• Proceedings of the Korean Information Science Society Conference
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• 2001.10c
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• pp.394-396
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• 2001

지금까지의 분산 컴퓨팅 시스템은 클라이언트의 요청을 서버에서 분산 처리하는 방식이었으나 SETI는 피어투피어 기술을 이용하여 이와 반대로 서버의 요청을 클라이언트에서 분산처리하는 방식을 취하고 있다. 여기서 데이터의 요청과 분산처리가 모두 클라이언트에서 이루어지는 분산시스템을 구성해볼 수 있다. 본 논문에서는 피어투피어 모델에 분산컴퓨팅을 적용하여, 기존 모델의 문제점을 해결한 새로운 피어투피어 모델을 제시해보고자 한다.

• Journal of the Korea Society of Computer and Information
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• v.15 no.3
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• pp.81-89
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• 2010

The research on peer-to-peer streaming schemes has largely focused on tree-push and mesh-pull structures. However, the tree-push structure has a defect that the tree restructuring time is long, and the mesh-pull structure has long startup delay and lag time from source servers. In this paper, we propose a new peer-to-peer live streaming scheme based on a push-mesh structure that takes advantages of tree-push and mesh-pull structure simultaneously. This structure basically provides the mesh-pull mechanism for data transmission and utilizes peers with high network upload capacity. It also supports the push mechanism along with paths from a source server, super peers, and selected general peers. By NS-2 simulation experiments, we finally show that our proposed scheme can achieve shorter startup delay than the mesh-pull structure, similar lag time to tree-push structure and best playback continuity among the three schemes.

• Journal of KIISE:Information Networking
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• v.35 no.4
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• pp.251-267
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• 2008

In this paper, we present a distributed topology control algorithm for constructing an optimized topology having a minimal search-time in unstructured peer-to-peer network. According to the proposed algorithm, each node selects the best nodes having higher hit-ratio than other nodes as many as the number being exponentially proportional to the hit-ratio of the node itself, and then it connects to them. The ensemble behavior of the proposed algorithm is very similar to the recrystrallizing phenomenon that is observed in nature. There is a partial order relationship among the hit-ratios of most nodes of constructed topology. Therefore once query message visits a node, it has a higher hit-ratio than the node that was visited last by the message. The query message even sent from freeloader can escape to the node having high hit-ratio by one hop forwarding, and it never revisits any freeloader again. Thus the search can be completed within a limited search time. We also propose the Chain-reactive search scheme using the constructed topology. Such a controlled multicasting reduces the query messages by 43 percent compared to that of the naive Gnutella using broadcasting, while it saves the search time by 94 percent. The search success rate of the proposed scheme is 99 percent.

• Journal of KIISE:Information Networking
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• v.37 no.3
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• pp.167-174
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• 2010

Recently the distributed topology control algorithm for constructing the Recrystallization Topology in the unstructured peer-to-peer network was proposed. In this paper, we prove that such a hierarchical topology is a scale-free power-law network. We present a model of a construction process of the distributed protocol, and analyze it based on a mean-field approximation and the continuum theory, so that we show that the constructed Recrystallization Topology is a scale-free network. In the proposed model, all nodes are born with some initial attractiveness and the system incorporates the rewiring of some links at every time step. Some old links are removed with the anti-preferential probability, and some new links are added with preferential probability. In other words, according to the distributed algorithm, each node makes connections to the more-preferential nodes having higher hit-ratio than other nodes, while it disconnects the anti-preferential nodes having lesser hit-ratio. This gives a realistic description of the local processes forming the recrystallization topology in unstructured peer-to-peer network. We calculate analytically the degree distribution. The analytic result indicates that the constructed network is a scale-free network, of which the scaling exponent is 3.

• Journal of the Korea Society of Computer and Information
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• v.12 no.6
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• pp.31-39
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• 2007

To perform on-line cyber education, it is indispensable to delivery contents file to participant users. When users' requests occur simultaneously in a shot period, server falls into overload phase. A common to avoid overload is a software solution based on P2P, which does no cost any additional expense. But, in this solution, it yields many problems such as service delay and system failure because of peer self-control. In this paper we propose an efficient load balancing policy based on P2P system. which is the contents delivery system for cyber education system using idle computing power in the proposed solution, we present server selection scheme called P2P-Pattern method, which results in minimum service delay. we can see that our scheme outperforms previous scheme.

• Electronics and Telecommunications Trends
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• v.22 no.5
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• pp.121-129
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• 2007

Single point of failure 문제를 해결할 수 있고, UCC로 대별되는 개인 분산 컴퓨팅 환경에서의 피어투피어(P2P)는 주요한 네트워킹 기술로 간주된다. 적지 않은 사용자들이 P2P 서비스를 사용하고 있는 시점에서 현재 제공되고 있는 P2P 범주별 서비스 동향을 간략하게 살펴보고, 주요 기술 이슈로 부각되는 과금 문제, 그리고 추후 통신 환경 변화에 따라 고려되어야 할 추가 기술 이슈들을 살펴보았다.

• Journal of Convergence for Information Technology
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• v.8 no.1
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• pp.37-42
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• 2018

This study focuses on investigating and comparing the lengths of the five words, vowels, and the ratio of the length of vowels to that of words among the Korean college students with the English native speaker. English sentences were read and recorded by Korean subjects to do this experiment. The vowel lengths were measured from a sound spectrogram, the Praat software program, and these data were analyzed through statistical analysis. I could easily tell that there were differences between the groups and they were significant. In the English front low vowel /${\ae}$/, I was able to find out that native subjects pronounced differently from Korean subjects, and the differences were significant. However, the pronunciation of the English diphthong /ai/, native subjects pronounced significantly shorter than Korean subjects.

• Journal of Convergence Society for SMB
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• v.6 no.4
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• pp.51-57
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• 2016

This study aims at investigating and comparing the vowel lengths of the eight stressed syllable vowels among the Korean college students with the English native speakers. To do this English sentences were uttered and recorded by twenty Korean subjects. Acoustic features were measured from a sound spectrogram with the help of the Praat software program and analyzed through statistical analysis. From the results of the experiment, I was able to find out that the differences of the lengths of the first syllable stressed vowels were significant. Especially in the pronunciation of the English front low vowel /${\ae}$/, native subjects pronounced significantly longer than Korean subjects, and this result could be used as a teaching material in pronunciation class.

• Review of KIISC
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• v.14 no.4
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• pp.10-18
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• 2004

상호운영성, 유연성, P2P(피어투피어), 역동성, 확장성 등 웹 서비스가 지닌 다양한 특성으로 인하여 웹 서비스 보안은 안전한 웹 서비스 운영을 위한 핵심요소라 할 수 있다. 웹 서비스의 기본 구성은 서비스 수요자와 제공자, 검색소로 구성되며 WSDL(Web Service Definition Language), UDDI(University Discovery and Integration of Business for Web), SOAP(Smple Object Access Protocol)등 세 개의 표준으로 서비스는 이루어진다. 이 중에서 특히 메시지 교환을 담당하는 통신 프로토콜인 SOAP는 웹 서비스 보안의 중심에 있으며, 웹 서비스 보안은 SOAP 메시지의 사용자 인증과 무결성, 기밀성을 보장하는 것으로 정의할 수 있다. SOAP는 HTTP를 통해 일반적으로 전송되므로 HTTP 상의 모든 위협을 가지게 되며 전송계층에 기반을 둔 보안을 생각할 수 있지만, 사실상 웹 서비스는 다수의 중간 중개자를 가질 수 있는 구조이기 때문에 단대단 보안(메시지 레벨의 보안)이 반드시 필요하다. 또한, 웹 서비스 상에서 단대단 보안을 보장하기 위해서는 각 객체와 키와의 연결이 중요하며 특정 객체에게 발행한 보안토큰의 신뢰성 화보를 위한 메카니즘을 필요로 한다. 본 논문에서는 이러한 보안 요구사항을 만족하기 위하여 XML 메시지 보안을 위한 전자서명 및 암호화 표준과 SOAP을 위한 W3C, OASIS의 통합표준을 중심으로 SOAP 메시지 보안기술을 분석하고자 한다.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.46 no.11
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• pp.1-11
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• 2009

A content based pub/sub (Publish/subscribe) services at the peer-to-peer network has the requirements about how to distribute contents information of subscriber and to delivery the events efficiently. For satisfying the requirements, a DHT(Distributed Hash Table) based pub/sub overlay networking and tree type topology based network construction using filter technique have been proposed. The DHT based technique is suitable for topic based pub/sub service but it's not good contents based service that has the variable requirements. And also filter based tree topology networking is not efficient at the environment where the user requirements are distributed. In this paper we propose the R-Tree algorithm based pub/sub overlay network construction method. The proposed scheme provides cost effective event delivery method by mapping user requirement to multi-dimension and hierarchical grouping of the requirements. It is verified by simulation at the variable environment of user requirements and events.