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Choi, Jonghyun,Kim, Won-Sik,Hong, Seong-Hyeon The Royal Society of Chemistry 2018 Nanoscale Vol.10 No.9
<P>SnO2-Fe2O3-C triple-shell hollow nano-spheres are fabricated by combining the template-based sol-gel coating technique and hydrothermal method, and their electrochemical performance as an anode for lithium ion batteries (LIBs) is investigated, particularly focusing on their structural stability and long term cyclability. To accomplish this, same-sized SnO2solid spheres, Fe2O3solid spheres, SnO2-Fe2O3solid spheres, SnO2-Fe2O3-C solid spheres, SnO2hollow spheres and SnO2-Fe2O3hollow spheres are prepared in a similar manner and their cyclic performances are compared. It is found that the as-synthesized 80 nm-sized SnO2-Fe2O3-C hollow sphere electrode exhibits an extraordinary reversible capacity (1100 mA h g<SUP>−1</SUP>after 100 cycles at 200 mA g<SUP>−1</SUP>) and excellent long cycle stability (475 mA h g<SUP>−1</SUP>after 1000 cycles at 2000 mA g<SUP>−1</SUP>), which are attributed to the Fe-enhanced reversibility of the Li2O reduction reaction, high electrical conductivity, high Li<SUP>+</SUP>ion mobility, and structural stability of the carbon-coated triple-shell hollow spheres.</P>
Choi, Woo June,Na, Jihoon,Choi, Hae Young,Eom, Jonghyun,Lee, Byeong Ha IOP Pub 2010 Measurement Science and Technology Vol.21 No.4
<P>A novel optical interferometric scheme for ultrahigh-speed three-dimensional morphometry is proposed. The system is based on wide-field optical coherence tomography (WF-OCT) but with optically chopped illumination. The chopping frequency is feedback-controlled to be always matched with the Doppler frequency of the OCT interferometer, which provides an efficient page-wide demodulation suitable for ultrahigh-speed volumetric imaging. To compensate the unwanted variation in the OCT Doppler frequency of the system, the illumination frequency is phase-locked with an auxiliary laser interferometer which shares the reference arm with the OCT interferometer. The two-dimensional (2D) interference signals projected on the 2D array pixels of a 200 Hz CCD are accumulated during one imaging frame of the CCD. Then, each pixel of the CCD demodulates the OCT signal automatically. Owing to the proposed active frequency-locked illumination scheme, the demodulation does not depend on the variation in the axial scanning speed. Volumetric topograms or/and tomograms of several samples were achieved and rendered with a sensitivity of 58 dB at an axial scan speed of 0.805 mm s<SUP>−1</SUP>.</P>
Material and Structure analysis and Recycling Processing for Additional Obligation WEEE in 2020
( Jonghyun Choi ),( Insang Jung ),( Jihwan Park ),( Wonhee Choi ) 한국폐기물자원순환학회(구 한국폐기물학회) 2019 ISSE 초록집 Vol.2019 No.-
In 2020, EPR items and categories will be changed. Items are to be 50 from 27 and new categories will be determined. New categories could be similar to the WEEE 2 categories. There are 22 new items in EPR items such as navigation, scanner, electric massage apparatus, treadmill and sewing machine, etc. However, we don’t have any research (weight, composition and hazardous material etc.) about these items. It is necessary to analyse the recycling process (methods, standards, etc.) of the obligation WEEE (EPR items) to be recycled after 2020 (22 items to be added) for proper recycling. Therefore, we dismantled22 kinds of items manually (2~3 products each items) to analyze weight, composition, hazardous materials etc. As a result, average composition of items was Metal (32.6%), Plastic (3.69%), Component (24.9%) and Waste (5.6%). With those results, we found out that the most valuable item was treadmill (9,170 won/ea) and the least item was sewing machine (- 6,289 won/ea). It took the longest time to dismantle sewing machine. Moreover, we suggest efficient recycling method which is better: mechanical process or manual process each item. Most item could be recycled by mechanical process, but several items could not be used mechanical process, because of size, composition, structure and hazardous material (i.e., refrigerant). As this research is initial stage for new items, further research is necessary.
Choi, Jonghyun,Kim, Won-Sik,Kim, Kyeong-Ho,Hong, Seong-Hyeon The Royal Society of Chemistry 2018 Journal of materials chemistry. A, Materials for e Vol.6 No.36
<P>Tin phosphide (Sn4P3) has emerged as an anode for sodium ion batteries (SIBs) due to its high reversible capacity and low redox potential. Sn4P3 shows a synergistic Na-storage reaction to form Na15Sn4 and Na3P, but suffers from large volume expansion and Sn aggregation during the Na<SUP>+</SUP> insertion-extraction resulting in poor cycle stability. Sn4P3 has also been considered a promising anode material for lithium ion batteries (LIBs), but very limited studies have been performed. Herein, core-shell Sn4P3-C (carbon) composite nanospheres are fabricated by carbonization/reduction and phosphorization of SnO2-GCP (glucose-derived, carbon-rich polysaccharide) nanospheres. The size of Sn4P3-C nanospheres is controlled to optimize their electrochemical performance as long-term stable anodes for SIBs and LIBs. Among them, the 140 nm-sized Sn4P3-C nanosphere electrode exhibits high reversible capacity, high rate capability, and ultra-long cycle stability as an anode for both SIBs and LIBs, delivering a high capacity of 420 mA h g<SUP>−1</SUP> after 2000 cycles (SIBs) and 440 mA h g<SUP>−1</SUP> after 500 cycles (LIBs) at a high current density of 2000 mA g<SUP>−1</SUP>. Hence, the Sn4P3-C nanospheres can be considered as a promising anode material for next generation SIBs and LIBs.</P>
( Jonghyun Choi ),( Yongwoo Jang ),( Haedong Kim ),( Jungwon Wee ),( Sinyoung Cho ),( Woo Sung Son ),( Sung Min Kim ),( Young Duk Yang ) 생화학분자생물학회(구 한국생화학분자생물학회) 2018 BMB Reports Vol.51 No.5
Anoctamin 1 (ANO1) is an anion channel that is activated by changes in cytosolic Ca<sup>2+</sup> concentration and noxious heat. Although the critical roles of ANO1 have been elucidated in various cell types, the control of its gating mechanisms by Ca<sup>2+</sup> and heat remain more elusive. To investigate critical amino acid residues for modulation of Ca<sup>2+</sup> and heat sensing, we constructed a randomized mutant library for ANO1. Among 695 random mutants, reduced Ca<sup>2+</sup> sensitivity was observed in two mutants (mutant 84 and 87). Consequently, the E143A mutant showed reduced sensitivity to Ca<sup>2+</sup> but not to high temperatures, whereas the E705V mutant exhibited reduced sensitivity to both Ca<sup>2+</sup> and noxious heat. These results suggest that the glutamic acids (E) at 143 and 705 residues in ANO1 are critical for modulation of Ca<sup>2+</sup> and/or heat responses. Furthermore, these findings help to provide a better understanding of the Ca<sup>2+</sup>-mediated activation and heat-sensing mechanism of ANO1. [BMB Reports 2018; 51(5): 236-241]