• International Journal of Highway Engineering
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• v.10 no.1
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• pp.123-134
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• 2008

Since the end treatments of guardrails installed on domestic roads have the shapes which can easily penetrate and turnover a vehicle, the occupant can be subjected to severe injury when a vehicle impacts the end treatments. In this study, the criteria of performance evaluation for end treatments are suggested which are suitable to domestic road circumstances. Based on the investigation for the installation and studies instances of end treatments, the mechanism of end treatments is examined and the new end treatment suitable to domestic road circumstances is suggested. The suggested end treatment was verified by computer simulation using d LS-DYNA programs and satisfied the suggested performance evaluation criteria for end treatments. And the developed end treatment was verified by full-scale vehicle crash test and satisfied the following three primary appraisal factors of the suggested performance evaluation criteria for end treatments; occupant risk criteria, structural adequacy, and after-collision vehicle trajectory. This study is the first to develop end treatments considering the occupant safety in Korea. Therefore, If the developed end treatments is installed on roads and highways, it can be expected that it will reduce the grave situation of end treatment accidents and increase the safety of roads.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.2B
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• pp.98-106
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• 2006

In order to provide a realtime transmission over a wireless LAM, we here present a new jamming based retransmission mechanism. In a legacy wireless LAN system, all stations use the binary exponential backoff algorithm to avoid collisions among frames. It is well known that the backoff algorithm causes more collisions as the numbers of active stations increases. This makes transmission of real time traffic hard. In the proposed scheme, when each station senses collisions, it promptly allows to send a jamming signal during a unique jamming window period which is determined by its own channel access count database(CACDB). This jamming windows is chosen not to be overlapped each other by using of CACDB, and thus channel access of another station is prevented. Hereafter the station gets the ownership of the medium when the wireless medium becomes idle after sending the jamming signal and sensing carrier, and then sends frame in medium. In our proposal, repeating collisions is never happened. We here assume that real time traffic use a frame of fixed length in order to make the time for receiving its ACK frame same. Comparing the proposed jamming-based retransmission scheme with the the 802.11 and 802.11e MAC by simulation. one can find that the proposed scheme have advantages in terms of delay, average backoff time, and average number of collisions per frame. One can find that the proposed scheme might be practically applicable to several applications of realtime traffic transmission in wireless LAN systems.

• The Magazine of the IEIE
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• v.32 no.7 s.254
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• pp.47-56
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• 2005

본 기고문에서는 센서네트워크 기술 중에서 하드웨어 플랫폼과 운영체제에 대한 현황을 기술한다. 하드웨어 플랫폼 및 운영체제의 경우 시장 초기진입 단계이므로 연구 개발 중인 플랫폼보다는 상용화된 플랫폼들을 소개하는데 주력한다. 또한, 상용화된 플랫폼을 이용하여 ZigBee 통신 성능을 실험하고 분석하였다. 먼저 ZigBee의 최대 전송률을 실험하였으며 무선 UM과의 주파수 충돌시의 전송률을 실험하였다. 실험 결과, 칩수준에서의 최대 전송률은 250kbps라고 하나 실제 성능은 이보다 낮은 150kbps를 기록하였다. 무선LAN과의 충돌 시에는 10$\~$20$\%$ 정도의 성공률만을 보이며 실내에서 무선 LAN의 영향을 더욱 많이 받는다는 결과를 얻었다.

• Proceedings of the Korean Information Science Society Conference
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• 1998.10b
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• pp.57-59
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• 1998

데이터베이스 관리시스템을 사용하여 오래 지속되는 작업을 지원하는 응용에서 각 트랜잭션들은 로크를 오랫동안 획득하고 있음으로 인하여 빈번한 로크 충돌 현상이 발생한다. 로크충돌 현상이 발생하는 경우에는 트랜잭션이 로크를 기다리게 되므로 응용의 성능이 현격히 저하된다. 이 논문에서는 오래 지속되는 작업을 순차적인 세부 트랜잭션들로 구성하여, 트랜잭션들 간의 로크를 연계시킴으로써 응용의 성능을 향상시키는 방법을 제안한다. 로크 연계과정에서는 트랜잭션 고립단계에 기반한 로크 강등 기법을 사용하여 동시성을 향상시킨다.

• Proceedings of the Korean Information Science Society Conference
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• 2001.04a
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• pp.490-492
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• 2001

본 논문은 ATM 멀티캐스트 스위치를 위한 새로운 복사망을 제안하였다. Lee의 복사망과 그 이후 제안된 복사망에서 문제가 된 오버플로우와 충돌 문제를 해결하기 위해 다중경로와 다중출력을 갖는 B-tree 네트워크를 사용하였다. 또한 높은 부하에도 충돌을 줄이고 복사망의 성능을 높이기 위해 B-Tree 네트워크의 각 SE에 출력 및 공유 버퍼 성격을 지닌 크로스포인트 버퍼를 추가한 IBBT 네트워크를 제안하였다. 제안된 복사망은 Lee의 복사망의 특성을 유지하며, 이 IBBT 네트워크를 복사망의 BBN에 적용하고, 셀 분할 알고리즘을 사용하여 복사망의 성능을 향상 시켰다.

• Journal of Navigation and Port Research
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• v.34 no.10
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• pp.727-733
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• 2010

An estimation algorithm of collision risk among multiple ships has been developed in order to reduce human error and prevent collision accidents. The algorithm is designed to calculate the collision risk among ships based on Fuzzy theory by using AIS data as traffic information. In this paper, to validate the algorithm, the AIS data of actual collision accident, which occurred between a product carrier and a cargo carrier in Busan harbor in 2009 are collected. The replay simulation is carried out on the actual AIS data and the collision risk is calculated in real time. In this paper, the features of the estimation algorithm of collision risk and the results of replay simulation based on AIS data of actual collision accident are discussed.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2008.05a
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• pp.55-58
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• 2008

RFID(Radio frequency IDentification) leader is collision of data, when recognizing the multiple tag the inside area. This collision became the cause which delays the tag recognition time of the leader. The protocol which prevents the delay of tag recognition time of the leader the place where representative it uses QT(Query Tree) algorithms, it uses a collision bit position from this paper and are improved QT-MTC(Query Tree with Multi-Tag Cognition) algorithms which it proposes. This algorithm stored the bit position which bit possibility and the collision where the collision happens occurs in the stack and goes round a tree the number of time which, it reduced could be identified two tags simultaneously in order, it was planned. A result of performance analysis, It compared in QT protocols and the this algorithm against the tag bit which is continued a tush efficiency improvement effect was visible.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.44 no.11
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• pp.25-32
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• 2007

In this paper, we propose the Group Separation Algorithm for RFID Tag Anti-Collision. We study the RFID Tag anti-collision technique of ALOHA and the anti-collision algorithm of binary search. The existing technique is several problems; the transmitted data rate included of data, the recognition time and energy efficiency. For distinction of all tags, the Group Separation algorithm identify each Tag_ID bit#s sum of bit #1#. In other words, Group Separation algorithm had standard of selection by collision table, the algorithm can reduce unnecessary number of search even than the exisiting algorithm. The Group Separation algorithm had performance test that criterions were reader#s number of repetition and number of transmitted bits for understanding tag. We showed the good performance of Group Separation algorithm better than exisiting algorithm.

• Aerospace Engineering and Technology
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• v.12 no.2
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• pp.123-130
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• 2013

Many countries tried to design the collision risk management system to protect their own satellites from collision probability due to the space debris. In this situation, KARI(Korea Aerospace Research Institute) is developing the KARISMA(KARI Conjunction Risk Management System) to protect our operating satellites from these space debris. The quality of this system is depending on the accuracy of orbit determination for the space debris which has collision risk. Therefore, this system must treat many kinds of measurement data types to estimate the orbit of space debris. In this paper, to handle the radar observation data widely used for these space debris, the orbit determination system was applied with simulated radar tracking data for the KOMSAT-2 which has precise orbit determination data.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.12 no.6
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• pp.999-1005
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• 2008

RFID(Radio Frequency IDintification) leader is collision of data, when recognizing the multiple tag the inside area. This collision became the cause which delays the tag recognition time of the leader. The protocol which prevents the delay of tag recognition time of the leader the place where representative it uses QT(Query Tree) algorithms, it uses a collision bit position from this paper and are improved QT-MTC(Query Tree with Multi-Tag Cognition) algorithms which it proposes. This algorithm stored the bit position which bit possibility and the collision where the collision happens occurs in the stack and goes round a tree the number of time which, it reduced could be identified two tags simultaneously in order, it was planned. A result of performance analysis, It compared in QT protocols and the this algorithm against the tag bit which is continued a high efficiency improvement effect was visible.