http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
Dongki Choi,Hun Lee,Sung‑Kyu Cho,Hyoung Chan Kim,Soong‑Keun Hyun,Sang Yong Shin 대한금속·재료학회 2020 METALS AND MATERIALS International Vol.26 No.6
In this study, heat affected zone (HAZ) specimens were fabricated by applying flux-cored arc welding (FCAW) and submergedarc welding (SAW) processes to steel plate with a thickness of 100 mm and yield strength of 460 MPa for use in offshoreplatforms. The correlation between microstructure and Charpy absorbed energy was investigated, and fracture mechanismswere analyzed. As distance from the fusion line increases, heat input and cooling rate decrease, making it difficult to formlow-temperature transformation microstructures in HAZ specimens and increasing the grain size of quasi-polygonal ferrite. The FCAW process is advantageous for low-temperature transformation microstructures because it has a lower heat inputand a faster cooling rate than the SAW process. Plastic deformation and ductile fracture occurred at low temperatures infine acicular ferrite and quasi-polygonal ferrite regions of HAZ specimens, but brittle fractures occurred in bainitic ferrite,granular bainite, and coarse quasi-polygonal ferrite regions. The unit crack path in the brittle fracture region was similar tothe grain size. In other words, as the volume fraction of fine acicular ferrite and quasi-polygonal ferrite increased in HAZspecimens, Charpy absorbed energy at low temperature increased.
Hamamelis virginiana Extract Protects from PM<SUB>2.5</SUB>-induced Inflammation via PAR-2 Signaling
Jiyoung CHOI,Gi-Yeon HAN,Dongki YANG,Joonseok CHA 한국생물공학회 2021 한국생물공학회 학술대회 Vol.2021 No.10
Dietary supplements and personal care products to protect from air pollution have been of great interest for decades. Epidemiology demonstrated that particulate matters (PM10 and PM2.5) are an actual threat to public health worldwide, but the detailed processes that these particles attack the cells are not fully understood. Here, we report that measuring intracellular calcium concentration ([Ca<SUP>2+</SUP>]i) in human respiratory or skin cells can illustrate pollutant challenges by triggering Ca<SUP>2+</SUP> influx in these cells. This signal was generated by protease-activated receptor-2 (PAR-2), confirmed by competition analyses, and the extract of Hamamelis virginiana (HVE), a native herb of North America, was able to control the calcium response and the expression of PAR-2. The increase of nuclear factor-kappa B (NF-κB), and the decrease of cell adhesion components could address severe damage status by air pollutants and the protection by HVE. Also, it was confirmed that HVE effectively inhibited ROS induced by UVB. The results presented here should help understand the underlying mechanism of PM insults and the beneficial effect of standardized HVE as a dietary supplement or cosmetical ingredient.
Cosolvent System에서 이온성 유기화합물의 생분해 및 흡착 특성
최정민 ( Jeongmin Choi ),윤홍진 ( Hongjin Yun ),오동기 ( Dongki Oh ) 한국환경농학회 2023 한국환경농학회 학술대회집 Vol.2023 No.0
The existing cosolvency-induced sorption model, which is used to predict the fate of organic solutes in a cosolvent system, is not capable of completely explaining the effects of various interactions between solutes, solvents, and sorbents. Hence, this study aims to evaluate the effect of functional groups and aromatic rings on sorption onto activated carbon in a methanol-water system. The experiment was conducted on a hybrid bioreactor, which consists of a Sorption module and a biodegradation module, was investigated for the enhanced treatment of a organic acid mixture. Benzoic acid, 1-naphthoic acid, and 9-anthroic acid were chosen as organic sorbates, and activated carbon was used as the sorbent. We also summarized information on the biodegradation of each kind of organic acids under cosolvent system. As the microbial population increases, it shows high organic acids removal efficiency. The equilibrium concentrations were analyzed via GC-FID. As explained by the existing cosolvency model, for organic acids at pH 3 (i.e., pK<sub>a</sub>>pH) and pH 7 (i.e., pK<sub>a</sub><pH), the sorption (K<sub>m</sub>) of organic acids decreased on adding methanol. On the other hand, this study showed unexpected results that do not consistent with the existing cosolvency model. At pH 7 for the CaCl<sub>2</sub> system, K<sub>m</sub> increases with increasing methanol volume fractions. A decrease in the dielectric constant of the liquid phase, caused by the presence of methanol, might result in an increase in K<sub>m</sub>. Regardless of the cosolvency power (σ), as the number of aromatic rings in the solute increases, K<sub>m</sub> is reduced in the order of benzoic acid > 1-naphthoic acid > 9-anthroic acid. In order to accurately predict the fate of acidic solutes in a variety of environment, studies for quantitatively estimating of effects of various interaction on the sorption should be conducted. Through the studies the current cosolvency induced sorption model can be advanced.
LYOO, YOUNGSOO,PARK, DONGKI,LEE, SANGMOK,CHOI, YIDON,JUNG, JIHYUN,JUN, TAEIL,AHN, HONGSUK,LEE, CHUL-HOON,LIM, YOONGHO 한국미생물 · 생명공학회 2001 Journal of microbiology and biotechnology Vol.11 No.2
Porcine pneumonia is caused by Pasturella multocida and Actinobacillus pleuropneumoniae. To identify a potent drug for antipneumonia therapy, several herbal compounds showing antibacterial effects were screened, and it was found that a methanol extract of Coptidis rhizoma root stem exhibited activity against both pneumonia-causing bacteria. Using an activity-guided fragmentation procedure, an isoquinoline alkaloid was isolated which would be responsible for the antibacterial activities against P. multocida and A. pleuropneumoniae.
Synthesis of Ultrathin Si Nanosheets from Natural Clays for Lithium-Ion Battery Anodes
Ryu, Jaegeon,Hong, Dongki,Choi, Sinho,Park, Soojin American Chemical Society 2016 ACS NANO Vol.10 No.2
<P>Two-dimensional Si nanosheets have been studied as a promising candidate for lithium-ion battery anode materials. However, Si nanosheets reported so far showed poor cycling performances and required further improvements. In this work, we utilize inexpensive natural clays for preparing high quality Si nanosheets via a one-step simultaneous molten salt-induced exfoliation and chemical reduction process. This approach produces high purity mesoporous Si nanosheets in high yield. As a control experiment, two-step process (pre-exfoliated silicate sheets and subsequent chemical reduction) cannot sustain their original two-dimensional structure. In contrast, one-step method results in a production of 5 nm-thick highly porous Si nanosheets. Carbon-coated Si nanosheet anodes exhibit a high reversible capacity of 865 mAh g(-1) at 1.0 A g(-1)-with an outstanding capacity retention of 92.3% after 500 cycles. It also delivers high rate capability, corresponding to a capacity of 60% at 20 A g(-1) compared to that of 2.0 A g(-1). Furthermore, the Si nanosheet electrodes show volume expansion of only 42% after 200 cycles.</P>