• 한국유체기계학회 논문집
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• 제17권6호
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• pp.89-94
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• 2014

The 4th generation SFR is being designed with a milestone of construction by 2028. It is important to understand the subchannel flow characteristics in fuel assembly through the experimental investigations and to estimate the calculation uncertainties for insuring the confidence of the design code calculation results. The friction coefficient and the mixing coefficient are selected as primary parameters. The two parameters are related to the flow distribution and diffusion. To identify the flow distribution, an iso-kinetic method was developed based on the previous study. For the mixing parameters, a wire mesh system and a laser induced fluorescence methods were developed in parallel. The measuring systems were adopted on 37 rod bundle test geometry, which was developed based on the Euler number scaling. A scaling method for a design of experimental facility and the experimental identification techniques for the flow distribution and mixing parameters were developed based on the measurement requirement.

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 1996년도 춘계학술발표회논문집(2)
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• pp.29-35
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• 1996

For the Reactor Coolant System(RCS) flow rate measurement by the secondary calorimetric heat balance method, the coolant temperature of the hot leg is needed. Several Resistance Temperature Detectors(RTD) are installed in the hot leg to measure the temperature, but the average value of RTDs does not correctly represent the energy-averaged(bulk) temperature because of the thermal stratification phenomenon. Therefore some correction is introduced to predict the bulk temperature, but the correction inevitably contains uncertainty because the stratification is not defined well quantitatively yet. Therefore a large uncertainty for the correction has been used for the conservative estimation. But unrealistically large uncertainty causes degradation of the measurement method and yields difficulty to meet the acceptance criterion in start-up flow measurement test. In this paper, an analytical estimation is made on the correction and the related uncertainty using the measured hot leg velocity profile of System 80 reactor flow model test and the measured temperatures of YGN 3&4 and PVNGS 1&2 start-up tests. The results reveal that the magnitude of the correction uncertainty is much smaller than that used in the previous design. Therefore, the confidence on the flow rate measurement method can be improved and the difficulty in start-up flow measurement test can be lessened if the smaller correction uncertainty obtained through this estimation is applied.

• 한국유체기계학회 논문집
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• 제10권6호
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• pp.17-23
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• 2007

In the present work, flow analysis has been performed in the steam turbine bypass control valve (single-path type) for two different cases i.e., case with steam only and case with both steam and water. The numerical analysis is performed by solving three-dimensional Reynolds-averaged Navier-Stokes (RANS) equations. The shear stress transport (SST) model and $k-{\varepsilon}$ model are used to each different case as turbulence closure. Symmetry condition is applied at the mid plane of the valve while adiabatic condition is used at the outer wall of the cage. Grid independency test is performed to find the optimal number of grid points. The pressure and temperature distributions on the outer wall of the cage are analyzed. The mass flow rate at maximum plug opening condition is compared with the designed mass flow rate. The numerical analysis of multiphase mixing flow(liquid and vapor) is also performed to inspect liquid-vapor volume fraction of bypass valve. The result of volume fraction is useful to estimate both the safety and confidence of valve design.

• 한국융합학회논문지
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• 제11권9호
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• pp.433-441
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• 2020

본 연구는 온라인 수업에 참여한 간호대학생의 딴짓에 영향을 미치는 요인을 파악하기 위해 수행하였다. 자료수집은 3개 대학에 재학 중인 간호대학생 304명을 대상으로 2020년 4월 20일부터 4월 30일까지 구조화된 자가 보고식 설문지 작성을 통해 수집하였다. 자료 분석은 SPSS 26.0 program을 이용하여 T-test, ANOVA, Pearson's correlation coefficient, multiple regression을 이용하였다. 연구결과, 딴짓은 흥미도(r=-17, p=.003), 이해도(r=-19, p=.001), 필요도(r=-12, p=.031), 학습동기(r=-12, p=.046), 자기조절효능감(r=-11, p=.040), 학습자신감(r=-14, p=.017), 강의만족도(r=-22, p<.001), 강의몰입(r=-24, p<.001)과 유의한 상관관계를 보였다. 또한 학습자신감(β= -.20), 토론 및 발표선호정도(β= .19), 강의몰입(β= -.15), 강의만족도(β= -.15)이 딴짓에 유의한 영향을 미치는 것으로 확인되었으며(F=9.95, p<.001), 모형의 설명력은 10.6%였다. 본 연구를 통해 온라인 수업에 있어 간호대학생의 딴짓을 감소시키기 위한 교수학습방법 및 프로그램의 개발을 제언한다.

• Physical Therapy Rehabilitation Science
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• 제1권1호
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• pp.33-39
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• 2012

Objective: The objective of this study is to investigate the effect of treadmill training with real optic flow scene on functional recovery of balance and balance self-efficacy in stroke patients. Design: Single blind, Randomized controlled trial. Methods: Nine patients following stroke were divided randomly into the treadmill with optic flow group (n=3), treadmill with virtual reality group (n=3), and control group (n=3). Subjects in the treadmill with optic flow group wore a head-mounted display in order to receive a speed modulated real optic flow scene during treadmill training for 30 minutes, while those in the treadmill with virtual reality group and control group received treadmill training with virtual reality and regular therapy for the same amount of time, five times per week for a period of three weeks. Timed up and go test (TUG) and activities-specific balance confidence scale (ABC scale) were evaluated before and after the intervention. Results: TUG in the treadmill training with optic flow group showed significantly greater improvement, compared with the treadmill training with virtual reality group and control group (p<0.05). Significantly greater improvement in the ABC scale was observed in the treadmill training with optic flow group and the tread mill training with virtual reality group, compared with the control group (p<0.05). Conclusions: Findings of this study demonstrate that treadmill training with real optic flow scene can be helpful in improving balance and balance self-efficacy of patients with chronic stroke and may be used as a practical adjunct to routine rehabilitation therapy.

• 한국컴퓨터정보학회논문지
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• 제17권2호
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• pp.69-76
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• 2012

본 연구의 목적은 웹상에서 이루어지는 컴퓨터 교과목 이러닝에서, 학습자의 학습만족도와 자기주도성, 플로우(flow) 경험의 연관관계를 파악하고, 경로분석을 활용하여 이들 요인간의 인과관계를 분석, 규명하는 것이다. 이를 위해 기존 이론 연구들을 바탕으로 학습만족도를 종속변인으로 하고 자기주도성과 플로우 경험을 독립, 매개변인으로 하는 구조모형을 기초로 하여, 각 요인의 하위 구성요인 간의 인과관계를 분석하였다. 총 193명 학생의 데이터가 분석에 이용되었으며, 주요 결과를 요약하면 다음과 같다. : 1. 학습자의 자기주도성은 플로우 경험을 매개변인으로 하여 학습만족도에 간접적으로 유의한(p<.01) 영향을 미치는 것으로 나타났으며, 플로우 경험은 학습만족도에 직접적으로 유의한(p<.01) 영향을 미치는 것으로 나타났다; 2. 자기주도성의 7개 하위 구성요인 중 '독창적 접근', '학습에 대한 사랑', '학습자적 신념' 등이 플로우 경험을 매개로 하여 학습만족도에 양(+)의 방향으로 간접적으로 유의한(p<.01) 영향을 미치는 것으로 나타났으며, 플로우 경험의 9개 하위 구성요인 중 '명확한 목표' 요인이 학습만족도에 양의 방향으로 직접적으로 유의한(p<.01) 영향을 미치는 것으로 파악되었다.

• 한국대기환경학회지
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• 제15권5호
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• pp.613-623
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• 1999

A Lagrangian particle dispersion mode l(LPDM) coupled with the prognostic flow model based on nonequilibrium level 2.5 turbulence closure has been dcveloped to simulate the dispersion from an elevated emission source. The proposed model did not require any empirical formula or data for the turbulent statistics such as velocity variances and Lagrangian time scales since the turbulence properties for LPDM were calculated from results of the flow model. The LPDM was validated by comparing the model results against the wind tunnel tracer experiment and ISCST3 model. The calculated wind profile and turbulent velocity variances were in good agreement with those measured in the wind tunnel. The ground level concentrations along the plume centerline as well as the dispersion codfficients also showed good agreement in comparison with the wind tunnel tracer experiment. There were some discrepancies on the horizontal spread of the plume in comparison with the ISCST3 but the maximum ground level concentrations were in a good confidence range. The results of comparisons suggested that the proposed LPDM with the flow model was an effective tool to simulate the dispersion in the flow situation where the turbulent characteristics were not available in advance.

• 대한기계학회논문집
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• 제14권5호
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• pp.1244-1253
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• 1990

본 연구에서는 Denton이 제시한 개선된 시간진행법을 이용하여 2차원 직선 정 지 익렬의 유동해석 프로그램의 개발을 목적으로 하고 있으며 기존 프로그램의 안정성 과 수렴의 개선에 역점을 두고 진행하였다. 수치계산 결과는 타당성을 입증하기 위 하여 실험결과 및 Braembussche의 특이점법 수치계산 결과와 비교 검토 하였으며 충격 파가 존재하는 천이음속의 유동에 대하여 수치계산을 실시하였다.

• Journal of Advanced Marine Engineering and Technology
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• 제14권1호
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• pp.90-98
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• 1990

The liquid ejector, having no moving, lubricating and leaking parts, is widely used as the various pumps because of its high working confidence and simplicity. Previously, computer aided design program for the small-sized liquid ejector was developed based on the one-dimensional flow analysis and the systematical laboratory level experiments. Through the present research, it is confirmed that the previously developed computer program to getermine the main design dimensions and to calculate the expected performance curve is satisfactorily applied to design the large liquid ejectors.

• 전기학회논문지
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• 제58권4호
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• pp.867-872
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• 2009

Peak expiratory flow rate(PEF) is one of the most important diagnostic parameters in spirometry. PEF occurs in a very short duration during the forced expiratory maneuver, which could lead to measurement error due to non-ideal dynamic characteristic of the transducer. In such case the initial slope of the flow rate signal determines the accuracy of the measured PEF. The present study considered this initial slope as a parameter to compensate PEF. The 26 standard flow rate signals recommended by the American Thoracic Society(ATS) were flown through the air flow transducer followed by simultaneous measurements of PEF and maximum transducer output$(N_{PEF})$. $N_{PEF}$-PEF satisfied a quadratic equation in general, however, two signals (ATS #2 and #26) having large initial slopes deviated from the fitting equation to a significant degree. The relative error was found to be in a linear relationship with the initial slope, thus, $N_{PEF}$ was appropriately compensated to provide accurate PEF with mean relative error less than only 1%. The 99% confidence interval of the mean relative error was less than a half of the error limit of 5% recommended by ATS. Therefore, PEF can be very accurately determined by compensating the transducer output based on the initial slope, which should be a useful technique for air flow transducer calibration.