• Proceedings of the Korea Water Resources Association Conference
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• 2021.06a
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• pp.57-57
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• 2021

최근 급격한 도시화와 기후변화로 인해 도시의 홍수피해가 증가하고 있으며, 복합적인 재난으로 악화되는 경우가 많아졌다. 복합재난으로 인한 피해를 줄이기 위해 재해발생 전·후 대응이 중요하며, 이를 위해 복원력 개념을 도입할 필요가 있다. 도시 배수 시스템의 복원력은 대상유역의 면적과 절대적인 침수량에 따라 좌우된다. 따라서 지역의 도시 배수 시스템의 복원력을 정확하게 평가하기 위해 대상유역의 정보를 반영한 지역 맞춤형 복원력 지수의 개발이 필요하다. 대상유역의 정보를 반영하기 위해 도시 배수 시스템의 배수능력을 복원력 지수에 적용하였다. 도시 배수 시스템의 배수능력을 나타내기 위해 시스템 잔류유량을 분모로, 침수량을 분자로 하여 복원력 지수를 계산하였다. 본 연구에서는 제안된 새로운 복원력 지수를 대구 비산 빗물펌프장에 적용하였다. 강우자료는 재현기간이 100년, 200년 그리고 300년 빈도의 확률강우량을 사용하였으며, 지속시간은 30분, 60분 그리고 90분으로 설정하였다. 침수량과 시스템 잔류 유량은 1분 단위로 EPA SWMM을 통해 값을 구하였다. 시스템 잔류 유량을 기반으로 하는 복원력 지수는 최소 0.995029에서 최대 0.998662로 나타났다. 본 연구에서 제안한 도시 배수 시스템 잔류 유량 기반 복원력 지수는 배수 시스템의 처리 능력을 반영한 지수라고 할 수 있으며 배수 시설의 설치, 교체 및 재건 등 수해 방재 계획 평가에 활용될 수 있다.

• Journal of Korean Society of Steel Construction
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• v.13 no.4
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• pp.327-335
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• 2001

The characteristics and production mechanism of residual stress generated by multi-pass welding of the steel pipe were elucidated from the results of three-dimensional thermal elastic-plastic FEM analysis. When the steel pipe was jointed by multi-pass welding, the stress components of circumferential direction and radial direction near welded joints on the inner surface and the outer surface of the pope were tensile. The stress component of axial direction on the inner surface was tensile and on the outer surface was compressive. On the other hands, the production mechanism of residual stress generated by multi-pass welding of the steel pipe was investigated. Residual stress generated by welding of the steel pipe was investigated not only by the thermal history but also by geometrical shape. Then, the generality of the production mechanism of residual stress generated by multi-pass welding was confirmed.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.5
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• pp.543-547
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• 2011

Primary water stress corrosion cracking has occurred in dissimilar weld areas in nuclear power plants. Residual stress is a driving force in the crack. Residual stress may be generated by weld or surface machining. Residual stress due to surface machining depends on the machining method, e.g., milling, grinding, or EDM. The stress is usually distributed on or near the surface of the material. We present the measured residual stress for machining on SA 508 and austenitic stainless steels such as TP304 and F316. The residual stress can be tensile or compressive depending on the machining method. The depth and the magnitude of the residual stress depend on the material and the machining method.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.5
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• pp.453-458
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• 2011

We study the effect of mechanical machining and heat treatment on the surface residual stress of TP 316L stainless steel. Electrical discharge machining (EDM), milling and grinding were applied to TP 316L plate specimens. The residual stress and hardness were measured and the effect of heat treatment on the surface residual stress was examined. The residual stress was measured by the X-ray diffraction method, which showed that the surface residual stress was related only to the stress magnitude and was independent of the compressive or tensile component. The surface residual stress was greatly decreased by the heat treatment, but it was not removed completely.

• Proceedings of the KWS Conference
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• 2010.05a
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• pp.84-92
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• 2010

현재 가동 중인 몇몇 가압 경수로 원전 안전 1등급 설비의 이종금속 용접부는 일차수응력부식균열(PWSCC : Primary Stress Corrosion Cracking) 발생의 세가지 조건(민감 재질, 부식 환경, 인장응력)을 동시에 충족하고 있다. 즉, 이종금속 용접부는 PWSCC에 민감한 재질인 Alloy 600 계열 합금으로 제작 또는 용접되어 있으며 고온 수화학 부식 환경 하에 놓여있다. 아울러 오스테나이트 스테인리스 강의 예민화 예방을 위한 용접 후열처리 미실시로 높은 인장 용접 잔류응력이 작용하고 있다. 이러한 이종금속 용접부의 특성상 PWSCC가 발생할 잠재성이 있을 뿐만 아니라 국내외적으로 Alloy 600 계열 합금으로 제작 및 용접된 가압 경수로 원전 안전 1등급 설비의 이종금속 용접부에 실제 PWSCC가 발생된 사례들이 다수 보고되고 있다. 운전 환경 및 재질 변화 없이 PWSCC 발생을 예방하기 위해서는 인장 잔류응력을 이완시켜 낮은 인장 또는 압축 응력화하여야 한다. 이러한 인장 잔류응력 이완방법들로는 PWOL(Pre-emptive Weld Overlay), 레이저 피닝(Laser Peening), MSIP(Mechanical Stress Improvement Process), 워터 제트 피닝(Water Jet Peening), IHSI(Induction Heating Stress Improvement) 방법들이 있는데 공정 시간이 짧고 열 에너지 원이 필요 없으며 전체적인 소성 변형을 야기시키지 않는 레이저 피닝을 본 연구의 대상 방법으로 한다. 본 연구에서는 동적 유한요소 해석을 통해 용접 잔류응력을 이완시키는 레이저 피닝의 효과를 검증하고 용접 잔류응력에 미치는 레이저 피닝 변수의 영향을 고찰하고자 한다. 내부 보수용접이 수행된 경수로 원전 가압기 노즐 이종금속 용접부에 레이저 피닝을 적용한 경우에 대해 상용 유한요소 해석 프로그램인 ABAQUS를 이용하여 동적 유한요소해석을 수행한 결과, 고온 수화학 일차수와 접하는 Alloy 600 계열 합금 내면에서의 인장 잔류응력이 상당히 이완됨을 확인하였다. 또한, 최대충격 압력이 증가할수록, 충격압력 지속시간이 증가할수록, 레이저 스팟 직경이 증가할수록 내표면 인장 잔류응력 이완 정도는 감소하나 이완되는 영역의 깊이는 증가함을 알 수 있다. 또한, 레이저 피닝 방향이 잔류응력 이완에 미치는 영향은 미미함을 알 수 있다.

• Journal of Korean Society of Steel Construction
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• v.16 no.5 s.72
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• pp.519-528
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• 2004

Most of ferrous b.c.c weld materials may experience martensitic transformation during rapid cooling after welding. And it is well known that volume expansion due to phase transformation could influence in the case of welding of high tensile strength steels on the relaxation of welding residual stress. To apply this effect practically, it is a prerequisite to establish a numerical model which is able to estimate the effect of phase transformation on residual stress relaxation quantitatively. In this study, we investigated the effect of phase transformation on the relaxation of welding residual stress through experiment. And three-dimensional thermal elastic-plastic FEM analysis is conducted to reproduce the effect of phase transformation on the relaxation of welding residual stress. Also we carried out the analysis of welding residual stress in welds of similar or dissimilar steels considering the effect of residual stress relaxation due to phase transformation.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.7
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• pp.717-722
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• 2011

The purpose of this study is to predict the residual stress in Al6061 during T6 heat treatment. In this study, the variable residual stress in case of the solid solution($530^{\circ}C$, 2h) and artificial ageing($175^{\circ}C$, 9h) of Al6061 subjected to T6 heat treatment is determined at different ageing times. A heat treatment experiment is conducted to determine the heat transfer coefficient, on the basis of which the residual stress during the T6 heat treatment is predicted. In order to take into account the relaxation of residual stress during artificial ageing, a Zener-Wert-Avrami function is used and elasto-plastic nonlinear analysis is conducted through FE-simulation. Further, the residual stress is measured by using the X-ray diffraction(XRD) method, and the result is compared with the result from the FE-simulation. It is found that the residual stress predicted form the FE-simulation is in good agreement with the residual stress measured by using the XRD method.

• Journal of the Korean GEO-environmental Society
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• v.11 no.9
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• pp.5-14
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• 2010

This study was aimed to suggest reliable information of shear strength characteristics due to change of saturation in the landfills or slopes during rainfall infiltration. According to the Mohr-Coulomb failure criteria, the characteristics of shear strength due to change of saturation were analyzed for the weathered residual soils which were sampled in the road construction site of Daejeon city. From the direct shear strength tests, the cohesions and the shear resistance angles were showed maximum values in the condition of optimum moisture content, and then decreased in the condition of wet side compaction. In this study, the cohesions were decreased more than 50% according to increasing saturation by infiltration for the compaction soils. But the reductions of the shear resistance angles were about $1{\sim}2^{\circ}$ which was small value, and thus the changes of the saturation were not nearly influenced the shear resistance angle. The influences of the saturation were seemed to very small for the residual strength parameters according to Mohr-Coulomb failure criteria.

• Journal of Chest Surgery
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• v.35 no.8
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• pp.580-583
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• 2002

Background: Obtaining precise hemodynamic and morphological information in the early postoperative period after surgical correction of congenital heart disease is important in determining the need for future medical or surgical intervention. We investigated the residual shunting after surgical repair of simple ventricular septal defect in order to know the incidence of residual shunting in the postoperative period and the natural history of small residual shunts located in the peripatch area. Material and Method: Forty three consecutive patients under one year of age who underwent patch repair of a simple ventricular septal defect were evaluated for incidence of residual shunts by echocardiography. Result: Eleven patients had echocardiographic residual shunt in the peripatch area at immediate postoperative period, however, there were no patients who needed reoperation due to deteriorated hemodynamic effect of residual shunt. The incidence of residual shunts was not significantly different with type of ventricular septal defect and material used for closure. During follow up period, two patients were lost and remaining nine patients no longer showed evidence of residual shunt. The mean time of last evidence of shunt was $4.2{\pm}3.6$ months after operation. Conclusion: Residual peripatch shunt flow was frequently noted in the immediate postoperative period following surgical repair of ventricular septal defect, however, most of them were disappeared within six months.

• Food Science of Animal Resources
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• v.27 no.3
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• pp.299-307
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• 2007

Changes in nitrite content, TBARS content and color of meat products during storage were examined as part of studies addressing the reduction of residual nitrite and to ensure the safety of meat products. All 4 kinds of domestic meat product tested, Vienna sausage, bacon, smoked-ham and Dduggalbi, manufactured by C and L domestic companies had very low contents of residual nitrite, for below the legal tolerance limit of 70 ppm, and the residual nitrite decreased with storage. The reduction in nitrite content differed with each product, showing the greatest reduction in Vienna sausage and the least reduction in bacon when stored at $4^{\circ}C$. On the other hand, when stored at $-20^{\circ}C$, the nitrite content of bacon decreased more rapidly than the other meat products. The results of this study show that the nitrite content of meat products decreases during storage, and that the rate of decrease is quite dependent on the storage temperature. In addition, the nitrite contents of most domestic meat products are very low compared to the legal limits, thus the health risks of nitrite in meat products might not be of great concern. More research on the reduction of residual nitrite and on the development of alternatives to nitrite is necessary.