• TTA Journal
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• s.67
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• pp.154-157
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• 2000

• The KIPS Transactions:PartC
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• v.9C no.3
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• pp.343-350
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• 2002

This paper describes the implementation of H.235 protocol for authentication and media stream encryption of multimedia conference systems. H.235 protocol is recommended by ITU-T for H.323 multimedia conference security protocol to prevent from being eavesdropped and modified by an illegal attacker. The implementation in this paper has used password-based with symmetric encryption authentication. Media streams are encrypted using the Diffie-Hellman key exchange algorithm and symmetric encryption algorithms such as RC2, DES and Triple-DES. Also, 128-bit Advanced Encryption Standard and 128-bit Korean standard SEED algorithms are implemented for the future extension. The implemented authentication and media stream encryption has shown that it is possible to identify terminal users without exposing personal information on networks and to preserve security of multimedia conference. Also, encryption delay time and used memory are not increased even though supporting media stream encryption/decryption, thus the performance of multimedia conference system has not deteriorated.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.9C
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• pp.842-852
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• 2002

The fast advance in the VoIP technologies gives a rich opportunity to create different kind of VoIP applications such as IP telephony services. The application level call signaling protocols such as ITU-T H.323 and IETF SIP provide the communication functions of end-to-end call setup and release. Currently, there is a lot of H.323 based VoIP products in the market, however SIP is considered as a suitable protocol for supporting applications in IP environments, so SIP based VoIP products and services begin to appear. In this paper, firstly we present the characteristics of some possible SIP based applications and describe the design and implementation of a VoIP example service named PC-to-PC Internet telephony service using the developed SIP network components. The PC-to-PC Internet telephony service and User Agent are developed in MS window 98/2000 using visual C/C++, and Proxy server and Registrar in Linux 7.0 using C, respectively.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.12C
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• pp.1238-1244
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• 2002

In this paper, H.235-based security mechanism for H.323 multimedia applications was implemented. H.235 covers authentication using HMAC, Diffie-Hellman key exchange, session key management for voice channel, and encryption functions such as DES, 3DES, RC2. Extra encryption algorithms such as SEED, and AES were also included for possible use in the future. And, we also analyzed the quality of service (QoS), the requirement of implementation, and interoperability to the result in this study. The results could be applied to secure simple IP phone terminals, gateways, or gatekeepers.

• Journal of the Chungcheong Mathematical Society
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• v.23 no.2
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• pp.323-333
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• 2010

The biproduct bialgebra has been generalized to generalized biproduct bialgebra $B{\times}^L_H\;D$ in [5]. Let (D, B) be an admissible pair and let D be a bialgebra. We show that if generalized biproduct bialgebra $B{\times}^L_H\;D$ is a Hopf algebra with antipode s, then D is a Hopf algebra and the identity $id_B$ has an inverse in the convolution algebra $Hom_k$(B, B). We show that if D is a Hopf algebra with antipode $s_D$ and $s_B$ in $Hom_k$(B, B) is an inverse of $id_B$ then $B{\times}^L_H\;D$ is a Hopf algebra with antipode s described by $s(b{\times}^L_H\;d)={\Sigma}(1_B{\times}^L_H\;s_D(b_{-1}{\cdot}d))(s_B(b_0){\times}^L_H\;1_D)$. We show that the mapping system $B{\leftrightarrows}^{{\Pi}_B}_{j_B}\;B{\times}^L_H\;D{\rightleftarrows}^{{\pi}_D}_{i_D}\;D$ (where $j_B$ and $i_D$ are the canonical inclusions, ${\Pi}_B$ and ${\pi}_D$ are the canonical coalgebra projections) characterizes $B{\times}^L_H\;D$. These generalize the corresponding results in [6].

• Transactions of Materials Processing
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• v.24 no.5
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• pp.323-331
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• 2015

Impact extrusion is an economical and productive process that can replace the multistage deep drawing process for producing deep rectangular cases. In the current work, a three-dimensional finite element analysis of the impact extrusion process of a commercial purity aluminum alloy (AA1070) was performed to predict loads, material flow, and deformed shapes using the Hansel-Spittel rheology law, which describes the flow stress at various temperatures and strain rates. The role of various process parameters such as friction, clearance between punch and die, aspect ratio and thickness of billet on the process and the shapes was analyzed.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 1997.12a
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• pp.323-329
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• 1997

• The Magazine of Kiice
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• v.2 no.1
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• pp.33-43
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• 2001

• Information and Communications Magazine
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• v.19 no.2
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• pp.32-43
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• 2002

• Korea Information Processing Society Review
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• v.8 no.2
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• pp.22-26
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• 2001