Song Garam Han Wonshik Kyung Jeongjin Seo Soohyun Cho

We performed annealing and angle resolved photoemission spectroscopy studies on electron-doped cuprate ${\mathrm{Pr}}_{1\ensuremath{-}x}{\mathrm{LaCe}}_{x}{\mathrm{CuO}}_{4\ensuremath{-}\ensuremath{\delta}}$ (PLCCO). It is found that the optimal annealing condition is dependent on the Ce content $x$. The electron number ($n$) is estimated from the experimentally obtained Fermi surface volume for $x=0.10$, 0.15 and 0.18 samples. It clearly shows a significant and annealing dependent deviation from the nominal $x$. In addition, we observe that the pseudo-gap at hot spots is also closely correlated with $n$; the pseudogap gradually closes as $n$ increases. We established a new phase diagram of PLCCO as a function of $n$. Different from the $x$-based one, the new phase diagram shows similar antiferromagnetic and superconducting phases to those of hole doped ones. Our results raise a possibility for absence of disparity between the phase diagrams of electron- and hole-doped cuprates

Pseudogap

10.1103/physrevlett.118.137001

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A New Grid Voltage Compensated Model Predicted Control for BESS PCS

2021 24th International Conference on Electrical Machines and Systems (ICEMS) (2022)

Jeongjin Seo Hanju Cha

A large power capacity power conditioning system for battery energy storage system operates at a low switching frequency due to limitation of power semiconductor devices. In this paper, a current control method of PCS operating with a low switching frequency of 600Hz and a sampling frequency of 1. 2kHz is studied. When operating at the low switching frequency, phase of the grid voltage shifts by 18 ° during one sampling period, and a new voltage compensation method is proposed. The experimental results show that current error is reduced to 1. 87A from 3. 86A, and effectiveness of the proposed method is confirmed.

Frequency grid

10.1109/icems56177.2022.9983083

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