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[가솔린엔진부문] 메탄올 혼합연료를 이용한 SI 엔진의 성능 및 배출물에 관한 실험적 연구
하철호(Chulho Ha),최승환(Seunghwan Choi),전충환(Chunghwan Jeon),장영준(Youngjune Chang) 한국자동차공학회 2000 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
In this experimental research, engine performances for cranking, accelerating and power output as using methanol blended fuel in a SI engine were studied. Distillation curve of the mixed fuel has a major effect on combustion characteristics. Thus combustion features of the methanol-gasoline blended fuel could be compensated by changing composition with respect to aromatic and non-aromatic components which exist in gasoline fuel. We compared experimentally with gasoline fuel, M30(methanol 30%, aromatic42%, non-aromatic28%) and M50(methanoI50%, aromatic30%, non-aromatic20%) for performance and exhaust gas. The experimental results show that engine combustion characteristics were changed in terms of fuel components by distillation curve and engine operating condition.
뿜칠 방수 멤브레인이 시공된 터널 라이닝의 수분이동에 관한 수치해석 연구
이철호(Chulho Lee),최순욱(Soon-Wook Choi),강태호(Tae-Ho Kang),장수호(Soo-Ho Chang) 한국암반공학회 2016 터널과지하공간 Vol.26 No.3
뿜칠 방수 멤브레인은 숏크리트 사이에 시공되어 라이닝 크랙을 통한 누수를 방지하는 목적으로 최근 유럽 국가를 중심으로 시공 사례가 늘어가고 있다. 뿜칠 방수 멤브레인은 방수 시트에 비해 복잡한 단면에도 시공이 용이하기 때문에 이용 사례가 늘어갈 것으로 전망된다. 뿜칠 방수 멤브레인은 폴리머로 구성된 재료로서 투수성이 매우 낮지만 수분의 이동에 의해 포화가 되고 이로인해 콘크리트 재료에 간극수압이나 동결 문제를 일으킬 수 있는 우려가 있다. 본 연구에서는 뿜칠 방수 멤브레인의 수분이동과 계절변화를 고려하여 숏크리트 라이닝의 열-습도 전달 장기 해석을 수행하였다. 해석을 통해 뿜칠 방수 멤브레인의 수분 흡수 작용과 수분이동으로 인한 상대습도 변화를 고찰할 수 있었으며 이로 인한 장기적 변화를 모사할 수 있었다. The sprayable waterproofing membrane is installed between shotcrete to provide crack bridging and hence prevent flow of liquid water as a waterproofing system. Because of its material characteristics, the sprayable membrane can be constructed at more complex structure than sheet membrane. The main component of the sprayable waterproofing membrane is a polymer-based material, therefore, moisture can migrate through sprayable waterproofing membrane materials by capillary and vapor diffusion mechanisms. The moisture transport mechanisms can have an influence on the degree of saturation and may influence the pore pressure and risk of freeze-thaw damage on concrete linings and membrane. In this study, long-term hygrothermal behavior was simulated with considering moisture transport and long-term effects on saturation of tunnel linings. From the simulation, due to water absorption and vapor transport properties of sprayable membrane, change of relative humidity and water content in tunnel lining can be evaluated.
TBM 운전조건을 고려한 스포크형 쉴드TBM의 굴진모사 연구
최순욱(Soon-Wook Choi),이효범(Hyobum Lee),최항석(Hangseok Choi),장수호(Soo-Ho Chang),강태호(Tae-Ho Kang),이철호(Chulho Lee) 한국암반공학회 2019 터널과지하공간 Vol.29 No.6
본 연구에서는 개별요소법을 사용하여 스포크형 쉴드TBM의 굴진을 모사하였다. 지반에 대해 수평응력계수를 사용하여 깊이에 따른 수평응력 증가를 모사하였고 TBM의 커터헤드에서 발생하는 토크를 기준으로 운전 조건을 부여하여 운전 범위 내에서 굴진을 하도록 설정하였다. 즉, 커터헤드에서 발생하는 토크의 값이 주어진 운전 조건을 넘어서는 경우 굴진속도를 일정하게 줄이고 반대로 운전 조건보다 낮은 경우에는 굴진 속도를 높이는 방안을 고려하였다. 이때 굴진속도 변경에는 운전자의 검토 시간을 고려하여 최소 변경 가능 요건을 부여하고 굴진 조건에 따라 이를 변경 가능하도록 하였다. 이러한 조건을 사용하기 위하여 사용자 프로그램을 별도로 작성하였으며, 결과를 통해 사전에 입력한 운전 범위 내에서 굴진 해석이 가능하였다. In this study, the discrete element method was used to simulate the excavation of spoke-type shield TBM. The horizontal stress coefficient was used for the ground to simulate the increase of the horizontal stress according to the depth, and the driving conditions were set based on the torque generated from the cutterhead of the TBM to excavate within the operating range. That is, when the value of the torque generated at the cutterhead exceeds the given operating condition, the speed of excavation is constantly reduced, and conversely, the method of increasing the speed of excavation is considered. The change speed of the excavation was given the minimum change requirement in consideration of the driver"s review time, and the change was possible according to the excavation conditions. In order to use these conditions, the user-subroutine was considered separately, and the results show that the DEM model were able to analyze the excavation within the considered operating range.
Automatic Thresholding Method for the Detection of Brain Ventricle in MRI Brain Images
Chulho Won,Dong-Hun Kim,Jyung-Hyun Lee,Sang-Hyo Woo,Chang-Wook Kim,Jin-Ho Cho 대한전자공학회 2007 ITC-CSCC :International Technical Conference on Ci Vol.2007 No.7
This paper suggests an algorithm that can detect a brain ventricle; compares that algorithm with the geodesic active contour model numerically and visually by applying real MRI brain images; and verifies the efficiency of the proposed algorithm.
Effect of hardfacing on wear reduction of pick cutters under mixed rock conditions
Chang, Soo-Ho,Lee, Chulho,Kang, Tae-Ho,Ha, Taewook,Choi, Soon-Wook Techno-Press 2017 Geomechanics & engineering Vol.13 No.1
A pick cutter is a rock-cutting tool used in partial-face excavation machines such as roadheaders, and its quality is a key element influencing the excavation performance and efficiency of such machines. In this study, pick cutters with hardfacing deposits applied to a tungsten carbide insert were made with aim of increasing their durability and wear resistance. They were field-tested by being installed in a roadheader and compared with conventional pick cutters under the same excavation conditions for 24 hours. The hardfaced pick cutters showed much smaller weight loss after excavation, and therefore better excavation performance, than the conventional pick cutters. In particular, the damage to and detachment (loss) of tungsten carbide inserts was minimal in the hardfaced pick cutters. A detailed inspection using scanning electron microscope-energy dispersive X-ray spectrometry and three-dimensional X-ray computed tomography scanning revealed no macro- or micro-cracks in the pick cutters. The reason for the absence of cracks may be that the heads of pick cutters are mechanically worn after the tungsten carbide inserts have been worn and damaged. However, scanning revealed the presence of voids between tungsten carbide inserts and pick cutter heads. This discovery of voids indicates the need to improve production processes in order to guarantee a higher quality of pick cutters.
TSL(Thin Spray-on Liner)의 특성 분석 연구
이철호(Chulho Lee),장수호(Soo-Ho Chang),신휴성(Hyu-Soung Shin),한진태(Jintae Han) 한국지반신소재학회 2014 한국토목섬유학회 학술발표회 Vol.2014 No.4
A TSL (Thin Spray-on Liner) which consists of polymers has a higher initial strength, faster construction time and higher waterproof performance than the cementitious shotcrete. In this study, two TSLs were considered as an alternative method to shotcrete. In order to evaluate characteristics of two TSLs, tension test by ASTM and standard tests by EFNARC were performed. From the series of laboratory tests, the average tension strength of material T and M were 3.24 and 4.82 MPa at 28 days after curing, respectively. And the material M which has higher content of polymer showed relatively higher adhesion than material T in the linear block test and gap shear test by EFNARC. To apply the TSL to field condition, it is needed to accumulate characteristics of TSL at various mixing ratios.
TSL(Thin Spray-on Liner)의 접촉 거동에 대한 수치해석 연구
이철호(Chulho Lee),장수호(Soo-Ho Chang),한진태(Jintae Han),김동욱(Dongwook Kim) 한국지반신소재학회 2015 한국토목섬유학회 학술발표회 Vol.2015 No.4
A TSL (Thin S=ray-on Liner) which consists of polymers has a higher initial strength, faster construction time and higher waterproof performance than the cementitious shotcrete. In this study, to obtain contact properties of TSL, numercial analysis was performed. Cohesive behavior of contact between TSL and block can be evaluated by using cohesive properties and the damage model. From the result, cohesive stiffness controled slope between force and displacement, the evolution energy controled level of force at the contact.