• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2001년도 춘계종합학술대회
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• pp.359-362
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• 2001

수중통신시스템은 과거 AM, FM 변ㆍ복조방식을 이용한 아날로그시스템이 개발되어 왔고, 최근에는 디지털 하드웨어 기술의 발전으로 디지털 변ㆍ복조 방식을 이용한 디지털통신시스템이 개발 이용되고 있다. 수중통신에 있어서 손실, 배경 잡음, 다중경로 등의 해양 환경 특성을 극복하는 것은 신뢰성 있는 통신 환경을 이룩하는데 중요하다. 특히 해면과 해저로 경계 지워진 천해 환경에서 다중경로에 의한 영향은 수중통신시스템의 성능을 좌우하는 중요한 요소 중의 하나이다. 이런 다중경포의 통신채널은 일반적으로 수지 채널과 수평채널로 구분 짓고 있으며, 수직채널은 직접 파와 반사 파의 경로차이가 크고, 수평채널은 직접 파와 반사 파의 경로차이가 수지채널에 비해 상대적으로 적게 나타난다. 본 논문에서는 수치모의 실험을 통해 세 가지 디지털 변ㆍ복조 방식인 FSK, BPSK, DPSK의 수직ㆍ수평 다중경로 통신채널에 대한 성능을 비교 검토하였다.

• 한국해안·해양공학회논문집
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• 제27권5호
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• pp.295-303
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• 2015

관성항과 비선형 항력항을 포함한 직립 슬릿벽에 의한 파의 산란을 고유함수전개법을 사용하여 해석하였다. 슬릿벽에서의 에너지 손실효과를 나타내는 비선형 항력항을 등가 선형화기법으로 선형화시켰다. Yoon et al.(2006)과 Huang(2007)이 제안한 실험식을 통하여 구한 항력계수를 적용한 해석결과는 Kwon et al.(2014)과 Zhu and Chwang(2001)의 수리모형 실험결과와 비교하였고, 서로 잘 일치함을 확인하였다. 개발된 해석모델을 이용하여 슬릿벽의 주요 설계변수들인 공극률, 잠긴 깊이, 슬릿 형상, 파랑특성 등을 바꿔가면서 슬릿벽에서의 에너지 손실효과를 평가하였다. 잠긴 깊이에 따라 다소 차이는 있지만 공극률이 0.1보다 작은 값에서 슬릿벽에서의 에너지 손실률이 가장 크게 일어났다. 현재의 해석해는 슬릿벽 방파제에 의한 소파효율을 예측하는데 유용하게 이용될 것이다.

• 한국실내디자인학회논문집
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• 제16권3호
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• pp.38-45
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• 2007

In the architectural space of modem age, expanding to the vertical and horizontal direction for the interaction between space and space is becoming an indispensable factor, and in this expansion, ramps are being positioned as one of the important factors. With an increased use of ramps, they show a variety of changes in types, functions and even concepts. The space where modem ramps are used exhibits a phenomenon that accommodates and expands many functions as well as the confined function of moving people, and is widening the scope of recognition on the functions of ramp. In addition, this phenomenon can be seen as an architectural reflection on the complexation trend of the modem society, the components comprising a ramp contact the body of experiencers closely and thus have a direct effect on their behavior or feeling, and owing to this, it is a space where new functions and meaning are highly likely to be derived. In this study, spaces where ramps are used stay away from an element of uniform vertical movement but have an independent environment within the entire space, thereby being used as a space dominating the nature of the building, not a subsidiary element of it. In this study, therefore, it could be known that spaces in which ramps are used are different in their meaning according to the patterns, not as an element of uniform vertical movement. In addition, these conclusions are the results by analyzing the patterns of ramps taking place in modem spaces and are thought to be helpful in understanding spaces where ramps are used.

• Advances in concrete construction
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• 제12권5호
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• pp.377-389
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• 2021

Reinforced concrete vertical silos are universal structures that store large amounts of granular materials. Due to the asymmetric structure, heavy load, uneven storage material distribution, and the difference between the storage volume and the storage material bulk density, the corresponding earthquake is very complicated. Some scholars have proposed the calculation method of horizontal forces on reinforced concrete vertical silos under the action of earthquakes. Without considering the effect of torsional effect, this article aims to reveal the expansion factor of the silo group considering the torsional effect through experiments. Through two-way seismic simulation shaking table tests on reinforced concrete column-supported group silo structures, the basic dynamic characteristics of the structure under earthquake are obtained. Taking into account the torsional response, the structure has three types of storage: empty, half and full. A comprehensive analysis of the internal force conditions under the material conditions shows that: the different positions of the group bin model are different, the side bin displacement produces a displacement difference, and a torsional effect occurs; as the mass of the material increases, the structure's natural vibration frequency decreases and the damping ratio Increase; it shows that the storage material plays a role in reducing energy consumption of the model structure, and the contribution value is related to the stiffness difference in different directions of the model itself, providing data reference for other researchers; analyzing and calculating the model stiffness and calculating the internal force of the earthquake. As the horizontal side shift increases in the later period, the torsional effect of the group silo increases, and the shear force at the bottom of the column increases. It is recommended to consider the effect of the torsional effect, and the increase factor of the torsional effect is about 1.15. It can provide a reference for the structural safety design of column-supported silos.

• 한국철도학회논문집
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• 제14권6호
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• pp.545-554
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• 2011

철도교량을 주행하는 열차의 진동사용성 확보를 위해 Eurocode, 신간선기준, 호남고속철도 설계지침 등에서는 교량의 처짐과 차체연직가속도로 진동사용성 기준을 제시하고 있다. 호남고속철도 설계지침 경우 Eurocode를 인용하였기 때문에 향후 열차의 주행속도와 경간길이의 향상 및 확장에 맞추어 철도교량의 진동사용성 기준을 보완함에 있어 철도선진국들에 비해 상대적으로 뒤처질 것으로 예상된다. 따라서 고속철도교량 기술의 국외의존도를 줄이고 기술경쟁력을 확보하기 위하여 주행속도의 증가와 열차-교량 진동전달특성 등을 고려할 수 있는 철도교량의 진동사용성 허용처짐을 제시하기 위한 연구를 수행하였다. 본 논문에서는 매개변수 연구와 열차-교량 상호작용해석을 수행하여 주행속도의 증가에 따른 차체연직가속도와 교량변위의 상관관계를 파악하였으며 주행속도의 증가와 더불어 차체연직가속도가 증가하는 경향을 확인하고 가속도증폭계수를 제안하였다. 그리고 교량의 처짐형상과 진동을 정현파와 조화운동으로 가정하고 진동전달함수와 가속도증폭계수를 이용하여 고속철도교량의 진동사용성 허용처짐을 수식으로 전개하였다.

• Journal of Electrical Engineering and Technology
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• 제1권2호
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• pp.263-267
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• 2006

A new thermal bimorph actuator for large out-of-plane displacement is designed, fabricated and tested. The deflecting beam is composed of polyimide, heater, and polyvinyl difluorides with tetrafluoroethylene (PVDF-TrFE). The large difference of coefficient of thermal expansion (CTE) of two polymer layers (polyimide and PVDF-TrFE) can generate a significant deflection with relatively small temperature rise. Compared to the most conventional micro actuators based on MEMS (micro-electro mechanical system) technology, a large displacement, over 1 mm at 20 mW, could be achieved. Additionally, we can achieve response time of 14.6 ms, resonance frequency of 12 Hz, and reliability ability of $10^5$ cycles. The proposed actuator can find applications where a large vertical displacement is needed while maintaining compact overall device size, such as a micro zooming lens, micro mirror, micro valve and optical application.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 1999년도 봄 학술발표회 논문집
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• pp.145-152
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• 1999

In the applying of the reinforced soil method, it would be possible to obtain reinforcement effect more than before in terms of economic if high water content clayey soils could be used as embanking material. Futhermore it would be possible to expect the expansion of the applying field of reinforced soil method too. In this study, the authors describe the analysis results on the behavior of 5 meter high walls reinforced with nonwoven geotextile having the permeability and woven geotextile or geogrid having large tensile strength on the soil ground. The behavior of the walls were investigated for about 100 days after construction and the deformations of reinforcements, lateral soil pressures, vertical and horizontal displacements of the walls were examined by automatical measuring system. It was found that this kinds of reinforcing system might effectively improve the performance of the steep walls by virtue of the reciprocal action between soil and reinforcements, and it might be concluded that construction of the clayey reinforced soil walls with three kinds of geotextiles could be done successfully even on the comparative weak ground.

• 통합자연과학논문집
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• 제5권4호
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• pp.220-228
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• 2012

District of Korea affected by westerly wind and heavy rainfall is predominantly distributed in the west and south of Honam district. So, this study is becoming a necessity. In this study, it is investigated that the characteristics of heavy rainfall occurred frequently in Honam district along the border of mT airmass after the end of rainy season due to atmospheric instability, lower (850 hPa) convergence and topographic effect. Our results show that heavy rainfall occurred in Honam district along the border of mT airmass results from the appropriate mechanism of the unstable vertical structure and moisture flux in the expansion and contraction of the border of mT airmass. All things considered, the improvement of the predictability of heavy rainfall occurred in Honam district along the border of mT airmass could be possible by the generalization of the results of this study.

• Interaction and multiscale mechanics
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• 제5권1호
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• pp.1-12
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• 2012

Considerable longitudinal rail forces and displacements may develop in continuous welded rail (CWR) track on long-span bridges due to temperature variations. The track stability may be disturbed due to excessive relative displacements between the sleepers and ballast bed and the accompanied reduction in frictional resistance. For high-speed tracks, however, solving these problems by installing rail expansion devices in the track is not an attractive solution as these devices may cause a local disturbance of the vertical track stiffness and track geometry which will require intensive maintenance. With reference to temperature, two actions are considered by the bridge loading standards, the uniform variation in the rail and deck temperature and the temperature gradient in deck. Generally, the effect of temperature gradient has been disregarded in the interaction analysis. This paper mainly deals with the effect of temperature gradient on the track-bridge interaction with respect to the support reaction, rail stresses and stability. The study presented in this paper was not mentioned in the related codes so far.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 1994년도 가을 학술발표회 논문집
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• pp.87-94
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• 1994

During the construction of externally prestressed 7-span continuous segmental bridge, cracks beyond permissible limit were found at anchor zone of expansion joint segment. To eliminate this problem, tension side of diaphragm was prestressed by post-tensioning bars in vertical and horizontal direction. To investigate this remedy is acceptable, stresses of reinforcing bars and concrete surface were measured for the real structure in the field. The measurement was performed through each step of prestressing sequence during construction. Also to investigage stresses induced by live load, static load test was performed and the results was analyzed. In this paper it will be presented the procedure and results for this experimental study along with comparison with analytical study.