• Annual Conference of KIPS
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• 2008.05a
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• pp.893-896
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• 2008

기존의 무선 센서 네트워크에서는 센서 노드는 하나의 전방향성 안테나와 하나의 무선 채널을 공유하여 데이터를 전송하므로 과다한 채널 경쟁과 센서 노드간의 데이터 충돌로 데이터 재전송이 자주 발생하여 불필요한 에너지의 소비가 많고, 소스 노드와 목적지 노드의 데이터 전송시 RTS(Request To Send)와 CTS(Clear To Send) 패킷을 사용하여 전파 전송 범위 전체에 대해 채널 예약을 하므로 공간의 활용도가 낮은 편이다. 본 논문에서는 전방향성 안테나의 문제점 및 단점을 보완하기 위한 방법으로 지향성 안테나를 사용하기 위한 SRDMAC(Spatial Reuse Directional MAC) 프로토콜을 제안한다. 제안된 프로토콜은 센서 노드 간의 데이터 전송시 충돌을 방지하여 데이터 재전송에 소모되는 에너지와 목적지 노드가 위치한 영역 일부분에만 데이터를 전송함으로 에너지 소모량을 줄일 수 있으며, 목적지 노드가 위치한 영역을 제외한 다른 영역의 이웃 노드와의 데이터 전송이 가능하므로 공간 재 사용율을 최대한 증가시킬 수 있다.

• Journal of Internet Computing and Services
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• v.10 no.2
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• pp.133-141
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• 2009

A tag collision problem occurs when many tags are placed in a interrogation zone in RFID system. A tag collision problem is one of core issues and various protocols have been proposed to solve the collision problems. Generally tree-based protocols generate unique prefixes and identify tags with them as quick as possible. In this paper, we propose the QT-BCS protocol which decreases the identification time by reducing the number of query-response. The QT-BCS protocol makes a prefixes using time slot and bit change sensing unit. This protocol compares the current bit of tags until the current bit is differ from the previous one. When this occurs, all of the bits scanned so far are transferred to slot-0 and slot-1 depending on the first bit value in Reader. Consequently, this method can reduce the number of queries by tracing prefixes easily. Simulation result shows QT-BCS is more efficient in identifying tags than Query Tree and 4-ary Query Tree protocol.

• Journal of the Korean Society of Marine Environment & Safety
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• v.27 no.1
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• pp.67-73
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• 2021

The purpose of this study is to obtain a safe area for a passing vessel between anchored vessels by developing a model to predict the collision risk, frequent collisions occur between the anchored vessel and the passing vessel through the anchorage. For this, this study selected the southern anchorage of Busan port, which is the largest harbor in Korea, as the target area and extracted and analyzed VTS (Vessel Traffic Service) data during the period in which anchored vessels were the most waited. The ratio of D/L for each bearing was obtained to determine the safe distance (D) passes based on the length (L) of the passing vessel between anchored vessels. Based on the average domain of the D/L ratio distribution, the percentage of anchored vessels within the scope of the pre-studied ship's domain was analyzed to obtain a domain reflecting the degree of risk of VTSOs. Further research will evaluate and analyze the collision risk of a passing vessel using Domain-watch, the minimum safe distance between anchored vessels, and the safe domain of a passing vessel through anchorage, to develop a model for VTS to manage anchorages more efficiently and safely.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.21 no.5
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• pp.103-111
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• 2021

The purpose of this study is to study a method for preventing collisions of multiple drones in controlled airspace. As a result of the study, it was proved that it is appropriate as a method to control drone collisions after setting accurate information on the ROI (Region of Interest) area estimated based on the expected drone path and time in the control system as a method to avoid drone collision. As a result of the empirical analysis, the diameter of the flight path of the operating drone should be selected to reduce the risk of collision, and the change in the departure time and operating speed of the operating drone did not act as an influencing factor in the collision. In addition, it has been demonstrated that providing flight priority is one of the appropriate methods as a countermeasure to avoid collisions. For collision avoidance methods, not only drone sensor-based collision avoidance, but also collision avoidance can be doubled by monitoring and predicting collisions in the control system and performing real-time control. This study is meaningful in that it provided an idea for a method for preventing collisions of multiple drones in controlled airspace and conducted practical tests. This helps to solve the problem of collisions that occur when multiple drones of different types are operating based on the control system. This study will contribute to the development of related industries by preventing accidents caused by drone collisions and providing a safe drone operation environment.

• Transactions of the Korean Society of Mechanical Engineers
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• v.15 no.1
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• pp.98-106
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• 1991

Future generation of robots will be considerably more autonomous than present robotic systems. The main objective of research on theoretical problems in robotics is to endow robotics system with basic capabilities they will need to operate in an intelligent and autonomous manner. This paper discusses the problem of collision free movement of robot manipulator. It is formulated in path planning with obstacle avoidance expressed in the term of the distance between convex shapes in the three dimensional space. The examples are given to illustrate the main feature of the method.

• Journal of Advanced Marine Engineering and Technology
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• v.21 no.1
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• pp.37-42
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• 1997

Turbulent flow characteristics of a two - dimensional oblique plate impinging jet(OPIJ) were experimentally investigated. The jet mean velocity and turbulent intensity profIles were also measured along the plate. The jet Reynolds numbers(Re, based on the nozzle width)ranged from 10, 000 to 35, 000, the nozzle - to - plate distance(H/B) from 2 to 16, and the oblique angle (a) from 60 to 90 degree. It has been found that the stagnation point shifted toward the minor flow region as the oblique angle decreases and the position of the stagnation point nearly coin¬cided with that of the maximum turbulent intensity.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2017.11a
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• pp.262-265
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• 2017

This study is to calculate the Real-Time Overlapped Area of ellipses with weight by Ship's Bumper Theory. In this paper, The Real-Time Overlapped Area of ellipses with weight can be used the important tool to feel the perceived risk evaluation by navigator. In this paper, through how to feel the risk of collision between the vessels in advance, We will study the technique to certify the perceived risk of collision from several different angles.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 2004.10a
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• pp.285-288
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• 2004

스마트 홈은 유비쿼터스 환경의 각종 센서와 정보가전에서 얻어지는 데이터에서 사용자의 Context를 추출하여 사용자에게 적응적인 서비스를 제공한다 지금까지의 Context는 사용자가 한 명일 경우를 가정하였지만 실제 집이라는 공간은 가족이라는 구성원이 함께 생활하는 공간으로 동시에 여러 개의 Context가 존재하며 이러한 Context는 서로 충돌할 수도 있다. 본 논문에서는 집에서 여러 Context들 간에 충돌이 일어났을 때 이를 해결하는 방법을 제안한다. 집은 여러 사용자가 공유하고 있지만 각 구성원의 침실이나 화장실처럼 한 개인의 영역이 존재한다 또한 침실은 쉬는 곳, 주방은 요리를 하고 음식을 먹는 곳, 거실은 가족끼리의 모임을 갖거나 TV 시청, 음악감상 등의 여가를 즐기는 곳 등 공간마다 나름의 용도를 가지고 있다 본 논문은 Context들간의 충돌을 조정을 위해 이러한 공간의 특성을 이용할 것을 제안한다.

• Proceedings of the KSME Conference
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• 2008.11b
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• pp.2804-2809
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• 2008

Experimental results and numerical computations were conducted to investigate the effect of the confined wall on the flow and heat transfer characteristics for a two-dimensional impinging jet. Experimental results and Numerical solutions were obtained by using the particle image velocimetry and the commercial CFD code (CFX 11), respectively. The parameters studied were jet Reynolds number (Re=5,000), conditions of confined wall (unventilate), nozzle to plate spacings ($H/W=1{\sim}16$), and nozzle to nozzle spacing (S/W=6). Experimental and numerical results were agreed well with each other. The maximum heat transfer point was found variation of nozzle to plate spacings.

• Annual Conference of KIPS
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• 2013.11a
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• pp.329-332
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• 2013

본 논문에서는 매크로기지국과 펨토기지국의 간섭을 회피하는 방법인 자원대체 간섭회피기법을 제안한다. 이 기법은 펨토셀 영역의 여유로운 자원을 할당받은 후에, 이기종망 간의 발생할 수 있는 충돌을 미리 검사하고 충돌이 예상되면 충돌가능자원을 회피하고 여유로운 자원으로 대체하여 통신을 한다. 본 기법을 적용하면 하향링크 및 상향링크에서 이기종망 간의 직교주파수를 적용하면서 발생할 수 있는 지연을 최소화 할 수가 있으며, 이기종망 간에서 주파수를 분할하여 통신을 하는 SFR 기법과 비교하여, 자원의 효율성을 높일 수가 있다.