• Journal of the Institute of Electronics Engineers of Korea TC
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• v.46 no.5
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• pp.56-63
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• 2009

The IEEE 802.11 standard has been used for wireless data networks such as wireless LAN, ad-hoc network, and vehicular ad-hoc network. Thus, the performance analysis of the IEEE 802.11 specification has been one of the hottest issues for network optimization and resource management. Most of the analysis studies were performed in a data plane of the IEEE 802.11 unicast. However, IEEE 802.11 broadcast is widely used for topology management, path management, and data dissemination. Thus, it is important to understand the performance of the broadcast scheme for the design of efficient wireless data network. In this contort, we analyze the IEEE 802.11 broadcast scheme in terms of the broadcast frame reception probability according to the distance from a sending node. Unlike the other works, our analysis framework includes not only the system parameters of the IEEE 802.11 specification such as transmission range, data rate, minimum contention window but also the networking environments such as the number of nodes, network load, and the radio propagation environments. Therefore, our analysis framework is expected to be used for the development of protocols and algorithms in a dynamic wireless data network.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.11 no.3
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• pp.1533-1556
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• 2017

The concept of trust in vehicular ad hoc networks (VANETs) is usually utilized to assess the trustworthiness of the received data as well as that of the sending entities. The quality of safety applications in VANETs largely depends on the trustworthiness of exchanged data. In this paper, we propose a self-organized distributed trust computing framework (DTCF) for VANETs to compute the trustworthiness of each vehicle, in order to filter out malicious nodes and recognize fully trusted nodes. The proposed framework is solely based on the investigation of the direct experience among vehicles without using any recommendation system. A tier-based dissemination technique for data messages is used to filter out non authentic messages and corresponding events before even going farther away from the source of the event. Extensive simulations are conducted using Omnet++/Sumo in order to investigate the efficiency of our framework and the consistency of the computed trust metrics in both urban and highway environments. Despite the high dynamics in such networks, our proposed DTCF is capable of detecting more than 85% of fully trusted vehicles, and filtering out virtually all malicious entities. The resulting average delay to detect malicious vehicles and fraudulent data is showed to be less than 1 second, and the computed trust metrics are shown to be highly consistent throughout the network.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.11 no.12
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• pp.5729-5744
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• 2017

Vehicular Ad Hoc Networks (VANET) in the large-scale road section usually have typical characteristics of large number of vehicles and unevenly distribution over geographic spaces. These two inherent characteristics lead to the unsatisfactory performance of VANETs. This poor performance is mainly due to fragile communication link and low dissemination efficiency. We propose a novel routing mechanism to address the issue in the paper, which includes a competition-based routing discovery with priority metrics and a local routing repair strategy. In the routing discovery stage, the algorithm uses adaptive scheme to select a stable route by the priorities of routing metrics, which are the length of each hop, as well as the residual lifetime of each link. Comparisons of different ratios over link length and link stability further show outstanding improvements. In the routing repair process, upstream and downstream nodes also compete for the right to establish repair process and to remain as a member of the active route after repair. Our simulation results confirm the improved performance of the proposed algorithm.

• Journal of Convergence for Information Technology
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• v.7 no.3
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• pp.165-171
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• 2017

Recently, the development and dissemination of smart devices linked to the network are being actively performed, and IOT(Internet of things) is issued form of mutually cooperative relationship through interoperation within smart devices. In this paper, we propose an innovative intelligent coffee shop management system by sharing and cooperatively controlling smart devices and Internet devices. The system can order smartphones including kiosk orders and beacon-based user identification. And it is a system that can make custom order without grasping user location information using geofence. The paper provides weather, temperature, time and user-based recommendation services based on Big Data. Therefore, the system is increased cost reduction and work efficiency than general coffee shops.

• Asian Pacific Journal of Cancer Prevention
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• v.14 no.8
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• pp.4939-4942
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• 2013

The absolute necessity of cancer registration for cancer control planning is well accepted. The registry at the national or local level can provide not only essential data for cancer incidence, mortality and survival but may also point to risk and protective factors and efficacy of interventions by conducting epidemiological research. Timely publication of research findings in PubMed indexed journals is of the essence, especially in examples that allow free access so that the widest dissemination of information can be achieved. The present commentary covers the scope of research in Asia or using Asian data the period 2008-2013, nearly 40% of a total of over 300 papers being published in the APJCP. In order to reach its full potential the registry should incorporate many skills. Cooperation for this purpose, whether it be national, regional, Asia-wide or international, is a high priority and the International Agency for Research on Cancer, together with the National Cancer Institute in Thailand and the APOCP/APJCP are staging an Asian Cancer Network Forum in Bangkok in February of 2014 to allow discussion of ways forward. It is hoped that representatives from all regions of Asia will decide to attend and a l so contribute country reports for publication in a special supplement of the APJCP.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.10 no.11
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• pp.5322-5342
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• 2016

In vehicle-to-vehicle (V2V) networks, where selfishness degrades node activity, countermeasures for collaboration enforcement must be provided to enable application of a sage and efficient network environment. Because vehicular networks feature both high mobility and various topologies, selfish behavior judgment and establishment of a stable routing protocol become intensely challenging. In this paper, a two-phase-based generous cooperative routing protocol (called GEC) is presented for V2V networks to provide resistance to selfishness. To detect selfish behaving vehicles, a packet forwarding watchdog and an average connection rate based on the multipath weight method are used, where evidence is gathered from different watchdogs. Then, multihop relay decisions are made using a generous cooperative algorithm based on game theory. Finally, through buffering of the multiple end-to-end paths and judicious choice of optimal cooperative routes, route maintenance phase is capable of dealing with congestion and rapidly exchanging traffic. Specifically, it is proved that the GEC is theoretically subgame perfect. Simulation results show that for V2V networks with inherently selfish nodes, the proposed method isolates uncooperative vehicles and is capable of accommodating both the mobility and congestion circumstances by facilitating information dissemination and reducing end-to-end delay.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2015.10a
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• pp.1015-1016
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• 2015

VANET is a technology for building a robust ad-hoc network between mobile vehicles as well as, between vehicles and RSU. Vehicles are moving and they only stay in the RSU area for a short time. When the number of requests is increased, an important challenge is to implement a suitable scheduling algorithm which serves as more requests as possible. $D^*S$ algorithm uses a priority weight, DS_Value, for selection of a request to get service. Priority weight is influenced only by deadline and data size parameters. We propose a packet scheduling using multilevel queue and show that using this idea leads to higher service ratio compare to previous algorithms.

• Journal of the HCI Society of Korea
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• v.12 no.3
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• pp.5-11
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• 2017

Korean traditional dance has cultural value and is human's cultural heritage. But they are in danger which is caused by lack of bearers and public interest. E-Learning of traditional dance using network technology and digital media can be a solution to extinction problem. The aim of this study is to propose the E-Learning courses and systems for learning traditional dance. E-Learning systems were evaluated in accordance with the HCI (Human Computer Interaction) user evaluation. This study contribute to overcoming distance constraints by offering synchronous E-Learning education system of traditional dance as intangible cultural heritage through new media experience.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.7B
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• pp.886-891
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• 2011

Multicast has been a key routing service for efficient data dissemination in underwater acoustic sensor networks. In sensor networks, there are several multicast routing protocol which reflects sensor network nature. However, existing routing scheme was not targeted at underwater acoustic sensor networks which is hard to provide battery continually. Therefore, a specialized routing algorithm is essential for acoustic sensor networks. In this paper, we propose angle aided multicast routing algorithm for decreasing routing computation complexity, including virtual Euclidean Steiner point. Simulation results show better performance than exist routing Position Based Multicast, Geographic Multicast Routing. such as low computation capability and limited power consumption.

• Journal of Information Technology Services
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• v.18 no.3
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• pp.95-115
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• 2019

In recent years, social media that has emerged with the development of network technology has changed the channels of information dissemination. The social Q&A community is a platform for knowledge-sharing activities in a question-and-answer manner based on Web 2.0. In knowledge-sharing activities, valuable new knowledge continues to be produced and will surely bring great benefits to individuals or businesses. In the social Q&A community, the user's subjective factors play a crucial role in influencing the user's continued use and participation in knowledge-sharing activities. In order for users to actively participate in knowledge-sharing activities in the community, it needs to grasp their subjective ideas. This study explores the issue of sharing knowledge by users of the social Q&A community "Zhihu", or how to drive community revitalization efforts from these. The three factors self-efficacy, self-development motivation, and social comparison tendencies were derived, and identify their relationship with knowledge-sharing activities and community-boosting efforts through empirical analysis. In addition, the influence of knowledge acquisition on knowledge provision was investigated through sense of reciprocity. Implications of the study findings and the future research directions were also discussed.