• Journal of Korea Society of Digital Industry and Information Management
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• v.13 no.4
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• pp.115-123
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• 2017

The mutual cooperation among nodes is very important because mobile nodes participating in MANET communicate with limited resources and wireless environment. This characteristic is important especially in environment that supports group communication. In order to support the secure multicast environment, it is important enough to affect performance to provide accurate authentication method for multicast group members and increase the integrity of transmitted data. Therefore, we propose a technique to provide the multicast secure communication by providing efficient authentication and group key management for multicast member nodes in this paper. The cluster structure is used for authentication of nodes in the proposed technique. In order to efficient authentication of nodes, the reliability is measured using a combination of local trust information and global trust information measured by neighboring nodes. And issuing process of the group key has two steps. The issued security group key increases the integrity of the transmitted data. The superiority of the proposed technique was confirmed by comparative experiments.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.5 no.1
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• pp.123-140
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• 2011

In this paper, we propose an Energy Efficient Media Access Control (EE-MAC) protocol for wireless sensor networks. The proposed scheme is designed to save power consumption and guarantee quality-of-service for real-time traffic. EE-MAC uses the superframe structure which is bounded by the transmission of a beacon frame and can have an active and an inactive portion. The active period is divided into the contention free period (CFP) for real-time traffic transmission and the contention access period (CAP) for non-real-time traffic transmission. We propose the exclusively allocated backoff scheme which assigns a unique backoff time value to each real-time node based on bandwidth allocation and admission control. This scheme can avoid collision between real-time nodes by controlling distributed fashion and take effect a statistical time division multiple access. We also propose the algorithm to change the duty cycle adaptively according to channel utilization of media depending on network traffic load. This algorithm can prolong network lifetime by reducing the amount of energy wasted on idle listening.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.23 no.54
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• pp.27-36
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• 2000

The problem of discovering association rules is an emerging research area, whose goal is to extract significant patterns or interesting rules from large databases and several algorithms for mining association rules have been applied to item-oriented sales transaction databases. Data warehouses and OLAP engines are expected to be widely available. OLAP and data mining are complementary; both are important parts of exploiting data. Our study shows that data cube is an efficient structure for mining association rules. OLAP databases are expected to be a major platform for data mining in the future. In this paper, we present an efficient and effective algorithm for mining association rules using data cube. The algorithm can be applicable to enhance the power of competitiveness of business organizations by providing rapid decision support and efficient database marketing through customer segmentation.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.14 no.2
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• pp.69-74
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• 2004

Threshold digital signature is very useful for networks that have no infrastructure such as ad hoc network Up to date, research on threshold digital signature is mainly focused on RSA and DSA. Though Schnorr's digital signature scheme is very efficient in terms of both computation and communication. its hard structure using interactive proof prevents conversion to threshold version. This paper proposes an efficient threshold signature. scheme based on the Schnorr's signature. It has a desirable property of scalability and reduces runtime costs by precomputation.

• Journal of Venture Innovation
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• v.1 no.2
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• pp.35-46
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• 2018

The research on the efficiency analysis of domestic auto parts companies is mostly based on the calculation of the magnitude of the performance creation such as the sales amount compared to the input assets. However, the performance indicators such as sales, operating profit, and net profit are directly related to the cost structure and This cost structure is affected by changes in the firm's asset and capital structure. As a result, it is considered that efficient capital procurement needs to be done at the same time to create efficient management performance through proper investment. This study focuses on this point and attempts to measure the efficiency of procurement capital relative to the sales and other performance indicators generated by the first 33 suppliers who supply parts to Hyundai Kia Motors. Among the methods of evaluating efficiency, the DEA model based on the linear programming method is most widely used as a nonparametric method but The efficient frontier-based DEA model has the limitation that it can not use the variables that have a downward influence on the efficiency. This is inadequate to directly consider variables such as borrowings and total liabilities related to capital procurement. In this study, the efficiency of capital procurement was measured using Worst Practice DEA and the improvement direction of the capital procurement aspect of domestic auto parts companies was suggested

• KIPS Transactions on Software and Data Engineering
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• v.5 no.4
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• pp.171-180
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• 2016

As social networking services such as twitter become increasingly popular, data streams are widely prevalent these days. In order to search data accumulated from data streams efficiently, the use of an index structure is essential. In this paper, we propose an update-efficient, disk-based inverted index structure for efficient keyword search on data streams. When new data arrive at the data stream, the index needs to be updated to incorporate the new data. The traditional inverted index is very inefficient to update in terms of disk I/O, because all index data stored in the disk need to be read and written to the disk each time the index is updated. To solve this problem, we divide the whole inverted index into a sequence of inverted indices with exponentially increasing size. When new data arrives, it is first inserted into the smallest index and, later, the small indices are merged with the larger indices, which leads to a small amortize update cost for each new data. Furthermore, when indices stored in the disk are merged with each other, we minimize the disk I/O cost incurred for the merge operation, resulting in an even smaller update cost. Through various experiments, we compare the update efficiency of the proposed index structure with the previous one, and show the performance advantage of the proposed structure in terms of the update cost.

• Journal of Technology Innovation
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• v.29 no.1
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• pp.39-73
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• 2021

The cooperative network structure influences the academic performance of the research institute. In particular, South Korea's Government-Funded Research Institutes(GRI) need to establish an efficient cooperative system as a leading national R&D implementer. This study applied the Small World structure, which has been discussed as an efficient network structure, and the centrality of representing the characteristics of nodes to the cooperative network of GRI in Korea. Based on the SCIE published data from 2010 to 2019, we analyze how the Small World characteristics and centrality of GRI contribute to academic performance using a network analysis and Feasible GLS regression. The GRI cooperative network has shown that the Small World network structure facilitates the academic performance. In addition, centrality indicating the degree of direct connection showed positive significance, but centrality indicating the degree of intermediary was not significant or negative. The results of this study explain that the higher the number of institutions that exchange and cooperate, the higher the academic performance, and the higher the performance of the institutions that serve as the center of cooperation. In addition, it was established that the stronger the cooperative network of GRIs have the characteristics of Small World, the more effective it is to create research results. This study applies centrality and Small World previously discussed as an efficient network structure to the GRI cooperation network and provide implications for establishing policies and strategies related to R&D cooperation among GRIs.

• Water Engineering Research
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• v.5 no.4
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• pp.195-206
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• 2004

This paper deals with oxygen transfer by air entrainment and energy dissipations by flow characteristics at the stepped drop structure. Nappe flow occurred at low flow rates and for relatively large step height. Dominant flow features included an air pocket, a free-falling nappe impact and a subsequent hydraulic jump on the downstream step. Most energy was dissipated by nappe impact and in the downstream hydraulic jump. Skimming flow occurred at larger flow rates with formation of recirculating vortices between the main flow and the step comers. Oxygen transfer was found to be proportional to the flow velocity, the flow discharge, and the Froude number. It was more related to the flow discharge than to the Froude number. Energy dissipations in both cases of nappe flow and skimming flow were proportional to the step height and were inversely proportional to the overflow depth, and were not proportional to the step slope. The stepped drop structure was found to be efficient for water treatment associated with substantial air entrainment and for energy dissipation.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2008.04a
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• pp.100-103
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• 2008

Recently Development of construction system that subjective operators share and control information efficiently based on the three-dimensional space and design information throughout life cycle of construction project is progressing dynamically. In case of civil structures which are infrastructure, Demand for structure of complex system which has multi-functions such as super and smart bridges and express rails is increasing and system development which computerizes and integrates process of structure design is in need. For that, research about link way between three dimensional modeling data and structure analysis programs should be preceded. In this research, therefore, research about interface design between three dimensional virtual modeling data to automate efficient civil-structure-design and nonlinear finite element analysis program which is made up of reinforced concrete material model that express material's character clearly.

• Journal of the Korean Magnetic Resonance Society
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• v.4 no.1
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• pp.41-49
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• 2000

To design more efficient peptide antagonist against the HBV, preSl(21-47) which carries the HBV receptor binding site for hepatocytes was synthesized and the solution structure of preSl(21-47) was investigated using CD spectroscopy and NMR spectroscopy in membrane-mimicking environments. According to CD spectra, preSl(21-47) has a random structure in aqueous solution, while conformational change was induced by addition of TFE and SDS micelle. Tertiary structures as determined by NMR spectroscopy shows that preSl(21-47) has a very flexible structure even in SDS micelle.