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김남길 ( Jin Nan-ji ),연규석 ( Yeon Kyu-seok ),주명기 ( Joo Myung-ki ),백종만 ( Baek Jong-man ),이윤수 ( Lee Youn-su ) 한국농공학회 2002 한국농공학회 학술대회초록집 Vol.2002 No.-
In this study, the effects of the number of coat and immersion period on strength properties, waterproofness and chemical resistance of painted and immersed cement mortars using two admixture were examined. Test results showed that the flexural and the compressive strengths of the coated and immersed cement mortars increase with increasing number of coat and immersion period. The water absorption of the coated and immersed cement mortars tended to decrease with increasing number of coated and immersion period. In the case of the change of weight and the immersion period for the solutions, a decreasing tendency was shown as the immersion period increases regardless of solution, with a little variation.
성숙도 방법을 이용한 불포화 폴리에스터 수지 폴리머 콘크리트의 압축강도 예측
최기봉,김남길,이윤수,연규석,Choi, Ki-Bong,Jin, Nan Ji,Lee, Youn-Su,Yeon, Kyu-Seok 한국농공학회 2017 한국농공학회논문집 Vol.59 No.6
This study investigated to predict the compressive strength of unsaturated polyester resin based polymer concrete using the maturity method. The test results show that the development of the compressive strength increased exponentially until an age of 24 hours. After 24 hours, the development of the compressive strength just increased gradually. This test result shows that the strength of unsaturated polyester resin based polymer concrete was developed mainly at the early age. Estimated datum temperature of unsaturated polyester resin based polymer concrete was $-20.67^{\circ}C$ which was much lower than of datum temperature ($-10^{\circ}C$) of Portland cement concrete. Also, this study result shows that the existing maturity index associated with Portland cement concrete was not applicable for polymer concrete because curing time of Portland cement concrete is different clearly with curing time of polymer concrete. The cause of different curing time was that there were different curing mechanisms between Portland cement concrete and polymer concrete. In order to best apply the experimental data to a model, CurveExpert Professional, the commercial software, was used to determine the predictive model regarding the compressive strength of unsaturated polyester resin based polymer concrete. As a result, Gompertz Relation or Weibull Model was an appropriate model as a predictive model. The proposed model can be used to predict the compressive strength, especially, it is more useful when the maturity is in the range between $40^{\circ}C{\cdot}h^{0.4}$ and $900^{\circ}C{\cdot}h^{0.4}$.
연규석 ( Yeon Kyu-seok ),김남길 ( Jin Nan-ji ),조규우 ( Jo Kyu-woo ),권택정 ( Kweon Taek-jong ) 한국농공학회 2003 한국농공학회 학술대회초록집 Vol.2003 No.-
Direct tensile tests were carried out for the tensile mmtbers of steel-reinforced polyrrer concrete with different steel diameters and steel ratios to figure out the effect of tensile strength of polyrrer concrete. In the experiments, polyrrer concrete with 1000 kpf/ cm<sup>2</sup> of compressive strength, steel with 5200 kpf/cm<sup>2</sup> of tensile strength, and the tensile mmtbers with 100 cm of constant length were used. Experimental results showed that, regardless of steel diameters and steel content, the strain energy exerted by concrete till the initial crack was 14-15% of the total energy till the point of yield: The energy was much larger than the one of high-strength cerrent concrete. The behaviors of tensile mmtbers of steel-reinforced polymer concrete were in relatively good agreemmt with the model suggested by Gupta-Maestrini (1990), which was idealized by the effective tensile stress-strain relationship of concrete and the load-strain relationship of members, while those showed a big difference from CES-FlP model and AO-224 equation suggested for the load-displacement relationship that was defined as the cross sectional stiffness of effective axis. Modified ACI-224 model code about the load-displacement relationship for the tensile members of steel-reinforced polymer concrete and theoretical equation for the polymer concrete tensile stiffness of polymer concrete suggested through the results of this study are expected to be used in an accurate structural analysis and design for the polymer concrete structural members.
폐고무분말을 혼입한 UP 폴리머모르타르의 경화수축 및 부착강도
연규석 ( Yeon Kyu-seok ),김남길 ( Jin Nan-ji ),최종윤 ( Choi Jong-yun ),백종만 ( Beck Jong-man ) 한국농공학회 2003 한국농공학회 학술대회초록집 Vol.2003 No.-
In this study, the MMA-modified paste mixed waste rubber powder, which has a small elastic modulus and a large modification, was produced by using the soft unsaturated polyester resin(up) as a binder. Then the adhesive properties according to the matrices in both underwater and air-dry conditions and the hardening shrinkage according to the contents of shrinkage reducing agent(SRA) and of MMA were surveyed. The experimental results show that, regardless of humidity of matrices the adhesive strength of polymer concrete was larger than cement concrete. the adhesive strength of MMA content of 20% was larger than MMA content of 30%. regardless of matrix materials the adhesive strength in water condition were 20-30% comparing with the air-dry condition. The case of MMA content of 20% showed the largest adhesive strength. In the hardening shrinkage experiment, the hardening shrinkage reduced as MMA and SRA contents increased, and the decrease of the hardening shrinkage by SRA was larger.
Lipopolysaccharide/D-Galactosamine에 의해 유도된 급성 간 손상 생쥐모델에서 굴가수분해물의 간 보호 효과
류지현(Ji Hyeon Ryu),김은진(Eun-Jin Kim),Chengliang Xie,Marie Merci Nyiramana,Adrian S. Siregar,박시향(Si-Hyang Park),조수범(Soo Buem Cho),송대현(Dae Hyun Song),김남길(Nam-Gil Kim),최영준(Yeung Joon Choi),강상수(Sang Soo Kan 한국식품영양과학회 2017 한국식품영양과학회지 Vol.46 No.6
산화스트레스와 염증은 간 손상의 진행과정에 중요한 인자로 작용한다. 굴가수분해물의 항산화 및 항염증 활성은 지질대사, 혈압 및 혈당, 면역기능의 조절과 같은 다양한 기능에 관여한다. 그러나 급성 간 손상 모델에서 굴가수분해물의 효과를 확인한 연구 결과는 아직 확인된 바 없다. 본 연구는 LPS/D-GalN에 의해 유도된 급성 간 손상 생쥐 모델에서 굴가수분해물의 효과를 확인하기 위해 수행되었다. 실험군은 대조군(생리식염수), LPS/D-GalN 간 손상군, LPS/DGalN과 굴가수분해물(100 mg/kg, 200 mg/kg, 400 mg/kg)의 병합투여군 및 LPS/D-GalN과 silymarin(25 mg/kg) 병합투여군으로 나누었다. 급성 간 손상 모델은 1 μg/kg의 LPS와 400 mg/kg의 D-GalN으로 유도되었다. 먼저 시료의 항산화 및 항염증 활성을 분석한 결과 굴가수분해물은 농도 의존적으로 높은 DPPH 및 ABTS 라디칼 소거 활성을 보였으며, 인간 정상 간세포주(Chang)에서 과산화수소에 의한 세포 내 활성산소의 생성을 유의적으로 감소시켰다. 또한, 굴가수분해물은 농도 의존적으로 높은 COX-2 및 5-LOX 억제능을 보였으며, LPS에 의해 활성화된 생쥐 대식세포주 RAW264.7에서 발현되는 TNF-α, IL-6 및 IL-1α의 염증성 사이토카인의 mRNA 발현률을 감소시켰다. 굴가수분해물 투여는 LPS/D-GalN에 의한 혈청 ALT 및 AST증가를 유의적으로 감소시켰으며, 간 조직의 출혈 및 간세포의 자멸사를 감소시켰다. 또한, 간 균질의 TNF-α, IL-1β 및 IL-6 함량을 감소시켰으며, 감소한 catalase의 활성을 유의적으로 증가시켰다. 이상의 결과로부터 굴가수분해물은 간 보호 효과를 가지는 것으로 판단되며, 급성 간 손상의 예방 및 치료에 도움이 될 수 있는 시료로 활용될 수 있을 것으로 기대된다. Oxidative stress and inflammation are key factors responsible for progression of liver injury. A variety of functions of oyster hydrolysate (OH) are affected by their antioxidant and anti-inflammatory activities. However, little is known regarding the effects of OH on a liver injury model. This study was performed to evaluate the effects of OH on acute liver injury induced by lipopolysaccharide/D-galactosamine (LPS/D-GalN) in mice. Experimental groups were divided into six groups as follows (each group, n=10): control (saline), LPS/D-GalN, LPS/D-GalN+OH (100 mg/kg), LPS/D-GalN+OH (200 mg/kg), LPS/D-GalN+OH (400 mg/kg), and LPS/D-GalN+silymarin (25 mg/kg, positive control). The experimental acute liver injury model was induced with LPS (1 μg/kg) and D-GalN (400 mg/kg). We first analyzed antioxidant and anti-inflammatory activities in OH. OH showed high DPPH and ABTS radical scavenging activities and reduced ROS generation in Chang cells in a dose-dependent manner. In addition, OH showed anti-inflammatory activities, such as inhibition of cyclooxygenase-2 and 5-lipooxygenase. Treatment with OH down-regulated tumor necrosis factor (TNF)-α, interleukin (IL)-6, and IL-1α expression levels in LPS-stimulated RAW264.7 cells. OH significantly reduced LPS/D-GalN-induced increases in the concentrations of alanine transaminase and aspartate aminotransferase in serum. In the LPS/D-GalN group, liver tissues exhibited apoptosis of hepatocytes with hemorrhages. These pathological alterations were ameliorated by OH treatment. Consistently, hepatic catalase activity was low in the LPS/D-GalN group compared to the control group, and catalase activity was significantly restored by OH treatment (P<0.05). Furthermore, OH markedly reduced the LPS/D-GalN-induced increase in TNF-α, IL-1β, and IL-6 levels in liver tissue. Taken together, these results show that OH has hepatoprotective effects on LPS/D-GalN-induced acute liver injury via inhibition of oxidative stress and inflammation, suggesting that OH could be used as a health functional food and potential therapeutic agent for acute liver injury.