• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.20 no.2
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• pp.45-53
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• 2020

Blockchain can control transactions in a decentralized way and is already being considered for manufacturing, finance, banking, logistics, and medical industries due to its advantages such as transparency, security, and flexibility. And it is predicted to have a great economic effect. However, Blockchain has a Trilemma that is difficult to simultaneously improve scalability, decentralization and security characteristics. Among them, the biggest limitation of blockchain is scalability, which is very difficult to cope with the constantly increasing number of transactions and nodes. To make the blockchain scalable, higher performance should be achieved by modifying existing consensus methods or by improving the characteristics and network efficiency that affect many ways of scaling. Therefore, in this paper, we propose a cluster-based scalable PBFT consensus algorithm called CBS-PBFT which reduces the message complexity O(n²) of PBFT to O(n), which is a representative consensus algorithm of blockchain, and the validity is verified through simulation experiments.

• Korea Trade Review
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• v.42 no.4
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• pp.49-68
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• 2017

This paper investigates the spillover effect of the U.S. Interest on Korea's interest rate as well as the role of exchange rate in the spillover effects, by utilizing a open macro model on the determinants of long-term interest rates. According to the cointegration estimation and the Impulse response function, it is found that, across both long-term and short-term, there exist the spillover effect of the U.S. Interest on Korea's interest rate. The fiscal deficit and expected exchange rate have significantly positive relationship with the Koreas's long-term interest rate. Further, foreign exchange market intervention in Korea did not have significant effect on the spillover effect. Thus, this study suggests that exchange rate flexibility would not be enough to restrain the spillover effects of the U.S. interest rate.

• Electronics and Telecommunications Trends
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• v.33 no.6
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• pp.139-153
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• 2018

The explosive interest in block chain, which was triggered by Bitcoin in 2009, is leading to substantial investment and the development of block chain technology. There is no dispute among experts that block chain will be the next generation of innovation. However, despite the high expectations for block chains, the related technology still has certain limitations. In addition to improving issues such as a low transaction throughput, inefficient agreement algorithms, and an inflexible governance structure, it is necessary to solve various problems for commercialization and full-scale spreading owing to the trilemma problem among the scalability, security, and decentralization. Under this situation, identification of the technology characteristics according to the generation is helpful for the development of the core technology requirements and commercialization blueprint in establishing an R&D direction. Therefore, in this article, the development of blockchain technology is divided into generations and analyzed in terms of the operational structure, consensus algorithm, governance, scalability, and security.

• Electronics and Telecommunications Trends
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• v.36 no.3
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• pp.119-132
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• 2021

To accommodate various mobile communication frequency bands, the study of metamaterial antennas have begun since the mid-2000s to solve the Trilemma problem between antenna gain-occupied bandwidth-size. As an adaptive reconfiguration function is required in a multi-array antenna system since 4G, the metamaterial array antenna using low-power variable elements has been used to change the basic structure of the antenna. Recently, reconfigurable intelligent surface (RIS), which is made of metasurface with reconfigurability, has been studied to effectively cope with the randomly varying radio channels and be used for various purposes such as reflection/transmission/modulation. As a result of RIS-related patent information analysis in this study, it was confirmed that most of the patents are metamaterial antennas and metamaterial array antennas, but the metasurface antenna technology was in the early stages. Particularly, as the intelligent metasurface antenna is in a more initial stage, the investment to R&D of RIS is urgent to secure patent competitiveness in B5G and 6G.

• The Southeast Asian review
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• v.27 no.4
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• pp.1-40
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• 2017

This study aims to examine the electricity/energy regime of Thailand, the largest energy-hungry country in the Mekong region. This study examined how the electricity/energy regime of Thailand has been shaped and changed up to the present, not only at the national level but also at the sub-regional level covering the Mekong region. Meanwhile, according to the Paris Agreement in 2015, which will get in to effect from 2020, developing countries as well as developed countries have been given voluntary responsibilities and reduction obligations in response to global climate change. Under the post 2020 Climate Change Regime, Thailand also needs to revise its existing electricity/energy policy. We reviewed the recent energy policy of Thailand and evaluated the possibility of transition to a sustainable energy system based on Energy Trilemma's analysis framework. And we examined the roles and impacts of the Thai civil society on the national power and energy planning as well as in the future climate change policy. As a result of the analysis, it can be seen that Thailand's electricity/energy regime has grown rapidly through the support of the West countries under the Cold War era. In particular, Electricity Generating Authority of Thailand(EGAT) played the key role in Thailand's energy policy. In addition, Thailand's geopolitical location and relatively high economic level compared to neighboring countries will continue to be of importance in the future construction of power grids in the region. Meanwhile, in the frame of Energy Trilemma, Thailand has still been vulnerable to environmental sustainability. Thai NGOs have resisted to as well as collaborated with the government to influence the existing electricity/energy policy in the various dimensions but their influence has weakened considerably since the coup in 2014. In conclusion, this study suggests to cooperate with government as well as civil society for sustainable energy transformation of Thailand and Mekong region.

• The Journal of Asian Finance, Economics and Business
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• v.8 no.2
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• pp.791-800
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• 2021

Along with the trend of financial globalization, Vietnam has undergone a process of increasing financial integration. The great capital inflow poses a problem for the monetary policy's ability to follow a planned target during the changes in the global financial markets. This paper aims to examine the impact of financial integration on monetary policy independence in Vietnam and investigate the role of foreign exchange reserves on this relationship. The research borrows from Mundell-Fleming's Trilemma theory. The results show that increasing financial integration reduces the independence of monetary policy in the short term, and foreign exchange reserves have not shown an apparent role in Vietnam. In addition, increasing exchange rate stability has a negative impact on the independence of monetary policy, but it has an impact on growing market confidence and partly supporting the management process of monetary policy in the short term. Therefore, in the long run, Vietnam needs to allow exchange rate flexibility more, but there should not be sudden changes; the size of foreign exchange reserves should be strengthened to facilitate the implementation of an independent monetary policy with an obvious impact in the context of an increasing scale of international capital flows in the future.

• Journal of Convergence for Information Technology
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• v.10 no.10
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• pp.65-70
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• 2020

With the appearance of Bitcoin that builds peer-to-peer networks for transaction of digital content and issuance of cryptocurrency, lots of blockchain networks have been developed to improve transaction performance. Recently, Joseph Lubin discussed Decentralization Transaction per Second (DTPS) against alleviating the value of biased TPS. However, this Lubin's trust model did not enough consider a security issue in scalability trilemma. Accordingly, we proposed a trust metric based on blockchain size, stale block rate, and average block size, using a sigmoid function and convex optimization. Via numerical analysis, we presented the optimal blockchain size of popular blockchain networks and then compared the proposed trust metric with the Lubin's trust model. Besides, Bitcoin based blockchain networks such as Litecoin were superior to Ethereum for trust satisfaction and data volume.

• 사회경제평론
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• v.31 no.3
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• pp.29-53
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• 2018

This study provides a model of inter-Korean economic cooperation suggesting that economic cooperation should be centered on industrial cooperation. As an independent economic zone, the two Koreas will go through a gradual and functional process of cooperation. Also, economic convergence through 'openness and integration' of both markets is a pre-requisite of successful economic integration on the Korean peninsula. This success of the process requires industrialization of North Korea. This study suggests a model of 'the Corea Industrial Development Community on the Korean Peninsula. It aims to support industrialization of the North Korean economy as well as promotion of South Korea's SME competitiveness. It would help meet the demand for improvement of living conditions of North Korean people. Main policy measures includes: 1) co-effort to develop North Korea's provincial industrial zones, 2) upgrading North Korea's 'Jangmadang' into a highly efficient distribution market. Finally, through the construction of the Joint Industrial Development Zone, it is necessary to create a production sharing module for both Korea's industries.

• Journal of Internet Computing and Services
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• v.20 no.4
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• pp.1-11
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• 2019

A Blockchain-based access control technology is one of the various use cases of blockchain and is used in many areas to transparently transfer and manage ownership of data between users without the trusted third party. The characteristics of transparency, Irreversibility, and decentralization provided by the public blockchain help to offer new benefits that existing access control technologies did not offer. However, various security issues facing the current blockchain are raising the issue of the safety of the technology. Therefore, in this paper, we analyze an overview of the blockchain-based access control technology and solutions of the security challenges faced. Moreover, we further present solutions that are not affected by the blockchain trilemma and models of access control technology based on them.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.43 no.4
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• pp.168-177
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• 2020

In recent years, importance of blockchain systems has been grown after success of bitcoin. Distributed consensus algorithm is used to achieve an agreement, which means the same information is recorded in all nodes participating in blockchain network. Various algorithms were suggested to resolve blockchain trilemma, which refers conflict between decentralization, scalability, security. An algorithm based on Byzantine Agreement among Decentralized Agents (BADA) were designed for the same manner, and it used limited committee that enables an efficient consensus among considerable number of nodes. In addition, election of committee based on Proof-of-Nonce guarantees decentralization and security. In spite of such prominence, application of BADA in actual blockchain system requires further researches about performance and essential features affecting on the performance. However, performance assessment committed in real systems takes a long time and costs a great deal of budget. Based on this motivation, we designed and implemented a simulator for measuring performance of BADA. Specifically, we defined a simulation framework including three components named simulator Command Line Interface, transaction generator, BADA nodes. Furthermore, we carried out response surface analysis for revealing latent relationship between performance measure and design parameters. By using obtained response surface models, we could find an optimal configuration of design parameters for achieving a given desirable performance level.