• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.05a
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• pp.191-195
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• 2003

충격음 저감재의 동탄성계수와 감쇠계수는 차단성능을 평가하는데 있어 중요한 물성치가 된다. 저감재의 동탄성계수는 뜬바닥구조의 고유진동수를 결정짓게 되며, 저감재의 동탄성계수가 높을수록, 즉 고유진동수가 높아짐에 따라 실험실 경량충격음레벨 저감량은 지수함수적으로 감소됨을 실험을 통해 알 수 있다. 또한, 저감재를 포함한 뜬바닥구조를 1자유도 진동계로 가정한 이론값과 실험실 경량충격음레벨 저감량의 결과가 비교적 잘 일치하는 것으로 나타났으며, 이 때 감쇠계수의 영향은 반드시 고려되어야 한다.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.20 no.2
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• pp.113-125
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• 2007

Improved numerical method to obtain the exact stiffness matrices is newly proposed to perform the spatially coupled elastic and stability analyses of non-symmetric and open/closed thin-walled beam on elastic foundation. This method overcomes drawbacks of the previous method to evaluate the exact stiffness matrix for the spatially coupled stability analysis of thin-walled beam-column This numerical technique is accomplished via a generalized eigenproblem associated with 14 displacement parameters by transforming equilibrium equations to a set of first order simultaneous ordinary differential equations. Next polynomial expressions as trial solutions are assumed for displacement parameters corresponding to zero eigenvalues and the eigenmodes containing undetermined parameters equal to the number of zero eigenvalues are determined by invoking the identity condition. And then the exact displacement functions are constructed by combining eigensolutions and polynomial solutions corresponding to non-zero and zero eigenvalues, respectively. Consequently an exact stiffness matrix is evaluated by applying the member force-deformation relationships to these displacement functions. In order to illustrate the accuracy and the practical usefulness of this study, the numerical solutions are compared with results obtained from the thin-walled beam and shell elements.

• Journal of Aerospace System Engineering
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• v.16 no.4
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• pp.88-94
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• 2022

The vibration mode measurement test measures the natural vibration characteristics of the target specimen. The measured natural mode characteristics are compared with the numerical analysis result to verify the reliability of the numerical analysis. If necessary, it is used to supplement the numerical analysis model of the specimen used for the dynamic characteristic analysis. In this paper, the natural frequency and natural mode of the external fuel tank are respectively obtained through the vibration mode measurement test and the numerical analysis, using the finite element model. The results are compared to verify the reliability of the numerical analysis model of the external fuel tank to apply to the entire aircraft model. To measure the vibration mode of the test specimen, a bungee cord was used, to simulate the free boundary condition for the test specimen. And, 3-axis accelerometers were installed on the test specimen. The response characteristics of the test specimen were measured, by excitation with an impact hammer. As a result of the test, after performing the frequency response analysis on the response acceleration, the natural frequency of the test specimen and its vibration mode were confirmed. The reliability of the numerical analysis model was verified by comparing the frequency and vibration mode, obtained through the test and the numerical analysis.

• Journal of Korea Entertainment Industry Association
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• v.13 no.8
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• pp.243-253
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• 2019

Geyonggi-geommu have developed based on the long history of Korean sword dance. Han Sung-joon, the great master of modern music and dance of Korea during the Japanese colonial period, collected and reconstructed folk dances that had disappeared or were cut off due to the policy to obliterate Korean culture through Chosun Music Dance Research Society. Since then, it has been passed down to Kang Sun-young and Kim Geun-hee that has designated as the Intangible Cultural Property No. 53. of Geyonggi-do in 2011. This study focuses on highlighting the uniqueness of Geyonggi-geommu for proper modeling and transmission of Geyonggi-geommu with historical significance so as to understand and preserve the Intangible Cultural Heritage. This study examines the transmission system of Geyonggi-geommu, followed by Kang Sun-young and Kim Geun-hee, originated by the master Han Sung-Joon of Geyonggi-geommu. Geyonggi-geommu has its uniqueness of using the pure Korean dance terminology established by the holder Kim Geun-hee at the time of designation of intangible cultural properties in Gyeonggi-do. The unique features of Geyonggi-geommu are performed and transmitted in two forms, Daemu(Group dance) and Holchum(Solo dance) which are not currently found in other regions. This is meaningful to passed down according to the original form of Geommu(Sword dance). In particular, the Holchum(Solo dance) is a form of artistic dance, showing the beauty of the sword dance during the Chosun Dynasty. In short, Gyeonggi-geommu can be described as an artistic dance with a soft and strong temperament considering its unique features.

• Journal of the Korea institute for structural maintenance and inspection
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• v.27 no.5
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• pp.120-129
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• 2023

Hanger cable tension is a major response that can determine the integrity and safety of suspension bridges. In general, the vibration method is used to estimate hanger cable tension on operational suspension bridges. It measures natural frequencies from hanger cables and indirectly estimates tension using the geometry conditions of the hanger cables. This study estimated the hanger cable tension of the Palyeong Bridge using a vision-based system. The vision-based system used digital camcorders and tripods considering the convenience and economic efficiency of measurement. Measuring the natural frequencies for high-order modes required for the vibration method is difficult because the hanger cable response measured using the vision-based system is displacement-based. Therefore, this study proposed a back analysis technique for estimating tension using the natural frequencies of low-order modes. Optimization for the back analysis technique was performed by defining the difference between the natural frequencies of hanger cables measured in the field and those calculated using finite element analysis as the objective function. The direct search method that does not require the partial derivatives of the objective function was applied as the optimization method. The reliability and accuracy of the back analysis technique were verified by comparing the tension calculated using the method with that estimated using the vibration method. Tension was accurately estimated using the natural frequencies of low-order modes by applying the back analysis technique.

• Journal of the Society of Disaster Information
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• v.20 no.2
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• pp.369-378
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• 2024

Purpose: This study aims to verify structural stability by manufacturing a 40m full-scale specimen composed of a segmental U-shaped PSC girder with integrated tensioning systems and a concrete slab, proceeding dynamic behavior tests, and compare the results of the tests with the results of numerical analysis. Method: Dynamic behavior tests were conducted on a full-scale, undamaged specimen using an impact hammer, and the natural frequency and damping ratio were measured and compared with numerical analysis techniques and the general damping ratio of the facilities. Result: The natural frequency of the numerical analysis model consisting of a girder and slab composite section was calculated to be 2.561Hz, the natural frequency of the full-scale specimen was measured to be 2.670Hz, and the damping ratio was calculated to be 0.42~0.68%. Conclusion: The natural frequency of the full-scale specimen was found to be 4.3% larger than that of the numerical analysis model. Since the masses of the full-scale specimen and the numerical analysis model are the same as 99.97%, it can be derived that the stiffness of the full-scale specimen has secured structural safety and stability. As a result, the dynamic behavior stability of the specimen was verified. The measured damping ratio of 0.42~0.68% was found to be a stable dynamic behavior compared to the PSC structures damping ratio of 0.5~1.0% in the elastic region.

• Journal of Digital Convergence
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• v.12 no.12
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• pp.529-535
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• 2014

This study is to establish the consistency of Subject-Verb agreement in quantifier phrase. Absence of consistency in English grammar is critical to the grammaticality. We focused on the grammar part, specifically, S-V agreement rule in quantifier phrase. We believe the existence of exceptional rules in quantifier S-V structure is not necessary as the basic grammar rule on S-V agreement is sufficient enough and adding exceptional rules just make it more difficult and confusing. We argue specific features indwelt in each quantifier are linked when quantifiers are used pronominally and the ${\pm}$feature plays an important role in quantifier S-V agreement structure. This study shows the solution to eliminate the ungrammaticality in typical English text books by simplifying quantifier S-V agreement to make it solid and systematic.

• Journal of Korean Association for Spatial Structures
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• v.7 no.5
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• pp.57-65
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• 2007

After measuring wind induced response for a high-rise steel building, the damping ratio and natural frequency were analyzed in this paper. In order to examine amplitude dependence, random decrement method was used. Two methods were analyzed by comparing dynamic properties from random decrement method and half powered-band width method. In addition, through serviceability evaluation during strong wind, compatibility of two methods to Japanese guidelines for the evaluation of habitability to building vibration and national building code of Canada was considered. The amplitude dependence of the damping ratio by RD method was shown and the amplitude dependence of the natural frequency was relatively very small in an aspect of engineering sense. Moreover, the measured building was satisfied with serviceability and Japanese guideline is stricter than NBCC code.

• Proceedings of the Korea Society for Energy Engineering kosee Conference
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• 2001.11a
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• pp.325-331
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• 2001

• Proceedings of the Korean Radioactive Waste Society Conference
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• 2012.05a
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• pp.365-366
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• 2012