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강일환,박태순 한국철도학회 2020 한국철도학회논문집 Vol.23 No.8
This study was conducted to investigate the effects of the sand gradation and cement fineness on cement asphalt mortar (CA mortar) for application to CA mortar in Korea. The CA mortar was prepared using three combined gradations of sand (CG1, CG2, and CG3) and three types of cement (C1, C2, and C3). The following basic properties of the CA mortar were analyzed: temperature of the mortar, flow value, air content, separation ratio, compressive strength, and expansion ratio. The test results showed that the separation ratio of the CA mortar increased and the flowability and compressive strength of the CA mortar decreased when the maximum sand size and gradation increased. The compressive strength of the CA mortar prepared with early hardening cement was higher than that of the CA mortar prepared with normal Portland cement. The temperature and expansion ratio of the CA mortar showed no significant relationship with the sand gradation or cement type.
라테라이트로 구성된 라오스 비포장도로의 품질 향상을 위한 개선공법의 적정치환두께 연구
강일환,김용주,권홍준 한국아스팔트학회 2023 한국아스팔트학회지 Vol.13 No.2
The main roads in Lao PDR are unpaved and made of laterite, which has the disadvantage of reducing bearing capacity during rainy season or squalls and causing soil and sand to flow out. In this study, the appropriate replacement thickness of three types of improvement methods (CTB, ATB, and Lean Con'c) was calculated through computer analysis to improve the quality of unpaved roads in Laos, which are mainly composed of laterite. As a result of engineering classification by sampling the soil of the unpaved road, A-2-7 (High-plasticity silts) according to the AASHTO classification and SP, CL, and ML according to the USCS classification were obtained. Based on engineering classification, the condition of unpaved roads was divided into 5 types (SP, SM, very stiff clay (dry season), medium clay, and very soft clay), and computerized analysis was performed in FLAC 3D using the HL-93 truck tandem model. was carried out. As a result of computer analysis, it was confirmed that the maximum deflection decreases according to the replacement thickness of the improved method. In the case of ATB, horizontal and vertical strains (εt,εz) were calculated to be the largest in all conditions. In the case of Lean Con’c, the horizontal strain and vertical strain were calculated to be the smallest in all conditions, and the amount of change according to replacement thickness was the smallest. As a result of calculating the appropriate replacement thickness in the upper layer of unpaved roads in all conditions, it is 10 to 20 cm for CTB, more than 20 cm for ATB, and 5 to 10 cm for Lean Con’c
강일환(Il-Hwan Kang),김형만(Hyung-Man Kim),왕학민(Hak-Min Wang),최갑승(Kap-Seung Choi) 한국자동차공학회 2005 한국자동차공학회 지부 학술대회 논문집 Vol.- No.-
As fuel cells approach commercialization, hydrogen production becomes a critical step in the overall energy conversion pathway. Reforming is a process that produces a hydrogen-rich gas from hydrocarbon fuels. Hydrogen production via autothermal reforming (ATR) is particularly attractive for applications that demand a quick stan-up and response time in a compact size. However. further research is required to optimize the performance of autothermal reformers and accurate models of reactor performance must be developed and validated. The design includes the requirement of accommodating a wide range of experimental set ups. Factors considered in the design of the reformer are capability to use multiple fuels. ability to vary stoichiometry. precise temperature and pressure control, implementation of enhancement methods, capability to implement variable catalyst positions and catalyst arrangement, ability to monitor and change reactant mixing, and proper implementation of data acquisition. A model of the system was first developed in order to calculate flowrates, heating, space velocity, and other important parameters needed to select the hardware that comprises the reformer. Predicted performance will be compared to actual data once the reformer construction is completed. This comparison will quantity the accuracy of the model and should point to areas where further model development is required. The end result will be a research tool that allows engineers to optimize hydrogen production via autothermal reformation.