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Joo‑Hyoeng Woo,Soo‑Jin Park,Sungwook Chung,Seok Kim 한국탄소학회 2019 Carbon Letters Vol.29 No.1
We have studied a method to prepare polydopamine-modified reduced graphene oxide-supported Pt nanoparticles (Pt– PDA–RGO). The Pt–PDA–RGO nanocomposites were synthesized by a wet-coating process, which was induced by selfpolymerization of dopamine. As an eco-friendly and versatile adhesive source in nature, dopamine could be easily adhered to surfaces of organic material and inorganic material via polymerization processes and spontaneous adsorption under weak alkaline pH conditions. To apply the unique features of dopamine, we synthesized Pt–PDA–RGO nanocomposites with a different quantity of dopamine, which are expected to preserve the improved Pt adsorption on graphene, resulting in the enhanced electrocatalytic performance. The morphology and micro-structure were examined by field emission scanning electron microscopy, transmission electron microscopy, and Fourier transform infrared spectroscopy. Compared to pristine Pt–deposited RGO (Pt–RGO), Pt–PDA–RGO (30 wt% dopamine against RGO) nanocomposites showed a superior electrochemical active surface area for a methanol oxidation. This could be related to the fact that the optimized c
전성욱 ( Sungwook Chun ),( Jung Eun Seo ),( Yun Jeung Rim ),( Jae Hong Joo ),( Yong Chan Lee ),( Yun Hee Koo ) 대한산부인과학회 2017 대한산부인과학회 학술대회 Vol.103 No.-
Objective: To evaluate the effect of hyaluronan-rich transfer medium on pregnancy and implantation rates in fresh and frozen-thawed embryo transfers in Korean women with previous implantation failure. Methods: This retrospective study included 283 blastocyst transfers in patients with previous embryo transfer failure at a private fertility clinic. In the study group (n=88), blastocyst transfers were performed using an hyaluronan-rich transfer medium prior to transfer, whereas blastocyst transfers without any treatment served as controls (n=195). According to the type of transfer (fresh elective or frozen-thawed), all the blastocyst transfers were divided into two study and two control groups. Results: The patient’s mean age, serum anti-Mullerian hormone level, causes of infertility, embryo quality, and the number of transferred embryos were comparable between the study and control groups. There were no significant differences in clinical pregnancy rate (45.5% vs. 43.1%), implantation rate (28.9% vs. 28.8%), and clinical abortion rate (10.0% vs. 8.3%) between the two groups, and these findings were not changed after subgroup analysis according to the type of transfer. Conclusion: The use of hyaluronan-rich transfer medium in the blastocyst transfer does not appear to have any significant effect on the implantation and pregnancy rates in patients with previous implantation failure.
Hong, Sungwook,Seo, Hwa-Jeong,Kwon, Young-Joo AMERICAN METEOROLOGICAL SOCIETY 2016 Journal of atmospheric and oceanic technology Vol.33 No.7
<P>This study proposes a sea surface wind speed retrieval algorithm (the Hong wind speed algorithm) for use in rainy and rain-free conditions. It uses a combination of satellite-observed microwave brightness temperatures, sea surface temperatures, and horizontally polarized surface reflectivities from the fast Radiative Transfer for TOVS (RTTOV), and surface and atmospheric profiles from the European Centre for Medium-Range Weather Forecasts (ECMWF). Regression relationships between satellite-observed brightness temperature and satellite-simulated brightness temperatures, satellite-simulated brightness temperatures, rough surface reflectivities, and between sea surface roughness and sea surface wind speed are derived from the Advanced Microwave Scanning Radiometer 2 (AMSR-2). Validation results of sea surface wind speed between the proposed algorithm and the Tropical Atmosphere Ocean (TAO) data show that the estimated bias and RMSE for AMSR-2 6.925- and 10.65-GHz bands are 0.09 and 1.13 m s(-1), and -0.52 and 1.21 m s(-1), respectively. Typhoon intensities such as the current intensity (CI) number, maximum wind speed, and minimum pressure level based on the proposed technique (the Hong technique) are compared with best-track data from the Japan Meteorological Agency (JMA), the Joint Typhoon Warning Center (JTWC), and the Cooperative Institute for Mesoscale Meteorological Studies (CIMSS) for 13 typhoons that occurred in the northeastern Pacific Ocean throughout 2012. Although the results show good agreement for low-and medium-range typhoon intensities, the discrepancy increases with typhoon intensity. Consequently, this study provides a useful retrieval algorithm for estimating sea surface wind speed, even during rainy conditions, and for analyzing characteristics of tropical cyclones.</P>
가스터빈용 소재 IN 738LC 합금의 미세조직 열화거동
유정훈,주성욱,신기삼,김의현,정진성,장성호,송기욱,하정수 국립7개대학공동논문집간행위원회 2002 공업기술연구 Vol.2 No.-
IN 738LC, used as gas-turbine for power generation, was heat treated at 750℃, 850℃, 950℃ for 1000, 2000, and 4000 hrs. and the microstructural evolution are examined using optical microscope, XRD, SEM/EDS. For comparison, part of gas turbine used for 18439 hours for power generation was also examined. The results showed γ´, the main strengthening elements in this alloy, was about 300 nm and was about 56% in as-cast samples. The volume fraction of γ´peaked at 2000 hours at 750℃ and then decreased at further or longer heat treatment. The average diameter of the γ´ which was about 200 nm increased to about 1㎛. Carbides were formed at dendrite, cell, or grain boundaries which was ascribed to the segregation caused by solute redistribution during solidification. It was found that the at low temperature, M_6C type carbides formed, whereas carbides of M_23C_6 type formed at higher temperature, or at longer degradation.
김창주(Chang-Joo Kim),이도현(Dohyeon Lee),허성욱(Sungwook Hur),박상선(Sang-Seon Park),조인제(In-Je Cho) 한국항공우주학회 2017 韓國航空宇宙學會誌 Vol.45 No.6
항공우주 시스템 개발에 있어 M&S (Modeling and Simulation)의 광범위한 사용이 보편화되고 있고 인증(Certification) 혹은 인정 (Accreditation)을 통해 부적절한 M&S의 사용으로 인한 사고나 위험을 제도적으로 방지하려는 노력이 있어 왔다. 본 연구는 이와 관련된 M&S의 VV&A (Verification, Validation, and Accreditation) 활동을 다루었다. 항공우주 M&S는 항공우주시스템 개발에 활용을 목적으로 하고 대부분 물리법칙 기반의 모델링 기법을 사용한다. 또한, 시제제작 후 검증용 데이터가 비행시험을 통해 최종 확보된다는 점에서 여타의 M&S와는 다른 접근방법이 필요하다. 본 연구는 이러한 특성을 고려하여 M&S 개발과 VV&A의 시작점이라 할 수 있는 항공우주 시스템 개발에 적합한 M&S의 수명주기 모델과 개발 패러다임을 다양한 문헌 연구를 토대로 제안하였다. The M&S (Model and Simulation) has been increasingly used in the wide area of applications and the official certification or accreditation of the M&S are becoming a mandatory requirement to prevent the risks and mishaps caused by the usage of inadequate M&Ss or by misuses of the M&S. This paper threats the VV&A (Verification, Validation, and Accreditation) for the M&S used in the development of the aerospace systems, where most M&S used in the development are derived from the physical laws and the final validation data are typically obtained through a series of flight tests after the prototype production. Considering these unique features, the paper proposes the M&S life-cycle model and development paradigm suitable for the aerospace-system development and accesses the proposed ones by comparative investigation on the relevant regulations and related literatures.