• 한국시뮬레이션학회논문지
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• 제32권3호
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• pp.67-74
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• 2023

반도체 제조라인(FAB)은 복잡하고 불확실한 운영환경에서 작동하는 대규모의 제조시스템 중 하나로 반도체 설비 운영을 담당하는 엔지니어들은 직관적이고 신속한 공정 스케줄링을 위해 가중치 기반 스케줄링을 널리 사용하고 있다. 가중치 기반 스케줄링에서 가중치 결정은 FAB 성능에 큰 영향을 미치므로 엔지니어들은 가중치 최적화를 위하여 시뮬레이션 기반 의사결정을 활용할 수 있다. 그러나 대규모 시뮬레이션은 많은 실험 비용을 요구하기 때문에 효과적인 의사결정을 위해서 신중한 실험설계가 요구된다. 본 연구에서는 적은 시뮬레이션 실행 내에서 효율적인 스케줄링을 도출하기 위해 세 가지 샘플링 대안(i.e., Optimal latin hypercube sampling(OLHS), Genetic algorithm(GA), and Decision tree based sequential search (DSS))에 대한 비교연구를 수행하였다. 시뮬레이션 실험을 통해 세 가지 대안이 단일 규칙보다 우수한 성능을 보였고, 그중 GA와 DSS가 최적화를 위한 효과적인 대안이 될 수 있음을 확인하였다.

• International Journal of Aeronautical and Space Sciences
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• 제17권3호
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• pp.423-431
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• 2016

In this study, wing design optimization for long-endurance unmanned aerial vehicles (UAVs) is investigated. The fluid-structure integration (FSI) analysis is carried out to simulate the aeroelastic characteristics of a high-aspect ratio wing for a long-endurance UAV. High-fidelity computational codes, FLUENT and DIAMOND/IPSAP, are employed for the loose coupling FSI optimization. In addition, this optimization procedure is improved by adopting the design of experiment (DOE) and Kriging model. A design optimization tool, PIAnO, integrates with an in-house codes, CAE simulation and an optimization process for generating the wing geometry/computational mesh, transferring information, and finding the optimum solution. The goal of this optimization is to find the best high-aspect ratio wing shape that generates minimum drag at a cruise condition of $C_L=1.0$. The result shows that the optimal wing shape produced 5.95 % less drag compared to the initial wing shape.

• 한국항공우주학회지
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• 제36권9호
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• pp.859-866
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• 2008

본 논문에서는 다수 비행체의 편대 비행 시 상호 기하학적 관계 유지에 필요한 유도 법칙과 비선형 시뮬레이션 결과를 제시하였다. 편대 내의 각 비행체는 편대 Leader를 제외하고 모두 Leader와 Follower의 역할을 동시에 맡으며, Leader에 의한 명령은 모든 Follower에게 분배되고 따라서 편대를 이루는 모든 비행체들의 동시기동비행(Synchronized Flight)을 가능하게 한다. 편대 비행 유도 법칙은 가까운 미래 시각에 예상되는 기하학적 오차 그리고 Lyapunov 안정성 이론에 근거하여 도출하였고, 정찰과 감시 임무 예제에 관한 고정밀 비선형 시뮬레이션 결과를 통하여 제안된 유도 법칙의 성능을 검증하였다

• 대한기계학회논문집A
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• 제31권1호
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• pp.55-61
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• 2007

Recently simulation model becomes an essential tool for analysis and design of a system but it is often expensive and time consuming as it becomes complicate to achieve reliable results. Therefore, high-fidelity simulation model needs to be replaced by an approximate model, the so-called metamodel. Metamodeling techniques include 3 components of sampling, metamodel and validation. Cross-validation approach has been proposed to provide sequnatially new sample point based on cross-validation error but it is very expensive because cross-validation must be evaluated at each stage. To enhance the cross-validation of metamodel, sequential sampling method using candidate points and representative cross-validation is proposed in this paper. The candidate and representative cross-validation approach of sequential sampling is illustrated for two-dimensional domain. To verify the performance of the suggested sampling technique, we compare the accuracy of the metamodels for various mathematical functions with that obtained by conventional sequential sampling strategies such as maximum distance, mean squared error, and maximum entropy sequential samplings. Through this research we team that the proposed approach is computationally inexpensive and provides good prediction performance.

• 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.

• 한국CDE학회논문집
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• 제17권5호
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• pp.303-311
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• 2012

Laparoscopic surgery is a surgical procedure which uses long laparoscopic instruments through tiny holes in abdomen while watching images from a laparoscopic camera through umbilicus. Laparoscopic surgeries have many advantages rather than open surgeries, however it is hard to learn the surgical skills for laparoscopic surgery. Recently, some virtual simulation systems for laparoscopic surgery are developed to train novice surgeons or resident surgeons. In this study, we introduce the techniques that we developed for laparoscopic surgical training simulator for cholecystectomy (gallbladder removal), which is one of the most frequently performed by laparoscopic surgery. The techniques for cholecystectomy simulation include modeling of human organs (liver, gallbladder, bile ducts, etc.), real-time deformable body calculation, realistic 3D visualization of surgical scene, high-fidelity haptic rendering and haptic device technology, and so on. We propose each simulation technique for the laparoscopic cholecystectomy procedures such as identifying cystic duct and cystic artery to clamp and cut, dissecting connective tissues between the gallbladder and liver. In this paper, we describe the techniques and discuss about the results of the proposed cholecystectomy simulation for laparoscopic surgical training.

• 한국산학기술학회논문지
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• 제15권3호
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• pp.1515-1521
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• 2014

본 연구는 간호학생의 급성 심근경색증 간호에 대한 시뮬레이션 기반 교육을 적용하고 비판적 사고, 문제해결력 및 학업성취도의 효과를 규명한 단일군 전후 원시실험설계이다. 대상자는 총 137명이었으며 중재기간은 2011년 9월부터 10월까지 총 6주간 시뮬레이션 기반 교육을 시행하고 중재 전후를 평가하였다. 자료분석은 SPSS Win17.0을 사용하였고, 평균과 표준편차, Paired t-test, 피어슨 상관계수를 이용하였다. 연구 결과 시뮬레이션 기반 교육프로그램은 비판적 사고, 문제해결력 및 학업성취도를 향상시키는 것으로 나타났다. 비판적사고가 증대될수록 문제해결력은 향상되는 것으로 나타났다. 반면 비판적사고 능력과 문제해결력은 학업성취도와 유의한 차이가 없었다. 시뮬레이션 기반 교육프로그램은 간호학생의 실무능력을 향상시키기 위해 유용한 학습방법임을 알 수 있었고, 임상현장에서 흔히 접할 수 있는 다양한 사례의 시나리오를 개발하여 실습교육에 적극 활용할 필요가 있다. 이를 위해서는 더 다양하고 적절한 실습교육방법에 대한 개발과 운영이 필요할 것으로 보인다.

• 대한간호학회지
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• 제47권6호
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• pp.842-853
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• 2017

Purpose: This study was conducted to identify effects of debriefing based on the clinical judgment model for nursing students on their knowledge, skill performance, clinical judgment, self-confidence and learner satisfaction during simulation based end-of-life care (ELC) education. Methods: Simulation based ELC education was developed in six steps as follows: selection of learning subjects and objects, development of learning tools, a trial run of simulation-based education, students' skill training, and evaluators' training. Forty-eight senior nursing students (25 in the experimental group and 23 in the control group) participated in the simulation-based ELC education using a high-fidelity simulator. Debriefing based on the clinical judgment was compared with the usual debriefing. Results: ANCOVA showed that there were differences in knowledge (F=4.81, p=.034), skill performance (F=68.33, p<.001), clinical judgment (F=18.33, p<.001) and self-confidence (F=4.85, p=.033), but no difference in satisfaction (t=-0.38, p=.704) between the experimental and control groups. Conclusion: This study found that debriefing based on the clinical judgement model is effective for supporting nursing students for reflecting on clinical judgment and improving their diverse competencies in complex clinical settings such as ELC.

• 문화기술의 융합
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• 제10권1호
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• pp.353-361
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• 2024

시뮬레이션 교육은 현장감있는 모의 상황에서 학습자가 반복적으로 학습하도록 하는 방법으로 직접간호 수행이 부족한 임상실습의 한계를 해결하여 간호대학생에게 필요한 의사소통능력, 학습자기효능감, 임상추론역량을 습득하고 개발하는 데 유용하다. 본 연구는 고충실도 시뮬레이터를 활용한 시뮬레이션 교육이 간호대학생의 의사소통능력, 학습자기효능감, 임상추론역량에 미치는 효과와 시뮬레이션 교육 효과성을 확인하기 위해 실시되었다. 연하곤란 대상자 간호 시나리오를 활용한 시뮬레이션 교육에 참여한 일개대학 간호학과 4학년 학생 84명의 자료를 SPSS/WIN 22.0 프로그램을 이용하여 분석하였다. 연구 결과 시뮬레이션 교육 후 의사소통능력, 학습자기효능감, 임상추론역량은 유의하게 증가하였으며, 시뮬레이션 교육 효과성은 2.64점(3점 만점)이었다. 따라서 간호대학생의 의사소통능력, 학습자기효능감, 임상추론역량 증진을 위해서 다양한 임상현장을 반영하여 실재감있는 시나리오의 개발 및 적용이 필요하다.

• 자동차안전학회지
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• 제15권2호
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• pp.42-48
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• 2023

In recent years, automated vehicles have garnered attention in the multidisciplinary research field, promising increased safety on the road and new opportunities for passengers. High-Definition (HD) maps have been in development for many years as they offer roadmaps with inch-perfect accuracy and high environmental fidelity, containing precise information about pedestrian crossings, traffic lights/signs, barriers, and more. Demonstrating autonomous driving requires verification of driving on actual roads, but this can be challenging, time-consuming, and costly. To overcome these obstacles, creating HD maps of real roads in a simulation and conducting virtual driving has become an alternative solution. However, existing HD maps using high-precision data are expensive and time-consuming to build, which limits their verification in various environments and on different roads. Thus, it is challenging to demonstrate autonomous driving on anything other than extremely limited roads and environments. In this paper, we propose a new and simple method for implementing HD maps that are more accessible for autonomous driving demonstrations. Our HD map combines the CARLA simulator and OpenStreetMap (OSM) data, which are both open-source, allowing for the creation of HD maps containing high-accuracy road information globally with minimal dependence. Our results show that our easily accessible HD map has an accuracy of 98.28% for longitudinal length on straight roads and 98.42% on curved roads. Moreover, the accuracy for the lateral direction for the road width represented 100% compared to the manual method reflected with the exact road data. The proposed method can contribute to the advancement of autonomous driving and enable its demonstration in diverse environments and on various roads.