• Structural Engineering and Mechanics
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• 제78권3호
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• pp.231-253
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• 2021

Pure bending loading conditions are not frequently occurred in practical engineering, but the flexural researches are important since it's the basis of mechanical property researches under complex loading. Hence, the objective of this paper is to investigate the flexural behavior of concrete-filled rectangular steel tube (CFRT) through combined experimental and numerical studies. Flexural tests were conducted to investigate the mechanical performance of CFRT under bending. The load vs. deflection curves during the loading process was analyzed in detail. All the specimens behaved in a very ductile manner. Besides, based on the experimental result, the composite action between the steel tube and core concrete was studies and examined. Furthermore, the feasibility and accuracy of the numerical method was verified by comparing the computed results with experimental observations. The full curves analysis on the moment vs. curvature curves was further conducted, where the development of the stress and strain redistribution in the steel tube and core concrete was clarified comprehensively. It should be noted that there existed bond slip between the core concrete and steel tube during the loading process. And then, an extensive parametric study, including the steel strength, concrete strength, steel ratio and aspect ratio, was performed. Finally, design formula to calculate the ultimate moment and flexural stiffness of CFRTs were presented. The predicted results showed satisfactory agreement with the experimental and FE results. Additionally, the difference between the experimental/FE and predicted results using the related design codes were illustrated.

• 혜화의학회지
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• 제8권1호
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• pp.625-641
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• 1999

Aging occurs as a part of maturation as the time progresses which manifests in the human body causing morphological and functional degeneration, eventually leading to death. This experimental study was conducted to investigate a herbal formula to fortify the heart with easy clinical applications. Sungshimsan was chosen to study its effects in heart lipid peroxide and metabolic enzyme system in senescence induced rats. After pre-treatment of Sungshimsan for 2 weeks at the dosage of A (100mg/kg), B (250mg/kg), C (350mg/kg), and D (500mg/kg), a lipid peroxide and metabolic enzyme system changes of the heart were meaured in 32 weeks old rats. The following results were obtained in this study: 1. The contents of lipid peroxide was significantly reduced in the experimental groups treated with greater than 2 weeks at 250mg/kg. 2. The enzymatic activity of cytochrome P-450, cytochrome b5, and NADPH-cytochrome P450 reductase were significantly decreased in the 250mg/kg, 350mg/kg, and 500mg/kg experimental groups. 3. The activity of glutathione and glutathione S-transferase were significantly increased in the 250mg/kg, 350mg/kg, and 500mg/kg experimental groups. 4. The activity of glutathione reductase and glutathione peroxidase were not influenced compared to the control group. 5. The activity of ${\gamma}$-glutamylcystein synthetase was significantly increased in the 250mg/kg, 350mg/kg, and 500mg/kg experimental groups. 6. The activity of enzymes detoxificatioon superoxide dismutase and catalase were not influenced compared to the control group. Summarizing above results suggest that the Sungshimsan has profound effects in the heart lipid peroxide, free radicals, and delaying the heart aging process. Further clinical researches and application can be anticipated on the topic of senility and gerontology.

• 한국수자원학회논문집
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• 제40권10호
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• pp.833-840
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• 2007

본 연구에서는 장애물이 없는 평탄지형의 제내지에서 제방붕괴에 의한 범람홍수파 선단의 전파 특성을 규명하기 위하여 제내지와 하도로 이루어진 실험수조에서 실험을 수행하여 전파 거리를 산정하였다. 실험에 의해 측정된 전파 거리를 시간에 대한 상관식으로 나타내기 위하여 댐붕괴에 의한 수로에서의 홍수파의 1차원 흐름 해석해인 Hitler의 해를 검토하고, 제내지 범람홍수파의 특성을 표현할 수 있도록 확장하여 실험식의 일반형을 제시하였다. 범람홍수파의 전파속도는 댐붕괴에 의한 흐름과 마찬가지로 초기수위가 지배적인 영향을 준다는 사실을 실험을 통해 밝혔으며, 실험결과를 무차원 시간 T와 무차원 전파거리 L로 나타내어 실험식을 도출하였다. 무차원 전파거리 L을 산정하기 위한 상수로서 k와 m이 도입되었는데, Hitter의 해에서는 k가 2이고, m이 0인 반면에 본 실험에서는 k와 m이 무차원 시간 T의 구간에 따라 달라지는 상수임을 알 수 있었다. 이는 전파속도가 제내지에서의 범람홍수심에 영향을 받기 때문이며, 전파거리와 최대수심의 포락선의 기울기가 변하는 L값이 일치한다는 사실로 확인할 수 있었다.

• 대한한의학방제학회지
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• 제22권1호
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• pp.177-192
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• 2014

Objective : In order to investigate the effect of Curcumae Longae Rhizoma(CLR) extract on the hepatocellular carcinogenesis and acute liver damage induced by diethylnitrosamine(DENA) and $CCl_4$ in rats. Methods : Experimental groups were subdivided into four; normal group (Nor), acute liver damage and hepatocellular cancer inducing control group (Con), and CLR extract 200mg/kg/day (CAA) or 400mg/kg/day (CAB) administered groups to Con. Thereafter the changes of the body weight, the liver weight and the weight of liver/100g body weight, total cholesterol, HDL cholesterol, triglyceride, the activities of AST, ALT, ALP, LDH, AFP, SOD, catalase were measured. And we observed by optical and electron microscopy. Result : 1. The body weight was decreased in Con compared with Nor for 5 weeks, but increased in Con compared with Nor from 6 week to 9 week. During experimental period of total 9 weeks, CAA and CAB were increased compared with Con. 2. The liver weight was increased significantly (p<0.05) in Con compared with Nor. The weight of liver/100g body weight was increased significantly (p<0.05) in Con compared with Nor and decreased significantly (p<0.05) in CAB compared with Con. 3. The level of total cholesterol was increased in Con and CAA compared with Nor, but there was not statistically significant. The level of triglyceride was decreased in Con compared with Nor. But increased in CAA and CAB compared with Con. The level of HDL-cholesterol was significantly increased (p<0.05) in CAA and CAB compared with Con. 4. The activities of AST, ALT were increased in Con compared with Nor, but decreased in CAA compared with Con, significantly decreased (p<0.05) in CAB compared with Con. 5. The activities of ALP, LDH were increased in Con compared with Nor, but decreased in CAA and CAB compared with Con. 6. The activities of AFP was increased significantly (p<0.05) in Con compared with Nor, but decreased significantly (p<0.05) in CAA and CAB compared with Con. 7. The activities of SOD were increased in Con, CAA and CAB compared with Nor, but decreased in CAA and CAB compared with Con. The activities of Catalase was more increased in CAA and CAB compared than Con. 8. The results of light microscopical observation, a number of hepatocytes were damaged in Con compared with Nor and CAB. 9. According to the electron microscopical observation, irregular nuclear membrane, condensed nucleoplasm was observed in Con, the experimental group was observed in the nucleus of the well-preserved and evenly developed nucleoplasm. Conclusions : These results suggest that administration of CLR extract suppress or retard on the hepatocellular carcinogenesis and acute liver damage induced by DENA and $CCl_4$ in rats.

• 대한한의학방제학회지
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• 제15권2호
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• pp.35-45
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• 2007

Objective : The purpose of this report was to provide the information activity and safety of Palmul-tang by analyzing domestic/international papers and theses about Palmul-tang, Methods: Domestic/international papers and theses related to Palmul-tang were reviewed and analyzed, These papers were then classified by year, experimental method and subject, Results: The following results were obtained in this study. 1. The study of Palmul-tang started from 1985 and was continuously increased. The study was mainly forcused on experimental model rather than clinical study. 2. As these studies were classified by subject, papers related to immune intensification were most abundant by 20 papers, Besides there were several papers related to cardiovascular activity, reproductive activity, anti-apoptotic activity and cerebral hemodynamics. 3. Among the papers related to immune intensification. the studies on recovery of fatigue were mostabundant by 10 papers and the studies of on immune cell and cytokine express were six. In addition to. several studies were associated with anti-cancer activity and anti-allergic activity. Recovery of fatigue was determined by measurement of fatigue markers in a living body such as lactate. CPK, pyruvate and triglyceride and assessment of exercise capability of animals such as swimming test. slopped plate test. Rota-rod test, and activity cage test after Palmul-tang treatment. 4. According to experimental data. it is supported that Palmul-tang has been used as Qi and Blood intensifier with immune intensification and recovery of fatigue. 5. The paper related to safety of Palmul-tang was only one paper which is studied on acute toxicity of Palmul-tang with experiment with ICR mouse. There was no study on evaluating safety by observing liver and kidney functions after Palmul-tang treatment Conclusion: Palmul-tang is being used in various ways associating with immune intensification. cardiovascular activity and reproductive activity. However. studies on efficacy and mechanism of Palmul-tang should be conducted at the molecular biology level and studies on safety of Palmul-tang need to be completed at the clinical level.

• 한국산학기술학회논문지
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• 제20권12호
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• pp.8-14
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• 2019

대표적인 하천횡단구조물 중 하나인 낙차공은 하천하상의 안정을 목적으로 설치되지만 이는 하천환경의 연속성을 차단하고, 수생태환경의 파괴를 야기하는 것으로 알려져 있다. 따라서 본 연구에서는 생태통로로서의 기능을 갖는 저낙차 자연형 낙차공을 모형으로 제작하여 실험실 실험을 수행하고, 적절한 지배인자 사이의 관계를 도출하여 국부세굴공 규모의 예측식을 제안하였다. 직선형과 6가지 상향 V 자형의 낙차공 모형에 대하여 각각 실험유량은 4가지로 총 28개의 조건에 대해서 실험을 수행하였다. 각각의 실험조건별 세굴실험 결과를 바탕으로 기존에 제안된 세굴심 추정식을 적용한 결과보다 최대세굴심이 다소 크게 발생함을 확인하였다. 따라서 낙차공 직하류부에서 발생하는 세굴공 발생 주요인자들 사이의 상관관계를 분석한 결과, 낙차공으로의 유입흐름 특성과 낙차공의 높이, 낙차공의 총횡단길이와의 상관관계가 높게 나타남을 확인하였다. 또한 이를 토대로 각 실험조건별 세굴심과 세굴길이에 상관관계가 높다고 판단되는 변수들을 무차원화하여 최대세굴공의 깊이와 길이 산정식을 각각 제안하였다. 향후 추가적으로 다양한 하상토 재료와 수심변화를 고려한 실험적 연구 및 수치해석 연구를 병행하여 보다 정확한 세굴심 산정식을 도출할 수 있다.

• Clinical and Experimental Pediatrics
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• 제51권7호
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• pp.704-712
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• 2008

목 적 : 최근 모유수유의 장점이 부각되고 있으나 모유가 미숙아 전용분유에 비해 열량을 포함한 영양소들이 미숙아들의 적절한 성장을 유도하기에는 낮아 이를 극복하기 위한 모유강화제가 개발되었다. 본원에서는 극소저체중출생아들을 대상으로 모유강화제를 첨가한 모유를 수유한 경우와 미숙아 전용분유를 수유한 경우를 비교하여 성장에 어떠한 효과를 미치는지 알아보기로 했다. 방 법 : 2005년 10월부터 2006년 12월까지 동아대학교의료원에서 출생하여 신생아 집중치료실에 입원한 출생체중 1,500 g 이하, 재태주령 33주 미만인 극소저체중출생아들을 대상으로 강화된 모유수유군과 미숙아 전용분유 수유군으로 나누어 전반적인 특징, 영양상태, 성장 추이 및 합병증의 발생 등을 전향적으로 비교 조사하였다. 대상 환자들 중 본원에서 추적관찰이 가능했던 환자들의 경우 외래에서 1, 3, 6개월에 걸쳐 체중, 신장, 두위를 측정하여 비교하였다. 결 과 : 두 군의 평균 재태주령 및 출생체중은 각각 $30^{+1}{\pm}2^{+1}$주과 $29^{+4}{\pm}2^{+1}$주, $1,281.30{\pm}178g$과 $1,234.32{\pm}193g$으로 통계학적으로 차이가 없었으며(P=0.26, P=0.38), 성비, 괴사성 대장염, 패혈증, 신생아호흡곤란증후군, 동맥관개존증, 뇌 내출혈 및 뇌실 내 출혈 등의 합병증의 비율, 평균 재원 기간에서도 유의한 차이는 없었다. 수유 시작 시기는 강화된 모유수유군과 미숙아 전용분유 수유군에서 각각 생후 $8.00{\pm}3.27$일 및 $8.86{\pm}5.37$일(P=0.99), 완전수유 도달 시기는 각각 수유시작 후 $41.78{\pm}20.47$일 및 $36.86{\pm}20.63$일로(P=0.55) 통계적으로 유의한 차이가 없었으며, 총정맥영양 기간 및 수유 곤란증상 횟수에도 유의한 차이는 없었다. 수유시작 시점부터의 체중, 신장, 두위의 성장 속도 및 절대치도 두 군 간에 유의한 차이가 없었으나 각 시점의 평균치를 비교하였을 때 수유 시작 후 7주째 체중은 강화된 모유수유군에서 더 빨리 증가하였다(P=0.03). 환자들의 초기 체중 감소 후 출생체중까지 회복되는데 걸리는 기간도 각각 $22.3{\pm}6.92$일 및 $24.32{\pm}10.68$일로 통계학적 차이는 없었으며(P=0.41), 체중 회복 후부터 퇴원까지의 체중 및 두위, 신장의 증가속도는 두 군에서 유의한 차이는 없었다. 퇴원 후 외래 추적 관찰을 한 각 군의 환자들의 체중, 신장, 두위의 평균치에도 유의한 차이는 없었다. 결 론 : 극소저체중출생아에서 모유강화제를 포함한 모유수유군과 미숙아 전용분유 수유군 간의 전반적인 성장 상태, 생화학적 검사 수치 및 합병증 발생에는 유의한 차이가 없어 모유 강화제는 고열량 수유를 필요로 하는 극소저체중출생아에서 부가적인 선택 사항이라고 하겠다.

• 한국산업융합학회 논문집
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• 제5권1호
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• pp.65-74
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• 2002

This paper intends to investigate such effects through experiments. The contents of the investigation are effects of position of repeated loading and unloading, passing frequency. For the purpose of the investigation an experimental load-deflection system is developed and the system is possible to measure deflection of the wall and earth pressure due to different size of strip loading and cyclic loading. The findings from the experiments are as follows: 1. As repeated loading approaches to the wall, the measured horizontal residual earth pressure agrees well with Rowe's empirical formula, while as the loading is far from the wall the earth pressure consists with Boussinesq's and Spangler's formulas. Also it is found that below 0.6m depth from ground surface the effects of repeated loading can be nearly neglected. 2. From comparison analyses of earth pressure theories and experimental results, a reagression equation is suggested herein, and earth pressure at any depth and maximum earth pressure due to cyclic loading can be estimated from the equation.

• 대한조선학회논문집
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• 제44권2호
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• pp.64-73
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• 2007

Turbulent flows around yacht sails were calculated to access the applicability of CFD for yacht design. Multi-block grid system was generated by using Gridgen package and Fluent was used to calculate flows around two sail system. A 30ft class sailing yacht designed and tested by KRISO was chosen. The interference effect between main and jib sails was analyzed. Pressure distribution on the sails was obtained and the center of effort was estimated. It was found that the jib angle affects the flow phenomena around a main sail due to the change of inflow angle. The location of center of effort is much different from the empirical formula based on a simple geometrical consideration. The calculated results are compared with the previous numerical and experimental results. Both CFD results are similar, but there are some discrepancies with experimental data. However, it is certain that CFD can be a very useful tool for yacht design.

• 한국해안·해양공학회논문집
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• 제32권3호
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• pp.161-169
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• 2020

테트라포드로 피복된 경사식방파제 상부구조물에 파가 경사 입사할 때의 파력 변화를 관찰하기 위한 수리모형실험을 수행하였다. 입사파향은 0, 15, 30, 45° 4가지로 변화시켰으며 상부구조물 전면 및 하부면에 파압계를 부착하여 수평 및 연직파력을 계측하였다. 실험을 통해 입사각과 구조물 전면이 이루는 각도가 증가할수록 수평 및 연직 파력이 모두 감소함을 확인하였다. 실험자료 분석 결과로부터 입사파향에 대한 수평 및 연직 파력 감소율 산정식을 각각 제시하였다.