• Fashion & Textile Research Journal
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• v.10 no.3
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• pp.371-376
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• 2008

Poly(ethylene-co-vinylacetate) (EVA) microspheres were prepared by thermally induced phase separation (TIPS) in toluene. The microsphere formation occurred by the nucleation and growth mechanism in metastable region. The effects of the concentration and component of the polymer and cooling rate on microsphere formation were investigated. The microsphere formation and growth were followed by the cloud point of the optical microscope measurement. The microsphere size distribution, which was obtained by particle size analyzer, became broader when the polymer concentration was higher, the content of vinyl acetate in EVA copolymer was higher, the cooling rate of EVA copolymer solution were lower. The content of disperse dye in EVA microsphere was obtained by TGA thermal analysis, the dye content of EVA15 and EVA18 were 3.5 and 2.0 wt% respectively.

• The Journal of the Korea institute of electronic communication sciences
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• v.6 no.3
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• pp.445-449
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• 2011

A P2P technique is the concept to share sources efficiently in distributed environment that is studying a lot. In these P2P systems, the server to support the contents-information have less overloads than the composed system as the server to have resources generally. In this paper, we suggest a P2P system to support conveniences for users that were connected with the information of joint-buying based on social network. The joint-buying information based on social network is supported by peers using a p2p system and these information to intermediate are supported by a P2P server.

• Journal of the Korea Institute of Military Science and Technology
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• v.17 no.4
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• pp.501-509
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• 2014

In NCW(Network Centric Warfare) environment, mobile nodes communicate through wireless link. But wireless link provides limited networking performance due to signal interferences or mobility of nodes. So it is quite challenge to acquire enough networking resources and use the resources efficiently. In this paper, we have proposed a P2P based tactical information sharing system which provides satisfactory visual information playout for mobile nodes(i.e., military personnel, vehicle,..) in NCW environment. Our proposed system consists of two components. One is caching-enabled switch which stores tactical information segments at its internal storage and then transports them to mobile nodes when require. Another is centralized scheduling algorithm which exploits networking resources more efficiently. To validate performance of proposed system, we performed series of experiments in wireless network testbed. Results show improved performance in terms of segment-missing ratio, networking resources usage, sharing time, and number of simultaneous playout mobile nodes with acceptable playout continuity(i.e., over 95%).

• Annual Conference of KIPS
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• 2008.05a
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• pp.822-825
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• 2008

최근 모바일 기술의 발달로 모바일 네트워크에서 사용자들이 가지고 있는 정보를 활용하는 P2P 서비스들이 많이 연구되고 있다. 그 중에 협력적 필터링(Collaborative Filtering, CF)을 이용한 추천 서비스는 모바일 네트워크 상의 다른 사용자의 정보를 수집하여 개인화된 추천을 수행한다. 기존에 연구 된 CF 추천 시스템에서 메시지 전달을 위해 broadcasting 방식 사용되었다. broadcasting 방식은 각 모바일 기기 주위의 모든 기기로 사용자 정보를 전송함으로써 많은 트래픽을 유발시킨다. 본 논문에서는 슈퍼 피어 방식을 이용하여 메시지 전송 양을 줄여, CF를 이용한 추천 서비스를 보다 효율적으로 하고, 추천성능을 유지하게 하였다. 실험을 통해 본 논문에서 제시한 방식이 broadcasting 방식의 메시지 양을 53% 감소시켰음을 보였다.

• Annual Conference of KIPS
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• 2007.11a
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• pp.546-549
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• 2007

최근 P2P 파일 공유 시스템은 다운로드 속도를 높이기 위해 한 파일을 블록 단위로 나누어 여러 피어로부터 동시에 내려 받는다. 그러나 악의적인 피어가 고의적으로 변조한 파일을 전송 받게 되면 해당 블록의 재전송으로 네트워크 자원이 소모되고, 블록들을 재 조합하여 파일을 구성하는데 걸리는 시간이 증가한다. 본 연구에서는 자원 절약을 위해 고의적 변조 파일을 P2P 시스템에서 배제시키는 방법을 제안하고자 한다. 제안하는 방법은 디렉토리 서비스를 담당하는 피어가 변조 블록에 대한 신고를 받아 그 신고 횟수가 임계치에 도달하면, 해당 변조 블록을 포함한 파일을 검색 결과에서 배제시킴으로써 P2P 상에 공유되는 것을 막는다. 또한 제안하는 시스템의 성능을 모의 실험을 통해 평가한 결과, 일반적인 P2P 시스템 및 피어 평판 관리 시스템을 적용한 P2P 시스템보다 제안한 시스템의 고의적 변조 파일의 공유 비율이 각각 22 배, 4 배 낮고, 올바른 파일은 항상 공유되는 것을 확인하였다. 그러므로 제안하는 방법을 기존 P2P 시스템에 적용할 경우, 고의적 변조 파일의 다운로딩에서 발생하는 네트워크 자원 낭비를 줄일 수 있고 피어의 다운로드 속도도 증가할 것이다.

• The KIPS Transactions:PartC
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• v.16C no.6
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• pp.773-782
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• 2009

A DHT(Distributed Hash Table) based P2P is a method to overcome disadvantages of the existing unstructured P2P method. If a DHT algorithm is used, it can do a fast data search and maintain search efficiency independent of the number of peer. The peers in the DHT method send messages periodically to keep the routing table updated. In a mobile environment, the peers in the DHT method should send messages more frequently to keep the routing table updated and reduce the failure of a request. Therefore, this results in increase of network traffic. In our previous research, we proposed a method to reduce the update load of the routing table in the existing Chord by updating it in a reactive way, but the reactive method had a disadvantage to generate more traffic than the existing Chord if the number of requests per second becomes large. In this paper, we propose an adaptive method of routing table update to reduce the network traffic. In the proposed method, we apply different routing table update method according to the number of request message per second. If the number of request message per second is smaller than some threshold, we apply the reactive method. Otherwsie, we apply the existing Chord method. We perform experiments using Chord simulator (I3) made by UC Berkeley. The experimental results show the performance improvement of the proposed method compared to the existing methods.

• The KIPS Transactions:PartC
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• v.16C no.6
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• pp.761-772
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• 2009

A DHT(Distributed Hash Table) based P2P is a method to overcome disadvantages of the existing unstructured P2P method. If a DHT algorithm is used, it can do a fast data search and maintain search efficiency independent of the number of peer. The peers in the DHT method send messages periodically to keep the routing table updated. In a mobile environment, the peers in the DHT method should send messages more frequently to keep the routing table updated and reduce the failure of a request. Therefore, this results in increase of network traffic. In our previous research, we proposed a method to reduce the update load of the routing table in the existing Chord by updating it in a reactive way, but the reactive method had a disadvantage to generate more traffic than the existing Chord if the number of requests per second becomes large. In this paper, we propose an adaptive method of routing table update to reduce the network traffic. In the proposed method, we apply different routing table update method according to the number of request message per second. If the number of request message per second is smaller than some threshold, we apply the reactive method. Otherwsie, we apply the existing Chord method. We perform experiments using Chord simulator (I3) made by UC Berkeley. The experimental results show the performance improvement of the proposed method compared to the existing methods.

• 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.

• The KIPS Transactions:PartC
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• v.18C no.1
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• pp.51-60
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• 2011

In this paper, we propose a P4P based P2P system for live multimedia streaming services. In order to satisfy the strict requirement of delay in live multimedia streaming, in the proposed scheme, the P4P server of network provider provides the network status information related to delay and congestion links to P2P system in addition to the information to optimize the network resource utilization. The P2P system server, then, makes the peering suggestion based on the information from the network server. Also, we propose a playback synchronization mechanism that enable each peer to start the playback within the limited variation from the playback positions of source peer. Through the simulation results, it is shown that the proposed scheme not only deals with the original objective of the P4P framework, i.e., effective network utilization, but also the live multimedia streaming requirements. It enhances the playback continuity, and reduces the playback start-up latency and the control overhead. In addition, the proposed scheme reduces the variation in playback positions of the peers.

• Journal of the Korean Society for information Management
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• v.37 no.4
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• pp.131-150
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• 2020

This study was conducted to ascertain a better understanding of researchers' perception of open peer review (OPR), which is being attempted to improve the problems of traditional peer review methods in recent journal publications. A survey was conducted on the Korean authors of a mega open access (OA) journals and the results were analyzed. The subjects of the survey were selected as Korean corresponding authors published on PLOS, an international OA journal and mega journal. The survey was conducted as an online questionnaire and a total of 238 responses were collected; the analysis was based on 202 valid responses. Data were analyzed by performing frequency analysis and average comparison between groups for the collected questionnaire results. As a result of analyzing whether there is a difference in perception of OPR depending on the age, research experience, and OPR experience of the researcher, researchers under the age of 44, researchers with research experience of 9 years or less, and researchers with OPR participation experience had differences in some OPR perceptions. Results show that researchers under the age of 44 want to change the current peer review approach, but they are not yet actively accepting OPR. As a result of analyzing the reasons why the researcher disagrees with OPR, they raised questions about lack of objectivity, increased burden of reviewers, emotions and relationships, and responded that the right to be forgotten was also necessary.