• The KSFM Journal of Fluid Machinery
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• v.16 no.3
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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.

• Proceedings of the IEEK Conference
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• 2003.07b
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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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• v.12 no.3
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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.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.27 no.6
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• pp.653-662
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• 2014

The data repositories for structural experiment information needs to be efficient to use in order to allow structural engineers and researchers to store and retrieve easily the information involved in the structural experiments. The data repositories can be evaluated in terms of the organization of the data repositories themselves and of the organization of the actual experiment information in the data repositories, which can be represented using classes and objects with their attributes. This paper proposes the evaluation criteria of attributes of the classes and objects. The evaluation criteria of the attributes of the classes, such as the number of attributes in class and the numbers of the data-valued and object entity-valued attributes, are used for understanding the complexity of the organization of the data repositories. The evaluation criteria of the attributes of the objects, such as the number of valued attributes in object, are used for describing how the actual experiment information is stored through the levels in the data repositories for the structural experiment information.

• Journal of Korean Elementary Science Education
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• v.40 no.3
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• pp.326-342
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• 2021

In this study, experimental guide materials for teachers were developed so that algorithm expression, the core of computational thinking, can be applied to experimental activities. The experimental manuals presented in text was converted into an algorithmic form with a linear, branched, and repetitive structure according to the information visualization process using flowchart symbols. As an example, an experiment guide materials was developed by applying an algorithm expression to an experiment to find out the properties of a magnet. The developed experiment guide materials is different from the existing experiment guide materials expressed only sequentially in that it has an algorithmic structure of branching and repetition in which the suitability and judgment of information are expressed, and that the experiment process is visualized and expressed. It is expected that the experimental guide materials developed in this study will help teachers to understand algorithmic thinking and to implement experiments using it.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.11 no.5
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• pp.991-996
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• 2007

Recently, a computational reconstruction method using an integral imaging technique, which is a promise three-dimensional display technique, has been actively researched. This method is that 3-D images can be digitally reconstructed at the required output planes by superposition of all of the inversely enlarged elemental images by using a hypothetical pinhole array model. However, the conventional method mostly yields reconstructed images having a low-resolution, because there are some intensity irregularities with a grid structure at the reconstructed mage plane by using square-type elemental images. In this paper, to overcome this problem, we propose a novel computational integral imaging reconstruction (CIIR) method using round-type mapping model. Proposed CIIR method can overcome problems of non-uniformly reconstructed images caused from the conventional method and improve the resolution of 3-D images. To show the usefulness of the proposed method, both computational experiment and optical experiment are carried out and their results are presented.

• Computers and Concrete
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• v.8 no.2
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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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• v.62 no.5
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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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• v.17 no.2
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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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• v.53 no.4
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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.