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이차원 수치해석에 의한 강지보 성능을 고려한 숏크리트 라이닝의 부재력 평가 방법
하태욱,김대영,신영완,양형식,Ha, Tae-Wook,Kim, Dae-Young,Shin, Young-Wan,Yang, Hyung-Sik 한국터널지하공간학회 2008 한국터널지하공간학회논문집 Vol.10 No.3
일반적으로 터널설계와 관련된 수치해석에서 강지보의 효과가 고려되지 않고 있다. 최근 연약한 지반에 위치하는 얕은 터널 건설의 증가에 따라 터널의 안정성 해석에 강지보가 굴착으로 재 분포된 하중의 일부를 부담한다는 개념 하에 숏크리트와 함께 강지보의 효과를 적용한 사례가 늘고 있다. 이와 같은 해석에서 강지보는 여러 방법으로 고려될 수 있다. 본 논문에서는 숏크리트와 강지보의 발생응력을 알아보기 위하여 FLAC 2D를 이용하여 (1) 강지보를 고려하지 않는 일반적인 방법, (2) 숏크리트의 모멘트를 고려하지 않는 등가합성단면법, (3) 숏크리트와 강지보의 압축력과 휨모멘트를 모두 고려하는 등가합성단면법, 그리고 (4) 각각의 빔 요소로서 모델링하는 방법을 포함하는 4가지 방법에 대해 수치해석을 실시하였다. 그 결과, 강지보의 지보효과를 고려한 경우가 그렇지 않은 방법에 비해 현실적이며 경제적인 설계에 접근할 수 있는 것으로 나타났다. 강지보를 고려하는 3가지 해석방법은 지반 조건에 따라 조금씩 다른 경향을 나타내므로 설계조건 및 상황에 맞는 적절한 사용이 필요하다. In general, the effects of steel ribs are not considered in the numerical analysis of tunnel design. However, attempts have been increased recently to consider these effects in the analysis of shallow tunnels in soft ground, based on the fact that the steel ribs embedded in the shotcrete take a role to support some portion of the redistributed load due to excavation. In such analyses, the steel ribs can be considered in four different methods: (1) a conventional method where the steel ribs are not considered, (2) a method using the equivalent composite cross section in which the bending moment of shotcrete is not considered, (3) a method using the equivalent composite cross section in which both the compressive stress and the bending moment for the shotcrete and steel rib are considered, and (4) a method using beam elements for the shotcrete and the steel rib, respectively. These methods are adopted in the numerical analysis using FLAC 2D to investigate stresses of both the shotcrete and the steel rib. The overall results show that the analyses are more practical and economical when the effects of steel rib are considered fer the methods (2), (3), and (4). Since the results of those analyses considering steel rib capacity may be different according to the ground condition, it will be necessary to consider the appropriate method among them in accordance with design conditions.
The MARS Simulation of the ATLAS Main Steam Line Break Experiment
하태욱,윤병조,정재준 한국에너지학회 2014 에너지공학 Vol.23 No.4
A main steam line break (MSLB) test at the ATLAS facility was simulated using the best-estimate thermal-hydraulic system code, MARS-KS. This has been performed as an activity at the third domestic standard problem for code benchmark (DSP-03) that has been organized by Korea Atomic Energy Research Institute (KAERI). The results of the MSLB experiment and the MARS input data prepared for the previous DSP-02 using the ATLAS facility were provided to participants. The preliminary MSLB simulation using the base input data, however, showed unphysical results in the primary-to-secondary heat transfer. To resolve the problems, some improvements were implemented in the MARS input modelling. These include the use of fine meshes for the bottom region of the steam generator secondary side and proper thermal-hydraulics calculation options. Other input model improvements in the heat loss and the flow restrictor models were also made and the results were investigated in detail. From the results of simulations, the limitations and further improvement areas of the MARS code were identified.
Solitary Lymphomatoid Granulomatosis at the Maxilla
하태욱,알파델 후세인 이브라힘,한다울,양우익,김동욱,조은애산드라 대한구강악안면병리학회 2019 대한구강악안면병리학회지 Vol.43 No.5
Lymphomatoid granulomatosis (LYG) is an uncommon Epstein-Barr virus (EBV)-associated B-cell lymphoproliferative disorder distinct from lymphoma. LYG primarily occurs in the lung with or without accompanied lesions in the skin, central nervous system, kidney, gastrointestinal tract, nose, eyes, liver and oral cavity. Solitary extrapulmonary LYG is extremely rare, and whether solitary lesions progress onto pulmonary development and dysfunction is controversial. Herein, we report a case on a solitary LYG in the maxilla gingiva with bone exposure in a patient who had been taking methotrexate for rheumatoid arthritis.
니켈페라이트 박막 N<sub>x</sub>Fe<sub>3-x</sub>O<sub>4</sub>를 이용한 선글라스 렌즈의 자외선 차단효과에 대한 연구
하태욱,이용희,최경서,차정원,Ha, T.W.,Lee, Y.H.,Choi, K.S.,Cha, J.W. 한국안광학회 2003 한국안광학회지 Vol.8 No.2
Nickel-ferrite $Ni_xFe_{3-x}O_4$ thin films with several composition for Ni on glass substrate was prepared by ferrite plating method in order to make sunglass which cut off ultraviolet and shield electromagnetic field. It has single phase of polycrystalline spinel structure and has gloss as mirror and has high hardness which is no scratch while scraping by using nail. The transmittance of nickel-ferrite thin film is lowered to zero below 400 nm manifestly. And it shows that the nickel-ferrite thin film in nickel composition rate x = 0.09 was most cut oil ultraviolet when compared with goods of other company in the cut off effect of ultraviolet. Therefore, sunglasses coated with $Ni_xFe_{3-x}O_4$ thin film can be used in removing ultraviolet and electromagnetic field. 자외선과 전자파를 동시에 차단하는 선글라스렌즈를 제작하기 위하여 유리가판 위에 자성재료인 페라이트에 Ni를 여러 가지 조성비로 첨가한 니켈페라이트 박막 $Ni_xFe_{3-x}O_4$을 페라이트 도금법으로 제작하였다. 이들은 모두 스피넬 구조의 단일상임을 확인할 수 있었으며 육안으로 관찰할 때 거울면과 같은 광택을 가졌으며, 손톱으로 긁었을 때 흠집이 생기지 않는 강도를 보였다. 니켈페라이트는 400nm 부근에서부터 급격히 투과율이 떨어져 자외선을 차단하는데 효과적인 양상을 보이고 있으며 그 중에서 x = 0.09의 Ni 조성비가 자외선 차단효과가 가장 좋은 깃으로 나타났다. 이는 타사제품과 비교하여 자외선 차단효과는 크게 떨어지지 않으므로, 전자파 차단효과가 있는 $Ni_xFe_{3-x}O_4$ 페라이트를 코팅한 선글라스를 착용함으로서 유해전자파와 자외선을 동시에 차단하는 효과를 얻을 수 있을 것이다.
MARS-CUPID 연계코드를 이용한 피동원자로건물냉각계통 격납건물 내부 열수력거동 분석
하태욱,이현진,이재룡,배성원 한국전산유체공학회 2022 한국전산유체공학회지 Vol.27 No.3
A passive containment cooling system (PCCS) has been designed to effectively remove the energy released to a containment by using condensation heat during a loss of coolant accident (LOCA) in a nuclear reactor. During the past few years, thermal-hydraulic performance of the PCCS has been analyzed using system scale codes, MARS and GOTHIC codes. In this work, thermal-hydraulic performance of the PCCS was analyzed again using the MARS-CUPID coupled code, which is a combinded code of the system scale and component scale, respectively. For a more realistic simulation, we modified Uchida correlation to take into account the effect of pressure in the MARS-CUPID coupled code. The simulation result showed the peak pressure of 4.31 bar, which is similar to the peak pressure obtained using the GOTHIC code. In this study, thermal-hydraulic performance of the PCCS considering uncertainty parameters, such as mass&energy release, heat transfer coefficient, and heat sink area, is also discussed.