• 한국항해학회지
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• 제17권1호
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• pp.61-78
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• 1993

Large offshore structure are to be considered for oil storage facilities , marine terminals, power plants, offshore airports, industrial complexes and recreational facilities. Some of them have already been constructed. Some of the envisioned structures will be of the artificial-island type, in which the bulk of structures may act as significant barriers to normal waves and the prediction of the wave intensity will be of importance for design of structure. The present study deals wave scattering problem combining reflection and diffraction of waves due to the shape of the impermeable rigid upright structure, subject to the excitation of a plane simple harmonic wave coming from infinity. In this study, a finite difference technique for the numerical solution is applied to the boundary integral equation obtained for wave potential. The numerical solution is verified with the analytic solution. The model is applied to various structures, such as the detached breakwater (3L${\times}$0.1L), bird-type breakwater(318L${\times}$0.17L), cylinder-type and crescent -type structure (2.89L${\times}$0.6L, 0.8L${\times}$0.26L).The result are presented in wave height amplification factors and wave height diagram. Also, the amplification factors across the structure or 1 or 2 wavelengths away from the structure are compared with each given case. From the numerical simulation for the various boundary types of structure, we could figure out the transformation pattern of waves and predict the waves and predict the wave intensity in the vicinity of large artificial structures.

• 대한기계학회논문집A
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• 제39권3호
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• pp.241-247
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• 2015

교량이나 배관과 같이 긴 길이의 구조물은 처짐 및 변형이 발생하기 쉽다. 이러한 구조물의 건전성 감시를 위해서는 국부적인 물리량 측정뿐만 아니라 전체의 형상 감시가 필요하다. 광섬유 브래그 격자(Fiber Bragg Grating; FBG) 센서는 광섬유에 다수의 센서 적용이 가능하여 대형 구조물 감시에 효과적이다. 본 연구에서는 FBG를 이용하여 구조물의 다점에서 변형률을 측정하고, 이를 바탕으로 구조물 전체의 형상 추정을 위한 연구를 수행하였다. 구조물의 정확한 감시가 가능하도록 3차원의 형상 추정을 연구하고 실험적 검증을 수행하였다. 실험 결과 구조물의 변형에 따른 형상 변화의 추정이 가능함을 확인하였고, 추가로 특정 위치에서의 처짐량을 실제 마이크로미터로 측정한 값과 예측된 값을 비교하여 검증하였다.

• Coupled systems mechanics
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• 제6권3호
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• pp.229-249
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• 2017

A new technique to mitigate irregular buildings with soil structure interaction (SSI) effect subjected to critical seismic waves is presented. The L-shape in plan irregular building for various reasons was selected, subjected to seismic a load which is a big problem for structural design especially without separation gap. The L-shape in plan building with different dimensions was chosen to study, with different rectangularity ratios and various soil kinds, to show the effect of the irregular building on the seismic response. A 3D building subjected to critical earthquake was analyzed by structural analysis program (SAP2000) fixed and with SSI (three types of soils were analyzed, soft, medium and hard soils) to find their effect on top displacement, base shear, and base torsion. The straining actions were appointed and the treatment of the effect of irregular shape under critical earthquake was made by using tuned mass damper (TMD) with different configurations with SSI and without. The study improve the success of using TMDs to mitigate the effect of critical earthquake on irregular building for both cases of study as fixed base and raft foundation (SSI) with different TMDs parameters and configurations. Torsion occurs when the L-shape in plan building subjected to earthquake which may be caused harmful damage. TMDs parameters which give the most effective efficiency in the earthquake duration must be defined, that will mitigate these effects. The parameters of TMDs were studied with structure for different rectangularity ratios and soil types, with different TMD configurations. Nonlinear time history analysis is carried out by SAP2000 with El Centro earthquake wave. The numerical results of the parametric study help in understanding the seismic behavior of L-shape in plan building with TMDs mitigation system.

• Coupled systems mechanics
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• 제12권3호
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• pp.277-295
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• 2023

Unsymmetrical high-rise buildings (HRBs) subjected to earthquake represent a difficult challenge to structural engineering, especially taking into consideration the effect of soil-structure interaction (SSI). L-shape in plan HRBs suffer from big straining actions when are subjected to an earthquake (in x- or y-direction, or both x- and y- directions). Additionally, the disastrous effect of seismic pounding may appear between two adjacent unsymmetrical HRBs. For two unsymmetrical L-shape in plan HRBs subjected to earthquake in three different direction cases (x, y, or both), including the SSI effect, different methods are investigated to mitigate the seismic pounding and thus protect these types of structures under the earthquake effect. The most effective technique to mitigate the seismic pounding and help in seismically protecting these adjacent HRBs is found herein to be the use of a combination of pounding tuned mass dampers (PTMDs) all over the height (at the connection points) together with tuned mass dampers (TMDs) on the top of both buildings.

• 한국공간구조학회논문집
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• 제16권1호
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• pp.73-84
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• 2016

This study analyzes the four composition elements : profile, anchorage and connection, material and member rigidity, stability, as the main composition design elements of flexure structure systems, in order to explore possibilities for more various structure designs in architectures with flexure structure system. It also examines typical design methods that use the mentioned four composition elements. At the results, this research presents an understanding of the differences between funicular shape and non-funicular shape and mechanical features of the shapes in the profile element, regarding to the ratio of rise height to span length(f/l). Also, the typical design methods are presented for the designable usages of the hinge joints and the fix joints, and for the applications of member rigidity expressed by the index of the ratio of member depth to span length(d/l). And it was presented that connection styles, addition of brace members, placement of shear walls are the main design methods in the stability element. This data would be useful to architectural designs concerning integrated design with structures.

• Journal of Species Research
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• 제6권2호
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• pp.190-194
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• 2017

Two new species of the genus Luffariella (Dictyoceratida: Thorectidae), L. tubula n. sp. and L. koreana n. sp. were collected from Jeju-do, Korea. These species differ significantly from the previously reported five species in terms of shape and skeletal structure. L. tubula n. sp. has two categories in thickness of secondary fibres which were different from other species. L. koreana n. sp. is very similar to L. variabilis from Tahiti in skeletal structure, but differs in sponge shape with irregular branching and indistinct surface conules. Primary fibres of the two new species are separated from secondary and tertiary fibres.

• Wind and Structures
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• 제32권2호
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• pp.127-142
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• 2021

Wind load acting on a standalone structure is different from that acting on a similar structure which is surrounded by other structures in close proximity. The presence of other structures in the surrounding can change the wind flow regime around the principal structure and thus causing variation in wind loads compared to a standalone case. This variation on wind loads termed as interference effect depends on several factors like terrain category, geometry of the structure, orientation, wind incident angle, interfering distances etc., In the present study, a three building configuration is considered and the mean pressure coefficients on each face of principle building are determined in presence of two interfering buildings. Generally, wind loads on interfering buildings are determined from wind tunnel experiments. Computational fluid dynamic studies are being increasingly used to determine the wind loads recently. Whereas, wind tunnel tests are very expensive, the CFD simulation requires high computational cost and time. In this scenario, Artificial Neural Network (ANN) technique and Support Vector Regression (SVR) can be explored as alternative tools to study wind loads on structures. The present study uses these data-driven approaches to predict mean pressure coefficients on each face of principle building. Three typical arrangements of three building configuration viz. L shape, V shape and mirror of L shape arrangement are considered with varying interfering distances and wind incidence angles. Mean pressure coefficients (Cp mean) are predicted for 45 degrees wind incidence angle through ANN and SVR. Further, the critical faces of principal building, critical interfering distances and building arrangement which are more prone to wind loads are identified through this study. Among three types of building arrangements considered, a maximum of 3.9 times reduction in Cp mean values are noticed under Case B (V shape) building arrangement with 2.5B interfering distance. Effect of interfering distance and building arrangement on suction pressure on building faces has also been studied. Accordingly, Case C (mirror of L shape) building arrangement at a wind angle of 45º shows less suction pressure. Through this study, it was also observed that the increase of interfering distance may increase the suction pressure for all the cases of building configurations considered.

• Journal of Advanced Marine Engineering and Technology
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• 제19권3호
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• pp.42-49
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• 1995

In this study, the optimum structural modification of the L-type structure by shape changes is suggested. The vibration characteristics of L-type structure are analyzed by the sub-structure synthesis method, and the coordinte sensitivities of each sub-structure are calculated and the change quantities of the positions to be modified are suggested by using the coordinate sensitivities. The results obtained are as follows : 1. The sensitivities of the natural frequency could be calculated by the sensitivity analysis. 2. The change quantities of the position to be modified could be suggested by the optimum structural modification method. 3. The developed program could reduce the process and time of computation, since the sensitivity was directly calculated by differential method, not finite difference method.

• 한국자원식물학회지
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• 제12권2호
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• pp.133-138
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• 1999

당근(Daucus carota L. cv. Hongshim)의 접합자배와 체세포배의 경정부의 구조는 주사전자현미경과 종단면 관찰을 통하여 이루어졌다. 접합자배의 경정부는 도립된 보우트형이고, 2ㆍ3ㆍ4자엽 체세포배의 경정부는 각각 도립된 보우트형, 피라미드형 및 볼록한 다이아몬드형으로 나타났다. 접합자배의 경정부는 다소 작은 세포들로 구성되어 있고, 초층과 내체의 구별이 된다. 체세포배의 경정부는 다소 큰 세포들이 불규칙하게 배열되어 있다.

• 한국정보전자통신기술학회논문지
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• 제1권3호
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• pp.3-8
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• 2008

본 논문에서는 H 평면에서 전방향성 방사패턴을 갖고 저자세를 갖는 평면형 안테나를 제안하였다. 전기적 소형 모노폴 안테나가 갖는 캐패시턴스 성분에 인덕티브 성분의 ENG(Epsilon Negative) 쉘 구조를 부설함으로써 임피던스를 매칭시켰다. ENG 쉘 구조는 4개의 계단형 L-슬롯으로 대칭된 인덕티브 로딩 구조로 이루어져 있다. 실제측정 결과 제안된 안테나의 임피던스 대역폭 ($VSWR{\leq}2$)은 150MHz (2.5 ~ 2.65GHz)를 나타내었고 최대 방사 이득은 중심 주파수 2.56GHz에서 1.12dBi를 나타내었으며 전방향성 방사패턴을 나타내었다. 제안된 안테나는 저자세 높이와 전방향성 방사를 요구하는 시스템에 적용될 수 있을 것으로 사료된다.