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Yang, Myung,Kim, Dai-Hong,Kim, Won-Sik,Kang, Tae June,Lee, Byung Yang,Hong, Seunghun,Kim, Yong Hyup,Hong, Seong-Hyeon IOP Pub 2010 Nanotechnology Vol.21 No.21
<P>SnO<SUB>2</SUB> nanoparticle coated single wall nanotube (SWNT) network sensors were fabricated by forming a SWNT network on the Pt patterned SiO<SUB>2</SUB><I>/</I>Si substrate using a dip coating method and subsequently depositing SnO<SUB>2</SUB> nanoparticles on the SWNT network by rf magnetron sputtering. Their H<SUB>2</SUB> gas sensing properties were investigated. The SnO<SUB>2</SUB>–SWNT network sensors stably and reversibly responded to H<SUB>2</SUB> gas even at room temperature and could detect H<SUB>2</SUB> gas down to 100 ppm. In addition to the low temperature detection, a remarkable finding was that the gas sensing behavior of SnO<SUB>2</SUB>–SWNT network sensors was changed from p-type to n-type with increasing SnO<SUB>2</SUB> deposition time (i.e. surface coverage of SnO<SUB>2</SUB> on SWNT). A schematic model was proposed to explain the switching of sensing behavior depending on the surface coverage of SnO<SUB>2</SUB> nanoparticles on the SWNTs. </P>
Seonguk Hong,Seunghun Kim 한국콘크리트학회 2019 International Journal of Concrete Structures and M Vol.13 No.7
Among fiber-reinforced composites, steel fiber has been widely-used for concrete infrastructure such as silos, tunnels, specifically aiming at reducing the weight of concrete and enhancing its strength by overcoming the brittleness. However, there is still little known about appropriate quality management and applicability assessment for steel fiber composites. This study fills this knowledge gap by testing the possibility of maintenance through steel fiber concrete thickness estimation and assessing the applicability of the quality management instrument. To this end, this study utilizes two different stress wave-driven non-destructive test methods: ultrasonic pulse velocity and impact-echo methods. The ultrasonic pulse velocity method was employed to estimate the compressive strength of steel fiber reinforced concrete, while the impact-echo method was applied to estimate the thickness of various steel fiber reinforced concrete members. As a quality management factor of concrete, correlations between steel fiber mixing ratios and compressive strengths were experimentally explored and validated by error ratios for twenty-four specimens. The reliability was relatively high overall. The average error rate of all the specimens with steel fiber mixing ratios of 0, 0.75 and 1% was 3.36%. Accordingly, the results prove the applicability of the non-destructive test methods for building quality management.
Seonguk Hong,Yongtaeg Lee,Seunghun Kim,Changsik Lee 대한건축학회 2016 Architectural research Vol.18 No.4
The structure must be periodically checked and measures must be taken to prevent deterioration in building construction. From this point of view, a nondestructive test is essential to estimate whether the construction of buildings is proper, and whether the dimension of depositing concrete is consistent and without damage. This study estimated the thickness of the concrete component of construction framework using the ultrasonic velocity method and the impact echo method, in order to investigate reliability of the estimation of the thickness of normal strength concrete and high strength concrete, leading to the following conclusions. In the estimation of the thickness of the concrete structures, specimens of normal strength of 24MPa and specimens of high strength of 40MPa demonstrated an average error rate of 5.1% and 2.2%, respectively. The impact-echo method, one of the non-destructive tests, is verified as an efficient diagnostic technique. With this information, we will determine specific standards for the maintenance of structures, and the re-creation of lost building blueprints.
류승훈(Seunghun Ryoo),홍문근(Moongeun Hong),유재한(Jaehan Yoo),이수용(Sooyong Lee) 한국추진공학회 2009 한국추진공학회 학술대회논문집 Vol.2009 No.11
액체로켓 엔진에서 산화제를 가스발생기에 공급하는 가스발생기 산화제 개폐밸브는 가스 발생기 연소압 이상의 높은 압력에서 구조적인 안정성을 확보하여야 한다. 본 연구에서는 내압 하중 조건을 받는 밸브의 경량화를 위하여 응력 집중 부위의 형상을 변화시켜가며 정적 응력 해석을 수행하였다. 그리고 최대 응력이 항복응력을 넘지 않으며 최소 중량을 가지는 밸브 형상을 제시하였다. 또한, 응력 집중부에 대한 전체 밸브 사이즈 변화의 영향도 살펴보았다. For the liquid rocket engine, the gas generator oxidizer shut-off valve which supplies the oxidizer to a gas generator needs structural safety under the internal pressure, which is higher than the chamber pressure. In this study, static stress analyses of the various design in the vicinity of the region where the stress is concentrated were performed for designing the lightweight valve, A lightest model of which the concentrated stress does not exceed the yield criteria has been suggested. Also, whole size effect of the valve on the concentrated stress was investigated.