• Journal of Information Processing Systems
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• 제11권1호
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• pp.95-103
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• 2015

This paper presents a memory efficient tree based anti-collision protocol to identify memoryless RFID (Radio Frequency Identification) tags that may be attached to products. The proposed deterministic scheme utilizes two bit arrays instead of stack or queue and requires only ${\Theta}(n)$ space, which is better than the earlier schemes that use at least $O(n^2)$ space, where n is the length of a tag ID in a bit. Also, the size n of each bit array is independent of the number of tags to identify. Our simulation results show that our bit array scheme consumes much less memory space than the earlier schemes utilizing queue or stack.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2011년도 춘계학술대회
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• pp.234-236
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• 2011

Saigon Port within the port system of the Vietnam Maritime sector is one of the port having highest throughput and productivity in the country. The marine traffic of Saigon water ways is the heaviest in Vietnam and the number of marine accidents in this area are much higher than the others area in Vietnam. In order to reduce the risk of the accident in Saigon fairway, this paper concentrates on marine accident frequency in this area. The marine traffic and the marine accident were analyzed to find out the probability of vessel collision and the marine traffic risk. It follows that the main shipping route through Saigon fairway has the high risk of ship-ship collision.

• 대한금속재료학회지
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• 제46권8호
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• pp.506-515
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• 2008

Recently, it is exceedingly required to produce metal powders with tailored shape and phase altogether in order to fabricate high performance functional parts such as magnetic core or electro-magnetic noise suppressor for high frequency usage. Therefore, the collision phenomena of in-flight droplets against chamber wall or neighboring in-flight droplets each other is investigated by a computational method in order to get useful information about how to design the atomizing system and how to tailor process parameters not to make irregular-shaped powders during gas atomization process. As a results, smaller powders, lower melt temperature are known to be favorable for droplets not to collide against chamber wall. In additions, powders of narrower size distribution range, lower droplet generation rate, lower melt temperature, lower gas velocity are desirable to prevent droplet-collisions against neighboring in-flight droplets.

• 해양환경안전학회지
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• 제27권2호
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• pp.238-246
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• 2021

어선과 같은 소형선박의 충돌사고는 큰 인명피해를 초래한다. 본 연구 이전에 선행된 연구에서는 충돌위험을 판단하고 경보를 발생시키는 소형선박 충돌예방 알고리즘을 개발하였다. 하지만 충돌경보와 같이 안전을 위해 제공되는 서비스는 위험을 예방할 뿐 아니라 이용자의 만족도 또한 어느 정도 수반되어야 효과적으로 기능할 수 있다. 본 연구에서는 소형선박 충돌예방 알고리즘의 실용성 향상을 위해 알고리즘을 개선하고, 알고리즘을 실제로 적용하여 개선결과 및 효과를 확인하고자 하였다. 충돌경보 서비스를 사용한 소형선박 운항자들을 대상으로 설문조사를 수행한 결과, 충돌경보의 정확도 향상과 경보 횟수 및 음량에 대한 사용자들의 요구사항이 확인되었다. 이에 따라 본 연구에서는 사용자 만족도 향상을 위해 알고리즘을 개선하였으며 실제 해상환경에서 개선된 알고리즘을 적용한 실선실험을 수행하였다. 그 결과 개선 전보다 경보 발생 빈도가 감소하였지만, 위험한 상황에서는 경보가 비교적 꾸준히 발생하였으며, 충돌경보의 정확성과 실용성이 향상된 것으로 분석되었다. 추후에는 개선된 알고리즘의 적정성에 대한 근거자료를 마련하여 알고리즘의 실용성과 신뢰성을 확보한다면 소형선박 충돌사고 예방에 효과적으로 기여할 수 있을 것이다.

• 해양환경안전학회지
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• 제23권3호
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• pp.231-241
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• 2017

The purpose of this study was to analyze traffic safety assessments for fishing vessels near the southwest offshore wind farm. This study applied a collision model for safety assessment. It also involved a spatiotemporal analysis of vessels engaged in fishing to identify fishing hotspots around the offshore wind farm. This study used data from fishing vessel location transmission devices gathered over 1 year in 2014. As a result, in September, when the average number of vessels engaged in fishing is high, 62 ships were operating in fishing section 184-6 and 55 ships in section 184-6. In addition, in fishing sections 184-8 and 192-2, where an offshore wind farm was located, there were 55 and 38 ships operating, respectively. As the recovery period for a seaway near wind farm turbines is 55 years, it was determined that safety measures are required in order to reduce collision frequency while allowing fishing vessels to navigate through offshore wind farms. Meanwhile, the return period of Seaway B between the groups of generators considered was 184 years. A safety zone for offshore wind farms should be installed covering a distance of at least 0.3 NM from the boundary of turbines. Then, the collision return period was derived to be close to 100 years. Through this traffic safety assessment, it has been concluded that such measures would help prevent marine accidents.

• 한국정보과학회논문지:컴퓨팅의 실제 및 레터
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• 제14권9호
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• pp.884-891
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• 2008

RFID 시스템이 그 규모가 커짐에 따라 리더 충돌에 따른 인식률 저하 문제가 대두되고 있다. 시분할 기법을 사용하면 충돌문제를 해결할 수 있지만, 전체 인식시간은 늘어가게 된다. 이 문제는 RFID를 이용한 실시간 재고관리를 위해 해결해야만 한다. 본 연구에서는 ARCM(Anti Reader Collision Manager)을 RFID 시스템에 두어 전체 인식시간을 개선하였다. ARCM은 효율적인 주파수 채널 사용으로 짧은 인식시간을 가지며 리더가 간섭을 회피해 태그를 인식할 수 있도록 RFID 시스템을 관리한다. ARCM을 사용한 결과, 기존의 시스템보다 최대 20%정도의 시간을 절약할 수 있었다.

• 한국통신학회논문지
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• 제32권8A호
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• pp.847-857
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• 2007

RFID(Radio Frequency IDentification) 리더기가 영역내의 다수의 태그를 인식하기 위해선 충돌방지 알고리즘이 반드시 필요하다. 본 논문은 Auto ID Class 0에서 정의한 충돌방지 알고리즘인 Bit-by-Bit(BBB) 이진트리 알고리즘의 충돌 위치를 스택에 저장하고 이를 통해 다음 질의어를 결정함으로써 성능이 크게 개선된 Stack-Bit-by-Bit(SBBB) 알고리즘을 제안한다. 시뮬레이션을 통한 검증결과 대표적인 충돌 방지 기술인 Query Tree(QT)는 물론 기존의 BBB 알고리즘에 비해 질의-응답 횟수, 질의어의 크기, 응답어의 크기의 모든 면에서 성능이 개선된 것을 확인할 수 있었다.

• 융합신호처리학회논문지
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• 제9권1호
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• pp.46-53
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• 2008

본 논문에서는 지능형 홈 시큐리티의 도어록 시스템으로 사용될 수 있는 13.56 MHz RFTD(Radio Frequency IDentification) 시스템 설계 및 구현에 관한 내용을 다룬다. RFID는 리더와 태그 및 호스트 컴퓨터로 구성되는 시스템으로서, 리더와 태그간의 유도성 결합이나 전자기적 결합방식에 의해, 태그의 정보를 주고받는 비접촉 시스템이다. RFID 리더의 송신부, 수신부를 PSPICE를 이용해 설계하고 시뮬레이션을 통해 동작을 검증하였다. 아울러 에러 검출 모듈과 맨체스터 코딩 모듈은 VHDL 언어를 이용해 설계하고 시뮬레이션을 통해 동작을 검증하였다. 데이터 처리부의 충돌방지(Anti-collision) 기능은 별도의 컨트롤러를 사용하여 소프트웨어적으로 구현하였다. 구현된 시스템의 성능시험을 위해 5개의 RF 태그 환경에서 실험한 결과 데이터의 충돌 없이 모든 태그의 데이터를 올바르게 인식하였다.

• 한국해양공학회지
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• 제37권3호
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• pp.111-121
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• 2023

This paper intends to introduce the applicability of HydroQus to a problem of a tanker collision against a semi-submersible type floating offshore wind turbine (FOWT). HydroQus is a plug-in based on potential flow theory that generates interactive hydroforces in a commercial Finite element analysis (FEA) code Abaqus/Explicit. Frequency response analyses were conducted for a 10MW capacity FOWT to obtain hydrostatic and hydrodynamic constants. The tanker was modeled with rigid elements, while elastic-plastic elements were used for the FOWT. Mooring chains were modeled to implement station keeping ability of the FOWT. Two types of fracture models were considered: constant failure strain model and combined failure strain model HC-LN model composed of Hosford-Coulomb (HC) model & localized necking (LN) model. The damage extents were evaluated by hydroforces and failure strain models. The largest equivalent plastic strain observed in the cases where both restoring force and radiation force were considered. Stress triaxiality and damage indicator analysis showed that the application of HC-LN model was suitable. It could be stated that applications of suitable failure strain model and hydrodynamics into the collision simulations were of importance.

• 한국항해학회지
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• 제12권1호
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• pp.71-84
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• 1988

For traffic proceeding in random directions on a plane surface the frequency of collision, if no avoiding action in taken ,is approximately proportional to the square of the traffic density and directly proportional to the size and speed of the ship, Avoiding is normally taken and the rte of collisions is therefore also governed by additional factors such as the visibility, the effectiveness of the collisionavoidance rules, the competence of personnel or watchkeeping attitude, the maneuverability of the ship and the efficiency of radar and other equipments. From the viewpoint of watchkeeper who is responsible for maneuvering, watchkeeping attitude such as lookout and action to avoid collision is the most controllable factor among those mentioned above. In practice, according to the investigation of the institution of marine courts, about 50% co collisions occurred is caused by disorbedience to steering and sailing rules of international regulations for preventing collision at sea including lookout. So we classify the process of collisions with first sight of another ship , assessment of risk of collisions and action to avoid collisions and make a factural survey about lookout and action to avoid collisions from the point on "time" and " distance", namely relationship among ship's size, speed, first sight time of another ship, action to avoid collisions ,and distance from sight of another ship to collision occurred. According to the results of the actual survey , we come to conclude that most of collisions occurred are due to improper lookout and ineffective action to avoid collision which means time lag from first sight of another ship to time of action taken to avoid collision is relatively long. is relatively long.