• 한국압력기기공학회 논문집
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• 제17권2호
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• pp.126-136
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• 2021

During operation of nuclear power plants, the fatigue assessment should be conducted repeatedly, considering changes of operating environments. For the case that cumulative usage factors (CUFs) may exceed the acceptance limit, flaw tolerance evaluation can be an alternative method to meet the regulatory requirements. In this respect, this paper analyzes the effects of the input variables for flaw tolerance evaluation based on ASME BPVC Section XI Appendix L. The reference analysis is performed for the example problem in NUREG/CR-6934. Then effects of the crack orientation, stress intensity factor solutions, thermal stress profiles, fatigue stress decomposition and fatigue crack growth curves are considered for the sensitivity analysis. The results show that the stress analysis considering the actual environment plays a crucial role in flaw tolerance evaluation.

• Fisheries and Aquatic Sciences
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• 제19권4호
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• pp.21.1-21.11
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• 2016

Background: The evaluation of suitable reference genes as normalization controls is a prerequisite requirement for launching quantitative reverse transcription-PCR (RT-qPCR)-based expression study. In order to select the stable reference genes in abalone Haliotis discus hannai tissues (gill and hepatopancreas) under heavy metal exposure conditions (Cu, Zn, and Cd), 12 potential candidate housekeeping genes were subjected to expression stability based on the comprehensive ranking while integrating four different statistical algorithms (geNorm, NormFinder, BestKeeper, and ${\Delta}CT$ method). Results: Expression stability in the gill subset was determined as RPL7 > RPL8 > ACTB > RPL3 > PPIB > RPL7A > EF1A > RPL4 > GAPDH > RPL5 > UBE2 > B-TU. On the other hand, the ranking in the subset for hepatopancreas was RPL7 > RPL3 > RPL8 > ACTB > RPL4 > EF1A > RPL5 > RPL7A > B-TU > UBE2 > PPIB > GAPDH. The pairwise variation assessed by the geNorm program indicates that two reference genes could be sufficient for accurate normalization in both gill and hepatopancreas subsets. Overall, both gill and hepatopancreas subsets recommended ribosomal protein genes (particularly RPL7) as stable references, whereas traditional housekeepers such as ${\beta}-tubulin$ (B-TU) and glyceraldehyde-3-phosphate dehydrogenase (GAPDH) genes were ranked as unstable genes. The validation of reference gene selection was confirmed with the quantitative assay of MT transcripts. Conclusions: The present analysis showed the importance of validating reference genes with multiple algorithmic approaches to select genes that are truly stable. Our results indicate that expression stability of a given reference gene could not always have consensus across tissue types. The data from this study could be a good guide for the future design of RT-qPCR studies with respect to metal regulation/detoxification and other related physiologies in this abalone species.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2006년도 추계학술대회 논문집
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• pp.322-327
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• 2006

Banwol bridge with steel plate girder and Pyongtaek bridge with PSC bos girder have been operated maintenance measuring system by the Seoul-Chonan of Kyongbu express railway. By analyzing the theoretical and experimental values of design load for these two bridge, the establishment of reference maintenance for measuring items was deduced from research. Two materials, steel and concrete plates, were considered as the upper structure. Actual measurement data for the behavior under speed, structural analysis results, and the presented references were analyzed and used to set up the reference establishment. The measuring items are stress(strain), displacement, dynamic acceleration, expansion movement, and dynamic frequency. The maintenance reference was established by comparing analytical and measuring values of the five items with respect to structural state class.

• Nuclear Engineering and Technology
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• 제48권6호
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• pp.1412-1422
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• 2016

Austenitic stainless steels (ASSs) are widely used for nuclear pipes as they exhibit a good combination of mechanical properties and corrosion resistance. However, high tensile residual stresses may occur in ASS welds because postweld heat treatment is not generally conducted in order to avoid sensitization, which causes a stress corrosion crack. In this study, round robin analyses on stress intensity factors (SIFs) were carried out to examine the appropriateness of structural integrity assessment methods for ASS pipe welds with two types of circumferential cracks. Typical stress profiles were generated from finite element analyses by considering residual stresses and normal operating conditions. Then, SIFs of cracked ASS pipes were determined by analytical equations represented in fitness-for-service assessment codes as well as reference finite element analyses. The discrepancies of estimated SIFs among round robin participants were confirmed due to different assessment procedures and relevant considerations, as well as the mistakes of participants. The effects of uncertainty factors on SIFs were deducted from sensitivity analyses and, based on the similarity and conservatism compared with detailed finite element analysis results, the R6 code, taking into account the applied internal pressure and combination of stress components, was recommended as the optimum procedure for SIF estimation.

• Geomechanics and Engineering
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• 제24권5호
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• pp.479-490
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• 2021

Pre-drainage of groundwater in the roof aquifer by boreholes is the main method for prevention of roof water disaster, and the drop in the water level during the drainage leads to the variation of the local stress in the overlying strata. Based on a multitude of boreholes for groundwater drainage from aquifer above the 1303 mining face of Longyun Coal Mine, theoretical analysis and numerical simulation are used to investigate the local stress variation in the process of borehole drainage. The results show that due to the drop in the water level of the roof aquifer during the drainage, the stress around the borehole gradually evolved. From the center of the borehole to the outside, a stress-relaxed zone, a stress-elevated zone, and a stress-recovered zone are sequentially formed. Along with the expansion of drainage influence, the stress peak in the stress-elevated zone also moves to the outside. When the radius of influence develops to the maximum, the stress peak position no longer moves outward. When the coal mining face advances to the drainage influence range, the abutment pressure in front of the mining face is superimposed with the high local stress around the borehole, which increases the risk of stress concentration. The present study provides a reference for the stress concentration caused by borehole drainage, which can be potentially utilized in the optimal arrangement of drainage boreholes in underground mining.

• 대한기계학회논문집A
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• 제27권5호
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• pp.724-733
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• 2003

Fatigue design rules for welds in the ASME Boiler and Pressure Vessels Code are based on the use of Fatigue Strength Reduction Factors(FSRF) against a code specified fatigue design curve generated from smooth base metal specimens without the presence of welds. Similarly, stress intensification factors that are used in the ASME B3l.1 Piping Code are based on component S-N curves with a reference fatigue strength based on straight pipe girth welds. But the determination of either the FSRF or stress intensification factor requires extensive fatigue testing to take into account the stress concentration effects associated with various types of component geometry, weld configuration and loading conditions. As the fatigue behavior of welded joints is being better understood, it has been generally accepted that the difference in fatigue lives from one type of weld to another is dominated by the difference in stress concentration. However, general finite element procedures are currently not available for effective determination of such stress concentration effects. In this paper, a mesh-insensitive structural stress method is used to re-evaluate the S-N test data, and then more effective method is proposed for pressure vessel and piping fatigue design.

• 한국자동차공학회논문집
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• 제19권5호
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• pp.113-117
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• 2011

The frame for automotive assembly can be deformed and remained on the residual stress due to high temperature thermal attacks when in welding. The frame deformation can be made to problems when in assembly with body and the residual stress can affect the negative effect on durability performance of the automobile. In order to analyze the frame deformation, the simplified test frame which had the similar shape (form) of the real automotive frame was fabricated. The contactless optical 3D scanner was used for the shape difference measurement of the frame between before and after the welding. The FE-model of the test frame was composed and the heat transfer and thermal stress simulation were performed. The simulated results were compared with the measured results for the reference of the frame design. The deformation shape of the frame by simulation was in good agreement with that by the experimental measurement.

• 대한임상검사과학회지
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• 제46권2호
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• pp.68-74
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• 2014

The purpose of this study is to provide an academic basis regarding the necessity of managing depression and stress among metabolic syndrome patients by understanding 5 components of metabolic syndrome, perceived stress, and degree of depression, and by investigating their association using the national nutrition survey reference. This study was conducted by using mental health surveys and health screening test data of the 5th (2010~2012) primitive data of the national health and nutrition survey. A total of 19,599 respondents over 19 years of age were selected for the final analysis. The level of depression and stress was set as the dependent variable to identify its connection with 5 components of the metabolic syndrome. For the stress recognition, none of the metabolic syndrome components showed a significant correlation. For experiencing the depression symptom, the fasting glucose among the factors showed a significant correlation (p<0.05) among the metabolic syndrome factors. When it falls within the criteria of fasting glucose of metabolic syndrome, it has a great probability of falling under the group who experienced greater depression symptoms. As a result of the analysis by controlling cardiovascular and cerebrovascular disease which is tightly related with metabolic syndrome and depression, this study observed that glucose out of 5 metabolic syndrome components is related with depression.

• Journal of Nutrition and Health
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• 제55권4호
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• pp.430-440
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• 2022

셀레늄은 산화스트레스 방어 기능으로 인체의 면역기능 유지에 필수적 역할을 하고, 세포의 항산화기능, 면역기능, 갑상선호르몬 조절, 약물이나 중금속 위해에 대한 방어, 만성질환의 위험 감소에 필수 역할을 하는 미량무기질이다. 셀레늄 섭취의 부족은 암, 심혈관질환, 당뇨병, 신경질환, 골관절 및 근육괴사와 약화, 갑상선질환, 염증성 질환 등 다양한 만성적 질환의 위험을 높인다. 본 논문은 2020 한국인 영양소 섭취기준에서 셀레늄의 제정과 개정 근거 기준에 대해 설명하고, 셀레늄 데이터베이스의 현황과 향후 2025 한국인 영양소 섭취기준 설정을 위한 필요 연구에 대해 논의하였다. 셀레늄의 2020 한국인 영양소 섭취기준은 2015년에 이어 혈장 셀레노프로테인 P 수준이 최대가 되는 셀레늄의 평균필요량을 지표로 사용하였고, 중국인 대상의 보고치에 한국인의 기준체중과 변이계수를 적용하는 방법이 적용되었으며, 2015년에 비해 참고체중치의 변경에 따라 성별, 연령별 셀레늄 섭취기준에서 약간의 개정이 있었다. 향후 셀레늄 섭취기준 설정의 발전을 위해서는 1) 한국인 대상의 혈장 셀레노프로테인 P의 최대수준을 나타내는 셀레늄 섭취량을 파악하기 위한 셀레늄 중재연구가 필요하고, 2) 셀레늄 섭취량 판정의 정확성을 높이기 위한 영양평가 프로그램내 식품 셀레늄 데이터베이스의 검토와 식품의 셀레늄 함량 분석을 확대해야 하며, 3) 국민의 셀레늄 섭취와 체내 생물학적 지표와의 관계를 건강한 일반인뿐만 아니라 질환자 및 운동선수와 같은 특수 환경의 대상자들로 확대하는 연구가 요구된다.

• 터널과지하공간
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• 제31권4호
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• pp.221-242
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• 2021

기존의 한국형 기준 처분시스템의 처분 효율을 높인 향상된 한국형 기준 처분시스템(Improved Korean Reference Disposal System, KRS⁺)의 열-수리-역학적 복합거동 성능평가를 위해 TOUGH2-MP/FLAC3D를 이용한 수치모델링 연구가 수행되었다. 사용후핵연료 처분 이후 방사성 붕괴열에 의해 처분시스템의 온도가 상승하고, 방사성 붕괴열이 빠르게 감소함에 따라 온도가 감소하여 최대 온도가 설계기준 온도인 100℃를 넘지 않는 것으로 나타났다. 완충재의 초기 포화도는 온도 상승으로 인한 공극수의 증발로 인해 감소하였다가 주변 암반으로부터 지하수가 유입되어 처분 약 250년 후 포화 상태에 이르렀다. 암반에서는 완충재와 암반의 흡입력의 차이로 인해 암반에서 완충재로 지하수가 유입되어 처분 직후 포화도가 감소하다가 이후 원계 암반으로부터 지하수가 유입되어 포화 상태에 도달했다. 처분시스템 내 열응력과 팽윤압 발생에 의한 주변 암반의 파괴 가능성을 평가하고자 모어-쿨롱 파괴기준식과 스폴링 강도를 사용하였다. KRS⁺ 처분시스템의 처분공의 간격을 감소시키면서 처분시스템의 열적 거동 변화를 확인하였는데, 처분공 간격이 5.5 m 이하에서는 완충재의 설계 기준 온도를 초과하게 된다. 다만, 벤토나이트 완충재 부피의 56.1%의 온도는 90℃ 이하로 유지되었다. 본 연구에서 사용한 수치해석 기법은 향후 응력 모델, 지온 경사 및 입력 물성을 변화시킨 다양한 조건에서의 처분시스템의 THM 복합거동 성능평가에 활용할 수 있을 것으로 판단된다.