• 한국유체기계학회 논문집
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• 제16권3호
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• pp.5-9
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• 2013

In this study, operational vibration experiment and analysis have been conducted for the 4-blade small vertical-axis wind turbine (VAWT) including the effect of tower elastic behavior. Computational structural dynamics analysis method is applied to obtain Campbell diagram for the VAWT with elastic tower. An open type wind-tunnel is used to change and keep the wind velocity during the ground test. Equivalent elastic tower is used to support the VAWT so that the effect of elastic stiffness of the tower can be considered in the present vibration experiment. Various excitation conditions with wind loads are considered and the dominant operating vibration phenomena are physically investigated in detail.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2003년도 하계종합학술대회 논문집 II
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• pp.731-734
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• 2003

An atomistic process modeling, Kinetic Monte Carlo simulation, has the advantage of being both conceptually simple and extremely powerful. Instead of diffusion equations, it is based on the definitions of the interactions between individual atoms and defects. Those interactions can be derived either directly from molecular dynamics, first principles calculations, or from experiment. In this paper, as a simple illustration of the kinetic Monte Carlo we simulate defects (self-interstitials and vacancies) diffusion after ion implantation in Si crystalline.

• Journal of the Optical Society of Korea
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• 제12권3호
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• pp.131-135
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• 2008

Computational integral imaging(CII) has the advantage of generating the volumetric information of the 3D scene without optical devices. However, the reconstruction process of CII requires increasingly larger sizes of reconstructed images and then the computational cost increases as the distance between the lenslet array and the reconstructed output plane increases. In this paper, to overcome this problem, we propose a novel CII method using a depth conversion technique. The proposed method can move a far 3D object near the lenslet array and reduce the computational cost dramatically. To show the usefulness of the proposed method, we carry out the preliminary experiment and its results are presented.

• 한국전산구조공학회논문집
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• 제27권6호
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• pp.653-662
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• 2014

구조실험을 위한 데이터 저장소는 구조실험에 관련된 실험정보를 구조공학자와 연구자들이 편리하게 저장하고 열람할 수 있도록 효율적인 구성을 가져야 한다. 데이터 저장소에 대한 평가는 데이터 저장소 자체적인 구성에 대한 평가와 데이터 저장소에 저장된 실제 정보의 구성에 대한 평가로 나눌 수 있다. 데이터 저장소의 자체적인 구성은 클래스로 나타낼 수 있고 데이터 저장소 내에 저장된 실제의 실험정보는 객체로 표현할 수 있는데 본 논문은 클래스와 객체가 가지고 있는 속성구성에 대한 평가요소를 제안한다. 클래스의 속성구성 평가요소로는 클래스내 속성수와 구체적인 값 또는 객체에 의해 구분한 속성의 종류별 수 등이 있는데 이러한 평가요소들을 이용하여 데이터 저장소가 정한 구성을 이해할 수 있다. 객체의 속성구성 평가요소로는 객체내 값있는 속성수 등이 있는데 데이터 저장소내의 실제 실험정보가 레벨별로 어떻게 저장되어 있는가를 파악할 수 있다.

• 한국초등과학교육학회지:초등과학교육
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• 제40권3호
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• pp.326-342
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• 2021

본 연구에서는 컴퓨팅 사고의 핵심인 알고리즘 표현을 실험 활동에 적용할 수 있도록 교사를 위한 실험 안내 자료를 개발하였다. 텍스트로 제시된 실험 매뉴얼을 순서도 기호를 사용하여 정보 시각화 프로세스에 따라 직선형, 분기형, 반복형 구조의 알고리즘 형태로 변환하였다. 그 예시로, 자석의 성질을 알아보는 실험을 알고리즘 표현을 적용하여 실험 안내 자료를 개발하였다. 개발된 실험 안내 자료는 정보의 적합성과 판단 여부가 표현된 분기 및 반복의 알고리즘 구조를 가지고 있다는 점과 실험 과정을 시각화하여 표현했다는 측면에서 기존의 순차적으로 표현된 실험 안내 자료와 차이가 있다. 본 연구에서 개발된 실험 안내 자료는 교사들의 알고리즘 사고에 대한 이해와 이를 적용한 실험 실행에 도움을 줄 수 있을 것이라 기대된다.

• 한국정보통신학회논문지
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• 제11권5호
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• pp.991-996
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• 2007

최근 3차원 디스플레이 기술로서 유망한 집적 영상 기술을 이용하여 3차원 물체에 대한 컴퓨터 재생 방식이 활발히 연구되고 있다. 이 방식은 집적 영상 기술로 픽업되는 요소 영상을 가상의 핀홀 배열 모델을 이용하여 컴퓨터적으로 특정한 거리의 재생 평면에 확대 중첩함으로서 3차원 영상을 효과적으로 재생하는 방식이다. 그러나 많은 수의 요소 영상은 일반적으로 사각형의 구조를 가지기 때문에 확대 중첩될 경우에 재생 영상에서 격자 구조의 밝기 불균일 문제로 인한 해상도를 떨어뜨리는 문제가 존재하였다. 본 논문에서는 이러한 문제점을 극복하기 위해서 원형 매핑 모델에 기초한 컴퓨터 집적 영상 재생 방식을 제안한다. 제안하는 방식은 기존의 방식에서 발생하는 3차원 재생 영상에서의 불균일 문제를 극복할 수 있으며 3차원 영상의 해상도를 개선할 수 있다. 제안된 방식의 유용함을 보이기 위해서 컴퓨터적 모의 실험과 광학적 실험을 수행하고 그 결과를 보고한다.

• Computers and Concrete
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• 제8권2호
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• pp.177-192
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• 2011

This research paper aims at computer based modeling of carbonation induced corrosion under extreme conditions and its experimental verification by incorporating enhanced electrochemical and mass balance equations based on thermo-hygro physics with strong coupling of mass transport and equilibrium in micro-pore structure of carbonated concrete for which the previous research data is limited. In this paper the carbonation induced electrochemical corrosion model is developed and coupled with carbon dioxide transport computational model by the use of a concrete durability computer based model DuCOM developed by our research group at concrete laboratory in the University of Tokyo and its reliability is checked in the light of experiment results of carbonation induced corrosion mass loss obtained in this research. The comparison of model analysis and experiment results shows a fair agreement. The carbonation induced corrosion model computation reasonably predicts the quantitative behavior of corrosion rate for normal air dry relative humidity conditions. The computational model developed also shows fair qualitative corrosion rate simulation and analysis for various pH levels and coupled environmental actions of chloride and carbonation. Detailed verification of the model for the quantitative carbonation induced corrosion rate computation under varying relative conditions, different pH levels and combined effects of carbonation and chloride attack remain as scope for future research.

• Structural Engineering and Mechanics
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• 제62권5호
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• pp.631-642
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• 2017

Accurate actuator tracking plays an important role in real-time hybrid simulation (RTHS) to ensure accurate and reliable experimental results. Frequency-domain evaluation index (FEI) interprets actuator tracking into amplitude and phase errors thus providing a promising tool for quantitative assessment of real-time hybrid simulation results. Previous applications of FEI successfully evaluated actuator tracking over the entire duration of the tests. In this study, FEI with moving window technique is explored to provide post-experiment localized actuator tracking assessment. Both moving window with and without overlap are investigated through computational simulations. The challenge is discussed for Fourier Transform to satisfy both time domain and frequency resolution for selected length of moving window. The required data window length for accuracy is shown to depend on the natural frequency and structural nonlinearity as well as the ground motion input for both moving windows with and without overlap. Moving window without overlap shows better computational efficiency and has potential for future online evaluation. Moving window with overlap however requires much more computational efforts and is more suitable for post-experiment evaluation. Existing RTHS data from Network Earthquake Engineering Simulation (NEES) is utilized to further demonstrate the effectiveness of the proposed approaches. It is demonstrated that with proper window size, FEI with moving window techniques enable accurate localized evaluation of actuator tracking for real-time hybrid simulation.

• International Journal of Air-Conditioning and Refrigeration
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• 제17권2호
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• pp.68-73
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• 2009

In this paper, a numerical study has been carried out to investigate the influence of volute geometries on the performance of a sirocco fan. In order to achieve an optimum volute design and explain the interactions between the different geometric configurations in the volute system, three-dimensional computational fluid dynamics and the 'design of experiment' method have been applied. Several geometric parameters, such as the volute expansion angle, the cut-off position and the bell mouth shape, are employed to improve efficiency and performance. $2^k$ factorial designs were performed to screen the most influential parameters and interactions, and showed that the cut-off position and the bell mouth shape are the most significant parameters. The optimum design was selected as a result of the response surface methodology, and effects of these parameters and their interactions were presented. From the results of computational analyses and experimental data, the performance and efficiency of the sirocco fan were successfully improved. Also, detailed effects of geometric variables of the volute system on the fan performance were discussed.

• Nuclear Engineering and Technology
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• 제53권4호
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• pp.1088-1099
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• 2021

Time-frequency analysis technique is an effective analysis tool for non-stationary processes. In the field of reactor neutron noise, the time-frequency analysis method has not been thoroughly researched and widely used. This work has studied the time-frequency analysis of the reactor neutron noise experimental signals under bubble disturbance and control rod vibration. First, an experimental platform was established, and it could be employed to reactor neutron noise experiment and data acquisition. Secondly, two types of reactor neutron noise experiments were performed, and valid experimental data was obtained. Finally, time-frequency analysis was conducted on the experimental data, and effective analysis results were obtained in the low-frequency part. Through this work, it can be concluded that the time-frequency analysis technique can effectively investigate the core dynamics behavior and deepen the identification of the unstable core process.