• 한국정보처리학회:학술대회논문집
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• 한국정보처리학회 2002년도 추계학술발표논문집 (중)
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• pp.1663-1666
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• 2002

PIM-SM은 특정 라우터를 RP(Rendezvous Point)로 설정하여 이 RP를 루트로 하고 한 그룹 내에서 공유하는 RPT(RP-rooted Shared Tree)를 사용한다. 초기에는 RPT를 통해 전송이 이루어지지만 마지막 홉 라우터에 트래픽 임계치의 값이 설정되어, 한 그룹에 대한 임계값이 초과되었을 경우 RPT에서 수신자가 소스를 루트로하는 SPT(Shotrest Path Tree)로 트리 전환을 시도한다. 그러나 RPT에서 SPT로 전환하는 동안 네트워크 내부의 전송상태 결여로 인해 패킷손실이 발생하고 소스의 데이터 패킷이 수신자에게 전달되지 못한 가능성이 발생한다. 본 연구에서는 유동적인 망의 전송되는 데이터의 양이 일시적으로 증가했을 때 임계치의 값에 따른 패킷 손실율을 조사하여 최적의 임계피를 찾아낸다.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2007년도 하계종합학술대회 논문집
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• pp.193-194
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• 2007

We propose The Fast Join Mechanism for overlay multicast. This mechanism is provided with RP(Rendezvous Point), SM(Session Manager) and overlay multicast nodes. The RP provides data transfer to overlay multicast nodes and the Session Manager controls overlay multicast nodes to maintain the overlay topology.

• 천문학회보
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• 제46권2호
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• pp.59.2-59.2
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• 2021

On March 6 2021, Apophis made a close approach to the Earth with a minimum distance of 0.11 AU when the apparent magnitude reached up to V~16. This was the most favorable condition to observe this asteroid until its 2029 encounter. The observations during this apparition were extremely important to determine major physical properties, such as size, rotational state, 3D shape model, surface mineral properties. So, we organized the observation campaign during the 2021 apparition. The main goals of our campaign are to refine the spin state and 3D shape model and check the surface composition variations. The campaign involved dozens of countries and included ground-based photometry and spectroscopy, and spacecraft observations. Our timely observation campaign will provide essential data in planning the operation scenario for the space mission. In this presentation, we will report the preliminary result of the Apophis observation campaign during the 2021 apparition.

• 로봇학회논문지
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• 제19권1호
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• pp.71-78
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• 2024

The paper presents a hardware-in-the-loop (HIL) system designed for satellite movement testing in the microgravity environment on the ground with two industrial robots. Especially, the paper deals with the contact between satellites during rendezvous and docking simulations of satellites using a robotic HILS system. For this purpose, the admittance control method plays a core role in preventing damage to the satellite or robot from contact force between satellites. The coordinate frames are transformed into the mass center of the satellite and the admittance control at the level of exponential coordinates is adopted to actively use the properties of Lie groups related to tracking errors. These methods effectively mitigate the risk of robot damage during inter-satellite contact and ensure efficient tracking performance of satellite movements.

• 정보처리학회논문지C
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• 제8C권1호
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• pp.60-67
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• 2001

인터넷에서 멀티미디어 서비스를 지원하기 위한 멀티캐스트 프로토콜은 트리 구성 방식에 따라 공유 트리 방식과 소스 기반 트리 방식으로 나눌 수 있는데, 공유 트리 방식이 확장성 측면에서 보다 우수하다고 알려져 있다. 공유 트리 방식에서 QoS를 만족시키기 위해 고려해야 할 핵심 사항 중 하나인 RP (Rendezvous Point) 선정에 대하여 일반적으로 QoS 제약 조건에 따라 별도의 과정을 거쳐 RP를 계산하는 방식으로 연구가 되고 있다. 또한 멀티캐스트 그룹 멤버가 동적으로 가입 또는 탈퇴를 할 경우에는 초기에 설정된 RP가 신규 멤버까지는 QoS를 만족시키지 못하는 경우가 발생하게 되므로, 신규멤버 까지 QoS를 보장하는 새로운 RP를 재선정할 필요가 있는데, RP재선정에 관한 기존 연구는 매우 미흡한 실정이다. 본 논문에서는 공유 트리 방식에서 RP 초기 선정 방식과 RP 재선정 방식에 RTCP(Real Time Control Protocol) 패킷을 이용하는 새로운 기법을 제안한다. 본 논문에서 제안하는 방식은 멀티미디어 서비스를 제공할 때 이용하는 RTCP 패킷을 그대로 활용함으로써 RP계산을 위한 별도의 정보 수집 과정을 필요로 하지 않는다. 모의 실험을 통하여 제안된 방식이 초기 RP선정 시 에는 임의 선정, 위상 기반 선정 방식보다 40∼50% 정도, 멀티캐스트 그룹멤버의 동적 변화 시에는 초기 RP를 그대로 이용하는 방식보다 50% 정도의 개선 효과를 보였다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제12권6호
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• pp.2513-2533
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• 2018

In cognitive radio technology, the overall efficiency of communications systems can be improved without allocating additional bands by allowing a secondary system to utilize the licensed band when the primary system, which has the right to use the band, does not use it. In this paper, we propose a fast and reliable common channel initialization protocol without any exchange of initialization messages between the cluster head and the member nodes in cognitive ad-hoc networks. In the proposed method, the cluster and member nodes perform channel-based spectrum sensing. After sensing, the cluster head transmits a system activation signal through its available channels with a predetermined angle difference pattern. To detect the cluster head's transmission channels and to join the cluster, each member node implements fast Fourier transform (FFT) and computes autocorrelation for the angle difference sequence of the received signal patterns. This is compared to the predetermined reference angle difference pattern. The join-request and channel-decision procedures are presented in this paper. Performance evaluation of the proposed method is presented in the simulation results.

• 한국컴퓨터정보학회논문지
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• 제6권2호
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• pp.116-122
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• 2001

기존의 멀티캐스트 보안 프로토콜은 DVMRP, CBT와 같이 비교적 규모가 큰 라우팅 프로토콜에 적합하도록 설계되어 있어서 사용자가 비교적 적고 호스트들간의 지역적인거리가 멀고 최단경로 라우팅 특성을 가지는 PIM-SM(Protocol Independent Multicast-Sparse Mode) 라우팅 프로토콜을 지원하는데 무리가 있다. 본 연구에서는 모든사용자간의 가입/탈퇴시 또는 서비스 사용 중에 사용자의 정당한 서비스 보호를 위해 서브그룹을 RP단위로 나누고, 송신자만의 비밀키를 따로 관리하는 보안 구조를 설계하였다. 그결과 데이터 전송 시 그룹 키에 의한 자료 변환 작업이 불필요하여 키 분배시간이 단축되고, 다른 보안 구조에 비해 구조가 보다 간단해졌다.

• 천문학회보
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• 제40권2호
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• pp.45.1-45.1
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• 2015

Hayabusa is the JAXA's space mission that succeeded in sample-return from S-type asteroid (25143) Itokawa. During the rendezvous phase, more than a thousand of images were taken with the Asteroid Multi-band Imaging Camera (AMICA). It is valuable to study the regional variation of the optical properties on the asteroid using these images to know the generality and uniqueness of the returned samples. In addition, AMICA images are important in that they provide unique data set at low phase angle (i.e Sun-Itokawa-AMICA's angle) that have not been explored in the previous asteroidal missions. At the previous conference (2015 KAS spring meeting), we introduced our preliminary data analysis of AMICA data without considering the shape model of Itokawa and mentioned. In this study, we present a new result obtained through further analysis, taking account of the shape model of the asteroid. We thus utilized "plate_renderer" tool to derive Hapke model parameters at different terrains. It is found that the opposition amplitude (parameter B0) is consistent with those of the other S-type asteroids while the opposition width (parameter h) is significantly narrower than those of the other S-type asteroids. At this conference, we plan to describe the regional variation of photometric properties on Itokawa.

• 한국실내디자인학회:학술대회논문집
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• 한국실내디자인학회 2006년도 춘계학술발표대회 논문집
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• pp.67-70
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• 2006

In modern society industrial structure is being altered in complex and various way owing to rapid technical development and economic development, and concerns and recognition for surrounding environment is being moth heightened. For this reason, modern people requite the environment which can be applied in more pleasant and convenient way, and in order to satisfy such requirements, importance of the interior design mote vividly stands out, and concerns or the society for the design is being more Heightened these days. Especially, as for the design of the office space, the study transforming the office, which is the rendezvous of the information, into the business environment with more comfortable and sensitivity, being free rrom the design concentrated on the business efficiency and economic feasibility, has been actively proceeded. As it is the reality that various and new types of the business spaces have appeared, new office landscape design is requited as the device to solve the matter related to the society change. It is purposed to propose the office space which is comfortable together with flowing sensitivity by applying the color plan that unconsciously controls the human sense through remodeling of mid size of the office space.

• Journal of Information Processing Systems
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• 제12권4호
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• pp.577-590
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• 2016

We studied the current state-of-the-art of Smart TV, the challenges and the drawbacks. Mainly we discussed the lack of end-to-end solution. We then illustrated the differences between Smart TV and IPTV from network service provider point of view. Unlike IPTV, viewer of Smart TV's over-the-top (OTT) services could be global, such as foreign nationals in a country or viewers having special viewing preferences. Those viewers are sparsely distributed. The existing TV service deployment models over Internet are not suitable for such viewers as they are based on content popularity, hence we propose a community based service deployment methodology with proactive content caching on rendezvous points (RPs). In our proposal, RPs are intermediate nodes responsible for caching routing and decision making. The viewer's community formation is based on geographical locations and similarity of their interests. The idea of using context information to do proactive caching is itself not new, but we combined this with "in network caching" mechanism of content centric network (CCN) architecture. We gauge the performance improvement achieved by a community model. The result shows that when the total numbers of requests are same; our model can have significantly better performance, especially for sparsely distributed communities.