• Corrosion Science and Technology
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• 제19권4호
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• pp.189-195
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• 2020

Two air vents situated on a heat transport pipe in district heating system were exposed to the same environment for 10 years. However, one air vent was more corroded than the other. It also had a hole on the top of the front-end pipe. Comparative analysis was performed for these air vents to identify the cause of corrosion and establish countermeasures. Through experimental observation of the damaged part and analyses of powders sampled from air vents, it was found that corrosion was initiated at the top of the front-end pipe. It then spread to the bottom. Energy dispersive X-ray spectroscopy results showed that potassium and chlorine were measured from the corroded product in the damaged air vent derived from rainwater and insulation, respectively. The temperature of the damaged air vent was maintained at 75 ~ 120 ℃ by heating water. Rainwater-soaked insulation around the front-end pipe had been hydrolyzed. Therefore, the damaged air vent was exposed to an environment in which corrosion under insulation could be facilitated. In addition, ion chromatography and inductively coupled plasma measurements indicated that the matrix of the damaged front-end pipe contained a higher manganese content which might have promoted corrosion under insulation.

• Geomechanics and Engineering
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• 제16권4호
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• pp.399-413
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• 2018

This paper addresses the issue of field measurement of excavation damage zone (EDZ) and its numerical simulation method considering both excavation unloading and blasting load effects. Firstly, a 2000 m-deep rock cavern in China is focused. A detailed analysis is conducted on the field measurement data regarding the mechanical response of rock masses subjected to excavation and blasting operation. The extent of EDZ is revealed 3.6 m-4.0 m, accounting for 28.6% of the cavern span, so it is significantly larger than rock caverns at conventional overburden depth. The rock mass mechanical response subjected to excavation and blasting is time-independent. Afterwards, based on findings of the field measurement data, a numerical evaluation method for EDZ determination considering both excavation unloading and blasting load effects is presented. The basic idea and general procedures are illustrated. It features a calibration operation of damage constant, which is defined in an elasto-plastic damage constitutive model, and a regression process of blasting load using field blasting vibration monitoring data. The numerical simulation results are basically consistent with the field measurement results. Further, some issues regarding the blasting loads, applicability of proposed numerical method, and some other factors are discussed. In conclusion, the field measurement data collected from the 2000 m-deep rock cavern and the corresponding findings will broaden the understanding of tunnel behavior subjected to excavation and blasting at great depth. Meanwhile, the presented numerical simulation method for EDZ determination considering both excavation unloading and blasting load effects can be used to evaluate rock caverns with similar characteristics.

• Journal of Welding and Joining
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• 제26권4호
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• pp.85-91
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• 2008

The grooving corrosion is caused mainly by the different microstructures between the matrix and weld which is formed during the rapid heating and cooling cycle in welding. By this localized corrosion reaction of pipes, it evolves economic problems such as the early damage of industrial facilities and pipe lines of apartment, and water pollution. So lots of researches were carried out already about grooving corrosion mechanism of ERW carbon steel pipe but there is seldom study for water hammer happened by fluid phenomenon and corrosion rate by flow velocity. In this study, the analysis based on hydrodynamic and fracture mechanics was carried out. ANSYS, FLUENT and STAR-CD were used for confirmation of flow phenomenon and stress on the pipe. As the results, fatigue failure is able to be happened by water hammer and grooving corrosion rate is increased cause by turbulent. Grooving corrosion is happened on the pipe, then friction loss of fluid is occurred from corroded part. Erosion can be happened enough in corroded region of microscopic size that wear "V" form. Also pipe is able to be damaged by water hammer effects because of corroded region is general acting as a notch effects. Corrosion depth was more than half of total thickness, it can be damaged from water hammer pressure.

• 한국작물학회지
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• 제58권3호
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• pp.226-231
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• 2013

국내 쌀 품종의 아밀로오즈 함량에 따른 총 11종 쌀가루의 아밀로오즈 함량, 손상전분, 수분함량, 수분흡수 지수(WAI), 수분용해지수(WSI), 입도분포 및 호화특성을 분석하였다. 국내 메성 쌀 품종 쌀가루의 아밀로오즈 함량은 9.95-21.52, 중간찰성은 11.69 및 찰성은 7.09%의 아밀로오즈 함량을 나타냈으며, 유색미 메성품종은 17.06-18.36% 및 유색 찰성 품종은 7.04%의 아밀로오즈 함량을 나타내는 것으로 확인되었다. 국내 쌀품종 쌀가루의 수분함량은 7.19-13.89%를 나타내었고, 수분흡수지수(WAI) 및 수분용해지수(WSI)의 경우 각각 남일 및 동진찰이 가장 높게 나타났고, 수분함량이 높은 시료의 경우 손상전분 함량이 낮은 것을 확인하였다. 국내 11품종의 쌀가루 입도 분포는 27.61- 189.67 ${\mu}m$를 나타내었으며 일반 메성 신동진 이 189.67 ${\mu}m$로 가장 높은 입도를 나타내었으며, 일반메성 품종인 남일이 27.61 ${\mu}m$로 가장 낮은 입도분포를 나타내는 것으로 확인되었다. 또한 본 연구결과 쌀가루의 수분함량이 낮은 시료가 전분입도가 낮으나 손상전분 함량이 높은 것으로 확인되었으며, 일반 메성 품종의 경우 수분함량 및 입도가 작은 시료는 최고 점도 및 최종점도가 높고, 유색메성품종의 경우 수분함량 및 입도가 작은 시료는 점도가 낮은 결과를 나타냈다.

• 한국식품과학회지
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• 제28권6호
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• pp.1078-1083
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• 1996

쌀보리를 정맥기를 사용하여 도정한 정맥에 대해 제분기의 종류를 달리하여 제분한 결과 보리가루는 입도 분포에서 차이를 나타내 Jet mill로 제분한 보리가루의 입자 크기가 가장 작았으며 그 다음으로 Pin mill과 Cyclotec sample mill에 의한 입자 크기가 작았고 Ball mill과 Fitz mill에 의한 보리가루가 가장 큰 것으로 나타났다. 보리가루는 입자크기가 작을수록 색이 밝고 전분 손상도가 높은 경향을 나타냈다. 보리가루의 표면구조는 크고 작은 전분 입자, 주름진 세포벽 물질 등으로 관찰되었으며 가루 입자의 형태 및 크기가 제분기의 종류에 따라 다소 차이를 나타냈다. 보리가루는 손상된 전분의 양이 많을수록 높은 수분흡수지수 및 보수력을 나타냈으며 수분용해도지수 역시 증가하는 경향을 보여주었다. 보리가루의 호화 특성을 측정한 결과 보리가루의 점도는 입자가 크게 분쇄된 Fitz mill에 의한 보리가루에서 가장 낮았으며 Pin mill과 Cyclotec mill에서 높게 나타났다. 아주 미세하게 분쇄된 Jet mill은 호화가 빨리 진행된 반면 점도의 상승은 크지 않아 지나친 전분의 손상은 점도를 떨어뜨리는 것으로 판단되었다.

• 한국군사과학기술학회지
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• 제13권6호
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• pp.1026-1033
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• 2010

The analysis of water-entry impact forces acting on the fin shaft of high speed water-entry body is described. During the entry of high speed body into water, the physical phenomenon and flow properties are analyzed. A proper analysis model is established and the method to estimate the flow force which causes impact torque at the fin shaft is described. It is assumed that the fin shaft is damaged by the force which is induced by contacting with cavity wall. The pressure distribution of fin and the maximum torque are estimated and compared with breaking force. Conclusively, it is hard to resist water-entry impact force in terms of the reinforcement of fin shaft. Additionally safe equipment is essentially required.

• Nuclear Engineering and Technology
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• 제56권4호
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• pp.1250-1253
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• 2024

Activity measurement of the primary circuit water of fission reactors is one method that can provide early detection of a damaged fuel assembly in the reactor core. This is an important aspect in the safe operation of the reactor and for radiation protection of staff. Radionuclides in the primary circuit water are produced by the activation of stable nuclides and the fission of fissile nuclides, mainly the isotope ²³⁵U. In the LVR-15 research reactor, measurement of the activity of the primary circuit water has been regularly undertaken since 1996. A water sample is taken from the primary circuit every week and the activities are measured four days later using gamma spectrometry. The results of these long-term measurements from 1996 to 2022 are presented. The activity time dependences of the individual radionuclides are discussed in relation to fuel assembly damage and for events connected to contamination of the water by objects inserted into the primary circuit during experiments carried out near the reactor core.

• 한국신뢰성학회지:신뢰성응용연구
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• 제15권3호
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• pp.197-206
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• 2015

Failure analysis of pre-insulated pipe (SPPS 380, 400A) transporting high temperature water ($95{\sim}110^{\circ}C$) for a plant was carried out. The damaged area (${\Phi}5mm$) of pre-insulated pipe was found only on welds. The chemical composition of damaged pipe meets specification of carbon steel pipes for pressure service (KS D 3562). As results of microstructure analysis, crack propagated from outer to inside after pitting corrosion occurred on the outside surface. The non-metallic inclusion existed on the end of crack. And the non-metallic inclusion continuously and linearly formed along with the bond line of welds. Based on SEM-EDS analysis, the nonmetallic inclusions have higher Manganese (Mn) and Oxygen (O) content but sulfur (S) was not detected. As results of water quality analysis, hydrogen ion concentration and minerals like Fe, Mg, Si were in low level. But the content of dissolved oxygen (11.2 ppm) was slightly higher than that of standard. It seems that the cause of damaged pipe is grooving corrosion due to MnO inclusion formed on bond line and corrosion took place nearby welds.

• 한국수자원학회논문집
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• 제38권1호
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• pp.37-48
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• 2005

본 연구에서는 국내ㆍ외의 하천자연도평가에 관한 방법을 조사하고, 국내에서 연구ㆍ제안된 하천자연도평가방법에 따라 내린천, 복하천과 안양천의 3개하천의 시범평가를 시행하였다. 시범평가 결과, 자연상태가 비교적 잘 보전된 내린천은 2등급, 인위적인 훼손에서 회복단계에 있는 복하천은 3등급, 인위적인 훼손이 심각한 안양천은 4등급으로 평가되어 비교적 하천의 생물서식처의 훼손정도를 적절히 반영하고 적용성이 우수한 것으로 검토되었다. 따라서 본 평가방법을 국가하천 및 지방1급하천 등 대하천에서도 적용이 가능하도록 평가부문 및 평가항목을 개선하여 하천의 생물서식처 복원을 위한 하천자연도평가 방법과 절차를 제안하였다. 금번 제안한 하천자연도평가는 하천형태와 하천환경의 2개 평가부문과 14개의 평가항목으로 구성하고, 평가척도는 자연성 저감정도에 따라 5등급으로 구분하였으며, 평가단위는 최적간격을 2,000m∼3,000m로 하였다.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2016년도 학술발표회
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• pp.326-326
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• 2016

단층은 지질학적 관점에서 국부적인 지구구조응력(tectonic stress)이 암반 내에 존재하는 어떤 면을 따라 파괴 분기값을 초과하는 경우에 발생하는 매우 큰 공간적 변이에 의한 파괴 면으로 정의된다. 이러한 단층의 수문지질학적 특성은 단층의 공간적인 분포와 간극의 연결성에 따라 변화된다. 단층의 형성이 단층 내의 간극의 생성과 파괴를 이끄는 과정이 포함될 때 단층을 따라 발생되는 변이와 간극의 변화 사이에 복잡한 관계가 존재한다. 본 연구에서는 단층의 기하학적 특성에 따라 변화되는 흐름 변화를 3차원 이산 균열망 모형을 통해 모의 및 분석을 수행하였다. 단층의 기하학적 특성에 대해 3가지 경우를 고려하였다. 첫 번째는 영역 중심에 위치한 폭이 매우 좁고 상대적으로 주위 암반보다 매우 높은 투수성을 가진 단층, 두 번째는 단층 주변에 손상지역(damaged zone)이 존재하는 경우 그리고 세 번째는 relay 구조를 가진 단층이다.