• 한국의류산업학회지
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• 제15권6호
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• pp.985-992
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• 2013

Polytrimethylene terephthalate(PTT) offers several advantageous properties such as good tensile strength, uniformity, stiffness, toughness, UV stability, resilience, stain resistance, outstanding elastic recovery, and dyeability. The effects of annealing temperature on physical properties and the structure of PTT filaments and yarn were investigated by measuring wide-angle X-ray diffraction (WAXD), density, optical birefringence, dynamic visco elasticity, and tensile testing. The intensity of maximum tan ${\delta}$ decreased and the temperature of maximum tan ${\delta}$ shifted to a higher temperature as the annealing temperature of filaments increased; however, it shifted to a lower temperature when the annealing temperature exceeded $130^{\circ}C$. In addition, crystallinity, density and D-spacing of (010) crystal face increased as the annealing temperature increased. Optical birefringence and specific stress were almost constant up to $100^{\circ}C$ and then decreased above $130^{\circ}C$. The shrinkage of PTT filament is 0 in boiling water when annealed above $130^{\circ}C$; consequently, the use of annealed fiber above $130^{\circ}C$ can remove thermal instability when dyeing PTT fiber. In the case of yarns, the thermal stability and physical properties of yarns showed the best effect when the ply number is less than 5, twist number is less than 400tpm, and the annealing time is 20minutes.

• 대한기계학회논문집A
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• 제25권8호
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• pp.1277-1286
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• 2001

Aluminum 5052/Aramid Fiber Reinforced Plastic(Al5052/AFRP) laminates are applied to the fuselage-wing intersection. The Al5052/AFRP laminates suffer from the cyclic bending moment of variable amplitude during the service. Therefore, the influence of cyclic bending moment on the delamination and the fatigue crack propagation behavior in Al5052/AFRP laminate was investigated in this study. Al5052/AFRP laminate composite consists of three thin sheets of Al5052 and two layers of unidirectional aramid fibers. The cyclic bending moment fatigue tests were performed with five different levels of bending moment. The shape and size of the delamination zone formed along the fatigue crack between Al5052 sheet and aramid fiber-adhesive layer were measured by an ultrasonic C-scan. The relationships between da/dN and ΔK, between the cyclic bending moment and the delamination zone size, and between the fiber bridging mechanism and the delamination zone were studied. Fiber failures were not observed in the delamination zone in this study. It represents that the fiber bridging modification factor should turn out to increase and that the fatigue crack growth rate should decrease. The shape of delamination zone turns out to be semi-elliptic with the contour decreased non-linearly toward the crack tip.

• Journal of Preventive Medicine and Public Health
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• 제36권1호
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• pp.71-76
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• 2003

Objectives : New organizational work systems, and their impact on the mental health of employees, are considered to beone of the most important topics in the area of industrial health. This study was conducted to compare job characteristics (job demand and decision latitude) levels, and psychosocial distress of workers in acompany introducing to new organizational work systems, to those of workers managed by traditional work systems. Methods ; A study sample of 627 shipbuilding workers (446the new work organizational system and 181 the traditional system) were recruited for this study. A structured-questionnaire was used to assess general characteristics, job characteristics(work demand, decision latitude), and psychosocial distress. Results : The decision latitude was not significantly higher in the new work system compared to the traditional system. However, the job demand was significantly higher in the new work system than in the traditional system. The psychosocial distress was higher within the new work system than the traditional system, but no significant relationships were found. The proportion of increased strain was significantly greater with the new system than the traditional system. Conclusion : These results suggest that increases in the decision latitude did not sufficiently compensate for higher job strain or increased work intensity. If the increase in the decision latitude was temporary, with the typical job demand remaining high, such work can be still be considered to have a job strain Futureresearch should consider psychosocial distress and fatigue as importantproblems caused by new work organizational systems, and should be performed to assess their impact through out industry.

• Journal of Preventive Medicine and Public Health
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• 제50권5호
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• pp.320-327
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• 2017

Objectives: The purpose of our study was to evaluate the association between the intensity of physical activity (PA) and prevalence of cardiovascular disease (CVD) using Korean representative data. Methods: We analyzed 39 804 participant data from the Korea National Health and Nutrition Examination Survey, 2007-2013. Exposure variable was three levels of PA (low, medium, and high) in a week, and outcome variable was prevalence of CVD based on patient self-recognition and doctor's diagnosis. Complex logistic regression analysis was performed to evaluate the relationship between level of PA and CVD adjusted by body mass index, hypertension, hypercholesterolemia, diabetes mellitus, stress recognition, household income, smoking, and current drinking. The indices of association w ere estimated as crude prevalence odds ratio (POR), adjusted POR, and their 95% confidence interval (CI). All statistical analyzes were performed using complex sample analysis procedure of the SPSS version 23.0. Results: When all variables were adjusted, only high level PA in women showed a significant association with stroke (adjusted POR by patient's self-recognition, 0.57; 95% CI, 0.32 to 0.99, adjusted POR by doctor's diagnosis, 0.55; 95% CI, 0.34 to 0.87) and CVD (adjusted POR by doctor's diagnosis, 0.68; 95% CI, 0.48 to 0.96). Conclusions: High level PA in women has a significant reverse association with prevalence of stroke and CVD in Korea. Further study for elucidating the mechanism will be needed.

• 한국초지조사료학회지
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• 제27권1호
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• pp.37-44
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• 2007

병원균 감염에 의한 식물체내 프롤린과 암모니아의 농도 변화와 그것의 스트레스 생리학적 의미를 구명하기 위하여 Rhizoctonia spp.를 처리 후 라지 펫치에 감염된 잔디의 생육 및 관련 화학적 성분을 감염이 되지 않은 대조구와 비교하였다. 라지 펫치에 감염된 잔디의 뿌리의 건사율은 대조구에 비해 약 30% 증가하였다. 가용성 단백질 농도는 병원균 처리후 6일째 잎의 경우를 제외하고는 라지 펫치 감염에 따른 유의적인 영향이 없었다. 암모니아 농도 역시 라지 펫치에 감염된 잎과 줄기에서 공히 유의적으로 증가하였다. 프롤린 농도는 잎과 뿌리에서 대조구에 비해 각각 3.4 및 4.5배 증가하였다. 이러한 결과들은 잔디에 있어 병원균 감염에 따른 프롤린의 축적은 스트레스 강도를 나타내는 민감한 표지물질로서 의미가 있음을 제시한다.

• 한국방사성폐기물학회:학술대회논문집
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• 한국방사성폐기물학회 2005년도 추계 학술대회 논문집
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• pp.87-95
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• 2005

삼중수소를 사용하는 자발광유리관의 제조에 필요한 4가지 핵심 기술 중 레이저를 이용한 밀봉/절단기술을 개발하였다. 상용 제품을 분석한 결과 유리관의 재질은 pyrex 이었고 레이저는 유리가공에 적절한 펄스형 이산화탄소 레이저를 사용하였다 유리관의 밀봉/절단에 영향을 미치는 인자들로는 레이저빔의 강도 지속시간 조사 방법, 유리관 내부의 압력 등이었다. 전 공정은 2단계로 이루어져 1단계에서는 삼중수소를 주입하고 유리관의 양단을 밀봉하였으며 2단계에서는 삼중수소가 봉입된 유리관을 원하는 길이로 밀봉/절단하였다. 각 공정에서 유리관의 밀봉은 defocusing된 레이저빔을 사용하였으며 절단은 focusing된 빔을 사용하였다. 밀봉/절단 후에는 잔여 열응력에 의한 파열을 방지하기 위하여 열처리를 하였다.

• 한국환경독성학회:학술대회논문집
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• 한국환경독성학회 1997년도 제20회 화학물질의 환경독성과 건강영향
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• pp.101-101
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• 1997

Comet assay, single cell gel electrophoresis has been known as useful, rapid, simple, visual, and sensitive technique for measuring the DNA breakage in mammalian ce1ls. For evaluation of DNA damage using comet assay, early studies reported a change in comet length and intensity with DNA damage using simple visual technique, such as fluorescence microscopy with eyespiece. In recent, some workers are observing and analyzing nucleotide of comets using quantitative fluorescence image analysis system to estimate 'tail moment', which is defined as the product of the tail length and the fraction of total DNA in tail. Our laboratory also adopted the image analysis software for qualification. In addition, many of the practical features of comet assay render it potentially attractive as useful tool for molecular toxicology and carcinogenesis, because the system is already showing considerable promise as rapid predictor in both in vitro and in vivo experimental designs. Recently, the comet assay becomes a attractive technique to study of apoptosis, because apoptotic fragmentation of nuclear DNA into nucleosomal sizes can be evaluated by the comet assay. So, we attempted to apply the comet assay to studying the effect of various stress on the apoptosis-sensitive cell lines. Particularly, focusing on the hyperthermic apoptosis, we could find that heat shock(44˚C for 60 minutes) was sufficient to induced apoptosis in these cell lines. But using the highly sensitive comet assay, we could not detect DNA breaks immediately after heat shock.

• 한국철도학회논문집
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• 제12권1호
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• pp.16-24
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• 2009

선형탄성파괴역학을 적용하여 균열이 발생한 변동하중하의 철도차량 대차틀에 대한 균열성장속도를 예측하였다. 이를 위하여 철도차량 대차틀의 균열발생사례를 분석하여 취약부위를 파악하였으며, 영업노선에서의 실동하중 측정과 구조해석을 통한 정하중 계산으로 대차틀 취약부에서 운행 중 받는 총 하중이력을 생성하였다. 총 하중이력에서 균열닫힘을 고려한 유효하중이력을 계산하였으며, 취약부 3곳에서 균열성장속도를 예측하고 일본에서 측정한 균열진전 사례와 비교하였다. 해석결과 초기길이 40mm의 균열이 급속한 균열성장을 일으키기까지는 약 50만km의 주행거리가 필요하며 이는 약 3.8년의 운행기간에 해당하므로 도시철도의 유지보수기간을 고려하면 임계균열로 도달하기 전에 충분히 감지할 수 있을 것으로 생각된다.

• Nuclear Engineering and Technology
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• 제52권8호
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• pp.1871-1880
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• 2020

Round robin analyses for vessel failure probabilities due to PTS events are proposed for plant-specific analyses of all types of reactors developed in Korea. Four organizations, that are responsible for regulation, operation, research and design of the nuclear power plant in Korea, participated in the round robin analysis. The vessel failure probabilities from the probabilistic fracture mechanics analyses are calculated to assure the structural integrity of the reactor pressure vessel during transients that are expected to initiate PTS events. The failure probabilities due to various parameters are compared with each other. All results are obtained based on several assumptions about material properties, flaw distribution data, and transient data such as pressure, temperature, and heat transfer coefficient. The realistic input data can be used to obtain more realistic failure probabilities. The various results presented in this study will be helpful not only for benchmark calculations, result comparisons, and verification of PFM codes developed but also as a contribution to knowledge management for the future generation.

• 한국산업보건학회지
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• 제15권1호
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• pp.61-70
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• 2005

This study investigated the spinal loads(L5/S1 disc compression and shear forces) predicted from four biomechanical models: one EMG model and three optimization models. Three objective functions used in the optimization models were to miminize 1) the cubed muscle forces : MF3, 2) the cubed muscle stress : MS3, 3) maximum muscle intensity : MI. Twelve healthy male subjects participated in the isometric voluntary exertion tests to six directions : flexion/extension, left/right lateral bending, clockwise/ counterclockwise twist. EMG signals were measured from ten trunk muscles and spinal loads were assessed at 10, 20, 30, 40, 50, 60, 70, 80, 90%MVE(maximum voluntary exertion) in each direction. Three optimization models predicted lower L5/S1 disc compression forces than the EMG model, on average, by 31%(MF3), 27%(MS3), 8%(MI). Especially, in twist and extension, the differences were relatively large. Anterior-posterior shear forces predicted from optimization models were lower, on average, by 27%(MF3), 21%(MS3), 9%(MI) than by the EMG model, especially in flexion(MF3 : 45%, MS3 : 40%, MI : 35%). Lateral shear forces were predicted far less than anterior-posterior shear forces(total average = 124 N), and the optimization models predicted larger values than the EMG model on average. These results indicated that the optimization models could underestimate compression forces during twisting and extension, and anterior-posterior shear forces during flexion. Thus, future research should address the antagonistic coactivation, one major reason of the difference between optimization models and the EMG model, in the optimization models.