• Proceedings of the Korea Information Processing Society Conference
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• 2007.05a
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• pp.822-825
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• 2007

RFID(Radio Frequency Identification) 시스템에서 다수의 리더가 동시에 동일한 태그의 인식을 시도하는 경우, 태그는 다수의 리더가 요청한 내용을 처리할 수 없기 때문에 리더 충돌이 발생하게 된다. 이러한 리더 간 간섭에 의한 충돌은 RFID 시스템의 태그 인식 효율 및 인식 속도의 저하 등에 대한 주요 요인으로 작용하기 때문에 이를 방지할 수 있는 효과적인 리더 충돌 방지 알고리즘이 요구된다. 이에 본 논문에서는 리더 충돌이 발생한 경우, 관리 리더(Master Reader)와 보조 리더 그룹(Assistant Reader Group)간의 계층적인 구조를 형성하고, 관리 리더를 통해 하위 리더 그룹을 관리하여 리더 충돌을 방지하는 리더 충돌 방지 알고리즘을 제안한다. 또한, 모의실험을 통해 제안하는 알고리즘의 성능을 분석하고 평가하였다.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2011.04a
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• pp.731-734
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• 2011

본 연구에서는 강재로 구성된 선박충돌방호공의 최대방호능력을 산정하기 위하여 선박과 충돌방호공을 모델링하고 충돌거동을 해석하였다. 이러한 비선형충돌해석은 매우 큰 요소망과 고도의 비선형성을 려해야하기 때문에 이의 해석비용이 일반적인 해석에 비하여 매우 크므로 해석의 경제성을 확보하기 의사정적해석방법을 이용하여 해석을 수행하였다. 이 과정에서 효율적인 해석을 위한 수치 해석기법이 추가되었다. 해석결과 얻어진 선박과 방호공의 에너지소산곡선을 바탕으로 충돌선박이 교량하부구조에 도달하는 시점을 추정하고 이를 바탕으로 대상선박의 최대충돌속도를 산정하였다.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2011.06a
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• pp.164-166
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• 2011

기존 연구에서 다중선박의 충돌위험도를 추정하는 알고리즘을 개발한 바 있다. 본 연구에서는 이를 기반으로, 실제 선박에 온보드형으로 설치하여, 운용할 수 있도록 전자해도 기반의 충돌위험도 표시 시스템을 설계하고, 그 표시 프로그램을 구현하였다. 국립해양조사원에서 배포하는 전자해도(IHO S-57) 파일을 이용할 수 있으며, 실시간으로 입력되는 해상교통 정보를 받아 충돌위험도를 계산하여, 표시할 수 있도록 구성하였다. 그리고, 개발된 프로그램의 성능을 검증하기 위하여, 선박운항 시뮬레이터를 이용하여, 실제 선박충돌사고의 AIS 데이터를 이용한 재생시뮬레이션을 수행하였다.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2023.05a
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• pp.245-245
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• 2023

감천항 내에는 벌크선석, 어획물 전용 냉동창고, 어획물 공동경매장 및 수리조선소등이 있다. 다양한 목적의 선석과 시설에 따라 조종불능선, 조종성능제한선, 견시불량선, 대형벌크선, 강제도선면제선박 및 어선등 이 감천항 방파제 부근수역을 이용한다. 특히 입출항하는 GT 20,000톤 - 50,000톤 크기의 벌크선박과 VHF교신이 되지 않는 어선들과 방파제 부근수역에서 조우상태가 되어 충돌사고 발생 위험이 존재한다. 따라서, 본연구는 선박 충돌사고를 예방하기 위하여 충돌위험요소를 확인하고 충돌위험요소 제거를 위한 방안을 모색하였으며, 또한 더욱 세심한 연구가 진행되기 위함을 목적으로 한다.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• v.1
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• pp.23-29
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• 2006

From a point of view of suggesting the method to avoid ship's collision, the speed of ships has to be considered sufficiently according to encounter angle of ships. But with respect to the establishment of Safe-Guard Ring of Ship Collision Avoidance Support Model in Close Quarters Situation that had been newly studied to avoid ship's collision, the ratio of own ship' speed to a target ship's speed was limited to about less than 1.7. Therefore in this paper, as doing a study concerned with the establishment of Safe-Guard Ring reflected the encounter angle and the speed of ships, we will propose the new model of ship collision avoidance for safe maneuver of ship's collision avoidance.

• Journal of the Korea institute for structural maintenance and inspection
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• v.23 no.1
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• pp.63-70
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• 2019

The number of vehicle-to-barrier collisions has increased due to improved driving environments. In addition, it is reported that the number of accidents led to impact severity larger than current capacity of a median barrier has increased. It is required to develop a high performance median barrier in order to secure expressway safety. This paper aims at proposing impact loading model and locations for a high performance median barrier based on analysis of median-barrier-related accident history. The SB6 test level (Impact severity: 420 kJ, Mass: 25 ton, Impact speed: 80 km/h, Impact angle: $15^{\circ}$) was suggested for target impact severity based on statistical data analysis. The suitable locations also were proposed from investigation of driver behaviors for installation and rehabilitation of high performance median barrier.

• Journal of the Korean Society of Propulsion Engineers
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• v.3 no.3
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• pp.31-39
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• 1999

In this paper, numerical experiment is attempted to analyze and compare the combustion efficiency of the burning sprays due to OFO, FOF triplet / FOOF split doublet injectors. Preconditioned Wavier-Stokes equation system with low Reynolds number $\kappa$-$\varepsilon$ model for turbulence closure, is LU-SGS time-integrated. Spray processes are modeled by DSF analysis with experimentally determined injection characteristics. n-heptane/air global reaction model approximates the combustion for simplicity, and the influence of turbulence on the chemical reaction is included using eddy dissipation model. The results showed the FOF triplet injector of highest combustion efficiency, whereas the OFO type of poet performance. It was also observed that the droplet mean diameter and the average gas temperature due to the mixing efficiency, are the representative parameters for the performance design of combustion.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.36 no.2
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• pp.113-120
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• 2023

This paper introduces a simulation method for the collision between roadblocks and vehicles using LS-DYNA. The need to evaluate the performance of anti-ram barriers to prepare for vehicle impact has increased since vehicle impact threats have been included as a design criterion for nuclear power plants. Anti-ram barriers are typically certified for their performance through collision experiments. However, because Koreas has no performance testing facilities for anti-ram barriers, their performance can only be verified through simulations. LS-DYNA is a specialized program for collision simulation. Various organizations, including NCAC, distributes numerical models that have been validated for their accuracy with collision tests. In this study, we constructed a finite element model of the most critical vehicle barrier module and simulated collision between roadblocks and vehicles. The calculated results were verified by applying the validation criteria for vehicle safety facility collision simulations of NCHRP 179.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.45 no.1
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• pp.33-41
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• 2008

As RFID technology is developing and increasingly being used in many applications, the implementation is changing from single reader to multiple readers even dense readers. Since the number of readers is increasing, there are more collisions between readers and much interference between readers and tags. Therefore, to avoid interference or collision, many algorithms have being proposed, such as Gen2 dense mode, LBT(listen before talk), TDMA based method. In this paper, we propose a null frame algorithm, which calculates the collision probability in frame slotted aloha scheme and use this information to avoid the possible collisions. Comparing with conventional scheme, our proposed algorithm has some advantages in terms of reader collision number and required frame numbers.

• Journal of the Korean Society for Marine Environment & Energy
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• v.12 no.1
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• pp.15-22
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• 2009

Auto-navigation algorithm have been studied to avoid collision and grounding of a ship due to human error. There have been many research on collision avoidance algorithms but they have been validated little on the real coastal traffic situation. In this study, a Collision Avoidance algorithm is developed by using Fuzzy algorithm and the concept of Changeable Action Space Searching (CAS). In the first step, on a basis of collision risk calculated from fuzzy algorithm in the current time(t=to), alternative Action Space for collision avoidance is planned. In the second step, next alternative Action Space for collision avoidance in the future($t=to+{\Delta}t$) is corrected and re-planned with re-evaluated collision risk. In the third step, the safest and most effective course among Action Space is selected by using optimization method in real time. In this paper, the main features of the developed collision avoidance algorithm (CAS) are introduced. CAS is implemented in the ship-handling simulator of MOERI. The performance of CAS is tested on the situation of open sea with 3 traffic ships, whose position is assumed to be informed from AIS. Own-ship is fully autonomously navigated by autopilot including the collision avoidance algorithm, CAS. Experimental results show that own-ship can successfully avoid the collision against traffic ships and the calculated courses from CAS are reasonable.