• 비파괴검사학회지
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• 제7권2호
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• pp.42-47
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• 1988

이상의 결과를 요약하면 다음과 같다. 1) 초음파 C-scan 법에 의하여 층간분리, 기지균열 등의 손상 정도, 크기 및 형태의 판별이 가능하며 충격손상은 주로 섬유의 주축방향으로 성장한다. 2) 복합재료의 인장파괴시 적층구조에 따라 상이한 AE 양상을 나타내며 이 원인은 파괴 mode의 차이에 기인한다. 3) 섬유의 파단은 기지파단의 경우 보다 강력한 AE activity를 나타내며 peak amplitude의 분포를 분석하여 파괴 mode의 해석이 가능하다. 4) 복합재료의 파괴강도는 적층구조, 충격 손상 등에 영향을 받으며 응력파 계수(SWF)의 측정에 의해 정성적 평가가 가능하다.

• 한국콘텐츠학회논문지
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• 제12권1호
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• pp.516-524
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• 2012

최근 K-pop은 아시아 국가를 비롯해 전세계적인 인기를 구사하고 있다. 드라마를 중심으로 확산되던 한류는 2005 이후 아이돌그룹 가수들을 위시로 한 K-pop 중심으로 재편되고 있다. 한류 팬들의 한류 소비행태는 단순한 콘텐츠 소비를 넘어서서 한류스타의 모방뿐 아니라 한글을 배우는 등 보다 발전된 행동으로 확대되고 있다. 이에, 본 연구는 K-pop의 주요 소비국인 중국, 일본, 태국, 베트남의 아시아 4개국을 대상으로 하여 K-pop 이용행동을 파악하고, K-pop을 좋아하는 이유를 파악하였다. 또한, K-pop이 한국에 대한 호감도와 한국방문의도에 어떤 영향을 미치는지 알아보았다. 분석결과, 국가별 K-pop 이용행동의 차이를 발견할 수 있었으며, K-pop 선호요인과 국가호감도과 한국방문의도 간 영향관계를 파악하였다. 연구결과는 향후 K-pop의 해외진출에 유용한 기초자료로 사용될 수 있을 것이다.

• 전기전자학회논문지
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• 제24권1호
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• pp.46-51
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• 2020

모바일 기기에서 Wi-Fi와 Bluetooth 연결이 일상화 되면서, Wi-Fi, Bluetooth 등의 두 개 이상의 이기종 무선 라디오를 하나의 칩에 통합한 Wi-Fi 및 Bluetooth 콤보 모듈이 보편화 되었다. 콤보칩 기법의 핵심 요건은 통합칩 사용으로도 사용자 경험(QoE)의 품질을 저하되는 등의 성능저하가 있어서는 안되며, 따라서 다양한 환경에서 이 요건을 보장하기 위해서는 콤보모듈의 행동을 특성화하고 이해하는 것이 매우 중요하다. 본 연구에서는 Wi-Fi / Bluetooth 콤보 통신 모듈을 장착한 모바일 기기에서 모바일 스트리밍을 이용할 경우, Bluetooth 사용이 사용자 체감 품질(Qualty-of-Experience)에 미치는 영향을 조사한다. 실측을 통한 실험 결과, Wi-Fi와 블루투스를 동시에 사용하는 환경에서는 Wi-Fi만을 이용하는 환경에 비해 최대 55%의 성능 저하를 보인 것으로 나타났다. 본 연구 이기종 통신 모듈의 사용에 따른 물리 및 링크 계층의 전송 스케쥴링이 최상위 사용자 계층의 성능에 미치는 영향을 밝혀냈다는 중요성을 갖는다.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2009년도 세계 도시지반공학 심포지엄
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• pp.157-171
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• 2009

A 151 storey super high-rise building located in an area of reclaimed land constructed over soft marine clay in Songdo, Korea is currently under design. This paper describes the design process of the foundation system of the supertall tower, which is required to support the large building vertical and lateral loads and to restrain the horizontal displacement due to wind and seismic forces. The behaviour of the foundation system due to these loads and foundation stiffness influence the design of the building super structure, displacement of the tower, as well as the raft foundation design. Therefore, the design takes in account the interactions between soil, foundation and super structure, so as to achieve a safe and efficient building performance. The site lies entirely within an area of reclamation underlain by up to 20m of soft to firm marine silty clay, which overlies residual soil and a profile of weathered rock. The nature of the foundation rock materials are highly complex and are interpreted as possible roof pendant metamorphic rocks, which within about 50m from the surface have been affected by weathering which has reduced their strength. The presence of closely spaced joints, sheared and crushed zones within the rock has resulted in deeper areas of weathering of over 80m present within the building footprint. The foundation design process described includes the initial stages of geotechnical site characterization using the results of investigation boreholes and geotechnical parameter selection, and a series of detailed two- and three-dimensional numerical analysis for the Tower foundation comprising over 172 bored piles of varying length. The effect of the overall foundation stiffness and rotation under wind and seismic load is also discussed since the foundation rotation has a direct impact on the overall displacement of the tower.

• Wind and Structures
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• 제13권5호
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• pp.413-431
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• 2010

The focus of this article is on the assessment of vertical wind vector components and their aerodynamic impact on lattice framework, specifically two distinct sections of a guyed transmission tower. Thunderstorm winds, notably very localized events such as convective downdrafts (including downbursts) and tornadoes, result in a different load on a tower's structural system in terms of magnitude and spatial distribution when compared to horizontal synoptic winds. Findings of previous model-scale experiments are outlined and their results considered for the development of a testing rig that allows for rotation about multiple body axes through a series of wind tunnel tests. Experimental results for the wind loads on two unique experimental models are presented and the difference in behaviour discussed. For a model cross arm with a solidity ratio of approximately 30%, the drag load was increased by 14% when at a pitch angle of $20^{\circ}$. Although the effects of rotation about the vertical body axis, or the traditional 'angle of attack', are recognized by design codes as being significant, provisions for vertical winds are absent from each set of wind loading specifications examined. The inclusion of a factor to relate winds with a vertical component to the horizontal speed is evaluated as a vertical wind factor applicable to load calculations. Member complexity and asymmetric geometry often complicate the use of lattice wind loading provisions, which is a challenge that extends to future studies and codification. Nevertheless, the present work is intended to establish a basis for such studies.

• 한국화재소방학회:학술대회논문집
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• 한국화재소방학회 1997년도 International Symposium on Fire Science and Technology
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• pp.439-449
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• 1997

Studies have been carried out to determine the effect of sprinklers on fires typical of a number of occupancies including simulated of office furniture, supermarkets, carpet displays, libraries, video stores and liquor stores. After surveys of actual fire loads, the experiments were conducted in a specially designed sprinklered fire-calorimeter with a collecting hood 6 m x6 m leading to a vertical duct 1 m in diameter. Details of the rig are given elsewhere [1]. Only well ventilated fires were studied. Rate of heat release and production of various toxic chemicals were monitored during the tests. Both sprinklered and unsprinklered fires were used. The results were used to establish the unsprinklered burning behaviour and the fire-control effects of sprinklers. Before sprinkler operation, the rate of fire growth could be modelled as 12_fires as given in NFPA 92B (1991 Edition) [2]. It was found that operation of sprirnklers controlled but did not extinguish the fires. This was expected as parts of the fire load were shielded from the spray. Also there were significant increases in the concentration of carbon monoxide when the sprinklers operated. Sprinklers had little effect on the concentrations of other toxic products measured. The results from the tests were extrapolated to large single storey buildings for the same occupancy classes and the results used to compare the required and the available escape times for different occupancies, particularly whether the use of sprinklers would improve the chances of escape from those premises. It was found that in most of the cases studied, adequate escape times will be available without any special measures. For very rapid fire growths, however, special measures, such as availability of trained staff may be needed. Standard response sprinklers will have little impact.

• Steel and Composite Structures
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• 제42권4호
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• pp.427-446
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• 2022

Cutouts in the beams or plates are often unavoidable due to inspection, maintenance, ventilation, structural aesthetics purpose, and sometimes to lighten the structures. Therefore, there will be a substantial reduction in the strength of the structure due to the introduction of the cutouts. However, these cutouts can be reinforced with the different patterns of ribs (stiffener) to enhance the strength of the structure. The present study highlights the influence of the elliptical cutout reinforced with a different pattern of ribs on the stability performance of such stiffened composite panels subjected to non-uniform edge loads by employing the Finite element (FE) technique. In the present formulation, a 9-noded heterosis element is used to model the skin, and a 3-noded isoparametric beam element is used to simulate the rib that is attached around a cutout in different patterns. The displacement compatibility condition is employed between the plate and stiffener, and arbitrary orientations are taken care by introducing respective transformation matrices. The effect of shear deformation and rotary inertia are incorporated in the formulation. A new mesh configuration is developed to house the attached ribs around an elliptical cutout with different patterns. Initially, a study is performed on the panels with different stiffener schemes for various ply orientations and for different stiffener depth to width ratios (d_s/b_s) to determine an optimal stiffener configuration. Further, various parametric studies are conducted on an obtained optimal stiffened panel to understand the effect of cutout size, cutout orientation, panel aspect ratio, and boundary conditions. Finally, from the analysis, it can be observed that the arrangement of the stiffener attached to a panel has a major impact on the buckling capacity of the stiffened panel. The stiffener's depth to width ratio also significantly influences the buckling characteristic.

• Proceedings of the National Institute of Ecology of the Republic of Korea
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• 제3권2호
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• pp.103-114
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• 2022

Zoological Parks house exclusive animal species, thus creating a source of education and awareness for visitors. Big cats like tigers and leopards are among the most visited species in zoos globally. However, they often display stressful or stereotypic behaviours. Such behaviours are influenced by multiple factors including visitors, animal history, and captive environment. To understand this impact, we investigated the behavioural response of tigers and leopards to visitation, captive, and biological factors. The behaviour of eight big cats housed in the National Zoological Park, New Delhi, was monitored using focal sampling technique during May and June 2019. We recorded the captive and biological factors and visitor density for the subjects. The study revealed high proportions of inactive and stereotypic behaviours amongst the species. Tigers and leopards were found to perform stereotypic behaviours for 22% and 28% of their time, respectively. Generalised Linear Models revealed a significant variation of stereotypy in association with the factors. Stereotypy was influenced by visitor density, age, sex, breeding history, coat colour, and enclosure design. Adults, males, white-coated, previously bred, and those housed in smaller and simple enclosures display more stereotypy than young, females, normal-coated, unbred, and those housed in larger and complex enclosures, respectively. A high density of visitors induced more stereotypic behaviours amongst the big cats. As providing entertainment and awareness amongst the public is one of the fundamental objectives of the zoo, visitors can not be avoided. Thus, we suggest providing appropriate enrichments that would reduce stereotypies and promote naturalistic behaviours.

• Geomechanics and Engineering
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• 제31권6호
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• pp.557-571
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• 2022

Landslides are often triggered by weak interlayers initiated in tailings dam foundations, and hazards gradually occur. This is serious for landslides in high tailings dams due to their high potential energy. Tailing samples with a fine-grained interlayer at a set dip angle were prepared. Consolidated undrained (CU) triaxial shear tests were carried out by using a high-pressure triaxial apparatus. The results were compared with the results under a low confining pressure. Four reasons were summarized for high tailings dams more prone to instability than low dams. The shear strength of the samples with dipping interlayers decreases with increasing dip angle. An obvious straight drop in the stress path after the peak occurs in samples with dipping interlayers at an angle of 60°. The effect of the interlayer on the mechanical behaviour of tailings is very sensitive, especially for the sample with a dipping interlayer at an angle of 60°. Shear slipping along the interlayer should be given more attention in tailings dams. Compared with the results under low confining pressure, the stress decreases continuously for the samples with dipping interlayers at large angles under high confining pressure. The positive pore pressure, which reduces the effective stress, occurred in tailings samples under high confining pressure. The residual strength of tailings under high confining pressure is smaller than that under low confining pressure. These factors increase the dam break risk and the disaster impact for high tailings dams.

• 한국공간구조학회논문집
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• 제24권2호
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• pp.31-41
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• 2024

This study aims to investigate the seismic response of a large span thin shell structures and assess their displacement under seismic loads. The study employs finite element analysis to model a thin shell structure subjected to seismic excitation. The analysis includes eigenvalue analysis and time history analysis to evaluate the natural frequencies and displacement response of the structure under seismic loads. The findings show that the seismic response of the large span thin shell structure is highly dependent on the frequency content of the seismic excitation. The eigenvalue analysis reveals that the tenth mode of vibration of the structure corresponds to a large-span mode. The time history analysis further demonstrates, with 5% damping, that the displacement response of the structure at the critical node number 4920 increases with increasing seismic intensity, reaching a maximum displacement of 49.87mm at 3.615 seconds. Nevertheless, the maximum displacement is well below the allowable limit of the thin shell. The results of this study provide insight into the behaviour of complex large span thin shell structures as elevated foundations for buildings under seismic excitation, based on the displacement contours on different modes of eigenvalues. The findings suggest that the displacement response of the structure is significant for this new application of thin shell, and it is recommended to enhance the critical displacement area in the next design phase to align with the findings of this study to resist the seismic impact.