• Nuclear Engineering and Technology
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• 제54권5호
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• pp.1825-1834
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• 2022

Performing high-fidelity computational fluid dynamics (HF-CFD) to predict the flow and heat transfer state of the coolant in the reactor core is expensive, especially in scenarios that require extensive parameter search, such as uncertainty analysis and design optimization. This work investigated the performance of utilizing a multi-fidelity reduced-order model (MF-ROM) in PWR rod bundles simulation. Firstly, basis vectors and basis vector coefficients of high-fidelity and low-fidelity CFD results are extracted separately by the proper orthogonal decomposition (POD) approach. Secondly, a surrogate model is trained to map the relationship between the extracted coefficients from different fidelity results. In the prediction stage, the coefficients of the low-fidelity data under the new operating conditions are extracted by using the obtained POD basis vectors. Then, the trained surrogate model uses the low-fidelity coefficients to regress the high-fidelity coefficients. The predicted high-fidelity data is reconstructed from the product of extracted basis vectors and the regression coefficients. The effectiveness of the MF-ROM is evaluated on a flow and heat transfer problem in PWR fuel rod bundles. Two data-driven algorithms, the Kriging and artificial neural network (ANN), are trained as surrogate models for the MF-ROM to reconstruct the complex flow and heat transfer field downstream of the mixing vanes. The results show good agreements between the data reconstructed with the trained MF-ROM and the high-fidelity CFD simulation result, while the former only requires to taken the computational burden of low-fidelity simulation. The results also show that the performance of the ANN model is slightly better than the Kriging model when using a high number of POD basis vectors for regression. Moreover, the result presented in this paper demonstrates the suitability of the proposed MF-ROM for high-fidelity fixed value initialization to accelerate complex simulation.

• International Journal of Aeronautical and Space Sciences
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• 제18권4호
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• pp.662-674
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• 2017

This paper describes the multidisciplinary design optimization (MDO) process of a tailless unmanned combat aerial vehicle (UCAV) using global variable fidelity aerodynamic analysis. The developed tailless UAV design framework combines multiple disciplines that are based on low-fidelity and empirical analysis methods. An automated high-fidelity aerodynamic analysis is efficiently integrated into the MDO framework. Global variable fidelity modeling algorithm manages the use of the high-fidelity analysis to enhance the overall accuracy of the MDO by providing the initial sampling of the design space with iterative refinement of the approximation model in the neighborhood of the optimum solution. A design formulation was established considering a specific aerodynamic, stability and control design features of a tailless aircraft configuration with a UCAV specific mission profile. Design optimization problems with low-fidelity and variable fidelity analyses were successfully solved. The objective function improvement is 14.5% and 15.9% with low and variable fidelity optimization respectively. Results also indicate that low-fidelity analysis overestimates the value of lift-to-drag ratio by 3-5%, while the variable fidelity results are equal to the high-fidelity analysis results by algorithm definition.

• 대한간호학회지
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• 제43권2호
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• pp.185-193
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• 2013

Purpose: Simulation-based learning has become a powerful method to improve the quality of care and help students meet the challenges of increasingly complex clinical practice settings. The purpose of this study was to identify the learning effects using high-fidelity SimMan and multi-mode simulation. Methods: Participants in this study were 38 students who were enrolled in an intensive course for a major in nursing at R college. Collected data were analyzed using Chi-square, t-test, and independent t-test with the SPSS 18.0 for Windows Program. Results: There were no statistically significant differences in learning effects between high-fidelity SimMan and multi-mode simulation group. However, skills in clinical performance in the high-fidelity SimMan group were higher than in the multi-mode group (p=.014), communication in clinical performance in multi-mode simulation group was higher than in the high-fidelity SimMan group (p<.001). Conclusion: Multi-mode simulation with a standardized patient is an effective learning method in many ways compared to a high-fidelity simulator. These results suggest that multi-mode simulation be offered to students in nursing colleges which cannot afford to purchase a high-fidelity simulator, or offered as an alternative.

• 여성건강간호학회지
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• 제26권3호
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• pp.240-249
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• 2020

Purpose: This study was conducted to investigate the effects of an education program using a high-fidelity simulator of labor and delivery on nursing knowledge, critical thinking, and clinical performance among nursing students who had not yet experienced clinical practicum. Methods: The development of a 5-week maternity nursing education programs using high-fidelity simulators included modules containing case-oriented scenarios, knowledge, and skills required for maternity care. A randomized controlled study was conducted to verify the effects of the developed program. Data were collected from October 21 to December 9, 2019. The experimental group (n=36) participated in a 5-week high-fidelity simulation program on care for the woman in labor, whereas the control group (n=36) received standard education as lecture and practice with delivery model. The collected data were analyzed using descriptive statistics (frequency, percentage, mean, and standard deviation), the Chi-square test, Fisher exact test, and t-test. Results: For participants who received education using the high-fidelity simulation program, nursing knowledge (t=2.33, p=.011), critical thinking (t=3.73, p<.001), and clinical performance (t=2.53, p=.006) were significantly higher than in the control group. Conclusion: Even for students with no clinical experience, high-fidelity simulation-based nursing education was effective in improving nursing knowledge, critical thinking, and clinical performance among nursing students. Nurse educators will be able to use this high-fidelity simulator effectively, especially in situations where direct clinical practicum may not be feasible.

• 한국간호교육학회지
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• 제23권1호
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• pp.95-107
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• 2017

Purpose: The aim of this study was to assess the efficacy of web-based simulation and high-fidelity simulation on acute heart disease patient care. Methods: The project used a comparative study design with two simulation-based training modalities. A total of 144 nursing students participated in this study: 76 students in a web-based simulation, and 68 students in a high-fidelity simulation. Participants rated their self-efficacy, problem-solving ability, interest in learning, level of stress, satisfaction with the simulation experience, and level of difficulty of the simulation. Results: The scores for self-efficacy, problem-solving ability, and interest in learning including interest in clinical training in the high-fidelity simulation group was higher than in the web-based simulation group. However, there were no significant differences in interest in learning, including interest in nursing knowledge, and in lab training, level of stress, satisfaction with the simulation experience, and level of difficulty of the simulation. Conclusion: A high-fidelity simulation of acute heart disease patient care might be beneficial to developing many more abilities for nursing students than would a web-based simulation. Also, since the web-based simulation improved interest in nursing knowledge, it could be a viable alternative to high-fidelity simulation. Further study is needed to verify the effects of varied levels of simulation-based care with more rigorous outcomes.

• 한국간호교육학회지
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• 제27권3호
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• pp.227-239
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• 2021

Purpose: This study used an exploratory sequential approach (mixed methods) design to explore essential meaning through comparing and analyzing the experiences of nursing students in virtual simulation practice and high fidelity simulation practice education in parallel. Methods: The study participants were 20 nursing students, and data were collected through focus group meetings from July 17 to August 5, 2020, and via online quantitative data from November 10 to November 15, 2020. The qualitative data were analyzed using Giorgi's phenomenological method, and the quantitative data were analyzed using descriptive statistics, the Mann-Whitney U test, Kruskal-Wallis H test analysis of variance and Spearman's ρ correlation. Results: The comparison between the two simulation training experiences was shown in five contextual structures, as follows: (1) reflection of the clinical field, (2) thinking theorem vs. thinking expansion, (3) individual-centered learning vs. team-centered learning, (4) attitudes toward participating in practical training, (5) metacognition of personal competency as a prospective nurse, and (6) revisiting the method of practice training. There was a positive correlation between satisfaction with the practice and the clinical judgment ability of high fidelity simulation, which was statistically significant (r=.47, p=.036). Conclusion: Comparing the experiences between virtual simulation practice training and high fidelity simulation practice training, which has increased in demand due to the Coronavirus Disease-2019 pandemic, is meaningful as it provides practical data for introspection and reflection on in-campus clinical education.

• 한국안광학회지
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• 제14권2호
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• pp.47-51
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• 2009

목적: 이 연구의 목적은 시기능 훈련 대상자들의 충실도에 따른 시기능 훈련 효과를 조사하였다. 방법: 시기능 훈련 대상자는 안질환과 조절이상 및 수직사위가 없는 양안시 이상자 75명(남자 40명, 여자 35명)을 대상으로 추적 관찰하였고, 훈련기간은 7주(49일)간 매주 한번은 원에 방문하여 시기능 훈련에 따른 변화를 측정하였다. 결과: 시기능 훈련 대상자의 원 방문율과 충실도가 높을수록 기능적이상, 감각적이상 및 자각적 증상이 개선되었다. 그리고 성공기준에 포함률도 높게 나타났다. 결론: 효과적인 양안시 이상을 개선하기 위하여서는 충실도를 높이는 방법이 중요하다.

• 국제학술발표논문집
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• The 8th International Conference on Construction Engineering and Project Management
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• pp.137-145
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• 2020

Providing safety training to construction workers is essential to reduce safety accidents at the construction site. With the prosperity of visualization technologies, Immersive Virtual Reality (IVR) has been adopted for construction safety training by providing interactive learning experiences in a virtual environment. Previous research efforts on IVR-based training have found that the level of fidelity of interaction between real and virtual worlds is one of the important factors contributing to the sense of presence that would affect training performance. Various interactive devices that link activities between real and virtual worlds have been applied in IVR-based training, ranging from existing computer input devices (e.g., keyboard, mouse, joystick, etc.) to specially designed devices such as high-end VR simulators. However, the need for high-fidelity interactive devices may hinder the applicability of IVR-based training as they would be more expensive than IVR headsets. In this regard, this study aims to understand the impact of the level of fidelity of interactive devices in the sense of presence in a virtual environment and the training performance during IVR-based forklift safety training. We conducted a comparative study by recruiting sixty participants, splitting them into two groups, and then providing different interactive devices such as a keyboard for a low fidelity group and a steering wheel and pedals for a high-fidelity group. The results showed that there was no significant difference between the two groups in terms of the sense of presence and task performance. These results indicate that the use of low-fidelity interactive devices would be acceptable for IVR-based safety training as safety training focuses on delivering safety knowledge, and thus would be different from skill transferring training that may need more realistic interaction between real and virtual worlds.

• 한국항공우주학회지
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• 제42권2호
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• pp.108-118
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• 2014

근사모델을 이용한 최적설계 문제에서는 설계변수의 수가 증가함에 따라 근사모델의 정확도를 확보하기 위한 계산 횟수가 급격히 증가한다. 이를 해결하기 위해 저정확도 모델을 바탕으로 고정확도 모델로 보정하는 Variable-Fidelity Modeling을 이용하였다. 본 논문에서 Variable-Fidelity Model로는 계층적 크리깅 모델을 이용하였으며, 다목적 유전자 알고리즘과 결합하여 최적화 프레임워크를 제안하였다. 이 방법의 유용성을 검증하기 위하여 천음속 영역에 대한 익형 최적 설계를 하였다. 설계변수로는 PARSEC의 파라메터를 이용하였으며, 서로 다른 격자수를 가지는 경우 그리고 서로 다른 정확도를 가지는 해석자를 이용한 경우에 관하여 해석을 수행하였다. 검증을 위해 단일 정확도 모델에 대한 최적화 결과와 비교하였다. 모든 경우에 관하여 파레토 라인이 유사하게 나오는 것을 확인 할 수 있었으며, 계산시간은 계층적 크리깅 모델을 이용한 Variable-Fidelity Model이 단일 정확도 모델에 비하여 훨씬 줄어들었다. 이를 바탕으로 본 논문의 방법이 단일 정확도를 가지는 모델에 대한 최적화 방법과 유사한 정확도를 가지며 더욱 효율적임을 확인 할 수 있다.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2006년도 추계 학술대회논문집
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• pp.208-208
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• 2006