• 대한기계학회논문집
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• 제18권3호
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• pp.701-706
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• 1994

The discharge coefficients of critical sonic nozzles were obtained in a high pressure gas flow standard system, which was a gravitational weighing system. The discharge coefficients of critical sonic nozzle farbricated according to ISO specifications are in good agreement with ISO correlation. The discharge coefficients for small inlet radius decrease significantly as the inlet length become short due3 to separation at the sharp-edged inlet. For nozzles having long inlet radius, the effects of inlet length on the discharge coefficients were relatively small, but the effects become significant at the short inlet length. The effect of separation at the sharp-edged inlet is stronger than that of the boundary layer growth. The experimental results support that the shape of critical sonic nozzles suggested by ISO specifications is excellent.

• 대한기계학회논문집B
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• 제27권7호
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• pp.948-955
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• 2003

Pressure coefficient in rotating discharge hole was measured to gain insight into the influence of rotation to the discharge characteristics of rotating discharge hole. Pressure measurements were done by the telemetry system that had been developed by the authors. The telemetry system measures static pressure using piezoresistive pressure sensors. Pressure coefficients in rotating discharge hole were measured in longitudinal direction and circumferential direction with various rotating speed and 3 pressure ratios. From the results, the pressure coefficient, and therefore the discharge coefficient, is known to decrease with the increase of Ro number owing to the increase of flow approaching angle to the discharge hole inlet. However, there exists critical Ro number where the decrease rate of discharge coefficient with the increase of Ro number changes abruptly; flow separation occurs from the discharge hole exit at this critical Ro number. Critical Ro number increases with the increase of length-to-diameter ratio, but the increase is small where the length-to-diameter ratio is higher than 3. The decrease rate of discharge coefficient with the increase of Ro number depends on the pressure recovery at the discharge hole, and the rate is different from each length-to-diameter ratio; it has tendency that the short discharge hole shows higher decrease rate of discharge coefficient.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2002년도 유체기계 연구개발 발표회 논문집
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• pp.331-336
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• 2002

Recently the critical nozzles with small diameter are being extensively used to measure mass flow in a variety of industrial fields and these have different configurations depending on operation condition and working gas. The curvature radius of the critical nozzle throat is one of the most important configuration factors promising a high reliability of the critical nozzle. In the present study, computations using the axisymmetric, compressible, Navier-Stokes equations are carried out to investigate the effect of the nozzle curvature on critical flows. The diameter of the critical nozzle employed is D=0.3mm and the radius of curvature of the critical nozzle throat is varied in the range from 1D to 3D. It is found that the discharge coefficient is very sensitive to the curvature radius(R) of critical nozzle, leading to the peak discharge coefficient at R = 2.0D and 2.5D, and that the critical pressure ratio increases with the curvature radius.

• 성인간호학회지
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• 제28권1호
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• pp.43-52
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• 2016

Purpose: The aim of this study was to identify demographic, clinical, physical, and psychosocial factors affecting discharge delay in lumbar spinal surgery patients who were treated according to a critical pathway. Methods: A sample of 170 patients with lumbar spinal surgery agreed to participate in the study, between April 1, 2014 and August 30, 2015. Data were analyzed by mean, standard deviation, t-test, ${\chi}^2$-test, ANCOVA, and logistic regression analysis using SPSS 22.0 program. Results: Approximately fifty-nine percent of the participants was delayed discharge. On logistic regression analysis, female gender (OR=2.63, 95% CI=1.40~4.94), age (OR=1.03, 95% CI=1.01~1.05), spondylolisthesis (OR=4.49, 95% CI=1.90~10.61), and spinal fusion operation (OR=4.14, 95% CI=1.89~9.05) were significant factors predicting discharge delay of the participants. However, discharge delay was not related with pain, physical function, depression, or family support. Conclusion: An analysis of discharge delay may assist in evaluating and revising critical pathway for optimal care. In addition, nurses need to understand the factors affecting discharge delay of the given population who were treated according to a critical pathway.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 추계학술대회
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• pp.532-537
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• 2003

Gas flow through orifice is encountered in many diverse fields of engineering applications. In order to investigate the critical gas flow through an orifice system, a computational analysis is performed using axisymmetric, compressible, Navier-Stokes equations which are numerically solved by a fully implicit finite volume method. In the present study, the discharge coefficients of two different types of orifices which are a straight-bore orifice and a sharp-edged orifice, are predicted to obtain the critical flow conditions. The present CFD data are compared with the previous experimental results. The present computational results show that the critical mass flow rate through orifice is well predicted and it is a strong function of Reynolds number. The discharge coefficient increases with the orifice diameter.

• 중환자간호학회지
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• 제4권1호
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• pp.25-35
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• 2011

Purpose: The purpose of this study was to evaluate the actual outcomes of early discharge program for extremely low birth weight (ELBW) infants. Methods: Medical records of 122 ELBW infants admitted in the neonatal intensive care unit from January 2000 to June 2006 and those of their 112 mothers were analyzed retrospectively. Results: After being applied early discharge program to ELBW infants' mothers, their infants' lengths of stay, gestational age and body weight at discharge, duration of completion of oral feeding, number of emergency room visits after discharge were decreased and number of breast milk feeding was increased. Conclusion: Early discharge program for ELBW infants can be an effective intervention for parents and their ELBW infants contributing to neonatal nursing practices.

• Nuclear Engineering and Technology
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• 제27권5호
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• pp.701-709
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• 1995

RELAP5 /MOD3/KAERl의 임계유동모델을 위한 실제적인 배출계수들을 9개의 MARVIKEN 임계유동실험 의 평가계산을 통하여 과냉각과 이상임계유동에 대하여 구하였다. 선택된 실험에는 높은 초기 과냉각도와 큰 노즐 세 장비(L/D)인 것들이 포함되었다. 코드의 평가결과는 RELAP5/MOD3/KAERI은 과냉각임계유동을 크게 예측하고 이 상임계유동은 작게 예측함을 보이고 있다. 이러한 결과들을 이용하여 임계유동모델의 실제적인 배출계수들을 반복법으로 정량화 하였다. 실제적인 배출계 수는 과냉각임계유동이 0.89 그리고 이상임계유동이 1.07로 결정되었으며 관련 표준편차는 각 각 0.0349과 0.1189이다. 본 연구로부터 얻어진 결과는 대형냉각재 상실사고의 실제적인 계통반응 계산과 비상노심냉각계통 성능평가에 적용할 수 있다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 추계학술대회논문집B
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• pp.652-657
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• 2001

Computational work using the axisymmetric, compressible, Navier-Stokes Equations is carried out to predict the discharge coefficient of mass flow through a micro-critical nozzle. Several kinds of turbulence models and wall functions are employed to validate the computational predictions. The computed results are compared with the previous experimented ones. The present computations predict the experimental discharge coefficients with a reasonable accuracy. It is found that the standard $k-\varepsilon$ turbulence model with the standard wall function gives a best prediction of the discharge coefficients. The displacement thickness of the nozzle wall boundary layer is evaluated at the nozzle throat and is well compared to a prediction obtained by an empirical equation. The resulting displacement thickness of the wall boundary layer is about 2% to 0.6% of the diameter of the nozzle throat for the Reynolds numbers of 2000 to 20000.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회B
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• pp.3003-3008
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• 2007

Critical nozzle has been frequently employed to measure the flow rate of various gases, but hydrogen gas, especially being at high-pressure condition, was not nearly dealt with the critical nozzle due to treatment danger. According to a few experimental data obtained recently, it was reported that the discharge coefficient of hydrogen gas through the critical nozzle exceeds unity in a specific range of Reynolds number. No detailed explanation on such an unreasonable value was made, but it was vaguely inferred as real gas effects. For the purpose of practical use of high-pressure hydrogen gas, systematic research is required to clarify the critical nozzle flow of high-pressure hydrogen gas. In the present study, a computational fluid dynamics(CFD) method has been applied to predict the critical nozzle flow of high-pressure hydrogen gas. Redlich-Kwong equation of state that take account for the forces and volume of molecules of hydrogen gas were incorporated into the axisymmetric, compressible Navier-Stokes equations. A fully implicit finite volume scheme was used to numerically solve the governing equations. The computational results were validated with some experimental data available. The results show that the coefficient of discharge coefficient is mainly influenced by the compressibility factor and the specific heat ratio, which appear more remarkable as the inlet total pressure of hydrogen gas increases.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2003년도 유체기계 연구개발 발표회 논문집
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• pp.167-173
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• 2003

For the measurement of mass flow rate at a wide range of operation conditions, it is required that the critical nozzle gas different diameters, since the mass flow rate through the critical nozzle depends on the nozzle supply conditions and the nozzle throat diameter. In the present study, both computational and experimental investigations are performed to explore the variable critical nozzle. Computational work using the 2-dimensional, axisymmetric, compressible Navier-Stokes equations are carried out to simulate the gas flow through variable critical nozzle. In experimnet, a cylinder with several different diameters is inserted into the critical nozzle to vary the nozzle throat diameter. Computational results are compared with the experimented ones. The computed results are in close agreement with experiment. It is found that the displacement and momentum thickness of variable critical nozzle are given as a function of Reynolds numbers. The discharge coefficient of the variable critical nozzle is predicted using an empirical equation.