• Journal of Communications and Networks
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• 제8권4호
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• pp.432-441
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• 2006

As the community antenna television (CATV) networks becomes ubiquitous, instead of constructing an entirely new broadband network infrastructure, it has emerged as one of the rapid and economic technologies to interconnecting heterogeneous network to provide broadband access to subscribers. How to support ubiquitous real-time multimedia applications, especially in a heavy traffic environment, becomes a critical issue in modern CATV networks. In this paper, we propose a time guaranteed and efficient upstream minislots allocation algorithm for supporting quality-of-service (QoS) traffic over data over cable service interface specification (DOCSIS) CATV networks to fulfill the needs of realtime interactive services, such as video telephony, video on demand (VOD), distance learning, and so on. The proposed adaptive fast expansion algorithm and the loading statistics with dynamic swapping algorithm have been shown to perform better than that of the multimedia cable network system (MCNS) DOCSIS.

• 해양환경안전학회지
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• 제5권1호
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• pp.37-45
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• 1999

In the decision of a collision avoidance action for navigators and intelligent ships, it is necessary to evaluate the degree of surrounding risks and to control them effectively. In this paper, we propose the new methodology for navigational risk evaluation and control at sea. In the methodology, navigation risk is evaluated in two dimensions using Even Risk Contour on the basis of the concept of contour line. In addition, the movement information of dangerous targets is assessed continuously and precisely with wide band data. The presented technique is useful for the safety navigation at the heavy traffic sea and will be applied for the ultra automatic ship.

• 한국산업융합학회 논문집
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• 제18권3호
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• pp.150-156
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• 2015

In this paper, it was proposed a new technology to improve the performance of the remote control in virtual reality applications. The operator must know the information of surroundings of the robot, collision possibility of the equipment, and force feedback of the manipulator. The time delay problem occurs in the tele-operating and it causes vibration and expressive power of the manipulator owing to bidirectional force feedback. We presented a new control method to control of the teleoperating system based on serial bus. The reliability is evaluated by simulation.

• 산업기술연구
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• 제15권
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• pp.5-13
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• 1995

Natural gas, which is getting more important as a fuel, should be liquefied and shipped in a special tank. During transportation, a spill of liquefied natural gas(LNG) could occur by a collision or even an accident. As a result, violent explosion called the superheat-limit explosion(SLE) can take place in some cases, unexpectedly. Such explosion may result from the formation of a superheated liquid which has attained the superheat-limit temperature when hot(water) and cold(LNG) liquids come into contact. Natural gas mixtures can be considered as discrete light components plus continuous heavy fractions where several continuous distribution function can be adopted. This work is aiming at prediction of the superheat-limit explosion condition by suing continuous thermodynamics development of algorithm to predict.

• Journal of Ship and Ocean Technology
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• 제3권1호
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• pp.12-26
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• 1999

A new concept of collision energy absorbing system for ;he New Oil-tankers with Advanced Double Hull Structure(NOAHS and NOAHS II) are presented through the joint-research pro-gran between Inha and Hamburg-Harburg University. A comparative study on col vision resistance of these proposed side structures with standard double hull structure of 310K DWT class VLCC, is carried out. The fatigue investigation of structural detail parts is also included. It contains a comparative fatigue study based on pertinent regulations of Classification Societies.

• Journal of information and communication convergence engineering
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• 제5권3호
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• pp.194-199
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• 2007

In this paper, a slotted CDMA_ALOHA protocol with hybrid ARQ is proposed for the wireless CDMA communication networks. The proposed protocol combines the characteristics of the slotted ALOHA, CDMA, and the hybrid ARQ, in order to increase the throughput by reducing the number of retransmissions when the channel experiences heavy traffic. The main feature of the proposed protocol is the utilization of the forward error correction capability to correct errors that appear after the CDMA dispreading of the packets. The base station does not need to ask so often for retransmission of erroneous packets. It will request for retransmission only when the FEC capability is exceeded. The performance of the proposed protocol is analyzed by considering the packet collision probability as well as the bit error probability. The numerical results show that the system throughput is closely related to the bit error rate of the wireless link and the FEC coding rate.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2004년도 추계 학술발표회 제16권2호
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• pp.381-384
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• 2004

Delaying and objection for the construction of storage spent-fuel disposal has prompted to consider expanding on-site storage of spent reactor fuel since it can eliminate the need for costly and difficult shipping and control of the spent fuel completely under the direction of the owner-utility. The dry storage unit developed in Canada can accommodate Korea heavy water reactor fuel elements and become a candidate for the Korean market. In this paper, finite element analyses were carried out in order to investigate the structural behavior of the nuclear spent fuel dry storage system, which is subjected to impact loads such as collision of a truck load and dropping of flask under the irregular operation.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2002년도 Proceedings of the International Welding/Joining Conference-Korea
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• pp.644-651
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• 2002

The formation and stability of stationary laser weld keyholes are investigated using a numerical simulation. The effect of multiple reflections in the keyhole is estimated using the ray tracing method, and the free surface profile, flow velocity and temperature distribution are calculated numerically. In the simulation, the keyhole is formed by the displacement of the melt induced by evaporation recoil pressure, while surface tension and hydrostatic pressure oppose cavity formation. At laser powers of 500W and greater, the protrusion occurs on the keyhole wall, which results in keyhole collapse and void formation at the bottom. Initiation of the protrusion is caused mainly by collision of upward and downward flows due to the pressure components.

• 한국항해항만학회지
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• 제38권1호
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• pp.19-27
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• 2014

선박이 천수 및 수로를 운항하는 경우, 바닥과 측벽의 영향으로 인해 선체침하 및 비대칭적인 힘이 선체 주위에 발생하여 바닥이나 다른 선박 혹은 수로의 벽에 충돌하는 현상이 발생한다. 특히, 수로가 많은 유럽이나 북미를 운항하는 해운회사와 항해사들은 선박의 충돌을 방지하기 위해서 중요한 문제로 다루고 있다. 본 연구에서는 선박의 안전한 항해를 위해 수치해석을 이용하여 선박과 수로의 벽 사이에 발생하는 유체역학적 힘인 횡력(Sway Force)과 선회 모멘트(Yaw Moment)를 정성적으로 추정하고자 하였다. 천수와 측벽효과(Bank Effect)를 해석할 수 있는 프로그램을 개발하여 크기가 다른 원유 운반선 2척에 대하여 선속, 수심 그리고 선박과 측벽 사이 거리의 변화에 따른 다양한 해석을 수행하였다. 계산된 결과는 시험 결과 및 기 발표된 수치해석 결과와 비교하였다.

• 한국인터넷방송통신학회논문지
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• 제19권4호
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• pp.47-54
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• 2019

전세계적으로 기후 변화의 영향에 따른 차량 추돌 사고에 대한 위험성이 중요한 이슈로 등장하고 있다. 고속주행차량의 속도제한을 위해 다양한 형태의 속도제한 표시장치가 고려되고 있으나 현재는 대부분 고정식 속도제한 표시기를 사용하고 있다. 4계절이 뚜렷한 우리나라의 경우에는 비가 많이 오는 우기나 눈이 많이 오는 계절이나 안개가 많이 발생되는 경우에는 차량 추돌 사고를 방지하기 위한 차량 속도 감속 제한이 필요하지만 기존에 설치되어 있는 고정식 표지판으로는 사고를 미연에 방지하는 것이 어려운 실정이다. 본 연구에서는 레인 센서와 차량 와이퍼 시스템 등을 결합 시킨 기후 변화에 따른 차량 속도 제한이 가변적으로 표시되는 LED 전광판의 프로토타입 모델을 제작하였다. 내리는 비나 눈의 양에 따라 기준속도의 100%, 80%, 50%로 3단계로 가변 표시되는 속도제한 표시기는 설치되는 장소에 따라 적절한 속도를 선택 지정하여 표시할 수 있다. LED 표시장치를 이용한 시각적인 효과로 인해 운전자들이 사전에 속도를 감속하게 하여 차량 추돌 사고를 미연에 방지하는데 효과적으로 이용될 것으로 기대 된다.