• The KIPS Transactions:PartD
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• v.8D no.1
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• pp.10-23
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• 2001

Transactions in real-time active databases have the notion of activeness where transactions are generated by external effects and another transaction. In this paper, we propose the multi version concurrency control algorithm for real-time active transactions. A real-time active transaction has a timing constraint in the form of a deadline until which the user wants to complete the transaction, and is characterized by triggering relationships which mean that association between a transaction that triggers the execution of another transaction and the triggered transaction. The triggering relationship is an important factor to resolve data conflicts among real-time active transactions. The proposed concurrency control mechanism resolves data conflicts by considering triggering relationships between conflicting transactions as well as priorities and precedence relationships. The conflict resolution mechanism considers association types of the triggering relationship such as abort and commit dependency, and then resolves data conflicts in favor of higher priority transactions. We also present the experimental results of our algorithm comparing other real-time active concurrency control algorithms.

• Journal of Navigation and Port Research
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• v.26 no.1
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• pp.8-14
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• 2002

The collisions of vessel at sea show high among the whole marine accidents. Especially, the accidents of fishing vessels take the largest portion of the collisions. Therefore, a technique to reduce these accidents should be developed. The automatic control for avoiding collision suggested in this study consists of two steps. The first is recognizing collision risk with fuzzy Theory and the other is maneuvering the model ship on the basis of collision risk calculated from the first step. The information form the position and estimated time of collision point(DCPA and TCPA) is used to assess the collision risk. To verify this system, a fishing vessel was simulated according to MMG mathematical model. The simulations result shows quite good application in avoiding the collision of ship.

• Journal of the Korea Computer Graphics Society
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• v.23 no.2
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• pp.23-27
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• 2017

We propose an inter-leg collision avoidance method that compensates the disadvantage of the data-driven biped control method. The data-driven biped control technique proposed by Lee et. al [1] sometimes generates the movement that the two legs intersect with each other while walking, which can not be realized in walking of a real person or a biped robot. The proposed method changes the angle of the swing hip so that the swing foot can move inward only after passing the stance foot. This process introduces an additional angle adjustment algorithm to avoid collisions with the stance leg to the original feedback rule of the stance hip. It generates a stable walking simulation without any inter-leg collisions, by adding minimal changes and additional calculations to the existing controller behavior.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2022.06a
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• pp.133-134
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• 2022

본 논문에서는 자율운항선박의 육상 관제 및 원격제어를 위해, 자율운항선박의 비상상황인식 기술 개발에 대한 기초연구를 수행한다. 자율운항선박 주변의 타선들의 이동 경로를 예측하고 이에 따라 자선의 이동경로와 비교하여, 충돌위험 영역을 식별함으로써 비상상황 인식이 가능하도록 한다. 먼저, 타선의 이동경로 예측을 위해서는 선박자동식별시스템 AIS 정보를 바탕으로, 해당 해역에서의 통항패턴을 분석하고 이를 기반으로 타선의 특정 시간 동안의 이동 경로를 예측한다. 예측된 타선의 이동경로와 함께 자선의 이동경로를 비교 분석함으로, 최근 접점 및 최근접점 거리 정보 기반의 충돌위험영역을 식별한다. 식별된 충돌위험영역의 위험도에 따라 육상 관제센터에서는 원격 제어를 통한 위험상황 회피가 가능하도록 활용할 수 있다. 제안된 방법은 AIS에서 얻어지는 실제 항적 데이터를 이용하여 초기 결과를 검증하였다.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.47 no.8
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• pp.558-565
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• 2019

A lot of studies on the survivability of missiles have been widely studied, since the technology of modern warships equipped with state-of-the-art defense systems has been improved. The survivability of missiles can be improved by attacking a target simultaneously using multiple missiles. For this reason, impact time control guidance (ITCG) laws have been widely studied. This paper deals with the effect of time-to-go estimate to ITCG laws. In this paper, two kinds of time-to-go estimate are first introduced in two-dimensional and three-dimensional environment and then ITCG laws are derived using the time-to-go estimate. Numerical simulations are performed to analyze the performance of the designed ITCG laws and the effect of time-to-go estimate is discussed.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2023.05a
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• pp.188-189
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• 2023

IMO가 정의하고 있는 자율운항선박의 자율도는 4단계로 구분되며, 완전 무인선박인 4단계를 제외한 나머지 단계에서는 자율운항선박에 대한 육상의 원격제어가 가능하도록 해야한다. 본 연구에서는 자율운항선박 기술개발사업을 통해 진행 중인 자율운항선박의 육상원격제어를 위한 비상상황인식 기술 개발에 대해 소개한다. 육상의 원격제어가 수행되어야 하는 비상상황에 대한 식별을 위해, 항적 정보를 이용한 타선 항로예측 기반의 충돌위험영역식별을 수행한다. 또한, 타선의 항적정보를 데이터베이스화하여 자율운항선박 운항 영역에 존재하는 현재의 선박에 대한 이상학적 식별을 수행한다. 제안된 기술은 울산 성능실증센터 및 자율운항선박 해상테스트베드 시험선에서의 기능 및 성능 검증을 위해 준비중이다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.20 no.12
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• pp.2259-2266
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• 2016

Recently dense wireless local area networks (WLANs) emerge as the number of WLAN cells and stations increases. In such dense WLAN environment, this paper proposes a new distributed medium access control (MAC) protocol. The proposed MAC protocol extends the previous CSMA with collision resolution (CSMA/CR) that uses a single collision detection (CD) phase and employs multiple CD phases to resolve more collisions. It checks the collision detection in each CD phase and stops the CD phase if consecutive non-detected CD phases occur more than the threshold. Therefore, the proposed protocol can control the number of CD phases adaptively according to the number of accessing stations and increase the probability of collision resolution while decreasing the packet overhead. The simulation results show that the proposed adaptive CSMA/CR protocol employs a variable number of CD phases according to the number of stations and achieves a greater throughput than the previous CSMA/CR protocol using the fixed number of CD phases.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2003.05a
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• pp.81-86
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• 2003

The studies on automatic ship collision avoidance system, which have been carried out last 10 years, are facing on new situation due to newly developed high technology such as computer and other information system. It was almost impossible to make it used in real navigation 3-4 years ago because of the absence of the tool to get other ship's information, however recently developed technology suggests new possibility. This study is carried out to develop the algorithm of automatic ship collision support system. The NOMOTO ship's mathematic model is adopted in simulation for its simplicity. The fuzzy reason rules are used for course-keeping system and for the calculation of Collision Risk using TCPA/DCPA. Moreover‘encounter type’ between two ships is analyzed based on Regulations for Preventing Collisions at Sea and collision avoidance action is suggested, Some situations are simulated to verity the developed algorithm and appropriate avoidance action is shown in the simulation.

• Journal of Navigation and Port Research
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• v.27 no.4
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• pp.375-381
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• 2003

The studies on automatic ship collision avoidance system, which have been carried out last 10 years, are facing on new situation due to newly developed high technology such as computer and other information system. It was almost impossible to make it used in real navigation 3-4 years ago because of the absence of the tool to get other ship's information, however recently developed technology suggests new possibility. This study is carried out to develop the algorithm of automatic ship collision support system. The NOMOTO ship's mathematic model is adopted in simulation for its simplicity. The fuzzy reason rules are used for course-keeping system and for the calculation of Collision Risk using TCPA/DCPA. Moreover ‘encounter type’ between two ships is analyzed based on Regulations for Preventing Collisions at Sea and collision avoidance action is suggested. Some situations are simulated to verity the developed algorithm and appropriate avoidance action is shown in the simulation.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2023.11a
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• pp.109-110
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• 2023

자율운항선박(Maritime Autonomous Surface Ships, MASS)은 4수준으로 구분되는데, 현재 세계적으로 수준 2-3 사이의 원격제어 자율운항선박이 상용화를 시작할 것으로 조사되었다. 원격제어 자율운항선박은 3 주요요소(MASS, 해상위성통신, 원격제어자)로 구성되는데, 주요한 문제는 통신 손실이다. 자율운항선박의 원격제어는 해사 위성통신을 이용할 수밖에 없는데, 이러한 해사 위성통신은 통신두절, 대용량 데이터 송수신에 의한 지연 등이 문제로 대두되고 있다. 본 연구의 목적은 제어 데이터 송수신 과정에서 발생하는 지연시간이 충돌사고에 미치는 영향을 식별하기 위한 것으로, 우선하여 이러한 영향을 식별할 수 있는 실험방법을 고찰하고자 한다. 실험방법은 선박조종시뮬레이터를 이용할 것인데, 그 이전에 제어지연이 발생하는 메카니즘을 구현하고, 이러한 메카니즘에 의해서 정량적 및 정성적 분석이 가능한 방법론을 검토하였다. 본 연구는 자율운항선박에서 발생할 수 있는 제어지연이 항해안전에 미치는 영향의 과학적 식별과 평가에 관한 하나의 기반이될 것으로 기대된다.