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셀룰로오스 아세테이트-g-폴리(L-락트산)(CA-g-PLA)의 특성과 CA/PLA 블렌드의 상용화제로서의 응용
최효성(Hyo Sung Choi),이이주(Yiju Lee),김영호(Young Ho Kim) 한국고분자학회 2020 폴리머 Vol.44 No.3
혼화성이 없는 셀룰로오스 아세테이트(CA)와 폴리(L-락트산)(PLA) 블렌드의 상용성을 향상시키기 위하여 CA와 PLA 두 고분자의 성질을 모두 갖는 CA-g-PLA를 합성하고 이들이 CA/PLA 블렌드의 상용화제로 활용가능한지 검토하였다. 여러 가지 그래프트율을 갖는 CA-g-PLA의 특성들을 적외선 분광분석기, 젤투과 크로마토그래프, 열중량 분석기, 시차주사 열량계 등으로 조사하였으며, CA(50)/PLA(50) 블렌드에 그래프트율이 서로 다른 CA-g-PLA를 일정 함량 첨가하거나 그래프트율이 일정한 CA-g-PLA를 서로 다른 함량으로 첨가한 CA(50)/PLA(50)/CAg-PLA 블렌드 필름들을 제조하여 물성과 모폴로지를 비교 분석하였다. 첨가하는 CA-g-PLA의 그래프트율이 커지거나 첨가량이 많아질수록 블렌드 시료의 파단응력과 파단변형률이 모두 증가하였으며, 블렌드에서의 상분리가 감소하여 CA-g-PLA가 CA와 PLA 블렌드의 상용화제로 작용하였다. In order to improve the compatibility of immiscible blends of cellulose acetate (CA) and poly(L-lactic acid) (PLA), CA-g-PLA having the properties of both CA and PLA polymers was synthesized and it was investigated whether it acts as a compatibilizer for CA/PLA blends. The characteristics of CA-g-PLA with various graft yields were examined by infrared spectroscopy, gel permeation chromatography, thermogravimetric analysis, and differential scanning calorimetry. Mechanical properties and morphologies of the CA(50)/PLA(50)/CA-g-PLA blend films prepared by adding a certain amount of CA-g-PLA having different graft yields or by adding different amounts of CA-g-PLA having a constant graft yield were analyzed. CA-g-PLA acted as a compatibilizer for the CA/PLA blends, judging from the results that both the stress and strain at the break of the blend films increased and the phase separation in the blends decreased as the graft yield or the added amount of CA-g-PLA increased.
유리질 중공체 GHM(Glass Hollow Microsphere)을 활용한 자기의 경량화
김근희,최효성,피재환,조우석,김경자,Kim, Geun-Hee,Choi, Hyo-Sung,Pee, Jae-Hwan,Cho, Woo-Seok,Kim, Kyeong-Ja 한국세라믹학회 2011 한국세라믹학회지 Vol.48 No.1
The pore generation technology using GHM (Glass Hollow Microsphere) was studied in order to reduce the weights of porcelain. In this study, we verify the property of modified slurry by adding GHM. The modified slurry was prepared by adding 1.0~2.5 wt%(K1), 1.0~6.0 wt%(K37) of GHM to the slurry for porcelain. The slurry viscosity were stable inside a content range of 1.0~2.5 wt%(K1), 1.0~6.0 wt%(K37). However, the viscosity of modified slurry increased more than 3.0 wt%(K1) and 6.5 wt%(K37). The formed specimen by slip casting was fired at $1229^{\circ}C$, $1254^{\circ}C$. As the amount of GHM content increased, the weight decreased and the addition of 1.0~2.5 wt%(K1), 1.0~6.0 wt%(K37) of GHM resulted in a weight drop of 30%(K1) and 25(K37). However, when the GHM content increased, the strength decreases over 70%. This is caused by the presence of a large volume of surface defects (pores) and defects from the agglomeration of GHM.
김봉환(Bong-Hwan Kim),최효성(Hyo-Sung Choi),김동건(Dong-Keon Kim) 한국기계가공학회 2011 한국기계가공학회지 Vol.10 No.3
In the present investigation, experimental studies were conducted on the fire suppression performance of twin-fluid water mist spray which is subjected to thermal radiation in a closed space. Downward-directed water-mist sprays, interacting with an under kerosene pool fire, were investigated in a test facility. The mass mean diameter of water-mist droplets were measured by PMAS under various flow conditions. The developed twin-fluid water mit spray nozzle satisfied the criteria of NFPA 750, Class 1. The mechanism of fire suppression by fine water mist was concluded to be the cooling of the fire surface which leads to the suppression of fuel evaporation. It was proved that the automatic twin-fluid water mist spray system under lower pressures could be applied to an industrial facilities.
성승미 ( Seung Mi Sung ),박정우 ( Jung Woo Park ),최효성 ( Hyo Seong Choi ),김지연 ( Jee Yeon Kim ),이병익 ( Byoung Ick Lee ) 대한산부인과학회 2008 Obstetrics & Gynecology Science Vol.51 No.10
Pelvic congestion syndrome (PCS), which is said to occur due to ovarian vein incompetence, is a recognized cause of chronic pelvic pain (CPP). It is difficult to diagnose PCS because of a variety of symptoms. In addition, it can be underestimated by Computed Tomographic or Magnetic Resonance Imaging. At this time, gonadal venography remains the definitive imaging modality to evaluate patients with PCS. Medical and surgical approaches are available to treat PCS. More recently, however, transcatheter embolotherapy (TCE) has been shown to be both safe and effective. We have experienced a case of pelvic congestion syndrome that was diagnosed by venography.
PIV를 이용한 중방식 도장용 에어리스 팁의 분사패턴 분석
윤순현(Soon-Hyun Yoon),최효성(Hyo-Sung Choi),김동건(Dong-Keon Kim),김봉환(Bong-Hwan Kim),조승완(Seung-Wan Cho) 한국해양공학회 2014 韓國海洋工學會誌 Vol.28 No.2
Heavy duty coating is playing an important role in the field of heavy industry in the development of the shipbuilding and plant industries. Heavy duty coating has the very important function of protecting steel under serious corrosive conditions. The airless tip used for heavy duty coating is an essential part that determines the spray pattern of the paint. This research investigated the injection properties of three airless tips(numbers 521, 523, and 525) by using particle image velocimetry(PIV). The velocity and turbulent intensity according to pressure change with each tip type were investigated by using PIV. If the pressure is greater, the turbulent intensity becomes stronger and the break up of particles becomes bigger as the tip number gets smaller. The velocity is the fastest in the center and decreases in the radial direction
황보현 ( Bo Hyun Hwang ),박지원 ( Ji Won Park ),박성찬 ( Sung Chan Park ),김선영 ( Sun Young Kim ),백지연 ( Ji Yeon Baek ),김대용 ( Dae Yong Kim ),장희진 ( Hee Jin Chang ),최효성 ( Hyo Sung Choi ),오재환 ( Jae Hwan Oh ) 대한임상종양학회 2011 Korean Journal of Clinical Oncology Vol.7 No.2
목적: 2기 직장암에 있어서 근치적 수술 후 보조 치료의 유용성에 대해서는 의견이 분분하다. 본 연구에서는 2기 직장암의 예후인자를 분석해보고자 하였다. 방법: 2000년 10월부터 2008년 12월까지 국립암센터에서 수술을 받은 총 200명의 2기 직장암 환자를 대상으로 하였다. 단변량 및 다변량 분석을 이용하여 생존율 분석을 하였으며 이를 근거로 2기 직장암 환자의 예후인자를 예측해보고자 하였다. 결과: 2기 직장암에서 5년 생존율과 5년 무병 생존율은 각각 89.2%, 89.0% 였다. 다변량 분석을 하였을 때 5년 생존율에 영향을 주는 예후 인자는 측방절제연의 침범이었고 5년 무병 생존율의 경우 나쁜 분화도와 측방절제연의 침범이 통계적으로 유의하였다. 결론: 측방절제연의 침범 여부가 5년 생존율의 독립적인 예후인자였고 암종의 분화도와 측방절제연의 침범 여부가 2기 직장암의 5년 무병 생존율에 있어서 독립적인 예후인자였다. Background: In stage II rectal cancer, it has remained controversial whether patients get the benefit from adjuvant treatment after curative resection. The aim of this study is to evaluate the prognostic factors of stage II rectal cancer. Methods: From October 2000 to December 2008, 200 patients with stage II rectal cancer underwent surgery at National Cancer Center. Univariate and multivariate survival analyses were performed to determine the prognostic factors in stage II rectal cancer. Results: In stage II rectal cancer, 5-year overall survival and disease free survival were 89.2% and 89.0%, respectively. For overall survival, there was no significant prognostic factor in multivariable analysis. For disease-free survival, tumor differentiation and circumferential resection margin were significant prognostic factors in multivariable analysis. Conclusion: Tumor differentiation and circumference resection margin are independent prognostic factors in disease free survival of stage II rectal cancer. Adjuvant treatment may be considered in patients with these factors.