• Journal of Korean Elementary Science Education
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• v.39 no.1
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• pp.40-53
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• 2020

This study analyzed the features of norms formed in mobile-based science problem-solving and interpreted them from the perspective of digital citizenship. For this, we implemented two mobile-based science problem-solving activities for nine elementary school preparatory teachers composed of two groups, and analyzed the norms observed in their activities. As a result, four norms were found as follows. First, the information presented as a basis should be scientifically reliable. Second, the information need to be searched widely, but the information should be selected and reconstructed in relation to the problem. Third, in a mobile environment, the ideas should be clearly expressed and understood. Fourth, courtesies in mobile interaction should be represented more politely than in face-to-face interaction. Based on the four norms found in this study, we discussed the characteristics and factors of digital citizenship for judging scientifically reliable and relevant information and expressing ideas clearer in mobile environment. Finally, we suggested the educational implications for fostering digital citizens who can judge and practice 'science issues' in a 'mobile environment'.

• Proceedings of the Korea Information Processing Society Conference
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• 2006.05a
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• pp.1081-1084
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• 2006

MVPN(Mobile Virtual Private Network)은 이동단말을 사용하는 이동근무자가 지역적 제한 없이 VPN 서비스를 제공받을 수 있도록 하는 기술이다. 현재 IPsec-based VPN의 비중을 고려해볼 때, MVPN 기술은 Mobile 사용자에게 이동성을 제공하기 위한 Mobile IP프로토콜과 IPsec 기반 VPN 기술의 공존이 주된 연구 내용이다. mobile IP가 IPsec-based VPN GW(Gateway)와 동작할 경우 비호환성 문제가 발생한다. IETF에서는 두 프로토콜 간의 비호환성을 해결하기 위해VPN GW의 외부에 홈 에이전트(x-HA)를 새롭게 추가하는 방안이 연구되고 있다. 이에, AAA(Authentication, Authorization, Accounting) 서버를 이용하여 신뢰성 있는 x-HA를 동적으로 할당하는 방안이 제시되었으나, 세션 키의 외부 노출과 네트워크 간 이동 시 최초 핸드오프 시간이 오래 걸리는 한계를 지닌다. 본 논문은 이와 같은 문제점을 해결하여 이동하는 원격 VPN 사용자에게 보다 안전하며 핸드오프 지연시간이 최소화된 통신을 제공하는 방안을 제안한다.

• Journal of Information Technology Services
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• v.6 no.3
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• pp.225-239
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• 2007

Mobile service is highly becoming in the limelight on information society by offering infringement problem about individual privacy or information by political and scientific interest This study is focusing on primary LBS application Mobile service that emphasize position confirmation, especially, looking for friends. The aim at this study grasps user productivity factor of LBS application Mobile service, and analyses whether some have relations with value and action determination of LBS application Mobile service. According to result, Mobile service applying position service is supported with usefulness and system quality, adaptedness. On the other hand, Usability and social effect, privacy weren't embossed by leading person. Mobile service applying position service is changed with a person who have experience looking for friend. This study has systematically analysed about LBS application service by leading person

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 1999.11a
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• pp.406-410
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• 1999

This paper supposes the SNMP network management system based upon Mobile Agent using the Naming and Directory Service, which is JNDI(Java Naming Directory Interface) technology. The Mobile Agent network system is expected to provide a solution for the conventional centralized network system. So, We have designed and implemented the network management system based upon Mobile Agent using JNDI

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.3 no.6
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• pp.628-646
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• 2009

Users want to browse and search various web contents with mobile devices which can be used anywhere and anytime without limitations, in the same manner as desktop. But mobile devices have limited resources compared to desktop in terms of computing performance, network bandwidth, screen size for full browsing, and etc, so there are many difficulties in providing support for mobile devices to fully use desktop-based web contents. Recently, mobile network bandwidth has been greatly improved, however, since mobile devices cannot provide the same environment as desktop, users still feel inconvenienced. To provide web contents optimized for each user device, there have been studies about analyzing code to extract blocks for adaptation to a mobile environment. But since web contents are divided into several items such as menu, login, news, shopping, etc, if the block dividing basis is limited only to code or segment size, it will be difficult for users to recognize and find the items they need. Also it is necessary to resolve interface issues, which are the biggest inconvenience for users browsing in a mobile environment. In this paper, we suggest a personalized adaptation system that extracts item blocks from desktop-based web contents based on user interests, layers them, and adapts them for users so they can see preferred contents first.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.4A
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• pp.528-538
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• 2000

Mobile computing system requires both precise identification and secure authentication scheme on remote mobile entities, which is based on the distributed mobile node. In this paper, existing discrete logarithm based $Schnorr^{[7]}$ like entity authentication schemes are improved by the analysis of performance and security on the hi-directional interactive proofs. And $EIGamal^{[14]}$ like efficient authentication schemes are also proposed. Then, these are enhanced with oblivious transfer based mono directional authentication schemes based on trusted third party for applying to the mobile agent based computing systems. Therefore, proposed schemes provide compatible performance and safety on mobile entity authentication processes.

• Journal of Computing Science and Engineering
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• v.5 no.4
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• pp.316-323
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• 2011

Recently, Proxy Mobile IPv6 (PMIPv6) has received much attention as a mobility management protocol in next-generation all-IP mobile networks. While the current research related to PMIPv6 mainly focuses on providing efficient handovers for unicast-based applications, there has been relatively little interest in supporting multicast services with PMIPv6. To provide support for multicast services with PMIPv6, there are two alternative approaches called Mobile Access Gateway (MAG)-based subscription and Local Mobility Anchor (LMA)-based subscription. However, MAG-based subscription causes a large overhead for multicast joining and LMA-based subscription provides non-optimal multicast routing paths. The two approaches may also cause a high packet loss rate. In this paper, we propose an efficient PMIPv6-based multicast protocol that aims to provide an optimal delivery path for multicast data and to reduce handover delay and packet loss rate. Through simulation studies, we found that the proposed protocol outperforms existing multicast solutions for PMIPv6 in terms of end-to-end delay, service disruption period, and the number of lost packets during handovers.

• Proceedings of the Korea Society for Simulation Conference
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• 2003.06a
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• pp.61-66
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• 2003

Mobile IP has been designed only to maintain communication as they move form place to place, so it doesn't guarantee Quality of Service(QoS). QoS in mobile IP is important to provide multimedia and real-time applications services in mobile, and it is closely related to handoff delay. Therefore, handoff delay problem is actively studied to guarantee QoS as a main issue in mobile IP research area Next generation Mobile IPv6 resolve this problem somewhat, triangle problem for first packet and handoff delay still remain. In this paper, we suggest SNMP Information-based routing that adds keyword management method to Information-based routing in active network in order to resolve such a problem, and then suggest QoS controlled handoff based on SNMP Information-Based routing. After modeling of suggested method and existing handoff method simulations we carried out with NS-2 for performance evaluation. The results of simulations show the some improvement on handoff delay, and therefore on QoS improvement.

• The Transactions of the Korea Information Processing Society
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• v.7 no.11
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• pp.3490-3499
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• 2000

There are two approaches, HA(Home Agent)-based and FA(Froegn Agent)-based mulicasting in mobile computing environments based on mobile IP. If we consider efficiency of routing and bandwidth the FA-based model is better than the HA-based model. But in the case of a MH(Mobile Host) moves frequently it shows bad connection durability because of join and graph delays. To overcome this and to support effective mobile multicasting we propose an extended FA-based multicast routing. In our model previous FA for wards multicast packets to MH. while new FA processes a jion request from MH. That is in general case our model supports FA-based multicasting for efficiency but it provides unicast-based mulicasting for connection durability when MH moves to new FN(Roreign Network). To evaluate our model, we analyze connecction durability, bandwidth, overheads and routing sosts in many situations and compare with previous works.

• Journal of KIISE:Software and Applications
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• v.35 no.3
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• pp.197-206
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• 2008

In the mobile Internet environment, frequent communications between a mobile device and a content server are required for searching or downloading learning materials. In this paper, we propose an efficient prefetching technique to reduce the network cost and to improve the communication efficiency in the mobile dictionary. Our prefetching-based approach can be explained as follows. First, we propose an overall framework for the prefetching-based mobile dictionary. Second, we present a systematic way of determining the amount of prefetching data for each of packet-based and flat-rate billing cases. Third, by focusing on the English-Korean mobile dictionary for middle or high school students, we propose an intuitive method of determining the words to be prefetched in advance. Fourth, based on these determination methods, we propose an efficient prefetching algorithm. Fifth, through experiments, we show the superiority of our prefetching-based method. From this approach, we can summarize major contributions as follows. First, to our best knowledge, this is the first attempt to exploit prefetching techniques in mobile applications. Second, we propose a systematic way of applying prefetching techniques to a mobile dictionary. Third, using prefetching techniques we improve the overall performance of a network-based mobile dictionary. Experimental results show that, compared with the traditional on-demand approach, our prefetching based approach improves the average performance by $9.8%{\sim}33.2%$. These results indicate that our framework can be widely used not only in the mobile dictionary but also in other mobile Internet applications that require the prefetching technique.