• Journal of the Korea institute for structural maintenance and inspection
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• v.9 no.4
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• pp.169-176
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• 2005

An analysis of the annual frequency of collapse(AF) is performed for each bridge pier exposed to ship collision. From this analysis, the impact lateral resistance can be determined for each pier. The bridge pier impact resistance is selected using a probability-based analysis procedure in which the predicted annual frequency of bridge collapse, AF, from the ship collision risk assessment is compared to an acceptance criterion. The analysis procedure is an iterative process in which a trial impact resistance is selected for a bridge component and a computed AF is compared to the acceptance criterion, and revisions to the analysis variables are made as necessary to achieve compliance. The distribution of the AF acceptance criterion among the exposed piers is generally based on the designer's judgment. In this study, the acceptance criterion is allocated to each pier using allocation weights based on the previous predictions.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.2
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• pp.125-135
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• 2012

The FE model for shot peening often assume that shots impact vertically on the engineering parts to generate compressive residual stresses. However, the shots obliquely impact on the surface in actual peening. In this work, we propose a 3D finite element (FE) model for evaluation of residual stress under angled shot peening. Using the FE model for angled multi-impact, we examine the effects of factors such as impact angle, impact pattern and the number of shots. Plastic deformation of shot is also considered. To validate the model, we then compare the FE solution with experimental result by X-ray diffraction (XRD). The proposed model will be a base of 3D multi-impact FE model with diverse impact angles.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2015.07a
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• pp.357-359
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• 2015

부산신항은 우리나라 최대이자 세계 제6위의 컨테이너화물 처리항만으로 자리매김을 하고 있다. 최근들어서 차세대의 친환경 선박으로 벙커C 연료유 대신에 LNG 연료유를 사용하는 선박개발이 본격화되고 있다. 이에 따라서 부산신항의 항만기본개발계획에 들어 있는 유류중개기지 축조 대신에 Bunker LNG(BLNG)터미널 축조를 검토하고 있다. 이 연구에서는 BLNG터미널 개발과 관련하여 초대형 컨테이너선의 남컨 및 북컨 터미널 입항접안에 장애요소로 작용하고 있는 토도의 유무 및 호란도 절개에 따른 해사안전법 상의 해상교통안전진단시행지침에서 규정하고 있는 위험요소에 대한 충돌확률과 선박 운항자의 주관적 평가를 중심으로 안전수역 확보에 대하여 종합적으로 평가, 분석하였다.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2013.06a
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• pp.471-473
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• 2013

주요 통항로에 설치된 해상교량과 해상풍력단지는 선박의 안전항해에 지대한 영향을 미친다. 특히, 90년대 들어 국내에 다수 건설된 해상교량은 과거에 경험하지 못한 대규모 선박-교량 충돌사고의 유발 가능성을 예고하고 있다. 또한 국내 군산지역에 구축될 해상풍력단지 역시 선박과의 충돌 가능성을 내포하고 있다. 이 논문에서는 과거에 연구 개발된 해상교량과 해상풍력단지의 안전성 평가기법을 조사하고, 향후 실용화 방안을 모색하였다. 연구결과, 기존 연구결과를 토대로 위기관리 시스템을 구축하면 궁극적인 해양사고 예방이 가능할 것으로 고려되었다.

• Proceedings of the Korea Society for Simulation Conference
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• 2001.05a
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• pp.133-133
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• 2001

무선 근거리 지역망(Wireless LAN;WLAN) 환경에서 다중 채널을 이용하여 실시간 서비스를 제공하기 위한 매체 접근제어 계층에서의 채널의 사용 구간 할당 방법을 제안하고, 컴퓨터 모의 실험을 통하여 제한된 방식의 실시간 서비스 지원 성능과 채널의 사용 효율을 분석한다. 제안한 채널 사용 구간 할당 방안은 개선된 매체 접근 제어 프로토콜 RICH-DP (Receiver-Initiated Channel-Hopping with Dual Polling)를 바탕으로 한다. 무선 환경에서 RTS-CTS를 사용하는 프로토콜은 SRMA, MACA, MACAW, IEEE 802.11, FAMA 등이 있다. 최근에 단일 채널을 환경에서 RICH(Receiver Initiated Channel-Mopping) 프로토콜이 제안되었다. RICH는 충돌 회피를 위해서 경쟁 구간에서 충돌 감지(carrier sensing)을 사용한다. RICH는 제한된 어플케이션에 국한되는 단절이 있다. 반면에 RICH-DP는 다중 채널 환경에서 충돌 감지와 특별한 코드(spreading code) 할당 없이 일반화된 충돌 회피를 제공한다. 실시간 서비스를 이용하자 차는 단말들로 하여금 RICH-DP를 사용하여 서비스를 제공할 때, 대역폭에 대한 정보를 AP(Access Point)로 전송토록 함으로써 비경쟁 구간에서 뿐 아니라, 경쟁구간에서도 높은 채널 효율이 얻어질 수 있도록 하고 있다. 제한된 방안의 성능 평가를 위한 모의 실험은 OPNET를 이용하여 실시간 서비스 데이터를 7개의 상태 천이를 갖는 VBR 소스로 모델링하고 비동기 트래픽들은 Poisson 소스로 모델링하여 실시간 서비스 단발들의 이용 대역폭과 채널 처리율과 시스템 지연시간을 성능 평가 인자로 하여 수행하였다. 논문에서 제한된 방법을 적용한 개선된 RICH-DP을 모의 실험을 통하여 분석한 결과 기존의 제한된 RICH-DP는 실시간 서비스에 대한 처리율이 낮아지며 서비스 시간이 보장되지 못했다. 따라서 실시간 서비스에 대한 새로운 제안된 기법을 제안하고 성능 평가한 결과 기존의 RICH-DP보다 성능이 향상됨을 확인 할 수 있었다.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.14 no.2
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• pp.149-156
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• 2016

The spent fuel stored in the pool is vulnerable to external impacts, since the severe reactor conditions degrade the structural integrity of the fuel. Therefore an accident during shipping and handling should be considered. In an extreme case, the fuel assembly drop can be happened accidentally during handling the nuclear fuel in the spent fuel pool. The rod failure during such drop accident can be evaluated by calculating the impact force acting on the fuel assembly at the bottom of the spent fuel pool. The impact force can be evaluated with the impact velocity at the bottom of the spent fuel pool. Since fuel rods occupies most of weight and volume of a nuclear fuel assembly, the information of the rods are important to estimate the hydraulic resistance force. In this study, the hydraulic force acting on the $3{\times}3$ short rod bundle model during the drop accident is calculated, and the result is verified by comparing the numerical simulations. The methodology suggested by this study is expected to be useful for evaluating the integrity of the spent fuel.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.7
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• pp.430-439
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• 2019

In this study, a nonlinear impact analysis was performed to evaluate the safety and damage of an eco-pillar debris barrier with a hollow cross-section, which was proposed to improve constructability and economic efficiency. The construction of concrete eco-pillar debris barriers has increased recently. However, there are no design standards concerning debris barriers in Korea, and it is difficult to find a study on performance evaluations in extreme environments. Thus, an analysis of an eco-pillar debris barrier was done using the rock impact speed, which was estimated from the debris flow velocity. The diameters of rocks were determined by ETAG 27. The impact position, angles, and rock diameter were considered as variables. A concrete nonlinear material model was applied, and the estimation of damage was done by ABAQUS software. As a result, the damage ratio was found to be less than 1.0 at rock diameters of 0.3 m and 0.5 m, but it was 1.39 when the diameter was 0.7 m. This study could be used as basic data on impact force in the design of the cross section of an eco-pillar debris barrier.

• Journal of the Korea institute for structural maintenance and inspection
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• v.19 no.4
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• pp.92-100
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• 2015

The aim of this study is to evaluate the fracture characteristics of ductile fiber reinforced cement based composites with 1.5 volume ratio of polyvinyl alcohol and steel fiber by high velocity impact of steel projectile. We used gunpowder impact facility to evaluate the fracture characteristics of ductile fiber reinforced cement based composites by collision of steel projectile, and the impact velocity was from about 150 to 1,000m/s. The results of evaluation on the fracture characteristics of ductile fiber reinforced cement based composites were penetration grade, which is the kinetic energy more than three times of no-fiber reinforced specimen (Plain). In addition, ductile fiber reinforced cement based composites did not occurred critical damage other than the debris. In the case of mass loss, Plain specimen was proportional to kinetic energy of steel projectile, while ductile fiber reinforced cement based composites was not significantly affected by kinetic energy of steel projectile. In particular, this tendency had a close relationship with the fracture characteristics of back side of specimens, and the scabbing inhibiting efficiency of PVA specimen was higher than S specimen. In the results of verifying relationship between front and back side calculated by local damage, scabbing occurred at the region close to the back side in the ductile fiber reinforced cement based composites unlike Plain specimen. Thus, in this study, we examined principal fracture behaviors of ductile fiber reinforced cement based composites under collision of steel projectile, and verified that impact resistance performance was improved as compared to Plain specimen.

• Transactions of the Korean Society of Automotive Engineers
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• v.18 no.6
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• pp.31-37
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• 2010

In proportion to increasing interest in vehicle safety, many country have regulated vehicle safety and performed NCAP(New Car Assessment Program). However vehicles which had good results in these compliance and NCAP frontal crash test have caused problems such as the fork effect and over-riding in real car-to-car accidents. To complement these issues, new frontal crash test modes using new barrier like FWDB and PDB have been developed by EEVC WG15. In this paper, FWDB frontal crash test was performed and the result was compared with the full frontal crash test using the rigid wall in order to comprehend the characteristic of FWDB. The results of FWDB test were compared with one of USNCAP and KNCAP. Using USNCAP data, vehicle performance like deformation and wall force were studied. A comparative study of dummy injuries was made by using KNCAP result. The results showed that vehicle performance of FWDB test like displacement and effective acceleration was similar in spite of absorbing energy of FWDB due to the greater vehicle deformation of rigid wall test. In FWDB test, driver dummy head bottomed out but most of injuries were superior to the injury of rigid wall test.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 2007.04a
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• pp.147-150
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• 2007

본 논문에서는 토픽맵 기반의 온톨로지 병합 과정에서 발생할 수 있는 충돌의 유형을 트리 구조로 정의하고 충돌 탐지 및 해결을 통하여 두 온톨로지를 하나로 병합하는 기법을 제안한다. 병합충돌은 의미적 대응 요소들의 유사값에 기반하여 엘리먼트기반, 구조기반 임시기반의 트리 구조로 분류되고 이 충돌 트리를 이용하여 두 매핑 요소사이의 병합충돌을 탐지하고 해결한다. 실험을 위해 토픽맵 질의언어 tolog를 사용하여 동서양 철학온톨로지 및 독일 문학온톨로지들의 병합 전과 후의 질의 결과를 비교하고 이를 정확율과 재현율로 병합 성능을 평가하였으며 그 결과 손실없는 병합이 가능함을 보였다.