• Proceedings of the KSR Conference
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• 2003.10c
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• pp.594-599
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• 2003

This paper proposed to compare and analyze the data throughput of ALOHA and Slotted-ALOHA method which were used to the communication of satellites in an early stage and apply to the data throughput of a transponder in an RFID system. The ALOHA method is the operation priority to a transponder but the Slotted ALOHA method is the operation priority to an reader in an RFID system. Because ALOHA method transmits the data to an reader as a authority of a transponder at random time when generating collisions, therefore, it seems reasonable to conclude that ALOHA method is inefficient for the data throughput and the efficiency of collision interval than Slotted-ALOHA method that synchronizes and controls the transponder in an reader.

• Journal of Institute of Control, Robotics and Systems
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• v.3 no.3
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• pp.227-237
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• 1997

Autonomous Underwater Vehicles(AUVs) have become an important tool for various purposes in subsea: inspection, recovery, construction, etc., and the development of autonomous control system is luglay desirable- thete zffe many problems associated with designing the control system for AUV due to unknown underwater envimn-Tnent, the possibility of subsystem failures, and unpredictable changes in the dynamics of the vehicle. In this paper, an autonomous control system based on the intelligent control theory to enhance operation efficiency of the ALTV is presented. The control system has a hierarchical structure which consists of mission planning level, mission control level, navigation level, and execution level. The performance of the control system is investigated by computer simulation. The results show that the proposed control system can be applied successfully to the AUV in spite of the possibility of failures in the vehicle and the collision hazard in the sea environment.

• Proceeding of EDISON Challenge
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• 2016.03a
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• pp.576-581
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• 2016

해양환경에서 큰문제가 되고 있는 아주 작은 크기의 플라스틱 입자인 미세플라스틱(Microplastic)은 잔류성이 크고 생물축적성이 있는 잔류성 유기오염 물질(POP)을 잘흡착하여 해양환경과 먹이사슬에 지대한 피해를 끼친다. 본 연구에서는 해양에 존재하는 대표적인 미세플라스틱 uPVC와 입자상의 잔류성 유기오염 물질 PAH를 원형 실린더로 가정하여 해양 환경에서 침강하고 있는 미세플라스틱이 잔류성 유기오염 물질에 의해 오염될 가능성을 알아보았다 이를 위해 표층및 심층수 환경에서 반지름에 따른 충돌효율과 접촉 시간을 구하여 두 실린더가 접촉할 시간의 기댓값인 기대 접촉시간을 계산하였다.

• Proceedings of the Korean Information Science Society Conference
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• 2005.07a
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• pp.427-429
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• 2005

Energy efficiency is the most challenging issue in wireless sensor network to prolong the life time of the network, as the sensors has to be unattended. Cluster based communication can reduce the traffic on the network and gives the opportunity to other sensors for periodic sleep and thus save energy. Passive clustering (PC) can perform a significant role to minimize the network load as it is less computational and light weight. First declaration wins method of PC without any priority generates severe collision in the network and forms the clusters very dense with large amount of overlapping region. We have proposed several modifications for the existing passive clustering algorithm to prolong the life time of the network with better cluster formation.

• Bulletin of the Korean Chemical Society
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• v.20 no.12
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• pp.1441-1446
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• 1999

Laser-induced fluorescence (LIF) spectroscopy has been applied to study the supersonic jet of radicals of nitric oxide (NO) and atomic iodine produced in the flash pyrolysis of precursors n-butylnitrite (CH₃(CH₂)₃ONO) and allyl iodide (C₃$H_5$I), respectively. The systematic population analysis with spectral simulations demonstrates that the precursors are efficiently pyrolyzed and that radical beams show a substantial supersonic cooling. In addition, absence of local equilibrium was observed in the distributions of two electronic spin-orbit states ²Π$_{1/2}$ and ²Π$_{3/2}$ of NO products and can be rationalized in terms of the efficiency of collision-induced energy transfer rates.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.13 no.8
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• pp.4060-4075
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• 2019

ACORN is an authenticated encryption algorithm proposed as a candidate in the currently ongoing CAESAR competition. ACORN has a good performance on security and efficiency which has been a third-round candidate. This paper mainly concentrates on the security of ACORN under the forgery attack and the non-repudiation of ACORN. Firstly, we analyze the differential properties of the feedback function in ACRON are analyzed. By taking advantage of these properties, the forgery attacks on round-reduced ACORN are proposed with a success probability higher than $2^{-128}$ when the number of finalization rounds is less than 87. Moreover, the non-repudiation of ACRON in the nonce-reuse setting is analyzed. The known collision can be used to deny the authenticated message with probability $2^{-120}$. This paper demonstrates that ACORN cannot generate the non-repudiation completely. We believe it is an undesirable property indeed.

• Journal of IKEEE
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• v.25 no.4
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• pp.728-734
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• 2021

In recent years, there has been a strong interest in the end-to-end autonomous driving based on deep reinforcement learning. In this paper, we present a reward function of latent SAC deep reinforcement learning to improve the longitudinal driving performance of an agent vehicle. While the existing reward function significantly degrades the driving safety and efficiency, the proposed reward function is shown to maintain an appropriate headway distance while avoiding the front vehicle collision.

• The Journal of Korea Robotics Society
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• v.17 no.2
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• pp.110-117
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• 2022

This paper describes a localization algorithm utilizing relative observations for multiple autonomous underwater vehicles (Multiple-AUVs). In order to maximize the efficiency of operation and mission accomplishment and to prevent problems such as collision and interference, the locations and directions of Multiple-AUVs must be precisely estimated. To estimate the locations and directions, we designed a localization algorithm utilizing relative observations and verified it with simulations based on sensor data sets acquired through real sea experiments. Also, an optimal combination of relative observation information for efficient localization is figured out through combining various relative observations. The proposed method shows improved localization results compared to those only using the navigation algorithm. The performance of localization is improved up to 58% depending on the combination of relative observations.

• Journal of Navigation and Port Research
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• v.39 no.3
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• pp.199-207
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• 2015

In ports of Korea, the marine traffic flow is congested due to a large number of vessels coming in and going out. In order to improve the safety and efficiency of these vessels, South Korea is operating with a Vessel Traffic Service System, which is monitoring its waters for 24 hours. However despite these efforts of the VTS (Vessel Traffic Service) officers, collisions are occurring continuously, the risk situation is analyzed that occurs once in about 20 minutes, the risk may be greater. It investigated to reduce these accidents by providing a safety standard for collision danger in a timely manner. Thus, this study has developed a risk prediction module to predict risk in advance. This module can avoid collision risk to adjust the speed and course of ship using a risk evaluation model based on ship operator's risk perspective. Using this module, the ship operators and VTS officers can easily be identified risks in complex traffic situations, so they can take an appropriate action against danger in near future including course and speed change. To verify the effectiveness of this module, this paper predicted the risk of each encounter situation and confirmed to be capable of identifying a risk changes in specific course and speed changes at Busan coastal water.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.1B
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• pp.42-48
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• 2002

In broadband wireless networks, the effective meeting of the QoS guarantees may strongly depend on the Contention Resolution Algorithm used in the uplink contention period. The time it takes a station to transmit a successful request to the base station, or request delay, must be kept low even during periods of high contention. If a request suffers many collisions, it cannot rely on the preemptive scheduler to receive low access delays. However, the conventional collision resolution algorithm has a problem that all collided stations are treated equally regardless of their delay from previous contention periods. Some requests may have very long request delay caused by continuous collisions. In this paper, we propose an adaptive collision resolution algorithm for fast random access in broadband wireless networks. The design goal is to provide quick access to the request with a high number of collisions. To do this, the proposed algorithm separates the whole contention region into multiple sub regions and permits access through each sub region only to the requests with equal number of collisions. The sub region is adaptively created according to the feedback information of previous random access. By simulation, the proposed algorithm can improve the performance in terms of throughput, random delay and complementary distribution of random delay by its ability to isolate higher priorities from lower ones. We can notice the algorithm provides efficiency and random access delay in random access environment.