• 소성∙가공
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• 제27권5호
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• pp.281-288
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• 2018

This study deals with the microstructure and tensile properties of 600 and 700 MPa-grade high-strength seismic reinforced steel bars. High-strength seismic resistant reinforced steel bars (SD 600S and SD 700S) were fabricated by TempCore process, especially the SD 700S specimen was more rapid cooled than the SD 600S specimen during the TempCore process. Although two specimens had microstructure of tempered martensite in the surface region, the SD 600S specimen had ferrite-degenerated pearlite in the center region, whereas the SD 700S specimen had bainite-ferrite-degenerated pearlite in the center region. Therefore, their hardness was highest in the surface region and revealed a tendency to decrease from the surface region to the center region because tempered martensite has higher hardness than ferrite-degenerated pearlite or bainite. The SD 700S specimen revealed higher hardness in the center region than SD 600S specimen because it contained a larger amount of bainite as well as ferrite-degenerated pearlite. On the other hand, tensile test results indicated the SD 600S and SD 700S specimens revealed continuous yielding behavior because of formation of degenerated pearlite or bainite in the center region. The SD 600S specimen had a little higher tensile-to-yield ratio because the presence of ferrite and degenerated pearlite in the center region and the lower fraction of tempered martensite enhance work hardening.

• 한국구조물진단유지관리공학회 논문집
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• 제25권6호
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• pp.262-269
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• 2021

본 논문은 SD700 확대머리철근의 겹침이음을 이용한 단차가 있는 보의 접합상세를 개발하기 위하여 실시한 구조성능평가 실험결과를 나타낸다. 실험변수는 주철근의 겹침이음길이, 철근 항복강도, 단부정착상세 등이다. 모든 실험체에 대하여 춤이 작은 보(B2)의 하부 주철근은 확대머리철근을 적용하였으며, 춤이 큰 보(B1)의 하부 주철근은 일자형 확대머리철근, 90° 갈고리형 확대머리철근 등 두 가지 상세로 이음방법을 적용하였다. 실험결과, SD500과 SD600을 적용한 실험체들은 겹침이음부에서 모두 휨파괴되었으며, 이로 인하여 최대내력은 유사하게 나타났다. SD500을 적용한 실험체들에 대하여, B1의 주철근을 90°갈고리형 확대머리철근으로 적용한 상세가 확대머리철근에 비하여 겹침이음부의 수평균열을 억제하였다. SD700의 확대머리철근을 사용한 실험체는 취성적인 정착파괴가 나타났으며, 겹침이음길이의 증가에 따라 최대내력이 증가하였다. SD700의 확대머리철근을 사용한 실험체들은 실험체정착길이/이론정착길이에 대한 실험내력/이론내력이 ACI 318-19 식은 1.30~1.48로 나타났으며, KDS-2021 식은 1.14~1.30로 평가되었다. 이를 볼 때, ACI 318-19 산정식이 보다 보수적으로 정착길이를 평가함으로써 더 큰 안전율을 가지고 있었다.

• 콘크리트학회지
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• 제27권3호
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• pp.24-27
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• 2015

• 도시과학
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• 제7권2호
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• pp.21-27
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• 2018

With the increase of the skyscraper center, the development of large-diameter and high-strength reinforcing bars is being carried out to solve the dense reinforcement. In case of the steel reinforced concrete with a small cross section such as beam-column joints, the development length becomes short when straight bars are used. Therefore, it is possible to solve the problem that the development length becomes short by using the bearing strength of the hooked bar and headed bar. In this study, the exterior beam-column joint test of SD700 hooked bar and headed bar with anchorage length of 20db was conducted to extend the development length limitation of hooked bar and headed bar. As a result of the evaluation of the anchorage strength using the design equation by KCI, the average of the [measured value]/[predicted value] ratio was 1.31 for the hooked reinforcing bars. In the case of headed bars, the average of the [measured value]/[predicted value] ratio was 1.12. In addition, in order to compare the anchorage performance of the hooked bar and the headed bar, the measured values were divided by the square root of the compressive strength of the concrete to compare the anchorage strength. Under the same conditions, the anchorage strength of headed bars was 8.5% higher than the hooked bars.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2008년도 추계 학술발표회 제20권2호
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• pp.289-292
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• 2008

본 논문에서는 고장력 철근이 적용된 휨부재의 구조성능과 사용성능에 대하여 실험적으로 연구하였다. 고장력 철근에 관련된 기존 연구결과에 따르면, RC보의 인장철근을 고장력 철근으로 사용할 경우, SD400에 비해 철근의 물량을 경감시킬 수 있는 장점이 있으나, 균열 폭과 처짐이 증가되는 등 부정적인 영향이 있다고 알려졌다. 따라서 본 논문에서는 고장력 철근을 사용함으로써 휨부재의 성능에 미치는 영향을 분석하는 것을 목적으로 하였다. 이에 철근강도를 변수로 SD400, SD600, SD700의 3개 시험체를 제작하여 실험을 수행하였다. 본 연구의 실험 결과, 동일 철근비 사용 시 고장력 철근의 부재 강성이 감소되는 현상을 나타내었으나, 부재의 전체적인 휨내력은 배근된 철근의 강도 및 철근량에 비례하여 나타나는 것을 확인할 수 있었다. 또한, 고장력 철근 사용시 균열갯수 및 최대 균열폭에 큰 변화가 없으므로 사용성 면에서 큰 문제는 없는 것으로 분석되었다.

• 대한간호학회지
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• 제46권5호
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• pp.642-652
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• 2016

Purpose: In this single repeated measures study, an examination was done on the effects of dialysate flow rate on dialysis adequacy and fatigue in patients receiving hemodialysis. Methods: This study was a prospective single center study in which repeated measures analysis of variance were used to compare Kt/V urea (Kt/V) and urea reduction ratio (URR) as dialysis adequacy measures and level of fatigue at different dialysate flow rates: twice as fast as the participant's own blood flow, 500 mL/min, and 700 mL/min. Thirty-seven hemodialysis patients received all three dialysate flow rates using counterbalancing. Results: The Kt/V ($M{\pm}SD$) was $1.40{\pm}0.25$ at twice the blood flow rate, $1.41{\pm}0.23$ at 500 mL/min, and $1.46{\pm}0.24$ at 700 mL/min. The URR ($M{\pm}SD$) was $68.20{\pm}5.90$ at twice the blood flow rate, $68.67{\pm}5.22$ at 500 mL/min, and $70.11{\pm}5.13$ at 700 mL/min. When dialysate flow rate was increased from twice the blood flow rate to 700 mL/min and from 500 mL/min to 700 mL/ min, Kt/V and URR showed relative gains. There was no difference in fatigue according to dialysate flow rate. Conclusion: Increasing the dialy-sate flow rate to 700 mL/min is associated with a significant increase in dialysis adequacy. Hemodialysis with a dialysate flow rate of 700 mL/min should be considered in selected patients not achieving adequacy despite extended treatment times and optimized blood flow rate.

• 대한상한금궤의학회지
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• 제4권1호
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• pp.29-36
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• 2012

Aim : To investigate the hepatotective effect of Gardenia jsaminodes and Glycine max aqueous extract against D-galactosamine (d-GalN, 300mg/kg body weight) was administered to the male Sprague Dawley (SD) rats. Materials and Methods : The study was carried out on male SD rats (age matched, weight $250{\pm}10g$). Experimental groups divided four: Normal group (Nor) was administered saline, Control (Con) group was administered saline after d-GalN treatment. Experimental group (Exp) was administered Gardenia jsaminodes (200 mg/kg; Ga group), Glycine max (700 mg/kg; Gl group), and Gardenia jsaminodes+Glycine max (200 mg/kg+700 mg/kg, GG group) during 14 days(n=5). Results : d-GalN administration induced hepatotoxicity in rats which was manifested by increased levels of alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase but decreased total cholesterol and triglyceride. Treatment with Gardenia jsaminodes extract significantly protected the liver in d-GalN administered rats. Conclusion : Gardenia jsaminodes aqueous extract and Gardenia jsaminodes+Glycine max extract possesses hepatoprotective potential, thus validating its use in alleviating toxic effects of d-GalN.

• 한국방재학회 논문집
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• 제8권2호
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• pp.1-5
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• 2008

본 연구는 상온에서 산소절단기로 철근의 절단시 절단부위로 부터의 고온수열범위와 수열온도를 측정하고 시뮬레이션 결과와 비교함으로써 현장에서 산소절단기를 사용한 철근절단의 가능성을 파악하는 것을 목적으로 하며 그 결과는 다음과 같다. 1. 산소절단기로 철근을 절단하는 경우 절단 부위로부터 1 cm 떨어진 위치의 수열온도는 $700^{\circ}C{\sim}1000^{\circ}C$의 범위에 있으나, 절단부위로부터 2cm떨어진 위치의 수열온도는 200$^{\circ}C$를 넘지 않는 것으로 나타났다. 2 각 직경, 종류별로 철근의 수열온도 분포를 시뮬레이션한 결과 산소 절단시험와 유사한 절단 거리에 따른 온도 분포를 보임으로서 철근 절단 거리에서 2cm 정도의 여유를 갖고 절단할 경우에는 고온 수열에 따른 취성변화가 발생되지 않는다.

• Nutrition Research and Practice
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• 제16권6호
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• pp.700-715
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• 2022

BACKGROUND/OBJECTIVES: Chronic colitis is a risk factor for colorectal cancer (CRC) development in both animals and humans. Previously, we reported that a diet rich in protein (with casein as the protein source) significantly increased the risk of mouse CRC development in a dose-dependent manner. In this study, we investigated the effects of different protein sources on the risk of colitis development. MATERIALS/METHODS: Balb/c mice were divided into 7 experimental groups: 20% casein (20C), 20C-dextran sulfate sodium (DSS), 40% casein-DSS (40CD), 40% whey protein-DSS (40WD), 40% soy protein-DSS (40SD), 40% white meat-DSS (40WMD), and 40% red meat-DSS (40RMD). Mice were fed an experimental diet for 4 wk and received 3% DSS in their drinking water for 6 days during the 4th wk of the experimental period. RESULTS: Compared to other groups, the 40CD group showed the most aggravated colitis with increased disease activity and inflammatory markers. In the 40RMD group, interleukin (IL)-6 levels were the highest among all the groups. The 40SD group showed conflicting effects, for example, elevated mortality and disease activity but decreased nitric oxide (NO) levels. The 40WD group showed attenuated colitis with increased IL-10 levels and decreased NO levels. The 40WMD group showed conflicting effects, including decreased NO levels and elevated fecal lipocalin-2 and IL-6 levels. CONCLUSIONS: These results suggest that, at levels of 40% in the diet, casein and red meat exacerbate colitis, whereas whey protein mitigates it the most effectively.

• 대한본초학회지
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• 제28권2호
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• pp.17-23
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• 2013

Objectives : To investigate the hepatoprotective effect of Gardeniae Fructus (Ga) and Glycine semen preparatum (Gl) aqueous extract against D-galactosamine (D-GalN, 300mg/kg body weight) was administered to the male Sprague Dawley (SD) rats. Materials and Methods : The study was carried out on male SD rats (age matched, weight $250{\pm}10$ g). Experimental groups (Exp) divided four : Normal group (Nor) was administered saline, Control (Con) group was only received D-GalN (300 mg/kg) intraperitoneally. Exp was orally administered Ga (200 mg/kg; Ga group), Gl (700 mg/kg; Gl group), and Chizadochi-Tang (200 mg/kg+700 mg/kg, GG group) after D-GalN treatment during 14 days (n=6). Results : D-GalN administration induced hepatotoxicity in rats which was manifested by increased levels of aspartate aminotransferase (AST), alanine aminotransferase (ALT), alkaline phosphatase (ALP) and lactate dehydrogenase (LDH) but decreased total cholesterol (HDL C) and triglyceride (TG). The serum TG concentrations were significantly increased ($^{\sharp}p$ <0.05) in the Ga group compared with Con. AST and ALP activities were significantly decreased ($^{\sharp}p$ <0.05) in the all experimental groups compared with Con. ALT activities were significantly decreased ($^{\sharp}p$ <0.05) in the Ga group compared with Con. LDH activities were significantly decreased ($^{\sharp}p$ <0.05) in the GG group compared with Con. On the light microscopic study, a number of vacuole were observed in the Con, but decreased in experimental groups. Conclusion : Ga aqueous extract and Chizadochi-Tang extract possesses hepatoprotective potential, thus validating its use in alleviating toxic effects of D-GalN.