• KSII Transactions on Internet and Information Systems (TIIS)
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• v.7 no.7
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• pp.1624-1637
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• 2013

In RFID systems, one important issue is how to effectively address tag collision, which occurs when multiple tags reply simultaneously to a reader, so that all the tags are correctly identified. However, most existing anti-collision protocols assume isotropic collisions where a reader cannot detect any of the tags from the collided signals. In practice, this assumption turns out to be too pessimistic since the capture effect may take place, in which the reader considers the strongest signal as a successful transmission and the others as interference. In this case, the reader disregards the other collided tags, and in turn, fails to read the tag(s) with weaker signal(s). In this paper, we propose a capture effect-aware anti-collision protocol, called Multi-Round Collision Tree (MRCT) protocol, which efficiently identifies the tags in real RFID environments. MRCT deals with the capture effect as well as channel error by employing a multi-round based identification algorithm. We also analyze the performance of MRCT in terms of the number of slots required for identifying all tags. The simulation results show that MRCT significantly outperforms the existing protocol especially in a practical environment where the capture effect occurs.

• Journal of Navigation and Port Research
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• v.45 no.6
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• pp.298-305
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• 2021

Identifying the effect of turning characteristics on collision avoidance for Maritime Autonomous Surface Ships (MASS) can provide a key to avoid the collision of MASS. The purpose of this study was to derive a method to identify the effect of turning characteristics, which can be changed by various rudder angles and the ship's speed, on collision avoidance. The turning circle was observed using a mathematical model of a 161-meter-long ship, and it was analyzed that the turning circle had an effect on collision avoidance through numerical simulations of collision avoidance for four collision situations of two ships. The evaluation results using the two variables, the minimum relative distance between two ships and the minimum time at the minimum relative distance, demonstrated that the rudder angle has a major influence on the change of the minimum relative distance, and the ship's speed has a major influence on the change of the minimum time. The evaluation method proposed in this study was expected to be applicable to collision avoidance as a measures in remote control of MASS.

• Journal of Ocean Engineering and Technology
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• v.14 no.2
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• pp.28-35
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• 2000

In this paper a complicated structural behavior in collision and its effect of energy transmission to the collision bulkhead was examined through a methodology of the numerical simulation to obtain a ideal bow construction and a location of collision bulkhead against heat on collision. At present the bow structure is normally designed in consideration of its specific structural arrangement and internal and external loads in these areas such as hydrostatic and dynamic pressure wave impact and bottom slamming in accordance with the Classification rules and the specific location of collision bulkhead by SOLAS requirement. By these studies the behavior of the bow collapse due to collision was synthetically evaluated for the different size of tankers and its operational speed limits and by the results of these simulation it provides the optimal design concept for the bow construction to prevent the subsequent plastic deformation onto or near to the collision bulkhead boundary and to determine the rational location of collision bulkhead.

• Journal of Ship and Ocean Technology
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• v.5 no.3
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• pp.36-44
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• 2001

The collision energy absorbing characteristics of side structure of the LNG carriers which have the cargo containment systems of the spherical and the membrane types are compared. A failure mechanism of the double hull side structures of 130, 000 $m^3$ class LNG carriers under sideways collision event has been simulated by using the detailed finite element calculations. In ship collision analysis, the finite element method based on explicit time integration has been use[1 with much success. Finite element modeling techniques for detail description of structural members antral ship motion regarding the dynamic behavior allowed to investigate the effect of bow shape and the initial contact position on side shell of collided ship. In the numerical simulations of the ship-to-ship sideways collision, the effect of the colliding bow shapes and the change of the colliding ship draft are investigated. The critical collision energy which is absorbed by a side structure of a collided ship until the fore-end of colliding ship arrives at the boundary of the cargo tank is calculated. The critical speed of specified colliding ships which can not penetrate the boundary of the LNG cargo tank of the collided ship under collision accident if evaluated.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2005.04a
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• pp.696-703
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• 2005

Recently, the collision problems between a bridge and a navigating ship are frequently issued at the stage of structure design. Even the many study results about vessel to vessel collision are presented, but the collision studies between vessel and bridge structure have been hardly presented. In this study, nonlinear dynamic analysis of vessel and fender system carry out using ABAQUS/Explicit commercial program with consideration of some parameters, such as bow structure we composed to shell element also ship's hull is modeling to beam element. Also, buoyancy effect is considered as spring element. The two types of fender systems was comparable with both collision analysis about steel materials fender system and rubber fender system On the purpose of study is analyzed the plasticity dissipated energy of vessel and fender system. We blow characteristic that kinetic energy is disappeared by plastic large deformation in case of collision. Also, We considered dissipated kinetic energy considering friction effect.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2007.12a
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• pp.376-382
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• 2007

A Collapse of bridge by ship's collision to the bridge post may lead a great calamity. This paper investigates on avoiding collision between a ship and bridge by improvement of environmental factors, submitting a counter plan of reducing collision effect by triangular type of collision protecting bar and ship maneuvering skills. Putting up collision protecting bar fences of triangular type around the bridge posts would decrease the collision impact force by 75 percent.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2000.04a
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• pp.195-204
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• 2000

In this paper a complicated structural behavior in collision and its effect of energy translation to the collision bulkhead was examined through a methodology of the numerical simulation to obtain a ideal bow construction and a location of collision bulkhead against head on collision. In the present the bow structure is normally designed in consideration of its specific structural arrangements and internal and external loads in these area such as hydrostatic and dynamic pressure, wave impact and bottom slamming in accordance with the Classification rules, and the specific location of collision bulkhead by SOLAS requirement. By these studies the behavior of the bow collapse due to collision was synthetically evaluated for the different size of tankers and its operational speed limits, and by the result of these simulation it provides the optimal design concept for the low construction to prevent the subsequent plastic deformation onto or near to the collision bulkhead boundary and to determine the rational location of collision bulkhead.

• Journal of Auto-vehicle Safety Association
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• v.10 no.3
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• pp.7-12
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• 2018

The Korean New Car Assessment Program (KNCAP) is a program to evaluate the safety of automobiles. In the safety assessment method, there are frontal collision, partial frontal collision, side collision, pillar collision, and left stability in the collision safety category. Among them, Korean in-depth analysis data shows that there are a lot of side collision accidents and it is necessary to protect them. This study will analyze the side collision accident that occurred in actual traffic accident based on Korea In-Depth Accident Study (KIDAS) and investigate the effect of center airbag on passenger in under side collision. In addition, with simulated side collision scenarios in the various side impact directions, it was investigated how the center airbag affects the driver and passenger in terms of kinematic and injury levels.

• 한국전산유체공학회:학술대회논문집
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• 2008.03b
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• pp.320-323
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• 2008

In this study the effect of collision model was evaluated in spray field by CFD. A collision is basically the interaction between droplets and criteria of collision is determined by drop Weber number, impact parameter, and drop-size ratio. Early developed collision model considered coalescence and grazing collision with the exchange of momentum. However in experimental research there were bouncing, coalescence, reflexive separating and stretching separating in interaction between droplets. In this study the collision considering such complex phenomena is modeled and was compared with the basic collision model.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.11a
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• pp.663-666
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• 2004

An analysis of the annual frequency of collapse(AF) is performed for each bridge pier exposed to ship collision. AF is computed for each bridge component and vessel classification. The summation of AFs computed over all of the vessel classification intervals for a specific component should equal the annual frequency of collapse of the component. The designer should use judgment in developing a distribution of the vessel frequency data based on discrete groupings or categories of vessel size by DWT. In the present study the effect of vessel classification on the annual frequency of collapse in the ship collision risk assessment is investigated by illustrative numerical examples based on the vessel frequency data of the domestic harbor. The DWT interval for larger vessels has more effect on the ship collision risk. Therefore the expert judgement in determining the larger DWT interval is required because the design impact lateral resistances of bridge components depend on the ship collision risk.