W 섬유강화 스테인레스강 복합재료의 열피로에 관한 연구

이지환 대한금속재료학회(대한금속학회) 1988 대한금속·재료학회지 Vol.26 No.1

In this paper was investigated the effect of thermal cycling on dimensional change and microstructural change of the interfacial region in W/stainless steel composites, which was hot pressed at 1100℃ and then exposed up to 200 h at 1200℃, with HfN coated and uncoated fibers. After thermal cycling, it was found that axial dilatation of the matrix in W/stainless steel composites with HfN coated fiber occurred conspicuously only in the early stage of cycling. However, the axial dilatation became nearly zero after several tens of cycles, which indicated that mechanical interactions exist between the matrix and the fiber did not exist any more. On the other hand, the matrix side of the interface in W/stainless steel composites with uncoated fiber became rough with increase of thermal cycling, and several voids were observed to be formed in the matrix.

SiC 입자강화 알루미늄합금기 복합재료의 분말압출에 관한 연구

이지환,서병권,조동철 대한금속재료학회(대한금속학회) 1997 대한금속·재료학회지 Vol.35 No.4

This paper was focused on the extrusion process of SiC_p/2024 Al composites. Aluminum powders mixed with SiC particles of 10, 20 Vol.% were degassed at 450℃ during 90min. Powder-extruded composites was extruded at 500℃ under the extrusion ratio of 25. The billet-extruded composites was extruded at 500℃ after hot pressing as a reference material. It was found that the relative density of powder-extruded composites was slightly lower than that of the billet-extruded composites. However, microhardness of the powder-extruded composites was superior to billet-extruded composites. This is attributable to the maintenance of aluminum powder property caused by short thermal-exposure time during powder extrusion process. The powder-extruded composites exhibits the lower tensile strength and elongation, comparing with billet-extruded composites. This may be due to smaller extrusion pressure, which could not be sufficiently eliminated interfacial defects such as pores.

국내 환경산업기술의 현황과 육성방안

李之煥 慶北大學校 經營大學院 1992 最高經營者課程 論文集 Vol.- No.15

산업부산물을 활용한 조기강도 촉진제 기술 개발을 위한 연구

이지환,이진우,이재삼,이강진,Lee, Ji-Hwan,Lee, Jin-Woo,Lee, Jae-Sam,Lee, Kang-Jin 한국건설순환자원학회 2013 한국건설순환자원학회지 Vol.8 No.1

본 연구에서는 OPC 및 BFS 혼입 콘크리트의 초기재령 압축강도 향상을 위해 산업부산물인 티탄석고, 정수오니를 활용하여 경제성을 만족하면서 콘크리트의 조기강도(재령 1, 3일)를 향상시킬 수 있는 촉진제(이하 HSB) 개발을 위한 기초적 연구를 실시하였다. 조강형 분체의 제조를 위한 산업부산물의 조합 비율은 기초 실험 및 성분분석을 통해 티탄석고(4) : 석회석(3) : 정수오니(3)의 비율로 조합을 확정하였으며, HSB의 혼입률은 사전시험을 거쳐(7~9) %가 적정한 것으로 나타났다. 페이스트 경화체의 SEM 촬영 결과 HSB 혼입을 통한 자극으로 인해 수화반응이 촉진되어 수화생성물이 다량 분포한 것을 SEM 측정을 통해 확인 할 수 있었으며, HSB 혼입 콘크리트 압축강도 측정결과 HSB를 혼입함에 따라 Plain 배합에 비해 초기재령에서 높은 압축강도 발현율을 나타내는 것을 확인할 수 있었다. 또한 GHSB에 비해 FHSB 배합이 더욱 우수한 강도를 나타내었으며, FHSB 치환율이 증가함에 따라 압축강도는 소폭 상승하는 결과를 나타내었다. 한편, HSB 및 혼합시멘트를 사용한 콘크리트의 경우 촉진재 종류에 관계없이 촉진재 치환율 9 %에서 Plain 배합 이상의 조기강도를 발현하는 것으로 나타났으며, 촉진재 종류에 따른 영향을 알아본 결과, GHSB에 비해 FHSB가 재령 1, 3일에는 더욱 우수한 조기강도 발현성능을 나타내었다. In this study utilize industry product for OPC(ordinary portland cement) and BFS(blast furnace slag) mixing concrete early age compressive strength elevation and executed study for high strength binder. Association ratio of industry product for high strength binder manufacture is Titanogypsum (4) : Limestone (3) : Waterworks Sludge by ratio of (3) as it is proper move. high strength binder mixing rate appeared that (7~9) % are proper via preliminary test. Could confirm that display high compressive strength incidence rate in early age than plain harmony according as mix high strength binder mixing concrete compressive strength high strength binder. Also, high strength binder generality that give function than high strength binder used in existing displayed more excellent intensity, and compressive strength displayed result that multiply single breadth according as high strength binder substitute that give function increases.

종합검진 환자의 우울 및 불안성향

이지환,이선옥,최연준,강희철 대한가정의학회 1995 Korean Journal of Family Medicine Vol.16 No.7

현대적인 한옥의 디자인으로 재해석한 천주교 종교시설 계획

이지환,김한희 한국실내디자인학회 2017 한국실내디자인학회 학술대회논문집 Vol.2017 No.10

Implementing Best Practice in Critically Ill Organophosphate Poisoned Patient Through Simulation-Based Learning Program

이지환,정성필,정현수 대한임상독성학회 2017 대한임상독성학회지 Vol.15 No.1

Purpose: Despite the clinical and socio-economic impact of acute poisoned patients, many of the treatments are not standardized in Korea. Moreover, no formal training that is specifically focused on clinical toxicology exists. Rather, training and education are conducted case by case in various institutions. This study was conducted to develop a standardized simulation-based clinical toxicology training curriculum for healthcare providers. This program will focus on specific assessment and treatment of critical toxicology patients, specifically those who have been poisoned with organophosphate. Methods: The study was performed using a pre- and post-design to determine the effects of implementation of this program. The study was conducted at eight different urban teaching hospitals in a simulated room in the clinical area. The study was targeted to 19 groups composed of emergency residents and nurses. Simulation-based learning was conducted for each group. Results: All 19 groups achieved the minimum passing score of 75%. Implementation of the program led to improved performance rates for overall management and cooperative moods competency (p<0.01). Inter-rater agreement between the two evaluators was excellent. In general, the participants thought the program was realistic and were able to recognize and improve the competencies needed to care for organophosphate poisoned patients. Conclusion: Simulation-based learning is an effective educational strategy that can be applied to improving and understanding proper care for rare but critical patients. This program was effective at improving team performance and cooperative moods when managing an organophosphate poisoned patient in the Emergency Department.

Inflammatory Cytokine and Osmolarity Changes in the Tears of Dry Eye Patients Treated with Topical 1% Methylprednisolone

이지환,김태임,민경,김세경,김응권 연세대학교의과대학 2014 Yonsei medical journal Vol.55 No.1

Purpose: To evaluate changes in clinical outcomes, inflammatory cytokine levels, and tear osmolarity in the tears of patients with moderate to severe dry eye syndrome before and after the application of topical 1% methylprednisolone. Materials and Methods: Thirty-two patients with moderate to severe dry eye unresponsive to previous aqueous enhancement therapy were enrolled. Five patients were lost to follow up, and twenty-seven patients were eligible for analysis. Patients were instructed to apply topical 1% methylprednisolone four times per day, as well as to continue applying their current therapy of preservative-free 0.1% sodium hyaluronate four times per day. Corneal and conjunctival staining scores, tear film breakup time (TFBUT), Schirmer test, and tear osmolarity were assessed at baseline,4 weeks, and 8 weeks. Tear samples were collected at every visit for cytokine analysis. Results: Corneal and conjunctival staining scores and TFBUT showed significant improvement at 4 (p<0.001, <0.001, <0.001 respectively) and 8 (p<0.001, <0.001, <0.001 respectively) weeks. Tear osmolarity decreased significantly at 8 weeks (p=0.008). Interleukin (IL)-1β, IL-8, and monocyte chemoattractant protein-1 were significantly decreased at 8 weeks compared with those at baseline (p=0.041, 0.001, 0.008 respectively). Conclusion: Short-term treatment with topical 1% methylprednisolone not only improved clinical outcomes, but also decreased tear osmolarity and cytokine levels. By measuring the changes in cytokine levels and tear osmolarity, we could objectively evaluate the anti-inflammatory effects of topical methylprednisolone applied in the treatment of patients with moderate to severe dry eye syndrome.

2002학년도 신입생 실태조사 보고서

이지환,김태희 부산대학교 학생생활연구소 2002 硏究報 Vol.34 No.-

We implemented the survey for the actual conditions of the new students in the year of 2002. Among total 4399 freshmen in Pusan national University, 2145(49.4%) students replied to the questionnaire for the actural conditions of the new students. Total 129 items in 6 areas including sociodemographic variables, variables about decision of school, variables about expected school life, trust, parenting style, and psychological health. For each items and scales, we presented frequency and percentage(or mean and SD) by sex and college and described its meaning. Finally, we abridged results of the survey by 6 areas.

YAG 레이저에 의한 이종금속판재의 접합특성

이지환 대한용접접합학회 1988 대한용접·접합학회지 Vol.6 No.1

This paper describes weldability of dissimilar metal plates with YAG laser for the use of a small-size electronic spring parts. Effects of welding conditions, combination of plates, thickness of upper plate are examined in relation to welding strength and microstructure of welded region. The obtained results are summarized as follows. Welding defects such as cavity and crack showed a tendency to easily occur in the case where 1) pulse duration is short, 2) laser power is high, 3) PBS plate with high thermal diffusivity is used for lower plate. Among these defects, the occurrence of cavity cased a drop of welding strength. This results from the reduction of welding area between upper and lower plates. In SK-5/SUS304 plates (thickness: 0.2/0.4mm/, welding strength was the highest in welding conditions: laser power is 30J/pulse, pulse duration 9ms, amount of defocus +2mm.