• Journal of the Korea Computer Graphics Society
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• v.3 no.1
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• pp.29-36
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• 1997

Most Virtual Reality Systems have been developed to support only a single user on a stand-alone system. With increasing availability of Internet, many people are taking strong interests in distributed Virtual Reality : the virtual environment is shared by many paticipants interacting over the network. To support sharing virtual environment and interactions on a network, we developed novel contributions to 3D world description and a network model. Interactive 3D world description is based on VRML, which is extended to support multi-user interactions. Then network model in our system consists of an architecture and a set of protocols for realizing a multi-user interactive shared 3D environment in IP multicast environment.

• Journal of Korea Technology Innovation Society
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• v.21 no.1
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• pp.300-330
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• 2018

Enterprises' participation in the collaboration research is one of the effective and typical methods through which technologies go into the market or are transferred to other sectors. This study reviews enterprises' participated collaboration research and analyzes their network for disaster and safety management area. From 2005 to 2016, 786 technical papers from four representative journals for disaster and safety management in Korea are compiled based on the authors whose affiliations are from enterprises. During the research period, collaboration research is found to be in an increasing trend in general. However, the number of technical papers with three or less authors is in a decreasing trend, whereas that with four or more authors is in an increasing trend. This fact implies that the range of enterprises' collaboration research is widening. Technical paper productivity and each entity's collaboration network are evaluated using participation-weight based author score. Over the research period, a few universities, which attract most of the enterprises, are found to have higher productivities and centralities. Public enterprises show higher participation weights. Also, sectors such as construction, engineering, and electronics demonstrate higher weights. This study is particularly meaningful because enterprises' participation status in collaboration research for disaster and safety management area is systematically analyzed for the first time in Korea. The network analysis result from this study will be especially helpful in establishing technology transfer strategy.

• The Journal of the Korea institute of electronic communication sciences
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• v.4 no.4
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• pp.265-269
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• 2009

A conference key agreement system is a scheme to generate a session key in a contributory manner in order to communicate with each other securely among participants. In this paper an efficient conference key agreement system is proposed by employing symmetric balanced incomplete block design(SBIBD), one class of block designs. The protocol presented not only minimizes the message overhead and message exchanging rounds but also makes every participant contribute evenly for generating a conference key. Our protocol constructs a conference key which takes modified Diffe-Helman form of ${\prod}_{i=0}^{v-1}R_i$, where v is the number of participants and $R_i$ is a random number generated from member i. In a special class of SBIBD, it takes only 3 rounds message exchange and message overhead is $O(v{\sqrt{v}})$. Our protocol can be proved as computationally difficult to calculate as discrete logarithms.

• Journal of KIISE:Computing Practices and Letters
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• v.14 no.5
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• pp.512-516
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• 2008

A conference-key agreement protocol is essential for computer network conferences that need secure communications. Especially, the fault-tolerant conference-key agreement can make a shared conference-key even if some make conferees disturb the key agreement processes. However, the performance of the previous fault-tolerant conference-key agreement protocols is decreasing significantly when the number of fake conferees is increasing. In this paper, we propose an efficient fault-tolerant conference key agreement protocol. Our scheme is based on the ID-based one round tripartite conference key agreement protocol. Simulation results show our scheme's efficiency against Yi's method especially when the number of fake conferees is large.

• 한국HCI학회:학술대회논문집
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• 2006.02b
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• pp.487-492
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• 2006

컴퓨터 네트워크의 발전에 의해 학습 공간의 시공간적인 확대와 교육 현장에서 교수-학습 과정에 대한 새로운 교수방법을 요구되었고, 유무선 방송, 인터넷 등을 이용하여 다양한 형태의 원격교육이 구체화되어 왔다. 하지만, 현재 운영되는 대부분의 원격교육시스템은 실질적인 학습 상황에서 단방향적인 개별 학습 형태를 보이고 있고, 사용자간의 쌍방향 상호작용을 위해서는 교수자나 학습자에게 일정 수준이상의 기술적 소양과 경제적 부담을 요구한다. 또한 교수자에게는 교수-학습 상황에서 발생하는 학습자 행동에 대한 실시간적인 모니터링과 학습자의 학습과정에 대한 평가의 어려움을, 학습자에게는 자기 반성의 기회를 제대로 제공하지 못하는 문제점을 안고 있다. 이에 본 연구에서는 원격교육에서의 협동학습 지원, 사용자의 기술적, 경제적 부담의 제거, 학습 전(全) 과정에 대한 원활한 모니터링과 피드백 기회의 제공을 목적으로 원격협동학습 시스템을 설계하고, 이를 개발하였다. 본 연구에 의해 개발된 원격협동학습 시스템은 원격협동학습을 지원하는 네트워크 화이트보드, 학습 과정 및 결과를 자연어로 저장하는 저장 모듈, 그리고 저장된 학습 스크립트 파일을 해석하여 재생하는 스크립트 인터프리터로 구성되었다. 네트워크 화이트보드는 소프트웨어적으로 구현되어 부가적인 장치가 불필요하고, 통신 서버를 분산하여 서버 구축에 대한 부담을 제거하였고, 학습 내용 화면을 대화창으로 사용하여 사용자의 사용 편리성을 제고하였다. 또한 원격학습의 장(場)에 교수자가 참여하여 실시간적 모니터링이 가능하고, 학습의 전(全) 과정 및 결과를 저장한 자연어 스크립트 파일에 의해서도 학습자 행동에 대한 모니터링이 가능하다. 저장된 자연어 스크립트 파일은 구현된 인터프리터를 이용한 재생뿐 아니라, 파일 자체만으로도 학습과정을 판독할 수 있고, 스크립트 파일에 대한 해석은 교수자에게는 학습자의 학습 과정에 대한 평가 및 피드백의 근거를, 학습자에게는 자신의 학습 행동에 대한 반성의 기회를 제공한다. 본 시스템은 기존의 원격교육시스템에 비해 장비 및 인터페이스 측면에서 간소화되었고, 원격교육에 면대면 학습 개념을 근사적으로 접목시킨 교수 모델로서의 충분한 가치를 제공하나, 실제적인 학습 적용과 효과에 있어서의 타당성은 차후 검증이 있어야 하고, 또한, 이에 따른 시스템에 대한 지속적인 보완도 필요하다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39B no.4
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• pp.234-241
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• 2014

xTo improve network inefficiency caused by network congestion around a content-source, content-centric networking (CCN) allows network nodes transmitting contents to temporarily cache received contents and then send back the cached contents if the nodes receive relevant request messages without forwarding the request messages to content-sources. However, because nodes receiving requested contents through CCN cannot recognize real senders of the received contents, the receivers need to verify each received contents before using them. But such a verification procedure can cause long service/operation delay. Hence, in this paper, we review the problem of contents verification, propose an improved verification procedure and evaluate its performance.

• Journal of Internet Computing and Services
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• v.14 no.2
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• pp.25-34
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• 2013

In this paper, we propose an activity-performer bipartite matrix generation algorithm for analyzing workflow-supported human-resource affiliations in a workflow model. The workflow-supported human-resource means that all performers of the organization managed by a workflow management system have to be affiliated with a certain set of activities in enacting the corresponding workflow model. We define an activity-performer affiliation network model that is a special type of social networks representing affiliation relationships between a group of performers and a group of activities in workflow models. The algorithm proposed in this paper generates a bipartite matrix from the activity-performer affiliation network model(APANM). Eventually, the generated activity-performer bipartite matrix can be used to analyze social network properties such as, centrality, density, and correlation, and to enable the organization to obtain the workflow-supported human-resource affiliations knowledge.

• Journal of Engineering Education Research
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• v.12 no.1
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• pp.17-23
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• 2009

This paper deals with the design and implementation of PBL for the computer network practice to improve learner's learning ability. This design is for college student's whose learning ability is low. I implemented the CNC-PBL in a class of second year students at Daeduk college. The result of the experiment showed that the CNC-PBL facilitated learner's self-directed learning process.

• TTA Journal
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• s.104
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• pp.14-18
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• 2006

요즈음 세계적인 유수 통신 사업자들이 새로운 서비스로 가장 큰 관심을 나타내고 있는 것이 IPTV이다. 이는 통신 사업자들이 브로드밴드 IP 네트워크 환경에서 비디오, 음성 및 데이터 정보들을 다양한 형태의 새로운 서비스 패키지로 엮어서 이용자들의 요구에 가장 잘 적응할 수 있게 만든 서비스 모델이 IPTV 서비스이기 때문일 것이다. 그런데 IPTV 서비스가 이용자들에게 고품질의 서비스 및 다양한 부가기능을 갖춘 고기능 부가서비스로 다가갈 뿐만 아니라 효율적인 통신 서비스 시장을 형성하여 나가기 위해서는 표준화의 요구 사항을 만족시켜야 할 것이다. 그러나 IPTV 관련 기술 및 서비스 기능들이 네트워크, 서비스 기능 및 특성, 가입자 액세스 기술, 서비스 품질, 네트워크 특성들이 고려된 종합적인 IPTV 표준화가 이루어지지 않았다. 따라서 각국의 통신 사업자뿐만 아니라 서비스 사업자 및 가입자 시스템 벤더들은 브로드밴드 통신 시장의 수요에 따라 IPTV 서비스의 endto-end 상호운용성(Interoperability)을 제공하기 위한 IPTV 표준화에 경쟁적으로 참여하고 있다. 최근에 ITU-T는 IPTV의 표준화를 위한 포커스 그룹 결성을 위한 준비 모임을 오는 4월 초에 제네바에서 개최하고 7월경에는 공식적으로 표준화 조직으로 결성할 예정이다.

• Journal of Korea Multimedia Society
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• v.7 no.4
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• pp.550-558
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• 2004

Previous researches on scalability problem of distributed virtual environment (DVE) have been mainly focused on spatial partitioning of area of interest (AOI). Congestion phenomena by avatar groups in AOI have been neglected relatively However, AOI congestion is highly related to scalability of DVE because it exhausts system resources such as network bandwidth and rendering time, and could be a bar to perform collaboration among participants. In this paper, this will be defined as the problem that must be solved for the realization of the scalable DVE, and a model will be proposed to measure and control congestion situation in AOI. The purposes of the proposed model are to prevent high density of participants in AOI, and to protect stable collaboration in DVE. For evaluation of the performance it is compared with a previous method by defining the resource cost model which is dynamically activated to AOI congestion.