• 한국구조물진단유지관리공학회 논문집
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• 제13권5호통권57호
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• pp.93-100
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• 2009

이 논문은 나노물질이 결합된 시간반사영역기(TDR)의 보의 변형에 관한 실험자료와 기존 구조 해석기법에 따른 변형간의 상관관계를 평가하기 위한 것이다. TDR의 동축케이블에 일정한 간격마다 나노물질 ($BaTiO_3$ powders and silver mixture)을 결합하여 토목구조물에 설치할 수 있도록 하였다. 실험결과,나노물질은 보에 설치된 동축케이블의 정확한 위치정보를 알려주었으며, TDR센서시스템과 Fourier series 를 활용하여 필터링 된 실험 자료는 보의 변형을 정확하게 알려주었다. 그러므로, 나노-TDR시스템과 Fourier filter를 활용하여 보의 변형에 관한 정확한 모니터링이 가능하였으며, 변형에 관한 보다 나은 해석이 가능하다는 점에서 기존의 TDR센서 혹은 광섬유 센서보다 진보한 시스템이라 할 수 있다.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2010년도 추계 학술발표회 3차
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• pp.72-77
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• 2010

The Incheon Bridge, which was opened to the traffic in October 2009, is an 18.4 km long sea-crossing bridge connecting the Incheon International Airport with the expressway networks around the Seoul metropolitan area by way of Songdo District of Incheon City. This bridge is an integration of several special featured bridges and the major part of the bridge consists of cable-stayed spans. This marine cable-stayed bridge has a main span of 800 m wide to cross the vessel navigation channel in and out of the Incheon Port. In waterways where ship collision is anticipated, bridges shall be designed to resist ship impact forces, and/or, adequately protected by ship impact protection (SIP) systems. For the Incheon Bridge, large diameter circular dolphins as SIP were made at 44 locations of the both side of the main span around the piers of the cable-stayed bridge span. This world's largest dolphin-type SIP system protects the bridge against the collision with 100,000 DWT tanker navigating the channel with speed of 10 knots. Diameter of the dolphin is up to 25 m. Vessel collision risk was assessed by probability based analysis with AASHTO Method-II. The annual frequency of bridge collapse through the risk analysis for 71,370 cases of the impact scenario was less than $0.5{\times}10^{-4}$ and satisfies design requirements. The dolphin is the circular sheet pile structure filled with crushed rock and closed at the top with a robust concrete cap. The structural design was performed with numerical analyses of which constitutional model was verified by the physical model experiment using the geo-centrifugal testing equipment. 3D non-linear finite element models were used to analyze the structural response and energy-dissipating capability of dolphins which were deeply embedded in the seabed. The dolphin structure secures external stability and internal stability for ordinary loads such as wave and current pressure. Considering failure mechanism, stability assessment was performed for the strength limit state and service limit state of the dolphins. The friction angle of the crushed stone as a filling material was reduced to $38^{\circ}$ considering the possibility of contracting behavior as the impact.

• 한국콘텐츠학회논문지
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• 제9권8호
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• pp.190-197
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• 2009

국내 지상파 방송사들은 제작사이면서 동시에 플랫폼이라는 특성 때문에 1차 창구로서의 광고 수익을 최대한 유지하면서, 자사 인터넷 다시보기 서비스와 계열 케이블 채널, 그리고 지상파 DMB 수익도 확보해야한다는 당면 과제를 안고 있다. 그러나 최근 들어 선행 창구인 지상파 방송사의 광고 수익이 감소하면서 후속 창구 유통에 대한 회의론까지 일고 있다. 이에 따라 선행 창구와 후속 창구간의 홀드백을 적절하게 유지하면서 유통 수익을 극대화할 수 있는 창구화(windowing) 전략이 절실한 시점이다. 따라서 이 연구에서는 지상파 방송 콘텐츠의 창구화 메커니즘을 살펴보고 그 과정에서 쟁점이 되는 이슈들과 함께 적절한 창구화 방안을 모색해 보고자 하였다. 분석 결과 지상파 방송 콘텐츠는 대개 1주일이내에 동시 다발적으로 유통되는 것으로 나타나 배급 주기가 매우 짧다는 것을 알 수 있다. 한편, 창구화 전략으로는 창구 다각화를 통해 누적 수익을 극대화하는 방안과 함께 배급의 순차보다는 개별 창구의 수익성 규모에 중점을 두고 특정 창구로 유통을 집중화시키는 전략이 있다. 방송 콘텐츠의 속성상 생명주기가 짧고, 창구별 배급 기간 중복율도 높기 때문에 방송 콘텐츠를 대상으로 일관된 창구화 전략을 실현한다는 것은 쉽지 않은 일이다. 따라서, 개별 콘텐츠와 각 창구의 특성이 고려된 적절한 창구화 전략이 그 어느 때보다 요구된다고 할 수 있다.

• Geomechanics and Engineering
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• 제10권6호
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• pp.737-755
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• 2016

The load transfer depth of a ground anchor is the minimum length required to transfer the initial prestressing to the grout column through the bonded part. A thorough understanding of the mechanism of load transfer as well as accurate prediction of the load transfer depth are essential for designing an anchorage that has an adequate factor of safety and satisfies implicit economic criteria. In the current research, experimental and numerical studies were conducted to investigate the load transfer mechanism of ground anchors based on a series of laboratory and field load tests. Optical FBG sensors embedded in the central king cable of a seven-wire strand were successfully employed to monitor the changes in tensile force and its distribution along the tendons. Moreover, results from laboratory and in-situ pullout tests were compared with those from equivalent case studies simulated using the finite difference method in the FLAC 3D program. All the results obtained from the two proposed methods were remarkably consistent with respect to the load increments. They were similar not only in trend but also in magnitude and showed more consistency at higher pullout loading stages, especially the final loading stage. Furthermore, the estimated load transfer depth demonstrated a pronounced dependency on the surrounding ground condition, being shorter in hard ground conditions and longer in weaker ones. Finally, considering the safety factor and cost-effective design, the required bonded length of a ground anchor was formulated in terms of the load transfer depth.

• Wind and Structures
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• 제22권2호
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• pp.211-234
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• 2016

Super long-span bridges provide people with great convenience, but they also bring traffic safety problems caused by strong wind owing to their high decks. In this paper, the large eddy simulation together with dynamic mesh technology in computational fluid dynamics (CFD) is used to explore the mechanism of a moving vehicle's transient aerodynamic force in crosswind, the regularity and mechanism of the vehicle's aerodynamic forces when it passes through a bridge tower's wake zone in crosswind. By comparing the calculated results and those from wind tunnel tests, the reliability of the methods used in the paper is verified on a moving vehicle's aerodynamic forces in a bridge tower's wake region. A vehicle's aerodynamic force coefficient decreases sharply when it enters into the wake region, and reaches its minimum on the leeward of the bridge tower where exists a backflow region. When a vehicle moves on the outermost lane on the windward direction and just passes through the backflow region, it will suffer from negative lateral aerodynamic force and yaw moment in the bridge tower's wake zone. And the vehicle's passing ruins the original vortex structure there, resulting in that the lateral wind on the right side of the bridge tower does not change its direction but directly impact on the vehicle's windward. So when the vehicle leaves from the backflow region, it will suffer stronger aerodynamic than that borne by the vehicle when it just enters into the region. Other cases of vehicle moving on different lane and different directions were also discussed thoroughly. The results show that the vehicle's pneumatic safety performance is evidently better than that of a vehicle on the outermost lane on the windward.

• 한국콘텐츠학회논문지
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• 제8권10호
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• pp.104-113
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• 2008

1990년대 중반 케이블 TV의 등장과 함께 국내에도 방송 유통 시장이 형성되면서 최고의 유통 상품으로 떠오르게 된 TV 드라마는 그 후 비디오 플랫폼이 지속적으로 증가하면서 2008년 현재까지 가장 선호되는 콘텐츠로 주목받고 있다. 이 연구는 IP-TV를 비롯한 인터넷 유통으로 또 하나의 유통 창구를 확보하게 된 방송 드라마를 중심으로 부가수익 창출 구조를 살펴보고 유통 창구들의 특성 및 방식에 대해 살펴보았다. 분석 결과, 2000년 이후 방송 드라마 유통의 최고 수익 처는 해외 시장이라고 할 수 있다. 한편, 최근에는 온라인 유통이 활성화 되면서 드라마 판매가 더욱 활기를 띄고 있다. 이와 같은 창구 유통뿐만 아니라, 최근에는 포맷 판매와 리메이크 등 다양한 유통 방식의 변화가 목격됨으로써 유통 메커니즘의 새로운 변화로 여겨지고 있다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2009년도 추계학술대회 논문집
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• pp.214-214
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• 2009

While critical properties of BSCCO wires rely considerably on grid direction upon BSCCO and have very complicated mechanism of generating a superconducting phase, making it difficult to improve properties of wires, YBCO thin-film wires which can be formed in a superconducting phase upon metal board through vapor deposition processing can get excellent direction and reduce manufacturing costs with more flexibility in improving critical properties; thus, they will be suitable for instrument application in the future. Contrary to BSCCO wires for which thick silver alloy covering materials should inevitably be used, moreover, YBCO thin-film wires have an advantage of making thickness and quality of covering materials different by usage. Such a property can be an important element to widen application of wires by presenting possibility of using thin-film wires as superconducting material for fault current limiter as well as for high power current application. In this study we intend to prepare YBCO thin-film wires with different stabilizer layers to analyze current application and current restriction properties by stabilizer layers on the basis of detailed researches on changes in current classification properties below critical value.

• 한국정밀공학회지
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• 제17권2호
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• pp.121-129
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• 2000

The robotic automation in NonDestructive Testing(NDT) is a promising field of research and it helps to expand the applications of NDT enormously. Especially, in the case of pipelines which are widely used in various industrial facilities, it is required to secure adequate ways of inspection in the usual maintenance activitites. In this paper, we present a robot system for inpipe inspection of underground urban gas pipelines. The robot is configured as an articulated structure like a snake with a tether cable. Two active driving vehicles are located in front and rear of the system, respectively and passive modules such as a NonDestructive Testing module and a control module are chained between the active vehicles. The proposed system has outstanding mobility by employing a new steering mechanism called Double Active Universal Joint, which makes it possible to cope with complicated configurations of underground pipelines. Characteristic features of the system are described and the construction of the system is briefly outlined.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2007년도 춘계종합학술대회
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• pp.69-72
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• 2007

최근 광대역 가입자망으로서 HFC 망을 고도화 할 수 있는 DOCSIS 3.0이 표준화되고 있다. DOCSIS 3.0에서는 상향 스트림 프레임에서 경쟁구간의 크기에 따라 프레임의 크기와 예약 구간의 크기에 영향을 받는다. 또한 경쟁구간을 통해 Request를 전송하려는 CM들의 Request 성공률에도 밀접한 관계가 있다. 이 때 다수의 CM들이 경쟁구간을 통해 대역 할당을 요청하기 때문에 발생하는 충돌을 최소화할 수 있는 경쟁구간 설정 알고리즘이 필요하다. 따라서 본 논문에서는 DOCSIS 3.0에서 사용하는 채널-결합 방식을 고려하여 경쟁구간 설정 알고리즘을 제안하였다. 성능 평가를 통해 기존 알고리즘 보다 경쟁구간의 이용률과 절약율에 있어서 더 좋은 성능을 나타냄을 확인하였다.

• Journal of Ship and Ocean Technology
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• 제6권1호
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• pp.27-33
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• 2002

Recently, the application of the electric propulsion system becomes popular because of its advantage over conventional propulsion. However, the complicated flow mechanism and interaction around the azimuth thruster are not fully understood yet, and the studies on the powering performance characteristics with azimuth/pod thrusters are now in progress. The experimental method developed in KRISO(Korea Research Institute of Ships & Ocean Engineering) is introduced and the results of the powering performance tests, consisting of resistance, self-propulsion and propeller open water tests for a cable layer with two azimuth thrusters are presented. For the analysis of powering performance with azimuth thrusters, it is necessary to evaluate the thrust/drag for components of a thruster unit, Extrapolation results could differ according to the various definitions of the propulsion unit; that is the pod, thruster leg and/or nozzle can be treated as hull appendages or as part of propulsion unit, The powering performances based on several definitions are investigated for this vessel. The results of the measurements for the 3-dimensional velocity distribution on the propeller plane are presented to understand the basis of the difference in propulsion characteristics due to the propeller rotational directions.