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Kim, Hyeongi,Kim, MinJung,Yoon, Young Hoon,Nguyen, Quoc Hai,Kim, Il Tae,Hur, Jaehyun,Lee, Seung Geol Elsevier 2019 ELECTROCHIMICA ACTA Vol.293 No.-
<P><B>Abstract</B></P> <P>A nanocomposite comprised of a bimetallic alloy of antimony (III) telluride embedded in a hybrid matrix of titanium carbide with amorphous carbon is synthesized via facile, scalable, and inexpensive high energy mechanical milling. The Sb<SUB>2</SUB>Te<SUB>3</SUB>-TiC-C nanocomposite is composed of nanosized Sb<SUB>2</SUB>Te<SUB>3</SUB> and TiC particles homogeneously dispersed in amorphous carbon, as characterized by X-ray diffraction and high-resolution transmission electron microscopy. Electrochemical measurements show that the Sb<SUB>2</SUB>Te<SUB>3</SUB>-TiC-C exhibits enhanced electrochemical reversibility, great cyclability, and high-rate capability compared to Sb<SUB>2</SUB>Te<SUB>3</SUB>-C and Sb<SUB>2</SUB>Te<SUB>3</SUB>. Additionally, the optimum TiC content is determined based on electrochemical performances. Among all Sb<SUB>2</SUB>Te<SUB>3</SUB>-TiC-C nanocomposites tested, Sb<SUB>2</SUB>Te<SUB>3</SUB>-TiC(30%)-C exhibits the best performances in terms of reversible volumetric capacity (463 mAh cm<SUP>−3</SUP> over 600 cycles, 80% retention) and high rate capability (5000 mA g<SUP>−1</SUP>, 80% of its capacity at 100 mA g<SUP>−1</SUP>). The improvement of electrochemical performance with optimal TiC content is attributed to the appropriate amount of TiC-C that acted as a mechanical buffer and highly conductive matrix during cycling while minimizing capacity sacrifices. The mechanism of lithium ion storage on Sb and Te in Sb<SUB>2</SUB>Te<SUB>3</SUB>-TiC-C is also investigated during the charge/discharge process.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Sb<SUB>2</SUB>Te<SUB>3</SUB>-TiC-C nanocomposite was synthesized by heat treatment and HEMM. </LI> <LI> Employment of TiC into Sb<SUB>2</SUB>Te<SUB>3</SUB>-C improved electrochemical performances. </LI> <LI> Sequential reactions between Sb or Te and Li + mitigates volume change. </LI> <LI> Optimum TiC content in nanocomposite was further determined experimentally. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>Nanocomposite of Sb<SUB>2</SUB>Te<SUB>3</SUB>-TiC-C is synthesized via a simple and scalable high-energy mechanical milling process and heat treatment as a high-performance anode material for lithium-ion batteries. The appropriate amount of TiC formation into Sb<SUB>2</SUB>Te<SUB>3</SUB>-C significantly improves the electrochemical performances.</P> <P>[DISPLAY OMISSION]</P>
Kim, Hyeongi,Nguyen, Quoc Hai,Kim, Il Tae,Hur, Jaehyun Elsevier 2019 APPLIED SURFACE SCIENCE - Vol.481 No.-
<P><B>Abstract</B></P> <P>Molybdenum diselenide-based carbon composites were prepared by a high-energy mechanical milling (HEMM) for anodes in lithium-ion batteries. In this paper, we have reported the effect of the type of carbonaceous matrix, for example, 2D graphite, 1D carbon nanotube, and 0D amorphous carbon, on the performance of MoSe<SUB>2</SUB>-carbon nanocomposite anodes. The combination of MoSe<SUB>2</SUB> and graphite showed the best electrochemical performance in terms of cycling stability and rate capability. This improvement is associated with the increased surface area along both lateral and vertical directions of MoSe<SUB>2</SUB>, and effective mixing between MoSe<SUB>2</SUB> and graphite due to HEMM. The facile exfoliation, size reduction, and homogeneous mixing of MoSe<SUB>2</SUB> upon the addition of graphite, were characterized by XRD, Raman spectroscopy, BET, SEM, and TEM. The MoSe<SUB>2</SUB>-graphite nanocomposite ((2D)MoSe<SUB>2</SUB>@(2D)Gr) exhibited enhanced Li storage (a reversible discharge capacity of 909 mAh g<SUP>−1</SUP> at 100 mA g<SUP>−1</SUP> after 200 cycles) and rate performance (611 mAh g<SUP>−1</SUP> at a current density of 3 A g<SUP>−1</SUP>) as compared to other MoSe<SUB>2</SUB>-carbon nanocomposites, as well as pure MoSe<SUB>2</SUB>. The reduced charge transfer resistance, increased diffusivity, and improved mechanical stability as confirmed by electrochemical impedance spectroscopy (EIS) and ex-situ SEM, further served to demonstrate the superiority of the (2D)MoSe<SUB>2</SUB>@(2D)Gr electrode.</P> <P><B>Highlights</B></P> <P> <UL> <LI> MoSe<SUB>2</SUB>@graphite (MoSe<SUB>2</SUB>@Gr) nanocomposite was developed by HEMM for anodes in LIBs. </LI> <LI> Surface area increase and well-mixing between MoSe<SUB>2</SUB> and graphite were confirmed. </LI> <LI> Excellent electrochemical performances of MoSe<SUB>2</SUB>@Gr were demonstrated. </LI> <LI> Optimum milling time was further investigated to improve the performances. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
김현기(Hyeongi Kim),최용민(Youngmin Choi),조영숙(Young-Sook Cho),성지혜(Jeehye Sung),함현미(Hyeonmi Ham),이준수(Junsoo Lee) 한국식품영양과학회 2014 한국식품영양과학회지 Vol.43 No.11
본 연구에서는 HPLC를 사용하여 채소류 식품군에서 비타민 K1의 분석법을 확립하고 이에 대한 분석법 검증하고자 하였다. 그 결과 본 시험법에서 표준용액의 피크유지시간과 부추 추출액의 피크유지시간이 일치하여 특이성을 확인하였다. 검량선의 상관계수(R<SUP>2</SUP>)는 0.9994 이상으로 높은 유의 수준을 보여 분석에 적합함을 알 수 있었으며, 검출한계는 0.1335 ng/injection volume(50 μL)이었고 정량한계는 0.2784 ng/injection volume(50 μL)으로 설정되었다. 일내, 일간분석에서 정밀도를 나타내는 변동계수(coefficient variation, CV)는 표준용액에서 각각 1.979%, 2.107%로 나타내었고 정확성은 99.439%로 나타내어 채소류에서 비타민 K1의 분석법이 적합한 시험법임이 검증되었다. 본 분석법에 따라 채소류의 비타민 K1을 분석한 결과 식품공전의 효소를 이용한 분석법보다 더 높은 추출률을 나타내었으며 다른 물질의 간섭 없이 분석 가능하여 채소류의 비타민 K1의 검출에 응용되어 이용될 수 있을 것으로 판단된다. The objective of this study was to compare two extraction methods for determination of vitamin K1(phylloquinone) in vegetables. In addition, analytical method validation parameters such as accuracy, precision, limit of detection (LOD), limit of quantification (LOQ), and linearity were calculated to ensure the method"s validity. Vitamin K1 was quantified by reversed-phase HPLC using post-column derivatization and fluorescence detection (Exλ=243 nm, Emλ=430 nm). Higher analytical values were observed using solvent extraction compared to those from the enzyme extraction method. The results from the method validation showed high linearity in the calibration curve with a coefficient of correlation (R<SUP>2</SUP>) of 0.9994. The LOD and LOQ were 0.1335 and 0.2784 ng/injection volume (50 μL), respectively. The inter-day precision and inter-day precision were 2.0% and 2.1%, respectively. Overall recovery was close to 100% (n=5). The phylloquinone contents ranged from 9.42 to 1,212.57 μg/100 g. Our study provides reliable data on the phylloquinone contents in commonly consumed vegetables in Korea.
김현기(Hyeongi Kim),김병민(Byeongmin Kim),백인수(Insu Paek),유능수(Neungsoo Yoo) 대한기계학회 2011 대한기계학회 춘추학술대회 Vol.2011 No.5
In this study, a sensitivity analysis was performed to see how the true north error of a wind vane installed to meteorological mast affects predictions of the wind speed and the annual energy production. Cross predictions of the wind speed and the AEP of a wind turbine for sites A and B in complex terrain were performed by changing the wind direction from -45° to 45° with an interval of 5°. A commercial wind resource prediction program, WindPRO, was used for this study. It was found that the prediction errors in the AEP caused by the wind direction errors occurred up to more than 20% according to the orography and the prevailing wind direction at that site.
Jo, Yunhui,Kim, Eun Ho,Sai, Sei,Kim, Jin Su,Cho, Jae-Min,Kim, Hyeongi,Baek, Jeong-Hwa,Kim, Jeong-Yub,Hwang, Sang-Gu,Yoon, Myonggeun MDPI 2018 INTERNATIONAL JOURNAL OF MOLECULAR SCIENCES Vol.19 No.11
<P>Glioblastoma, the most common primary brain tumor in adults, is an incurable malignancy with poor short-term survival and is typically treated with radiotherapy along with temozolomide. While the development of tumor-treating fields (TTFields), electric fields with alternating low and intermediate intensity has facilitated glioblastoma treatment, clinical outcomes of TTFields are reportedly inconsistent. However, combinatorial administration of chemotherapy with TTFields has proven effective for glioblastoma patients. Sorafenib, an anti-proliferative and apoptogenic agent, is used as first-line treatment for glioblastoma. This study aimed to investigate the effect of sorafenib on TTFields-induced anti-tumor and anti-angiogenesis responses in glioblastoma cells in vitro and in vivo. Sorafenib sensitized glioblastoma cells to TTFields, as evident from significantly decreased post-TTFields cell viability (<I>p</I> < 0.05), and combinatorial treatment with sorafenib and TTFields accelerated apoptosis via reactive oxygen species (ROS) generation, as evident from Poly (ADP-ribose) polymerase (PARP) cleavage. Furthermore, use of sorafenib plus TTFields increased autophagy, as evident from LC3 upregulation and autophagic vacuole formation. Cell cycle markers accumulated, and cells underwent a G2/M arrest, with an increased G0/G1 cell ratio. In addition, the combinatorial treatment significantly inhibited tumor cell motility and invasiveness, and angiogenesis. Our results suggest that combination therapy with sorafenib and TTFields is slightly better than each individual therapy and could potentially be used to treat glioblastoma in clinic, which requires further studies.</P>
김병민(Byeongmin Kim),김현기(Hyeongi Kim),백인수(Insu Paek),유능수(Neungsoo Yoo) 대한기계학회 2011 대한기계학회 춘추학술대회 Vol.2011 No.5
Wind resource estimation at the East sea of Korea was performed. The two NCAR satellite wind data sets measured for five years from 2005 to 2009 were used for the prediction of the wind resource of the East sea. For the wind resource map, a commercial program world-widely used for the wind resource prediction was used. Based on the simulation results, it was found that the sea near Pohang and Ulsan has higher wind resources compared with other regions considered. Also, based on the wind resource and the capacity factors predicted, the sea outside the harbor of Pohang is considered to be economically viable for an offshore wind farm if it is constructed with wind turbines having a hub height of 100m or higher.