• 한국추진공학회지
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• 제9권3호
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• pp.101-119
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• 2005

초소형 연소시스템의 응용을 위한 기초 자료로서, 열 및 운동량 손실이 예혼합화염의 연소불안정성에 미치는 영향에 대하여 수치적으로 연구하였다 고차정확도를 갖는 수치해석기법을 이용한 수치실험에서 운동량 손실은 Darrieus-Landau (D-L) 불안정성을 증진시키는 효과를 보였고 열손실은 diffusive-thermal (D-T) 불안정성을 활성화시키는 효과를 나타냈다. 이러한 영향은 화염의 비선형적 거동구간에도 유효하여 다중 셀의 분할 및 통합과정에서도 중요한 역할을 했다.

• Nuclear Engineering and Technology
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• 제55권8호
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• pp.3088-3101
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• 2023

A pressurized vessel-pipe-safety valve (PVPSV) combination is a commonly used configuration in nuclear power plants, and a good numerical model is essential for the system design, sizing and performance optimization. However, owing to the large-scale and cross-scale features, it is still a challenge to build a system level numerical model with both high accuracy and efficiency. To overcome this, a novel system level modeling method which can synthesize the advantages of various models is proposed in this paper. For system modeling, the analytical approach, the method of characteristics (MOC) and the surrogate model approach are respectively adopted to predict the dynamics of the pressure vessel, the connecting pipe and the safety valve, and different models are connected through data interfaces. With this system model, dynamic simulations were carried out and both the stable and the unstable system responses were obtained. For the model verification purpose, the simulation results were compared with those obtained from experiments and full CFD simulations. A good agreement and a better efficiency were obtained, verifying the ability of the model and the feasibility of the modeling method proposed in this paper.

• 한국산학기술학회논문지
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• 제17권3호
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• pp.177-189
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• 2016

본 연구는 간호대학생에게 고충실도 시뮬레이터를 활용한 모성간호 시뮬레이션 교육을 적용하고, 그 효과를 평가하기 위한 단일군 전후설계 유사실험연구이다. 간호학과 4학년에 재학 중인 학생들에게 고충실도 환자 시뮬레이터를 활용하여 임부, 산부, 산욕부 간호에 대한 시뮬레이션 교육을 실시하였고, 교육기간은 2014년 11월 10일부터 3주간이었으며, 차시별 3시간씩 총 9시간에 걸쳐 진행되었다. 교육 전후 설문을 통해 자료수집을 실시하였고, 분석에 사용된 대상자 수는 83명이었다. 수집된 자료는 IBM SPSS Statistics 20.0 프로그램을 이용하여 실수와 백분율, 평균과 표준편차, paired t-test, independent t-test, Pearson's correlation coefficients를 분석하였다. 시뮬레이션 교육 후 시뮬레이션 효과성은 총점 26점 만점에 17.4이었으며, 시뮬레이션 교육 전과 후에 의사소통능력(t=4.58, p=<.001)과 모성간호 수행에 대한 자신감(t=9.70, p=<.001)은 유의하게 향상되었으나, 문제해결능력에는 차이가 없었다. 임상실습에 만족하는 경우에 시뮬레이션 교육 후 시뮬레이션 효과성(t=2.09, p=.040), 문제해결능력(t=3.13, p=.002), 의사소통능력(t=3.54, p=.001), 모성간호 수행에 대한 자신감(t=2.64, p=.010)이 유의하게 높은 것으로 나타났으며, 시뮬레이션 효과성은 문제해결능력(r=.494, p<.001), 의사소통능력(r=.361, p<.001) 및 모성간호에 대한 자신감(r=.497, p<.001)과 유의한 양의 상관관계가 있었다. 따라서 현 임상실습의 한계에 대한 대안이자, 학생들의 임상 간호에서 필요한 역량을 강화하기 위한 전략으로써 고충실도 시뮬레이터를 활용한 모성간호 시뮬레이션 교육이 적용될 수 있으며, 이 때 학습 과정 동안 학습자의 학습경험이 학습성과로 이어질 수 있도록 하기 위한 체계적인 시뮬레이션 교수학습 전략이 필요할 것이다.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2014년도 제49회 KOSCO SYMPOSIUM 초록집
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• pp.175-178
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• 2014

The flame cell dynamics in 2-D opposed nonpremixed tubular configuration was investigated using high-fidelity numerical simulations. The diffusive-thermal instability occurs as the $Damk{\ddot{o}}hler$ number, Da, approaches the 1-D extinction limit of the tubular flames and several flame cells are generated depending on Da, and flame radius. In general, the number of flame cells are found close to the largest wave number from the linear stability analysis. It was also found from the displacement speed analysis that during the local flame extinction and cell formation, negative edge flame speed is observed due to small gain from reaction compared to large loss from diffusion.

• International Journal of Aeronautical and Space Sciences
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• 제17권4호
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• pp.579-592
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• 2016

CNUSAIL-1, to be launched into low-earth orbit, is a cubesat-class satellite equipped with a $2m{\times}2m$ solar sail. One of CNUSAIL's missions is to deploy its solar sail system, thereby deorbiting the satellite, at the end of the satellite's life. This paper presents the design results of the attitude control system for CNUSAIL-1, which maintains the normal vector of the sail by a 3-axis active attitude stabilization approach. The normal vector can be aligned in two orientations: i) along the anti-nadir direction, which minimizes the aerodynamic drag during the nadir-pointing mode, or ii) along the satellite velocity vector, which maximizes the drag during the deorbiting mode. The attitude control system also includes a B-dot controller for detumbling and an eigen-axis maneuver algorithm. The actuators for the attitude control are magnetic torquers and reaction wheels. The feasibility and performance of the design are verified in high-fidelity nonlinear simulations.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2005년도 제31회 KOSCO SYMPOSIUM 논문집
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• pp.281-286
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• 2005

To understand fundamental characteristics of combustion in a small scale device, the effects of the momentum and heat loss on the stability of laminar premixed flames in a narrow channel are investigated by two-dimensional high-fidelity numerical simulation. A general finding is that momentum loss promotes the Saffman-Taylor (S-T) instability which is additive to the Darrieus-Landau (D-L) instabilities, while the heat loss effects result in an enhancement of the diffusive-thermal (D-T) instability. These effects are also valid in nonlinear behavior of the premixed flame. The simulations of multiple cell interactions are also conducted with heat and momentum loss effects.

• Advances in aircraft and spacecraft science
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• 제4권2호
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• pp.125-144
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• 2017

This paper summarises the design of a gust generator and the comparison between high fidelity numerical results and experimental results. The gust generator has been designed for a low subsonic wind tunnel in order to perform gust response experiments on wings and assess load alleviation. Special attention has been given to the different design parameters that influence the shape of the gust velocity profile by means of CFD simulations. Design parameters include frequency of actuation, flow speed, maximum deflection, chord length and gust vane spacing. The numerical results are compared to experimental results obtained using a hot-wire anemometer and flow visualisation by means of a tuft and smoke. The first assessment of the performance of the gust generator showed proper operation of the gust generator across the entire range of interest.

• Advances in aircraft and spacecraft science
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• 제10권6호
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• pp.521-543
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• 2023

Reynolds-averaged Navier-Stokes (RANS) models are extensively employed in industrial settings for the purpose of simulating intricate fluid flows. However, these models are subject to certain limitations. Notably, disparities persist in the Reynolds stresses when comparing the RANS model with high-fidelity data obtained from Direct Numerical Simulation (DNS) or experimental measurements. In this work we propose an approach to mitigate these discrepancies while retaining the favorable attributes of the Menter Shear Stress Transport (SST) model, such as its significantly lower computational expense compared to DNS simulations. This strategy entails incorporating an explicit algebraic model and employing a neural network to correct the turbulent characteristic time. The imposition of realizability constraints is investigated through the introduction of penalization terms. The assimilated Reynolds stress model demonstrates good predictive performance in both in-sample and out-of-sample flow configurations. This suggests that the model can effectively capture the turbulent characteristics of the flow and produce physically realistic predictions.

• Nuclear Engineering and Technology
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• 제55권12호
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• pp.4659-4663
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• 2023

The use of iodine S values derived using the International Commission Radiological Protection (ICRP) phantoms may introduce significant bias in internal dosimetry for Koreans due to anatomical variability. In the current study, we produced an extensive dataset of Korean S values for selected five iodine radioisotopes (I-125, I-129, I131, I-133, and I-134) for use in radiation protection. To calculate S values, we implemented Monte Carlo simulations using the Mesh-type Reference Korean Phantoms (MRKPs), developed in a high-quality/fidelity mesh format. Noticeable differences were observed in S value comparisons between the Korean and ICRP reference phantoms with ratios (Korean/ICRP) widely ranging from 0.16 to 6.2. The majority of S value ratios were lower than the unity in Korean phantoms (interquartile range = 0.47-1.28; mean = 0.96; median = 0.69). The S values provided in the current study will be extensively utilized in iodine internal dosimetry for Koreans.

• International Journal of Aeronautical and Space Sciences
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• 제9권1호
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• pp.66-75
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• 2008

In this work, we explore the feasibility of roll-pitch-yaw integrated autopilots for high angle-of-attack missiles. An investigation of the aerodynamic characteristics of a surface-to-air missile is presented, which reveals the strong effects of cross coupling between the longitudinal and lateral dynamics. Robust control techniques based on $H_{\infty}$ synthesis are employed to design roll-pitch-yaw integrated autopilots. The performance of the proposed roll-pitch-yaw integrated controller is tested in high-fidelity nonlinear five-degree-of-freedom simulations accounting for kinematic cross-coupling effects between the lateral and longitudinal channels. Against nonlinearity and cross-coupling effects of the missile dynamics, the integrated controller demonstrates superior performance when compared with the controller designed in a decoupled manner.