• 한국추진공학회지
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• 제9권1호
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• pp.61-66
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• 2005

혼합챔버 내에서 패브리 초킹(Fabri choking)이 발생한다는 가정을 이용하여 이차목을 갖는 환형분사 초음속 이젝터의 이론 해석을 수행하였다. 부유동 압력을 예측하기 위해 혼합챔버 입구에서 패브리 초킹면 사이를 비혼합 이론(non mixing theory)을 이용하여 계산하였다. 혼합챔버의 수축각에 의해 발생하는 깔때기 모양의 경사충격파를 이차원 경사충격파로 모사하였고, 패브리 초킹면의 주유동에만 영향을 미친다고 가정하였다. 또한 패브리 초킹면의 주유동 압력과 부유동 압력이 같다는 물리적인 제한조건을 사용하였다. 그 결과 혼합챔버의 수축각이 4도보다 작은 조건에서 실험값을 잘 예측하는 것을 확인하였다.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 1996년도 봄 학술발표회 논문집
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• pp.27-39
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• 1996

배관을 구속시키기 위한 원통형 배관 지지대 (Trunnion Pipe Support)가 부착된 배관의 응력해석 을 위하여 유한요소해석을 사용하였다. 해석결과로 부터 얻어진 응력은 두께에 대한 평균 및 선 형 응력으로 분류 되었으며, 분류된 응력값은 압력에 의한 일차응력계수(B$_1$)와 이차응력계수(C$_1$), 모멘트에 의한 일차응력계수(B$_2$)와 이차응력계수(C$_2$)를 추정하기 위하여 ASME Code에 정의된 것과 일치하게 해석되었다. 무차원의 함수로써 응력계수에 대한 경험식을 개발하기 위하여 여러 모델의 해석을 수행하였다.

• Nuclear Engineering and Technology
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• 제14권2호
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• pp.92-101
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• 1982

• 한국재료학회지
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• 제30권2호
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• pp.51-56
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• 2020

In this study, three kinds of metal chills such as SS400, AC4CH and brass, with different thicknesses of 40 ~ 80 mm, were applied for low pressure casting of Al-Si alloy to control cooling rate. The microstructural characteristics with increasing cooling rate were represented using factors including D₁, D₂, size of primary α phases and shape factor and size of eutectic Si. The tensile properties were investigated and additionally analyzed based on the microstructural characteristics. As the cooling rate increased, D₁, D₂, and sizes of primary α phases and eutectic Si apparently decreased and the shape factor of eutectic Si increased to over 0.8. The ultimate tensile strength (UTS) and yield strength (YS) increased with decreasing D₁, D₂, and size of primary α phases, while elongation increased with decreasing size of eutectic Si and concurrently increasing shape factor of eutectic Si. This indicated that the primary α phases and eutectic Si in Al-Si alloy were refined with increasing cooling rate, resulting in improvement of UTS and YS without sacrificing elongation. After the tensile test, preferential deformation of primary α phases was observed in the Al-Si alloy produced at higher cooling rates of more than 0.1 K/s.

• Asian-Australasian Journal of Animal Sciences
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• 제12권1호
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• pp.9-14
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• 1999

Factors affecting gene gun-mediated expression of the human erythropoietin gene were investigated in primary cultured oviduct cells from laying hens. The human erythropoietin gene was transfected by a gene gun method at $1.25{\mu}g$ per dish, and cultured in a synthetic serum-free medium for 72 hrs. The concentration of human erythropoietin mRNA was determined by RNA : RNA solution hybridization. In experiment 1, the effect of changing the shooting pressure of DNA-coated microparticles with nitrogen gas was tested at 20 and $60kgf/cm^2$. The results showed that the erythropoietin mRNA concentration was significantly higher at 60 than $20kgf/cm^2$. In experiment 2, the effects of supplementing the medium with fetal calf serum at 10%, and raising the shooting pressure from 60 to $80kgf/cm^2$ on the cell number and erythropoietin gene expression were examined. Although supplementation with fetal calf serum significantly increased the cell numbes compared with no supplemented controls (p < 0.05), erythropoietin mRNA concentration per $10^3$ cells was not affected. Raising the shooting pressure from 60 to $80kgf/cm^2$ did not affect either of the parameters, In experiment 3, the effect of supplementing ascorbate 2-phosphate at 0.5 mM was tested. The results indicated that the ascorbate supplementation significantly increased the cell number (p < 0.05), and tended to increase erythropoietin mRNA concentration (p < 0.1). Thus, for human erythropoietin gene expression by using the gene gun method, shooting pressure with nitrogen gas should be sufficient at $60kgf/cm^2$ and supplementation with ascorbate phosphate would be useful to enhance not only the cell proliferation but also erythropoietin gene expression.

• 한국추진공학회지
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• 제13권5호
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• pp.21-28
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• 2009

본 연구는 초음속 축소형 디퓨저의 설계 및 시동 특성에 영향을 주는 변수를 파악하기 위하여 상온의 공기와 질소 가스를 사용하여 실험을 수행하였다. 1차 노즐의 목 면적의 변화, 1차 노즐 전단의 압력 변화, 디퓨저 길이와 직경의 비($L_d/D_d$) 그리고 디퓨저의 팽창부 유 무에 따른 디퓨저의 시동 특성을 알아보았다. 실험 결과 1차 노즐의 직경이 감소할수록 디퓨저 시동압력은 증가하였으며, 디퓨저의 예측 모델과 비교하여 90~98%의 장치 효율을 확인하였다. 또한 $L_d/D_d$가 8.4이상인 디퓨저와 팽창부의 유 무에 관계없이 디퓨저는 정상적으로 시동하였다. 본 실험 결과는 실물형 고고도 환경 모사 장치의 개발에 있어서 기초 자료로 활용될 것이다.

• 한국지반공학회논문집
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• 제24권5호
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• pp.107-115
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• 2008

본 연구는 1차압밀 중의 크리프의 영향과 Yin이 제안한 탄-점-소성 모델에 대한 적용성을 검토하였다. 탄성모델을 이용한 일반적인 압밀이론은, 1차압밀 과정을 표현할 수 있으나 2차압밀을 표현할 수 없다. 이러한 결과는 2차압축을 표현할 수 있는 점성에 기인하며, 때로는 Ladd 등(1977)이 제안한 가정 A 및 B와 같은 스케일효과(실험실 공시체와 현장조건 사이의 점토층 두께의 차이)와 관련되어진다. 통상적으로 1차압밀 중의 크리프의 존재는 많은 연구자에 의해 확인되어졌으며, 가정 B가 잘 맞는 것으로 되어있다. 한편, 대형압밀시험을 통해 가정 A와 B의 중간적인 특성이 Aboshi(1973)에 의한 가정 C로써 제안되어졌다. 본 연구에서는 1차압밀 중의 침하-시간관계에 대한 크리프의 영향을 명백히 하기 위해, peat와 점토에 대해 분할형 압밀시험기를 이용하여 가정 B의 압밀시험을 행하였다. 그리고 Yin의 탄-점-소성 모델을 이용하여 실험결과를 해석하였다. 얻어진 결과는 다음과 같다. 1차압밀 종료시에 분할 공시체의 압축은 과잉간극수압 소산속도의 차이에 의해 동일하지 않았다. 또한 분할형 압밀시험기에 의해 측정된 평균변형률과 Yin의 EVP 모델을 이용한 해석치는 잘 일치하였다. 그러나 과잉간극수압의 소산에 대해서는 측정치가 Yin 모델에 비해 빨리 소산되었다.

• Tribology and Lubricants
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• 제5권2호
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• pp.48-54
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• 1989

The effects of angular misalignment, coning and the temperature difference between the primary seal ring and the seal seat on the pressure distribution in mechanical face seals are analyzed. The modified Reynolds equation for the temperature dependent viscosity was solved by a finite difference approximation and Gauss-Seidel method. It is shown that the amplitude of pressure is significantly affected by the misalignment of the seals and a large temperature difference between the rotor and the stator.

• 한국농촌간호학회지
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• 제9권2호
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• pp.45-58
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• 2014

Purpose: To determine the knowledge and treatment compliance with hypertension, directions for the aspects of implementation, and related factors to patients with hypertension using Primary Health Cares and Private Clinics Hospitals. Method: General characteristics and High blood pressure-related properties(17 questions), Hypertension knowledge measures(20 questions), and Treatment Compliance(22 questions) were used. Result: 1. The patients of Private Clinics Hospitals had statistically significantly higher drinking habits than Primary Health Care centers. The patients of Private Clinics Hospitals had statistically significantly higher rate of no family history of hypertension than Primary Health Care centers. 2. Primary Health Care centers had statistically significantly higher knowledge of hypertension than Private Clinics Hospitals. Primary Health Care centers had statistically significantly higher treatment compliance than Private Clinics Hospitals. Conclusion: Both Primary Health Care centers and Private Clinics Hospitals are high medication compliance but low lifestyle compliance with hypertension. We need to recognize the importance of lifestyle compliance, to apply proper programs and to provide therapists' aggressive intervention.

• Journal of Korean Biological Nursing Science
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• 제21권4호
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• pp.275-282
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• 2019

Purpose: This study aimed to identify the differences in blood pressure among adults in the community according to age and time of the blood pressure measurement. Methods: This was a secondary analysis study, using data from a 2015 community health survey, conducted by the Korea Centers for Disease Control and Prevention. The data of three-time-measured blood pressure were collected from 337 subjects, 25, 35, 45, 55, 65, 75 years old, which are median ages by each age group. Results: The primary systolic pressure was significantly higher than the secondary systolic pressure (t= 3.46, p= .001) and the tertiary systolic pressure (t= 4.83, p= .001). The secondary systolic pressure was higher than the tertiary measurement (t= 2.05, p= .041). There was no significant difference between the three-time-measured values for diastolic pressure. There was a significant interaction between measurement times and age in the systoic blood pressure readings (F= 1.95, p= .036). However, there was no significant interaction between measurement times and age in the diastolic blood pressure readings (F= 1.03, p= .418). Conclusion: The findings suggest that attention must be paid to the use of blood pressure values in studies or one-time-measured clinical blood pressure values. In particular, the differences in systolic pressure readings taken at different times in the older age groups were significant. Therefore, it is more important to carefully assess blood pressure in adults over the age of 45 compared to other age groups.