• Journal of KIISE:Information Networking
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• v.34 no.3
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• pp.175-185
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• 2007

In IEEE 802.15.4 (Low-Rate Wireless Personal Area Network) specification, a successful reception and validation of a data or MAC command frame can be confirmed with an acknowledgment. However, the specification does not support security for acknowledgment frame; the lack of a MAC covering acknowledgments allows an adversary to forge an acknowledgment for any frame. This paper proposes an identity authentication mechanism at the link layer for acknowledgment frame in IEEE 802.15.4 network. With the proposed mechanism there is only three bits for authentication, which can greatly reduce overhead of device. The encrypted bit stream for identity authentication will be transmitted to device by coordinator within association process. Statistical method and simulation results prove that our mechanism is successful in handling MAC layer attack.

• Proceedings of the Korea Information Processing Society Conference
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• 2005.11a
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• pp.973-976
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• 2005

In IEEE 802.15.4 (Low-Rate Wireless Personal Area Network) specification, a successful reception and validation of a data or MAC command frame can be confirmed with an acknowledgment. However, the specification does not support security for acknowledgment frame; the lack of a MAC covering acknowledgments allows an adversary to forge an acknowledgment for any frame. This paper proposes an identity authentication mechanism at the link layer for acknowledgment frame in IEEE 802.15.4 network. With the proposed mechanism there is only three bits for authentication, which can greatly reduce overhead. The encrypted bit stream for identity authentication will be transmitted to device by coordinator within association process. Statistical method indicates that our mechanism is successful in handling MAC layer attack.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.11B
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• pp.989-997
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• 2008

The reverse acknowledgment (RA) scheme supports a fast loss recovery for negative acknowledgment (NAK)-based selective repeat automatic repeat request (SR-ARQ) by detecting a retransmission failure quickly before a retransmission timer expires. In this paper, we evaluate the performance of a NAK-based SR-ARQ protocol with the RA scheme and compare it with the conventional NAK-based SR-ARQ protocol. Particularly, we propose a simple analysis model for the transport delay of the NAK-based SR-ARQ protocol considering the traffic condition, the retransmission persistence, the timer-based retransmissions and the RA scheme's behavior. Both NAK-based SR-ARQ protocols with and without the RA scheme are implemented by using the OPNET simulator. We verified the analysis model's accuracy through the simulation results. Also, we evaluate the performance of the NAK-based SR-ARQ protocol with the RA scheme based on analysis and simulation results.

• Journal of Communications and Networks
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• v.9 no.3
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• pp.236-246
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• 2007

This paper investigates the performance of the transmission control protocol (TCP) transport protocol over IEEE 802.11 infrastructure based wireless networks. A wireless link is generally characterized by high transmission errors, random interference and a varying latency. The erratic packet losses usually lead to a curbing of the flow of segments on the TCP connection and thus limit TCP's performance. This paper examines the impact of the lossy nature of IEEE 802.11 wireless networks on the TCP performance and proposes a scheme to improve the performance of TCP over wireless links. A negative acknowledgment scheme, selective negative acknowledgment (SNACK), is applied on TCP over wireless networks and a series of ns-2 simulations are performed to compare its performance against that of other TCP schemes. The simulation results confirm that SNACK and its proposed enhancement SNACK-S, which incorporates a bandwidth estimation model at the sender, outperform conventional TCP implementations in 802.11 wireless networks.

• Proceedings of the Korea Information Processing Society Conference
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• 2010.11a
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• pp.1046-1049
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• 2010

Custody transfer method is often managed by the general architecture of Delay Tolerant Network (DTN) to provide reliability in the communications through storage and forward paradigm, but can be inefficient when the acknowledgment messages are lost, or the network becomes congested. In this paper we describe a new architecture that is particularly efficient for the custody transfer method. Because, it provides an additional control of acknowledgment messages, consolidate knowledge and services, using the advantage of the cross-over architectures and distribution control through local and global services.

• Journal of Nutrition and Health
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• v.52 no.6
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• pp.628-628
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• 2019

• Research in Mathematical Education
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• v.25 no.1
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• pp.21-43
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• 2022

Investigating the relationship between intrinsic and extrinsic motivation and their effects on affective mathematics engagement in a cultural context is critical for determining which types of motivation promote affective mathematics engagement and the relationship with cultural affordance. The investigation in the current study is comprised of two dependent studies. The results from Phase 1 indicate that attitude and emotion are better explained by extrinsic motivation, while self-acknowledgment and value are better explained by intrinsic motivation. The results of Phase 2 indicate that the Korean sample has greater extrinsic motivation, attitude, and emotion, while the U.S. sample has greater intrinsic motivation, self-acknowledgment, and value. The key outcome for this research is that disentangling cultural affordance from the emotional and cognitive structures is impossible.

• Nutrition Research and Practice
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• v.7 no.3
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• pp.242-242
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• 2013

• 제어로봇시스템학회:학술대회논문집
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• 2002.10a
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• pp.38.5-38
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• 2002

1. Introduction 2. System Configuration 3. Performance Evaluation 4. conclusion 5. Acknowledgment

• Journal of Sasang Constitutional Medicine
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• v.23 no.4
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• pp.514-525
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• 2011

1. Objectives This study aims to find out identify the recognition and attitude about the research ethic among Constitutional medicine researchers. 2. Methods This survey was conducted to the 37 researchers who were currently participating in Korea Constitution Multicenter Study guided by Korea institute of Oriental medicine(KIOM). The survey consist of 4 parts that level of acknowledgment about the systems and laws on clinical research ethic, clinical research experiences and education, the level of acknowledgment about Institutional Review Board(IRB) and the recognition about overall research ethic. 3. Results Thirty one questionnaires were collected. Most researchers had low level of acknowledgment about the guidelines of basic research ethic. It was proved that more than 65% of the respondents have never received education for clinical research ethic. Moreover, 70% of them felt the need for education of clinical research ethic. In addition, most of the respondents recognized the fact that IRB is responsible for ethically implementing clinical research. 39% of the researchers thought that they themselves have a firm ethical viewpoint, while the rest of the group showed somewhat difficulty on their own ethical implementation of clinical research. 4. Conclusions Most of researcher had partial awareness of regulations and laws on clinical research ethic. And Educational needs of research ethic was high. Therefore education and Public Relations need to be done to extend research ethic. Moreover, standardized course of education on research ethic should be developed and activated.