• The Journal of the Korea Contents Association
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• v.8 no.1
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• pp.160-168
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• 2008

We completed a new cluster system based on WDM by proposing virtual topology reconfiguration schemes. The key idea of the proposed scheme Is to construct a set with the longest chains of requests of connecting nodes which need to be assigned a wavelength. All the sets have no common factor, that is, there is no duplicated link among the requests of connecting. After making the set satisfying this condition, we could assign a wavelength to per corresponding set. We could reconfigure a virtual topology with this scheme collectively. we compared our scheme to existing approaches by the OWns simulation tool. As the results, we gained improved performances, reducing 10% of blocking rate and improving 30% of ADM utilization in terms of the blocking probability and the ADM utilization.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.44 no.2
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• pp.49-57
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• 2012

The reduction of greenhouse gas emission currently becomes more urgent task for Korean Industries, especially for the paper industries because of the new regulation based on the low carbon-green growth law. In order to reduce effectively the greenhouse gas emission, the development of greenhouse gas emission inventory has been widely considered as one of the basic processes and has been applied to many industries. In this study, the fundamental schemes and the cases of greenhouse gas inventories were investigated. Especially, the major considering units for paper industries were suggested to develope greenhouse emission inventory of paper industry.

• The Journal of Korean Association of Computer Education
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• v.7 no.3
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• pp.35-43
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• 2004

Internet-based P2P computing with independent machines suffers from frequent disconnections and security threats caused by leaving, failure, network diversity, or anonymity of participated machines. Replication schemes of shared resources are used for solving these issues in many studies and implementations. We propose an operational replication scheme in P2P computing to share computing resources, and the scheme verifies the correctness of operation against faults and security threats. This verifications are carried out periodically on replicated and dependent working units without global message exchanges over the whole system. The verified working units are treated as checkpoints, and thus they could be put to practical use for fault-tolerance with rollback recovery.

• The Journal of the Korea Contents Association
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• v.8 no.4
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• pp.71-78
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• 2008

We propose the scheme that supports continuously service when a user tries to contact new target network in broadband convergence network even though the network resource for the service is not enough. The proposed scheme transforms original service capacity into suitable QoS for the target network using the scalable service techniques in the oncoding/decoding and supports handover for the user. We analyzed the handover blocking probability of two schemes using queueing system to show the improvement of performance by the proposed scheme. Subsequently, we showed that the handover blocking probability in the proposed scheme is lower than that in the existing scheme.

• The Journal of the Korea Contents Association
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• v.8 no.4
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• pp.55-62
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• 2008

Adaptive modulation and Coding(AMC) scheme is promising technique to support the demands for high data rates and wideband proposed for 4G mobile communication system standards. In this paper, adaptive modulation and coding(AMC) based on OFDM system is analyzed through simulation for single user case and compared with SISO-OFDM and SFBC(Space frequency block coding)-OFDM. The performance analysis in terms of capacity for downlink system environments with different values of constellation size under multipath fading channel is done. The adaptive modulation and coding technique is based on perfect estimation channel. It has been observed that SFBC(Space-frequency block coding)-OFDM system gives better performance in terms of capacity.

• The Journal of Korean Association of Computer Education
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• v.4 no.2
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• pp.51-61
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• 2001

With the advance of computer and communication technologies, a lot of virtual schools provide web-based classes that provide learning environments out of temporal and spatial constraints and many research works on the web-based classes have been proposed. Various techniques are required to build the virtual schools efficiently. One of them is the scheme for transaction management. However, existing transaction management schemes have inappropriate features for supporting web-based classes. In this paper, we propose a new locking-based transaction processing protocol that satisfies the requirements after presenting the requirements for transaction management to support web-based classes. In the protocol, a new method, called mark, is adopted to satisfy the requirements. The proposed protocol also eliminates unnecessary delays or abortions and thus, the proposed protocol can improve the performance of database systems.

• Journal of Korean Tunnelling and Underground Space Association
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• v.5 no.1
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• pp.33-42
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• 2003

The use of tunnels in major transportation schemes has increased considerably during the last decade especially in urban area. The state of stress and the displacements in a zone around a tunnel will be modified by the construction of a tunnel. Therefore, it is necessary to study the influence factors for the nearby tunnels. This paper describes the design concept and analysis method on the closely spaced tunnels. The main purpose of the present paper is to study the influence of tunnel construction on the behaviour induced in the liners of nearby tunnels. The effects of tunnel proximity and alignment, liner stiffness and settlements are also reviewed in this paper. The paper then introduces the design and analysis methods for the closely spaced tunnels which is very useful in practice.

• Proceedings of the Korea Contents Association Conference
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• 2005.05a
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• pp.91-96
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• 2005

Recetly, the term Personal Public Key Infrastructure (PKI) was introduced to supprot reliable and authenticated service in a Personal Area Network (PAN). However, traditional public key signature schemes and certificate status management are not suitable for a PAN environment since mobile devices that constitute the PAN have limited computing capability. In this paper, we propose a new scheme that efficiently provides signature generation and certificate status management for mobile devices. Based on hash chain technique, we intend to reduce computational overhead on signature generation, and further, to minimize communication overhead for managing certificate status.

• The Journal of the Korea Contents Association
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• v.16 no.4
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• pp.56-64
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• 2016

With the development of information technologies and the wide spread of smart devices, the number of users of social network services has increased exponentially. Studies that identify user preferences and recommend similar users in these social network services have been actively done. In this paper, we propose a new scheme to recommend social network friends with similar preferences through the moving pattern analysis of mobile users. The proposed scheme removes the meaningless trajectories via companions, short time trajectories, and repeated trajectories to determine the correct user preference. The proposed scheme calculates user similarity using the meaningful trajectories and recommends users with similar preferences as friends. It is shown through performance evaluation that the proposed scheme outperforms the existing schemes.

• Journal of Korean Association for Spatial Structures
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• v.8 no.2
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• pp.105-113
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• 2008

Shell-typed structures can make resistance to external forces efficiently, and have merits to construct the large-span structures with thin thickness. This merits are highly depending on the shape of structure. Therefore designers want to the optimum shape, but it is not so easy to find the shape. So far there are many schemes to find more optimum shape, and those methods have their own characteristics. In this study, the authors introduce a relatively easy approach to find optimum shape by the finite element method considering geometric nonlinearity. We are finding the optimum shape of a shell-typed structure using line elements, and compared the results by various analytic models.