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Kyuwon Han(Kyuwon Han),Soocheol Kim(Soocheol Kim),Hoesung Yang(Hoesung Yang),Kwang Soo Cho(Kwang Soo Cho),Kangbok Lee(Kangbok Lee),Ho-Sik Han(Ho-Sik Han) 한국화재소방학회 2022 International Journal of Fire Science and Engineer Vol.36 No.2
Photoelectric smoke detectors, which operate by reacting to the scattering of light caused by particles entering the light path, are widely used and extremely sensitive. Owing to higher standards imposed by Underwriters Laboratories, researchers have begun analyzing the properties of smoke particles. In particular, several wavelengths are used to classify particles by their scattering reactivity. The performances of actual smoke detectors are limited by their hardware and price. Therefore, properties that can distinguish particle types in these limited conditions must be determined. In addition, algorithms for extracting valid data intervals from unstable scattering data must be developed. In this study, scattering intensity ratios for three wavelengths are derived via simulations of light scattering by particles. An upper cumulative sum is defined for the three wavelengths, and an index for the start of particle inflow is extracted. In addition, valid intervals are extracted based on the scattering intensity ratios and the moving variance of adjacent wavelengths, and the properties of each particle are defined using the extracted indexes. For verification, a data acquisition device that can obtain data using the three selected wavelengths (470, 525, and 850 nm) from two sensors is designed. Five types of fire sources and non-fire alarm sources are selected and used in a test chamber designed to generate particle data. After applying the algorithm, the data in the valid data intervals can be used to derive a sample mean scattering intensity ratio that is more constant than that of the overall data or the data processed using the CUSUM index. In addition, the fire sources have a higher sample mean scattering intensity ratio than water vapor, which is a non-fire alarm source. The scattering intensity ratios for smoke particles can be extracted in real time via a comparison with experimental results obtained from the selected sensors.
Monte Carlo Study of Layered Heisenberg Ferromagnet
Kyuwon Lee 한국자기학회 2001 Journal of Magnetics Vol.6 No.4
Monte Carlo simulation was employed to study the phase transition in the classical Heisenberg ferromagnet with variable interlayer interactions. The measured transition temperatures show a strong logarithmic dependence on J/J', where J and J' are the intralayer and the interlayer exchange interaction, respectively. The results were compared with the theoretical expectations and an empirical formula for the critical coupling was btained.
Direct Reprogramming of Human Dermal Fibroblasts Into Endothelial Cells Using ER71/ETV2
Lee, Sangho,Park, Changwon,Han, Ji Woong,Kim, Ju Young,Cho, Kyuwon,Kim, Eun Jae,Kim, Sangsung,Lee, Shin-Jeong,Oh, Se Yeong,Tanaka, Yoshiaki,Park, In-Hyun,An, Hyo Jae,Shin, Claire Min,Sharma, Shraya,Yo Grune & Stratton 2017 Circulation research Vol.120 No.5
<P>Conclusions: This study for the first time demonstrates that ER71/ETV2 alone can directly reprogram human postnatal cells to functional, mature ECs after an intervening transgene-free period. These rECs could be valuable for cell therapy, personalized disease investigation, and exploration of the reprogramming process.</P>
멜라닌 생성 및 항산화 활성에 미치는 그라비올라 잎 추출물의 영향
이규원(Kyuwon Lee),장지원(Jiwon Jang),박수민(Sumin Park),강기훈(Kihun Kang),윤혜수(Hyesoo Yoon),하예진(Yejin Ha),전소정(Sojeong Jeon),고혜주(Hye Ju Ko),김문무(Moon-Moo Kim),오영희(Yunghee Oh) 한국생명과학회 2019 생명과학회지 Vol.29 No.6
본 연구의 목적은 그라비올라 잎의 항산화 효능과 멜라닌 생성 촉진효과를 조사하는 것이다. 먼저 AMME와 유기용매 별 분획물의 항산화 효능을 확인하기 위해 DPPH radical 소거능과, reducing power를 수행하였다. AMME와 유기용매별 분획물은 농도에 비례하여 항산화 효능이 증가하였으며, 그 중 ethyl acetate 분획물에서 가장 높은 항산화 효능을 보였다. 항산화 효능을 보인 분획물들의 멜라닌 생성에 미치는 영향을 확인하기 위해 tyrosinase activity를 수행한 결과 AMME, ethyl acetate, hexane 분획물에서 농도에 비례하여 멜라닌 생성 촉진효능이 나타났다. 그 중에서 AMME 유기 용매 별 분획물에서 멜라닌 합성 효능이 가장 좋은 hexane 분획물을 칼럼크로마토그래피를 통해 12가지 분획물로 나누어 항산화 실험과 멜라닌 합성실험을 수행하였다. 그 중 Fig. 8에서 DPPH radical 소거능과 환원력이 가장 우수한 것으로 나타났다. In vitro melanin 합성 실험 결과, Fr. 7은 64 μg/ml 농도에서 260%의 멜라닌 합성 효능을 보였고, Fr. 8은 64 μg/ml 농도에서 184%의 멜라닌 합성 효능이 관찰되었다. 최종적으로 B16F1 세포에서 Fr. 8의 4 μg/ml 농도에서 34%의 멜라닌 합성 효능을 보였다. LC-MS 결과 Fr. 7이 617의 분자량을 나타냈고, Fr. 8이 분자량 619의 분자량을 나타냈다. FT-IR 결과 Fig. 7과 Fig. 8 모두 Bis(2-hydroxyethly)dimerate와 비슷한 유효성분을 나타냈다. 이상의 결과로 그라비올라 잎은 천연 항산화제 또는 멜라닌 생성 촉진효과와 관련 있는 모발 제품 개발에 응용가능성이 있다고 판단된다. The purpose of this study was to investigate the effect of methanolic extracts of graviola, Annona muricate leaves (AMME) on antioxidant activity and melanin production. First of all, DPPH radical and reducing power were performed to determine the antioxidant effect of AMME and organic solvent fractions. AMME and organic solvent fractions showed antioxidative activity in a concentration dependent manner. The ethyl acetate fraction of AMME among organic solvent fractions showed the highest antioxidant activity. Moreover, tyrosinase activity was performed to confirm the effect of organic fractions on melanin production. AMME, ethyl acetate, and hexane fractions increased tyrosinase activity a dose dependent manner. Next, the hexane fraction with the best effect on melanin synthesis in AMME organic solvent fraction was divided into 12 fractions by silica column chromatography. Among them, the fraction 7 and 8 showed the highest DPPH radical scavenging activity and reducing power. In addition, the fraction 7 and 8 at 64 μg/ml showed melanin synthesis by 260% and 184%, respectively. Finally, the fraction 8 at 4 μg/ml showed melanin synthesis by 34% in B16F1 cells. LC-MS analysis showed that fraction 7 and fraction 8 have a molecular weight of 617 and 619, respectively. FT-IR analysis showed that fractions 7 and 8 is similar to bis(2-hydroxyethly)dimerate. Above results suggest that graviola leaves extracts could be applicable to the development of natural antioxidants or hair cosmetics which are related to the promoting effect of melanin production.
이규원(KyuWon Lee),장주섭(JooSup Jang),김경훈(Kyunghoon Kim),윤영환(Younghuwan Yoon),김형의(Hyoungeui Kim),정동수(Dongsoo Jeung) 한국자동차공학회 2002 한국자동차공학회 Symposium Vol.2002 No.11
Axial piston pumps of benl axis have been commonly used in hydraulic systems because they have a lot of merits such as high pressure level. best etliciency, low shear force on pistons and low operating costs. But, they have a few demerits like that they have the non-uniformity of flow rate and relatively high number of moving parts. Especially, non-uniformity of flow rate, which is caused by the discontinuous arrangement of pistons with the angular pitch, generates pressure ripples that affect on hydraulic systems. The purpose of this paper is to understand the process of the generation of discharge pressure ripples and to predict the amplitude of those in axial piston pump of bent axis in advance. The geometric of the pump and process of the generation of discharge pressure ripples are presented, and the modeling of the pump is developed in AMESim environment, and then the simulation is carried out. Finally, to verify the simulated modeling, the simulated results are compared with experimental results.
이규원(Kyuwon Lee),장주섭(Joosup Jang),김경훈(Kyunghun Kim) 한국자동차공학회 2002 한국자동차공학회 춘 추계 학술대회 논문집 Vol.2002 No.5_3
Pressure ripples which are inevitably generated by a fluctuation of flow rate caused by a pump have an effect on noises, vibrations, and control performance in hydraulic transmissio line. In this study, parallel line is introduced to hydraulic transmission line as the method for a reduction in the pressure ripples. The dynamic characteristics of the hydraulic transmission line are analyzed by a transfer matrix in frequency domain and the length ratio of the parallel line to the main line between upstream junction and downstream junction is calculated for a complete reduction in the pressure ripples. The usefulness of that is confirmed by a simulation.