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Lee Y.,Korea National University of Education | Choi J.,Korean Bible University
Internet and Higher Education | Year: 2013

This study examined the effects of internal academic locus of control (ALOC), learning strategies, flow experience, and student satisfaction on student retention in online learning courses. A total number of 282 adult students at the Korea National Open University participated in the study by completing an online survey adopted from previous studies to measure the levels of five variables: internal ALOC, use of learning strategies, flow experience, satisfaction, and retention. We employed a structural equation model (SEM) to test our conceptual model using AMOS 18.0. The research findings indicate that there were significant direct effects between internal ALOC and retention, between satisfaction and retention, between internal ALOC and satisfaction, between flow and satisfaction, and between learning strategies and flow. Moreover, we noted the significant mediating effects of student satisfaction and students' experience of flow on their retention in the model. © 2012 Elsevier Inc. All rights reserved.

Lee J.-H.,Telecom Bretagne | Bonnin J.-M.,Telecom Bretagne | You I.,Korean Bible University | Chung T.-M.,Sungkyunkwan University
IEEE Transactions on Industrial Electronics | Year: 2013

IPv6 mobility management is one of the most challenging research topics for enabling mobility service in the forthcoming mobile wireless ecosystems. The Internet Engineering Task Force has been working for developing efficient IPv6 mobility management protocols. As a result, Mobile IPv6 and its extensions such as Fast Mobile IPv6 and Hierarchical Mobile IPv6 have been developed as host-based mobility management protocols. While the host-based mobility management protocols were being enhanced, the network-based mobility management protocols such as Proxy Mobile IPv6 (PMIPv6) and Fast Proxy Mobile IPv6 (FPMIPv6) have been standardized. In this paper, we analyze and compare existing IPv6 mobility management protocols including the recently standardized PMIPv6 and FPMIPv6. We identify each IPv6 mobility management protocol's characteristics and performance indicators by examining handover operations. Then, we analyze the performance of the IPv6 mobility management protocols in terms of handover latency, handover blocking probability, and packet loss. Through the conducted numerical results, we summarize considerations for handover performance. © 2012 IEEE.

Doh I.,Ewha Womans University | Lim J.,Korean Bible University | Chae K.,Ewha Womans University
Mobile Information Systems | Year: 2011

In medical sensor networks, sensor nodes on a body of the patient sense the vital data and deliver them to the server system through mobile devices or gateways in the middle. However, when these linking devices do not function because of the battery outage or the system fault, the server system could not get patients' data during that period, and this situation could lead to serious problems. In this paper, to cope with this problem, we propose a distributed authentication mechanism in which substituted devices could be authenticated to deliver patients' data to the server system in the unusual situation. © 2011-IOS Press and the authors. All rights reserved.

Yan Z.,Beijing Jiaotong University | Zhou H.,Beijing Jiaotong University | You I.,Korean Bible University
Journal of Wireless Mobile Networks, Ubiquitous Computing, and Dependable Applications | Year: 2010

In this paper, we propose a Network-based NEtwork MObility supporting scheme (N-NEMO) in Proxy Mobile IPv6 (PMIPv6) network, which is an issue still up in the air for the basic PMIPv6 protocol. The N-NEMO, like PMIPv6, bases mobility support on network functionality, thus enabling conventional (i.e., not mobility-enabled) IP devices to change their point of attachment without disrupting ongoing communications. As a result, N-NEMO enables off-the-shelf IP devices to roam within the fixed infrastructure, attach to a mobile network and move with it, and also roam between fixed and mobile points of attachment while using the same IP address. Besides, a tunnel splitting scheme is used in N-NEMO to differentiate the inter-Mobility Access Gateway (MAG) mobility and intra-MAG mobility. The analyzing results show that N-NEMO reduces the signaling cost significantly and enhances the efficiency and scalability of network mobility in the PMIPv6 context.

Qian Z.,Nanjing University | Chen C.,Nanjing University | You I.,Korean Bible University | Lu S.,Nanjing University
Computers and Mathematics with Applications | Year: 2012

Current research on UHF RFID system security mainly focus on protecting communication safety and information privacy between a pair of specific tags and its corresponding interrogation reader. However, instead of stealing detailed private information of tags, adversaries may just want to estimate the cardinality of tags, which is named counting attack. Unfortunately, most existing protocols are vulnerable to counting attack. To defend against this attack, in this paper we propose ACSP, a novel Anti-Counting Security Protocol. ACSP employs session identifier and provides a corresponding authentication metric to verify the commands sent by the reader. To handle counting attack, ACSP periodically updates the session identifier, and securely identifies tags with encryption. We evaluate the performance of ACSP through theoretical analysis and qualitative comparison. Results show that ACSP can efficiently withstand counting attack as well as defending against regular security threats as existing protocols. © 2011 Elsevier Ltd. All rights reserved.

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